The Pressure Vacuum vent valve-also known as P V valve is a device-which inhibits evaporation losses while protecting the tank from bursting or implosion due to over pressure or over vacuum.

When the positive pressure exceeds the set pressure point. Pressure pallet opens to release the excess pressure and bring the tank back to normal operation condition.

If vacuum is formed within, the storage tank, and exceed the Set vacuum point, the vacuum pallet will lift gradually and suck the air from out side until the vacuum is reduced below its set point and thus protect the tank from implosion.