All CSDs are equipped with a rotating cutter head, which is able to cut hard soil or rock into fragments. The cutter head is a rotating mechanical device, mounted in front of the suction head and rotating along the axis of the suction pipe. The cut soil is then sucked in by dredge pumps. CSDs cut the soil according to a pre-set profile. The dredged material is then pumped ashore using pumps and a floating pipeline or loaded into a split hopper barge moored alongside, which in turn can then offload the dredged sediment at the designated location. The cutting action of a CSD is powerful and, combined with the suction action, the material can be ‘cut’ into suitably sized pieces. These pieces are then sucked into the suction pipe as a solid/water slurry and pumped to the surface using pumps mounted on a structural device which extends towards the seabed known as ‘the ladder’.
ARE CSDS FLEXIBLE?
CSDs are sensitive to rough seas and are not easily moved whilst working. They are however characterized by high production rates and the ability to effectively handle a wide range of materials – silts, clays, sand, gravel, cobbles, and fractured and solid rocks. The most powerful cutters can dredge strong rocks effectively on a continuous basis. In addition, the self-propelled CSDs can travel long distances and be deployed in remote locations, far from their home port. They can work in shallow waters and they also have flexible discharge alternatives: They can transport the dredged material between dredging and disposal sites without the need for other equipment. They can then discharge material through pipelines to the placement site and with the use of booster pumps in the discharge lines, they can do this at considerable distances from the work site. Of course they can also discharge into barges. The decision of which method to use will be determined by where the dredging is taking place and what the final destination of the material is.