Mineral Mines & Quarries Inspectorate | Alert | No.427 V | 23 May 2023

Fingertip severed when caught in a motorised hood tarp system

What happened?

A truck driver at a quarry was attempting to release a jammed tray tarp wire by hand when the tarp pulley operated unexpectedly, trapping and amputating the tip of his left index finger.

How did it happen?

On the day of the incident, the driver activated the tarp switch and saw that the dog trailer's tarp wouldn’t move as the mechanism was jammed. The driver exited the cab, stood on the draw bar between the truck and dog trailer and attempted to free the tarp wire by pulling on it. While doing so, the tarp released, and the wire moved as the motor was energised. The driver’s index finger was caught in the tarp pulley system, and his fingertip was amputated.

• The truck and the dog trailer were fitted with an electric motorised tarping system to cover their trays.
• The in-cab switch on the tarping system had recently been changed to a load break switch that when pressed on, started the tarping cycle, and stayed on until the tarping was completed and stopped. The switch then turned off when the tarp motor current reached 5 amps, de-energising the motor.
• The previous in-cab switch for the tarping system only kept the system energised if the switch was physically held in the “on” position.

Key issues

• Isolation of motors must be performed prior to any work being carried out.
• The load break switch did not de-energise when the tarp mechanism jammed.
• The controls to prevent the tarp wire pulley system from jamming were not considered or were ineffective.

Recommendations

• Elimination - Before adjusting an electrical tarp system, the system must be isolated.
• Separation - People must not be in the danger zone when the system is energised, or touch any part of the system.
• Substitution - When plant operation or components are changed, the change management process should include but not be limited to:
• risk assessment of the change with experienced and competent persons
• suitably qualified persons carry out changes
• verification that the changes work as designed and as expected
• workers are trained in plant changes and expectations to operate plant.
• Engineering - Guards should be installed for rotating pulleys of the tarping system to make the nip points inaccessible by any driver/worker.
• Any adjustment of the tarp system should be conducted from a tarp stand, or by using a fit-for-purpose ladder at a designated safe location.
• Administrative - The operation and maintenance of the tray tarp system must be conducted as per the operator’s manual to ensure the correct method is identified and appropriate controls are in place.
• Personal Protective Equipment - Gloves should be worn when carrying out tasks where there is a risk from handling the mechanical components and wires.

Note: The critical control isolation must be implemented irrespective of other controls being considered.

All site senior executives should ensure that truck drivers’ site inductions include the following:

• climbing onto the body or chassis of the truck is not permitted while in the quarry.
• the operation and maintenance of the tray tarp system must be conducted as per the operator's manual.
• any adjustment of the tarp system should be conducted from a tarp stand, or by using a fit-for-purpose ladder at a designated safe location.
• before adjusting an electrical tarp system, the system must be isolated.