Troubleshooting Common Slew Bearing Issues: A Comprehensive Guide

Slewing rings (slew bearings) are precision components rigorously tested and certified before leaving the factory. However, during installation, operation, or prolonged use, various operational anomalies can occasionally arise. Below is a detailed troubleshooting guide covering the four most common issues: inflexibility, abnormal noise, excessive shaking, and gear breakage.

1. Slew Bearing Lacks Flexibility / Stiff Rotation

If a brand-new or operating slewing bearing exhibits sluggishness or a retention phenomenon, use the following methods to inspect and resolve the issue:

• Inflexibility in Brand-New Products (Idling): Check the manufacturing date. If stored for an extended period (e.g., over six months) in cold climates, the grease inside the raceway may have become viscous. Solution: Apply external rotational force; if it rotates smoothly without other abnormalities, it can be used normally. If accompanied by unusual noises, inspect for transit damage and contact our after-sales service.
• Inflexibility Post-Installation: This is often caused by poor matching between the host machine’s mounting surface and the bearing surface, preventing the axial clearance from compensating for deformation and putting the bearing into a negative clearance state (sometimes accompanied by noise). Other causes include poor gear meshing or foreign objects trapped between the gears. Solution: Re-machine the mounting plane to meet specifications, or use shim adjustments. Re-adjust the gear backlash according to requirements—paying special attention to the position of maximum gear runout. Ensure the meshing area is free of foreign debris, or swap out for a bearing with slightly larger internal clearance.
• Inflexibility During Operation: This is typically caused by insufficient lubrication over time, or a damaged sealing strip allowing foreign objects (such as dust in poor working conditions) to invade the raceway. Check the gear meshing condition for foreign objects or broken teeth. If the bearing remains locked after taking these measures, internal raceway damage may have occurred; notify our after-sales department.

2. Abnormal Noise (Abnormal Sound)

While a slight, uniform rolling sound of steel balls during idle rotation in a brand-new bearing is normal, distinct and loud secondary noises indicate abnormal conditions.

• Slight Noise in New Products: Minor idling noise usually disappears naturally after dozens of revolutions. If it persists, it may stem from minor transit deformation, but if rotation remains smooth and normal, it is safe to install and use. If the noise is loud or remains after 2–4 months of use, contact our after-sales department.
• Noise Post-Assembly/Trial Run: Inspect whether the mounting surface meets flatness requirements. Poor flatness causes negative raceway clearance and noise (refer to the post-installation inflexibility solutions). Alternatively, poor gear meshing that alternates between too tight and too loose—especially at the maximum runout point—can create loud noises.
• Noise During Operation: First, verify that the sound originates from the slew bearing rather than adjacent steel structures or components (a quick check is to halt the slew bearing rotation while keeping other parts running). Common causes include:
  • Insufficient grease causing ball-to-spacer collisions (easily resolved by greasing).
  • Foreign debris like sand or iron shavings trapped in the raceway, often accompanied by difficult rotation and potential seal damage.
  • Loose mounting bolts leading to elastic deformation and localized negative clearance. If these checks fail to resolve the noise, contact our service team.

3. Excessive Shaking / Play

Once loaded, a slewing bearing typically exhibits a clearance roughly 3 to 5 times its initial factory inspection value (measured via the three-point method), which is acceptable for continued operation. Exceeding this usually points to external factors:

• Loose Mounting Bolts: Causes operational shaking. Immediately inspect and retighten all inner and outer ring mounting bolts to standard specifications.
• Insufficient Rigidity in Supporting Structures: Weak steel structures deform elastically under load, creating overall bearing wobble. Solution: Reinforce the structural strength supporting the bearing.
• Overloading: Verify whether the equipment has been operating under overloaded conditions and strictly adhere to operational guidelines.
• Raceway Crushing from Prolonged Overload: If chronic overloading has crushed the raceway and caused excessive clearance, notify our after-sales service department immediately.

4. Gear Breakage

If a slewing bearing suffers a tooth fracture, protect the scene immediately and notify our after-sales service department for structural analysis. Breakages generally trace back to installation or operational errors:

• Installation-Related Causes:
  • Improper gear backlash adjustment failing to meet standards, causing poor mesh during operation.
  • Failure to align the gear mesh adjustment at the point of maximum gear runout, causing the pinion to jam and break against the bull gear. Always adjust clearance at the green-painted marker point and test-run.
  • Non-parallel gear axes leading to poor meshing. Ensure parallel alignment of both gear axes.
  • Loose mounting bolts disrupting proper gear depth and meshing.
• Operation-Related Causes:
  • Violating operating protocols, including overloading, excessive rotation speeds, or the host machine violently colliding with obstacles.
  • Foreign objects jamming into the meshing zone between the gear and pinion. Keep the gear interface clean and conduct regular inspections.