LHD scare

AN UNUSUAL incident has revealed various defects with the load-haul-dump vehicle that trapped its operator underneath the cabin, near the section tag board of an undisclosed coal mine in New South Wales.
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Blair Price

The Mine Safety Operations branch safety alert on the matter did not mention any injuries but said the experienced LHD operator was found under the cabin and caught by the driver’s side (left) rear wheel.

Before the incident the operator had transported material from the coal face to the surface.

“During the trip out of the mine he stopped at the section tag board and alighted from the LHD,” MSO said.

“The LHD reportedly moved forward (inbye) trapping the operator. The ground conditions were a hard flat surface with slight gradient in forward direction.”

There was other evidence the operator did not perfectly exit the LHD.

“It appears the operator’s cap lamp cord was caught around the control levers in the cabin as he alighted,” MSO said.

The subsequent investigation found the following defects with the LHD:

  • The roller on the door interlock valve was worn and broken causing the valve to malfunction. It also prevented the second door interlock valve from functioning by blocking the control air flow;
  • The park brake valve shaft had free play in the shaft movement;
  • There was a delay in brake activation when the operator’s door was opened before the brakes would apply; and
  • The brake systems were functional when tested dynamically.

Relevant manufacturers and suppliers were recommended to review the relationship between the door interlock design and the park/emergency brake and assess its reliability along with brake system maintenance plus tradesmen maintenance competencies and training.

The following recommendations were made to mine management:

  1. Review maintenance checklists on the mobile plant braking system against OEM recommendations
  2. Include procedures in the maintenance system for inspecting and testing all automatic valves that operate the braking systems. Note: particular care to be taken in the visual/physical inspection of valves/components
  3. Verify the competency of personnel who carry out inspection, tests and maintenance on braking systems. The training should consider MDG39 and any relevant machine-specific brake requirements
  4. Review operator training to specifically instruct, test and assess the shutdown procedures on vehicles. This should include:

    a) Stopping the machine by applying the service brake;

    b) Steering the wheels towards the rib;

    c) Applying the warning to not use the park/emergency brake to stop a moving machine unless it is a real emergency;

    d) Applying the park brake when stationary and checking the brake pressure gauge decays to zero;

    e) Checking that the park brake indicator changes state to indicate the park brake is applied (if fitted);

    f) Ensuring the brake pressure is zero before opening the operator’s door; and

    g) Not using the door interlocks to apply the park brake.

  5. Operational training should include a hazard warning that loose clothing and the cap lamp cord may become caught on the control levers in the operator’s cabin.