Research On Optimization Design Of Key Design Scheme For Type-C Independent Tank LNG Carrier

In recent years,designing and construction of small and medium-sized Type C Independent Liquid Cargo Tanks LNG(Liquefied Natural Gas)carrier to transfer,transport and filling gradually becomes the focus of the industry;but domestic design,construction of LNG carrier is still in the initial stage.QIYUAN 28000m3 LNG carrier is one of the first domestic independent design,construction of LNG carrier,practice the new technology,new specification and new rules in the application of LNG carrier,but also demonstrated the limit of design.Taking QIYUAN 28000m3 LNG carrier as the research object,specific research into the following four parts and conclude is given:1.The preferred technology of the main deck arrangementThe type C tank LNG carrier main deck arrangement compared with ordinary cargo vessel increased deck tank,boil-off gas treatment,Gas combustion unit,compressor room,storage tank DOME,and embarkation equipments,even including hose saddle seat,rubber fender and so on.Although LNG carrier length-width ratio is opposite bigger,there is enough space to decorate a variety of facilities on the length direction,but its width limited,especially in the bow and stern mooring areas.By comparing the same type of ship and operation experience,to detailed analysis and research of the above regions,reasonable optimization of regional arrangement.Comparison of domestic and foreign ship design,quantitative design before and after the design indicators to determine the preferred main deck arrangement.2.The preferred technology of the liquefied tank cradlePast LNG carrier Type C Independent tank cradle used LEG/LPG carrier design,is semicircle,laminated wooden lies between the cradle and tank;through simplified method calculation,by needed laminated wooden thickness at least to reached 518 mm,far more than the general thickness requirement of 250 mm to 400 mm.And ship principle dimension have been determined,when the design if increase the height of 118 mm,the whole ship module dimensions and side shell need to be redesigned to meet the overall raised.And the increase of height(laminated wooden relative sliding)is bound to increase the width of the laminated wooden,increased the difficulty of design and construction costs.Therefore consider adopting a new way of design,welding cradle and tank into an organic whole,laminated wooden is installed between the cradle and the double bottom deck,so as to meet the design requirements of the vessel,reduce the cost of installation and construction.Established 3D FE model in ANSYS to study the steady state temperature field of the cradle,determine the material selection of surrounding structures within the reasonable scope.Compared with the design and construction cost of the two type cradles,it is determined that the welding cradle and tank into an organic whole,laminated wooden is installed between the cradle and the double bottom deck is the preferred scheme.3.The preferred technology of the STS(Ship to Ship Transfer)system rubber fenderType C Independent tank LNG carrier main purpose is ship to ship transfer and LNG transit,therefore generally consider to install rubber fender.Detailed analysis of ship to ship transfer fender configuration scheme,and the calculation method of the effective impact energy when the ship is moored to the ship,based on the calculation method of Chinese standard,British standard,Japanese standard,determine reasonable calculation method and the fender type preferred selection,ensuring the safety of LNG ship to ship berthing,and gives the base of the fender design,layout,and fender suspension and grinding side border.4.The preferred technology of the side sprayIndependent C-type tank LNG ship in the loading and unloading process,is likely to occur so that leakage and leakage,low temperature liquid on the hull structure of the steel plate will cause low temperature cold brittle damage;detailed analysis of two kinds of domestic and foreign side of the way(outboard spray and sink spray)design,construction,maintenance advantages and disadvantages,quantitative comparison,it is clear that the tank spray is better than the outboard tube spray,should be given priority to use.The above four parts research in the international and domestic few studies,pioneering significance,and also the optimization of real ship design method,reduce the cost of the Type C Independent tank LNG carrier in the area of design,construction,improve the overall structural safety of the ship,for subsequent domestic LNG carriers design,construction to provide the corresponding solutions.