Repair of pipelines on sea-bed - where each end of replacement pipe is located inside chamber permitting welding at atmos. pressure

摘要

The pipeline is lifted off the seabed, and the damaged portion is removed by cutting. The two cut ends of the good portions of the pipeline are then each closed by a plug. A replacement pipe is then lowered to the seabed; and each end the replacement pipe enters work-chambers, each of which contains two valves. One valve is welded to each end of the replacement pipe before the latter and the work chambers are lowered to the seabed, where the chambers are used for making welded joints at atmos. pressure between the pipe ends and the valves, and for welding telescopic pipes between the valves.