Caught a repair on old pipe during shutdown

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Hi, I’m not a super experienced pipe welder by any means but I’m at the point where I’m getting most of my work UT’ed with ultrasound. Up until a couple weeks ago I had a 100% record over the last year until a shut down on a high pressure steam line where we cut into an existing 6 inch line and put in a “T”, all up hand, 6010 root, 7018 fill and cap. The welds were a little restricted but wasn’t really an issue but I remember having real problems running the roots, also running less hot to avoid burning through the root which I did a few times and repaired on hot pass, key hole sputtering like we never had a good ground. Anyways the UT guy called a repair on one quarter of one joint for intermittent lack of fusion. The guy didn’t explain very well what was wrong, the joint had been mitered and I thought initially it was a lack of penetration and I had just been on auto-pilot and missed an edge, I’m still not sure if it was supposed to be lack of fusion or if the guy uses that term to describe everything. The weird part is the repair was called on the one quarter that was actually in the open that I had easy access to, on one side was a chilled water line we had taken the insulation off of to get room to be able to run a grinder, on that side i found just what I can describe as garbage coming up through the fill pass when I ground a few weird spots, like weird looking porosity with some black crap, I fixed that and the quarter of the pipe where that was passed fine, lol. When I did the actual repair I found nothing grinding into it, just looked like perfect clean steel the whole way through, then I went straight through where the old root had been with a 1/8th wheel for a new gap to get rid of anything. Same problems running the root on that quarter , arc constantly sputtering, did one inch at a time, feathered, kept going…I’m not an old hand but I don’t suck at this and I’m im thinking there was a magnetism issue or being old pipe it was just dirty but it had been running steam so not sure how dirty it could have been. Also the chilled line was dripping on us the whole time so we were careful not to get rods wet but maybe it happened anywaysIm like some input from more experienced guys out there what this sounds like? Also how to mitigate and potential causes in the future, the magnetism thing only occurred to me the next day, we actually changed the ground clamp out before the repair because we thought it might have been that. Thanks if you’ve got the time to give me some input,Mike
Reply:I'm less experienced than you, but I'd say if there was magnetism in the pipe, you'd be fighting it the hole time,  probably just some crap in the area contanimating the weld.We've done so much, for so long, with so little. Were now qualified to do anything with nothing !
Reply:You need a gauss meter, or field indicator. Use it to test the pipe for magnetism. One trick an old welder showed me - wrap you work lead several times around the pipe. If arc blow gets worse, wrap it the other way. You can keep adding coils until it becomes manageable.https://www.bergeng.com/product/MF-2480.html
Reply:Being an old "hobby" welder, I too claim no particular expertise in pipe welding. That said. I have welded old water heaters and old steel pipe and have had similar trouble due to the base metal condition. Despite not having done careful detailed examination, I attribute my problem to small pockets of intergranular corrosion, sometimes very obvious but usually so small they are either obliterated or just not seen when cutting and grinding the metal but still there under the surface.Is there any chance your steam line had a similar area, perhaps where the inner surface had originally had a very small manufacturing defect and where the steam later acted to cause one or more similar pockets of corrosion or at least had trapped moisture? When you cut the line to get room for the T, what happened to the removed piece? If still around, it might be interesting to section, grind and polish the edge or inner surface(s) and then chemically treat it to see if any defects could be discovered.
Reply:

Originally Posted by cwby

You need a gauss meter, or field indicator. Use it to test the pipe for magnetism. One trick an old welder showed me - wrap you work lead several times around the pipe. If arc blow gets worse, wrap it the other way. You can keep adding coils until it becomes manageable.https://www.bergeng.com/product/MF-2480.html
Reply:

Originally Posted by Oldiron2

Being an old "hobby" welder, I too claim no particular expertise in pipe welding. That said. I have welded old water heaters and old steel pipe and have had similar trouble due to the base metal condition. Despite not having done careful detailed examination, I attribute my problem to small pockets of intergranular corrosion, sometimes very obvious but usually so small they are either obliterated or just not seen when cutting and grinding the metal but still there under the surface.Is there any chance your steam line had a similar area, perhaps where the inner surface had originally had a very small manufacturing defect and where the steam later acted to cause one or more similar pockets of corrosion or at least had trapped moisture? When you cut the line to get room for the T, what happened to the removed piece? If still around, it might be interesting to section, grind and polish the edge or inner surface(s) and then chemically treat it to see if any defects could be discovered.
Reply:This gouge you mention, was it inside the pipe or on the outside? And did it by chance line up with the area you were having problems with?Quality Assurance ManagerAWS CWI / ASNT Level II VT MT UTCertified Welder-ASME-AWS-API