Application areas:

These oils are recommended for lubrication of textile and machine tools, spindle bearings, timing gears, centrifugal separators, positive displacement blowers and hydraulic systems of certain high precision machine tools. Every vacuum pump type has its own specific requirements for oil, and the oil needs to be inspected and periodically replaced. Vacuum pump oils come in hydrocarbon, silicone, PFPE, semi-synthetic, full synthetic and other varieties made for certain vacuum applications.
vacuum pump oil works as a mechanical lubricant and a medium for trapping gas molecules. It is chemically stable, not reactive to most gases and materials and has a low vapor pressure. All substances will boil or otherwise shed molecules into a vacuum. Over time, a pressure will build up, called vapor pressure, contaminating the vacuum. Substances like water will boil heavily into a vacuum. Other substances, like glass, will boil very little.

Every vacuum pump type has its own specific requirements for oil, and the oil needs to be inspected and periodically replaced. Vacuum pump oils come in hydrocarbon, silicone, PFPE, semi-synthetic, full synthetic and other varieties made for certain vacuum applications. Vacuum pump oil works as a mechanical lubricant and a medium for trapping gas molecules. It is chemically stable, not reactive to most gases and materials and has a low vapor pressure. All substances will boil or otherwise shed molecules into a vacuum. Over time, a pressure will build up, called vapor pressure, contaminating the vacuum. Substances like water will boil heavily into a vacuum. Other substances, like glass, will boil very little.
“Oil” is a bit of a misnomer because modern pump oil technology has evolved well beyond the original distilled petroleum products. There are now double- and triple-distilled oils available, as well as hydro-treated oils, low sulfur oils, silicone-based synthetic oils, and flushing oils used to clean the pump. Due to the wide variety of formulations available, these are often now referred to as pump “fluids” rather than pump “oils”. The oil in a vacuum pump serves several purposes. In addition to providing lubrication for mechanical components such as found in rotary vane pumps, the oil also provides the following:

• A seal across the vanes and duo seal between the high pressure and low-pressure side of the pump.
• Cooling of the pump by conducting heat from the stator to the outer casing where it can be dissipated.
• Protection of the metal parts from corrosion caused by the pumped gas.

In diffusion pumps, the oil is used to trap and remove gas molecules from the vacuum chamber through kinetic motion. Due to these multiple roles, the properties of the oil selected by the manufacturer must be carefully evaluated. If the oil is not properly selected, pump performance will be negatively affected and the pump possibly even damaged.

Different pump oil formulations are specifically designed for different pumps and different vacuum applications. Therefore the user of the vacuum system must have a basic understanding of pump oils in order to make the correct selection. SAE 30 motor oil, for example, is not properly refined for use in a vacuum pump, has inadequate chemical resistance, and contains additives such as rust inhibitors that would separate out from the base fluid and deposit on interior surfaces as a gummy residue. Vacuum pump oil additives are limited to corrosion resistance, anti-oxidation, and anti-foaming. Although vacuum pump oil costs much more, it cannot be substituted by motor oil. In order to choose the correct pump oil, it is useful to understand vapor pressure, viscosity, and distillation methods.