page_title: Liquid-ring pump
section_title: Single- and multistage
hierarchical_section_title: Liquid-ring pump / Types and Applications / Single- and multistage
caption_attribution_description: Čeština: SIHI liquid-ring vacuum pump in bioethanol producing plant.
context_page_description: A liquid-ring pump is a rotating positive-displacement pump.
  They are typically used as a vacuum pump, but can also be used as a gas compressor.
  The function of a liquid-ring pump is similar to a rotary vane pump, with the difference being that the vanes are an integral part of the rotor and churn a rotating ring of liquid to form the compression-chamber seal. They are an inherently low-friction design, with the rotor being the only moving part. Sliding friction is limited to the shaft seals. Liquid-ring pumps are typically powered by an induction motor.
context_section_description: Liquid-ring systems can be single- or multistage. Typically a multistage pump will have up to two compression stages on a common shaft. In vacuum service, the attainable pressure reduction is limited by the vapour pressure of the ring-liquid. As the generated vacuum approaches the vapour pressure of the ring-liquid, the increasing volume of vapor released from the ring-liquid diminishes the remaining vacuum capacity. The efficiency of the system declines as a result.
  Single-stage vacuum pumps typically produce vacuum to 35 Torr (mm Hg) or 47 millibars (4.7 kPa), and two-stage pumps can produce vacuum to 25 Torr, assuming air is being pumped and the ring-liquid is water at 15 °C (60 °F) or less. Dry air and 15 °C sealant-water temperature is the standard performance basis, which most manufacturers use for their performance curves.
caption: Single-stage vacuum pump
  in bioethanol plant
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