Balance dice

SVRP update: The perils and pitfalls of PST devices

David Sear - 7 April 2016

Ed Holtgraver raises concerns about partial stroke testing (PST) devices

About the author

Mr David Sear
David Sear is Online Editor. He is contributing to articles, interviews and reports to KCI’s magazines and websites. David also works on videos for KCI Television.
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Earlier in the year I was given a thorough introduction to the topic of SIS valve assemblies reliability prediction by industry expert Henk Hinssen.

Those of you who have had the opportunity to meet Henk will know he never does things by half. So when asked to assess the reliability of emergency shutdown (ESD) valves in upstream applications, he spoke to dozens of involved parties – including manufacturers and users – at great length.

His message was simple: there are shortcomings in various areas – ranging from the technical to the practical – which have to be addressed if end users are to have the required degree of confidence in their ESD systems.

Soon after that conversation, Henk introduced me to Ed Holtgraver, who gave a clear example of potential technical shortcomings in so-called partial stroking of valves. In my naivety I had assumed that PST systems enjoyed industry-wide acceptance, but I’ve since had to review that opinion.

Consider what Ed had to say early on in our conversation:

“…my experience is that many PST systems simply do not work as intended.”


“…many end users have had such poor experiences with PST systems that claim to improve safety that they have banned such products from their plants.”

Those statements might sound bold, but Ed underpinned them with strong arguments when revealing possible weaknesses in both mechanical stop and pressure regulation systems.

If you’d like to know more, why not read Ed’s interview on “the perils and pitfalls of PST devices” in the April issue of Valve World?

And in the meantime, if you have views to share, or wish to put a question to Henk or Ed, then please do get in touch with me at

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