Welding after hydrotest

[1169]

Would it be permissible to weld non pressure parts to the interior of a vessel after hydro testing when not subject to PWHT?
I know that UG- 99 a.1 indicates that all fabrication should be complete before hydrotesting, but does this not apply only to pressure envelope?

Thanks for any information

 

[tickle]

Generally you are not allowed to weld to any pressure containing component including the inside of the pressure vessel shell.

 

[metengr]

What exactly are you referring to when you say the interior of the pressure vessel surface? If you are welding a non-pressure part directly to the vessel wall (the pressure boundary), the answer is re-hydrotest to meet the requirements of UG-99.

If you are adding trim that is not welded directly to the vessel wall, this can be done with approval from the AI.

 

[mw25]

Dear metengr,
Why do you think AI should be consulted for this?
Only reason i could think is, this additional attachment may affect structural integrity of vessel. Just curious.
Thanks.

 

[metengr]

Yes, the AI should be aware of any type of weld repair activity (especially after post hydrotesting). I had come across one situation where an internal, non-pressure part attachment was inadvertently missed on a vessel. The hydrotest was completed. The AI was consulted and they allowed the attachment to be welded (not bolted) after the hydrotest because the attachment was a non-pressure part and was not directly welded to any pressure boundary of the vessel (it was considered trim).

 

[deanc]

mw25:

Why not ask? Keep yourself out of trouble.It may be simple as a phone call. If this does not take place it raises questions about your entire program. Do audits and hold points ring a bell?

Remember who the last guy to sign the Data Report is.

 

[GenB]

I think there is a par. in the Code that allows connections up to 2" to be welded after PWHT and 1/2" after hydro.
GB