How a Liquid Ring Vacuum Pump Works

Liquid Ring Vacuum Pumps 

Liquid ring vacuum pumps are rotating positive displacement machines providing process vacuum in industrial applications such as chemical, electrical power, environmental, food & beverage processing and packaging, marine, mining, oil & gas, pharmaceutical, pulp & paper and textiles. These types of pumps utilize water or other process compatible liquid as the sealant. The simple operation, with no contacting parts, make liquid ring vacuum pumps a safe and reliable choice for handling dirty and potentially dangerous gas streams.  Liquid ring pumps are available in single and dual stage designs and also configured as compressors for even more versatility.

Principle Of Operation

The seal liquid forms the ring inside a pump body as the impeller spins creating small chambers for gas to be trapped. The axis of the rotor is eccentric from the body allowing the liquid to almost fill, and then almost empty each rotor chamber during a single revolution, forming the compression of the gas for the pumping action. Vacuum inlet and atmospheric discharge ports provide flow paths for the gas mixture being handled. Heat of compression of the gas is dissipated into the seal liquid, and some of the liquid flows out to discharge. The exhaust gas and residual water discharge is separated from the gas stream and directed to the house exhaust and returned to the pump respectively.  Seal fluid is replaced by a constant flow of cooler makeup seal fluid.  

Characteristics Of Liquid Ring Vacuum Pumps


Characteristics Of Liquid Ring Vacuum Pumps 

  • Accepts Carryover - Soft solids, moisture, slugs, chemicals and more will not harm the pump. These impurities will simply be washed out through the pump discharge 
  • Cool & Quiet Operation - The pump runs cool owing to the circulation of the sealing water inside the pump. The operation is relatively quiet - not exceeding 85 dBA. 
  • Constant Operation for Any Vacuum Level - Pump can operate constantly and continuously at any vacuum level - from 29 in. HG Vac. to atmospheric pressure. 
  • Easy Maintenance - Liquid ring vacuum pumps have few parts and only one moving part, the rotor. This benefits the user with less wear and simpler, affordable maintenance. 
  • Longer Pump Life - Pumps are robust in construction and has only one moving part, the rotor, which is mounted on a shaft supported by a set of bearings designed for a long service life of continuous operation. 
  • Environmentally Friendly - Pumps do not require oil change, filter, oil-pans, condenser or etcetera. For that reason, plant rooms run clean, free of oil contamination and oil discharges to sewers. 

A Closer Look Inside Liquid Ring Vacuum Pump Technology

Inside Flat Sided Liquid Ring Vacuum Pump

Flat Sided Liquid Vacuum Pump

inside the liquid ring vacuum pump Conical Pump

Conical Liquid Vacuum Pump

The Technology Behind Liquid Ring Vacuum Pumps 

The design technology behind liquid ring vacuum pumps is advanced to achieve optimum, reliable performance in rigorous demands of harsh industrial environments. Liquid ring vacuum pumps are an economical and robust solution engineered to meet specific customer requirements. 


Condensation Of Vapors Can Yield A Capacity Bonus 

Dry air or a dry gas mixture is compressed from vacuum to atmospheric pressure in a liquid ring pump much the same way as it would be in any other displacement type pump, except that there is less of a temperature rise of the gas stream through the pump. 

Humid air or gas mixtures containing condensable vapor behave quite differently. Some of the vapor that enters a liquid ring pump condenses when it is cooled by the lower temperature seal liquid. The condensate mixes with the seal liquid. Now, it occupies a much reduced space as contrasted with its former volumetric dimension when it was a component of the inlet gas stream. This volumetric reduction becomes a capacity bonus. 

Only vapor that can be condensed early enough to escape compression contributes to the inlet capacity bonus. In each rotor chamber, the condensation must occur before that chamber passes its inlet port. Any condensation that occurs after cutoff will not have an effect on pump inlet capacity. 

Liquid ring vacuum pumps can handle large amounts of liquid through its inlet port with a negligible reduction of gas capacity. To maximize the condensation bonus some of the liquid is often sprayed into the inlet piping, upstream of the vacuum pump itself.