Diverless Underwater GMA Welding for Pipeline Repair Using a Fillet Welded Sleeve

The hyperbaric GMA welding procedure development carried out for underwater pipeline repair using a fillet welded sleeve is described. The fillet welded sleeve for repair offers greater alignment and installation tolerances than those associated with V-butt welding. In comparison with the hyperbaric TIG process, currently operated offshore with diver-assistance, GMA welding offers a relatively high deposition rate and is well suited to fillet joints. Parameter development enabling the stable deposition necessary for a large fillet weld is described, in addition to the repeatability of the weld quality and results from material property testing. Positional linear fillet welding work has been performed on API 5L X65 pipeline and sleeve material, using a specially developed metal-cored wire at an initial target depth of 360m. Previous work has demonstrated the robust nature of the hyperbaric GMAW process, with results produced at water depths down to 2,500m. The procedure development forms part of the Remote PRS programme, designing, building and testing a diverless underwater hyperbaric GMA welding repair spread, to be operated fully remotely.