A cutter dredger, also known as a cutter suction dredger, is one of the most widely used types of dredgers for breaking up and removing compacted soil, sand and clay. Below, we explain how a cutter dredger works, which interchangeable heads it can be fitted with, and how the different Bell Cutter Dredger models compare.
A cutter dredger works from a stable catamaran hull: two floating pontoons connected by a central deck that houses the engine room and the dredge pump. This layout keeps the vessel steady while the cutter head at the bow breaks up the soil and the pump draws the loosened material away as a water-and-solids mixture, ready to be pumped straight to a discharge point or a barge.
The whole process is controlled from a spacious, climate-controlled wheelhouse with a clear view over the cutter and the surrounding work area. Two joysticks operate the dredging process, with the key readings, such as production, pump pressure and depth, shown on screens in the cabin, so the operator can adjust the cutting speed and swing to the soil conditions in real time.
Because the pump and cutter are combined in one vessel, a cutter dredger can work continuously without needing a separate crane or barge to carry the equipment, which makes it one of the most efficient ways to remove compacted soil, sand and clay from a worksite.
What makes a cutter dredger so versatile is that the head at the front can be swapped to match the soil. Bell cutter dredgers can be fitted with four interchangeable heads:
The cutter head is a high-torque head for agitating compacted layers of soil, sand and clay. Depending on the model, it works at a cutting depth of 9 up to 15 metres, and water jet nozzles built into and around the head keep it clean and create a better mixture underwater.
The double cutter head was originally developed for free-hanging use but has proven just as effective in a fixed set-up. With double the cutter power and high-pressure water jets around and between the two rotating heads, it is built for the hardest soil layers.
The sand production head is aimed at maximum production in loose layers of silt, sand and gravel. Water jet nozzles around the cage create a high-solids mixture underwater, which the pump then removes at maximum efficiency.
The flat barge head is used to empty barges. A water jet ring around the head loosens the material so it can be pumped away, without needing a separate cutting action.
Switching between heads means a single dredger can move from consolidated ground to loose sediment to barge-emptying work without changing vessels, which is exactly why cutter dredgers are described as multifunctional.
Bell builds four cutter dredger models, each sized for a different combination of cutting depth and production. The BCD 250M dredges and cuts up to 9 metres deep, driven by a Bell 250 pump with a 1250 m3/h mixture capacity. The BCD 300-350L and 300-350HD step up to a 300 kW Bell 300 pump, with the HD version cutting up to 15 metres and suction to 21 metres. The BCD 400 is the largest in the range, built around the Bell 400 pump for a 3500 m3/h mixture capacity, 18 metres cutting depth and 21 metres dredging depth.
All four models share the same catamaran layout and interchangeable-head system described above, so the choice mostly comes down to the depth and volume your project needs.
Once the cutter head loosens the soil, the Bell dredge pump takes over. The pump draws in the water-and-solids mixture through the suction bore and pushes it out through the discharge line, either straight to shore, into a barge, or over a long distance with the help of a booster station if the discharge point is far away.
Bell dredge pumps are built with a large spherical passage, so stones and debris pass through without clogging the line, and changeable wear parts keep maintenance straightforward. The mixture capacity and discharge distance depend on the pump size and the soil type, which is why matching the right cutter dredger model and head to the project is the first step in planning a dredging operation.
Our cutter dredgers are built in-house and available for sale and rental, with a choice of interchangeable heads matched to your soil conditions. Have a look at the full Bell Cutter Dredger range, or contact us to discuss depth, capacity and head configuration for your specific site.
