Performing SPOT PWHT and Second Hydrotest

[Masoudt301]

Dear Friends
In an ASME VIII DIV 1 vessel which PWHT and Hydrotest have been done on that, it needs Internal ANODES to be installed with fillet weld. As this is a non-pressure item, the following concerns may be caused:
1- Is it necessary to perform SPOT PWHT on the support?
2- Is it necessary to perform Hydrotest after welding?

AS you all know ASME VIII stated that “A hydrostatic test shall be conducted on all vessels after all fabrication has been completed,……”.
It would be my pleasure to read all your helpful comments.
Thank you in advance.

 

[nickelkid]

Has the vessel already been stamped?
I do not think you will be able to get away without another hydro, but what does the AI say?

 

[metengr]

Section VIII, Div 1 unlike Section I does not permit welding after hydrotesting has been completed, in other words the vessel is stamped. You may be able to perform this work under an R-Certificate or API 510 as a repair.

 

[Duwe6]

What metengr said.

Two reasons: Sect VIII is only for building vessels. It stops sometime between the application of the "U" stamp and the first drop of product being put into it. Depending on 'Jurisdiction' and country the vessel is located in, either R-stamp contractor plus their AI [not yours, not the fabrication AI or [rarely] an API-510 Inspector and an 'approved repair organization' will have to do the work.

Second Reason: The real meaning of the U-stamp is "You don't touch it" . ALL work requires an approved 'organization' - a construction company with certified welders, tested & approved WPS's [welding procedures] and a knowledgeable Quality Control dept that works to an approved Quality Control Manual, PLUS an AI - Authorized Inspector - that independently inspects the repair plan, repair/revision work, and the testing of the repair work [including the qualifications of the testing tech's].

And I would be surprised if the Inspector would require a re-hydro. His/her call, but re-hydro is only appropriate when the changes cause the Max Working Pressure MAWP to change. Spot PWHT would probably not be requires for the fillets,unless there is a "for process" reason, like amines, ammonia, etc. And this is up to the Inspector to help you understand the rules, and keep $$$$ from happening.