Most Chinese sub-sea pipelines are buried in Bohai Sea less than 60m water depth, where air diving are widely used For the application of offshore pipelines repair, the hyperbaric TIG welding process under high air pressures has been successfully developed. Firstly, the hyperbaric welding test chamber is designed and constructed in laboratory, and the welding machine is manufactured. Then, special welding experiments are carried out based on 16Mn steel plates and pipes under l-7bar air pressures, and high weld quality is obtained. Lastly, the sea-trial of the welding machine and the welding procedure is carried out in Bohai Sea in China, and a perfect all-position 5G girth weld of 16Mn steel pipe is achieved.
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