Summary
A conventional crawler-mounted mobile crane was being used to lift and align sheet piles and drive them into the ground. During the final alignment, the crane's auxiliary hoist brake pedal inadvertently released, dropping the overhaul ball. The overhaul ball struck the top of the sheet pile and then struck a worker who was in a work bucket hooked onto an adjacent sheet pile. The worker in the bucket received fatal injuries.

Conclusions

Findings as to causes

• The welder was in the elevated work bucket hooked on the top of an installed sheet pile. He was struck and fatally injured by the falling overhaul ball of the crane's auxiliary hoist line when the auxiliary hoist brake pedal inadvertently released.

• The crane operator/foreman had a conflict of job responsibilities. Not only did he have to operate the crane but he also had to coordinate on-site activities outside of the crane. This can cause a situation with divided attention.
• There are insufficient feedback mechanisms (audible or visual) to indicate to the crane operator/foreman that the brake has been applied successfully.
• The pedal force needed to apply the brake exceeded the established standard. The crane operator/foreman may have experienced right leg muscle fatigue at the end of the day. This may have affected his ability to safely operate the brake pedal and latching mechanism.
• No secondary, positive, drum brake system (such as a ratchet and pawl) was available to prevent the overhaul ball from dropping in the event of an inadvertent release of the hoist brake pedal.