The excavator can rotate left and right during work, so the slewing device is indispensable, and the slewing bearing is an important part of the rotating device. The excavator slewing bearing is mainly used to support the mass and working load of the body, which is also where the excavator is prone to failure. 

Structure and characteristics of excavator slewing bearing

The excavator slewing bearing is a force-transmitting component for the relative rotational motion of the upper and lower vehicle bodies, which is used to support the quality of the upper and lower vehicle bodies and bear the working load. The inner seat ring is connected to the lower body, the outer seat ring is connected to the upper body, and the inner gear ring on the inner seat is engaged with the pinion of the rotary motor. When the rotary motor rotates, the pinion drives the body to rotate.

Features of excavator slewing bearing

(1) The operation is light and flexible, and the rotation resistance is small

(2) Compact structure and small size (mainly height)

(3) Easy maintenance and shortened length

(4) It is composed of ring gear, seals, screws, etc. It is easy to install and convenient for specialized centralized production

(5) There is no central pivot, other parts can be installed in the intermediate space

The application range of slewing bearings is very wide, mainly used in lifting machinery (truck cranes, tower cranes, etc.), construction machinery (excavators, loaders, etc.), transportation machinery, material processing machinery, metallurgical machinery, food processing machinery, and Military equipment (tanks, anti-aircraft artillery, snow, rocket launchers, etc.), medical machinery, scientific research equipment, etc.


the disassembly and maintenance method of the excavator slewing bearing

Disassembly method

1. Choose a suitable maintenance site.

Before disassembling and assembling the excavator slewing bearing, it is necessary to determine the appropriate maintenance and replacement site: the site should be relatively flat, with a large operating space, which is convenient for the separation and lifting of the upper and lower parts of the excavator during the disassembly and assembly process.

2. The hoisting process should be careful.

In the process of replacing the excavator slewing bearing, the superstructure of the excavator needs to be transferred to another place. At this time, the commonly used lifting tool is a crane. Whether it is dismantling or installing, the lifting wire rope must be hung up to ensure safety.

3. Do not use a jack.

Some people sometimes do not choose to use a crane during disassembly and assembly, and use jacks and bricks to pad the upper half. However, it is recommended not to use the above method because the risk index is very high.

4. Select the appropriate slewing bearing.

There are many manufacturers of excavator slewing bearings on the market, and the product quality is also different. Since you have chosen to replace the new slewing bearing, remember not to only try to be cheap, but to choose reliable and durable excavator slewing bearings.

5. Screws should be tightened and lubricated

When installing a new excavator slewing bearing, remember to replace the tightening screw to prevent dark damage. In addition, lubricating oil must be applied to the new excavator slewing bearing, which can effectively reduce internal friction and prolong the service life of the bearing, and then lubricate and maintain regularly.

Excavator slewing bearing maintenance method

Hydraulic excavators are generally slewing bearings with a single row of four-point contact ball internal gears. The maintenance of excavator slewing bearings mainly includes lubrication and cleaning of raceways and inner gear rings, maintenance of internal and external oil seals, and maintenance of fastening bolts.

1. Raceway lubrication

During the use of the excavator, adding grease to the raceway can reduce the friction and wear between the rolling elements, the raceway and the pad. The space of the raceway cavity is small, and the grease extension line needs to be manually filled with a manual spray gun.

The raceway cavity is generally supplemented with 2# lithium-based grease for lubrication, and the filling cycle is generally 100h. Under special conditions such as dust, high temperature and continuous operation, the filling cycle should be appropriately increased. When adding grease, it is necessary to rotate the slewing bearing and add °~25° every 15 minutes. When adding grease, pay attention to observe the outer sealing ring of the slewing bearing. Stop filling when you see grease leaking one turn from the outer seal.

When adding grease to the raceway cavity, you should avoid using “fixed oiling”, “single point oiling” and other bad oiling methods, because the above bad oiling methods will cause local oil leakage during rotation, and even cause permanent attention to the rotation The bearing oil seal should not be mixed with different types of grease to avoid premature replacement. When replacing the severely deteriorated grease in the rotating raceway, when adding the grease, the slewing bearing should be rotated slowly and evenly so that the grease can be evenly filled into the raceway. This process can not be rushed, and it needs to complete the metabolism of oil step by step.

2. Maintenance of gear flexible zone

If you put the rubber pad under the metal cover, fasten it with bolts. If the bolts are loose or the rubber pads fail, water can leak from the metal cover into the lubrication cavity of the rotating ring gear (grease pan), causing premature grease failure, reduced lubrication, and increased gear wear and corrosion.

The method of replacing the grease in the lubricating cavity of the ring gear is as follows:

Support the excavator with the working device, and the operator enters under the crawler frame of the excavator and opens the metal cover;

Secondly, drop the excavator on the ground, start the excavator to rotate about 10 times, and drain the grease again. The lubricating cavity of the ring gear of the slewing bearing is also filled with 2# lithium-based grease. The replacement cycle is generally 2000h, and the filling amount is determined according to the model of the excavator.

3. Maintenance of internal and external oil seals

The inner and outer oil seals of the slewing bearing are of rubber sealing strip structure, which bears less pressure. The outer oil seal is located on the lower surface of the inner ring gear of the slewing bearing to prevent foreign matter such as external sand particles from the slewing bearing from entering the raceway, causing wear of the rolling elements and raceways; the inner oil seal is located on the upper surface of the outer ring of the slewing bearing to prevent the inner gear ring Lubrication cavity grease enters the raceway cavity.

When the rotor rotates, check whether the inner and outer oil seals of the rotating bearing are in good condition. If it is damaged, it should be repaired or replaced in time. During the process of inserting the slewing ring gear and the slewing motor reducer pinion, the grease is mixed with the gear oil. When the temperature rises, the grease will become thinner, and the thinner grease will be pushed to the upper end surface of the ring gear and penetrate into the raceway through the inner oil seal, causing the outer oil seal to leak and dripping oil, which will accelerate the damage to the rolling elements and the raceway. and outer oil seal.

Some operators think that the lubricating cycle of the slewing bearing is the same as that of the boom and stick, and it is necessary to add grease every day, which is actually wrong. This is because too much grease is added, which will result in too much grease in the raceways. At the same time, impurities will enter the inside of the rotating bearing raceway, accelerating the wear of the rolling elements and the raceway.

4. Maintenance of fastening bolts

When the slewing bearing bolts are tightened, the force should generally not be exceeded. When the tensile force of the bolt exceeds the tensile strength of the bolt itself, the preload will not be formed. In order to ensure the reliability of the bolt work, the 10.9-strength bolts should be replaced according to this type of bolts. The material should be 45# steel, quenched and tempered at medium temperature, and the hardness is HRC39 flat washers. Spring washers are prohibited.

If 10% of the bolts of the slewing bearing are loose, the rest of the bolts are in a state of tension and fracture. Loose bolts can cause deformation and shock, resulting in increased bolt loosening and more loosening, resulting in bolt breakage and even crashes and deaths. Therefore, after the first 100 hours and 500 hours of slewing ring work, check the bolt preloads. After that, the pre-tightening hoop should be checked every 1000 hours of work to ensure that the bolts have sufficient pre-tightening force.

5. Adjustment of gear clearance

When the slewing bearing gear is assembled with the output gear of the slewing motor reducer, the gear backlash should be adjusted by the high point of the radial runout of the inner pitch circle of the slewing bearing. At the maximum radial runout point of the inner pitch circle of the excavator slewing bearing, the backlash Sh of the gear of the rotary motor reducer is 0.03m (m is the gear module).

When adjusting the gear gap, pay attention to observe whether the connecting bolt between the rotary motor reducer and the rotating platform is loose, whether the gear is inserted, and whether the centering gap is too large or too small. This is because if the clearance is too large, the excavator will penetrate the gear when starting and stopping, and it is easy to produce abnormal noise; if the clearance is too small, the slewing bearing and the pinion of the rotary motor reducer will be stuck, or even broken teeth.

When adjusting, pay attention to observe whether the positioning pin between the rotating motor and the rotating platform is loose. The positioning pin and the pin hole belong to an interference fit. The positioning pin not only plays a positioning role, but also increases the tightening strength of the rotating motor reducer bolt, reducing the Possibility of loosening of the rotary motor reducer.

6. Static electricity maintenance

The positioning pin is a conical structure, which is used to fix the insert and prevent the insertion from moving. The insert is located in the non-load bearing position of the rotating load, above the main load plane.

The re-loosening of the fixed positioning will cause displacement and displacement, causing the raceway to change at the insertion position. When the rolling elements move, they collide with the inserts, producing abnormal noise. Cover with soil and watch for displacement.

7. It is strictly forbidden to wash the slewing bearing with water

It is strictly forbidden to wash the slewing bearing with water, invading the washing water and impurities, dust entering the raceway of the slewing bearing, corroding and damaging the raceway, resulting in the replacement of grease, destroying the lubrication state, and deterioration of the grease; avoid any solvent contacting the slewing bearing oil seal, so as not to cause oil seal corrosion .

Under normal circumstances, after the excavator rotates, its slewing bearing is prone to noise, impact and other faults. Operators should pay attention to observation, timely inspection and troubleshooting. Only correct and reasonable maintenance of the slewing bearing can ensure its normal operation, give full play to its performance and prolong its service life.

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