The function of gas ballast valve in rotary vane vacuum pump

The gas ballast valve is set in rotary vane vacuum pump to remove condensable gas. Usually, the pumped gas is a mixture of permanent gas and condensable gas. In the process of compression and exhaust, when the partial pressure of condensable gas exceeds the saturated vapor pressure corresponding to the pump temperature, the condensable gas will condense and mix in the pump oil, circulate with the pump oil, and evaporate again into steam when returning to the high vacuum side. This will affect the pumping performance of the pump and aggravate the pollution degree of the pump oil. The method of gas stabilization or aeration can effectively prevent the condensation of condensable gas, that is, the controlled permanent gas (usually dry air at room temperature) is mixed into the compressed gas through the gas ballast hole in the compression process, so that the partial pressure of the condensable gas does not reach the saturated vapor pressure corresponding to the pump temperature, the pressure of the compressed gas has reached the exhaust pressure, the exhaust valve is opened, and the condensable gas The body is discharged with the permanent gas. Oil sealed mechanical vacuum pump is generally equipped with air ballast device, so it is also called air ballast pump. The air ballast valve (aerator) consists of throttle valve and check valve. 

The throttle valve controls the volume of air mixing, and the check valve prevents backflow when the gas pressure in the pump chamber is higher than the aerated pressure. There are generally two kinds of setting of air ballast hole: one is near the pump exhaust port, when the compression chamber and the exhaust port are connected, start to aerate; the other is set on the end cover, when the end of suction, when the rotor turns another angle (100 ~ 150), it will expose the air ballast hole and start to aerate. In the process of aeration, the limit pressure of the pump will rise and the pumping rate will decrease. When the pressure is low, the noise caused by the pump oil impacting the exhaust valve can be reduced by properly opening the air ballast valve and mixing a small amount of gas.

The pump can be pumped out at high speed (90 ℃). In order to prevent oil injection and oil return, improve the lubrication conditions of the pump and expand the application range of the pump, the vane pump is also equipped with various accessories, such as oil mist catcher, molecular filter, dust filter, chemical filter, oil filter, etc. With the progress of technology and the improvement of process requirements, the structure of vane pump is becoming more perfect and its performance is constantly improved.


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