what is the function of an oil/gas separator for a fuel dispensing system

An oil/gas separator is a pressure vessel used for separating well fluids produced from oil and gas wells into gaseous and liquid components.

There are more or less air in the underground tank. When fuel dispenser dispensing oil from the tank, some air may brought into the fuel dispenser, which may cause the the metering system not accurate. By the oil/gas separator in the pumping unit, the air will be reduced maximally to grantee the accuracy of the whole unit.

The separation working principle could be briefly described below.
The end cap of oil-gas separator may channelize the flow and increase the flow rate. When oil flows from the pump outlet to the separator, the sectional area gets smaller and smaller, and the flow rate gets higher and higher. Under the action of flow channelizing arc of end cap of the oil-gas separator, liquid oil flows forward spirally down the inner wall of separator. The gas density and centrifugal force is low, and oil and gas are separated; the gasses are gradually built in the center, and the gas-oil mixture is discharged into the oil return chamber through the vent-pipe subassembly. When the liquid oil is built up inside the oil return chamber to a certain extent, the floater floats upward due to the effect of the buoyancy force and drives the valve core to move up, the float valve is opened, and the liquid oil flows back to the pump intake.


                                                     Functional diagram of oil and gas separator