An automated laser-based approach promises to speed up the task of cutting sheet piling under water. The Laser Zentrum Hannover e.V. (LZH) and the Institute of Materials Science of the Leibniz Universität Hannover, Germany, have developed a technique that uses a disc laser for torch cutting, leaving divers with only a supervisory role.

If sheet piling needs to be dismantled, divers must cut the walls into smaller pieces using a cutting torch. Normally, a diver can cut about 20 meters a day, which corresponds to a speed of about 0.07 meters per minute. The new disc laser method can be used to separate the metal sheets, which are usually 10 millimeters thick for sheet piling, at speeds of up to 0.9 meters per minute.Metal sheets can be cut under water by using a laser. Source: LZHMetal sheets can be cut under water by using a laser. Source: LZH

Poor visibility, currents or uneven surfaces make working underwater more difficult. The researchers achieved a position tolerance of about two millimeters in their process, enabling the system to react robustly to possible impacts during underwater operation. The method was tested with two scenarios: standalone metal sheets were cut underwater, and the sheets were backfilled with concrete. In the second scenario, leaking of molten material through the cutting kerf is achieved by tilting the laser head at an angle of 20 degrees.

Sensors reliably determine whether a cut is completed or not. Otherwise the diver often cannot see this due to the poor visibility underwater. The laser safety necessary for this process can be guaranteed if the diver wears conventional safety goggles under the helmet.