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?

2 comments

2 Comments

terry_mitchell7d ago

Heard of guys using packing rope on big gaps before.

briannguyen7d 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.