Rotary Vane vs Oil Sealed Liquid Ring

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 Comparison of Rotary Vane Vs Oil-sealed Liquid Ring Vacuum Pumps Non-Chemical Applications

The heart of all vacuum systems are the vacuum pumps. For most non-chemical (General vacuum service, Vacuum Forming, Vacuum Chucking, Vacuum Degassing, Central Laboratory Vacuum, Central Medical Vacuum, etc) applications, vacuum pumps typically are either a lubricated sliding vane (Rotary Vane) vacuum pump or a liquid ring vacuum pump. Liquid ring vacuum pumps can be either water sealed (requiring a continual cooling water or water purge), or oil-sealed (known as Vmax) which are air-cooled.Oil Lubricated Rotary Vane

During the 1970's and 1980's water-sealed vacuum pumps were being replaced by air-cooled Rotary Vane vacuum pumps primarily due to water savings (Vmax oil-sealed air-cooled liquid ring vacuum pumps were not available at that time). During the 1990's, Rotary Vane (Busch®) vacuum pumps were the most common type being installed, primarily due to an emphasis on electrical efficiency, since rotary vane pumps are approximately 10-15% more efficient (CFM per HP). Per the EPA(1) :“On the negative side, there have been problems with the vulnerability of these pumps should water be carried into (or accumulated in) them. In this situation, the pumps must be taken out of service to remove the liquid; the result is a shortened service life. By contrast the liquid-ring pump can usually withstand an accident of this type with very little damage.”  

 What is usually not considered in the evaluations, however, is the life cycle costs including maintenance (labor, oil, filters, repairs) of the vacuum pumps. Rotary vane vacuum pumps, on clean service, are recommended to change oil every 500 to 750 hrs of operation (about every 3 weeks for continuous service). The Vmax only requires oil changes once every year (10,000 hrs on clean service); for typical dirty applications- every 6 months. Water accumulation in the oil (very common problem), can damage the rotary vane pump because the vanes and bearings rely on the lubricating oil for operation, whereas the Vmax oil-sealed liquid-ring vacuum pump uses external greased bearings and the oil is used for sealing, not lubrication.(see How a Liquid Ring Pump Works). Triplex VMAX # VMX0303 Oil Sealed Liquid-ring

 The EPA(1) recommends “When liquid-ring pumps are used, oil is recommended as the seal liquid”, because the oil-sealed Vmax eliminates the potential for rusting, corrosion and hard water deposits when using water as the sealant. The oil-sealed Vmax offers many advantages in non-chemical vacuum applications, when low maintenance and high reliability are important.

  • Lower maintenance (oil change once per year)
  • Quieter Operation (78 dBA vs 85 dBA)
  • Higher Reliability (able in ingest liquid without damage)
  • Air-cooled
  • Small Footprint

(1) (1) US-EPA Alternative Wastewater Collection Systems EPA/625/1-901/024

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