Structural Integrity of Independent Prismatic Tanks Type B for Liquefied Gas Carriers

The idea of the independent prismatic tank type B (hereinafter called as prismatic type B) system was crystallized in 1970's and a group of the concerns in Japan developed its design standard while this Society (NK) played an active role. With the design standard thus developed, nvmber of LPG carriers and an Ethylene carrier of this system were built with the NK class in the beginning of 1980's, and nothing has been reported of serious deficiencies and troubles. Nevertheless, on the occasion of adopting this system for large LNG carriers, the authors attempted to review the design standard to verify their reliability based on the actual experiences of designs, constructions, inspections, operations etc. of the ships. We conclude that the prevailing design standard for the system is quite resonable and this independent prismatic tank type B system is one of the LNG tank systems with high reliability.