Module 4 - P&ID Symbology

Module from the Instrumentation Engineering Curriculum curriculum.

P&ID SYMBOLOGY & INSTRUMENT IDENTIFICATION · Learning Objectives · 1. Read ISA 5.1 instrument identification tags (e.g., FIC-101, TT-205) 2. Identify standard P&ID symbols for instruments, valves, and equipment 3. Understand line types (process, instrument, electrical, pneumatic) 4. Interpret control scheme notation on P&IDs · ISA 5.1 Instrument Tag Structure

Position	Content	Examples	Description	Notes	Common Combinations	Typical Tag
1st Letter	Measured Variable	F=Flow, T=Temp, P=Pressure, L=Level, A=Analysis	What is being measured	Always first letter in tag	—	FIC-101
2nd Letter (optional)	Modifier	D=Differential, F=Ratio, Q=Totalize, J=Scan	Modifies the measured variable	Not always present	FD=Differential Flow, PD=Differential Pressure	PDIC-205
3rd Letter	Readout/Function	I=Indicate, R=Record, C=Control, T=Transmit	What the instrument does (passive)	Can have multiple function letters	TIC=Temp Indicate+Control, FRC=Flow Record+Control	TIC-301
4th Letter	Output Function	C=Control, S=Switch/Safety, A=Alarm, V=Valve	What action the instrument takes	S used for safety shutdown functions	—	PSHH-401
Loop Number	Unique identifier	101, 205, 301-A	Unique within a unit or area	Typically: area-sequence (100s, 200s)	—	FIC-101
Suffix	Parallel or redundant	A, B, C, or 1, 2, 3	Identifies parallel instruments in same service	A/B for redundant, 1/2/3 for multiple taps	—	TT-301A/B
Common Instrument Letter Combinations
Tag Prefix	Full Name	Function	Typical Location	Example Application	DCS/PLC Function
FIC	Flow Indicating Controller	Measures flow, displays, controls valve	Control room DCS display	Feed flow control to reactor	PID output to control valve
TI	Temperature Indicator	Displays temperature only	Local gauge or DCS display	Process line temperature monitoring	Display only, no control
LT	Level Transmitter	Measures and transmits level signal	Field (on vessel), signal to DCS	Drum/vessel level measurement	4-20 mA to DCS AI
PCV	Pressure Control Valve	Self-contained pressure regulator	Field (on pipe or vessel)	Pressure regulation (no DCS)	No DCS function (standalone)
PSHH	Pressure Switch High-High	Safety shutdown on high-high pressure	Field, wired to SIS	Emergency depressure initiation	SIS input, trips ESD valve
AIT	Analyzer Indicating Transmitter	Measures composition, displays, transmits	Analyzer shelter or field	H2S in fuel gas, O2 in flue gas	4-20 mA to DCS AI
XV	On-Off Valve (solenoid/actuated)	Binary valve — open or close	Field (on pipe)	Emergency isolation valve, ESD valve	DCS/SIS digital output
FY	Flow Relay/Converter	Signal converter or relay	Marshalling cabinet	I/P converter (4-20mA to 3-15 psi)	Signal conditioning
Source: ISA 5.1-2022, FOS Chief Files — PID Templates, PID Drawings.PDF, IPE-EP-12-1-1 (Control Systems)

Source: Instrumentation_Engineering_Curriculum_v1.xlsx · Sheet: Module 4 - P&ID Symbology

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