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My old foreman in Pittsburgh said to always pre-heat the 2-inch plate, even if the spec didn't call for it.
We were on a rush job for a new pressure vessel six years back, and the prints just said to weld it. I was young and wanted to save the hour of setup. I skipped the pre-heat and went straight to the root pass. The weld looked fine until the hydro test, when we got a nasty crack right along the HAZ. He made me cut it out and start over, which cost us two days. That crack was a $5,000 lesson I never forgot. Anyone else have a boss who drilled in a rule that saved your butt later?
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williams.sage1d ago
My first lead hand in a Calgary fab shop had a rule about checking fit-up with a feeler gauge before any critical weld. He said if you could slide a 0.015" shim in the gap, you had to re-fit it. I thought it was overkill on some pipe spools until I saw a guy skip it. His weld looked perfect but failed an x-ray from lack of fusion in a hidden gap. The rework shut that line down for half a shift. I've used that gauge on every tight fit since.
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paige3311d ago
Ever wonder how many of those "overkill" rules are just from guys who already paid for the lesson? Like @williams.sage said about the feeler gauge, it's always the hidden gap that gets you. My old boss had a thing about grinding off mill scale on any load-bearing joint, even if you were just tacking. He said the scale traps impurities and you'll get porosity. Saw a guy skip it on some structural bracing, and the tacks looked solid. Whole thing popped loose when they went to lift it, dropped a beam corner-first into the shop floor. That sound is hard to forget.
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