Rotary vane vacuum pumps move fluid through the pump using a rotating assembly in the pumping chamber. Typically there are two or more rotating vanes that move the gas or fluid from inlet to outlet. Rotary vane vacuum pumps are positive displacement pumps. The volume of fluid that is transferred by rotary vane pumps depends upon the size of the housing and the area between each adjacent vane. Larger pumps may have additional impeller vanes. As the rotor turns, the ends of the vane barely touch the housing creating a seal from inlet to outlet. The inlet and outlet are often perpendicular, however for vacuum service applications two inlets may be used, one for air supply and the other for the pumped media. The fluid is pressurized as the volume between the vanes lessens during one half-cycle and is suctioned through an intake port during the other half-cycle.
The movement of the media through the pump can be broken down into three phases in rotary vane pumps: 1) Air or fluid moves through the inlet also known as open to inlet (OTI). 2) The vane rotates clockwise or counterclockwise and seals the media between the vanes and the housing wall also known as closed to inlet and outlet (CTIO). With fluids, this volume should remain constant throughout the cycling process. Gases and/or air may be compressed in this phase causing the pressure to increase before the next phase. 3) The media is moved through to the outlet. This is also referred to as the open to outlet (OTO) volume. The rotor blades are positioned to contain a specific volume of air or fluid. The cyclical movement of the vane creates a smooth flow as the fluid is transferred through the pumping chamber. Generally, materials can be chosen for the vane. For example, carbon vanes can be used with inert gases and a variety of other media types. The vane can be internal or external, rigid or flexible.
The manufacturer for rotary vane vacuum pumps can often give the displacement of the pump. The surface dimensions of the housing and rotary assembly may be considered when calculating flow rate. In some rotary vane pumps, as the flow rate increases, the pressure in the pump chamber increases. Various requirements may be needed including vacuum service or air compression. As with most rotary pumps, the viscosity of the media will affect the speed of the drive chosen. The flow rate is also proportional to the motor speed. Magnetic drive, belt drive or direct drive can be chosen for powering rotary vane pumps.
Rotary vane vacuum pumps can be used in a number of applications providing a pressure or vacuum source for laboratory applications and as well as other automation applications. Smaller sizes may have a maximum flow of 3 LPM with pressures ranging from 80-120mbar.
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