A PRELIMINARY STUDY ON THE DEVELOPMENT OF A NOVEL MARINE GROWTH CLEANING ROBOT FOR JACKET PLATFORMS

摘要

As the underwater structures of offshore Jacket platforms are always immersed in seawater, the marine growth, which include various forms of algae, slime, and seaweed, barnacles, mussels and other species of adhesive shellfish, will attach to steel-pipe surface and will accelerate structural corrosion and impair structural safety. Currently, routine cleaning and inspection task is undertaken by divers using cleaning jets in normally every 3-5 years. The cleaning duration for one single platform will take up more than two months, even up to half a year, due to the constraints of weather windows and limited working hours of divers. It is a risky job for divers not only because of huge pressures that water-jets produce, but also the harsh working conditions of poor visibility, unexpected vortex and waves around platform, and etc. Underwater robots are being developed for various applications in offshore oil industry ranging from inspection to maintenance and cleaning of submerged surfaces and constructions. This paper introduces a novel underwater robot specializing in cleaning marine growth for offshore Jackets. Since the diameter of steel-pipes varies from about 600mm to 2000mm, a self-adapted mechanism is designed. The self-adaption mechanism makes the robot travel on pipes in different directions with high mobility and clean continuous region of underwater pipes' surface at the same time. Two key issues have been studied in this paper. The magnetic adhesion method is adopted in the robot. A sensitivity study on the distance between steel-pipes and thickness of steel pipes with the adhesion force are conducted both using finite element method and experiments. Besides, the flushing capability for various nozzles has been simulated using computational fluid dynamics method. The proposed underwater robot is needed in the inspection and maintenance of offshore Jacket platforms. Compared with traditional maintenance by divers, it is more efficient, economic and safe.