Discussion on the application of heavy duty open gear lubrication

Heavy-duty open gears are key mechanical components for many companies, and their reliability and maintenance economy are of great concern. Although the application is extremely extensive, the importance of open gear lubricants is well known, but a practical and comprehensive article is rare. The article is aimed at the lubrication maintenance and failure analysis of heavy-duty open gears that are of concern to enterprise users. Based on the experience of the author over the years, combined with many practical application cases from the mining, cement and power industries, reference is made to some equipment manufacturers and equipment users. And the technical exchange experience between peers, rich in information for everyone to discuss.
1. Introduction of open gears Heavy-duty open gears are common transmission methods in the raw material processing industry. They are widely used in large-scale equipment such as electric power, mining, cement, steel, chemical, paper and other industries, such as: ball mills, tube mills, rod mills. Machine, rotary kiln, dryer, granulator, drum pulper, etc. The main features of open gear transmission are: heavy load, low speed, large structural size and high tooth surface roughness, and harsh working conditions (such as dust, high temperature, impact load, etc.). It can transmit very high forces and moments (some double-tooth drive units can reach >2×5000KWh@drive power), so the tooth surface is subjected to extremely high stress; the open gear is usually in mixed friction state (starting and stopping) , excessive shear force, impact load, etc.), in addition to the rolling friction at the pitch circle position, there is a large amount of sliding friction during the meshing process. Therefore, in order to effectively protect the lubrication, extend the service life of the gears, reduce the loss of spare parts, stop the loss, and improve the operational stability of the equipment, the open gear must use the appropriate open gear lubricant and reasonable lubrication method. If the open gear fails to select the appropriate open gear lubricant in the initial stage, the result is that the oil consumption is huge, and the gear will still have excessive wear, plastic deformation, pitting, peeling, more serious chipping, etc. problem. It takes a lot of manpower and material resources, but it still does not reach the ideal lubrication state of open gear lubricants. For open-type gears, the most prone problems are scratches, plastic deformation, pitting, spalling, and abrasive wear. The reason for this type of problem is not only related to the material, design, processing, installation and other factors of the gear itself, but also an important factor is the performance of the open gear lubricant.
2. The working condition characteristics of the open gear lubricating oil open gear determine that the open gear lubricating oil used must have the following properties: a, strong adhesion (good adhesion, not easy to fall and loss) b, High anti-wear and extreme pressure resistance (FZG test level ≥ 12, four-ball welding load > 650KG) c, with a certain oil film strength (can reduce the impact of impact load on the tooth surface) d, contains a certain proportion of solid additives and EP (Extreme pressure) additive (for boundary lubrication and emergency lubrication) e, good spraying (spraying system) or flow performance (oil pool lubrication) f, wide operating temperature range (for winter and summer) q, open gear lubricant Good physical and chemical stability (long life, low loss, not easy to deteriorate, anti-heat oxidation stability is especially important for rotary kiln open gear) h, a certain degree of resistance to external environment (such as dust, water, etc.) Capability i, easy to use and maintain j, no harm to the environment and operators. The earliest open gear lubricants are asphalt. Asphalt products are extracted from petroleum refining residue, usually with extreme pressure additives and solvents, and have a high viscosity. The oil film formed is relatively thick and can withstand high temperatures. However, because of environmental protection and leakage, it is gradually replaced by new open gear lubricants. Subsequent development of pure oil. Pure oil products, whether mineral or synthetic, are usually filled with extreme pressure additives and the base oil is highly viscous. Because the transparency is easy to observe the tooth surface, the sealing requirements are high and the leakage is not easy to handle. The compound oil is based on pure oil, with the addition of a solid lubricant to improve the impact load resistance and increase the emergency lubrication function. Adhesive lipids are thickened high viscosity base oils thickened with a thickening additive and a solid lubricant. Due to its high bearing capacity, oil film thickness, high temperature resistance and water resistance, excellent anti-wear performance, good self-sealing property, easy leakage, easy to dynamically observe the distribution of tooth surface load and many other advantages, it has a dominant position in the market.