GB798334A - Improvements in or relating to liquid storage tanks - Google Patents

Abstract

798,334. Tanks. SHELL RESEARCH, Ltd. Feb. 13, 1957 [March 15, 1956], No. 8190/56. Class 69 (1). In a liquid storage tank the surface of the liquid is covered by a lightweight metal screen formed by a rigid horizontal framework of metal strip, the framework comprising a peripheral curb 1 of similar shape to but slightly smaller diameter than the cross-section of the tank wall, a much smaller continuous central member 4, and a plurality of radial struts 5 each extending from the central member to the curb, a collar 8 of rubber or neoprene secured to the curb to seal the gap between the curb and the tank wall, each compartment of the framework being formed into a liquid-tight trough by securing a sheet of metal foil with upturned edges of the surfaces of the strips 5 surrounding the compartment and the screen being joined to a plurality of wires 9 which are led out of the upper part of the tank above the normal maximum liquid level and are under tension such that the screen will float on the surface of the liquid introduced into the tank beneath it. The tank may be of circular crosssection, the curb being correspondingly circular. The central member is a regular polygon to each corner of which the inner ends of the struts 5 are secured. An additional strut 6 is joined across one diagonal of the central member 4. The sealing collar 8 is supported on an outwardly projecting flange 2 formed on the upper edge of the curb 1. An inwardly projecting flange 3 is provided on the lower edge of the curb 1. This flange together with flanges 7 formed on the struts 5 provides additional support for the foil sheets. These sheets may be of aluminium or aluminium alloy. One or more openings are provided in the screen for sampling and dipping operations. The wires 9 to which the screen is joined pass out through glands 10 (Fig. 3), in the tank roof and then over pulleys 11, 12 so that they can be joined to counter balance weights hanging down outside the tank walls. The wires are connected to an electrical earth to provide a path for the conduction of any static charge generated in the liquid.