INTEGRAL DESIGN OF TRAILING SUCTION HOPPER DREDGERS Dredging equipment further optimized for prosperous dredging

摘要

An efficient modern Trailing Suction Hopper Dredger (TSHD) is of an integral design based on numerous interdependent boundary values. Her main dredging performance is expressed in loading, dredging and transport capacity at one side, whilst to be installed power and investment cost are at the other. The loading capacity at design draught defines mainly the overall dimensions of the vessel. The dredging capacity is in most cases decisive for the total installed power. The required dredging power is defined as the "Specific Energy" per unit of time, for loosening the soil and pumping it into the hopper. The energy needed for loosening the soil, is developed at the dragheads, mainly by a combined effort of jetting and cutting. The jetting energy is developed with jetpumps, whilst the cutting energy is developed by the ship propulsion force through a well designed suction pipe system. For the purpose of predicting and balancing all these powers to be installed and the force equilibrium of the suction pipes, a new integral design tool has been developed. This to attain the specified average mixture concentration. The transport capacity, is defined as the loading capacity multiplied by the laden speed at design draught. This can be optimized by varying the hull form, mainly with respect to block coefficient and the corresponding dimensions, resulting in an optimum sailing speed at optimum installed power. Different hull forms have different cost. All above mentioned variables will result in different alternative designs mat can be reviewed for the most relevant operational conditions, using an exploitation cost calculation. Results will be demonstrated. It will be clear that an improved overall system also required improvements of subsystems and individual components; this will be demonstrated for "in house" newly developed systems and components such as advanced propulsion systems, remote controlled sophisticated dragheads, high efficiency pumps, improved hopper designs and integrated automation of modern TSHD. At all relevant steps, shown in the one line diagram of the dredging process, the improvements contribute to change the more "traditional handicraft" of the past to a more efficient real "industrial process" for future even more prosperous dredging.