AMSJ » Malfunctioning fail-safe brake hospitalises worker

Malfunctioning fail-safe brake hospitalises worker

Fail safe brake interlocks
Fail safe brake interlocks

Authorities are investigating how a mine employee became injured despite safeguards in place.

Resources Safety and Health Queensland (RSHQ) wants to know exactly how a runaway, light vehicle recently struck and injured an underground worker.

Investigators revealed the operator exited the cabin to open a barricade outside a mobile equipment operating area when the vehicle rolled backwards, struck him and kept moving down the decline for about 100 metres.

“The vehicle came to rest after striking the decline wall with the tray. The worker sustained injuries as a result of the incident,” RSHQ said in a mineral mines and quarries inspectorate alert.

The wreck was fitted with fail-safe brakes on the rear axle, a dash-mounted control panel, and an interlock between the brakes and OEM door switches. One defective part prevented safeguards from activating after multiple precautions were not taken.

“The original equipment manufacturer door switch had been previously damaged in such a way as to prevent the interlock function,” the alert said.

“The vehicle was not in gear, park brake not applied and wheels not turned into the wall when the uncontrolled movement occurred. Pre start inspections for the light vehicle did not include testing of the interlock functions for the fail-safe brake.”

RSHQ concluded fail-safe systems with interlocks can malfunction and not operate as intended. It recommended “regular function testing” of interlocks.

“[This] can detect hidden failures [and,] where field devices such as switches perform a safety function, the robustness of the device and probability of failure in the usage environment should be considered in the design,” the alert said.

The authority also recommended the following:

  • monitor and supervise administrative and procedural controls
  • light vehicle operators must follow correct park-up procedures
  • establish periodic audits to test light vehicle fleets fitted with fail-safe brakes
  • ensure light vehicle training material includes pre start inspection requirements for fail-safe brake systems
  • ensure pre start and maintenance for light vehicles includes inspection and function tests for fail-safe brakes
  • urgently audit all in service, light vehicle fail-safe braking systems to ensure both the brakes and installed interlocks (e.g. doors, seatbelts, engine) function correctly. Test both the brake-apply and brake-lift inhibit functions of interlocks.

Investigations were still continuing at the time of publication.

Click here to read the full alert.

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AMSJ April 2022