Regarding the issue of installing check valves on the floating roof drainage pipes of storage tanks

The requirement in standard GB 50341 for installing check valves on single-disc floating roof drainage pipes is aimed at preventing the floating roof from sinking due to the loss of buoyancy in case of abnormal conditions inside the floating roof tank (such as a drop in the liquid level). In such situations, the check valves prevent external liquids or gases from flowing back into the tank, thus protecting the structure of the tank and the contents stored within it. As for the reason why a check valve is not required in double-disc floating roof drainage pipes, it is because the design of a double-disc floating roof itself consists of an inner floating roof and an outer floating roof, which together form a sealed space. This sealed space helps to reduce evaporation losses, and to some extent, it allows the pressure within this space to compensate for changes in external pressure. Therefore, there is no need for a check valve to prevent backflow of external liquids or gases, as is the case with single-disc floating roofs. .