Gagging of PSVs 2

[That1Guy]

I've been tasked with writing a procedure on gagging of PSVs for our plant. I've been looking and I don't see any code based direction on limits for gagging of live PSVs, but since the relief valves are usually your last line of defense on overpressure of equipment, I thought I might just be missing something. I am far from a code expert, so any assistance I can get on where to look or whether or not there are even codes in existance that restrict gagging of in-operation PSVs would be extremely helpful.

The situation is for gagging of in-service PSVs, not for use in hydrotesting. I have the skeleton of the procedure developed, but I don't know if disabling of a relief device in operation is allowed by code.

If anyone can assist with some wisdom, I would really appreciate it.

Thanks!

 

[Duwe6]

ASME and NBIC *only* allow gagging or closing a block valve on a PSV if the valve is constantly attended 'manned' by an Operator. The assumption is that the Operator is in communication with the Control Room, or can see a pressure gauge that will tell him/her that there is an overpressure condition and that the pressure must be immediatly be relieved. Your Operator is the Pressure Safety Relief 'Device'. And this means that that Operator cannot walk away from that valve for any reason, unless the gag is removed.


Other than a carefully monitored and applied hydrostatic test, there is no allowable Code rule that lets anypne gage a Safety Device and walk away from it.

This onl;y applies to Pressure Safety Devices, not pressure relief valves being used for pressure control by recirculation. If it is not a Safety Device, it can be left gagged.

If it is a Safety Device protecting a vessel, boiler, or pipe system, there is no Code, engineering, or moral excuse to defeat a necessary Safety Device.

 

[That1Guy]

Duwe6,
"ASME and NBIC *only* allow gagging or closing a block valve on a PSV if the valve is constantly attended 'manned' by an Operator. " Do you have the location of this section / comments? If I can reasonably deny management's request to gag a valve, this discussion at my plant becomes academic in nature. However, without some sort of documented reason, I don't think this is going to go away that quickly.

In my personal opinion, I would not want to see a PSV gagged at all. However, I can imagine scenarios where this could be desired and this is what I'm in the process of defending against.

 

[Duwe6]

Look in UG-135 and Appx M Sect-5.
I'll look up the NBIC reference for a star

 

[don1980]

LSPE,

You won't find any code rules or guidance that specifically discusses gagging. Instead, ASME Sec VIII says that pressure vessels must be protected. The general requirements are found in UG-125. UG-126 through UG-140 contains the specific requirements related to different types of relief devices.

Gagging a PSV is effectively the same as taking the safety valve out of service for maintenance/testing. The user is responsible for establishing and maintaining a management system that ensures a vessel is not operated without overpressure protection, and ASME Sec VIII Appendix M explains interim measures for protecting a vessel if the PSV is out of service. Refer to Appendix M, M5.3 for a list of owner responsibilities. Then refer to M5.6 for guidance in how that can be done. Although this section deals with isolating a PSV by closing the inlet valve, it effectively covers the same situation you describe (gagging). Review this section and make sure that whatever you're doing is in compliance with these safety guidelines.

 

[That1Guy]

That is the information I needed. Thanks for your assistance. This should allow me to reasonably explain why we cannot write a procedure on gagging of relief devices.

Stars for both of you.

 

[BenThayer]

for hydrotesting our equipment, we have a regulator that we will dial in to the pressure we want to achieve in addition to a calibrated pressure indicator.

that way, we are effectively not allowing ourselves to exceed the test pressure.

 

[Duwe6]

NBIC [current ed.]: Part 2 2.5.4 h) no valves, except as provided for in Part 1, 5.3.6 e), and in accordance with your local Jurisdiction. I interpret 'no valves' to also include gagging, as either defeats the safety device

Part 1, 5.3.6 e) when Safety Device is defeated, an operator must be "stationed there during the period of operation while the valve remains closed"

And the final word will be from your Authority Having Jurisdiction -- AHJ. Probably your state Boiler and Pressure Vessel Inspection committee. Asking to run with required PSV's gagged will get you laughed out of the state office, and probably cause a immediate, painful State Inspection.