Vacuum Technology

How to select vacuum oil?

This article is to introduce how to select vacuum oil for quality vacuum pumps from China.

The oil becomes saturated with contaminants after a long time running. Consequently, the pump’s vacuum level is not as high as before. Make sure the color of the vacuum oil is transparent light yellow during operation. If the oil color is darkened, it means too much contaminants in the oil; if the oil color becomes milky white, it means the oil is emulsified due to much vapor absorbed in the oil. It is required to replace the oil immediately when the color change is observed. Maintaining clean oil ensures the required ultimate vacuum of a vacuum pump.

Normally vacuum oil is kind of a mineral oil without additives. However, some synthetic base oil with additives can be also used in vacuum pumps after the pump manufacturer tests and proves the performance.

Now let’s learn how to select the proper oil to replace the spoiled one:

First of all, make sure the selected oil suits vacuum pump.
Check and confirm the kinematic viscosity of the oil.

(Kinematic viscosity is a measure of a fluid’s internal resistance to flow under gravitational forces. High viscosity offers better ultimate pressure and in the meantime, the high resistance may result in difficulties of pump start-up and operation at low temperature. On the contrary, low viscosity brings smooth pump operation at any time but cannot achieve ultimate pressure sometimes. Generally speaking, the viscosity for small pumps is low and that for big-sized pumps is high. )

Find genuine oil or equivalent type in the market.

It’s the best to get the genuine oil. However, it’s not always possible, or too expensive to have the genuine oil. In this case, you can source other brand oil with similar viscosity instead.

For example, the genuine vacuum oil of your vacuum pump is NEOVAC MR-100 (Moresco Japan) with viscosity grade of 46. You can buy Edwards Ultragrade 15 (viscosity of 38) or 17 (viscosity of 55) to replace it and vice versa.