Some of the major dredging companies are Royal Boskalis Westminister, Jan De Nul, DEME and Van Oord Dredging and Marine Contractors.This includes both the excavation and removal of a variety of materials – sediment, sand, rock and debris – from waterways, such as harbours, ports, lakes and rivers, usually for the purpose of deepening or cleaning them. They can be equipped with grabs, buckets or a shovel installation. Hard or other difficult to loosen materials cannot be dredged.Īmphibious dredgers have the unusual feature of being able to work afloat or elevated clear of the water surface on legs. As with jet-lift dredgers there are no moving parts in the flow system. The dredging action is intermittent and suitable only for easily flowing material.Īir lift dredgers are very similar to the jet-lift dredgers but the medium for inducing water and material flow is high pressure air injected at the month of the suction pipe. The unit is generally suspended from a crane on land or from a small pontoon or barge. The mixture is then pumped out and the cycle repeated. The inlets are then opened and water and material drawn in. A chamber with inlets for bed material is pumped out with the inlets closed. Pneumatic dredgers work on the evacutor principle. Cutter suction dredgers are suitable to dredge hard soil or to pump o\up large amounts of sand in shallow water.Īugur suction operates in the same manner as the cutter suction, except that the mechanical cutting tool is a rotating Archimedean screw placed at right angles to the suction pipe. When the hopper is full, the ship sails to its destination, the reclamation area.Ĭutter suction has to be towed to their work site by tugboats. The excess water is drained of via the overflow pipes. Sand pumps transfer the sand dredged up by the suction head into the hold or hopper. When the vessel starts dredging, the ship reduces its speed to some 1 to 2 knots and then lowers the suction pipes on both sides of the ship all the way to the seabed.
Suction dredging is mostly done in a very dynamic environment,Ī trailing suction hopper dredger is a large ocean going vessel. Then redeposit the stream material back onto the bottom of the Through a separation system to recover valuable minerals, and TheyĪre commonly used to pull material up from a stream bottom, run Suction dredges are essentially underwater vacuum cleaners.
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