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Control Valve · Glossary

What is Partial Stroke Testing?

Symbol: PSTonline valve testControl Valve

Partial stroke testing moves a shutdown valve a small amount, typically 10 to 20 %, to prove it is not stuck, without stopping the process.

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Partial Stroke Testing Explained

PST detects many dangerous failures, such as a seized stem or failed solenoid, between full proof tests. This can lower the average probability of failure on demand of the safety function.

It does not prove tight shut off or full travel, so full stroke and leak tests are still needed at the proof test interval.

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Calculators for Partial Stroke Testing

CalculatorPartial Stroke Test CalculatorFree online calculator with formula and worked example.CalculatorPFDavg CalculatorFree online calculator with formula and worked example.

Free Downloads

Free downloadESD Valve Stroke Test Report FormatFree download in Excel and PDF.Free downloadESD Valve Proof Test ProcedureFree step by step procedure, Word and PDF.

Frequently Asked Questions

What is Partial Stroke Testing?

Partial stroke testing moves a shutdown valve a small amount, typically 10 to 20 %, to prove it is not stuck, without stopping the process.

How far does a partial stroke move?

Commonly about 10 to 20 % of travel, small enough not to upset the process.

What is PST diagnostic coverage?

The fraction of dangerous failures the test can detect, used in PFDavg calculations.

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