In mechanical equipment, (reducers) play a crucial role, and choosing the appropriate lubricating oil is crucial for the normal operation and long-term use of reducers.
I. The lubricating effect of gear oil for reducers
According to statistics, approximately 80% of component damage is caused by friction and wear. To a certain extent, wear can be reduced by reasonably selecting materials, and adopting a reasonable lubrication method is an effective way to reduce friction. Lubricating oil has many functions, such as cooling, flushing, protection, sealing, rust prevention, load relief, shock absorption, and it can also serve as a carrier of additives and constitute structural materials.
In gear transmission, the main role of lubricating oil is to reduce frictional resistance and wear, thereby maximizing the service life of mechanical components.
II. Precautions in the lubrication management and use of gear oil
1. Reducer systems with centralized thin oil lubrication: Such systems have strict requirements for the temperature of the lubricating oil or oil tank, and often use coolers (steam cooling) or cooling coils (water cooling) for temperature reduction. Although gear oil is required to have good anti-emulsification performance, once a large amount of water penetrates into the oil, it is very easy to emulsify. After the gear oil with extreme pressure anti-wear agents emulsifies, the additives will hydrolyze or precipitate and separate, not only losing the original performance but also generating harmful substances, causing the gear oil to deteriorate rapidly and become unusable. Therefore, emulsified oil must not be used anymore. For lubrication systems cooled by water (or steam), it is necessary to strictly prevent water (or steam) leakage to avoid damage to the reducer.
2. Reducer systems with pump circulation lubrication: Pay attention to the pressure difference of the pump and clean the filter screen in time. If the pressure difference of the pump increases significantly in a short period, or the frequency of cleaning the filter screen increases significantly, and the amount of oil sludge and metal abrasive debris on the filter screen increases significantly, to a certain extent, it indicates that the use state of the lubricating oil is not good. This may not only be a problem of materials and design, but also an improper selection of lubricating oil, such as inappropriate viscosity, or heavy-duty oil should be used instead of medium-duty oil, that is, a higher-grade gear oil should be selected, and usually, the effect will be significantly improved.
3. Do not mix new oil with old oil (rather than topping up as prescribed), and do not add high-viscosity oil just because the viscosity drops. Doing so may have an effect in the short term, but the performance of the oil will drop significantly, and at the same time, the lubrication conditions of the equipment will deteriorate, resulting in increased wear and shortening the service life of the equipment to a certain extent. In addition, due to different main agents, when mixed, the additives may interact and fail, bringing serious consequences to the equipment.
4. Regarding the oil change period: Theoretically, a short oil change period can better reduce the wear of the friction pair, extend the service life of the equipment, and provide a guarantee for its normal operation. However, considering economic benefits, the oil should be used more accurately and effectively. To determine whether to change the oil and when to change the oil, in addition to following the prescribed oil change period, factors such as the start-up time and operation rate of the equipment should also be considered comprehensively to maximize the role of the oil.
5. Regular monitoring: Regularly monitor the oil temperature, vibration, and noise of the oil-using equipment. When the lubrication conditions deteriorate and cause tooth surface damage, it usually directly causes a significant increase in vibration and noise.
III. Selection of viscosity
Viscosity is an important physical and chemical indicator of gear oil, and the meshing speed of gears is the main basis for selecting viscosity. The appropriate viscosity of reducer gear oil should be able to reduce the internal friction of the lubricating oil, thereby significantly reducing the wear on the gear surface and the noise and vibration during transmission.
The viscosity of reducer lubricating oil is mainly achieved through base oil and viscosity index improvers. The viscosity of the base oil of lubricating oil is related to the molecular structure and molecular weight. The larger the average molecular weight, the greater the viscosity of the oil product. In terms of base oil, mineral oil-based lubricating oils are divided into three types: lubricating oils refined from paraffin-based crude oil, lubricating oils refined from naphthenic-based crude oil, and lubricating oils refined from intermediate-based crude oil. Among them, the viscosity-temperature performance of lubricating oils refined from paraffin-based crude oil is better than the other two. High-quality viscosity index improvers not only require strong thickening ability and good shear stability, but also need to have good low-temperature performance and thermal oxidation stability. Viscosity index improvers with poor shear stability have their main chains broken under the action of shear stress, reducing the molecular weight and thinning the oil product, thereby having a series of adverse effects on wear and fuel consumption. For lubricating oils of the same viscosity grade, if non-refined base oil and poor-quality viscosity index improvers are used, although a certain viscosity standard can be achieved through blending, the viscosity-temperature performance, shear stability and other properties are not good, and the expected service life cannot be achieved either. Therefore, for low-speed and heavy-load cement reducers, such lubricating oils should be avoided as much as possible, and high-quality advanced lubricating oils should be selected because both the base oil and the viscosity index improver are of higher quality.
The greater the viscosity of gear oil, the stronger the ability to protect the tooth surface from various damages, and the less the wear of the reducer. However, when the viscosity is too high, abrasive particles are not easy to precipitate, reducing the flushing effect and heat absorption and cooling effect of the lubricating oil on the tooth surface, resulting in poor lubrication. At the same time, abrasive particles suspended in the oil enter the meshing area, easily causing abrasive wear. In addition, excessive viscosity will also increase the transmission resistance, increase the tooth surface temperature, and increase power consumption. Generally speaking, when the viscosity increases by one grade, the energy consumption increases by approximately 1% to 5%, and the stability and anti-emulsification performance of the oil will also decline. However, high viscosity has obvious benefits in reducing noise and preventing oil leakage. In addition, for equipment with uneven loads, frequent startups, and working in high-temperature environments, the viscosity should be appropriately higher.
To sum up, reducers should use high-grade lubricating oils with appropriate viscosities. For large reducers with low speed and heavy load, extreme pressure and heavy-duty gear oils with high viscosity should be selected as much as possible, because they have better extreme pressure anti-wear, thermal oxidation stability, anti-corrosion and rust prevention, and excellent anti-emulsification performance. It is easy to form a chemical film on the gear meshing surface, thereby protecting the gear tooth surface and minimizing the wear of the reducer.