363 Common P&ID Symbols: An Engineer’s Library
Looking for a library of common P&ID symbols?
Scroll down or use the table of contents on the left to navigate this page and see the different P&ID symbol types commonly used by engineers.
What Does P&ID Mean?
P&ID is an abbreviation meaning ‘Piping and Instrumentation Diagram‘.
Piping and Instrumentation Diagrams are graphical representations of a process system. These 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, including symbols that represent actuators, equipment, flow elements, instrumentation, piping fittings, valves. and more.
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:
- Atmospheric tanks
- Compressors & Blowers
- Drivers
- Filters
- Heat exchangers
- Heaters
- HVAC
- Pumps
- Stacks
- Vessels
Atmospheric Tanks
Atmospheric tanks are containers for holding a variety of liquids at atmospheric pressure. There are various types as follows:
ATMOSPHERIC TANK
BARREL
DOME ROOF
FLOATING ROOF
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
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
REACTORVERTICAL 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&ID 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.
3-WAY VALVE
4-WAY VALVE
4-WAY VALVE ALTERNATE
ANGLE GLOVE VALVE
AUTO RECIRCULATION
BACK PRESSURE REGULATOR (SELF-CONTAINED)
BACK PRESSURE REGULATOR WITH EXTERNAL TAP
BALL CHECK VALVE
BALL VALVE
BUTTERFLY VALVE
DIAPHRAGM
DIAPHRAGM VALVE
DIFFERENTIAL PRESSURE REDUCING REGULATOR
ELECTRO-HYDRAULIC VALVE
EXCESS FLOW VALVE
EXCESS FLOW VALVE-2
EXCESS FLOW VALVE-3
FLANGED VALVE
FLOAT-OPERATED VALVE
GATE OR GENERIC VALVE
GENERIC ROTARY VALVE
GLOBE VALVE
GAUGE ARRANGEMENT
HYDRAULIC VALVE
INDICATOR 3
KNIFE VALVE
METERING COKE
MINIMUM FLOW VALVE
NEEDLE VALVE
PIGGING BALL VALVE
PILOT OPERATED RELIEF VALVE WITH REMOTE SENSOR
PINCH VALVE
PISTON CHECK VALVE
PLUG VALVE
POST INDICATOR
POWERED VALVE
PRESSURE AND VACUUM RELIEF VALVE
PRESSURE RELIEF OR SAFETY VALVE
RAM VALVE
ROTARY VALVE
RUPTURE DISC (FOR PRESSURE RELIEF)
RUPTURE DISC (FOR VACUUM RELIEF)
SELF DRAINING VALVE
SLIDE VALVE
SPRING GATE VALVE
STEAM BLOWDOWN VALVE
STOP CHECK VALVE
SWING CHECK VALVE
TEMPERATURE REGULATOR FILLED SYSTEM TYPE
THREADED SW/BW VALVE
TILTING DISK SWING CHECK VALVE
VACUUM RELIEF VALVE
VALVE POSITION INDICATION - NO
VALVE WITH BLEED CONNECTION
V-BALL VALVE
WAFER CHECK VALVE
WEIGHT GATE VALVE
Y-PATTERN GLOBE VALVE
FAQ - System Integration
What is a P&ID Drawing?
P&IDs are schemes/drawings representing a process system comprised of piping, equipment, instrumentation, and control systems. It depicts the system as a series of symbols and codes to describe the overall circuit.
What are P&ID Symbols?
P&ID symbols are used to represent components in a system. Each component has a unique symbol, detailed with codes to identify the function and measurements of the device.
How do you read P&ID symbols and codes?
For symbols comprised on a 12mm circle, the top letters are the functional indicator, the bottom numbers are the measurement on control value and the following suffix indicated whether there are multiple instruments in a chain.
The first letter (functional indicator) is based on the ISA code. The functions are as follows:
The table above shows the common code symbols, however, some codes can be chosen uniquely for each project.
HH and LL can also be used to indicate very high (maximum) or very low (minimum) values.
If the circular symbol is encompassed by a square, the components are integrated as a function in a DCS or PLC.
DCS – Distributed Control System
PLC – Programmable Logic Control
Symbols for Power Supply
- AS -Air Supply
- IA – Instrument Air
- PA – Plant Air
- ES – Electrical supply
- GS – Gas Supply
- HS – Hydraulic Supply
- NS – Nitrogen Supply
- SS- Stream Supply
- WS – Water Supply
How do you read P&IDs?
To read a P&ID you need to be aware of the relevant symbols and codes. For circular symbols, the dividing line suggests the type of mounting used for the device. Continuous dividing line – the instrument is suitable for control room mounting. Dotted dividing line – the instrument is suitable for technical room mounting. No line – the instrument is suitable for field application. Control Signals for components show their input and output – e.g. electrical or hydraulic signals. They are depicted by the lines entering and leaving the component – e.g. a dashed or wavy line.
What is an FV in a P&ID?
As mentioned above, the functional identification consists of a first letter, designating the measured or initiating variable (examples include F-flow, P-pressure, T-temperature, L-level). In the case of FV, the first letter F stands for flow. The second (and sometimes third and fourth letters) are modifiers, for example:
- FT – Flow transmitter
- FC – Flow controller
- FY – I/P transducer
- FV – Flow control valve