ISA codes for Process Instrumentation

ISA process instrumentation codes - and combinations

It is common to make letter combinations in PI&D diagrams according ANSI/ISA S5.1-1984 (R 1992) "Instrumentation symbols and identification".

In addition to the letter combination a succeeding number as a unique identification of the actual instrument is commonly used. The numbering practice varies - some use a sequential number, others use a number related to the process line number or similar.  

First Letter

First letter indicates a measured or initiating variable, or a modifier, such as Current (I), Speed (S) or Flow (F).

Measured or Initiating Variable

  • A - Analysis
  • B - Burner, combustion
  • C - User's choice
  • D - User's choice
  • E - Voltage
  • F - Flow rate
  • G- User's choice
  • H - Hand
  • I - Current (electrical)
  • J - Power
  • K - Time, time schedule
  • L - Level
  • M- User's choice
  • N- User's choice
  • O- User's choice
  • P - Pressure, vacuum
  • Q - Quantity
  • R - Radiation
  • S - Speed, frequency
  • T - Temperature
  • U - Multivariable
  • V - Vibration, mechanical analyses
  • W - Weight, force
  • X - Unclassified
  • Y - Event, state or presence
  • Z - Position, dimension

Modifier

  • D - Differential
  • F - Ration (fraction)
  • J - Scan
  • K - Time rate of change
  • M - Momentary
  • Q - Integrate, totalizer
  • S - Safety
  • X - X-axis
  • Y - Y-axis
  • Z - Z-axis

Second or Succeeding Letters

Second or succeeding letters indicates a readout or passive function, output function or a modifier function.

Readout or Passive Function

  • A - Alarm
  • B - User's choice
  • E - Sensor (primary element)
  • G- Glass, viewing device
  • I - Indication
  • L - Light
  • N- User's choice
  • O- Orifice, restriction
  • P - Point (test connection)
  • R - Record
  • U - Multifunction
  • W - Well
  • X - Unclassified

Output Function

  • B - User's choice
  • C - Control
  • K - Control Station
  • N- User's choice
  • S - Switch
  • T - Transmit
  • U - Multifunction
  • V - Valve, damper, louver
  • X - Unclassified
  • Y - Relay, compute, convert
  • Z - Driver, actuator

Modifier Function

  • B - User's choice
  • H - High
  • L - Low
  • M - Middle, intermediate
  • N- User's choice
  • U - Multifunction
  • X - Unclassified

Examples - P&ID codes

 Flowmeter - Indicating

  • FI 001

Temperature - Transmitter

  • TT 001

Control Valve

  • FV 001

Position Switch - High Level

  • ZSH 001

Related Topics

  • Documentation - Documentation of process control systems - Block Flow Diagrams (BFD), Process Flow Diagrams (PFD), Piping and Instrumentation Diagrams (P&ID) and more
  • Process Control - Instrumentation and process control systems - engineering and documentation
  • Temperature Measurement - Measurement of temperature - probes, sensors and transmitters

Related Documents

Tag Search

  • en: ISA process instrumentation codes
  • es: ISA c√≥digos instrumentaci√≥n proceso
  • de: ISA Prozessinstrumentierung Codes

Search the Engineering ToolBox

- "Search is the most efficient way to navigate the Engineering ToolBox!"

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your SketchUp model with the Engineering ToolBox - SketchUp Extension/Plugin - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!

Translate the Engineering ToolBox!
About the Engineering ToolBox!

Support the ToolBox

If you find the Engineering ToolBox useful and want this website to be available tomorrow - and the days after tomorrow - enable ads or make a contribution!

Contribute to the Engineering ToolBox

close