Background
Some mining operations are permitting excavator operators to pick up and relocate equipment using the ground engagement tool (GET) or bucket tooth of an excavator. In these instances, the site’s risk assessment process has found the lifting practice to be acceptable although a competent person has not assessed the suitability of using the bucket teeth as a lifting point.
An excavator GET or bucket tooth is typically attached to the body of the excavator bucket with an adaptor piece. The adaptor piece is welded or pinned to the bucket body and the bucket tooth tip is commonly attached to the adaptor using connecting pin(s).
Bucket tooth tips and adaptors are typically made from hardened material for wear resistance. Depending on the fabrication technique (casting or forged), this material may be brittle and suddenly fail, especially if shock loading occurs (e.g. lifting).
Bucket teeth are not normally designated or engineered by the manufacturer for lifting. They are designed for soil loading during earth moving operations, where they may be subjected to high stress loading and potential damage, which can reduce their strength.
Summary of hazard
The use of unrated lifting points on an excavator has the potential to expose workers to harm by the:
- sudden failure of a bucket tooth or sling, which can lead to
- loss of control of the lifted load
- a failed bucket tooth becoming a projectile hazard to surrounding workers, including the excavator operator
- instability of the excavator if the lifted load exceeds the excavator’s tipping load.
Contributory factors
- Inadequate visual inspection of bucket teeth for damage during earth moving operations (due to position of potential damage, location of bucket and operating environment).
- Damage to the sling through excessive:
- bending due to the bucket tooth dimensions not meeting the recommended bending radius of the sling
- wear on the fibres of the sling from abrasive surface of the bucket tooth (i.e. no wear protection).
- Irregular inspection of slings for damage.