Trailing suction hopper dredger
A trailing suction hopper dredger is a ship that has a full sailing capacity used to maintain navigable waterways, deepening the maritime canals that are threatened to become silted, to construct new land elsewhere or to replace sand eroded by storms or wave action on the beaches. This is made possible by large powerful pumps and engines able to suck sand, clay, silt and gravel. Operation. Properties. A trailing suction hopper dredger is self-loading/unloading and sometimes equipped with a pressurized discharging system. Loading. From the side of the ship one or two suction pipes  descend to the bottom of the seabed. On the end of the pipe a so-called trailing drag head is connected. This head is comparable to a large vacuum cleaner and is trailed along the seabed. In the head there are nozzles connected to a high pressure water installation that are capable of loosening the material on the seabed. Due to lower pressure in the pipe, the material will be sucked inward and discharged in the hopper. The vessel should always have a positive speed over the ground. It is possible to regulate the density of the sucked substance. If  the head is lowered, more material will be sucked but this risks damaging the installation because the material can get stuck inside the pipes. Once the mixture is loaded inside the hopper, the substance will sink and the water is discharged overboard, saving on storage space. A trailing suction hopper dredger can only suck relatively loose substance because the steel teeth are not so big. Harder substances such as rock or ironbased rock must be destroyed by a cutter. Discharging. There are several ways to discharge a TSHD. The most common way is dumping the material. Equipment. A trailing suction  hopper dredger is equipped with the following equipment: Functions. A dredging vessel and particularly a TSHD is mostly used for