I'm not sure, but it sounds like something like a relief valve would be a possibility. I'm of the opinion that metal fatigue was probably not the cause, however, after something like this fails, 2 issues that would concern me, is the remaining base metal fatigued ? Say the welder cleans up the edges, welds the bottom on again, but where the weldment penetrates the base metal or remaining part of the cylinder, was it weakened by the fact that it failed under pressure. The metal had to have stretched, he said the metal failed not the old factory weld. The steel fabrication shop, we have known for a long time, but having some knowledge on steel fab from being in construction, I would not think anyone in their shop would be qualified to do pressure vessel welding, I've had fitters on one job that were qualified to weld in refineries, doing 20" butt welded dual temp pipe lines for buildings, so what you mention about procedure and being an AWS instructor would make it clear, and very simple, just replace the thing, and check the pressures on the system, install a new pressure relief valve etc. Personally, I would not be comfortable around something like that after being repaired. In one respect it is really none of my business, his son mentioned this to me, and I would hate to see someone injured or killed by a repair that should never have been done, he stated that the bottom of the cylinder literally blew off and went flying. I'll pass along the information, and do appreciate everyones advice here as always, thanks !
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