Rotary vane pump

A rotary vane vacuum pump is an oil-sealed rotary displacement pump. The pumping system consists of a housing, an eccentrically installed rotor, vanes that move radially under centrifugal and resilient forces and the inlet and outlet. The inlet valve, if available, is designed as a vacuum safety valve that is always open during operation. The working chamber is located inside the housing and is restricted by the stator, rotor and the vanes. The eccentrically installed rotor and vanes divide the working chamber into two separate compartments with variable volumes. As the rotor turns, gas flows into the enlarging suction chamber until it is sealed off by the second vane. The enclosed gas is then compressed until the outlet valve opens against atmospheric pressure. The outlet valve is oil-sealed. When the valve is open, a small amount of oil enters the suction chamber and not only lubricates it but also seals the vanes against the housing (stator).

Gas ballast valve
In the case of gas ballast operation, a hole to the outside is opened, which empties into the sealed suction chamber on the front side. As a result, the pressure needed to open the outlet valve is attained at relatively low compression during the compression pumping phase. This allows a displaced gas/vapor mixture to be expelled before the vapor starts to condense. The final pressure reached during operation with gas ballast is higher than in operation without gas ballast.

(Schema: FU-Berlin; Fachbereich Biologie, Chemie, Pharmazie; organisch-chemisches Grundpraktikum; Gasballast)