Flange bolt snapped on a 200 psi line, here's what saved the job

Up in a refinery outside Baton Rouge last month, I was torquing a heat exchanger flange and one of the 1.25 inch studs gave way with a crack that echoed off the pipe rack. The gasket wasn't seated yet, so I had about 40 minutes before the supervisor wanted pressure back on that loop. I could have drilled and extracted it, but the threads were seized from years of steam service. Instead, I used a portable stud gun and welded a nut onto the broken end, backed it out in under 10 minutes, and swapped in a fresh B7 stud. That delay cost us maybe 2 hours total, but we avoided a full hydro test and a 200 psi blowout. Anyone else ever trust a stud gun over a die grinder in a tight spot, or am I the only one who swears by it?

2 comments

2 Comments

emma_dixon701mo ago

Wait, did you have to bump the torque sequence on the remaining studs after that, or did the flange just close up fine with the fresh one? That's the part that always sketches me out in a hot service like that.

ray1361mo ago

You ever read that old millwright forum thread about flange prep on steam lines? The guy who did a live swap on a 600 psi header said he always backs off the two studs on either side of the replaced bolt a quarter turn, then pulls them back up in a star pattern, never just tightens the new one alone. That way the gasket doesn't get pinched uneven. I did that once on a water line and it still took three passes with a torque wrench before the dial stopped moving. So yeah, I'd bump the sequence on the remaining ones, even if it's a pain in a hot service. Better than chasing a leak a week later.