Analysis of the causes of oil leakage in the gearbox
- The pressure difference between the inside and outside of the reducer: During the operation of the reducer, the friction and heating of the moving pair, as well as the influence of environmental temperature, cause the temperature of the reducer to increase. If there are no ventilation holes or the ventilation holes are blocked, the internal pressure gradually increases. The higher the internal temperature, the greater the pressure difference with the outside world. Under the pressure difference, lubricating oil leaks out from the gap.
- Unreasonable structural design of the gearbox
1) The inspection hole cover plate is too thin, and it is easy to deform after tightening the bolts, causing uneven joint surfaces and oil leakage from the contact gap;
2) During the manufacturing process of the gearbox, if the casting is not annealed or aged, and internal stress is not eliminated, deformation will inevitably occur, resulting in gaps and leakage;
3) There is no oil return groove on the box, and lubricating oil accumulates in the shaft seal, end cover, joint surface, etc. Under the pressure difference, it leaks out from the gap;
4) The design of the shaft seal structure is unreasonable. Early reducers mostly used oil groove and felt ring-type shaft seal structures, which caused deformation of the felt during assembly and sealed the gaps on the joint surface. If the contact between the journal and the seal is not very ideal, due to the poor compensation performance of the felt, the seal will fail in a short period of time. Although there are oil return holes in the oil ditch, they are easily blocked and the oil return effect is difficult to exert. - Excessive fuel consumption
During the operation of the gearbox, the oil pool is stirred violently, and the lubricating oil splashes everywhere inside the machine. If the amount of oil added is too much, a large amount of lubricating oil will accumulate in the shaft seal, joint surface, etc., leading to leakage. - Improper maintenance process
- During equipment maintenance, oil leakage can also occur due to incomplete removal of dirt on the joint surface, improper selection of sealant, reverse installation of sealing components, and untimely replacement of sealing components.
Countermeasures for Treating Oil Leakage in Gear Units - Improving the breathable cap and inspection hole cover plate: One of the main reasons for oil leakage is that the internal pressure of the gearbox is greater than the external atmospheric pressure. If we try to balance the internal and external pressure, oil leakage can be prevented. Although reducers all have breathable caps, the breathable holes are too small, which can easily be blocked by coal powder and oil stains. Moreover, every time you refuel, you need to open the inspection hole cover plate. Opening it once increases the possibility of oil leakage, causing leaks to occur in areas that were originally not leaking. To this end, an oil cup-type breathable cap was made, and the original thin inspection hole cover plate was changed to a thickness of 6 mm. The oil cup-type breathable cap was welded onto the cover plate, with a diameter of 6 mm for easy ventilation and pressure equalization. When refueling, oil was added from the oil cup without opening the inspection hole cover plate, reducing the chance of oil leakage.
- Smooth flow. To prevent the excess lubricating oil thrown on the bearing by the gear from accumulating at the shaft seal, it is necessary to allow the excess lubricating oil to flow back to the oil pool in a certain direction, that is, to achieve a smooth flow. The specific method is to create a return oil groove tilted inward in the center of the lower pad of the bearing seat, and also create a gap at the straight end of the end cover, which is facing the return oil groove. This way, excess lubricating oil flows back to the oil pool through the gap and returns oil groove.
- Improving the shaft seal structure
Reasons and treatment methods for gearbox oil leakage
1) Improvement of the shaft seal of the gearbox with a half-shaft output shaft: Most equipment such as belt conveyors, screw unloaders, and impeller coal feeders have a half-shaft output shaft, making the modification more convenient. Disassemble the gearbox, remove the coupling, take out the gearbox shaft seal end cover, machine the groove on the outer side of the original end cover according to the matching skeleton oil seal size, and install the skeleton oil seal, with the side with the spring facing inward. When reinstalling, 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 on the outer side of the end cover. Once the oil seal fails, the damaged oil seal can be removed and the spare oil seal can be pushed into the end cover, thereby saving the time-consuming and laborious processes of disassembling the reducer and coupling.
2) Improvement of the shaft seal of the gearbox with a full shaft output shaft: The output shaft of the gearbox with a full shaft transmission has no coupling. If the transformation is carried out according to the 2.3.1 plan, the workload is too large and unrealistic. In order to reduce workload and simplify installation procedures, a detachable end cover was designed, and an attempt was made to open the oil seal. The outer side of the detachable end cover is machined into a groove. When installing the oil seal, the spring is first taken out, and the oil seal is sawn off into an open shape. The oil seal is then placed on the shaft from the opening, and the opening is docked with adhesive, facing upwards. Then, the spring is installed and the end cover is pushed in. - Using new sealing materials. For leakage at the static sealing point of the gearbox, new polymer repair materials can be used to stick and block. If there is oil leakage at the static sealing point during the operation of the reducer, surface engineering technology’s oil emergency repair agent, adhesive polymer 25551 and 90T composite repair material, can be used to block the oil leakage, thus achieving the goal of eliminating the oil leakage.
- Carefully implement the maintenance process. When repairing the gearbox, it is necessary to carefully follow the process regulations. The oil seal should not be installed upside down, the lip should not be damaged, the outer edge should not be deformed, the spring should not fall off, the joint surface should be cleaned, the sealant should be evenly applied, and the amount of oil added should not exceed the scale of the oil scale.
- Wiping. After treatment, the static sealing point of the gearbox can generally achieve no leakage or leakage. However, due to aging, poor quality, improper assembly, and high surface roughness of the shaft, individual dynamic sealing points still have small leaks. Due to the poor working environment, coal dust adheres to the shaft, making it appear oily. Therefore, it is necessary to wipe the oil stains on the shaft after the equipment stops running.
Of course, choosing a good gearbox is also very important if you don’t want the gearbox to leak oil, and the MKD gearbox is a good choice. Contact us now.
