VECV1001 Process industry practice

REVISIONAugust 2000

Process Industry PracticesVessels

PIP VECV1001Vessel/S&T Heat Exchanger Design CriteriaASME Code Section VIII, Divisions 1 and 2

PURPOSE AND USE OF PROCESS INDUSTRY PRACTICES

In an effort to minimize the cost of process industry facilities, this Practice hasbeen prepared from the technical requirements in the existing standards of majorindustrial users, contractors, or standards organizations. By harmonizing thesetechnical requirements into a single set of Practices, administrative, application, andengineering costs to both the purchaser and the manufacturer should be reduced. Whilethis Practice is expected to incorporate the majority of requirements of most users,individual applications may involve requirements that will be appended to and takeprecedence over this Practice. Determinations concerning fitness for purpose andparticular matters or application of the Practice to particular project or engineeringsituations should not be made solely on information contained in these materials. Theuse of trade names from time to time should not be viewed as an expression ofpreference but rather recognized as normal usage in the trade. Other brands having thesame specifications are equally correct and may be substituted for those named. AllPractices or guidelines are intended to be consistent with applicable laws andregulations including OSHA requirements. To the extent these Practices or guidelinesshould conflict with OSHA or other applicable laws or regulations, such laws orregulations must be followed. Consult an appropriate professional before applying oracting on any material contained in or suggested by the Practice.

This Practice is subject to revision at any time by the responsible Function Teamand will be reviewed every 5 years. This Practice will be revised, reaffirmed, orwithdrawn. Information on whether this Practice has been revised may be found athttp://www.pipdocs.org.

© Process Industry Practices (PIP), Construction Industry Institute, TheUniversity of Texas at Austin, 3208 Red River Street, Suite 300, Austin,Texas 78705. PIP member companies and subscribers may copy this Practicefor their internal use.

September 1997 IssuedFebruary 1999 Complete RevisionAugust 2000 Revision

Not printed with State funds.

REVISIONAugust 2000

Process Industry Practices Page 1 of 58

Process Industry PracticesVessels

PIP VECV1001Vessel/S&T Heat Exchanger Design CriteriaASME Code Section VIII, Divisions 1 and 2

Table of Contents

1. Introduction..................................31.1 Purpose ............................................. 31.2 Scope................................................. 3

2. References ...................................42.1 Process Industry Practices ................ 42.2 Industry Codes and Standards .......... 42.3 Other References .............................. 52.4 Government Regulations ................... 6

3. Definitions ....................................6

4. General .........................................74.1 Applicable PIP Documents ................ 74.2 ASME Code Requirements................ 7

4.2.2 Applicable Code ScopeExemptions ................................... 7

4.2.3 Waste Heat Recovery Vessels ..... 74.3 National Board Registration............... 74.4 Jurisdictional Compliance.................. 74.5 Units of Measurement ....................... 84.6 Language........................................... 84.7 Documentation to be Provided to the

Manufacturer...................................... 8

5. Design...........................................85.1 Design Pressure and Temperature ... 8

5.2 MAWP and Coincident MaximumTemperature .................................... 10

5.3 Minimum Design Metal Temperatureand Coincident Pressure ................. 11

5.4 External Pressure Design................ 115.5 Cyclic Service .................................. 11

5.5.1 Number of Cycles........................125.5.2 Fatigue Analysis ..........................125.5.3 Fatigue Loading Data ..................12

5.6 Welded Pressure JointRequirements .................................. 12

5.7 Postweld Heat Treatment ................ 145.8 Wind Load ....................................... 15

5.8.1 User Selections from ASCE 7 .....155.8.2 Determination of Wind-Induced

Forces .........................................175.9 Seismic Loads ................................. 17

5.9.1 General Requirements and Datafrom ASCE 7 ...............................17

5.9.2 Seismic Loads for Ground-Supported Equipment..................18

5.9.3 Seismic Loads for Structure-Mounted Equipment ....................18

5.10 Design Loads andLoad Combinations.......................... 195.10.1 Dead Load...................................195.10.2 Operating Live Load ....................195.10.3 Pressure Load .............................195.10.4 Thermal Load ..............................195.10.5 Test Load ....................................205.10.6 Wind Load ...................................205.10.7 Seismic Load...............................20

PIP VECV1001 REVISIONVessel/S&T Heat Exchanger Design Criteria August 2000ASME Code Section VIII, Divisions 1 and 2

Page 2 of 58 Process Industry Practices

5.10.8 Piping and SuperimposedEquipment Loads ........................ 20

5.10.9 Load Combinations ..................... 205.11 Wind-Induced Vibration of Vertical

Vessels.............................................215.11.1 Vortex Shedding Ranges ............ 225.11.2 Corrective Action......................... 22

5.12 Formed Heads .................................235.13 Flanges.............................................23

5.13.1 ASME B16.47, Series A.............. 235.13.2 ASME B16.47, Series B.............. 235.13.3 Custom-Designed Flanges per

Code ........................................... 245.13.4 Custom-Designed Lap Joint

Flanges ....................................... 255.13.5 Lap Joint Flanges NPS 24 and

Smaller........................................ 275.13.6 Slip-on Flanges ........................... 275.13.7 Threaded and Socket Weld

Flanges ....................................... 285.13.8 Flange Facing and

Surface Finish ............................. 285.13.9 Piping Connections ..................... 295.13.10 Quick Opening Closures ............. 295.13.11 Flanges - Pass Partition Areas . 295.13.12 Flanged Joints .......................... 29

5.14 Nozzles.............................................295.15 Manways ..........................................315.16 Anchor Bolts .....................................325.17 Internals............................................335.18 Vessel Supports ...............................34

5.18.1 General ....................................... 345.18.2 Vertical Vessels .......................... 345.18.3 Horizontal Vessels ...................... 365.18.4 Stacked Exchangers ................... 37

5.19 Heat Exchanger ComponentDesign ..............................................385.19.1 Tubes .......................................... 385.19.2 Tubesheets ................................. 385.19.3 Tube-to-Tubesheet Joints ........... 395.19.4 Tube Bundles.............................. 405.19.5 Expansion Joints......................... 415.19.6 Vapor Belts ................................. 425.19.7 Exchanger Covers....................... 425.19.8 Pass Partition Plates................... 435.19.9 Floating Heads............................ 435.19.10 Kettle Type Exchangers............ 435.19.11 Instrument, Vent, and

Drain Connections ...................... 445.19.12 Nameplates and Stampings ..... 445.19.13 Shell and Bonnet Design .......... 44

5.20 Heat Exchanger Thermal .................445.20.1 Fouling Factors Selection ........... 445.20.2 Fluid Side Selection .................... 455.20.3 Exchanger Configuration ............ 465.20.4 Flow Arrangement....................... 475.20.5 Tube Selection ............................ 485.20.6 Bundle Design and

Tube Layout ................................ 49

5.20.7 Thermal Performance..................505.20.8 Hydraulic Performance ................525.20.9 Vibration ......................................53

6. Materials .....................................536.1 Material Specifications .....................53

6.1.1 External Attachments ..................536.1.2 Internal Attachments....................53

6.2 Source of Materials ..........................546.3 Corrosion/Erosion Allowance ...........54

6.3.1 Basis............................................546.3.2 Corrosion Loss ............................546.3.3 Erosion Loss................................54

6.4 Gaskets ............................................55

7. Testing ........................................557.1 Hydrostatic Test ...............................55

7.1.1 UG-99 Standard HydrostaticTest..............................................55

7.1.2 Horizontal Vessels.......................557.1.3 Vertical Vessels ...........................557.1.4 Test Temperature ........................55

7.2 Pneumatic Test ................................567.3 Proof Test.........................................56

8. Vessel Rigging Analysis/LiftingRequirements.............................568.1 Impact Factor ...................................568.2 Vertical Vessels................................568.3 Local Stresses..................................578.4 Welds ...............................................57

AppendicesA - General Considerations for Pressure Relief

Valve ApplicationB[V] - Welded Pressure Joint Requirements

FormB[E] - Welded Pressure Joint Requirements

FormC - Equivalent Pressure Formulas for Bending

Moment and Axial Tensile LoadD - Minimum Clearance for Nozzle Adjacent to

Integral Tubesheet

REVISION PIP VECV1001August 2000 Vessel/S&T Heat Exchanger Design Criteria

ASME Code Section VIII, Divisions 1 and 2


1. Introduction

Note to Readers: This Practice contains design criteria for pressure vessels and shell-and-tube heat exchangers. Corresponding subject matter for pressure vessels and shell-and-tubeheat exchangers is covered by paragraphs identically numbered. Paragraphs pertaining topressure vessels are preceded by [V]. Paragraphs pertaining to shell-and-tube heatexchangers are preceded by [E]. Paragraphs pertaining to both are preceded by [V/E]. Inaddition, ASME Boiler and Pressure Vessel Code, Section VIII, Division 2 requirements areshown in braces { }.

This Practice should be used for pressure vessels built to Division 1 or Division 2 of theASME Boiler and Pressure Vessel Code, henceforth referred to as the Code. Shell-and-tubeheat exchangers are limited to Division 1 in this Practice.

1.1 Purpose

[V] The primary focus of this Practice is to communicate vessel design criteria andmethodology from the User to a Designer. This Practice is also intended as guidancefor the development of purchase specifications covering the construction of newpressure vessels which meet the philosophy and requirements of Section VIII,Division 1 {or 2} of the Code.

[E] The primary focus of this Practice is to communicate vessel design criteria andmethodology from the User to a Designer. This Practice is also intended as guidancefor the development of purchase specifications covering the construction of newshell-and-tube heat exchangers which meet the philosophy and requirements ofSection VIII, Division 1 of the Code and TEMA Standards of the TubularExchangers Manufacturers Association.

1.2 Scope

1.2.1 [V/E] This Practice must be used in conjunction with PIP VEDST003,PIP VEDV1003, PIP VEFV1100, and PIP VESV1002 in order to comprise acomplete vessel purchase specification.

1.2.2 [V/E] Many recognized and generally accepted good engineeringconstruction practices are included herein. However, in light of the manydiverse service applications of Code vessels, these practices must beemployed with engineering judgment and supplemented as appropriate withrequirements related to specific materials of construction, service fluids,operating environments, and vessel geometries. Accordingly, provisions ofthis Practice may be overridden or supplemented by an OverlaySpecification.

1.2.3 [V/E] Standardized pre-designed (off-the-shelf) vessels and heat exchangersare not within the scope of this Practice, but are covered in PIP VESSM001.



2. References

The following documents are only those specifically referenced in this Practice. Inapplications where laws or regulations issued by municipal, state, provincial, or federalauthorities cover pressure vessels, those laws or regulations should be reviewed prior to theinitiation of design work since the requirements may be different or more restrictive thanthose covered in this Practice. Short titles will be used herein when appropriate.

2.1 Process Industry Practices (PIP)

For the following reference documents, the latest edition issued at the date ofcontract award shall be used.

− PIP VEDST003 - Shell and Tube Heat Exchanger Specification Sheet

− PIP VEDV1003 - Vessel Drawing/Data Sheet and Instructions

− PIP VEFV1100 - Vessel/S&T Heat Exchanger Standard Details (27 Detailsand Index)

– PIP VESSM001 - Specification for Small Pressure Vessels and HeatExchangers with Limited Design Conditions

− PIP VESV1002 - Vessel/S&T Heat Exchanger Fabrication SpecificationASME Code Section VIII, Divisions 1 and 2

2.2 Industry Codes and Standards

For the following reference documents, if Table U-3 {AF-150.1} of the Code lists anedition or addenda different than the latest edition issued, the edition listed in TableU-3 {AF-150.1} shall be used. For documents not listed in Table U-3 {AG-150.1},the latest edition or addenda issued at the date of contract award shall be used.

• American Institute of Steel Construction (AISC)

– AISC Manual of Steel Construction

• American National Standards Institute (ANSI)

– ANSI/ASME B36.10M - Welded and Seamless Wrought Steel Pipe

– ANSI/ASME B36.19M - Stainless Steel Pipe

• American Petroleum Institute (API)

– API 650 - Welded Steel Tanks for Oil Storage

• American Society of Civil Engineers (ASCE)

– ASCE 7 - Minimum Design Loads for Buildings and Other Structures




• American Society of Mechanical Engineers (ASME)

− ASME Boiler and Pressure Vessel Code

Section I - Power Boilers

Section II - Materials, Parts A, B, C, D

Section VIII - Pressure Vessels, Divisions 1 and 2

Section IX - Welding and Brazing Qualifications

– ASME B1.1 - Unified Inch Screw Threads (UN and UNR Thread Form)

– ASME B16.5 - Pipe Flanges and Flanged Fittings, NPS 1/2 through NPS 24

– ASME B16.11 - Forged Fittings, Socket-Welding and Threaded

– ASME B16.47 - Large Diameter Steel Flanges, NPS 26 through NPS 60

• International Conference of Building Officials (ICBO)

– Uniform Building Code (UBC)

• Manufacturers Standardization Society of the Valve and FittingsIndustry, Inc. (MSS)

– MSS SP-44 - Steel Pipeline Flanges

• Tubular Exchanger Manufacturers Association (TEMA)

− Standards of the Tubular Exchanger Manufacturers Association

• Welding Research Council (WRC)

– WRC Bulletin 107 - Local Stresses in Spherical and Cylindrical Shells Dueto External Loadings

2.3 Other References

– “Design Equations for Preventing Buckling in Fabricated TorisphericalShells Subjected to Internal Pressure,” G.D. Galletly, Proceedings:Institution of Mechanical Engineers. London: Vol. 200 No. A2.

– Dynamic Response of Tall Flexible Structures to Wind Loading. JosephVellozzi, Ph.D., P.E. U.S. Department of Commerce, National Bureau ofStandards, Building Science Series Number 32, 1966.

– Process Equipment Design. Brownell and Young. Wiley & Sons Publishers,1959.

– “Stresses in Large Cylindrical Pressure Vessels on Two Saddle Supports,”L.P. Zick, Pressure Vessels and Piping: Design and Analysis, A Decade ofProgress. Vol. 2, 1972.

– “Wind Loads on Petrochemical Facilities,” ASCE Task Committee on Wind-Induced Forces, Wind Loads and Anchor Bolt Design for PetrochemicalFacilities. (ISBN-0-7844-0262-0)



2.4 Government Regulations

• U. S. Environmental Protection Agency (EPA)

– Clean Air Act Amendments 1990

• U. S. Department of Labor, Occupational Safety and HealthAdministration (OSHA)

– OSHA 29 CFR 1910.106(b)(5)(ii) - Flammable and Combustible Liquids

– OSHA 29 CFR 1910.119 - Process Safety Management of Highly HazardousChemicals

– OSHA 29 CFR 1910.146(k)(3)(ii) - Permit-Required Confined Spaces forGeneral Industry

3. Definitions

Code: ASME Boiler and Pressure Vessel Code Section VIII, Division 1{or 2}. References toDivision 2 are identified in braces { }.

Construction: An all-inclusive term comprising materials, design, fabrication, examination,inspection, testing, certification (Code stamp and Manufacturer’s Data Report),{Manufacturer’s Design Report} and pressure relief

Designer: The party responsible for defining and specifying the mechanical designrequirements (e.g., Vessel Drawing/Data Sheet {User’s Design Specification}) consistentwith User criteria for use by the Manufacturer. The Designer is frequently an engineeringcontractor, but could be the User, third party consultant, or the Manufacturer. The Designeris also considered the thermal Designer with respect to heat exchanger design.

Manufacturer: The party entering into a contract with the Purchaser to construct a vessel inaccordance with the purchase order

National Board: The National Board of Boiler and Pressure Vessel Inspectors, anorganization comprised of chief inspectors of various governmental jurisdictions in theUnited States and Canada. Vessels meeting requirements of the Code, except those stampedwith the Code “UM” symbol, may be registered with the National Board.

Overlay Specification: Technical requirements that supplement or override the provisions ofthis document, such as a User specification or a project specification

User: The party responsible for establishing construction criteria consistent with the Codephilosophy and service hazards. “User” refers to the owner and/or operator of the equipment.

Vessel: This term may be used as a non-specific reference to a pressure vessel or a shell-and-tube heat exchanger.




4. General

4.1 Applicable PIP Documents

[V/E] All vessels shall be designed in accordance with this Practice,PIP VEDST003, PIP VEFV1100 (applicable details), PIP VEDV1003, andPIP VESV1002.

4.2 ASME Code Requirements

4.2.1 [V/E] Pressure vessels within the scope of this Practice shall satisfy allapplicable requirements, including Code symbol stamping.

4.2.2 Applicable Code Scope Exemptions

[V/E] The Code Scope exemptions that represent across-the-boardacceptance are those covered under Code Paragraphs U-1(c)(2)(h){AG-121(h)} and U-1(c)(2)(i) {AG-121(i)}, as follows:

4.2.2.1 [V/E] U-1(c)(2)(h) {AG-121(h)}: Vessels not exceeding 15 psig,with no limitation on size [see Code Paragraph UG-28(e){AD-300}]

4.2.2.2 [V/E] U-1(c)(2)(i) {AG-121(i)}: Vessels having an insidediameter, width, height, or cross-section diagonal not exceeding6 inches, with no limitation on length of vessel or pressure

Note: The 6-inch dimension is in the corroded condition.

The above is not intended to prohibit the use of other Scope exemptions inCode Paragraph U-1(c)(2); however, such use shall be by agreement with theUser.

4.2.3 Waste Heat Recovery Vessels

[V/E] Steam generating vessels associated with waste heat recoveryoperations shall be constructed and stamped with the Code “U” symbol inaccordance with Code Section VIII, Division 1. Dual Code symbol stampingof such vessels (both Section I “S” symbol and Section VIII, Division 1 “U”symbol) is not permitted.

4.3 National Board Registration

[V/E] National Board registration of vessels stamped with the Code “U” {“U2”}symbol is required.

4.4 Jurisdictional Compliance

[V/E] All aspects of the work shall comply with applicable local, county, state, andfederal rules and regulations. This includes, but is not limited to, the rules andstandards established by EPA and OSHA. (See Section 2.4.)



4.5 Units of Measurement

[V/E] U.S. customary (English) units shall be regarded as standard; metric (SI) unitsmay be included for reference only and shall not be interpreted as a preciseconversion.

4.6 Language

[V/E] The language of all documents shall be either English or include the Englishtranslation.

4.7 Documentation to be Provided to the Manufacturer

[V/E] The following information shall be provided to the Manufacturer with thepurchasing inquiry:

4.7.1 [V] Design requirements to be provided to the Manufacturer shall be perPIP VEDV1003, with additional drawings or details as necessary.

4.7.2 [E] Design requirements to be provided to the Manufacturer shall be perPIP VEDST003, with additional drawings or details as necessary.

4.7.3 [V/E] Welded pressure joint requirements, including:

• Type of Category A, B, C, and D joints (see Appendix B[V] orB[E])

• Type and degree of nondestructive examination to be applied to thejoints (see Appendix B[V] or B[E])

4.7.4 [V/E] Quality Overview Plan, as shown in PIP VESV1002, Appendix A.

4.7.5 [V/E] Documentation Schedule and Manufacturer’s Data Package, as shownin PIP VESV1002, Appendix B.

4.7.6 [V] {User’s Design Specification}

5. Design

5.1 Design Pressure and Temperature

[V/E] The design pressure and coincident maximum metal temperature shall bedetermined by the Designer by carefully considering all operating phases andassociated loadings (e.g., liquid head and other sources of pressure variation, such asthat resulting from flow) that the vessel may experience during the specified projectlife, such as:

• Initial startup

• Normal operations

• Temporary operations

• Emergency shutdown

• Emergency operations




• Normal shutdown

• Startup following a turnaround or an emergency shutdown

• Cleaning, steam out, and decontamination

• Upset conditions

• Environmental restraints on relief venting

• [E] Tube failure [Code Paragraph UG-133(d)]

[V/E] The margin above the maximum anticipated operating pressure selected toestablish the design pressure and coincident maximum metal temperature must becarefully considered for each vessel component as a function of the overall objectivewith respect to pressure relief, coupled with the uncertainties in determining whatactual pressures will be developed. For example, where minimization of severelyflammable or acutely toxic environmental hazards is a controlling designrequirement, the establishment of a design pressure and associated MaximumAllowable Working Pressure (MAWP) {MAWP replaced by Design Pressure inDivision 2, AD-121.1} that will provide containment without actuation of thepressure relief device may be a consideration.

[V/E] As will be noted with reference to Appendix A, this margin is also dependentupon the operational characteristics of the pressure relief device. For example, whenthe maximum anticipated operating pressure of a gas/vapor service can be identifiedwith confidence, and when metal-seated, direct spring-operated valves will be used,the design pressure is frequently established by dividing the maximum anticipatedoperating pressure by 0.90. However, when a pilot-operated pressure relief device isused, the design pressure is sometimes established by dividing the maximumanticipated operating pressure by a factor as high as 0.98.

[V/E] Refer to the Overlay Specification for any margins to be applied to themaximum operating pressure(s) and coincident temperature(s).

[V/E] Also use of Code Case 2211, entitled “Pressure Vessels with OverpressureProtection by System Design, Section VIII, Divisions 1 and 2,” may be anappropriate option. Note that prior jurisdictional acceptance may be required and thatthis Code Case Number shall be shown on the Manufacturer’s Data Report.Likewise, with permission from the authority having legal jurisdiction over theinstallation of pressure vessels (should one exist), the advantages of using theprovisions of Code Case 2203, entitled “Omission of Lifting Device Requirementsfor Pressure Relief Valves on Air, Water over 140° F, or Steam Service, SectionVIII, Divisions 1 and 2,” should be considered.

[E] The shell side and tube side design pressures and temperatures shall be reviewedto determine extreme conditions that may be encountered. During transients (startup,pressure relief, or shutdown, etc.), the shell side or tube side fluid may be absent, notflowing, or auto-refrigerating with design pressure in the other chamber. Forcomponents subjected to both shell side and tube side conditions, the more severecondition shall control. The following additional conditions shall be considered:



5.1.1 [E] The exchanger shall be designed for full pressure on either side withatmospheric (or full vacuum if specified) on the other side. If an exchangeris designed for differential pressure, the Data Sheet and nameplate shall soindicate.

5.1.2 [E] Fixed tubesheet exchangers cannot generally be operated at thecoincident nameplate temperature-pressure conditions. The basis fordifferential thermal expansion used in the design shall be defined and shallbecome a fabrication drawing requirement. (See PIP VEDST003.)

5.2 MAWP {Design Pressure} and Coincident Maximum Temperature

5.2.1 [V/E] The MAWP {Design Pressure} to be marked on the Code nameplateis defined as the maximum gauge pressure permissible at the top of acompleted vessel in its normal operating position at the designatedcoincident metal temperature for that pressure. (See Code Appendix 3{AD-121} for definitions of MAWP and Design Pressure.) This MAWPmay be determined from the design pressure or from calculations based onthe specified nominal component thickness, but reduced by the specifiedcorrosion allowance.

[V/E] The maximum permissible set-to-operate pressure of a single safetyrelief device cannot be higher than the MAWP {Design Pressure}. (SeeCode rules when multiple safety relief devices are employed.)

[V/E] See Code Paragraph UG-20(a) {AD-121} for Code rules relative todetermining the coincident maximum metal temperature to be stamped onthe nameplate. A suitable margin consistent with the uncertainties withwhich the true maximum mean-metal temperature can be determined shouldbe included. The maximum design temperature rating shall be increased tothe highest temperature possible without affecting the thickness of the shellor heads and without changing the pressure class for nozzle flanges. Whenappropriate, a vessel may be designed and Code stamped for more than onepressure/coincident maximum metal temperature condition.

5.2.2 [V/E] To provide for future field tests, the vessel and foundation (providedby others) shall be designed so that any component in the corroded conditionwill withstand the combination of hydrostatic test pressure at the top of thevessel (as defined in Code Paragraph UG-99 {Article T-3}) and thehydrostatic head of the vessel full of water when the vessel is in its operatingposition without exceeding the stress levels defined in Section 5.10.9(4).Vessel designs that include such features as conical sections withoutknuckles, torispherical heads with an inside crown radius/head thickness(L/t) ratio greater than 500, openings in the shell that exceed the dimensionallimits given in Code Paragraph UG-36(b)(1) {Not Division 2 Applicable},thermal gradients, or body flanges may require special analysis for futuretests. Refer to Section 5.10 for additional requirements that apply. Note thatthe equipment foundation must also be designed to support the loading of afuture test.




5.3 Minimum Design Metal Temperature (MDMT) and Coincident Pressure

[V/E] The MDMT and coincident pressure to be marked on the Code nameplateshall be selected by the Designer in consideration of the operating phases such asthose listed in Section 5.1 and of the Code rules in Paragraph UG-20(b) {NotDivision 2 Applicable}. Reliable administrative procedures to control thepressure/coincident temperatures during transient operations (e.g., startup andshutdown) are often appropriate from a materials of construction selection point ofview. For example, when considering the effects of auto-refrigeration on carbon andlow-alloy steels, such procedures make it appropriate to consider operations belowthe MDMT stamped on the nameplate, provided the reduction in MDMT for thecoincident general primary membrane tensile stress results in a temperature that is nocolder than that permitted in Code Paragraph UCS-66(b) {AM-218.1}. Whenatmospheric temperatures govern the metal temperatures during startup or normaloperations, the lowest 1-day mean atmospheric temperature at the installation sitemust be considered. Figure 2-2 from API 650 may be used to establish the lowest1-day mean temperatures insofar as applicable. The mean metal temperature duringshop and future field pressure testing shall also be considered during the vesseldesign stage. During the pressure test, the pressure-resisting components andattachments, that when welded to pressure-retaining components are judged to beessential to the vessel’s structural integrity, shall have a temperature at least 30ºFwarmer than the MDMT to be stamped on the nameplate, but shall not exceed 120ºF.(See Section 6.1.)

5.4 External Pressure Design

[V/E] In a manner similar to that described in Section 5.1, the Designer shallestablish the external design pressure and coincident temperature by determiningrequirements for external pressure based on the expected operation of the vessel andadding a suitable operating margin.

[V/E] If the vessel is not designed for full vacuum, and if the use of vacuum reliefdevices is selected, consideration must be given to the effects of introducing air intothe vessel. Vessels in steam service shall be designed for full vacuum, andconsideration shall also be given for vessels in services that may be subject to steamout. Consideration shall also be given to external pressures caused by suddencooldown of gases or vapors in the vessel or by the sudden emptying of the vesselcontents.

[V/E] Code-required stiffening rings for shells under external pressure shall beplaced on the outside of the vessel, shall have a thickness not less than 3/8 inch, andshall have a ring width-to-thickness ratio no greater than 10. Stiffening rings shall beattached by continuous fillet welds on both sides of the ring.

5.5 Cyclic Service

[V/E] The required service for all vessels shall include consideration by the Designerof cyclic service. Code Paragraph UG-22(e) {AD-160} mandates that cyclic anddynamic reactions from any mechanical or thermal loading source be considered indesign. Batch operation vessels and vessels having agitators, for example, quite



frequently fall into this category. The following guidelines {AD-160} arerecommended as a starting point when determining if cyclic analysis will berequired. The need for a fatigue analysis by the Manufacturer shall be stated on theData Sheet by the Designer.

5.5.1 Number of Cycles {See AD-160.2}

[V/E] Code vessels should be considered to be in cyclic service when thetotal number of cycles in the following three items (1.+2.+3.) exceed 1000cycles in the desired design life of the vessel:

1. The expected number of full range (design) pressure cycles, includingstartups and shutdowns

2. The expected number of operating pressure cycles in which the rangeof pressure variation exceeds 20% of the design pressure

3. The expected number of thermal cycles where the metal temperaturedifferential between any two adjacent points exceeds 50ºF (For adefinition of adjacent points, see Code Section VIII, Division 2,Paragraph AD-160.2, footnote 3.)

5.5.2 Fatigue Analysis

[V/E] In cases where the preliminary guidelines in Section 5.5.1 indicate thata fatigue analysis may be required, the rules in Code Section VIII, Division2, Paragraph AD-160, “Fatigue Evaluation,” are recommended for use withsound engineering judgment as a guideline for establishing further action. Afatigue analysis shall always be performed for agitator mounting nozzles andtheir attachment to the vessel. (See Sections 5.12.2 and 5.14.1.)

5.5.3 Fatigue Loading Data

[V/E] The applicable fatigue loading conditions shall be stated onPIP VEDV1003 and PIP VEDST003.

5.6 Welded Pressure Joint Requirements

5.6.1 [V/E] Consistent with the service-specific needs of each vessel,consideration must be given to the type of welded pressure joints to befurnished in the pressure-boundary components. Consideration shall also begiven to the type/degree of nondestructive examination to be applied to thesejoints. (See User’s responsibilities under the Code as outlined in the CodeForeword. See also Code Paragraph U-2(a) {AG-301}.) As a minimum,specific Code requirements must be met. In order to provide a means ofcommunicating the requirements to the prospective manufacturers in amanner that is not open to dispute, the Code has provided the Welded JointCategory system in Code Paragraph UW-3 {AD-400}. A Welded PressureJoint Requirements Form for documenting and transmitting the neededinformation for each welded joint category (location) is included inAppendix B[V] or B[E]. Also included in these Appendices is a completedform showing the requirements described in Section 5.6.2, illustrating theuse and usefulness of this form for communicating welded pressure joint




requirements to manufacturers for quotations and purchase specifications.Notes A through C of the Nondestructive Examination Notes (Page 2 of theForm) are standard examination notes that may be selected by the User. Theremaining options or User-defined options may be added as appropriate.

5.6.2 [V/E] The welded pressure joint requirements are to be selected consistentwith service-specific needs; however, the following shall apply as aminimum:

5.6.2.1 [V/E] Welded joints of Categories A, B, and, when used, butt-typeCategories C and D shall be Type No. 1 of Code Table UW-12{AF-221}. Note that this excludes the use of permanent weld jointbacking strips and the use of butt welds with one plate offset[Code Figure UW-13.1(k)]. (See Section 5.6.2.3.)

5.6.2.2 [V/E] Non-butt joints that connect nozzles (including manwaysand couplings) to the vessel wall (Code Category D joints) shall befull penetration welds through the vessel wall and through theinside edge of reinforcing plates, when used. Nozzle necksdesignated to extend beyond the inside surface of the vessel wallshall have a fillet weld at the inside corner. (See Section 5.6.2.4.)

5.6.2.3 [V/E] {Not Division 2 Applicable} The minimum degree ofexamination of welded butt joints shall be spot radiography perCode Paragraph UW-52, such that, in combination with therequirements of Section 5.6.2.1, a joint efficiency not lower than0.85 will result. In applying the rules of Code Paragraph UW-52,the increments of weld shall be selected so as to include allCategory A, B, and C butt welds, except Category B or C buttwelds in nozzles and communicating chambers that exceed neither10 inches nominal pipe size nor 1-1/8 inches wall thickness.

5.6.2.4 [V/E] The need for examining the accessible surfaces of thecompleted Category D corner joint welds by magnetic particle,liquid penetrant, ultrasonic, or other nondestructive methods shallbe considered on a case-by-case basis. For example, see optionalNote E in the Nondestructive Examination Notes of the WeldedPressure Joint Requirements Form.

5.6.2.5 [V/E] Use either Appendix B[V] or B[E] to document specifiedrequirements.

5.6.2.6 [E] Tubesheet-to-shell (or channel) weld joints shall be any fullpenetration weld permitted by Code Figure UW-13.2 or FigureUW 13.3, except as follows:

5.6.2.6.1 [E] Weld joints that employ a permanent backing stripare not permitted.



5.6.2.6.2 [E] To avoid the potential for crevices generatedduring fabrication, Code Figures UW-13.2 (d), (e-2)and (i) are not permitted.

5.6.2.6.3 [E] Exchangers having any of the following designconditions shall employ tubesheet-to-shell (orchannel) weld joints per Code Figures UW-13.2 (a),(f) or (k), or Figure UW-13.3:

• Tube side MAWP exceeding 600 psig

• Shell side MAWP exceeding 1000 psig

• MDMT colder than minus 20°F

• High-alloy tubesheet and adjoining shell (orchannel) with the weld joint exposed to theprocess fluid

• Shell (or channel) inside diameter (ID) largerthan 48 inches with carbon steel, low-alloysteel, or clad steel tubesheet material; or largerthan 30 inches with high-alloy or nonferroustubesheet material

5.6.2.7 [E] For the purpose of determining required tubesheet-to-shell (orchannel) weld sizes in accordance with Code requirements, a fixedtubesheet shall be considered supported (not less than 80% of thepressure load is carried by the tubes) if:

[(AtEt)/(AsEs)] ≥ 4.0

Where:

At = Total cross-sectional metal area of tubes, sq. in.Et = Modulus of Elasticity of tube material at mean metal

temperature, psiAs = Cross-sectional metal area of shell based on actual

thickness less corrosion allowance, sq. in.

Es = Modulus of Elasticity of shell material at mean metaltemperature, psi

5.7 Postweld Heat Treatment (PWHT)

5.7.1 [V/E] Vessels shall be postweld heat treated per applicable sections of theCode in accordance with material specifications or when specified by theUser due to service such as ammonia, caustics, amines, or wet hydrogensulfide. Requirements for PWHT of carbon and low-alloy steels are providedin Table UCS-56 {AF-402.1} of the Code. Alternative PWHT requirementsof Code Table UCS 56.1 {AF-402.2}, “Alternative Postweld Heat TreatmentRequirements for Carbon and Low-Alloy Steels,” shall not be employed.




5.7.2 [V/E] PWHT provides reduction of residual stresses due to forming andwelding and softens heat-affected zones. Some steels can be damaged withincertain temperature zones below PWHT temperature. A materials engineershall be consulted regarding the need for PWHT beyond the requirements ofthe Code and dependent on service conditions. The resultingrecommendation shall be included on the Data Sheet, PIP VEDV1003, orPIP VEDST003.

5.8 Wind Load

5.8.1 User Selections from ASCE 7 (References are to ASCE 7-95,unless otherwise specified)

Note: Local codes or regulations may require compliance with UBC orother rules for wind load design.

[V/E] Wind load design requirements that shall be used for U.S. locationsare covered in ASCE 7; however, simply specifying wind loads inaccordance with ASCE 7 is an incomplete specification since choices existwithin ASCE 7 that the Designer must make. The Designer shall determineand specify on the Data Sheet, PIP VEDST003, or PIP VEDV1003 thefollowing items:

5.8.1.1 Classification Category (from Table 1-1)

[V/E] There are four Classification Categories. This selection allowsthe Designer to determine the Importance Factor, I, from Table 6-2.The Importance Factor is needed to determine the Velocity Pressure.Category II (formerly Category I in ASCE 7-93 and earlier editions)has been the industry standard; however, in some cases it may beappropriate to select Category III.

5.8.1.2 Basic Wind Speed (from Figure 6.1)

[V/E] The Designer shall make this determination by knowing thegeographic location of the equipment’s point of installation.

[V/E] There are different units of measurement for wind speed thatmust be recognized for design. The basic wind speed in ASCE 7 is interms of a 3-second gust. This is the mean wind speed averaged over3 seconds. All U.S. codes before ASCE 7-95 use wind speed in termsof the fastest mile. These wind speed numbers cannot be usedinterchangeably in design. Interchanging these wind speed valuescan produce results that may be 40% or more in error.

5.8.1.3 Exposure Category (from Paragraph 6.5.3)

[V/E] There are four Exposure Categories from which to select.Velocity Pressure Coefficients, Kz, are provided in Table 6-3 as afunction of the selected Exposure Category. Exposure Category Cshould be selected for most Gulf Coast sites. For other than coastalplant sites, Exposure Category B is often selected. The Designer



shall make this determination by knowing the geographic location ofthe equipment’s point of installation.

5.8.1.4 Topographic Factor, Kzt (from Paragraph 6.5.5 and Figure 6-2)

[V/E] Wind speed-up over isolated hills and escarpments must beconsidered for Exposure Category B, C, or D where the upwindterrain is free of such topographic features for a distance of 1 mile or50 times the height of the hill or escarpment, whichever is less.Wind speed-up over isolated hills and escarpments must also beconsidered for structures situated on the upper half of hills or nearthe edge of escarpments. For Exposure Categories B and C, windspeed-up does not need to be considered when the height of hills orescarpments is less than 30 feet and 60 feet respectively, whichwould be typical for the Gulf Coast region.

5.8.1.5 Gust Effect Factor

[V/E] For flexible structures such as a tall vertical process vessel, aGust Effect Factor, Gf , is another essential variable needed todetermine the wind forces involved. The instructions in ASCE 7 inthis regard are as follows:

• [V/E] Gust Effect Factors for main wind-force resistingsystems of flexible buildings and other structures shall becalculated by a rational analysis that incorporates the dynamicproperties of the main wind-force resisting system.

• [V/E] For flexible vertical vessels, defined as vessels with afundamental (natural) frequency of vibration less than 1 Hertz[including vessels with a height-to-diameter (h/D) ratio greaterthan 4, where h is the total height of the vessel and D is thevessel diameter measured to the mid-thickness of the vesselwall], the recommendation is that Gf be determined usingeither the analysis method given in Paragraph 6.6 of theCommentary Section of ASCE 7 or some other rational analysismethod that incorporates the dynamic properties of the mainwind-force resisting system. When employing equation C6-9 inParagraph 6.6, use 0.01 as the damping ratio, β, for steelconstruction.




5.8.1.6 Force Coefficients

[V/E] Force Coefficients, Cf, formerly called “Shape Factors,” arealso needed to determine wind-induced forces acting on the vessel.Typical factors are provided in Table 6-7. The following arerecommendations for Cf to be used in design:

Vessel Description Cf

A. For all horizontal vessels and for verticalvessels having an h/D ratio not greaterthan 1

0.5

B. For vertical vessels having an h/D ratiogreater than 1 (applies to that portionof vessel without spoilers)

See Table 6-7 formoderately smoothsurfaces

C. For that portion of vertical vesselsprovided with spoilers as recommendedin Section 5.11.2.1 or 5.11.2.2 of this Practice

See Table 6-7 for veryrough surfaces

5.8.2 Determination of Wind-Induced Forces

[V] ASCE 7 does not provide the complete methodology needed to accountfor wind-induced forces on common appurtenances to pressure vessels suchas ladders, platforms, handrails, piping, etc. The report entitled “Wind Loadson Petrochemical Facilities” (see Section 2.3 of this Practice) providesguidelines and examples for the determination of the total wind-inducedforces on pressure vessels, including those from appurtenances. If mostdetail items (ladders, platforms, piping, etc.) of the vessel are known or canbe estimated with reasonable accuracy, the Detailed Method described inthis report shall be used for the vessel design.

[E] See PIP VEDST003 for specific loading information, when applicable.

5.9 Seismic Loads

Note: Local codes and regulations may require compliance with UBC or otherrules for seismic design.

5.9.1 General Requirements and Data from ASCE 7 (References are toASCE 7-95, unless otherwise specified)

[V/E] The seismic design requirements and the specification of criteriavariables for the calculation of seismic response loads for the design ofvessels are in ASCE 7. The calculation of seismic forces for vessels isgoverned by one of two methods. For vessels mounted on the ground, seeSection 5.9.2 of this Practice. For vessels mounted above grade within astructure, see Section 5.9.3 of this Practice. The first step in an analysis is toperform an eigenvalue analysis of the vessel in order to calculate its firstnatural period (horizontal direction, in the installed position). This is doneby dividing the vessel into an appropriate number of mass and stiffness



elements per the theory of structural dynamics. For long pieces ofequipment, more elements are normally required for an accurate analysis. Ageneral rule is to use the diameter of the vessel as the minimum longitudinallength of each element. For vertically-oriented vessels, the mass points arenumbered starting at the first point above grade. For horizontally orientedvessels, only one mass point is normally required because the vessel has thecenter of gravity of the majority of its mass concentrated at one level abovethe ground. For vessels that can be shown to have uniform properties in massand stiffness, the closed form handbook solution for natural period may beused.

[E] See PIP VEDST003 for specific loading information, when applicable.

[V/E] The design of pressure retaining elements (both internal and external)shall permit allowable stress multiplying factors which do not exceed thosefound in Code Paragraphs UG-23(c) and (d) {Table AD-150.1}. The loadcombination factors of ASCE 7, Paragraphs 2.4.3 and 2.4.4, are notpermitted. The design of supports shall meet the requirements inSection 5.18 of this Practice.

5.9.2 Seismic Loads for Ground-Supported Equipment

[V/E] The governing equation for horizontal seismic base shear of ground-supported equipment is:

V = CsW

where:

Cs = 1.2Cv/(RT2/3)

Cs (seismic design coefficient) should not be less than 0.5Ca , but need notbe greater than 2.5Ca/R.

Cv , Ca are site-specific coefficients based on Soil Profile Type and valuesof Av and Aa as determined from the corresponding contour maps.

R is Response Modification Factor based on nonbuilding structure typeand vessel contents if applicable (ASCE 7 Table 9.2.7.5).

T is the first natural period of the equipment to be calculated

W is the operating weight of the equipment.

The lateral horizontal seismic forces induced at the levels or mass points ofthe equipment and in the direction causing the highest stresses shall bedetermined from the rules in ASCE 7. The Designer shall specify the site-specific values on the Data Sheet, PIP VEDV1003, or PIP VEDST003.

Note: ASCE 7, Section 9.2.7.2, requires that the calculated shear beincreased for vessels with hazardous contents, if they are supported bystructures similar to buildings. Other special requirements may apply forspecial cases such as vessels with fundamental period T, less than




0.06 sec, storage tanks, and irregular equipment structures. The designershall be responsible for such special analysis and design requirements.

5.9.3 Seismic Loads for Structure-Mounted Equipment

[V/E] For equipment mounted in a structure above grade, the governingequation for seismic force is:

Fp = 4.0 Ca Ip Wp

where:

Ca = seismic coefficient

Ip = component importance factor = 1.5

Wp is the operating weight of the equipment.

Fp is the horizontal seismic force applied at the center of gravity of theequipment and in the direction causing the highest stresses.

If the above method of calculating the floor-mounted equipment seismicforce is too conservative, the alternate method may be used. See equations9.3.1.2-2 through -5 in ASCE 7. Note that this method requires thecalculation of the fundamental period T of the structure that the equipment ismounted in.

5.10 Design Loads and Load Combinations

[V/E] The Designer shall determine the following loads and specify them on theVessel Drawing/Data Sheet. Design loads are defined and classified as follows:

5.10.1 Dead Load (L1)

[V/E] Dead Load is the installed weight of the vessel, including internals,catalyst or packing, refractory lining, platforms, insulation fireproofing,piping, and other permanent attachments.

5.10.2 Operating Live Load (L2)

[V/E] Operating Live Load is the weight of the liquid at the maximumoperating level, including that on trays.

5.10.3 Pressure Load (L3)

[V/E] Pressure Load is the MAWP {Design Pressure} (internal or external atthe coincident temperature) considering the pressure variations through thevessel, if any. MAWP may be equal to the design pressure (see Codefootnote 34). For vessels with more than one independent chamber, see CodeParagraph UG-19(a) {AD-102}.

5.10.4 Thermal Load (L4)

[V/E] Thermal Loads are the loads caused by the restraint of thermalexpansion/interaction of the vessel and/or its supports.



5.10.5 Test Load (L5)

[V/E] Test Load is the weight of the test medium, usually water. Designbasis shall consider that the vessel will be tested in its normal operatingposition. (See Section 5.2.2.)

5.10.6 Wind Load (L6)

[V/E] Wind Load shall be determined in accordance with Section 5.8.

5.10.7 Seismic Load (L7)

[V/E] Seismic Load shall be determined in accordance with Section 5.9.

5.10.8 Piping and Superimposed Equipment Loads (L8)

[V/E] Loads caused by piping other than the Dead Load in Section 5.10.1and those caused by superimposed equipment shall be considered asapplicable.

5.10.9 Load Combinations

[V/E] Vessels and their supports shall be designed to meet the most severeof the following load combinations: (See Section 5.18 for vessel supports.)

1. L1+L6 Erected Condition with full Wind Load

2. L1+L2+L3+L4+L6+L8 Design Condition with full Wind Load(include both full and zero pressure conditions (L3) for check ofmaximum longitudinal tensile and compressive stress)

3. L1+L2+L3+L4+L7+L8 Design Condition with Seismic Load(include both full and zero pressure conditions to determine L3 forcheck of maximum longitudinal tensile and compressive stress)

4. L1+(F)L3+L5+(0.25)L6 Initial (New uncorroded) Hydrostatic TestCondition and Future (corroded) Hydrostatic Test Condition withvessel in normal operating position and with 50% of design windvelocity (25% of Wind Load)




F is the appropriate Code test factor that, when multiplied by thelowest ratio (for the materials of which the vessel is constructed) ofthe stress value S {stress intensity value Sm} for the test temperatureof the vessel to the stress value {stress intensity value Sm} for thedesign temperature, established the minimum required hydrostatic testpressure at every point in the vessel.

Following are the Division 1 Code hydrostatic test factor requirementsin UG-99, UG-101(c), Code Case 2046, and Code Case 2055-1:

• 1.5 for contruction to 1998 and earlier editions (4.0 designmargin)

• 1.3 for construction to 1999 and later addenda/editions(3.5 design margin)

For Division 2, the hydrostatic test factor is 1.25.

The general primary membrane tensile stress in the corroded condition(or when no corrosion allowance is specified) under this loadcombination shall not exceed {AD-151.1}:

• 90% of the Specified Minimum Yield Strength at 100°F forcarbon and low-alloy steels

• The Specified Minimum Yield Strength at 100°F for austeniticstainless steels

(See examples of design considerations described in Section 5.2.2 andtesting requirements in Section 7.)

5. Lift Condition: See Section 8.

5.11 Wind-Induced Vibration of Vertical Vessels

[V/E] Vertical vessels having an h/D ratio (not including insulation thickness, butincluding skirt height) greater than 15 may vibrate due to vortex-excited resonanceunless sufficient external appurtenances or wind spoilers are present to disrupt theairflow over the vessel, thereby preventing the generation of the vortices with theundesirable predominant frequency. (In general, the addition of spoilers is typicallymore feasible than changing the natural frequency of the vessel or providingsupplementary damping.) In the case of cylindrical pressure vessels that have beendetermined to be candidates for wind-induced vibration, it has been found thatspoilers are only required for the top third of the vessel height and that normalattachments in this region (e.g., ladders and piping) will be effective as spoilersprovided the maximum circumferential distance between them is 108 degrees (30%of the vessel circumference).

[V/E] Vessels with an h/D ratio of 15 or greater that do not have a significantnumber of effective attachments shall be investigated for dynamic behavior due towind excitation as described by Vellozzi (see Section 2.3) and Sections 5.11.1.1,5.11.1.2, and 5.11.1.3. Other similar proven evaluation methodology may be used.



5.11.1 Vortex Shedding Ranges

[V/E] Vessels may vibrate in any of three vortex shedding ranges.

5.11.1.1 [V/E] Lower Periodic Vortex Shedding Range: When theReynolds number is less than 300,000 and the Strouhal number isapproximately 0.2, vibration due to periodic vortex shedding mayoccur with tall slender vessels that have very low fundamentalfrequencies.

5.11.1.2 [V/E] Random Vortex Shedding Range: When the Reynoldsnumber is between 300,000 and 3,500,000, random vortexshedding occurs. When the Strouhal number is approximately 0.2,the random vortex oscillations may lock-in and become periodic,causing the vessel to vibrate.

5.11.1.3 [V/E] Upper Periodic Vortex Shedding Range: When theReynolds number is above 3,500,000 and the Strouhal number isapproximately 0.2, self-excited vibration will occur when thenatural frequency of the vessel corresponds with the frequency ofvortex shedding.

5.11.2 Corrective Action

[V/E] When it has been determined that a vessel may vibrate and theattributes of the vessel (e.g., normal attachments) cannot be changed to put itin a range where vibration will not occur, wind spoilers in accordance withSection 5.11.2.1 or 5.11.2.2 shall be added to the top-third of the vessel.

5.11.2.1 [V/E] Helical Spoilers: Use a three-start system of spoilers in ahelical pattern on the top third of the vessel. An optimumconfiguration consists of spoilers with an exposed width beyondinsulation of 0.09D and a pitch of 5D, where D is the diameter ofthe top third of the vessel. The spoiler system may be interruptedto provide clearance at vessel appendages.

5.11.2.2 [V/E] Short Vertical Spoilers: Use a three-start system of shortvertical spoilers arranged in a helical pattern on the top-third of thevessel. The exposed width beyond insulation of the spoilers shouldbe 0.09D and the pitch (height of one helical wrap) between 5Dand 11D. There should be a minimum of eight (8) spoilers over thepitch distance (each complete helical wrap) and a minimum of 1.5helical wraps over the top-third of the vessel. The spoiler systemmay be interrupted to provide clearance at vessel appendages.

5.11.2.3 [V/E] Projected Area: When spoilers as described in Sections5.11.2.1 and 5.11.2.2 are added to a vessel, the column projectedarea normal to wind, Af, and the corresponding force coefficient,Cf, for the column height where spoilers have been added (seeSection 5.8.1.6) shall be used when designing the vessel andsupporting structure to calculate the overturning load. The columnprojected area shall be calculated using the projected diameter




taken at the outside edge of the spoilers multiplied by the height ofthe section under consideration.

5.12 Formed Heads

5.12.1 [V/E] Design rules to prevent buckling of thin fabricated torispherical headssubjected to internal pressure are not yet available in Division 1 or Division2 of the Code. Accordingly, for L/t ratios greater than 500, design checks ofthe Code-required thickness should be made based on equations for perfecttorispheres that have been modified to reflect experimental results onfabricated models (see Section 2.3, Galletly). This check may reveal the needfor a head thickness greater than the Code-required minimum thickness.

Note: L is the inside spherical or crown radius and t is the minimumrequired thickness of the head after forming (corroded condition).

5.12.2 [V/E] When an agitator is mounted on a nozzle (or studding outlet), in aformed head, the head thickness determined from Code formulas forpressure loadings and static local loadings analysis is often not sufficient toprovide the rigidity and stress levels acceptable for the dynamic loadings thatwill be applied. Before ordering the head, the agitator manufacturer shall beconsulted regarding the recommended minimum head thickness for theagitator installation under consideration.

5.13 Flanges (see PIP VESV1002, Section 6.3.16)

[V/E] The Designer is responsible for ensuring that the facings, bolt circle, numberof bolts, and size of bolts of vessel nozzles match the mating piping flanges. Flangesfor all flanged vessel nozzles equal to or smaller than NPS 24 shall meet therequirements of ASME B16.5. Body flanges in this size range may be either perASME B16.5 or custom-designed per the Code. For nozzles larger than NPS 24 andfor body flanges of any size, the options available (as follows in Sections 5.13.1through 5.13.4) to the User must be carefully selected as a function of the need.

5.13.1 ASME B16.47, Series A (NPS 26 through NPS 60)

[V/E] These are standard carbon, low-alloy, and austenitic stainless steelflanges of the integral hub, welding neck style that are dimensionally thesame as MSS SP-44 flanges. The materials covered are identical with thosein Materials Groups 1 and 2 of ASME B16.5. Line valves and machinerynozzles may be provided with flanges of MSS SP-44 dimensions. Therefore,vessel nozzle flanges that meet the dimensions of Series A flanges may beeither necessary or desirable. Series A and Series B flanges are notdimensionally compatible in all sizes.

5.13.2 ASME B16.47, Series B (NPS 26 through NPS 60)

[V/E] These are standard carbon, low-alloy, and austenitic stainless steelflanges of the integral hub, welding neck flange style that are dimensionallythe same as flanges covered under the now obsolete API 605. The materialscovered are identical with those in Materials Groups 1 and 2 ofASME B16.5. Machinery nozzles may be provided with flanges of Series B



dimensions. Therefore, vessel nozzle flanges that meet the dimensions ofSeries B flanges may either be necessary or desirable. Series A and Series Bflanges are not dimensionally compatible in all sizes.

5.13.3 Custom-Designed Flanges per Code

5.13.3.1 [V/E] Custom-designed flanges may be required when:

a. Materials of construction covered in ASME B16.5 orASME B16.47 are not appropriate for the service conditions.

b. For NPS 26 through NPS 60, the desired flange style is otherthan the welding neck type (e.g., lap joint, slip-on) coveredin ASME B16.47.

c. Design conditions for the intended service applicationexceed the pressure-temperature ratings of ASME B16.5 orASME B16.47 flanges.

d. Service requirements result in significant mechanicalloadings other than pressure. The pressure-temperatureratings of both ASME B16.5 and ASME B16.47 are basedprimarily on pressure loadings and accordingly, the flangesmay not be suitably designed for externally applied momentor axial thrust loadings (e.g., as imposed by mating piping,weight, wind, or seismic loadings), resulting in leak-tightness problems. See Appendix C for the method usuallyemployed for considering such mechanical loadings.

e. Rigidity requirements of ASME B16.47 flanges aresometimes below recommended guidelines, even whenflanges are subjected only to pressure loadings within thepressure-temperature ratings, or for those flanges designedin accordance with Code Appendix 2 {Appendix 3}. SeeCode Appendix S-2 {Appendix M} for Rigidity Indexguidelines.




5.13.3.2 [V/E] Recommended minimum gasket contact widths are shown inthe following table:

Vessel OD(inches)

Gasket Contact Width(inches)

≤ 36 1

36 < OD ≤ 60 1-1/4

OD > 60 1-1/2

Notes:1.Gasket Contact Width is the recommended minimum

width of the gasket in contact with both flange faces.

2. For 3-ply corrugated metal gaskets, the gasket ODshall be a minimum of 1/4 inch less than the raisedface or lap ring OD. (See Section 5.13.4.4.)

5.13.3.3 [V/E] Design flanges not only for the design pressure, but also forother loadings that will be applied to the joints during the projectlife (e.g., externally applied bending moment and axial thrustloadings.) [See Section 5.13.3.1(d).]

5.13.3.4 [V/E] Select flange thickness so that, considering all loadings thatwill be applied [see Section 5.13.3.1(d)], the Rigidity Index asdefined in Appendix S-2 {Appendix M} of the Code is ≤ 1.0,based on the recommended value of KL of 0.2 or K1 of 0.3, asapplicable.

5.13.3.5 [V/E] Flange bolts shall not be less than 3/4 inch nominaldiameter. Flange bolt holes shall be 1/8 inch larger than thediameter of the bolts.

5.13.3.6 [V/E] Nubbins are permitted only by agreement with the User.

5.13.4 Custom-Designed Lap Joint Flanges

[V/E] Practices relative to lap joint flanges that experience has shown willresult in a level of damage tolerance, leak-tightness integrity, and gasketreplacement capability equivalent to the welding neck style are as follows:



5.13.4.1 [V/E] The recommended radial lap width is as shown in thefollowing table:

Nozzle Vessel OD(inches)

Radial Lap Width(inches)

OD ≤ 18 1

18 < OD ≤ 36 1-1/2

36 < OD ≤ 60 1-3/4

OD > 60 2

Note: Radial Lap Width shall be measured fromthe toe of the lap-to-shell attachment weld to theouter edge of the lap ring. (See Section 5.13.4.4.)

5.13.4.2 [V/E] The gasket contact width is as shown in the Table inSection 5.13.3.2.

5.13.4.3 [V/E] Finished lap ring thickness is a minimum of 3/16 inchgreater than the nominal wall thickness of the nozzle/shell towhich it is attached. This thickness will allow possible futurere-machining of the lap and should be sufficient to allow the lapsto be machined front and back, if necessary to maintain parallelsurfaces after repair.

5.13.4.4 [V/E] If the values in the Tables in Sections 5.13.3.2 and 5.13.4.1are not used, the gasket/lap/flange design shall be configured sothat the gasket load reaction on the lap (defined as “G” in CodeAppendix 2 {Appendix 3}) is as close as practicable to beingcoincident with the reaction of the flange against the back of thelap (taken at the midpoint of contact between the flange and lap).The Code does not treat the gasket reaction and flange/lap reactionindependently [see Code Figure 2-4(1) {Figure 3-310.1(a)}].However, this recommended configuration is believed to promoteimproved joint performance because it minimizes the amount ofbending in the lap ring resulting from applied forces.

5.13.4.5 Lap Type Flange-to-Shell Clearance

[V/E] The difference between the flange inside diameter (ID) andthe shell OD shall not exceed:

• 1/16 inch for nominal diameters up to and including NPS 12

• 1/8 inch for nominal diameters over NPS 12 through 48 inchesOD

• 3/16 inch for nominal diameters over 48 inches OD

5.13.4.6 Flange Bevel and Lap Ring Weld

[V/E] The fillet weld attaching the lap ring to the shell shall be anequal leg fillet weld with the leg dimension equal to the nominalshell thickness (+1/16 inch, -0). The difference between the diameterof the flange bevel where the lap ring contacts the surface of the




flange and the nominal diameter at the toe of the lap ring attachmentweld at the back of the lap ring shall be 1/8 inch (+1/16 inch, -0).

5.13.5 Lap Joint Flanges NPS 24 and Smaller

[V/E] When ASME B16.5 lapped flanges are specified, the User iscautioned to make the checks/inspections necessary to ensure that theflanges actually are ASME B16.5 lapped flanges.

[V/E] For certain of the smaller sizes in each pressure class, the length-through-hub (dimension Y) of the slip-on flange and the lapped flange arethe same. (This is true through NPS 12 for Class 150, through NPS 8 forClass 300, etc.) Accordingly, since the slip-on flange is more commonlyused, flange manufacturers typically modify the small slip-on flanges tomake the lapped style. This modification consists of machining the cornerradius of the bore as specified in ASME B16.5 (dimension r) and removingthe raised face. The latter change is permitted in Interpretation 3-5 ofASME B16.5, provided the resulting flange meets the requirements for alapped flange, including flange thickness, or a length-through-hubdimension.

[V/E] The caution is focused on larger sizes where the length-through-hub(dimension Y) for lapped flanges is greater than that of the slip-on style.Some flange manufacturers have furnished the modified versions of theseslip-on flanges as lapped flanges, calling them short-hubbed lapped flanges.These flanges do not comply with ASME B16.5 and, as a result, do notcomply with either the Code or OSHA when Code construction is mandated.The strength of the short-hubbed flanges cannot generally be justified byCode calculations.

5.13.6 Slip-on Flanges

[V/E] Slip-on flanges are limited to use under the following conditions:

1. [V/E] ASME B16.5 standard forged flanges for design pressuresand coincident temperatures not exceeding the pressure-temperature ratings for Class 150 flanges as specified inASME B16.5, except that the maximum design temperature shallnot exceed 650°F

2. [V/E] {Not Division 2 Applicable} Custom-designed flanges perCode Figure 2-4(8), (8a), (9), (9a), (10), or (10a) for designtemperatures not exceeding 650ºF; and for flange thickness notexceeding 3 inches

3. [V/E] Corrosion allowance does not exceed 1/16 inch (1.6 mm)

4. [V/E] Carbon or low-alloy steel flanges attached to solid high-alloy necks are limited to design temperatures no higher than450ºF, unless a higher temperature is justified by a complete stressanalysis and approved by the User



5. [V/E] MDMT is not colder than minus 20ºF for carbon and low-alloy steels

6. [V/E] Vessel is not for lethal service (Code requirement)

7. [V/E] Vessel or nozzle is neither for cyclic pressure ortemperature service nor subjected to cyclic loadings fromassociated equipment

8. [V/E] For vessels not in hot hydrogen service (Hot hydrogenservice is defined as hydrogen partial pressure exceeding 100 psia,with a corresponding coincident temperature exceeding 400ºF.)

5.13.7 Threaded and Socket Weld Flanges

[V/E] Threaded and socket weld flanges shall not be used. (See Section5.13.9.)

5.13.8 Flange Facing and Surface Finish

5.13.8.1 [V/E] Flanges, except for lapped flanges, shall either have a raisedface or shall have a construction that provides outer confinementto the gasket if required by Section 5.13.8.3. The height of a raisedface shall be 1/16 inch or a greater height when required byASME B16.5 or ASME B16.47, or as specified by the User. Forsome User-designated services, flat-face flanges or ring jointfacings may be required.

5.13.8.2 [V/E] Standard flanges and factory-made lap joint stub ends shallhave a surface finish in accordance with ASME B16.5 orASME B16.47, as applicable. For standard flanges in servicesrequiring special consideration (e.g., hydrogen) and for customflanges and shop-fabricated lap joint stub ends, the gasket contactsurface shall have either a serrated concentric or serrated spiralfinish having a resultant surface finish from 125 - 250 µ inchaverage roughness.

5.13.8.3 Confined Joints

[V/E] For any of the following conditions, gasketed flange jointdesigns (body flange and nozzle joints) larger than NPS 24 shallprovide outer confinement of the gasket:

• Design pressure 300 psi or higher

• Design temperature hotter than 500°F

• MDMT colder than minus 20°F

• Cyclic pressure or temperature service

• Joint requires metallic gasket

Note: Robust metal reinforced gaskets (e.g., spiral-wound withouter gauge ring, double-jacketed corrugated metal gaskets witha corrugated metal filler, etc.) are exempted.




5.13.9 Piping Connections

[V/E] All piping connections to vessels shall be either flanged or butt-welded. The minimum size shall be NPS 1-1/2. The use of threadedconnections is not recommended because of the potential for crevicecorrosion and notch sensitivity. Threaded connections for vents and drains orinstrument connections are permissible when specified by the User. Whenused, the minimum size shall be NPS 3/4 Schedule (Sch) 160 or 6000#coupling. (See ASME B16.11.) Nozzle sizes NPS 1-1/4, 2-1/2, 3-1/2, and 5shall not be used.

5.13.10 Quick Opening Closures

[V/E] Swing bolts (eye bolts) shall be of one-piece construction withoutwelding. Hinge pins shall be solid (not rolled) and of the same material asthe swing bolts.

5.13.11 Flanges - Pass Partition Areas

[E] In multi-pass heat exchangers, the total gasket sealing areas of the passpartition plate(s) shall be included when calculating the minimum initial boltload required to seat the gasket (Wm2).

5.13.12 Flanged Joints

[E] Removable channels or bonnets, channel covers, and floating headcovers shall be attached with through-bolted flanged joints, except TEMAType D stationary head designs.

5.14 Nozzles

5.14.1 [V/E] Nozzles supporting agitators, pumps, or other mechanical equipmentshall be suitably reinforced to withstand the mechanical loadings specifiedby the device manufacturer. Likewise, nozzles for pressure relief devicesshall be designed and reinforced for thrust reaction. Use of heavier nozzlenecks, conventional reinforcing pads with properly contoured fillet welds,and formed heads of appropriate stiffness are the elements that result in adesign suitable for an infinite number of cycles. Gussets shall not be used tostrengthen, stiffen, or reinforce nozzles, unless demonstrated by calculationsto be suitable for the specified cyclic life or thermal condition.

For such nozzles, consideration shall be given to the dimensionalrequirements of the device as supplied by the device manufacturer (e.g.,tolerances).

5.14.2 [V/E] Surface-attached nozzles as shown in Code Figures UW-16.1(a),(a-1), (a-2), (a-3), and (b) {Figures 610.1(a) and (b)}, and those with internalreinforcing pads, are not permitted.

5.14.3 [V/E] Nozzle locations (including manways) and their reinforcing pads, ifnecessary, shall preferably not interfere with or cover pressure vessel weldseams [see PIP VESV1002, Section 5.2.2(c)]. When located in heads other



than hemispherical heads, all the nozzle reinforcing shall preferably bewithin the spherical portion of the head.

5.14.4 [V/E] Vessels shall be provided with sufficient connections to permitpurging, pumpout, venting, decontamination, pressure relieving, anddraining. Vortex breakers shall be provided on pump suction nozzles. (SeePIP VEFV1124.)

5.14.5 [V/E] For vessels supported by a skirt, the flange of any nozzle in the bottomhead shall be located outside the skirt.

5.14.6 [V/E] In establishing nozzle and manway projections, clearance should beprovided for removing flange stud bolts from between the flange and vesseland for accessing flange stud nuts. Clearance for flange studs and nutsshould be considered when nozzles penetrate insulation or platforms.

Minimum projection from the outside of the vessel wall to the nozzle faceshall be:

• 8 inches for nozzles up to and including NPS 8

• 10 inches for nozzles larger than NPS 8

Round up the dimension from the face of the nozzle to the vessel centerlineor reference line to the next larger 1/2-inch increment.

5.14.7 [V/E] Minimum nozzle neck nominal thickness for carbon steel nozzles shallbe per Code Paragraph UG-45, except in no case shall the nominal thicknessselected for NPS 3 and smaller be thinner than Sch 80.

5.14.8 [V/E] Minimum nozzle neck nominal thickness for high-alloy and non-ferrous alloy nozzles shall be per Code Paragraph UG-45, except in no caseshall the nominal thickness selected for NPS 3 and smaller be thinner thanSch 40S.

5.14.9 [V/E] {Not Division 2 Applicable} When there is concern that an overstresscondition may exist, the local membrane and surface stresses due to localloads (e.g., piping loads, platform loads, etc.) shall be determined using theWRC Bulletin 107 procedure, or other local stress analysis procedures. Forlocal loads and pressure, the allowable stresses are 1.5S for local primarymembrane stress and 3S for primary membrane plus secondary bendingstress at nozzles, platform lugs, etc. S shall be the Code-allowable stress atthe design temperature.

5.14.10 [E] Nozzles shall not be located closer to an integrally attached tubesheet,either shell side or tube side, than shown in Appendix D.

5.14.11 [V/E] Openings exceeding the size limits stated in Code ParagraphUG-36(b)(1) shall meet the supplemental rules of CodeAppendix 1-7(a) and (b). (Code Case 2236 covering alternative design rulesfor large openings shall only be used with User’s agreement.)

5.14.12 [V/E] A minimum of three safety retainer clips shall be welded to the nozzleneck at the back of NPS 4 and larger lap joint flanges that face upward.




(Facing upward is defined as inclination of the nozzle from the horizontal atan angle of 30 degrees or greater.) These clips shall be located so that aspacing of one length-through-hub dimension (dimension Y inASME B16.5) will exist between the back of the lap and the face of theflange. This will allow for future painting of the nozzle neck in this region.

5.15 Manways

[V/E] The location, quantity, and size of manways and internal ladder rungs shall bespecified to ensure that all interior areas are accessible as required. Minimumrequirements regarding manway and inspection openings are covered in CodeParagraph UG-46 {Article D-10}, “Inspection Openings.”

5.15.1 [V/E] Service conditions, size, and configuration of the vessel may justifymanways other than (or in addition to) those mandated by the Code.

5.15.1.1 [V] Vessels with mixers/agitators shall be provided with at leastone manway that does not require removal of the mixer/agitator.

5.15.1.2 [V] Unless other provisions (e.g., body flanges) are made for trayremoval, trayed towers shall have at least two manways, one at thetop and one at the bottom. Additional manways shall be asspecified by the User.

5.15.2 [V/E] Manways shall be usable from a ladder, platform, or grade.

5.15.3 [V] Vessels smaller than 3 feet ID that are subject to internal corrosion,erosion, or mechanical abrasion shall be equipped with inspection openingsas described in Code Paragraph UG-46 {Article D-10}. Vessels in this sizecategory may justify the use of body flanges.

5.15.4 [V] Vessels 3 feet ID and larger that are subject to internal corrosion,erosion, or mechanical abrasion shall be equipped with one or more flangedand blinded manways.

5.15.5 [V/E] The nominal recommended manway size is NPS 24 with a finished IDnot less than 23 inches. Manways shall not be smaller than NPS 18 or have afinished ID of less than 17 inches. Larger diameter manways should be usedto satisfy additional needs such as, but not limited to, installation ofinternals/catalyst, packing, maintenance requirements, long projection due tothick insulation, etc.

5.15.6 [V/E] To provide utility for entry and exit, vessel geometry, and location ofaccess platforms shall be considered when locating manways. Internalladders or grab rungs may be needed at manway locations for entry and exit.

5.15.7 [V/E] Provisions shall be made for lifting devices (fixed or portable) atmanways for personnel rescue as described in OSHA 29 CFR 1910.146.

5.15.8 [V/E] Manways shall be equipped with either a davit or a hinge to facilitatehandling of the blind flange. Manways oriented with the nozzle neck axis ina horizontal plane shall be equipped with a hinge in accordance withPIP VEFV1116 or a davit in accordance with PIP VEFV1117. Attach the



davit-socket bracket to the nozzle neck when lap joint flanges are employed.Manways on the top of vessels oriented with a vertical nozzle neck axis shallbe equipped with a davit in accordance with PIP VEFV1118.

5.15.9 [V/E] Consideration may be given for use of suitable process connections asmanways and handholes. (Consider both size and location.)

5.15.10 [V/E] When approved by the User, flanges and their pressure-retainingcovers for manways may be custom-designed, with due consideration beinggiven to providing a Rigidity Index in accordance with the recommendationsin Code Appendix S-2 {Appendix M}. A detail sketch describing the flange,cover, bolting, and gasket, as well as Code calculations supporting thedesign, shall be provided.

5.16 Anchor Bolts

5.16.1 [V/E] Materials for anchor bolts shall be selected from one of the following:

1. Carbon steel: A-36 or A-307 Grade B

2. Low-alloy steel: A-193 B7. The User’s written approval shall beobtained for the use of this low-alloy material.

5.16.2 [V/E] The allowable design stress, as calculated using the tensile stress areaof the threaded portion, shall not exceed the following (see Note):

• [V/E] Carbon steel: 20,000 psi

• [V/E] Low-alloy steel: 30,000 psiNote: For vessels on concrete foundations, the allowable stress ofanchor bolts may be limited by the strength and dimensions of theconcrete for the bolt spacing selected. Allowable stresses used inthe final design shall be agreed to by the structural engineer.

• [V/E] Anchor bolts selected shall not be smaller than 3/4 inch, shallbe selected in multiples of 4, and shall straddle normal centerlines.

• [V/E] Anchor bolting shall be furnished and installed by the User.

5.16.3 [V/E] Anchor bolts shall be selected with the following threads and thetensile stress area shall be selected accordingly:

• [V/E] Bolts 1 inch and smaller in diameter: Coarse thread series,ASME B1.1

• [V/E] Bolts larger than 1 inch in diameter: 8 thread series,ASME B1.1

5.16.4 [V/E] For vessels on concrete foundations, the allowable concrete bearingstress used in design shall be 1800 psi.

Note: This value is based on the use of concrete with an ultimate strength,f'c, of 3000 psi for which the minimum allowable bearing is (0.7)(0.85)f'c(approximately 1800 psi for 3000 psi concrete).




Higher values may be used consistent with the ulitmate strength chosen (ifknown) and other provisions of state-of-the-art concrete foundation design.The design loadings for anchor bolts embedded in concrete may bedetermined by either the simplified method (neutral axis of bolt pattern atcenterline of vessel) or the shifted neutral axis method (See Section 2.3,Brownell and Young). However, the use of the latter method isrecommended for large vertical vessels because of the economic benefit.

Note: The neutral axis shift method does not apply for vessels supportedby steel structures.

5.16.5 [V/E] Anchor bolts embedded in concrete foundations shall be zinc-coated(hot dip galvanized or mechanically zinc-coated) so that the addition of acorrosion allowance is not required.

5.17 Internals

[V/E] Functional design of trays and other removable internals are outside the scopeof this Practice.

5.17.1 [V/E] Removable internals shall be sized to pass through designated vesselopenings. On vessels with internals where a vessel manway is not located inthe top head, internal rigging clips shall be provided to facilitate handling ofthe internals.

5.17.2 [V/E] Vessel internals such as distributors, dip tubes, baffles, andthermowells should not be located near manways in a manner that wouldinterfere with personnel access or rescue. Special consideration should begiven to the area directly below manways and to head knockers abovemanways. In some circumstances, the addition of grab rungs may benecessary.

5.17.3 [V/E] In services the User has defined as corrosive, welding of vesselinternals attached to a pressure boundary component shall be continuous onall surfaces in order to eliminate corrosion pockets. All seams and cornerjoints shall be sealed.

5.17.4 [V/E] Internal piping and baffles shall be mounted in a manner that will notunduly restrict thermal expansion. Consideration shall be given to vibrationand the possibilities of fatigue failure. Where vibration and fatigue aregoverning design requirements, internal non-pressure parts (e.g., baffles thatmay be subject to vibration or cyclic loading) shall be continuously welded.

5.17.5 [V/E] Internal bolting in vessels, especially where vibration is expected(e.g., where agitators are installed), shall either be double nutted, tack-welded to the clip (or baffle), or have a lock wire placed in the nut/bolt orother supports.

5.17.6 [V/E] The nominal chemical composition of internal non-pressure pipingshall be compatible with that of the inside surface of the vessel and theprocess. Flanges for internal non-pressure piping may be fabricated fromplate but must conform to ASME B16.5 Class 150 bolting dimensions.



5.17.7 [V/E] Vessel internals and all portions of each vessel shall be self-drainingto ensure complete elimination of liquid from the vessel when drained.

5.17.8 [V/E] For integrally clad and/or weld overlayed vessels, lightly loaded (asdefined in Code Section VIII, Division 2, Paragraph AD-912, footnote 4)supports, such as those for trays, baffles, etc., may be welded directly to thealloy clad or weld overlay. Where supports are carrying an appreciable load(> 25% of the allowable stress for fillet welds), such as packing bed supportrings, the Designer shall determine and specify whether the support shall bewelded directly to the base metal.

5.18 Vessel Supports

5.18.1 General

5.18.1.1 [V/E] Code-allowable stresses {design stress intensity} shall beused for vessels and their supports. For combinations ofearthquake or wind loadings with other loadings listed in CodeParagraph UG-22 {AD-110}, the allowable stresses {design stressintensity} may be increased as permitted by Code Paragraph UG-23(c) {AD-151.1}. See Section 5.10.9 for load combinations to beconsidered. See also Code Appendix G {AD-940}.

5.18.1.2 [V/E] For structural-shape support members in compression whereslenderness ratio is a controlling design consideration, no increasein the allowable compressive stress is permitted.

5.18.1.3 [V/E] For supports outside the scope of the Code, either Code-allowable stresses {design stress intensity} or, for structuralshapes, those in the AISC Manual of Steel Construction may beused.

5.18.1.4 [V/E] The MDMT for the vessel support assembly shall not bewarmer than the lowest 1-day mean atmospheric temperature at theinstallation site. (See Section 5.3.)

5.18.1.5 [V/E] Localized shell stresses at all support-to-shell locations shallbe considered, as applicable, for wind load, earthquake, and allother loadings described in Paragraph UG-22 {AD-110} of theCode. (See Sections 5.8, 5.9 and 5.18.2.5.)

5.18.1.6 [V/E] Where reinforcing pads are used under supports,consideration shall be given to stresses due to possible temperaturedifferentials among the vessel, pads, and supports.

5.18.2 Vertical Vessels

5.18.2.1 [V/E] Vertical vessels shall normally be designed as self-supporting units and shall resist overturn based upon wind orearthquake loadings (as described in Sections 5.8 and 5.9) andother applicable loadings per Paragraph UG-22 {AD-110} of theCode.




5.18.2.1.1 Skirts or lugs shall be used to support towers or largevertical vessels and are preferred for vessels havingtop-entering agitators.

5.18.2.1.2 Leg supports shall be limited to spherical andcylindrical vessels that meet the following:

• Design temperature does not exceed 450°F

• Service is noncyclic and nonpulsating (SeeNote 1.)

• Vessel h/D ratio does not exceed 5 (Height isthe distance from base of support to the toptangent line of the vessel.) (See Note 2.)

Note 1: Vessels having agitators experiencetransient transverse forces due to dynamicbending moments from the agitator andsloshing of the liquid. Therefore, the designof leg-supported vessels with agitatorsrequires the application of experience-basedengineering judgment to ensure thatdisplacement stiffness and stress levelsessential to satisfactory operation areprovided.

Note 2: Caution is advised for leg-supportedvessels that may be within h/D ≤ 5 but couldhave excessive axial and/or bending loadson the legs or an overstress condition in thevessel wall.

5.18.2.2 [V/E] Skirts shall be attached to the bottom head by a continuousweld sized so as to provide for the maximum imposed loadings.The preferred skirt attachment detail shall be butt type (skirt buttedto knuckle portion of head such that the centerlines of the skirtplate and the head flange are the same diameter, or such that theOD of the shell and the OD of the skirt coincide). A lapped typeskirt design (skirt lapped to straight flange of head) may also beused. See Figure AD-912.1 of Division 2 of the Code for someillustrative weld attachment details and associated minimum weldsizes. All butt weld joints within the skirt shall be Type No. 1 ofCode Table UW-12 {AF-221}. Alignment tolerance at plate edgesto be butt-welded shall be per Code Paragraph UW-33{AF-140.2}. The type of skirt attachment detail, the style ofanchor ring assembly (e.g., single ring with gussets, single ringwith chairs, double ring with gussets, etc.), and the type/degree ofnondestructive examination of the skirt assembly welds shall be amatter of agreement between the User and the Designer.



5.18.2.3 [V/E] Skirt diameter permitting, one or more 24-inch diameter orlarger openings shall be provided to allow free access forinspection and/or maintenance work inside the skirt. Other openinggeometries are acceptable and are a matter of agreement betweenthe User and the Designer.

5.18.2.4 [V/E] When the skirt is to be provided with insulation orfireproofing, all openings shall be provided with rings or collarsprojected to equal the insulation or fireproofing thickness. Sleevesshall be of sufficient size to provide clearance for painting,insulation, and expansion. Sleeve material shall be the samematerial composition as that portion of the skirt and shall becontinuously fillet-welded inside and outside.

5.18.2.5 [V/E] The skirt for stainless steel or other high-alloy steel vesselsshall be of a material with essentially the same coefficient ofexpansion as the head to which it is attached when the maximumtemperature stamped on the Code nameplate is hotter than 450°F.The length of this high-alloy steel portion of the skirt shall not be

less than 2 ( )Rt , where R is the mean skirt radius and t is skirt

thickness, in inches. The lower portion of these skirts may beconstructed of carbon or low-alloy steel. When the maximumtemperature stamped on the Code nameplate is 450°F or colder,the entire skirt may be made of carbon or low-alloy steel. In allcases, the materials and thicknesses selected shall be suitable forthe maximum and minimum design metal temperatures and theimposed loadings.

5.18.2.6 [V/E] Corrosion allowance for the skirt and base ring shall bespecified separately from the vessel corrosion allowance.

5.18.3 Horizontal Vessels

5.18.3.1 [V/E] Horizontal vessels shall be designed for two saddle supportsattached by welding. Design of saddle supports and calculation oflocalized shell stress may be determined by the L. P. Zick method.(See Section 2.3 and Code Appendix G {AD-940}).

The minimum saddle support contact angle shall be 120 degrees.For vessels, saddle supports shall be located a maximum distanceof Ro/2 from the head tangent line, where Ro is the shell outsideradius.

5.18.3.2 [V/E] Saddle wear plates, when required, shall have the followingproportions:

• Thickness: Established by design, but not less than thesmaller of shell thickness or 3/8 inch




• Width: Width of saddle plus 5t each side of the saddle,where t = cylindrical shell thickness in the corrodedcondition

• Extension Beyond Horn of Saddle: r/10, where r = radiusof cylindrical shell in corroded condition

The wear plates shall have a minimum radius of 2 inches on thecorners, shall be continuously welded to the shell, shall beprovided with one 1/4 inch drilled telltale hole (or equivalentventing) per segment, and shall be vented to the atmosphere. Ventholes shall be located at the low point of the wear plate and shallnot be plugged during hydrostatic testing.

5.18.3.3 [V/E] One of the saddles shall be designated as the fixed saddle inwhich holes shall be provided to receive the anchor bolts. Theother saddle shall be designated as the sliding saddle in whichslotted holes shall be provided. The diameter of the bolt holes andwidth of the slot shall be 1/4 inch larger than the bolt diameter.The length of the slot shall be: 2αDL∆T

Where:

α = Coefficient of thermal expansion of shell material, in/in °F

DL = Length between saddle supports, measured to centerline of anchor bolts, inches

∆T = Greatest absolute value of: ambient temperature at installation (but not warmer than 70°F) minus the maximum or minimum shell temperature to be stamped on the Code nameplate, °F

The anchor bolts are to be located at the center of the bolt holes(fixed saddle) or the midpoint of the slot (sliding saddle). Allsliding saddles shall be provided with slide plates. Slide plates areto be furnished by others. Examples of standard details that maybe used (non-mandatory) are shown on PIP VEFV1105 andPIP VEFV1106.

5.18.3.4 [V/E] The bottom of the saddle supports shall extend at least1 inch below nozzles or other projecting vessel components.Alternatively, a temporary member shall be attached at eachsupport to provide necessary extension until the vessel is placed inpermanent position.

5.18.3.5 [V/E] Saddles to be used in conjunction with weigh cells or slideplates require design considerations to accommodate theapplicable loadings.

5.18.4 Stacked Exchangers

5.18.4.1 [E] Stacked exchangers shall have the lower shell(s) designed towithstand the superimposed load of the upper exchanger(s) filled



with water or operating fluid (whichever is greater) withoutdistorting the shell in a manner that could cause binding of tubebundle(s).

5.18.4.2 [E] When two or more exchangers are stacked, a 1/2-inchshimming allowance shall be provided between intermediatesupports.

5.18.4.3 [E] The lower fixed support of stacked exchangers shall bedesigned for the full bundle pulling load for removal of any upperbundle.

5.18.4.4 [E] Consideration shall be given to the effects of differentialthermal expansion between exchangers.

5.18.4.5 [E] Component (i.e., bonnet, cover, etc.) lifting lugs shall be givenspecial consideration. Two or more lifting lugs located at45 degrees from the top centerline shall be provided to permitremoval of the component without difficulty.

5.19 Heat Exchanger Component Design

5.19.1 Tubes

(See Section 5.20.5 for additional information.)

5.19.1.1 [E] Tubes may be either welded or seamless.

5.19.1.2 [E] Corrosion allowance need not be added to tubes.

5.19.2 Tubesheets

5.19.2.1 [E] Tubesheets shall be designed for full design pressure on eitherside, with atmospheric pressure or specified vacuum on the otherside. Differential pressure design may only be used when approvedby the User.

5.19.2.2 [E] Manufacturer shall calculate the value of Xa (the ratio of thetube bundle axial stiffness to the tubesheet bending rigidity) asdefined in Code Paragraph AA-2.4. These calculations shall besubmitted with the mechanical design calculations.

5.19.2.2.1 [E] If the value of Xa is less than 3.0, the tubesheetshall be designed in accordance with CodeAppendix AA rules or the methods provided in thereferences in TEMA RGP-RCB-7. For values of Xa

equal to or greater than 3.0, the tubesheet may bedesigned in accordance with TEMA, Code rules, or thereferences in TEMA RGP-RCB-7.

5.19.2.2.2 [E] Tubesheets exceeding the scope of TEMA shall bedesigned in accordance with Code rules or TEMARGP-RCB-7 references, regardless of the value of Xa.




5.19.2.3 [E] Tubesheets welded to a carbon steel shell or channel shall beof carbon steel or clad carbon steel. Solid alloy tubesheets may bewelded to a carbon steel shell or channel, provided one of thefollowing is met:

1. [E] The thermal coefficients of expansion do not vary morethan 15% from the tubesheet to the shell or channel over theoperating temperature range.

2. [E] A stress analysis is performed by the Manufacturer andapproved by the User for the joint between the tubesheet andthe shell or channel.

3. [E] The tubesheet is welded to a relatively short cylindricalsection of the same material, and a stress analysis of thejunction of the alloy and carbon steel cylindrical section isperformed and approved by the User.

5.19.2.4 [E] In addition to TEMA requirements for tubesheet cladding,consideration shall be given to providing adequate claddingthickness under pass partition and gasket grooves.

5.19.2.5 [E] Loose liners and plug-welded strip liners are not permitted.

5.19.2.6 [E] Confining gasket grooves shall be provided for all exchangerswith gasketed pass partition joints.

5.19.3 Tube-to-Tubesheet Joints

5.19.3.1 [E] When the type of joint is not specified, expanded joints withgrooves shall be used for tubesheets of homogeneous material.Expansion may be by roller, hydraulic pressure, or other Userapproved method.

5.19.3.2 [E] If tube-to-tubesheet leakage is deemed to be detrimental to theprocess, seal-welded and expanded joints are to be used. Transientoperations may also warrant seal-welded and expanded tube joints.Seal-welded and expanded joints with grooves shall be used forintegrally clad tubesheets.

5.19.3.3 [E] Strength-welded tube-to-tubesheet joints are to be used whenexpanded joints cannot carry the expected tube load or when theresidual interface pressure due to expansion (tube rolling orhydraulic expansion) is compromised during operation. The loss ofresidual interface pressure can occur with high temperatureapplications or when significant differential thermal expansionoccurs between the tube and the tubesheet.

5.19.3.4 [E] The special close fit tolerances for tube holes as stated inTEMA shall be mandatory for:

• Austenitic tubes with expanded and grooved tube-to-tubesheet joints



• Seal-welded or strength-welded tube-to-tubesheet joints

• Hydraulically expanded tube-to-tubesheet joints

5.19.4 Tube Bundles

5.19.4.1 [E] The minimum mean bend diameter of U-tubes shall not be lessthan 3 times the nominal tube OD.

5.19.4.2 [E] The end baffle spaces shall be equal to or greater than thecentral baffle space.

5.19.4.3 [E] 1. Cross-baffle metallurgy and thickness shall be selectedconsidering the corrosivity of the shell side fluids andthe intended design life.

2. Cross baffles that resist corrosion shall have a thickness noless than the greater of that specified by TEMA or1/8 inch.

3. Cross baffles susceptible to corrosion shall have a thicknessnot less than the greater of the TEMA minimum, 2 timesthe corrosion allowance, or 3/16 inch.

5.19.4.4 [E] Each support plate and baffle in horizontal exchangers shall beprovided with a 1/2 inch x 90 degree notch in the bottom fordraining.

5.19.4.5 [E] All TEMA Type S and T (with removable shell cover)exchangers shall have a floating head support plate located4 to 6 inches from the inside face of the floating tubesheet.

5.19.4.6 [E] Except for shell side isothermal boiling, isothermalcondensing, or kettles, bypass sealing devices shall be provided asfollows:

• Seal strips are required when the radial clearance betweenshell and the outer tubes exceeds 5/8 inch.

• Exchangers with vertical cut baffles (baffle cut parallel toshell side nozzle centerline) shall have seal strips installed toseal the bypass areas caused by the omission of tubes.

• Dummy tubes, rods, or seal strips shall be provided for anypass partition lanes that are parallel to the shell side flow.

• Seal strip thickness shall not be less than the greater of 75%of baffle thickness or 1/4 inch.

• For vertical cut baffles (baffle cut parallel to shell sidenozzle centerline), seal strips shall not extend into the inletor outlet baffle spaces. For horizontal cut baffles (baffle cutperpendicular to shell side nozzle centerline), seal stripsshall extend from the front or stationary tubesheet to the lastbaffle or support plate.




• One pair of seal strips or one dummy tube shall be providedfor each five(5) tube rows between baffle cuts. Minoradjustments may be made to suit actual tube layout.

5.19.4.7 [E] Exchangers with removable tube bundles weighing20,000 pounds or more shall have bundle skid bars.

5.19.4.7.1 A minimum of two skid bars shall be provided. Thebars shall be 1/2 inch minimum thickness by 1-1/2inch minimum height flat bar. The skid bars shall belocated no more than 30 degrees from the verticalcenterline.

5.19.4.7.2 The skid bars shall extend from the stationarytubesheet to floating head support plate (TEMA TypesS and T) or end baffle (TEMA Types P, U, and W).

5.19.4.7.3 When skid bars interfere with nozzle openings, theskid bars shall be terminated at the baffle or supportplate adjacent to the nozzle. A tie rod/spacer ofadequate strength to carry the bundle pulling loadshall be located close to the tube field and within3 inches of the skid bar and shall extend from thetubesheet or baffle/support plate on one side of thenozzle to the baffle/support plate on the other side ofthe nozzle.

5.19.4.8 [E] Perforated or slotted impingement plates shall not be used.

5.19.4.9 [E] Multiple exchangers of the same TEMA size and material,either stacked or parallel, shall have interchangeable componentsto the maximum extent possible.

5.19.5 Expansion Joints

5.19.5.1 [E] Shell expansion joints shall be of the “thick wall” flanged andflued type or flanged only type. “Thin wall” bellows type shallonly be used by User agreement, shall conform to CodeAppendix 26, and shall have the welding stubs of the samematerial as the shell.

5.19.5.2 [E] The design of expansion joints shall be performed by anymethod of stress analysis (e.g., finite element analysis), includingTEMA Paragraph RCB-8, which can be shown to be applicable toexpansion joints. The allowable stresses and cycle life for designshall conform to Code Appendix CC. The need for and design ofexpansion joints shall satisfy the following condition:

• Differential thermal expansion encountered in the mostadverse combination of temperature combinationsanticipated and specified by the User – for all normaloperating (including shutdown and startup) and upset



conditions or operation based on metal temperaturesrather than fluid temperatures and MAWP rather thanoperating pressures

5.19.5.3 [E] Shell expansion joints shall be ventable and drainable in theoperating position.

5.19.5.4 [E] Expansion joints for single pass floating head units may be ofthe “thin wall” bellows type. The expansion joint manufacturershall provide the bellows with welding stubs of the same materialas the tail pipe material. The design of the expansion joint shallconform to Code Appendix 26.

5.19.5.5 [E] The expansion joint-to-shell weld shall not be located less than

2 ( )Rt from the back of the tubesheet, where R is the outside

radius of the shell, in inches, and t is the actual thickness of theshell less corrosion allowance, in inches.

5.19.6 Vapor Belts

5.19.6.1 [E] The design of vapor belts shall include:

• Effect of pressure loads

• Longitudinal stresses produced by operating and testpressures (in other than fixed tubesheet designs)

• Consideration of flexibility produced when designing theexchanger shell, tubes, and tubesheet. When a sleeve typevapor belt is used, the design shall be considered flexibleand designed per Section 5.19.5.1.

5.19.6.2 [E] Vapor belts may be used as expansion joints provided allrequirements of Section 5.19.5 are met. Whether or not vapor beltsare used as expansion joints, vapor belt flexibility shall beconsidered in the design of exchanger shell, tubes, and tubesheets.

5.19.7 Exchanger Covers

5.19.7.1 [E] TEMA Type T exchangers (except kettle type reboilers) shallhave removable shell covers.

5.19.7.2 [E] When full diameter tubesheets are specified on exchangerswith removable tube bundles, the following shall apply:

1. Retaining studs are recommended to maintain the gasketseal on the shell side of the tubesheet with the channel (orbonnet) removed. Retaining studs shall be installed in 25%of the boltholes (four minimum).

2. The tubesheet shall be designed to withstand shell side ortube side hydrostatic test pressure with bonnet/channel orshell removed.




5.19.7.3 [E] Mitered 90 degree reducing elbows for thermosyphon reboileroutlet heads shall conform to the following requirements:

1. No less than three (3) changes in direction at the inside andoutside contour

2. Cyclic loading is not a governing design requirement.

3. Meridian (change of direction) angles between adjacentsections shall be approximately equal for gradual flowtransition.

4. The general contours shall be similar to those ofcommercial forged reducing elbows.

5.19.8 Pass Partition Plates

[E] Drain holes shall not be provided in pass partition plates.

5.19.9 Floating Heads

5.19.9.1 [E] Floating heads shall be designed and dimensioned inaccordance with Code Figure 1-6(d).

5.19.9.2 [E] Nubbins shall only be used by agreement with the User.

5.19.9.3 [E] Floating heads shall be designed with respective corrosionallowance applied to the inside and outside of the floating headand flange. Corrosion allowance on the OD of the flange shall beadded to the recommended edge distance for the selected bolt size.

5.19.10 Kettle Type Exchangers

5.19.10.1 [E] If a weir plate is required, the weir plate shall becontinuously welded all around to the shell and shall be ofsufficient height to flood the top row of tubes with a minimumof 2 inches of process fluid during normal operation.

5.19.10.2 [E] Consideration shall be given to draining both sides of theweir.

5.19.10.3 [E] Rails shall be provided to support and guide the tube bundle.Rails shall be welded to the shell. A hold down bar or angleshall be provided directly above the floating head or the last U-tube support plate.

5.19.10.4 [E] All kettle type exchangers shall either have a 3-inchminimum length cylindrical section (includes flanged hub, ifany) between the shell flanges and conical transitions or beprovided with other alternatives for cone-to-flange fit-up andbolting clearance. For kettle type exchangers with tubesheetsintegral with the shell, the minimum length of cylindrical sectionbetween the tubesheet and the conical transition shall be the



greater of 3 inches or ( )Rt , where R is the mean radius of the

cylindrical section and t is the thickness of the section.

5.19.11 Instrument, Vent, and Drain Connections

5.19.11.1 [E] Additional connections (such as specified by TEMA) shallnot be provided in the nozzle necks.

5.19.11.2 [E] Consideration should be made to placing vents in thetubesheet to meet specific process needs. When vents/drains arespecified to be in the tubesheet, installation shall be per standarddetails. (See PIP VEFV1127.)

5.19.12 Nameplates and Stampings

5.19.12.1 [E] Required nameplate markings shall not be stamped directlyon the exchanger.

5.19.12.2 [E] In addition to required Code information, the followinginformation shall be stamped on the nameplate:

• User’s equipment item number

• Initial test pressures

• Purchase order number

5.19.12.3 [E] Exchanger nameplates shall be located on the shell in anaccessible location. Manufacturer shall show the nameplatelocation on the dimensioned outline drawing.

5.19.13 Shell and Bonnet Design

[E] The use of commercially produced NPS pipe for shell and bonnetsections NPS 24 and smaller is recommended. When specifying NPS pipeas an acceptable option for rolled plate, consider Manufacturer’s tolerancewhen specifying inside diameters if internals such as minimum tube countsare critical.

5.20 Heat Exchanger Thermal

[E] Thermal design of shell-and-tube heat exchangers must consider safety,operation, maintenance, and initial cost aspects of the intended service. Each heatexhanger unit requires independent design. The thermal design method to be usedmust be acceptable to User and Designer. The Designer shall be sufficiently trainedto perform the calculations and properly interpret the results.

5.20.1 Fouling Factors Selection

5.20.1.1 [E] An arbitrary rule to distinguish between clean and dirty serviceis to define a service as dirty when the fouling factor equals orexceeds 0.002 hr ft2 °F/BTU. A lower fouling factor implies aclean service.




5.20.1.2 [E] Fouling factors should be supplied from previous experienceor similar service. If not available, the fouling factors for eachfluid should be selected from TEMA. The fouling factor is basedon the heat transfer surface contacting the fluid. The total foulingfactor is the sum of the outside fouling factor and the insidefouling factor related to the outside surface.

Do not use arbitrarily high fouling factors to provide thermaloverdesign or to compensate for uncertainties in thermal propertiesor process design. High heat transfer coefficients should not beexpected when high fouling factors are used; low heat transfercoefficients should not be expected when low fouling factors areused. The percentage of surface area added as a result of thefouling factor should be reviewed.

5.20.1.3 [E] The service overall heat transfer coefficient divided by theclean overall heat transfer coefficient determines the fraction ofsurface required for the heat exchanger to meet the processrequirements when the exchanger is “clean.” The balance of thesurface exists for fouling. Excessive surface available for foulingcan be expensive, promote fouling, and make the exchangerdifficult to control when it is clean. A review of the cleanexchanger performance is required.

Note: A “clean” reboiler with low-pressure steam may requirea wide range control valve or low outlet pressure for control.

5.20.2 Fluid Side Selection

[E] When the fluids have not been assigned a side, the following guidelinesmay be used to select the fluid side: (Consideration shall be given to themaintenance, operation, size, and cost.)

5.20.2.1 Favoring Shell Side Fluid Placement

• More viscous services

• Lower flow rate service

• Low available pressure drop

• Clean service

5.20.2.2 Favoring Tube Side Fluid Placement

• Cooling water service

• Slurry service

• High-pressure service

• Higher fouling service

• Service requiring more expensive materials



5.20.3 Exchanger Configuration

[E] The various configurations have certain advantages and disadvantageswith regard to maintenance, operation, and cost. Selection of the properconfiguration is of prime importance and affects the thermal designcharacteristics significantly. The various configurations are defined inTEMA.

5.20.3.1 Fixed Tubesheet Units

[E] Advantages:

• Typically lowest cost design

• No gasketed joint between tube side and shell side fluids

• Shell side has no gasketed girth joints

• Can handle temperature crosses with counterflow designs

• Low circumferential bypass area around the bundle

• Straight tubes allow mechanical tube side cleaning

[E] Disadvantages:

• Shell side cannot be mechanically cleaned

• Limited access for internal shell inspection

• Limited differential thermal expansion allowed without theuse of an expansion joint

5.20.3.2 U-Tubes

[E] Advantages:

• Typically lowest cost removable bundle design

• No thermal expansion problems between shell and tubes

• Removable bundle for shell side mechanical cleaning

• Allows for internal shell inspection

• Low circumferential bypass area

• For tube side high-alloy and high-pressure, typically lowercost than fixed tubesheet

• No gasketed joint between tube side and shell side fluids

[E] Disadvantages:

• Tube side not easily mechanically cleaned

• Only tubes at bundle periphery can be easily replaced

• Can have large pass lane bypass area under certain bafflearrangements




• U-Bends are susceptible to vibration problems, unlessproperly supported

5.20.3.3 TEMA Type S (non-pull through floating head)

[E] Advantages:





[E] Disadvantages:

• Higher cost

• Internal gasketed joint

• Larger circumferential bypass area

• Labor intensive to pull bundle

5.20.3.4 TEMA Type T (pull through floating head)

[E] Advantages:





[E] Disadvantages:

• Highest cost

• Internal gasketed joint

• Largest circumferential bypass area around the bundle

5.20.3.5 TEMA Type F (two pass shell)

[E] Use of the TEMA Type F shell requires User’s approval.Consideration should be given to differential pressure andtemperature across the longitudinal baffle, heat transfer through thelongitudinal baffle, and flow bypassing around the removablelongitudinal baffles.

5.20.4 Flow Arrangement

5.20.4.1 [E] Liquids, in general, are to be arranged in an upward flowdirection in order to facilitate liquid filling without gas pockets.Particulate-laden liquids, such as boiler water blowdown, may beconsidered for a downward flow arrangement to assist in theexhaustion of solids when velocities warrant such arrangement.



5.20.4.2 [E] Two phase flows, in general, are to have the hot stream(condensing) flow downward and the cold stream (boiling)upward. Exceptions are “falling film evaporation” and “refluxcondensation,” which will have downward liquid and upwardvapor flows. Mist flow may warrant flow in either direction.

5.20.4.3 [E] Gases may flow down or up consistent with the Log MeanTemperature Difference (LMTD) calculation.

5.20.5 Tube Selection

(See Section 5.19.1 for additional information.)

5.20.5.1 Diameter

[E] The preferred tube size for use in heavy tube side fouling (dirtyservice) (0.002 hr ft2 °F/BTU or greater) is 1 inch OD. For lighttube side fouling (clean service), 3/4 inch OD tubes are preferred.

5.20.5.2 Length

[E] Specify commonly used tube lengths, if practical.

5.20.5.3 [E] Recommended Tubewall Thickness

Tube Material Tube Wall Thickness

BWG inches mm

Carbon steel, low-alloy steel,aluminum, and aluminum alloys

14* 0.083* 2.1*

Copper and copper alloys 16* 0.065* 1.7*

High-alloy steel and other non-ferrous materials

16** 0.065** 1.7**

Titanium 20** 0.035** 1.2**

BWG = Birmingham Wire Gauge * = minimum ** = average

5.20.5.4 [E] Enhanced Surface Tubes and Turbulence Promoters

The use of enhanced surface tubes or tube inserts requires anagreement between the User and the Designer. Enhancements maybe quite effective in one process, but not effective in another.Designers may offer enhancements as an alternate.

Enhanced surfaces are available in many forms such as low fin,sintered metal, oval or deformed tubes, or tubes with longitudinalfins. Inserts are used to promote turbulence. Spiral inserts may alsoreduce fouling buildup.

Low fin tubes may be used under the following conditions:

• Deposition of solid matter on the tube surface from the shellside stream is not a problem.




• Tube side inlet temperatures are well above the shell sidestream pour-point temperature.

• Surface tension will not “hold” the condensate in the fins.

• Tube external corrosion is not expected.

5.20.6 Bundle Design and Tube Layout

5.20.6.1 Tube Layout

5.20.6.1.1 [E] Removable bundle designs and square (or rotatedsquare) tube pattern should be considered for dirtyshell side service. (See Section 5.20.1.2.) Cleaninglanes of 1/4 inch minimum are to be maintainedthroughout the bundle.

5.20.6.1.2 [E] Triangular pattern can be used for clean shell sideservices, independent of whether the bundle isremovable or not. An expanded pitch triangular designcan be used in dirty services only when sufficientcleaning lanes are provided by the tube layout andwhen approved by User.

5.20.6.2 Baffles

5.20.6.2.1 [E] In horizontal exchangers, the horizontal cut (bafflecut perpendicular to shell nozzle axis) singlesegmental baffles are the most commonly used andgenerally preferred for single-phase shell side service.In horizontal exchangers, vertical cut (baffle cutparallel to shell nozzle axis) baffles may be used tominimize liquid pooling in two-phase service.

Vertical exchangers should have baffles cutperpendicular to the inlet flow path.

To avoid flow-induced tube vibration, the tube fieldmay be modified to provide “no tubes in the bafflewindow.” Intermediate tube supports may be providedto further reduce vibration probability.

5.20.6.2.2 [E] Multi-segmental baffles (usually double,occasionally triple segmental) are used to reduce theshell side pressure drop.

5.20.6.2.3 [E] Special baffle designs (e.g., rod, disk and donut,longitudinal, spiral baffles, etc.) require User’sapproval.



Baffles utilizing rods are used to reduce shell sidepressure drop and probability of flow-induced tubevibration.

Longitudinal baffles (TEMA Type F shell) allow themaximum LMTD correction factor.

“De-tuning” baffles are used in gas service shell sidewhen required to prevent acoustic vibration.

5.20.6.2.4 [E] U-tube bundles: The baffle adjacent to the tubebends shall be located in the straight portion of thetubes not more than 2 inches from the tangent line ofthe bends.

5.20.6.2.5 [E] Tie rods and spacers: Peripheral tie rods andspacers for positioning baffles shall be located so thatthe outside of the spacers coincides with the outerperiphery of the baffles. The ID of the spacer shall notbe greater than the OD of the tie rod plus 1/8 inch.

5.20.7 Thermal Performance

5.20.7.1 [E] Condensing Heat Transfer

For accurate condenser design, the temperature difference shouldbe calculated incrementally. The temperature and heat transfer ofthe condensing vapor mixtures will vary with the fractioncondensed. Even with pure components, the condensingtemperature will not be constant if there is significant pressuredrop. The effect of delta P on delta T should be checked, especiallyif the overall delta T is small.

For rough calculations, a straight line temperature may be used forthe condensing zone. For final design, the results should always bechecked using stepwise increments. When the vapor entering acondenser is superheated (temperature above the dew point) orwhen the condensate is subcooled (temperature below the bubblepoint), special considerations are required.

If the temperature of the heat transfer surface (tube walltemperature) encountered is less than the dew point of the vapor,the vapor will begin to condense on contact and a wet wallcondition will occur. In such cases, a condensing heat transfercoefficient is used (just as in the case of saturated vapor) and theMean Temperature Difference (MTD) is based on the dew pointtemperature rather than the superheated vapor temperature.

If the tube wall temperature is greater than the dew point of thevapor, a dry wall condition occurs. In such cases, the single phasegas heat transfer coefficient is used and the actual vapor




temperature is used to calculate the MTD for the increment of theexchanger at dry wall conditions.

Some subcooling of condensate usually occurs in total condensers.Condensers can sometimes be designed to accommodate subcoolingby flooding a portion of the shell with condensate. However, theaccuracy of predicting subcooling performance is low because thetrue liquid level and subcooling MTD are almost impossible todetermine. If required, significant subcooling duty should be donein a separate liquid cooler.

5.20.7.2 Water Cooled Services (Cooling Water on Tube Side)

[E] When the cooling water is on the tube side, water velocitysignificantly affects the fouling rate, erosion, corrosion, andresulting maintenance of installed equipment. The Designer shouldtherefore attempt to select an optimal velocity with considerationsgiven to installed and maintenance cost. The following tabulatedvalues for minimum and maximum velocities and maximum tubewall temperature provide accepted practical limitations. Site-specificwater quality and treatment practices may justify deviations fromthese limits.



Minimum Velocity Ft/sec

Material CTW Closedloop

Brackish Rawsurface

Seawater

Ferrous 5* 3 --- --- ---

Nonferrous 5* 3 4 5 5

* Lower minimum velocities may be necessary in some cases due tohydraulic limitations. Consideration should be given to the water qualityand higher fouling factors for these cases.

Maximum Velocity Ft/sec

Material CTW Closedloop

Brackish Rawsurface

Seawater

Ferrous 10 16 --- --- ---

Admiralty 8 --- --- --- ---

Al-Brass 8 --- 6 --- ---

Cupro-Nickel

12 --- 7 7 7

Aust. SS --- 16 --- --- ---

Monel 16 16 14 14 14

Titanium 16 16 16 16 16

Maximum Contacted* Metal Surface Temperature, °°°°F Material CTW Closed

loop Brackish Raw

surface Seawater

All Material 140 No Limit 140 120 140

* Beneath any fouling layer on the waterside when there is no fouling on thehot side.

Blanks in the above tables indicate that the listed material isgenerally not specified for the application.

5.20.8 Hydraulic Performance

[E] The requirement for thermal design described in Section 5.20 alsoapplies to the hydraulic design.

[E] The User and the Designer shall agree on the pressure drop designfactors. Pressure drop considerations include:

• Mill tolerance of tubes

• Fouling build up on tube side and shell side

• Piping between exchangers in series

• Piping for thermosyphon reboilers




5.20.9 Vibration

[E] The Designer shall include a check for flow-induced tube vibration. Themethod of vibration analysis shall be acceptable to the User. The vibrationanalysis shall consider, as a minimum, vortex shedding, fluid elasticinstability, turbulence excitation (buffeting), and acoustic resonance.Generally, the natural frequency (or harmonics) of the tubes should not bewithin 20% of the predicted flow vibration frequency produced by anyexcitation mode, unless the vibration amplitude is within accepted practices.

6. Materials

6.1 Material Specifications

[V/E] Materials not specified by the User shall be selected based on known oranticipated process conditions and approved by the User.

[V/E] The cost of heating the test fluid for shop or future field hydrostatic tests (sothat the temperature of the pressure-resisting components is MDMT plus 30°Fduring the test) should be a consideration when selecting the materials ofconstruction and the associated MDMT to be stamped on the vessel.

6.1.1 External Attachments

[V/E] External attachments welded to pressure-resisting components shall bemade of Code-approved materials. (External attachments such as nozzlereinforcing pads and stiffening rings are, by Code definition, pressure-resisting components.) The material selected is often the same type as thepressure-resisting component to which it is attached. The selection of thetype of external attachment material and the specific ASME SA materialspecification should be made with due consideration being given to thefollowing:

1. Potential problems associated with welding dissimilar materials

2. Compatibility with the Code nameplate maximum and minimumdesign metal temperatures

3. Whether or not the attachment is essential to the structural integrity ofthe vessel (see Code Paragraph UCS-66 {AM-204})

4. Differential thermal expansion characteristics and associated stresses

5. Corrosion resistance

6. Painting requirements

7. Suitability for the anticipated loadings

6.1.2 Internal Attachments

[V/E] See Section 5.17 for commentary.



6.2 Source of Materials

[V/E] If the User restricts sources of fabrication materials, the prospectivemanufacturers must be informed at the time of bidding. Some reasons for restrictionsmay include but are not limited to:

• Maintenance of a specific alloy composition

• Compliance with government requirements

• Compatibility with existing equipment

• Compliance with User procurement policies

6.3 Corrosion/Erosion Allowance

6.3.1 Basis

[V/E] The required design life shall be based on written agreement betweenUser and Engineering Contractor. Allowances specified by the Designershall be based on need and can best be determined by past experience insimilar operating environments. If no past experience is available, such aswith a new process, a materials engineer should examine the process andmake judgment on the expected corrosion rate. Corrosion allowance shouldnot be arbitrary; rather, it should be compatible with design liferequirements.

6.3.2 Corrosion Loss

[V/E] Additional metal thickness must be added to compensate foranticipated loss due to metal reacting with the environments to which it issubjected (including cleaning operations, shutdowns, etc.).

6.3.2.1 [V/E] Internal corrosion loss due to the process conditions affectsall pressure-containing parts. Internal structural parts mayexperience corrosion loss on more than one surface. Bolted partsare frequently constructed of different materials and need to beassessed separately.

6.3.2.2 [V/E] External corrosion may result from exposure of bare metalto the atmosphere, especially in coastal areas and under insulation.Other equipment operating nearby may influence corrosion (e.g.,cooling towers).

6.3.3 Erosion Loss

[V/E] Additional metal thickness must be added in specific locations wheremetal loss is expected due to stream flow that is of high velocity or abrasivefor any reason. Erosion loss usually occurs within a definable area, andcompensation can be made as follows:

• Weld overlay of the area with the intent that the overlay is sacrificial




• Addition of a welded wear plate with the intent that the plate issacrificial

Note: Use caution when using this method in hydrogen service.

• Internal refractory linings, if appropriate

• Increase of inlet nozzle size

6.4 Gaskets

[V/E] In no case shall the nominal thickness of sheet or laminate service gasketingbe greater than 1/16 inch.

7. Testing

[V/E] All new pressure vessels shall be pressure tested prior to being placed in service. Thefollowing paragraphs provide guidance and references to design and executionconsiderations relative to hydrostatic and pneumatic pressure testing.

7.1 Hydrostatic Test

7.1.1 UG-99 Standard Hydrostatic Test

[V/E] All provisions of this Code paragraph must be met when thehydrostatic test is employed. Paragraph UG-99(b) {AT-302}, includingfootnote 34 {Not Division 2 Applicable}, shall be considered to be thestandard hydrostatic test. The test pressure or applicable Code paragraphnumber shall be specified on the Data Sheet.

7.1.2 Horizontal Vessels

[V/E] A horizontal vessel designed to support a full weight load of watershall be tested while resting on its support saddles, without additionalsupports or cribbing.

7.1.3 Vertical Vessels

7.1.3.1 [V/E] Short vertical vessels may be shop-tested in the erectedposition, depending on their height and the shop capability.

7.1.3.2 [V/E] Tall vertical vessels may be shop tested in the horizontalposition. These vessels must be adequately supported during thetest to prevent damage.

Note: Design shall be per Section 5.10.9(4) regardless of testorientation.

7.1.3.3 [V/E] Vertical vessels being tested in the erected position, whethershop or field, shall have consideration given to the additionalpressure and weight due to the fluid head. (See Section 5.2.2.)

7.1.4 Test Temperature

[V/E] See PIP VESV1002, Section 6.3.8.



7.2 Pneumatic Test

[V/E] Caution: Pneumatic testing presents hazards that must be addressed as partof the engineering design of the pressure vessel.

(Reference Code Paragraph UG-100 {AT-400}, “Pneumatic Test” and CodeParagraph UW-50 {Not Division 2 Applicable}, “Nondestructive Examination OfWelds On Pneumatically Tested Vessels.”)

[V/E] Due to the additional hazards of pneumatic testing, vessels shall be designedto minimize the possibility of failure during the test. The vessels shall be constructedof materials that ensure fracture toughness during the test. Additional nondestructiveexamination may be required of main seams, nozzle attachments, and some structuralattachments. All such nondestructive examination shall be performed in accordancewith Code methods and acceptance criteria.

[V/E] Large diameter low-pressure designs, vessels with exceptionally large volume,service that would not allow residual water in the process, and designs that wouldforce great overdesign of the vessel and foundation only to support a water full testmay be considered for pneumatic testing.

7.3 Proof Test

[V/E] (Code reference - Paragraph UG-101, “Proof Tests To Establish MaximumAllowable Working Pressure.”) Proof tests are highly individualized and are notincluded in this Practice.

8. Vessel Rigging Analysis/Lifting Requirements

8.1 Impact Factor

[V/E] Unless otherwise specified by the User, a minimum impact factor of 1.5 shallbe applied to the lift weight for designing lifting devices. The basis for the lift weightmust be established during the design phase of the vessel so that the design of liftingdevices includes all components to be included in the lift (e.g., trays,ladders/platforms, insulation, additional piping with insulation, etc.).

8.2 Vertical Vessels

[V/E] Vertical vessels having h/D ratios greater than 8 and weighing more than25,000 pounds shall have bending stresses in the vessel shell/skirt checked from theloadings imposed during the lift from the horizontal to vertical position. Calculatedgeneral primary membrane tensile stress shall not exceed 80% of the material’sspecified minimum yield strength at 100ºF. Calculated compressive stress shall notexceed 1.2 times the B factor obtained from the Code. Vessel lifts are recommendedto be made when wind speeds are less than 33% of design wind velocity and theresulting wind load (at 33% design wind velocity) is included in the consideration ofthe lift.




8.3 Local Stresses

[V/E] Local stresses in the vessel shell/head/skirt/base rings from the liftingattachments (e.g., lugs, trunnions, etc.) shall be determined for the imposed loadingsusing local stress analysis procedures such as WRC Bulletin 107 or other acceptedlocal stress analysis procedures (e.g., finite element analysis). For the riggingcondition, the allowable stresses as shown in Section 5.14.9 shall be used.

8.4 Welds

[V/E] Shear stresses for fillet welds on the lifting attachments to the vesselshell/head shall not exceed 0.55 times the Code-allowable stress {design stressintensity} at 100ºF for the material selected.



This page is intentionally blank.

APPENDIX A

General Considerationsfor

Pressure Relief Valve Application


Page A-2 Process Industry Practices

General Considerations for Pressure Relief Valve Application

A general comparison of operational characteristics is given for the different types of pressure reliefvalves in common industrial use. The influence on operating margin, from set pressure, isconsidered.

Operational characteristics of direct spring-operated and pilot-operated pressure relief valvesshould be known by the User as well as the Designer. Direct spring and pilot-operated reliefvalves are available for use on applications that must meet Code requirements. The approximatereseating pressure for direct spring-operated valves is 93% of the set pressure in gas or vaporservice and 85% of set pressure for National Board tested safety relief valves in liquid service.Many older liquid service safety valves, requiring 25% overpressure to be full open, have areseating pressure as low as 70% of the set pressure. The reseating pressure for pilot-operatedvalves is typically specified in the same range as the direct spring valves. However, the reseatingpressure of pilot-operated valves can be lowered to a value slightly above atmospheric by addinga manual blowdown connection which can be operated either locally or remotely. Pilot-operatedvalves are used in this fashion as remote, manual, emergency, blowdown valves. The versatilepilot-operated valve has some significant application limitations. Pilot-operated pressure reliefvalves are supplied with filters to protect against foreign matter and are generally recommendedfor relatively clean service. A summary detailing when, and when not, to use pilot-operated valvesis given below.

USE DO NOT USE

• Clean gas or vapor service • Corrosion of wetted part is possible

• Clean liquid service • Polymerization process

• Coking service

• Abrasive or dirty service

• Freezing of contents at ambient temperature ispossible

The point where leakage begins to be a concern when using direct spring-operated valvesdepends on the disk seat design. Metal-to-metal contact seats will begin to leak at about 90% ofset pressure. O-ring soft seat disk type direct spring-operated valves will not leak below 95% ofset pressure. Pilot-operated valves will not leak below 98% of set pressure. The recommendedmaximum equipment operating pressure is slightly below, but many times considered to be equalto, the start-to-leak limit for the valve.

APPENDIX B [V]

Welded Pressure

Joint Requirements Form


Page B[V]-2 Process Industry Practices

Welded Pressure Joint Requirements

DESIGN BASIS

SHELL AND CONE THICKNESS BASED ON: JOINT EFFICIENCY E = _________

DISHED HEAD THICKNESS BASED ON: JOINT EFFICIENCY E = _________

WELDED PRESSURE JOINT REQUIREMENTS

JOINT LOCATIONPARAGRAPH UW-3

TYPE OF JOINT NDE(SEE LETTERED NOTES)

CATEGORY A (SEE NOTE 5) TYPE NO. (1) OF TABLE UW-12

CATEGORY BHEAD -TO-SHELL

TYPE NO. (1) OF TABLE UW-12

OTHER

CATEGORY CBODY FLANGES

NOZZLE FLANGES FIGURE 2-4

CATEGORY D SEE GENERAL NOTE (6)

GENERAL NOTES:1) Unless otherwise indicated, all references on this form are to ASME Code paragraphs, tables, and figures. All nondestructive examination shall be performed per Code methods.2) Joints supplied shall be either detailed or identified by use of standard AWS welding symbols on the vessel Manufacturer's drawings.3) Permanent weld joint backing strips are not permitted.4) Separate internal nozzle reinforcing plates are not permitted.5) The flat plate from which formed heads are to be made shall be either seamless or made equivalent to seamless in which all Category A welds are Type (1) and fully radiographed per UW−51 before forming. After forming, the spin hole, if it remains in the final construction, shall be closed with a metal plug which is butt-welded in place with the weld meeting the Category A weld joint requirements shown in the table.6) Category D welds shall be per Figure UW-16.1 using full penetration welds through vessel wall and through inside edge of external reinforcing plates, when used. Nozzle necks designated to extend beyond the inside surface of the vessel wall shall have a fillet weld at the inside corner.

ITEM NUMBER: ____________________________________

WELDED PRESSUREJOINT REQUIREMENTSPRESSURE VESSELS

EXCLUDING HEAT EXCHANGERS

VESSEL ASSEMBLY DWG.: __________________________ DRAWN BY CHECKED BY DATE DRAWING NUMBER

PAGE 1 OF 2



Process Industry Practices Page B[V]-3

Nondestructive Examination Notes

A. Full radiography shall be per Paragraph UW-51. For welded pipe components, this appliesonly to Categories B and C butt joints. For exclusions, see Paragraph UW-11(a)(4).

B. Spot radiography shall be per Paragraph UW-52. For welded pipe components, this appliesonly to Categories B and C butt joints. For exclusions, see Paragraph UW-11(b).

C. Spot radiography shall be per Paragraph UW-52. Rules of UW-11(a)(5)(b) must be satisfied.The Manufacturer is cautioned to select the appropriate increments of weld for establishingthe spot radiography requirements for the vessel. [See UW-52(b)(4).]

General Note: Notes D through H are examples of user options that are sometimesselected for critical services. Other options may be provided as appropriate.

D. When joint thickness exceeds 2 inches, examine (using MT or PT) the root pass after back-chipping to sound metal and all accessible surfaces of completed welds of Categories A, B,C, and D butt type joints.

E. When design is based on a joint efficiency of 1.00, examine (using MT or PT) Categories Cand D non-butt type joints after back-chipping or gouging root pass to sound metal andaccessible surfaces of completed weld.

F. When nozzles are attached with a full penetration weld through the nozzle wall, the cut edgeof the opening in vessel walls thicker than 1/2 inch shall be examined using MT or PT. Theexamination shall be made before nozzle attachment and a re-examination shall be madeafter attachment, when accessible.

G. Examination (using MT or PT) of completed welds shall be made after PWHT for thefollowing:

1. Vessels or vessel parts for which impact testing is required2. Welds joining non-impact tested low-alloy steels thicker than 1-1/4 inches3. Welds joining carbon steels thicker than 2 inches4. When required by Code

H. Butt welds exempt from radiography by Paragraph UW-11(a)(4) shall have accessiblesurfaces of completed welds MT or PT examined. (Only applies to designs employing impact-tested steels when Category A joints are based on a joint efficiency of 1.00.)

Item Number:

Vessel Assembly Dwg.:

Reference paragraphs are contained in Division 1 of the ASME Code.MT = Magnetic Particle ExaminationPT = Liquid Penetrant Examination

PAGE 2 OF 2


Page B[V]-4 Process Industry Practices

EXAMPLE

Use Of Welded Pressure Joint Requirements Form

To illustrate the use and usefulness of the Welded Pressure Joint Requirements form for communicating weldedpressure joint requirements to manufacturers for quotation and purchase specification purposes, the followingcompleted form shows the requirements described in Sections 5.6.2.1, 5.6.2.2, 5.6.2.3, and 5.6.2.4. With reference tothe lettered Nondestructive Examination Notes (page 2 of the form), note that other options are available for convenientuse or may be provided.

DESIGN BASIS

SHELL AND CONE THICKNESS BASED ON: JOINT EFFICIENCY. E = __0.85_______

DISHED HEAD THICKNESS BASED ON: JOINT EFFICIENCY. E = __0.85_______





B

CATEGORY BHEAD -TO-SHELL

TYPE NO. (1) OF TABLE UW-12 B

OTHERB

CATEGORY CBODY FLANGES

--

NOZZLE FLANGES FIG. 2-4 (6)B

CATEGORY D SEE GENERAL NOTE (6)--

GENERAL NOTES:1) UNLESS OTHERWISE INDICATED. ALL REFERENCES ON THIS FORM ARE TO ASME CODE PARAGRAPHS.

TABLES AND FIGURES. ALL NONDESTRUCTIVE EXAMINATION SHALL BE PERFORMED PER CODE METHODS.2) JOINTS SUPPLIED SHALL BE EITHER DETAILED OR IDENTIFIED BY USE OF STANDARD AWS WELDING

SYMBOLS ON THE VESSEL MANUFACTURER'S DRAWINGS.3) PERMANENT WELD JOINT BACKING STRIPS ARE NOT PERMITTED.4) SEPARATE INTERNAL NOZZLE REINFORCING PLATES ARE NOT PERMITTED.5) THE FLAT PLATE FROM WHICH FORMED HEADS ARE TO BE MADE SHALL BE EITHER SEAMLESS OR MADE

EQUIVALENT TO SEAMLESS IN WHICH ALL CATEGORY A WELDS ARE TYPE (1) AND FULLY RADIOGRAPHEDPER UW−51 BEFORE FORMING. AFTER FORMING, THE SPIN HOLE, IF IT REMAINS IN THE FINALCONSTRUCTION, SHALL BE REPAIRED WITH A METAL PLUG THAT IS BUTT-WELDED IN PLACE WITH THEWELD MEETING THE CATEGORY. A WELD JOINT REQUIREMENTS SHOWN IN THE TABLE.

6) CATEGORY D WELDS SHALL BE PER FIG. UW-16.1 USING FULL PENETRATION WELDS THROUGH VESSELWALL AND THROUGH INSIDE EDGE OF EXTERNAL REINFORCING PLATES WHEN USED. NOZZLE NECKSDESIGNATED TO EXTEND BEYOND THE INSIDE SURFACE OF THE VESSEL WALL SHALL HAVE A FILLET WELDAT THE INSIDE CORNER.

ITEM NUMBER: ________PIP 123456___________________

WELDED PRESSUREJOINT REQUIREMENTSPRESSURE VESSELS

EXCLUDING HEAT EXCHANGERS

VESSEL ASSEMBLY DWG.: ___PIP 123456______________DRAWN BY CHECKED BY DATE DRAWING NUMBER

PAGE 1 OF 2

APPENDIX B [E]

Welded Pressure

Joint Requirements Form


Page B[E]-2 Process Industry Practices

Welded Pressure Joint Requirements

DESIGN BASISSHELL THICKNESS BASED ON: JOINT EFFICIENCY E = _________(SHELL)

JOINT EFFICIENCY E = _________(CHANNEL)

DISHED HEAD THICKNESS BASED ON: JOINT EFFICIENCY E = _________(SHELL)

JOINT EFFICIENCY E = _________(CHANNEL)





SHELLCATEGORY B

HEAD-TO-SHELLTYPE NO. (1) OF TABLE UW-12

SIDE OTHER

CATEGORY C TUBESHEETS

NOZZLE FLANGES

FIGURE UW-13.2

FIGURE 2-4



TUBECATEGORY B

HEAD-TO-CHANNELTYPE NO. (1) OF TABLE UW-12

SIDE OTHER

CATEGORY C

BODY FLANGES

NOZZLE FLANGES

FIGURE 2-4

FIGURE 2-4


GENERAL NOTES:1) Unless otherwise indicated, all references on this form are to ASME Code paragraphs, tables, and figures. All nondestructive examination shall be performed per Code methods.2) Joints supplied shall be either detailed or identified by use of standard AWS welding symbols on the vessel Manufacturer's drawings.3) Permanent weld joint backing strips are not permitted.4) Separate internal nozzle reinforcing plates are not permitted.5) The flat plate from which formed heads are to be made shall be either seamless or made equivalent to seamless in which all Category A welds are Type (1) and fully radiographed per UW−51 before forming. After forming, the spin hole, if it remains in the final construction, shall be closed with a metal plug which is butt-welded in place with the weld meeting the Category A weld joint requirements shown in the table.6) Category D welds shall be per Figure UW-16.1 using full penetration welds through vessel wall and through inside edge of external reinforcing plates, when used. Nozzle necks designated to extend beyond the inside surface of the vessel wall shall have a fillet weld at the inside corner.

ITEM NUMBER: ____________________________________

WELDED PRESSUREJOINT REQUIREMENTS

SHELL AND TUBE HEAT EXCHANGERS

VESSEL ASSEMBLY DWG.: __________________________ DRAWN BY CHECKED BY DATE DRAWING NUMBER

PAGE 1 OF 2



Process Industry Practices Page B[E]-3

Nondestructive Examination Notes

A. Full radiography shall be per Paragraph UW-51. For welded pipe components, this appliesonly to Categories B and C butt joints. For exclusions, see Paragraph UW-11(a)(4).

B. Spot radiography shall be per Paragraph UW-52. For welded pipe components, this appliesonly to Categories B and C butt joints. For exclusions, see Paragraph UW-11(b).

C. Spot radiography shall be per Paragraph UW-52. Rules of UW-11(a)(5)(b) must be satisfied.The Manufacturer is cautioned to select the appropriate increments of weld for establishingthe spot radiography requirements for the vessel. [See UW-52(b)(4).]

General Note: Notes D through L are examples of user options that are sometimesselected for critical services. Other options may be provided as appropriate.

D. When joint thickness exceeds 2 inches, examine (using MT or PT) the root pass after back-chipping to sound metal and all accessible surfaces of completed welds of Categories A, B,C, and D butt type joints.

E. When design is based on a joint efficiency of 1.00, examine (using MT or PT) Categories Cand D non-butt type joints after back-chipping or gouging root pass to sound metal andaccessible surfaces of completed weld.

F. When nozzles are attached with a full penetration weld through the nozzle wall, the cut edgeof the opening in vessel walls thicker than 1/2-inch shall be examined (using MT or PT). Theexamination shall be made before nozzle attachment and a re-examination shall be madeafter attachment, when accessible.

G. Examination (using MT or PT) of completed welds shall be made after PWHT for thefollowing:

1. Vessels or vessel parts for which impact testing is required2. Welds joining non-impact tested low-alloy steels thicker than 1-1/4 inches3. Welds joining carbon steels thicker than 2 inches4. When required by Code

H. Butt welds exempt from radiography by Paragraph UW-11(a)(4) shall have accessiblesurfaces of completed welds MT or PT examined. (Only applies to designs employing impact-tested steels when Category A joints are based on a joint efficiency of 1.00.)

J. Non-butt type joints attaching tubesheets shall be MT or PT examined (usually on exchangerslarger that NPS 24, or any size having design pressure on the tubesheet attachment sideexceeding 300 psi) as follows:

1. Before welding, examine the cut surfaces per Paragraph UG-93(d)(4).2. For joints per Figure UW-13.2(f), (j), or (k), examine the deposited groove weld

surfaces after machining weld flush with tubesheet.3. For double-welded joints, after back chipping the reverse side of weld metal first

deposited and before additional welding, examine the back-chipped surfaces.4. Examine all accessible surfaces of completed weld.5. After welding, re-examine all cut edges examined per Item 1 above that remain

exposed.

K. Tubesheet stock material exceeding 3 inches in thickness shall be ultrasonically examinedafter cutting to final size per ASME SA-578 Acceptance Level 1, Supplementary RequirementS1 (applies to nonclad material).


Page B[E]-4 Process Industry Practices

L. Clad tubesheet material shall be ultrasonically examined after cutting to final size perASME SA-578 Acceptance Level 1, Supplementary Requirement S7 (applies to clad materialof any thickness).

Item Number:

Vessel Assembly Dwg.:

Reference paragraphs are contained in Division 1 of the ASME Code.MT = Magnetic Particle ExaminationPT = Liquid Penetrant Examination

PAGE 2 OF 2

APPENDIX C

Equivalent Pressure Formulas for

Bending Moment and Axial Tensile Load


Page C-2 Process Industry Practices

Equivalent Pressure Formulas for Bending Moment and Axial Tensile Load

When sustained bending moments or axial thrust loadings are applied to the flanged joint duringoperation in sufficient magnitude to warrant consideration in the flange design, the designpressure, P, used in the calculation of total hydrostatic end load, H, in the flange designcalculations should be replaced by the following design pressure:

PFLG = P + PEQ

The equivalent pressure PEQ is determined as follows:

PEQ = 16M

G

4F

G3 2π π+

Where:

M = Sustained bending moment applied across full section at flange during the designcondition, in-lb

F = Sustained axial tensile force applied at flange, lb

G = Diameter at location of gasket load reaction, in (See Appendix 2 {Appendix 3} of theCode for full definition.)

Note: Experience has shown that axial tensile forces resulting from a properly designedpiping system have no significant effect on the flange design and hence are typically notincluded in the PEQ determination.

Therefore, the hydrostatic end load, H, used in the flange calculations is determined as follows:

H = 0.785 G2 PFLG

Dynamic Bending Moment

PEQ = 8M

G3π

Where:

M = Bending moment, as defined above, but including dynamic bending moment (e.g.,seismic moment) applied across full section at flange during the design condition,in-lb

Other Terms = Same as above

APPENDIX D

Minimum Clearance forNozzle Adjacent to Integral Tubesheet

VECV1001 Process industry practice

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