Generally, it is normal for a small amount of oil leakage to occur in the outer oil seal under working conditions. The so-called normal means that the amount of grease leaking through the outer seal of the slewing bearing is approximately equal to the amount of grease added to the slewing bearing. However, when there is a large amount of grease leakage on the excavator, it must be checked. Due to the particularity of the lubricating structure of the rotary part, it is necessary to analyze whether there is indeed a leak and determine the location of the problem before the problem can be finally solved. The specific inspection steps and methods are as follows:
(1) Whether the maintenance is correct
The refueling cycle of the rotary bearing cavity should be between 150 ~ 250h (the maintenance cycle recommended by the manufacturer is 250h, but in actual work, it can be shortened according to the working intensity and frequency of the rotary part) If the filling is too frequent, a large amount of grease will leak out.
(2) Whether the hydraulic oil or gear oil of the rotary motor has entered the cavity of the rotary ring gear
If this kind of leakage occurs, after opening the inspection cover of the rotary ring gear grease, it will be found that the grease has become thinner. This thinning is characteristic of mixing hydraulic oil or gear oil.
（3） Whether the original grease filled in the equipment is selected correctly
Due to the fact that the original equipment filled with grease may be incorrect, there may be a situation where the grease becomes thinner as the temperature of the rotary bearing or the rotary ring gear rises slightly. If the thinned grease is pushed to the upper end surface of the inner ring gear by the driving gear of the rotary motor during the meshing process, it will flow into the bearing cavity through the inner oil seal, and finally the grease will drip out from the outer oil seal.
(4) Is the outer oil seal missing?
Check carefully along the rotary oil seal to determine whether it is local, section leakage or even peripheral leakage. Check whether the whole rotary oil seal is missing.
(5) Whether the outer oil seal is fixed
The outer oil seal should be relatively fixed with the sealing groove of the lower frame. The key to the inspection is to observe when the excavator is rotating. If the oil seal also rotates at the same time when the device rotates, it means that the existing oil seal has been loosened in the sealing groove, and the outer oil seal must be replaced. Taking this method has a certain degree of danger, so pay attention to safety, but this is one of the important methods to check whether the rotary oil seal does indeed play a sealing role.
(6) Is there any obvious damage to the inner oil seal
Open the rotary gear ring oil and grease inspection cover and check whether there is a large amount of grease reduction in the gear ring oil chamber and whether there are fragments of broken oil seals. If there is a large decrease in grease, it means that the grease has been leaked.
(7) It is determined that the grease leaked from the bearing cavity
Or the grease of the rotating ring gear cavity is filled with different colors of grease into the bearing cavity. After a period of use (such as about 150h), after the oil in the bearing cavity has been basically replaced with the filled grease, then leak according to the surrounding The grease color determines whether it is the grease of the rotating ring gear or the grease of the bearing cavity. This is one of the methods to determine whether the inner seal has failed from the outside.
(8) Observe whether there is any abnormality in the rotation of the equipment
If the equipment exhibits abnormal noise or unevenness during the slewing motion, the bearing gap may be too large and uneven, causing the bearing to squeeze oil from the outer oil seal during rotation.
(9) Check the inner oil seal
After the above inspections have been completed and the existence of the problem is eliminated, the problem can be concentrated on the oil seal in the bearing. Remove the bolts around the slewing part, remove the oil pipe from the walking part, and lift the upper frame part with a crane. Since this method requires the use of a crane and the workload of the entire process is relatively large, this is the last step to check and solve the problem. Therefore, it is recommended to use this method after all the previous steps have been completed and other possibilities are excluded.
