Common P&ID Symbols: A Definitive Guide

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Looking for a library of common P&ID symbols?

Scroll down and use the table of contents on the left to navigate this page and see the different symbol types most commonly used by engineers.

What Does P&ID Mean?

P&ID is an abbreviation meaning ‘Piping and Instrumentation Diagram’.

Piping and Instrumentation Diagrams are fundamental to every standardized engineering project.

These two-dimensional diagrams function as a blueprint for the engineering system’s design.

Piping and Instrumentation Diagrams detail the specific processes within a plant or industrial facility.

P&IDs follow a selection of industry-standard engineering symbology to highlight the required instruments, equipment, pipe, and interconnecting lines.

Knowing what the various symbols represent is vital to a user understanding a P&ID.

For engineers and designers, knowing the symbology legend can also improve P&ID collaboration.

We recommend using the table of contents to navigate this comprehensive directory of common Piping and Instrumentation Diagram symbols.

The symbols are organized in sections including equipment, fire and safety, flow elements, instrumentation, piping, valves, and more.

P&ID Equipment Symbols

The common P&ID equipment symbols are organized into ten categories:

  1. Atmospheric tanks
  2. Compressors & Blowers
  3. Drivers
  4. Filters
  5. Heat exchangers
  6. Heaters
  7. HVAC
  8. Pumps
  9. Stacks
  10. Vessels

Atmospheric Tanks

Atmospheric tanks are containers for holding a variety of liquids at atmospheric pressure. There are various types as follows:

SLOPED BOTTOM

SUMP 1

SUMP 2

Compressors & Blowers

Compressors and blowers are used to move air and/or gas through an operational process. Compressors typically operate at a high pressure-to-volume ratio, while blowers operate at a low-pressure ratio.

CENTRIFUGAL BLOWER

CENTRIFUGAL COMPRESSOR

COMPRESSOR SILENCERS

LIQUID RING COMPRESSOR

POSITIVE DISPLACEMENT BLOWER

RECIPROCATING COMPRESSOR

SCREW COMPRESSOR

Drivers

Drivers are used to fuel components in the plumbing circuit, for example; pumps, compressors/ any process that requires energy input. The most common driver used is the electric motor.

DIESEL ENGINE

ELECTRIC MOTOR

TURBINE DRIVER

Filters

Filters eliminate impurities from the passing fluid using physical, chemical, or biological processes to remove the contaminants.

FILTER

FILTER ALTERNATE

Heat Exchangers

Heat exchangers are pieces of equipment used to transfer heat between fluids and can be used in both cooling and heating processes. The fluids are separated by a physical barrier.

AIR COOLED EXCHANGER (LOUVERS OPTIONAL)

HAIRPIN EXCHANGER

PLATE AND FRAME EXCHANGER

SHELL TUBE EXCHANGER WITH BOOT

SPIRAL HEAT EXCHANGER

TEMA TYPE AEL

TEMA TYPE AEM

TEMA TYPE AFS

TEMA TYPE BEM

TEMA TYPE BEU

TEMA TYPE BKU

TEMA TYPE NEN

VERTICAL CONDENSER

Heaters

Heaters use the heat transfer process to heat water above its initial temperature using energy.

DIRECT FIRED HEATER

ELECTRIC HEATER

IMMERSION HEATER

HVAC

HVAC equipment is used for heating, ventilation, and air conditioning or cooling.

CATADYNE HEATER

EXHAUST FAN

UNIT HEATER

Pumps

Pumps are used to move liquid through a plumbing system. Pumps are often used to move liquid vertically using an energy input.

AIR DRIVEN PUMP

CENTRIFUGAL SUMP PUMP

HORIZONTAL CENTRIFUGAL PUMP

LIQUID RING VACUUM PUMP

METERING PUMP

POSITIVE DISPLACEMENT PUMP

PROGRESSIVE CAVITY PUMP

PUMP

RECIPROCATING COMPRESSOR

RECIPROCATING COMPRESSOR 2

RECIPROCATING PUMP

ROTARY COMPRESSOR

ROTARY COMPRESSOR AND SILENCERS

SCREW PUMP

TURBINE PUMP

VERTICAL CAN PUMP

VERTICAL INLINE PUMP

Stacks

Stacks are used for exhaust air from a variety of processes.

FLARE STACK

INCINERATOR STACK

VENT STACK

Vessels

Vessels are containers used to hold gases or liquids at a higher or lower pressure from the ambient air.

BAG

BOILER

FILTER

FLUIDIZED BED COLUMN

GAS BOTTLE

HORIZONTAL VESSEL WITH BOOT

HORIZONTAL VESSEL

KNOCK OUT DRUM

LEVEL TABLE

PACKING COLUMN

REACTOR

STAGGERED BAFFLE TRAYS COLUMN

TRAY COLUMN

VERTICAL VESSEL

VERTICAL VESSEL WITH LEGS

VERTICAL VESSEL WITH SKIRT

Fire & Safety Symbols

Fire and safety symbols represent the emergency response equipment used within a plant or facility. These include eyewash stations, fire hydrants, sprinklers, and more.

EYE WASH

FIRE HYDRANT MONITOR

FIRE MONITOR

FIRE HYDRANT

FOAM CHAMBER

FUTURE FIRE HYDRANT BLIND FLANGE

FUTURE HOSE STATION LOCATION

FUTURE POST INDICATOR VALVE

HOSE STATION

HOSE WHEEL

POST INDICATOR VALVE

SAFETY SHOWER

SAFETY SHOWER AND EYE WASH

SPRAY SPRINKLER

Flow Elements

Flow elements represent functional pieces of equipment that help keep the plant processes moving in a designated direction. These include switches, nozzles, and orifices.

ANALYZER

AVERAGING PITOT TUBE

CORIOLIS METER

FLOW CONDITIONER

FLOW CONDITIONING DEVICES

FLOW GLASS

FLOW NOZZLE

FLOW SWITCH

FLUME

GENERAL-SYMBOL-IN-LINE-ELEMENT-XX

MAGNETIC

ORIFICE IN QUICK CHANGE FITTING

ORIFICE

PITOT TUBE

POSITIVE DISPLACEMENT

ROTAMETER OR PURGE (SHOWN WITH OPTIONAL INTEGRAL VALVE)

RESTRICTION ORIFICE

TARGET

THERMAL MASS FLOWMETTER

TURBINE OR PROPELLER

ULTRASONIC

VENTURI

WEDGE METER

VORTEX

WEIR

Instrumentation Symbols

Instrumentation symbols include meters, transmitters, sensors, indicators, and a variety of other symbols used to record and display measurements.

ANALYZER TRANSMITTER

COMPUTER

COMPUTER INDICATOR

CORIOLIS FLOW SENSOR

DIAMOND

DIAPHRAGM METER

DISPLAYED CONFIGURABLE

DISPLAYED PROGRAMMABLE DEVICE

DOUBLE

FLOW CONTROLLER

FLOW ELEMENT

FLOW INDICATOR

FLOW METER

FLOW NOZZLE METER

FLOW RECORDER

FLOW TRANSMITTER

FLUME METER

INDICATOR 4

INDICATOR 5

PROGRAMMABLE INDICATOR

LEVEL ALARM

LEVEL CONTROLLER

LEVEL GUAGE

LEVEL INDICATOR

LEVEL RECORDER

LEVEL TRANSMITTER

MAGNETIC

MANHOLE

ODOMETER

PILOT TUBE TYPE FLOW

PRESSURE CONTROLLER

PILOT TUBE

PRESSURE INDICATOR

PRESSURE INDICATOR 1

PRESSURE RECORDER

PRESSURE RECORDING

PRESSURE TRANSMITTER

QUICK CHANGE

ROTARY METER

ROTAMETER

SAMPLER

STRAIGHTENING VANES

SOCKET CONNECTION

TARGET METER

TEMP CONTROLLER

TEMP INDICATOR

TEMP TRANSMITTER

TEMP RECORDER

TEMPERATURE ELEMENT

THERMOMETER

TRANSDUCER

TURBINE METER

ULTRASONIC METER

V-CODE METER

UNIT CONTROL PANEL

TURBINE METER

VENTURI

VORTEX SENSOR

WEIR METER

WEDGE METER

Miscellaneous Symbols

A number of other miscellaneous items can be found in P I D symbols including mechanical and electrical components.

AGITATOR MIXER

AIR FILTER

AIR RELEASE HEAD

ANODE

APRON CONVEYOR

AUTO DRAIN

BATTERY LIMITS

BI-DIRECTIONAL PRIMARY SECONDARY & INSTRUMENT LINE CONNECTOR

BREATHER

CALIBRATION COLUMN

CENTRIFUGE

CLEAN OUT

CLOSED DRAIN

COIL

CONVEYOR

CORROSION COUPON

CRUSHER

CYCLONE SEPARATOR

DAMPER

DESUPERHEATER

DETONATION ARRESTOR

DRYER

E-CELL

EJECTOR EDUCTOR

EJECTOR

ENVIRONMENTAL BOX

EQUIPMENT INSULATION

EXHAUST HEAD

EXPANSION JOINT

FILTER AIR-INTAKE

FLAME ARRESTOR

FLEXIBLE HOSE

FLOW ARROW

FUTURE & EXISTING

GAP

GOOSE NECK VENT

GRADE

HOLD CLOUD

HOPPER BIN

HORN

INJECTION QUILL

IN-LINE MIXER

IN-LINE SILENCER

INSTRUMENT AIR SUPPLY

INSTRUMENT GAS SUPPLY

INSULATION KIT

ITEMS TO BE REMOVED DEMOLISHED

JACKETED OR DOUBLE CONTAINMENT

MEDIA TRAP

MONORAIL HOIST

NOTE TAG

NOZZLE TAG

OPEN DRAIN

PACKAGED EQUIPMENT LIMITS

PRIMARY (AG & UG)

PRIMARY SECONDARY AND INSTRUMENT LINE CONNECTOR

PULSATION DAMPENER

PURGE CONNECTION

REMOVABLE SPOOL

REVISION CLOUD

REVISION TRIANGLE

SAMPLE CONNECTION

SCALE

SCREW CONVEYOR

SECONDARY UTILITY (AG & UG)

SIGHT FLOW INDICATOR

SLOPED LINE INDICATOR

STEAM TRAP

SWIVEL OR ROTARY JOINT

TEST POINT

THIEF HATCH

TIE-IN SYMBOL

TRACING MANIFOLD

TRANSITION PIECE

TRUCK GROUND LOCATION

TUBE COIL

UTILITY CONNECTOR

VENDOR SUPPLIED

VENT SILENCER

VENT TO ATMOSPHERE WITH END CAP

VENT TO ATMOSPHERE WITHOUT END CAP

VIBRATING CONVEYOR

VORTEX BREAKER

Piping Fittings

Piping fittings include caps, couplings, silencers, rings, strainers, and a mix of other equipment to connect piping within the design.

BARRED TEE

BASKET STRAINER

BELL MOUTH

BLANK

BLEED RING

BREAKTHROUGH

CAP

CLAMPED FLANGE COUPLING

COMPRESSOR SILENCERS

CONCENTRIC (OR GENERIC) REDUCER

COUPLING

DOUBLE LINE NOZZLE MANWAY

DRAIN SILENCER

DRAIN

DRIP PAN ELBOW

DUPLEX STRAINER

ECCENTRIC REDUCER

ELECTRICAL BOUNDED

FIELD-WELD

FLANGE SET OR FLANGE WITH BLIND FLANGE

FLOW INDICATOR

FRONT FACING NOZZLE MANWAY

HOSE CONNECTION

OPEN FIGURE 8 BLIND

PLUG

SIGHT GLASS

SINGLE LINE NOZZLE

SPACER

THREADED SW CAP

TRACED LINE

T-TYPE STRAINER

UNION

VENT

WELDED CONNECTION

Y-TYPE STRAINER

Valve Symbols

Valves control flow within engineering designs. We’ve broken these into two categories: Actuators and Self Regulated Relief Valves

Actuators

Actuator valves use a mechanism to open and close a valve. They are often manually controlled.

CYLINDER PISTON

DIAPHRAGM

ELECTRO-HYDRAULIC

FAIL OPEN

HANDWHEEL - USED WITH ANY ACTUATOR

INTERLOCKING CYLINDER PISTON (4-WAY VALVE SWITCHING)

MANUAL OPERATOR

MOTOR OPERATED

PRESSURE BALANCED DIAPHRAGM

SINGLE SOLENOID WITH MANUAL RESET

SINGLE SOLENOID WITH REMOTE RESET

SINGLE SOLENOID

TYPICAL CONTROL VALVE WITH POSITIONER

VALVE WITH BLEED CONNECTION 3-WAY SOLENOID VALVE

Self Regulated & Relief Valves

Self-regulated relief valves often referred to as safety valves, are used to release pressure from a system.

These valves are used to control the build-up in a system and do not require manual operation.