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Had to patch a 3/8 inch crack in a 50 year old boiler shell last week
Old steel was brittle. Couldn't weld it directly without risk of making it worse. Tried something my old foreman mentioned once. Cut a small patch plate, but drilled the holes oversize by 1/16 inch. Used high temp bolts with Belleville washers. Lets the patch flex a tiny bit with heat cycles. Held pressure through a full 24 hour test. Anyone else have a go-to method for these sketchy old vessel repairs?
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leoyoung6mo ago
My uncle worked in a power plant that had a similar problem with an old feedwater heater. They used a method called cold stitching with tapered pins. It's basically like riveting but done cold to avoid stress on the brittle metal. They drilled holes along the crack, drove in the special pins, and peened them over. It sealed the crack and held for years without needing heat. That flex idea with your washers seems to follow the same logic of letting the metal move.
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roset346mo ago
Sounds like your uncle knew his stuff. My version of cold stitching was using a whole tube of JB Weld on a cracked lawnmower block. It held until the vibration shook it loose and shot a piece of plastic into my shin. So yeah, letting things flex is probably smarter than my brute force and hope method.
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joseph5295mo ago
Ouch, did you need stitches for that shin? That's a wild story. @leoyoung's uncle had the right idea with that cold stitching method, letting the metal work instead of fighting it. My dad always said a stiff fix breaks first. Your JB Weld story proves that rule. Sometimes the simple, flexible fix is the one that lasts.
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