Recommended a second hydrotest if PWHT done after first hydrotest?

[AWDMIKE]

I have a new pressure vessel which is not Code stamped. For process conditions it is required to be PWHT, but this requirement was added after the vessel had been hydrotested. The vessel is still at the shop and will now receive a PWHT.

Is it recommended to perform a second hydrotest after the PWHT is complete? Any responses are appreciated.

 

[vesselfab]

if this was a code vessel, it would have to be hydrotested after the pwht.

Hydrotest is the last thing to be done after all fabrication processes are complete.

but this is not a vessel.

If it were me, i would re hydro and roll the cost into the adder for pwht.

 

[metengr]

Is it recommended to perform a second hydrotest after the PWHT is complete? Any responses are appreciated.

Yes. See Section VIII, Div 1 UG-99.

 

[unclesyd]

I think a few more details are required as OP states this is not a code vessel and the PWHT is required for process reasons. Granted the second hydro would be preferred approach if it's just a stress relief that is needed for process conditions a lower temperature approach might be the way to go.

 

[stanweld]

Assuming that the contract specification required design, fabrication and testing to be done per ASME VIII but stamping was not required due to location of installation, the vessel should be rehydrotested.

 

[AWDMIKE]

Thank you for all of the responses. We've decided that the vessel will be re-hydrotested after the PWHT.