TIL an old welder's trick for a stubborn flange gasket in a cramped space

I was wrestling with a 6-inch flange on a feedwater heater in a Philly plant last month, and this guy named Frank from the pipefitters saw me struggling. He walked over, took a look, and just said 'Heat the bolt, not the nut, with a rosebud for ten seconds and it'll walk right off.' It worked perfectly on the first try. What's the best piece of simple advice you've ever gotten on the job that saved you hours of headache?

4 comments

4 Comments

the_max2mo ago

Man, that's a solid trick. I gotta ask though, what's the actual science there? Like, does heating just the bolt make it expand faster than the nut to break the rust bond, or is it about the threads themselves? I feel like knowing why it works would help me figure out where else to use it.

diana_kim662mo ago

Oh good question! I mean, maybe the heat also helps burn off any old grease or gunk that's acting like glue in there too.

jakewhite2mo ago

My old truck taught me that trick with its rusted exhaust bolts.

the_max1mo ago

Yeah the heat definitely helps burn off any oil or gunk that's seized things up, I've seen that on old brake calipers where the slide pins get all crusty. But the real trick with exhaust bolts is the expansion thing - when you heat the bolt itself, it expands faster than the nut or the manifold it's threaded into. I've had good luck hitting just the bolt head with a propane torch for like 30 seconds then giving it a quick shot of penetrating oil right after it cools a little. The oil gets drawn into the threads as the bolt contracts. That combo works on suspension bolts too, not just exhaust stuff.