Trailing suction hopper dredgers, cutter suction dredgers and backhoe dredgers
As shipbrokers, DSB has access to a wide range of trailing suction hopper dredgers, cutter suction dredgers and backhoe dredgers.
Trailing suction hopper dredgers
How TSHDs operate
These vessels range from small for coastal and harbour maintenance work, to large for extensive capital dredging projects.
Suction pipes are lowered to the seabed, and pumps transfer the spoil and water to the vessel’s hold or hopper. Here, water is drained off and the spoil retained until it can be discharged.
TSHDs discharge collected sand and spoil by:
- Emptying it through the hopper’s underside doors when in a dumping zone.
- ‘Rainbowing’ it through a snout on the bow discharging, or through a floating pipe, to the shore. Used especially in land reclamation. Once the spoil is ashore, its weight keeps it there while the water runs off back into the sea.
See below video of Jan de Nul TSHD in action.
How CSDs operate
Some CSDs are self propelled but most are towed into place They’re then held in position using heavy pike-like structures called ‘spuds’; to stabilise the vessel during dredging, anchors are deployed.
See below video animation of CSD Beaver B50 in action, swinging and changing spuds.
A cutting head gouges the seabed into small chunks of rock and spoil which is then sucked through the connected cutter suction pipe. An ejector system moves debris through a floating pipeline to the shore or to barges for removal.
How backhoe dredgers operate
Backhoes, also known as dipper dredgers or mechanical dredgers, are rectangular pontoons and can be self propelled for positioning on site, and non self-propelled. They all tend to use a walking spud to move, and rely on help from workboats. Small backhoes can be track mounted and worked from the banks of rivers or ditches.
Bucket or grab size depends on the type of dredge material – from light sand to basalt rock – and the excavator power. Dredged material is loaded into split hopper barges or placed on shore.
See below video of backhoe dredger ‘New York’ with Liebherr P996, working in the port of New York.