Welding of Attachment after hydro-static Test 5

[ahmadire]

Dear Experts,
Are we allowed to attach some clips after Hydro-static Test on pads which are previously welded on P.V's shell as per ASME code?
Please share your thoughts
Thanks

 

[Caloooomi]

Does it have a U-stamp?

After hydro test, I thought it was considered finished and as such, you would need to get an R-stamp in order to do anything further?

 

[viper3982]

UG-99 STANDARD HYDROSTATIC TEST
(a) A hydrostatic test shall be conducted on all vessels
[highlight #FCE94F]after
(1) all fabrication has been completed, except for operations
which could not be performed prior to the test[/highlight]
such as weld end preparation [see U-1(e)(1)(-a)], cosmetic
grinding on the base material which does not affect
the required thickness; and
(2) all examinations have been performed, except
those required after the test.
The completed vessels, except those tested in accordance
with the requirements of UG-100 and UG-101, shall
have satisfactorily passed the hydrostatic test prescribed
in this paragraph.

ALSO, and this could depend on the AI's interpretation, it falls under the scope of ASME until the data report is signed. I.E.: you could re-hydro the vessel prior to signing the data report and it's still under ASME. Once the data report is signed, to modify the vessel, an R-stamp is required.

 

[metengr]

Agree with above. If the vessel is completed, meaning the hydrotest and data reports are signed and the vessel has been stamped, the vessel is no longer under construction rules. Any welding must be done under API or NBIC.

 

[r6155]

ahmadire: Yes, you can
U-1 (e)(2) where nonpressure parts are welded directly to either the internal or external pressure retaining surface
of a pressure vessel, this scope shall include the design,fabrication, testing, and material requirements established
for nonpressure part attachments by the applicable paragraphs of this Division;3

ENDNOTES
3 These requirements for design, fabrication, testing, and material for nonpressure part attachments do not establish
the length, size, or shape of the attachment material. Pads and standoffs are permitted and the scope can terminate
at the next welded or mechanical joint

Regards
r6155

 

[viper3982]

r6155,

"(e) In relation to the geometry of pressure containing
parts, the scope of this Division shall include the
following:
...(2) where nonpressure parts are welded directly to
either the internal or external pressure retaining surface
of a pressure vessel, this scope shall include the design,
fabrication, testing, and material requirements established
for nonpressure part attachments by the applicable
paragraphs of this Division;3"

So all that is saying is that non-pressure parts welded directly to the pressure retaining surface are included in the scope of this section (VIII). How does that say that you don't have to test the vessel in accordance with the requirements of the scope of section 8?

EndNote 3 is saying that you could have a 1"x1" clip or a 1milex1mile clip and it's still under the scope of the section (size doesn't matter) and that the boundary of the attachment needing to be within the scope of the section ends with the next welded joint past the welded connection to the pressure vessel

r/

 

[viper3982]

Followup,

Sorry, I just re-read the original question: Clips attached to pads attached to the pressure vessel.
RTFQ, huh?

r1655 is correct.
r/

 

[jte]

viper-

You aren't the first and you won't be the last.

And yes, I would not be concerned about any type of rehydrotest for a typical structural attachment weld onto a typical repad in a post-construction environment.

 

[moltenmetal]

Just to make this clearer: if you so much as strike an arc on the pressure retaining envelope of a pressure vessel after the hydrotest, you must re-hydrotest. So no, you can't weld insulation support studs or guard mounting clips directly to the interior or exterior of the shell, heads or nozzle necks etc. of a pressure vessel after it has been hydrotested, but before it has been put in service, without having to repeat the hydrotest. But that's not what the OP asked in this case.

You are free to weld to components which are NOT part of the pressure boundary, but which were welded to the pressure boundary before the hydrotest. An example would be a repad, a poison pad, a leg or support bracket, and presumably a lifting lug. That would of course assume that the welding you're doing would be entirely limited to the non-pressure retaining component and would not result in depositing weld material on the pressure retaining boundary.

Yes, the scope of the vessel can terminate in a nozzle, i.e. a piece of pipe, to which piping will later be welded. The weld between the vessel and the piping becomes subject to the piping code and its NDE requirements.

Once the vessel is in service, post-fabrication codes apply and sometimes specific NDE can be performed instead of repeating the hydrotest.

 

[ahmadire]

Thank you all for your sharing thoughts