New on the South African market, imported from the UK, the Liquivac liquid-ring vacuum pump has the ability to pump liquids or combinations of liquids, gases, foam and fine solids and has many applications, such as pump priming, vessel emptying, ground dewatering spill recovery, removing liquids from vacuum pro- cesses and wash-down recovery to name but a few. The Liquivac has advantages of discharge heads of up to 3 bar, suction lifts to 8,5 m, air-flow priming rate of 40 m3/h and liquid flow rates of up to 35 m3/h. The units are available in configurations ranging from cast-iron body with stainless-steel rotating parts or all wetted parts in stainless steel and mechanical seals to suit many applications. John Crane mechanical seals are standard but others can be used on request.

The heart of all Liquivac pumps is a twin-start helical rotor mounted eccentrically in a cylindrical barrel. On initial installation, the pump should be primed with a suitable liquid. During start-up, surplus liquid is displaced through the discharge port plate, the remainder forms a liquid ring retained and supported by the suction and discharge port plates. The liquid ring forms a seal between the top tips of the rotor and the underside of the rotor boss. This arrangement creates a series of crescent-shaped cavities travelling from suction to delivery. Any product, such as liquids, air, foam, emulsions or vapours exposed to suction would be drawn in to these cavities and discharged through the pump.

The large clearances between the rotating and stationary parts allow the pump to handle solids of up to 2 mm in diameter.

The Liquivac liquid-ring vacuum pumps are available from Vac-Cent Services.

Vac-Cent Services was formed in 1987 with the objective of retaining the manufacturing licence for Nash liquid-ring vacuum pumps and compressors and related products, in South Africa. The main markets being serviced since 1981 still remain pulp and paper, chemicals, food, coal, mining, power and wastewater. In addition to the Nash product range, Vac-Cent Services was appointed the sole distributor locally of the Frese automatic flow-control valve range. The main markets for this valve range have been air conditioning and water distribution since 1990. New current markets include refri-geration and mining.

Always striving to offer the market the most current and up-to-date technology, the Edwards Chemical Dry Pump Agency was obtained in 1995, with its main markets being the chemical and pharmaceutical industries.

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