Overlapping weld seams - ASME VIII-1 2019 - Lethal Service 2

[CuMo]

I've been trying to find further information but so far not successful.

As far as my knowledge goes: it is permitted to fillet weld a nozzle reinforcing pad on top of a main circumferential or longitudinal butt weld seam (Type A or B)
provided the main seam is first 100% X-Ray examined and the intersecting welds are as perpendicular as possible, also maintaining 2t (or 50mm) weld toe to toe distance (whichever is greater).

I am designing a Ti Gr.2 (SB-265) vessel in lethal service to ASME VIII-1 2019 but the client wants some nozzles to be re-positioned so that inevitably
some nozzle pads will have to sit on top of circumferential weld seams.

Are you aware of anything in ASME VIII-1 2019 that will forbid such practice?

I'd like to avoid overlapping weld seams if possible but if the code doesn't explicitly forbids it - then we have no reason to say 'No'.

Any help appreciated.
Many thanks!

P.S. The vessel is not U-stamped.

 

[r6155]

NO PADS FOR LETHAL SERVICE !!!

Regards

 

[DriveMeNuts]

I'm not aware of any rules that prevent you fillet welding on top on a butt weld seam if it has been X-Ray'd. I think PD 5500 does have a 40mm gap rule.
However, I advise against it, especially for cyclic duty.

If the weld were to fail and you were hauled before a court judge, what would your expanation be?

As per r6155, Pads may be an issue.

 

[CuMo]

If we expected welds to fail - then we might as well not weld anything at all.
What exactly is the question the judge is going to ask me?
I've asked for some advice - not conspiracy theories.

Thanks r6155 but why not if the code allows it? I'm not saying you're wrong but just shouting "NO" doesn't help not only me but folks who would read this topic later.
If you don't want to spend valuable time - please just don't bother at all.

https://cstools.asme.org/Interpretation/InterpretationDetail.cfm?TrackingNumber=8826

https://www.eng-tips.com/viewthread.cfm?qid=351252

I've missed these before - probably not using the correct search phrase but it looks like fillet welded pads are (were) permitted back then for lethal service.

https://cstools.asme.org/Interpretation/InterpretationDetail.cfm?TrackingNumber=14677

 

[SnTMan]

CuMo, pads are not prohibited in lethal service as noted, but it is generally considered EXTREMELY POOR PRACTICE. As a client, I would not permit it. Particularly in titanium. Having said that, I'd have provided a specification requiring integral reinforcement.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[r6155]

CuMo
We are in year 2020 and we have the tools to make things safe.
For lethal service the cost of safety is the most important.
ASME VIII requirements are not sufficient for lethal service.
A particular specification is required.
i.e.:
Only butt welds are allowed, and 100% RT
Flange class 300, minimum
Helium leak test.
Etc, etc

Regards

 

[DriveMeNuts]

In your OP you seem to be saying that you would like to not do it however because the code doesn't prohibit it, then there is no reason not to do it. It reads as though you are reluctantly willing to take a punt on it if pressured by your customer, releasing yourself from making any Engineering judgement. The test that I apply to situations like this is I ask myself how I would reply if the Engineering Tribunal asked me why I chose to fillet weld on top of a buttweld. If my reply is "because the code doesn't say I can't, and I was pressurised to do so by the customer", then that is me pleading ignorant, which is not acceptable and I would definitely lose my Engineering charter membership and potentially much worse if it was escalated to criminal proceedings.

If we are not to consider the last sentence of your post, then why did you write it?

You are the Engineer. If you feel uncomfortable, then say no. I would explain to my customer that the reliability of pads are too chaotic and therefore I have made my own engineering judgement that it is not going to happen.

 

[weldstan]

Agreeing with SnTMan, repads in Ti PV's should not used and I know they are used. They pose real problems in repairing and I have had to direct many such repairs in the past.

 

If we expected welds to fail - then we might as well not weld anything at all.
What exactly is the question the judge is going to ask me?
I've asked for some advice - not conspiracy theories.
Thanks r6155 but why not if the code allows it? I'm not saying you're wrong but just shouting "NO" doesn't help not only me but folks who would read this topic later.
If you don't want to spend valuable time - please just don't bother at all.

That kind of reaction is not consistent with a healthy professional outlook. The ASME B&PV Code originated out of concerns for public safety, and that ethos must be central to the practice of all PEs.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[CuMo]

I don't disagree with anyone of you all except with the ironic metallurgist maybe. I would read his comment as ironic only because it contradicts itself.
If the ASME VIII-1 committee were so concerned for public safety as he said and thought pads in lethal service posed such a great danger to public safety - they would have prohibited them from use but they haven't (Maybe this is due, who knows...).
So not sure whether to trust him or the committee.

If I was in the position to change the contract - no problem.
I believe though that if we went that route and increased thicknesses (design) accordingly so that pads are not to be used - we would've easily lost the contract due to price increase to some other company that would do exactly the same as what we're doing now... go figure...
We have manufactured quite a few Titanium vessels with nozzle comp-pads and all of them were subject to ridiculous amount of scrutiny.

Good news is - I have managed to do some changes to the design so no pads are to intersect major weld seams.
All welds are full pen except the fillets at the pads O/D. Full X-Ray/UT/Dye Pen will be applied as applicable.

Thanks all!

 

[r6155]

CuMo
You must do a lethal design training course. Your client too.
Meanwhile consult a defense attorney.

Regards

 

[CuMo]

Do you think the committee would like to split the costs?

 

[r6155]

Due to your answer I now add that you must do a training course in ASME VIII Div.1.

Regards

 

[BJI]

If you read question 3 of the below interpretation, it would appear that an external pad does not meet the requirements of UW-2(a)(1)(d). I am not sure how UW-16.1 (h) could be permitted..

VIII-1-98-113: Question (1): May reinforced pads attached with fillet welds as shown in Fig. UW-16.1 sketches (a-2) or (h) of Section VIII, Division 1, be used on vessels designed for lethal service per UW-2(a)(1)(d)?
                     Reply (1): Yes.

                     Question (2): Are the welds attaching pad type reinforcement to the vessel as shown in Fig. UG-40 sketches (a-1) through (a-4), with or without a                               nozzle neck, classified as part of the Category D joint?

                     Reply (2): Yes.

                     Question (3): If the reply to Question (2) is yes, do the Category D joints shown in Fig. UG-40 sketches (a-l) through (a-4) meet the requirements of                             UW-2(a)(1)(d)?

                     Reply (3): Of the four sketches cited, only sketch (a-2) meets the requirements of UW-2(a)(1)(d).

 

[DriveMeNuts]

BJI,
Question 3 refers to bolted set in flanges, which have nothing to do with reinforcing pads.
Question 1 clearly states that UW-16.1(h) is acceptable.

And the formatting of your post is atrocious.

 

[BJI]

Thanks for the correction, I read it as UW-16.1 not UG-40. Obviously from my reply I am aware that it states option (h) is acceptable but seems questionable (not a detail I would use for non-lethal service either).

For me it comes down to inspectability, and fillet / pad arrangements don't really cut it. As for weld proximity, this is commonly handled with adequate inspection and weld procedures, suitable to the metallurgy.

Regarding the formatting, I would like to say I will do better next time but I am sure I will copy and paste again.

 

CuMo,

I won't waste any more of my precious time working on this, but I'll just say that the free help you are receiving here at no cost represents several career's worth of relevant experience. Yet you responded aggressively with apparent sarcasm and talk of 'conspiracy theories'. This is a forum for professionals, not the comment section of the Toronto Sun.

Have a great day and stay safe (Covid-19 is not fake news).

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."