Instrument Abbreviations Used in Instrumentation Diagrams (P&ID) ~ Learning Instrumentation And Control Engineering Learning Instrumentation And Control Engineering

Instrument Abbreviations Used in Instrumentation Diagrams (P&ID)

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Typically instrument abbreviations used in P&IDs consist of two letters: the first indicating the process variable and the second indicating the instrument/controller function. For example, the instrument abbreviation “PI” denotes a “Pressure Indicator”. Occasionally, a third letter is included in the instrument abbreviation to describe a simultaneous function or a special function. For example: the abbreviation “FRC” represents a “Flow Recorder and Controller” which describes both the recording and control functions and the abbreviation “PAL” denotes a “Pressure Alarm Low” which describes
an alarm used in the event of a low pressure condition.



 The table below contains some of the instrument abbreviations used in conjunction with P&ID symbols in instrumentation diagrams. I have dealt with some of them before but for the purpose of emphasis and completeness let us go through again. The list here is by no means exhaustive but it is a good starting point for beginners to P&IDs:


Instrument Abbreviation

Expansion

Functions Performed
FC

 Flow controller
Flow measurement and control

LC

 Level controller
Level control

FE

 Flow element
Flow sensor

LG

 Level gauge

Level measurement

FIC

 Flow indicator and controller
Indicating flow as well as controlling flow
LA
Level alarm
Indicating level alarm

FR

Flow recorder

Recording flow

LAH

Level alarm high
Indicating high level

FRC

Flow recorder and controller
Flow recording; controlling flow

LAHH

Level alarm high high
Indicating very high level

FT

Flow transmitter
Transmitting flow signal

LAL

Level alarm low
Indicating low level
FA
Flow alarm
Indicating flow alarm
LI
Level indicator

Level indication

LIC

Level indicator and controller
Indicating level; controlling level

PC

Pressure controller
controlling pressure

TC
Temperature controller
Controlling/regulating temperature

PI

Pressure indicator
Indicating pressure

TI

Temperature indicator

Indicating pressure

PIC

Pressure indicator and controller
Indicating pressure; controlling pressure

TIC

Temperature indicator and controller

Indicating temperature; controlling temperature

PR

Pressure recorder

Recording pressure

TR

Temperature recorder

Recording temperature

PRC

Pressure recorder and controller

Recording pressure; controlling pressure

TRC

Temperature recorder and controller

Recording temperature; controlling temperature

PSV

Pressure safety valve
Relieving excess pressure in case of high pressure situation

TT

Temperature transmitter
Transmitting measured temperature signals

PT

Pressure transmitter

Transmitting measured pressure signals
TW

Thermowell

Houses temperature sensors

RV

Relief valve

To relieve excess pressure in case of high pressure

TY

Temperature relay/transducer
Converts electrical signals to pneumatic signals
PSH

Pressure switch high
A pressure switch used to indicate high pressure alarm

ZI

Position/limit indicator
Indicates whether a valve is open or close
SDV

Shut down valve

A valve initiating shutdown
ZSC

Position/unit switch closed

Limit switch indicating a valve is closed

ZSO

Position/unit switch open
Limit switch indicating a valve is open

SDY

Shutdown relay

A transducer attached to a shutdown valve
USD

Unit shutdown
Initiate Shut down of a process unit

Read also:
Instrument Abbreviations Used in Instrumentation Diagrams (P&IDs) II
Instrument Abbreviations Used in Instrumentation Diagrams (P&IDs) III

Below are some common P&ID symbols used with the instrument abbreviations discussed above for developing P&ID drawings
 


Tag Numbers on P&ID Symbols
Numbers on the P&ID symbols in instrumentation diagrams represent instrument tag numbers. Often these numbers are associated with a particular control loop (e.g., Temperature indicator and controller 123) as shown in the diagram below:

One easy way to learn how to read P&ID drawings and become proficient in it is to look at a lot of Piping and instrumentation diagrams; both simple and complex ones! (please don’t get scared). By so doing, you will eventually become good at reading P&IDs. Any good instrumentation textbook should contain one or two sections dedicated to understanding how to interpret and read P&ID drawings.

For a detailed list of common symbols used in P&IDs checkout:
Common P&ID symbols used in developing instrumentation diagrams