Welding Tips and Tricks

I remember working a SS tig piping job a few years ago, and the welder and I were working on very thin wall SS piping, most of it between 2" and 6" in diameter. Now, every 10 welds or so, one of his joints would totally collapse like a half crushed cake can.

When I asked him what he thought about it, he said something about the forces of contraction, and well, I did'nt buy it.

But the main problem was, he nor I knew what was cuasing it or how to prevent it, so we went through the rest of the job re-fitting one or two sections a day.(I can still remember the boss bitching about it. We called him big-head Ted)

Anyone got the skinny on this?

-Rick

Ive never seen this happen but Ill bet ya it was a combination of a couple things-One, pipe not properly supported, two-gettin the damn thing too hot, and 3-not letting it cool down between passes(although three might not apply if its single pass welds).

Mig and tig are going to put alot more heat into the pipe than fluxcore or arc welding will, cause will flux/arc welding you have to stop every 30 seconds or so, get a new rod, chip off flux, brush it out, etc.. Tig and mig you can go till you gotta reposition (or with tig run out of filler wire), but even when you do stop usually it wont be nearly as long as chippin off flux.

I've TIGed a lot of sch 5 4" SS, and I've never seen a weld "collapse". He's pushing it, and welding at the upper limit for heat. What color are his welds? I'm guessing grey. If you're doing it right, this doesn't happen.

You should never have enough of the pipe hot enough for the entire thing to fail.

Steve

I don't remember the color of the welds, but I do remember having a problem purging the pipeline, we just didnt seem to get enough gas flow from the bottles. Also, this guy took pride in "running hot and fast" so maybe there was something there. Also, the thickness of the SS was about...18 guage. Pretty thin to be running so hot like he was.

thanks,

-Rick