The gas is sucked in from the air inlet, and the sucked gas is compressed and discharged out of the pump. Realize that the pumped gas is transported from the pumped space to the atmosphere outside the system from the direction of the air inlet to complete the pumping effect. When the rotor rotates once, two parts of gas are sucked in and two parts of gas are discharged.

The functions of the mechanical pump oil in the mechanical vacuum pump are:
(1) Seal the exhaust valve to prevent the atmosphere from entering the pump through the exhaust valve.

(2) A small amount of pump oil enters the pump from the exhaust valve and other gaps, which play the role of lubrication and cooling, and form an oil film at the gap between the rotor and the pump body, the rotor and the rotary vane, etc., which improves the sealing performance and prevents the pump from discharging. The higher pressure gas in the cavity leaks back into the suction cavity.

(3) When the vacuum degree is high, the amount of gas is small, and the gas in the exhaust cavity after compression is still not enough to open the exhaust valve. If there is vacuum pump oil in the pump cavity, the incompressibility of the oil can be used to open Exhaust valve realizes exhaust.

In order to ensure that the mechanical vacuum system has good vacuum performance, there are certain requirements for the vacuum pump oil:
(1) The saturated vapor pressure of the mechanical pump oil should be sufficiently low, usually at 20°C, the saturated vapor pressure should not be greater than 5.3x10-3 Pa;

(2) The mechanical pump oil should have a suitable viscosity. Generally, the viscosity at 50 °C should be in the range of (47~57x10-6 m2/s).