GB1378492A - Buoyant vessels - Google Patents

Abstract

1378492 Carrying liquefied gases F H TURNER 2 Dec 1971 [4 Dec 1970 24 March 1971 21 June 1971 (3)] 57645/70 7680/71 28906/71 28907/71 and 28909/71 Heading B7A A floating storage tank or, as illustrated, a barge for carrying liquid methane has prestressed concrete walls made up of panels 15 each having outer and inner layers 15a and 15b separated by struts 15c. The barge is compartmented, Figs. 2 and 4 (not shown), by bulkheads made of similar panels. Corner joints are formed by concrete girders such as those shown at 16a and 16b. Rods 19 connect the panels and are tensioned after assembly. Tanks for methane may be located in the compartments or, as illustrated in Fig. 6 (not shown), the panels may themselves form the tank walls. In the latter case, the panels are covered with layers of thermal insulation which are themselves covered with a layer of aluminium or steel mesh and a layer of aluminium, steel or GRP sheet supported on a thin concrete backing. In order to avoid undue cooling of the concrete structure, thermal conductors, Fig. 4 (not shown), may be embedded in the vessel walls to conduct heat into the walls from the exterior of the vessel. Alternatively, electric or fluid circulation elements may be used to heat the walls. The methane in the tanks may, to avoid boil off, be cooled by heat exchangers, Fig. 2 (not shown), through which liquid nitrogen is circulated by a plant on the barge. If methane is allowed to boil off from the tanks, the vapour may be passed from the barge through a porous bronze plate located below the waterline, Fig. 7 (not shown), so that the methane is dispersed as an anti-pollution measure. When the barge is berthed, a tender carrying refrigerating plant may liquefy methane taken from the tank vapour spaces and then return it to the tanks. The tender may also be used to vaporize liquid methane from the tanks and to supply it to a point of use.