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Reasons for oil leakage in reducers: 1. Pressure difference between the inside and outside of the reducer: During operation, friction at the moving parts generates heat, and the ambient temperature also contributes to an increase in the reducer’s temperature. If there are no ventilation holes or these holes are blocked, the pressure inside the reducer gradually increases. The higher the internal temperature, the greater the pressure difference with the outside environment, and under this pressure difference, the lubricating oil leaks out through the gaps. 2. The structural design of the reducer is unreasonable. 1) The inspection hole cover is too thin; it tends to deform after the bolts are tightened, resulting in an uneven joint surface and oil leakage from the contact gaps. 2) During the manufacturing of the reducer, the castings were not subjected to annealing or aging treatments, so the internal stresses were not eliminated, which inevitably leads to deformation and the formation of gaps, causing leaks. 3) There are no oil return channels on the gearbox body, so lubricating oil accumulates at the shaft seals, end covers, joint surfaces, etc.; under the effect of pressure differences, this oil leaks out through the gaps. 4) The design of the shaft seal structure is unreasonable. Early reducers often used oil groove and felt ring types of shaft seal structures; during assembly, the felt was compressed and deformed to seal the gaps at the joint surfaces. If the journal does not make ideal contact with the seal, the seal fails within a short time due to the extremely poor compensating ability of the felt. Although there are oil return holes on the oil groove, they tend to clog easily, making it difficult for the oil to be returned. 3. Excessive oil quantity: During operation of the reducer, the oil reservoir is greatly agitated, causing the lubricating oil to splash around inside the machine. If too much oil is used, it will accumulate in areas such as shaft seals and joint surfaces, leading to leaks. 4. Improper maintenance procedures: During equipment maintenance, oil leakage can occur due to incomplete removal of dirt from the mating surfaces, improper selection of sealing materials, incorrect orientation of seals, or failure to replace seals in a timely manner. How to address oil leakage in reducers: 1. Improve the breather cap and inspection hole covers: One of the main reasons for oil leakage is when the pressure inside the reducer is higher than the external atmospheric pressure; by balancing the pressure inside and outside the machine, oil leakage can be prevented. Although reducers are all equipped with ventilation caps, the ventilation holes are too small and prone to getting clogged by coal dust and oil residues. Moreover, each time oil needs to be added, the cover of the inspection hole must be removed, and each such removal increases the risk of oil leakage, causing leaks even in areas that were previously leak-free. To this end, an oil cup-type vent cap was designed; the original thin cover for the inspection hole was replaced with one that is 6 mm thick. The oil cup-type vent cap was welded to this cover, and the diameter of the vent hole is 6 mm, which facilitates air circulation and helps achieve pressure equalization. Additionally, fuel can be added through the oil cup, eliminating the need to open the inspection hole cover and thus reducing the risk of oil leakage. 2. Unobstructed flow: To prevent the excess lubricating oil thrown onto the bearings by the gears from accumulating at the shaft seals, it is necessary to allow this excess oil to flow back to the oil sump in a specific direction, thus ensuring unobstructed flow. The specific method involves creating an oil return groove that slopes inward toward the inside of the machine at the center of the lower bearing shell, and also making a cut at the straight edge of the end cover, with this cut aligned with the oil return groove. In this way, excess lubricating oil flows back to the oil sump through the cut and the oil return groove. 3. Improvement of the shaft seal structure: 1) Improvement of the shaft seal for reducers whose output shaft is a half-shaft: The output shafts of reducers in most equipment such as belt conveyors, screw unloaders, and impeller coal feeders are half-shafts, making modifications relatively easy. Disassemble the reducer, remove the coupling, and take out the shaft seal end cover of the reducer. According to the dimensions of the accompanying skeleton oil seal, machine a groove on the outside of the original end cover, then install the skeleton oil seal with the spring-sided portion facing inward. During reinstallation, if the end cover is more than 35 mm away from the inner end face of the coupling, a spare oil seal can be installed on the shaft outside the end cover. In the event that the oil seal fails, the damaged one can be removed and the spare seal inserted into the end cover, thereby avoiding time-consuming and labor-intensive procedures such as disassembling the reducer or removing the coupling. 2) Improvement of the shaft seal for reducers with a solid output shaft: Reducers that use solid shaft transmission do not have couplings on their output shafts; if the modification is carried out according to scheme 2.3.1, the workload would be too large and it would not be practical. To reduce the workload and simplify the installation process, a split-type end cover was designed, and open-type oil seals were tried out. A machining groove is provided on the outside of the separable end cover. When installing the oil seal, first remove the spring, cut the oil seal to create an opening, slide the oil seal over the shaft through this opening, seal the opening together using adhesive with the opening facing upward, then reinstall the spring and push the end cover into place. 4. Use of new sealing materials: For leaks at static seal points of reducers, new polymer repair materials can be used for bonding and plugging. If oil leaks from the static sealing points while the reducer is in operation, it can be sealed using the oil-level emergency repair agent based on surface engineering technology, as well as the composite repair materials Vinyl-Polymer 25551 and 90T, thereby eliminating the oil leakage. 5. Strictly follow the maintenance procedures: When maintaining the reducer, it is necessary to adhere strictly to the established procedures. The oil seal must not be installed in the wrong direction; its lip must not be damaged, and its outer edge must not be deformed. The spring must not fall off, the mating surfaces must be cleaned thoroughly, the sealing compound must be applied evenly, and the amount of oil added must not exceed the mark indicated on the oil gauge. 6. Wiping: The static sealing points of the reducer can generally be made leak-free through proper maintenance. However, due to factors such as aging of seals, poor quality of seals, improper installation, and high surface roughness of the shafts, some of the dynamic sealing points still experience minor leaks. Moreover, because of the harsh working environment, coal dust sticks to the shafts, causing them to appear oily; therefore, it is necessary to wipe away the oil from the shafts after the equipment has stopped operating. Other common faults include: 1) Wear of the bearing housings in the reducer, which encompasses wear of the housing’s bearing box, the bearing housings inside the box, and the gearbox’s bearing housings; 2) Wear of the shaft diameter of the reducer gears, with the most significant wear occurring at the shaft ends and keyways; 3) Wear of the bearings on the reducer’s drive shafts.