B31.1 Guidance - Welding In The Proximity of Existing Pipe Butt Welds 2

[tc7]

Hello-
My situation requires rerouting an existing pipe run.

The application uses high pressure pipe, ASTM A106 Grade A, schedule 80, 6-inch NPS and ASME B16.9 wrought fittings and ASTM A105 forged flanges.

The pipe arrangement requires that cuts to the existing pipe be very close to existing butt welds and even cutting at exiting butt welds at elbows, tee’s and flanges.
Does B31.1 address restrictions, about rewelding in the immediate area of an existing weld, i.e., must I remain a minimum distance or xx-inches from an existing weld?
And B31.1 restrict the removal of a butt weld on a fitting and re-using that fitting?

Thanks for helping.

 

[metengr]

tc7;
Nice to hear from you again. There is no guidance in B31.1 regarding distance between welds in piping or piping components and re-welding existing welds. This is left up to the engineer of record to decide along with concurrence from the owner/client.

 

[tc7]

Hello Met, thanks for your usual rapid reply. I’ve been busy with routine work so I don’t often get back to the site.

Ideally on a few elbows (all are short radius) I would prefer to cut through the existing butt weld and use what remains of the existing weld as the base material to cut a new bevel for the new joint. However, I don’t know what weld rod the previous weld was made with and I worry about working into someone else’s old work where I have no history.
Alternatively, I could leave the existing butt weld at these elbows alone and cut into the straight pipe, say ½-inch or 1-inch away and create a new butt joint at that point, staying away from all old material
IN YOUR OPINION, do you have a preference on either approach?

Lastly, I presume we do not need to worry about HAZ in the pipe and fitting alloys mentioned, so rewelding in the areas of the old work presents no metallurgical issues that I need to address ? do you agree?

Thankyou again.

 

[metengr]

tc7;
If it were me, I would leave the original fabrication welds on the fittings alone and add a butt weld to the piping system for fit-up/alignment purposes. Not the most ideal situation but there is nothing in the Code to prohibit it. Cutting and re-welding original fabrication butt welds could be problematic as you have stated versus adding an additional butt weld in proximity of an original fabrication weld.

I don't like prepping and re-welding original fabrication welds in components because of potential weld defect concerns and the original weld heat affected zone.