Tried a 3/8-inch gap on a boiler flange and it didn't leak

Everyone says you need a tight fit, like 1/16 inch, on those old cast iron flanges or you'll get a blowout. On a job in Toledo last month, the old gasket material was fused on and I couldn't get it all off without grinding for hours. I left about a 3/8-inch gap in one spot, packed it with high-temp rope, and torqued it down. Fired it up to 150 psi and it held solid for the whole three-day test. Maybe the rule is too strict for some repairs. Has anyone else had a seal hold with a bigger gap than the book says?

3 comments

3 Comments

terry_mitchell1mo ago

Heard of guys using packing rope on big gaps before.

briannguyen1mo ago

My uncle's old farm boiler in Kentucky had a gap you could fit a pencil in. He used like three different sealants and it ran for years, kinda like what terry_mitchell said about packing rope. Makes you wonder how many "rules" are just old habits.

the_piper20d ago

Yeah, I used to be one of those "tight fit or bust" people honestly. Reading this makes me realize there's a lot more room for improvisation than I thought, especially with the right materials like that rope. Guess it's good to keep an open mind when the old rules don't work with real-world conditions lol.