Heat insulating wall structure for a fluid-tight tank and the method of making same

A fluid-tight and heat insulating wall structure for a fluid-tight heat insulated tank, comprising a self-supporting and rigid outer wall, a fluid-tight primary barrier consisting of a substantially flexible membrane-like impervious inner wall spaced from said outer wall;

• and an intermediate heat insulating structure, a fluid-tight secondary barrier embedded in said heat insulating structure, fastening means to secure said intermediate heat insulating structure to said inner wall and to said primary barrier, said intermediate heat-insulating structure and said fastening means being capable of transferring loads from said primary barrier to said outer wall, said primary barrier being applied against and supported by said intermediate heat insulating structure, said inner wall of said primary barrier being made from thin corrugated sheet metal formed with at least one set of spaced substantially parallel corrugations projecting inwards from the inside only;
• said intermediate heat insulating structure including from the inside towards the outside;
• (i) a separating layer of a heat-insulating and load distributing material selected from the group consisting of balsa wood, plywood and rigid cellular materials, said separating layer being in continuous contact with said fluid-tight secondary barrier and secured thereto and comprising at least one set of spaced substantially parallel slots each extending through at least a major part of the thickness of said separating layer and each located substantially at a corrugation of said primary barrier and extending along the said corrugation, (ii) the aforesaid fluid-tight secondary barrier (iii) at least one heat insulating layer.