Engineers at the Laser Zentrum Hannover (LZH) and the Leibniz Universität Hannover (LUH) are developing a process for automated, underwater laser cutting which could improve the cutting speed by a factor of seven. Once finished, the process could be used for dismantling nuclear power plants or sheet piling, and the maintenance and repair of offshore structures.
Underwater construction on offshore wind farms, bridges or locks must presently be done by scuba divers. For maintenance and repair of metal constructions, a number of processes are available, but these are time consuming and difficult for the divers.
At the moment, mainly light arc oxygen cutting is being used for underwater cutting where the electrodes are hand-guided. Depending on the material thickness, divers need a work day to cut 20m of material. For a diving period of five hours this means a cutting speed of only 7cm per minute.
With a laser-based automated process, the cutting speed should be dramatically increased. 'During pilot tests, we have already achieved a cutting speed of 0.5m per minute for 10mm thick steel,' said Dr Jörg Hermsdorf, head of the Machines and Controls Group at the LZH. 'With this process, underwater metal working could be considerably faster and thus less expensive. Our goal is to make the work of the divers safer and more efficient.'
The process is being developed for dismantling sheet pilings in two to six metres deep water. For this, it is crucial that the pilings including the interlocks are reliably cut, as post processing is time-consuming and expensive. Since metal parts corrode underwater and are subject to overgrowth, the process is supposed to function reliably, even for varying material thicknesses and pollution levels.
The project 'Laser cutting underwater for higher productivity – LuWaPro' is supported by the German Federation of Industrial Research Associations 'Otto von Guericke'.