Slewing bearing failure is rarely sudden. It is typically the culmination of a slow degradation process that leaves behind telltale forensic evidence. Understanding these failure modes and implementing a proactive maintenance strategy can transform your operation from reactive to predictive, avoiding catastrophic downtime and expensive repairs.

Common Failure Modes and Their Root Causes

1. Spalling (Fatigue Failure):

   • What it is: The most common failure mode. It appears as pitting or flaking on the raceways or rolling elements.

   • Cause: Natural subsurface material fatigue after a high number of load cycles. It can be accelerated by overloading, contamination (acting as stress concentrators), or improper lubrication.

   • Diagnosis: Increased vibration and noise, often cyclic in nature.

2. Brinelling (Plastic Deformation):

   • What it is: Indentations in the raceway at the position of the rolling elements.

   • Cause: Static overload (e.g., dropping a load), impact loads, or shock during transport without the lock being engaged. False Brinelling can occur from vibration while stationary, causing fretting wear.

   • Diagnosis: Visible dents, increased torque and vibration as rollers pass over the indentations.

3. Wear:

   • What it is: General material loss from surfaces in contact.

   • Cause: Contamination (dust, grit, abrasive particles) ingressing past failed seals. Inadequate lubrication or use of the wrong lubricant type.

   • Diagnosis: Increased internal clearance, leading to loss of precision and higher levels of metallic debris in the grease.

4. Seal Failure:

   • What it is: Damage or degradation of the lip seals.

   • Cause: Aging and hardening, physical damage during installation, or exposure to chemicals or extreme temperatures.

   • Diagnosis: Visible signs of damage or extrusion. Evidence of grease leakage or contaminant ingress.

5. Cracked or Broken Gear Teeth:

   • What it is: Fracture of the internal or external gear teeth.

   • Cause: Incorrect backlash (too little or too much), shock loading on the drive system, or material defect.

   • Diagnosis: Visible upon inspection, often accompanied by metal chips in the housing and loss of drive functionality.

Implementing a Predictive Maintenance (PdM) Program

Reactive maintenance (run-to-failure) is the most expensive strategy. A PdM program monitors bearing health to schedule intervention before failure.

• Vibration Analysis: The cornerstone of PdM. Accelerometers mounted on the bearing housing can detect the specific frequency signatures associated with spalling, gear mesh issues, and imbalance. Trends over time provide the clearest warning of developing faults.

• Oil Analysis (Debris Monitoring): For bearings with a closed lubrication system,定期取油样分析. Analytical Ferrography can identify the type, size, and concentration of wear particles, pinpointing the exact component that is degrading.

• Visual and Acoustic Inspection: Regular inspections for leaks, loose bolts, and unusual noises are simple yet effective first-line checks.

• Torque Monitoring: A gradual increase in rotational torque can indicate a lack of lubrication, contamination, or the onset of Brinelling.

The Repair or Replace Decision

When a fault is detected, a cost-benefit analysis is needed. Repair by a specialized workshop (involving re-grinding raceways, replacing rolling elements, and re-gearing) can be a cost-effective option for large, expensive bearings. For smaller or severely damaged units, replacement is often the more reliable choice.