PRV resetting frequency

[GarethChem]

Hi everyone

I have tried searching for an answer on the forums and google and can't find anything conclusive. I used to work for a company who said that every time that a PRV lifted, it had to be taken out and reset as the spring became unreliable (though this was never done in practice, this was part of regulations).

The company that I am working for now is involved in turnkey projects. During commissioning, some of the PRVs would lift multiple times, but they were never taken out to be checked/reset.

My question is: will a PRV lifting effect the time until the next check/reset? Should it be checked every time it lifts?

Thanks
Gareth

 

[Duwe6]

". . . taken out and reset as the spring became unreliable."
Utter hogwash, bovine excrement, etc. And not part of any North American rules/regulations.

It is a spring, not a buckling pin. The 'proper reason' to pull a 'popped' PRV is if you cannot tell if it has reclosed tightly. Unlike the idiots on the control panels at Three-Mile Island nuke, try to remember that PRV's are Positive Opening devices. They are not Positive Closing devices.

After it has lifted & relieved, check for simmering and weeps. If it is tight, it is just fine. The only thing that should be done is to shorten the Test & Reset interval, as opening and closing may have disturbed [widened due to the slam of closing] the thin, lapped contact surface between the disk and nozzle. But if it closes tightly, be happy and keep running until a convenient Shut-Down date.

 

[waqasmanzoor]

As an operation person, I can say NO.

However, you should grease the PSV "check nut" and perform overhauling of the PSVs from time to time. The PSV spring is usually not exposed to any "harsh" liquids, so the life of spring is very LONG generally. I am saying this owing to my operational experience with a large number of PSV in the oil and gas environment.

Each time a PSV pops open, it saves you and it proves that it's working normal

However, I do suggest to perform periodic checking of PSVs, to ensure the PSV DISK does not stick to its seat and the PSV remains ready to pop at high pressure

In actual operational practice, it is generally said that if the VERIFIED the operation of safety instrumentation during start up or before start up then as per MURPHY's law, it would not operate during EMERGENCY

And that also includes verifying that compressor over-speed tripping instrumentation is working fine, during start up.

 

[waqasmanzoor]

Sorry, there is a typo in the last two lines and I'm unable to find an option to edit the post...

Here's the corrected line..

--- it is generally said that if we have not VERIFIED the operation of safety instrumentation during start up or before start up then as per MURPHY's law then it would not operate during EMERGENCY

 

[Duwe6]

". . .perform overhauling of the PSVs from time to time."
Yes. Based on the service fluid that each PSV sees, they need to be pulled and sent to a "VR"-stamp holding PSV facility for a certified test, and refurbishment as required. We use 1-year for Dirty & Fouling service, 3-years for clean product and cooling water, 5-years for steam, ammonia and other extremely clean refrigerants.

Working on a PSV yourself is a very bad idea. You need the knowledge, library, and experience of a VR shop. And you still cannot certify your work as fully meeting ASME & NBIC Code. Just send them out.