METHOD OF PUMPING GAS

摘要

A method of pumping a gas stream containing a condensable species and a light gas and an apparatus therefore, the method comprising the steps of conveying the gas stream to a multistage vacuum pump comprising an inlet stage and an exhaust stage downstream from the inlet stage, and adding to the gas stream upstream of or at the inlet stage a purge gas heavier than said light gas to both inhibit migration of the light gas from the exhaust stage towards the inlet stage and to inhibit condensation of the condensable species within the pump.