Rotary Vane Pump Operating Principle
Rotary vane pumps operate by expanding volume at the inlet and compressing that volume at the exhaust. This is accomplished by placing the rotor eccentrically inside of the cylindrical housing, such that it is nearly touching the housing at the top, and is distanced from the bottom. This rotor houses the vanes, and when it spins, centrifugal force causes these vanes to be slung out of the grooves they sit in until they contact the cylinder wall. When the vanes are in this extended position, they create an effective gas barrier that splits the pump cavity into multiple sections.
As they rotate, the sections exposed to the inlet port will continually be expanding, and the sections exposed to the exhaust port will continually be contracting. This causes the process gas to be drawn into the inlet, compressed within the pump, and expelled out the exhaust port. As the vanes are physically in contact with the cylinder wall, lubrication is required. This lubrication also aids sealing between the sections of the cylinder, as well as facilitates heat transfer away from the site of compression. These actions combine in a way that allows oil-lubricated rotary vane pumps to be capable of very low base pressures, and as such, they are suitable for applications requiring vacuum levels as low as 0.375 Torr.
