Pressure hydrostatic test or pressure relief device, which is greater?

[Cesaredu]

I dont know to pressure vessel wich is greater if pressure hydrostatic (Ph= 1.3*Pdesign) (ASME VIII) or set pressure relief device Psv, that pressure must be less than the Ph?

can u help me?

Best regards for all,

 

[racookpe1978]

You will usually find that, if the relief valve is left in place (not removed/blanked off), your hydrostatic test pressure will seldom get very far above the setpoint of the pressure relief valve for your system. 8<)

 

[rustbuster]

The relief valve must be set at or below the MAWP, hydrotest is 1.3 x MAWP.

 

[Cesaredu]

Thanks,

But that is only if the vessel is new ??? or not.
Because i have pressure vessels but they have many years in operation.

Best regards,

 

[metengr]

Cesaredu;
Please check the nameplate information against the set point of the PRV tag.

 

[Cesaredu]

They dont have any name plate, its a problem!! , i just have MAWP of the real thickness.

Thanks,

 

[JohnGP]

Cesaredu,

Regardless of whether the vessels are new or not, the PRV must not be set higher than the MAWP, as rustbuster stated - see UG-134 in ASME VIII Div1.

I may have misunderstood your original question - if you are wanting to re-hydrotest existing vessels, then you would need to remove or isolate any PRVs if you are testing above MAWP - see for example paragraph 6.5 in API-510.

Cheers,
John

 

[racookpe1978]

I got the impression he was concerned - not just about re-hydrotesting old vessels - but in determining what the hydro-test pressure/max operating pressure should for those existing vessels (the ones with "no label found") in the first place. That is, back-calculate from the vessel wall thickness what the original design pressure/operating pressure/hydro-pressures would be. (Or, he was trying to find out what the set pressure on the old relief valves was supposed to be for the old vessels.)

All of those conditions become potentially deadly situations.

 

[JohnGP]

Well, hopefully from the above replies he has the answer he was looking for?

 

[Cesaredu]

Yes, thanks for all, API 520 was the solution there is a chart very explicit for pvs !!, but i still have a question, code asme VIII div 1... its only for new vessels? i dont know where i could find that information.

Best regards for all,

 

[gr2vessels]

Yes, the ASME VII -1 is the design code for new pressure vessels. You can use sections, paragraphs or formulas of ASME VIII-1 when instructed by other relevant standards.
Cheers,
gr2vessels