Repair of slewing ring of the hottest hydraulic ex

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Repair of slewing ring of hydraulic excavator

1 fault phenomenon and cause analysis

a Sumitomo s2800fj hydraulic excavator has worked for 8664h. During the construction of a construction site, the dump truck hit the counterweight of the excavator. Later, it was found that a lot of butter was thrown from the sealing device of the slewing ring, and there was an abnormal sound inside the slewing ring. When turning to the front and left side of the machine, there was a creaking sound inside the slewing ring. Support the ground with a bucket, keep one side of the track off the ground, and then put it down. It is found that the axial clearance of the slewing bearing is large. Then land the bucket on the ground and extend the stick. It is found that there is also a large radial clearance between the slewing bearings. The swing motor and the swing reducer are normal. Therefore, it is preliminarily judged that the steel ball and isolation sleeve inside the slewing bearing are damaged, which increases the axial and radial clearance of the slewing bearing, and the sealing device may be damaged

disassemble and inspect the slewing ring. Tomorrow of rotary branch automobile tire materials: Bio base bearing 1. The State Council No. 46 civilization confirms the outer seat ring of the high-pressure warning line of the combustion performance utilization range of thermal insulation materials and is connected to the car. The inner seat ring is connected with the lower carriage. Remove all oil pipes on the swing motor and seal the head of the oil pipe with clean plastic film. Lift the upper carriage gently with a crane, loosen the outer ring bolts of the slewing ring, and remove them all. Separate the upper carriage from the lower carriage

(pay attention to the balance of the upper carriage), and the slewing ring is still connected to the lower carriage. As shown in Figure 1, drive out the taper pin 2, then take out the plug 3 with screws, and then take out the steel ball and isolation sleeve with iron wire. After the steel was replaced again and the sensor ball and isolation sleeve were all taken out, it was found that only two isolation sleeves could see the original shape, and the rest were all squeezed into fragments. Clean the steel balls with diesel oil. More than 30 steel balls have serious pits and obvious deformation, and the rest have pits to varying degrees. After the outer race is removed, clean the butter on the inner and outer race raceways, and the pitting can be clearly seen in the sun at the front and left parts of the inner and outer raceways (the forward direction of the machine)

when the excavator is hit, it is equivalent to suddenly exerting a very large impact force on the radial direction of the slewing ring, causing damage to some isolation sleeves in the slewing ring (the isolation sleeve is made of nylon as shown in Figure 2, which is relatively soft). If it continues to work, the isolation sleeve will be damaged more and more, which will increase the gap between the inner and outer seat rings, throw butter out of the gap between the inner and outer seat rings, and the raceway, isolation sleeve and steel ball will not be lubricated, This will aggravate the damage of the raceway, isolation sleeve and steel ball, resulting in abnormal sound and stagnation of the excavator during rotation

2 repair and installation of slewing ring

2.1 repair of slewing ring

if a new slewing ring is replaced, it needs to be imported, and the price is expensive, about 100000 yuan, and the supply cycle is also relatively long. The excavator itself is an old machine, so it is not necessary to replace the new slewing ring, so it is decided to repair the original slewing ring. Due to the timely discovery of the problem, the damage of the inner and outer raceways of the slewing ring is not very serious. After observation and measurement, the inner and outer raceways of the slewing ring are deformed, but the raceway has pockmarks, which can still be used. Therefore, it was decided to replace the isolation sleeve, steel ball and sealing device for repair. The diameter of the steel ball of the original slewing ring is 28.48mm after measurement, while domestic products can only buy steel balls with a diameter of 28.60mm, which is 0.12mm larger than that of the original machine. There are 136 isolation sleeves and steel balls in the slewing ring of the original machine. The length of the steel ball and spacer sleeve in the raceway is 16.32 (136) longer than the original × 0.12), the size of each isolation sleeve should be reduced by 0.12mm to ensure that the isolation sleeve and steel ball in the slewing ring are just full of the raceway. When purchasing steel balls, the matching method shall be adopted, and the diameter error of steel balls must be less than 0.002mm. More spacer sleeves should be made for assembly. If it cannot be guaranteed to be the same as the original number at the end of installation, the size of some isolation sleeves should be reduced until they are the same as the original number of slewing ring isolation sleeves and steel balls and fill the whole raceway

2.2 installation of slewing ring

first, clean the inner and outer seat rings (including the raceway), steel balls, isolation sleeves, sealing devices and bolt holes of the slewing ring, and place the outer seat ring on the inner seat ring, basically ensuring that the raceways of the inner and outer seat rings are on the same plane, then put the steel balls and isolation sleeves into the raceway through the radial holes (as shown in Figure 1), and place them in the order of one steel ball and one isolation sleeve until they are full, Plug plug 3 and tighten taper pin 2. When assembling the sealing device, apply sealant to the part contacting the sealing device and the sealing groove to ensure the sealing effect. Rotate the slewing ring to see if it is clamped. If it is clamped, repair it to make it rotate flexibly. Finally, although a large amount of high thermal conductivity, electrical conductivity and corrosion resistance materials are also required to fill the grease nipple of the outer race through the rotary support to fill the raceway with grease, and fill the oil pool of the rotary pinion and the rotary large ring

use a crane to lift the upper part of the excavator, align the lower end of the slewing platform with the outer seat ring of the slewing ring, align and position the upper and lower parts of the excavator through the bolt hole with a round steel similar to the bolt diameter, and then assemble the bolts. The threads of the bolts should be coated with loctite locking glue. The bolts are installed symmetrically in a triangle, as shown in Figure 3. First install the first set of 3 bolts. Install the second set of 3 bolts. The bolts cannot be tightened at the beginning. After all the bolts are installed, tighten the bolts one by one with a torque wrench. The tightening torque is 650n M. After installation, start the machine and make it rotate until it returns to normal

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