Device for thermal insulation of a prestressed concrete vessel which affords resistance to the pressure of a vaporizable fluid contained in said vessel

A device for thermal insulation of a prestressed concrete vessel which affords resistance to the pressure of a vaporzable fluid contained within said vessel in two phases separated by an interface, at least two families of coplanar through-passages being arranged in the lower and upper portions of the pressure vessel so as to permit positioning of ducts for the admission of said fluid in the liquid state and the discharge of said fluid in the gaseous state, wherein said device comprises:

• two shells disposed respectively within the lower and upper portions of said pressure vessel, the upper shell being closed by a lid, said shells which have different diameters being covered with a metallic heat-insulation and being adapted to delimit between said vaporizable fluid and the internal wall of said pressure vessel a chamber filled with fluid in liquid phase up to the level of the liquid-vapor interface of said fluid and filled with gas above said level, the arrangement of said shells in overlapping relation being such as to constitute a cold-fluid liquid seal, the lower shell being separated from the inner surface of the pressure vessel;
• means whereby said shells are each supported by said pressure vessel at the level of at least three of said vessel through-passages of a given family, said means being such as to permit of radial expansion of said shells at the level of said through-passages;
• leak-tight means placed at the level of the through-passages and capable of absorbing the radial expansion of said shells.