Centrifugal pump
Rotating pump for liquids. Tag as P-### on the line it serves.
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P&ID Symbols Chart
Common piping and instrumentation diagram symbols used in process engineering — pumps, vessels, exchangers, valves, and instrument bubbles — with free examples you can edit.
P&ID · every result uses this diagram type · ⌘↵ to run
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Live sample · Feed tank → pump → reactor loop — type above to make your own
P&ID examples using equipment symbols
Open a process draft that already uses pumps, vessels, exchangers, and valves, then rename tags.
Vessel / tank
Vertical or horizontal vessel for hold-up, flash, or storage.
Heat exchanger
Shell-and-tube or air-cooled exchanger transferring heat between streams.
Control valve
Throttling valve with an actuator; often paired with a control loop.
Relief / PSV
Pressure safety valve protecting equipment; discharge path matters.
Compressor
Raises gas pressure. Show suction KO drum and aftercooler when relevant.
Column
Tray or packed distillation / absorption column with overhead and bottoms.
Instrument bubble
ISA-style tag for flow/pressure/temperature indication or control.
Try these symbol-heavy examples
Open a process draft that already uses pumps, vessels, exchangers, and valves, then rename tags.
P&ID symbols (piping and instrumentation diagram symbols) show how a plant is built and controlled: equipment, lines, valves, and instrument loops. They are denser than a process flow diagram (PFD). This page is a practical legend for the shapes FreeDiagram draws when you describe a process in plain English.
How to read P&ID symbols
Find the major equipment
Tanks, pumps, exchangers, columns, and compressors carry tags like P-101 or E-201.
Follow the process lines
Lines show stream direction between equipment. Note line numbers when your project uses them.
Locate valves and instruments
Control valves, check valves, PSVs, and ISA bubbles (FIC, PIC, TIC) show how the unit is operated and protected.
Draft from a sentence
Describe the unit on the P&ID or process flow diagram maker; treat the output as a working draft for review.
P&ID symbols vs flowchart symbols
Flowchart symbols describe business or software steps. P&ID symbols describe physical plant: equipment outlines based on ISA-5.1 / ISO 10628 conventions, valves, and instrumentation.
A PFD is the high-level cousin of a P&ID: major equipment and main streams, fewer instruments. Teams usually agree the PFD first, then flesh out the P&ID for construction and operations.
Always have a qualified engineer review safety-critical drawings. FreeDiagram output is a drafting aid, not a stamped deliverable.
Frequently asked questions
What does P&ID stand for?
Piping and instrumentation diagram — a detailed drawing of process equipment, piping, valves, and instruments.
Where can I find a P&ID symbols chart?
This page lists common equipment and instrument symbols FreeDiagram uses. Project standards may add company-specific marks.
Is this free?
Yes. No signup to read the legend. Generation has hourly fair-use limits; export SVG or PNG.
P&ID vs PFD symbols?
PFDs show major equipment and streams. P&IDs add valves, line details, and instrument loops. Use the matching maker for each level of detail.
Related engineering tools
P&ID maker, process flow diagrams, and flowchart symbols.
Free P&ID Maker
Describe your process system and get a professional Piping and Instrumentation Diagram in seconds. No account, no software, no cost.
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Describe the equipment and streams in your process, and get a process flow diagram (PFD) with standard equipment symbols. Free, no signup.
Flowchart Symbols and Meanings
A clear chart of the standard flowchart shapes and what each one means, plus free examples you can open and edit. No signup; hourly fair-use limits apply when you generate.
Free AI Flowchart Maker
Describe any process in plain English and FreeDiagram draws the flowchart instantly — decision branches, loops, and all. Free, hourly fair-use limited, no signup.