Underwater laser cutting has been achieved with several advantages over common technologies such as saws, automatic wire saws and plasma cutting machines

Due to the growing demand for renewable energy, the need for modern technologies to dismantle existing underwater infrastructure is also growing.

For example, in order to boost the power of an offshore wind farm to a higher level, the existing old steel frame, which may be below sea level, must first be removed so that engineers can rebuild the steel frame for higher power.

In laboratory tests, researchers at the Fraunhofer Institute for Materials and Beam Technology IWS(Fraunhofer IWS) have developed a short-wave green laser cutting method for underwater cutting - which offers several advantages over commonly used technologies such as saws, automatic wire saws and plasma cutters.

According to the researchers, this technology is possible because with a short-wave green laser of more than 1 kilowatt class, this cutting power is required. The researchers say blue lasers with shorter wavelengths could be used in the future.

The researchers say that when existing green lasers operate in water, the water can use pressure to drain the resulting melt out of the incision, which eliminates performance disadvantages such as power loss and the need for additional gas lines.

The Fraunhofer researchers said that while cutting metals with lasers is not a completely new method, it is usually done in a dry environment using infrared or other long-wave laser radiation, with the auxiliary gas coaxially aligned with the beam, removing the molten metal created in the process.

Short-wave green lasers cut steel in an underwater environment.

In the ocean, however, water scatters long waves of light in all directions. As a result, most of the laser power is dissipated over a short distance. Auxiliary gases also require complex piping systems.

Compared to most industrial lasers, lasers with shorter wavelengths can penetrate water without significant loss; Therefore, these lasers can also be used in underwater environments. This medium is abundant in the ocean and can replace the cutting gas needed in dry environments without the need to lay gas pipelines.

In addition, gases and gas mixtures (such as air) can be compressed to a certain extent before being used for practical applications. Water, on the other hand, is difficult to compress. Therefore, as a cutting medium, the technology can remove the melt residue at the interface with little force and time loss.

Project leader Patrick Herwig, head of the laser cutting group at Fraunhofer IWS, said the method could also lead to the construction of compact underwater robots with laser attachments. Because designers can design these units to be smaller and more efficient than existing automatic sawing machines, these attachments can work into such areas even for some hard-to-access underwater structures.

In addition, unlike sawing, the disassembly team does not need to constantly load the laser cutter with new blades or other consumables. In addition, such systems produce no waste and do not release harmful substances into the atmosphere. The researchers say this particular advantage is important when dismantling old nuclear power plants. In such cases, steel components often need to be removed underwater before new construction can proceed. If cutting gas is used, radioactive waste may come to the surface along with bubbles.

As a next step, the researchers hope to further develop the concept proven at laboratory scale into a practical application system.

Source: Old one compiled