P&ID Flow Element and Equipment Symbols
Symbols for primary elements and equipment around instruments: orifice plates, venturis, magnetic flowmeters, rotameters, thermowells, pumps, vessels and heat exchangers.
Orifice plate
Restriction flow element: two short lines across the pipe, with tappings to a DP transmitter.
Venturi or flow nozzle
Shaped flow element with converging and diverging sections.
Magnetic flowmeter
Inline flow element, often drawn as a pipe section with the letter M inside a circle (project legends vary).
Variable area flowmeter (rotameter)
Tapered tube with float; usually drawn vertical with a local indicator (FI).
Thermowell
Protective well for a temperature element inserted into the pipe or vessel.
Centrifugal pump
Pump: circle with a tangential discharge.
Vessel or tank
Vertical vessel with dished heads.
Heat exchanger
Shell and tube or general heat exchanger: circle with a zigzag tube line.
How to Read These Symbols
Symbols for primary elements and equipment around instruments: orifice plates, venturis, magnetic flowmeters, rotameters, thermowells, pumps, vessels and heat exchangers. Instrument symbols and identification letters follow ISA 5.1. Valve, equipment and some line symbols vary between companies and with ISO 10628, so every project issues a legend sheet: when it differs from this page, the legend sheet wins.
Frequently Asked Questions
What is the P&ID symbol for an orifice plate?
Two short parallel lines across the pipe, tagged FE, with impulse lines to a DP transmitter.
How is a pump shown on a P&ID?
A circle with a tangential discharge line.
Where can I find all symbols used on a project?
On the project P&ID legend (symbol) sheets, which take priority over general conventions.
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