Restoration of vessel shell wall to nominal

[Jman69]

As we know, some helpers are heavy handed and tend to grind the heck out of something when you instructed them to just blend it. Just bleeenndd it. Grrr
Anyways, I have a vessel made from SA-516-70, 2" in thickness with a minimum thickness of 1.8125". The helper ground it down below the minimum and now we are required to use weld metal buildup and follow that up with a MT/PT. I expected them to bring it back to the nominal thickness. They didn't. They built it up to just above the minimum and below the nominal thickness.
My thoughts were that this vessel was designed at a nominal thickness and being new construction, it should meet the designed minimal and nominal thickness. Now , of course im being asked to "Show me in code where it says that! My response is that code does not have the answer for everything. You designed it this way and that is where your answer comes from. Don't want to keep the animal in the tree if there is now reason to.
Any thoughts on this would be appreciated.

Jmann

 

[metengr]

Yes, what is the thickness stated on the Manufacturer's data report? That is the wall thickness that should be targeted for restoration.

 

[BenStewart]

Which code and what was the grinding for? Has the vessel been PWHT?

Weld toe grinding? Have a look at 6.2.5.7 in VIII-2. Something similar is in Annex C part C.4 of PD5500. Or was this grinding to blend out an LTA? See MA 32-5 in VIII-1 or 4.14 of VIII-2.

If the location is now above minimum thickness it will be satisfactory in the as-is condition but what about when you remove any corrosion allowance, will it still be compliant at it's end of life?

 

[DSB123]

Sack the muppet with the grinder!!

 

[Jman69]

Metenger, I agree with that statement but the key word in your statement is should, I cannot tell them they should. Should is a opinion and shall is a must. As far as the data report, Ill be the one signing off on it and the report will state the nominal for the shell and a minimum for the heads. I would say that it is good general fabrication practice to bring it back to nominal but I cannot enforce it from a code standpoint. At least I cannot find anything. Your response is very appreciated.

BenStewart, Code is Sec. VIII Div. 1 and will still be above minimum when the corrosion allowance is removed.

Jman

 

[chicopee]

I have no dealt with pressure vessels for a long time but I still get interested reading the related forum. To me nominal thicknesses does not necessarily represent the calculated thicknesses. If the repaired part meets the calculated thickness plus corrosion allowance then you can sign off.

 

[metengr]

Perhaps this Interpretation from the 2013 NBIC will help you

INTERPRETATION 13-07

Subject: Part 3, 3.3.3 s) and 3.3.4.3 a)

Edition: 2013

Question: When performing weld metal buildup of wasted areas of pressure retaining items, is the wall thickness required to be restored to the thickness listed on the Manufacturers Data Report?

Reply: No. The minimum thickness after build-up shall be the original thickness of the pressure retaining item minus the corrosion allowance.