Abstract: A steel storage tank with a novel structure for recovering vapors through perforations in the center column is described. Vapors trapped between the floor and the minimum elevation of a floating roof fluid storage tank are recoverable through perforations in the supporting center column. The vapors are removed through adjustable elevation vents in the center column where they are routed to a vapor recovery system.

Abstract: A steel storage tank with a novel means for recovering vapors through perforations in the center column is described. Vapors trapped between the floor and the minimum elevation of a floating roof fluid storage tank are recoverable through perforations in the supporting center column. The vapors are removed through adjustable elevation vents in the center column where they are routed to a vapor recovery system.

Abstract: An improved storage tank of the type having a bottom, side walls and a floating roof in which the improvement comprises support legs and support sleeves for selectively supporting the floating roof at first and second elevations. The support legs engage the tank bottom and extend upwardly therefrom. The support sleeves are attached to the floating roof and extend downwardly therefrom. The support sleeves surround the support legs and are vertically moveable relative thereto from first positions in which the support sleeves engage the tank bottom to support the floating roof at the first elevation and second positions in which the floating roof may be supported by the support legs at the second elevation.

Abstract: An improved fluid storage tank of the type having a bottom, side walls and a floating roof. A plurality of first support legs extend upwardly from the bottom. A plurality of second support legs extend from the floating roof. A power device attached to the floating roof is provided to rotate the roof between a first position in which the first and second support legs are not aligned, allowing the roof to be supported at a first elevation, and a second position in which the first and second support legs are aligned, allowing the roof to be supported at a second elevation.