How to Read Piping and Instrument Diagrams

CM4120Chemical Plant Operations

A P&ID is:

Language of SymbolsSchematic of ProcessDisplays Relative Orientation/ConfigurationCommunication ToolGraphical Table of Contents

A P&ID is not:

Piping IsometricEquipment Fabrication DiagramScale DrawingControl Logic DiagramSomething that conveys Process Information!

Line Designator - First Letter

C - CondensateG - Gas (not a process fluid)L - Process FluidS - SteamV - Vent or VacuumW - Water

Line Designator - Pipe Size

Following line numberis the line size

Given in inches

Line Designator - Pipe Spec.

A – 316 SS tubingw/.038” wall

C - 316 SS pipeSchedule 40

D - Carbon SteelSched. 40 (steam)

H - Copper Tubing

Equipment Symbols

Equipment Symbols

Equipment Designations

D - Distillation TowerE - Heat ExchangerF - FilterM - Misc. EquipmentP - PumpR - ReactorT - Tank

Manual Valve Symbols

Control Valve Symbols

Valve Failure Positions

Instrument Symbols

Control Symbols

ISA Instrument Identification

Transmitters/sensing elements:– FT – flow transmitter– LE – level element

Indicators:– AI – analytical indicator– LI – level indicator– PAH – pressure alarm high

Controllers:– TIC – temp indicating controller– FFIC – ratio flow controller

Controlled devices:– FY – flow transducer– LV – level valve

ISA – The International Society for Automation

References

Riggs, Chemical Process Control, 2nd

edition, Appendix A, 2001.

The Engineering Tool Box,http://www.engineeringtoolbox.com/p

&id-piping-instrumentation-diagram-d_466.html

International Society of Automation, Instrument Symbols and Identification, 1992.