Field Pressure Testing

[CobusvanJ]

Hi,

Please help me with the following questions regarding field pressure testing (Vessels are ASME VIII Div. 1):

1. The supplier of a vessel to a client of ours managed to ship the vessel to site without final release inspection, and now the vessel requires major repairs (i.e. a 1200mm flange that is skew has to be cut off and rewelded). The vessel has not been commissioned. In this case of a major repair on site before commissioning, does a test pressure have to be repeated at shop test pressure value?

2. We have two vessels that were seperately shop pressure tested that will be welded together nozzle-to-nozzle on site. Somewhat like a column with a heat exchanger hanging off it. Does the combined assembly have to be pressure tested again?

 

[metengr]

1. The supplier of a vessel to a client of ours managed to ship the vessel to site without final release inspection, and now the vessel requires major repairs (i.e. a 1200mm flange that is skew has to be cut off and rewelded). The vessel has not been commissioned. In this case of a major repair on site before commissioning, does a test pressure have to be repeated at shop test pressure value?

Was the vessel code stamped and data report completed? If so, this repair can be done in the field either under API 510 or the NBIC. A pressure test may be required OR comprehensive NDT of the repair weld(s).

If the vessel was not Code stamped or a final hydrotest was not completed, the vessel re-work could be done in the field and ,yes, a final hydrotest would be required.

2. We have two vessels that were separately shop pressure tested that will be welded together nozzle-to-nozzle on site. Somewhat like a column with a heat exchanger hanging off it. Does the combined assembly have to be pressure tested again?

Again, same question applies to (1) with corresponding replies.

 

[Duwe6]

In my experience -- USA, with A.I.'s

1) Usually no, unless the rework changes the MAWP, i.e. an Alteration. If its an Alteration, generally "yea".

2) NO Assuming each vessel has it's own U1, you are done with hydro, unless the Owner's Pipe Inspector requires it. Typically, NDE-in-lieu-of-hydro is allowed. BASIS: 1st connection out from the vessel, per ASME Sect VIII, is not a vessel weld - it is part of the piping. Your field weld will be "1st connection out", not inside the vessel's certification hydro boundary. Where the U1 stops, it is the Owner's responsibility.

 

[rhg]

This is a new pressure vessel under construction and not yet finished. Hence, has not be completed.
As per UG-99 "The completed vessel,........., shall have satisfactorily passed the hydrostatic test.....".

This is the cost of a bad work: a lesson to learn.

Regards

rhg

 

[Duwe6]

rhg I've gotta disagree, somewhat. IF the 2 vessels in item 2) were designed as one assembly and are listed on the same U1 then the requirements of UG-99 have NOT been met.

However, if each of the 2 vessels has its own U1, and the final hydro and final certification on both U1's was signed off by the AI, UG-99 has been satisfied. Makes the field-welds to attach them to each other as I described - Owners responsibility, not a Sect VIII item. Two U1's equals two separate, discrete vessels.

Yes, this is 'hair-splitting', but when working to ASME you are expected to be able to accurately split hairs. It really stands for Always, Sometimes, Maybe, and Except. Just the new guys think ASME is American Society of Mech Engrs.