Welding on the sea bottom "in the dry" but under many atmospheres of pressure (compression). In hyperbaric welding of undersea pipelines, a large frame is lowered into the water and clamped to the pipeline. Then an open-bottomed, box-like enclosure is placed in the center of the frame over the pipe. Power lines and life-support umbilicals are connected to the box. The sea water is displaced with breathing-gas mixtures for the diver-welders permitting them to do their work in the dry but high-pressure atmosphere.
