Oil reservoir evacuation for pumping condensable vapours through oil sealed rotary vane pumps

Condensable vapours cause oil deterioration or corrosion of the pump interior. Evacuation of the oil reservoir promises advantages to other methods of protection. At an oil temperature of approximately 70°C and an evacuation to approximately 40 mbar, the dew points of nearly all interesting vapours are avoided and the oil is cleaned by permanent ‘distillation’. Evacuation is done by a corrosion resistant all-PTFE diaphragm pump with vapour condensation and collection at atmospheric pressure. Gas ballast via proper inlets purges the system. A 2-rotary plus 2-diaphragm stage system is described and results are reported.