Working principle of rotary vane vacuum pump

Rotary vane vacuum pump (rotary vane pump for short) is an oil seal mechanical pump, belongs to a low vacuum pump with working pressure range of101325~1.33×10^-2（Pa）It may be used alone or as a pre-vacuum pump of high vacuum pump or other ultra-high vacuum pump. It has been widely used in production and scientific research departments, such as metallurgy, machinery, military, electronics, chemicals, light industry, petroleum and pharmaceutics.
Rotary vane pumps can be sealed container extraction in the dry gas, with gas ballast if the device may also be a certain amount of pumping gas condensate. But it is not suitable for the high oxygen extraction, corrosive to metal, to pump oil from a chemical reaction and gas containing dust particles.

The rotary vane pump working principle diagram is shown as below. Rotary vane pumps are mainly made up of pump body, rotors, rotary vanes, terminal covers, springs and other components. Eccentrically mounted rotary vane pump chamber a rotor, rotor cylindrical surface tangent to the pump cavity (they have very small gaps), and the rotor slot with a spring with two rotary vane. Rotates, centrifugal force and spring tension against the inner wall and the top of rotary vane pump chamber to maintain contact, rotary vane rotor driven rotary slide along the inner wall of the pump chamber. 
Two rotary vanes divide the crescent-shaped space, which is surrounded by the rotors, the pump chamber and the two end caps into A, B and C three parts, as shown in Fig. When the rotor rotates in the direction of the arrow, the volume of the intake port through the space A is gradually increased, and is in the process of breathing. The volume through the exhaust port space C is gradually reduced, and is in the process exhaust. The volume of the space B is gradually decreasing center, it is in the compression process. Since the volume of the space A is gradually increased (i.e., expansion), the gas pressure is reduced, the pump entrance to the external gas pressure is greater than the pressure inside the space A, so the gas inhalation. When the space A suction port isolation, that go to the location of space B, the gas began to be compressed, the volume gradually reduced, and finally connected with the exhaust port. When compressed air over the exhaust pressure, exhaust valve is compressed gas pushed, the gas passes through the reservoir tank is discharged to the atmosphere. Continuous operation by the pump achieves continuous pumping. If the exhaust gas transferred to another level (low vacuum level), low-grade vacuum pumped through the airway, and then compressed by the low vacuum level back to the atmosphere, that is composed of a two-stage pump. Then the total compression ratio borne by the two, thus increasing the limit vacuum.