Welding and Defect Acceptance

During offshore pipeline installation, the occasional weld defect repair may be carried out just after the sternmost tensioner and before the next roller support in the repair station. The local stresses at the weld repair are intensified during the weld excavation process. Defects exceeding the project criteria are thoroughly removed; however, the removal of excess material should be minimized to minimize local stresses. The determination of safe weld excavation sizes for repair is one of the more difficult evaluations in pipeline installation engineering. This subject has attracted much attention because of personnel safety and the risk of the pipeline parting or buckling on the ramp during excavation. This chapter presents an analytical method of determining safe weld excavation lengths, preventing both plastic collapse and fast fracture of the pipe during weld defect repair.