Initiatives to maximize safety and reduce cost are leading to the phasing out, as far as possible, of manned diving operations in the North Sea. But at the present time there is no fully mechanized orrobotic, diverless underwater welding system available to the industry for use at any depth, deep or shallow (Ref 4). So welding systems for underwater repair of fatigue cracks are presently dependent on the use of divers in a dry hyperbaric "habitat" to manually weld complex geometries on large thick tubular intersections (called ''nodes"). This project will develop underwater robotic welding repair equipment for inspection and maintenance contractors, operating in the offshore, maritime and nuclear industries. The "state of the art" hydraulic manipulators, currently in use offshore, are not capable of moving with the degree of precision required for welding operations. The necessary precision (+/ 0.2 mm) can only be achieved on a practical basis using an electric robot. Teleoperated electric robot arm welding systems developed for repairs in the nuclear industry are capable of producing only single pass welds on thin materials and have not yet been adapted for repairing cracks in thick steel (typically 25 mm thick) underwater. In this project a submersible welding electric robot arm with a controller, will be developed to deploy and move the welding system. For offshore work the prototype robotic welding system will be delivered and clamped to underwater node sections on platforms by a large ROV (Remotely Operated Vehicle), of the type presently used by inspection and maintenance contractors. The welding process used will be friction stitch welding which has recently been developed for repairing thick steels and can be used in water to produce sound welds.
This technique involves drilling a hole in the crack and filling it by rotating a consumable bar in the hole and producing a friction weld. Cracks are repaired by producing a series of such welds overlapping each other. During this project hydraulically powered stitch welding head will be developed for deployment on the submersible electric robot arm. The broad project partnership includes a robot manufacturer (Sweden), a friction welding equipment manufacturer (UK), a contractor who will use the equipment in the offshore and maritime industries (Norway) centres for welding research in the offshore, maritime and nuclear industries (Germany and Portugal), a robotic software company, and a testing centre for the offshore industry (UK). The total budget is 3.7MECU. Cost savings of approximately 8 MECU over 5 years in the offshore industry and approximately 4 MECU in the maritime transportation industry will be possible if the technology is successfully developed. Safety will be enhanced by replacing men in the hazardous under water environment with a robotic system. Furthermore the quality and repeatability of welds will be improved by replacing manual welding with a fully mechanised system. This project complies with 1.1.3M (Area 1 Medium term) of the Workprogramme and the Maritime systems of the future Task Force.
Funding SchemeCSC - Cost-sharing contracts
AB21 7GB Aberdeen
MK12 5RB Milton Keynes
AB32 6TQ Aberdeen
187 66 Taeby