UNDERWATER WET REPAIR WELDING AND STRENGTH TESTING ON PIPE-PATCH JOINTS

The underwater wet welding method for repairing of submerged structura l members has been intensively developed during the last years. It is an economical and especially more time-independent procedure. The shor tened repair duration is a major advantage in regions with rough sea c limate as the North Sea area. During research projects the weldability and fatigue performance of pipe-patch connections have been tested. T hese joints are in use for repairing of collision indents. The shape o f the actual used repair patch was optimized to the requirements of un derwater wet welding at high tensile strength steels as BS4360 Gr 50D. Steel materials in this grade shaw problems in regard to high hydroge n susceptibility, and therefore cold cracking. The fatigue behavior of the patch-welded pipe structural member has been investigated. First test series were carried out using as-welded joints. In a second part of the project, post-weld-treated connections were tested The weld sea ms on these joints were partially ground or hammer peened. The rest re sults have been evaluated by means of the hot-spot concept and then fa ced with actual code requirements. Extensive strain gage measurements and finite-element calculations have been carried out to provide the s tress state in the structural details.