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Learned about hydrogen annealing in a old trade manual...
I was flipping through a 1982 Boilermaker handbook I picked up at a flea market in Gary, Indiana for $3. There was a section on hydrogen annealing that I never heard about from any of the old timers at my shop. Apparently, for certain thick-walled pressure vessels, you gotta hold the metal at 1200 degrees for like 4 hours per inch of thickness to let trapped hydrogen diffuse out. The book said if you skip this step on a repair weld, you risk hydrogen cracking that could split the vessel open under pressure. I asked my foreman about it and he just shrugged and said they don't teach that anymore since modern electrodes are low hydrogen. Still, made me wonder how many shortcuts we take now that those old guys would have called dangerous. Has anyone else run across some old technique that makes you think twice about today's methods?
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brooke7676d ago
Wouldn't it be scary if we're just relying on luck with these new rods?
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williamb296d ago
Read a similar thing in an old welding textbook from the 70s I found at a library sale. It said for big boiler drums, you'd wrap the whole thing in ceramic blankets and let it cool down real slow over a couple days to keep hydrogen from getting trapped in the grain structure. The book even had pictures of charred chunks of steel that cracked right in half from skipping the step. Makes you wonder if the modern low hydrogen rods are really that foolproof or if we just got lucky so far on some jobs. Those old timers had a lot of hard lessons baked into their methods that we probably forgot for good reason.
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