The Various Mechanical Pump Oils

There are five primary types of mechanical pump oil. The advantages and disadvantages of these various materials are explained below and in Table 7.7. 

The Hydrocarbon Oils. These oils are the most common and least expensive. They are composed of paraffinic, naphthenic, and aromatic hydrocarbons and provide excellent sealing qualities. When these oils are properly distilled, they can exhibit low vapor pressures (10 4 to 10 6 torr). However, they oxidize quickly when heated, have a tendency to form sludge and tars, and are likely to foam if pumping against atmospheric pressure (as opposed to a vacuum). 

Many of the negative properties of hydrocarbon oils can be overcome by the use of additives which inhibit oxidation, reduce foaming, disperse contamination, 

Pump Oil Type Good Points Negative Points 

Chlorofluorocar- bon (CFC) (e.g Halo-Vac ) Extremely nonreactive and will only ignite under extreme circumstances. Less expensive than perfluoropoly-ethers. Should not be used in pumps with aluminum parts. Heating over 280°C will produce HF gas. Difficult to clean. Viscosity varies with temperature. Has a rather high vapor pressure. 

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