Protection against vacuum, overpressure, overflow-spillage

BV 91 and BV 95 - Overpressure protection
As the liquid fills the tank, the air or gas is compressed and pushes up the ball for exhaust. The tank is protected against overpressure while remaining watertight once the overpressure evacuated.

BV 95 - Protection against vacuum, overflow-spillage
When emptying a tank, the space occupied by the liquid creates a vacuum. As the atmospheric pressure is higher, this creates a phenomenon of air suction through the ventilation valve. This assembly can also protect the tank from overflow-spillage

BV 91 - Protection against vacuum, overpressure, overflow-spillage
The ventilation valve BV 91 lets air or gas flow in both directions protecting the tank against vacuum and overpressure. An excessive filling of the tank by the liquid will apply the ball on its seat thus avoiding an overflow-spillage.

BV 95
Warning: The opening pressure of these BV 95 cannot be exactly stated, the spring has a plastic coat so, its features are not constant. The opening pressure value could be between 0.04 and 0.13 bar, it depends of the valve size. However, these values are for information only, they depend of operating conditions.