In a vacuum pump, vacuum pump oil not only serves as the medium for obtaining vacuum, but also plays a role in lubricating, cooling, and sealing mechanical friction points.
1. The extremely low vapor pressure is the most important performance of vacuum pump oil. As vacuum pumps require a vacuum degree of 1.33 × 10-4Pa (10-6mm Hg) and high requirements below 1.33 × 10-4Pa (10-6mm Hg), the evaporation of vacuum pump oil is required to be extremely low. Generally, paraffin based narrow fraction lubricating oil is used, and for diffusion vacuum pumps, low vapor pressure silicone oil or other synthetic oils can also be used.
2. A vacuum system with appropriate viscosity and good viscosity temperature characteristics utilizes the continuous change in pump chamber volume to form an exhaust effect, requiring lubricating oil to have appropriate viscosity and good viscosity temperature characteristics.
3. The vacuum pump with good thermal oxidation stability continues to develop at a high speed. Due to the high-speed friction between the sliding plate and the pump body, the oil temperature rises, which intensifies the thermal and oxidation effects of the oil. Diffusion pumps often operate at high ambient temperatures, causing an increase in vapor pressure and a decrease in vacuum degree within the system. Therefore, it is required that the vacuum pump oil has good thermal oxidation stability.
4. Good corrosion resistance and emulsification resistance. If the gas sucked in by the vacuum pump is corrosive, it will corrode the metal parts inside the pump and cause chemical changes to the oil. In addition, the inhaled air often contains water vapor, causing emulsification of vacuum pump oil, so good corrosion resistance and emulsification resistance are required. The emulsification of vacuum pump oil used in vacuum dehydration process is more prominent.
5. A higher flash point requires that the vacuum pump does not carry any lightweight components to avoid affecting the saturated vapor pressure of the oil.
6. The lower ultimate pressure limit pressure is an important performance indicator for vacuum pump oil to understand the ultimate pressure of the vacuum pump at the lowest vacuum limit pressure.
