I have a queries on whether it is permissible to do welding of small of pipe support clip on vessel with only fillet welding after completion of shop hydrostatic test.
cmryu,
You don't specify if your question is per Code rules or other, nor other pertinent specifics such as material type, etc, so, a second hydrotest may or may not be required. If your question centers around Code rules, talk to your AI. If we're talking carbon steel, chances are good that you won't have to re hydro. Customer requirements may differ, but, we have done welding after hydro many times without a second hydrotest.
My understanding of the code is that if the welding is not affecting the structural integrity of the vessel such as seal welding of tube ends on tube sheets than no hydro is required. Fillet welding is more than seal welding, so is the fillet performed on structural component of the vessel? if yes than I agree with doct9960.
I think possibly the disagreement lies in the fact that ASME Sec VIII states that the hydro will be performed after the completion of welding. Thankfully, NBIC rules allow welding without re hydrotest.
cmryu;
This is one of those areas where internal conflicts arise with Code bodies. Section I permits welding of P-No 1 pressure retaining materials after hydrostatic testing under restrictive conditions. See PG-54.3.2
My counterparts in the SG and SC of Section VIII don't see it this way. Philosophical differences I suppose. Anyway, do the clip welding after the vessel is commissioned into service. The NBIC or API provide rules for this activity.
Just to expand slightly on metengr's comments, 'commissioned into service' can be stated as 'after the data report has been signed'.
Metengr, if you disagree please let me know.
cmryu,
Is the clip welded to a pressure retaining boundary. If not, I don't see where you have any concern. If it is welded to a pressure boundary, can you change to detail?
In the first place, NOT EVEN A SINGLE TOUCH OF WELDING ROD SHOULD BE DONE ON THE PRESSURE VESSEL AFTER HYDROTEST. Even then, if you have to weld, there are 2 possiblities.
1. Welding is allowed, if you do a second hydrotest after welding.
2. Welding is allowed on the repad, if the repad is already welded to the vessel before hydrotest.
Folks, we do not live in an absolute world. Anyone who has specified a vessel shell to be 1/2" thick and gone out and UT'd that shell and gotten a reported thickness of 0.500" please raise your hand.
As some of the previous responders have pointed out, life exists after the hydrotest. Real world issues include things like weld buildup to repair corroded areas, adding clips for various reasons, adding nozzles, etc etc. Many times the AI will not call for a hydrotest for these situations. Each situation is individual and needs to be assessed individually. Making absolute statements in a nonabsolute world is not realistic. Yes, I'd rather see things done perfectly. Yes, I've seen "R" stamps go on vessels before they were ever placed into service (no second hydro for the "R" stamp). Yes, I've seen "R" stamp nameplates inadverdently switched on major process vessels (in this case for rerates). Yes, believe it or not, I've seen a single vessel with two adjacent U stamp nameplates (long story there, and I don't agree with the logic).
When I review this case in details, we have to consider why we have to hydro test after welding.
The purpose is to verify leakage on surface of vessel.
However, when we need additiona welding Vessel Long or Cir or nozzle as penetrated welding,
Absolutely, in this case, this carbon vessel should be performed Hydro test once again.
But this vessel is subject to addition welding on surface of vessel of course, this is on pressure boundry but Not direct wleding into pressure boundry like as pipe support clip or Internal support clip ( Demister support ring)
Consequently, this kind of welding is not necessary for mandatory requirement of Hydro test. regardless of ASME rule.
Anyone opinion, pls let me know.
cmryu;
I believe we are attempting to split hairs with words regarding pressure boundary definitions. Your AI has the final call on this. There are Code rules established that unfortunately one size fits all does not work.
I don't necessarily agree with my counterparts that are involved with Section VIII, and sometimes they don't agree with me. So, follow what your AI requires and move on.
As I stated earlier, weld the clip to the vessel using an R-Certificate under the NBIC, as a repair.
