Types and Applications of Liquid Ring Pumps

photo courtesy of Vooner

What is a liquid ring pump? It is a rotating positive displacement pump. Liquid ring pumps are mostly used as vacuum pumps but can also double up as gas compressors. They function like rotary vane pumps, but the vane in a liquid ring pump takes a prominent role the rotor. It swirls a ring of liquid that goes round and round to form the compression chamber seal.

If you are in need of a liquid ring pump for your business, you will be interested in any information that you can find about them. As well as visiting companies that supply them, magazines and good old internet are rich sources of information.

Types and uses of liquid ring pumps

A short forage into a site like CVN Vooner Paper Machinery or a check into other companies that deal with liquid ring pumps will give you a variety of pumps to choose from. However, it does no harm to look at a few of them and their applications.

Single and multistage systems

• • Multistage: It has two compression stages on a shared shaft. When used for vacuum purposes, the obtainable pressure reduction is lessened by the vapour pressure of the ring-liquid. The increasing amount of moisture unleashed from the ring liquid reduces when the generated vacuum nears the vapour pressure.
  • Single stage: As the name suggests, this one has only one stage. It produces a vacuum of 35 Torr whilst the multistage one gives out 25.

Recirculating the ring liquid

• • Some ring liquid has the discharge stream which is liquid that is set apart from the gas stream by other external equipment.
  • The discharge ring is chilled off by a heat exchanger and then it goes back to the pump casing.
  • There are contaminants in some systems which get trapped in the ring liquid. When this happens, the contaminants are concentrated as the liquid goes on recirculating. Ultimately, some harm is done and pump life is curtailed.
  • In systems which do not recirculate, the hot liquid is treated as waste. Therefor,e cooler water is added as a replacement.

The type of liquid

• These vacuum pumps can support any liquid which is appropriate for the process for which it is intended.
• The vapour force must be apt though for sealing purposes. The most common liquid used for sealing is water, followed by oil.
• Oil barely has any vapour force, so air is used to cool oil-sealed vacuum pumps.
• This capacity to be compatible with any liquid makes the liquid ring pump ideal for recovering vapour. As long as the coolant, usually water, is cold enough to keep the force of the sealing liquid low enough to pull the relevant vacuum, all is well.
• Liquid ring pumps that use ionic liquids have their vacuum pumps pressure lowered from 70 mbar all the way to below 1 mbar.

Any information on liquid pumps and the appropriate ones for your requirements is readily available on websites and company sites like CVN Vooner Paper Machinery should you wish to purchase or make enquiries.  

Author: Charlie Brown