Piping and Instrument Diagrams
CM4120 Chemical Plant Operations
A P&ID is: A P&ID is not: Language of Symbols Schematic of Process
Displays Relative Orientation/Configuration Communication Tool Graphical Table of Contents Piping Isometric Equipment Fabrication Diagram Scale Drawing Control Logic Diagram Something to Convey Process Information!
Line Designator - First Letter
W - Water or Heat Transfer Fluid L - Process Fluid G – Gas (not a process fluid) V - Vent or Vacuum S - Steam C - Condensate
Line Designator - Pipe Size
Following line number is the line size Given in inches
Line Designator - Pipe Spec.
A – 316 SS tubing w/.038” wall C SS pipe Schedule 40 D - Carbon Steel Sched. 40 (steam) Sched. 80 (Syltherm) H - Copper Tubing
D - Distillation Tower E - Heat Exchanger F - Filter M - Misc. Equipment P - Pump R - Reactor T - Tank
Manual Valve Symbols
Control Valve Symbols
Valve Failure Positions
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
References for ISA symbols:
Riggs, Chemical Process Control, Appendix A The Engineering Tool Box,
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