P&ID Symbols

COMPLETE REVISION April 2008

Process Industry Practices P&ID

PIP PIC001 Piping and Instrumentation Diagram

Documentation Criteria

PURPOSE AND USE OF PROCESS INDUSTRY PRACTICES In an effort to minimize the cost of process industry facilities, this Practice has been prepared from the technical requirements in the existing standards of major industrial users, contractors, or standards organizations. By harmonizing these technical requirements into a single set of Practices, administrative, application, and engineering costs to both the purchaser and the manufacturer should be reduced. While this Practice is expected to incorporate the majority of requirements of most users, individual applications may involve requirements that will be appended to and take precedence over this Practice. Determinations concerning fitness for purpose and particular matters or application of the Practice to particular project or engineering situations should not be made solely on information contained in these materials. The use of trade names from time to time should not be viewed as an expression of preference but rather recognized as normal usage in the trade. Other brands having the same specifications are equally correct and may be substituted for those named. All Practices or guidelines are intended to be consistent with applicable laws and regulations including OSHA requirements. To the extent these Practices or guidelines should conflict with OSHA or other applicable laws or regulations, such laws or regulations must be followed. Consult an appropriate professional before applying or acting on any material contained in or suggested by the Practice.

This Practice is subject to revision at any time.

© Process Industry Practices (PIP), Construction Industry Institute, The University of Texas at Austin, 3925 West Braker Lane (R4500), Austin, Texas 78759. PIP member companies and subscribers may copy this Practice for their internal use. Changes, overlays, addenda, or modifications of any kind are not permitted within any PIP Practice without the express written authorization of PIP.

Note: PIP PIC001, Piping and Instrumentation Diagram Documentation Criteria, incorporates symbols previously published in standards owned and copyrighted by The Instrumentation, Systems, and Automation Society (ISA). These are printed with agreement from ISA.

PRINTING HISTORY November 1998 Issued April 2008 Complete Revision

Not printed with State funds

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COMPLETE REVISION April 2008

Process Industry Practices P&ID

PIP PIC001 Piping and Instrumentation Diagram

Documentation Criteria

Table of Contents

1. Introduction.................................2 1.1 Purpose............................................ 2 1.2 Scope............................................... 2

2. References ..................................2 2.1 Process Industry Practices .............. 2 2.2 Industry Codes and Standards ........ 3 2.3 Government Regulations ................. 3

3. Definitions...................................3

4. Requirements..............................5 4.1 General ............................................ 5 4.2 Format.............................................. 6 4.3 Equipment...................................... 11 4.4 Piping ............................................. 17 4.5 Instrumentation and Controls......... 20

Appendixes Appendix A – Tables and Symbols Appendix B – Cover Sheets Appendix C – Example P&IDs

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PIP PIC001 COMPLETE REVISION Piping and Instrumentation Diagram Documentation Criteria April 2008

1. Introduction

1.1 Purpose This Practice provides requirements for designers preparing Piping and Instrumentation Diagrams (P&IDs).

1.2 Scope This Practice describes the requirements for P&ID format and content. The Practice is independent of time in a facility life cycle and encompasses design, construction, operations, and maintenance.

This Practice covers the generation of new P&IDs and does not apply to the revision of existing P&IDs. This Practice also applies to P&IDs provided by packaged equipment vendors.

This Practice applies to all diagrams that fit the definition of a P&ID in Section 3.

The requirements provided in this Practice can be applied to any CAD system used for developing the P&IDs and are not vendor, hardware, or software specific.

The requirements provided in this Practice provide a balance between showing all data on P&IDs and making P&IDs legible and easy to read. While this Practice is expected to incorporate the majority of requirements of most users, individual applications may involve requirements that will be appended to and take precedence over this Practice. Determinations concerning fitness for purpose and particular matters or application of the Practice to particular project or engineering situations should not be made solely on information contained in these materials.

The example P&IDs included in the Appendixes of this Practice are not intended to recommend specific design details or requirements. Example P&IDs are included to provide an illustration of how the elements of this Practice are combined into a P&ID.

Electronic native files for the text, symbols, and cover sheets are available to PIP Member Companies for input to members’ CAD systems. Development of project-specific cover sheets is recommended using the PIP native files as a starting point. Additions and/or deletions are allowed to meet requirements. Cover sheet borders and title blocks can be altered.

2. References

Applicable parts of the following Practices, industry codes and standards, and references shall be considered an integral part of this Practice. The edition in effect on the date of start of P&ID development shall be used, except as otherwise noted. Short titles are used herein where appropriate.

2.1 Process Industry Practices (PIP) – PIP INEG1000 – Insulation Design and Type Codes – PIP PCCIP001 – Instrument Piping and Tubing Systems Criteria – PIP PCSIP001 – Instrument Piping and Tubing Systems Specifications

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COMPLETE REVISION PIP PIC001 April 2008 Piping and Instrumentation Diagram Documentation Criteria

– PIP PNE00001 – Design of ASME B31.3 Metallic Piping Systems – PIP PNSM0001 – Piping Line Class Designator System

2.2 Industry Codes and Standards

• American National Standards Institute (ANSI) – ANSI/FCI 70-2-2003 – Control Valve Seat Leakage

• American Society of Mechanical Engineers (ASME) – ASME Boiler and Pressure Vessel Code

Section VIII – Pressure Vessels

• The Instrumentation, Systems, and Automation Society (ISA) – ISA 5.1 – Instrumentation Symbols and Identification – ISA 5.2 – Binary Logic Diagrams for Process Operations – ISA 5.3 – Graphic Symbols for Distributed Control / Shared Display

Instrumentation, Logic and Computer Systems – ISA 84.01 – Application of Safety Instrumented Systems for the Process Industries

• Tubular Exchanger Manufacturers Association (TEMA) – TEMA Standards

2.3 Government Regulations

• Occupational Safety and Health Administration (OSHA) – OSHA 29 CFR 1910.119 – Occupational Safety and Health Standards, Process

Safety Management of Highly Hazardous Chemicals

3. Definitions

For the purposes of this Practice, the following definitions apply:

accessible: Term applied to a device or function that can be used or seen by an operator for the purpose of performing control actions (e.g., set point changes, auto-manual transfer, or on/off actions) (Reference ISA 5.1)

automated valve: Any valve with a locally or remotely controlled actuator. Examples are throttling control valves and on/off block valves. Actuators are typically air-operated (diaphragm or piston), electric or hydraulic, some with a spring-return function. Manually-operated valves are sometimes tagged as automated valves (e.g., if a manual valve is fitted with position switches).

auxiliary P&ID: Used to show details to unclutter other P&IDs (e.g., lube oil system, sample systems, instrument details)

Basic Process Control System (BPCS): Control equipment and system installed to regulate normal production functions. It may contain combinations of single-loop pneumatic controllers, single-loop electronic controllers, Programmable Logic Controllers (PLCs), and Distributed Control Systems (DCSs). The BPCS is required to operate the process. Examples of control


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functions included in the BPCS are cascade control, override control, and pump start/stop. Also known as Basic Regulatory Controls. (See also HLCS and SIS)

bubble: Circular symbol used to denote and identify the purpose of an instrument or function. The bubble usually contains a tag number. (Synonym for balloon) (Reference ISA 5.1)

design pressure: Pressure used in the design of a vessel component together with the coincident design metal temperature for determining the minimum permissible thickness or physical characteristics of the different zones of the vessel. (Reference ASME Boiler Pressure Vessel Code, Section VIII, Division 1, Appendix 3)

fail closed (FC): Characteristic of an automated valve that causes the valve to close as a result of specific malfunctions, including loss of signal or motive power. (Reference ISA 5.1)

fail indeterminate (FI): Characteristic of an automated valve that causes the valve to move to an unknown position as a result of specific malfunctions, including loss of signal or motive power. Some automated valves will not stay at the last position upon failure and instead move with the process differential pressure. Additional equipment may be needed to meet the definition of FC, FO, or FL. (Reference ISA 5.1)

fail locked (FL) last position: Characteristic of an automated valve that causes the valve to remain in the last (locked) position as a result of specific malfunctions, including loss of signal or motive power. Automated valves may fail indeterminately without additional equipment. (Reference ISA 5.1)

fail open (FO): Characteristic of an automated valve that causes the valve to open as a result of specific malfunctions, including loss of signal or motive power. (Reference ISA 5.1)

hand switch (HS): Any operator-manipulated discrete control device, including hardwired panel switches and software points.

heat exchanger type: Type designation shall be shell and tube, plate and frame, spiral, etc. For shell and tube exchangers, use the three-letter designation describing stationary head, shell, and rear end or head, in that order, in accordance with TEMA.

Higher Level Control System (HLCS): Provides sophistication above that of the BPCS. The HLCS is not necessary to operate the process. HLCS functions are typically based in process computers or higher level DCS hardware that interacts with the process by manipulating set points in the BPCS. Examples of control functions in the HLCS are statistical process control and model predictive control. (See also BPCS and SIS)

interlock: System that, in response to a predetermined condition, initiates a predefined action. Typically comprised of binary (on/off) signals and logic used for process control, sequencing, or protective interruption of normal process control functions. Protective interlocks are typically further defined as being either safety-related or commercial-related (asset or production protection).

isolation valve: A valve used for isolation of process equipment while performing activities such as purging, de-pressuring or de-inventorying. This valve is also commonly referred to as the primary block valve.

line class: Section of the Piping Material Specifications that provides a listing of piping components for specific design conditions.


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logic solver: Control equipment that performs the logic function. It can be either hardwired (e.g., relays) or Programmable Electronic Systems (e.g., DCS-based or PLC-based, including dual-redundant or triple-redundant microprocessors).

packaged equipment: One or more pieces of equipment furnished by a vendor with supportive devices and components to perform a specific operation as a unit

Piping and Instrumentation Diagram (P&ID): Detailed graphical representation of a process including the hardware and software (i.e., piping, equipment, and instrumentation) necessary to design, construct and operate the facility. Common synonyms for P&IDs include Engineering Flow Diagrams (EFDs), Utility Flow Diagrams (UFDs), and Mechanical Flow Diagrams (MFDs)

Programmable Electronic System (PES): Logic performed by programmable or configurable devices (Reference ISA 84.01)

root valve: First valve or valves between the process and an auxiliary device (e.g., an instrument) that contacts the process and is used to isolate the device from the process. This valve is typically a line class valve used for shut-off and isolation.

Safety Integrity Level (SIL): One of four possible discrete integrity levels (SIL 1, SIL 2, SIL 3, and SIL 4) of Safety Instrumented Systems. SILs are defined in terms of Probability of Failure on Demand (PFD). (Reference ISA 84.01)

Safety Instrumented Systems (SIS): Systems composed of sensors, logic solvers, and final control elements for the purpose of taking the process to a safe state if predetermined conditions are violated. Other terms commonly used include Emergency Shutdown System (ESD or ESS), Safety Shutdown System (SSD), and Safety Interlock System (SIS). (Reference ISA S84.01) (See also BPCS and HLCS)

skirt: Cylindrical supporting structure, welded to the bottom of a vertical vessel and extended to the base support

tagged: For the purposes of labeling instrumentation and control components, a hardware device or a software point that is identified with an ISA style tag number

Tight Shut-Off (TSO): Tight Shut-Off is defined in this Practice as ANSI Class V or ANSI Class VI in accordance with ANSI/FCI 70-2

trim: Item attached to equipment as an integral component, identified as part of the equipment that is exposed to the process, and having a function local to the equipment being served. Examples are vent and drain valves, instrument bridles, blind flanges, plugs, or other miscellaneous items associated with a piece of equipment. Typically, trim is purchased independently from the equipment.

4. Requirements

4.1 General 4.1.1 Most details available from other types of documentation (e.g., instrument loop

diagrams and vessel data sheets) should not be included on P&IDs.


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4.1.2 This Practice uses the concepts of typical details with implied components where appropriate to simplify P&IDs. (See the cover sheet in Appendix B for examples.) Additional examples can be added as required.

4.1.3 While the intent of this Practice is to simplify the P&IDs through the use of implied components and cover sheets, this may not be compatible with the work processes or design software used for a project. Therefore, this Practice does not require the use of implied components. It is the responsibility of the project team to determine the compatibility of implied components with project needs and work processes (e.g., safety reviews, material take-off method, integration plan, etc.).

4.2 Format 4.2.1 Layout

Comment: The layout and orientation statements specified herein are recommended as optimal, and slight deviation, although not encouraged, may be required due to space constraints.

4.2.1.1 Piping Orientation

1. The top of a horizontal line and the left side of a vertical line shall be the top of a pipe.

2. The bottom of a horizontal line and the right side of a vertical line shall be the bottom of a pipe.

3. A note shall be used to clarify the orientation as required.

4.2.1.2 Drawing size shall be 22 inches x 34 inches.

4.2.1.3 Each P&ID shall be laid out to avoid clutter and allow future modifications. No more than three pieces of major equipment shall be shown on a P&ID. A set of pumps in the same service shall be one piece of equipment for the purpose of a P&ID layout in accordance with Appendix C.

4.2.1.4 Flow Orientation

1. Primary flow shall be shown on each P&ID from left to right.

2. Flow-through equipment shall be shown relative to actual arrangement (e.g., cooling water supply in bottom of exchanger tube bundle and cooling water return out top).

4.2.1.5 Primary process lines shall be shown heavier than secondary and utility lines as described in Section 4.2.3.

4.2.1.6 Connector Symbols

1. Off-page and off-plot connectors for primary, secondary, and instrumentation lines shall be shown entering the P&ID horizontally 0.25 inch from the left inside borderline and exiting 0.25 inch horizontally from the right inside borderline in accordance with Appendix C.

2. Utility connectors can be shown at any convenient location on the body of the P&ID.


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4.2.1.7 Utility P&IDs

1. Utility collection/distribution P&IDs shall be laid out relative to plot plan orientation in accordance with Appendix C.

2. To depict plot plan orientation, utility off-page connectors for a utility connection/distribution P&ID may be positioned vertically in accordance with Appendix C.

3. If match lines are required on utility collection/distribution P&IDs, the lines shall match the connecting drawing match lines in accordance with Appendix C.

4.2.1.8 Connector Descriptions

1. Service description, connector number, P&ID number, and origin/destination shall be shown for off-page and off-plot connectors in accordance with Appendix A-3.

2. Origin/destination shall be shown as an equipment number, line number, or loop number.

3. Service description for a piping off-page and off-plot connector shall be shown as name of fluid (e.g., Cracked Gas) or line description (e.g., Reactor Feed, Tower Overhead).

4. Service description for an instrument off-page and off-plot connector shall be shown as a line function (e.g., Low Level Override) or equipment to be controlled (e.g., PV-10014A/B).

5. Text associated with off-page and off-plot connectors on the left side of the P&ID should be left justified; text associated with off-page and off-plot connectors on the right side of a P&ID should be right justified.

4.2.1.9 Equipment arrangement shall be shown relative to its elevation to grade (e.g., pumps at bottom of P&ID) in accordance with Appendix C.

4.2.1.10 A control valve actuator shall be shown above a horizontal line or left of a vertical line.

4.2.1.11 If a control valve identification bubble is required, the center point of the bubble shall be shown 0.5 inch above and 0.5 in away from the actuator in a horizontal line or 0.5 inch to the left and 0.5 inch away from the actuator in a vertical line.

4.2.1.12 The center point of an instrument bubble shall be shown 0.5 inch directly above an in-line instrument in a horizontal line or 0.5 inch directly left of an in-line instrument in a vertical line. Examples are restriction orifices and stand-alone thermowells.

4.2.1.13 Pump and compressor driver piping, instrumentation, and auxiliaries can be shown on a separate, auxiliary P&ID. “Primary” P&ID and auxiliary P&ID shall be cross-referenced.

4.2.1.14 Typical details shall be used if clutter can be eliminated without detracting from clarity. These details shall be shown on the P&ID, on an auxiliary P&ID, or on a cover sheet.


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4.2.4.2 Equipment Information

1. Equipment numbers shall use a text height of 0.16 inch at a weight of 0.03 inch.

2. Equipment numbers shall be underlined.

3. Equipment title and data shall use a text height of 0.1 inch at a weight of 0.02 inch.

4. Equipment text shall be justified at the top and center.

5. Equipment numbers, titles, and data for fixed or static equipment (i.e., exchangers, vessels, tanks, towers, filters, and material handling) shall be shown within 2 inches from the top inside borderline of the P&ID, directly above the equipment, and on the same horizontal plane as other equipment identification.

6. Equipment numbers, titles, and data for rotating equipment (i.e., pumps, blowers, compressors, and agitators) shall be shown within 2 inches from the bottom inside borderline of the P&ID, directly below the equipment, and on the same horizontal plane as other equipment identification.

7. Equipment number, title, and data shall be shown once for identical equipment with the same number, title, and service (e.g., P-601A/B).

4.2.4.3 Line Numbers

1. Line numbers shall be shown in accordance with Appendix A-3. See example shown in Appendix C.

2. Line numbers shall use a text height of 0.1 inch at a weight of 0.02 inch.

3. Line number text shall be placed 0.06 inch from the line and shall be lined up vertically 0.25 inch from the connector.

4. Line numbers at entering off-page and off-plot connectors shall be justified at the top and left.

5. Line numbers at exiting off-page and off-plot connectors shall be justified at the top and right.

6 Line numbering shall be shown with the orientation of the line. 4.2.4.4 Text Arrangement

1. Text shall be shown horizontal if possible.

2. Vertical text shall be placed to the left of supporting graphics if possible.

3. Vertical text shall be read from bottom to top.

4.2.4.5 Abbreviations shall be in accordance with Appendix A-1.

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4.2.4.6 Control Valve Information

1. Control valve failure action abbreviation shall be shown at 0.06 inch directly below the control valve in horizontal lines and 0.06 inch to the right of the control valve in vertical lines. See examples shown in Appendix C.

2. If the valve size is not line size or easily inferred from adjoining pipe, reducers, or equipment, control valve size shall be shown between the actuator and valve body symbol. If necessary, control valve size can be repositioned so as not to be obscured by other items shown on actuator (i.e., position switches, handwheels, etc.). See examples shown in Appendix C.

3. Control valve seat leakage criteria (i.e., tight shut-off [TSO]) shall be shown between the actuator and valve body symbol. If necessary, control valve leakage criteria can be repositioned so as not to be obscured by other items shown on the actuator (i.e., position switches, handwheels, etc.). See examples shown in Appendix C.

4.2.4.7 For PSVs, PSEs, and pressure control valves (PCVs), the device size and set pressure shall be shown close to the identification bubble. See examples shown in Appendix C.

4.3 Equipment 4.3.1 General

4.3.1.1 Equipment Symbols

1. Equipment symbols shall be shown in accordance with Appendix A-2.

2. Equipment shall be shown with simple outline representation.

3. Discretion shall be exercised for equipment symbols to not dominate the drawing, but the symbols shall be drawn large enough for clear understanding.

4. Equipment shall not be drawn to scale.

5. Equipment shall be shown relative to associated equipment both in size and general orientation.

4.3.1.2 Nozzles

1. Nozzles, including spares, shall be shown on equipment as single lines.

2. Manways shall be shown as double lines.

3. Process and utility nozzles may be labeled.

4. Nozzle sizes shall be shown, unless the size is implied by piping connections.

4.3.1.3 Equipment not specifically identified in this Practice shall be shown with an equipment symbol that is a reasonable representation of the equipment as it will exist in the field.

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4.3.1.4 Equipment shall be identified by a classification letter and sequence number. Classifications used in this Practice are shown in Section 4.3.12.

Comment: The classifications shown in Section 4.3.12 are used on the example P&IDs contained in Appendix C for illustrative purposes only. The classifications are only one example of classifications allowed by this Practice.

4.3.1.5 Equipment Item Number and Title/Service shall be shown as a minimum. Section 4.3.13 provides a complete list of equipment data for all equipment addressed in this Practice. For equipment not covered in this Practice, equipment data shall be shown as necessary.

4.3.1.6 Internals for equipment shall be shown as dashed lines as described in Section 4.2.2.2. Details of internals that have no significant bearing on the piping design and layout or equipment operation shall be omitted.

4.3.1.7 Equipment elevations shall not be shown unless the elevations are necessary to specify process requirements for associated equipment location or orientation relative to one another.

4.3.1.8 Associated trim (e.g., vent and drain valves, instrument bridles) for equipment shall be shown.

4.3.1.9 Auxiliary system requirements for individual pieces of equipment (e.g., lube oil systems, seal flush systems, turbine gland leak-off piping, sample systems) shall be shown on auxiliary P&IDs.

4.3.1.10 Jacketing and tracing requirements for equipment shall be shown.

4.3.1.11 The type of insulation (e.g., personnel protection, heat conservation) for equipment shall be shown as part of the equipment data. Insulation thickness shall be shown where applicable.

4.3.2 Agitators 4.3.2.1 The term agitator shall apply to mechanical mixers and aerators.

4.3.2.2 Agitators shall be shown in accordance with Appendix A-2.

4.3.3 Blowers 4.3.3.1 Blower symbols shall be shown as centrifugal or positive displacement

as required.

4.3.3.2 Blowers shall be shown in accordance with Appendix A-2.

4.3.4 Compressors 4.3.4.1 The compressor symbol shall be shown for each stage of multistage

compressors.

4.3.4.2 Multistaged compressors can be shown on multiple P&IDs.

4.3.4.3 Compressors shall be shown in accordance with Appendix A-2.

4.3.5 Drivers 4.3.5.1 Drivers shall be shown with the driven equipment and shall use the

symbols for motors, diesel engines, and turbines.

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Table 1: Equipment Classifications

CLASS SUBJECT DESCRIPTION A Mixing Equipment Agitators, Aerators, Mechanical Mixers

B Blowers Centrifugal Blowers, Positive Displacement Blowers, Fans

C Compressors Centrifugal, Reciprocating, Screw, Vacuum

D Mechanical Drivers Electric and Pneumatic Motors, Diesel Engines, Steam and Gas Turbines

E Heat Exchangers Unfired Heat Exchangers, Condensers, Coolers, Reboilers, Vaporizers and Heating Coils, Double Pipe, Spiral, Plate & Frame, Air Coolers

F Furnaces Fired Heaters, Furnaces, Boilers, Kilns

P Pumps Horizontal and Vertical Centrifugal, Positive Displacement, Vertical Canned, Screw, Gear, Sump

R Reactors

T Towers / Columns

TK Tanks API atmospheric and low pressure

U Miscellaneous Equipment

Filters, Bins, Silos

V Vessels Separators, Driers, Accumulators, Drums

4.3.13 Equipment Data

The following equipment information shall be shown on the P&ID in relation to the appropriate equipment symbol and in accordance with Section 4.2.4.2: 4.3.13.1 Agitators, Mixers

• Equipment/Item Number • Title/Service • Power Requirements • Materials of Construction

4.3.13.2 Blowers

• Equipment/Item Number • Title/Service • Capacity (Flow and D/P) • Power Requirements • Materials of Construction

4.3.13.3 Compressors

• Equipment/Item Number • Title/Service • Capacity (Flow and D/P)


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4.5 Instrumentation and Controls 4.5.1 Symbols

4.5.1.1 Instrument and control symbols shall be shown in accordance with Appendix A-4. (Reference ISA-5.1 for additional details)

4.5.1.2 The conventions established by ISA-5.1 shall be followed for tagging and numbering of instrument and control devices. (Reference Appendix A-4)

Comment: The tagging and numbering scheme described in the following example is used on the example P&IDs contained in the Appendixes for illustrative purposes only. This example tagging and numbering scheme is only one example of tagging and numbering schemes described in this Practice. The tagging structure is shown in the following example:

01 FC 100 01

01 – Plant Number (shall not appear on P&IDs or in a bubble)

FC – Function Identifier (e.g., Flow Controller)

100 – Equipment (or P&ID) Number (optional)

01 – Loop Sequence Number.

Breaks in the instrument bubble may be used to accommodate longer tag numbers.

4.5.1.3 All measurement types shall be identified by an ISA symbol.

4.5.1.4 If necessary, a descriptive text label may be added (e.g., analysis components like CO, H2, CH4, or unique flow measurement devices like “Mass”).

4.5.1.5 Interlock symbols shall be depicted as follows:

a. For discrete, hardware-based interlocks, the conventional diamond symbol shall be used in accordance with ISA-5.1 and ISA-5.2.

b. For PLC-based interlocks, the diamond-in-a-box symbol shall be used in accordance with ISA-5.1 and ISA-5.2.

c. For DCS-based interlocks, the DCS symbol (bubble-in-a-box) shall be used.

d. For PLCs integral to the DCS, the PLC symbol (diamond-in-a-box) shall be used.

Comment: Reference Appendix A-4 and Section 4.5.6 for additional information.

4.5.1.6 Directional arrows on instrumentation signal lines shall be used only if the function is not obvious (e.g., cascades, selectors, interlocks).

4.5.1.7 Instrument function symbols, shown in Appendix A-4, shall be used to clarify the function of certain tagged instrument bubbles. The symbol shall be placed outside the bubble at the upper right.


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3. The symbols shown in Appendix A-4 shall be used for pressure and temperature regulators.

4.5.3.2 Automated Valves

1. Automated valve fail actions shall be shown with text (FC/FO/FL/FI) in accordance with ISA-5.1. (Reference Section 4.2.4.6)

Comment: Using stem arrows as outlined in ISA-5.1 is not recommended.

2. For multi-port automated valves, FL and FI shall be used where appropriate.

Comment: FO and FC shall not be used; instead, arrows shall be used to show fail position flow paths. Note that multiple arrows may be required.

3. Valves with different fail actions for loss of signal and for loss of motive power require an explanatory note.

4. Valve body sizes shall be shown for all automated valves if not line sized or otherwise implied. (Reference Section 4.2.4.6)

5. Automated valve specifications or commodity codes shall not be shown.

6. For automated valves, tight shut-off requirements shall be identified by using the abbreviation “TSO.” (Reference Section 4.2.4.6)

Comment: TSO defines the seat shut-off requirements for a new valve. Testing requirements, if any, are defined in other unit operation documents.

4.5.3.3 Identifying Tags

1. Valve identifying tags with bubbles shall not be shown if the associated loop tag is readily apparent.

2. An identifying tag with a bubble shall be shown for split range valves, self-contained regulators, or valves located on a separate P&ID from its controller. (Reference Section 4.2.1.6)

4.5.3.4 The ranges (e.g., 0-50%, 50-100%) shall be shown for split range control valves.

Comment: The preferred labeling is controller percentage output because it applies to both pneumatic and electronic systems.

4.5.3.5 Valve positioners shall not be shown unless necessary to clarify loop operation (e.g., if used with trip solenoids or pneumatic trip relays).

Comment: If shown, valve positioners are normally included with the automated valve symbol and are not tagged.


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4.5.6 Interlocks and Alarms 4.5.6.1 Interlocks shall be shown only symbolically on the P&ID.

4.5.6.2 The functional definition shall be shown on auxiliary documents (e.g., binary logic diagrams, descriptive narratives, truth tables).

Comment: Interlocks can be designed for a variety of functions, from simple process sequences to complex safety shutdown systems. A variety of hardware can be used for implementation (e.g., DCS, PLC, relays, redundant, fault-tolerant Safety Interlock Systems).

Alarms can be similarly designed in a variety of ways. Alarms come from hardware, over serial links, from DCS software and can be shown on a variety of facility documents, including P&IDs, alarm summaries, logic and loop diagrams, and operating procedures.

Because of this variety, along with individual owner interpretations of the requirements of OSHA 1910.119 and ISA -84.01, many documentation aspects of interlock and alarm system design should be defined by the owner.

4.5.6.3 Logic functions or interlocks shall be shown with the proper symbols in accordance with Section 4.5.1.

4.5.6.4 Binary logic gates, input/output tables, or descriptive narratives shall not be shown.

4.5.6.5 All logic function and interlock symbols shall contain an identification that provides reference to a unique logic diagram, narrative, truth table, or program. The reference shall be located within the interior of the symbol. The format of the reference shall be determined by the owner. Descriptive text or a note reference can be placed outside the symbol.

4.5.6.6 If Safety Instrumented Systems (SIS) are distinguished from other interlock systems, the preferred method shall be to add an “S” prefix to the unique interlock identification.

4.5.6.7 Each interlock shall be uniquely labeled, using a serial (not parallel) tagging scheme. The “S” prefix shall not be used to distinguish a unique interlock label.

Comment: A valid tagging scheme shall be I-100, I-101, SI-200, SI-201. The scheme I-100, SI-100 should not be used.

4.5.6.8 The type of logic solver hardware or level of redundancy shall not be shown except through the normal use of ISA symbols and the input and output signals described in Section 4.5.1 and the Appendixes.

4.5.6.9 Classifications or Safety Integrity Levels (SIL) shall not be shown for interlocks.

4.5.6.10 All operator-initiated interlock trip and reset hand switches shall be shown.


SAMPLE

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4.5.6.11 If used, all bypass hand switches for SIS interlocks shall be shown, including all individual initiator and system bypass switches.

Comment: Unnecessary clutter can be avoided by use of a table or reference note if large numbers of bypasses are necessary.

4.5.6.12 All hardwired alarms shall be shown.

4.5.6.13 All alarms that require engineering or other review and approval based on safety or operability shall be shown.

4.5.6.14 Hardware-based diagnostic alarms shall be shown.

4.5.6.15 Software-based diagnostic alarms shall be shown only if safety or operationally related (e.g., defined in safety reviews).

Comment: Measurement out-of-range alarms are an example of software diagnostic alarms not generally shown.

4.5.6.16 Required alarms shall be shown with tag and level (e.g., PAH), but alarm trip points or settings shall not be shown.

4.5.6.17 For alarms based on analog measurements, the functional tag (e.g., PI) shall be shown inside the bubble and the alarm levels shall be shown outside the bubble.

4.5.6.18 High alarms (e.g., H, HH) shall be placed at the upper right outside the bubble, and low alarms (e.g., L, LL) shall be placed at the lower right outside the bubble.

Comment: The alarm modifier (A) should not be shown.

4.5.6.19 For discrete alarm points (on/off signals), the complete functional tag and alarm level (e.g., PAH) shall be shown inside the bubble.

4.5.6.20 Standard ISA-5.1 abbreviations shall be used for both trip and alarm functions (e.g., LSHH and LAHH).

4.5.7 DCS Points 4.5.7.1 A DCS point shall be shown if operations manipulates the process with it

or receives information from it, or if the point is essential to understanding the functional operation of the process controls.

Comment: It is not necessary for every point configured in a DCS to be shown. It is not necessary for implied functions (e.g., I for indicate, R for recorder) to be included in every DCS point tag.

It is not the intent of this section to define which DCS points to show for every supplier of a DCS or each type of system that can communicate with a DCS via a software link (e.g., analyzer data highways, anti-surge control systems, vibration monitoring systems, Safety Instrumented Systems, PLCs, tank gauging systems).


SAMPLE

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Appendixes Summary

The Appendixes of this Practice contain tables of commonly used symbols, abbreviations and other identifiers; typical details; and example P&IDs.

Appendix A contains symbols and text grouped by function. The symbols and text are shown the same size as would be utilized for a standard, full-size (22 inches x 34 inches) P&ID.

Appendix B contains the same data as Appendix A, organized into cover sheets. Cover sheets are also commonly referred to as lead sheets or legend sheets.

Appendix C contains example P&IDs that illustrate the text and utilize the symbols and legends on the cover sheets.

Comment: The cover sheets and P&IDs are drawn as standard, full-size (22 inches x 34 inches) P&IDs, but reduced to standard 8-1/2 inch x 11-inch pages for electronic distribution purposes. It is recommended that the cover sheets and P&IDs be printed on 11-inch x 17-inch pages.

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Appendix A – Tables and Symbols A-1 Format Tables and Symbols

1. Abbreviations 2. Miscellaneous Symbols

A-2 Equipment Tables and Symbols 1. Pumps 2. Compressors and Blowers 3. Drivers and Agitator/Mixer 4. TEMA Type Exchangers 5. Miscellaneous Exchangers 6. Storage Tanks 7. Storage Tanks 8. Storage Sphere and Furnace 9. Miscellaneous Vessel Details

10. Jacketed Pressure Vessels A-3 Piping Tables and Symbols

1. Line Data Identification 2. Line Service Codes 3. Piping Line Symbols 4. Valve Symbols 5. Piping Specialty Items 6. Piping Fittings 7. Connectors and Tie-In Symbol 8. Drain Connectors 9. Notes

A-4 Instruments & Controls Tables and Symbols 1. Instrument Identification Letters 2. General Instrument Symbols 3. Instrument Function Symbols 4. Instrument Line Symbols 5. Primary Element Symbols (Flow) 6. Control Valve Actuator Symbols 7. Self-Actuated Devices 8. Miscellaneous Instrument Symbols

Process Industry Practices Page A-1

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SAMPLE

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Appendix B – Cover Sheets

B-1: Symbols and Nomenclature – Typical Piping B-2: Symbols and Nomenclature – Typical Instrumentation B-3: Symbols and Nomenclature – Typical Equipment B-4: Typical Details with Implied Components

Note: The example cover sheets in this Appendix are not all-inclusive of the potential uses of implied components. The implied component examples shown do not cover all actual occurrences or design possibilities for instrument assemblies, such as the level bridles shown. The user must ensure that the cover sheets capture their piping/instrument requirements for their use of implied components. There are many more systems that may require a cover sheet explanation to show the implied components – pump seals, sampling systems, analyzer systems for example, as well as other types of level systems than those shown here.

Process Industry Practices Page B-1

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SAMPLE

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Appendix C – Example P&IDs C-1: Example P&ID 1 C-2: Example P&ID 2 C-3: Example Utility P&ID

Note: The examples shown on the sample P&IDs in this Appendix are not all-inclusive of the potential uses of implied components. The user must ensure that the cover sheets capture their piping/instrument requirements for their use of implied components. There are many more systems that may require a cover sheet explanation to show the implied components – pump seals, sampling systems, analyzer systems for example, as well as other types of level systems than those shown here.

Process Industry Practices Page C-1

SAMPLE

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SAMPLE

NOT FOR

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SE

BASKET STRAINER

FLAME ARRESTOR

ANGLE VALVE

ANGLE BALL VALVE

ANGLE CHOKE VALVE

ANGLE CONTROL VALVE

THREE WAY VALVE

THREE WAY CONTROL VALVE

CONTINUOUS DRAIN

VANES CONTROL VALVE

HAND OPER. VANES VALVE

EXPANSION JOINT

SILENCER

OPEN DECK DRAIN

SAMPLE POINT

DIAPHRAGM SEAL

REMOTE TERMINAL UNIT

RUPTURE DISC

SCRAPPER TEE/SPHERE REE

SPECIALITY ITEM

FLEXIBLE HOSE

SS

PROCESS/UTILITY LINE

ELECTRICAL LINE

INSTRUMENT GAS/

ELECTRICAL TRACED LINE

CAPILLARY LINE

VENDOR LIMIT LINE

CENTER LINE

HYDRAULIC LINE

FUTURE

SS TUBING (PROCESS)

SCOPE OF WORK/LINE RATING

CHANGE (WITH PIPING SPEC.

M

B

S

M

JOHANNUS MINORE HOC FAECIT

JOHANNUS MINORE HOC FAECIT

S

RTU

NC

LC/LO

LO/LC

I

PSV

101

203

24

INLET SIZE, INCHES

ORIFICE CODE LETTER

OUTLET SIZE, INCHES

INSTR.

PIPING

1/2"

INSTR.

PIPING

PIPI

PI11.1

(TYPICAL FOR PI,PT,PIC,PSH,PSL,PSHL)

TAKE OFF CONNECTIONS- PIPING : 3/4", VESSELS : 1.5" FLANGED

ALL DIAPHRAGM SEAL TYPE INSTR. TO HAVE 1.5" FLANGED TAPPING.

3/4"

*PIPI

LO3/4"

1/2

"

3/4

"

3/4

"1/2

"

3/4"

PIPI

INSTR. PIPING

PDI PDI

1/2"

1/2"

INS

TR

.

PIP

ING

MANIFOLD(PER SPECS.)

(TYPICAL FOR PDI,PDT,PDSH,PDSL,PDSHL)

TAKE OF CONNECTION-PIPING : 3/4", VESSELS : 1.5" FLANGED

11.2

11.3

LINES IDENTIFICATION

LINES PIPING SYMBOLS NOTES:- GENERAL

CENTRAL CONTROL PANEL

1-1/2"

LO

A

RAIN CAP

SHUT DOWN

NORMALY LOCK OPEN INTERCHANGABLE TO LC

NORMALY LOCK CLOSE INTERCHANGABLE TO LO

ESD/FSD VALVES

NORMALY CLOSED

NORMALLY OPENNO

ST

BURIED

STEAM TRAP

UNION

INSULATION JOINT

ADAPTER (TUBING PIPE)

FLOW ELEMENT ORIFICE/

TURBINE METER

POSITIVE DISPLACEMENT METER

ROTAMETER

SONIC METER

ELECTRIC MOTOR

PILOT TUBE

VENTURI METER

DRAIN PLUGGED

DRAIN FLANGED

STRAIGHTENING VANE (FLANGED)

ANALYSER

FILTER

CAP (THREADED)

BLIND FLANGE

CAP (WELDED)

HOSE CONNECTION

OFF/ON SKID OR SHOP FABRICATED

T-TYPE STRAINER

Y-TYPE STRAINER

FUSIBLE PLUG

1/2

"

L L L L

1. HIGH POINT VENT AND LOW POINT DRAIN NOT SHOWN ON P&ID SHALL BE SHOWN ON PIPING

ISOMETRIC / GENERAL ARRANGEMENT DRAWINGS .

2. ALL SAFETY VALVES DISCHARGE & EQUIPMENT DEPRESSURIZING LINES SHALL BE FREE DRAINING

TO VENT HEADER AND HAVE NO POCKETS UPTO AND INCLUDING HEADERS.

3. ALL ISOLATION VALVES IN TAPPINGS OF INSTRUMENTS (SUCH AS PRESSURE, LEVEL AND FLOW

SWITCHES) CAUSING SHUTDOWN SHALL BE LOCKED OPEN.

4. LINE NUMBERS SHALL BE INDICATED AS PER LINE LEGEND.

11. INSTRUMENT ISOLATION VALVES SHALL BE AS PER DETAILS GIVEN BELOW. ALL VALVES SHALL

BE AS PER APPROPRIATE PIPING/INST. SPECS. DIAPHRAGM SEAL ALSO AS PER SPECS. ALL TAKE

OFF CONNECTIONS SHALL BE SW (SOCKET WELD) UNLESS OTHERWISE SPEIFIED.

o o o

X X X

GATE VALVE

GLOBE VALVE

CHECK VALVE

BUTTERFLY VALVE

PLUG VALVE

BALL VALVE

NEEDLE VALVE

SPRING LOADED VALVE

DIAPHRAGM VALVE

CONTROL VALVE

CONTROL VALVE WITH HAND WHEEL

SELF ACTUATED PCV (DOWN STREAM)

SELF ACTUATED PCV (UP STREAM)

HAND OPERATED VALVE

PISTON OPERATED VALVE

MOTOR OPERATED VALVE

SHUT DOWN VALVE

BALL CONTROL VALVE

BUTTERFLY CONTROL VALVE

PILOT VALVE (XPV)

SLOPE(DOWN WARD)

HAMMER BLIND

SPECTACLE BLIND

FLANGE

REDUCER/EXPANDER

LOCALLY MOUNTED

LOCAL PURGED

PANEL MOUNTED /

LOCAL,PANEL MOUNTED

BACK PANEL MOUNTED

BACK LOCAL PANEL

COMPUTER FUNCTION

COMPUTER LOCAL PANEL

DCS/DIDC

FUNCTION BLOCK

INTERLOCK

RUNNING LIGHT,LOCAL

RUNNING LIGHT,PANEL

RUNNING LIGHT,LOCAL PANEL

SOLENOID VALVE(2 WAY)

SOLENOID VALVE(3 WAY)

POSITIVE CHOKE

ADJUSTABLE CHOKE

CONTROL VALVE W/POSITIONER

FOUR WAY VALVE

QUICK EXHAUST VALVE

DESIGNATION)

PNEUMATIC LINE

N2 NITROGRN CATRIDGE

I SENIOR ORIFICE

RESTRICTION ORIFICE

TEMPORARY STRAINERTS

(WITH LIQUID SEAL)

SET PR, KG/CM2G

6. DRAINS OF LEVEL INSTRUMENTS (NON-SOUR SERVICES) SHALL BE PIPED TO NEAREST DECK

DRAIN FUNNEL WITH 1/2" TUBE PIPE.

5. ALL INSTRUMENTS SHALL BE PROVIDED WITH ISOLATION VALVES FOR MAINTENANCE PURPOSE.

PUMPS IN SOUR SERVICE SHALL BE PIPED TO CLOSED DRAIN HEADER RESPECTIVELY.

BE PIPED WITH VALVE TO NEAREST DECK DRAIN FUNNEL. CASING DRAINS AND VENT FOR

7. FOR PUMPS HANDLING SWEET LIQUID, CASING VENTS, DRAINS AND BASE PLATE DRAINS SHALL

DISSIMILAR MATERIALS.

8. PROTECTION AGAINST GALVANIC CORROSION TO BE PROVIDED WHEREVER REQUIRED BETWEEN

9. ALL VENT GAS PIPING SHALL BE FREE DRAINING WITH NO POCKETS.

THE PIPE. WELL FLUID SAMPLES SHALL BE TAKEN FROM VERTICAL PORTION OF THE PIPE. ALL GAS

10. ALL LIQUID SAMPLE POINTS EXCEPT FOR WELL FLUID SAMPLES SHALL BE TAKEN FROM CENTER OF

SAMPLES SHALL BE TAKEN FROM TOP OF THE PIPE.

SP

IT SHOULD BE ENSURED THAT THESE VALVES SHALL BE EASILY ACCESSIBLE.

1/2"

INSTR.

VORTEX FLOW METER

765432

A

B

C

D

E

F

NOTES

FLOW SHEET & INSTRUMENT LEGEND

PIPING & INSTRUMENTATION DIAGRAM (P&ID)

DRAWING NO.- 0REV.

ISSUE

ISSUED FOR BID

OIL AND NATURAL GAS CORPORATION LTD.

OFFSHORE DESIGN SECTION, E & C DIVISION

MR, MUMBAI

28.02.06

DATE

0

NO. APPR.BY CHD

RVG SG

DEVELOPMENT OF C-SERIES STRUCTURE

7045-OD-1002

brighter tomorrowmaking

Process Diagrams

OBJECTIVESAfter studying this chapter, the student will be able to:

• Review process diagram symbols.

• Describe the use of process diagrams and the information they contain.

• Draw a process flow diagram.

• Draw a process and instrument drawing.

• Describe the various process equipment relationships.

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Key TermsElectrical drawings—symbols and diagrams that depict an electrical process.

Elevation drawings—a graphical representation that shows the location of process equipment inrelation to existing structures and ground level.

Equipment location drawings—show the exact floor plan for location of equipment in relation tothe plan’s physical boundaries.

Flow diagram—a simplified sketch that uses symbols to identify instruments and vessels and todescribe the primary flow path through a unit.

Foundation drawings—concrete, wire mesh, and steel specifications that identify width, depth,and thickness of footings, support beams, and foundation.

Legends—a document used to define symbols, abbreviations, prefixes, and specialized equipment.

Process and instrument drawing (P&ID)—a complex diagram that uses process symbols todescribe a process unit; also called piping and instrumentation drawing.

Chapter 12 ● Process Diagrams

252

Types of Process Diagrams

Process diagrams can be broken down into two major categories: processflow diagrams (PFDs) and process and instrument drawings (P&IDs),sometimes called piping and instrumentation drawings. A flow diagram is asimple illustration that uses process symbols to describe the primary flowpath through a unit. A process flow diagram provides a quick snapshot ofthe operating unit. Flow diagrams include all primary equipment and flows.A technician can use this document to trace the primary flow of chemicalsthrough the unit. Secondary or minor flows are not included. Complex con-trol loops and instrumentation are not included. The flow diagram is usedfor visitor information and new employee training.

A process and instrument drawing is more complex. The P&ID includes agraphic representation of the equipment, piping, and instrumentation. Mod-ern process control can be clearly inserted into the drawing to provide aprocess technician with a complete picture of electronic and instrumentsystems. Process operators can look at their process and see how the en-gineering department has automated the unit. Pressure, temperature, flow,and level control loops are all included on the unit P&ID.

Basic Instrument Symbols

Process technicians use P&IDs to identify all of the equipment, instru-ments, and piping found in their units. New technicians use these drawings

30678_12_ch12_p251-270.qxd 06/09/2006 11:14 Page 252

Basic Instrument Symbols

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GlobeValve

GateValve

Reboiler

Three-WayValve

Check Valve

Shell & Tube Heat Exchanger

BleederValves

PneumaticOperated

CentrifugalPumps

RotaryCompressor

ManualOperated

Valve

Gauge

VacuumPumpReciprocating

Compressor

Turbine

Orifice

PneumaticOperated

Butterfly Valve

Compressor &Silencers

Single PassHeat Exchanger

U-TubeHeat Exchanger

SafetyPSV

Butterfly

Ball

SolenoidValve

CLOSED

S

VALVES

PUMPS & TURBINECOMPRESSORS

HEAT EXCHANGERS

Bin

Tank

Tower

Drum or Condenser

Mixer

Mixing Reactor

Minor Process

Pneumatic

Hydraulic

Capillary Tubing

Electromagnetic Signal

Electric

X X X X XX

L L L

VESSELS

Furnace

Liquid RingCompressor

Hairpin Exchanger

CondenserHeater

Centrifugal Compressor

Towerwith Packing

Centrifugal Compressor(Turbine Driven)

T

Gear Pump

Vertical

Screw Pump

Rotameter

Four-WayNeedle Angle

LINE SYMBOLS

Major Process

Future Equipment

Plug

Diaphragm

M

H

Hydraulic BackPressureRegulator

BackPressureRegulator

MotorReliefPRV

Induced-Draft Cooling Tower

Forced-Draft Cooling Tower Flow Indicator

Flow Transmitter

Flow Recorder

Pressure Indicator

Pressure Transmitter

Pressure Recording Controller

FI

FT

FR

PI

PT

PRC

Temp Indicator

Temp Transmitter

Temp Recorder

Level Indicator

Level Transmitter

Level Controller

TI

TT

TR

LI

LT

LC

Figure 12.1a Process and Instrument Symbols

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during their initial training period. Knowing and recognizing these symbolsis important for a new technician.The chemical processing industry has as-signed a symbol for each type of valve, pump, compressor, steam turbine,heat exchanger, cooling tower, basic instrumentation, reactor, distillationcolumn, furnace, and boiler (Figure 12.1). There are symbols to representmajor and minor process lines and pneumatic, hydraulic, or electric lines,and there is a wide variety of electrical symbols.

Flow Diagrams

New technicians are required to study a simple flow diagram of their as-signed operating system. Process flow diagrams typically include the majorequipment and piping path the process takes through the unit. As operatorslearn more about symbols and diagrams, they graduate to the much morecomplex P&IDs.


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MASTER ➁

Flow Indicator

Flow Transmitter

Flow Recorder

Pressure Indicator


FI

FT

FR

PI

PT

Temp Indicator

Temp Transmitter

Temp Recorder

Level Indicator

Level Transmitter

Level Controller

TI

TT

TR

LI

LT

LC

F I C

55

Variable BeingMeasured

Remote Location(board mounted)Control Loop

Instrument

Remote Location(behind control panel)

Field Mounted

LR Level Recorder

TC Temp Controller

PR Pressure Recorder

Pressure ControllerPC

65 55

5565

65 55

Flow ControllerFC

PIC

PRC

LA

105

40

25

IP

Transducer

Pressure IndicatingController

Pressure RecordingController

Level Alarm

FE Flow Element

TE Temperature Element

LG Level Gauge

AT Analyzer Transmitter

What It Does

Figure 12.1b Process and Instrument Symbols (continued)

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Some symbols are common among plants; others differ from plant to plant.Some standardization of process symbols and diagrams is taking place.The symbols used in this chapter reflect a wide variety of petrochemicaland refinery operations.

Figure 12.2 is a PFD that shows the basic relationships and flow pathsfound in a process unit. It is easier to understand a simple flow diagram if itis broken down into sections: feed, preheating, the process, and the finalproducts. This simple left-to-right approach allows a technician to identifywhere the process starts and where it will eventually end. The feed sectionincludes the feed tanks, mixers, piping, and valves. In the second step, theprocess flow is gradually heated for processing. This section includes heatexchangers and furnaces. In the third section, the process is included. Typ-ical examples found in the process section could include distillationcolumns or reactors.The process area is a complex collection of equipmentthat works together to produce products that will be sent to the final section.

Flow Diagrams

255

MASTER ➁

Furnace

Feed Tank

Bottoms Tank

Boiler

Cooling Tower

Reactors

ProductTank

2

ProductTank

1

Vacuum Pump

Column

Drum

Figure 12.2 Process Flow Diagram (PFD)

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Process and Instrument Drawings

A P&ID is a complex representation of the various units found in a plant(Figure 12.3). It is used by people in a variety of crafts. The primary usersof the document after plant startup are process technicians and instrumentand electrical, mechanical, safety, and engineering personnel.

In order to read a P&ID, the technician needs an understanding of theequipment, instrumentation, and technology. The next step in using a P&IDis to memorize your plant’s process symbol list. This information can befound on the process legend. Process and instrument drawings have a va-riety of elements, including flow diagrams, equipment locations, elevationplans, electrical layouts, loop diagrams, title blocks and legends, and foun-dation drawings. The entire P&ID provides a three-dimensional look at thevarious operating units in a plant.

Process LegendThe process legend (Figure 12.4) provides the information needed to inter-pret and read the P&ID. Process legends are found at the front of the P&ID.The legend includes information about piping, instrument and equipment


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MASTER ➁

F-105

Tk-10

Tk-16

B-105

CT-105

Rx-105C-105

FCV

I/P

TT TC

I/P

PT

PC

PCV

I/P

LT

LC

I/P

I/PLT LC

TE TT TC I/P

P-10

P-11

Rx-106

P-12

V-1

D-105

Tk-12

Tk-14

P-13

P-14

V-2 V-3

V-4

V-5

V-6

EX-105

V-7

P-15

FT

FC

Figure 12.3 Process and Instrument Diagram (P&ID)

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257

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GlobeValve

GateValve

Three-WayValve

BleederValves

ManualOperated

Valve

Gauge

Orifice

SAFETY (Gases)

Ball

Solenoid ValveCLOSED

S

Rotameter

Four-Way

Angle Plug

Diaphragm

Butterfly

CheckValve

ReliefValve

Pneumatic

Pneumatic

Pinch Valve

Stop Check

Knife Valve INDUCED DRAFTCrossflow

NATURAL DRAFTCounterflow

FURNACE

BOILER

VacuumPump

Centrifugal

Drum

GearPump Positive

Displacement

Dome RoofTank

Sphere

Rotary ScrewCompressor

Progressive Cavity

Screw Pump

ReciprocatingPump

Sump Pump

Horizontal

Vertical

Internal FloatingRoof Tank

Cone RoofTank

Plate and FrameHeat Exchanger

Air Cooled Exchanger(Louvers Optional)

Double-PipeHeat Exchanger

CC

Spiral Heat Exchanger

Condenser

Heater

SinglePass

Chimney

Two Pass

Draw Off

GenericTray

Demister

SprayNozzle

PackedSection

Manway

VortexBreaker

VALVE SYMBOLS

EQUIPMENT SYMBOLS

Minor Process

Pneumatic

Hydraulic

Capillary Tubing

Electromagnetic, SonicOptical, Nuclear

X X X X

L L L

Major ProcessFuture Equipment

Connecting Line

Non-Connecting Line

Non-Connecting Line

Jacketed or Double Containment

Mechanical Link

Software or Data Link

• • • •

Electric

Flow Indicator

Flow Transmitter

Flow Recorder

Pressure Indicator


FI

FT

FR

PI

PT

Temp. Indicator

Temp. Transmitter

Temp. Recorder

Level Indicator

Level Transmitter

Level Controller

TI

TT

TR

LI

LT

LC

LR Level Recorder

TC Temp. Controller

PR Pressure Recorder

Pressure ControllerPC

65 55

5565

65 55

Flow ControllerFC

PIC

PRC

LA

105

40

25

IP

Transducer

Pressure IndicatingController

Pressure RecordingController

Level Alarm

FE Flow Element

TE Temperature Element

LG Level Gauge

AT Analyzer Transmitter

APPROVED

GENERAL LEGEND

DRAWING NUMBER

REVISION 1

PC

E

DATE 10-6-99

PAGE 1 OF 30

OO6543

DISTILLATION UNIT

LINE SYMBOLSEQUIPMENT CONT.

INSTRUMENT SYMBOLS

PREFIXES ABBREVIATIONSCW- cooling waterMU- makeupFW- feed waterSE- sewer

RX- reactorUT- utilitiesCA- chemical additionIA- instrument air

D- drumC- columnCT- cooling tower

TK-tankF- furnaceEX- exchanger

P- pumpV- valve

Figure 12.4 Process Legend

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symbols, abbreviations, unit name, drawing number, revision number,approvals, and company prefixes. Because symbol and diagram standard-ization is not complete, many companies use their own symbols in unitdrawings. Unique and unusual equipment will also require a modified sym-bols file.

Foundation DrawingThe construction crew pouring the footers, beams, and foundation usesfoundation drawings (Figure 12.5). Concrete and steel specifications aredesigned to support equipment, integrate underground piping, and providesupport for exterior and interior walls. Process technicians do not typicallyuse foundation drawings, but these drawings are useful when questionsarise about piping that disappears under the ground and when new equip-ment is being added.

Elevation DrawingElevation drawings (Figure 12.6) show the location of process equipmentin relation to existing structures and ground level. In a multistory structure,the elevation drawing provides the technician with information about


258

MASTER ➁

N

WE

S

64' 0"

28' 0"

28' 0"

6' 0"

8' 0"

10' 0"

6-8-10 Method

2' x 64' x 18"Load-Bearing

Beam

18"4"

12"

Estimating Materials: cu. yds. = width x length x thickness

27

Remesh RemeshOver Plastic

Remesh

Rebar in All Beams

32' 0"

90

Figure 12.5 Foundation

30678_12_ch12_p251-270.qxd 06/09/2006 11:14 Page 258

equipment location.This information is important for making rounds, check-ing equipment, developing checklists, catching samples, and performingstartups and shutdowns.

Electrical DrawingElectrical drawings (Figure 12.7) include symbols and diagrams that de-pict an electrical system. Electrical drawings show unit electricians wherepower transmission lines run and places where power is stepped down orup for operational purposes.

A process technician typically traces power to the unit from a motor controlcenter (MCC). The primary components of an electrical system are theMCC, motors, transformers, breakers, fuses, switchgears, starters, andswitches. Specific safety rules are attached to the operation of electricalsystems. The primary safety system is the isolation of hazardous energy“lock-out, tag-out.” Process technicians are required to have training in thisarea. Figure 12.7 shows the basic symbols and flow path associated withan electrical drawing. Electrical lines are typically run in cable trays toswitches, motors, ammeters, substations, and control rooms.

A transformer is a device used by industry to convert high voltage to lowvoltage. The electric department always handles problems with transform-ers. Electric breakers are designed to interrupt current flow if design condi-tions are exceeded. Breakers are not switches and should not be turned on


259

MASTER ➁

EL 16' 0"

EL28' 0"

EL-40' 0"

TK-105

RX-105

TK-200

TK-300

RX-106

RX-300 C-300

D-56

Figure 12.6Elevation Drawing

30678_12_ch12_p251-270.qxd 06/09/2006 11:14 Page 259


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V Voltmeter: measures voltage Vs Voltmeter Switch

27

Power Transformer: reduces high voltage

Potential Transforming Symbol

Under Voltage Relay

M Motor MCC Motor Control Center

Switch

Fuse

Circuit Breaker: a protective devicethat interrupts current flow through anelectric circuit

A

As

50

51

Ammeter: measures electric current Ammeter switch

Transformer Overcurrent Relay (Instantaneous)

Transformer Overcurrent Relay (Time delay)

Motor Circuit Contacts

Current Transformer: reduces high voltage to instrumentation.

BOILERSteamTurbine

Generator

69,000 Volts

69 KV

13,200 V13, 800 V2,300 V

13.2 KV13.8 KV2.3 KV

OnOff

Motor

2.3 KV or480 Volts

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MAINTRANSFORMER

As

A

27

V

Vs

MCC #1

480V BUS MAIN POWER DISTRIBUTION

ELECTRIC POWER PLANT

M M

MotorStarter

MotorStarter

Figure 12.7 Electrical Drawing

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or off. If a tripping problem occurs, the technician should call for an electri-cian. Fuses are devices designed to protect equipment from excess cur-rent. A thin strip of metal will melt if design specifications are exceeded.During operational rounds, technicians check the ammeters inside theMCC for current flow to their electrical systems. Voltmeters, electricaldevices used to monitor voltage in an electrical system, are also checkedduring routine rounds.

Equipment Location DrawingEquipment location drawings (plot plans) show the exact location ofequipment in relation to the plant’s physical boundaries (Figure 12.8). Oneof the most difficult concepts to explain to a new process technician is thescope and size of modern chemical processing. Most chemical plants andrefineries closely resemble small cities; they have well-defined blocks andareas connected by a highway of piping and equipment. Equipment loca-tion drawings provide information about the neighborhood.

Loop DiagramsA loop diagram traces all instrument connections between the field instru-ment and the control room panel. This includes instrument air lines, wiringconnections at field junction boxes, and control room panels and frontconnections.

Electrical One-Line DiagramsLike the piping in process systems, the wiring in a unit follows a path. Electri-cal diagrams show a flow path for distributing power throughout the unit and


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TK-100TK-100

P-100P-200

P-300P-400

D-200

P-500A

EX-200

EX-202

TK-1 TK-2

TK-3 TK-4

TK-1 TK-2

TK-3 TK-4

P-201

20' 0"

10' 0

"

20' 0

"

18' 0" 8' 0"

20' 0

"

8' 0

"

6' 0

"

18' 0"

8' 0"

16' 0"

20' 0"

C-200C-200

TK-200TK-200

TK-400TK-400TK-300TK-300

Figure 12.8Equipment Location

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to all electrical equipment. These diagrams show the different voltage levelsin the unit, electrical equipment such as transformers, circuit breakers, fuses,and motors and horsepower required. It also includes start/stop switches,emergency circuits, and motor control centers. Process technicians can usethese diagrams to trace a system from the power source to the load.

Review of Basic and Specialized Symbols

Piping and ValvesEach plant will have a standardized file for their piping symbols. Processtechnicians should carefully review the piping symbols for major and minorflows; electric, pneumatic, capillary, and hydraulic elements; and futureequipment (Figure 12.9). The major flow path through a unit illustrates the


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Y-type Strainer

Duplex Strainer

Basket Strainer

D Detonation Arrestor

F Flame Arrestor

T Steam Trap

S In-Line Silencer

DS Desuperheater

Ejector / Eductor

Exhaust Head

S Vent Silencer

RSRemovable Spool

Flexible Hose

Expansion Joint

XXX Breather

Vent Cover

In-Line Mixer

Diverter Valve

Rotary Valve

Pulsation Dampener

Flange

Minor Process

Pneumatic

Hydraulic

Capillary Tubing

Electromagnetic, SonicOptical, Nuclear

X X X X

L L L

Major Process

Future Equipment

Connecting Line

Non-Connecting Line

Non-Connecting Line

Jacketed or Double Containment

Mechanical Link Software or Data Link• • • •

Electric

Figure 12.9Piping Symbols

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critical areas a new technician should concentrate on. A variety of othersymbols are included on the piping. These include valves (Figure 12.10),strainers, filters, flanges, spool pieces, insulation, piping size, pressure rat-ing, material codes, and steam traps.

Pumps and TanksPumps and tanks come in a variety of designs and shapes. Common pumpand tank symbols are shown on Figure 12.11.

Compressors, Steam Turbines, and MotorsBecause compressors and pumps share a common set of operating prin-ciples and are classified as dynamic or positive displacement, the sym-bols for compressors may closely resemble those for pumps (compare


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GlobeValve

GateValve

Three-WayValve

BleederValves

PneumaticOperated

ManualOperated

Valve

Gauge Orifice

SAFETY (Gases)

Butterfly

Ball

Solenoid ValveCLOSED

S

Rotameter

Four-Way

Needle

Angle

Plug

Diaphragm

Butterfly Butterfly

CheckValve

CheckValve

ReliefValve

M

Pneumatic Motor Hydraulic

M H

M H M

Ball

H M

Pneumatic Motor HydraulicMotor

Motor orHydraulic

Pneumatic

Motor

M

GATE VALVES

GLOBE VALVES

BALL VALVES

BUTTERFLY VALVES

DIAPHRAGM VALVES CHECK VALVES

PLUG VALVES

Motor orHydraulic

Motor orHydraulic

Plug

Pinch Valve

Stop Check

Knife Valve

RELIEF (Liquids)

Figure 12.10Valves

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Figures 12.11 and 12.12). In most cases, the compressor symbol is slightlylarger than the pump symbol.

In the multistage, centrifugal compressors, the narrowing of the symbol fromleft to right denotes compression of the gas before it is released. This is insharp contrast to the steam turbine symbol, which illustrates the opposite ef-fect as the steam expands while passing over the rotor. Modern P&IDs showthe motor symbol connected to the driven equipment. This equipment maybe a pump, compressor, mixer, or generator. Figure 12.12 illustrates thestandardized symbols for compressors, steam turbines, and motors.

Heat Exchangers and Cooling TowersHeat exchangers and cooling towers are two types of industrial equipmentthat share a unique relationship. A heat exchanger is a device used to


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Vacuum Pump

CENTRIFUGAL PUMPS

Bin Tank

Drum

GearPump

Vertical

Screw Pump

POSITIVE DISPLACEMENT PUMPS

Positive Displacement

Dome RoofTank

Open TopTank

Tank

Sphere Onion Tank

STORAGE SYMBOLS

Progressive Cavity

PositiveDisplacement

Screw Pump

Vertical CanPump

Reciprocating Pump

Sump Pump

Horizontal

Vertical

Vertical

Internal FloatingRoof Tank

Cone RoofTank

Double WallTank

External FloatingRoof

Figure 12.11 Pumps and Tanks

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transfer heat energy between two process flows. The cooling tower per-forms a similar function, but cooling towers and heat exchangers use dif-ferent scientific principles to operate. Heat exchangers transfer heat energythrough conductive and convective heat transfer, whereas cooling towerstransfer heat energy to the outside air through the principle of evaporation.Figures 12.13 and 12.14 illustrate the standard symbols used for heatexchangers and cooling towers.

The symbol for a heat exchanger clearly illustrates the flows throughthe device. It is important for a process technician to be able to recog-nize the shell inlet and outlet and the tube inlet and outlet flow paths. Aheat exchanger with an arrow drawn through the body illustrateswhether the tubeside flow is being used to heat or cool the shellsidefluid. The downward direction indicates heating; the upward direction il-lustrates cooling.


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Figure 12.12 Compressors, Steam Turbines, and Motors

STEAM TURBINE

Doubleflow Turbine

RotaryCompressor

ReciprocatingCompressor Rotory

Compressor & Silencers

CENTRIFUGAL COMPRESSORS

Centrifugal Compressor

Centrifugal Compressor(Turbine Driven)

PD COMPRESSORS

Rotary ScrewCompressor

PositiveDisplacement

Blower

Liquid RingVacuumCentrifugal

Blower

CentrifugalCompressor

Reciprocating Compressor

Motor

MOTORS

Turbine Driver

Diesel Motor

Agitator or Mixer

Axial Compressor

T

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Plate and FrameHeat Exchanger

Air Cooled Exchanger(Louvers Optional)

Double-PipeHeat Exchanger

CC

Spiral Heat Exchanger

Shell and Tube Heat Exchanger

Single PassHeat Exchanger

U-TubeHeat Exchanger

Hairpin Exchanger

CondenserHeater

Reboiler

Figure 12.13Heat Exchangers

INDUCED DRAFTCrossflow FORCED DRAFT

Counterflow

HYPERBOLICChimney Tower

NATURAL DRAFTCounterflow

Figure 12.14Cooling Towers

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The symbol for a cooling tower is designed to resemble the actual devicein the process unit. Cooled product flows out of the bottom of the tower andto the processing units. Hot water returns to a point located above the fill.The symbol will not show all of the various components of the cooling towersystem, but it will provide a technician with a good foundation in coolingtower operation and enough information to clearly see the process.

Furnaces and BoilersThe standard symbols file for furnaces and boilers is shown in Fig-ure 12.15. If a proprietary process includes several types of equipment nottypically found on a standard symbol file, the designer will draw the deviceas it visually appears in the unit.

Distillation ColumnsDistillation columns come in two basic designs, plate and packed (Fig-ure 12.16). Flow arrangements vary from process to process. The sym-bols allow the technician to identify primary and secondary flow paths.Distillation is a process designed to separate the various components ina mixture by their boiling points. (See Chapter 15.) A distillation column isthe central component of a much larger system. This system typically in-cludes all of the equipment symbols found in this chapter. Plate distillationcolumns include sieve trays, valve trays, and bubble-cap trays. Packedcolumns are filled with packing material, rings, saddles, sulzer, androsette.

ReactorsReactors (Figure 12.17) are stationary vessels and can be classified asbatch, semibatch, or continuous. A reactor is designed to allow chemi-cals to mix together under specific conditions to make chemical bonds,break chemical bonds, or make and break chemical bonds to form newproducts.


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Furnace Boiler

Figure 12.15Furnace and Boiler

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Sources of Informationfor Process Technicians

Information used by process technicians comes from a variety of sources.Some of these sources are:

• Operating training manuals• Process descriptions• Process control manuals• Equipment summaries• Safety, health, and environment regulations• Operating procedures• Startup and shutdown procedures


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PLATE TOWERBubble-cap, Sieve, Valve

PACKED TOWERSaddle, Ring, Sulzer, Rosette

Single Pass

Chimney

Two Pass

Draw Off

Generic Tray

Demister

Spray Nozzle

Packed Section

Manway

Vortex Breaker

Figure 12.16Distillation Symbols

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• Emergency procedures• Process diagrams• Technical data books• Detailed equipment vendor information

Summary

Process flow diagrams (PFDs) and process and instrument drawings(P&IDs) are used to outline or explain the complex flows, equipment, in-strumentation, electronics, elevations, and foundations that exist in aprocess unit. A PFD is a simple flow diagram that describes the primaryflow path through a unit. A P&ID is a complex representation of the variousunits found in a plant. Standardized symbols and diagrams have beendeveloped for most pieces of industrial equipment, process flows, andinstrumentation.

Summary

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Hydrocracking Hydrodesulfurization Reformer

Fluid CatalyticCracking

Fluid Coking TubularReactor

FluidizedReactor

Mixing Reactor Alkylation

Figure 12.17Reactor Symbols

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MASTER ➁

Review Questions1. Describe a process flow diagram and a process and instrument drawing.

2. Draw the symbols for a gate, globe, and automatic valve.

3. Draw the symbols for a centrifugal pump and positive displacement pump.

4. Draw the symbols for a blower and a reciprocating compressor.

5. Draw the symbols for a steam turbine and centrifugal compressor.

6. Draw the symbols for a heat exchanger and a cooling tower.

7. Draw the symbols for a packed distillation column and plate distillation column.

8. Draw the symbols for a furnace and a boiler.

9. Draw a simple process flow diagram using the symbols from questions 2–8.

10. What information is obtained from a loop diagram?

11. What information is available on electrical one-line diagrams?

12. What information is contained on a plot plan drawing?

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P&ID Symbols

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