Can I weld supports to repad after hydrotest?
Can I weld supports to repad after hydrotest?
(OP)
Do to time restraints and scheduling of the outside inspectors I would like to weld the supports onto the re-pads of a pressure vessel after we hydrotest the shell. Is this ok since the welds from the pads to the shell are already done?
Thanks
Thanks





RE: Can I weld supports to repad after hydrotest?
RE: Can I weld supports to repad after hydrotest?
Yes, the AI should be involved, but a modestly savvy client will have issued purchase documentation which would have included a vessel spec as well. This issue may be addressed in the spec.
A further complication can arise from PWHT requirements - the assumption would be that these welds would not require PWHT if they were Code boundary, but this is not made clear in the original post.
RE: Can I weld supports to repad after hydrotest?
Thanks for the replies.
RE: Can I weld supports to repad after hydrotest?
Did somebody get the AI upset? And thank you for posting the resolution to your issue. Not many folks will do that. And we do prefer to be able to 'close the loop' on problems.
RE: Can I weld supports to repad after hydrotest?
I would say no too. If the Code of Construction is ASME Section VIII Div. 1, read UG-99(a).
Hints:
"all fabrication has been completed"
"all examinations have been performed"
RE: Can I weld supports to repad after hydrotest?
I believe an engineer should be able to argue with the AI and prevail his good judgement and experience over the simple following a letter of the code.
Cheers,
gr2vessels
RE: Can I weld supports to repad after hydrotest?
From a purely engineering perspective, setting aside treating these code rules as if they were carved in stone tablets and given to Moses, or Acts of Parliament (incidentally they ARE given the force of legal regulation by some jurisdictions): assuming the modification doesn't substantially alter the design of the vessel by introducing significant loads previously unaccounted for, and the work (welding) is permitted (i.e. no PWHT required, the vessel isn't lined etc.), are done properly and inspected (and documented) in a way that ensures the soundness of the pressure envelope metal is maintained, I'm not sure why on earth we'd prohibit this kind of modification and absolutely require a huge vessel to be re-hydro'd instead. But in the OP's case, that's a matter for discussion with the AI, whose profession makes him or her more of a "stone tablet" kind of person in my experience.
RE: Can I weld supports to repad after hydrotest?
And yes, some AI's have the "Tablets of Stone" mentality, some have more of a "Functional Engineering" mentality. But the final responsibility resides with them and their company [not really the fab shop], so they must have that authority. Things get disfunctional pretty quickly when responsibility and authority are not kept togather.
RE: Can I weld supports to repad after hydrotest?
The AI cannot sign the Manufacturer's Data Report if the vessel is not constructed to the rules of ASME VIII Div 1. It is as simple as that.
RE: Can I weld supports to repad after hydrotest?
Ok, let me pose two and a half scenarios for you and please provide us with your interpretation:
1) A vessel with a weld-end nozzle is provided to a client. A connecting pipe is welded to the nozzle stub. Does this vessel require a hydrotest for Section VIII Div. 1 reasons? On the basis of which paragraph?
2) A vessel is provided with pads on the bottom shell/head to which legs are attached. The vessel is delivered to the field and the legs are found to be too long. The legs are cut short and new baseplates are welded to them. Does this vessel require a hydrotest for Section VIII Div. 1 reasons? On the basis of which paragraph?
2)a) A vessel is provided with pads on the bottom shell / head, the sole intent of these pads is to allow for a "landing" for legs which will be welded on in the field. The pads are not intended to meet any Section VIII Div. 1 requirement. After welding the legs on to the pads, does this vessel require a hydrotest for Section VIII Div. 1 reasons? On the basis of which paragraph?
RE: Can I weld supports to repad after hydrotest?
If on the other hand a doubler pad is welded onto the shell before the hydrotest and then supports are welded on top of it that after the hydrotest then this is okay as the doubler pad does not contribute to retaining the internal pressure.
That is my interpretation. Of course you might find an AI that is Okay with a few tack welds.
RE: Can I weld supports to repad after hydrotest?
The OP is about a vessel that has not left the vessel manufacturer shop. The scenarios you mentioned are post-construction activities. In my opinion, after a vessel leaves the shop, any modifications or alterations to it are no longer in the scope of ASME Section VIII Div 1. I guess they would fall under a Repair Code like NBIC.
For Scenario 2, let us say the vessel is still in the manufacturer shop. In my opinion, the modifications to the legs does not require re-hydro because the modifications are done on structural components, not on a vessel component like the repad mentioned in the OP. Although the repads are for non-pressure attachments, I consider them as vessel components that are essential to the structural integrity of the vessel. Why else would they provide repads for the mentioned supports? Those repads are probably required to minimize local stress at the attachment areas.
RE: Can I weld supports to repad after hydrotest?
I do not agree with the rules in Section VIII, Div 1, but since I am a member of Section I standards committee we do allow for post hydro welding with no re-hydrotest, as defined in PW-54. Maybe Section VIII needs to follow the "mother code" for common sense. Boy, I hope I don't open a can of worms with my fellow code volunteers on Section VIII.
RE: Can I weld supports to repad after hydrotest?
U 1 (e)(2) -where non pressure 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 non pressure part attachments by the applicable para-graphs of this Division(3)
End note 3- These requirements for design, fabrication, testing, and material for non pressure part attachments do not establish the length, size, or shape of the attachment material. Pads and stand offs are permitted and the scope can terminate at the next welded or rmechanical joint
A doubler/ pad plate is a non pressure structural attachment. Based on the footnote 3, ASME Sec VIII scope ends at next welded or mechanical joint which will be a welded joint between pad and support. In line with U1(e)(1)(a) which allow scope termination at first welded joint with external piping, I would guess that "next weld" which is the scope termination for non pressure pad, can be allowed after hydotest.
RE: Can I weld supports to repad after hydrotest?
1) That connection weld is specifically under the piping Code
2) Structural item, with the weld well-removed from any pressure-boundary atachment
2a) "The pads are not intended to meet any Section VIII Div. 1 requirement. . ." so again, not a pressure boundary item.
New Ques. #3) ljas wants to attach to a repad, not near the repad-to-vessel weld. Legal?
per sanshu1111's Code citation, it depends if in the opinion if the repad is "non-pressure boundary" or not. For this instance, the cognizant AI feels it is, sanshu & I do not.
RE: Can I weld supports to repad after hydrotest?
Nice post! This is exactly what I was driving at in my previous post. Whether or not the vessel has left the shop doesn't really matter. The point in my mind would be that just as Section VIII Div. 1 allows for a weld directly to the pressure boundary - pipe to weld end nozzle - without a Section VIII mandated hydrotest, a weld of a support to a repad should not fall within the scope of Section VIII either. Clearly, the support itself is excluded from the scope - I don't think anybody would argue that.
So the question is whether or not a weld may be made to a repad provided for the purpose of attaching supports post-hydrotest. I think the reference above clearly answers that.
metengr
Agree that cost and schedule are nothing but attempts at an excuse and are no reason at all for arguing for breaking the rules. I think the question here lies in interpretations of what the rules are, and I think sanshu helped to clarify that quite a bit in this case in the post above.
The
RE: Can I weld supports to repad after hydrotest?
Didn't see your post earlier - I suppose we were both typing at the same time.
For the record, I agree with your thoughts on my questions. That doesn't necesserely make us right, but at least there are two of us who agree on this.
I think my 2)a) question answers your 3) question. If one could legally perform this weld in the field, then why on earth would it not be ok to do in a shop, either before or after the U stamping ceremony? doct was indicating he felt there would be a distinction; I don't see it. Once the U stamp is on then NBIC governs. I get it. But as far as I know, NBIC claims no more scope than VIII-1 does. Thus, it doesn't matter.
RE: Can I weld supports to repad after hydrotest?
It's Friday and I'm down to my fifth pint of beer, so forgive me if I am incoherent.
I love these healthy discussions, especially when experts and experienced people like you and metengr are involved. Since I've joined Eng-Tips back in 2006, I have valued the technical insights and opinions from both of you. (For those who are new to the forum, check out who the top 2 MVP's in the forum are.
jte said:
jte, I strongly believe there should be a distinction. It all boils down to accountability. I believe that after a vessel is completed, stamped and got out of the vessel shop...anything unfortunate that happens to it as a result of alterations/modifications or as a result of stupidity done by others, the damage done to the vessel is no longer the responsibility of the original Code of Construction and the vessel manufacturer. In my line of work in the vessel drafting/designing, we call it CYA...cover your ass. (I first heard the term from a Parsons/ex-Fluor vessel engineer back in the 90's when I was a fresh grad)
The footnote #3 in U-1(e)(2) still befuddles me. I didn't find it in ASME VIII-Div.2 or other codes. I believe that footnote can only be found in ASME VIII-Div.1. I have a different interpretation to the sentence, "Pads and standoffs are permitted and the scope can terminate at the next welded or mechanical joint." For example, we have a platform clip with a repad. In my opinion, the scope of ASME and the responsibility of the vessel manufacturer is up to the clip. The bolting and the platform that attaches to the clip are outside the scope of ASME. If you say the scope of ASME is just up to the weld of the clip, then who is responsible for sizing the clip and the weld? The structural engineer who stamps my L&P drawings does not want to be responsible for the vessel clips and welds, whether they are on the vessel or on the repads.
Going back to the OP, it was not mentioned what type of supports are welded on the repads.
1. To jte & Duwe6, allow me to pose this scenario and let me know your interpretations:
Put yourselves in the shoes of the AI. If Ijas wants to weld support saddles or support lugs on the repads of the vessel after the hydrotest, would you allow it and would you sign the Manufacturer's Data Report and certify that to the best of your knowledge and belief, the Manufacturer has constructed the vessel in accordance with ASME BPV Code? (By support saddles and lugs, I mean the structural supports that hold the vessel in place.)
2. To Ijas, since you were gracious enough for informing us that the AI rejected your request to weld the supports after hydro...can you share why the AI rejected it?. When you mentioned "supports" in your OP, what type of supports are they?
Thanks,
doct
RE: Can I weld supports to repad after hydrotest?
For minor loads, unreservedly YES*. For a major load, probably not. And if allowed, it would be treated as an 'oops' and not automatically allowed whenever they paint themselves into a corner.
*ASSumes that it gets attached by the "A" team of fitters & welders, not the guy running a broom or grinder.
RE: Can I weld supports to repad after hydrotest?
Lets take an example of a small PV where a simple support (a simple plate)is directly welded (without any pad) to the shell (pressure part). This support may be bolted or welded to another structural member for vessel mounting, is this weld or bolted connection within code scope? In my opinion, its not. Providing a properly designed support is still a responsibility of manufacturer
I think all of us would prefer to have a completed vessel including the supports before the hydrotest. We are however trying to understand the scope limit of the code.
I think it is also better not to call such structural pads as "Reinforcement pads" which are not a code requirement but provided as a good engineering practice or to meet the criteria of local loadings
RE: Can I weld supports to repad after hydrotest?
We have manufactured it and have conducted hydro test but the name plate bracket was not welded to the vessel ,we can't weld it to the saddle since it is in the site and we r only manufacturing tube side which is in shop,
My concern is that is there any clause under which i can make the welding after hydrotest with a relevant argument,
although i have gone through the entire discussion above and have come to a conclusion that there is no escape from this as per code,
but slight expectation i m putting my concern in to the discussion
Stephen
RE: Can I weld supports to repad after hydrotest?
RE: Can I weld supports to repad after hydrotest?
now it had repair in tube sheet and tubes so we manufactured new tube side only , we are using old shell for shell side and it is a kettle type exchanger
Stephen
RE: Can I weld supports to repad after hydrotest?
RE: Can I weld supports to repad after hydrotest?
Stephen
RE: Can I weld supports to repad after hydrotest?
Regarding your "would you sign off on it?" question: Yes, I would.
Regarding accountability: CYA is all well and good. I had more typed up here, but I'll just point out that there are more "opportunities" for difficult decisions when evaluating in service equipment than in designing new stuff. I'll leave it at that.
RE: Can I weld supports to repad after hydrotest?
For America:
The ASME AI is interested in the design and fabrication of pressure envelope and any components welded directly to it such as a support pad. With respect to fabrication, this is where the ASME AI's accountability ends.
The AI is interested in the local stresses in the pressure shell that are the result of loading on the supports or brackets attached to the support pad, however the AI is not interested in assessing the design of the support itself or inspecting anything to do with the attachment of the support to the support pad. You could attach supports or brackets to the support pad using bubble gum and the AI wouldn't care.
End Note 3 specifies the termination point of the vessel is the surface of the support pad and “Nonmandatory” Appendix G "suggests" good practice regarding design of supports and attachments. There are no compulsory requirements.
The support would ideally be designed by a structural engineer but the immediate support bracket is often designed by a vessels engineer. The design and fabrication of the support bracket including the pad attachment weld should be inspected by a 3rd party structural inspector.
For Europe:
In order for the vessel to be CE marked, the design of the whole assembly of vessel and supports is assessed in accordance with PED by a 3rd party organisation that has both vessel and structural design appraisers. Similarly another organisation will have fabrication inspectors that are certified to inspect both vessel and structural fabrication.
I suspect when your AI is saying "NO", maybe he actually means "I don't care, it is nothing to do with me, but just in case I'll cover my back side by saying NO".