A new type of vacuum pump for corrosive gases and vapors

Abstract

A vacuum pump is described based on a novel gas pumping principle. A rotating drum is partially filled with a liquid, which is made to flow round the outside of the drum, as in a liquid ring pump, leaving the center clear. A probe is held in the rotating liquid and is shaped to create a low-pressure region on its surface where there is a hole which connects, through the static hub of the drum, to the vessel to be evacuated. The center of the drum is connected, through suitably placed holes in the central hub, to atmosphere. Gas is drawn from the vessel thought the hole in the probe into the circulating liquid. Centripetal force acts on the gas bubbles in the liquid ring to propel them towards the center where they burst at the gas/liquid interface. The gas then escapes to atmosphere through the outlet hole system. Small experimental pumps have achieved vacua better than 0.1 mbar and speeds of 10 m3/h. Higher vacua and faster pumping speeds are thought to be attainable. There are no rubbing components inside the pump and there is, therefore, no need for the working liquid to be a lubricant. Also, choice of materials in contact with the possibly aggressive gases is not restricted by the need for rubbing compatibility. A corrosion-resistant laboratory pump is described with a 3 m3/h pumping speed and a 0.5 mbar ultimate vacuum.