Common P&ID Symbols: A Definitive Guide
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:
- Atmospheric tanks
- Compressors & Blowers
- Heat exchangers
Atmospheric tanks are containers for holding a variety of liquids at atmospheric pressure. There are various types as follows:
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.
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.
Filters eliminate impurities from the passing fluid using physical, chemical, or biological processes to remove the contaminants.
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.
Heaters use the heat transfer process to heat water above its initial temperature using energy.
HVAC equipment is used for heating, ventilation, and air conditioning or cooling.
Pumps are used to move liquid through a plumbing system. Pumps are often used to move liquid vertically using an energy input.
Stacks are used for exhaust air from a variety of processes.
Vessels are containers used to hold gases or liquids at a higher or lower pressure from the ambient air.
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.
Flow elements represent functional pieces of equipment that help keep the plant processes moving in a designated direction. These include switches, nozzles, and orifices.
Instrumentation symbols include meters, transmitters, sensors, indicators, and a variety of other symbols used to record and display measurements.
A number of other miscellaneous items can be found in P I D symbols including mechanical and electrical components.
Piping fittings include caps, couplings, silencers, rings, strainers, and a mix of other equipment to connect piping within the design.
Valves control flow within engineering designs. We’ve broken these into two categories: Actuators and Self Regulated Relief Valves
Actuator valves use a mechanism to open and close a valve. They are often manually controlled.
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.