1 fault phenomenon and analysis
A Zuyou S2800FJ hydraulic excavator has worked for 8664h. In a construction site, the dump truck hits the weight of the excavator. Later, it was found that a lot of butter was thrown from the sealing device of the slewing bearing, and at the same time there was abnormal noise inside the slewing bearing. When it turned, every time it turned to the front and left of the machine, the slewing ring squeaked. Keep the track on the ground and then lower it with a shovel, and find that the backlash of the support shaft is large. Then, with the bucket bucket at the bottom, the arm is extended, and it is found that the slewing ring also has a large gap in the radial direction. Swing Dunda and rotary speed reducers are all normal. Therefore, it is initially judged that the ball and the spacer sleeve inside the slewing bearing are damaged, the axial and radial clearances of the slewing bearing are increased, and the sealing device may be damaged.
Disassemble the slewing bearing. Turn back to the outer ring of the bearing and connect with the car. Inside the seat and get off. Remove all the tubing on the swing motor and seal the head of the tubing with a clean plastic film. Use a crane to gently lift the upper vehicle, and then loosen the bolts of the outer ring of the turn support and remove them, and then separate the upper and lower wheels (pay attention to the balance). The slewing bearing angle is connected with the vehicle. As shown in FIG. 1, the taper pin 2 is punched out, and then the plug 3 is removed by screws, and then the steel ball and the spacer are removed by the wire. After the steel ball and the isolation sleeve were all removed, only two of the isolation sleeves were found to be able to see the original shape, and the rest were all crushed into pieces. The steel ball was cleaned with diesel oil. More than 30 steel balls had serious pits and obvious deformation. The others had different degrees of pitting. After removing the outer race, clean the butter on the raceways of the inner and outer races. The inner and outer raceways can be clearly seen in the sun under the sun on the front and left parts (forward direction of the machine).
When the excavator is hit, it is equivalent to abruptly exerting a very large impact force in the radial direction of the slewing bearing, resulting in damage to the part of the isolation sleeve inside the slewing bearing (separation sleeve shown in Figure 2, made of nylon, softer), such as Continuing the work, more and more damage will be caused to the isolation sleeve, which will increase the gap between the inner and outer races. Butter will be thrown out of the gap between the inner and outer races. The raceways, spacers and steel balls will not be lubricated. As a result, the deterioration of the raceways, spacers, and steel balls is exacerbated, resulting in abnormal sound and jamming of the excavator during rotation.
2 Slewing bearing repair and installation
2.1 Slewing Ring Repair
If the replacement of the new slewing ring needs to be imported, and the price is high, about 10 million, the lead time will be longer. The excavator itself is an old machine and there is no need to replace the new slewing bearing, so it is decided to repair the original slewing bearing. Due to the timeliness of the problems found, the damage to the inner and outer races of the slewing ring is not very serious. After observation and measurement, the inner and outer raceways of the slewing bearing are deformed, but the raceway has pitting points and can still be used. Therefore decided to take a replacement spacer, steel ball and sealing device repair method. The diameter of the original slewing bearing steel ball measured 28.48mm, while the domestic product can only buy a steel ball with a diameter of 28.60mm, which is 0.12mm larger than the original steel ball diameter. There are 136 isolation sleeves and steel balls in the original machine slewing bearing. The length of the ball and spacer in the raceway is 16.32 (136×0.12) longer than the original. The size of each spacer must be reduced by 0.12 mm in order to ensure that the spacers and balls in the slewing ring are just filled with raceways. When purchasing steel balls with matching methods, you must ensure that the ball diameter error is less than 0.002mm. Isolation sleeves also have to do more for selection when assembling. If the final number is not guaranteed to be the same as the original number, the size of some spacers should be reduced until the number of spacers and steel balls is the same as the original slewing ring and the entire raceway is filled.
2.2 Slewing Bearing Installation
Firstly, clean the inner and outer races (including raceways), steel balls, isolation sleeves, sealing devices and bolt holes of the slewing ring, and place the outer race on the inner race to ensure that the inner and outer seats are basically secured. The raceways of the rings are on the same plane, then the steel balls and spacers are put into the raceways through the radial holes (as shown in Figure 1), placed in a separate sleeve in the order of one steel ball until they are full, and then the plugs are blocked 3 Block and tighten the taper pin 2. When assembling the sealing device, apply a sealant to the portion of the sealing device that contacts the sealing groove to ensure the sealing effect. Rotate the slewing ring to see if there is any seizure. If there is a seizure, repair it so that it can rotate flexibly. Finally, grease is added through the grease fitting of the outer ring of the slewing bearing so that the raceway is filled with butter, and butter is filled in the rotating pinion and the oil pool that rotates off the ring.
Lift the excavator's car with a crane and align the lower end of the swing platform with the outer race of the slewing ring. After aligning, align the car with the bolt with a diameter similar to that of the bolt. Locating, then assembling the bolts, the threads of the bolts should be coated with Loctite anti-loose glue. The bolts are symmetrically installed in a triangle as shown in Fig. 3. First install the first group of 3 bolts. Then install the second group of 3 bolts. At the beginning, the bolts cannot be tightened. After all the bolts are installed, tighten the bolts one by one with a torque wrench. The tightening torque is 650 N·m. After the installation is completed, start the machine and make it rotate and other operations until it returns to normal.
