A haul truck became dislodged from two hydraulic jacks—crushing one and knocking over the other—while two tyre fitters were removing and rotating tyres during a scheduled maintenance activity.
Two self-propelling hydraulic jacks—each rated to 181 tonnes—supported the haul truck’s rear suspension mounts. Using a tyre handler, the tyre fitters removed the haul truck’s rear right tyres (positions 5 and 6) and started removing its rear left tyres (positions 3 and 4). While the tyre fitters were removing the haul truck’s final rear left tyre (position 4), the vehicle became unstable and shifted to the right, dislodging from the hydraulic jacks and coming to rest on the ground. The haul truck crushed one hydraulic jack beneath its rear axle and knocked over the other.
Takeaways
- Consider load redistribution. Removing multiple tyres can significantly alter weight distribution and centre of gravity. Conduct stability checks at each stage of the process.
- Supplement hydraulic jacks with engineered secondary supports or mechanical locking systems, where practicable. Don’t rely solely on hydraulic systems.
- Maintain exclusion zones. Ensuring that no workers were in the haul truck’s footprint prevented any injuries from occurring.
- Plan staged removal activities. Develop and follow procedures that account for progressive imbalance during multi-tyre maintenance tasks.
Summary
Tyre maintenance on large mobile plant involves significant stored energy and changing load conditions. Even when using high-capacity equipment, the progressive removal of components can compromise stability. Robust engineering controls, staged risk assessment and strict exclusion zones are essential to prevent serious harm.
