04.06.2010 | Author / Editor: G. Hopp / Marcel Dröttboom
When constructing the deep-water Jade Weser Port in Wilhelmshaven, Germany, a cutter-suction dredger is presently being used, which can only be described as the superlative of dredgers. The drive concept is not only reliable and energy efficient, but also line friendly – which simplifies the service for the complete suction dredger.
The so-called Jade Weser Port is a deep-water port that is presently being constructed in Wilhelmshaven on the North Sea coast. This deep-water port will be unaffected by the tide. As a consequence, new areas of land are being continually established at the mouth of the Jade River.
Three years ago when plans for implementing the Jade Weser Port were firmed up, it became quickly clear: for the huge amounts of earth to be dredged, the existing cutter-suction dredger capacities would not be sufficient to finish the work in the allotted time period. This triggered Bunte, the construction company that had been awarded the order to build the deep-water port, based in Papenburg, Germany to purchase a new ‘mega dredger’. However, it soon became apparent that the shipyards capable of taking on such a project could not complete the planning and design of such a piece of equipment in the time available. As a consequence, the Bunte Company handled the project themselves.
Pirat X was created. This is a ship that is a good 100 metres long and 16 metres wide, and in fact it looks more like a floating crane when you see its enormous winch for raising and lowering the suction pipe. In normal operation, the suction pipe is equipped with a cutting head that loosens up the ground. The suction head is driven by a hydraulic motor with a 1 MW rating. The suction equipment has three pumps connected in series. Underwater pump 1 is located at the end of the suction pipe. This has a power demand of approx. 850 kW and is driven by an electric motor. Pump 2 is located at the upper end of the suction pipe and is followed by pump 3; both have a power demand of 1.8 MW and are directly driven by diesel engines.
Underwater pump 1 has the task to draw-up the water with the sand that has been loosened by the cutting head and pump this though the suction pipe to pump 2. Pumps 2 and 3 are responsible for transporting the drawn-up sand to the specified dump location. The water-sand mixture with a grain size of 0.3 mm is transported through a 4 kilometres long pipe construction with siphon water intakes and floating pipe 800 mm in diametre. To prevent the sand from being deposited in the pipes, the minimum flow rate of 4.5 m/s must not be fallen below.
With the maximum delivery rate of water-solid mixture of 12000m3/h, per day up to 70000 m3 of sand are retrieved and hydraulically pumped. At the end of the project, in about two years, the dredger will have transported 22000000 m3. With its cutting head, the dredger can operate down to 32 metres. When operating in deeper water, the cutting head is removed and is replaced by a pipe extension arrangement with hinged joint and vertical suction pipe. This can be used in depths of between 45 m and 50 m. This pipe is equipped with numerous jet nozzles at the end of the suction pipe. Pressurized water is directed towards the bottom through these nozzles to loosen up the ground.
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