Double-walled tank for low-temperature liquids

Claim 1

A double-walled tank for low-temperature liquids, such as a liquid gas, comprising an upwardly extending inner tank forming a primary safety casing, said inner tank having a generally horizontally arranged base and an upwardly extending side wall and at least said base being formed of metal, an upwardly extending outer tank enclosing and spaced outwardly from said inner tank and forming a secondary safety casing, a thermal insulation layer located between said inner tank and said outer tank, wherein the improvement comprises a ring of prestressed concrete at least laterally enclosing the junction of said side wall and the base of said inner tank so that compressive stress is provided in said side wall of said inner tank when it is in use, said ring being L-shaped in radial section and having an upwardly extending leg and a generally horizontally extending leg with said upwardly extending leg at the lower end thereof bearing against the outside surface of said metal base at least at the bottom portion of said side wall extending upwardly from the junction with said base, said generally horizontally extending leg is annular and is located below and in contact with the lower surface of said base extending radially inwardly from the junction with said side wall with the radially inner edge of said generally horizontally extending leg spaced a significant distance outwardly from the upwardly extending axis of said inner tank, and a thermal insulation material located below and extending downwardly from said base of said inner tank radially inwardly of the radially inner surface of said generally horizontally extending leg of said ring.