Box type Local Hydrotest 1

[gitsunil]

I enclose herewith some past job data where one of the VENDOR has carried out Local hydrotest by BOX TYPE arrangements (for site joints). Request to assist me how to support this type of arrangement with respect to ASME code? Is there any back up/ technical literature/ handbooks which explain/ elaborate this procedure? Further, differences if LOCAL BOX is applied internally/ externally (since when applied externally – hydrotest pressure is also applied externally). What could be the alternates?

Thanking you,


Best regards,
Sunil Agrawal
Tecnimont Private Limited

 

[r6155]

1)Corner Joints are nonpermissible in ASME VIII
2)Look at ASME PCC-2 Article 5.2

Regards

 

[JStephen]

A hydrotest is both a proof test of weld/vessel strength and also a leak test for welds. That kind of arrangement could accomplish the leak testing but not the proof testing.

 

[gitsunil]

Thank you for reply, what is the main difference between lest testing & proof testing?


Best regards,
Sunil Agrawal
Tecnimont Private Limited

 

[FormerAIS]

UG-99 requires that the entire vessel undergo a hydrostatic test, not just the welds. The material is tested to ensure ASME Compliance as well as the welds.


Quality is not an act, it is a habit - Aristotle

 

[r6155]

gitsunil, you need to contact a pressure vessel engineer.

Regards

 

[Dhurjati Sen]

Dear gitsunil,

It seems to me that the VENDOR could not weld those joints in the shop i.e. before hydro-test, for whatever reasons and now they have done it at site and instead of complete hydro-test of the reactor once again they are doing something ingenious !!!

You raise the NC, or ask the CLIENT to raise one.

You need to perform NDE of the those joints like LPI & USFD and close the NC.

Regards.

DHURJATI SEN

https://www.nace.org/people/dhurjatisen

 

[marty007]

We have built a couple of vessels that need to be shipped in two pieces, and for some reason can't be hydrotested in the field in the final position (refractory lined internals).

What we normally do is:[ol 1]
[li]Build the complete vessel in our shop, including welding of this field joint.[/li]
[li]Have the vessel inspected by the AI, and have the vessel U-1 form signed and nameplate attached.[/li]
[li]Cut the weld open again, and install any internals that need to be installed (refractory is our normal situation)[/li]
[li]Ship the vessel in two pieces to the field.[/li]
[li]The field completes the final closure seam - this work is now deemed a REPAIR under the rules of NBIC[/li]
[li]NBIC states that a hydrotest should be performed unless it is not practical. In our cases, the refractory couldn't get wet, so a hydrotest was not practical. Different customers have accepted different levels of inspection. Some will accept 100% RT and PT and leave it at that. Others have requested boxes like you've described for a local leak test. In either case though, this is now within the rules of NBIC[/li]
[/ol]

The important thing here is that ASME requires a hydrotest of the complete vessel. A box like this should not be acceptable to the AI. If you have to ship a vessel in two pieces, consider following the procedure listed above.