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P&ID Selecting between two pumps

P&ID Selecting between two pumps

P&ID Selecting between two pumps

I have an application where I have to holding tanks with LOW and HIGH level float switches in each tank. The outlets of each tank tie together and are the suction to a duplex pump skid. I want to know what the proper symbols are to show on the P&ID that either set of float switches can turn the pumps on or off. For lack of something better, I was planning to show it like the sketch I attached.

RE: P&ID Selecting between two pumps

I was trained to never show that level of detail on P&IDs. Nothing wrong with it but it clutters them up. My training would only require one interlock symbol for the switches and pumps. Pump controls would be handled on the loop sheets and elementary wiring diagrams. If the logic is complex enough, do a separate logic diagram. I'm sure others can provide much better guidance.

Pamela K. Quillin, P.E.
Quillin Engineering, LLC

RE: P&ID Selecting between two pumps

I agree with Pamela. Loop diagrams show detailed function, P&IDs show general function.

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