Pressure switch

ISA 5.1-2009/2022 (primary element symbols) / PIP PIC001

Drawn as

A bubble with PSH, PSL, PSHH or PSLL on an impulse line from the process.

Meaning

Pressure switch giving a discrete alarm or trip. Old-style or package protection. Becomes pressure-switch.

Variants

On modern plants the same letters often mean a trip point inside the DCS/SIS from a transmitter; then the bubble has a bar or a square
Packaged machines (lube oil, seal gas) still use real switches