Formation and prevention of lubricating oil paint film problems

December 30, 2023

Formation and prevention of lubricating oil paint film problems

First, what is paint film

In recent years, in the management of lubricating oil, paint film has attracted more and more attention, because it will cause some harm to the safety of equipment operation.

The so-called paint film is actually a polymer hydrocarbon polymer, the color is basically brown, from light brown to dark brown, brown have. In the use of a period of time after the mechanical equipment oil, there will be a common phenomenon of paint film.

Paint film is most commonly found in the oil of steam turbines and in the oil of hydraulic systems with relatively high pressure (such as injection molding machines, printing equipment, etc.).

Second, the characteristics of the paint film

First, the overall size is particularly small, basically in 1μm or even smaller.

Second, it has polarity and is easy to adsorb on the surface of the metal. This is more likely to cause damage to the friction surface.

Third, the harm to the equipment

① The gap between the friction surfaces is reduced, the friction is increased, and the valve core will be glued together in serious cases, resulting in poor operation.

② Blocking filtration resulting in poor lubrication of equipment;

③ The paint film deposited on the cooler causes poor heat dissipation, oil temperature rise, and oil oxidation acceleration;

④ The paint film will adhere to solid particles, causing equipment wear.

Therefore, we must eliminate and prevent the production of paint film in the operation of the equipment.

Four, how is the paint film formed

Paint film is the product of oil deterioration, the formation mechanism is as follows:

(1) Oil oxide. The oxidation of hydrocarbon oil follows the mechanism of free radical chain reaction and produces peroxides such as antelope acid, vinegar and alcohol after oxidation. These peroxides further polycondensation reactions produce high molecular weight polymers such as paint film and sludge. The difference between paint film and mud, in comparison, the paint film generation temperature is higher, and the low temperature is more conducive to the generation of mud, and the mud contains a certain amount of water.

(2) The oil "micro-combustion" causes the formation of paint film. In general, the hydraulic oil will dissolve a certain amount of air (<8%), when the dissolution limit is exceeded, the air entering the oil exists in the form of suspension in the oil. Once the hydraulic oil is pumped from the low pressure zone into the high pressure zone, these small bubbles suspended in the oil are compressed rapidly, resulting in a rapid increase in the temperature of the oil microzone, sometimes even causing the oil microzone up to 1100°C, resulting in the oil microzone adiabatic "micro-combustion, the formation of extremely small size of the insoluble matter.

(3) Spark discharge is also one of the reasons for the formation of paint film. If the oil passes through a small gap such as the valve core and the precision filter element, the internal friction between molecules generates static electricity, which is suddenly discharged after accumulation, resulting in micro-high temperature above 10000℃, resulting in oil oxidation. Therefore, high temperature is the main reason for the formation of paint film.

5. Detection of paint film

Paint film Tendency Index (VPR). The VPR method developed by US analysts laboratory is as follows:

A 1.2μm filter membrane filters a certain amount of oil, and then the colorimetry of the filter membrane deposits is evaluated to calculate VPR. VPR ranges from 0 to 100. If VPR is less than 40, the paint film tends to be normal. If VPR is greater than 40 and less than 80, it should be noted that if VPR is greater than 80, the paint film tendency is severe.

Six, removal of paint film

The "soft particles" that are easy to generate paint film and sludge in the oil account for more than 80% of the total particles in the oil, because of the small size of such "soft particles" (about 1μm). If the ultrafine mechanical filtration method is used, it is easy to cause the blockage of the filter element and the filtration effect is poor, while the electrostatic oil cleaning device uses the electrostatic field force to adsorb the particle pollutants in the oil on the dust collection body of the electrostatic field, so as to achieve the purpose of oil purification, so it can effectively remove the small particle pollutants in the oil, and the scale capacity is large. Therefore, it is widely used in foreign countries to remove paint film and sludge in oil.

Vii. Conclusion

① The paint film is very harmful, must be highly concerned;

② Prevention: reduce the possibility of oil oxidation, eliminate high temperature, it is recommended to configure online monitoring automatic purification device; Tank negative pressure operation; Ensure oil pressure, flow and oil cooler work normally

The electrostatic purification device can not only effectively remove the paint film insoluble matter in the oil, but also wash the paint film that has been deposited on the metal surface, ensure the safe operation of the equipment and extend the service life of the oil.

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