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P&ID Symbols (Complete List & PDF)

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Table of Contents

A complete collection of the most used P&ID symbols for lines, piping, valves, instruments, pumps, compressors, pressure equipment and other mechanical equipment, and the PDF file for P&ID symbols to download


P&ID is the acronym for “Piping and instrumentation diagram”, i.e. a very detailed diagram showing the processes happening within a plant, the involved equipment, and their interconnections.

A set of standardized P&ID symbols is used by process engineers to draft such diagrams. P&ID symbols exist for all major components and lines, such as valves, vessels, instruments, pumps, compressors, and towers. The ISA S5.1, ISO 10628, and BS 5070 cover the standardization of P&ID symbols and guide process engineers in their plant design activities.

The most common P&ID symbols are listed below:


Line P&ID symbols


Clamped Flange Coupling P&ID symbolClamped Flange Coupling symbol
Coupling P&ID symbolCoupling symbol
End Caps 01 P&ID symbolEnd Caps 01 symbol
End Caps 02 P&ID symbolEnd Caps 02 symbol
Flange P&ID symbolFlange symbol
Flanges P&ID symbolFlanges symbol
Reducers P&ID symbolReducers symbol
Removable Spool P&ID symbolRemovable Spool symbol
Union P&ID symbolUnion symbol


Gate Valve symbolGate Valve P&ID symbol
Normally Closed Gate Valve symbolNormally Closed Gate Valve P&ID symbol
Ball Valve symbolBall Valve P&ID symbol
Normally Closed Ball Valve symbolnormally closed ball valve P&ID symbol
Globe Valve symbolglobe valve P&ID symbol
Butterfly Valve symbolbutterfly valve P&ID symbol
Check Valve symbolcheck valve P&ID symbol
Plug Valve symbolplug valve P&ID symbol
Needle Valve symbolneedle valve P&ID symbol
Self Draining Valve symbolself draining valve P&ID symbol
Integrated Block and Bleed Valve symbolintegrated block and bleed valve P&ID symbol
Auto Recirculation Valve symbol
Angle Valve symbolangle valve P&ID symbol
Angle Globe Valve symbolangle globe valve P&ID symbol
3-way Valve symbol3way valve P&ID symbol
Y Blowdown Valve symbolY blowdown valve P&ID symbol
Angle Blowdown Valve symbolAngle Blowdown valve P&ID symbol


Filters P&ID symbols


Analyser Transmitter P&ID symbolAnalyzer Transmitter symbol
AND Gate P&ID symbolAND Gate symbol
Averaging Pitot Tube P&ID symbolAveraging Pitot Tube symbol
Behind Control P&ID symbolBehind Control symbol
Behind Local Control P&ID symbolBehind Local Control symbol
Computer P&ID symbolComputer symbol
Computer Indicator P&ID symbolComputer Indicator symbol
Coriolis Flow Sensor P&ID symbolCoriolis Flow Sensor symbol
Correcting Element P&ID symbolCorrecting Element symbol
 Diamond P&ID symbol Diamond symbol
Diaphragm Meter P&ID symbolDiaphragm Meter symbol
Displayed Configurable P&ID symbolDisplayed Configurable symbol
Displayed Programmable Indicator P&ID symbolDisplayed Programmable Indicator symbol
Double P&ID symbolDouble symbol
Flow Controller P&ID symbolFlow Controller symbol
Flow Element P&ID symbolFlow Element  symbol
Flow Indicator P&ID symbolFlow Indicator  symbol
Flow Meter P&ID symbolFlow Meter symbol
Flow Nozzle Meter P&ID symbolFlow Nozzle Meter symbol
Flow Recorder P&ID symbolFlow Recorder symbol
Flow Transmitter P&ID symbolFlow Transmitter symbol
Flowmeter P&ID symbolFlowmeter symbol
Flume Meter P&ID symbolFlume Meter symbol
Indicator 01 P&ID symbolIndicator 01 symbol
Level Alarm P&ID symbolLevel Alarm symbol
Level Controller P&ID symbolLevel Controller symbol
Level Gauge P&ID symbolLevel Gauge symbol
Level Indicator P&ID symbolLevel Indicator symbol
Level Meter P&ID symbolLevel Meter symbol
Level Recorder P&ID symbolLevel Recorder symbol
Level Transmitter P&ID symbolLevel Transmitter symbol
Magnetic Flow Meter P&ID symbolMagnetic Flow Meter symbol
Manhole P&ID symbolManhole symbol
NOT Gate P&ID symbolNOT Gate symbol
Odometer P&ID symbolOdometer symbol
On Central Control Panel P&ID symbolOn Central Control Panel symbol
On Local Control Panel P&ID symbolOn Local Control Panel symbol
OR Gate P&ID symbolOR Gate symbol
Pitot Tube P&ID symbolPitot Tube symbol
Pitot Tube Type Flow Meter P&ID symbolPitot Tube Type Flow Meter symbol
Pressure Controller P&ID symbolPressure Controller symbol
Pressure Gauge P&ID symbolPressure Gauge symbol
Pressure Gauges P&ID symbolPressure Gauges symbol
Pressure Indicating controller P&ID symbolPressure Indicating controller symbol
Pressure Indicator P&ID symbolPressure Indicator symbol
Pressure Recorder P&ID symbolPressure Recorder symbol
Pressure Recording Controller P&ID symbolPressure Recording Controller symbol
Pressure Transmitter P&ID symbolPressure Transmitter symbol
Programmable Indicator P&ID symbolProgrammable Indicator symbol
Quick Change Meter P&ID symbolQuick Change Meter symbol
Rotary Meter P&ID symbolRotary Meter symbol
Rotometer P&ID symbolRotometer symbol
Sampler P&ID symbolSampler symbol
Shared Indicator 01 P&ID symbolShared Indicator 01 symbol
Shared Indicator 02 P&ID symbolShared Indicator 02 symbol
Socket Connection P&ID symbolSocket Connection  symbol
Speciality Item P&ID symbolSpecialty Item symbol
Steam Traced P&ID symbolSteam Tracer symbol
Straightening Vane P&ID symbolStraightening Vane symbol
Support Bracket P&ID symbolSupport Bracket symbol
Support Leg P&ID symbolSupport Leg symbol
Support Ring P&ID symbolSupport Ring symbol
Support Skirt P&ID symbolSupport Skirt symbol
Target Meter P&ID symbolTarget Meter symbol
Temperature Controller P&ID symbolTemperature Controller symbol
Temperature Element P&ID symbolTemperature Element symbol
Temperature Indicator P&ID symbolTemperature Indicator symbol
Temperature Recorder P&ID symbolTemperature Recorder symbol
Temperature Transmitter P&ID symbolTemperature Transmitter symbol
Thermometer P&ID symbolThermometer symbol
Thermometers P&ID symbolThermometers symbol
Transducer P&ID symbolTransducer symbol
Turbine Meter P&ID symbolTurbine Meter symbol
Ultrasonic Meter P&ID symbolUltrasonic Meter symbol
Unit Control Panel P&ID symbolUnit Control Panel symbol
V Cone Meter P&ID symbolV Cone Meter symbol
Venturi P&ID symbolVenturi symbol
Venturi Meter P&ID symbolVenturi Meter symbol
Vortex Sensor P&ID symbolVortex Sensor symbol
Wedge Meter P&ID symbolWedge Meter symbol
Weir Meter P&ID symbolWeir Meter symbol


The symbology for the identification of the measurement and control instrumentation on the flow and process diagrams and on the P&ID (Piping & Instrument Diagram), commonly called P&I (Piping & Instrumentation), is generally compliant with the Standard ISA (Instrumentation Society of Automation) identified as S.5, that is composed of identification codes and graphic symbols.

The symbology of the instrument it is placed in a circle of 7/16 “or 12 mm (see below), was in the top there is the functional identification (of the instrument or device) composed with max 5 letters, and in the bottom there is identification of the loop (measurement and/or control) consists of a progressive number of 3 or 4 numbers, followed by a literal suffix to identifies two or more identical instruments inserted in the same chain and therefore having the same functional identification;

The circle that identifies the instrument or device has:

  • Continue Line in the center: for an instrument suitable for control room mounting
  • The dotted line in the center: for an instrument suitable for technical room mounting
  • No line in the center: for an instrument suitable for field application

If an instrument has a circumscribed square means that it is an integrated instrument as a function in a DCS (Distributed Control System) or PLC (Programmable Logic Controller).

First Letter
(Measured variable)
Later letters
Loop number
Functional identificationLoop identification

Instrumentation symbology

Graphical representation of a temperature recorder controller of the 101A loop, suitable for control room mounting
The following tables show:
– Table 1 identifying the function of the instruments or devices
– Table 2 the graphic identification of the valves
– Table 3 the graphic identification of the actuators
– Table 4 identifying the safety conditions of the valves and actuators

At the end will also be reported the literal and graphic symbols of the power supplies and signals of the instrumentation.


Measured variableModifiedPassive functionActive functionModifier
or combustion
CUser (1) choiceControl
DUser (1) choiseDifferential
EVoltageElement (primary)
GUser (1) choiceGlass (2)
HHandHigh (3)
KTime scheduleTime rate              of changeControl station
LLevelLightLow (4)
MUser (1) choiseMomentaryMeddle
or intermediate
NUser (1)
OUser (1) choiceOrifice
or restriction
PPressure or vacuumPoint test
QQuantityTotalize or integrate
WWeight or forceWell
XDangerAxis XUnclassifiedUnclassifiedFault
YEventAxis YCalculation module (5)
ZPosition                   or dimensionAxis ZUnclassified final element
(1) It must be chosen uniquely for each project. For example C – Conductivity; D – Density; etc.
(2) Glass instruments that allow the visualization of process data
(3) Very high or maximum is indicated with HH
(4) Very low or minimum is indicated with LL
(5) To define the Y function on a diagram, add the specific symbol of the relay or convert to a square of 6 mm on the side of the graphical sign of the instrument (in the north-east position).


Instrumentation valves symbols


Actuators for instrumentation valves symbols
Actuators for instrumentation valves symbols




AS –  Ais Supply:
IA – Instrument Air
PA- Plant Air
ES –  Electrical Supply
GS –  Gas Supply
HS –  Hydraulic Supply
NS –  Nitrogen Supply
SS  – Steam Supply
WS – Water Supply


The table shows the symbology of control signals for instrumentation

Symbology for instrumentation signals
Symbology for instrumentation signals


Cavity Pump P&ID symbolCavity Pump symbol
Centrifugal Pumps 01 P&ID symbolCentrifugal Pumps 01 symbol
Centrifugal Pumps 02 P&ID symbolCentrifugal Pumps 02 symbol
Centrifugal Pumps 03 P&ID symbolCentrifugal Pumps 03 P&ID symbol
Centrifugal Pumps 04 P&ID symbolCentrifugal Pumps 04 P&ID symbol
Centrifugal Pumps 05Centrifugal Pumps 05
Gear Pump P&ID symbolGear Pump symbol
Horizontal Pump P&ID symbolHorizontal Pump symbol
ISO Centrifugal Pump P&ID symbolISO Centrifugal Pump symbol
ISO Diaphragm Pump P&ID symbolISO Diaphragm Pump symbol
ISO Gear Pump P&ID symbolISO Gear Pump symbol
ISO Liquid Pump P&ID symbolISO Liquid Pump symbol
ISO Positive Displacement Pump P&ID symbolISO Positive Displacement Pump symbol
ISO Progressive Pump P&ID symbolISO Progressive Pump symbol
ISO Screw Pump P&ID symbolISO Screw Pump symbol
Liquid Ring Vacuum Pump P&ID symbolLiquid Ring Vacuum Pump symbol
Peristaltic Pump P&ID symbolPeristaltic Pump symbol
Positive Displacement Pump 01 P&ID symbolPositive Displacement Pump 01 symbol
Positive Displacement Pump 02 P&ID symbolPositive Displacement Pump 02 symbol
Positive Displacement Pump 03 P&ID symbolPositive Displacement Pump 03 symbol
Proportionating Pump P&ID symbolProportionating Pump symbol
Pump 01 P&ID symbolPump 01 symbol
Reciprocating Pump 01 P&ID symbolReciprocating Pump 01 symbol
Reciprocating Pump 02 P&ID symbolReciprocating Pump 02 symbol
Rotary Gear Pump P&ID symbolRotary Gear Pump symbol
Rotary Pump P&ID symbolRotary Pump symbol
Screw Pump 01 P&ID symbolScrew Pump 01 symbol
Screw Pump 02 P&ID symbolScrew Pump 02 symbol
Submersible Pump P&ID symbolSubmersible Pump symbol
Sump Pump P&ID symbolSump Pump symbol
Turbine Pump P&ID symbolTurbine Pump symbol
Vacuum Pump P&ID symbolVacuum Pump symbol
Vertical Pump 01 P&ID symbolVertical Pump 01 symbol
Vertical Pump 02 P&ID symbolVertical Pump 02 symbol


AC Air Compressor P&ID symbolAC Air Compressor symbol
Air Compressor P&ID symbolAir Compressor symbol
Axial Compressor symbol
Centrifugal Blower P&ID symbolCentrifugal Blower symbol
Centrifugal Compressor 01 P&ID symbolCentrifugal Compressor 01 symbol
Centrifugal Compressor 02 P&ID symbolCentrifugal Compressor 02 symbol
Centrifugal Compressor 03 P&ID symbolCentrifugal Compressor 03 symbol
Centrifugal Compressor 04 P&ID symbolCentrifugal Compressor 04 symbol
Compressor 01 P&ID symbolCompressor 01 symbol
Compressor 02 P&ID symbolCompressor 02 symbol
Compressor Silencers P&ID symbolCompressor Silencers symbol
Compressor Vacuum Pump P&ID symbolCompressor Vacuum Pump symbol
Diaphragm Compressor P&ID symbolDiaphragm Compressor symbol
Ejector Compressor P&ID symbolEjector Compressor symbol
Gas Blower P&ID symbolGas Blower symbol
Liquid Ring Compressor P&ID symbolLiquid Ring Compressor symbol
Piston Compressor P&ID symbolPiston Compressor symbol
Reciprocating Compressor 01 P&ID symbolReciprocating Compressor 01 symbol
Reciprocating Compressor 02 P&ID symbolReciprocating Compressor 02 symbol
Reciprocating Compressor 03 P&ID symbolReciprocating Compressor 03 symbol
Ring Compressor P&ID symbolRing Compressor symbol
Roller Vane Compressor P&ID symbolRoller Vane Compressor symbol
Rotary Compressors 01 P&ID symbolRotary Compressors 01 symbol
Rotary Compressors 02 P&ID symbolRotary Compressors 02 symbol
Rotary Compressors and Silencers P&ID symbolRotary Compressors and Silencers symbol
Screw Compressor P&ID symbolScrew Compressor symbol
Selectable Compressor P&ID symbolSelectable Compressor symbol
Turbo Compressor P&ID symbolTurbo Compressor symbol


Bag P&ID symbolBag symbol
Bag ISO P&ID symbolBag ISO symbol
Barrel P&ID symbolBarrel P&ID symbol
Barrel ISO P&ID symbolBarrel ISO symbol
Bin P&ID symbolBin symbol
Boiler P&ID symbolBoiler symbol
Brackets Vessel P&ID symbolBrackets Vessel symbol
Column P&ID symbolColumn symbol
Cone Roof Tank P&ID symbolCone Roof Tank symbol
Covered Tank P&ID symbolCovered Tank symbol
Dished Ends Vessel P&ID symbolDished Ends Vessel symbol
Dome Boiler P&ID symbolDome Boiler symbol
Dome Roof Tank P&ID symbolDome Roof Tank symbol
Double Wall Tank P&ID symbolDouble Wall Tank symbol
Drum P&ID symbolDrum symbol
Electrical Heating Vessel P&ID symbolElectrical Heating Vessel symbol
Floating Roof Tank P&ID symbolFloating Roof Tank symbol
Fluidized Bed Column P&ID symbolFluidized Bed Column symbol
Gas Bottle P&ID symbolGas Bottle symbol
Heating Cooling Jacket Vessel P&ID symbolHeating Cooling Jacket Vessel symbol
Hot Liquid Boiler P&ID symbolHot Liquid Boiler symbol
Internal Floating Roof Tank P&ID symbolInternal Floating Roof Tank symbol
Knockout Drum P&ID symbolKnockout Drum symbol
Mixing Vessel P&ID symbolMixing Vessel symbol
Onion Tank P&ID symbolOnion Tank symbol
Open Bulk Storage P&ID symbolOpen Bulk Storage symbol
Open Tank P&ID symbolOpen Tank symbol
Packed Tower P&ID symbolPacked Tower symbol
Packing Column 01 P&ID symbolPacking Column 01 symbol
Packing Column 02 P&ID symbolPacking Column 02 symbol
Pit Vessel P&ID symbolPit Vessel symbol
Plate Tower P&ID symbolPlate Tower symbol
Staggered Baffle Tray Column P&ID symbolStaggered Baffle Tray Column symbol
Tank 01 P&ID symbolTank 01 symbol
Tank 02 P&ID symbolTank 02 symbol
Tank 03 P&ID symbolTank 03 symbol
Tank 04 P&ID symbolTank 04 symbol
Thermal Insulation Vessel P&ID symbolThermal Insulation Vessel symbol
Tray Column P&ID symbolTray Column symbol
Vertical Vessel P&ID symbolVertical Vessel symbol
Wastewater Treatment P&ID symbolWastewater Treatment symbol


AC Generator P&ID symbolAC Generator symbol
AC Motor P&ID symbolAC Motor symbol
DC Generator P&ID symbolDC Generator symbol
DC Motor P&ID symbolDC Motor symbol
Diesel Motor P&ID symbolDiesel Motor symbol
Electric Motor P&ID symbolElectric Moto symbol
Gear P&ID symbolGear symbol
Generator P&ID symbolGenerator symbol
Motor 01 P&ID symbolMotor 01  symbol
Motor 02 P&ID symbolMotor 02 symbol
Motor Driven Turbine P&ID symbolMotor Driven Turbine symbol
Motor Generator P&ID symbolMotor Generator  symbol
Step Motor P&ID symbolStep Motor symbol
Turbine P&ID symbolTurbine  symbol
Turbine Driver P&ID symbolTurbine Driver symbol
Vertical Turbines P&ID symbolVertical Turbines symbol


Heat Exchangers P&ID symbols



You can download most P&ID symbols in PDF format by clicking on the following link:

pdf iconP&ID symbols for piping


About the Author

Alessandro Brunelli

Author: Dott. Prof. Alessandro Brunelli – Professor of Instrumentation, Automation, and Safety of Industrial Plants

Cavaliere dell’ Ordine al Merito della Repubblica Italiana (OMRI N. 9826 Serie VI)

Author of “Instrumentation Manual” (available in IT):

  • Part 1: illustrates the general concepts on industrial instrumentation, the symbology, the terminology and calibration of the measurement instrumentation, the functional and applicative conditions of the instrumentation in normal applications and with the danger of explosion, as well as the main directives (ATEX , EMC, LVD, MID, and PED);
  • Part 2: this part of the book deals with the instrumentation for measuring physical quantities: pressure, level, flow rate, temperature, humidity, viscosity, mass density, force and vibration, and chemical quantities: pH, redox, conductivity, turbidity, explosiveness, gas chromatography, and spectrography, treating the measurement principles, the reference standard, the practical executions, and the application advantages and disadvantages for each size;
  • Part 3:illustrates the control, regulation, and safety valves and then and simple regulation techniques in feedback and coordinates in feedforward, ratio, cascade, override, split range, gap control, variable decoupling, and then the Systems of Distributed Control (DCS) for continuous processes, Programmable Logic Controllers (PLC) for discontinuous processes and Communication Protocols (BUS), and finally the aspects relating to System Safety Systems, from Operational Alarms to Fire & Gas Systems, to systems of ESD stop and finally to the Instrumented Safety Systems (SIS) with graphic and analytical determinations of the Safety Integrity Levels (SIL) with some practical examples.

Download the PDF – Instrumentation Handbook

You can download an excerpt of the “Instrumentation Manual” (Brunelli, 2018-2019) by clicking on the following link:

pdf iconInstrumentation Handbook

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20 Responses

  1. Professor,
    When showing a local indicating pressure transmitter (PIT) with a signal to the DCS PI – what does the “I” stand for on the DCS symbol. Also,
    does a local PIT go to a DCS PALL or Local PSLL go to DCS PALL

    Thank you

    1. You are welcome, Sir. Have you seen the platform projectmaterials.com? We offer several services for people engaged in project business:
      – Academy (150+ not-too technical articles about piping and steel, to know the basics)
      – Stockists Directory (directory of 1000+ stockists of piping products that you can search and contact)
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      With our best regards, Projectmaterials Lugano Switzerland

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