(1) If it is determined that the problem is caused by the seal, you need to remove the old seal, clean the seal groove with diesel or gasoline, and completely insert the new seal into the seal groove. It should be noted that there is a joint after the sealing strip is formed into a ring, and the two sides of the joint need to be glued together with double-tube universal glue (such as acrylic glue).
(2) If the lubricating grease is deteriorated due to the leakage of the rotary motor, the rotary motor must be repaired to solve the problem fundamentally, and then the grease of the entire rotary ring gear should be replaced.
(3) If the leakage is caused by improper selection of grease, the grease of the rotating ring gear should be replaced completely. At the same time, it should be noted that the same brand of grease should also be used in the bearing cavity. Lithium molybdenum-based grease should be used, and the viscosity of this grease will not be reduced at high temperature.
(4) Correctly control the maintenance cycle of the slewing bearing, that is, lubricating grease must be added every 150 to 250 hours of work. The oil injection can be completed several times, that is, the excavator refills every 90 ° of rotation. The filling volume is limited to the overflow of grease from the outer oil seal.
(5) If the slewing bearing is damaged, the entire slewing bearing must be replaced. Due to the particularity of the structure of the Caterpillar excavator and the diversity of the scene, it is prone to damage due to oil leakage and damage to the slewing bearing, slewing ring gear or slewing motor. Therefore, leakage should be prevented and dealt with in a timely manner. This article will introduce some maintenance methods summarized from practice.
1. Structure and lubrication principle of slewing bearing
In fact, the grease lubrication of the rotary part of the Carter excavator is divided into two chambers: the rotary bearing lubrication chamber and the rotary ring gear lubrication chamber.
Slewing bearing lubrication is accomplished through the lubrication nozzle located on the outer ring of the slewing bearing. Lubricating grease is added to the slewing bearing. The slewing ring gear is lubricated by the pre-added grease. The slewing bearing has two inner and outer (or up and down) rubber strips as oil seals. The outer oil seal is fixed to the inner ring (fixing plate) of the slewing bearing of the lower frame to prevent dust and debris from entering the slewing bearing. The inner oil seal is located on the outer ring (movable plate) of the bearing to prevent the grease in the rotating ring gear from entering the bearing. The same brand of grease is used for the slewing ring gear and the slewing bearing. Refer to Figure 1 for its structure and Figure 2 for the cross-section structure of the oil seal. The rotary oil seal gradually becomes thinner and finally forms a sharp corner. Only the elasticity of the rubber itself is reached by the protruding sharp corner portion pressing the end face of the rotary bearing by the deformation of the rubber. Sealing effect (Figure 2 shows the shape of the sealing strip before deformation). This kind of seal has a slight effect on preventing grease leakage, but the pressure bearing is not high. Once the pressure is increased due to too much oil or the working temperature increases, the grease will still leak through the oil seal. Under normal circumstances, the amount of leakage is related to many factors such as the amount of filling, the working speed and frequency of the rotating part, and the on-site temperature. Therefore, there is ambiguity between normal and abnormal leakage.
2. Inspection method for leakage of rotary bearing
Normally, 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 grease filling cycle of the rotary bearing cavity should be between 150 ~ 250h (the maintenance cycle recommended by the manufacturer is 250h, but the actual work 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 penetrated into the cavity of the rotary ring gear. If such a 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 Because the grease filled in the original equipment may be incorrect, the grease may become thinner as the temperature of the rotary bearing or the 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) Check whether the outer oil seal is missing carefully along the rotary oil seal to determine whether it is a local, section leak or a uniform peripheral leak. 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) Whether there is any obvious damage to the inner oil seal. Open the rotary gear ring grease inspection cover and check whether the gear ring oil chamber has a large amount of grease reduction 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) Determine whether the leakage is the grease in the bearing cavity or the rotary ring gear cavity. Add different colors of grease into the bearing cavity. After a period of use (such as about 150h), the oil in the bearing cavity has been basically replaced. After filling the grease, determine whether it is the grease of the rotating ring gear or the grease of the bearing cavity according to the color of the grease leaking around. 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 is not stable during the rotation movement, it may be that the bearing gap is too large and uneven, causing the bearing to remove oil from the outside Extruded from the oil seal.
(9) Checking the inner oil seal After the above inspections have been completed and the problems are eliminated, the problem can be concentrated on the inner oil seal of 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.
