A safety measure for hot work that’s unheard of, but makes perfect sense. Everyone discussed some things, which was also a way to broaden our knowledge

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　　I met an expert who told me about an amazing welding task: it involved a 200m3 storage tank that had previously contained flammable liquids. A leak was found at the connection between the valve pipes at the bottom of the tank and the tank itself, and welding repairs were necessary. After transferring the contents from the tank, it was taken into account that the chemicals originally present in this tank were not suitable for cleaning with water, as well as the future use of the tank. They use a large barrel placed inside the tank, into which a pre-calculated amount of urea is poured. Add hydrochloric acid slowly again. It produces carbon dioxide and ammonia. Then let it stand overnight so that carbon dioxide sinks to the bottom and ammonia escapes. Gas testing was conducted on the second day, and there was no ammonia gas in the upper part of the tank. There is no oxygen at the bottom. Start welding to repair the tank! Finally, remove the large barrel that originally held urea. 　　This was a case of working with fire a long time ago; perhaps due to the limitations of those times, dry ice or nitrogen was not used.