Hydraulic actuator

ISA 5.1-2009/2022 (final control element actuators) / PIP PIC001

Drawn as

A cylinder rectangle on the stem with a piston line and "H", fed by a hydraulic signal line (a line with "L" marks).

Meaning

Hydraulically powered cylinder, typical on wellhead valves (SSV/USV, wing valves) supplied from the wellhead HPU through the wellhead control panel.

Variants

Wellhead surface safety valves are often drawn as a gate with a hydraulic piston and spring, tagged SSV or USV
The hydraulic supply line may be drawn without marks and just labelled HPU