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Work principle of the water or liquid ring vacuum pump


The water ring vacuum pump (i.e water ring pump) is a kind of rough vacuum pump, and its limit vacuum is 2000~4000Pa(abs). If connect an ejector with it, the limited vacuum can reach to 270~670Pa. And the pump can also be used as a compressor, then it is called water ring vacuum compressor. The water ring compressor is belong to the low pressure compressor, its pressure scope is 1~2*105Pa(refers to the meter show).


The water ring vacuum pump is widely used in the petrol, chemical, mechanical, mine,light industry, pharmacy, and foodstaff. Accompanying the vacuum applicable technology develops rapidly, the water ring vacuum pump usage in the vacuum area is regarded by the people more and more. Since the gases in the pump cavity are compressed under the same temperature, the water ring vacuum pump can pump the gases that are flammable, explosive, or containing the moisture and dust.


The operating water can be also replaced by other liquids. In spite of which liquid as the operating liquid, the pump are generally called liquid ring vacuum pump. The water ring vacuum pump is used mostly and extensively.


Work principle of the water ring vacuum pump

See the picture

In the pump casing the proper volume water is used us operating liquid.
When the impeller turns clockwise, the water sprays around. Operated by means of the centrifugal force, the water forms a closed round ring defined by casing shape and with almost same thickness. The inner surface of the water ring bottom is just tangent with the impeller hub and the inner surface of the water ring top just touchs the tip of the impeller vane(in fact, there is a definite depth that the vane in the water ring). At the moment, a crescent shape space forms between the impeller hub and the inner surface of the water ring.

And the crescent space is as well as divided into many little spaces whose quantities is equal to the impeller vanes' number. If regard the impeller bottom at zero degree as the beginning point, when the impeller turns from zero degree to 180 degree, the little space volume becomes larger and larger and communicates with the inlet port on the port plate. Here, the gases are pumped in. When the pumping process are ended, the little space is isolating with the inlet port.

Accompanying the impeller turns continually, the little space becomes smaller and smaller, so the gases are compressed. Till the little space is communicated with the discharge port, the gas is pumped out.


Totally, the water ring vacuum pump depends on the volume changing to achieve the suction, compressure, and discharge process. So it is belong to the transformable volume vacuum pump.

Comparing with other mechnical vacuum pumps, the water ring vacuum pump has many advantages as bellow:

  • Structure compact,manufacture precision low requirements, machining easy.
  • Pump speed is higher, normally it can couple directly with the motor. So using the less structure size to achieve the larger discharge volume, and the occupation area is also small.
  • The gases are compressed under the almost same temperature, i.e. the temperature changes little during the gases compressed.
  • It is not necessary to lubricate the pump cavity for there aren't metal rub surface in it and the rub cost is very little. The seal between the rotate parts and the fixup parts can use the water ring directly.
  • Suction equably,running reliable and calmly, operation easier, and maintaining conveniet.

 

The water ring vacuum pump also has disadvantages:

  • Low efficiency: normally is about 30% and better 50%.
  • Low vacuum: this is not only restricted by the pump structure, but also by the liquid saturation pressure. When to use the water as operating liquid, the limited vacum can reach to 2000~4000Pa, and to use the oil, the limited vacuum can reach to 130Pa.
In conclusion,because the gases in the pump cavity are compressed under the almost equal temperature, the water ring vacuum pump can pump the gases that are flammable, explosive. And because without the discharge valve and rub surface, it can pump the gases that containing the dust, coagulable moisture and steam mixture. For these outstanding characteristics, the water ring vacuum pumps are still used widely in spite of its low efficiency.


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