TL;DR
Swing bearing wear shows as axial play above 3 mm and metallic grease. Measure play at the rim and pull a grease sample before planning a bearing changeout.
What you might see
- grinding noise during upper structure rotation
- visible gear grease thrown outward
- excessive upper-structure play measured at rim
- increased swing cycle time
Likely causes
Bearing wear from abrasive rock dust contaminating the grease path
Inadequate greasing intervals allowing metal-to-metal contact in the raceway
Overloading during digging cycles, exceeding rated bucket payload
Seal damage on the bearing race allowing water and grit ingress
Required tools
- Dial indicator with magnetic base
- Grease sample kit
- LOTO kit
- Tape measure
Safety first
- Lock out swing drive motors before taking any measurements near the bearing or swing gear.
- Falling material hazard from residual ore in the bucket. Lower bucket fully before working near the upper structure.
- Working near large rotating machinery requires a spotter and high-visibility PPE.
Procedure
- 1
Park the shovel on level ground with the bucket lowered and the engine shut down.
- 2
Lock out the swing drive motor at the motor disconnect.
- 3
Measure axial play (vertical movement of the upper structure relative to the lower) at four equally spaced points around the bearing rim using a dial indicator. Record all readings.[1]
- 4
If axial play exceeds 3 mm at any point, escalate to a bearing specialist for replacement planning.[1]
- 5
Collect a grease sample from the bearing race lubrication port and send it for particle count and ferrous content analysis.
- 6
Inspect the bearing seal by looking for grease contaminated with black grit around the lower rim. Contaminated grease indicates a damaged seal.
- 7
Check and record the grease injections per the lubrication schedule. Under-greased bearings wear faster in dusty environments.
- 8
If wear is within tolerance, increase greasing frequency and schedule a re-measurement at the next 500-hour service.
Sources
Caterpillar CAT 6060 / 6090 Hydraulic Mining Shovel / Excavator general technical documentation, Caterpillar
Caterpillar large mining shovel service documentation, swing bearing inspection criteria (general)
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Stop fixing the same fault twice.
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