Development And Design For A50000DWT Semi-submersible Vessel

The definition of semi-submersible vessel comes from its goods operationpattern. When the semi-submersible vessel is going to carry the large oceanengineering project, its normal operation procedure is as follows. First, the ballasttanks are filled with ballast water through pumps or gravity method to make the partof main hull below the water line with certain depth meanwhile the superstructuresand deck machinery are still above the water line. Second, the project structure ismoved straightly over the upper deck of semi-submersible vessel or the ship is movedjust below the cargo and then the location is fixed. Third, the ballast tanks aredischarged to make the vessel floating up to the predefined waterline and then thegoods are carried onto the deck. Such character enables the semi-submersible vesselto carry not only the heavy goods which can handled by crane or throughroll-on/roll-off onto the deck but also the huge ocean engineering product with largescale in dimension and/or extraordinary weight through semi-submersible abilitywhile the heavy crane cargo ship, roll-roll ship and heavy lift vessel can’t handle suchgoods. With regard to the semi-submersible vessel, the present rules and regulations donot have the clear and systematic illustration except the Chinese ClassificationSociety (CCS) which has the simplified expression. The ship design can’t rely on therules especially in some important aspects. The development and design for a realproject must face the different questions and problems. The discussion is held amongthe Classification Society, ship owner and design department. The further research ismade to the rules and regulations which can provide the good basis for the design fora large semi-submersible heavy lift vessel.The development and design from structural point of view for a50000DWTheavy lift vessel mainly on such aspects as the general arrangement design, ballastsystem, movable buoyancy casing, structure strength and light ship weight control isdiscussed in this thesis. Some conclusions found in the thesis can be a good referenceto similar design for the large type semi-submersible vessel.