Vacuum Pumps - Rotary Vane Pumps - Self Priming Pumps

There are several type of vacuum systems available in the market to meet the different needs of different industries. But sometimes it is possible that one cannot find the vacuum pump of his needs and so it needs to be custom built. And this is the most exciting and unique feature of vacuum pumps. Because of number of options in vacuum pumps it is good to gather information about the different options and about your need and then make your decision.

One type of vacuum pump is the rotary vane pump. They are a part of positive displacement pump category. They move the fluid through the pump using the rotating assembly in the pumping chamber. It usually takes one or two rotating vanes to move the gas or the fluid from the inlet to the outlet. As the bulk of the fluid is transferred by the rotary vane pumps the end of the vane barely brushes the housing part and thus creates the seal from the inlet to the outlet.

The movement of the pump can be broken down into three different phases in the rotary vane pumps:

1. Gas or the fluids move through the inlet.


2. The vanes rotate either clockwise or anticlockwise to seal the media between the vanes and the housing wall. Due to the fluids, this volume should remain constant throughout the entire cycling process.


3. Then the gas or fluid is moved through the outlet. The rotor blades are positioned in such a way that it contains a specific volume of the fluid. Due to the cyclic movement of the vanes it creates a smooth flow as the gas or fluid is transferred through the pumping chamber.

Following characteristics of vanes make the rotary vane pumps being used widely by different industries for different applications:

• Can be made from several materials.


• Have the flexibility of being able to choose the inert gases and many different type of gases.


• Can either be internal or external.


• Can also be rigid or flexible.

One will wonder whether these options will be available when he purchases the rotary vane vacuum pumps already assembled. But one can tell his needs in the pump and it can be customized. There are other things that need to be considered while rotary vane pumps is being built. The surface dimensions of the housing and the rotary assembly might be considered while calculating the flow rate. The other requirements that might be included is the vacuum service or air compression.

There are various other options, but this can give the idea of what a rotary vane pump can do.

The self priming pumps are a special form of centrifugal pump that eliminates the necessity for external priming devices. If a centrifugal pump is found on top of the suction vessel or sump , it should be primed before it is started, to get rid of air from the suction line and casing, and to fill the suction line and casing with liquid. This should be done before starting the pump, otherwise the pump won't pump, and the air can harm the pump bearings. The priming operation on a regular centrifugal pump that's operating with a suction lift is done by pulling a vacuum at the top of the pump casing, using a vacuum pump or the plant vacuum systems. A self priming pump eliminates the requirement for this external priming mechanism.

The operating self priming centrifugal pumps work like any other pump that's operating with a suction lift and that has been properly primed. When the pump shut down or stops working, the liquid drains out of the suction line and back to the sump. However, as a result of the special design of the over-sized self priming pump casing, a amount of liquid remains within the bottom of the casing. When the pump is started again, the pump goes through a priming cycle, which generally takes several minutes. Throughout the priming cycle, the liquid that had remained in the pump casing is pushed by the impeller out the discharge, along side some of the air that is in the casing. This creates a vacuum at the impeller inlet, which draws liquid up the suction line. The priming cycle continues till all of the air is pushed out of the discharge and the water has worked its way up the suction line to the impeller. Then, the pump is totally primed and begins pumping like every primed centrifugal pump.

Self priming pumps can be used anywhere where a pump is running with a suction lift. The pump is also costlier than a regular centrifugal pump, however it eliminates the external priming mechanisms, and eliminates any bearings or motors in the sump that other pump types would possibly need. Normally, suction lifts are restricted to approx. twenty feet with self priming pumps.