grinding of socket welded stainless pipe joint 1

[valveguy2]

I have recently observed some 1" schedule 80 socket welded joints that were ground in order to "dress up" the weld. In the process, both the pipe and fitting were ground. Question: Is there any code requirement that specifically prohibits or limits the grinding of stainless pipes, welds, and/or fittings? Is the ASTM A312/A312M allowable wall thickness tolerance (12.5%) applicable?

 

[racookpe1978]

Depends how deep the ground-out areas actually are.
What the shape of the grind cuts are: Some will threaten pipe integrity. Some - most actually that shallow or incidental and with non-sharp edges - will not matter.

EVERY pipe can be ground during and before welding to provide a clean surface!

 

[weldstan]

The minimum calculated wall thickness or minimum fillet/socket weld size cannot be breached.

 

[Duwe6]

"Is the ASTM A312/A312M allowable wall thickness tolerance (12.5%) applicable?"
Absolutely. If the 12½% is not violated, you are done - accept the prep & fitup. If the welder got carried away and went below that limit, the overground area can be welded up to nominal wall thickness. [you are already going to weld]. If you decide to calculate the Minimum Wall [vs. 12½% less than nominal], you have to take into account the bending stresses and tension [pipe span is in tension]. Not a trivial calculation.

 

[DekDee]

Have you performed dye penetrant testing ?
As an ex pipe welder and welding inspector I get highly suspicious when I see stainless steel welds that have been ground.
What may look perfectly acceptable to the naked eye may look a bit different once tested.
Cheers,
DD

 

[kgy0001]

I agree with the other answers to your question, especially since I cannot see the weld in question. Post a picture along with operating specifics and maybe we can help more. Also, an older pipewelder on-site would be highly qualified to help you out.

As far as your question: yes, there will be an inspection code.

All codes allow levels of grinding and undercut.

But which code is applicable for your situation: ASME B31.1, B31.3, API 1104, or one of the AWS codes? Let me know and I will share a copy with you, if needed.

 

[sjrfc2]

The 12.5% tolerance is on piping wall. For the socket welds, the weak link is the throat of the fillet weld. Depending on joint and code, the size of the fillet varies. It used to be that B31.1 would stipulate grinding the toe to get less of a stress raiser. Per Appendix D you were required to use 2.1 as the SIF of the fillet unless the toe was blended in (then you could use 1.3). More recent versions allow 1.3 although the notes for fillet welds in Appendix D still state that grinding or blending the toe is encouraged to aid fatigue life.

If it's grinding at the toe, it might be standard practice to increase fatigue life. If it's grinding at the throat, it should be checked against required fillet profile to make sure you have enough throat.