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Fault Analysis: Why Is There Abnormal Noise from the Excavator’s Slewing Bearing?
Updated at:
2026-03-12 09:40
The excavator’s ability to swing left and right during operation depends on its slewing unit, with the slewing bearing serving as a critical component of the slewing mechanism. The excavator’s slewing bearing primarily supports the weight of the superstructure and withstands operational loads; it is also one of the most common failure points in excavators.
Because excavator slew bearings typically operate under heavy-load conditions and in harsh working environments, they are prone to failure, with common symptoms including various abnormal noises. So what causes these unusual sounds, and what steps should be taken to diagnose and eliminate the fault?
First, it is important to note that when a newly manufactured slewing bearing is run under no-load conditions, a uniform rolling sound produced by the steel balls is perfectly normal. Similarly, if minor unusual noises occur shortly after installation, they are usually harmless and will typically dissipate after a period of running-in. However, what we are discussing here are louder and more distinctive noises; such abnormal sounds should prompt immediate attention.
, uneven mounting surface, loose mounting bolts
When abnormal noises occur, it is necessary to determine whether the issue stems from improper installation. If the flatness of the mounting surface fails to meet the specified requirements, negative clearance may develop in the raceway, leading to noise. Additionally, poor meshing of the pinion gear can also cause abnormal noise and may result in tooth breakage. Furthermore, if the mounting bolts become loose, the slewing bearing will undergo elastic deformation, creating negative clearance at the deformed locations; in such cases, immediate inspection and tightening of the bolts to the specified torque are required.
Second, there is a foreign object in the slewing bearing.
When foreign matter such as sand particles or metal chips is present inside the slewing bearing, non-periodic vibrations will occur, often accompanied by sluggish rotation. In such cases, it is essential to thoroughly clean the bearing, shaft, housing bore, and mating components before installation, and to promptly remove any contaminants from the lubricant. Furthermore, avoid using plastic cages made from impure materials or containing embedded foreign particles; only in this way can the associated abnormal noises be eliminated.
Third, abnormal noises caused by grease-related issues.
Excavator slew bearings are lubricated with grease, and abnormal noises are very likely caused by lubrication issues. Common causes include insufficient grease in the raceway, uneven grease application, degraded or poor-quality grease, and improper selection of the lubricant. To resolve this problem, simply use the appropriate lubricant, replenish it promptly, and replace it as needed.
Fourth, abnormal noises caused by damaged sealing strips.
Inspect the sealing strip for wear, as its design plays a critical role in maintaining seal integrity. If the sealing strip does not fully conform to the slewing bearing, grease leakage is likely to occur. In addition, the aging resistance and grease resistance of the sealing material are also important factors to consider.
Fifth, abnormal noises caused by cracks, dents, or rust.
When the rolling surfaces of a slewing bearing exhibit cracks, pitting, or rust, and a periodic vibration resembling that of riveted rivets is also heard, the damage manifests as continuous spalling on the raceways but intermittent spalling on the balls. Moreover, the characteristics of this noise vary to some extent depending on installation and lubrication conditions. The remedy is to avoid striking the bearing during installation and to use high-viscosity grease.
Sixth, severe wear of the raceway and rolling elements.
If an excavator emits unusual noises during slewing, it is highly likely that the slewing bearing raceway and rolling elements have suffered severe wear, necessitating repair of the slewing bearing.
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