Why do floating roof tanks not require breather valves and vacuum valves
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I know why a breathing valve isn’t necessary, but a vacuum valve isn’t needed either; in case the pump empties the tank, it should be impossible to function without a vacuum valve, right?
The floating roof has a minimum height requirement, and it is not allowed to be emptied.
The space between the bottom of the floating roof and the bottom of the tank is about 1 meter; a bottom support frame and positioning ropes are installed. The side in contact with the tank wall is made of elastic material, so there is no need to consider the impact of low liquid levels on the floating roof during use. For more details, consult the design agency or the supplier.
Our unit uses an internal floating roof tank + nitrogen seal + breather valve, with xylene as the medium
Internal floating roof tanks are generally equipped with ventilation holes around the perimeter and a central ventilation hole that lead directly to the atmosphere, eliminating the need for breather valves and vacuum valves； Internal floating roof tanks can reduce the vapor loss from fixed-roof tanks by 80–90%; if the substance is not highly toxic, a nitrogen purge system is generally not necessary ； If a nitrogen seal must be installed, the ventilation holes around it need to be sealed off, while a breathing valve is attached to the central ventilation hole; this practice is not common