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Liquid Ring Vacuum Pumps

Hi-vac is the largest manufacturer of vacuum pumps in Africa and the second largest in the Southern Hemisphere. Since its inception, Hi-vac has supplied in excess of 5000 pumps to the mining industry in South Africa alone and continues to be an approved and reputable supplier to this industry in respect of supply, repair and spares contracts for all the mining groups.

In addition, Hi-vac is a leading supplier of liquid ring vacuum pumps to the Atomic Energy Industry, who have the highest concentration of Hi-vac supplied stainless steel vacuum pumps in service. Hi-vac is also a leading supplier to such varied customers as Paper and Pulp Mills, Sugar Refineries, Food Processing Plants, Chemical Plants, Brick Yards and Plastics Plants. Centralised vacuum systems and autoclave/steriliser pumps have also been supplied to both government and private medical facilities.

Product Range

Hi-vac manufactures 35 models of pump ranging in capacity from 18m³/hr to 12 500m³/hr at a vacuum of 25mm HG (absolute), when the pump is combined with an air ejector a vacuum of 3mm HG (absolute) can be obtained.

Liquid Ring Vacuum Pumps

are constantly becoming more important in modern plant production processes. Their design and principle of operation offers many advantages over other types of rotary gas pumps. Liquid Ring Vacuum Pumps can be used on a very large scale for widely divergent applications.

As the impeller rotates, the liquid is thrown out by centrifugal force and air is drawn in through the suction port. After the suction port is passed, the service liquid is forced back into the spaces between the impeller blades, gradually compressing the air or gases. When the spaces between the impeller blades reach the discharge point, the liquid ring will force the air compressed between the blades into the discharge port.

Operating Principle

The diagram to the right shows a cross section of the Liquid Ring Vacuum Pump. It operates on the rotary liquid piston principle, the shaft and the impellers being the only moving parts.

The shaft and impeller assembly is mounted eccentrically relative to the pump casing. As the impeller rotates the service liquid (which is continually supplied to the pump), is forced outwards by centrifugal force to form a liquid ring revolving concentric to the pump casing.

Because of the eccentric position of the impeller, the liquid ring will move towards and away from the shaft, resulting in a liquid piston action which displaces the air or gases between the spaces of the impeller blades.

Design Features

Liquid Ring Vacuum Pumps offer the following advantages:

  • High Vacuum. Up to 25mm Hg absolute, and higher (with other service liquid).

  • Long Life and Low Maintenance Cost. The impellers and shaft are the only moving parts.
    The impellers have no contact with the casing. There are no sliding vanes or valves.

  • Vibration-free and Noiseless Operation. Rugged construction and absence reciprocating parts ensure vibration-free and noiseless operation.

  • Non-pulsation Gas Flow.

  • No Internal Lubrication.

  • Liquid and Vapour Handling. Liquid Ring Vacuum Pumps are capable of handling large quantities of vapour. Small amounts of liquid drawn in from the system will pass through the pump without causing damage.

  • Low Starting Torque.

  • Different Service liquids may be used.

  • Materials of Construction. Pumps can be constructed from a wide range of materials to suit corrosive conditions.

  • Delivery of Absolutely Oil-free Air. When unit is used as a compressor.

Maximum Vacuum

Maximum vacuum and capacity obtainable by Liquid Ring Vacuum Pumps depends directly on the vapour pressure or the service liquid.. Higher vacuum and capacities than indicated in the capacity tables may be achieved by using the following methods.

  • Using a special oil as the service liquid instead of water. The low vapour pressure of the oil allows maximum vacuums down to 12mm Hg absolute. In addition the capacity in the higher vacuum range will increase.

  • By placing one or more gas ejectors in the series with the pump.

  • By operating a Liquid Ring Vacuum Pump in series with a mechanical booster , ultimate power vacuums down to 1mm Hg absolute and capacities up to 8000 m3/h are obtainable with this combination.


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download tables
Capacity Tables - GDM Series.pdf
Capacity Tables - GDH Series.pdf

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