Low temperature liquefied gas tank of a membrane type

Claim 1

A membrane-type tank for storing low-temperature liquefied gas, comprising: a rigid outer vessel; a heat-insulating, pressure-resistant intermediate layer provided on the inside of said outer vessel; a double-walled inner vessel disposed inside said intermediate layer and including a primary inner vessel made of a flexible membrane and adapted to contain low temperature liquefied gas therein and a secondary inner vessel made of a flexible membrane and enclosing said primary inner vessel therein, said membranes being made of low-temperature resisting metal, said double-walled inner vessel being supported so as to be flexibly deformed by the internal pressure exerted by the liquefied gas contained therein to come into close contact with the inside surface of the heat-insulating layer wherein said primary and secondary inner vessels are in close contact with each other over substantially the entire area thereof, whereby the internal pressure is supported by the outer vessel through the heat-insulating intermediate layer, the membrane forming the secondary inner vessel having a smaller wall thickness than the membrane forming the primary inner vessel, and the radius of curvature at curved edge portions of the secondary inner vessel being smaller than the radius of curvature of corresponding edge portions of the primary vessel.