In order to guarantee that emergency shutdown (ESD) valves of a Safety Instrumented Function (SIF) also operate fault-free when a safety hazard occurs, their perfect functioning must be regularly checked. Therefore the Partial Stroke Test (PST) is the perfect solution.

During this test, the valve movement is checked by using the valve positioner SIPART PS2 through partially opening or closing without stopping the process. The valve stroke is usually 10 to 15%. With this test method maintenance costs and plant shutdown times can be clearly reduced (up to 50%).

The PST from Siemens is conform to SIL2 and contains preconfigured function blocks, which provide operator alarms and feedbacks on the valve function and apply PFD calculations to determine the time of the next Full Stroke Test. Ready-to-use faceplates are available for visualization on the operator system.

Hardware

Software

	Online valve test without interfering with production
	Test covering different types of failure
	Preventive diagnostics
	More flexible tests and longer test intervals
	Minimization of duration for bypassing the ESD valve or for process shutdown
	Lower failure probability of valve when required
	Feedbacks concerning Full Stroke Tests required to retain the SIL