The valve is driven 10 to 20 percent of travel and returned, quick enough that process flow barely notices. That reveals the most common dangerous failure, a valve seized open, and lets a site stretch the interval between full proof tests that require a shutdown. Digital positioners and dedicated test panels run the test and log travel and pressure data.
Partial stroke test on the ESD valve failed, it never moved off the open limit, so it's getting written up as a dangerous fault.
Also heard as
- PST
- partial stroke
Related terms
Stroke
To run an automated valve through its full travel to prove it moves, seats and reports position correctly.
Positioner
A device on a control valve that compares the control signal with actual valve position and adjusts air to match.
Fail-closed
Describes a valve that springs shut when it loses air, power or its control signal.
Actuator
The powered device that opens, closes or positions a valve using air, hydraulic oil or an electric motor.