Pipeline weld repairing method and apparatus

Repair apparatus for repairing a weld joint between pipe section in a pipeline that have been welded together, the apparatus comprising

• (a) NDT equipment for detecting a weld defect, wherein the weld joint has a surface and the NDT equipment is configured to identify a defect located beneath the surface of the weld joint;
• and
• (b) a weld excavating machine comprising
• a tool guiding apparatus, on which a mechanical weld excavating tool is mounted;
• and
• a stop mechanism for selecting a depth of excavation into the pipe wall, the stop mechanism being arranged to allow selection of a depth of excavation that is short of cutting through the pipe wall
• wherein
• the tool guiding apparatus is arranged for fixing to a pipeline;
• the mechanical weld excavating tool is mounted and guided around the pipes in a circumferential direction;
• and
• the weld excavating machine is suitable for use in repairing a circumferential weld joint formed between two pipe sections in a pipeline, and is arranged to excavate into the pipes at a preselected circumferential region around the pipes corresponding to the region of the weld defect detected by the NDT equipment.

A method for repairing a weld joint between pipe sections when laying pipelines underwater at sea, the weld joint having a surface and a defective weld region that includes a defect located beneath the surface of the weld joint, wherein the method comprises the steps of:

• providing a weld excavating machine comprising a weld excavating tool and a tool guiding apparatus,
• guiding the weld excavating tool by the tool guiding apparatus,
• using the weld excavating tool to remove material from the defective weld region, thereby forming an excavation, and
• using a welding apparatus to weld the excavation and fill the excavation with weld material;
• and wherein
• the method is a method of repairing a circumferential weld joint formed between two pipe sections in a pipeline and comprises the steps of:
• identifying the defective weld region in the circumferential weld joint,
• arranging the tool guiding apparatus in fixed relation to the pipeline by fitting the tool guiding apparatus to the outside of the pipes;
• guiding the weld excavating tool around the pipe and along the weld joint by means of the tool guiding apparatus,
• and
• arranging the weld excavating machine to excavate into the pipes at a preselected circumferential region around the pipes so as to provide an excavation suitable for girth welding.

A pipe-laying vessel comprising:

• (a) NDT equipment for detecting a weld defect located in a region beneath the surface of a weld joint;
• and
• (b) a weld excavating machine for use in repairing a circumferential weld joint formed between two pipe sections in a pipeline, the weld excavating machine comprising
• a tool guiding apparatus, on which a mechanical weld excavating tool is mounted such that the weld excavating tool may be moved and guided around the pipes in a circumferential direction;
• and
• a stop mechanism for selecting a depth of excavation into a pipe wall, the stop mechanism being arranged to allow selection of a depth of excavation that is short of cutting through the pipe wall,
• wherein
• the tool guiding apparatus is arranged for fixing to a pipeline;
• and
• the weld excavating machine is arranged to excavate into the pipes at a preselected circumferential region around the pipes corresponding to the region of the weld defect detected by the NDT equipment.