Views:13 Author:Site Editor Publish Time: 2019-04-12 Origin:Site
Due to the special structure of the Caterpillar excavator and the diversity of the site conditions, the slewing bearing of the Caterpillar excavator is prone to failures caused by oil leakage, such as the slewing bearing, the rotating ring gear or the slewing motor. Therefore, the leakage should be prevented and treated in time. This article will introduce some of the repair methods that have been summarized in practice.
1. Structure and lubrication principle of slewing bearings
In fact, the grease lubrication of the rotary part of the excavator is divided into two chambers: the lubrication chamber of the rotary bearing and the lubrication chamber of the rotary ring gear.
Lubrication of the slewing bearing is accomplished by filling the grease fitting on the outer ring of the slewing bearing with grease, which is accomplished by pre-added grease. The slewing bearing has two rubber strips inside and outside (or upper and lower) as the oil seal, and the outer oil seal is fixed on 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 (moving plate) of the bearing to prevent grease from rotating the ring gear from entering the bearing. The rotary ring gear and the slewing bearing use the same brand of grease. See Figure 1 for the structure, the cross-sectional structure of the oil seal is shown in Figure 2, the rotary oil seal is gradually thicker and thicker, and finally a sharp angle is formed. Only the elastic part of the rubber itself is pressed against the end face of the slewing bearing by the deformation of the rubber. Sealing effect (Figure 2 shows the shape before the sealing strip is deformed). This kind of sealing has a slight effect on preventing grease leakage, but the pressure is not high. Once the internal pressure is increased due to excessive oiling or working temperature rise, the grease will still leak through the oil seal. Under normal circumstances, the amount of leakage is related to various factors such as the amount of filling, the working speed and working frequency of the rotating part, and the temperature of the field. Therefore, there is ambiguity that is defined for normal and abnormal leakage.
2. Slewing bearing leakage inspection method
Usually, it is normal to have a small amount of oil leakage in the outer oil seal under working conditions. The so-called normal, refers to the rotation axis
The amount of grease leaking from the outer seal is approximately equal to the amount of grease added to the slewing bearing. However, when there is a large amount of abnormality in grease leakage on the excavator, it is necessary to check. Due to the particularity of the lubrication structure of the rotary part, it is necessary to analyze whether there is a leak and determine the problem, in order to finally solve the problem. The specific inspection steps and methods are as follows:
(1) Is the maintenance correct?
The grease filling cycle of the slewing bearing cavity should be between 150~250h (the manufacturer’s recommended maintenance cycle is 250h, but the actual
The work can be shortened according to the working intensity and frequency of the rotating part). If the filling is too frequent, it will cause a large amount of grease to leak out.
(2) Whether the hydraulic oil or gear oil of the swing motor is caught in the cavity of the rotating ring gear
If there is a leak in this case, after opening the inspection cover of the rotating ring grease, you will find that the grease has been
Thinning. This thinning is a feature of mixing hydraulic oil or gear oil.
(3) Is the grease originally added to the equipment selected correctly?
Since the grease added to the original equipment may be incorrect, there may be cases where the temperature of the slewing bearing or the rotating ring gear is slightly increased and the grease becomes thin. If the thinned grease is pushed by the driving gear of the swing motor to the upper end surface of the ring gear 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?
Carefully check along the rotary oil seal to determine whether it is a partial, segmental leak or a uniform peripheral leak. Check the entire rotary oil seal for missing.
(5) Is the outer oil seal fixed?
The outer oil seal should be relatively fixed to the seal groove of the lower frame. The key to the inspection is that it must be observed while the excavator is performing a rotary motion. If the oil seal is also rotating at the same time when the device is rotated, the existing oil seal has been loosened in the seal groove and the outer oil seal must be replaced. There is a certain risk in adopting this method, so it is necessary to pay attention to safety, but this is one of the important methods to check whether the rotary oil seal does seal.
(6) Is there any obvious damage to the inner oil seal?
Open the rotary ring gear grease inspection cover and check whether there is a large amount of grease in the ring gear oil chamber and whether there is any broken piece of oil seal. If the grease is greatly reduced, it means that the grease has been leaked.
(7) Determine whether the oil leaking from the bearing chamber or the grease in the rotating ring gear chamber
Adding 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, it is determined according to the color of the leaking grease. The grease in the ring is also the grease in the bearing cavity. This is one of the methods to initially judge whether the inner seal is invalid or not.
(8) Observe whether the equipment is rotating abnormally
If the equipment has abnormal noise or unevenness during the rotary motion, the bearing clearance may be too large and uneven, causing the bearing to squeeze oil from the outer oil seal during the rotation.
(9) Check the inner oil seal
After the above checks have been completed and the problem has been eliminated, the problem can be concentrated on the oil seal inside the bearing. Take out the peripheral bolts of the swivel part, and remove the oil pipe of 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 above steps have been completed and other possibilities are excluded.