The performance of lubricating oil in the rail train transmission system is directly related to the stable operation of the train and the equipment life. However, the performance of lubricants is not static. As the main environmental factors affecting the aging of lubricating oil, the high humidity and contaminated particles are particularly significant in the complex and changeable climate conditions. This paper will discuss the action mechanism and coping strategies of these environmental factors on lubricating oil from the perspective of temperature difference between north and south and humidity difference between east and west in China.
Environmental challenges to lubricants in China
North-south temperature difference and lubricating oil viscosity change
China has a large geographical span, from tropical Hainan to Mohe in the cold zone, the temperature difference is significant. In winter, the northern region is often as low as-30 C, while the southern region can be maintained above 10 C. This temperature difference puts forward very high requirements on the viscosity temperature performance of lubricating oil. In low temperature environment, the viscosity of lubricating oil increases and the mobility becomes, which may lead to poor lubrication of gearbox and bearing, while in high temperature environment, the viscosity of lubricating oil decreases, and the bearing capacity decreases, which is easy to form boundary lubrication and even dry friction.
East and west humidity difference and lubricating oil emulsification
The humidity in eastern coastal areas is high, especially in summer, and the relative humidity of air can exceed 90%. The western inland area is known for its dry weather and frequent dust weather. Humid air is easy to introduce moisture, through the sealing system into the gearbox or the bearing, causing the emulsification of lubricating oil phenomenon. Emulsion will destroy the integrity of the lubricating oil film, resulting in decreased lubrication performance, and even accelerate the pitting and peeling of the gear surface.
The threat of contaminating particles
In the western sandstorm, dust particles in the air may enter the gear box or bearing through a breathing valve or sealing device. The contaminated particles act as abrasives in the lubrication system to accelerate the wear of gear and bearing surfaces, while accelerating the oxidation and aging of lubricating oil. These particles may also block the filter, further deteriorate the operation of the lubrication system.
Mechanism of action of high humidity and contaminated particles on lubricating oil

1. Chemical changes caused by water content
The infiltration of water not only leads to the emulsification of lubricants, but also triggers chemical reactions that accelerate oxidation. In the environment of high humidity, the antioxidants in the lubricating oil will be rapidly consumed quickly, resulting in the acid value of the oil and further corrosion of the metal surface.
2. Mechanical damage of particle pollution
Particle contamination creates small pitting losses in the gear boxes and bearings, which develop into cracks over time to shorten the service life of the equipment. In addition, these particles will also accelerate the aging reaction of the lubricating oil, so that the lubrication cycle is greatly shortened.
Coping strategy: optimize the seal design and lubricating oil management
Improvement in the seal design
To reduce the effects of high humidity and particle contamination, the sealing design of the gearbox and bearings can be optimized:
Enhance the waterproof performance of the sealing ring using high quality material sealing ring, and design a multi-channel sealing structure to effectively prevent moisture infiltration.
Filter moisture and particles in the air improved breathing valve design, equipped with hygroscopic materials and particle filtration device to prevent dust and water vapor entry.
Lubricating oil type selection and management
According to the climate conditions, lubricating oil with low viscosity and excellent viscosity temperature can be selected.
Regular detection and replacement of lubricating oil using oil analysis technology, such as particle counting, acid value determination and moisture content analysis, monitor the aging degree of lubricating oil, timely replacement.
Antioxidant and anti-emulsifier should add special additives according to the operating condition of the equipment to delay the aging process of lubricating oil.
High humidity and pollution particles are the two major environmental factors of lubricating oil aging, especially in diverse countries like China, the impact is particularly significant. By improving the seal design, optimizing lubricating oil selection and strengthening oil management, these challenges can be effectively addressed to ensure the smooth operation of EMU trains in a variety of environmental conditions.