P&ID Symbols: ultimate free, and complete, guide

P&ID Symbols for Piping, Equipment, Lines, and Instrumentation (with PDF Download)

P&ID Symbols: ultimate free, and complete, guide

P&ID Symbols for Piping, Equipment, Lines, and Instrumentation (with PDF Download)

This article offers a comprehensive assortment of widely utilized P&ID symbols for pipes, fittings, valves, strainers, and various process equipment like pumps, compressors, motors, heat exchangers, and towers, ready for immediate download. Simply right-click on the desired P&ID symbol to download and incorporate it into your work. Additionally, at the article’s conclusion, there’s a PDF file containing the most critical P&ID symbols employed in process and plant engineering available for your use. All images are FREE TO USE!



P&ID symbols refer to the standard notations and graphical representations used on Piping and Instrumentation Diagrams (P&IDs) to depict the components and systems involved in process flows within a facility. These symbols are essential for engineers, operators, and workers to understand the layout, operation, and interconnections of the piping, instruments, equipment, and control systems of a process plant.

P&IDs serve as critical documents in the design, operation, and maintenance of process industries, such as chemical plants, oil refineries, water treatment facilities, and power plants. The symbols on these diagrams represent various elements, including:

  • Piping: Lines that indicate the direction of flow, along with specifications about the pipe size, material, and number.
  • Valves: Devices that control the flow of materials through the piping system, represented by specific symbols for gate valves, globe valves, check valves, ball valves, butterfly valves, etc.
  • Fittings: Components that connect sections of piping, change the direction of flow, or enable branching, including elbows, tees, reducers, and flanges.
  • Instruments and Sensors: Devices that measure and control process parameters like pressure, temperature, flow rate, and level, indicated by unique symbols that specify their type and function.
  • Process Equipment: Units involved in the process operations, such as pumps, compressors, heat exchangers, tanks, and reactors, each with its distinctive symbol.
  • Control Loops and Signal Lines: Representations that show how instruments are interconnected and how signals are transmitted between devices for process control.

The use of standardized P&ID symbols allows for a universal understanding of the P&ID diagrams, facilitating communication, design accuracy, safety analysis, and regulatory compliance across the industry. Various standards organizations, including the International Organization for Standardization (ISO), the American National Standards Institute (ANSI), and the Instrumentation, Systems, and Automation Society (ISA), provide guidelines on the representation of P&ID symbols to ensure consistency and clarity.


P&ID diagrams (Piping and Instrumentation Diagrams) provide a schematic representation of the functional relationship between piping, instrumentation, and system components within a project. They offer a detailed overview of the process flow, including equipment, valves, and instrumentation, crucial for design and operational understanding.

Piping isometrics, on the other hand, are detailed 3D representations of piping systems depicted in 2D, focusing on the physical layout of individual pipes. They show the pipe’s dimensions, material, bends, fittings, and fabrication details, essential for construction and installation.

In short, P&IDs offer a conceptual view of the entire system’s operation, while piping isometrics provide detailed construction and assembly guidance for the piping itself.

Learn more about piping isometrics and their difference vs. P&ID diagrams.


To create a P&ID from the beginning, follow these steps: Start with a BFD to outline the main process and flow directions. Then, move to a PFD to detail the process, showing major equipment and flow conditions. Finally, develop the P&ID, incorporating all piping, equipment, instrumentation, and control details necessary for construction and operation. Each step builds upon the previous, adding more detail and specificity.

Learn more about these 3 typical steps to create a P&ID diagram for a process plant/project.






Other mechanical/electrical/digital lines P&ID symbols:




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 
Centrifugal Pumps 04 P&ID symbolCentrifugal Pumps 04 
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



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 is placed in a circle of 7/16 “or 12 mm (see below), At the top there is the functional identification (of the instrument or device) composed with max 5 letters, and at the bottom, there is the 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 identification Loop 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 identifies 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 variable Modified Passive function Active function Modifier
A Analysis   Alarm    
B Burner
or combustion
C User (1) choice     Control  
D User (1) choice Differential      
E Voltage   Element (primary)    
F Flow Fraction      
G User (1) choice   Glass (2)    
H Hand       High (3)
I Current   Indicate    
J Power Scan      
K Time schedule The time rate              of change   Control station  
L Level   Light   Low (4)
M User (1) choice Momentary     Meddle
or intermediate
N User (1)
O User (1) choice   Orifice
or restriction
P Pressure or vacuum   Point test    
Q Quantity Totalize or integrate      
R Radioactivity   Record    
S Speed
Safety   Switch  
T Temperature     Transmit  
U Multivariable   Multifunction Multifunction Multifunction
V Vibration     Valve  
W Weight or force   Well    
X Danger Axis X Unclassified Unclassified Fault
Y Event Axis Y   Calculation module (5)  
Z Position                   or dimension Axis Z   Unclassified 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 valve 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


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

pdf iconDownload P&ID symbols for piping


Analyser Transmitter P&ID symbolAnalyzer Transmitter P&ID symbol
AND Gate P&ID symbolAND Gate P&ID symbol
Averaging Pitot Tube P&ID symbolAveraging Pitot Tube P&ID symbol
Behind Control P&ID symbolBehind Control P&ID symbol
Behind Local Control P&ID symbolBehind Local Control P&ID symbol
Computer P&ID symbolComputer P&ID symbol
Computer Indicator P&ID symbolComputer Indicator P&ID symbol
Coriolis Flow Sensor P&ID symbolCoriolis Flow Sensor P&ID symbol
Correcting Element P&ID symbolCorrecting Element P&ID symbol
 Diamond P&ID symbol Diamond P&ID symbol
Diaphragm Meter P&ID symbolDiaphragm Meter P&ID symbol
Displayed Configurable P&ID symbolDisplayed Configurable P&ID symbol
Displayed Programmable Indicator P&ID symbolDisplayed Programmable Indicator P&ID symbol
Double P&ID symbolDouble P&ID symbol
Flow Controller P&ID symbolFlow Controller P&ID symbol
Flow Element P&ID symbolFlow Element  P&ID symbol
Flow Indicator P&ID symbolFlow Indicator  P&ID symbol
Flow Meter P&ID symbolFlow Meter P&ID symbol
Flow Nozzle Meter P&ID symbolFlow Nozzle Meter P&ID symbol
Flow Recorder P&ID symbolFlow Recorder P&ID symbol
Flow Transmitter P&ID symbolFlow Transmitter P&ID symbol
Flowmeter P&ID symbolFlowmeter P&ID symbol
Flume Meter P&ID symbolFlume Meter P&ID symbol
Indicator 01 P&ID symbolIndicator 01 P&ID symbol
Level Alarm P&ID symbolLevel Alarm P&ID symbol
Level Controller P&ID symbolLevel Controller P&ID symbol
Level Gauge P&ID symbolLevel Gauge P&ID symbol
Level Indicator P&ID symbolLevel Indicator P&ID symbol
Level Meter P&ID symbolLevel Meter P&ID symbol
Level Recorder P&ID symbolLevel Recorder P&ID symbol
Level Transmitter P&ID symbolLevel Transmitter P&ID symbol
Magnetic Flow Meter P&ID symbolMagnetic Flow Meter P&ID symbol
Manhole P&ID symbolManhole P&ID symbol
NOT Gate P&ID symbolNOT Gate P&ID symbol
Odometer P&ID symbolOdometer P&ID symbol
On Central Control Panel P&ID symbolOn Central Control Panel P&ID symbol
On Local Control Panel P&ID symbolOn Local Control Panel P&ID symbol
OR Gate P&ID symbolOR Gate P&ID symbol
Pitot Tube P&ID symbolPitot Tube P&ID symbol
Pitot Tube Type Flow Meter P&ID symbolPitot Tube Type Flow Meter P&ID symbol
Pressure Controller P&ID symbolPressure Controller P&ID symbol
Pressure Gauge P&ID symbolPressure Gauge P&ID symbol
Pressure Gauges P&ID symbolPressure Gauges P&ID symbol
Pressure Indicating controller P&ID symbolPressure Indicating controller P&ID symbol
Pressure Indicator P&ID symbolPressure Indicator P&ID symbol
Pressure Recorder P&ID symbolPressure Recorder P&ID symbol
Pressure Recording Controller P&ID symbolPressure Recording Controller P&ID symbol
Pressure Transmitter P&ID symbolPressure Transmitter P&ID symbol
Programmable Indicator P&ID symbolProgrammable Indicator P&ID symbol
Quick Change Meter P&ID symbolQuick Change Meter P&ID symbol
Rotary Meter P&ID symbolRotary Meter P&ID symbol
Rotometer P&ID symbolRotometer P&ID symbol
Sampler P&ID symbolSampler P&ID symbol
Shared Indicator 01 P&ID symbolShared Indicator 01 P&ID symbol
Shared Indicator 02 P&ID symbolShared Indicator 02 P&ID symbol
Socket Connection P&ID symbolSocket Connection P&ID symbol
Speciality Item P&ID symbolSpecialty Item P&ID symbol
Steam Traced P&ID symbolSteam Tracer P&ID symbol
Straightening Vane P&ID symbolStraightening Vane P&ID 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

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About the Author

Picture of Alessandro Brunelli

Alessandro Brunelli

Dr. Prof. Alessandro Brunelli serves as a distinguished Professor of Instrumentation, Automation, and Safety of Industrial Plants at the prestigious Politecnico di Milano in Italy. His esteemed career is marked by a notable contribution to the field of industrial automation, for which he has been honored with the prestigious title of "Cavaliere dell’Ordine al Merito della Repubblica Italiana (OMRI N. 9826 Serie VI)," recognizing his significant achievements and dedication. As an accomplished author, Prof. Brunelli has penned several influential works, including the "Instrumentation Manual" (available in Italian), which has become a vital resource for professionals and students alike. His commitment to advancing the field of automation and engineering extends beyond academia; he is an active participant in various automation and engineering associations both within Italy and internationally, contributing his expertise and insights to foster innovation and excellence in the industry. https://www.linkedin.com/in/alessandro-brunelli-a43b8a67/ As an accomplished author, Prof. Brunelli has penned several influential works, including the "Instrumentation Manual" (available in Italian), which has become a vital resource for professionals and students alike. His commitment to advancing the field of automation and engineering extends beyond academia; he is an active participant in various automation and engineering associations both within Italy and internationally, contributing his expertise and insights to foster innovation and excellence in the industry. https://www.linkedin.com/in/alessandro-brunelli-a43b8a67/

Should you wish to reach out to the author of this article, we invite you to contact us via email

32 Responses

  1. I appreciate you mentioning the symbology used to denote the measurement and control equipment on the flow and process diagrams. My shop needs work, and I mainly want to replace the glass. To assist me with refurbishment, I’ll look for a glass shop drawing service.

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  4. It’s awesome that this article talked about process engineers create such diagrams using a set of standardized P&ID symbols. I’m glad that you explain it thoroughly and now it makes more sense. You did a great job of explaining the valve manifold box.

  5. Good afternoon employee,

    Is it possible to obtain an accredited symbol book (P&ID) from you? This for a number (approx. 7 pieces) in the Dutch language?
    Thanks in advance!


    Thomas de Jong

    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)
      – RFQs (if you have an RFQ/MTO and need offers, you can simply post it on the platform and let suppliers come to you)
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      We help buyers and sellers of materials for projects! We hope you can pass this information to your friends and colleagues, to help us grow our community!
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  6. 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. I means indicator showing the process variable measured by the transmitter and this is the same reading send to DCS

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