SPB is the initials of S (for Self-supporting), P (for Prismatic shape) and B (for IMO type B). This paper is to present the historical background and the main featune of SPB LNG containment system which is based on the orthodox shipbuilding technology. The author has been involved in the gas carrier technology for more than 20 years. In 1961, he began the development of a large gas carrier technology, which has resulted in the building of large gas carriers among which the typically important ships from the view point of historical development are an LPG carrier A (46,500 M^3 built 1965,the world largest at that time and the original design of following ships and SPB), an LPG/NH_3 carrier B (19,500 M^3 built 1967, the first gas carrier of USCG apply and for NH_3 use in Japan), Ethylene carriers (built 1968,AI-alloy 5083-0 tanks for 104℃ use), and an LPG carrier (built 1980,80,000 M^3 IMO Type B). Those are all of the self-supporting prismatic tank technology, and give the basis of developing SPB LNG containment system together with the abundant experience of constucting land LNG storage tanks. The self-supporting prismatic LNG tank of Al-alloy 5083-0 is well known that it has been used with a great success for LNG transport since Methane Pioneer in 1959, followed by Methane Progress and Methane Princess, and Esso LNG carriers. The ethylene carriers mentioned above are the similar self-supporting tank design with Al-alloy 5083-0 material. Taking into full account of the reputed success record of those gas carriers of self-supporting prismatic tanks, our team succeeded to apply the IMO type Bconcept to the self-supporting prismatic LNG tank utilizing progressed analytical and experimental methods and enabled the rationalized SPB LNG containment system. The design has been given full approvals as IMO type B by USCG as well as the world major classification societies (ABS,BV,DNV,LRS,NK and GL).
