Grease will separate out oil during storage and use, a small amount of oil separation is normal, and excessive oil separation will directly lead to the destruction of the grease structure or even loss of use value. Proper storage and use techniques can effectively control oil separation.

1. The composition of lubricating grease

  Grease is composed of base oil + thickener + additives. The main component is base oil (mineral oil or synthetic oil). The thickener acts like a sponge and is composed of a fibrous structure. The base oil and additives are stored in it. Just as the sponge will flow out of water when squeezed, the "sponge" of the grease will also be squeezed out of the base oil, and the grease is "squeezed" in two main ways: mechanical extrusion and high temperature.

Why does grease separate into oil?

  From the above we can see that it is normal for grease to separate oil. If the grease does not have the ability to release the oil, then there is no way to lubricate, because the lubrication depends on the base oil, and the thickener has almost no lubricating effect.

The amount of oil in the grease is related to the content of the thickener. From the composition of the grease, we can see that the content of the thickener in the grease is different. Think of a sponge. It is not difficult to understand that the content of the thickener The higher the value, the less likely the base oil is to separate out and the less oil is separated.

  So is the more thickening agent contained in the grease, the better? Of course not, obviously with too much thickener the base oil gets sucked in tightly. Grease that cannot release base oil, how to lubricate? Therefore, the thickening process of grease needs to find this compromise point.

2. The way of grease separation

  Similarly, there are two ways to separate grease oil, static oil separation and dynamic oil separation. In addition to the quality factors of the grease itself, these two factors can also cause oil separation.

  (1) Static oil separation: Affected by storage conditions, including: storage temperature, storage time, vibration of the container during storage and transportation, whether the surface of the grease is smoothed, and any of the following conditions, the oil separation will be relatively obvious:

    ①、Low grease consistency (NLGI00, NLGI0, NLGI1)

    ②、Lower viscosity of base oil (ISO68 and below)

Under normal shelf life and storage conditions, the oil separation caused by these conditions will not affect the performance of the grease.

(二）Dynamic oil separation: Dynamic oil separation is mainly due to the oil separation caused by the mechanical extrusion or high temperature of the grease during use. Dynamic oil separation has a great influence on the use of grease and should be controlled.

Exacerbating dynamic oil separation

  1、Excessive grease addition: High temperatures can result, resulting in increased grease oxidation and rapid separation of base oil and thickener.

  2、Mechanical reasons: improper installation of equipment, high load, poor lubrication such as improper selection of clearance, and high temperature in bearing operation.

  3、Dry grease: The dry grease adheres to the equipment and causes blockage, the base oil flows away from both sides, and the thickener accumulates on the blockage. Due to poor local lubrication, this situation will cause the temperature to rise, and the high temperature Exacerbated base oil and thickener separation. Therefore, the old grease that adheres to the oil should be removed when the oil is changed.

  4、The grease is contaminated: dust and dirt fall into the grease, so attention should be paid to sealing during storage.

  5、Mixing of different greases: The colloidal structure of the thickener is destroyed, causing oil separation.

  6、The oil separation performance of lubricating grease is not only affected by composition and production process, but also affected by storage and use conditions. Therefore, correct storage, transportation and use methods should be used to prevent the loss of oil in grease.