Code welds on inside surface of pressure boundaries?

[flakyman]

Hi,
The question is about attachment welds on the pressure boundaries. In lay-man terms I understand the pressure boundaries as the metal surface responsible for keeping the pressurized media contained. I also understand that the welded attachments on the outer surface of the pressure boundaries are supposed to be ASME Section VIII code welds. However my confusing is about the inside surface. Do the welds attaching various attachments to the inside surface of the pressure boundary also need to be code welds. e.g baffle plates. The engineer in me is saying that it needs to be code weld as well but I could be wrong. I would appreciate if people with more experience in this forum would share their thoughts on this.

Thanks,

JP

 

[XL83NL]

Welds on the outside could alter (pressure retaining) base material properties, if not performed properly. Therefore they can affect the integrity of the pressure containment, hence are code welds.

Couldnt this just as well be the case when youre welding on the inside?
I think the answer is obvious. I dont have a Code reference for my suspicion, so maybe someone can back me up on that part.

Otherwise I stand corrected.

 

[GenB]

Permanent welds on attachments to ASME Coded pressure vessel boundaries must be made by qualified welders/welded operators. Mean Code welding.

 

[moltenmetal]

What is fascinating is that any time you strike an arc to the pressure boundary of an ASME vessel, you need to re-hydrotest it afterward except when it's a weld attachment to piping (i.e. a plain end pipe nozzle rather than a flange or threaded coupling). However, unless I've missed it, ASME says nothing about attacking the interior or exterior surface of the pressure boundary with grinders or other material removing equipment. You'd think that any "hot work" done directly to the pressure boundary, not limited to just welding, would be best completed prior to hydrotesting.

 

[XL83NL]

However, unless I've missed it, ASME says nothing about attacking the interior or exterior surface of the pressure boundary with grinders or other material removing equipment.

The only 'grinding exemption' I know of is in UG-99

UG-99 STANDARD HYDROSTATIC TEST
(a) A hydrostatic test shall be conducted on all vessels
after:
(1) all fabrication has been completed, except for operations
which could not be performed prior to the test
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) ...

 

[metengr]

What is fascinating is that any time you strike an arc to the pressure boundary of an ASME vessel, you need to re-hydrotest it afterward except when it's a weld attachment to piping (i.e. a plain end pipe nozzle rather than a flange or threaded coupling)

The hydrostatic testing above and exemption in UG-99 only applies during construction of the vessel, and not in-service vessels. Once the vessel is hydrostatically tested, stamped, and has a signed code data report, repairs to be performed in-service are under another in-service repair code.

 

[Duwe6]

"Permanent welds on attachments to ASME Coded pressure vessel boundaries" almost got it

Any welding on an ASME pressure boundary is required to be performed by a certified welder, using a qualified Welding Procedure. Welding, including tiny tacks, that were done by unqualified welders are deemed defects, and have to be completely removed, using an approved repair procedure.

i tell my folks: "the U-stamp means 'U' don't touch it". Wait until an "R" or "U" stamp-holding outfit arrives.