Hannover, Germany - Recognizing that current methods for underwater maintenance and repair of offshore windfarms, bridges, and locks are time-consuming and difficult on scuba divers, engineers at the Laser Zentrum Hannover e.V. (LZH) and the Leibniz Universität Hannover (LUH) are developing a process for automated, underwater laser cutting.
Currently, most underwater cutting uses the light-arc oxygen cutting method, which involves hand-guided electrodes. Depending on material thickness, divers need a workday to cut 20m worth of material. For a diving period of five hours, this yields a cutting speed of only 7cm/min.
However, with the engineering team's laser-based automated process, cutting speed should increase by a factor of seven. "During pilot tests, we have already achieved a cutting speed of 0.5m/min for 10mm-thick steel," says Dr.-Ing. 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."
|Underwater laser cutting is a fast and thus economical alternative to conventional processes. (Courtesy: LZH)|
The process is being developed for dismantling sheet pilings in water 2 to 6m deep; therefore, 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 finished laser cutting process could also be used for maintenance and repair of offshore structures and other hydraulic structures. Dismantling of nuclear power plants is also a future utility for the technology.
The project "Laser cutting under water for higher productivity – LuWaPro" is supported by the German Federation of Industrial Research Associations "Otto von Guericke" e.V. (AiF).