Cavity drying method for explosion-welding underwater parts - by alternately flushing with nitrogen and liquids, then filling with helium

摘要

The method of drying a water filled contg. e.g. in an explosively welded underwater construction, comprises removing the water and replacing by a water-miscible liq. This is then removed and replaced by a second liq. miscible with the first and having a high vapour pressure. A gas introduced into the cavity can the replace this second liq. This second liq. can be a mixture of isopropanol and trichlorotrifluoro-ethene or can be dichloro-difluoromethane. The gas used is nitrogen, subsequently itself replaced by helium. When the component is immersed in seawater, a determineralised water flow can first be used for washing out the cavity. The method improves the quality of welded joints in underwater pipes.