Examination of oil vapours emitted from an oil-sealed rotary pump using gas–liquid chromatography and mass spectrometry showed their molecular weight was significantly less than the average value of the parent oil.
It was suspected that the predominantly low molecular weight of the vapour was due to the evolution of inherent light fractions in the oil and to cracking products resulting from friction processes in the pump. To separate these effects small amounts of lubricants were subjected to controlled frictional working conditions under vacuum. The emitted vapour was analysed by a rapid scan mass spectrometer and the residual fluid examined for changes in composition by gas–liquid chromatography.
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