Piping / Mechanical Handbook

PIPING/MECHANICALHANDBOOK

BECHTEL CONSTRUCTION OPERATIONSINCORPORATED

https://boilersinfo.com

Second Edition.

Bechtel Corporation 1997. All rights reserved. Contains confidential information proprietary to Bechtelnot to be disclosed to third parties without Bechtel's priorwritten permission.

Printed in the United States of America.


© 1996 Bechtel Corp. Piping/Mechanical Handbook FRWD-1

Forward

This handbook is not under controlled distribution. Rather, it is intended for use as a training textin conjunction with detailed training provided by subject matter experts. The handbook has beendeveloped to assist in the training and development of Bechtel Piping and Mechanical FieldEngineers and Superintendents and is part of Bechtel's overall technical training program. Thehandbook is also intended to provide useful guidelines, information, and data to assist fieldpersonnel in making day-to-day decisions. All reference materials included in this handbook arefor illustration purposes only and shall not be used for actual work execution.

The handbook is not intended to replace codes, standards, procedures, or engineeringspecifications. The handbook does, however, provide a ready reference guide that may be usedin conjunction with the project requirements.


© 1996 Bechtel Corp. Piping/Mechanical Handbook TOC-1

Table of Contents

Piping/Mechanical Handbook

TABLE OF CONTENTS

SECTION 1 CORPORATE PIPING/MECHANICAL PROCEDURES

SECTION 2 SAFETY

SECTION 3 DUTIES AND RESPONSIBILITIES

SECTION 4 PIPING/MECHANICAL DESIGN DRAWINGS

SECTION 5 PIPE SIZES AND MATERIALS

SECTION 6 PIPE JOINTS AND BENDING

SECTION 7 VALVES

SECTION 8 STRAINERS AND TRAPS

SECTION 9 FIELD PIPING GUIDELINES

SECTION 10 UNDERGROUND AND EMBEDDED PIPING SYSTEMS

SECTION 11 INSULATION AND HEAT TRACING

SECTION 12 HANGERS AND SUPPORTS

SECTION 13 CLEANING AND FLUSHING METHODS

SECTION 14 LEAK TESTING

SECTION 15 MECHANICAL EQUIPMENT

SECTION 16 PUMPS

SECTION 17 AIR COMPRESSOR SYSTEMS

SECTION 18 HEAT EXCHANGERS

SECTION 19 HVAC SYSTEMS

SECTION 20 CHILLER SYSTEMS

SECTION 21 FANS AND BLOWERS

SECTION 22 CONVEYOR SYSTEMS

SECTION 23 CRUSHERS AND PULVERIZERS

SECTION 24 BEARINGS AND LUBRICATION

SECTION 25 GLOSSARY

SECTION 26 REFERENCES


© 1996 Bechtel Corp. Piping/Mechanical Handbook 1-1

Section 1

Corporate Piping/Mechanical Procedures

General

Piping and Mechanical components form the heart of almost all industrial construction projects. Whether the project is for a Mining and Metals, Petroleum, Chemical, Power, or Defenseapplication, the mechanical system requirements have many common features.

Due to the diversity of markets that Bechtel serves, however, it is not possible to develop a singlecorporate procedure applicable to the installation of piping and mechanical systems for all Bechtelprojects. As a result, Bechtel corporate procedures require that each construction project developspecific installation procedures or guidelines that are appropriate for the project. Theseprocedures must address specific customer requirements and local regulations. The project mustalso provide:

• Craft training

• Periodic inspection of tools and equipment

• Preplanning of work operations

• Monitoring and inspection of completed work

To assist construction projects in the development of project specific procedures, GenericConstruction Project Procedures have been developed. These procedures provide a startingpoint for the development of the project procedures and normally are based on proceduresdeveloped at other construction projects.

The following corporate instruction requirements are applicable:

SITE MANAGERS MANUAL

Site Managers Manual Instruction S4.4, Field Engineering, defines the general responsibilities ofthe Field Engineering as part of the project construction team. Instruction S4.5, Quality ControlProgram, defines the project requirements to develop and implement a construction qualitycontrol program on the project.

FIELD ENGINEERING MANUAL

The Field Engineering Manual contains several instructions that are applicable to Piping andMechanical work on projects. These include:

Instruction F2.4, Project Procedure Development, provides requirements for the development ofproject specific procedures

Instruction F3.1, Project Quality Control Plan, provides requirements for the development of aproject specific quality control plan.

Instruction F3.2, Project Constructability Program, provides requirements for implementing aconstructability program on the project.

Instruction F4.3, Construction Rigging Plans, establishes specific requirements for the preparationof rigging plans for Bechtel construction sites.


Section 1 Corporate Piping/Mechanical Procedures

1-2 Piping/Mechanical Handbook 1996:Rev.2

Instruction F4.5, Welding Control, provides requirements for developing and implementingwelding controls on the project.

Instruction F4.6, Standard Engineering Deliverables, summarizes agreements between theBechtel corporate Construction and Engineering Committees on standard engineering designdeliverables that will be provided for each project.

Instruction F5.1, Quantity Reporting, summaries requirements for developing a project quantityreporting plan.

GENERIC CONSTRUCTION PROJECT PROCEDURES

The following generic procedures related to the control of Piping and Mechanical work activitiesare typical of the types of Generic Construction Project Procedures that are available:

03501-1, Underground Piping Installation

03502-1, Above Ground Piping Installation

03502-2, Field Fabrication of Pipe Spools

03505-1, Pressure Testing of Piping

03507-1, Insulation Installation

03602-1, Rotating Equipment

03603-1, Column, Vessel, Tank, and Exchanger Installation

03606-1, Boilers and Fired Heaters

Additional generic procedures related to Piping and Mechanical work operations are available onthe On-Line Reference Library.

CONSTRUCTION QUALITY MANUAL

Instruction Q3.5, Quality Verification, describes the corporate requirements for the implementationof a independent inspection program on construction projects.

SAFETY PROCEDURES

Corporate safety procedures and requirements are addressed in Section 2 of this handbook.



Section 2

Safety

GENERAL

Bechtel is committed to a ZERO INJURY safety philosophy in all of its construction work activities.The installation of piping components and mechanical equipment can result in serious accidentsand injuries if not properly planned and executed. As a consequence performing piping andmechanical installation work safely is one of the principle features of Bechtel's overall safetyprogram.

OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION (OSHA) SAFETY REGULATIONS

Requirements for safe construction rigging work practices in the United States are defined in theCode of Federal Regulations Title 29 Part 1926, Safety and Health Regulations for Construction.This document is organized into various "subparts" that each address a particular aspect ofconstruction work operations. The subparts applicable to piping and mechanical work operationsare discussed below:

Subpart D - Occupational Health and Environmental Controls

This subpart establishes requirements for noise, ventilation, illumination, and hazardous materialscontrols. Since many piping and mechanical work activities involve performing the work in tightquarters with high noise levels, a clear understanding of the provisions of this subpart isimportant.

A hardhat, safety glasses, and hearing protection (e.g. ear plugs) should always be worn inthe work area.

Subpart E - Personal Protective and Life Saving Equipment

This subpart establishes minimum requirements for the use of fall protection devices includingsafety belts, lifelines, lanyards, and safety nets. The execution of piping and mechanical workoperations often requires individuals to work in elevated locations subject to falls and therequirements of this subpart are designed to prevent serious injuries that could result from a fall.

Subpart G - Signs, Signals, and Barricades

This subpart establishes minimum requirements for signaling and controlling traffic flows. Sincepiping and mechanical work operations often involve rigging and the movement of equipment andmaterials on roadways, the requirements of this subpart define the minimum signaling andbarricading requirements required.

Subpart H - Materials Handling, Storage, Use, and Disposal

This subpart provides minimum requirements for the use of material handling equipment includingrope, slings, chains, shackles, and hooks. The requirements of this subpart are very specific andit is important that material handling capacities are clearly understood.


Section 2 Safety


Subpart I - Tools - Hand and Power

This subpart defines requirements for the handling and use of hand tools, power operated tools,abrasive wheels and tools, and jacks. All of these devices are used extensively in piping andmechanical work activities and requirements of the subsection must be understood.

Subpart J - Welding and Cutting

Since almost all piping and mechanical work operations involve welding and cutting operations,the requirements of this subpart are directly applicable to all work activities. Particular emphasisshould be placed on the requirements for fire prevention.

Subpart K - Electrical

This provisions for electrical lockout in this subpart are important for work that is performed in thevicinity of energized electrical systems.

Subpart N - Cranes, Derricks, Hoists, Elevators, and Conveyors

This subpart provides specific requirements for the control of heavy lift rigging equipment at theconstruction site. The subpart addresses requirements for rigging hand signals, rigging equipmentand hardware inspections, posting of crane load charts, and rigging work execution.

Subpart T - Demolition

This subpart defines safety regulations for the demolition of buildings and materials. Since manyretrofit work operations involve demolition activities, these regulations would be directlyapplicable.

ROLE OF THE FIELD ENGINEER IN SAFETY

The Piping or Mechanical Field Engineer is a direct contributor to the safety of the workoperations at the construction site. Since all safe work operations must begin with preplanning,the Field Engineer makes a direct contribution to safety by reviewing the planned work with safetyin mind. The Field Engineer is typically responsible to develop a detailed work package for workplanned by the Superintendent, verify the required materials are available and obtain the requiredpermits to perform the work. The following specific types of questions might be asked by theField Engineer to ensure the work can be done safely:

• How will the materials get to the work location? Can preassembly be done to avoidperforming work in tight or cramped quarters?

• Does the work require the use of hazardous materials? Are MSDS sheets available at the sitefor all materials that are required to be used?

• Have all the required permits (e.g. confined space entry permits) been obtained to allow thework to be performed? Are there any special requirements that supervision or the craft needto be aware of prior to starting the work?

• Have all special equipment tagging requirements been satisfied?

• Are all the required materials available on the site? Have the materials been inspected fordamage or flaws that might cause injury during installation?


Safety Section 2

1996:Rev.2 Piping/Mechanical Handbook 2-3

• Has a thorough review for potential underground obstructions such as existing utilities,energized electrical cables and process lines been performed prior to authorizing the work toproceed?

• Is the proposed work site free of potential fire hazards? Is the housekeeping adequate?

• Are trenches or excavations adequately sloped or shored? Is a special shoring designrequired due to the depth or location of the excavation or trench?

• Have required rigging plans been prepared and approved? Have the requirements of theapproved rigging plan been reviewed with the craft who will perform the work?

• Is the scaffolding required to perform the work properly erected? Is a special scaffold designrequired to access the work location?



Section 3

Duties and Responsibilities

GENERAL

Exact duties and responsibilities of the Piping or Mechanical Field Engineer vary from project toproject depending on the scope of the work and the specific contractual requirements. A genericposition description for a Mechanical Field Engineer is shown in Attachment 3-1. A genericposition description for a Piping Field Engineer is shown in Attachment 3-2.

QUALITY

Ensuring the quality of the work done on a project is one of the major goals and objectives of theField Engineer. This goal is more than making sure that the craft are using the latest drawingrevision or that a system has been installed to project specifications. It must include monitoringhow the client perceives the progress toward project completion.

To keep job quality at the highest level possible and maintain a positive client perception of thework that has been completed, the Field Engineer must ensure that:

• Project specifications and standards are met

• Work discrepancies are quickly identified and corrected

• Quality standards are maintained - do not compromise

• Teamwork within the organization is developed and maintained

• Materials are properly controlled

• Constructability reviews are performed before work is released for construction

• Construction safety is considered in all work released to the craft for work

• Project quantities are properly reported and forecast

MATERIAL CONTROL

Field Engineering material control duties will vary from project to project. A sample of materialcontrol duties may include:

• Preparing Field Material Requisitions (FMR)

• Preparing Material Receipt Instructions (MRI)

• Performing receiving inspection of material delivered to the construction site

• Verifying that the proper paperwork has been received from the vendor with each order

• Designating proper material storage levels

When preparing requisitions and ordering material the Field Engineer must provide a completematerial description of each item needed. For example, when specifying 2 1/2 inch diameter A106grade B seamless carbon steel pipe, schedule 40, a key word in the material specification couldbe seamless. If the word seamless did not appear in the material requisition, the wrong materialcould be delivered to the site.


Section 3 Duties and Responsibilities


Suppliers and the Field Procurement buyer may not be aware of all project specifications and thejob could incur additional costs and schedule delays from restocking or replacing incorrectmaterial. Material stock codes which completely define particular materials should be usedwhenever possible to ensure the right material is purchased, received, and released forinstallation.

Field material storage is normally handled by the Field Procurement group. The Field Engineer,however, should have a working knowledge of required storage levels including requirements fornitrogen blankets, and lay-up and should periodically check material laydown and warehouseareas for proper storage. The Field Engineer should also ensure that any required maintenanceis performed on equipment while in storage.

CONSTRUCTABILITY

Constructability, as defined by the Construction Industry Institute (CII), is "the optimum use ofconstruction knowledge and experience in planning, design, procurement, and field operations toachieve overall project objectives.”

Constructability is an ongoing process of integrating construction knowledge and experience intoconceptual design, procurement, detailed engineering, and field construction operations whichprovides the opportunity to reduce project costs and improve project schedules.

The ability to influence project costs and to incorporate construction experience and methods intoa project plan and design is greatest during the very earliest stages of a project. Therefore, thegreatest benefit of the constructability process will be derived with the earliest establishment andimplementation of a constructability plan on a project.

Bechtel's Constructability Program provides construction input to the design process by takingideas and lessons learned on projects and applying them to present and future projects within thecompany. The Constructability Handbook describes the Bechtel Constructability Program in moredetail. The Field Engineer plays an important role in the successful implementation of theBechtel's Constructability Program.

Bechtel’s corporate Lessons Learned and Best Practices are compiled and are available throughseveral ways:

• On-Line Reference Library (OLRL) contains lessons learned and best practices sectionswhich can be accessed by computer link to a regional office. This information is listed bygeneral subject title and can be retrieved at the construction site.

• Periodic construction newsletters and bulletins which provide information from other projectsand corporate initiatives.

• Periodic project meetings to review site progress and project lessons learned.

• The final Project Historical Report for completed projects which compile significant lessonslearned on the project.


Duties and Responsibilities Section 3


The Field Engineer participates in the Constructability Program in several ways:

• Review project designs for constructability and suggest enhancements to improve theconstruction process on the project.

• Since the construction craft build what the engineer visualizes, solicit constructability ideasfrom the craft and craft supervision to take advantage of their knowledge of what can andcannot be built.

• Contribute to the corporate Lessons Learned Program to ensure that project field experienceis captured for use by future projects.

LESSONS LEARNED

The Field Engineer can make an important contribution to the organization by sharingexperiences and knowledge with the rest of the company. Proposed Lessons Learned aretypically recorded on a form similar to that shown in Attachment 3-3 and are submitted to sitemanagement for review and approval. Approved lessons are entered into the corporate On-LineReference Library (OLRL).

Project Lessons Learned should be identified and submitted at all stages of the project and mustnot be used as a dumping ground for identifying problems. Do not submit a problem statement orexisting condition without offering a suggested solution or opportunity for improvement.

SAFETY

New personnel on the site are typically given a general safety orientation covering the following:

• Specific job requirements

• Potential hazards

• General refresher of safety practices expected from each worker

The Field Engineer plays a very important role in the administration of the safety program at theconstruction site. Some typical responsibilities include:

• Ensure that work is preplanned with safety in mind

• Monitor work areas for safety and housekeeping

• Maintain personal safety and set the example

• Develop appropriate safety permits, clearances, and tagging requirements

• Monitor subcontractor work for safe practices

• Ensure Material Safety Data Sheets are available for the materials in use at the site

• Ensure field design activities take worker safety into consideration




COST AND SCHEDULE

Project Cost Performance

Work performance at the job is tracked using the Jobhour Reporting System. A weekly costreport showing cost codes by each discipline is standard. The cost codes are tracked andevaluated to indicate how individual commodities are performing. An example is cost code P-11that follows 2-inch diameter and smaller carbon steel pipe. Pipefitters, Teamsters, and OperatingEngineers all charge to this cost code.

Parallel to the labor charges, the Field Engineer prepares a periodic report showing acceptedquantities completed for the same time frame. The cost department then uses the quantitiesreported to calculate earned job-hours which is the product of the installed quantities and thebudget unit rate. The budget unit rate is the number of job-hours the project has been given toinstall a unit length of pipe (usually a foot or a meter).

The actual job-hours charged are then divided by earned job-hours to calculate a cost codeperformance factor (PF). A PF of 1.0 or less indicates that materials are being installed at lessthan the budget for the project and is favorable. A PF greater than 1.0 indicates that budgets arebeing exceeded. In summary,

EARNED JOB-HOURS = (BUDGET UNIT RATE) X (QTY INSTALLED)

PERFORMANCE FACTOR = (ACTUAL JOB-HOURS) / (EARNED JOB-HOURS)

Project Schedules

The project plan or schedule is made up of several smaller plans. They include a 90/180 dayplan, near term schedules (1 to 4 weeks), and daily work schedules. The 90/180 day schedule isbased on a code account structure. Each activity will show the quantities to be installed and themanpower to be utilized for each period. Manpower will be summarized at the bottom and brokendown by craft. A summary of all 90/180 day schedules will yield total project manpowerrequirements by craft.

The near term schedule describes in detail all the resources required and quantities of work to beaccomplished to achieve interim milestone dates. This level schedule is what the Field Engineernormally will use to plan material, work packages, and testing that will be required on the project. The schedule provides the definition of what will be needed on the project in the coming weeks.

The basic guidance for project scheduling is to plan your work and work your plan.

FIELD CRAFT SUPPORT/COMMUNICATION

It is important that the Field Engineer develop the habit of checking with craft supervision eachmorning on what is being worked in assigned areas or on assigned systems. This will help plandaily work activities and allows for review of completed work for quality and progress reporting.

One aspect of field support is to discuss with the craft the work ongoing. This develops goodopen communication and there will not be any "we vs. they" attitudes. Problems or questionsshould be reviewed early to prevent major reworks or confusion on how something wascompleted.



Another part of craft support is problem resolution. This may involve discussions with thesupervisor, Project Field Engineer, or Design Engineer to resolve and correct the condition. Itmay also require the generation of nonconformance reports, discrepancy reports, field changerequests, or field change notices to document the resolution of the problem.

TYPICAL JOB ACTIVITY FLOW

Early Project Phase

• Review engineering drawings

• Meet client representatives

• Review quantity tracking requirements

• Order field material

• Help in temporary site services layout and design

• Do underground piping

• Scope hydrostatic tests and system turnovers

• Order testing equipment

• Review schedules taking material and scoping needs into consideration and discuss anyconcerns with supervision

• Work with supervision and project controls on erection sequences of large equipment andassist in developing rigging plans.

Peak Construction Project Phase

• Receive and track material

• Provide field support to superintendents and craft

• Review completed installations for correctness against drawings

• Punchlist any discrepancies in completed work

• Start hydrostatic testing and releasing for insulation

• Set equipment as it arrives

• Lubricate stored material as needed and maintain lubrication records

• Maintain client interface

• Continue quantity reporting

Project Completion Phase

• Develop punchlists and complete physical work

• Tie-in equipment

• Complete hydrostatic, flushing, and start-up testing

• Complete valve packing and flange torque checks

• Complete as-builts

• Turnover systems to client




• Surplus extra material




SAMPLE MECHANICAL FIELD ENGINEER POSITION DESCRIPTIONATTACHMENT 3-1

POSITION: MECHANICAL FIELD ENGINEER

The Mechanical Field Engineer is responsible to the Project Field Engineer for adherence tospecifications for all equipment installation work.

DUTIES AND RESPONSIBILITIES:

• Provides technical assistance to the Mechanical or Equipment Superintendent, AreaSuperintendent and Area Engineer and keeps them informed on matters relating to qualitycontrol.

• Establishes with the client personnel, parameters on testing, installation and turnover ofsystems and major equipment.

• Determines area priorities for equipment installation through consultation with AreaSupervision.

• Establishes communications with Design to resolve field problems.

• Reviews the project schedule and working with the Mechanical or Equipment Superintendentand Area Engineer, develops the 90/180 day schedules as required.

• Performs inspection of all equipment installation work in progress on a continuing basis. Witnesses tests and completes final equipment checks and tests prior to client turnover.

• Assists the Mechanical Superintendent and Area Engineers in solving equipment problems.

• Implements inspections of equipment installations.

• Executes field takeoffs from design drawings and provides input to the quantity trackingsystem.

• Reports weekly installed quantities to the Cost Engineer.

• Writes material requisitions for all equipment testing equipment, spare parts, gaskets, andlubricants required for the job.

• Maintains an open dialogue with site and factory vendor representatives to assessrequirements and needs for having vendor representatives at the site.

NOTE: Having vendor representatives at the site is normally required during the startup oflarge and/or complex product moving systems such as pumps, compressors, turbines,conveyors, boiler systems, and moving/feeding systems.

• Assists Area Engineers on equipment related problems to obtain vendor information,substitutions and other design related problems.

• Assists the Field Procurement Supervisor in the inspection and receipt of piping materials andin the setting up of site controls for storage, protection, and maintenance of permanent plantequipment and associated materials.

• Maintains as-built information for equipment installations.

• Determines the scope of any equipment installations not shown on the design drawings, suchas seal water piping.



• Establishes with the design office, those permanent materials and construction materials to beordered by the field, establishes cut off dates for Regional Office material requisitioning andissues field material requisitions as required.

• Assists the Superintendent in establishing equipment delivery priority.

• Monitors off-site equipment fabrication through expediting to coordinate the proper priorityflow of equipment to the site. Also maintains updated delivery schedules from the fabricator.

• Determines the amount of equipment erection to be done in the field. Designs the fieldfabrication and assembly facilities for field pre-assembly work with a complete building layoutand material list. Coordinates efforts with craft supervision to determine the amount ofprefabrication work is to be performed and how much will be fabricated at the site prior to fielderection.

• Monitors code-designed systems to coordinate flow of information to welding and materialcontrol to properly control code documentation.

• Prepares necessary documentation for installation and/or repair of code-stamped equipment.

• Implements regular maintenance schedule for equipment in field storage and installedequipment prior to turnover to the client.

• Maintains maintenance records as required for turnover to the client.

• Develops labor saving methods of equipment installation such as prefabrication of assembliesor off-site pre-assembly.



SAMPLE PIPING FIELD ENGINEER POSITION DESCRIPTIONATTACHMENT 3-2

POSITION: PIPING FIELD ENGINEER

The Piping Field Engineer is responsible to the Project Field Engineer for adherence tospecifications for all piping installation work.

DUTIES AND RESPONSIBILITIES:

• Provides technical assistance to the Piping Superintendent, Area Superintendent and AreaEngineer and keeps them informed on matters relating to quality control.

• Establishes with the client personnel, parameters on testing, installation and turnover ofsystems.

• Determines area priorities for piping installation through consultation with Area Supervision.

• Establishes communications with the Piping Design Group to resolve design problems.

• Reviews the project schedule and working with the Piping Superintendent and Area Engineer,reviews the 90/180 day schedules as required.

• Performs inspection of all piping work in progress on a continuing basis. Witnesses tests andcompletes final P&ID checks prior to turnover to the Client.

• Assists the Piping Superintendent and Area Engineers in solving piping problems.

• Issues job wide inspection criteria that may be over and above the normal piping inspection.

• Executes field takeoffs from design drawings and provides input to the project quantitytracking system.

• Reports weekly installed quantities to the Cost Engineer.

• Assists Superintendent in establishing pipe spool, pipe support, and valve delivery priority.

• Writes material requisitions for all pipe testing equipment, test blinds, gaskets, etc. requiredfor the job.

• Assists Area Engineers on piping related problems to obtain vendor information, substitutions,and other design related piping problems.

• Assists the Field Procurement Supervisor in the inspection and receipt of piping materials andin the setting up of project controls for storage and protection of piping materials.

• Maintains record prints with as-built information for all piping systems when required. Underground systems must be as-built prior to backfill.

• Determines the scope of any piping areas not shown on the normal piping drawings, such assteam tracing, package unit interconnection piping, and lubrication systems on equipment.

• Establishes with the design office, those permanent materials and construction materials to beordered by the field, establishes cut off dates for Regional Office material requisitioning andissues field material requisitions as required.

• Analyzes the need for field shop spooling and assists supervision in determining the amountof piping to be shop fabricated.



• Monitors the off-site spool fabrication to coordinate the proper priority flow of spools to thesite. Also maintains updated delivery schedules from the fabricator through the expeditingdepartment.

• Monitors code designed systems to coordinate flow of information to welding and materialcontrol in order to properly control this documentation.

• Develops labor saving methods of pipe installation such as prefabrication of assemblies,bending, or off-site pre-assembly.

• Determines the amount of small bore pipe (two inch and under) fabrication to be done in thefield. Develops field sketches of site fabrication facility based on input from Superintendentand craft General Foremen. Field sketches to provide a complete building layout and materiallist. This will require close coordination with supervision to determine how much will befabricated at the erection point and how much is fabricated in the weld bay.

• Designs both large and small bore piping hangers when required.

• Generates piping insulation, penetration sealing, painting, and heat tracing releases.



SAMPLE PROJECT LESSON LEARNED REPORTATTACHMENT 3-3

Project InformationProject Number:

Project Name: Project Description:

Customer Name: State (Province) /

Country:

Construction Manager: Global Industry Unit: Advanced Systems

Type of Contract: Engineering Procurement Construction (Direct Hire) Construction

Management Startup Maintenance

Value of Contract: 0Construction Type: Green Field

Lesson InfomationDate: Title:

Category: ArchitecturalKeywords:

Existing Condition:

Solution:

Photo Available: Electronic Format Paper (Hard) CopyPlease transmit (attach) photos with (to) this form.

Impact InformationPlease provide actual or best estimate information if available

Cost of Equipment /Material (in dollars) to

Implement:

0 0 0Engineering Procurement Construction

Cost of Equipment /Material (in dollars)

Savings:




Cost of Labor (in dollars)to Implement:


Cost of Labor (in dollars)Savings:


Schedule (in weeks) toImplement:


Schedule (in weeks)Savings:

0 0 0Engineering Procurement ConstructionApproval Information

Originator: Date: Site Manager: Date:

Construction Manager: Date:

Field EngineeringManager:

Date:

Disposition:


Section 4

Piping/Mechanical Design Drawings

GENERAL

The primary drawings that a Piping/Mechanical Field Engineer will use in the course of completinga field assignment are:

• Piping and Instrument Diagram (P&ID)

• Piping Isometric

• Plot Plans

• Piping Class Sheets

• Piping Support Details and Hanger Drawings

• Vendor Drawings and Manuals

• Instrument and Tubing Drawings

• Standard Instrument Details

• Steam Heat Tracing Drawings

These drawings along with project installation specifications provide quality guidelines for properlycompleting the assigned system.

Piping and Instrument Diagram

The single most important drawing for the installation of piping systems is the Piping andInstrument Diagram (P&ID). It provides the base design description of the required pipe routingand sizing, flow direction and slope, instrumentation and controls, insulation, heat tracing, andequipment and/or instrument references. This provides a road map to finding other drawings,vendor data, and piping information to properly complete the installation. The P&ID does nothowever provide dimensional data or physical locations of any commodities.

The Piping Line List and the Instrument Index are issued documents which often provide thisinformation.

PIPING ISOMETRIC AND PLOT PLAN DRAWINGS

Piping Isometric and Plot Plan drawings provide plant references and physical dimensioning thatare not on the P&ID. Along with dimensioning and locating the pipe itself, the drawings also showthe physical installation guides, including:

• Hanger location references to plant coordinates and piping commodities

• Specific installation details and/or requirements

• Material requirements for both the shop and/or field

• Correct valve orientation

• Existing equipment outlines

Section 4 Piping/Mechanical Design Drawings


• Pull or dismantling space

• Piping class

• Pressure test requirements

• Spools

• Welds (including welded attachments)

• Valves

• Hangers

• Specialty items with unique tag numbers

For bulk piping systems, Engineering supplies a detailed Bill of Material for each drawing listingthe required material including material description, quantities, stock code numbers, flangegasket, and flange bolting. Other information that engineering provides includes coating andslope requirements for the detailed piping system, connecting equipment nozzle numbers, taporientations, stress relief and NDE requirements for piping welds, and standard details for ventsand drains.

PIPING CLASS SHEETS

Piping class sheets specify the material and code requirements for designated piping systempressure and temperature ratings. A sample Piping Class Sheet is shown in Attachment 4-1.

HANGER DRAWINGS

Hanger drawings provide a detailed drawing of the pipe support, and include the following:

• Detailed bill of materials

• Building location and elevation reference

• Piping dimensional reference for installation location

• Welding requirements

• Line reference numbers

• Design loads (on some projects, hanger loads are determined from standard load tablesand/or charts based on pipe size, span, and support member size)

VENDOR DRAWINGS AND MANUALS

Drawings supplied by vendors will vary by manufacturer but generally provide:

• Outline drawings

• Material types

• Parts listing

• Weights and Centers of Gravity

• Field test requirements

Piping/Mechanical Design Drawings Section 4


• Operating pressures and temperatures and data (e.g. pump curves)

• Start-up, operating, and maintenance procedures

INSTRUMENT AND TUBING DRAWINGS

Design Engineering provides a standard set of drawings for the Mechanical Field Engineer to usein the installation process. The Piping/Mechanical Field Engineer will match the instrumentcategory and service fluid and instruct the craft in which detail should be used. The standardusually will show routing, vents and drains, manifolds, bill of material and stock codes.

HEAT TRACING DRAWINGS

Heat tracing drawings provide the Mechanical Field Engineer with:

• Heat tracing category

• Plant location

• Piping isometric and line number

• Manifold locations with specific tap numbers for tie-in of both steam and condensate tubing.

Section 4 Piping/Mechanical Design Drawings


SAMPLE PIPING CLASS SHEETATTACHMENT 4-1

Class (XXX)ASME B31.1 Power Piping Code

Primary Rating 150 LB @ 600 oF

Pipe: 26" and larger Seamless ASTM A-672, Gr. B70 SCH. (laterif required).

12" thru 24" Seamless ASTM A-106, Gr. B STD. WALL2 1/2" to 10" SCH. 402" and smaller SCH. 80

Fittings: 26" and larger ASTM A234 GR. WPBW seam weld, buttweld, wall thickness to match pipe

2 1/2" thru 24" ASTM A234 GR WPB or WPBW seamlessor seamweld, butt weld, wall to match pipe

2" and smaller ASTM A-105 3000# socket weld SCH. 80Flanges: ASTM A-105, bored to match pipe.

26" and larger 150# welding neck R.F.2 1/2" thru 24" 150# slip-on, R.F.2" and smaller 150# socket weld, R.F.

Plate: ASTM A515 GR. 70Bolting: Bolts Stud bolts, ASTM A-193 GR. B7

Nuts Heavy hex, ASTM A-194, GR 2HGaskets: All Sizes SEE NOTE 2

ASBESTOS FREE SPIRAL WOUNDValves: SEE PS-22Joints: Welded except at flange equipment connections. Field weld end

preparation and weld end transition (ref. PS-06)Notes: 1. This piping shall not be used where service temperature exceeds

775 oF.2. Flexitallic Style CG with Flexite-Super filler or equal for design

temperature not exceeding 1000 oF. Metal Strip used shall bestainless steel TP304.

3. Pipe minimum walls (pipe schedules) are based on designconditions of 200 PSIG @ 400 oF.


Section 5

Pipe Sizes and Materials

STANDARD PIPING SIZES

Piping is divided into three major categories:

• LARGE BORE PIPE generally includes piping which is greater than two inches in diameter

• SMALL BORE PIPE generally includes piping which is two inches and smaller in diameter

• TUBING is supplied in sizes up to four inches in diameter but has a wall thickness less thanthat of either large bore or small bore piping and is typically joined by compression fittings

The term diameter for piping sizes is identified by nominal size. The manufacture of nominalsizes of 1/8 inch through 12 inches inclusive is based on a standardized outside diameter (OD). This OD was originally selected so that pipe with a standard wall thickness will have the insidediameter (ID) of the size stated. The 14 inch and larger sizes have the OD equal to the nominalpipe size. Pipe sizes 3/8 inch, 1 1/4 inches, 3 1/2 inches, 4 1/2 inches, and 5 inches are consideredto be nonstandard and should not be used except to connect to equipment having these sizes. Inthese cases the line is normally increased to a standard size as soon as it leaves the equipment.

Tubing is sized to the outside diameter for all applications and pressure rating is dependent onvarying wall thicknesses. Refer to industry handbooks for more information.

Schedule (Wall Thickness)

Pipes are manufactured in a multitude of wall thicknesses, these have been standardized so thata series of specific thicknesses applies to each size of piping. Each thickness is designated by aschedule number or descriptive classification, rather than the actual wall thickness. The originalthicknesses were referred to as standard (STD), extra strong (XS), and double extra strong(XXS). These designations or weight classes have now either been replaced or supplemented byschedule numbers in most cases.

Schedules begin with 5 and 5S, followed by 10 and 10S, then progress in increments of tenthrough Schedule 40 (20, 30, 40) and finally by increments of twenty to Schedule 160 (60, 80,100, 120, 140, 160). Wall thickness for schedule 40 and STD are the same for sizes 1/8 to 10inches. Schedule 80 and XS also have the same wall thickness for 1/8 inch through 8 inchdiameter pipe.

Schedules 5 and 10 are generally used for stainless steel piping. Even though it is available inschedules allowing thinner walls, schedule 80 is generally the minimum size used for 2 inch andsmaller carbon steel piping. This may result in pipe that is stronger than needed, but the greatermechanical strength of schedule 80 pipe is required where threaded connections are used. Theextra wall thickness also allows for longer spans between supports.

Length

Pipe is usually supplied in random lengths. The shortest, longest, and average length may varyfor piping of different materials, sizes, and wall thickness schedules. Typically an average lengthof 20 feet is used for carbon steel pipe, but double random lengths are available from mostsuppliers and is generally preferred, especially for rack installations.

Section 5 Pipe Sizes and Materials


Pipe ends

Pipe may be obtained with plain, beveled, or threaded ends. Plain ends (PE) are cut square andreamed to remove burrs. This type of end is needed when being joined by mechanical couplings,socket weld fittings, or slip-on flanges. Beveled ends (BE) are required for most butt-weldapplications. Threaded ends (TE) are used with screwed joints and are ordered noting threadson both ends or one end (TBE or TOE).

NOTE: Electrical conduit dies cannot be used to cut pipe threads since this type of threadedconnection will typically fail the piping pressure test. The electrical conduit threads are straightversus tapered for piping.

STANDARD PIPING MATERIALS

Carbon Steel Pipe

Carbon Steel is one of the most commonly used pipe materials. The specifications that covermost of the pipe used are published by the American Society for Testing and Materials (ASTM)and American Society of Mechanical Engineers (ASME). Carbon Steel Material specificationASTM A106 is available in grades, A, B, and C. These grades refer to the tensile strength of thesteel, with grade C having the highest strength. Common practice is to manufacture the pipe asA106 Grade B.

ASTM A53 is also commonly specified for galvanized or lined pipe or as an alternate to A106. The testing requirements for A53 are less stringent than for A106. Three types of carbon steelpipe are covered by A53. These are type E or electric resistance welded, type F or furnace-buttwelded, and type S or seamless. Type E and S are available in grade A and B, comparable togrades A and B of A106.

Stainless Steel Pipe

Austenitic Stainless Steel pipe commonly referred to as "stainless steel" is virtually non-magnetic. Stainless steel is manufactured in accordance with ASTM A312 when 8-inch or smaller sizes areneeded. There are eighteen different grades, of which type 304L is the most widely used. Grade316L has high resistance to chemical and salt water corrosion, and is therefore used inapplications where this characteristic is needed. The "L" denotes low carbon content and is bestsuited for welding. Larger sizes (8 inches and up) of stainless steel pipe are covered by ASTMA358. Extra light wall thickness (Schedule 5S) and light wall (Schedule 10S) stainless steel pipeis covered by ASTM A409.

Chrome-Moly Pipe

Chromium-Molybdenum Alloy Pipe is commonly referred to as "chrome-moly". Ten grades of thistype pipe material are covered by ASTM A335. Appropriate grades of chrome-moly pipe aresometimes used in power plants applications requiring good tensile property retention at hightemperatures, especially when the added corrosion resistance of stainless steel is not required. Chrome-moly pipe is used extensively in heat exchangers. Special care must be exercised whenfabricating or welding this material, since it must be annealed (stress relieved) after being joined.

Pipe Sizes and Materials Section 5


Plastic Pipe

Thermoplastic Pipe is commonly referred to plastic pipe and is categorized into two principalgroups.

Thermoplastic pipe is available in a great variety of plastic compositions including:

• Polyvinyl chloride (PVC)

• Polyethylene (PE)

• Acrylonitrile-butadiene-styrene (ABS)

• Polyamide (nylon)

• Polypropylene

Thermoplastic pipe is most commonly supplied in PVC material. It also comes in many gradeslike steel pipe. It can be obtained threaded or with plain ends for solvent (cement) or thermalwelding. Solvent welding joining is normally used. Some types also include the use of couplings.

Advantages of this material it is very easy to install, and its light weight and socket joints make iteconomical for temporary services.

Disadvantages are the temperature limitations and the support spacing required to preventsagging.

Thermosetting (Fiberglass) Pipe is made of a plastic that takes a permanent set or hardenswhen heated to the curing temperature in the mold. After this initial set the material cannot besoftened by heat or be thermally welded. The principal thermosetting plastic is made of fiberglassreinforced epoxy, the strongest is helically interweaved glass filaments under tension.

Fiberglass pipe can be obtained in a great variety of sizes and wall schedule like steel pipe. There are three types of connection methods used to join fiberglass pipe:

• Threaded ends for screwed joints

• Plain for use with socket type fittings

• Adhesive welded bell and spigot taper joints

The adhesive consists of a plastic resin and a catalyst, which thermally set after being mixed andapplied as a joint filler material.

Concrete Pipe

Concrete Pipe is made from a mixture of portland cement, sand, gravel, and water. It ismanufactured as:

• Plain (unreinforced)

• Reinforced concrete pipe

• Prestressed concrete pressure pipe

Section 5 Pipe Sizes and Materials


The usual method for joining this pipe is by bell and spigot ends. The spigot end of one pipe isinserted into the bell of the mating piece, then the joint is sealed with mortar or a joint compound. It may also have a provision for a rubber gasket to seal the joint.

Copper Piping

Copper Piping is typically joined with solder fittings and is used for potable water lines in plumbingsystems and for air lines in service air systems.

Nickel and Nickel Alloy Piping

Nickel and Nickel Alloy Pipe has a great resistance to alkalis such as caustic soda and potash. Nickel and nickel alloys are sometimes used for high temperature applications. Inconel, Incoloy,and Monel are commonly used nickel alloys.

Cast Iron Piping

Cast Iron Pipe has good corrosion resistance. Ductile iron is commonly used for undergroundpiping in fire protection systems.

Duriron pipe is a form of cast iron that has a high silicon content that makes it extremely hard. Itschief advantage is strong resistance to most commercial acids. This pipe is sometimes used forwater treatment chemicals and acid drainage systems. Cast iron pipe is used for floor drains,sewage, fire protection, or where heavy loads may occur over the underground service pipe.

Special Piping Applications

Other piping materials such as plastic lined, glass lined, concrete lined, and steam jacketed areutilized in special project applications.


Section 6

Pipe Joints and Bending

GENERAL

Pipe joints are used to couple runs of piping, provide branches from main runs, change directionof piping, join different diameters or schedules, and connect to valves and equipment. Thecommon types of joints are:

• Butt welds

• Socket welds

• Screwed joints

• Bolted flanges

• Mechanical couplings

Butt welded joints similar to those shown in Figure 6-1 are the most common type of joint used for2 1/2 inch and larger piping systems. This type of joint is not normally used on 2 inch and smaller

FIGURE 6-1 - BUTT WELD JOINTS

Section 6 Pipe Joints and Bending


piping, except when high stress, corrosion, or other conditions that would effect joining or the typeof joining process. The end preparations must be of a standard type similar to the examplesshown. The end preparations are designated by welding codes and standards.

Using configurations similar to that shown in Figure 6-2, backing rings are sometimes used toprevent weld splatter, filler metal intrusion, and globules from forming inside the pipe duringwelding. The ring serves as an alignment aid and becomes a permanent part of the pipe joint.Backing rings are not used in systems when there is a concern that particles may becometrapped between the pipe and ring.

Socket welded joints are almostexclusively used in joining small borepiping. As shown in Figure 6-3, thejoint is fit up by slipping the plain endinto the socket connection. Anadvantage with this type of joint is thatthe filler metal cannot enter the mainpipe bore. The socket weld relies on acircumferential weld for both its sealingand strength which is one reason it isused instead of screwed or flangedjoints.

The inside diameter of the socket is a few thousandths larger than the outer diameter of thepiping, so that it will fit into the socket. A gap of 1/16 inch at the bottom of the socket is normallyrequired to allow expansion between the bottom of the fitting and the pipe. This prevents theweld from possibly cracking due to thermal stress during welding or high temperature services.

Threaded or screwed joints similar to those shown in Figure 6-4 are normally used on lowpressure systems since there is a greater potential of leaks through the threaded connection.Pipes and fittings for screwed joints in low pressure systems usually have National Pipe Taper(NPT) threads. Pipe threads are cut by dies and the resultant threads are rough and imperfect. A

FIGURE 6-2 - BACKING RING CONFIGURATION

FIGURE 6-3 - SOCKET WELD JOINT AND COUPLING

Pipe Joints and Bending Section 6


pipe joint compound or thread sealant must be used to prevent leakage around the threads. Thejoint compound also acts as a lubricant when tightening the fitting to the pipe.

Bolted Flange Joints similar to that shown in Figure 6-5 are required where pipe, pipingcomponents, or equipment must be disassembled for maintenance. They are required whenjoining glass, high density polypropylene (HDPE), or other lined piping. Sometimes they are usedto join prefabricated shop spools.

FIGURE 6-4 - THREADED OR SCREWED JOINTS

FIGURE 6-5 - BOLTED FLANGE



Bolted flanges are not generally used for critical applications subjected to pressure ortemperature extremes, or systems containing radioactive or highly corrosive fluids. As anexception, special precision machined sealing surfaces are sometimes used for severe serviceapplications, and may be seal welded when necessary.

FIGURE 6-6 - WELDED 90 DEGREE ELBOWS



Welded Pipe Fittings

Elbows make an angle between adjacent pipes. As shown in Figure 6-6, there are standardelbows of 90 degrees and 45 degrees. Special order angles are also available. The centerline toface dimension for long radius 90 degree elbow is 1.5 times the nominal pipe diameter. Forexample, a 6 inch diameter long radius has a face to centerline dimension of 9 inches. While ashort radius 90 degree elbow is only 1 times the face to centerline dimension. The 6 inch shortradius elbow has a 6 inch face to centerline length.

Reducing Elbows like the type shown in Figure 6-7 are 90 degree elbows with two different sizeends. The face to centerline dimension is that of the larger nominal dimensional standard longradius elbow.

FIGURE 6-7 - REDUCING ELBOW FIGURE 6-8 - 180 DEGREE RETURN

180 Degree Return fittings similar to one shown in Figure 6-8 are used for making a 180 degreeangles in piping systems.

Reducing Tee pipe fittings similar to the one shown in Figure 6-9 are the same as a standard teeexcept that the branch line connection is smaller in size. When stating the size for the reducingtee, the run sizes are stated first and the branch size last. For example, 6 inch x 6 inch x 4 inch.

FIGURE 6-9 - REDUCING TEE PIPE FITTING FIGURE 6-10 - STRAIGHT TEE PIPE FITTING

Straight Tee pipe fittings have three openings as shown in Figure 6-10. Two have the same axiswhile the third is perpendicular to this axis for connecting a branch line.

Concentric Reducers similar to the one shown in Figure 6-11 are pipe fittings with differentnominal diameters on each end while maintaining the same centerline and is used to connectdifferent sizes of piping.



An Eccentric Reducer is a pipe fitting with different nominal diameters on each end. As shown inFigure 6-12, this fitting is flat on one side with an eccentric centerline. When measuring thecenterline difference, the ID rather than the OD must be used because of possible wall thicknesschanges in the fitting. Eccentric reducers are used for connecting different size pipes especiallyat centrifugal pump inlet connections for preventing air pockets which may cause the pump tocavitate.

Pipe Caps similar to the one shown inFigure 6-13 are specialized fittings thatare used to close an open pipe end.

Straight Lateral pipe fittings have three outlets as shown in Figure 6-14, two of which have thesame axis and a third on the side joined at a 45 degree angle from the main axis for the purpose

of connecting a branch line.

As shown in Figure 6-15, Reducing Lateral fittingsare similar to straight laterals except that thebranch connection is smaller in size.

Weldolets similar to that shown in Figure 6-16 areintegral reinforcement fittings used for branchconnection strength.

As shown in Figure 6-17, Weld Saddle fittings areused to reinforce intersecting welded joints. They

are not intended for use as a pressure retaining fittings.

FIGURE 6-11 - CONCENTRIC REDUCER FIGURE 6-12 - ECCENTRIC REDUCER

FIGURE 6-13 - PIPE CAP

FIGURE 6-14 - STRAIGHT LATERAL PIPE FITTINGS

FIGURE 6-15 - REDUCING LATERALPIPE FITTING



Threaded and Socket Weld Pipe Fittings

Full Couplings as shown in Figure 6-18 areused to join a pipe segment to another pipeor pipe fitting.

Screwed Unions like the detail shown inFigure 6-19 is basically a screwed joint thatcan be disassembled within a completedsystem for subsequent maintenance.Unions are normally furnished with steel tosteel and stainless steel seats. It ispreferred that unions be installed so thatflow enters the end with the union ring or nut.

Another precaution is that when the craft arewelding a socket weld union that care must betaken to not let arcing occur across the faces.This is caused by not having the union tight whenwelding and will usually cause the fitting to leakduring hydrostatic testing. A union may also havea restriction orifice or dielectric washer or gasketinstalled between the seating.

Reducing unions similar to the detail shown inFigure 6-20 provide a pipe line size reduction andare also sometimes referred to as a reducers orcouplings.

FIGURE 6-16 - WELDOLET DETAIL FIGURE 6-17 - WELD SADDLE DETAIL

FIGURE 6-18 - FULL COUPLING JOINT

FIGURE 6-19 - SCREWED UNION DETAIL

FIGURE 6-20 - REDUCING UNION



A Swage Nipple is a reducing fitting used tojoin piping of different sizes. Care must betaken in matching the correct pipe schedulesand end styles when ordering. Swages areavailable in both concentric and eccentrictypes. A concentric swage nipple detail isshown in Figure 6-21.

Reducing Inserts as shown in Figure 6-22 areused for insertion into a larger fitting to connecta smaller pipe. Reducing inserts for small borepiping are available in a multitude of sizecombinations, so that reduction can be madefrom any nominal size pipe to any other smallernominal size.

The inserts are available in three styles,depending on the amount of reduction, and in3000 and 6000 psi ratings. Inserts are alsoavailable for reducing from a nominal pipe size toa tubing size. These inserts are used forinstrumentation connections. Reducing inserts forchanging from socket welded fittings to threadedpipe can be obtained by special order.

Pipe Nipples are available in various materials, or can be made in the field to a required length.As shown in Figure 6-23, Stock nipples are available as fully threaded close nipples, or in variouslengths with both ends threaded (TBE). They also can be supplied with either a plain end or buttweld end.

Bushings similar to the detail shown in Figure 6-24 areused to join a smaller size pipe to a larger fitting orvalve. Bushings are available with hexagon head(wrenching flats) or a flush head (face bushing). Theyare available in a full range of reductions, so that asingle bushing may be used to reduce from any size toone of a smaller size. Some clients will not allow theuse of this type fitting.

FIGURE 6-21 - CONCENTRIC SWAGE NIPPLE

FIGURE 6-22 - REDUCING INSERT

FIGURE 6-23 - PIPE NIPPLES

FIGURE 6-24 - BUSHING DETAIL



As shown in Figure 6-25, 90-Degree StreetElbows is a standard 90 degree fitting withone end having a integral nipple. Streetelbows are used to combine a directionalchange with a fitting to fitting screwed jointmake-up.

Half-Couplings similar to the detail shown inFigure 6-26 are used to join a smaller branchto a butt weld main run. Half-couplings mustbe shaped to fit the pipe and beveled forwelding. They are generally ordered pre-beveled if they are to be field welded.

Half-couplings are allowed only in 2-inch andsmaller sizes and only where the branch does notexceed one-fourth of the nominal main branchpipe size. Thus a 2-inch half coupling can go ona 8-inch and larger pipe only.

Pipe cap and bar plug closures similar to thedetails shown in Figure 6-27 are used for closingopen pipe ends.

Pipe Flanges

Flanges are manufactured in a variety of shapes, sizes, and materials. Shape variations arerequired to match the different methods of pipe attachments and different types of seals.

Attachment methods include:

• Threading

• Socket welding

• Butt welding

• Lapped joints

Seal variations are required for different flange facing styles. Raised face flanges are thestandard. Others facing styles include flat, ring joint, small tongue and groove, large tongue andgroove, and seal welded. The facing style as well as the type of gasket and service conditions

FIGURE 6-25 - 90 DEGREE STREET ELBOWDETAIL

FIGURE 6-26 - HALF COUPLING DETAIL

Figure 6-27 - PIPE CAP AND BAR PLUG DETAILS



affect the requirements for flange surface finish. The service conditions include pressure,temperature, corrosive, and fluid state.

A serrated flange surface finish is the most common and uses a soft gasket. The serrations arein the form of concentric rings, but spiral serrations (somewhat like a phonograph record) are alsocommon. A smooth finish is used for harder gaskets and on ring joints, tongue and groove, andmost high pressure services.

Flanges are divided by classes, which isnormally rated by working pressure inpounds per square inch (psi). They areavailable in a variety of primary pressureratings (classes), ranging from 25 psi to2500 psi. Pressure ratings are affectedby the strength of the material, theservice temperature, and size of theflange. Pressure ratings are explained inmore detail in the piping class section.Flange hubs have a larger outsidedimension for larger size pressure ratingsand may also have additional bolting toservice the increase in pressure. Table6-1 lists the outside diameter of a 4 inchflange for various pressure ratings.

Each type of flange is available with any one of several different styles of facing. One style offacing may be more commonly used for a particular type of flange, however. Facings can be aflat face with a large full face contact gasket, a ring joint style used with ring gasket having a smallcontact surface area, and patented facings that use a metal to metal seal without a gasket.

Selection of the proper flange facing depends on a combination of many factors which includeflange material, gasket material, bolt strength, operating pressure and temperature, and fluidproperties contained. A facing having a large contact area and a serrated finish might be usedwith a thick, relatively soft rubber gasket if the piping is for cold water flowing at low pressures.Such a facing is not practical for use with a hard gasket like a metallic type, because excessivebolt loads would be required to obtain an effective seal. Where a hard gasket is required, afacing having both a small and smooth contact area would be needed, thus reducing the bolt loadrequired for sealing and likewise lowering flange stress. The following descriptions cover themore common styles of facings available.

Flat Face Facings are commonly used for mating with 125 pound cast iron flanges on equipment,valves, or fittings. They are used in conjunction with a full face gasket which minimizes the strainon the flanges and thus reduces the chances of cracking the more brittle non-steel flange.

Raised Face Facing is the most common facing on steel flanges. A facing height of 0.06 inch(about 1/16 inch) is customary for 150 and 300 pound flanges. A facing height of 0.25 inch iscommon on 400 pound and higher classes of flanges. The raised face dimension on the 150 and300 pound class is included in the minimum flange thickness. On the other classes, the raisedface must be added to the flange thickness.

TABLE 6-1 - 4 INCH FLANGE OUTSIDEDIAMETERS FOR VARIOUS PRESSURE

RATINGS

Pressure Rating Outside Diameter

150 psi 9 inches

300 psi 10 inches

600 psi 10 3/4 inches





Tongue and Groove Facing has a gasket that is confined within the groove. The gasket contactsurface is considerably smaller than the total face area thus reducing the bolt load for effectivesealing. Confinement of the gasket within the groove prevents blowout and precludes extensionof the gasket into the bore area. Another advantage is that gasket erosion is virtually eliminatedby the minimal contact between the gasket and line fluid. The groove face is almost alwaysinstalled on the valve or equipment. An installation preference of the tongue flange on thedownstream side, but this does not affect the seal and is thus not required. When ordering youmust specify whether the tongue or groove face is required.

Ring Joint Facing uses a solid metal ring gasket, so the sealing surface on the flanges must beaccurately machined to a very smooth finish. The ring gasket must likewise be accuratelymachined from solid metal. This style of facing is the most expensive, but it is the most effectivefor high operating pressure and temperatures.

The narrow gasket contact surface and very smooth finish enable a tight seal with relatively lowbolt loads. The ring gasket is octagonal or oval shape so that the seal is made tighter by theincreasing sealing force that results from the internal pressure of the line fluid. Gasketdeterioration is prevented by selection of a material that is compatible with the fluid. Therecessed sealing surfaces are inherently protected from mechanical damage during handling andstorage, but it is essential that the finish be protected from corrosion if the flanges are not madeof a corrosion resistant material.

Seal Welding Facings are sometimes used on systems encountering severe service conditions.The two common styles are Sarlun and Sargol. The sealing surfaces are accurately machined toa very smooth finish and are joined without a gasket. This metal to metal seal is adequate forsome applications, but a seal weld is sometimes necessary. The design incorporates a lip tofacilitate the making of the seal weld.

Flange Styles

Weld Neck Flanges like the sample shown in Figure 6-28 are the most common type of flangeused and preferred for the majority of service conditions. The long tapered hub and gentletransition provides reinforcement of the flange. This increases the strength of the fitting anddistributes stresses so that this style flange can withstand extreme temperature, shear, impact,bending, and vibratory loading. The flanges can be bored to match any special ID requirementsand should be ordered to match the piping being used.

FIGURE 6-28 - WELD NECK FLANGE FIGURE 6-29 - SOCKET WELD FLANGE



As shown in Figure 6-29, Socket Weld Flanges are counterbored to accept the end of the pipe.The flange is attached to the pipe by an external fillet weld and has the same inherentweaknesses as the slip-on flange. Socket weld flanges are most commonly used on two inch andsmaller piping. The socket size must be specified to match the corresponding outside diameter orschedule of the pipe.

Slip-on Flange shown in Figure 6-30 is sometimes preferred because of its lower installation costand because it can accommodate slight misalignment. The calculated strength of the slip-onflange under internal pressure is approximately two-thirds that of the weld neck style flanges, andits life under fatigue is about one-third that of the weld neck. For these reasons, the slip-onflange is limited in its use. ANSI B31.1 code for power piping restricts the use of slip-on flangesto the 300 lb rating for sizes exceeding 4 inch diameter.

The Threaded Flange shown in Figure 6-31 is attached by screwing the flange onto the threadedend of the pipe. As with other threaded fittings, its use is restricted to systems having relativelylow operating temperatures and pressures. Cyclic thermal or bending stresses may causeleakage through the threads after a few cycles. Sealing with an external fillet weld may berequired for some applications.

The Lap Joint Flange shown in Figure 6-32 ischiefly used in piping systems that will befrequently dismantled. The flange is free torevolve on the pipe thus avoiding the problem ofaccurate alignments. Its pressure holdingcapability is the same as slip-on flanges, butfatigue is only a tenth that of weld necks. Theuse of this type of flange should be avoided inhigh bending locations.

Orifice Flanges are used for instrumentationconnections and typically are used inconjunction with an orifice plate and flowmeterto measure or indicate flow. The flanges havefour small holes drilled through to the processfluid. These holes are tapped for connectinginstrument lines, and are plugged when not

FIGURE 6-30 - SLIP-ON FLANGE FIGURE 6-31 - THREADED FLANGE

FIGURE 6-32 - LAP JOINT FLANGE



used. The orifice plate has a hole that is smaller than the bore of the pipe. This smaller sizecreates a flow restriction and a pressure drop occurs on the downstream side of the plate. Thedifferential pressure drop is measured through the mating flanges which is used for theinstrument readout. The flanges are furnished in pairs and usually have integral jacking bolts topermit spreading the flanges to remove the orifice plate.

Orifice flanges are not required for uninstrumented restriction plates used for flow restriction.Nevertheless, they are sometimes used, even though not required for instrumentation, becausethe jack bolts permit easy removal of the restriction plate. Orifice flanges are available in 300pound and higher pipe classes. They are made as threaded, slip-on, and weld neck flange types.The weld neck type is preferred because the other methods require that the pipe be drilled thoughthe pipe wall after the flanges are attached. The orifice tap locations and orientations arecovered under a separate section.

Insulating Flanges can be any one of the basicstyles. A typical insulating flange detail isshown in Figure 6-33. Sometimes the insulatedjoint is made with two different types of flanges,such as where a threaded cast iron flange froman underground line is mated to a weld neckcarbon steel flange of an exposed line. In thiscase, an insulated joint is used to preventelectrolysis. Another example is wheredissimilar metals are joined together. A copperor bronze flange has electromotive force (EMF)that differ from the EMF of a steel flange. Theflanges are insulated from each other by adielectric gasket and bolting. These gaskets,sleeves, and washers are available as kitsspecified by flange type, size, and pressurerating. Micarta is a strong, tough, and durablebrand of plastic material that is often used asthe dielectric insulator. It is important that longerbolts are ordered since they do not usually come with the kits.

Blind Flanges are used to blank off the open ends of flanged piping, valves, and equipment.

FLANGE BOLTING

Flanges have equally spaced bolts in multiples of four, so that valves or fittings can be positionedto face in any quadrant. Identification symbols are used for flange bolting. The symbol is on thetop of the head of machine bolts or on one end of a stud bolt. All bolting must be long enough toensure that the bolt will have one or two full threads showing beyond the nut when the joint iscomplete.

Both excessive or inadequate initial bolt stress can cause leakage at the joint. Accurateprestressing of the connection is required for proper operation. Prestressing methods include:

• Tightening by hand wrench

• Tightening by calibrated power torque wrench

FIGURE 6-33 - INSULATING FLANGE DETAIL



• Hydraulic tensioning

• Bolt or stud elongation measurement correlation to stress

Bolts or studs that are 1 3/4 inch or larger should be prestressed by either direct hydraulictensioning or by elongation measurement.

Before prestressing, all bolts should be thoroughly coated with an antiseize compound to allowremoval. Bolting sequencing is not performed in a clockwise rotation, but across the face toproperly draw the flanges together. Also stress on the bolting should be increased in a stepmanner to bring the bolts up equally to prevent from rolling the gasket. Both of these two actionshelp in stopping poor gasket setting, which can cause leakage.

To assemble bolted flange connections:

• Thoroughly clean the flange faces prior to fitup

• Rig the flanges into position with the bolt holes aligned and check the flange faces forparallelism using a dial indicator or other means

• Provide a coating of an antiseize compound on the flange bolts and install the gaskets, bolts,and nuts

• Tighten flange bolts in the following incremental steps using a sequence pattern shown inAttachment 6-1

Step 1: 25% of minimum required stress or torque



NOTE: Minimum required stress or torque values to be determined from project technicalspecifications

• If leakage occurs during hydrostatic testing, relieve the test pressure on the system, tightenthe flange bolts in the following incremental steps using a sequence pattern shown inAttachment 6-1, and repressurize the system


• If leakage continues, proceed to next step


NOTE: Acceptability of tightening flange bolts to 200% of minimum required stress or torqueto be confirmed using project technical specifications

• If leakage persists after additional tightening, check for the following after the completion ofthe hydrostatic testing:

4 Flange alignment

4 Flange surface defects or dirt

4 Flange bolt thread failure

• Reassemble the joint using a new gasket and recheck the flange for leakage

NOTE: Depending on code and project criteria, zero flange leakage may or may not be acriteria for acceptance of the hydrostatic test



The Flanged Connection Data Sheet shown in Attachment 6-2 provides a method of recordingflange assembly work. Attachment 6-3 provides a table of bolt and stud torque values andAttachment 6-4 provides a summary of the technical data to convert bolt or stud elongation toinduced stress.

GASKETS

The function of a gasket is to provide a seal between flange sets. Gaskets are normally rated tomatch the flanges being used. It would be possible to list hundreds of different gaskets if all thevarious materials, compositions, constructions, and shapes were considered. Service conditionssuch as pressure, temperature, and corrosiveness of the fluid must be considered when thegasket is selected. The primary materials are rubber, asbestos or fiber, and several types ofmetal. The common thickness of gaskets are approximately 1/8 inch. Flat or full face gasketsprovide sealing on low pressure systems with low to moderate temperatures.

Spiral wound gaskets provide better temperature and pressure resistance than flat face gaskets.They are normally color coded by the manufacture to allow for inspection after the joint iscompleted by the craft. This coding identifies both the windings and filler material. Thesestandards are titled "Color Coding of Gaskets" published by the Fluid Sealing Association. Agood installation practice is to have the flange faces coated with a graphite lubricant (i.e. never-Seize) to allow the gasket to be removed without having to spend extra time cleaning the flangeface surfaces.

FLEX JOINTS

When the temperature of a pipe system is changed, there is a corresponding change in bothlength and diameter. The amount of this expansion or contraction is directly proportional to thedimension of the pipe and change in temperature.

There are four methods to handle expansion:

• Inherent flexibility in the pipe through fittings, changes in direction, and loops

• Packless expansion joints

• Slip joints

AXIAL MOVEMENT LATERAL OFFSET ANGULAR ROTATION

FIGURE 6-34 - TYPES OF EXPANSION JOINT MOVEMENTS



• Swivel joints

As shown in Figure 6-34, expansion joints give a system flexibility by permitting motion betweenpipe sections or equipment.

Bellows type expansion joints are used for low and intermediate pressures. They have sectionsmade of a ductile material such as rubber, copper, or stainless steel, that permit repeated flexingwithout fatigue failure. Both axial and angular movement is allowable. Three types of bellowstype expansion joints are shown in Figure 6-35.

For higher service pressures, the bellows can be reinforced with special bands to limit radialexpansion.

Sleeve or slip joints as shown in Figure 6-37 are used on plain end piping, and provided axialmovement from 2 to 12 inches and little angular misalignment. They also can be used to connectdifferent size piping. The principal disadvantage of a slip joint is that it depends on packing forfluid tightness. The use for swivel joints are primarily in low pressure steam and water systems.A sample expansion joint is shown in Figure 6-36.

Mechanical Couplings also can also fall into this category of connection. They are available inseveral different material grades for different services and can be used to join different types of

NON-EQUALIZING SELF-EQUALIZING HYPTOR

FIGURE 6-35 - TYPES OF BELLOWS TYPE EXPANSION JOINTS

FIGURE 6-36 - EXPANSION JOINT WITH REMOVABLE SPACERS



material not normally connected, such as PVC to carbon steel. They also will allow smallmisalignments both axially and transversely in the connection.

Installation and Handling Guidelines

The following guidelines apply to the handling and installation of expansion joints:

• The joints should be moved to the installation site in the original shipping containers or onshipping pallets.

• The joints should never be rolled or dragged into place.

• The joints should not be lifted with a chain, rope, or sling which bears on the corrugations,sliding sleeve (for slip-type) tie rods, limit rods, shipping bars, or lubrication or packing fittings.

• If lifting will deflect an expansion joint, lifting beams or strong backs should be used.

• Remove end caps, remove desiccant, and inspect for cleanness just prior to installation.

• Piping installation should be substantially complete prior to installing the expansion joint andshould be properly aligned with hangers, anchors, and guides installed.

• Do not distort the expansion joint to compensate for piping misalignment.

• Determine if the expansion joint must be precompressed prior to installation. This is normallyrequired when the installation temperature varies substantially from the system operatingtemperature.

• Ensure bellows type expansion joints are properly oriented for flow through the joint.

• Check the interior and exterior of the expansion joint for objects that have become lodgedbetween the corrugations or in the slip joint that could affect the operation of the joint.

FIGURE 6-37 - SLIP TYPE EXPANSION JOINT



• Check the bellows, lining, end connections, and shipping braces for nicks, cuts, or dents.

• Make sure purge and drain connections and/or lubrication or packing fittings will be accessibleafter installation.

• Prior to welding, protect the expansion joint from arc strikes or weld splatter with flameretardant blankets or sheet metal.

• Prior to hydrotesting, verify that:4 Shipping rods, braces, and spacers are removed4 Protective paper cover on the sliding sleeve joints is removed4 Piping system temporary hydrostatic test and permanent anchors, guides, and supports

are installed

• The expansion joint is capable of withstanding the hydrostatic test pressure

• Insulation should not be installed in direct contact with the bellows corrugations or in thevicinity of the sliding joint.

• After installation, provide a protective cover over the expansion joint to protect it from damage.

PIPE BENDING

Bending of Ferrous Pipe and Tubing of small diameters (under 2 1/2 inch OD) of standard andrelatively light wall thicknesses is usually bent cold. Larger diameter and heavier wall pipe isgenerally bent hot. Where the quantity of identical bends is substantial and the heavy bendingequipment is available, cold bending may be more economical than hot bending. The bendingradius, the number of identical bends required, and the chemical composition and metallurgicalproperties of the pipe material are the deciding factors.

Industry experience has demonstrated the practicability of using a piping bending radius of fivepipe diameters to keep expensive friction losses, erosion, and turbulence to a minimum. Fortubing, many different bending radii are used in accordance with the requirements of the design.

Cold Bending

Cold Bending is done extensively with pipe in nominal diameters up to 2 1/2 inch OD and withtube in diameters up to 4 inch OD, little use is made of cold bent piping in larger diameters.

In a ram-type bender two pressure dies are mounted in a fixed position on the frame of themachine. Their mounting pins, however, are free to rotate. The bending form is attached directlyto the piston rod of the hydraulic cylinder. Although normally the pipe is bent to the radius of thebending form, bending to larger radii is possible by limiting the advancement of the ram.

As the cold working of the bending operation becomes more severe, the inside of the pipe mustbe supported with mandrels.

Hot Bending

Hot Bending is extensively used for making individual bends in piping of sizes 2 1/2 inches andlarger. Prior to hot bending, the pipe is generally sand filled. This facilitates more uniformbending and minimizes excessive thinning and ovality. The sand also helps to maintain the pipe



at the hot-bending temperatures and thus provides longer bending cycles within a limitingtemperature range.

The pipe is normally heated in specially designed furnaces. The furnace directs the gas flames ina circular path along the furnace wall. This avoids direct impingement of the flames on the pipesurface, which minimizes hot spots, excessive oxidation, and scaling. Temperatures for heatingprior to hot bending of ferrous piping materials normally range from 1900 °F to 2050 °F. When ithas reached the bending temperature, the pipe is placed on bending tables where it is bent to thespecified radius. On ferrous materials, hot bending is generally not done below 1600 °F.Sometimes, several heating and bending cycles may be required.

After the pipe is bent and cooled, the sand is removed from the inside of the piping. In carbonand low-alloy steel, the excessive scale on the pipe inside is removed by turbining, blasting, orother cleaning methods.

Where sand filling is not done, it may be advantageous, in the case of ferrous and somenonferrous materials, to fill the pipe inside with argon or nitrogen gas. This will minimize scalingand eliminate subsequent cleaning operations. The change in wall thickness of hot bends usuallyis slightly greater and more nonuniform than in cold pipe bends. For hot-bent piping, a five-diameter radius is most widely used. However, hot bends can be made to smaller radii.



TYPICAL FLANGED BOLTING SEQUENCESATTACHMENT 6-1

4 BOLT FLANGED CONNECTION 8 BOLT FLANGED CONNECTION

12 BOLT FLANGED CONNECTION 16 BOLT FLANGED CONNECTION



TYPICAL FLANGED BOLTING SEQUENCESATTACHMENT 6-1

20 BOLT FLANGED CONNECTION

24 BOLT FLANGED CONNECTION



ATTACHMENT 6-2

FLANGED CONNECTION DATA SHEET

NUMBER.: PROJECT NO.: PAGE 1 OF

PROJECT NAME:

FLANGE TYPE: FLANGE RATING:

PIPING CODE:

BOLT/STUD MATERIAL GRADE/SPECIFICATION:

NUMBER OF BOLTS OR STUDS REQUIRED:

NUT MATERIAL GRADE/SPECIFICATION:

GASKET TYPE:

CLEANING SOLUTION:

METHOD OF FLANGE TIGHTENING: TORQUE BOLT ELONGATION

MINIMUM REQUIRED TORQUE OR BOLT STRESS:

TIGHTENING SEQUENCE TORQUE OR BOLT ELONGATION STEPS:

SEQUENCE STEP 1 (25% OF MINIMUM): SEQUENCE STEP 2 (50% OF MINIMUM): SEQUENCE STEP 3 (100% OF

MINIMUM):

VERIFICATION CHECKS: YES NO N/A

FLANGE FACES CLEAN

FLANGE FACES ALIGNED

CORRECT GASKET INSTALLED

CORRECT BOLT/NUT SIZE

CORRECT BOLT/NUT MATERIAL

CORRECT TIGHTENING SEQUENCE

FINAL TORQUE/BOLT ELONGATION:

M&TE USED:

DESCRIPTION CALIBRATION DUE DATE DESCRIPTION CALIBRATION DUE DATE DESCRIPTION CALIBRATION DUE DATE

REMARKS:

FIELD ENGINEER: DATE:



FORM T_FLANGE.DOT 1996:REV.0



INDUCED BOLT STRESSATTACHMENT 6-3

BOLTDIAMETER

THREADSPER INCH

ROOT AREA(SQ. IN.)

ROOT TO SHANKRATIO (A1/A2)

1/2" 13 0.1257 0.6415/8" 11 0.2018 0.6583/4" 10 0.302 0.6837/8" 9 0.419 0.6971" 8 0.551 0.702

1 1/8" 8 0.728 0.7321 1/4" 8 0.929 0.7571 3/8" 8 1.155 0.7781 1/2" 8 1.405 0.7951 5/8" 8 1.680 0.8101 3/4" 8 1.980 0.8231 7/8" 8 2.304 0.834

2" 8 2.652 0.8442 1/4" 8 3.423 0.8612 1/2" 8 4.292 0.8742 3/4" 8 5.259 0.885

3" 8 6.324 0.8953 1/4" 8 7.487 0.9023 1/2" 8 8.749 0.9093 3/4" 8 10.109 0.915

4" 8 11.567 0.921

NOTE: BOLT DATA SHOWN ABOVE BASED ON:

1/2" TO 1": COARSE THREAD, SERIES UNC AND NC

1 1/8" TO 4": 8 THREAD SCREWS, SERIES 8N



INDUCED BOLT STRESSATTACHMENT 6-3

30,000 PSI 45,000 PSI 60,000 PSIBOLT

DIAMETER(IN)

TENSIONLOAD(LB)

APPROX.TORQUE(LB-FT)

TENSIONLOAD(LB)


TENSIONLOAD(LB)


1/2" 4257 30 6386 45 8514 605/8" 5780 60 10170 90 13560 1203/4" 9060 100 13590 150 18120 2007/8" 12570 160 18855 240 25140 3201" 16530 245 24795 368 33060 490

1 1/8" 21840 355 32760 533 43680 7101 1/4" 21870 500 41805 750 55740 10001 3/8" 34650 680 51975 1020 69300 13601 1/2" 42150 800 63225 1200 84300 16001 5/8" 50400 1100 75600 1650 100800 22001 3/4" 59400 1500(*) 89100 2250(*) 118800 3000(*)1 7/8" 69120 2000(*) 103680 3000(*) 138240 4000(*)

2" 79560 2200(*) 119340 3300(*) 159120 4400(*)2 1/4" 102690 3150(*) 154035 4770(*) 205380 6360(*)2 1/2" 123760 4400(*) 193140 6600(*) 257520 8800(*)2 3/4" 157770 5920(*) 236655 8880(*) 315540 11840(*)

3" 189720 7720(*) 284580 11580(*) 379440 15440(*)3 1/4" 224610 - 336915 - 449220 -3 1/2" 262470 - 393705 - 524940 -3 3/4" 303270 - 454905 - 606540 -

4" 347010 - 520515 - 694020 -

NOTES:1. TORQUE VALUES SHOWN AS (*) FOR INFORMATION ONLY; USE DIRECT TENSION

OR BOLT ELONGATION ON THESE SIZES2. UNIT ELONGATIONS FOR INDUCED BOLT STRESSES:

a. 30,000 PSI: 0.0010 IN/INb. 45,000 PSI: 0.0015 IN/INc. 60,000 PSI: 0.0020 IN/IN

3. THIS TABLE NOT TO BE USED WHERE INDUCED BOLT STRESS WILL APPROACH OREXCEED YIELD STRESS ON THE BOLT MATERIAL. SPECIFICALLY, DO NOT USE THISTABLE FOR ASTM A307 MACHINE BOLTS OR ANY STAINLESS STEEL BOLTINGEXCEPT FOR SA-564, GR. 630 (17-4PH).

4. UNIT ELONGATIONS BASED ON A MODULUS OF ELASTICITY OF 30,000,000 PSI



ELONGATION METHOD BOLT AND STUD TENSIONINGATTACHMENT 6-4

Elongation-Stress CorrelationThe correlation of bolt or stud induced stress to total bolt elongation can be defined by thefollowing linear equation:

S = E * e/LWhere: S = Induced Stress at the Thread Root Area (psi)E = Modulus of Elasticity (30,000,000 psi)e = Bolt or Stud Elongation (inches)L = Effective Bolt or Stud Length (inches)

The effective bolt or stud length is determined as shown below:

Bolt or stud elongations during the tensioning process should be measured with a calibrated dialindicator or other comparable instruments, accurate to with 0.001 inches. Measured elongationsmust be with 10% of the calculated value to ensure accurate tensioning.

For fully threaded bolts or studs, the required elongation to achieve a given stress can becomputed as:

e = L * SE

For a given induced stress level, a unit elongation, (e/L in units of inches/inch), can therefore becalculated as:

eL

= SE

Values of unit elongation for three different induced stress levels are shown in Attachment 6-3.When a bolt or stud is not fully threaded, the required elongation to achieve a certain inducedstress level can be determined as follows:

eTOTAL = (S/E) * {l1 + (A1/A2) * l2}



Where: eTOTAL = Total Bolt Elongation (inches)S = Stress to be Induced in Area A1 (psi)E = Modulus of Elasticity (30,000,000 psi)l1 = Length of Engaged Bolt Thread (inches)l2 = Length of Bolt Shank (inches)A1/A2 = Ratio of Root Area to Shank Area (dimensionless)

The following figure illustrates the these definitions:

Example: For a 1 inch diameter bolt

Required Induced Stress, S = 45,000 psi

Modulus of Elasticity = 30,000,000 psi

A1/A2 = 0.702 (See Attachment 6-3)

l1 = 2 inches

l2 = 4 inches

eTOTAL =45,000 psi

30,000,000 psi* {2" + (0.702) * (4")}

eTOTAL = 0.00721 inches

NOTE: If an allowance for the unthreaded portion of the bolt shank had not been made in theabove calculation, the required bolt elongation would have been determined to be 0.009 inchesresulting in an induced stress of 56,156 psi which is 25% higher than intended.


Section 7

Valves

GENERAL

In industrial piping, the control of flow is very important. Mechanical devices used for flow controlare called valves. The principal functions of valves are:

• Starting and Stopping Flow

• Regulating or Throttling Flow

• Preventing Back Flow

• Regulating Pressure

• Relieving Pressure

Steel valves are classified by nominal pipe size (NPS) and by pressure-temperature serviceratings. There are two service ratings; a Primary Rating and a Cold Working Pressure Rating:

• The Primary Rating is a pressure rating established by standards and accepted practice at anelevated temperature.

• The Cold Working Pressure Rating is the rating at ambient temperature (minus 20°F to100°F). This rating is referred to as the CWP (Cold Working Pressure) Rating. This rating is ofmost interest when determining hydrostatic testing limits.

The Primary Rating is expressed in terms of steam. Steam ratings are used as a basis fordetermining the suitability of a material for a given application. The Cold Working PressureRating is usually designated by the mark WOG, which stands for Cold Water, Oil or Gas,non-shock.

Cast and forged steel valves bear amark such as 150, 300, 600, etc. These figures denote the maximumpressure in pounds per square inch(psi) at a certain temperature (usually800 °F) for which an item is suited. Acertain 600-pound valve may besuited for 600-pound pressure attemperatures up to 850 °F. But if thetemperature exceeds that point, sayup to 1000 °F, the valve is notrecommended for pressures over170 pounds.

As tabulated in Table 7-1, all ratingsare the maximum allowable non-shock pressure (psig) at the tabulated temperature (°F). Thepressure-temperature tables should be consulted to select the pressure class of product requiredto meet the conditions of the intended service.

TABLE 7-1 - HYDROSTATIC TEST PRESSURES AT100°°F OR LESS

PressureClass

Maximum AllowablePressure

150 425 psi

300 1100 psi

600 2175 psi

900 3250 psi

1500 5400 psi

2500 Contact Vendor

Section 7 Valves


VALVE MATERIALS

Valve Body and Bonnet

Valve bodies and bonnets are made of brass or bronze mainly in the smaller sizes and formoderate pressures and temperatures. Cast iron is used in all sizes up to working steampressures of 250 pounds, temperatures of 450 °F, and hydraulic pressures of 800 pounds. Caststeels are used for more severe service. For high temperature service, valve bodies of thechromium-molybdenum alloy steels are available. Forged steel is used in small valve bodieswhich are machined and drilled out. This is not a practical method in larger sizes, although valvesup to 8 inches have been made from solid stock. For the more corrosive services, valves made ofAISI Type 304 and Type 316 stainless steels are available as standard sizes.

Castable materials used for valve bodies and bonnets include:

• Cast Carbon Steel (ASTM A216, Grade WCB)

• Cast Chrome-Moly Steel (ASTM A217, Grade C5 and Grade WC9)

• Cast Type 304 Stainless Steel (ASTM A351, Grade CF8)

• Cast Type 316 Stainless Steel (ASTM A351, Grade CF8M)

• Cast Iron (ASTM A126) and Cast Bronze (ASTM B61 and B62)

Forged materials include:

• Carbon Steel (ASTM A105 an A181)

• Chrome-Moly Steels (ASTM A182, Grades F5, F11 and F22)

• Stainless Steels (ASTM A182, Grades F-304, F-316 and F-347)

In some cases, valve bodies may be the same material as the pipe.

VALVE CONSTRUCTION

Valves are manufactured in standard sizes ranging from 1/2 inch through 36 inch nominal pipesize. Valves may be as simple as a small plug valve (cock) having only four parts, or as complexas a motor-operated control valve having hundreds of parts. The valves most frequentlyencountered will have several parts that are functionally comparable and bear the same or similarnames.

Body

The valve body connects to the system piping, houses the internal valve parts, and provides apressure boundary as well as the passage for fluid flow. Bodies are made from a great variety ofmetals and alloys. Thus, a body material can be selected on the basis of compatibility withsystem piping and suitability for service conditions.

Most valves for ordinary uses have bodies made from appropriate grades of iron, steel or bronzecastings. Cast bodies are prone to have material flaws that may elude detection by all surfacetype nondestructive examinations and their detection is only possible through use of volumetricmethods such as ultrasonic or radiographic examination. Forgings contain fewer defects and are

Valves Section 7


therefore generally used for the bodies of valves in critical service piping. Some very large valvebodies are made from two or more forgings that are machined and welded together, then runthrough a final machining process to true up interfacing surfaces. For critical services, aradiographic examination is then performed.

Trim Materials

The removable internal metal parts that contact the line fluid are collectively known as the valvetrim. This includes parts such as the seat ring, disc or plug, glands, spacers, guides, bushings,and internal springs. Parts not considered trim include the body, bonnet, packing, yoke, andsimilar items. Valve trim parts are frequently made of materials that are compatible with but notthe same as the body material. Likewise, trim parts of different materials are often used withinthe same valve assembly. Discs or plugs, and seat rings are pressure-retaining parts and need toconform to specification requirements.

Disc

Most valves have a disc or plug that stops flow through the valve when pressed against astationary seat, or seats, in the body (closed) position. In the open position, the disc is movedaway from the seat to allow fluid flow. The plug or ball performs the same functions in plugvalves and ball valves. Many different styles of discs are used. Some bear little resemblance tothe flat, circular shape for which they were originally named, but the name is almost universallyrecognized for this valve part.

Seat

Valves may be provided with integral seats or replaceable seat rings, depending on the valvesize. Small valves generally have screwed-in or welded-in seat rings, while larger valves haveseating surfaces made up of a hardened treatment of the base body metal. Fluid flow through thevalve is shut off by the seal formed between the disc and the seat.

The valve leakage rate is a function of the effectiveness of this seal.

Industry Standards

Valve body thickness and other design data are given in applicable valve standards. Standardsfor metallic valves and their components have been established by ASTM and are mostlyincorporated in ANSI, while the American Petroleum Institute (API) has developed various valvespecifications for its industry. In addition, other standards of beneficial interest to the valve userare available, particularly those published by the Manufacturers' Standardization Society of theValve and Fittings Industry (MSS).

Some of the commonly used standards follow:

ANSI B2.0 - Pipe threads

ANSI B16.1 - Cast iron pipe flanges and flanged fittings

ANSI B16.5 - Steel pipe flanges, flanged valves and fittings

ANSI B16.10 - Face-to-face and end-to-end dimensions of ferrous valves

ANSI B16.20 - Ring-joint gaskets and grooves for steel pipe flanges

Section 7 Valves


ANSI B16.21 - Nonmetallic gaskets for pipe flanges

ANSI B16.34 - Steel valves, flanged, and butt welding ends

ANSI/ASTM A181 - Forged or rolled-steel pipe flanges, forged fittings, and valves and parts forgeneral service

ANSI/ASTM A182 - Forged or rolled alloy steel pipe flanges, forged fittings, and valves and partsfor high temperature service

MSS SP-25 - Standard marking system for valves, fitting, and flanges

NISS SP-45 - Bypass and drain connection standard

API 593 - Ductile iron plug valves

API 594 - Wafer-type check valves

API 595 - Cast-iron gate valves

API 597 - Steel venturi gate valves

API 599 - Steel plug valves

API 600 - Steel gate valves

API 602 - Compact cast steel gate valves

API 603 - Class 150 corrosion resistant gate valves

API 604 - Ductile iron gate valves

API 606 - Compact carbon steel gate valves (extended bodies)

API 609 - Butterfly valves to 150 psig and 150 °F.

API 6D - Pipeline valves

VALVE CATEGORIES

The main valve categories, based on the different body styles include:

• Gate Valves

• Globe Valves

• Check Valves

• Plug Valves

• Ball Valves

• Butterfly Valves

• Safety Relief Valves

Besides these main categories, various other types of valves such as 3-Way, Swing, Stop Check,Diaphragm, and Pinch valves are available for special purposes. Control Valves, which may usebasic design features of any of these main valve categories but which serve special operatingfunctions, are described in later in this manual. Valves can be obtained with ends flanged,threaded for screwed connections, recessed for socket welding, or beveled for butt welding.

Valves Section 7


Gate Valves

Gate Valves have a significant feature of having less flow obstruction and lower turbulence withinthe valve creating only a small pressure drop across the valve. A typical cross section view of agate valve is shown in Figure 7-1.

The main variations of gate valvedesigns are by the type of disc orwedge. These include the solidwedge disc, double disc, flexiblewedge disc and split wedge discand vented disc. Three types ofdiscs are shown in Figure 7-2. Solidwedges are of one piececonstruction, solid web type. Theseating surfaces are precisionmachined to a mirror finish toprovide full seating contact betweenthe wedge and seats.

The double disc makes closure bydescending between two parallel ortapered seats in the valve body. Double disc with parallel faces areseated by being spread against thebody seats. A disc spreader makescontact with a stop in the bottom ofthe valve and forces the disc apart.

Flexible wedge discs are of onepiece construction but are cut outbetween the two seats in such away as to provide a small degree offlexibility. It is this "flexibility" thatmakes the disc tight on both facesover a wide range of pressures.

FIGURE 7-1 - GATE VALVE CROSS-SECTION VIEW

FIGURE 7-2 - GATE VALVE DISK TYPES

Section 7 Valves


The split wedge disc is a two piece, wedge disc that seats between matching tapered seats in thebody. The spreader device is simple, and integral with the disc halves.

Vented discs generally used in cryogenic services are a flexible wedge with a hole drilled in oneside to allow even seating pressure on a downstream wedge for positive shutoff.

Globe Valves

As shown in Figure 7-3, Globe Valves are commonly constructed with its inlet and outlet in lineand with its port opening at right angles to the inlet and outlet. This seating constructionincreases resistance to the flow and permits close regulation of fluid flow. The globe valve isused principally in throttling service to control the flow to any desired degree. Flow is in thebottom (under the seat) and out the top.

The main variations of globe valvedesign are by the type of disc. Typicaldisc types are shown in Figure 7-4. These include plug type, compositionand conventional discs.

The plug disc is cone shaped with theseat ring having a matching coneshaped center. The wide bearingsurfaces of the long, tapered plug typedisc and matching seating offers highresistance to the cutting effects of dirt,scale, and other foreign matter.

The composition disc unit consists of ametal disc holder, composition disc andretaining nut. The flat face of thecomposition disc seats like a capagainst the seat opening. The disc isnormally circular shaped, approximatelya 3/16 inch thick flat piece of material(compressed fiber or plastic). Closureis effected against a thin lip protrudingfrom and actually constituting the valveseat.

FIGURE 7-3 - GLOBE VALVE CROSS SECTION VIEW

FIGURE 7-4 - GLOBE VALVE DISC TYPES

Valves Section 7


The conventional disc is the oldest kind of globe valve. The basic design feature is a flatsurfaced though slightly tapered valve seat that is fitted with a disc of convex configuration thatused the taper in the seat for closing. This type of seating has only a narrow line of contact thatnormally assists an easy pressure tight closure.

Check Valves

Check Valves are entirely automatic in their operation and are activated internally by the flow offluid or gases which they regulate. As shown in Figure 7-5, check valves permit the flow in onlyone direction and if the flow stops or tries to reverse its direction, the check valve closesimmediately and prevents backflow. As soon as the pressure in the line is re-established, thecheck valve opens and the flow is resumed in the same direction as before.

There are three basic designs of checkvalves:

• Swing check

• Lift check

• Wafer (2 swinging flappers closed by aspring)

Swing Check Valves

In the swing check, the disc is hinged at thetop and seats against a machined seat inthe tilted bridge wall opening. As shown inFigure 7-6, the disc swings freely in an arcfrom the fully closed position to oneproviding unobstructed flow. The valve is kept open by flow, with the size of the opening varyingwith the volume of the flow.

Lift Check Valves

For lift check valves, the flow is the same as through the globe valve. Consequently, there isturbulence within the valve and some pressure drop occurs.

A general detail for a Lift Check Valve is shown in Figure 7-6. Lift check valves can be dividedinto three different types.

Horizontal-Lift Check Valve

The horizontal-lift check valve has an internal construction similar to the globe valve. The disc,which is seated on a horizontal seat, is equipped with guides above and/or below the seat and isguided in its vertical movement by integral guides in the seat bridge or valve bonnet. The disc isseated by backflow, or by gravity when there is no flow, and is free to rise and fall depending onthe pressure under it. These valves are normally only installed in the horizontal position, however,can be installed in a vertical position with upward directed flow.

FIGURE 7-5 - CHECK VALVE DETAIL

Section 7 Valves


Vertical-Lift Check Valve

The vertical-lift check valve has the same guidingprinciple as the horizontal lift check. It isequipped with a free-floating guided disc thatrests when inoperative on the seat. These valvesare of practical use only when installed in avertical piping system with an upward directedflow.

Ball Check Valve

The ball check valve is similar to the horizontal orvertical lift check valve. Instead of a guide disc, aball serves as the flow control medium. Whenoperating, the ball is constantly in motion,reducing the effect of wear on any particular areaof its sphere.

On some vertical-lift check valve designs, thedisc or ball is spring loaded for improvedperformance in vertical applications.

Plug Valves

As shown in Figure 7-7, Plug Valves are composed of a tapered or cylindrical plug fitted snuglyinto a correspondingly shaped seat in the valve body. The plug is provided with an opening inline with the flow opening in the valve body. The porthole or flow opening in the plug may beround, oblong or diamond shaped. The valve is opened by turning the plug so that the opening inthe valve body and plug are in line and is closed by turning the plug so that the plug opening is atright angles to the valve body opening. Small plug valves are usually referred to as plug cocks.

Plug valves are either lubricated or non-lubricated. For non-lubricated valves, the plug may beinserted from the top or bottom of the valve body. The use of cylindrical plugs is often preferredsince they are less likely to experience galling or freezing than conical plugs. In some designs,plastic seats are often molded into grooves of the plug to provide better seals, and bottom springsassist in operation.

The lubricated plug valve is designed with grooves in the plug which permits the lubricant to sealand lubricate the valve as well as to function as a hydraulic jacking force to lift the plug within thebody, thus permitting easy operation. The lubricant is forced into its various distribution channelsby a special lubricant gun that fits a button head fitting on top of the plug. The straightwaypassage through the port offers no opportunity for sediment or scale to collect. The valve plug,when rotated, wipes foreign matter from the plug.

FIGURE 7-6 - CHECK VALVE DESIGNS

Valves Section 7


Ball Valves

Ball Valves are used in many of theprocessing industries. As shown inFigure 7-8, a ball valve is similar to a plugvalve except the plug in a ball valve isspherical instead of being tapered orcylindrical. Like the lubricated plugvalves, these valves are quick opening. They also provide a very tight closure onviscous or hard to hold fluids. Ball valvesare non-sticking and pressure dropthrough the valve is reduced to aminimum due to the full pipe size openingin the ball.

Ball valves are made in three generalpatterns:

• Venturi port

• Full port

• Reduced port

The venturi port has a reduced diameterventuri configuration. The full port valve hasan inside diameter equal to the insidediameter of the pipe. The reduced portgenerally involves one pipe size smaller thanthe line size.

Butterfly Valves

Butterfly Valves are low pressure valves ofsimple design, which are used to control andregulate flow. They are characterized by fastoperation and low differential pressure drop. They require only a quarter turn from closedto full-open position. Butterfly valves are notintended for pressure tight services. Rubberseat butterfly valves are manufactured in awide range of sizes, from 2 inch diameter to11 feet in diameter and more. However, inindustrial applications valves are usuallyfound in ranges from 2 to 24 inches.

FIGURE 7-7 - PLUG VALVE DETAIL

FIGURE 7-8 - BALL VALVE DETAIL

Section 7 Valves


As shown in Figure 7-9, the butterfly valve consists of the valve body, shaft and butterfly disc, andsealing gland. As shown in Figure 7-10, the valve design has been diversified by introducingthree different valve bodies without variations in the interaction between seat and disc. Theflanged butterfly valve has a short valve body and is flanged at both ends. If necessary, weldingends, in lieu of flanges, can be provided. Butt welding of butterfly valves is not a standardconnecting method and is not desirable because of possible damage to the seating surfaces. The lug-wafer butterfly valve has a shortened valve body with protruding lugs whose bolt circlematches adjoining flanges.

FIGURE 7-9 - BUTTERFLY VALVE DETAIL

FIGURE 7-10 - BUTTERFLY VALVE DESIGNS

Valves Section 7


Tapped holes can be provided and cap screws can be used to fasten the lugs individually to eachflange, thus permitting the valve to be used as a dead-end valve also. The wafer butterfly valveconsists of a short body like the lug wafer but without the lugs. This valve can be inserted andcentered between two adjoining flanges. Gaskets may be molded onto the body or may have tobe inserted for a satisfactory flanged joint.

Most butterfly valve component parts are of metallic materials with stem and disc often furnishedin a higher alloy material than that of the body because of service requirements. The valve body,which is also the valve seat when the butterfly disc reaches a perpendicular position, is often linedwith rubber or plastic materials to provide a pressure tight shutoff. When the stem protrudesthrough the valve body, a gland sealing is provided to eliminate fluid loss at this point.

Safety and Relief Valves

Safety and Relief Valves are mounted directly on piping, pressure vessels, and equipment that issubject to potentially dangerous overpressure in case controls malfunction. They are set to openautomatically at a set pressure to relieve system pressure before it gets high enough to causedamage. A typical safety relief valve is shown in Figure 7-11.

Safety Valves are also known as pop safetyvalves. They are a spring loaded, quickopening, full flow valve for systems containingpressurized, compressible fluids such assteam, air, or other vapors or gases. Manufacturers set and test each safety valvein accordance with code requirements, thenseal the set pressure and overpressureadjusting devices. The set pressure isadjusted by increasing or decreasing thespring compression. Spring pressure holdsthe valve closed until the set pressure isreached, at which time the system fluidpressure forces the valve completely open. Spring pressure forces the valve disc back tothe seat when the fluid pressure drops slightlybelow the opening pressure. The differencebetween the opening (set) pressure and theclosing (resetting) pressure is calledblowdown. The blowdown can be adjusted byan adjusting ring that forms a chamber(huddling chamber) below the disc. The valveis usually equipped with a hand lever so that itcan be tested periodically. Hand levers areprohibited, however, for noxious andflammable gas applications.

FIGURE 7-11 - SAFETY RELIEF VALVE DETAIL

Section 7 Valves


Relief Valves are similar to a safety valve but open only slightly at set pressure. Instead ofimmediate full opening, they open wider if the pressure increases above the set pressure. Reliefvalves are normally used for liquids, such as water or oil, where release of a small volume willrapidly lower the pressure.

Safety Relief Valves combine the features of a relief valve and a safety valve. The valve willcrack open to slowly relieve built-up pressure or pop fully open in case of rapid pressureincreases. The valves are suitable for liquid and saturated steam service. A typical application isin hot water heating systems, where steam might be generated by uncontrolled heating. Thediameter of the piping on the downstream side of the relief valve is always larger than the pipingon the upstream side.

Depending on client requirements, all safety and relief valves are required to be tested 30-90days prior to start-up to verify valve set points.

Rupture Discs

A cruder and much less costly device than spring loaded or electrically actuated safety valves forpressure relief is the rupture disc.

A rupture disc is a pre-bulged membrane made of various metals, depending on the service forwhich it is intended. A disc may be used instead of a safety valve or installed ahead of a safetyvalve if:

• The disc has ample capacity

• The maximum pressure rating of the disc does not exceed maximum allowable pressure ofthe system being protected

• The area of the disc is at least equal to the area of an equivalent relief valve

• The disc is guaranteed to burst within plus/minus 15 percent of its specified bursting pressure.

In most cases where a safety valve is used in conjunction with a rupture disc, the rupture disc isset to relieve at 20 percent above the safety valve. The safety valve will take care of all normalover pressurization, while the rupture disc will take care of excessive pressures and will protectthe system in case of safety valve failure.

VALVE STEM VARIATIONS

The stem is the link that connects the valve operator or actuator to the sealing disc, plug, or ball. A particular motion (travel) is necessary to open and close a valve. Linear motion is needed forgate and globe valves, whereas rotary motion is needed for ball, plug, and butterfly valves. Stems should always be oriented between the horizontal and vertical position.

Types of stems for gate, globe and angle valves are shown in Figure 7-12 and are summarizedas follows:

Valves Section 7


Rising Stem with Outside Screw and Yoke (OS&Y)

In this arrangement the outermost part of the stem is threaded. The stem is smooth along thepart that is inside the valve, and is sealed (packed) so that the threads are isolated from the fluidsthat are in the line. Two styles are available; one having the handwheel fixed to the stem so thatthey rise together, and the other having a threaded sleeve that causes the stem to rise throughthe handwheel. In both styles, the position of the stem indicates the position of the valve disc.

Rising Stem with Inside Screw

This is the simplest and most commonstem arrangement for smaller size lowto moderate pressure gate, globe, andangle valves. The threaded part of thestem is inside the valve body and thestem packing is along the smooth partthat projects to the outside. Thethreads are thus in contact with theprocess fluid inside the valve. The stemand handwheel rise when the valve isopened, thus indicating the position ofthe valve disc. Only the smooth end ofthe stem is exposed to the atmosphere.

Non-rising Stem with Inside Screw

In this arrangement the stem turns, butdoes not rise when the valve is opened.Instead, the disc travels up and downthe stem threads when the stem isturned to open and close the valve. The stem threads are exposed to theline fluid; thus limiting use to fluids thatwill not corrode or erode the threads orleave deposits on them.

Sliding Stem

This stem does not turn. Instead, it is moved straight out or in to open and close the valve. Themost common application is for handlever operated quick opening valves. Other applications arein control valves that are operated by hydraulic or pneumatic cylinders.

BONNET DESIGN VARIATIONS

The joint between the body and bonnet must be pressure tight under the service conditions forwhich the valve is to be used. Bonnets are made of materials that are the same as or compatiblewith the valve body. The bonnet is a pressure retaining component of the valve; thus bonnets

FIGURE 7-12 - GATE, GLOBE, AND ANGLE VALVESTEM VARIATIONS

Section 7 Valves


must conform to code requirements. Several types of bonnets are available for various serviceconditions. The basic types that are most commonly used are:

• Threaded Bonnet

• Union Bonnet

• Bolted Bonnet

• Pressure Seal Bonnet

• Seal Welded Bonnet

The Threaded Bonnet shown in Figure 7-13is the simplest and least expensive bonnetjoint. A metal to metal seal is effectedbetween the body and bonnet. This type issuitable for many small low pressure valveapplications. It is commonly used in theseapplications where the valve will not requirefrequent dismantling.

The Union Bonnet also shown in Figure 7-13is a two piece design consisting of thebonnet and a ring that slips over the bonnet.The ring is called a bonnet ring or unionbonnet ring. It has internal threads thatmate with external threads on the valvebody. Metal to metal seals are effectedbetween the body and bonnet and the bonnet and ring.

The Bolted Bonnet type shown in Figure 7-13 uses a gasket to seal the joint between the bodyand bonnet. The bonnet has a flange that is bolted to a mating flange on the body. Variousflange facings and gasket styles are used. Some designs have the bonnet secured by studs thatare screwed into tapped holes in the valve body. Others have machine bolts or studs with a nuton each end, in which case the body flange has holes drilled through to match the holes in thebonnet flange.

In a Pressure Seal Bonnet, the bonnet gasket is placed in a recess between the bonnet and thevalve body. A retaining ring is positioned above the gasket (seal ring). The gasket is wedgeshaped, so that line pressure pushing outward against the underside of the bonnet will cause thebonnet to wedge the gasket tightly against the body wall. Thus the higher the pressure, the tighterthe seal. The sealing surface along the body wall must be accurately machined, ground, orlapped to a very smooth finish.

Seal Welded Bonnet is sometimes referred to as the breechlock design. The usual arrangementis a threaded bonnet that is screwed into the body until a metal to metal seal is formed between abonnet lip and mating body lip. The lips are then seal welded. The joint is leaktight, and willremain so as long as disassembly is not required.

FIGURE 7-13 - BONNET VARIATIONS

Valves Section 7


STUFFING BOX AND SEALS

Most stem operated valves have their stem sealed by packing that is compressed between thestem and bonnet. The area within which the packing is compressed is commonly called thestuffing box or packing box. The packing is usually compressed by tightening a packing nut orpacking gland bolts. As shown in Figure 7-14, various stuffing box arrangements are available.

Packing Nut without Gland

This arrangement includes an internally threaded packing nut that is screwed onto matchingexternal bonnet threads. The packing is compressed between the inside walls of the nut and thetop of the bonnet.

Packing Nut with Gland

In this arrangement, a gland is provided betweenthe packing nut and the packing. The glandabsorbs the packing nut torsion, thus preventingpacking gall.

Bolted Gland

A gland, gland flange, and gland bolts with nutsare used in this arrangement. The packing iscompressed by tightening the nuts on the glandbolts. The mating surfaces on the gland andflange are similar to a ball and socket joint. Thisallows the flange to swivel if the nuts are unevenlytightened on the gland bolts, thereby maintaininguniform pressure on the gland and packing.

Injection Type

In this arrangement, an injector fitting is providedon the valve bonnet. A passageway leads fromthe fitting to the stuffing box area within thebonnet. The packing is replenished by injectingplastic material through the injector fitting. Thepacking can thus be replenished while the valve isopen, closed, or being cycled. This feature isadvantageous for valve applications entailingconsiderable packing wear.

Lantern Type

The Lantern Ring is a spacer between rings of packing. During fabrication, it is relieved toprovide voids that act as cooling chambers or collect fluid that leaks past the lower packing rings. Lantern rings with an upper and lower set of packing are used in power plant valve stuffing boxeswhere stem leakage detection is desirable in high pressure, high temperature services. Theleakage is drained off through a leakoff fitting in the bonnet, thus providing for essentially zeroleakage through the upper packing rings. During system turnover, valves should be checked to

A = Packing Nut without GlandB = Packing Nut with GlandC = Bolted GlandD = Injection TypeE = Lantern Type

FIGURE 7-14 - STUFFING BOX ANDSEALS

Section 7 Valves


determine if the packing is installed since suppliers may ship valves with the packing loose (i.e.uninstalled).

VALVE TRIM

Bronze trim is commonly used in valves intended for mild service, such as water at moderatetemperatures and pressures. Stainless steel is used where increased strength, durability, andcorrosion resistance are required. Type 316 stainless steel forgings conforming to ASTM A182are suitable for many general service applications. Alternatively, these parts may be machinedfrom type 316 bar stock conforming to ASTM A276. Severe service applications may requirehardened grade 630 (17-4PH) wrought stainless steel trim conforming to ASTM A564.

Additional erosion and corrosion resistance for severe service applications can also be attainedby applying Stellite or Colmonoy hard facing to the seating surfaces of grade 316 stainless steeltrim. These hard facings are patented alloys; Stellites being various compositions of tungsten andchromium particles in a cobalt base, and Colmonoy being very hard crystals of chromium boridein a nickel base. Where severe corrosive conditions are a prime consideration, the trim may beone or a combination of various nickel or cupronickel alloys known by trade names such asHastelloy, Inconel, and Monel.

Non-standard trim such as Stellite can significantly increase the price and delivery time of valvesand require special coordination with design engineering and procurement.

Valve Operators

Externally operated valves are opened, closed, or adjusted by applying some type of force to thestem. There are two basic types of operators for applying this force:

• Manual

• Powered

The simplest form of manual operator is the handwheel. Electric motors or solenoids, or hydraulicor pneumatic devices may be used on powered operators. Actuating devices for powered

FIGURE 7-15 - MANUAL HANDWHEELS

Valves Section 7


operators are sometimes automatic, such as for control valves, and sometimes are manuallyswitched, such as a push-button switch for an electric motor operated valve. Power operatedvalves often also have a handwheel for emergency operation in case of a power failure.

Manual Operators

FIGURE 7-16 - HANDWHEEL TYPES

Section 7 Valves


The handwheel is the most common means of operating smaller low pressure valves with arotating stem. In the simplest form, the force applied to the handwheel is transmitted directly tothe stem. The amount of manual power that would be required to turn the handwheel on a largehigh pressure valve makes this arrangement impractical for such applications. A variety ofmanual operators as shown in Figure 7-16.

As shown in Figure 7-15, wrenches or keys are sometimes supplied on small shutoff valveshaving a removable operator as a safety feature. The operator must be placed on the stem toopen or close the valve, and is then removed. Hand levers are used to turn the stem on valvesthat are fully opened or closed by one-quarter or one-half turn. Examples of this arrangement areplug, ball, and butterfly valves. Hand levers are also used on manually operated sliding stemvalves.

A Hammer Blow Handwheel is used on large valves that would be somewhat difficult to operatewith an ordinary handwheel. The handwheel is turned rapidly and forcefully until the twohandwheel lugs strike the anvil that is attached to the stem. This hammering action increases thetorque that is transmitted to the stem to force the disc tightly against the seat in large valves thatrequire high torque for complete shutoff, or to free a disc that is wedged against the seat. Whenextra torque is not needed, the handwheel is simply turned in the same manner as any otherhandwheel (prior to final seating during closing or after initial freeing during opening).

Gears are supplied for many large high pressure valves requiring more operating torque that canbe directly applied through a handwheel. Gear operators are used to multiply the torque from thehandwheel. Bevel gears, spur gears, or worm gears may be used.

Extension Stems are used to operate a valve from a distance or to extend the stem through aplatform, floor, or wall. Extension stems are often used in nuclear power plants so that valves inradiation zones can be operated from shielded areas. They are available as straight extensions,with universal joints, or with right angle gear drives. A right angle drive is commonly used to avoidline of sight orientation of operators for valves in high radiation systems. Floor stands or wallsleeves are sometimes used for this purpose.

FIGURE 7-17 - FLOOR STAND AND CHAINWHEEL DETAILS

Valves Section 7


Floor Stands, shown in Figure 7-17, are used to guide, support, and shield an extension stem fora valve that is operated through a floor or platform. Floor stands are available in a variety ofstyles, with or without indicators.

Chain Wheels, also shown in Figure 7-17, permit operation of the valve from floor level when thevalve is above a normal reach. The chain wheel can be attached to the handwheel, or it canreplace the handwheel. Hammer blow chain wheels are also available.

Pneumatic Cylinder Operators

Pneumatic cylinders, shown in Figures 7-18 and 7-19, are ideally suited for fast operation of largegate valves. The cylinder contains a double acting piston. Pressurizing one end will push thepiston back to open the valve, and pressurizing the other end will reverse the action. The airsupply is controlled by a small 4-way valve or a 2-way valve with a spring loaded piston. Thisvalve may be manually operated or may have a manually or automatically controlled solenoidoperator. The cylinder can be used on sliding stem valves, or adapted to externally threadedrising stem valves.

The pneumatic piston operator designed for reciprocating stem positioning, may easily beadapted for butterfly valves and other types of valves by use of proper linkages and mountingbrackets. Other types used for quarter turn actuation are:

• Cylinder with rack and pinion

• Cylinder with linkage

• Electric gear drive rotary with linkage

• Electric gear drive rotary direct connected,hydraulic or pneumatic rotary vane

• Cylinder with spiral thread

The Hydraulic Cylinder operates on the sameprinciple as the pneumatic cylinder, and hassimilar applications. A hydraulic pumping unitis usually needed to supply pressurizedhydraulic fluid.

Cylinders with rack and pinion may employ adouble end piston with one rack and pinion orpressure at one end may be replaced by aspring. Two separated double end pistons,each carrying a rack, may be ported to give anadditive output.

Cylinder mounting methods due to the varietyof bonnet and stem configurations becomes amajor consideration. When the actuatordesign is controlled by the company producingthe valve, both may be designed for oneanother.

FIGURE 7-18 - VALVE PNEUMATICOPERATORS

Section 7 Valves


In many cases, the bonnet bolts are used to hold a bracket. Flange bolting offers a firm and welloriented point for bracket attachments. A spindle on a pipe saddle makes the unit easilyremovable. Pipe brackets suspending the actuator above the valve place no stress on the valvebody. The bracket may be screwed to an end connector.

Use of a solenoid (a soft iron core that can move within the field set up by a coil surrounding thecore) is a common means of opening or closing a valve. Instrumentation valves are sometimesoperated by an electric solenoid. This application is typically used on small valves, butoccasionally is used on valves up to 4 inches in size. The solenoid may be controlled by amanually operated pushbutton switch, but it usually has remote or automatic controls. The valveis normally held in one position, such as closed, by a spring. As shown in Figure 7-20, thesolenoid moves the stem to the opposite position, such as fully open, and the spring returns thestem to the original position when the solenoid is de-energized. A typical application is for lowpressure air service, especially in instrumentation.

Solenoids cannot actuate large valves or valves with high pressure drops without undesirablelarge solenoid currents. For such service, the solenoid operates a small pilot valve to admit linepressure for operation of the main valve.

For on-off control, particularly where short valve strokes are needed, solenoids offer a highresponse speed. They are coupled to the valve stem either directly, or indirectly throughmechanical or pneumatic mechanisms.

Solenoid operated valves are used extensively for emergency shutoff service or automaticopening of a valve simultaneously with the operation of a pump or other piece of equipment. Many electric valves used for emergency shutoff are magnetic, but cannot be considered assolenoid operated. The valve may be globe or rotating gate type, and, in either case, held openby electromagnets. Upon loss of current (due to the action of a pilot switch or failure of electricalservice), the valve closes by a combination of spring action, weight of parts, and sometimes, fluid

FIGURE 7-19 - PNEUMATIC VALVE OPERATOR DETAIL

Valves Section 7


flow in the line.

Valves Section 7


Control Valves

Control valves are a functional rather than a design classification. Control valves have designfeatures that have been developed and refined specifically for improvement of control valveperformance. As shown in Figure 7-21, control valves have an actuator that is powered byenergy from an independent source. The actuator moves the valve closure member in responseto an external signal. The movement is proportionate to the signal. Valve closure memberposition changes in relation to the valve port or ports are thus controlled by and in proportion tothe external signal. Fluid flow through the valve is controlled by the valve closure member, sothat position changes will throttle, stop, start, or alter the routing of the flow. Control valves cantherefore be used to regulate a variety of process conditions, including flow rate, pressure,temperature, liquid level, and input or output routing.

Item No. Description Item No. Description1 Body 10 Stem2 Bonnet 11 Spring Retainer3 Main Disc 12 Stem Pin4 Pilot Disc 13 Plunger5 Disc Inserts 14 Fixed Core6 Piston Ring 15 Coil Base7 Disc Pin 16 Coil8 Sleeve 17 Coil Cover9 Spring 18 Lock Nut

FIGURE 7-20 - SOLENOID MOTOR ACTUATED VALVE

Section 7 Valves


Variations in control valveconfigurations are practically endless,but the most common arrangementshave a globe type valve with speciallydesigned trim and a pneumaticallyoperated diaphragm actuator. Ball,butterfly, diaphragm, rotary plug, andsliding gate valves are also used ascontrol valves. Actuators can also bepneumatic pistons (cylinders),hydraulic cylinders, electric solenoids,and various combinations of these.

It is particularly important to maintainaccess and removal space for controlvalves when selecting an installationlocation.

Control Valve Actuators

Pneumatically operated control valve actuators are the most popular type in use, but electro-hydraulic actuators are also widely used. The spring and diaphragm pneumatic actuator is mostcommonly specified, due to its dependability and its simplicity of design. Pneumatically operatedpiston actuators provide integral positioner capability and high stem force output for demandingservice conditions. Adaptations of both spring and diaphragm and pneumatic piston actuatorsare also available for installation on rotary shaft control valves.

Electro-hydraulic actuators are more complex and more expensive than pneumatic actuators.They offer advantages where no air supply source is available, where low ambient temperaturescould freeze condensed water in pneumatic supply lines, or where usually large stem forces areneeded. The following is a summary of the design and operating characteristics of some popularactuator styles:

Diaphragm Actuators

These are widely available in a great range of sizes. The two basic types of diaphragm actuatorsare shown in Figure 7-22. One type is generally called a direct acting diaphragm actuator, andthe other a reverse acting diaphragm actuator.

The direct acting type has a spring that holds the valve in the open position when the air chamberabove the diaphragm is not pressurized. Air pressure counteracts the spring force, and fluidpressure against the valve closure member, to push the valve stem downward. The air pressureis controlled by a positioner, so that the pressure is increased when the valve closure membermust be moved closer to the set (for closer throttling), and further increased if the valve is to becompletely closed. The reverse acting type works in the opposite manner. The spring force holdsthe valve in the closed position and air pressure moves it to a partially open (throttled) or fullyopen position. The chamber above the diaphragm in a reverse acting diaphragm actuator mustbe vented.

FIGURE 7-21 - CONTROL VALVE

Valves Section 7


Diaphragm actuators are simple, reliable, and available in a multitude of sizes, which is why theyare used on most control valves. However, the diaphragm will not withstand high pressure.Thus, a very large actuator is needed to operate a valve having high unbalanced or generatedforce.

Item No Description Item No Description15 Packing Box Gasket 39 Diaphragm17 Yoke 40 Diaphragm Plate18 Cap Screw 41 Diaphragm Washer19 Gasket 43 Upper Diaphragm Case20 Packing Nut 44 Lower Diaphragm Case21 Snap Ring 45 Diaphragm Case Cap Screw

22/22A Actuator Spring 46 Diaphragm Case Nut26 Actuator Stem 56 Travel Indicator Scale30 Packing Box 57 Machine Screw31 Nut (Actuator Stem) 70 Ball & Retainer32 Yoke Packing 71 Spring Barrel33 Spring Guide 72 Spring Barrel Cap34 Spring Button 73 Ball Bearing Race35 Pipe Plug 74 Cap Screw36 Spring Adjuster 76 Spacer Ring37 Bushing

FIGURE 7-22 - DIAPHRAGM ACTUATORS

Section 7 Valves


Piston Actuators

Unlike diaphragm actuators,hydraulic and pneumatic cylindersare made to withstand highpressures. Therefore, these areoften more suitable for a valvethat requires high operating force.The cylinder contains a singleacting or double acting piston. Asshown in Figure 7-23, the singleacting piston is spring loaded andfunctions in much the samemanner as a diaphragm actuator.The double acting piston is movedback and forth by pressurizing orincreasing the pressure on oneside while concurrently exhaustingor decreasing the pressure on theother side. Double actingpneumatic pistons with positionersare more commonly used than theother piston types for controlvalve actuators.

Electro-Hydraulic Actuators

These actuators require onlyelectrical power to the motor andan electrical input signal from acontroller. They are ideal forisolated locations wherepneumatic supply pressure is notavailable but where precisecontrol of valve plug position isneeded. The units are usuallyself contained, including motor,pump, and double actinghydraulically operated pistonwithin a weather proof orexplosion proof casing.

Item No. Description Item No. Description1 Yoke 19 Connector2 Stem Lock 20 Regulator-Positioner

Assembly3 Stem Lock Bolt 21 Elbow4 Stem Lock Nut 22 Actuating Tubing

Assembly5 Piston Rod 23 Rate Spring6 Piston Rod O-Ring 24 Dome7 Adapter Screw O-Ring 25 Spring Button Assembly8 Base Plate 26 Seal Tube Retainer9 Base Plate O-Ring 27 Seal Tube Gasket10 Nut (Actuator Stem) 28 Spring11 Piston Rod Washer 29 Dome Retaining Ring12 Piston Rod O-Ring 30 Adapter Screw13 Travel Stop 31 Adapter Nut14 Seal Tube 32 Stem Boot15 Seal Tube O-Ring 33 Travel Plate16 Caution Plate 34 Travel Plate Screw17 Drive Screw 35 Travel Plate Nut18 Loading Tubing

Assembly36 Name Plate

FIGURE 7-23 - PISTON ACTUATOR

Valves Section 7


Valve Positioners

Many valve positioners have been developed and are presently available. In function, they arealike, although there are various shapes, styles, and operating principles. Positioners aregenerally mounted on the side of diaphragm actuators and on the top of piston actuators. Theyare connected mechanically to the valve stem or piston so that stem position can be comparedwith the position dictated by the controller.

An auxiliary positioner is used for systems where it is necessary to:

• Split range the controller output to more than one valve

• Amplify the controller output signal pressure above the standard range to provide increasedactuator thrust or stiffness

• Provide the best possible control with minimum overshoot and fastest possible recoveryfollowing a disturbance or load change where long controller instrument lines are involved

Pneumatic Positioners

The positioner schematic shown in Figure 7-24 shows a pneumatic positioner connected fordouble acting service on a piston actuator. Tension on the range spring provides feedback to thepositioner, which will vary as the stem position changes. The spring loading force is appliedthrough the lever and cam to the positioner's input capsule. Control instrument pressure isapplied between the diaphragms in the input capsule. Therefore, the input capsule serves as aforce balance member, matching the valve stem position (as measured by tension on the rangespring) to the control instrument signal.

When the opposing forces balance exactly, the system will be in equilibrium and the stem will bein the exact position called for by the control instrument. If the opposing forces are not inbalance, the input capsule will move up or down, and by means of the pilot valves, will change theoutput pressures. This will move the stem until the tension on the range spring opposes exactlythe control instrument pressure.

FIGURE 7-24 - PNEUMATIC POSITIONERS - SCHEMATIC

Section 7 Valves


Electro-Pneumatic Transducers

Shown in Figures 7-25 and 7-26, the transducer receives a direct current input signal and uses atorque motor, nozzle flapper, and pneumatic relay to convert the electric signal to a proportionalpneumatic output signal. Nozzle pressure operates the relay and is piped to the torque motorfeedback bellows to provide a comparison between input signal and nozzle pressure. Thetransducer can be mounted directly on a control valve and operate the valve without need foradditional boosters or relays. On-off electro-pneumatic transducers are also available and arecommonly used to replace solenoid valves in intrinsically safe systems.

Control Valve Bodies and Trim

Basic body styles are essentially the same as those used for manually operated valves. Globe,angle, and Y-pattern bodies are used and these have a reciprocating valve closure member thatfunctions in the same manner as the disc in a comparable manually operated valve. However, ina control valve, the closure member is called a plug or valve plug instead of a disc. Again, this isa reciprocating plug and not the rotary plug that constitutes the closure member in a plug valve.

Rotary plugs are also used in some control valves. Ball valves, butterfly valves, and diaphragmvalves are sometimes used as control valves. The globe style body, however, is the mostcommonly used type. Plugs and seats in globe style control valves are much more specializedthan comparable parts of manually operated globe valves. Several different plug shapes areused, and each shape is designed for a specific combination of fluid characteristics and operatingconditions.

FIGURE 7-25 - ELECTRO-PNEUMATIC POSITIONER - SCHEMATIC

Valves Section 7


VALVE BODIES

As shown in Figure 7-27, valve bodies come in single ported, double ported, and three way bodyconfigurations.

Single Port Valve Bodies

This is the most common body style and is simple in construction. The bodies are available invarious forms including globe, angle, bar stock, forged, and split constructions. These aregenerally specified for applications with stringent shutoff requirements.

Many modern single seat valve bodies use a cage style construction to retain the seat ring,provide valve plug guiding, and provide a means for establishing a particular flow characteristic.The cage style trim offers advantages in ease of maintenance and in interchangeability of cagesto alter valve flow characteristics. Cage style, single seat valve bodies can also be easilymodified by change of trim parts to provide reduced capacity flow, noise attenuation, or reductionor elimination of cavitation. Normal flow direction is most often up through the seat ring and, inthe case of valves with cage style trim, the flow direction is out through the openings in the cagewall.

Double Ported Valve Bodies

FIGURE 7-26 - ELECTRO-PNEUMATIC TRANSDUCER

Section 7 Valves


In this style, force on the plug tends to be balanced as flow tends to open one port and close theother. These valves normally have higher capacity than single ported valves of the same linesize. Many double ported bodies are reversible, so the valve plug can be installed as either "pushdown to open" or "push down to close." Port guided valve plugs are often used for on-off or lowpressure throttling service. Top and bottom guided valve plugs furnish stable operation for severeservice conditions.

Three Way Valve Bodies

Three pipeline connections to provide general converging (flow mixing) or diverging (flow splitting)service. Designs utilize cage style trim for positive valve plug guiding and ease of maintenance.

FIGURE 7-27 - VALVE BODY TYPES

FIGURE 7-28 - BALANCED PLUG - CAGE TYPE

Valves Section 7


Balanced Plug, Cage Style Valve Bodies

As shown in Figure 7-28, this body style is single ported in the sense that only one seat ring isused. Cage style trim is used to provide valve plug guiding, seat ring retention, and flowcharacterization. In addition, a sliding piston ring type seal between the upper portion of the valveplug and the wall of the cage cylinder virtually eliminates leakage of the upstream high pressurefluid into the lower pressure downstream system. Interchangeability of trim permits choice ofseveral flow characteristics, noise attenuation or anticavitation components. For most availabletrim designs, the standard direction of flow is in through the cage openings and down through theseat ring.

Valve Bonnets

The bonnet normally provides a means of mounting the actuator to the body and houses thepacking box. On control valve bodies with cage style trim, the bonnet furnishes loading force toprevent leakage between the bonnet flange and the body and also between the seat ring and thebody. The tightening of the body to bonnet bolting compresses a flat sheet gasket to seal thebody to bonnet joint, compresses a spiral wound gasket on top of the cage, and compressesanother flat sheet gasket below the seat ring to provide the seat ringbody seal. The bonnet alsoprovides alignment for the cage (which in turn guides the valve plug) to ensure proper valve plugseat ring alignment.

Valve Plugs

The valve plug is the moveable part of a globe style control valve assembly which provides avariable restriction to fluid flow. Several valve plug styles are available. Three common plugstyles are shown in Figure 7-29. Each is designed to provide a specific flow characteristic, topermit a specified manner of guiding or alignment with the seat ring, or to have a particularshutoff or damage resistance capability.

Valve plugs are designed for either two position or throttling control. In two position applications,the valve plug is positioned by the actuator at either of two points within the travel range of theassembly. In throttling control, the valve plug may be positioned at any point within the travelrange as dictated by the process requirements. Although some valve plugs are reversible, mostare designed for either "push down to open" or "push down to close" action. The contour of thevalve plug surface adjacent to the seat ring is instrumental in determining the inherent flowcharacteristic of a conventional globe style control valve.

Common flow characteristics include:

Linear Flow

A valve with an ideally linear inherent flow characteristic produces flow rate directly proportional tothe amount of valve plug travel, throughout the travel range. For instance, at 50 percent of ratedtravel, the flow rate is 50 percent of maximum flow and at 80 percent of rated travel, the flow rateis 80 percent of maximum flow.

Section 7 Valves


Equal Percentage Flow

For equal increments of valve plug travel, the change in flow rate with respect to travel may beexpressed as a constant percent of the flow rate at the time of the change. The change in flowrate observed with respect to travel will be relatively small when the valve plug is near its seat andrelatively high when the valve plug is nearly wide open. Therefore, a valve with an inherent equalpercentage flow characteristic provides precise throttling control through the lower portion of thetravel range and rapidly increasing capacity as the valve plug nears the wide open position.

Quick Opening Flow

A valve with a quick opening flow characteristic provides a maximum change in flow rate at lowtravels. The curve is basically linear through the first 40 percent of valve plug travel, then flattensout noticeably to indicate little increase in flow rate as travel approaches the wide open position.

Cages for Globe Valve Bodies

In valve bodies with cage guided trim, flow characterization is determined by the shape of the flowopenings or "windows" in the wall of the cylindrical cage. As the valve plug is moved away fromthe seat ring, the cage windows are "opened" to permit flow through the valve. Standard cageshave been designed to produce linear, equal percentage, and quick opening inherent flowcharacteristics.

Cage guided trim in a control valve provides a distinct advantage over conventional valve bodyassemblies in that maintenance and replacement of internal parts is much simplified. Theinherent flow characteristic of the valve can be easily changed by installing a different cage.

Valve Plug Guiding

Accurate guiding of the valve plug is necessary for proper alignment with the seat ring andefficient control of the process fluid. The common methods used are listed below:

Equal Percentage Linear Quick Opening

FIGURE 7-29 - VALVE PLUGS

Valves Section 7


Top and Bottom Guiding

Valve plug is aligned by guide bushings in the bonnet and bottom flange.

Cage Guiding

The outside diameter of the valve plug is in close proximity to the inside wall surface of thecylindrical cage throughout the travel range. Since bonnet, cage, and seat ring are self-aligningon assembly, correct valve plug/seat ring alignment is assured when valve closes.

Top Guiding

The valve plug is aligned by a single guide bushing in the bonnet or valve body.

Top and Port Guiding

Valve plug is aligned by a guide bushing in the bonnet or body and also by the valve body port.

Stem Guiding

Valve plug is aligned with the seat ring by a guide bushing in the bonnet that acts on the valveplug stem.


Section 8

Strainers and Traps

STRAINERS

Various devices are used to remove suspended matter from piped fluids. The devices are calledby many names, depending on how they are made and where they are used. Examples include:

• Absorbers

• Filters

• Screens

• Sediment Separators

• Strainers

These classifications may overlap or even be synonymous in many cases. For the purposes ofthis handbook, all particle removing devices will be categorized as strainers.

Strainers remove solid particles from liquids as compared to filters which are used either toremove solids from liquids and gases, or to separate heavier fluids (liquid or gas) from lighterfluids. Strainers generally have a permanent screen that can be cleaned by emptying, washing,or blow down. Filters have a permanent element or a replaceable element that is disposed ofwhen clogged. Filters generally intercept smaller particles than do strainers.

Strainers are generally placed in the main line, so that all of the process fluid passes throughthem. A strainer used as a sediment separator in a pump intake line, to protect the pump, wouldhave to be a full-flow strainer. In other cases a partial-flow strainer would be adequate, and asmall branch or bypass line is used for such applications. Partial flow filtration may be adequateto prevent buildup of particles that are generated in small quantities, such as corrosion productsin condensate lines.

Strainers are either permanent plant components designed for the life of the plant or temporarycomponents for the removal of constructionresidue during initial startup. In either case,space for maintenance and removal accessmust be maintained.

Types of Strainers

Several common types of strainers include:

• Basket Strainers

• Wye Strainers

• Self-cleaning Strainers

• Tee Strainers

• Start-up Strainers

FIGURE 8-1 - SINGLE BASKET STRAINERS

Section 8 Strainers and Traps


The type designations are the result of descriptive names related to the strainer shape, strainerhousing configuration, unique features of the strainer, or the intended use.

Basket Strainers

These strainers have a basket likescreen in a housing that oftenresembles a check valve body or apipe tee with the branch outletclosed, especially in the smallersizes.

The larger sizes have speciallydesigned bodies that sometimesresemble cylindrical or cubical tankswith side outlets and a removabletop. Some have integral vents anddrains. The basket (screen) can bemade of perforated metal ifrelatively large particles are to beintercepted, or of woven wire (wirecloth) for smaller particles. Perforated metal screens aredesigned by hole size and center-to-center spacing.

Wire cloth screen size is usually designated by a mesh number such as 20 mesh, which wouldhave a grid of 20 openings per linear inch in each direction or 400 openings per square inch. Particles larger than the screen openings are trapped in the basket.

The basket must be periodically removed, emptied, cleaned, and reinserted. Basket strainers arethus not suitable for lines carrying fluids that areheavily contaminated with coarse particulatematter. They do provide protection against anylarge particles that might occasionally bedislodged from piping walls or equipmentcomponents. Single basket strainers shown inFigure 8-1 are adequate for many applications,but duplex basket configurations shown inFigures 8-2 and 8-3 are sometimes needed. Thetwin configuration allows switching so that flowcan continue through one basket while the otheris cleaned. Basket strainers are normallypermanent line components.

FIGURE 8-2 - DUPLEX STRAINER BASKET DETAIL

FIGURE 8-3 - DUPLEX BASKET STRAINER

Strainers and Traps Section 8


Wye Strainers

As shown in Figure 8-4, the housing for this type of strainer resembles a Y-pattern valve body ora lateral pipe fitting with the branch end at the bottom and is typically used in steam systems. Particles are trapped inside a cylindrical screen cartridge, and removed through a blowdown orcleanout port in the Y-branch closure. The port is either plugged during normal operation, orconnected to a blowdown valve and drain line. The screen may be perforated metal or wire cloth. The wire cloth screen size is usually designated by mesh number, in the same manner as basketstrainers. Wye strainers are suitable for permanent applications and are more appropriate thanbasket strainers in lines that are susceptible to considerable scale buildup.

Self-Cleaning Strainers

These are also called scraper strainers. Asshown in Figure 8-5, they are made in verticalpatterns and Y-patterns and the bodies aresimilar to those of basket strainers and wyestrainers. An important difference is that self-cleaning strainers have a hand operated ormotor driven scraper inside the screen. Thetypical scraper is a helically curved knife-likeelement that is turned to dislodge particlesfrom the screen wall. The particles settle tothe bottom of the strainer housing, fromwhere they are periodically blown down. Self-cleaning strainers are advantageous inapplications where fluid impurities arecontinuously removed at a relatively high rate.Otherwise, the intercepted particles mightcollect along the screen wall area nearest tothe outlet, thus impeding flow.

FIGURE 8-4 - WYE STRAINERS

FIGURE 8-5 - SELF-CLEANING STRAINERS



Tee (Bathtub) Strainers

Shown in Figure 8-6, these strainers aresometimes called tee strainers because ofthe housing shape, and sometimes calledbathtub strainers because of the screenshape. They can be used in permanentapplications requiring only infrequentcleaning, but are primarily intended fortemporary use during startup. A significantadvantage with this type of strainer is thatthe screen can be easily removed anddiscarded once it is no longer needed. The housing remains in place as a permanent line component and the flowcharacteristics of the line are not disturbedor materially altered by removal of the

screen.

Startup Strainers

These strainers are temporarily placed in the line for use during startup. They are placed in linesegments leading to equipment not having permanent strainers. Their purpose is to intercept construction residue that would damage equipment and pumps if not removed from the line fluid. Figure 8-7 shows various startup strainers designed to intercept the following constructionresidue:

• Dirt

• Corrosion scale

• Weld spatter

• Foreign materials

• Loose materials such as nuts andbolts

Startup strainers are removed after thelines have been purged. Removal of thestrainer leaves the affected pipe section inan unimpeded flow condition for normaloperation. The following describes thevarious types commonly used:

• Flat Strainers (Pancakes)

• Conical Strainers

• Perforated Metal Strainers

Flat strainers can be perforated platewithout a screen, perforated plate with a wire cloth overlay, and a flat ring (orifice plate) with awire cloth screen. These strainers cause considerable flow restriction, and can quickly become

FIGURE 8-6 - TEE STRAINERS

FIGURE 8-7 - STARTUP STRAINERS



clogged in a heavily contaminated line. The flat strainer is installed between two flanges, thus it iseasily removed when no longer needed. A spacer ring of the same thickness as the strainer platemust be installed between the flanges when the strainer is removed.

Conical strainers and basket strainers are the preferred type where there is adequate line spacefor installation. They are installed in a removable pipe section (spool), with the ring between twoflanges. The most effective flow direction for these strainers is that they be installed with thecone pointed upstream. The cone is obtainable as:

• Perforated metal without wire cloth

• Perforated metal with wire cloth on the outside or inside (this is the preferred choice)

• Unreinforced wire cloth (this is not a preferred choice since it is subject to failure)

• Multi-mesh wire cloth which is a fine mesh of small diameter wire reinforced by a more openmesh of larger diameter wire

It is not good practice to install perforated metal strainers with wire cloth inside the cone with thecone pointed downstream. If the cone is pointed downstream, a broken strainer will releasecollected material into the pump. If the cone is pointed upstream, however, the strainer willcollapse plugging the line and the trapped materials will not be released.

A spacer ring must be installed between the pipe flanges when the strainer is removed.Alternatively, the cone may be cut from the strainer ring and the ring used as the spacer.

Strainer Screen Material

As previously mentioned, there are two basic styles of screen material:

• Perforated metal plate

• Wire cloth

Each is available in various sizes, and madefrom several metals or alloys. Commonmaterials are carbon steel, various stainlesssteels, brass, bronze, copper, aluminum,nickel, monel, Hastelloy, and titanium. Asshown in Figure 8-8, perforated metal screensizes are normally designated by hole sizeand center-to-center spacing of the holes,but some catalogs list hole size and numberof holes per square inch. Wire cloth isdesignated by mesh number, wire size, andstyle of weave.

Mesh number designates the number of openings per lineal inch. The openings are counted fromcenter-to-center of adjacent wires. A square mesh as shown in Figure 8-9 is the most commonpattern for strainer screens, but oblong (rectangular) meshes are also made. Square mesh hasthe same count (number of openings) in each direction, and can be designated in two ways:

• By count in each direction

FIGURE 8-8 - STRAINER SCREENMATERIAL TYPES



• By a single number that applies to both directions

A square mesh screen having 20 openings per lineal inch could thus be called a 20 x 20 mesh ora Number 20 mesh. Both counts are needed for an oblong mesh, such as 5 x 10 mesh for 5openings in one direction and 10 openings in the other direction. The clear opening (space)between adjacent parallel wires is also sometimes specified, instead of mesh number. In thiscase, the cloth is called, "space cloth" rather than wire cloth. Strainers are made with wire clothhaving a square mesh as fine as 100 x 100.

The preferred method of designating wire size is by diameter, in decimal parts of an inch, such as0.016 inch diameter wire. Wire as small as 0.0045 inches is used for strainer screens (100 x 100mesh, 0.0055 inch opening).

Weave

A plain weave as shown in Figure 8-10 is the most common weave for wire cloth used for strainerscreens. Plain weave wire cloth has parallel wires running the length of the cloth (warp wires),and these are crossed at right angles by wires running across the width of the cloth (shute wires). The crossing wires alternately pass over one and under the next wire, in each direction.

The wires are crimped (corrugated)to lock them in place. A doublecrimp is most common. A dutchweave, instead of plain weave, issometimes used. The dutchweave has warp wires that arelarger than the shute wires. Thereare many more weave styles, butthey are rarely used for strainerscreens.

STEAM TRAPS

FIGURE 8-9 - STRAINER SCREENS AND MESHES

FIGURE 8-10 - MESH WEAVES



A steam trap is really a separating trap, it is able to separate condensate and steam. When asteam trap discharges condensate it does so from a higher pressure to a lower pressure. If thepressure at the outlet side of the trap was the same or higher than the pressure at the inlet side,the trap would not be able to work. With an inlet pressure greater than the outlet pressure,condensate will be discharged and depending on the pressure differential, can be made to travelquite a long way including up vertical slopes.

Steam traps can be broadly divided into four main groups:

• Mechanical

• Thermodynamic

• Impulse

• Thermostatic

Mechanical Traps

As the name implies, the traps in this group do the job mechanically, using the difference indensity between steam and condensate. They open to condensate and close to steam by theaction of a float, which may be either a closed float (generally a hollow ball) or a device shapedlike a bucket with the open end either facing upward (open top bucket trap) or downward (invertedbucket trap). The movement of the float operates a valve.

Ball Float Type

As shown in Figure 8-11, the ball float steam traps are sometimes referred to as closed floattraps, or just float traps. There are different kinds of floats.

Outwardly, ball float traps vary in size and shape according to the manufacturer. The mechanicalmovement inside, however, is similar in all of them with some variations. A very simple exampleof the type of mechanical movement involved in this type of trap is the ball valve in toilet tank. Inthis case, a metal arm is connected to a valve at one end and a hollow metal ball at the other. The ball rises and falls with the water level and either opens or closes the valve depending on thewater level. The valve action in turn fills the tank to the desired level.

With a ball float trap, condensate from the plantenters the inlet port. As the condensate water levelrises, the ball rises with it which enables the water tothen able to flow out through the valve. When theflow of condensate to the trap slows, the water levelin the trap falls which lowers the ball and covers theoutlet.

When steam follows the condensate, the ball sealsoff the valve, and the steam cannot escape. Theaddition of more condensate flowing to the trap willre-float the ball and will gradually uncover the valveso that the water can again escape. Depending onthe rate of condensation, the flow of condensate fromthe trap will vary which is described a continuous

FIGURE 8-11 - BALL FLOAT TYPETRAP



discharge action.



Loose Float Type

The advantage of this type of steam trap is that it has no working parts. This results in little or nomaintenance or repairs.

The principle disadvantage of this type trap, is that the outlet is lower than inlet. This provides awater seal through which the steam cannot blow. While this provides a positive steam seal, itmeans that air cannot get out to activate the trap. As a consequence, air has a tendency to lock-up the steam trap and must be removed from the system. To alleviate this situation, a hand aircock has to be fitted to the trap.

Another disadvantage of this type of trap is that there may be difficulty in getting proper seating ofthe large ball on the small outlet hole.

Float and Lever Type

In this type of trap, the float arm connects the ball to the outlet valve. As the ball rises, themovement gradually opens the valve and lets out some of the water. If condensate is coming tothe trap more quickly than it is releasing, the ball will continue to rise with the rising water leveland open the valve wider releasing more water. Until an equilibrium is reached in condensateentry and discharge, the ball will continue to rise until it reaches the limit of travel. If the trap isproperly sized, the ball should never reach the limit of travel unless the outlet valve is partlyblocked by a foreign object such as a piece of rust or pipe scale.

If the trap is correctly sized for the operating conditions and the outlet is not blocked, the ball willstop rising at a certain point. This will occur when the flow of condensate leaving the trapmatches the flow into it. As the flow of water to the trap declines, the water level inside the trapwill fall and the ball will fall with it. As a result, the outlet valve will begin to close. When the flowof condensate to the trap increases, the reverse occurs and the flow of water from the trap willincrease.

Advantages of This Type

This type of trap will work equally well with either heavy or light condensate load and is notaffected by wide and sudden pressure changes.

Disadvantages of This Type

It is possible for the ball float and the thermostatic element to be damaged by water-hammer orby condensate with corrosive substances in it. If the trap is fitted with a thermostatic air release, itshould not be used on superheated steam.

A general disadvantage applicable to all ball float traps and others in the mechanical group is thatthe size of the discharge hole is governed by the power of the float and the steam pressure.

Bucket Type (Mechanical)

In this type, the trap valve is operated by a bucket instead of a ball float as those previouslydescribed. The bucket normally has straight sides on either of the two basic traps:



• Open top bucket trap

• Inverted bucket trap

Open Top Bucket Trap

As shown in Figure 8-12, the operation of an opentop bucket trap can best be explained by comparingits operation to an open drinking glass in a washbasin. If the drinking glass is set right side up in thebasin and then the basin is filled with water, thedrinking glass will float. If a hand is held above theglass as the water continues to fill, the glass willcontinue to rise until it reaches the hand where it willbe stopped. With the water continuing to fill thebasin, the water will eventually crest the lip of theglass and spill into the glass. The glass will thensink to the bottom of the basin.

With the open top bucket trap, condensate enters and begins to fill the body of the trapsurrounding the bucket. The bucket floats, taking with it the spindle and valve. When the valvereaches the seat, the bucket cannot rise any more and as the condensate level continues to rise,it soon reaches the top of the bucket and begins to spill into it. When the bucket is full, it drops tothe bottom of the trap, drawing the valve away from its seat. The pressure of the steam followingthe condensate into the trap forces the water out and up the central tube. It passes through andleaves the trap.

As the condensate has been blown out, the bucket becomes buoyant and floats once again toclose off the valve. The cycle continues depending on whether condensate or steam is coming tothe trap. It should be noted that this type of trap has a steam blast discharge due to the suddenrelease of condensate and steam from the trap.


Traps of this type are usually sturdy, and there is not much in them that can go mechanicallywrong. Under certain conditions, they can be used on superheated steam. They can be used onhigh pressure systems and can withstand water-hammer better than most types of mechanicaltraps.


Normally, this trap makes no provision for air venting, so an air cock is usually provided at the topof the trap. This cock can be replaced with a thermostatic air vent, or liquid expansion type vent.

Inverted Bucket Type

As shown in Figure 8-13, the inverted bucket type trap can also be explained with the sameanalogy of the drinking glass and the wash basin. In this example, the wash basin is filled first. The drinking glass is then held upside down and sunk carefully and evenly toward the bottom of

FIGURE 8-12 - OPEN BUCKET TYPETRAP



the basin. The glass will tend to push upward as it is being immersed. If the hand is removedfrom the inverted glass, the glass will at once bob up to the surface of the water.

This is the same type of action that occurs witha inverted bucket steam trap. As condensateenters the trap, the water level in the trap risesboth inside and outside the bucket. The bucketremains at its lowest position and the valve isopen. With the valve open, the condensatewater is able to escape quickly through theopen valve.

When steam enters the trap, however, it blowsinto the inverted bucket and floats it. Thismovement closes the valve and the trap is nowshut which prevents the steam from escaping. When additional condensate enters the trap, thesteam in the bucket is blown out and the bucketsinks which opens the discharge valve to let outthe water. This type of trap has a blastdischarge.

Advantage of This Type

The working parts of the traps are simple and mechanically reliable. Under certain conditions, thetrap can be used on superheated steam and can withstand all but the most severe water-hammerconditions.


This type of trap does not respond very well to fluctuations of pressure or condensate load. There should always be a small amount of water in the bottom of the trap body to act as a sealaround the lip of the bucket. It is possible for the trap to lose this water seal which allows steamto blow through the outlet.

This situation can happen when there is a sudden drop in steam pressure which causes some ofthe condensate in the trap to flash into steam. This permits the water seal around the base of thebucket to escape allowing the bucket to sink and opening the valve. If the rate at whichcondensate is coming to the trap is less than the rate at which the pressure is blowing it outthrough the open valve, the water does not get a chance to collect at the bottom of the trap andremake the seal. If significant pressure variation is expected, a check valve should be used onthe line in front of the inverted bucket trap.

In a superheated steam system, the high temperature of the steam can also cause thecondensate to flash and cause the inverted bucket trap to lose its water seal. Once again, acheck valve in front of the trap will avoid this situation.

FIGURE 8-13 - INVERTED BUCKET TYPETRAP



THERMODYNAMIC GROUP

Thermodynamic traps work on the difference in velocity between steam and condensate flowingacross a simple valve disc. They close to high velocity steam but open to lower velocitycondensate.

Thermodynamic steam traps are mechanically simple. The trap consists of body which carriesthe inlet and outlet connections, a top cap, and a freely floating disc. The body has twoconcentric seat rings formed in it. The inner ring surrounds the inlet orifice and the outer ring isclose to the top cap. Between the two seat rings is the outlet passage. The seat rings and thedisc are ground flat to allow the disc to seat on both the rings at the same time and seal off theinlet from the outlet and close the trap tight.

The top cap includes a projecting boss which acts as a stop for the disc, limiting its upward travel. Thus, there is always a space between the top of the disc and the underside of the cap. Thisspace is called the control chamber. This chamber and the gap left between the edge of the discand the side of the cap are an important feature in the operation of the trap.

When the disc seats on the outer ring, it seals off the control chamber from the outlet. If the trapis connected to a cold system because steam has not been turned on yet, the trap will initiallyreceive air and cold condensate at comparatively low pressure when the steam supply valve isopened. The condensate then passes up the inlet orifice, lifts the disc, and flows radially outwardand into the outlet passage.

As the system warms up, the pressure in the steam space increases and starts to push thecondensate faster through the trap. The condensate also gets hotter and as it drops in pressurein passing through the trap from inlet to outlet, some of it flashes to steam. When this happens ina thermodynamic trap, a mixture of flash steam and condensate begins to flow radially across theunderside of the disc from the center toward the edge. Because the flash steam occupies alarger volume than the same weight of condensate the speed of flow increases. As thecondensate continues to get hotter, more flash steam is formed and the flow across the undersideof the disc continues to increase.

When the pressure of condensate and flash steam increases as it speeds up going through thetrap, the static pressure against the disc falls. This drop in static pressure causes the disc tomove toward the seat rings and results in a reduction in the speed and dynamic pressure of thecondensate and flash steam. The repositioning of the disc causes the static pressure in the trapto rise and the disc will push away from the seats again.

As the disc throttles the condensate and flash steam load, some of the condensate and steam isdeflected up through the gap between the edge of the disc and the cap and fills the controlchamber. This produces a static pressure which presses down on the entire top surface of thedisc. This is sufficient to overcome the inlet pressure and forces the disc firmly against the seat.

In this closed position, the inlet is sealed off from the outlet by the inner seating ring and the flashsteam and condensate are trapped in the control chamber by the outer seating ring. As heat islost from the control chamber, the pressure on the top of the disc falls until it is no longer strongenough to hold the disc down against the inlet pressure and the disc rises and the trap againdischarges condensate.



If there is no condensate waiting to be discharged when the trap opens, a tiny amount ofhigh-pressure steam will rush through it and cause the disc to seat again. This is why the trap iscalled thermodynamic. It opens because of thermal losses from the top cap and closes due tothe dynamic action of steam or flashing condensate.


Thermodynamic traps will work over the full range of pressures up to the maximum for which thematerials used without any adjustment or change of valve size. They can be used onsuperheated steam and at high pressures and are not damaged by water-hammer or vibration. They are very small in size and yet have a large condensate handling capacity.

There is only one moving part, the hardened stainless steel disc. Because they are made fromstainless steel, they will stand up to corrosive condensate.


Thermodynamic traps are not reliable if the inlet pressure falls much below 8 psi or the back-pressure rises above 50 percent of the inlet pressure. This is because in either circumstance thespeed of flow across the underside of the disc is reduced too much for the necessary lowpressure to occur. If the pressure at the trap inlet builds up slowly during startup, it can dischargea lot of air. But, if the pressure builds up quickly, high speed air can shut the trap in the sameway as steam, and it will bind.

IMPULSE TRAPS

Impulse traps depend on the ability of condensate at high temperature and pressure to flash tosteam at a lower pressure. The flashing of condensate to steam governs the movement of asliding type valve by causing pressure changes in a control chamber above the valve.

As shown in Figure 8-14, the sliding main valve is hollowwith an orifice at the top, and has machined on it a smallexternal disc which acts as a piston. The piston discmoves up and down with the cylinder and is a guide forthe valve unit. At the bottom position, the main valveseals into the seat orifice, but there is still a path for thecondensate to flow through the trap by way of theclearance between the piston, cylinder and the orifice inthe main valve body.

This is the position of the valve when the system is not inuse. When steam is on the system, trapped air and thencondensate reach the trap, and the resultant pressureunder the piston lifts the main valve, and the trapdischarges its contents. Some of the condensate willpass up the gap between the piston and the conical

cylinder into the chamber above the valve and through the orifice out the trap discharge. Whenthis happens, there is a drop in pressure as the water flows through the gap so that the pressureabove the piston will be lower than that below it. Therefore, the valve will be held open.

FIGURE 8-14 - IMPULSE TYPE TRAP



When the condensate temperature equals that of the steam temperature, some of it flashes tosteam as it passes through the gap into the chamber above the piston valve. The steam collectsin the chamber where it tries to escape through the orifice in the piston valve.

Because it has a much greater volume than an equal weight of condensate, the flash steam takeslonger to pass through orifice and starts building up a higher pressure in the chamber. This willeventually force the piston-valve down the cylinder.

Due to the taper of the conical section, the rate of flow is reduced and the trap settles down todischarging condensate at the designed rate.

If steam reaches the trap, the pressure will build up above the piston-valve and close it. Becauseof the orifice, there is always a leak of steam across the trap. Due to this feature, it does notprovide a dead shutoff.


An impulse trap, although small in size, can handle a large volume of condensate. These trapswill work over a great range of steam pressures with no dimensional changes in valve size. These traps can be used on high pressure and superheated steam systems, but will leak steam ifno condensate is present. The valve is not subject to air-binding.


Impulse traps do not provide a dead seal and will leak steam even on very light loadingconditions. Dirt can easily affect the performance because of the small clearance between thepiston and cylinder. Impulse traps will pulsate on light loads causing noise, water-hammer, andmechanical damage. They will not work against back pressures if it is greater than 40 percent ofthe inlet pressure.

THERMOSTATIC TRAPS

The traps in the thermostatic group open or close according to the temperature inside theirbodies. At any given pressure, saturated steam has a certain fixed temperature, but condensateat the same pressure can cool down to a lower temperature. Thermostatic traps detect steamfrom condensate because of this difference in temperature. The valve is operated by athermostatic element which are either balanced pressure type or liquid expansion type.

It consists of a thermostatic element with a valve plug on the bottom of the element. The upperpart of the element is permanently attached so that any movement of the element due toexpansion or contraction must take place at its free end. When the element expands, the valveenters the seat area and seals it off. The element is filled with a alcohol mixture that has a lowerboiling point than water. Thus, the element will expand when it is subjected to steam andcondensate temperatures. This expansion continues until the plug is held firmly in the seat.

The pressure inside the element, created by the expansion of the alcohol, will hold the valvefirmly in the seat until the mixture is cooled and allows the element to contract. The line pressurethen lifts the valve off the seat and allows the condensate and air to escape. Dischargetemperature is less than that of the steam. This type of trap works intermittently. It is thedifference in temperature between the steam and the condensate that operates the trap, by



setting up the difference in pressure between the inside and the outside of the thermostaticelement.

Advantage of This Type

Although this type of trap is usually small in size, it has a large condensate handling capacity. When the trap is cold, the valve is wide open, giving the trap the ability to discharge air onstartup. The trap will not freeze in exposed positions, unless the condensate backs up in theexhaust line due to some malfunction in the system. The trap will automatically adjust itself toany variations in steam pressure up to its designed pressure. The trap is easily maintained.

Disadvantage of This Type

The thermostatic element is made of a very flexible type of material which is easily damaged bythe action of water-hammer and possible corrosion. The trap does not work well in superheatedsystems.


Section 9

Field Piping Guidelines

PIPE ROUTING

The following parameters are typically used to check or perform pipe routings:

• Check proposed pipe routing against civiland architectural drawings for concretewall, masonry block wall, and structuralsteel locations.

• Check proposed pipe routing againstequipment locations, and electrical cableroutings.

• Route the pipe to reduce the quantity ofhangers by allowing the piping to besupported from the building steel.

• Run piping to minimize both the totalfootage and number of field connections.Field connections should be easy toreach and allow for occasional directionaladjustment in either horizontal or verticalaxes.

• Check piping connections to equipment, look at nozzle elevation and orientation,piping size, pressure rating and flange facing style.

• Refer to insulation schedule for thickness and spacing requirements to accommodatemovements.

• Always maintain head room clearances consistent with good engineering practices4 3'-0" minimum clear width for walkways4 6'-8" above walkways per OSHA 1910.37 paragraph(i)4 13'-0" above any traffic, but not below the pipe way structure4 22'-0" at a railroad crossing

• Avoid routing pipe within electrical panel door swing areas

• Avoid placing pipe in any equipment removal areas

• Maintain adequate clearance from the floor to permit easy field erection

• Provide sufficient number of bends per design criteria to accommodate thermalexpansion

• Make sure valves and other in-line devices are accessible for operations andmaintenance

• Trap or drain all steam and air lines

Section 9 Field Piping Guidelines


• Vent all high points in liquid lines

• Drain the low points at all pockets

• Run parallel piping runs together toallow multiple line usage of hangers

• Check proper valve orientation anddismantling space

Consider how the piping will besupported and what types of hangerscan be used. Do not route pipediagonally across the plant. It willoccupy more space and can be difficultto support.

Vent and Drain Requirements

Vents are installed to remove air from fluid systems at their high points. Drains serve toremove fluid from the low points or pockets. Hydrostatic testing of the piping system mayrequire additional vents and drains to be added to support removal of either air or fluid,while the client may have them plugged after the testing to eliminate possible leak paths. Additional drains may be required during startup testing and flushing.

Relief Valve Vent Requirements

Relief blow-offs should always be directed or located away from human traffic, air intakes,or confined spaces.

Instrument Tap Orientation

The major types of instrument taps are pressure, temperature, and flow monitoring. Noneof these connections should be located in the lower half of the horizontal pipe. Thepreferred location is based on a combination of the type of instrument and the system flowmedium (gas, liquid, or steam). Most gases are lighter than air and consequently are bestmonitored with a top connection on a horizontal pipe line. These systems are also subjectto condensation or moisture on the bottom. Liquid or steam on the other hand is bestsuited to a side connection at the centerline because of potential air at the top of the pipeor condensate or dirt on the bottom of the pipe.

Other types of flow control design considerations include:

• Flanges are often required in the header and must be accounted for in the routing.

• Make sure clearances are provided from other pipe and structures.

Field Piping Guidelines Section 9


• Straight runs of piping should be on the upstream and downstream side of the flowelement. A rule of thumb to use if no design information exists is to provide ten (10)diameters upstream and five (5) diameters downstream from the flow element.

Sample points are required to provide operational sampling of the piping fluid. Theyshould be located in sections of the line that will see continuous flow, and should not belocated in stagnant flow areas. It is preferred that these connections be oriented at thehorizontal centerline or slightly above this centerline. Under no circumstance should theconnection be made from the bottom of the pipe.


Section 10

Underground and Embedded Piping Systems

UNDERGROUND PIPING

Underground piping is installed early in the project concurrently with civil foundations, earth work,and electrical duct banks. Prior to beginning any excavation, existing buried commodities mustbe reviewed to identify any potential obstructions. In instances where underground obstructionscannot be avoided, excavation is performed manually or by the use of an air spade or hydrostaticexcavation system.

Excavation activities at operating facilities must be done only with the approval and closeinvolvement of plant operations and maintenance personnel. Excavation permits documentingverification of existing commodity locations is normally required at all Bechtel construction sites.

Typical buried piping systems include:

• Fire protection

• Storm water sewers

• Potable water

• Natural gas

• Drainage piping

Fire protection is usually installed in a ring around the site to encompass the work area with aheader provided for all branches. The system must meet National Fire Protection Codes (NFPA)and any local code requirements. The fire protection system equipment is supplied withUnderwriters Laboratory (UL) or Factory Mutual (FM) approval and must be so identified.

Depending on the type of piping system used, thrust blocks are installed for fire protection pipingat changes in direction, at tees, and at fire hydrants . Thrust blocks provide lateral restraint towaterhammer and loads imposed by water flow. They are usually constructed of poured concreteor concrete block constructed at desired locations after the piping system has been installed andtested.

Storm Water and Drainage systems are installed at the same time as the fire protection system,but require that the slope and elevation of the pipe be maintained and checked per the designdrawings prior to the backfill of the trench. Specified slope tolerances ensure the completedsystem will maintain a self-cleaning fluid velocity and prevent the formation of traps and pockets. The pipe material used for drainage systems may include pre-cast concrete, carbon steel, PVC,or HDPE.

Coatings

Coating and lining systems provide excellent corrosion resistance properties and provide therequired smoothness to maintain flow capacity in the line. External coating systems protect steelpipe by electrically insulating the coated pipe from the environment. When reinforced, thecoatings provide additional resistance to physical damage.

Section 10 Underground and Embedded Piping Systems


Common types of underground pipe coatings include:

• Coal-Tar Enamel

• Coal-Tar Epoxy

• Hot or Cold Epoxy Enamel Applied Tape

Coal-Tar enamel is typically applied in a shop environment. To apply the coating, hot enamel isplaced on the pipe wall surface and then the exterior coating is covered with paint or kraft paper. Pipe shipped or stored at cold temperatures (typically encountered in the winter months) mayrequire a different coating system since the coal-tar enamel is subject to cracking in cold weather.

The Cold-Applied Tape process uses a cold primer and cold-applied tape. This can be used onsteel pipe for soil conditions. Tape with both polyvinyl chloride and polyethylene backings areused. Thickness of tapes vary depending on the overlap and performance conditionrequirements including where mechanical damage may occur due to handling and construction.

Testing of underground piping coatings is done with high voltage, low amperage holiday detectorsand is done immediately prior to backfilling.

Cathodic Protection

This method of protecting underground piping is typically provided when soil resistivity is low. Pipe protection can be provided by either sacrificial anodes or an impressed current system. Thiswill help prevent accelerated corrosion of the underground system.

Cathodic protection systems are usually specialized installations and their design, installation, andinspection are best left to specialists.

EMBEDDED PIPING

The installation of piping systems embedded in concrete should comply with the followinginstallation guidelines:

• Verify top of concrete elevations for floor drains, equipment drains, and clean-outs to ensureembedded piping is properly positioned. Pay particular attention to floor slope requirements.

• Piping that penetrates slabs or walls must be extended beyond the concrete surface to allowsufficient space to make up the next joint.

• The embedded portion of piping systems must be hydrostatically tested prior to concreteplacement.

• Do not embed mechanical joints in concrete unless specifically required by the designdrawings.

• Check project requirements for cutting or modifying reinforcing bar and for added reinforcingat penetrations prior to embedded piping installation.

• As-built embedded piping systems prior to concrete placement.

• Do not secure embedded piping by welding to other piping or to reinforcing bar.


• Ensure that embedded piping is adequately secured so that it will not move during theconcrete placement. See Figures 10-1 through 10-6 for typical support details.

FIGURE 10-1 - TYPE A - SUPPORT ANCHOREDTO MUD MAT

FIGURE 10-2 - TYPE B - PIPE CLAMPSUPPORTED FROM REBAR MAT

FIGURE 10-3 - TYPE C - PIPE SECURED TOREBAR MAT WITH TIE WIRE

FIGURE 10-4 - TYPE D - SUPPORT PIPE FROMREBAR SUPPORT FRAMEWORK

FIGURE 10-5 - TYPE E - PROVIDE SUPPORTFRAME FOR LARGE PIPING

FIGURE 10-6 - TYPE F - PROVIDE CLAMP ANDROD TO SUPPORT PIPE



• Provide sufficient restraint for the piping system to resist floating, movement, or deflection ofthe piping resulting from the concrete placement buoyant forces. Table 10-1 providesapproximate buoyant forces and allowable pipe spans. The suggested allowable spanscalculated based on:

L = [SaZ/1.2F]1/2

Where the following applies to the pipe in question:

Sa = Allowable Stress (1500 psi)

Z = Section Modulus (in3)

F = Greater of Wt or Br (lb/ft)

L = Span (ft)

• Protect all piping openings prior to the concrete placement to prevent concrete from enteringthe system. Plastic or metal caps, expandable test plugs, or wood or metal blind flanges areacceptable. Cloth or paper is not acceptable.

• Protect valves located in the vicinity of the concrete placement by providing a wooden orplastic enclosure around the valve.

• Make sure the embedded piping is properly coated per project requirements prior to concreteplacement.

• All embedded piping testing and welding documentation must be complete prior to theconcrete placement.

• If system connects to a piece of equipment nearby, check equipment location andconfiguration drawings.


TABLE 10-1SUGGESTED MAXIMUM SPANS FOR EMBEDDED CARBON STEEL PIPING

Pipe Size(inches)

Schedule Wt

(lbs/ft)Br

(lbs/ft)L

(feet)1" 40 (STD) 2.05 N/A 9'

80 (XS) 2.48 N/A 9'1 1/2" 40 (STD) 3.60 0.24 11'

80 (XS) 4.40 N/A 11'2" 40 (STD) 5.10 1.00 12'

80 (XS) 6.30 N/A 12'2 1/2” 10S 5.89 3.23 12'

40 (STD) 7.86 0.97 13'80 (XS) 9.50 N/A 13'

3" 10S 7.94 5.69 13’40 (STD) 10.78 2.44 14’80 (XS) 13.11 N/A 15’

4” 10S 11.78 10.95 14’40 (STD) 16.30 5.77 16’80 (XS) 19.96 1.58 16’

6” 10S 23.77 26.62 14’40 (STD) 31.48 16.93 18’80 (XS) 39.86 7.33 20’

8” 10S 36.97 47.46 15’40 (STD) 50.30 32.27 20’80 (XS) 63.20 17.46 22’

10” 10S 55.54 75.89 15’40 (STD) 74.70 54.04 22’60 (XS) 87.10 39.84 24’

12” 10S 76.33 108.79 16’STD 98.60 83.36 24’XS 112.30 67.56 25’

14” 10 98.70 123.70 19’30 (STD) 114.30 105.80 24’XS 129.60 88.26 26’

16” 10 123.80 167.30 19’30 (STD) 141.70 146.80 24’40 (XS) 159.30 126.60 27’

18” 10 152.00 217.70 19’STD 171.80 194.50 24’XS 191.80 171.60 28’

20” 10 182.00 274.60 19’20 (STD) 204.60 248.60 24’30 (XS) 226.80 223.20 28’

22” 10 215.50 337.90 18’20 (STD) 240.30 309.40 23’30 (XS) 265.20 281.00 28’

24” 10 251.20 407.90 18’20 (STD) 278.40 376.70 23’XS 304.90 346.20 28’

WHERE: W t = Total Weight of Pipe and Water in Pipe (lbs/ft)Br = Resultant Buoyant Force Based on 150 lb/ft3 Concrete (Buoyant Force Minus Weight of Empty Pipe) (lbs/ft)L = Suggested Maximum Span (ft)

NOTES: 1. Spans are based on maximum combined bending and shear stress of 1500 psi and a maximum mid spandeflection of 0.1".

2. This table not intended to limit placement of supports wherever special conditions exist.


Section 11

Insulation and Heat Tracing

THERMAL INSULATION

Insulation is defined as any material that resists the transfer of heat energy. The purpose ofthermal insulation is therefore either to keep heat confined in the mechanical system or to keep itexcluded from the system by preventing or resisting heat transfer. Typical insulation details areshown in Figure 11-1.

The four functions ofinsulation for hot piping andequipment are:

• Conserve heat

• Protect personnel

• Maintain temperature forprocess control

• Preventing fluid freezingin cold climates

There are two basic types ofthermal insulation:

• Mass Insulation

• Reflective Insulation

Mass insulation is made upof small pockets or spacesthat trap air or gases that areseparated by solidstructures. The voidsprovide resistance to theheat transfer process.

Mass type insulation includes:

Calcium Silicate which is a compound of lime and silica with reinforcement fibers molded into pipeshapes, sizes, including elbows. It is used in applications with system temperatures up to 1200oF. Even though the dust caused by working with Calcium Silicate may be a safety concern, theinsulation material is more rigid and more durable than other insulating materials.

Mineral-Fiber Insulation which is available in both blankets and shapes. It is made from rock andslag fibers which have been bonded together. It is used in applications with system temperaturesto 1500oF.

FIGURE 11-1 - TYPICAL INSULATION DETAILS

Section 11 Insulation and Heat Tracing


Glass Type insulation is available in several forms including glass wool, fiber board, and feltedglass fibers. Some forms of glass type insulation are designed for temperature services up to1000oF.

Reflective insulation materialsinclude Aluminum or StainlessSteel sheets or foil used for theconstruction of reflectiveblankets. The temperature limitsfor the aluminum materials areapproximately 1000oF. Thestainless steel materials areadequate for temperature rangesup to 1500oF.

The inner layer of insulation isnormally installed as theinsulating material and the outermetal cover is installed to protectthe insulation from damage. Insulating jackets or protectivecovers are usually aluminum orstainless steel sheeting.

Personnel protection insulation isnormally provided on hot pipingthat is not required to beinsulated for designrequirements but which can bereached by a person standing onthe ground or the nearestplatform. Normally personnelprotection insulation is providedon uninsulated piping withoperating temperatures above140oF and within 7 feet of theground or 3 feet from theplatform edges or ladders.

Flange connections typically have removable sections or a flexible blanket assembly placed overthe joint which permit easy future removal. Nameplates, code plates, pipe plugs and blind nipplesshould be left exposed or have a small removable section of insulation placed over them.

Removable insulation covers should be:

• One piece construction wherever possible

• Fabricated in multiple sections when a one piece cover exceeds 60 pounds total weight

• Constructed with edges that butt tightly together to minimize heat loss and provide a cover ofneat finished appearance

• Resistant to water, oil, and steam

FIGURE 11-2 - TYPICAL PIPE INSULATION SECUREMENTDETAILS

Insulation and Heat Tracing Section 11


• Constructed to prevent the entry of fluids or moisture into the internal insulating material

• Constructed to fit snugly around the contours of the component being insulated, includingvalves, flanges, straight pipe, and fittings

• Constructed with no sharp edges or protrusions on the outer surface

Equipment Insulation

Equipment insulation blocks, boards, or blankets are normally attached to the equipment surfacewith joints staggered and the edges tightly butted and sealed with insulation cement, except inthose cases where expansion or contraction joints are provided. Typical equipment insulationdetails are shown in Figure 11-3. Insulation is normally attached by one of the following methods:

• Vendor furnished and installed attachment devices

• Welded attachments installed to secure the insulation

• Stainless steel, copper coated steel, or aluminum steel wire

• Stainless steel or aluminum bands

Insulation Jacketing and Surface Finish

Prior to the installation of the insulation jacketing, the installed insulation must be verified to becomplete and properly installed. Joints provided for thermal expansion or contraction must befilled with insulating mastic material or mineral fiber batting.

The jacketing on both piping and equipment insulation should be fastened with bands whereverpossible. When bands cannot be used due to the piping or equipment configuration, thejacketing may be secured with sheet metal screws. Typical details for securing insulation topiping is shown in Figure 11-2.

Jacketing joints and openings must be sealed with a caulking material when the insulation systemcontains a moisture or vapor barrier and the system is installed outdoors. Removable insulationjacketing must overlap adjacent pipe by an amount equal to the insulation overlap.

ACOUSTICAL INSULATION

Acoustical insulation, like thermal insulation has two layers. The absorptive layer typicallyconsists of a glass or mineral fiber and the barrier layer being loaded vinyl, such as Sound Fabmanufactured by Sound Coat Company or loaded mastic, such as Muffl-Lag manufactured byChildress Products Company. Some installations will have thermal insulation already existing andin those instances, the acoustical absorptive layer is applied directly over the thermal insulationwithout modifying the thermal system.

Section 11 Insulation and Heat Tracing


HEAT TRACING

Four typical heat trace systems include:

• Electrical Heat Trace

• Bare Steam Trace

• Heat Transfer Cemented Steam Trace

• Hot Water

FIGURE 11- 3 - TYPICAL EQUIPMENT INSULATION DETAILS

Insulation and Heat Tracing Section 11


Electrical heat trace systems are installed by simply wrapping electrical trace around piping andequipment to provide mild winterization protection. Some high temperature piping systemsrequire the use of a layer of insulation between the pipe and heat trace to avoid damage to theheat trace.

Bare Heat Transfer Cemented Steam Trace and Hot Water Trace systems are applied by placingand banding tubing along the piping runs and looping the tubing around equipment and valves. The function of the steam trace is to maintain the process fluids at temperature levels that provideproper flow characteristics.

Insulation Materials

Insulation materials made from asbestos and certain other fibers can pose serious health hazardsand special precautions must be taken when handling these materials. Check the manufacturer’sMaterial Safety Data Sheet (MSDS) for special handling instructions.


Section 12

Hangers and Supports

GENERAL

Pipe supports are designed to restrain piping in relation to an axis. The X-axis by normalconvention is north and south, the Y-axis is up-down, and the Z-axis east-west. They may becombined into several categories for pipe supports:

• Gravity - load of pipe and insulation

• One Axis - loading along one axis with either positive and/or negative values

• Two Way - loading in two planes both positive and negative directions

• Anchor - loads in three planes along with resistance to moments from three axes

Rod Hangers

The rod hanger is a simple gravity support using a threaded rod between the structure and thepiping. This hanger provides an inexpensive method of supporting most pipe sizes. Figure 12-1shows various types of rod hanger components that are typically used with this type of support.

C-CLAMP BEAM CLAMP WELDED ATTACHMENT

PIPE CLAMP ADJUSTABLE RING HEAVY DUTY PIPE CLAMP

FIGURE 12-1 - ROD HANGER COMPONENTS

Section 12 Hangers and Supports


Spring Can Supports

A Spring Can support is a rod hanger with a spring inserted. This hanger provides the samerelative load carrying capacity in both the cold and hot conditions where thermal growth would bein the vertical axis. Manufacturers generally supply spring cans in six different styles to suit anyconstruction condition or orientation. As shown in Figure 12-2, spring can styles vary by heightspace, rod type, and access conditions available as follows:

• Type A are for unrestricted height spaces

• Type B are suited for limited spaces

• Type C is also utilized in limited space with a single plate structural attachment

• Type D places the spring can above the supporting steel with adjustment from the top

• Type E places two spring cans above the supporting steel in a trapeze arrangement

• Type F are used for floor mounted supports

FIGURE 12-2 - SPRING CAN APPLICATIONS

Hangers and Supports Section 12


• Type G are designed to use two rods like a trapeze style support

Spring cans are shipped to the job with both the hot and cold load shown and travel stopsinstalled to maintain the cold load setting until the completion of startup activities or turnover tothe client.

Frame or Box Hangers

A Frame or Box hanger is made up fromsmaller structural steel shapes that arewelded together to provide support inone or more axes. They are primarilyused as two-way loading restraints. Thelabor and material cost for this type ofsupport can be higher than the twoprevious styles. A typical two-way boxhanger is shown in Figure 12-3.

Anchors

Anchors are normally weldeddirectly to the pipe system toprovide a three-way directionand three-way rotationrestraint and anchorage forthe piping system.

Sway Struts

A Sway Strut is amanufactured support. Thishanger will provide supportin both positive and negativedirections in one plane whileallowing lateral movement. A typical sway strut detail isshown in Figure 12-4.

FIGURE 12-3 - TWO-WAY RESTRAINT BOX HANGER

FIGURE 12-4 - SWAY STRUT ASSEMBLY



Shock Arrestors

Mechanical and HydraulicShock Arrestors bothprovide movement restraintduring dynamic loadingwhile allowing the pipeunrestrained motion undernormal plant operatingconditions. Themechanical snubber actslike a axial clutch thatconverts linear motion intoangular acceleration.

The hydraulic snubber operates on fluid velocity. When the motion of the pipe exceeds a setpoint value, the velocity of the fluid in the snubber is stopped and the assembly becomes a rigidstrut. A typical hydraulic shock suppressor detail is shown in Figure 12-5. Both these supportsare recommended for piping subjected to shock, sway, or vibration caused by earthquakes, waterhammers, or other transient forces.

FIGURE 12-5 - HYDRAULIC SHOCK SUPPRESSOR

PIPE STRAP SPRING CUSHION HANGER PROTECTION SADDLE

SADDLE SUPPORT STANDARD U-BOLT RISER CLAMP

FIGURE 12-6 - HANGER COMPONENTS



Hanger Components

A variety of hanger components are available to support piping systems. Each component isdesigned for a specific function and examples are shown in Figure 12-6.

Pipe Guides and Rollers

Pipe guides and rollers provide gravity support while still allowing piping system thermalexpansion and contraction. Typical guide and roller details are shown in Figure 12-7.

Socket Clamp Assemblies

Socket clamps support and restrain bell and spigot piping connections and are typically used infire protection systems. Typical socket clamp assembly details are shown in Figure 12-8.

ROLLER CHAIR PIPE GUIDE PIPE SLIDE

FIGURE 12-7 - PIPE GUIDES AND ROLLERS

PIPE ANCHOR 1/4 BEND SPIGOT END ANCHOR

1/8 BEND ANCHORS

FIGURE 12-8 - SOCKET CLAMP ASSEMBLIES



PIPE SUPPORT MATERIAL

Structural steel is the most common material used for pipe supports. This section will definesome of the common codes and standards associated with structural steel and review somecommon materials, shapes, and connections.

Structural Steel Codes and Standards

The following codes and standard associations cover the majority of requirements for bothstructural steel and pipe supports.

American Institute of Steel Construction

AISC is a nonprofit trade association representing and serving the fabricated structural steelindustry of the United States.

The AISC publishes the Manual of Steel Construction, the Specification for the Design,Fabrication and Erection of Structural Steel for Buildings, the Code of Standard Practice for SteelBuildings and Bridges.

American Iron and Steel Institute

AISI Specification for the Design of Cold Formed Steel Structural Members. This specificationcovers the design of structural members which are cold formed to shape from carbon and lowalloy steel sheet or strip used for load carrying purposes in buildings. There is a similarspecification for cold formed stainless steel structural members.

Steel Structures Painting Council

SSPC produces a two volume manual. Volume I covers good painting practice and Volume 2covers painting systems and specifications.

Common Material Grades

The AISC Specification for the Design, Fabrication and Erection of Structural Steel for Buildingsstates that structural steel must conform to any one of a number of ASTM grades of steel.

The carbon range for most of the structural steels is 0.15-0.29 percent (mild carbon steel), withmanganese up to 1.60 percent.

ASTM A36 (structural steel) is a weldable mild carbon steel and has a guaranteed minimum yieldof 36 ksi for all shapes and for plates up to 8 inches in thickness. This grade of steel isconsidered to be the workhorse steel and is the most common steel in use today.

ASTM A529 (structural steel with a 42 ksi minimum yield point) is a higher strength carbon steelavailable in plates and bars up to 1/2 inches in thickness or diameter and shapes. Where 0.02percent copper is specified, A529 has an atmospheric corrosion resistance equal to twice that ofstructural carbon steel without copper. This steel is used in the relatively light structural membersof standard steel buildings.

ASTM A242 (high strength, low alloy structural steel) is a very broad specification stipulatingminimum mechanical properties and limits the maximum carbon and manganese for weldability. The specification is limited to material up to 4 inch plate. Generally, these steels have enhanced



atmospheric corrosion resistance of at least two times that of carbon steels with copper, or fourtimes carbon steel without copper.

When self weathering (unpainted) steels are specified, A242 is normally specified with the addedrequirement that the steel have from four to six times the corrosion resistance of carbon steel. Self weathering is the term used to describe a steel that has chemical properties allowing it toform a very dense and tight oxide (rust), which in effect seals the base metal from furtheroxidation and therefore affords a means (other than a coating) of protecting the steel from furthercorrosion. For this to occur, the steel must be exposed to the elements (alternately dry and wet). The tight oxide, or patina as it is called, gives a deep-brown appearance and is frequently used instructures for aesthetic reasons, as well as from the low maintenance point of view.

ASTM A441 (high strength, low alloy structural manganese vanadium steel) is a weldable steelwith reasonable moderate carbon and manganese content with an added alloy to increasestrength. A441 is suitable for welding, riveting, or bolting. The atmospheric corrosion resistanceof this steel is about twice that of carbon steel. This specification is limited to material up to 8inches in plate and bar thicknesses. For thicknesses over 4 inches, the yield point is 40 ksi.

ASTM A572 (high strength, low alloy columbium-vanadium steels of structural quality) covers sixgrades or strength levels for shapes, plates, sheet piling, and bars. Grades 42 and 50 areintended for bolted or welded construction of all structures, while grades 60 and 65 are intendedfor bolted construction of bridges and for welded or bolted construction of other applications. Available grades vary for groupings of shapes and thicknesses of plates. When 0.20 percent minimum copper is specified, the A572 steels provide atmospheric corrosion resistance similar toA242 and A441 steels.

ASTM A588 (high strength, low alloy structural steel with 50 ksi minimum yield point to 4 inchesthick) was specifically created to maintain a higher yield point level for heavier shapes and thickerplates. The specification covers shapes, plates, and bars for welded and bolted construction. Itis intended primarily for use in welded bridges and buildings where savings in weight and addeddurability are important. The atmospheric corrosion resistance is about four times that of carbonsteel without copper. The material makes available all shapes at a 50 ksi yield stress level. Plateyield points vary from 42 ksi to 50 ksi, depending upon the thickness of the material (the 50 ksiyield applies to material up to 4 inches in thickness). Similar to A242, this grade of steel is alsoused for self-weathering applications. A588 also has enhanced toughness characteristics(resistance to sudden fracture in the presence of notches, dynamic loads, and reducedtemperatures).

ASTM A514 (high yield strength quenched and tempered alloy steel plate, suitable for welding) isa heat treated steel in plates in thicknesses up to 6 inches and is primarily intended for use inwelded bridges and other structures.

ASTM A53 (welded and seamless pipe) grade B covers hot formed seamless and welded blackand hot dipped galvanized round steel pipe in nominal sizes 1/8 inch to 26 inches inclusive withvarying wall thicknesses. Grade B furnishes a guaranteed minimum yield of 35 ksi, although 36ksi is used in the AISC Manual design tables. Type E (electric resistance welded) and type S(seamless) are both provided. Both are suitable for welding.

ASTM A500 (cold formed welded and seamless carbon steel structural tubing in rounds andshapes) covers steel round, square, rectangular, or special shaped structural tubing for welded orbolted construction. The tubing is provided in welded sizes with a maximum periphery of 64



inches and a maximum wall thickness of 0.500 inches, and in seamless with a maximumperiphery of 32 inches and a maximum wall thickness of 0.500 inches. It is produced in threegrades, A, B, and C, and, depending on whether it is round or shaped (square, rectangular, orspecial) tubing, the yield point varies from 33 ksi to 50 ksi. Under the specification, the maximumsizes would be about 20 inches diameter round, 16 by 16 inches square, or 20 by 12 inchesrectangular (although these maximum sizes may not be produced).

ASTM A501 (hot formed welded and seamless carbon steel structural tubing) covers square,round, rectangular, or special shaped structural tubing for welded or bolted construction. Squareand rectangular (common sizes 3 inches by 2 inches to 10 inches by 6 inches) tubing is furnishedin sizes 1 inch to 10 inches across the flat sides with wall thicknesses 0.095 inches to 1.000 inch,depending on size, and round tubing is furnished in nominal diameters 1/2 inch to 24 inches withnominal (average) wall thicknesses 0.109 to 1.000 inch, depending upon size.

ASTM A618 (hot formed welded and seamless high strength, low alloy structural tubing) coversthree grades of square, rectangular, round, and special shaped tubing for welded and boltedapplications in buildings and bridges. For enhanced corrosion resistance, grades I and III arespecified.

ASTM A570, grades 45 and 50 (hot rolled carbon steel sheets and strip, structural quality).

ASTM A606 (steel sheet and strip, hot rolled and cold rolled, high strength, low alloy, with im-proved corrosion resistance).

ASTM A607 (steel sheet and strip, hot rolled and cold rolled, high strength, low alloy, columbiumand/or vanadium).

Steel Product Classification

In response to a recognized need to improve and standardize the designation for structural steelshapes, the Committee of Structural Steel Producers of AISI developed standard nomenclaturefor structural steel shapes. These designations enable all mills to use the same identification inordering, billing, and specifying. These designations for various types of shapes are presented inthe AISC Manual of Steel Construction.

Sheet piling sections begin with the letter P for piling, with the succeeding letter or letters definingthe configuration followed by a two digit number, which indicates the weight of the section inpounds per foot. H-piles are designated by HP followed by the section depth, and the weight ofthe section in pounds per foot.

Steel plate is designated by all dimensions in inches, fractions of an inch, or decimals of an inch. As an alternative, thickness may be specified in pounds per square foot. The semifinishedproduct of the mill goes through rolling mills to produce structural steel shapes, plates, bars,pipes, tubes, or sheet.

The W-Shape Section is the most commonly used shape; it has two horizontal elements, calledflanges, and a vertical member, referred to as a web. This shape was previously called a wideflange shape, and was designated by the symbol WF. Essentially, W shapes have the inner andouter edges of the top and bottom flange parallel. The same inside to inside of flange dimensionis maintained (with a slight variation by groups) for a given depth category of shape. The



designation W 24 x 76 means a W shape, nominally 24 inches deep (outside to outside of flange)and weighing 76 pounds per lineal foot of span.

The S-Shape Section is a rolled shape that also has two parallel flanges and a web. However,the inner surfaces of the flange have a slope of approximately 162/3 % (2 inches in 12 inches). These shapes were previously called American Standard beams. The designation S 24 x 100means an S shape 24 inches deep (outside to outside of flange) and weighing 100 pounds perlineal foot of span. Some of the S24 and S20 groupings have depths in excess of 24 inches and20 inches, respectively.

The American Standard Channel Section is a cross section that was formerly designated by aturned symbol depending on whether the section's web was vertical or horizontal. However, thesymbol C is now used regardless of the orientation of the web. The inner surface of both flangesof the C shape have a slope of approximately 16 2/3 percent (2 inches in 12 inches). Thedesignation C12 x 20.7 indicates an American Standard Channel with a depth (outside to outsideof flange) of 12 inches and a weight of 20.7 pounds per lineal foot. To indicate the position of thechannel (web horizontal or vertical), the engineer may indicate the appropriate position by the oldsymbol in addition to the usual designation.

The letter HP indicates bearing pile shapes having two parallel flanges with parallel flangesurfaces and a web element. The web and flange thicknesses and the width of flange and depthof section are nominally equal in the HP shape. A HP 14 x 73 designates an HP shape nominally14 inches in depth (outside to outside of flange) and 73 pounds per lineal foot.

The letter M refers to shapes that cannot be classified as W, HP, or S shapes. Similarly, MCdesignates channels that cannot be classified as American Standard Channels. These shapesare not as readily available as W, S, HP, or C shapes.

Angle Shapes have two legs of rectangular cross section that are normal to one another. Theinner and outer surface of each leg is parallel. Equal leg or unequal leg angles are available. The thickness of each leg is the same. The symbol L is used to designate an angle shape. L 6 x4 x 5/8 designates an unequal leg angle whose large leg is 6 inches long and 5/8 inches thick andwhose short leg is 4 inches long and 5/8 inches thick.

Structural Tees (WT or ST Sections) are obtained by splitting the webs of various beams. Theymay be split from a W shape (WT) or from the S shape (ST). These shapes have a singlehorizontal flange and a web or stem. WT 12 x 38 designates a structural tee cut from a W shapewhose depth (tip of stem to outside flange surface) is nominally 12 inches and weighs 38 poundsper lineal foot.

Bars are generally classified as 6 inch or less in width and 0.203 inch and over in thickness. These sections can be rectangular (flat), circular, or square. An example is Bar 2 1/2 x 1/2indicates a flat bar 2 1/2 inches wide and 1/2 inch thick. Widths are normally specified in 1/4 inchincrements and thicknesses are normally specified in 1/8 inch increments.

Plates are rectangular in shape, generally over 6 inches in width and 0.230 inches and over inthickness or over 48 inches in width and 0.180 inch and over in thickness. Sheared plates arerolled between horizontal rolls and trimmed (sheared or gas cut) on all edges. Universal plates(UM) are rolled between horizontal and vertical rolls and trimmed (shear or gas cut) on the endsonly.

Types of Connectors



There are two basic types of structural steel connecting methods:

• Bolting

• Welding

Sometimes bolting and welding are combined on a single connection.

Welding is as economical as any mechanical means of connecting. AWS D1.1 is the nationallyaccepted specification that covers all the facets of welding in the United States. It is referred to inthe AISC Specification, as well as in most other specifications and codes.

The two basic types of structural steel bolts include, the "common" or machine bolt (ASTM A307)and the high strength bolts (ASTM A325 and A490). ASTM A193 bolts may also be specified forsome pipe hangers. The chemical and physical properties of bolting materials are found in theapplicable ASTM Specification. The AISC Manual includes a reprint of Specification forStructural Joints Using ASTM A325 or A490 Bolts. These specifications cover the hardwarerequirements, allowable working stresses, installation procedures and methods, as well asinspection procedures. Table 12-1 shows typical tensile strengths for common bolting materials:

Common bolts are also referred to as A307, machine, unfinished, or rough bolts. These boltsshould meet ASTM A307, Specification for Low Carbon Steel Externally and InternallyThreaded Standard Fasteners. This type of bolt is significantly cheaper than high strength bolts.They generally have heads and nuts with no marking on the head surface. The bolts areavailable in 1/4 to 4 inch diameter.

Threads are unified coarse thread series (UNC Series), class 2A (see ANSI B1.1, Unified ScrewThreads). Common bolts are easily tightened by using spud wrenches. The tension induced byturning is usually low, and it is usually considered that no clamping force is developed.

The most common mechanical fastener is the high strength A325 bolt with heavy hexagonal nutsand having heavy hexagonal heads. These bolts have shorter thread lengths than other bolts. A325 bolts come in three types.

Type 1 is produced from a medium carbon steel (available sizes are from 1/2 inch to 1 1/2 inch indiameter).

TABLE 12- 1 - STRUCTURAL BOLTING STRENGTHS

BOLT TYPEMIN YIELDSTRENGTH

MIN TENSILESTRENGTH

A307 60 ksi

A325 (to 1" dia.) 92 ksi 120 ksi

(1 1/8" - 1 1/2") 81 ksi 105 ksi

A490 125 ksi 150 ksi

B7 105 ksi



Type 2 is produced from low-carbon martensite steel and is limited to 1/2 inch to 1 inch diametersizes. This type should not be hot dipped galvanized.

Type 3 is produced from steels with self weathering characteristics comparable to ASTM A588and A242 steels and are available in sizes from 1/2 inch to 1 1/2 inch in diameter.

Identifying marks on the heads of each of the three types of A325 bolts distinguish them. At theoption of the manufacturer, Type 1 bolts are identified by the mark "A325" and the manufacturer'ssymbol and by three radial lines 120° apart. Type 2 bolts are identified by three radial lines 60°apart. Type 3 bolts are identified by the mark "A325" underlined and, at the option of themanufacturer, any other additional marks to identify the bolt as a self weathering type.

The A490 bolt is stronger than the A325 bolt and is produced from an alloy steel. A490 bolts aremarked by "A490" and the manufacturer's symbol.

The heavy hexagonal nuts for A325 bolts are similarly marked for identification on at least oneface. These marks are the manufacturer's symbol and the number "2" or "2H," by three equallyspaced circumferential lines or by the mark "D" or "DH." The nuts for A325 type 3 bolts aremarked on one face by three circumferential marks and the number "3" in addition to any othermarks desired by the manufacturer. A490 nuts are marked by "2H" and the manufacturer's markor by "DH." Washers for A325 type 3 bolts bear the mark "3" near the outer edge of one face andany other marks desired by the manufacturer.

All high strength bolts (HSBs) are heat treated by quenching and tempering. High strength boltsinstalled in bearing connections not subject to direct tension are only required to be brought to asnug tight condition and do not require any specific pretensioning. A snug tight condition isdefined as sufficient tightening to bring the two faying surfaces of the bearing connection intocontact without the evidence of a gap.

HSBs that are used in slip limited connections and connections subject to direct tension arerequired to be pretensioned. This pretension, induced by nut rotation, produces a high clampingforce, which allows the contact surfaces to carry loads solely by friction. With this pretension,there will be little or no increase in internal bolt tension when a load is applied to the connection. Tightening may be accomplished by direct tensioning, turn of the nut, torque wrenches, or loadindicating washers.

Torque control bolts are also commonly used for high strength bolts that require pretensioning. These bolts are supplied with a spline that twists off at the predetermined torque required topretension the bolt.

All HSB dimensions conform to ANSI B18.2.1, American National Standard for Square and HexBolts and Screws and the heavy hex nut dimensions conform to ANSI B18.2.2. Threads areUnified Coarse Thread Series as specified by ANSI B1.1, American National Standard forUnified Screw Threads and have class 2A tolerances for bolts and class 2B tolerances for nuts. Dimensions of the washers conform to those of the Specification for Structural Joints Using ASTMA325 or A490 Bolts issued by the Research Council on Riveted and Bolted Structural Joints ofthe Engineering Foundation. Unless otherwise specified, washers are circular.

A second basic specification covering HSBs is entitled Structural Joints Using ASTM A325 orA490 Bolts, which is approved by the Research Council on Riveted and Bolted Structural Joints(RCRBSJ) of the Engineering Foundation. This specification is endorsed by both AISC and the



Industrial Fasteners Institute (IFI). The specification covers the design and assembly of structuraljoints using high strength bolts. The AISC Specification dealing with HSBs conforms to theRCRBSJ specification. This specification covers:

• The specification requirements for bolts, nuts, and washers

• The dimensions of the bolts, nuts, and washers

• Bolted parts

• Permissible joint surface coatings (paint is permitted without consideration as to type inbearing joints and certain contact surface coatings are permitted with friction joints)

• Design stresses for applied tension, shear, and bearing

• Acceptable installation procedures which include the minimum tension corresponding to thesize and grade of fastener

• Required inspections

Oversized and Slotted Holes

All standard holes for HSB should be 1/16 inch greater than the nominal bolt diameter. The holescan be punched (provided the thickness of material is no more than 1/8 inch greater than thenominal bolt diameter), sub-punched and reamed or drilled.

Oversized holes for HSB are not allowed to be more than:

• 3/16 inch greater than the nominal bolt diameter for bolts equal to or less than 7/8 inch indiameter

• 1/4 inch greater than the nominal bolt diameter for 1 inch diameter bolts

• 5/16 inch greater than the nominal bolt diameter for 1 1/8 inch and greater diameter bolts

Oversized holes can be used in any or all plies of slip limited connections. Hardened washersshould be used over oversized holes in an outer ply.

Short slotted holes are nominally 1/16 inch wider than the nominal bolt diameter, and have amaximum length 1/16 inch greater than the maximum allowable oversize hole size. Short slottedholes may be used in any or all plies of both slip limited and bearing type connections. In bearingconnections, the slots should be normal to the direction of loading. In slip limited connections, theslots may be in the direction of loading. Hardened washers must be used over exposed shortslotted holes.

Long slotted holes are also nominally 1/16 inch wider than the nominal bolt diameter and have alength larger than 2 1/2 times the nominal bolt diameter. In bearing connections, the slots shouldbe normal to the direction of loading. These slots may be used in slip limited connectionsregardless of direction of loading. A minimum 5/16 inch thick plate structural steel grade washer orcontinuous bar having standard holes completely covering the slot should be used where longslotted holes are used on an outer ply of the connection. If hardened washers are required, theymust be placed over the outer surface of the plate washer or continuous bar. The slots may beused in only one of the connected parts of either bearing or slip limited connections at anindividual contact surface.



Bolting Installation Procedure

Both ASTM A325 or A490 bolts may be installed by any of the installation methods mentionedpreviously. Tightening may be done by turning either the bolt head or the bolt nut and preventingthe unturned element from turning. All fasteners in a connection should be tightened to theminimum tension called for in the specification.

Turn of the Nut Tightening

The turn of the nut tightening method is a strain control procedure, as contrasted with a torquecontrol procedure (as is the case with the torque wrench, torque control bolt or calibrated wrenchmethods). The effectiveness of the method depends on the uniformity of the starting point fromwhich rotations of the turned element (usually the nut) are measured. This starting point is calledthe snug tight position. This position is defined as the position at which the faying surfaces of theconnection are in full contact and no gap is present. After the snug condition is achieved, furthernut rotation results in bolt elongation or deformation, which produces the required clamping force. Required nut rotations are stipulated in the specification.

The normal bolt tightening procedure is to bring enough bolts into a snug tight condition so theconnection surfaces have good contact. Additional bolts are then placed in the remaining holesand these bolts are also brought to a snug tight condition. All bolts are then tightened by theamount prescribed by the specification. The tightening procedure should systematically progressfrom the most rigid part of the connection to the free edges. To retain a uniform level ofdeformation in all the bolts, the required nut rotation is different for different bolt lengths.

This method of bolt torquing is the least consistent and requires the highest intensity of inspectionto verify proper torquing since the inspection must be done at the time of tightening.

Calibrated Wrench Tightening

When using calibrated wrenches to tighten a connection, efforts must taken to ensure the torquewrench is properly calibrated. This installation method is one of torque control. The tighteningprocedure is further checked by verifying during actual installation that the turned element rotationfrom snug position is not greater than the prescribed amount. The identical recommendedsequence of tightening designated for the turn of the nut method is prescribed for this method ofinstallation.

It is recommended that the wrench be used to verify previously tightened bolts which may haveloosened by the tightening of other bolts in the same connection. This retightening is notconsidered to be reuse of the bolt. A325 bolts may be reused, but A490 and galvanized A325bolts may not be reused after pretensioning.



Direct Tension Tightening

Direct tension devices pull the bolt to apply the required pretension to the bolt. An example of adirect tension system is the Huck Bolt tensioning system.

Torque Control Bolts

Torque control bolts are the easiest bolting system to install, torque, and inspect. Using a lightweight electric torque wrench, the bolts are installed and tightened. When the required boltpretension is achieved, the twist off wrench attachment breaks off ensuring proper tightening.

Bolt Inspection

The inspection of bolts installed by the turn of nut or calibrated wrench method is usually made atthe time of installation to ensure that the proper procedure is used. An additional inspectionmethod is through the use of an inspecting wrench (a torque or power wrench), which can beadjusted in the same manner as described for calibrated wrench tightening. With the directtension indicator, inspection is also made at the time of installation.

CONCRETE ANCHOR BOLTS

Concrete anchor bolts are used to fasten hanger base plates and other commodities to concretewalls and floors. Typically, a hole is drilled into the concrete and the anchor is set tomanufacturers directions. There are several suppliers of concrete anchor bolts with a variety ofstyles. Construction site installation specifications or instructions must be followed when installingany type of concrete anchor. Three typical concrete anchor bolting methods include:

• Concrete Expansion Anchor

• Adhesive Bonding

• Maxi-Bolts

To install a concrete expansion anchor, a hole is drilled in the concrete that is only slightly largerthan the anchor bolt diameter. After the hole is drilled, it should be checked for proper depth,angularity, and cleanliness. The anchor is typically inserted by lightly hammering the anchor intothe hole. A protective device should be used on the threads to prevent damage whilehammering. After the anchor is set in the hole, the base plate is placed over the anchors and theanchor nuts tightened. The bolt anchors itself in the concrete hole by the expansion of thewedges at the bottom of the anchor bolt when the anchor nut is tightened.

Adhesive anchors are installed in a similar manner as expansion anchors. The anchor hole isdrilled to a prescribed size, and the hole is filled with a bonding compound or chemical cartridge. The anchor bolt is then inserted into the hole per manufacturer recommendations. Theadvantage of this type of anchor include:

• There are fewer mechanical components involved

• The user can be much surer of obtaining the desired holding capacity when the bolt is set

• The exact location of the anchor bolt holes is not critical



Maxi-bolts are also installed in a similar manner as expansion anchors except that a seconddrilling operation is performed that cuts a conical shape at the bottom of the hole. This conicalshape accepts the maxi-bolt sleeve wedges that expand when the bolt is tightened and providethe holding force that secures the bolt. This particular anchor is called a "ductile anchor". Thismeans that failure of the anchor system will occur in the anchor bolt itself rather then from anchorwithdrawal or pull-out from the concrete as can happen with the previous two systems.

Do not mix different styles of concrete anchors on the same baseplate. If possible, it is alsorecommended that the project only use a single type of concrete anchor to reduce tooling andtraining.

HANGER INSTALLATION GUIDELINES

• Check that the correct materials and sizes are installed.

• Check that the installation specification tolerances are satisfied.

• Check that the location and orientation of the pipe is correct.

• Check that pre-engineered components are installed per supplier instructions.

• Install spring cans with the travel stops in the cold load setting

• Verify that material substitutions are acceptable such as:4 Larger hanger rod sizes4 Larger structural shapes4 Thicker plate materials

• Locking devices should be installed on all bolted connections, by methods such as:4 Double nuts4 Half or jam nuts4 Staking4 Locking nuts

• Welding substitutions are normally allowed by installation specifications. One example wouldbe placing the weld metal on the inside of a wide flange rather than on the outside of theflange. Even though the weld symbol on the hanger drawing pointed to the outside of theflange.

LINE BALANCING

This process sets the hanger loads at the design cold load setting position for critical systems asspecified in the design documents. The process involves using several dynamometers tomeasure the actual loads at the hangers. A typical set-up is as follows:

• Verify all rigid supports are carrying a load.

• Verify that all piping is insulated and at ambient temperature. Water systems should be filled.

• Verify that the spring cans are at their cold load setting with the travel stops removed.

• Install the dynamometers at the first three consecutive rigid supports, counting from theterminal end.



• Adjust the tension at each dynamometer until all are carrying the design cold load as indicatedon the support drawing.

• The readings should be within plus or minus five percent of their design load reading, if not,adjust the tension in the adjacent support within the plus or minus 5 percent goal.

• With all the dynamometers reading their design goal, check and adjust the closest spring canif needed.

• Recheck the dynamometers on the end and adjust if required.

• Transfer the load from the first dynamometer to the hanger by adjusting or shim as needed.

• After the load transfer, check the other supports again and if within range, remove thedynamometer and proceed to the next hanger.

• Set-up and adjust the next hanger down the line. Repeat for the second and third andcontinue the process on down the line. When branches exist, do one branch at a time. Branches less than 2 inch are generally excluded from the balancing process.

Pump Alignment

Pump alignments are easier when the first few piping supports closest to the pump areadjustable. If a rigid hanger is within the first few supports, have the hanger built with larger gapsaround the pipe and position the pipe correctly with shims. The shims should only be tack weldedto allow for possible future modification during pump alignment.


Section 13

Cleaning and Flushing Methods

MAINTAINING CLEANLINESS DURING CONSTRUCTION

The following guidelines should be followed to maintain system cleanliness during fabrication,installation, and rework operations:

• To keep a system clean, start with clean materials. During work operations, keep thematerials in a clean condition.

• Apply rust preventatives to the internal surfaces of carbon steel components. Preventativesmust normally be removed prior to turnover.

• Keep openings into components sealed when work is not actually in progress.

• Perform localized cleanup after completing work operations and prior to reclosing the system.

• Protect clean systems in the vicinity of foreign matter or dirt producing work operations. Thiscan be done by establishing clean areas and by using internal dams or external encapsulationwhen systems are opened.

• Establish a foreign object and access control procedures for clean areas.

• Immediately remove all visible metal particles or chips after cutting.

• Do not use flame cutting in areas where slag may blow into inaccessible surfaces.

• Do not cut pipe in a vertical position if there is a possibility of cutting chips falling intoinaccessible areas.

• Clean grinding dust from a ground out area prior to breaking through the wall or root pass toprevent the dust from entering the clean system.

• Use magnetic drill bits to drill holes in carbon or alloy steel pipe to minimize the entry of metalparticles. Frequently clean holes during the drill operation.

• Use hole saws when cutting chips cannot be easily removed form internal surfaces. Holesshould be cleaned just prior to breaking through and the plug should be immediately beremoved.

• Clean the ends of threaded pipe to remove lubricant and metal chips at the completion ofthreading.

• Provide an oil-free air blow of all field fabricated piping assemblies, including valves, toremove loose foreign material.

• Seal the openings in completed field fabricated piping assemblies until installed. Providedesiccant on the inside of the completed pipe assembly if required by the projectspecifications.

• Prior to fitting or bolting up flanged or other mechanical joints, clean flange faces of millvarnish or other preservatives.

• Cover tack welded pipe joints to prevent the entry of dust until the joint is to be welded out.

• Follow access control and foreign object control procedures when working on clean systems.

Section 13 Cleaning and Flushing Methods


Cutting Lubricants

Cutting lubricants can have a detrimental effect on a number of critical process systems includingvacuum, oxygen, and argon systems. Wherever possible, lubricants on critical systems should beremoved after the completion of cutting, threading, drilling, or hole sawing. If there is a possibilitythat the lubricant will remain in the system, the type of lubricant used should be approved by theengineer or the manufacturer of the affected equipment.

In general, lubricants used on stainless or carbon/alloy systems should meet the following criteria:

• Contain less than 1% by weight total organic and inorganic halogen (chloride, fluoride,bromide, and iodine)

• Contain less than 200 ppm by weight of inorganic halogen

• Contain less than 1% by weight sulfur

• Contain less than 1000 ppm by weight low melting point metals (lead, bismuth, zinc, mercury,antimony, and tin). No individual low melting point metal must exceed 200 ppm. Mercurymust not exceed 50 ppm.

Ordinary oil based cutting lubricants may be used on non-critical carbon and alloy steel systems. The cutting lubricants used on lube oil and hydraulic systems must be compatible with the oilsnormally used during system operation.

Desiccants

Desiccant bags are used to control the humidity level in enclosed systems. The bags arenormally placed in a perforated container attached to the pipe end cap. The container is notnormally allowed to come in contact with the interior surface of the pipe. Humidity indicating cardsshould also be placed at an opening remote from the desiccant bag location. A transparentplastic end cap is used to permit monitoring of the card. The location and number of desiccantbags should be marked on the outside of the pipe or on the end cap.

The quantity of desiccant required may be computed as follows:

U = 1.2V

Where:

V = Volume of the interior system in cubic feet

U = Units of desiccant which is defined as the quantity of desiccant that will absorb 3.0grams of moisture at 20% relative humidity with air temperature at 77 oF as statedby the manufacturer.

The desiccant used should consist of nondeliquescent, nondusting, chemically inert, dehydratingagents. Desiccants satisfying military specification MIL-D-3464, Type II satisfy this requirement. The desiccant should be provided in bags and contain less than 0.25% halogen. The bagsshould be puncture, tear, and burst resistant. If the dessicant bag is opened inside a pipingsystem, the system should be immediately cleaned to remove the dessicant material.

Cleaning and Flushing Methods Section 13


Cleanliness Requirements for Field Purchased Materials

Stainless steel materials must be delivered to the site in a "metal clean" condition and thesurfaces must be free of particulate foreign material such as metal particles, chips, weld slag,filings, grinding dust, or rust. Surfaces should also be free of organic films and foreign materialssuch as oils, grease, paints, and nonsoluble preservatives or inhibitors.

Carbon steel and alloy steel materials should be free of particulate foreign materials (metalparticles, chips, weld slag, or filings). Thin, nonflaking, soft, scattered rust film is permissible,however, hard rust, mill scale, or heavy rusting is not acceptable since it will be more difficult toclean at the site and will increase construction costs. The pipe surfaces should also be free oforganic films and foreign materials such as oils, grease, and paints. A water soluble, inorganicrust preventative coating (such as phosphate preservatives) should be applied to the interior pipesurface after cleaning. Pickled piping should be coated with a light oil film or rust preventative.

Phosphate preservatives are composed of 0.5% by weight.

MECHANICAL CLEANING METHODS

The following is a summary of various mechanical methods used in cleaning piping andcomponents:

Handwiping

• Cloths or rags should be lint-free

• Water or solvent is typically used in conjunction with the handwipe cleaning process

Wire Brushing

• Either hand or power driven wire brushing is an effective method of cleaning small sections ofpiping

• Use corrosion resistant brush material on stainless steel components and do not use thesame brushes on both stainless and carbon steel

Tube Cleaning Brushes

• Air, water, or electric powered expanding type power brushes that drive air or water throughthe brush provides a method of power flushing the interior surfaces of piping

• The water used to flush the interior surfaces of the piping must be compatible with the pipingsystem cleanliness

• Do not use air driven brushes that require lubricated air if the motor air enters the pipe

• Do not use tube cleaning brushes through valves, strainers, flow orifices, or other sensitivecomponents

• Avoid using tube cleaning brushes through socket welded or short radius fittings



Grinding

• Grinding wheels and discs used for cleaning should only be vitrified or resinoid bondedaluminum oxide or silicon carbide

• Aluminum oxide flapper wheels and buffing discs provide effective mechanical cleaning onexterior surfaces

• Rotary files can be used for localized cleaning but should be faced with tungsten or titaniumcarbide

Shot or Grit Blasting

• Blasting is typically performed to the Steel Structures Painting Council (SSPC) standards

• Do not blast through sensitive components

• Only use iron-free grit for blasting stainless steel surfaces

• Sand grit may be used on carbon steel buttwelded piping

• Do not blast areas requiring liquid penetrant examinations

• For 2 inch and smaller piping, a radial type blast nozzle may be inserted into the pipe to blastthe interior surface

Mechanical cleaning operations are usually followed by hand cleaning of accessible internalsurfaces and by air blow or water rinse of inaccessible internal surfaces. Air blowing is preferredafter a shot or grit blast.

VACUUM CLEANING

Vacuum cleaning can be used for the removal of metal chips and airborne foreign materials whileworking or for local cleanup subsequent to work operations.

AIR BLOWING

Filtered, oil-free compressed air is used in the following applications to clean piping:

• Local cleanup of foreign material produced during erection or fabrication

• Drying of previously wetted systems

Care must be exercised to direct the air blow and particles away from internal surfaces of thecomponents being cleaned. Particles must also not be blown through or at sensitive components.

SOLVENT CLEANING

The following solvents are typically used to clean piping:

• Alcohol4 Ethyl alcohol (Ethanol)4 Methyl alcohol (Methanol) anhydrous4 Isopropyl alcohol

• Acetone



• Toluene (Toluol) which is useful in removing silicone based lubricants

• Naphtha

• Distilled Petroleum Spirits or Mineral Spirits

NOTE: This solvent is preferred due to its low flammability potential.

It is important to note that alcohol, acetone, toluene, and naphtha are extremely hazardous andflammable and must be dispensed in sealed containers and only used in well ventilated locations. Refer to the manufacturer Material Data Safety Sheet (MSDS) for important information on howto safety use these products. In general, prolonged exposure to the skin must be avoided.

For lined piping, solvents used for cleaning must be compatible with the lining material. Whenbristle brushes are used in conjunction with solvent cleaning, they must be nonshedding.

WATER BLAST CLEANING

Water blast cleaning or hydrolasing consists of a high pressure (more than 1000 psig), lowvolume (20 gpm or less) water jetting of the internal surfaces of the piping system to remove rust,mill scale, oil, and other foreign materials. Radial type spray nozzles that drag the supply hose orpush type cleaning nozzles should be used. When cleaning carbon steel or alloy steel piping,0.5% to 1% by weight of trisodium phosphate should be used.

Water quality must be compatible for use on the piping system being cleaned. The hydrolaserwater jet must not come in contact with valve seats, flow nozzles, or other sensitive components. After cleaning carbon steel and alloy steel systems, the pipe must be dried by air blowing or othermethods.

SYSTEM FLUSHING METHODS

Several methods of system flushing are used to clean piping systems. In general, the water usedfor flushing must be compatible with the system being cleaned. After the completion of the flush,carbon steel and alloy steel systems must be air dried.

Recirculating Flush

This flushing method uses a single batch of water which is recirculated under pressure throughthe piping system in a closed path at a prescribed velocity through strainers, filters, ordemineralizers to remove debris and water impurities.

Velocity Flush

A cleaning technique that utilizes the ability of the rapidly flowing liquid or air to scrub, sweep, andscour foreign material from internal walls of the system. Particles picked up in the flush are sentout as waste or trapped and collected on mesh screens or filters. The effective velocity shouldexceed the design flow rate by two times through the system to perform as desired.



Soaking Method

This process is used when it is not possible to achieve flow by the recirculating method due to theinlet connections or tube shapes for vessels. The disadvantage of this method is that it requires astronger solution to perform the cleaning and sampling is not as accurate.

Acid Cleaning

This process cleans the internal surfaces of water touched pressure parts to remove mill scaleand rust. The acid solution reacts with iron scale and forms ferric oxide.

Chemical Cleaning

This process uses the circulation of a hot alkaline water or citric acid solution through the pipesystems to remove oil, grease, fitting lacquers, preservatives, inhibitors, and possible siliceousmaterials from carbon steel piping and equipment. The hot alkaline water is followed by an acidsolution flush to remove iron oxide and mill scale. The acid solution flush liquid is neutralized andflushed out of the piping system.

CLEANING ADDITIVES

Wetting Additives

Wetting agents are used to improve the contact of a cleaning solution with the pipe andequipment. The additives reduce the surface tension of the cleaning solution and therebyenhance the cleaning of the metal. Because they are detergent based, the wetting agents tendto foam which may not be acceptable in all applications.

Anti-Foam Agent

These agents are sometimes used when detergents are added to chemical cleaning solutions. Their use maintains a low foaming level during cleaning and discharging of the solution to thewaste collection system or tank.

Acid Inhibitors

When added to the cleaning solutions, these inhibitors allow higher cleaning temperatures andslow the reaction between the cleaning solution and the piping or equipment base metal.

Chemical Cleaning Set-up

Temporary equipment is usually required to perform any on-site cleaning. A P&ID should bemarked up and reviewed showing:

• Scope of the cleaning

• Desired flow path

• All temporary piping and instruments

• Heating source for the operation

• Strainer and filter locations

This type of cleaning operation is best subcontracted to specialty subcontractors.



Temporary Piping

All temporary pipe should adhere to the following:

• Pipe should be Schedule 40 minimum

• Welded joints should be used to prevent leaks

• Check gaskets to ensure they are compatible with the heat and chemicals being used

• Monitor the system to prevent over pressurization

Temporary Instruments

• Make sure temporary glass site gauges installed

• Provide differential pressure gauges across strainers to indicate fouling or flow reduction

• Install temperature indicators to monitor flushing temperatures

Solution Heating Equipment

There are two methods for heating chemical cleaning solutions.

• Direct contact method

• Steam supply heat exchanger

Flushing Safety

Safety measures such as warning signs, barriers, or temporary personnel insulation should beconsidered. Review all chemical flushing with the Site Safety Representative before starting theflush. Safety and OSHA regulations must be observed for proper protection of personnel andequipment.

Chemical Cleaning Set-up

Mechanical cleaning (line-pig) can be used to knock loose dirt and sand particles and remove oiland grease from the interior piping walls. Filtered well water, plant water, or city water is normallyused for line-pigging of the system. The drums and coolers required for the cleaning are normallyprepared by the vendors prior to the equipment arriving at the site.

Following the mechanical cleaning and field assembly of required temporary piping, the acidsolution is applied to remove scaling. Whenever possible, agitate the piping to shake any loosematerials free. After the acid cleaning, rinse the system with fresh water. When using citric acid,a fresh water rinse is not normally performed.

The descaled pipe is then passivated to prevent further corrosion by applying a phosphatecoating. Any of three different solutions are typically used:

• Monosodium phosphate

• Disodium phosphate

• Sodium nitrate



Note: When using citric acid in the first step, raise the pH level to 9 or 10 with ammonia and thenadd sodium nitrate.

After being passivated, the system is dried using dry nitrogen or filtered, dry compressed air. Donot flush the passivated system with water. After drying, inspect the piping to be sure it is freeof rust, mill scale, or other foreign material and restore and close the system tightly. Blanket thesystem with inert gas, apply a rust preventative, or fill the system with oil to minimize rusting in thesystem. Finally, paint, varnish, or otherwise protect the exterior pipe and fitting surfaces.

For systems provided with an inert gas blanket, a periodic check of the system should be made toensure the gas blanket remains in the system.

Lube Oil Flushing

Prior to any lube oil flushing operation, it is important to check supplier, engineering, and clientrequirements for the flushing operation to ensure that the criteria for the conduct and acceptanceof the flush is clearly understood. It is best to have a specific procedure or instruction defining theflushing operation approved by all parties prior to the start of the work.

The first step in lube oil flushing is to chemically clean and passivate all associated piping, heatexchangers and vessels. The following are the normal steps used in a lube oil flush:

• Prepare jumpers around seals and bearing housings as close as possible to the bearings.

• Charge the system with the specified oil. If this oil is not available, Turbine Oil 32 may besubstituted with supplier and/or engineering approval. The fill amount should give anoperating level near that for which the system was designed.

• Install 100 mesh screen in the return line to the reservoir.

• Circulate the flushing oil for a minimum of 4 hours at the maximum recommended temperaturewhile hammering the piping, switching valves, and cycling bearing and seal oil rundown tanks(if so equipped). Clean the 100 mesh screen and circulate the flushing oil for 4 more hourswith continued hammering and cycling. Remove and inspect the 100 mesh screen again. The screen should be essentially clean with no evidence of magnetic particles or dirt on thescreens. If not, repeat the flushing process in 4 hours increments until the screens are clean.

• When clean, remove all temporary jumpers, and reconnect all permanent piping. Install 100mesh screens at the inlet to each bearing. Install blinds in the seal oil system, if so equipped,so as not to flush through the seals. If the unit has a oil lube coupling, install 100 meshscreen in the oil outlet line to the coupling.

• Unless otherwise specified by the supplier, continue to circulate the flushing oil in 4 hourincrements until all screens are clean.

• When clean, remove temporary jumpers, reconnect all permanent piping, remove screens,replace filters and clean filter housings. Check pump inlet screens and clean if needed.

• Circulate oil for a minimum of 8 hours.

• Discard filters and clean the filter housings. The client may want to see the discarded screensto verify the adequacy of the lube oil flush.

• Drain the flushing oil, inspect and clean reservoirs, replace filters, charge with service oil andcontinue circulating until the system is turned over to startup or the client.



Note: If service oil was used for flushing and the system is clean, there may not be a reason todrain the flushing oil. The client should concur with this decision.

Plant Steam Start-up

The set-up to perform plant steam starting begins when the system is being placed in service. Begin with a walkdown of the system looking for any discrepancies, checking the hydrotestingrestoration. The following steps represent one method to start-up for plant steam and are donewith concurrence and direction of Startup and/or Client representative:

• Check gaskets and valve line ups.

• Tag-out the system as needed

• Open drain valves

• Close all steam trap inlets to prevent clogging

• Start Boiler and open isolation valves

• As the system heats up let the condensate and steam run freely out the open drains. After thecondensate has slowed to a steady rate begin opening steam trap branches and closing thedrains.

• Replace or repair any steam trap not functioning properly.


Section 14

Leak Testing

GENERAL

Leak testing is required by most codes prior to initial operation and each piping system must betested to ensure leak tightness. The field test is normally a hydrostatic leak test. There areseveral other types of testing depending on service fluid and there are six different testingmethods that can be used at most construction sites.

• Hydrostatic testing which uses water under pressure

• Pneumatic testing which uses gas or air under pressure

• Inservice testing which involves a walkdown for leakage when the system is put into operation

• Vacuum testing which uses negative pressure to check for leakage

• Static head testing which is normally done for drain piping with water with a known static headpressure left in a standpipe for a set period of time

• Tracer leak method for inert gas leak detection

Hydrostatic Leak Testing

The test fluid used for the test is normally water unless there is a possibility of damage fromfreezing or if the system operation will have adverse effects from any residual water left in thepiping. One example would be in a cryogenic system which operates at a very cold temperature. Moisture from the hydrostatic test would need to be removed prior to placing the system intooperation. Removal of this moisture could impede the startup process.

Test pressure is normally set at 1.5 times the design pressure of the line depending on theapplicable piping code or standard used for the design and construction. The source for thedesign pressure is the Line Designation Table issued by engineering.

Pneumatic Leak Testing

The fluid medium used for pneumatic testing is either compressed air or nitrogen gas. The testpressure by code is usually 1.1 times the design line pressure. Pneumatic testing involves thepotential hazard of releasing energy stored in the compressed gas. Care must be taken bygradually increasing pressure in steps up to the test pressure, holding only as long as the coderequires, then reducing to the design pressure for inspection of the joints. The inspection of jointsis done utilizing a soapy-water mix that bubbles when air is escaping.

Inservice Leak Testing

This category of testing is limited in scope to what is allowed by code (ASME B31.3, Category D,Fluids, for example). The pressure shall be gradually increased in steps until the operatingpressure is reached. Then the pipe shall be inspected. This test is usually completed by theclient when the system is put into service by the client.

Section 14 Leak Testing


Vacuum Leak Testing

This is the hardest type of test with which to find a leak. One method is the pressure decayprocess in which a fixed vacuum pressure is maintained on the system for a preset time. Locating a leak using this method is quite difficult. Traditional methods of a candle or smokemachine have been used, but with larger sized units, this is not practical. Gas detection methodscan be used when sampling is done at the ejector area.

Static Head Leak Testing

This test method is also known as a drop test. In most cases an additional piece of pipe mayhave to be added to the highest point to reach the required head pressure. After the system isfilled, the water height is noted. After the required hold period (e.g. 3 hours), the height ischecked for any decrease and the hold time is recorded. Check and correct any joint(s) that arevisually leaking.

Tracer Leak Method

The use of helium gas for leak detection is employed for this type of testing. The processintroduces small amounts of gas into the system or vessel under air pressure. This allows fordetection using an aspiration probe across areas of potential leakage.

LEAK TEST PERFORMANCE

When the system nears completion, the first step in preparing for testing is to develop a punchlist(or moan list) of the open items still requiring construction completion. To develop the punchlist, adesk review between the P&ID drawings and piping isometrics for any discrepancies should bedone. Review valve types, flow directions, branch tie-ins, and any material changes (i.e. specbreaks). Check all in-line equipment and components to verify they can withstand the testpressure.

After the cross check is complete, inspect the system using the piping isometrics and/or P&ID's. Typically, systems are inspected for:

• Completed and torqued flanges with no missing bolts or gaskets

• All gravity supports installed

• Proper pipe routing

• Correct valve type and orientation

• Vents and drains installed to allow proper filling and draining

• Proper material type verified using color codes or markings, and heat numbers recorded ifrequired by code

• All required piping stress relief, weld examinations, and welding documentation completedand acceptable

For gas systems, additional gravity supports may be required to be temporarily added to supporthydrostatic test weights.

Leak Testing Section 14


Since requirements vary from project to project, the project will normally prepare a specificchecklist of items that need to be checked before hydrostatic testing is allowed to proceed.

Test Package Preparation

The P&ID along with a leak test cover sheet make up a test package. The test cover sheet hasthe test number, date, test pressure, material fluid type, release and acceptance signatures. Testresults should be recorded on a pressure test data sheet similar to the one shown in Attachment14-1.

Obtain a clean set of P&ID drawings and mark up the scope of the leak test, show boundaryvalves or test blind locations. Also identify any valves which must have the internals removed ormust be blocked in position.

The test pressure is calculated by using the code requirements for the leak test method times thelargest design line pressure. Check the required test pressure by reviewing all line numberswithin the test boundary against the Line Index for the highest design pressure. Two checks forproper test pressure are that equipment will not be over pressured by reviewing the vendor printsand vendor equipment manuals for maximum allowable test pressures and also the elevation ofthe test gauges versus the piping should be reviewed for head loss. Head loss is the elevationdifference between the test gauges and the piping being tested (Head Loss in PSIG = ElevationDifference in feet X 0.4327 PSI/FT).

Test release authorizations depend on the project and may include the welding field engineer,instrumentation field engineer, mechanical field engineer, hanger field engineer, quality controlinspector, superintendent, third party representative, and client representative. The piping orhanger field engineer will have to verify that the lines are supported to handle the hydrostatic testloads. The client may also walkdown the package before the test can be performed.

Hydrostatic Test Preparation

A sample hydrostatic test setup is shown in Attachment 14-2.

All joints, including welds and flanges, of the system to be tested are left uninsulated andexposed for examination during the test. Some insulation may be installed on straight runs orpreviously tested piping. Piping designed for vapor or gas must be reviewed and checked toensure that it can support the weight of the test liquid.

All gravity supports should be installed or provisions made to provide temporary shoring for thetest. Also check that all spring cans have the travel stops installed to handle the hydrostatic testloading. Expansion joints shall have testing restraints installed to prevent any over pressurizationdamage. Equipment which is not to be tested shall be disconnected from the system or isolatedby test blinds. All non-boundary valves in the test boundary should be in the open position.

Tagging and lock out of any valves or blinds to be used as isolation points for system tests mustbe done per project procedures. Tagging provides protection for both the craft doing the test andany person who will come in contact with the system being tested. A valve line up data sheetsimilar to the one shown in Attachment 14-3 is normally used to summarize required valvepositions to support the test.



Calibrated relief valves that are sized to pass the full flow of the equipment used to fill the systemshould be installed as close as possible to the filling connection and to the low point of thesystem. The relief valve set pressure should be set to prevent system pressure from exceeding:

• The maximum allowable pressure of the lowest rated component in the test boundary

• The maximum allowable seat or backseat pressure for boundary valves

• The maximum allowable set pressure for gagged system relief valves

• The maximum allowable pressures established by the applicable code or project specification

To fill the system, it is preferable that the system be filled from the lowest points possible to avoidair from being trapped in the system. For sloped piping systems, filling should be done againstthe slope. The system should be monitored during filling to identify any leakage due to statichead.

Entrapped air should be vented from the system to the greatest extent possible prior to thepressure test. The presence of entrapped air will not prevent the required test pressure frombeing attained but it will take longer to achieve the required pressure. This occurs becauseadditional liquid must be added to the system as the air is compressed. Entrapped air may alsobe absorbed into solution at higher test pressures and may come out of solution if liquidtemperatures are increased. This makes test pressures difficult to maintain. Large amounts ofentrapped air can be disclosed by tapping on the pipe in the area where trapping is suspected.

Over pressurization can occur in systems that are filled with water during a cool period (e.g. in themorning) and that are then allowed to heat up during a warmer period (e.g. the afternoon) beforethe test is completed. A way to prevent this from happening is to not leave the test gaugesunattended and bleed the line pressure to maintain the maximum allowable test pressure.

Test Gauges

Test equipment used should be recorded on a pressure test data sheet similar to the one shownin Attachment 14-1. Calibration checks of the pressure test gauges should be performed per theproject specifications. 1% accuracy gauges are generally acceptable. Always depressurize thegauge after the test and verify the gauge returns to a "zero" reading.

Pressurizing the system should be done slowly and visual checks of the system should beperformed during the pressurization to identify any leaks that occur. Test pumps should have acapacity greater than the allowable system leakage to maintain the required test pressure. Twoor more test pumps can be used for this purpose. During the test, it may be required to correctleakage from flanged joints, screwed connections, valve bonnets and other mechanical or glandtype joints.

If the system examination pressure is different than the maximum test pressure, the systemshould be held at the test pressure for the prescribed period before it is lowered to theexamination pressure. When examining the system for leakage, any condensation on the systemshould be wiped from the system to provide a clear view of the piping joints.

After the testing is completed, the system should be drained and laid up. The piping may besimply drained and left to air dry or have hot air blown through to remove any water. In drainingthe system, the following precautions should be exercised:



• First, make sure all system vents are open

• Vents on tanks pressure vessels should be open and functional to avoid damage duringdraining

• The rate of drainage should not exceed the allowable rate of the building or temporarydrainage system

• Disposal of test liquids containing surface preservatives or other water additives must meetlocal and project environmental requirements

• Make sure temporary piping and instrument connections are relieved of pressure prior tobeing disconnected

• Make sure downstream pressure is relieved in systems containing check valves if the valveswere not gagged open

The system may be left in a wet lay up condition to prevent internal rusting. When a wet lay upoccurs the system should have tags on the valves warning of the pipe conditions.

Cold Weather Testing

In general, hydrotesting with water should not be performed when the air temperature is at orbelow 40 oF. Unless, a suitable method is used to heat the test water and piping. During coldweather, the following options may be utilized to warm the metal temperature to acceptablelevels.

• Steaming the line

• Running warm water through the pipe

• Energizing steam tracing on the line

NOTE: This may be a safety hazard and should be avoided if possible unless the pipinginsulation is completed except for the area adjacent to the field welds that need to beobserved during the test.

Another alternative may be to mix antifreeze with the hydrotest water. Use of antifreeze may notbe allowed on some projects, however, since there may be environmental concerns with usingand disposing of a large volume of antifreeze.

Finally, extra care and caution should be used when draining systems in cold weather to assureall pockets are drained and no water remains that may freeze.

Pneumatic Testing

Pneumatic testing can be performed completely with gases or with a combination of liquid andgas. In the case of the later, the test method is referred to hydropneumatic testing. This testmethod requires a smaller volume of gas to pressurize the system and as a consequencereduces the danger associated with pneumatic testing.

Typically, pneumatic tests are conducted with filtered, oil-free air, nitrogen, carbon dioxide, orother suitable nonflammable gas. Test temperatures are normally equal to the vessel or systemtemperature and above the nil-ductility transition temperature. Compressors or gas cylinders with



regulators may be used as the pressure source. The pressure source should have a capacitygreater than the allowable system leakage rate to maintain the required test pressure.

When performing any type of pneumatic testing, the following safety precautions must be takento avoid a rupture in the system or the test equipment:

• Correctly sized and calibrated relief valves are installed

• All personnel in the area of the test are notified that the test will be performed

• All unnecessary personnel are removed from the area

• The immediate area is blocked or roped off per project safety procedures

• The pressure source is connected and temporary piping is capable of withstanding the testpressure

• Properly calibrated test gauge is installed in the system to monitor the pressure build up

• If leakage is discovered, the system must be released and the leakage repaired prior toproceeding with the test

When performing pneumatic testing, the test gauge(s) is normally installed at a remote locationsome distance from the system undergoing testing. For larger pneumatic tests, a sonic detectoris used for examination from a safe distance. For smaller pneumatic tests (less than 100 psig), aleak detector solution may be used to examine for system leakage. Acceptable leak detectionsolutions include:

• A solution of liquid soap and water

• Linseed oil

• A commercially available leak detection solution

If verification of leak rate is required, flowmeters and totalizing meters are used to monitor thetest.

After the test is completed, the pressure in the system is relieved. The following precautionsshould be exercised when releasing the system pressure:

• Make sure any residual downstream pressure is relieved in systems containing check valvesthat were not gagged open

• Make sure temporary piping and instrumentation is relieved prior to disconnecting thepressure source

• Gases should be vented to the outside atmosphere and not inside the building

Test Blinds

Test Blind thickness requirements are tabulated in Attachment 14-4. It is important to orderrequired blinds and longer bolting as early as possible to avoid project schedule delays.



ATTACHMENT 14-1

PRESSURE TEST DATA SHEET

TEST NUMBER.: PROJECT NO.: PAGE 1 OF

PROJECT NAME:

TEST INFORMATIONTEST INFORMATION

SYSTEM DESCRIPTION:

DESCRIPTION OF TEST BOUNDARIES:

PIPE CLASS: DESIGN TEMPERATURE: DESIGN PRESSURE:

TEST METHOD: HYDROSTATIC PNEUMATIC OTHER(SPECIFY):

TEST MEDIUM: APPLICABLE CODE:

TEST REQUIREMENTSTEST REQUIREMENTS

REQUIRED TEST PRESSURE: TEST TEMPERATURE:

REQUIRED TEST DURATION: AMBIENT TEMPERATURE:

GAUGE PRESSURE CALCULATIONGAUGE PRESSURE CALCULATION

ELEVATION DIFFERENCE BETWEEN GAUGE AND HIGH POINT:

TIMES FACTOR:

PLUS REQUIRED TEST PRESSURE:

EQUALS REQUIRED GAUGE PRESSURE:

PRE-TEST REVIEWSPRE-TEST REVIEWS


CODE INSPECTOR: DATE: TEST RESULTSTEST RESULTS

TEST DATE: START TIME: AM PM

FINISH TIME: AM PM

ACTUAL GAUGE PRESSURE: PRESSURE DROP: IN: minTEST EQUIPMENTTEST EQUIPMENT

TYPE: RANGE: CAL. DATE: CAL. DUE:




REMARKS:

TEST ACCEPTANCETEST ACCEPTANCE


CODE INSPECTOR: DATE: FORM T_HYDRO.DOT 1996:REV.0



SAMPLE HYDROSTATIC TEST SETUPATTACHMENT 14-2



SAMPLE HYDROSTATIC TEST SETUPATTACHMENT 14-2

NOTES:

1. 18” GBD78 DESIGN PRESSURE = 350 PSIG

CODE MINIMUM TEST PRESSURE = 1.5 x 350 PSIG = 525 PSIG

CODE MINIMUM TEST PRESSURE INCLUDING HEAD =

(1.5 x 350 PSIG) + (63 FT HEAD x 0.4327 PSI/FT) = 553 PSIG

MAXIMUM TEST PRESSURE = 974 PSIG (18” LINE); 1100 PSIG (1/2”, 3/4”, & 1” LINES)

2. 10” GCD24 DESIGN PRESSURE = 400 PSIG

CODE MINIMUM TEST PRESSURE = 1.5 x 400 PSIG = 600 PSIG

CODE MINIMUM TEST PRESSURE INCLUDING HEAD =

(1.5 x 400 PSIG) + (20 FT HEAD x 0.4327 PSI/FT) = 609 PSIG.

MAXIMUM TEST PRESSURE = 912 PSIG (10” LINE); 925 PSIG (1/2”, 3/4”, & 1” LINES).

3. ACTUAL TEST PRESSURE WHEN TESTED TOGETHER 10” GCD24 WILL SET THE TESTPRESSURE FOR 18” GBD78 AS FOLLOWS:

CODE ALLOWABLE MINIMUM TEST PRESSURE AT POINT A IS 609 PSIG LESS 25’ 4-1/2” HEAD TOACCEPTANCE GAUGE, OR:

(1.5 x 400 PSIG) + (20 FT HEAD x 0.4327 PSI/FT @ 70 °F) - (25.375 FT HEAD x 0.4327 PSI/FT @70 °F) = 598 PSIG.

THIS SATISFIES CODE MINIMUM ALLOWABLE TEST PRESSURE FOR BOTH LINES AND FALLSWITHIN MAXIMUM ALLOWABLE TEST PRESSURE FOR BOTH LINES.

4. POINT A: POINT AT WHICH CODE MINIMUM TEST PRESSURE MUST BE SATISFIED FOR GCD24LINE (609 PSIG).

5. POINT B: POINT AT WHICH CODE MINIMUM TEST PRESSURE MUST BE SATISFIED FOR GBD78LINE (553 PSIG).

6. PUMP GAUGE READING: 598 PSIG + (72 FT x 0.4327 PSI/FT) = 629 PSIG

7. MINIMUM HOSE WORKING PRESSURE SHOULD BE 700 PSIG. BURST PRESSURE SHOULD BE1000 PSIG MINIMUM.

8. RELIEF VALVE SETTING: 625 PSIG x 106% + (2 FT HEAD x 0.4327 PSI/FT @ 70 °F) = 664 PSIG.

9. OPERATOR GAUGE READING: 598 PSIG + (56 FT HEAD x 0.4327 PSI/FT) = 622 PSIG.

10. ACCEPTANCE GAUGE:

MINIMUM GAUGE RANGE = 1.5 x 598 PSIG = 797 PSIG.

MAXIMUM GAUGE RANGE = 4 x 598 PSIG = 2392 PSIG.

USE 0 - 1000 PSIG GAUGE WHICH HAS 5 PSIG GRADATIONS AND 1/4% ACCURACY.

11. ACCEPTANCE GAUGE READING:

609 PSIG AT POINT A - (25.375 FT HEAD x 0.4327 PSI/FT) = 598 PSIG.

READING GAUGE AT 600 PSIG DUE TO GAUGE GRADUATIONS WHICH STILL FALLS WITHINCODE MAXIMUM ALLOWABLE TEST PRESSURE.

ATTACHMENT 14-3



VALVE LINE-UP DATA SHEET

TEST NUMBER.: PROJECT NO.: PAGE 1 OF

PROJECT NAME:

SYSTEM:

VALVE NUMBER DESCRIPTION POSITION TAG NUMBER

REMARKS:

INITATOR: DATE:

REVIEWED BY: DATE: FORM T_VLV_LU.DOT 1996:REV.0



TEST BLIND FABRICATION DATAATTACHMENT 14-4

A = BLIND PLATE DIAMETER GENERAL NOTES:B = PADDLE HANDLE WIDTH 1. PLATE MATERIAL TYPESC = HANDLE HEIGHT A-36, S=12,600 PSID = BLIND THICKNESS A-285 GR. C, S=18,350 PSIt = required blind thickness A-570 GR. 36, S=16,300 PSId = nominal diameter of pipeP = line design pressure (psig)S = allowable material stress

t = d3

16x

PS

Note: This will provide a safety factor of 1.7 of yield. These same values may be used for A36plate, however, the safety factor will be reduced to 1.4

TEST BLIND THICKNESS SCHEDULE A285 Grade C

t, Test Blind Thickness

PIPESIZE

TESTPRESSURE

100 300 500 700 1000 1500 2000

A B C

1 2 1 41/2

11/2 27/8 1 51/8

2 35/8 1 51/4

3 5 1 61/81/8

1/41/2

1/43/8

1/25/8

4 63/16 1 63/41/8

1/43/8

3/81/2

5/83/4

6 81/2 11/2 111/21/4

3/83/8

1/25/8

3/4 1

8 105/8 11/2 125/81/4

1/25/8

3/47/8 11/8 11/4

10 123/4 11/2 14 3/85/8

3/4 1 11/8 11/4 11/2

12 15 11/2 151/21/2

3/4 1 11/8 13/8 15/8 17/8

18 161/4 11/2 161/25/8 1 3/8 15/8 17/8 21/4 25/8

20 23 11/2 173/45/8 11/8 11/2 13/4 21/8 21/2 27/8

A = BLINDDIAMETER

B = GRIPWIDTH

C = HEIGHT FROM CENTER OF PADDLE TO TOP OFGRIP


Section 15

Mechanical Equipment

GENERAL

Mechanical equipment can generally be classified in three major groups:

• Stationary Equipment or non-rotating equipment including columns, vessels, drums, heatexchangers, filters, shop fabricated tanks, unassembled components such as condensers,and field erected tanks.

• Rotating Equipment including horizontal and vertical packaged process pumps, large commonbed frame or individual base mounted pumps and drivers, vertical and horizontal direct or beltdriven compressors, and large process fans.

• Process equipment items which are not specifically defined as either stationary or rotating. These include Package or Skid Mounted Units, Conveyor Assemblies, Cranes and Monorails,Valve Operators, Heaters, and Boilers.

Storage and Maintenance

Equipment must be properly stored and protected at the construction site to maintain theequipment in a condition equivalent to its condition when it was shipped by the supplier. Specificinstructions for storage and maintenance at the construction site are typically provided by themanufacturer or supplier in the equipment manual or installation instructions. The Field Engineeris responsible to ensure that these instructions are followed.

In operating plants, special instructions for storage and preservation of permanent plantequipment and materials are sometimes provided by the client which may exceed manufacturerrequirements. Equipment storage typically includes the following:

• All nozzles and openings are cleaned, coated, and covered with temporary wooden, plastic, ormetal covers which are taped or otherwise secured to the flange or fitting.

• For outside storage, equipment cribbing and enclosures are sometimes provided to protectthe equipment from the elements.

• Contact rust preventatives, desiccants, vapor phase inhibiting oils, or other substancesspecified by the supplier or manufacturer is applied or installed.

• Internal strip heaters are installed in electric motors or other items to prevent condensationfrom forming.

• A routine program of equipment shaft rotation, lubrication, and motor meggering isestablished.

• An inert gas purge is established to prevent condensation from forming.

CONSTRUCTION PERFORMANCE

Pre-Installation Checklist

The installation of major equipment is normally preplanned through the preparation of aninstallation checklist that describes the tasks to be performed and lists the working documents tobe used in performing each task.

Section 15 Mechanical Equipment


This checklist is assembled using project documents including vendor instructions, manufacturerdesign drawings, engineering specifications, code requirements, and client requirements. TheMechanical Field Engineer also notifies the vendor when it is necessary for site work.

Rigging and Transport

Rigging diagrams and studies may be prepared by the Mechanical Field Engineer with the inputand guidance of the responsible Superintendent. All rigging work operations must be preplannedto ensure the safety of the lift. However, formal rigging plans and diagrams are required for alllifts exceeding fifty (50) tons. The minimum documentation for a rigging plan is typically a singlesketch indicating pick points, weights, load radius, crane type, and critical clearances. Whereverpossible, the rigging diagram should be cross referenced to any vendor supplied instructions. Ifvendor instructions are not available, the Mechanical Field Engineer should obtain the requiredinformation to ensure that supplier and manufacturer instructions are understood and compliedwith.

Rigging diagrams (for equipment less than 50 tons) may be prepared by the Mechanical FieldEngineer with the input and guidance of the responsible superintendent. These plans typically donot require formal approval, however.

Before loading any equipment for transportation from one location to another, vendor shippingdocuments should be checked for transportation blocking and tie-down requirements. Theblocking provided must provide adequate support to avoid excessive loadings on shafts,couplings, running gear, and moving parts. All packing, shipping bolts, tie-downs, dampers, andcushions must be replaced if damaged and tightened prior to transport.

Maintenance

Vendor supplied equipment storage and maintenance instructions must be reviewed before theequipment arrives on the site. Necessary preventative maintenance instructions must then beprovided to the craft. These instructions must take the conditions at the construction site and theduration of the storage into consideration.

Judgment must be exercised in the implementation of preventative maintenance duringconstruction to avoid meaningless maintenance or to prevent equipment damage. Examples ofthis may include:

• Vendor instructions may require that lubricating oil be changed every three months. Sincethis requirement may assume that the equipment is in operation, this maintenance action maybe excessive during construction when the equipment is not in operation. In this instance, amore reasonable maintenance action is to verify every three months that the oil reservoir isstill full and that the oil has not separated.

• Vendor instructions for electric motors may require that the motor be greased every month. Performing this maintenance action during construction could damage the motor since thegrease is not being consumed by the operating motor and the excessive grease could causethe motor to fail when put into operation. In this case, a more reasonable approach would beto perform no periodic greasing until the motor is put into operation.

Mechanical Equipment Section 15


In determining the required preventative maintenance, the Mechanical Field Engineer must verifythat the maintenance action is reasonable for a piece of equipment in storage during constructionand must consider the consequences of the maintenance action on the equipment itself.

Prerequisites to Setting Equipment

The following items must be checked prior to setting equipment on its foundation:

Foundation and Anchor Bolt Preparation

• Tops of foundation surfaces are cleaned and roughened.

• Check anchor bolt sleeves for foreign material which may have accumulated and recheckimmediately before positioning the equipment.

• Check anchor bolts for plumb, alignment, and projection.

• Correct any bent or misaligned bolts.

• Equipment centerlines and elevations

• After surface preparation, establish the North-South and East-West centerlines and thecenterlines of pump nozzles and mark the centerlines on the foundation.

• Establish a reference elevation mark on the foundation at approximately six (6) inches belowthe bottom of the sole or base plate.

Equipment Preparation

• Before placing the equipment, check pipe flanges, nozzles, conduit, junction boxes, and anyother items which require external connection to verify they are in the locations shown on thedrawings.

• Remove all traces of loose foreign material from the underside of the base which will be incontact with the grout.

Leveling and Adjustment of Machinery

• Check that the equipment is placed on the foundations and properly supported to preventwarping.

• Level the equipment with jack screws, flat shims, or pairs of wedges. Use of single wedges isnot a good practice.

• Ensure that the shims or pairs of wedges provide proper support for the equipment andprevent distortion of the base prior to grouting.

Shimming

• Shims are typically saw cut, cold rolled steel plates, 2" x 4" from 1/16" to 3/4" thick and may bespecified in the erection drawings.

• Shims should be free of burrs and not flame cut or sheared. The Mechanical Field Engineershould approve the use of a shim size smaller than 2" x 4" since smaller sizes may not provideadequate support.

• Do not use galvanized, laminated, or painted shims.



• Shim packs are placed adjacent to and on either side of the anchor bolts with sufficientintermediate packs to support the equipment without strain or distortion of the base.

• Shims should not protrude from equipment base.

• Use an adequate number of shims to permit leveling and alignment of the equipment withoutflex or distortion of the foundation.

• Use a maximum number of thick shims.

• After checking, the Surveyor should spray paint the shim packs to indicate proper elevation forsetting the equipment has been verified. This will permit an easy check if the equipment hasbeen altered after survey verification.

• Place dry pack grout around the shim pack to protect against movement.

• When required by the project specifications or supplier instructions, remove shims aftergrouting.

• Shim removal should be done immediately after the initial set of the grout but typically not lessthan 24 hours after grouting.

• Make sure that the equipment frame is supported on the grout, and not on the leveling screwsor shims.

• Sole Plates are typically set to within 1/16" of the reference centerlines and leveled to within0.003" measured diagonally across the corners prior to setting the equipment.

• If two or more plates are required, each additional plate should be set in relation to the firstplate so the variation in elevation is within the prescribed tolerance (typically 0.005").

• Check that foreign material is removed from bottom of the sole plate before placing it on thefoundation.

• Place steel plates (typically 3/16" X 1" square) under the leveling screws to prevent them fromcutting into the concrete foundation.

• Check location, elevation, and leveling of sole plates.

• Do not place equipment on an ungrouted sole plate.

Leveling

All machinery must be leveled by a precision (machinist) level on machined surfaces of the baseor sole plates to the accuracy recommended by the manufacturer's installation instructions. Normally the accuracy requirement is not great for small machinery items, but becomes quitecritical for extremely heavy or large pieces of machinery. An accurate machinist's level reading amaximum of 0.005 inch per foot, per graduation, is normally used for leveling. All equipmentshould be leveled and checked before grouting.

Unless otherwise required by the manufacturer, the driven unit should be first set to the correctelevation and this elevation used as the datum to set the driver unit. Electric motors and turbinesare usually positioned from the driven equipment. Equipment should be positioned and leveled towithin 1/16" of the design centerline location by means of shims placed under the machined feet orbases. A sufficient number of shims should be provided under motors (minimum of 0.012"thickness) and turbines (minimum 0.020" thickness) to allow for hot alignment of the equipmentwithout foundation changes.



The flange faces of pumps and turbines and the machined surfaces of motor and pump mountsmust be plumb and level when the equipment is set. If there is a discrepancy between the pumpflanges and the mounting surfaces, the cause for the discrepancy must be determined beforeallowing the connection to proceed. All equipment anchor bolts should be tightened firm, equal,and sufficient to hold the equipment against accidental disturbance. There should be sufficientanchor bolt adjustment available to permit further tightening after the grout has set.

Prior to beginning the actual alignment of the equipment, the following preplanning should bedone:

• Make sure the equipment is properly set and leveled

• Make sure the right coupling has been supplied for the equipment

• Make sure the right tools are available and are properly calibrated

• Tag out or lock out electrical motors

• Remove preservative materials from the equipment that will interfere with the alignment work

• Review the manufacturer's alignment instructions thoroughly

• Check for strain imposed on the equipment housing by improper attachment to the base plateby loosening the driver and driven hold down bolts (retighten bolts after check)

• Locate the magnetic center of the drive motor (if the location is not marked on the shaft, themid-point of the shaft's horizontal travel may be used instead)

Rough Shaft Alignment

For rotating equipment requiring coupling alignment, a Coupling Alignment Data Sheet should beprepared. A sample sheet is shown in Attachment 15-1. The rough alignment is accomplishedprior to grouting to assure that no machining of the base plate is required to obtain the finalalignment.

Dial indicators calibrated to a standard test block are employed in determining the run out at theoutside diameter and face. Readings should be within the tolerances specified by themanufacturer. If these are not available, the angular alignment shall be corrected to 0.002" TIRand parallel alignment shall be corrected to within 0.001" TIR. Shims are used to bring the driverinto satisfactory alignment.

The end clearance (gap) shall be within tolerances specified by the manufacturer, or to within0.002" if such information is not available.

The machinery must be free of strain and distortion in the rough aligned position. Hold downbolts should be loosened and tightened, using the dial indicator on the coupling to assure thatunits are uniformly supported. Soft feet must be corrected.



FIGURE 15-1 - CHECKING RIM RUNOUT WITH ADIAL INDICATOR

FIGURE 15-2 - DETERMINING FACE RUNOUTWITH A DIAL INDICATOR

FIGURE 15-3 - DETERMINING ANGULARALIGNMENT USING THICKNESS GAUGES

FIGURE 15-4 - DETERMINING ANGULARALIGNMENT USING A DIAL INDICATOR

FIGURE 15-5 - DETERMINING PARALLELALIGNMENT USING A STRAIGHTEDGE AND A

THICKNESS GAUGE

FIGURE 15-6 - DETERMINING PARALLELALIGNMENT USING A DIAL INDICATOR



For sleeve bearing motors, the motor must be located so that the coupling gap does not exceedthat specified by the coupling manufacturer when the motor is centered at the midpoint of its axialtravel. Following alignment, the coupling shall be coated with the coupling lubricant and protectedwith a non-absorbent covering to prevent entry of foreign material. Couplings should not bemade up or lubricated until just prior to startup of the equipment to facilitate alignment checks anddriver testing.

Typical runout and alignment work methods are shown in Figures 15-1 through 15-6.

Grouting

With the coupling disconnected, the equipment is grouted per the manufacturer instruction or theproject specification. After the grout has thoroughly set (usually 7 days), the foundation boltsshould be tightened and all leveling points rechecked to be sure that the machinery was notdisturbed during grouting.

After the grout has set and alignment rechecked, piping connections can be installed. Flangefaces must be parallel and in line with equipment flanges to avoid strain from being transferred tothe equipment. At each equipment flange, a test blind should be installed with a gasket on eachside. This test blind should be left in place until final equipment alignment.

Preparing for Storage

Prior to final installation, the equipment storage instructions should be reviewed. For equipmentthat is to be set in an area in which other work is in progress, special requirements may berequired. These may include the construction of enclosures or the covering of equipment toprevent damage or contamination by work activities around the storage area.

FINAL INSTALLATION

Cleaning and Lubrication

Contact rust preventatives, desiccants, vapor phase inhibiting oils and other substances used asa preservative should be removed in accordance with the vendor or manufacturer requirementsprior to initial lubrication. Nozzles, bearing housings, and strainers should be inspected for dirt orother foreign matter. Internals should be cleaned and dried.

The removal of contact firm film type preservatives should be done either wiping the surface withsolvent soaked cloths or by flushing internal cavities with solvents. With either approach, thesolvents used should not harm the item or other interconnecting material.

Internal Preservatives which are compatible with the operating lubricant may remain in placeprovided evidence of compatibility is available.

Manufacturer or vendor instructions should be consulted for required lubrication specifications. The list of recommended lubricants shall be obtained from the customer. Generally the equipmentlubricant specified shall be maintained and topped off as necessary prior to turnover.



Installation of Packing (if not installed by manufacturer)

Pumps shall not be packed until immediately prior to startup. A record should be made of thetype and number of packing rings installed. Each ring of packing must be firmly seated in thestuffing box. Do not seat packing by forcing packing rings one on top of the other.

The cut of the packing is to be installed per vendor recommendations. Alternate the cut ofsuccessive rings at 45 degrees on either side of the shaft centerline. Check to see that lanternrings are in proper alignment with the flushing or sealing lines connected to the stuffing box. Thehigh pressure throttle bushings on multi-stage pumps must be piped to a point of lower pressureto prevent backpressure from allowing foreign material to enter the system.

Installation of Mechanical Seals (if not installed by manufacturer)

Care must be taken in handling mechanical seals to ensure that dirt or other foreign material doesnot come in contact with any part of the mechanical seal assembly. The stuffing box should beflushed to remove all foreign material and the seal must be installed absolutely clean. A light coatof machine oil should be placed on the seal face to protect the seal face during startup. Checkthe seal flushing line to ensure that there is a flow of liquid across the seal faces and that thestuffing box is flooded before starting the pump.

Rotation Check and Magnetic Centering

When an electric motor is coupled to mechanical equipment, the axial position of the motor andthe axial clearance in the coupling should be established with the motor rotor on its electrical orrotating center. If the electric center is not marked, the rotating center shall be considered themid-position between the two extremities of the rotor end play. The direction of rotation of themotor shall be verified by the Electrical Field Engineer.

Motor Run-In

After rotation is checked, the coupling half is secured on the motor and the coupling guard isinstalled. If the coupling guard cannot be installed, a safety screen must be provided around themotor coupling. It is important to observe all electrical safety precautions when performing therun-in. The motor run-in typically is performed for two hours and the Electrical Field Engineernormally monitors the motor for vibration and heat-up of the bearings.

Coupling Installation, Belt or Chain Alignment

Couplings should be mounted, gapped, and lubricated in accordance with the manufacturerinstructions. The type, manufacturer, and serial number of the coupling should be recorded onthe Coupling Alignment Data Sheet. A check should be made on all tapered bore couplings toassure that a minimum of 75 percent contact is made between the bore and the tapered shaftend.

Coupling guards, Vee belts, chains, and any other exposed moving components should beverified to be installed in accordance with manufacturer instructions.

Typical belt or chain driven alignment work methods are shown in Figures 15-7 and 15-8.



FIGURE 15-7 - DETERMINING FACE RUNOUT WITH A STRAIGHTEDGE

FIGURE 15-8 - SHAFT ALIGNMENT AND BELT TENSIONING USING A STRAIGHTEDGE

Piping Fit-Up



After Hydrostatic Testing and prior to final piping fit-up, an inspection of equipment nozzlesshould be made to ensure that no foreign material has contaminated the wetted parts. Allshipping blocks and protective coatings should be removed and bearings inspected and cleaned.

To minimize rework, piping installation should begin at the equipment nozzle. System closureshould be at a point where pipe strain, due to misalignment, is dissipated at the equipmentnozzle.

Piping should be connected to the equipment and bolted up with dial indicators on the shafts ofthe equipment to ensure that the fit-up does not violate the alignment of the driven equipment. Flange to flange connections must be free of stress deflection. Stress relieving should not beperformed on installed piping systems to remove piping strain without an approved procedure toavoid damage to equipment or piping.

Generally, final pipe fit-up is performed in accordance with approved erection procedures. Auxiliary piping and instrument connections are installed per the manufacturer requirements andproject specifications.

Final Alignment

Rotating equipment should be rechecked for alignment after connecting piping has beentightened. If movement of dial indicators exceeds the tolerance, the piping alignment should becorrected and procedure repeated. If two or three pumps have a common piping manifold, theymust be checked simultaneously to ensure that adjustment of one pump is not affecting theothers. Axial and angular alignment must conform to the tolerances established by themanufacturer.

When required by the manufacturer, adjustments for thermal expansion must be incorporated intothe alignment procedure. Generally the expansion limits of rotating equipment may be dependenton many variables such as size, type, and application. For alignment of this type, themanufacturer's instructions must be consulted. The driven unit should be set to correct elevation. This elevation should be verified by survey instrument and entered as the "datum" on theCoupling Alignment Data Sheet.

The following general information applies to alignments:

Factory Mounting and Alignment

Machinery mounted on a common baseplate at the factory may be properly aligned prior toshipment. All baseplates are somewhat flexible and cannot be relied on to maintain the factoryalignment. Alignment checks should be performed in the field to ensure that the factoryalignment has been maintained.

Field Mounting of Driver

When the driven unit is factory installed and the driver is field installed, the hold down bolt holesshould not be drilled and tapped until the motor has been initially aligned.



Aligning Pumps

After the pump is installed, the suction and discharge flanges should be aligned. The drivershould then be aligned to the pump. During piping installation, shaft movement should bemonitored with alignment tools to make sure no stresses build up in the pump to pipingconnections.

Flexible Coupling Alignment

The manufacturer normally specifies a minimum separation for the coupling halves so they willnot strike one another when the driver rotor moves toward the driven machinery. An allowancefor thrust bearing wear should also be made in setting the coupling halves.

Alignment of Gear Type Couplings

Gear type coupling covers must be moved to allow room for alignment measurements on thecoupling hubs.

Turbomachinery Alignment

The alignment of large turbomachinery is complex and must be performed in accordance withspecific manufacturer instructions.

Factors Affecting Misalignment

The following factors may contribute to misalignment after proper installation:

• Movement of the foundation

• Piping strains caused by:4 Improper pipe support4 Improper pipe alignment to the driven machinery4 Strains caused by thermal expansion or contraction of the connecting piping

• Wear on the bearings

• Distortion of the baseplate by an adjacent heat source

• Shifting of the building structure

• Improper grouting of the baseplate

• Excessive variation in ambient temperature

• Improper shim support

Alignment Tools

The following manual tools are normally used for alignments:

• Magnetic base dial indicator holder

• Dial indicators with 0.0005" and 0.001" divisions and a minimum face diameter of 1.25"

• Adjustable clamping straps for mounting dial indicators

• Thickness gauges

• Extension mirror(s)



• Vernier caliper

• Inside micrometer

• Straightedge

There have been recent enhancements in alignment tools that have greatly simplified alignmentwork. The following are two examples of alignment devices that are currently available:

Alignment Computers

Alignment of rotating equipment can be a very time consuming activity on a construction project. Quite often, alignments are performed over and over in an attempt to achieve specified couplingalignment tolerances. Alignment computers are available to provide useful adjustmentrequirements which can drastically reduce this alignment period.

The "Coach and Coach II" alignment computers manufactured by Acculign, Inc., of Willis, Texashave been used successfully on a number of Bechtel Construction projects. These are selfcontained, hand held units which come with software programs for virtually every alignmentsituation. Both units offer identical features and differ only in the alignment methods they arecapable of handling.

Features of these units include:

• The ability to select a sketch matching the alignment method used.

• Easy entry of alignment readings and data

• A "Class of Alignment" feature that eliminates unnecessary fine tuning and tells the craft whento quit.

• The computer will calculate and display angular misalignment of the coupling. Additionally,information is provided to the user for shim changes and required horizontal movements toimprove alignments.

• Automatic checks are performed to make sure the dial indicator and micrometer readings addup.

• The unit will calculate the fourth coupling reading if only three readings are possible.

Laser Alignment Systems

Bechtel has also successfully used laser alignment equipment for precision alignments. Thesedevices are particularly effective when aligning long shafts to precise tolerances. Bechtelcurrently owns an "Optalign" laser alignment system manufactured by Pruftechnik AG ofIsmaning, Germany.

The laser alignment system offers greater precision and faster speed than dial indicator systemsduring the alignment process.



INSTALLATION CHECKS

The following installation checks are to be used as guides for the installation and inspection of thevarious types of equipment:

Pumps

• Mount motors on the baseplate; many new pumps are shipped with their drivers mounted andare rough aligned at the factory

• When the driver half of the coupling is installed in the field, it must be shrunk (not driven) onthe driver shaft

• Driver pads must not be marked and drilled until shaft centerlines of both the driven machineand driver line up, coupling faces parallel, and the distance between shafts is checked to fitthe coupling used. When the driver does not contain thrust bearings, the motor must beplaced in the center of its axial travel to measure coupling spacing. This initial alignment mustbe accurate enough to eliminate the necessity of undercutting bolting, reaming the motor feet,or shifting the driven equipment.

• Driver pads must be drilled and tapped to a minimum depth equal to the bolt diameter, andthe bolts shall be long enough to engage thread to this same depth.

• Suction and discharge flanges shall be covered to prevent entry of foreign material.

• Make final alignment of pump and driver for cold setting, or approximate hot setting. Couplings should not be out more than 0.003" from desired setting, set for hot condition asrecommended by manufacturer.

• Alignment should be done with suction and discharge piping disconnected and then checkedagain after bolting up the connecting piping.

• Greasers and lube glasses should be removed and tagged to avoid damage duringconstruction, and should be replaced prior to turnover.

• Check rotation, nameplate speed and horsepower against the data sheets and driver.

• Run-in the uncoupled motor prior to turnover and check bearing temperature and vibrationduring the run-in. Make the first check within 15 minutes from the start of the run-in and checkstarter operation. Remove preservative oils, if necessary and install all operating lubricants.

• Install temporary startup strainers in suction piping.

• Check all vents, drains, seals, flushing, and bypasses for conformance to specifications anddrawings. Flush seal oil lines before connecting to seals.

• Install permanent packing if pump is shipped with temporary packing. Certain pumps mayhave mechanical seals.

• Clean suction strainers if water is being circulated prior to startup.



Large Compressors

• Have manufacturer representative check all components and auxiliaries prior to grouting.

• Grout under supervision of manufacturer representative.

• Pickle lube oil, seal oil, and suction piping where required by specification. Inspect lines whichwere pickled by manufacturer in shop.

• Clean and flush all lubricating and seal oil systems before installing operating lubricants perspecifications and manufacturer recommendations.

• Install temporary startup strainers. Visually inspect all suction lines to be sure all solids areremoved.

• Perform cold alignment as directed by manufacturer's representative and obtain the approvalof the manufacturer's representative on the Alignment Data Sheet.

• Perform running tests as directed by manufacturer's representative and check all auxiliaries,safety devices, control, and instruments for proper operation.

• Perform hot check of alignment and dowel, if required. Determine if this must be witnessed bythe customer's representative.

• Obtain written confirmation from the manufacturer's representative that the installation wasmade in accordance with recommendations provided.

Large Synchronous Motors

• Have the manufacturer's representative check the installation and the breaker settings.

• Check all safety devices and interlocks.

• Check rotation and ability of machines to synchronize.

• With motor running, check motor temperature indicators and select hottest point and connectto temperature alarm.

• Check that the second motor will synchronize with first motor operating.

Turbines (Small Auxiliary)

• Mount turbine on baseplate.

• Perform alignment for cold or for approximate hot setting. Follow manufacturerrecommendations.

• Install any lube oil piping required.

• Remove preserving lubricants, if necessary, clean and install running lubricants prior to turnover.

• Install all accessories required and insulate if required.

• Check operation and setting of overspeed trip, when uncoupled (by startup).



Circulation Test

Circulation tests are performed by construction when specified in the contract documents:

• As part of the mechanical acceptance test and prior to startup of the plant, all equipment isoperated with water or other media as specified. Caution must be taken to not overload themotors driving any of the equipment.

• Operation must be under close supervision to prevent damage to the equipment and iscontinued until the equipment has demonstrated its ability to operate continuously in asatisfactory manner.

• Equipment having suction strainers or filters are operated with water or other media until thestrainers or filters remain reasonably clean.

Final Acceptance and Records

Records should be maintained which provide verification of completion and summaries ofreadings and calculations for work performed. Documentation should include but not be limited tothe following:

• Completed Checklist

• Manufacturer's Installation Instructions

• Rigging Diagrams (as necessary)

• Coupling Alignment Data Sheet - Preliminary

• Coupling Alignment Data Sheet - Final

• Equipment Maintenance Record

• Any special instructions required for installation.

• Acceptance by the manufacturer and/or client representative.



ATTACHMENT 15-1

COUPLING ALIGNMENT DATA SHEETPROJECT NO.: UNIT NO.: PAGE 1 OF

PROJECT NAME:

DESCRIPTION: EQUIPMENT NO.:

SYSTEM / SERVICE: PO/ITEM NO.:

LOCATION:

REFERENCE DOCUMENT NO. REV. NO. REMARKS

MANUFACTURER: MFG S/N:

COUPLING TYPE: S/N & MODEL:

MANUFACTURER RECOMMENDED GAP:

SINGLE ROTATION DOUBLE ROTATION

RIM RUNOUT A FACE RUNOUT A ANGULAR ALIGNMENT

RIM RUNOUT B FACE RUNOUT B OFFSET (PARALLEL) ALIGNMENT

ALIGNMENT: HOT COLD INDICATOR ON: DRIVER DRIVEN

ALL READINGS TO NEAREST: 0.0005 INCH OTHER:

NOTE: RUNOUT READINGS TAKEN FACING PUMP COUPLING, ROTATING CLOCKWISE

INSPECTION DESCRIPTION ACCEPTED NOT ACCEPTED N/A REMARKS

HOLD DOWN BOLT CHECK COUPLING CLEANLINESS PUMP/MOTOR BASE GROUT COUPLING GUARD INSTALLED PIPE STRAIN CHECKED

FIELD ENGINEER: DATE: FORM T_ALIGN1.DOT 1996:REV.0



ATTACHMENT 15-2

CHAIN OR BELT DRIVEN EQUIPMENT ALIGNMENT SHEET

PROJECT NO.: UNIT NO.: PAGE 1 OF

PROJECT NAME:

DESCRIPTION: EQUIPMENT NO.:

SYSTEM / SERVICE: PO / ITEM NO.:

LOCATION:

REFERENCE DOCUMENT NO. REV. NO. REMARKS

MANUFACTURER: MFG S/N:

BELT/CHAIN TYPE, SIZE:

INSPECTION DESCRIPTION ACCEPTED NOT ACCEPTED N/A REMARKS

EQUIPMENT SHAFTS PARALLEL INVERTICAL & HORIZONTAL PLANES

PULLEYS/SPROCKETS ALIGNED BELT/CHAIN TENSION CORRECT HOLD DOWN BOLT CHECK PULLEY / BELT CLEANLINESS EQUIPMENT BASE GROUT GUARD INSTALLED PIPE STRAIN CHECKED


FOLLOW-UP ALIGNMENT CHECKSALIGNMENT CHECK NO.: 1 2 3 4

DATE FIELD ENGINEER INITIALS PARALLELISM

PULLEY/SPROCKET ALIGNMENT

BELT/CHAIN TENSION

PIPE STRAIN CHECKED

FORM T_ALIGN2.DOT 1996:REV.0


Section 16

Pumps

GENERAL

There are more pumps in use than any other type of industrial machine except for electricalmotors. Pump capacity is expressed as the flow rate, or volume, usually in gallons per minute, atwhich the pump can discharge against a given pressure or head. Total head is the sum of thetotal suction lift plus the discharge head.

Total dynamic suction lift is the sum of two factors:

• Vertical distance of the pump above the liquid

• Frictional resistance in the suction pipe

Total discharge head is the sum of three factors:

• Vertical distance of discharge above the pump

• Frictional resistance in the discharge pipe

• Pressure required at the end of the pipe

The two main divisions of pumps are positive and non-positive displacement.

POSITIVE DISPLACEMENT PUMPS

Positive displacement pumps as the name implies work on the principle of displacement. Liquidenters the pump through the suction port and is ejected forcibly out the discharge port bydisplacement. The two types of positive displacement pumps are reciprocating pumps and rotarypumps.

Reciprocating Pumps

The three types of Reciprocating pumps are:

• Piston

• Plunger

• Diaphragm

These pumps are normally used in boiler feed systems, hydraulic systems, and in self primingapplications. Reciprocating pumps can be described as pumps that have a backward andforward motion. The motion of the piston as it moves away from the cylinder head draws liquidinto the cylinder through a suction valve. On the return stroke, the suction valve closes and theliquid is forced out through the discharge valve.

The difference between a piston and a plunger pump are:

• The piston is shorter than the stroke while plunger is longer than the stroke

• The seal on the piston pump is on the piston while the seal on the plungerpump is on the cylinder

Section 16 Pumps


The diaphragm type pump employs a rubber or neoprene bladder in place of the piston orplunger. This type of pump is used to remove water from trenches, flooded foundations, drains,and other places where there is a high proportion of mud, silt, or sand to the water.

Rotary Pumps

There are four basic types of rotary pumps:

• Vane

• Screw

• Gear

• Lobe

Rotary pumps are typically used to pump oil in hydraulic systems. They are simple in design,have few parts, and like reciprocating pumps are positive acting. Rotary pumps use a rotarymotion to carry the fluid from the inlet to the outlet. The pumps consist primarily of two cams orgears, one of which is rotated from an outside source of power. A close fitting casing surroundsthe gears and contains the suction and discharge connections.

The liquid fills the spaces between the gear teeth and is carried around the outside of the gears. When gear teeth mesh, the liquid is squeezed out and into the discharge port. After the liquid isdischarged, the gear teeth separate which creates a partial vacuum and allows new liquid to fillthe void. This process creates an even and continuous flow. Since this style of pump requiresclose clearances, the pumps perform best when the liquid has some lubricating properties.

NON-POSITIVE DISPLACEMENT PUMPS

Centrifugal Pumps

Centrifugal pumps, as shown in Figure 16-1, are supplied in single and multi-stage designs. Thistype of pump utilizes centrifugal force to add energy to the liquid. A centrifugal pump takes liquid

from the center of impeller vane rotation andthrows it outward and away from the center ofrotation into the casing or volute. In theprocess, energy is imparted and the liquidpumped. This pump is used to pump water inrelatively low volume and pressure conditions.

FIGURE 16-1 - CENTRIFUGAL PUMP

Pumps Section 16


Diffuser-Type Centrifugal Pump

Diffusion or turbine type centrifugal pumps are used in high pressure and high temperatureapplications. They differ from the casing type in that the rotating impeller is surrounded within thecasing by stationary guide vanes. The diffusion vanes provide gradually expanding passages inwhich the direction of flow is sharply changed and the velocity head becomes pressure headbefore the water reaches the circumference of the casing and flows toward the discharge outlet. In the diffuser type pump, the velocity head is converted into pressure head more completely thanthe volute type, and its efficiency may be higher.

Multistage Pumps

The multistage centrifugal pump is essentially a high head or high pressure pump. It consists oftwo or more stages depending on the pressure required in the system. Each stage is essentiallya separate pump. However, they are all located in the same housing and all impellers areattached to the same shaft.

The first stage receives the water directly from the source through the suction pipe, builds thepressure up to the correct single stage pressure, and passes it on to the next succeeding stage. In the last stage, the pressure has reached its design value and is discharged into the pipingsystem. Multistage pumps are installed for continuous service, handling hot or cold liquids,industrial, pipe line, and boiler feeds.


Section 17

Air Compressor Systems

GENERAL

The air compressor is the heart of any compressed air system. The compressor takes inatmospheric air, compresses it to the pressure desired, and pumps the air into supply lines or intoair receivers, which act as short term accumulators.

Compressed air has many uses:

• Powering air operated tools and devices such as rams or multiport valves

• Operating delicate instruments

• Agitating and atomizing liquids

• Blowing soot

• Conveying materials

There are a number of variations in the design, construction, and method of air compression incommercially available air compressors.

Compressor Functions

Atmospheric air is a mixture of gases, mainly nitrogen and oxygen and always contains somewater vapor.

Pascal's Law states that when a gas is confined under pressure in a closed container, thepressure is transmitted equally in all directions by the gas. For this reason, compressed gastanks are cylinders with spherical ends to contain the pressure more effectively.

To better understand how compressors work, it is important to understand what changes takeplace in atmospheric air to produce pressure. The air pressure stays constant as long as thetemperature and the container size remain the same. By adding heat to the container the airmolecules become more active which increases the internal container air pressure. This pressureincrease can be read on the pressure gauge. This is reflective of Charles' Law, which states:

"If the volume of a confined quantity of gas remains the same, the change inpressure of the gas varies with the change in the temperature of the gas."

The implication is that as the temperature increases, the pressure increases proportionally. Charles' Law also states:

"If the pressure of a confined quantity of gas remains the same, the change involume of the gas varies with the change in the temperature of the gas."

The implication here is that as the temperature changes, the volume changes proportionally.

We can also change the pressure by reducing the size of the container. By squeezing the massof air into a smaller space, molecular travel is restricted. There is no speed change but themolecules hit the walls with greater frequency, so the pressure is greater. This action is reflectiveof Boyle's Law, which states:

Section 17 Air Compressor Systems


"The absolute pressure of a confined quantity of gas varies inversely with itsvolume, if its temperature does not change."

This means that as the volume is decreased in a closed container, the pressure will increase.

Since air cannot be compressed without its temperature changing, Boyle's and Charles' Lawsoperate together according to the Ideal Gas Law.

Using compressed air to perform work requires the application of all the points covered thus far. Pascal's Law states that pressure developed in a confined gas is equal at every point touched bythe gas. If Piston 1 moves 5 inches displacing 50 cubic inches of air (5 inches x 10 squareinches), the 50 cubic inches of air acts on the 50 square inches of Piston 2, causing it to move1 inch (50 cubic inches divided by 50 square inches). The 5 to 1 pressure increase is directlyopposite of the 1 to 5 piston travel decrease.

It is important to understand these basic principles when dealing with compressors.

Basic Types of Compressors

There are two major design classifications of compressors:

• Positive displacement

• Dynamic

Positive Displacement Compressors

In positive displacement compressors, successive volumes of air are confined within a closedspace and pressure is increased by reducing the volume in the closed space. Units of this typemay be further classified as reciprocating or rotary. These classifications in turn can besubdivided by design features.

Reciprocating Compressors

This type of compressor draws air into the cylinders through valves during the suction stroke. Atthe end of the discharge stroke, air leaves at higher pressure. Separate valves are provided forinlet and outlet of the air.

The arrangement of reciprocating compressor frames and cylinders vary with capacity, dischargepressure, intended service, drive, and other factors. Compressed air pressures range from100-6,000 psi.

Some elements of reciprocating compressors are:

• Cylinders, heads, pistons, inlet and discharge valves

• Power transmitting parts, including piston and connecting rods, crosshead, crankshaft, andflywheel

• Lubrication system

• Cooling system

• Controls

Air Compressor Systems Section 17


Reciprocating Compressors are classified according to their operation:

• Single or double-acting

• Single or multistage

A compressor that compresses air at only one end of the cylinder is called a single-actingcompressor, while a compressor that compresses air at both ends of the cylinder is called adouble acting compressor.

A stage is a step or cycle that the compressor uses to compress air to its final pressure. A singlestage compressor is one which draws air in from the atmosphere and compresses it to its finalpressure in one stroke. Multistage compressors draw air in at atmospheric pressure andcompress it in two or more strokes. The compressor can be constructed with multiple cylinders,each with a different piston diameter.

In general, single stage compressors are more economical for pressures below 100 psi, withmultistage compressors being more economical above 100 psi. The Compressed Air and GasInstitute provides performance ratings on various types of compressors.

Rotary Compressors

Although compressed air over 100 psi is commonly used, many plants require lower pressure air(50 to 75 psi) with a moderate-to-high flow. Compressors that supply air for these types ofapplications are usually of the rotary type.

Rotary compressors are also classified into twoseparate types:

• Positive displacement

• Dynamic

Rotary compressors with mechanically separatedinlet and discharge ports are positive displacementtype, while those with no method of separating theports are dynamic type rotary compressors.

Positive displacement rotary compressors includesliding vane, dry screw, wet screw, liquid ring, andlobe types. Dynamic compressors include centrifugaland axial flow types that are similar to liquid pumps.

Sliding Vane rotary compressor traps air betweenvanes as the rotor passes inlet opening. As the rotor

turns toward the discharge port, the volume of between any two vanes decreases. This causesair pressure to rise to rated discharge value. Vanes slide in and out of slots as the rotor turns,and are held against the casing by centrifugal and spring force.

Rotary Compressor pressures vary from 50 psi for one stage to much higher pressures foradditional stages. Capacities are up to 5,000 cfm, approximately.

The Two Lobe rotary compressor has identical impellers held in a fixed relationship to each otherby external gears. When impellers rotate, each traps air between its outer surface and the

FIGURE 17-1 - SINGLE STAGE ROTARY



casing. When the impeller upper tip passes the top edge of the casing, it permits discharge tobegin. The bottom tip of the impeller pushes enclosed air into the discharge piping, compressingit against the backpressure. Lobe type two- and three-element designs have capacities from 5 toapproximately 50,000 cfm. Pressures above 15 psi are obtained by operating two or more unitsin series.

The Liquid-Piston rotary compressor has a round multiblade rotor that revolves in an ellipticalcasing partly filled with liquid, usually water. When the rotor turns, the blades form a series ofbuckets, which carry the liquid. The liquid follows the casing contours due to centrifugal force andalternately leaves and returns to the space between blades (twice each revolution). As liquidleaves the bucket, air is drawn in. When liquid returns, it compresses the air to dischargepressure. Liquid-piston compressors handle up to approximately 5,000 cfm. Single-stage units,as shown in Figure 17-1, can develop pressures to 75 psi.

Dynamic Compressors

Dynamic compressors use rotating elements to accelerate air. Velocity is converted to staticpressure by a diffusing action. Total energy in a flowing air stream is constant. Entering anenlarged section, flow rate is reduced and some of the velocity energy turns into pressure energy.Thus, static pressure is higher in the enlarged section. Dynamic compressors include centrifugal,axial, and mixed-flow designs. They are designed to deliver large amounts of air (as high as100,000 cfm) at pressures up to 125 psi.

Smaller units are used for low pressure operations. These are usually considered to be blowersrather than compressors, but still have the same construction as their larger counterparts.

Centrifugal Compressors usually take in air at the impeller eye, accelerating it radically. Somestatic pressure rise occurs in the impeller, but most is in the diffuser section of the casing, wherevelocity is converted to static pressure. Multistage compressors handle 500 to over 150,000 cfmat pressures as high as 150 psi. Typical of all centrifugal compressors, the impeller must rotate athigh speeds to be efficient.

Axial-flow compressors accelerate air in a direction generally parallel to the shaft. Units resembleturbines; each pair of moving and stationary blade rows forms a stage. Pressure rise per stage isrelatively small. Axial blowers have capacities from a few cfm to more than 100,000 cfm atpressures from 1 to 50 psi.

Compressor Accessories

Although the compressor is key to any air system, a number of auxiliary devices are needed toensure reliability, continued operation, and reduced maintenance of both the compressed airsystem and the system(s) it serves. Accessories can be broken down into two major categories:

• Primary air treatment

• Secondary air treatment

Primary air treatment is treatment of the air prior to and after it leaves the air compressor. The airis treated because it is taken from dirty or contaminated surroundings. In addition, air alwayscontains some moisture. Treatment of the air to remove contaminants and moisture is performedby certain accessories including:



• Intake air filters

• Inter and aftercoolers

• Moisture separators

• Traps

• Dryers

• Receivers

• Silencers

Intake Air Filters are filters that remove most of the dirt and other solid contaminants prior to theair entering the compressor. The filter units can be of the wet or dry type, depending onapplication. Dry filters usually have a felt or cotton material packed into a wire screen and may bein the form of a replaceable cartridge element. All of these filters may be cleaned with anappropriate solvent.

Wet filters are mounted in a shallow oil reservoir. Air entering the top of the filter is directeddownward into the oil and then upward through the filter medium. Any oil carried along with theair is trapped on the filter, along with any dirt or other contaminants.

Intercoolers and aftercoolers are used to transfer the heat generated by the compression of air toeither a cooling water medium or to the atmosphere. The intercooler is a cooler that is usedbetween stages on multistage compressors. Less power is needed to compress the air becausecooling between stages reduces the volume of air that is compressed in the next stage.Aftercoolers are similar to the intercoolers and can also be cooled by air or water.

Caution must be exercised as to the amount of cooling provided. If too much cooling is providedto the intercooler, the air will be cooled to a temperature at which the water vapor in the aircondenses. Water forming in the intercooler can be carried into the compressor high-pressurestage and cause mechanical damage. Cooling provided by the aftercooler usually cannot lowerthe temperature of the air enough to condense all of the water vapor. This means that somewater vapor is still in the air, along with some oil vapor, when it leaves the compressor.

Moisture Separators remove the water and oil vapors that are condensed in the aftercoolers. Most systems have mechanical separators which give the air a swirling motion or cause the air tosuddenly change direction.

On the swirling type, centrifugal force moves the oil and moisture to the outside of the separatorwhile the separated air travels up through a center passage. With a sudden change in direction,the heavier droplets of oil and water cannot change direction as easily, slam into the separatorwall, and drop into the bottom of the separator while the air is directed to the discharge line. Oilscrubbers work on this principle. Other types utilize a large chamber that lowers the air velocity,allowing the particles to drop to the separator bottom. Separators of this type remove up to 95percent of the liquid from the airstream.

Traps are devices that may either be separate from or integral to the moisture separator. Mostare float trap arrangements where in accumulation in the bowl lifts the float, opens the trap valve,and allows the moisture to drain. The drain valve is positioned above the bottom of the bowl toprevent solid particles from lodging between the valve and seat. The accumulation of sludge isremoved through a drain plug.



Dryers are used to condense the moisture in the compressed air after the aftercoolers. It isimportant to reduce the moisture content of the compressed air as much as possible to preventthe condensation of this air when reduced to atmospheric pressure while being used. There areseveral types of dryers used in the industry.

The refrigerated air dryer utilizes a heat exchanger, moisture separation section and refrigerationsystem. The warm air first enters a heat exchanger to lower its temperature slightly. The air thencomes into contact with the refrigerant coil which lowers the air temperature to about 35 oF, whichwill cause the water vapor to condense. The air then flows back through the heat exchanger priorto entering the system. The moisture is then drained away, removing most of the water vapor. For more complete moisture removal other filter dryer combinations must be used.

The other major dryer-type unit is the adsorption dryer. This unit is usually a dual dryerarrangement with one chamber in use at a time. The other chamber is regenerated and placedon standby. An automatic timer is used to switch dryer chambers, but the chambers may bemanually switched over as well. Air enters the four-way valve and is directed to the left chamber.

Inside the chamber, the air passes downward through a desiccant bed and the up through areturn tube in the center. Air is then directed through another four-way valve and into the airsystem. As the air passes through the desiccant bed, moisture is attracted to the surface of eachgranule of desiccant material and held on the surface. While air is being dried in the leftchamber, the right chamber is being regenerated.

Heated air flows through the discharge line, up through the desiccant, and out the inlet line. Thewarm air carries away the moisture in the desiccant bed. After a prescribed length of time, theheat is turned off and the hot desiccant bed is allowed to cool down. It is then placed in standbyand is ready for air drying.

Prefilters are used with these dryer units to prevent any particles from being carried into thedesiccant bed. Afterfilters are used to prevent desiccant from being carried into the rest of thecompressed air system. It is also very important to prevent oil and other impurities from passinginto the desiccant bed, since they would clog up the passages and cover the surface of thedesiccant granules.

Receivers are tanks used to store the compressed air. They must be sized correctly for thevolume of air in the system and for peak air flow demand to ensure the overall system pressuredoes not drop too low.

Secondary air treatment is used to ensure the proper operation of the pneumatic system in orderto protect components and increase their service life. The following types of equipment areinvolved in secondary air treatment:

• Separators

• Filters/strainers

• Lubricators

Separators are similar to the separators used for primary air treatment. They are either thegravity or centrifugal type. The gravity type removes only large particles from the air. Thecentrifugal type may be of several different designs which will remove either large or minuteparticles, depending on the requirements of the system.



Filters will be referred to as micron-filters. A micron is approximately 0.00004 inch in size. Smokeparticles usually range on the order of 0.01 to 1 micron in size. Compressed air has dust particleswhich range between 0.1 and 10 microns in size and fine oil particles in the 0.01 to 0.8 micronrange. Filters are classified as surface or depth. Surface filters collect particles on a singlesurface and depth filters collect particles on several layers which have openings in the filter mediaof several different sizes.

Wire mesh surface filters or strainers are used to remove larger particles in the compressed airsystem. Strainers used in the line may be made of metal ribbons, discs, or plastic impregnatedpaper. Ribbon elements are usually tapered with the thicker section on the outside and usuallyremove particles larger than 40 microns. A strainer is usually placed in line just ahead of the filter.

Depth filters may be of the dry or wetted type and are used according to application. Dry filtersrely on the filter medium to remove particles. Wetted filters depend on a coating or a bath of oil toaid in collecting and holding particles. Air leaving the wetted filter will always contain some oil.

One type of dry filter is the adsorption type which consists of an adsorbing medium, such ascarbon or chemicals. Particles collect on the surface of the material, drop off the filter, and settlein the bottom of the bowl. Absorption filters, such as desiccant filters, are also used. These drawthe moisture vapors into an absorbing medium. Most absorbing filters use material whichchanges color as it absorbs the moisture. Most of these types are in the 0.5 micron and aboverange.

In a wetted filter, such as the oil bath type, air is directed through the top of an oil bath prior topassing through the filter medium. The filter medium, coated with oil, holds the particles. Thesefilters are very efficient and can remove 100 percent of particles 3 microns and larger. They canalso be cleaned whenever necessary, while most of the dry-type filters must be replaced.

Lubricators are used to ensure the addition of lubricating oil to the compressed air for use withtools, controls, and cylinders which require lubricated air to reduce wear and corrosion. The air isfirst routed through a strainer and filter and then lubricated to ensure that the air supplied toequipment requiring lubrication is water-free and uncontaminated.

The Fine Lubricator supplies a fine, suspended oil mist into the airstream. Metered oil from thereservoir enters the oil mixing chamber and is atomized by a small stream of air. This oil-airmixture is directed against a deflector which separates oil droplets larger than 2 microns. Thelarger oil droplets fall into the reservoir, and the oil mist leaves the lubricator and mixes with themain airstream. Vanes or flow guides are usually provided to vary the amount of lube oil withchanges in air flow.

Typical Compressed Air System Arrangements

Air enters the compressor through the intake filter, where dust and other impurities are removed. The air then enters the first stage through the intake valves, and is compressed. In this stage, thepressure is elevated and heat is produced during the compression cycle.

The air then goes to the intercooler and gives up some of its heat to the cooling water flowingthrough the intercooler tubes. Moisture in the air is also condensed during the cooling cycle. Themoisture is removed from the cooler by means of a trap.



The cool air then enters the intake valves of the second stage, where the pressure is elevatedeven more. During the compression cycle, heat is once again produced. The hot air leaves thesecond stage and enters the aftercooler, where the cooling water, flowing through the tubes,cools the air and condenses the moisture in the air.

The air leaving the aftercooler enters a moisture separator which is a mechanical device used forremoving the moisture from the air. The collected water is removed by a trap.

A prefilter is installed downstream of the moisture separator to filter out moisture and condensedoil.

The air enters a dryer where the air is removed of moisture adsorption. Condensed moisture isremoved by traps if the desiccant becomes saturated. This type of dryer is called theregenerative type, because it can be rejuvenated by heat.

The receiver stores the air. Any water that collects in the receiver is removed by traps. The airthen finally enters the distribution system.

Typical Compressor Safety Devices

Some typical compressor safety devices include:

Relief Valves

Located on each compressor stage discharge sides to relieve excessive pressure.

Overspeed Shutdown

Trips out drive when compressor exceeds predetermined safe speed.

Oil-Failure Shutdown

This device protects bearings by stopping unit when oil pressure fails.

Jacket-Water Valve

Shuts down compressor if water pressure fails.

Over-Pressure Shutdown

Stops compressor when discharge pressure goes above pre-set safety value.

Excessive Temperature Shutdown

For isolated compressors this gives protection against high discharge temperature.

Main-Bearing Protection

Thermal shutdown devices stop compressor if bearing temperature goes too high.

TROUBLESHOOTING GUIDE

The following are some of the problems that occur in water and air-cooled compressors:



Water-Cooled Compressors:

Problem Discharge pressure low

Cause Demand greater than compressor's capacity; rings worn; leaky packing;wrong speed; excessive leakage in system

Problem Not enough capacity

Cause Too much leakage in piping or valves; discharge pressure too high; wrongspeed, clogged filter; worn piston and rings

Problem Compressor does not deliver air

Cause Dirty intake filter; suction line clogged; improper installed valves

Problem Excessive compressor vibration

Cause Unit not properly secured to foundation; wrong type of foundation; piping notcorrectly supported; incorrect alignment

Problem Compressor overheats

Cause Broken valve strips; not enough cooling water; air-intake filter clogged;discharge pressure too high; internal leakage

Problem Compressor overloads motor

Cause Belts on driver too tight; pressure or speed too high; discharge line clogged;wrong motor hookup

Problem Compressor knocks

Cause Loose flywheel or pulley; too much clearance in wrist-pin bushing, crankpin, ormain bearings; loose valve or piston nut

Air-Cooled Compressors:

Problem Not enough capacity

Cause Excessive leakage in pipes, fittings, or valves; discharge pressure too high;wrong speed; clogged intake filter; worn pistons and rings; leaky cylinderhead gaskets; belt slips; intercooler leaks

Problem Compressor overheats

Cause Valve strips broken; direction of rotation wrong; intake filter clogged;discharge pressure too high; internal leakage; not enough lubricating oil

Problem Compressor knocks

Cause Loose flywheel of pulley; loose valve in cylinder or loose unloader; excessiveend play in motor rotor; too much wristpin or crankpin bearing clearance; beltnot aligned; unlevel mounting



Problem Excessive compressor vibration

Cause Unit not properly secured to foundation; wrong foundation; shipping blocksnot removed from under base; motor rotor out of balance; one cylinder in atwo cylinder unit not working; incorrect alignment

Problem Circuit breaker trips

Cause Low voltage; press switch differential too small; unit starting against a fullload; motor defective; compressor or motor binding

COMPRESSOR OPERATION AND MAINTENANCE

The best guide to compressor operation and maintenance is the manufacturer's instructionmanual. It is important to carefully follow the manufacturer installation instruction and associatedauxiliaries.

Once a compressor is on the line and working right, regular inspection, lubrication, andoverhauling, when done properly pay big dividends. The instruction manual is the best guide forrequired service.

Air Removal Equipment

Compressors have uses other than compressing air for the operation of tools. Compressors arealso used for the removal of air from a system or piece of equipment, such as condensers, toimprove operation and efficiency. Any of the various types of compressors discussed above canbe used for this job.

In the specific case of condensers, air that enters the condenser must be removed to maintain avacuum. If the air and gas were allowed to remain, they would blanket the tube surfaces, reduceheat transfer, and eventually destroy the vacuum. A high vacuum must be maintained at all timesto reduce the turbine back pressure, increase turbine efficiency, and recover the condensate atthe lowest possible temperature.

Another important system from which air is removed is the condenser waterbox. The coolingwater level in the condenser waterbox should be as high as possible. Air that is entrained in thecooling water collects in the top section of the waterboxes and if allowed to remain, wouldeventually replace the cooling water. This would then restrict water flow through the top sectionof condenser tubes and would reduce the condenser's ability to maintain a vacuum.

Air Ejectors (Steam-Jet Air Pumps)

Steam jet air pumps operate by converting the energy of high pressure, high temperature steaminto a high velocity jet. This conversion is accomplished through a steam nozzle. The highvelocity jet entrains and accelerates the air and gases at the suction chamber of the steam jet.

Motive steam and non-condensables then pass through a diffuser, which is designed to compressthe mixture to a pressure greater than that existing at the suction of the jet without creatingexcessive turbulence. One or more stages may be used.



During the initial evacuation and operation periods, a hogging jet and a set of operating jets,respectively, are required. Thus, the hogging jet handles larger quantities of air than do theoperating jets.

A hogging jet compresses air from the condenser to atmospheric pressure, in one stage. In mostcases, the motive steam and entrained air are discharged to the atmosphere.

A two-stage steam jet is frequently used to remove the non-condensables from a condenserduring operation. This ejector is furnished with an intercooler and aftercooler. By compressing intwo-stages, and by use of coolers to condense the motive steam, the steam consumption of themultistage ejector is maintained at a minimum. Condensate from the main condenser is used asthe cooling medium.

This permits recovery of the available heat in ejector motive steam. The air ejector drains areusually returned to the main condenser, and this condensate is returned to the system.

Steam jet equipment has the following advantages:

• High reliability due to no moving parts

• Very low maintenance

• Lower initial cost

• Operation at practically no cost.

Mechanical Vacuum Pumps

Steam ejectors have been used widely in the past. Recently, the trend has shifted to mechanicalpumps. Mechanical vacuum pumps can be used for both initial and continual evacuation of theair in leakage to a unit during operation.

Mechanical vacuum pumps have desirable features:

• They lend themselves most economically to push button operation from a remote point.

• They eliminate the need for auxiliary steam and costly high pressure steam piping.

• Since they discharge vapor and gases to the atmosphere, the possible recycling of non-condensables is eliminated.

• They can be located without restrictions that might be imposed by other types of equipment.

• Since they are not dependent on steam for operation, they can be operated at any timedesired, during the startup of a unit.

A typical two-stage mechanical vacuum pump. Operation would be as follows:

Hogging Sequence:



During initial air evacuation only the first stage is used. Air and non-condensables enter the gasinlet flow to the first stage; the first stage discharges the air to the separator tank. Here the airand non-condensables are exhausted to atmosphere.

Holding Sequence:

At approximately 7 inches Hg absolute (ABS) the second stage comes into operation. Gas andnon-condensables enter the inlet of the first stage, then discharge to the second stage. Thesecond stage discharges to the separator, where the air and non-condensables separate from thewater. The air and non-condensables are exhausted to atmosphere.

Air-Leakage Meters

Air leakage meters are installed in vent piping from the aftercondenser in steam ejectors or in gasdischarge lines on mechanical pumps. There are various designs of piston type meters.

Air leakage meters are important in determining how much air leakage is occurring in the system. Comparing air leakage on running units with new unit operation can warn the operator ofexcessive air leakage or faulty equipment.


Section 18

Heat Exchangers

GENERAL

A heat exchanger or interchanger is a device which transfers heat from one fluid to anotherthrough a container wall. In a typical process industry application, a heat exchanger may be avessel in which an outgoing processed hot liquid transfers some of its heat to an incoming coldliquid about to be processed. The amount of heat transferred is therefore not lost and can beused again.

Heat exchangers can also be used to cool process fluids. For example, an outgoing cold gasmay take up part of the heat from an incoming warmer gas, as in a liquid-air plant.

Double Pipe Exchangers

As shown in Figure 18-1, a double pipe or fintube exchanger consists of two pipes, one insideanother. The inner tube is usually finned to provide a larger surface for heat transfer. Doublepipe exchangers are used where flow and necessary temperature transfer are rather small.

Fintube exchangers are generally used when one fluid is gaseous, viscous, or of small quantity. They are particularly desirable for high pressure services because their small diameter isconducive to low cost construction. Their modular design assures maximum flexibility ofapplication since sections can be stacked vertically or horizontally to attain desired heat transfer. It is also easy to reuse these units in other services since one or more sections may be used asneeded. The fins can be welded to the tube to form a unit. Fins can also be formed by anextrusion process. For special applications they may be on the inside or on both inside andoutside of the parent pipe.

1. SHELL ASSEMBLY 8. FINTUBE STUB END FLANGE 15. SHELL NOZZLE BOLTING2. TUBE ASSEMBLY 9. TUBE RETURN BEND CONNECTOR 16. BRACKET BOLTS3. COVER PLATE 10. TUBE RETURN BEND CONNECTOR 17. COVER GASKET4. COMPRESSION FLANGE 11. TUBE RETURN BEND CONNECTOR 18. FINTUBE GASKET5. SEALING RING 12. SHELL NOZZLE COMPANION FLANGE 19. SHELL NOZZLE GASKET6. SPLIT RING 13. COVER PLATE BOLTING 20. NAMEPLATE7. FINTUBE FITTING FLANGE 14. TUBESIDE BOLTING

FIGURE 18-1 - DOUBLE PIPE EXCHANGER

Section 18 Heat Exchangers


FIGURE 18-2 - TEMA SHELL AND TUBE EXCHANGER TYPES

Heat Exchangers Section 18


The shell side is furnished with companion flanges so that piping can be connected to a beveledend. Tubeside connections are supplied with a flanged assembly to allow the tube hairpin to bedisconnected from the piping. The tube or hairpin section will be pulled from the return bendhousing end.

These units are almost always installed as multiple modules. They are normally spoken of inmultiples such as "3 wide by 2 high" which refers to 6 modules installed in 2 layers, 3 side by sideunits. Support saddles are provided with bolt holes on all four sides for modular bolting and arenot fixed to the shell assembly, leaving foundation spacing. Sometimes one or two units arebolted to vertical steel columns.

Shell and Tube Exchangers

Shell and tube type exchangers of the type shown in Figure 18-3 are most commonly specifiedfor process plants. These exchangers are designed in accordance with the TEMA (TubularExchanger Manufacturers Association) code. Figure 18-2 lists typical TEMA shell and tube heatexchanger types. TEMA also specifies exchanger part types in a letter code.

Referring to the type AES exchanger shown in Figure 18-4, flow entering the nozzle, Item 6, atthe channel or tubeside end meets the pass partition, Item 1, and is diverted into the tubes. Thetubes, Item 13, route flow to the other end and back to the channel outlet nozzle. Shell side fluidenters nozzle, Item 11, and makes contact with the outside of the tubes. Transverse baffles, Item17, are located so that they force the fluid to flow up and down, making the most efficient tubecontact and attaining maximum heat transfer on its way to the outlet nozzle.

1. PASS PARTITION 12. IMPINGEMENT BAFFLE 23. GASKET2. BLIND FLANGE 13. TUBE 24. BACK-UP RING3. LIFTING RING 14. TIE ROD 25. SPLIT-KEY RING4. CHANNEL FLANGE 15. SPACER 26. VENT CONNECTION5. CHANNEL CYLINDER 16. SHELL CYLINDER 27. SHELL COVER CYLINDER6. CHANNEL NOZZLE 17. TRAVERSE BAFFLE 28. SHELL COVER HEAD7. CHANNEL FLANGE 18. SUPPORT PLATE 29. FLOATING HEAD COVER8. STATIONARY TUBE SHEET 19. STUD 30. FLOATING TUBE SHEET9. SHELL FLANGE (CHANNEL END) 20. HEX NUT 31. DRAIN CONNECTION10. INSTRUMENT CONNECTION 21. SHELL FLANGE (COVER END) 32. SUPPORT SADDLES11. SHELL NOZZLE 22. SHELL COVER FLANGE

FIGURE 18-3 - TYPICAL SHELL AND TUBE HEAT EXCHANGER



The tube bundle iscomprised of thetubesheet, Item 8, andthe tubes attached to thetubesheet. By removingthe channel section, theentire tube bundle can bepulled out from theexchanger for cleaning,repairs or totalreplacement. Not allexchangers haveremovable tube bundles. Nonremovable tubebundle exchangers arecalled fixed tubesheettypes.

Kettle Type Exhangers

In the kettle type exchanger shown in Figure 18-5, the heating fluid always enters the channel topnozzle, Item 4, and exits via the bottom channel nozzle. The main purpose of the shell side is tovaporize liquid entering the shell nozzle, Item 7, near the shell flange, Item 13. Vapor exitsthrough the shell nozzle, Item 7, at the top of the exchanger shell. The weir, Item 10, is a dam

FIGURE 18-4 - TEMA TYPES AES SHELL AND TUBE EXCHANGER

1. CHANNEL COVER 7. SHELL NOZZLE 13. SHELL FLANGE2. CHANNEL FLANGE 8. LIQUID LEVEL CONNECTION 14. SUPPORT3. INSTRUMENT CONNECTION 9. SHELL COVER 15. TIE RODS AND SPACERS4. CHANNEL NOZZLE 10. WEIR 16. SUPPORT PLATES5. PASS PARTITION 11. CHANNEL 17. TUBES6. SHELL 12. TUBESHEET

FIGURE 18-5 - TEMA KETTLE TYPE SHELL AND TUBE EXCHANGER

Heat Exchangers Section 18


designed to keep the tube bundle covered with liquid at all times. Surplus liquid overflows theweir and into the shell cover area. A level controller is piped to the Liquid Level Connections,Item 8, and maintains liquid level in this section at about half the weir height. Surplus liquid exitsvia the shell nozzle, Item 7, in this section. Normally a level gage allows visual examination of theliquid level behind the weir.

Air Cooled Heat Exchangers

Air cooled heat exchangers are those in which the cooling is done by blowing or drawing airacross finned tubes. Air cooled exchangers may be either induced draft as shown in Figure 18-6or forced draft as shown in Figure 18-7 which means that the fans may either be mounted abovethe tube sections, drawing the air up through the tubes and exhausting to the atmosphere, or thefans may be mounted below the tube sections, drawing the air from the atmosphere and forcing itup through the sections. The commodity temperature from the coolers can be controlled by:

• The use of two speed fans

• Adjustable louvers

• A combination of the two

Two speed fans have the definite advantage of conserving horsepower and are usually provided. The range of control gained by this means is obviously limited and, for this reason, adjustablelouvers are quite often provided where more precise control is required such as in extremely cold

FIGURE 18-6 - INDUCED DRAFT AIR COOLED HEAT EXCHANGER



climates. The louvers may be manually or automatically controlled by the commodity outlettemperature. The fans may also have adjustable pitch blades for further temperature control. This is usually done automatically through a hydraulic drive.

A significant feature of the dry coolers is the finned tubes. It is necessary that the tubes havethese fins to increase the surface in contact with the air where the heat transfer rate is usuallyquite low. Since these fins must be relied on to conduct the bulk of the heat from the commodityinside the tubes to the air outside, it is important that they maintain a good thermal bond with thetubes at all times.

There are several different types of fin construction. The best and most durable type is that inwhich the fins are an integral part of the tube itself and are formed by extrusion of the tubethrough a die. This type of tube, however, is usually rather expensive. At least one manufacturerattaches the fins by routing a groove in the tube wall and forcing the fin tightly into this groove. Insome cases, the fin is wrapped around the tube and then soldered to the tube. This provides avery high thermal efficiency. In some cases, the fins are wound in a tight helix about the tube andsoldered at each end. This design depends on pressure to hold the fin against the tube and airgaps between the fin and tube reduce the thermal transfer.

FIGURE 18-7 - FORCED DRAFT AIR COOLED HEAT EXCHANGER


Section 19

HVAC Systems

GENERAL

Plant Heating System

The plant heating system:

• Maintains the minimum design ambient air temperature for equipment protection during normalplant operating conditions and during plant shutdown

• Provides heating for personnel comfort in the offices and in other occupied areas

As an example, the plant heating system would provide heating for the following areas in a fossilpower plant:

• Turbine and boiler areas

• Auxiliary services area

• Control room complex area

• Administration, shops, and warehouse building

• Flue gas desulfurization building

• Water treatment building

Heating systems for the surge pond pump house, cooling tower pump house, coal handling area, andother yard buildings are not part of this system.

The major components of the plant heating system include:

• Heat exchanger

• Heating water boiler

• Hot water circulating pumps

• Hot water expansion tank

• Air separator

• Chemical feeder

• Fan coil units

Heating and Ventilating Systems

The heating and ventilating systems perform the following typical functions:

• Provides adequate ventilation to dissipate heat rejection from operating equipment

• Maintains space design temperature ranges for various modes of plant operation, includingshutdown, in conjunction with the plant heating system

• Furnishes filtered ventilation air to minimize airborne dust in the plant

HVAC Systems Section 19


• Provides air movement from the turbine area towards the boiler area to minimize backflow of coaldust

• Removes contaminated air to eliminate health hazards, nuisances, or fire dangers

• Pressurizes areas to minimize outside air infiltration

The heating and ventilation requirements are based on the following:

• Minimum amount of outside air necessary to provide building pressurization

• Heat losses during low ambient outdoor air conditions

• Heat gains from mechanical and electrical equipment

HVAC System Design

Heating, ventilating, and air conditioning systems provide the proper atmospheric environment forthe facility. The criteria for the facility environment may be based on personnel occupancy or onmechanical or electrical equipment operation requirements. The HVAC system maintainstemperature, humidity, and dust levels within established limits to satisfy health regulations andlimits established by the equipment design. The following codes are normally used for the designof HVAC systems:

ASHRAE American Society of Heating, Refrigerating and Air Conditioning Engineers

SMACNA Sheet Metal and Air Conditioning Contractors National Association

AMCA Air Moving and Conditioning Association

In establishing the design criteria for the HVAC system, both outdoor and indoor conditions areconsidered. Outdoor design conditions can be determined from the ASHRAE Data Book,Weather Bureau data, or site meteorology data. Designs are typically based on conditions thatwill not be exceeded by more than 1 percent of the time on either extremely hot summer days orextremely cold winter days.

Indoor design criteria will vary on the intended use of the facility. All office areas and areashousing sensitive electrical and instrumentation equipment are typically air-conditioned andmaintained at an ambient temperature of 75°F ± 5°F with a maximum relative humidity of 60percent throughout the year. In the unoccupied areas of the facility, the indoor design conditionsare determined by the electrical and mechanical equipment ambient requirements. Generally,these areas are typically maintained at a maximum temperature of 104°F during the summer anda minimum of 50°F during the winter.

HVAC systems also serve to prevent the accumulation of explosive gases and to regulatebuilding pressures. For example, certain areas of the facility may contain equipment and materialthat release combustible gases such as hydrogen or methane. To prevent accumulation andconcentration of these gases, the HVAC system may be designed to provide large air-change inthese areas. Battery rooms and coal silos are typical examples of this type of condition.

In some cases, it is also desirable to control building air pressures when control of air flowdirection is necessary. In these cases, the HVAC system is used to provide negative or positive

Section 19 HVAC Systems


pressure boundaries inside the building. An example of this application is in the negative pressureboundary established to prevent the release of coal fumes from a coal silo.

Air-Conditioning Loads

To size the air-conditioning system, the system must accommodate not only external heat andcooling but also internally generated heat and cooling loads. The following are examples of theloadings typically considered in a HVAC system design:

• Heat transfer from the outside

• Heat load from equipment

• Heat transfer from hot pipes and equipment

• Lighting systems

FIGURE 19-1 - AIR-CONDITIONING SYSTEM FUNCTIONAL DIAGRAM



• Personnel

• Infiltration

• Outside air supplied to the air-conditioning system

The process of calculating the load on an HVAC system is interactive since several factorscontribute to the loadings. Generally, a factor of safety is included in the preliminary calculationsto minimize the impacts of subsequent changes.

A typical functional diagram for an air-conditioning system is shown in Figure 19-1. A functionaldiagram for a split or air cooled condenser system is shown in Figure 19-2.

Typical HVAC Equipment

The following are some of the typical types of HVAC equipment:

Disposable Low/Medium Efficiency Filters

These filters are made of glass fibre material. Filters with high dust holding capacity are made ofpleated media formed as bags (usually 36 inches deep) to provide a large surface. Another typeis the automatically renewable media roll filter which uses a motor to continuously move the largeroll of filter media that is located in the path of the air flow.

FIGURE 19- 2 - FUNCTIONAL DIAGRAM OF SPLIT SYSTEM (AIR COOLED CONDENSER)

Section 19 HVAC Systems


High Efficiency Particulate Air (HEPA) Filters

These filters are designed to provide a particulate removal efficiency of 99.97 percent for 0.3micron particle size. It consists of a fiberglass media enclosed in a particleboard frame.

Fans

Vaneaxial, propeller, centrifugal, and power roof ventilation fans are commonly used in HVACsystems. Centrifugal fans are designed with forward curved, backward curved, or radial fanblades. The forward curved blades have lower initial costs but the backward curved designs havelower operating costs. Fan bearings are typically rated for approximately 100,000 hours ofoperation. Fan sound levels are typically limited to no more than 95 db at 5 feet from the fan.

Air Handling Units (AHU)

AHU’s consist of a fan and a cooling coil mounted inside a sheet-metal box. The fan sectionlocated downstream of the cooling coil section is insulated on the inside with thermal and soundinsulation. Cooling coils are either direct expansion or chilled water type. Cooling coils are madeof copper-nickel tubes with aluminum fins. Copper fins are used in highly corrosive atmosphereapplications. For heating systems, the coil is a hot water, steam, or electric heating coil. Coils aretypically designed for 150 psig. AHU’s are also called fan coolers.

FIGURE 19- 3 - SIMPLIFIED REFRIGERATION CYCLE



Chillers

Chillers generate chilled water for use in the cooling coils of air handling units. The machineconsists of a package consisting of a centrifugal refrigeration compressor, a tube and shell heatexchanger called a compressor and another tube and shell heat exchanger called an evaporator. A simplified refrigeration cycle is shown in Figure 19-3. There are two types of chillers:

• Open type in which the motor, compressor, and their coupling are open to the atmosphere.

• Hermetic type in which the compressor and motor are hermetically sealed in a steel shell.

Chillers are capable of capacity control down to 10 percent of its full capacity. Due to concernsrelated to ozone depletion in the atmosphere, the refrigerant used in chillers is being changedfrom freon to other materials.

Ducts

Sheet-metal ducts are used to distribute filtered, cooled, and heated air to conditioned areas. Duct design and fabrication are typically done in accordance with the SMACNA code. Ducts forair-conditioned areas are typically designed for an air velocity less than 1500 feet per minute. Insome applications such as in power plants, however, ducts may be designed for air velocitiesover 2000 feet per minute. Air flow measuring stations are used in duct systems at points whereaccurate air flow measurement is required.


Section 20

Chiller Systems

GENERAL

A liquid chilling system cools water, brine, or other secondary refrigerant liquid for air-conditioningor refrigeration purposes. The system may be either factory assembled and wired or shipped insections for erection in the field. The most frequent application is water chilling for airconditioning, although both brine cooling for low temperature refrigeration and chilling of fluids inindustrial processes are also common uses.

The basic components of a liquid chilling system include a compressor, a liquid cooler(evaporator), a condenser, a compressor drive, a refrigerant flow control device, and a controlcenter, and may also include a receiver, an intercooler, or a subcooler. In addition, certainauxiliary components may be employed, such as an oil cooler, an oil separator, an oil returndevice, a purge unit, an oil pump, a refrigerant transfer unit and additional control valves.

Principles of Operation

Liquid (usually water) enters the cooler where it is chilled by refrigerant liquid evaporating at alower temperature. The refrigerant gas produced is drawn into the compressor, which increasesthe pressure of the gas so that it may be condensed at a higher temperature in the condenser. The condenser cooling medium is warmed in the process. The condensed liquid then flows to theevaporator through a metering device.

Both hermetic and external drive liquid chilling machines are available. An external drive machineuses a compressor which may be driven by a turbine, an engine, or an external electric motor. The compressor driver is easily accessible for repair or replacement. A drive shaft seal isnecessary to isolate the refrigerant and oil from the atmosphere.

A hermetic unit employs a hermetic compressor with an electric motor totally enclosed in arefrigerant atmosphere. The possibility of refrigerant leakage to the outside through a shaft sealis eliminated and motor operating noise is subdued by the housing. Since forced refrigerantcooling of the motor is very effective, smaller, less expensive motors are used. The need for aheavy external base to preserve motor to compressor shaft alignment is eliminated. Hermeticmachines are less expensive than external drive machines and are quieter.

External drive machines are often used because of a desire to apply steam turbine, gas turbine,gas engine, or synchronous motor drives.

Liquid Chiller Controls

The chilled liquid temperature sensor sends an air pressure (pneumatic control system) orelectrical (electronic control system) signal to the control circuit, which modulates compressorcapacity in response to leaving or return chilled liquid temperature change with load.

The water temperature controller is a thermostatic device which unloads or cycles the com-pressor(s) when the cooling load drops below minimum unit capacity. An anti-recycle timer issometimes used to limit starting frequency.

Section 20 Chiller Systems


On centrifugal or screw compressor chillers, a current limiter or demand limiter limits compressorcapacity during periods of possible high power consumption (such as pulldown) to preventexcessive current draw.

Reciprocating Liquid Chillers

The reciprocating compressor is a positive displacement machine which maintains fairly constantvolume flow rate over a wide range of pressure ratios. Three types of compressors are commonlyused in liquid chilling machines:

• Welded Hermetic

• Semi-hermetic

• Direct Drive Open

Open liquid chillers are usually more expensive than hermetic chillers, and are declining in use forthis reason. Hermetic motors are generally suction gas cooled in which the rotor is mounted onthe compressor crankshaft.

Condensers may be evaporative, air, or water cooled. Water cooled versions may be either tubein tube or shell and coil for low cost, or shell and tube for compactness. Most shell and tubecondensers can be repaired, while the other types must be replaced if a leak occurs on therefrigerant side.

Air cooled condensers are much more common than evaporative condensers. Less maintenanceis needed for air cooled heat exchangers than for the evaporative type. Remote condensers canbe applied with packages without condensers.

Coolers are usually direct expansion, in which refrigerant evaporates while flowing inside tubesand chilled liquid is cooled as it is guided several times over the outside of the tubes by shell sidebaffles. Tube in tube coolers are sometimes used with small machines.

The thermal expansion valve modulates refrigerant flow from the condenser to the cooler tomaintain enough suction superheat to prevent any unevaporated refrigerant liquid from reachingthe compressor.

Oil cooling is not usually required for air conditioning. However, oil cooling may be accomplishedby a refrigerant cooled coil in the crankcase or by a water cooled oil cooler. Oil coolers are oftenused when extra oil cooling ability is needed.

Control Considerations

A reciprocating chiller is distinguished from centrifugal and screw compressor operated chillers byits use of increments of capacity reduction rather than continuous modulation. Therefore, uniquearrangements must be used to establish precise chilled liquid temperature control whilemaintaining stable operation free from excessive on/off cycling of compressors, or unnecessaryloading and unloading of cylinders.

To help provide good temperature control, return chilled liquid temperature sensing is normallyemployed by units with steps of capacity control. Leaving chilled liquid temperature sensing has

Chiller Systems Section 20


the advantage of preventing excessively low leaving chilled liquid temperatures if chilled liquidflow falls significantly below the design value.

Centrifugal Liquid Chillers

The centrifugal compressor offers a wide range of capacities continuously modulated over alimited range of pressure ratios. By altering items such as number of stages, compressor speed,impeller diameters, and choice of refrigerant, it can be used in liquid chillers having a wide rangeof chilled liquid temperatures and cooling fluid temperatures. Its ability to operate at greatlyreduced capacity makes for more on-line time with infrequent starting.

Both open and hermetic compressors are used. Open compressors may be driven by steamturbines, gas turbines or engines, or electric motors, with or without speed changing gears.

Packaged electric drive chillers may be of the open or hermetic type and use two pole, 50 Hz or60 Hz polyphase electric motors, with or without speed increasing gears. Hermetic units use onlypolyphase induction motors. Speed increasing gears and their bearings in both open andhermetic type packaged chillers operate in a refrigerant atmosphere and the lubrication of theircontacting surfaces is incorporated in the compressor lubrication system. Magnetic and SCR(silicon controlled rectifier) motor controllers are used with packaged chillers.

Flooded coolers are commonly used, although direct expansion coolers are employed by somemanufacturers in the lower capacity ranges. The typical flooded cooler uses copper tubes whichare mechanically expanded into the tube sheets, and in some cases, into intermediate tubesupports as well.

Since refrigerant liquid flow into the compressor increases power consumption, mist eliminators orbaffles are often used in flooded coolers to minimize refrigerant liquid entrainment in the suctiongas.

The condenser is generally water cooled, with refrigerant condensing on the outside of coppertubes. Very large condensers may have refrigerant drain baffles which direct the condensatefrom within the tube bundle directly to the liquid drains, reducing the thickness of the liquid film onthe lower tubes.


The chilled liquid temperature sensor in centrifugal systems is usually placed in thermal contactwith the leaving chilled water. In electrical control systems, the electrical signal is transmitted toan electronic control module which in turn controls the operation of an electric motor or motorspositioning the capacity controlling inlet guide vanes. A control limiter is usually provided onelectric motor-driven machines. An electrical signal from a current transformer in the compressormotor controller is sent to the electronic control module. The module thus receives indications ofboth the leaving chilled water temperature and the compressor motor current. The portion of theelectronic control module responsive to motor current is called the control limiter.

Additional operating controls are needed for appropriate operation of oil pumps, oil heaters, purgeunits and refrigerant transfer units. An anti-recycle timer also is included to prevent excessivelyfrequent motor starts. Multiple unit applications require additional controls for capacity modulationand proper sequencing of units.



Safety controls must be provided for the protection of the unit under abnormal conditions. Safetycutouts that may be required are:

• High condenser pressure

• Low evaporator refrigerant temperature or pressure

• Low oil pressure

• High oil temperature

• High motor temperature

• High discharge temperature

Screw Liquid Chillers

The screw or helical rotary compressor is a positive displacement machine with nearly constantflow performance. Compressors for liquid chillers are oil injected, resulting in several benefitsover non-oil injected screw compressors, including:

• Reduced operating noise

• Lower operating speed

• Increased thermal and volumetric efficiencies

• Ability to operate at very high pressure ratios

• Elimination of timing gears

• Lower discharge temperature

• Smaller condensers when a portion of the total heat rejection is accomplished by an oil cooler

The cooler may be flooded or direct expansion. The flooded cooler is more sensitive to freeze-up, requires more refrigerant, and requires closer evaporator pressure control. The directexpansion cooler requires closer mass flow control, is less liable to freeze, and returns oil to theoil system rapidly.

A suction gas high pressure liquid heat exchanger is sometimes incorporated into the system toprovide subcooling.

Flooded coolers are used in units with a capacity larger than about 400 tons. Direct expansioncoolers are also used in larger units in the range up to 800 tons.

The condenser may be included as part of the liquid chilling package when water cooled. Aircooled liquid chilling packages are also available. When remote air cooled or evaporative cooledcondensers are applied to liquid chilling packages, a liquid receiver generally replaces the watercooled condenser on the package structure. Water cooled condensers are the cleanable shelland tube type.

Oil cooler loads are substantial because oil injected into the compressor absorbs a portion of theheat of compression. Oil cooling is by one the following methods:

• A water cooled oil cooler using condenser water, evaporative condenser sump water, chilledwater, or a separate water or glycol to air cooling loop.



• An air cooled oil cooler using an oil to air heat exchanger

• Refrigerant cooled oil cooler (where oil cooling load is low)

• Liquid injection into the compressor

• Condensed refrigerant liquid thermal recirculation


The screw chiller provides continuous capacity modulation, from 100 percent capacity down to 10percent or less. Leaving chilled liquid temperature is sensed for capacity control. Safety controlscommonly required are:

• Oil failure switch

• High-low pressure cutout

• Cooler flow switch

• High oil or discharge temperature cutout

• Hermetic motor inherent protection

• Oil pump and compressor motor overloads.

The compressor is automatically unloaded before starting. Once it starts operating, the slidevalve is controlled hydraulically by a temperature load controller energizing the load and unloadsolenoid valves.

The temperature load controller provides protection against motor overload due to higher thannormal condensing temperatures or low voltage conditions. An anti-recycle timer is used toprevent overly frequent recycling. Oil sump heaters are energized during the off cycle. A hot gascapacity control is used to prevent automatic recycling at no load conditions such as is often

FIGURE 20-1 - FLOODED TYPE LIQUID COOLER



required in process liquid chilling. A suction to discharge starting bypass is sometimes used toaid starting and to allow the use of standard starting torque motors.

Liquid Coolers

The liquid cooler, or evaporator, is the part of a chiller system in which the refrigerant isvaporized, thereby producing a cooling effect on the water, brine, or any other stable fluid.

Flooded Shell and Tube Type

In the flooded cooler, the refrigerant is vaporized on the outside of bare or augmented surfacetubes which are submerged in evaporating liquid refrigerant within a closed shell. The cooledliquid flows through these tubes, which may be straight, U-shaped, or coiled. See Figure 20-1 fora typical detail.

Space is usually provided above the tubes submerged in the boiling refrigerant for the separationof liquid droplets from the leaving vapor. This space may or may not contain liquid dropleteliminators, depending on the particular cooler design.

Ammonia flooded coolers are usually designed with bare steel tube surfaces, while floodedcoolers using other common refrigerants will usually be designed with nonferrous tubes havingextended or otherwise enhanced surface on the refrigerant side.

Refrigerant feed methods for flooded coolers often control, in some manner, the liquid level in thecooler, although the liquid refrigerant flow is sometimes metered in accordance with operatingconditions. This control can be accomplished by a low pressure float valve, a high pressure floatvalve on single cooler systems, a constant pressure expansion valve, a thermostatic expansionvalve, a float switch and solenoid valve combination, a restrictor, or a fixed or variable orifice.

The suction connections, or refrigerant outlets from coolers used with centrifugal compressors,are usually high on the side of the shell, or at the top, above the eliminator section. They may beround or take the form of a transition section from a flared rectangular or elliptical opening to around connection.

Coolers for centrifugal compressors ordinarily have integrally finned or otherwise augmentednonferrous tubing for water cooling service. Ferrous tubes may be used for material compatibilityand prime surface tubes may be used when the relationship of inside and outside heat transfercoefficients does not justify extra external surface.

Direct Expansion Coolers

A direct expansion cooler, as shown in Figure 20-2, is generally of the shell and tube type, withthe evaporating refrigerant inside the tubes and the liquid cooled on the shell side. Usually, abaffle arrangement (segmental type design) is provided on the shell side to increase the shell sidevelocity across the tubes and thereby increase the coefficient of heat transfer.

The refrigerant feed device is usually a thermostatic expansion valve controlled by the amount ofsuperheat in the refrigerant vapor leaving the evaporator. Dual valve operation may be applied,particularly on large size chillers and where load variations extend beyond the capability of one



valve alone. A superheater may be used beyond the liquid valve control point to furthersuperheat suction vapor by heat exchange with warm refrigerant liquid from the condenser.

The direct expansion cooler is especially suitable where the liquid is to be cooled to a temperatureapproaching its freezing point. Any malfunction of the system that results in freezing, unlessrepetitive, normally does not seriously damage the cooler. Direct expansion coolers are pairedwith positive displacement compressors such as reciprocating, rotary, or screw types. The liquidchilled is most commonly water, although applications with brines are also common.

An important item in the performance of a direct expansion cooler is the number of refrigerantpasses through the shell. Increasing the number of passes increases the uniformity of distributionof the liquid refrigerant among the individual tubes of the various tube passes.

FIGURE 20-2 - DIRECT EXPANSION TYPE LIQUID COOLER


Section 21

Fans and Blowers

GENERAL

Fans and blowers are air moving devices used for space or process ventilation. They may alsobe used to handle other gaseous substances in a closed process system or as a fuel-air mixer forcombustion.

The fan is also the heart of any air conditioning system. It is an air pump which creates apressure difference and causes air flow. The impeller does work on the air, imparting to it bothstatic and kinetic energy, varying in proportion to the fan type. A general diagram of a fanidentifying key components is shown in Figure 21-1.

1. BLADE 5. BACK PLATE 9. HOUSING2. SHROUD 6. INTERMEDIATE SHROUD 10. SHROUD STIFFENER (OUTER)3. HUB 7. INDUCTOR VANE 11. INLET CONE4. SHAFT 8. SHROUD STIFFENER (INNER)

FIGURE 21-1 - FAN COMPONENTS

Section 21 Fans and Blowers


Fans are generally classified as centrifugal fans or axial flow fans according to the direction of airflow through the impeller. In addition, the mixed flow fan combines the characteristics ofcentrifugal and axial flow fans.

FIGURE 21-2 - TYPES OF CENTRIFUGAL FANS

Fans and Blowers Section 21


Centrifugal Fans

The centrifugal fan, shown in Figure 21-2, is a radial flow fan. The air is turned as it passesthrough the impeller or wheel which is usually housed within a scroll. It is designed to acceleratethe air by centrifugal action, which creates the necessary pressure difference to cause flow. General drive arrangements of centrifugal fans is shown in Figure 21-3 and directions of rotationand discharge are shown in Figure 21-4.

FIGURE 21-3 - CENTRIFUGAL FAN DRIVE ARRANGEMENTS



Forward Curve

The forward curve centrifugal fan is characterized by the shape of the tip of the blades which areactually curved forward in the direction of rotation. Blades are always located at the very tip ofthe wheel, are usually narrow in proportion to the diameter of the wheel, and are closely spaced.

The performance characteristic of this fan is one of increasing pressure with decreasing volume. The horsepower required by this fan decreases from the point of free delivery, where the fan isoperating against no pressure, to the point of shutoff, where no air is flowing. The decrease israpid near the free air end, leveling off near the no flow end of the volume curve.

The forward curve centrifugal fan is available in single width, single inlet, and double width-doubleinlet types. Light, medium, and heavy duty designs in many sizes are available. This type of fanis primarily used for handling air for general ventilation, heating and air conditioning systems, androof ventilators. It is more sensitive to poor inlet or outlet conditions than other types.

Radial Blade Fans

The radial blade centrifugal fan is best known, in variations of the paddle wheel design, as amaterials handling fan or a mill exhauster. As these names imply, it is used primarily on systemshandling dust, shavings, paper, cuttings, moisture, heat, corrosives, or for actually conveyingmaterials such as grain, plastic beads, wool, and other solids. The fan housing is usually made ina heavy gauge fabricated steel, cast iron, cast aluminum, or other material. The heavyconstruction is intended to provide resistance to abrasion, impact, and corrosion.

The performance characteristic of the radial blade fan shows that for a given speed, the pressurerises, as the air flow is restricted. When the maximum pressure point is reached, the pressuredecreases slightly as the flow is further decreased to the point of shutoff. The efficiency reachesa maximum at approximately the point of highest pressure. The maximum horsepower is at freedelivery, and it decreases as resistance pressure is applied to the fan.

FIGURE 21-4 - DIRECTION OF ROTATION AND DISCHARGE FOR CENTRIFUGAL FANS



Radial blade centrifugal fans of light construction are often used for handling air only. They arealso good fans for general application. They can be operated successfully in parallel or in series. By nature of their construction, they can be run at high speeds, and therefore develop highpressures.

Backward Curve Fans

The backward curve blade centrifugal fan is commonly used for all types of ventilating systemsexcept those carrying abrasive or other materials that might build up on the blades. There aremany blade width and angle designs of this type of fan. Some fans are designed with bladeshaving airfoil sections which help to increase efficiency and reduce noise level. These fans aresomewhat larger than other types for a given capacity, but they usually show the highestefficiency and have the most desirable performance characteristics. This fan has a wider rangeof useful performance in the region of maximum efficiency.

Axial Flow Fans

The axial flow, or propeller type fan, as shown in Figure 21-5, consists of a rotating propeller orfan wheel, which imparts motion to the air or gas by an action similar to that of a screw. Itemploys the aerodynamic principles of an airplane wing, where the motion and angle of an airfoilcreate the pressure difference necessary to cause flow. Once thought to be usable only foroperation at very low pressures (less than one inch), propeller fans are now being used for

FIGURE 21-5 - AXIAL FAN COMPONENTS



applications in all pressure ranges. The three general types of axial flow fans are shown in Figure21-6.

Propeller Fans

A motor and propeller mounted together with an orifice ring comprise what is most often referredto as a ventilating fan. There are many variations of this arrangement. Some have long shaftextensions, direct connected as shown below while others have bearings and sheaves for beltdrive and close coupled belted arrangements. This particular fan style is used mostly forapplications which require the handling of large volumes of air at pressures up to one inch ofwater. There are propeller designs available which will operate in the range of the tubeaxial fansat normal speeds and will reach two or three inches static pressure. Propellers having true airfoilsections are more efficient than those made of stampings.

The width of the propeller blade and the number of blades is not indicative of the fan's capacity orits ability to work against pressure. The designer strives for a fan to have an almost flat powercurve characteristic. Generally, fans with narrow to medium width blades and two to eight blades,have what is termed a flat power curve. The power requirement rises only slightly from free air toabout the midrange and then drops slightly with an upswing near the condition of no flow. Increasing the number of blades will usually decrease the free air volume and increase its abilityto work against pressure. These light duty, wide blade fans are seldom used for industrialapplications.

Tubeaxial Fan

The tubeaxial fan is a propeller fan mounted in a cylindrical tube or duct and is often called a ductfan. It may be direct connected or belt driven. The best belt driven designs have the belt andbearing housings enclosed to isolate them from the airstream. Fans of this type may use avariety of propeller designs and operate in normal pressure ranges up to four inches water gauge.

FIGURE 21-6 - AXIAL FLOW FAN TYPES



This particular arrangement of the propeller fan, by virtue of its construction, is most adaptable toventilating of industrial processes. It can be built of materials which will stand up under lightabrasion, temperatures of up to 800 oF or more, or air heavily contaminated with corrosivechemicals or explosive vapors. The tubeaxial performance characteristics are similar to those ofthe orifice type propeller fan. It is very easily installed as the fan itself becomes a portion of thedust system and will operate equally well at the inlet, in the middle, or at the discharge end of theduct. These fans can operate in parallel or they can be staged by mounting them in series. Some tubeaxial fans have fairly large hubs (fifty percent or more of the wheel diameter). Thisincreases the ability to work against pressure for a given speed or conversely enables the fan towork against the same pressure at a lower speed.

Vaneaxial Fan

The vaneaxial fan is a variation of the axial flow design which operates in the medium to highpressure ranges. Two to twelve inches water gauge is the expected pressure range for a singlestage. The performance of the vaneaxial fan shows the pressure to rise steeply to a maximumpoint and then dip sharply. The pressure rises again to a higher value at the point of shutoff. Theincreased operating pressure characteristic is the result of a combination of propeller and guidevanes. The vanes may be located at either the inlet or the discharge. In some designs, both inletand discharge vanes are used. The function of the vanes is to recover energy of rotation andconvert it into useful work. The efficiency of the vaneaxial fan rises to a maximum near themidrange peak pressure point. Its efficiency is higher than the efficiency of other types of axialflow fans.

Vaneaxial fans can be designed to handle high temperatures and chemically contaminated air,but are not recommended for abrasives, dust, stringy materials, or overspray. If dirt is allowed tobuild up on the guide vanes and fan blades, it will spoil the performance of the fan.

Mixed Flow Fans

The mixed flow or compound flow fan combines the actions of both the basic axial and centrifugaltypes. It is similar in external appearance to the axial flow fan. The physical application would bethe same as that of the axial flow type, and its performance has characteristics which arecommon to both centrifugal and propeller fan designs. Although the mixed flow fan is not new inbasic design, its development has lagged behind the centrifugal and propeller fan development.

As shown in Figure 21-7, the mixed flow fan casing iscylindrical and incorporates the venturi inlet to theimpeller and guide vanes at the discharge. The impellerhas blades which form an entry similar to that of thepropeller fan. The blade configuration is carried off at anangle and the discharge edge has the design of the tipsof a centrifugal wheel.

The mixed flow fan impeller, with its compound bladecurvature, is made to discharge the air conically. Thecasing and guide vanes provide for the recovery of theradial component of discharge and convert the dischargeto axial flow. The performance is similar to that of the

forward curve centrifugal fan.

FIGURE 21-7 - MIXED FLOW FAN



The zone of maximum efficiency is broader than for the centrifugal fan which makes it moreversatile for application in the higher efficiency ranges. The efficiency of the mixed flow fan is notas high as that of the vaneaxial fan.

The mixed flow fan combines the best performance features and physical characteristics of thecentrifugal fan and the vaneaxial fan. The mixed flow fan can be installed as a part of its ductsystem since its flow is axial. It is larger and heavier than the vaneaxial fan but smaller andlighter than the centrifugal.


Section 22

Conveyor Systems

GENERAL

Conveyors include all fixed and portable equipment for conveying material between two fixedpoints with a continuous or intermittent forward drive. A typical conveyor layout is shown inFigure 22-1.

Overhead Conveyors

Overhead conveyor systems are defined in two general classifications:

• Trolley conveyors

• Power and free conveyors

Each type of overhead conveyor serves a definite purpose.

Trolley conveyors, often referred to as overhead power conveyors, consist of a series of trolleysor wheels supported from or within an overhead track and connected by an endless propellingmeans, such as chain, cable, or other linkages. Individual loads are usually suspended from thetrolleys or wheels. Trolley conveyors are utilized for transportation or storage of loads suspendedfrom one conveyor which follows a single fixed path. Track sections range from lightweight "tee"members or tubular sections, to medium and heavy duty I-beam sections. Normally this type ofconveyor is continually in motion at a selected speed to suit its function.

Power and free conveyor systems, as shown in Figure 22-2, consist of at least one powerconveyor, but usually more, in which the individual loads are suspended from one or more freetrolleys. The free trolleys are not permanently connected to the power source and are propelledby the conveyor through all or part of the system. Additional portions of the trolley system may bepropelled manually or by gravity.

The load carrying member of a trolley conveyor is the trolley or series of wheels. The load hanger(carrier) is attached to the conveyor and generally remains attached unless manually removed.

FIGURE 22-1 - TYPICAL TROLLEY CONVEYOR LAYOUT AND DETAIL

Section 22 Conveyor Systems


The trolley conveyor can employ any chain length consistent with allowable propelling means anddrive(s) capability. The track layout always involves horizontal turns and commonly has verticalinclines and declines.

The following components or devices are used on trolley conveyor applications:

Trolley Assembly

The assembly includes the wheels and their attachment portion to the propelling chain or cable.Assemblies are adapted to particular applications to suit loading, duty cycle and manufacturerdesign.

Carrier Attachment

These are made in three main styles:

• Enclosed tubular type in which the wheels and propelling means are carried inside

• Semi-enclosed tubular type in which the wheels are enclosed and the propelling means isexternal

• Open tee or I-beam type in which the wheels and propelling means are carried externally

Sprocket or Traction Wheel Turns

Any arc of horizontal turn is available. Standards usually vary in increments of 15 to 180 degrees.

Roller Turns

1. RECLAIMING EMPTY CARRIERS 5. DELIVERY TO ASSEMBLY LINES2. LOADING CARRIERS AT WORK STATIONS 6. PICK-UP OF ASSEMBLED COMPONENTS3. INSPECTION AND ROUTING 7. DELIVERY TO SHIPPING AREAS4. OVERHEAD STORAGE

FIGURE 22-2 - TYPICAL POWER AND FREE CONVEYOR ROUTING

Conveyor Systems Section 22


Any arc of horizontal turn is available. Standards usually vary in increments of 15 degrees from15 to 180 degrees.

Track Turns

These are horizontal track bends without sprockets, traction wheels, or rollers.

Track Hangers, Brackets, and Bracing

These conform to track size and shape, spaced at intervals consistent to allowable track stressand deflection applied by loading and chain or cable tensions.

Chain Take-Up Unit

These units are required to compensate for chain wear and variable ambient conditions, this unitmay be traction wheel, sprocket, roller, or track turn type. Adjustment is maintained by screw,screw spring, counterweight, or air cylinder.

Incline and Decline Safety Devices

An "anti-backup" device will ratchet into a trolley or the propelling means in case of unexpectedreversal of a conveyor on an incline. An "anti-runaway" device will sense abnormal conveyorvelocity on a decline and engage a ratchet into a trolley or the propelling means. Either devicewill arrest the uncontrolled movement of the conveyor.

Drive Unit

Usually sprocket or caterpillar type, these units are available for constant speed or manualvariable speed control. Drive motors commonly range from fractional to 15 horsepower.

Equipment Guards

Often it is desirable or necessary to guard the conveyor from contaminants. Employees mustalso be protected from accidental engagement with the conveyor components.

Transfer Devices

Usually unique to each application, automatic part or carrier loading, unloading, and transferdevices are available.

Power and Free Conveyor

The power and free conveyor is used wherever there is a requirement for other than a single fixedpath flow (trolley conveyor). Power and free conveyors may have any number of automatic ormanual switch points. A system will permit scheduled transit and delivery of work to the nextassigned station automatically. Accumulation (storage) areas are designed to accommodate in-process inventory between operations. A typical power and free conveyor operation diagram isshown in 22-3.

Addition of secondary free track surface is provided for the work carrier to traverse. This freetrack is usually disposed directly below the power rail but is sometimes found alongside the powerrail. The power and free rails are joined by brackets for rail (freetrack) continuity. The powerchain is fitted with pushers to engage the work carrier trolley.



The pushers are pivoted on an axis parallel to the chain path and swing aside to engage thepusher trolley. The pusher trolley remains engaged on level and sloped sections. At automatic ormanual switching points, the leading dispatch trolley head which is not engaged with the chain ispropelled through the switch to the branch line. As the chain passes the switching point, thepusher trolley departs to the right or left from pusher engagement and arrives on a free line,where it is subject to manual or controlled gravity flow. Automatic switching from a powered lineto free line Power and Free work carriers is done with a code device on the work carrier and adecoding (reading) device along the track in advance of the track switch. On each carrier, thefree trolley carries the code selection, manually or automatically introduced, which identifies it fora particular destination or routing. As the free trolley passes the reading station, the trolleyintelligence is decoded and compared with a preset station code and its current knowledge of theswitch position and branch line condition. A decision is then made which results in the correctpositioning of the rail switch.

Automatic switching from a free line to a powered line Power and Free work carriers can bereentered into the powered lines either manually or automatically. The carrier must be integrated

Entering the work station: Trolleys 1 and 2 are entering a work station whose operator has closed the stop. The lever arm will rise upon contacting the stop, the pusher pawl will tower and disengage from the pusherand the first trolley will stop. In like manner, the second trolley will halt behind the first.

Accumulating at work station: Trolleys 1 and 2 have accumulated behind the closed stop. Trolley 3 isapproaching and will pause behind Trolley 2.

Release from work station: The operator has completed work on the live loaded trolleys and opened thestop Trolleys 1 and 2 are already in motion and moving away. Trolley 3 is about to be engaged with the nextpusher and Trolleys 4 and 5 will move out on the following two pushers in sequence. As each trolley movesaway, the following lever arm lowers, the pawls rise and the pusher pawl engages the next oncoming pusher.

FIGURE 22- 3 - POWER AND FREE CONVEYOR OPERATIONS



with traffic already on the powered line and must be entered so that it will engage with a pusheron the powered chain.

Power and Free conveyor components are the same as on trolley conveyors described above. The following are some of the components unique to power and free systems:

Track Switch

This is used for diverting work carriers either automatically or manually from one line or path toanother. Automatic track switch stops are usually operated pneumatically or electromechanically. Track switches are also used to merge two lines into one.

Trolley Stops

This device is used to stop work carriers which operate either automatically or manually on a freetrack section or on a powered section.

Storage

Portions or spurs of Power and Free conveyors are usually dedicated to the storage oraccumulation of work carriers.

NONCARRYING CONVEYORS

Flight Conveyors

Flight conveyors, similar to the diagram shown in Figure 22-4, are used for moving granular,lumpy, or pulverized materials along a horizontal path or on an incline seldom greater than about40 percent. Their principal application is in handling coal.

Flight conveyors may be classified as:

• Scraper type in which the element (chainand flights) rests on the trough

• Suspended flight type in which the flightsare carried clear of the trough by shoesresting on guides

• Suspended chain type in which the chainrests on guides, again carrying the flightsclear of the trough

These types are further differentiated as singlestrand and double strand. For lumpy material,the latter has the advantage since the lumpswill enter the trough without interference.

The continuous flow conveyor serves as a conveyor, as an elevator, or as a combination of thetwo. It is a slow speed machine in which the material moves as a continuous core within a duct. The element is formed by a single strand of chain with closely spaced impellers, somewhatresembling the flights of a flight conveyor.

FIGURE 22-4 - FLIGHT CONVEYOR



Continuous flow conveyors and elevators do not require a feeder. They are self loading tocapacity and will not overload, even though there are several open or uncontrolled feed openings.This occurs because the duct fills at the first opening and automatically prevents the entrance ofadditional material at subsequent openings.

Screw Conveyors

The screw or spiral conveyor,shown in Figure 22-5, is usedwidely for pulverized or granular,noncorrosive, nonabrasivematerials when:

• The required capacity ismoderate

• The distance is not more thanabout 200 feet

The path is not too steep it canbe made dust tight by a simplecover plate. If the lengthexceeds that advisable for asingle conveyor, separate ortandem units are arranged. Screw conveyors may be inclinedand a standard pitch helix willhandle material on inclines up to35 degrees. The standard screwconveyor helix has a pitchapproximately equal to its outsidediameter. Short pitch screws areadvisable for inclines above 29degrees. Three basic conveyorflight and pitch types are shownin Figure 22-6.

Variable pitch screws, with short pitch at the feed end, automatically control the flow to theconveyor so that the load is correctly proportioned for the length beyond the feed point. With ashort section either of shorter pitch or of smaller diameter, the conveyor is self-loading to capacityand does not require a feeder.

FIGURE 22-5 - SCREW CONVEYOR DISCHARGE TYPES

STANDARD PITCH SINGLE FLIGHT STANDARD PITCH WITH PADDLES DOUBLE FLIGHT STANDARD PITCH

FIGURE 22-6 - BASIC CONVEYOR FLIGHT AND PITCH TYPES



Ribbon screws are used for wet and sticky materials which might otherwise build up on thespindle. Paddle screws are used primarily for mixing materials such as mortar and pavingmixtures. One typical application is to churn ashes and water to eliminate dust.

Standard designs have a plain or galvanized steel helix and trough. For abrasives and corrosivessuch as wet ashes, both helix and trough may be of hard faced cast iron. For simple abrasives,the outer edge of the helix may be faced with a renewable strip of stellite or similar extremely hardmaterial.

CARRYING CONVEYORS

Apron Conveyors

Apron Conveyors, as shown in Figure 22-7, are specified for granular or lumpy materials. Sincethe load is carried and not dragged, less power is required than for screw or scraper conveyors. Apron conveyors may have a stationary skirt or side plates to permit increased depth of materialon the apron. Sizes of lumps are limited by the width of the pans and the ability of the conveyorto withstand the impact of loading. Only end discharge is possible. The apron conveyor consistsof two strands of roller chain separated by overlapping apron plates, which form the carryingsurface, with sides 2 inches to 6 inches high. The chains are driven by sprockets at one end,take-ups being provided at the other end. The conveyors always pull the material toward thedriving end. For light duty, flangeless rollers on flat rails are used. For heavy duty, single flangedrollers and T rails are used.

Bucket Conveyors and Elevators

Open top bucket carriers are similar to apronconveyors, except that dished or bucket shapedreceptacles take the place of the flat orcorrugated apron plates used on the apronconveyor. The carriers will operate on steeperinclines than apron conveyors (up to 70degrees) since the buckets prevent materialfrom sliding back. Neither sides extendingabove the tops of buckets nor skirtboards arenecessary.

V-bucket carriers are used for elevating and conveying nonabrasive materials, principally coalwhen it must be elevated and conveyed with one piece of apparatus. The length and height liftedare limited by the strength of the chains and seldom exceed 75 feet. The carrier consists of twostrands of roller chain separated by V-shaped steel buckets. Material is received on the lowerhorizontal run, elevated, and discharged through openings in the bottom of the trough of theupper horizontal run. The material is scraped along the horizontal trough of the conveyor, as in aflight conveyor.

FIGURE 22-7 - APRON CONVEYOR



Pivoted bucket carriers, shown inFigure 22-8, are used primarily wherethe path is a run-around in a verticalplane. Their chief application has beenfor the dual duty of handling coal andashes in boiler plants. They requireless power than V-bucket carriers, asthe material is carried and not draggedon the horizontal run. The lengthseldom exceeds 500 feet and theheight lifted seldom exceeds 100 feet. They can be operated on any inclineand can discharge at any point on thehorizontal run.

The carrier consists of two strands ofroller chain, with flanged rollers,between which are pivoted buckets,usually of malleable iron. The materialis fed to the buckets by a feeder at anypoint along the lower horizontal run, iselevated, and is discharged on theupper horizontal run. The tripper ismounted on wheels so that it can bemoved to the desired dumping position,engages the cams on the buckets andtips them until the material runs out. The buckets always remain verticalexcept when tripped. The chain rollersrun on T rails on the horizontal sectionsand between guides on the verticalruns.

Bucket elevators are of two types:

• Chain and bucket in which the buckets are attached to one or two chains

• Belt and bucket in which the buckets are attached to canvas or rubber belts

Either type may be vertical or inclined and may have continuous or noncontinuous buckets. Bucket elevators are used to elevate any bulk material that will not adhere to the bucket. Belt andbucket elevators are particularly well adapted to handling abrasive materials which would produceexcessive wear on chains. Chain and bucket elevators are frequently used with perforatedbuckets when handling wet material, to drain off surplus water. The length of elevators is limitedby the strength of the chains or belts. They may be built up to 100 feet long.

Continuous bucket elevators usually operate at 100 ft/min or less and are single or double strand. The contents of each bucket discharge over the back of the preceding bucket.

POSITIVE DISCHARGE CENTRIFUGALDISCHARGE

FIGURE 22-8 - BUCKET CONVEYORS ANDELEVATORS



Belt Conveyors

The belt conveyor is a heavy duty conveyor available for transporting large tonnages over pathsbeyond the range of any other type of mechanical conveyor. The capacity may be severalthousand tons per hour, and the travel distance several miles. It may be horizontal or inclinedupward or downward, or it may be a combination of these. There are special belts with moldeddesigns to assist in keeping material from slipping on inclines. They will handle pulverized,granular, or lumpy material. A sectional view of a typical belt conveyor is shown in Figure 22-9.

In its simplest form, the conveyor consists of a head or drive pulley, a take-up pulley, an endlessbelt, and carrying and return idlers. The spacing of the carrying idlers varies with the width andloading of the belt and usually is 5 feet or less. Return idlers are spaced on 10 foot centers orslightly less with wide belts. Sealed antifriction idler bearings are used almost exclusively, withpressure lubrication fittings.

Belt width is governed by the desired conveyor capacity and maximum lump size. The standardrubber belt construction has several plies of square woven cotton duck or synthetic fabric such asrayon, nylon, or polyester cemented together with a rubber compound and covered both top andbottom with rubber to resist abrasion and keep out moisture. Top cover thickness is determinedby the severity of the job and varies from 1/16 to 3/4 inch. The bottom cover is usually 1/16 inch. Byplacing a layer of loosely woven fabric, called the breaker strip, between the cover and outsidefabric ply, it is often possible to double the adhesion of the cover to the carcass. The belt is ratedaccording to the tension to which it may safely be subjected which is a function of the length andlift of the conveyor.

High Strength Belts are used for belt conveyors of extremely great length, a greater strength perinch of belt width is available through the use of improved wearing techniques that provide

FIGURE 22-9 - SECTIONAL BELT CONVEYOR EXPLODED VIEW



straight warp synthetic fabric to support the tensile forces. The number of plies is reduced to twoinstead of as many as eight so as to give excellent flexibility. Widths to 60 inches are available.

These belts are used for long single length conveyors and for high lift, extremely heavy dutyservice such as for taking ore from deep open pits, thus providing an alternative to a spiralingrailway or truck route.

Idler Pulleys-Troughing idlers are usually of the three pulley type with the troughing pulleys at 20degrees. 35 and 45 degree idlers are also common which increase the volume capacity of a belt. The bearings, either roller or ball type, are protected by felt or labyrinth grease seals against theinfiltration of abrasive dust. A belt running out of line may be brought into alignment by shiftingslightly forward one end or the other with a few idler sets. Return belt idler pulleys are shown inFigure 22-10 and troughed and flat idler pulleys are shown in Figure 22-11.

Drive Belt slip on the conveyor drive pulley is destructive. There is little difference in tendency toslip between a bare pulley and a rubber lagged pulley when the belt is clean and dry. A wet beltwill adhere to a lagged pulley much better, especially if the lagging is grooved. Heavy dutyconveyors exposed to the possibility of wetting the belt are generally driven by a head pulleylagged with a 1/2 inch rubber belt and with 1/4 by 1/4 inch grooves spaced 112 inches apart andpreferably, diagonally as a herringbone gear.

Conveyor drive motors generally have high starting torque, moderate starting current inrush, andgood characteristics when operating under full load. Typically double squirrel cage AC motors areused.

For Heavy Duty Belt Conveyor Drives intended for extremely heavy duty, it is essential that thedrive torque be built up slowly or serious belt damage will occur. For this reason, drives are

Return belt idlers carry the empty belt on the returnrun. Available options include a rollers, or urethanetreads.

Return belt training idlers train the belt and protect itsedges from injury caused by misalignment. Alsoavailable with rubber steel tread rolls. Positive actiontype for belts operating in one direction. Actuating shoetype for reversible belts. For quicker, more sensitivebelt alignment, a 2-roll design is also available.

Return belt rubber tread idlers are used when wet orsticky materials tend to cling to the belt, wherecorrosion resistance is required, or where chemicalattraction to iron or steel is involved.

Caster-camber return belt training idlers train returnbelt operating in one direction when handling materialsthat tend to adhere to carrying side of belt. Alsoeliminates build-up on frame members. Available withsteel or rubber tread rolls..

Return belt beater idlers remove excessive amountsof tenacious materials that adhere to the belt.

FIGURE 22-10 - RETURN BELT IDLER PULLEYS



typically dynamic clutches. This has a magnetized rotor on the extended motor shaft, revolvingwithin an iron ring keyed to the reduction gearing of the conveyor. The energizing current isautomatically built up over a period that may extend to 2 minutes, and the increasing magneticpull on the ring builds up the belt speed.

For Take-ups for short conveyors, a screw take-up is normally used. For long conveyors, aweighted gravity take-up is normally used to allow for occasional cutting and resplicing of the belt.

Trippers and Shuttle Conveyors

The load may be removed from the belt by a diagonal or V-plow, but a tripper that snubs the beltbackward is standard equipment. Trippers may be:

• Stationary

• Manually propelled by crank

Troughed belt idlers for general carrying service areavailable with roll inclinations of 20° and 35°.

Variable troughed belt idlers placed between the final troughing idler and the head pulley support the beltduring its transition from a concave to a flat contour. The end rolls can be adjusted vertically to match thechanging contour of the belt during this critical period oftransition.

Troughed belt rubber cushion idlers protect the beltby absorbing impacts at loading and transfer points. Design features include removable end brackets.

Flat belt idlers are used for handling bulk materialswhere it is desirable to plow off material at one or moreintermediate points along the conveyor..

Troughed belt training idlers automatically train beltsand protect belt edges from injury caused bymisalignment. Positive action type for belts operating inone direction; actuating shoe type for two- directionaloperation (reversing).

Flat belt rubber cushion idlers protect the belt byabsorbing impacts at transfer points. Fixed shaft type isfor average service. Live shaft type is for heavy dutyservice.

Troughed belt picking and feeder conveyor idlerscarry the load in a wide, thin layer where picking andsorting are required or where a shallow bed of materialis required to minimize degradation. Standard designfeatures rubber cushion center roll and steel end rolls. Also available with all steel or all rubber cushion rolls.

Flat belt training idlers automatically train the belt andprotect the belt edges from injury caused bymisalignment. Available in the positive action type forbelts operating in one direction.

FIGURE 22-11 - FLAT AND TROUGHED IDLER PULLEYS



• Propelled by power from one of the snubbing pulleys or by an independent motor.

The discharge may be chuted to either side or back to the belt by a deflector plate.

Magnetic pulleys are frequently used as head pulleys on belt conveyors to:

• Remove tramp iron, such as stray nuts or bolts, before crushing

• Concentrate magnetic ores from nonmagnetic material

• Reclaim iron from foundry refuse

A chute or hopper automatically receives the extracted material as it is drawn down through theother non-magnetic material, drawn around the end pulley on the belt, and finally released as thebelt leaves the pulley.

Fixed or movable type trippers are used for discharging material between the ends of a beltconveyor. A self propelling tripper consists of two pulleys, over which the belt passes. Thematerial is discharged into the chute as the belt bends around the upper pulley. The pulleys aremounted on a frame carried by four wheels and are power driven. Taking power from theconveyor, the tripper is actuated by a lever on the frame and stops alongside the rails andenables the tripper to move automatically between the stops and distribute the material.

Shuttle conveyors are frequently used in place of trippers for distributing materials. They consistof a reversible belt conveyor mounted upon a movable frame and discharging over either end.

Feeders

When material is drawn from a hopper or bin to a conveyor, an automatic feeder is typically used. A reciprocating plate feeder, consisting of a plate mounted on four wheels, forms the bottom ofthe hopper. When the plate is moved forward, it carries the material with it. When it is movedback, the plate is withdrawn from under the material and allows it to fall into the chute. The plateis moved by connecting rods from cranks. The vibrating feeder consists of a plate inclineddownward slightly and vibrated by:

• A high-speed unbalanced pulley

• Electromagnetic vibrations from one or more solenoids

• The slower pulsations secured by mounting the plate on rearward inclined leaf springs

Pneumatic Conveyors

The pneumatic conveyor transports dry, free flowing, granular material in suspension within a pipeor duct by means of a high velocity airstream or by the energy of expanding compressed airwithin a comparatively dense column of fluidized or aerated material. A typical pneumaticconveyor system is shown in Figure 22-12. Principal uses are:

• Dust collection

• Conveying soft materials, such as chemicals (soda ash, lime, salt cake)

• Conveying hard materials, such as fly ash, cement, silica metallic ores, and phosphate



For conveying soft materials, a fan is used to create a suction. The suspended material iscollected at the terminal point by a separator upstream from the fan. The material may be movedfrom one location to another or may be unloaded from barge or rail car. Since abrasion is noproblem, steel pipe or galvanized metal ducts are satisfactory.

For conveying hard materials, a water jet exhauster or steam exhauster is used on suctionsystems, and a positive displacement blower on pressure systems. A mechanical exhauster mayalso be used on suction systems if there is a bag filter or air washer ahead of the exhauster.

The power requirement for pneumatic conveyors is much greater than for a mechanical conveyorof equal capacity, but the duct can be led along practically any path. The vacuum cleaner actionprovides dust free operation, sometimes important when pulverized material is unloaded fromboxcars through flexible hose and nozzle.

FIGURE 22-12 - TYPICAL PNEUMATIC CONVEYOR SYSTEM


Section 23

Crushers and Pulverizers

GENERAL

In the processing of minerals, ores, rocks, and other similar materials, it is usually necessary toreduce large pieces of material to small particle sizes. This cannot be done in a single step, butinstead generally requires two or three steps, depending on the physical nature of the materialand the particle size required. The rough, preliminary, or secondary breaking of large pieces intosmaller pieces is termed crushing. This may be accomplished by impact, attrition, shear, orpressure, or by a combination of all four.

• Impact crushing requires one body to strike another with a sharp blow.

• Attrition crushing refers to grinding or rubbing the material between two surfaces.

• Shear crushing size reduction is accomplished with a cutting or cleaving action.

• Pressure crushing is accomplished when large pieces are crushed between two surfaces withdirect pressure.

Various machines and devices are employed in the industry to achieve crushing. Jaw Type,Gyratory, and Roll Type crushers will be discussed.

Pulverizing or grinding is generally related to those operations where the size of the product issmall. The fineness of the product will vary with the type of material and may be as large as oneinch or as small as one micron or less. In some fields, grinding may cover product sizes evenoutside of these ranges. Since the product may be as large as one inch, the feed can be as largeas five inches. Grinding equipment will be discussed under three different categories:

• Impact machines

• Roller mills

• Attrition mills

JAW TYPE CRUSHERS

Jaw crushers operate on the principle of compression in which the material is squeezed with greatforce between a fixed surface and a movable surface. The fixed surface is often referred to asthe anvil jaw. The two jaws form a V-shaped chamber, wide at the top and narrow at the bottom,within which the crushing takes place. The other two walls of the chamber are formed by theframe. Both jaws are usually essentially flat, except that in some models they may have shallowvertical ribbing. A few models use curved jaw surfaces, to reduce any tendency to clog.

The surface of the movable jaw forms an angle of a little less than 30 degrees with the verticalanvil jaw. In some designs, both jaws lean back from the vertical to form an angle with each otherof about the same size. The swinging jaw is suspended at one point and receives its motion froman eccentric shaft on which it rides at its unsupported end. Jaw crushers must be designed andbuilt for heavy duty, so that bearing design and lubrication are important.

In operation, the charge is introduced at the top. As the swinging jaw moves out, the charge slipsdown. When the jaw moves in, the space remaining is too small, placing the material undersevere compression, and resulting in crushing. On the next outward motion, the crushed material

Section 23 Crushers and Pulverizers


slips down again into a narrower space, and the cycle is repeated. It typically takes 8 to 10 suchslips for most of the material to reach the bottom, where it is discharged. The width of thedischarge is adjustable, and controls the size of the final product. At the end of its working stroke,the movable jaw is brought back to its starting position by a spring acting through a tension rod. The jaws may operate between 200 and 3,000 openings per minute. Jaw crushers are generallybelt-driven, and are usually fitted with heavy flywheels.

The two oldest types of jaw crushers are the Blake crusher and the Dodge crusher.

Blake-Type Crusher

In the Blake or double toggle crusher shown in Figure 23-1, the swing jaw is suspended from thetop. Its bottom lip has the maximum motion. The eccentric acts on the pitman which in turnaffects a toggle joint. One toggle plate rests on the frame, while the other imparts motion to themovable joint. Maximum force is exerted when the jaw is at the extreme of travel on its workingstroke, which is where this great force is most needed. The discharge opening is adjustable. Theswing jaw tends to force the material upward, causing a rubbing action against the jaws. Suchrubbing action results in rapid wear on the jaw faces, increases the amount of fines produced,and tends to reduce the effective capacity of the crusher. In most models, the fixed jaw is verticaland flat, while the movable jaw face may either be flat or curved, and set at an angle from thevertical.

Since there is considerablemotion between the jaws at thepoint of discharge, there tendsto be a large variation in thesize of the product dischargedfrom the Blake type crusher. The jaw faces are usually madeof a special hard alloy due tothe amount of wear in serviceand are so arranged as to beeasily removed for replacement. Since the Blake type crusherhas its maximum motion at thedischarge end, it has aminimum tendency to chokeand may therefore be used formaterials that have sometendency toward caking.

Variations of the Blake type are the Denver and Dalton types which are also top pivoted. Thesemodels which are sometimes called single toggle types, also have an overhead eccentric whichgives the movable jaw some up and down motion.

Dodge Type Crusher

In the Dodge type crusher shown in Figure 23-2, the swinging jaw is pivoted at the bottom. Thedischarge opening has almost no motion and the greatest movement is at the top. While thecapacity of a given size Dodge is less than that of the same size Blake, the final product

FIGURE 23-1 - BLAKE TYPE OR DOUBLE TOGGLE JAWCRUSHER

Crushers and Pulverizers Section 23


discharged is of more uniform size. The Dodge does not, however, readily clear itself whenchoked and is therefore limited in use to free flowing materials. The Dodge also cannot take aslarge sized feed as does the Blake. For these reasons, the Dodge is less commonly used thanthe Blake and is normally used where:

• Tonnage requirements are lower

• The material is dry and free flowing

• Considerable fines are desired

GYRATORY CRUSHER

The gyratory crusher, shown in Figure 23-3, has a central vertical, cone shaped rotating element,working in a conical chamber which is open at the top. The truncated cone crushing head ismounted on a vertical shaft which in turn is driven eccentrically. This gives the crushing headboth a rotary motion and a gyratory motion. The space between the cone and the chamber wall

1. FRAME 11. PITMAN EYE BOLT 22 LEFT HAND SIDE LINER2. MAIN BEARING CAP 12. PITMAN JAW SPRING CAP 23 RIGHT HAND SIDE LINER3. OIL WELL COVER 13. SWING JAW AND PITMAN

WELL COVER24 PLAIN STATIONARY JAW PLATE

4. OIL WELL COVER SPRING 14. SWING JAW COVER 25 PLAIN SWING JAW PLATE5. SWING JAW SHAFT BOX 15. SWING JAW 26 HOPPER6. BREAKING PLATE 16. FLYWHEEL 29 STATIONARY JAW PLATE BOLT7. SHIM 17. ECCENTRIC SHAFT 30 SWING JAW PLATE BOLT8. PITMAN 18. LOOSE PULLEY 31 BOG BOLT9. PITMAN CAP 19. TIGHT PULLEY 32 OUTBOARD BEARING10. PITMAN PIN 20. SWING JAW SHAFT 33 OUTBOARD BEARING CAP

FIGURE 23-2 - DODGE TYPE CRUSHER



decreases gradually, with the narrowest gap being at the bottom of the crushing space. At thislevel, the material drops out of the crusher through a chute.

The material to be crushed is fed into the open top. As the crushing head gyrates, it comescloser to the chamber wall at one spot and moves away from the chamber wall on the oppositeside. A material charge is loaded when the gap is at its maximum. At the next half gyration, thisgap is reduced which places the material under compression and results in the crushing action. The size of the final product may be adjusted by raising or lowering the central shaft, thuschanging the spacing between the crushing head and the chamber wall. In the larger gyratories,the shaft extends beyond the truncated cone of the crushing head, and is supported by a bearingin a spider across the open top. Gyratory crushers are essentially continuous in action. Gyratorycrushers may be designed for either primary crushing of large material, or for smaller, lighter "finereduction" work.

1. FEED OPENING 7. BEVEL GEARS 13. V-BELT2. MANTLE 8. ROLLER BEARINGS 14. DUST SEAL3. 2-ARM SPIDER 9. SHAFT 15. TWO PIECE MANTLE4. POWER DRIVE 10. SPIDER ARMS AND RIMS 16. BRONZE BEARINGS5. MACHINE HOUSING 11. BOTTOM DISCHARGE 17. HYDRAULIC ADJUSTMENT6. CONCAVE INTERIOR 12. LOCKNUT 18. FEED POINT

FIGURE 23-3 - GYRATORY CRUSHER



ROLL TYPE CRUSHERS

Single roll toothed crushers,shown in Figure 23-4, functionby impact, shear andcompression. They pull thematerial between the roll anda fixed anvil. They areparticularly useful for friablematerials, even when wet andsticky. Made in sizes withcapacities to 800 tons perhour and greater, suchcrushers produce a negligiblequantity of fines.

Double roll crushers consist of two identical steel rimmed rolls mounted with their axes horizontal,on suitable bearings and frame, made to revolve toward each other at equal speeds. Each roll isdriven by its own pulley. The material to be crushed is fed from above, and is dischargedbeneath the rolls. In the usual form, one roll is made movable so that tramp iron or otherunbreakable material may be passed without damage to the equipment. This is accomplished bymounting the bearings of one roll on a slide, and holding the roll to its work by springs and tensionrods. The diameter of the roll is generally greater than the width of the face, and may run two orthree times as great. The distance between the rolls, called the crusher setting, is adjustable andcontrols both the size of the final product and the capacity.

Crushing rolls are generally used for secondary or intermediate crushing. Their capacity is high.The rolls may be smooth, or may have tooth like or knife like projections.

IMPACT MACHINES

As the name implies, the primary force behind size reduction in these units is impact. It may beimpact created between the particles themselves, but more often it is impact between the par-ticles and adjacent parts of the mill. Other forces such as attrition, compression, and shear mayalso contribute to a lesser extent.

Hammer Mills

The hammer mill is generally defined as a unit with the hammers mounted on a horizontal shaft orto discs on the shaft, with feed entering the top, sides, or ends of the unit but with dischargealways at the bottom. The hammer mill is one of the more versatile comminuting or pulverizingmachines. It can be used for a variety of materials and over a wide range of product sizes. Onereason for this is the number of arrangements that can be made within the machine.

The hammer can be fixed, swinging, or the rolling ring type. As shown in Figure 23-5, thehammers can have different sizes, shapes, and numbers which are particularly suitable for thematerial or size reduction desired.

FIGURE 23-4 - SINGLE-ROLL CRUSHER



Up-Running Type Hammer Mills

As shown in Figure 23-6, the Up-Running Type Hammer Mill impacts the feed with the hammerswhile it is suspended in the air and is thrown against the breaker plate where further impactoccurs. The breaker plate is generally designed so the material rebounds into the path of thehammers for further impact. This is particularly true when no grates or screens are used at thebottom of the mill because all the grinding has to occur in the area between the breaker plate andthe hammers. Oversize material which cannot pass through the grate openings is then subjectedto further action by the hammers.

FIGURE 23-5 - HAMMER MILL HAMMER TYPES

REVERSIBLE HAMMERMILL NON-REVERSIBLE HAMMERMILLUP-RUNNING DOWN-RUNNING

FIGURE 23-6 - HAMMERMILLS



Down-Running Type Hammer Mills

As shown in Figure 23-6, the Down-Running Type Hammer Mill subjects the material to impact bythe hammers while it is supported against the breaker plate. This type of hammer mill is used forfriable materials since the unit provides a shorter period of grinding action than in the up-runningmachine. With some materials, there is a tendency for plugging with this type of mill so units are

made with a traveling breaker plate.

Rolling Ring Type Hammer Mills

As shown in Figure 23-7, the RollingRing Type Hammer Mill provides someimpact action but the majority of thegrinding occurs by the compressiveforces imparted to the material as it iscaught between the rolling ring andgrinding plate or screen. The basicmachine is still a hammer mill,however.

Vertical Hammer Mills

There are a number of varieties ofVertical Hammer Mills but they all havethe common feature of fixed hammerson a vertical shaft. Size reductiontakes place by the impact action of thehammers and attrition between the

particles and on the walls of the unit.

One of the more popular types of vertical hammer mills uses air classification to remove materialfrom the grinding zone and additional air and mechanical separation in a separate chamber withoversize material returned for regrinding. As the feed enters, it is subjected to the impact of thehammers. The heavier, larger particles are thrown to the outside by centrifugal force and aretherefore subject to the impact by hammers traveling at the highest linear speed. Air enteringthrough the bottom carries the fines material up into the classifying chamber where it is separatedinto product and oversize. The air can be recirculated after removal of the product or it can bedischarged with or without fines separation.

FIGURE 23-7 - ROLLING RING HAMMER MILL



Horizontal Impact Mills

As shown in Figure 23-8, material is fed to theHorizontal Impact Mill on to a rotating disc. As thefeed comes to the rotor, it begins to pick up somecircumferential velocity, and centrifugal force moves ittoward the periphery of the rotor where it comes incontact with impact pins on the rotor. This results insome pulzerization, but additional grinding takes placeas the material strikes the stationary pins in thehousing of the unit.

ROLLER MILLS

The primary crushing or grinding action in roller mills isa compression mechanism. Impact forces wouldrarely come into play, but attrition may be important,especially in the finer sizes. All roller mills operate bycompressing the material between the surfaces with atleast one of them rotating.

Single Roll Crushers

The action of Single Roll Crushers depends on the tooth design present on the single roll. Variations may range from a few protrusions distributed along the length and diameter of the rollto a number of toothed segments similar to saw blades. As the material is fed to the machine, itis subjected to the impact of the teeth or the housing, plus shearing action as the teeth try to drawthe material through the unit. Sometimes the teeth may run through channels to give a combingeffect and discharge may be through a screen.

Crusher Rolls

Crusher Roll grinding equipment consists of a set of rolls rotating toward each other at the sameor different speeds. The coefficient of friction between the material and the rolls is utilized todraw the material down into the nip of the roll where it can be subjected to the compressivecrushing action. Smooth rolls are sometimes used, but the effective friction can be increasedconsiderably by corrugating the rolls or by using saw tooth rolls. The corrugations can be variedin depth, sharpness, design, number of cuts per inch, and spiral pattern. The type of corrugationand the relative speed of the two rolls will cause the compressive crushing to be supplemented bycutting, shearing, and tearing action.

Roller Mills

In addition to being a general category of crushing rolls, Roller Mills are also a specific type of rollthat operates with rollers rotating against a stationary ring. Crushing in a roller mill takes place asthe rollers revolve against the pulverizing or bull ring and material is fed between the rollers andthe ring by plows moving ahead of the rollers. The rollers themselves are attached to a freelyswinging vertical shaft which is fastened to a spider on the main vertical shaft. No power issupplied to the rollers. Their rotation is caused by friction between the rollers and the material

FIGURE 23-8 - HORIZONTALIMPACTOR



being crushed. The crushing force is obtained by the centrifugal force imparted to the rollers asthe central shaft rotates. Commercial units normally have 5 or 6 rollers.

Bowl Mills

The Bowl Mill is similar to the roller mill and takes its name from the bowl whose rim serves as oneof the grinding surfaces. Unlike the roller mill, the bowl of this unit rotates while the roller journalsremain stationary. The centrifugal forces developed in the bowl cause the material to gravitate tothe rim, where it is crushed between the rollers and the rim. Compression springs force the rollersagainst the material, and adjustments can be made to the roller journals to establish the properangle to the ring and to compensate for wear. Because of the centrifugal force on the material, italways lines the grinding ring so there is no direct contact between the rollers and the ring. Theaction in the mill causes the material to move upward and out of the grinding zone where thefines are removed by the air stream for classification and the oversize returns to the feed line forfurther pulverizing.

Ring Roll Mills

Ring Roll Mills are similar to a bowl mill except that the pulverizing roll rotates in a vertical planeinstead of in a horizontal plane. As with the bowl mill, the ring rotates and the roller journals arestationary. The compression springs on the rollers will develop a force up to 60,000 pounds onthe rollers. Centrifugal force holds the material on the ring and prevents metal to metal contact. As the material is reduced in size, it falls off both sides of the ring and escapes to the bottom ofthe mill where it is taken away for separate classification.

ATTRITION MILLS

Grinding by attrition is generally most applicable when the product has to be fine. The attritioncan be either between the material and surfaces of the mill or between the particles themselves. Wear of the mill parts is quite high where the attrition is between the mill and the material, so selfattrition is very desirable.

Disc Mills

This is probably the most widely used type of attrition mill and the term "attrition mill" is often usedsynonymously with "disc mill". There are a large number of varieties of disc mills, some operatingin horizontal planes and others in vertical planes. In some, grinding takes place across arelatively wide disc face, and in others only a small ring is used as the grinding surface. They allhave in common the establishment of the product size by the clearance between the matingparts, and all grinding is accomplished between the material and the mill parts so grinding platewear can be high.

In the single runner disc mill one disc is rotated while the other remains stationary. In a doublerunner unit both discs rotate, usually in opposite directions, but differential speeds in the samedirection can be used. The grinding plates are usually an alloy steel and various patterns areused on the surface to accomplish various grinding objectives. The clearance between the platesis usually adjustable, with spring loading, in increments as small as 0.001 inch while the unit is inoperation.



Material is fed into the center of the discs with a special feeder plate which is usually used toimpart a radial flow of the feed into the grinding space between the discs. Centrifugal forcecarries the material to the outside as it is ground.

Impeller Attrition Mills

This type of unit is somewhat of a jet mill and a disc mill combined. Feed enters the center of themill and is carried to the inside periphery by an impeller. The inside periphery of the unit is of acorrugated or stone construction, and as the material is processed, attrition takes place until theproduct is fine enough to escape through a clearance port. In some units, the inner peripheryconsists of conical shaped corrugated baffle plates in which one of the plates rotates but in someunits, only the impeller rotates. The clearance between the two baffle plates can be adjusted togive the desired product size. Most of the grinding is accomplished by jet attrition action butimpact and shear forces may also come into play.

Fluid Energy Mills

As the name implies, fluid energy is used to accomplish the size reduction in these units. Generally the fluid is air at 45-115 psi or steam at 100-250 psi. The fluid is admitted throughnozzles tangential to the periphery of the unit and carries the material around the unit until is hasbeen reduced to a size that can be carried out by the exit fluid stream. The size reduction takesplace by impact and attrition between the particles and to some extent with the inside of the unit. Centrifugal force acting on the larger particles keeps them in the machine.

Vibro Energy Mill

The Vibro energy mill accomplishes its pulzerization by means of vibration energy which causesmaterial to be subjected to attrition, impact, and shear forces. The unit consists of an annularchamber which is caused to vibrate by an electric motor and eccentric weights. A verticalplanetary gyration is superimposed on a horizontal planetary gyration each at 1150 cycles perminute and results in a three dimensional, high frequency vibration of the unit.


Section 24

Bearings and Lubrication

GENERAL

The function of a bearing is to keep the shaft or rotor in correct alignment with stationary partsunder the action of radial and transverse loads. Bearings that give the rotor its radial positioningare known as line bearings, while bearings that locate the rotor axially are known as thrustbearings. In most cases, thrust bearings serve in a dual capacity as both thrust and radial (line)bearings. Bearings may be rigid or self aligning. Self aligning bearings will automatically adjust tochanges in the angular position of the shaft.

Bearings must be made of materials which will withstand varying pressures and yet permit thesurfaces to move with minimum wear and friction. In addition, they must be held in position withvery close tolerances to permit freedom of movement and quiet operation. To meet theserequirements, good bearing materials must possess a combination of the followingcharacteristics:

• The compressive strength of the bearing alloy at maximum operating temperatures must besuch that it can withstand high loads without cracking or deforming.

• Bearing alloys must have great resistance to high fatigue factors to prevent cracking andflaking under different operating conditions.

• Bearing alloys must have high thermal conductivity to prevent localized hot spots withresultant fatigue and seizure.

• The materials used in bearing alloys must be capable of retaining an effective oil film.

• These alloys must have a resistance to corrosion.

Bearings are generally classified as:

• Sliding surface (friction) bearings

• Rolling contact (antifriction) bearings

Sliding Surface or Friction-Type Bearings

Sliding surface bearings may be defined in a broad sense as those which have sliding contactbetween their surfaces. If each surface is not lubricated, sliding friction is developed as eachbody slides or moves on the surface of the other.

Examples of sliding surface bearings include

• Journal bearings

• Guide bearings

• Thrust bearings

Journal Bearings

Journal bearings are extensively used in industry and may be subdivided into different styles ortypes. The most common journal bearings are solid bearings, half bearings, and two part or split

Section 24 Bearings and Lubrication


bearings. A typical solid journal bearing application is the wrist or gudgeon pin bearing in a trunkpiston of an engine. These bearings are commonly referred to as bushings.

The split type journal bearing is used extensively in marine propulsion shafting and also in theautomotive industry. They are less expensive than a full bearing of any type since the load isexerted in only one direction. The split bearing is used more frequently than any other frictiontype bearing and can be adjusted to compensate for wear. Allowances can be easily made toprovide the proper clearance for lubrication film between the journal and bearing shell.

Guide Bearings

Guide or cross head bearings act as steady points for guiding the longitudinal motion of a shaft orother part. These bearings are found in reciprocating units of machinery, such as aircompressors, and are used to convert the rotary motion of the crankshaft into the reciprocatingmotion of the piston.

Thrust Bearings

Thrust bearings are used to limit the movement of the shaft in a longitudinal direction while it isrotating. Thrust bearings sometimes are combined functionally with journal bearings.

Antifriction Type or Rolling Contact Bearings

Rolling contact bearings, more commonly known as roller bearings or ball bearings, are definedas bearings which have rolling contact between their surfaces. These bearings take advantage ofthe fact that it requires less energy to overcome rolling friction than sliding friction. In this type ofbearing, the rollers or balls are usually assembled between two rings, or races, while the contactfaces of these rings are contoured to fit the balls or rollers. The basic difference between rollerand ball bearings is that with roller bearings the load surfaces consist of two straight line contactpoints, while the load surfaces of ball bearings consist of two tiny spots. These contact areas arediametrically opposite each other in both types. Theoretically, the area of the spot or line ofcontact is infinitesimal. Various types roller bearings are shown in Figure 24-1.

FIGURE 24- 1 - TYPES OF ROLLER BEARINGS

Bearings and Lubrication Section 24


The amount of contact will differ depending upon the distortion of the bearing material under theimposed load. Therefore, bearing materials must be made of hardened steel to withstanddistortion under load. Distortion will create unwanted friction which defeats the purpose of havingbearings.

Bearings having small contact areas and subjected to high loading conditions must be carefullylubricated if they are to have the antifriction properties they are designed to provide. Improperlubrication will cause cracking and pitting and will bring about the generation of enough heat toblue the steel, and possibly weld the bearing components together. If these conditions areallowed, the bearing will completely fail.

Both sliding surface and rolling contact bearings may be further classified according to theirfunction. These can be radial, thrust, and angular contact bearings. Radial bearings aredesigned to carry a load in a perpendicular direction to the rotational axis and to limit motion in aradial direction.

Thrust bearings only carry axial loads, a force parallel to the axis of rotation which tends to causeendwise motion of the shaft.

Angular contact bearings are actually a combination of radial and thrust bearings and can supportboth radial and thrust loads. They are rarely used alone, however, if they are used alone, theymust be mounted in a manner similar to single row tapered roller bearings. Normally, angular

FIGURE 24- 2 - ANTI-FRICTION ROLLER BEARING MOUNTINGS



contact ball bearings are used in pairs with their side faces especially ground at the factory topermit them to be mounted side by side.

Some ball, tapered roller, and cylindrical roller bearings are also made with tapered bores. Thistype of bearing may be mounted directly on the shaft.

The simplest forms of radial bearings are the integral and the insert types. The integral bearing isformed by surfacing a part of the machine frame with the bearing material. The bearing must beresurfaced when the maximum allowable clearance is reached because there is no way ofcompensating for wear.

The insert bearing is a plain bushing inserted into and held in place in the machine frame. Theymay be made into solid or split bushings consisting of the bearing material alone, or may beenclosed in a shell or casing.

The insert solid bushing bearing, like the integral type, has no means for adjustment due to wearand must be replaced when the maximum clearance is reached.

Various types of roller bearing mountings are shown in Figure 24-2.

Pivoted-Shoe Type of Radial Bearing

The pivoted shoe is a more complicated design of radial bearing. This type consists of a shellcontaining a series of pivoted pads or shoes, faced with a bearing material.

The plain pivot or single disc type of thrust bearing consists of the end of a journal extending intoa cup shaped housing, the bottom of which holds the single disc of bearing material. The multi-disc type thrust bearing is similar to the plain pivot bearing except that several discs are placedbetween the end of the journal and the housing. Alternate discs of bronze and steel are generallyused. The lower disc is fastened in the bearing housing and the upper one to the journal, whilethe intermediate discs are free.

The multi-collar thrust bearing consists of a journal with thrust collars integral with, or fastened tothe shaft. This type of collar fits into recesses in the bearing housing which are faced withbearing metal. The design of this bearing is frequently used on horizontal shafts carrying lightthrust loads.

Kingsbury Thrust Bearing

The pivoted shoe thrust bearing is similar to the pivoted shoe radial bearing except that it has athrust collar fixed to the shaft which runs against the pivoted shoes. This type of bearing isgenerally suitable for both directions of rotation and is commonly found on the inboard end of amulti-stage centrifugal pump. It is extensively used in marine main propulsion units to transmit thethrust from the propeller to the hull of the ship. Without this bearing, a ship would not be able tomove.

This type of bearing utilizes the pivoted segmental shoe thrust pads and is commonly installed inmulti-stage pumps. It consists of pivoted segments or shoes (usually six) against which the thrustcollar revolves and operates on the principle that a wedge shaped film of oil is more readilyformed and maintained than a flat film. It can, therefore, carry a heavier load for any given size. The wedge shaped oil film will be further discussed in the lubrication section.



In a segmental pivoted shoe thrust bearing, the upper leveling plates, against which the shoesrest, and the lower leveling plates equalize the thrust load among the shoes. The base ring,which supports the lower leveling plates, secures the plates in place and transmits the thrust onthe bed or housing structure of the unit concerned. Shoe supports located between the shoesand the upper leveling plates enable the shoe segments to assume the angle required to pivot theshoes against the upper leveling plates.

Pins and dowels hold the upper and lower leveling plates in position allowing plenty of playbetween the base ring and the plates to ensure freedom of movement of the leveling plates. Thebase ring is kept from turning by its notched construction which secures the ring to its housing.

When the bearing is operational, the bearing faces are separated by an oil film so that there is nometallic contact. The oil film forms automatically when the bearing begins to turn and ismaintained by the movement of the bearing. Because bearing faces take up an inclined position,the oil film between the shoes and the collar is wedged shaped, the thin end pointing in thedirection of rotation.

In vertical installation the bearing is usually mounted in an oil pot or bath. Rotation of the collar orrunner maintains circulation of the oil, thus removing the heat from the wedge shaped film. Thisheat is then dissipated from the outer surface of the container or is carried away through coolingcoils. When the unit is at rest, the oil film is not present and the starting frictional resistance ishigh. During starting and stopping, there is some rubbing between the metals, but, as the fullarea of the shoes bears against the collar or runner, the bearing is able to start without heating.

In most horizontal thrust bearings, such as are used in steam turbines, the lubricating oil system ispressurized by an independent pump. In vertical thrust bearings, the rubbing of the metallic partslasts about one quarter of a turn of the shaft, with the oil film increasing with the speed. Thisrubbing can be heard quite distinctly in some vertical machines and is usually accompanied bynoticeable vibration. If this symptom persists, the unit should be stopped and the probleminvestigated.

The clearances that the manufacturer of the equipment has determined must be carefullyobserved. These clearances take into consideration temperature changes, pressures, and speedof rotation, and must be adhered to for equipment safety.

Shielded or Sealed Bearings

The shielded or sealed bearing belongs in the same family group as the antifriction or rollingcontact bearings. It is very popular because of unique design features which make it highlyresistant to airborne contamination and is sometimes referred to as a "sealed for life" bearingbecause it never needs lubrication. Ball bearings are usually a part of the bearing and areattached to the outer race.

Shielded bearings have variations in their design. Some use a shield (grease plate) and seals toprotect the bearing, while others have integral closures. Shields or seals may be located in thebearing itself.

Sealed bearings contain a seal lip which rubs against the inner race and shuts off that side of thebearing so that it keeps the lubricant in and dirt out. When two seals are used, they will keep agrease lubricant in for the life of the bearing and should permit no ingress of contaminants. The



shields that are used do not have a lip, but have a narrow clearance that will only let oil and smallparticles of dirt pass.

Consideration must be given to the speed, shaft, lubricant, and atmospheric conditions in whichthe bearing has to work before selecting a particular bearing.

When a shielded bearing is installed in a housing in which the grease space has been filled, thebearing in running will tend to expel excess grease past the shields or accept grease from thehousing when the amount of grease in the bearing itself runs low.

Seals of leather, rubber, felt, plastic, or cork may be used, but they must bear against the rotatingmember. Severe pressure must be avoided and some lubricant must be allowed to flow into thearea of contact. Otherwise, the seal may burn and cause seizure with subsequent scoring of therotating member.

Selection of Ball and Roller Bearings

Some of the advantages of ball and roller bearings are as follows:

• Their starting friction is low.

• The axial space is less.

• An accurate shaft alignment can be maintained.

• Replacement is relatively simple.

• Simple lubrication is all that is required.

• Both radial and axial loads can be carried by certain types.

For a specific application, five choices must be made in selecting a ball or roller bearing:

• The bearing series

• The type of bearing

• The size of bearing

• The method of lubrication

• The type of mounting

These considerations must be flexible enough to encompass expected life and cost andmaintenance philosophy. The following questions examine the possible background and theexpected function of the bearing in the machine in which it is installed:

• Can the bearing be expected to withstand removal and re-installation for further use?

• Is it to be used in a situation where it cannot receive maintenance attention over its useful lifeexpectancy?

• Will it be fairly free from abuse during its operational life span?

• Does it have to be adjustable to take up wear?

• Can the wear of the housing or shaft be tolerated during the overhaul period?



A list of this nature can prevent many problems if the correct bearing for the job is installed at thestart of any project. Other considerations may become factors, such as environment, load, shafts,and tolerances. Vendor recommendations and bearing manufacturers are direct sources ofinformation for the type of bearing needed for a particular application.

General Bearing Handling Precautions

There are many problems which arise from improper handling of rolling element bearings. Toensure that the bearing is capable of achieving its designed life span and that it performs withoutobjectionable noise, temperature rise, or excursions from normal operational design, the followingprecautions are recommended:

• Use the best bearing available for the application. It may cost more, but it is less than the costof the replacement value of a new rotating element.

• Keep a new replacement bearing in the manufacturer supplied protective coverings as long aspossible before installation.

• Do not use a brass or bronze bar to drive the bearing on to the shaft or housing. This materialsplinters readily and the splinter can lodge in the bearing with devastating results. If nohydraulic presses are available, a mild steel bar is a much better substitute. Mild steel issofter than the hardened steel of the bearing.

• Follow manufacturer instructions in handling and assembling the bearings.

• Always work with clean tools, clean dry hands, and in a clean working area.

• Never wash or wipe bearings prior to installation unless special procedures and instructionsstate otherwise.

• Do not spin uncleaned bearings, nor spin any bearing with a compressed air gun.

• Avoid scratching or nicking bearing surfaces.

• Never strike or press on race flanges.

• Always inspect the mounting areas on the shaft and housing before installation of the bearingto ensure that proper fits will be maintained.

• If bearings have to be cleaned, use lint free rags.

• Protect dismantled bearings from dirt and moisture.

• Follow manufacturer instructions when heating bearings for mounting on shafts.

• During the installation of the bearing into the housing or onto the shaft, ensure that the racesare started evenly so that they will not cock.

• Treat used bearings, which may be reusable, as if they were new ones.

• All dirt must be considered abrasive. It is important that all housings, shafts, and covers bethoroughly clean prior to removal or installation of bearings.

• Use clean filtered solvent or flushing oil to clean bearings.

Most of the preceding precautions are basically common sense activities, but they are oftenoverlooked in bearing installation and maintenance. Bearing failures can be expected but when a



bearing fails prematurely, operational conditions and not the bearing itself is the cause. Do notblame a bearing for failing if any of the following situations occur:

• Loads or speeds were increased.

• The bearing rusted or became contaminated in use or storage.

• Lubrication schedules were not observed or there was improper lubrication.

• The wrong lubricant has been used. It is not unusual to find maintenance and operationalpersonnel who believe that any lubricant will do for any type of bearing. This belief hasprobably been more the blame for early bearing failure than any other single fault in theindustry. Lubricants have certain characteristics built into them to withstand adverseoperational working conditions that the bearing may be exposed to.

These are common occurrences that have extremely adverse effects on bearings.

General Bearing Maintenance

Bearing maintenance not only includes the replacement of worn out bearings, but periodicinspection, lubrication, and protection. Proper bearing maintenance takes time to make properobservations, check bearing temperatures, ensure proper lubricants, and ensure that machineryis not operated under overload conditions for extended periods of time. The extra time takenduring regular maintenance procedures or overhauls can eliminate emergency breakdown andextra work at a later time.

The downward load is distributed among several of the ball bearings, each applying a force onthe outer ring. The condition shown is with the inner ring rotating with the shaft and the outer ringstationary. If the conditions were reversed, where the outer ring rotated and the inner ring wasstationary, the load distribution would be over the upper third of the inner ring. Certain wearpatterns can be created while the bearing is operational. If a ball bearing is used to support ashaft having thrust or axial loads, the load is distributed through the opposite sides of the innerand outer rings. When the thrust loading becomes excessive, the wear pattern will be locatednear the edge of the raceway, which may cause damage.

When bearings are fitted too tightly into their housing or onthe shaft, a condition known as "preloading" occurs,whereby the rollers are squeezed between the two ringsand overload the race surfaces. As shown in Figure 24-3,a preloading condition occurs when the gap a point Adiffers from that a point B. This displace the balls in therings and induces a stress on the bearing.

It can be seen that proper installation is important to properbearing life. Extreme caution must be exercised whenmounting bearings. Improper mounting can be determinedwhen the bearing is removed. Once it is removed and acheck is made on the bearing, the shaft and mountingshould also be inspected to ensure that these are not

damaged.

FIGURE 24- 3 - ILLUSTRATIONOF BALL BEARING PRELOADING



During routine inspections, checks should be made on the bearing and housing for rust, cracks,broken rollers or rings, broken or cracked separators, and overheating. If any of these conditionsexist, the bearing should be replaced.

Among the many reasons for bearing failure, such as improper loading, misalignment, improperinstallation and others, improper lubrication remains by far the most common reason. In addition,many bearings are subjected to moisture and corrosive fluids that react with the bearing surface,causing chemical breakdown of the metal.

LUBRICATION

One of the main reasons for using a lubricant is to make moving parts slide or roll with greaterease. Other factors, however, must also be considered. The lubricant must also:

• Control friction by reducing wear and corrosion

• Dampen shock

• Limit temperature

• Help to form a seal

Most lubricants today are designed to do these things in their normal day to day functions.

With the technological advances that have been made in modern machining operations, mirrorlike finishes are easily achieved on bearing and journal surfaces. Even these finely finishedsurfaces, however, contain areas that are made up of miniature mountain ranges which canreadily be seen under a microscope. When surfaces come in contact in the absence of alubricant, these points will flatten and cold weld when the unit is at rest.

With dry machined surfaces, major frictional force shears these welded points. This generatesheat and also introduces debris in the contact area which must be eliminated. This is part of thelubricants function. It must be able to help dissipate heat build-up and to flush out undesirableelements.

To understand the mechanics of lubrication, the basics of friction must be understood. Friction isthe force that resists sliding motion. The term "coefficient of friction" relates this friction force tothe normal load applied to the surface. In other words, it is simply the friction force divided byload applied.

Regardless of the size of the contact area, if parts are made of the same material and support thesame weight, they will have the same coefficient of friction because the friction force isindependent of any apparent contact area. When trying to move one surface means shearing thecold welded spots of contact, the friction force depends on the shear resistance of the metals atthat point. The force required to overcome this static friction resistance accounts for the largestpart of friction on dry machined surfaces. In simple language, this means that the friction force tobe overcome before the moving part can slide or rotate is greater than that needed to keep thebody moving. The immediate effect of introducing a lubricant is to reduce the coefficient of frictionand let the moving parts slide with less effort being expended.

When a full film of lubricant separates the surfaces, friction is created within the lubricant itself asthe fluid splits into layers to permit the movement. The top layer sticks to the top surface, while



the bottom layer sticks to the bottom surface. Each successive layer travels at a lower speed,thus shearing the layers on either side.

The sliding lubrication fluid layers is similar to the action of a deck of cards when the top card ispushed with the bottom card held in position. With this motion, the deck splits into layers. It isthis sliding of layer upon layer that contributes to the fluid's internal friction. If dealing with aheavy oil (oil with a greater viscosity), the layers of oil are much tougher to slide by one another. A low viscosity oil will have less frictional build-up. This build-up of layers within the lubricanttransforms it into a hydrodynamic oil film and involves factors that must be taken intoconsideration, including:

• Clearance

• Bearing grooving

• Point of oil application

• Speed

• Load

• Viscosity of the lubricant

In developing the fluid film formation, the mechanics are straightforward. As the journal beginsturning, it starts to roll uphill within the bearing. This action makes the journal slightly off centersince the clearance is crescent shaped and the wedge end of the crescent tucks into the loadarea. As the speed of rotation increases, oil is dragged out of the crescent forming a thin film inthe bearing load area. Due to the convergence of the shaft with the bearing, oil will leave thehigh load area at a higher average velocity than it had when it entered. Therefore, there is sometendency for the fluid to back up in the wedge shaped load area. Since oil cannot be squeezedinto a smaller volume, its pressure builds up and supports the journal load.

Viscosity

In considering the load supporting capabilities of an oil, viscosity becomes an important factoronce the journal speed and bearing load has been established by the designer. Viscosity isbasically a measure of a fluid's internal resistance to motion. For example, in comparing the flowcharacteristics of syrup versus kerosene, it is observed that kerosene flows much faster thansyrup. This is due to the syrup having a greater viscosity factor than kerosene.

By increasing viscosity, more loading can be supported without the possibility of overheatingtaking place. A limit to viscosity must also be considered due to the higher bearing temperaturesresulting from the normal increase in fluid friction. It is important to determine a bearing'soperational temperature and the true viscosity of the lubricant at that temperature because oilviscosity decreases as temperature increases.

Viscosity is the property that helps oil to resist being squeezed out as load is applied. One of thereasons why low viscosity oils are used in handling heavy loads is that viscosity actually increasesslightly as the load pressures the fluid lubricant. A good rule of thumb is to use lightweight oil forhigh speeds and low loads. Heavy oils are used for slow speeds and heavy loads.

The oil should not be fed in at the top of a bearing if the bearing is subjected to upward loading. Understanding how an oil wedge is formed is the most important concept of hydrodynamic



lubrication. When oil enters the slider bearing at the left and exits at the right side, theconvergence of the two surfaces causes the oil to leave the wedge area at a higher averagevelocity than it entered with. Because of this convergence, back pressure builds up in the wedgearea. Since the oil cannot be compressed into a smaller volume, the pressure builds up instead. This pressure build-up exists even when both surfaces are curved, as in a conventional slidingbearing.

If the wedge lifts the journal off the bearing surface and keeps the journal and the bearing surfaceseparated during running, the oil pressure drops off suddenly when it leaves the wedge area andenters the area where the journal and bearing surfaces diverge. Under certain circumstances,the pressure may drop below atmospheric. Because liquids cannot withstand tension, the oil filmbreaks up, and air or oil vapor bubbles form in the diverging area.

When bearing loads increase or change direction, the shaft will shift its position until all the forcesare in equilibrium. Some of the oil in the bearing area will be squeezed and will flow around theshaft. Due to viscosity, the oil under this condition will push back this shift in shaft position. Thisresistance actually adds to the load carrying ability of the oil film, provided the shaft continuesrotating. This situation cannot last forever under a constantly increasing load. However, it is mosteffective in carrying reciprocating loads imposed on a piston's wrist pin or connecting rod bottomend.

Additives

Lubricants today are called on to do more and withstand greater loads. To meet these demands,various chemicals or additives are frequently mixed with selected base mineral oils to give thelubricating oil better characteristics. The following exemplify typical additives:

Anti-Oxidants

These fall under two general classifications:

• The true oxidation inhibitor which deters oxygen reaction with oil

• The catalytic poison, or metal deactivator, which neutralizes the catalytic actionof elements such as iron and copper

Oxidation is common in mineral oils exposed to air, especially at high temperatures. Onceoxidation gets established, property changes within the oil can be expected. Under theseconditions:

• Oil can become quite corrosive towards some metals

• Viscosity and neutralization values increase

• The color darkens

• Insolubles form and deposit form later in the process

For each 18 oF rise, the oxidation rate practically doubles itself. Iron, copper, and lead speed upoxidation in varying degrees. Oxidation inhibitors are an immediate answer since they improve oilstability and extend the useful life. If the oil has been in service for an extended period of time,these inhibitors tend to lose their effectiveness.



Detergents

The aim of detergents is to maintain cleanliness in internal combustion engines. The detergentacts purely in a physical manner in the crankcase by keeping it clean. In the piston ring area, itkeeps sludge or lacquer from plugging up the ring grooves.

Viscosity Index

The viscosity index additive is a colloidal substance that improves the viscosity of a mineral oil byraising the oil's viscosity as the additive is dispersed through the oil. The resultant viscosity isalso less affected by temperature changes until the temperature reaches the point where thecolloid goes into a true solution.

Rust Inhibitors

Rust inhibitors can be broken into two categories. The first is used in turbine oil circulatingsystems and is usually a polar type material whose surface activity forms an adsorbed film onmetal parts. This film prevents moisture from reaching the metal surfaces. Fatty acids are oneexample of such compounds.

The second type is used in engine oils where the engine works in the presence of heavy moistureor salt mists or where bromides in leaded fuels are present. By chemical action, a coating isformed on the surface of the metal part that is to be protected.

Pour-Point Depressants

When an oil containing dissolved wax is chilled, the wax will crystallize. This may prevent the oilfrom flowing. Pour point depressants lower the temperature at which this crystallization occurs. The pour point of a given oil is the temperature at which flow ceases under specified coolingconditions.

Oiliness and Extreme Pressure Compounds

Oiliness and lubricity additives reduce the coefficient of friction in the thin film region. Extremepressure compounds usually contain chlorine, sulfur, or both by forming a chlorine-sulfur salt onthe metal surface. This helps to minimize the wearing effect of metal to metal contact. Toencompass all of the possible conditions that involve high and low torques, it is frequentlynecessary to use an oiliness additive such as the fatty materials, plus conventional sulfur andchlorine compounds. This helps to prevent welding and seizure of contacting surfaces when theoil film is broken.

Types of Oils

Apart from being aware of the many additives which can be obtained to satisfy special applicationrequirements and improve the performance of fluids, the designer must also be acquainted withthe wide variety of oils, both natural and synthetic, which are now on the market. Each has itsown special features which make it suitable for specific functions and which limit its utility inothers.



Lubricating Greases

Greases are used in place of fluid lubricants because, at times, fluid lubricants experienceproblems with retention, relubrication, and churning. Greases are made up from petroleum basedoils thickened by dispersions of soap, but can also consist of synthetic oils with soap or inorganicthickeners, or oil with siliceous dispersions. In all cases, the thickening agent must be carefullyprepared and mixed with the fluid. This agent serves to immobilize the oil and functions as astorehouse from which the oil bleeds slowly. The thickener itself possesses lubricatingcharacteristics, but the oil bleeding from the body of the grease functions as the main lubrication.

It has been shown that when the oil content has dropped to the level of 50 percent of the totalweight of the grease, the lubricating quality of the material is no longer reliable. In someapplications where a wetter or softer grease is used, this level of unreliability may be as high as60 percent.

Successful application of a grease depends on a relatively small amount of mobile lubricant (theoil bled out of the bulk) to replenish the small amount of lubricant contained in the bearing beinglubricated. It is possible that a space may exist between the bearing surface and the bulk of themobile grease during operation. If this space becomes large enough, then a critical delay periodwill take place before the lubricant in the bearing can be replenished. Since most lubricants aresubjected to attrition due to thermal degradation, evaporation, shearing, or decomposition in thebearing area, this delay can be detrimental to the operation of the bearing. To prevent this fromleading to failure, grease is normally applied so that the material in the cavity of the bearingmakes contact with the bearing in the lower quadrants. This ensures that the excess originallypacked into it impinges on the material in the reservoir.

It is good practice to select a good grease which has a low slump factor, and a reservoirconstructed to prevent churning. The initial action of the bearing when starting up will then be topurge itself of excess grease and establish a flow path for bleed oil to enter the bearing.

In setting up a greasing lubrication program, careful consideration must be given to its applicationbecause of the different characteristics that each grease displays. In some cases it may bebeneficial to bring in a consultant from an oil company and the bearing designer to determine thecorrect grease for the job. The machine manufacturer usually takes this into consideration duringthe design phase of the machine.

Greases are selected on the basis of the following requirements:

• Hardness

• Stability

• Water Resistance

The hardness of a grease is expressed by a number system, ranging from 0 to 6. The higher thenumber, the harder the grease. The softer the grease, the easier it is to apply and the more oil itcontains.

The stability of the grease is that property which helps it retain its original consistency while inuse. If the consistency of the grease changes as it becomes older, it is said to be unstable and isan indication that the wrong grease was selected.



Water resistance is the ability of a grease to resist dilution by water. Grease used for bearingswhere rain or moisture can collect may require additives to enhance the water resistantproperties.

Types of Grease

Greases are made with a variety of soaps. The most popular are the lithium, or soda soapgrease, and the modified clay thickened materials. Lithium based greases can handletemperature extremes, while a number of soda soap greases have been found to work well up to285 oF.

Greases also vary in volatility and viscosity according to the oil base used. Volatility will affect theuseful life of the bulk applied to the bearing and the viscosity will affect the load carrying capacityof the grease. These factors have to be considered when selecting a grease.

When used in gear boxes and slow speed journal bearings, a number of greases are thickenedwith carbon, graphite, molybdenum disulfide, lead, or zinc oxide. To inhibit fretting corrosion orwear in sliding or oscillating mechanisms, these grease additives provide greater protection ofmoving parts. Listed below are some of the greases available and their applications:

Multipurpose Grease

This type of grease combines the properties of two or more specialized greases to function over abroader range of conditions and applications. Some of the more popular greases have a soapbase of lithium, barium, or calcium complex.

The lithium base is capable of standing up to temperature extremes, is highly water resistant, andcan be pumped with little effort. Some of these lithium based greases possess high mechanicalstability.

The barium base is lower in cost and offers a high resistance to water. It can operatecontinuously up to 275 oF and is compatible in most types of bearing applications. The high soapcontent, however, makes its use very restrictive, and as a result, barium base greases are notwidely available. The calcium complex grease is an excellent water resistant type and has amelting point of over 400 oF. It also resists breakdown and softening.

Specialized Greases

The scope of these greases lacks the wide application that the multipurpose greases have. Specialized greases include those with a calcium or sodium soap base or a mixture of the two. Aluminum or lead are often added to these greases. Synthetic greases also fall in this category. Soap based greases may have up to 3 percent water contained within the grease, but still exhibitexcellent water resistant properties.



Calcium soap grease offers good water resistance in general plant use with temperatures up to160 oF. Beyond this temperature, the grease tends to lose the water required to maintain itsstability and separates into its original oil and hard soap. High melting point grease types areavailable that are capable of holding up to 250 oF.

Sodium grease is a commonly used bearing lubricant, and is good for moderately hightemperatures of up to 250 oF with a continuous rating at that temperature. It also possesses goodadhesive and cohesive properties.

Aluminum soap base grease has reasonable water resisting capability and can be used up to180oF.

Lead soap combines extreme pressure (E.P.) characteristics with good water resistance. It issuitable for use in heavy industrial machinery at temperatures up to 175 oF or higher.

The synthetic greases combine a synthetic fluid with a standard soap. They can withstandextremes of temperatures and are water resistant. Although more costly, they have superiorproperties over petroleum oils including viscosity index property. They also have little or no effecton natural or synthetic rubbers. Synthetic greases that are specifically formulated for hightemperature use do not leave the residual deposits which are commonly found with conventionalgreases.

Silicone greases are completely synthetic and are usually graded according to the temperatureranges that they will be used in. For example, one grade adequately accommodates ball bearingtemperatures ranging from -100 oF to 300 oF. A second grade is rated from -20 oF to 450 oF. When considering high temperature grades of grease, the bearing itself must be able to withstandthese anticipated temperatures.

Solid Lubricants

A solid lubricant is a solid material placed between two moving surfaces preventing metal to metalcontact, thus reducing friction and wear. Their application is such that they fit in the boundaryand mixed film area. In the hydrodynamic region there is no wear, only fluid friction. Thepossibility that the oil film can breakdown, particularly during startup and shutdown, is overcomeby the use of solid lubricants. Natural graphite, colloidal graphite, and molybdenum disulfide, areminerals that form these solid lubricants.

Natural graphite is a black lustrous mineral and is used as a lubricant in dry form or as a mixturewith oil or grease. It is not recommended as an oil mix in general lubrication systems as it tendsto be heavy and will settle to plug up filters and passageways. It is used quite extensively in themanufacture of oil-less bearings.

Colloidal graphite is manufactured from anthracite coal and petroleum coke in an electric furnace. It is almost chemically pure and is inclined to be a soft greasy substance. For commercial use itis mixed with distilled water, mineral lubricating oil, or glycerin and varnish. In some cases,particularly in the high temperature field, the liquid that is mixed with the graphite is only used totransport the lubricant to its working area. Selection of the vehicle depends on the temperaturesthat it will be exposed to.

These graphite films are tough and highly resistant to abrasion. A film of only 0.003 inchthickness exhibits good bearing strength and displays good resistance qualities to abrasion. The



film can be applied by either dipping or spraying. It is unaffected by weather, fuels, lubricants,water, or dilute acids.

Molybdenum disulfide closely resembles graphite in appearance but is twice as dense. It is achemical combination of molybdenum and sulfur and has a unique molecular structure whichforms the basis for its excellent lubrication qualities. Each lamina of the compound is composedof a layer of molybdenum atoms that are flanked on either side with a skirt of sulfur atoms. Dueto a strong metal to sulfur bond, one of the sulfur layers hangs on to metal surfaces, while theother side of the molecule slides easily over the adjacent molecules because of a weak sulfur tosulfur bond.

Due to its low coefficient of friction at high temperatures, an effective subfilm of the productremains. Oxidation starts slowly at 750 oF and continues slowly, until it becomes high at 1050 oF. This lubricant is popular in high speed applications such as the machine tool industry.

Applying Lubricants

Probably the oldest and easiest method of applying a lubricant to a single bearing is to use ahand held oil can. This method copes adequately with very low speed machine parts which mayonly operate on an intermittent basis.

In fast moving highly loaded machinery it is necessary to use an automatic oiling device for eachbearing. The ring hangs on the shaft and has its lower end immersed in an oil well which is anintegral part of the bearing housing. As the shaft starts to rotate, the oiler ring, due to its contactwith the shaft, starts to revolve. As it revolves, it starts to drag oil from the oil well upwards towhere a scraper device removes it from the ring surface and distributes the oil to the bearingsurfaces. Once through, the oil gravitates back to the bearing oil well.

Another method is to have an oil well situated on top of the bearing, or adjacent to it, and have oilwick feeders siphoning oil from the oil well to its appointed lubrication point. With the possibleexception of the ring-oiler, these "once through" methods are not suitable for large, high speedpieces of machinery. A forced circulation type of lubrication technique is required to providecontinuous oil circulation. The advantages of a circulation system are that:

• They provide adequate oil supply for both cooling and lubrication

• Oil consumption is lowered by recirculation

• Dirt is removed by the flushing action of the oil

An external pump forces oil through all of the bearings in the unit, and provision is made forcollecting and recirculating the oil.

In turbines and diesel engine installations, the lubricating oil can be used to control, cool, andprovide hydraulic power in addition to its lubrication functions within the unit. This type of systemuses a centralized form of lubrication. The circulating pump takes suction from a reservoir, forcesit through a cooler and then into a header system. An arterial system of pipe lines branches outfrom the header to individual bearings. In diesel engines, the oil proceeds to cool the insidecrowns of the pistons after it has lubricated all bearing surfaces before returning to the sump or oilwell. Strainers in the reservoir remove particles of dirt before the oil enters the cycle once more. An oil conditioner is usually provided in this type of system in an effort to extend the life of the oiland to reduce bearing wear.



Centralized oil systems show many advantages. The old hand lubrication method does notprovide an accurate distribution of oil or guarantee the delivery at the proper time. It alsoprovides a safety hazard as many bearings require a lot of personal attention and access to themmay involve ladder climbing while the machinery is in motion. The centralized system eliminatesthis by automating the task. It is also much more economical.

Storage and Handling

Storage of lubricants must be conducted in such a manner that will provide complete protectionfrom contaminants such as dust, dirt, moisture, and other impurities. If absolute purity is requiredof the supplier, this standard must be maintained in-house during storage and application. Goodstorage can eliminate a host of problems. The following list of rules should be used as aguideline in providing this protection.

• Where possible, all lubricants should be stored in a clean, dry oil house that can be heatedduring cold weather.

• Oil, particularly grease drums, should not be stored in actual contact with steam pipes or anyheated surface, as overheating may change the physical characteristics of the oil.

• If indoor space is inadequate for storing all lubricants, the lower quality grades should beselected for outdoor storage.

• Turbine, diesel, transformer, or automotive oils should not be stored in the open. Coldweather can cause separation of fatty oils from compound type oils.

• When storing oil drums outside, they should be laid on their sides on skids to prevent moistureaccumulating on the heads.

• Where possible, oil stored in open areas should be shielded from the sun and weather.

• All flammable materials should be kept out of the storage area and fire extinguishers shouldbe placed at convenient locations.

• Avoid storing oil tanks made of galvanized metals. The zinc contained in the galvanizing mayreact with the oils, especially with compounded oils.

• Wherever practical, sealed measuring pumps should be used with filters and indicating metersfor pumping oils out of drums and tanks. This helps establish good oil consumption recordkeeping.

• Handling should be kept to a minimum to keep oils and greases clean and to avoid costlyspillage’s.

• Clean oils should not be stored in the same area as dirty oils to avoid confusion.

• All oil containers should be clearly identified with the noun name and numerical grade of theoil they contain.



• When applying oils and greases by hand, the lubrication points should be wiped clean using alint free cloth to prevent ingress of potential contaminants and plastic caps should be fitted forprotecting lubrication points.

The basic rules for storing and handling oils and greases are:

• Keep lubes free from water and dirt

• Keep them away from extremely high or low temperatures

• Use same handling equipment for same product

• Maintain general cleanliness in applying all lubricants.

The operator must get to know the ingredients, the physical and chemical properties, and correctapplications of all lubricants at his disposal. A well planned schedule must also be available if alubrication program is to succeed.


Section 25

Glossary

The following are some common field terms related to Piping and Mechanical work activities:

Alkaline Cleaning - The removal of organic particulates by converting them to an emulsifiedcompound.

Alloy Steel - All steels contain carbon and small amounts of silicon, sulfur, manganese, andphosphorus. Steels which contain intentional additions of elements other than these, or whichexceed 0.60% silicon, or 1.65% manganese and/or 0.60% copper, are termed alloy steels.

Anchor - A pipe fixture that resists all piping forces and movements.

Angular Alignment - An alignment condition in which the coupling flange faces are parallel whenrotated in a coupled unit. Angular misalignment occurs when the shaft axes are concentric at thecoupling but are not parallel to each other.

Annealing - A softening heat treatment (see heat treatment).

Ash Handling - Collects and disposes of all the ash from the furnace hoppers, fly ash from theeconomizer, and dust collection hoppers.

Austenitic Stainless Steel - Low carbon, iron-chromium-nickel stainless alloys containingsufficient nickel to provide an austenitic (FCC) structure at normal temperatures. These alloysusually cannot be hardened by heat treatment, but can be hardened by cold working. They arenormally non-magnetic, but sometimes become slightly magnetic on cold working. These have2xx or 3xx designations. There are a few precipitation hardening grades.

Austenite - The FCC structure of steel, known also as gamma.

Average Wall - See dimensions.

Bevel - An angular cut on the I.D. or O.D. of a tube, fitting, or flange welding end.

Billet - As used in the manufacture of flanges, a round or RCS (Round Corner Square) bar withdimensions and other characteristics suitable for forging into flanges.

Bloom - A semi-finished piece of steel, resulting from the rolling or forging of an ingot. A bloom issquare or not more than twice as wide as thick, and usually not less than 36 sq. in. in cross-sectional area.

Bright Anneal - A final anneal in a controlled atmosphere to retain a shiny cold rolled finish (seeheat treatment).

Brinell Hardness - A common hardness test (ASTM E10). The tensile strength of a steel (ksi) isapproximately one half of the Brinell Hardness.

Cable Tray - The portion of the raceway system that is used to hold electrical cable.

Camber - The amount of curvature or deviation from exact straightness over any specified lengthof tubing.

Section 25 Glossary


Carbide - A compound consisting of carbon and other elements; the most common carbides insteel are iron and chromium carbides.

Carbide Precipitation - A phenomenon of carbides coming out of a solid solution, occurring instainless steel when heated into the range of 800- 1600 degrees Fahrenheit (Chromium CarbidesPrecipitation).

Carbon Steel - A steel consisting of essentially iron, carbon, manganese, and silicon.

Carburizing - Adding carbon to the surface of iron-base alloys by heating the metal below itsmelting point in contact with carbonaceous solids, liquids or gases. Desired hardness andtoughness properties are developed in the high carbon "case" by quenching and tempering.

Cementite - Iron carbide, a constituent of steel.

Charpy Impact Test - A test for toughness, involving an impact test on a notched specimen(ASTM E23).

Check Analysis - An analysis of the metal after it has been rolled or forged into semi-finished orfinished forms. It is not a check on the ladle analysis, but is a check against the chemistryordered.

Chloride Stress Cracking - Cracking under a sustained stress in a chloride containingenvironment. Austenitic stainless steels may be susceptible.

Cladding - A thin layer of metal coating that is bonded to metal core. An example would be astainless lining placed on a carbon steel tank.

Cleanness - The condition of having dirt and other foreign material removed to required levels.

Clinkers - A stony matter fused together, slag or cinder that will not burn and is a byproduct fromcoal burning.

Coefficient of Thermal Expansion - A physical property value representing the change in lengthper unit length, the change in area per unit area or the change in volume per unit volume per onedegree increase in temperature.

Cold Alignment - The alignment made when the equipment is at the ambient temperature.

Cold Drawing - A process in which tubing is drawn at room temperature through a die and over amandrel to achieve its final size. It may provide a better surface finish, closer tolerances, lighterwalls, smaller diameters, longer lengths, or a different combination of mechanical properties thanthose possible through hot finishing or direct welding.

Cold Working - Permanent plastic deformation and work hardening of a metal below itsrecrystallization temperature.

Combination Support - A component which carries both deadweight and thermal loads andwhich limits piping movement in a lateral direction.

Conduit - A pipe or tube for protecting electrical wires or cable

Glossary Section 25


Condensate - Steam taken from low pressure systems, or turbine, into the condenser formingcondensate (water). The condensate is collected and reused as feedwater for boilers.

Conditioning - The removal of surface defects (seams, laps, pits, etc.) from steel. Conditioning isusually done when the steel is in a semifinished condition (bloom, billet, slab). It may beaccomplished, after an inspection, by chipping, scarfing, grinding, or machining.

Corrosion - Chemical or electrochemical deterioration of a metal or alloy.

Corrosion Resistance - The ability to resist attack by corrosion.

Coupling Gap - The space between the flanges of the couplings which allows longitudinalmovement of the shafts. The width of this gap is specified by the manufacturer. Equipmentwhich experiences a considerable temperature rise during operation will have an elongation ofboth shafts which will result in a decrease in the coupling gap.

Creep Strength - The constant nominal stress that will cause a specified quantity of creep in agiven time at a constant temperature. It is a measure of a product ability to withstand prolongedstress or load without significant continuous deformation.

Critical Temperature - The temperature that must be exceeded to transform the steel structure toaustenite. It is likely to be important when metals are used above about a half of their absolutemelting temperature (above about 600 oC in steels).

Deaerator - A component designed to liberate air and gases from boiler feed water.

Deadweight Analyzed Piping - Piping below 200 oF in which the supports only need toaccommodate the weight of the piping, fluid, insulation, valves, piping components, andassociated hardware.

Decarburization - The loss of carbon from the surface of an iron base alloy as the result ofheating in an environment which removes the carbon. In medium or high carbon steels,decarburization leads to a pronounced lowering of the fatiue limit.

Density - The mass per unit volume of a substance, usually expressed in the steel industry inpounds per cubic inch.

Dimensions -

• O.D. - Outside Diameter. Specified in inches and fractions of an inch, or inches and decimalsof an inch, or in the metric system.

• I.D. - Inside Diameter. Specified in the same units as the O.D.

• Wall - Wall Thickness or Gage. Specified in either fractions or decimals of an inch or by a"wire gage" number, and/or “schedule" number.

• Nominal - The stated value of the O.D., I.D., or wall dimension as used in discussion and intables. It need not be the theoretical (actual) size. A 1.5 inch standard pipe has an O.D. of1.61 inches.

• Maximum and Minimum - The stated permissable dimensional limits.

• Basic Size - The exact theoretical size.

Section 25 Glossary


• Minimum Wall - Generally, the lightest wall permitted within specified tolerances. A "minimumwall, tube, or fitting" is one whose wall thickness is not permitted to fall below the specifiednominal measurement.

• Average Wall - A tube or fitting whose wall thickness is permitted to range over or under thespecified nominal wall measurement within certain defined tolerances.

Demineralized Water (Grade A) - Water that meets requirements for high purity. Where nototherwise specified, water of the following quality generally meets the criteria of demineralizedwater:

• pH at 25 oC 6.0 to 8.0

• Chloride < 0.15 ppm

• Fluoride < 0.10 ppm

• Conductivity at 25 oC < 2.0 mmhos/cm

Ductility - The ability of a tube to deform plastically. Frequently, elongation during tensile testingis used as a measurement of this property.

Duplex Steel - The designation used for certain chromium/nickel/moly steels which exhibitmicrostructures consisting of ferrite zones in an austenitic matrix at ordinary temperatures. Duplex steels retain much of the formability of the austenitic grades but may have twice the yieldstrength and the chloride stress cracking resistance of the ferritic grades.

Dye Penetrant Inspection - A simple sensitive non-destructive test employing dye or afluorescent chemical and sometimes black light to detect defects open to the surface.

Eccentricity The displacement of the I.D. of the tube with respect to its O.D. Eccentricity resultsin the variation of wall thickness normal to seamless tubing.

Eddy Current - Non-destructive testing method using eddy current flow for the purpose ofrecognizing a surface or near surface defect in the piece being tested.

Elastic Limit - A measure of the maximum stress that may be applied to a product without leavinga permanent deformation or strain after the stress is released.

Electric Furnace Process - One of the common methods used for melting and refining stainlessand some alloy steels. It involves the use of electric power as the sole source of heat, therebypreventing contamination of the steel by impurities in the fuel as in other melting processes.

Electric Resistance Welded Tubing - Tubing made from strip by electric resistance heating andpressure, the strip being part of the electrical circuit. The electric current, which may beintroduced into the strip through electrodes or by induction, generates the welding heat throughthe electrical resistance of the strip.

Elongation - The amount of permanent stretch, usually referring to a measurement of aspecimen after fracture in a tensile test (ASTM E8). It is expressed as a percentage of theoriginal gage length, which should be specified.

Endurance Limit - The maximum stress below which a material is presumed to endure an infinitenumber of stress cycles. This applies to carbon or low alloy steels. Otherwise a specific numberof cycles, usually 107 is stated.

Glossary Section 25


Equalizing or Reinforcing Rings - Devices which reinforce an expansion joint bellows againstinternal pressures. Equalizing rings are approximately T-shaped in cross section and reinforcingrings are round in cross section.

Etch Test - Exposure of a specimen to acid attack for the purpose of disclosing the presence offoreign matter, defects, segregation pattern, or flow lines.

Expansion Joint - A device containing one or more bellows or sliding joints used to absorbdimensional changes, such as those caused by thermal expansion or contraction in a pipeline orvessel.

Expediting Reports - Special reports issued by the procurement department, based on factoryvisits by expediters.

External Cover - A device used to protect the exterior surface of an expansion joint bellows frommechanical damage.

Extrusion - Production process in which steel is forced by compression through a die into solids(round or special shape) or through a die and over a mandrel to form a tubular shape. Ananalogy is squeezing toothpaste from a tube.

Face Runout - The perpendicular relationship of the coupling face to the shaft axis.

Fatigue Limit - (Synonymous with Endurance Limit)

Ferrite - The normal room temperature structure of iron and steel, BCC; also called alpha.

Ferritic Stainless Steels - The designation used for straight chromium stainless steels whichpossess the microstructures consisting mainly of ferritic (BCC) structure at ordinary temperatures.Ferritic stainless steels are divided into two classifications; hardenable, and non-hardenable. Thehardenable grades will exhibit a martensitic microstructure when rapidly cooled. These steelshave 4xx designations.

Ferritic Steel - Magnetic steel. The common grades are A-53 and A-106 Carbon Steel, A-335Chrome-Moly, and Cast Iron.

Feedwater - Condensate used to feed the boiler system.

Ferrous - Any material containing iron, e.g., carbon steel, stainless steel, chrome-moly, wroughtiron, malleable iron, and cast iron.

Filtered Air - Compressed air which has been passed through a 10 micron filtering medium.

Finish - In the steel industry, refers to the type of surface condition desired or existing in thefinished product.

Finish Machine Size - Normally specified in terms of the maximum machined O.D.and theminimum machined I.D. as applied to tubular parts. Finish machine size represents the size ofthe part as it comes from the final machining operation. From this size, the forging mill cancalculate a forging size which will be guaranteed to clean up upon machining.

Flexible Coupling - A mechanical device used to connect the driver shaft to the driven equipmentshaft. This connector is flexible to allow slight movement in any direction, to absorb vibration, to

Section 25 Glossary


allow longitudinal shaft drift, and to allow movement caused by thermal differentials. Flexiblecouplings are not used to allow or compensate for misalignment.

Flushing - Flowing water or other fluids through a component or system at adequate velocity tosuspend and carry away foreign materials.

Fly-Ash - A fine, solid particle of non-combustible ash carried out of a bed of solid fuel by thedraft.

Foreign Material - Any undesirable material on the surface of an item, in the atmosphere, or inprocess liquids or gases that may be considered detrimental to the operation of the systemcomponents.

Forging - A general term to describe the shaping of metal by hammering or squeezing, usually ina die, at hot working temperatures.

Fracture Strength - As usually related to the tensile test, fracture strength, or true breakingstrength, is defined as the load on the specimen at the time of fracture.

Fracture Toughness - (Kc) A material property, measurable in the lab, that correlates the stressneeded to break a high strength material, with the size of any flaw present.

Full Anneal - To put in the fully soft condition (see Heat Treatment).

Gages, Gauges - A measurement of thickness. There are various standard gages such asUnited States Standard Gage (USS), Galvanized Sheet Gage (GSG), Birmingham Wire Gage(BWG).

Galvanic Corrosion - Corrosion associated with the presence of two dissimilar metals in asolution (electrolyte). In principle, it is similar to bathtype plating in the sense that the anodesurface has lost metal (corroded).

Grain Size - A measure of the size of individual metallic crystals usually expressed as anaverage. Grain size is reported as a number in accordance with procedures described in ASTMgrain size specifications (ASTM E112). Apparent Ferrite Grain Size is the average of the size ofthe ferrite grains as microscopically viewed in the normalized or annealed condition. AusteniticGrain Size, which is usually measured by the McQuaid-Ehn method, represents the austeniticgrain size of a material at a prescribed temperature above the upper critical, frequently 1700°F. For austenitic stainless steels, the grain size does not change upon cooling and is that observedmicroscopically at room temperature.

Gantry Crane - A traveling crane on a platform supported by towers or the side frames runningoverhead.

Guide - A two directional restraint.

Hanger/Support - A component designed to carry deadweight, fluid flow dynamic, seismic,and/or thermal loads.

Hardenability - The ease of hardening a steel (obtaining martensite) as cooling from austenite.

Glossary Section 25


Hardness - A measure of the degree of a material's resistance to indentation. It is usuallydetermined by measuring resistance to penetration, by such tests as Brinell (ASTM E10),Rockwell (ASTM E18), and Vickers (ASTM E92).

Heat Treatment - A combination of heating and cooling operations applied to a metal or alloy inthe solid state to obtain desired conditions or properties. Heating for the sole purpose of hotworking is excluded from the meaning of this definition. See various types below:

• Age Hardening - Hardening by time dependent precipitation from a supersaturated solidsolution, usually after rapid cooling or cold working. Naturally aged refers to atmospherictemperature. Artificially aged refers to elevated temperatures. Aging occurs more rapidly athigher temperatures (synonymous with precipitation hardening). Over-aging leads tosoftening.

• Air Hardening - When the hardenability is high enough such that air cooling from austenitegives a martensitic structure.

• Annealing - Annealing is a heat treatment process which usually involves a relatively slowcooling after holding the material for some time at the annealing temperature. The purpose ofthe annealing treatment may include the following:(a) to induce softness(b) to remove internal stresses(c) to refine the grain size(d) to modify physical and/or mechanical properties(e) to produce a definite microstructure(f) to improve machinability

• Bright Anneal - Carried out in a controlled furnace atmosphere, so that surface oxidation isreduced to a minimum and the product surface remains relatively bright.

• Drawing - Synonymous with TEMPERING, which is preferable.

• Full Anneal - Heating to a temperature above the critical and slow cooling.

• Isothermal Anneal - Austenitizing a heat treatable alloy and cooling to and holding at atemperature at which austenite transforms to a relatively soft ferrite-carbide aggregate.

• Normalize - Normalizing is a process which consists of heating to a temperatureapproximately 100°F above the upper critical temperature and cooling in still air.

• Quenching - A process of rapid cooling from an elevated temperature, by contact with liquidsor gases.

• Soft Anneal - A high temperature stress relieving anneal usually performed in thetemperature range of 1250°F to 1350°F. This anneal reduces hardness and strength of a coldworked steel to achieve near maximum softness.

• Solution Anneal - Heating steel into a temperature range wherein certain elements orcompounds dissolve, followed by cooling at a rate sufficient to maintain these elements insolution at room temperature. The expression is normally applied to stainless and otherspecial steels.

• Stabilizing Anneal - A treatment applied to austenitic stainless steels wherein carbides ofvarious forms are deliberately precipitated. Sufficient additional time is provided at the elevatetemperature to diffuse chromium into the areas adjacent to the carbides (usually grainboundaries). This treatment is intend to lessen the chance of intergranular corrosion.

• Stress Relieving - A heat treatment which reduces internal residual stresses that have beeninduced in metals by casting quenching, welding, cold working, etc. The metal is soaked at a

Section 25 Glossary


suitable temperature for a sufficient time to allow readjustment of stresses. The temperatureof stress relieving is always below the transformation range. Finish anneal, medium anneal,and soft anneal (sub-critical) describe specific types of stress relief anneals.

• Tempering - Reheating quenched or normalized steel to a temperature below thetransformation range (lower critical) followed by any desired rate of cooling.

Hot Alignment - The alignment made when the rotating equipment is within 10% of its operatingtemperature. Hot alignment is usually an Owner function after turnover. If the vibration of therotating equipment is within established criteria, hot alignment is not usually necessary.

Hot Finished Seamless Tubing - Tubing produced by rotary piercing, extrusion, and other hotworking processes without subsequent cold finishing operations.

Hot Rolled ERW Tubing - As welded electric resistance welded tubing made from hot rolled stripor sheet.

Hot Working - The mechanical working of metal above the recrystallization temperature. Themetal does not work harden.

Huey Test - A corrosion test for stainless steels. The weight loss per unit area is measured aftereach of five 48-hour boiling cycles in 65% nitric acid. The test results are calculated and reportedas the average corrosive rate of the five cycles in inches per month (ipm). The test is used todetermine the suitability of a material for nitric acid service. Since most of the weight loss is dueto intergranular attack, the Huey test is commonly used as an indication of the resistance of astainless steel to intergranular corrosion.

Hydrostatic Test - A pressure test to determine the structural integrity and leak tightness of asystem or component using a test medium of water or a liquid compatible with the system orcomponent.

Impact Testing - There are several methods of determining the toughness of a steel, but the Izodand Charpy notched-bar tests (ASTM E23) are used quite widely. In both tests, notched samplesare cooled or heated to the desired test temperature, then struck once with a pendulum whichfractures the specimen. The energy required to fracture the specimen, the impact strength, ismeasured in foot-pounds.

Inaccessible Area - Areas or openings in a component which are not readily accessible forcleaning or inspection during and after fabrication, and where dirt, liquids, or other foreignmaterials may be trapped during fabrication.

Inclusions - Particles of nonmetallic impurities, usually oxides, sulphides, silicates, which aremechanically held in metals and alloys during solidification.

Induction Heating - A process of heating by electrical induction.

Ingot - A cast metal shape suitable for subsequent rolling or forging.

Intergranular Corrosion - A type of electrochemical corrosion that progresses preferentiallyalong the grain boundaries of an alloy, usually because the grain boundary regions containmaterial anodic to the central regions of the grain.

Glossary Section 25


Internal Sleeve - A device which minimizes contact between the inner surface of the expansionjoint bellows and the fluid flowing through it.

Internal Soundness - Refers to condition of inside material, lack of defects, pipe segregation,and non-uniformity of composition.

Isophase Bus - Connects the generator to the transformers and are made with aluminumconductors.

Isothermal Anneal - See Heat Treatment.

Izod Impact Test - See Impact Strength Testing

Jominy Test - Hardenability test performed usually on alloy steels to determine depth and degreeof hardness resulting from a standard end quenching method with cold water (ASTM A255).

Killed Steel - Steel deoxidized with an agent such as silicon or aluminum used to react with (kill)the gases escaping during solidification. All continuous cast steels and other than low carbonsteels are killed.

Ladle - A large vessel into which molten steel or molten slag is received and handled.

Ladle Analysis - Chemical analysis obtained from a sample taken during the pouring of the steel.

Laminations - Defects resulting from the presence of blisters, seams, or foreign inclusionsaligned parallel to the worked surface of a metal.

Lap - A surface defect caused from folding the surface of an ingot, bloom, or bar during hotrolling operations and then rolling or forging the fold into the surface.

Lateral Expansion - A measure of the ductility of a steel as a result of the impact testingspecimen examination. It's expressed as the transverse dimension of the specimen after impactfracture versus the original dimension.

Limit Stops and Rods - Devices used to restrict the range of movement of an expansion joint.

Loops - A closed electrical circuit usually transmitting information from a remote or field mounteddevice back to the control room or any central information gathering station.

Machinability - A measure of the relative ease with which steel may be machined. Special freemachining grades have added sulfur to produce brittle chips.

Machining - The deliberate removal of metal by one or more of several processes.

Macroetch - A testing procedure for locating and identifying porosity, pipes, bursts, unsoundness,inclusions, segregations, carburization, flow lines from hot working, etc. Surface of the test pieceshould be reasonably smooth or even polished. After applying a suitable etching solution, thestructure developed by the action of the reagent may be observed without a microscope.

Magnetic Center - The point at which the motor shaft will equalize its longitudinal travel while inoperation. This point is usually indicated on the shaft extension by the manufacturer. Uponstarting, the motor armature will move longitudinally within the housing until it finds the magnetic

Section 25 Glossary


center of the coil. The larger the motor, the more movement and time required to find themagnetic center.

Magnuflux Test (Magnetic Particles Test) - This test is conducted by suitably magnetizing aferrous material and applying a prepared wet or dry magnetic powder or fluid which adheres to italong lines of flux leakage. It shows the existence of surface and slightly subsurfacenonuniformities.

Malleability - The property that determines the ease of deforming a metal when the material issubjected to rolling or hammering. The more malleable metals can be hammered or rolled intothin sheet.

Mandrel - (1) A device used to retain the cavity in hollow metal products during working. - (2) Ametal bar around which other metal may be bent, formed or shaped.

Maraging - A process of improving the mechanical strength of certain special high nickel steels. The name was derived from two hardening reactions; martensite and aging. The maragingstrengthening mechanism is based on the age hardening (precipitation hardening) of extra-lowcarbon martensite.

Martensite - A constituent in quenched steel formed without diffusion and only during rapidcooling below the martensitic start (Ms) temperature. Martensite is the hardest of thetransformation products of austenite. The carbon is forcibly retained in solution. The more thecarbon content, the harder the martensite and the more brittle the steel.

Material Test Report - Definition of a document released by a manufacturer reporting test resultsuniquely related to the product supplied for a specific purchase order.

McQuaid-Ehn Test - A special test for revealing the austenitic grain size of ferritic steels whenthe steel is heated to 1700°F. and carburized. There are eight standard McQuaid-Ehn grain sizes- sizes 5 to 8 are considered fine grain and sizes under 5 are considered course grain.

Mechanical Cleaning - The removal of foreign material by mechanical means such as wiping,abrasive blasting, brushing, grinding, sanding, chipping, water jetting, or air blowing.

Mechanical Properties - Those properties of a material that reveal the elastic and plasticreactions when force is applied, or that involve the relationship between stress and strain; forexample, the modulus of elasticity, hardness, tensile strength and fatigue limit. These propertieshave often been referred to as "physical properties," but the term "mechanical properties" iscorrect.

Mechanical Tubing - Used for a variety of mechanical and structural purposes, as opposed topressure tubing, which is used to contain or conduct fluids or gases under pressure, it may be hotfinished or cold drawn. It is commonly manufactured to consumer specifications coveringchemical analysis and mechanical properties.

Metallography - The science dealing with the constitution and structure of metals and alloys asrevealed by the unaided eye or by such tools as low powered magnification, optical microscopes,electron microscopes, and diffraction or X-ray techniques.

Glossary Section 25


Metric System of Measurements - In the metric system of measurements, the principal unit forlength is the meter; the principal unit for volume, the liter; and the principal unit for weight, thegram. The following prefixes are used for sub-divisions and multiples:

Section 25 Glossary


micro = 1 /1,000,000;milli = 1 /1000;centi = 1 /100;deci = 1 /10;deca = 10;hecto = 100;kilo = 1000;mega = 1,000,000.

In abbreviations, the sub-divisions are frequently used with a smaller letter and the multiples witha capital letter, although this practice is not universally followed everywhere the metric system isused. All the multiples and the subdivisions are not used commercially. Those ordinarily used forlength are kilometer, meter, centimeter, and millimeter; for area, square meter, square centimeterand square millimeter; for volume, cubic meter, cubic decimeter (liter), cubic centimeter, and cubicmillimeter. The most commonly used weights are the kilogram and gram. The metric system waslegalized in the United States by an Act of Congress in 1966.

Microcleanliness - Refers to the extent or quality of nonmetallic inclusions observed byexamination under a microscope.

Micro-Etch - Micro-etching is used for the examination of a sample under a microscope. Etchingsolutions tend to reveal structural details because of preferential chemical attack on the polishedsurface.

Minimum Wall - Any wall having tolerances specified all on the plus side.

Modulus of Elasticity - The ratio of stress applied to a material and the resulting strain occurringat the stresses below the elastic limit.

MCC - Motor Control Centers provide a enclosure or panel housing for electrical breakers, andinstruments. The motor control center is also a sub-feed for lighting, heating, and smaller motors.

Non-Destructive Testing - Methods of detecting defects without destroying or permanentlychanging the material being tested. Test methods include ultrasonic, eddy current, magneticparticle, liquid penetrant, x-ray, hardness testing, and all kinds of positive material identificationsystems.

Non-Ferrous - Any non-iron alloy, such as copper, brass, bronze, aluminum, and plastic.

Notch Brittleness - Susceptibility of a material to brittle fracture at points of stress concentration.

Notch Sensitivity - A measure of the reduction in strength of a metal caused by the presence ofstress concentration.

Offset Length - The length of pipe perpendicular to an expanding or moving section of pipe (forexample, between the intersecting pipe and the first restraint) which absorbs the movement bybending.

Oil-Free Air - Air that is apparently oil free as available from an oil-free air compressor, or airwhich has been passed through a combination oil absorber filtering unit reducing oil vapor to 1ppm maximum.

Glossary Section 25


Orifice - A small opening that is used to control or measure flow rate in the process fluid.

Ovality - The difference between the maximum and minimum outside diameters of any one crosssection of a tube or a fitting. It is a measure of deviation from roundness.

Oxidation - In its simplest terms, oxidation means the combination of any substance with oxygen.Scale developed during heat treatment is a form of oxidation.

Oxide - A compound consisting of oxygen and one or more metallic elements.

Parallel (Offset) Alignment - An alignment condition in which the axis of rotation of both themotor and the driven unit are located within identical vertical and horizontal planes. Parallelmisalignment occurs when the shaft axes are parallel but not concentric.

Particulate Matter - Finite or small particles of foreign material such as dust, slag, scale, or weldsplatter which can be seen or verified as individual particles without magnification.

Passivate - The changing of the chemically active surface of a metal to a much less active stateby the application of the proper chemical treatment or by allowing natural oxidation to occur byexposure to air. An example of chemically passivating stainless steel would be to immersestainless in a hot solution of approximately 10 to 20 percent by volume nitric acid and water.Anodizing of aluminum is another example.

Pearlite - A mixture of ferrite and cementite that occur in steels.

Pitting Corrosion - Non-uniform corrosion usually forming small cavities in the metal surface.

Photomicrograph - A photographic reproduction of an object magnified more than ten timesused to show microstructure characteristics of steel.

Physical Properties - Those properties not specifically related to reaction to external forces. These include such properties as density, electrical resistance, coefficient of thermal conductivityand melting point.

Pickling - Use of solutions, usually acids, to remove surface oxides from a steel product, mayalso be used to provide a desired surface finish.

Piercing - A seamless tube-making method in which a hot billet is gripped and rotated by rolls orcones and directed over a piercer point which is held on the end of a mandrel bar.

Pit - A sharp, usually small, depression in the surface of metal.

Pitting - Localized corrosion of metal resulting in surface defects.

Plane Strain Fracture Toughness - The minimum fracture toughness of a material.

Plenum - A device used to balance flow into several chambers or paths.

Pneumatic Test - A pressure test to determine the leak tightness of a system or componentusing a test medium of nonflammable gas compatible with the system or component.

Porosity - Unsoundness caused in cast metals by the presence of blowholes, shrinkage cavities,or in a weld caused by gases that did not escape the molten weld metal.

Section 25 Glossary


Positive Material Identification - The definition used for any kind of non-destructive chemicalanalysis capable of positively identify a grade of steel.

Post Weld Heat - Provides stress relief in the welded joint after the weld has been completed. This is primarily required for thicker carbon steel or carbon steel alloys or for process reasons(e.g. amine systems).

Pressure Tubing - Tubing produced for the purpose of containing or conducting fluids or gasesunder pressure.

Profilometer - An instrument used for measuring surface finish. The vertical movements of astylus as it traverses the surface are amplified electromagnetically and recorded (or indicated) asthe surface roughness.

Purge Connections - Connections used to inject a liquid or gas between an expansion jointbellows and the internal sleeve to keep the area clear of corrosive media.

Pyrometer - An instrument of any of various types used for measuring temperatures.

Quenching - See Heat Treatment.

Random Length - Tubing produced to a permissible variation in length.

Recrystallization - The reversion of distorted cold worked microstructure to a new soft, strain-freestructure during annealing. Typically, the required temperature is above half the melting pointunless the material is very heavily cold worked.

Reduction of Area - A measure of ductility determined in a tensile test. It is the percentagechange in cross sectional area after working.

Relay - An electromagnetic device for remote or automatic control, actuated by variations in theconditions of an electrical circuits and in turn operating other electrical devices.

Restraint - A component which controls or limits the movement of piping. A restraint is generallyspecified as single or two directional by the planes in which they restrict movement.

Rimmed Steel - A steel that is not killed, where the gases escaping during solidification areallowed to escape. The steel froths.

Rim Runout - The concentricity of the coupling flange perimeter in relationship to the shaft axis.

Rockwell Hardness - A hardness test (ASTM E18).

Rust - Corrosion products, consisting largely of iron oxide. Such oxides may vary in color fromred to black and may form a loosely adherent covering to a tightly adherent light film.

Scale - An oxide of iron which forms on the surface of hot steel.

Seam - A tight, but unwelded imperfection on the surface of a wrought metal product.

Segregation - Nonuniform distribution of alloying elements, impurities or microphases.

Semi-Killed Steel - Steel that is incompletely deoxidized to permit the evolution of carbonmonoxide, thereby offsetting solidification shrinkage.

Glossary Section 25


Sensitization - Sensitization of stainless steel is defined as a susceptibility to preferential grainboundary attack. Material which exhibits grain boundary carbide precipitation may or may not besensitized.

Service Water - Provides cooling water for the turbine and a heat sink for other processes orsystem equipment.

Shear Value - Definition of fracture mode of an impact testing specimen. It is usually recorded aspercent of the total specimen area fractured in shear mode, rather than cleavage mode. It is anindication of the fracture propagation properties of the tested steel. The higher the shearpercentage, the lower the sensitivity to fracture propagation.

Soft Anneal - See Heat Treatment.

Specification - A document defining the measurements, tests, and other requirements to which aproduct must conform - typically covering chemistry, mechanical properties, tolerances, finish,reports, marking and packaging.

Stabilizing Elements - Chemical elements added intentionally to a stainless steel to help preventsensitization phenomenon due to chromium carbide precipitation. Such elements (Titanium,Columbium, Tantalum) have the function to preferentially form carbide compounds, thuspreventing the formation of chromium carbides. Typical stainless steel stabilized grades are 321,347 and 348.

Stress Corrosion Cracking - Cracking of metals under combined action of corrosion and stress. The stress can be either applied or residual. Austenitic stainless steels are especiallysusceptible to cracking in chloride containing environments. Usually, it only occurs above aparticular temperature.

Strip - A flat-rolled steel product which serves as the raw material for welded tubing.

Structural - Includes the building steel above and below grade for all Steel structures.

Sump - A pit or reservoir serving as the collection point for drainage systems.

Swaged - A mechanical reduction of the cross sectional area of a metal, performed hot or cold byforging, pressing or hammering.

Tap Water (Potable Water) - Water that meets public health standards for potable or drinkingwater.

Tempering - See Heat Treatment.

Tensile Strength - The maximum load per square inch of original cross-sectional area carriedduring a tension test to failure of the specimen. This term is preferred over the formerly-usedultimate strength. The tensile test is described in ASTM E6 and E8.

Terminal Point - The end of the pipe which connects to a larger pipe branch connection orequipment connection. This point is considered a moving anchor for hanger analysis.

Thermal Analyzed Piping - Piping over 200 oF in which a thermal analysis is required due toexpansion of the system in addition to deadweight support.

Section 25 Glossary


Thermal Conductivity - A measure of the ease with which heat is transmitted through a material.

Thermal/Deadweight Analyzed Piping - Piping below 200 oF which must be analyzed for thermalexpansion due to thermal growth in excess of 0.1" in any direction.

Thermal Expansion - The change in pipe length resulting from temperature changes from agiven base temperature. The temperature change may be due to the temperature of the fluid orgas or due to changes in the ambient temperature.

Thermocouples - A device used to record temperature in process fluids or during post weld heattreatment.

Tie Rods - Rods or bar devices which restrain an expansion joint from the thrust due to internalpressure.

Tolerance - Permissible variation.

Torsion - A twisting action resulting in shear stresses and strains.

Toughness - A measure of ability to absorb energy and deform plastically before fracturing.

Transformation Temperature - The temperature at which a change in phase occurs in steels. The term is sometimes used to denote the limiting temperature of a transformation range.

Transverse Tension Test - A tension test for evaluating mechanical properties of a material in adirection transverse to that of rolling.

Traveling Racks - Devices used at intakes for the plant water system Screens/Trash to removedebris from the water.

Ultimate Strength - See Tensile Strength.

Ultrasonic Testing - The method of detecting defects in tubes or welds by passing highfrequency sound waves into a material then monitoring and evaluating the reflected signals.

Upsetting - A metal-working operation similar to forging, generally used to thicken the ends oftubes prior to threading.

Vacuum Breakers - Devices used to prevent collapsing of vessels or piping.

Vickers Hardness Test - A common hardness test (ASTM E92).

Water Box - A box for holding water, used as a transition area between the condenser andcirculating water piping.

Work Hardening - Hardening of a metal as a result of cold working (see Cold Working).

Yield Point - The stress in a material at which plastic deformation begins.

Yield Strength - The stress at which a material exhibits a specified deviation from proportionalityof stress and strain. An offset of 0.2% is most frequently used.


Section 26

References

The following references are applicable to Piping/Mechanical work activities:

AISC Manual of Steel Construction, published by the American Institute of Steel Construction, Inc.,400 North Michigan Avenue, Chicago, Illinois 60611

ASTM Order Department, 1916 Race Street, Philadelphia, PA 19103, Telephone: 215-299-5585,FAX: 215-977-9679

Cameron Hydraulic Data Handbook, published by Ingersoll-Rand Corporation, Woodcliff Lake, NJ

Chemical Engineering Magazine, published by McGraw-Hill, Inc., 1221 Avenue of The Americas,New York, N.Y. 10020, Telephone: 212-512-2000

Electric Light and Power Magazine

Engineering News Record, published by McGraw-Hill, Inc., 1221 Avenue of The Americas, NewYork, N.Y. 10020, Telephone: 212-512-3549, FAX: 212-512-3150

Federal and Military Specifications, Standardization Document Order Desk, Bldg. 4, Section D, 700Robbins Avenue, Philadelphia, PA 19111-5094, Telephone: 215-697-2179, FAX: 215-697-2978

Fluid Flow Handbook published by Crane

Handbook of Air Conditioning System Design, prepared by the Carrier Air Conditioning Company,McGraw-Hill Book Company, 1221 Avenue of The Americas, New York, N.Y. 10020

HILTI Corporation, manufacturer of concrete fasteners, P.O. Box 21148, Tulsa, OK 74121,Telephone: 800-879-7000, FAX: 800-879-7000

ITT Grinnell Pipe Support Catalog

Lokring Corporation, manufacturer of mechanical piping couplings, 396 Hatch Drive, Foster City, CA 94404, Telephone: 415-578-9999, FAX: 415-578-0216

McMaster-Carr Catalog

Mechanical Engineering Magazine, published by the American Society of Mechanical Engineers,United Engineering Center, 345 East 47th Street, New York, NY 10017, Telephone: 212-705-7722,FAX: 212-705-7674

Mechanical Estimating Guidebook, by John Gladstone, McGraw-Hill Book Company, 1221 Avenueof The Americas, New York, N.Y. 10020

National Insulation and Abatement Contractors Association, 99 Canal Center Plaza, Suite 222,Alexandria, VA 22314, Telephone: 703-683-6422, FAX: 703-549-4838

Navco Piping Datalog published by the National Valve and Manufacturing Company (NAVCO),c/o Basic Engineers, P.O. Box 15238, Pittsburgh, PA 15238, Telephone: 412-826-1900

Section 26 References


Phillips Driscopipe, Inc., manufacturer of high density polyethylene piping, P.O. Box 83-3866, 2929North Central Expressway, Suite 300, Richardson, Texas 75083, Telephone 800-527-0662, FAX: 214-783-2689

Pipe Fitters Handbook/Manual, published by Tube Turns, a division of Chemetron Corporation, P.O.Box 32160, Louisville, KY 40232

Pipe Fitters Handbook/Manual, published by Grinnell Supply Sales Co., Marketing/Design Services,Providence, RI 02903

Piping Guide, Volumes 1 and 2, published by Syentek Book, P.O. Box 277, Cotati, California 94928

Piping Handbook, Edited by Reno C. King, McGraw-Hill Book Company, 1221 Avenue of TheAmericas, New York, N.Y. 10020

Plant Engineering Magazine

Power Engineering Magazine, published by Pennwell Publications, 1250 South Grove Avenue, Suite302, Barrington, Illinois, 60010-5066, Telephone: 708-382-2450, FAX: 708-382-2977

Power Magazine, published by McGraw-Hill, Inc., 1221 Avenue of The Americas, New York, N.Y. 10020, Telephone: 609-426-5667, FAX: 609-426-7635

Quicky Guide to Math Functions

Standard Handbook for Mechanical Engineers (formerly Marks’ Mechanical Engineers’ Handbook),Edited by Theodore Baumeister, McGraw-Hill Book Company, 1221 Avenue of The Americas, NewYork, N.Y. 10020

Steam Book published by Crane

Steel Structures Painting Manual, Volumes 1 and 2, published by the Steel Structures PaintingCouncil, 4400 Fifth Avenue, Pittsburgh, PA 15213

Stockham Valves and Fittings, Box 10326, Birmingham, Alabama 35202 Telephone: 205-592-6361

Swagelok Tube Fittings, manufactured by Crawford Fitting Company, 29500 Solon Road, Solon,Ohio, 44139

Troubleshooters’ Handbook for Mechanical Systems, by Robert Henderson Emerick, P.E.,McGraw-Hill Book Company, 1221 Avenue of The Americas, New York, N.Y. 10020

Victaulic Corporation, manufacturer of mechanical pipe couplings, P.O. Box 31, Easton, PA 18044-0031, Telephone: 215-559-3300, FAX: 215-250-8817

Henry Vogt Machine Company, Manufacturer of Heat Recovery Steam Generators (HRSG), P.O.Box 1918, Louisville, Kentucky 40201-1918, Telephone: 502-634-1500, FAX: 502-634-0549,

Welded Pipe Fitting Handbook published by Ladish

Yarway Industrial Steam Trapping Handbook

Piping / Mechanical Handbook

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