Oil-Tank Breather Valve CB/T692-94 has simplex type and duplex type. Simplex oil tank breather valve is spring type, duplex oil tank breather valve is gravity type. When the pressure in the tank exceeds atmospheric pressure, the breather valve will open and discharge the pressure until the tank pressure and atmospheric pressure keep the balance.When the tank pressure is below the atmospheric pressure value (i.e. low negative pressure), the valve will inhale until the tank the pressure and atmospheric pressure balance.
Now PV valve is replacing the oil-tank valve.