The dredger with an electric submersible dredge pump with the capacity by pulp reaching 720 m3/h, while the output by soil is not less than 200 m3/h, at the head of up to 22 m.w.c. The pump head ensures the handling of sand and gravel mixtures at the distance up to 350 meters horizontally. The dredging depth reaches 30 meters. The dredger has been designed with the implementation of a completely new concept of soil intake due to the application of a submersible pump. It was specially designed for operation with highly viscous mixtures having the high content of solid particles. The dredger should not be equipped with soil withdrawal frame and the system of soil suction (in particular, suction pipeline and ripping device).
The suggested design foresees the installation of an electric submersible pump with a built-in motor, as well as a mechanic agitator. The latter ensures an uninterrupted load of the concentrated mixture to the suction pipe. In such a way, the pumping of pulp with the 60%-concentration of solid inclusions is ensured.
The pump is equipped with a low-speed electric motor with high starting torque. The motor power is 110 kW. A service factor of the motor is 1.35. Hence, the pump can work at significant overloads. The speed of the pump shaft rotation is 590 rpm ensuring the pump flow parts’ wear resistance. The provisional lifetime of flow part details is no less than 2000 hours. The dredger electric power supply - 3-phase from the shore 400 V grids.
The system of the dredger electric equipment and automation ensures all electro-technic protection measures, as well as control of current consumption, input voltage, and submersible pump insulation resistance.The dredger is protected against possible heeling and water availability in bilges. The device detecting the availability of water in pontoons will inform the staff about its penetration. The dredger can work in semi-automatic mode employing an industrial programmable logic controller which ensures the operation within the range of admissible pump current consumption and in permanent contact with the soil.
The dredger is equipped with a water jet system comprising a centrifugal pump and a jet ring with nipples mounted directly on a dredge pump. The jet pump creates the pressure of at least 8 bars which are sufficient to loosen compressed soils with clayish inclusions. This technology makes it possible to continuously pump water-sand mixture with a high density. Thus, hydraulic excavation operations are carried out with high efficiency.
The dredger construction comprises the hull consisting of two central and two side pontoons. The hull plan dimensions are 18.0m x 6.7 m. It is assembled in the form of the trimaran. The dredger weight is 40 tons. The dredge pump is installed at the suspension at the forepart of pontoons. Lifting and submerging of the pump is carried out with the winch by means of towing force through gantry with a block mechanism. To ensure the pump smooth lifting and submerging, the winch drive is equipped with a frequency converter.
The dredger transportation and maneuvering within the water body are carried out using four mooring winches installed on side pontoons in the corners of a dredger. The dredger has got a modular design, thus, it can be transported by trucks. To assemble a dredger on the site by means of a crane truck, 3 days are sufficient.
The dredger is easy in operation maintenance. The spare parts’ replacement is carried out directly on the dredger without the need to dismount the pump. Special assembly platform is foreseen with this purpose. The maintenance personnel for the dredger should include 2 employees including the servicing of the discharge site.
If necessary, the dredger can be equipped with discharge pipelines from PE, power cable, and steel pontoon-type floaters.