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Tianjing [Whale]

Made in China, the Whale is a self-propelled cutter suction dredger, and when launched was the No. 1 self-propelled cutter-suction dredger in Asia and the world's third. As one headline put matters "Reclamation monster "whale": build the island like steamed buns, change the South China Sea minutes!" The whale, China's self-developed cutter suction dredger, is a sharp weapon for reclaiming sand and filling the sea.

With a total length of 127.5 meters [415 feet], a beam of 22 meters and a draft of 6 meters. The gross tonnage is 6,369 tons, the maximum digging depth is -30 meters, the maximum discharge distance is 6,000 meters and the excavation efficiency is 4500 cubic meters per hour. Its technical performance indicators and reamer dredging capacity was the highest in Asia and one of the largest three self-propelled cutter-suction dredgers in the world.

The total installed power of 20020 kilowatts, the excavation strength of 40 MPa rock, with unlimited navigation and loading capacity of the sea area, suitable for a variety of sea conditions of large dredging projects. The ship is equipped with the most advanced international suction cutter suction dredger automatic control system, enabling unmanned control.

In the dredging of an underwater bottom a cutting member of a dredging device, such as for instance the cutter head of a cutter suction dredger in stationary position, is advanced over the underwater bottom. Dislodged soil particles are suctioned up via a suction pipe connected to the dredging device.

During dredging operations it is important to obtain the highest possible production. This means that with the chosen dredging implement the largest possible quantity of soil with the smallest quantity of water i.e. a mixture of the highest concentration, has to be aimed at. If the dredging apparatus is a bucket dredger, the degree of filling of the buckets (which can be seen visually) is controlled by controlling the cutting depth. If the apparatus is a cutter suction dredger or a dredging apparatus having a digging wheel and suction conduit, the concentration is measured in the suction conduit and the signal obtained there is used to adjust the cutting depth.

In a cutter suction dredger the loosening force is related to the torque occurring at the cutter head as well as to the horizontal tension in the cables which displace the cutter head. With a digging wheel there also exists a relation between the torque at the digging wheel and the required horizontal tension. There also exists a relation between the loosening forces and the stress in the material of the suction tube or ladder.

Dredge cutterheads are generally hemispherical with a multiplicity of hard rock cutting teeth or replaceable edges projecting outwardly from helical support arms or blades disposed about the hemispherical surface of the cutterhead. An example of such a dredge cutterhead is disclosed in Bowes, Jr., U.S. Pat. No. 4,891,893. The cutterhead has a hub which fits around a shaft that provides the torque for turning the cutterhead in its operation of dredging. The cutterhead encounters all kinds of materials, including rock, sand and clay which must be removed from the bed being dredged.

Conventional cutterhead arms are shaped to minimize wear, but are not designed to move material. However, one of the problems encountered by cutterheads is that the material loosened by the cutting teeth must be directed into a suction pipe in order to be removed from the bottom of the waterway. As the cutterhead moves across the waterway bottom, the cutting teeth dig below the bed to loosen material. Unfortunately, a substantial portion of the material loosened by the cutting teeth does not reach the suction mouth, which is generally located adjacent to the lower side of the ring of the cutterhead. Instead, some of the loosened material quickly falls off the trailing edge of the digging arm and tumbles onto the following arm.

The vessel was invested by TianAn and designed jointly with Shanghai Jiaotong University and VOSTA LMG in Germany and was constructed by China Merchants Heavy Industry (Shenzhen) Co., Ltd. With the most powerful excavation system in the dredge, the reamer power reaches 4200 kilowatts, which not only dredges clays, compacted sand and gravel but also rocks with compressive strength up to 40 MPa. The number of subsea blasting projects can be greatly reduced, the engineering safety factor can be increased, and marine pollution can be reduced.

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