Maintenance of slewing bearing of hydraulic excavator

Hydraulic excavators generally use single row four point contact ball internal tooth slewing bearings. When the excavator works, the slewing bearing bears complex loads such as axial force, radial force and overturning moment, and its reasonable maintenance is very important. Cleaning and maintenance of oil seal and inner and outer ring gear, and lubrication of inner and outer ring gear. Now I will elaborate from seven aspects.

1 raceway lubrication

The rolling element and raceway of slewing bearing are easy to be damaged and failed, and the failure rate is high. When the excavator is in use, adding grease to the raceway can reduce the friction and wear between the rolling body, raceway and gasket. The space of raceway cavity is narrow and has strong anti grease filling ability. Manual oil injection gun is required for manual oil injection. When filling the raceway cavity with grease, avoid using bad filling methods such as "static refueling" and "single point refueling". This is because the above poor oil filling method will cause local oil leakage of the slewing ring and even permanent oil seal of the slewing ring. Sexual damage, resulting in grease loss, impurity invasion and accelerated raceway wear. Be careful not to mix different types of grease to avoid premature failure. When replacing the severely deteriorated grease in the slewing bearing raceway, rotate the slewing bearing slowly and evenly to make the grease fill the raceway evenly. This process can not be done too quickly. It needs to complete the metabolism of oil step by step.

2 maintenance of gear meshing area

Open the metal cover on the base of the slewing platform and observe the lubrication and wear of the slewing bearing gear and the pinion of the slewing motor reducer. A rubber pad shall be placed under the metal cover and fixed with bolts. If the bolt is loose or the rubber pad fails, water will penetrate into the lubrication chamber (oil collecting pan) of the rotating gear ring from the metal cover, resulting in premature failure of the grease, reduced lubrication effect, and increased gear wear and corrosion.

3. Maintenance of inner and outer oil seals

During the use of the excavator, check whether the inner and outer oil seals of the slewing ring are intact. In case of damage, it shall be repaired or replaced in time. Damage to the sealing ring of the rotary motor reducer will cause the gear oil in the reducer to leak into the ring gear lubrication cavity. During the meshing process between the slewing ring gear and the pinion of the slewing motor reducer, the grease is mixed with the gear oil, the temperature increases, and the grease becomes thin. The diluted grease will be pushed to the upper surface of the inner ring gear and penetrate into the raceway through the inner oil seal, resulting in oil leakage and dripping of the outer oil seal, resulting in accelerated damage to the rolling element, raceway and outer oil seal.

Some operators believe that the lubrication cycle of the slewing ring is the same as that of the boom and stick, and grease must be added every day. In fact, this is wrong. This is because too frequent re greasing will cause too much grease in the raceway, resulting in the overflow of grease at the inner and outer oil seals. At the same time, impurities will enter the slewing bearing raceway and accelerate the wear of rolling elements and raceways.

4 maintenance of fastening bolts

If 10% of the bolts of the slewing ring are loose, the remaining bolts will be subjected to large forces under tensile and compressive loads. Loose bolts will produce axial impact load, which will aggravate and loosen more bolts, lead to bolt fracture, and even crash and death. Therefore, after the first 100h and 504h of the slewing ring, the bolt pre tightening torque should be checked. After that, the pre tightening torque shall be checked every 1000 working hours to ensure that the bolts have sufficient pre tightening force.

The tensile strength of bolts will decrease after repeated use. Although the torque reaches the specified value during reinstallation, the preload of the bolt will also be reduced after tightening. Therefore, when retightening the bolts, the torque should be 30-50 n · m greater than the specified value. The tightening sequence of slewing bearing bolts shall be tightened several times in the 180 ° symmetrical direction. At the last tightening, all bolts shall have the same preload.

5 adjustment of gear clearance

When adjusting the gear clearance, observe whether the connecting bolts between the slewing motor reducer and the slewing platform are loose