Liquid ring pump

A liquid ring pump ( well water ring vacuum pump, liquid ring vacuum pump or liquid ring compressor called ) is used for conveying and compression of gases, which is why it actually is not technically a pump, but a compressor. It is often used as a vacuum pump, especially in the plant and process engineering, for example in the chemical industry. As a liquid ring vacuum pump, it serves at the fire venting the suction for water pumping from open water.

Functional principle of liquid ring pump

In the cylindrical housing of the liquid vacuum pump is a star-shaped, eccentrically located impeller / impeller. The fluid contained in the housing ( normally water ) is in rotation by centrifugal force to a liquid housing concentric ring which seals the impeller chambers. Impeller and casing not touch, sparking is not possible. Due to the eccentricity of the blades dive to different depths into the liquid ring: The ring acts as a piston alternately sucks and compresses. There are also designs with 8-shaped housing ( double eccentricity) in which the impeller is centered in the housing. In the lids that seal the side of the impeller, have recesses, so-called lateral channels, into which the liquid ring and thereby presses the eccentric geometry which is required for generating the pressure difference of the individual chambers produced.

The operating fluid has four functions:

  • Sealing: no contact between the impeller and casing ( no lubrication, no sparks )
  • Compaction: ring segment acts as a piston ( drawn in and compressed between the blades by eccentricity )
  • Cooling: the compression is isothermal ( the specific heat of the working fluid is much higher than that of the gas )
  • Condensation: the vapors are condensed at the inlet and the suction power improved the volumetric pump

The suction capacity of the liquid ring pump is reduced by the proportion of the saturation vapor pressure at the suction pressure, and therefore, the suction pressure of the liquid ring pump is not less than the saturation vapor pressure of the operating fluid being used. The resulting compression in the compression and condensation heat is removed via the working fluid. This is often attributed as an external circuit from the pressure side to the suction side, while cooled with a heat exchanger.

Benefits

  • Sparks through contact between metals is prevented due to the operating fluid used, liquid ring pumps are therefore suitable for the conveying and compression of explosive gas mixtures
  • Insensitive to liquid / vapor and particulates
  • Isothermal compression (high efficiency, use possible with products that tend to polymerize or decompose at high temperature )
  • Oil Free ( no contamination )
  • High security for the compression of gases and vapors ignition -capable ( seal with the operating fluid )
  • Simple design for corrosion resistant materials
  • Insensitive to co-promotion of solid particles or fibers
  • Can also be used as a scrubber
  • Can also be used as a capacitor
  • Relatively quiet and low-vibration operation
  • No maintenance (only at the shaft seal )

Disadvantages

  • High power consumption due to friction loss
  • The gas to be conveyed is saturated at the outlet with operating liquid
  • Does an operating fluid or cooling of the working fluid
  • Maximum achievable vacuum limited ( up to max. Mbarabs about 1013 with water as a working fluid, or approximately 10 mbarabs with other liquids )
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