DESIGN AND CONSTRUCTION OF BILOBE CARGO TANKS

摘要

An outline of tank design procedure in LPG Carriers is presented. Some interesting problems of design and construction of bilobe cargo tanks are considered, especially those related to stiffening rings, tank supports, and swash bulkheads. Stress concentration in the joint of structural members is analysed both analytically and numerically by employing the theory of shells of revolution and the finite element method respectively. Two main problems of misalignment in bilobe tank production are considered, i.e. eccentricity of Y-joints and out-of-roundness of hemisipherical heads. In order to avoid tank reconstruction, reinforcement of the structural members depending on the value of eccentricity is recommended to decrease the misalignment effect. Hydraulic test confirmed success of this action, but the Classification Society reserves the right to reduce the periodic inspection intervals. Fatigue analysis is performed for high-cycle wave induced load and low-cycle tank loading and offloading. For this purpose the ship motion and load in waves are determined by the strip method. The complete ship and tank structures are modelled within FEM analysis. All numerical examples are illustrated in case of 6500 m{sup}3, 8350 m{sup}3 and 17000 m{sup}3 LPG Carriers. The obtained results may generally be used for improving cargo tank design and construction.