closing speed for pop action pilot operated PSV

[MortenA]

Doing a surge study on a fire water system.

I have the idear that a slower closing psv might help.

Does anybody here know if the closing time for a pop action pilot operated valve could be made adjustable? Preferrably so that the opening time was as high as possible - and the closing time slower.

I know that convetional wisdom dictates that a psv is "instantaneous" - but what is that? I have assumed that the travel time from open to closed/closed to open is 1/4 of a second. But increasing the closing time to e.g. 2 secs could propably just give the edge that i need in some cases.

References to manufacotr who can provide this data or articles on the subject would be greatly appreciated.

Best regards

Morten

 

[MortenA]

I realise now that the use of the work "pop" perhaps is a bit misleading since this is obvioulsy liquid service. Still im thinking about a pilot operated valve that opens fully at the set point and closes fully at the re-set point

A question along this line: API 520 part 1 igure 24 shows this relationship. Is there a limit to how low the DB can be for such a valve - technical or by code? I do ofcourse understand that you may risk that the reseat pressure is so low that the valve wont re-set - but thats not whan im concerned about here and now.

Best regards

Morten