The working principle of the Anti-Overflow Valve (AOV)
Unloading State
Before unloading, the disc valve is in the open and positioned state.
A transparent oil unloading pipe is connected between the tanker truck and the tank farm's oil unloading port.
Open the oil unloading valve on the tanker truck.
Fuel flows from the tanker truck into the oil tank.
Full Tank State
When the fuel height in the tank reaches the lower float, the float rises. Through the linkage device on the float, the positioning pin is released, and the disc valve closes under the action of fuel gravity.
When the disc valve is closed, the relief valve in the center of the disc valve opens instantly to reduce the back pressure during sudden closing, playing a protective role.
The disc valve reminds the operator to close the oil unloading valve on the tanker truck.
Emptying State
After stopping oil unloading, about 1/3 of the remaining fuel in the oil unloading pipe flows into the tank from the top vent.
If the tanker truck's oil unloading valve is not closed in time, the fuel will continue to flow into the tank through the vent until the upper float closes.
At this time, the anti-overflow valve will be completely closed to prevent fuel from entering the tank and avoid the tank being full.
The corresponding95% of height of the oil unloading upper limit capacity is the liquid level height at which this float works.
Reset State
After closing the oil unloading valve in time, as the oil in the oil unloading pipe drops to a level that cannot resist the pressure of the disc valve, and when the force of the lower spring is insufficient, the disc valve will open and be positioned on the fixed pin. At this time, the residual fuel in the oil unloading pipe will be quickly unloaded into the tank.
If it is found that the oil unloading valve has not been closed in time after the oil unloading is completed, the upper float should be closed first, and then the oil unloading valve should be closed. After that, the remaining fuel can be unloaded into the tank after opening the connection.
When disconnecting, pay attention to observe whether there is residual oil in the transparent oil unloading pipe to avoid fuel leakage.
