Experimental Study of Pumping Condensable Vapors by Oil Free Vacuum Scroll Pumps

Abstract

When operating a vacuum pump, it is often necessary to pump out liquid vapors or vapor-gas media that can condense in its working cavities. To prevent condensation in displacement pumps including scroll pumps, gas ballast device is used. The maximum tolerable water vapor pressure at the inlet and maximum pump capacity by water vapor are the main parameters of a pump with gas ballast device. The highest water vapor pressure at the inlet and the maximum capacity of the oil-free scroll vacuum pump by water vapor were determined experimentally. For this purpose pumping speed, gas flow through the gas ballast device, and gas temperature at the scroll vacuum pump outlet were measured on a specially designed stand. A method for calculating the partial pressure of water vapor in scroll vacuum pumps using a mathematical model of pumping process is proposed. Experimental and calculated results are in good agreement.