System protecting e.g. oil tanks from flotation by high water, comprises one-way filling valve at base of tank and vent valve high on tank

摘要

A filling valve (14) is fitted to the storage tank (2). Should the water level rise in the space where the tank is installed, this opens, but at the same time will not permit efflux from the tank. At the highest point on the tank, an automatic vent valve (15) is fitted. The filling valve is below the tank, or in the lower part of the tank. It is a non-return valve or flap, which opens on a low pressure differential, and which may operated by a sensor and controller. An independent claim is included for the corresponding method.