Welding of tubes in tube plates for heat exchangers - using bushes and TIG welds to minimise heating of tubes or plates so their corrosion resistance is not impaired

摘要

Both the tubes and the tube plates form pptes. when heated in a critical range; and such pptn. markedly reduces their corrosion resistance. To avoid this problem, a bush is first welded or rolled into each hole in the plate. Both ends of the bush project beyond each side of the plate. The bushes are made of the same material as the plate, or of a purer or more highly alloyed material, and possess a slightly larger bore dia. than the external dia. of the tubes. The plate contg. the bushes is heat treated; and then a tube is welded in each bush using the min. amt. of heat. Useful e.g. with highly alloyed stainless steels or Zr, so their corrosion resistance is not impaired by heat arising from a welding process.