Hazard Summary:

A worker was critically injured while working inside a crusher chamber. The unit was a Cedarapids Model #3645, which is a double-impeller impact breaker powered by a diesel engine. Using a jackhammer powered by a portable generator/welder set, the worker was removing material packed between the striker bars. The diesel engine was off and the clutch between the engine and the crusher was disengaged.

When the worker was nearly finished, the crusher operator told him he was about to start the diesel engine in order to warm it up and prepare for further tasks. The worker, believing he was protected by the disengaged clutch, remained inside the chamber.

The operator cranked the diesel, using battery power. When the engine cranked slowly and did not start, the operator thought this was caused by a weak or discharged battery, until he heard his coworker screaming for help. The worker's left leg was trapped between the impeller hammer and a striker bar. He was released and taken to hospital, where his foot was amputated above the ankle.

The investigation revealed that the clutch was partially engaged. This caused the crusher impeller to turn and probably also caused the slow cranking of the engine and its failure to start.

Locations and Sectors:

Crushing operations in mining, construction and industrial plants.

Recommendations:

• With all diesel-powered crushers, the engine should be stopped, locked and tagged at a disconnect switch in the engine cranking circuit before beginning any work that may endanger a worker. Crushers not equipped with a disconnect switch enabling the startup system to be locked out should be retrofitted immediately.
• Locking and tagging out a disengaged clutch is not recommended, because a clutch can fail or stick wholly or partially.
• When the clutch is disengaged and not sticking or binding, the rotating impeller hammers can turn freely and may be set in motion by a worker inside the chamber, causing crushing injuries to any worker caught between one or more hammers and the striker bar. For this reason a means of preventing the impeller and the hammers from moving when the clutch is disengaged must be in place before any work inside the crusher chamber begins.
• All crusher operators must be given proper training, including information, instruction and supervision adequate to protect the health and safety of workers at all times. Equipment manuals should be used during training and should be available to the operator for easy reference in the workplace.
• Training and procedures must be documented in writing and kept on file.

Please photocopy Ministry of Labour Alerts, distribute them widely and post them where people will see them.

Produced by the Mining Health and Safety Program, Ministry of Labour

Alert 7/0495 ISSN 1195-5228