In a casual conversation at breakfast with a friend we discussed our shop projects. He went on to tell me about his air compressor rebuild. He went on to say that the old tank has sprung leaks over the years and that he had welded on patches. He finally decided that a new tank was in order. A 100 pound propane cylinder was too long so he cut it in half, took out a piece and welded it back together. My ears perked! I asked, "Tom, did you test the tank after welding?" "No, how do you do that? The first time I just started the pump and went into the house."
I asked him to at least perform a hydrostatic test. He was not sure how to do this so I walked him through it. I wanted him to take it to at least twice the working pressure. He wants to run 100 PSI, so 200 PSI minimum test. I offered a gauge and suggested to use a grease gun (filled with water) to develop the pressure once the tank is filled with water and all air is removed. We discussed plugging the relief, the pressure switch and the compressor.
I would not repair a tank. They are too inexpensive not to scrap and replace. Especially when you consider what could happen.
Next Sunday at breakfast I'll get an update.
Bob