Repair of Grinding Gouge 2

[steris]

Hi All - We're trying to settle a debate internally. We have a Section VIII Div 1 vessel where the shell wall was hit by a cutting wheel while removing a weld. The shell wall is 1/4" thick and made of formed plate; the gouge groove is about 1/8" deep x 1/8" wide and 1" long (very smooth/regular surface). We have qualified procedures to make this repair and restore the 1/4" thickness. The debate is, does this repair invoke UG-42 and require NDT of the repair site or is this really no different than a cover pass on a butt weld?

One school of thought is that if we cut all the way through the plate to separate it into two piece, did edge prep, and then welded it together, we could treat it like a normal butt weld joint; we could take the joint efficiency hit and avoid NDT. Further, this school of thought is that UW-42 applies more to surface buildup like buttering and is not meant for small local repairs.

The other school of thought is that UW-42 is the most closely applicable section as we don't see any other section that discusses repair (maybe UG-78 but this isn't a defect in material as received). Barring any other section that is applicable, UW-42 would govern.

Any help would be appreciated!

Best,
Steris

 

[r6155]

1) Magnetic particle or Liquid penetrant before welding
2) Weld with the same procedure for butt weld
3) Grind to smooth
4) Repeat item 1)

Regards

 

[SnTMan]

steris, looks to me like UW-42 would apply. I'd see no need to go looking for anything else. I'd also say NDE before welding, while it may not be required, is good practice.

Regards,

Mike

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

 

[RJW000]

Has this vessel been in service?

 

[0707]

After repair
grind smooth
MT
Digital Rx
Us testing
Hidrostatc testing

 

[steris]

The vessel hasn’t been put into service. It hasn’t even been stamped yet - it’s still being manufactured. The issue with NDT, is that all NDT is contracted out and scheduling is very difficult. We were hoping to find a way to do this without NDT.

 

[r6155]

@ steris
What were you thinking when you prepared the offer?

"...contracted and scheduling is very difficult. We were hoping to find a way to do this without NDT." This is not a VALID reason to avoid NDE.
IMHO this is incorrect workmanship.

Regards

 

[steris]

When NDT is required, it is done. Scheduling issues can make it non-ideal so we only do it when necessary. That said, if it’s not required, we don’t do it. The gist of my question was whether there is another applicable section other than UW-42. If there’s not so be it. The code rules are long and even after 15 years of working on them, I still learn new things… hence, there’s no harm in asking questions.

Anyway, thanks all for the help.

 

[weldstan]

Take a look at the base material spec and see what it requires to make such repairs.

 

[r6155]

@ steris
UW-42 is very clear, like my post on 21 Apr 23.
But you insist on avoiding it. There is no chance for you.
You can make any query but if it does not suit you, you reject it.

Regards

 

[steris]

@weldstan - thanks for that advice! I hadn't thought of looking at the material spec for allowances on repair.

One thing that jumps out to me is that SA-480(21) allows for weld repair of the base material up to 1/3 of the thickness. This isn't applicable to our issue because we exceed that limitation, however more as a thought experiment... if there was a defect that was within the 1/3 limit, what would be the justification for performing a repair as allowed in the material spec in lieu of UW-42? What I mean is where these two parts seemingly give conflicting rules, what would be the justification for choosing one rule over the other?

Thanks again for the help!

 

[DVWE]

What I mean is where these two parts seemingly give conflicting rules, what would be the justification for choosing one rule over the other?

One is raw material, so you follow that spec.

One is a part of a vessel, so you follow the code of construction.

The devil is in the details; she also wears prada.

 

[r6155]

@ steris
This is a new pressure vessel under construction with a major non-allowable defect, and you are attempting to repair it without any NDE.
I reckon this new pressure vessel will be a piece of junk before long.

Regards

 

[DVWE]

Alright, here's my take on it after looking into it a little.

I am of the opinion that UG-78 is more applicable than UW-42. UW-42 is specifically for weld build up in instances where thickness may have been lost or where thickness was never there to begin with. I wouldn't classify a gouge as this.

UG-78 does not say materials "as received".

I would simply follow what is required by UG-78 and present a weld repair plan to the inspector.

NDE should be applied as good practice as mentioned above, although not necessarily required.

Whether or not PWHT is required, look to UCS-56 (f) for guidance. Now, you don't have to follow that to the letter of the law unless it's applicable, but use it for guidance. Pay particular attention to the last sentence in UCS-56 (f).

The devil is in the details; she also wears prada.