In its basic design, a rotary vacuum pump has a circular rotor that rotates within a huge, round cavity. The position of the rotor within the cavity is what causes the eccentricity of the pump’s motion as the centers of the two elements are never aligned with each other. At the suction end of the pump, the volume of the vane chambers increases, pulling the fluid inside, whereas, at the discharge side of the pump, the vane chambers pressure decreases, causing the fluid to go out of the pump. The succeeding rotations process the same amount of fluid several times.
A rotary vacuum pump is best distinguished with its three major features detailed as follows.
Multi-stage pump: the pump comes both in a single-stage and two-stage varieties. The two-stage pumps can achieve a lower pressure than their single-stage counterparts. Moreover, the ballast gas has low effects on the ultimate pressure as it is only admitted at the high-pressure stage.
Pump oil: otherwise known as the operating fluid, pump oil serves various tasks in a rotary vacuum pump. It lubricates all of the moving parts of the pump, fills the dead volume and the narrow gap between the inlet and outlet. It also compresses the gap between the vanes and the working chamber while ensuring that there is an optimal temperature balance through heat transfer.
Safety valve: a rotary vacuum pump can be outfitted with a safety valve. This safety element separates the pump from the working chamber in case of a standstill, whether it is intentional or not. It also utilizes the displaced gas to vent the pumping system to prevent oil from entering into the pumping chamber. After switching on the pump, the safety valve opens when the pressure in the pump has reached the same pressure in the working chamber.
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