Flameproof alternator electrical protection systems | Resources Safety & Health Queensland Skip to content
Print notice
Alert Banner

Mines safety alert no. 221 | 17 April 2009 | Version 1

Flameproof alternator electrical protection systems


  1. Review maintenance strategies for testing protection systems fitted to alternators on underground mobile diesel machines.
  2. If these maintenance strategies do not exist:
    1. All alternators must be tested without delay to ensure the correct operation of the protection systems.
    2. Review maintenance programs to ensure that testing occurs on the introduction of machinery to site and as part of a scheduled program.
  3. Ensure that flameproof light fittings and supply cables on mobile diesel machines are adequately protected.

Review, with the machine operators, the potential severity of incidents resulting from careless operation of underground mobile diesel machines.

Investigations are ongoing and further information may be published as it becomes available. The information in this publication is what is known at the time of writing.

We issue Safety Notices to draw attention to the occurrence of a serious incident, raise awareness of risks, and prompt assessment of your existing controls.


Investigations into the incidents revealed the following:

  • The protection systems on the alternators fitted to the diesel machines did not operate.
  • Later testing of these alternators proved the protection systems were operational.
  • There was no evidence of sparking on the light fittings or cables involved.

Testing of the alternator protection systems on underground mobile diesel machinery was not occurring, neither on the machines introduction to site, nor as part of a scheduled maintenance program. Further investigation at other sites has identified similar deficiencies.

Mine Type

Coal mine - underground


In two recent incidents at the same underground mine, electric cables supplying lights on underground diesel machines were torn from their flameproof light fittings. On each occasion the electrical protection systems fitted to the alternators failed to operate.


Flameproof lights, flameproof alternators and cables fitted to underground mobile diesel machines.


Failure of flameproof equipment in a hazardous zone.


Incident 1

A flameproof light on an underground diesel loader was dislodged from its mountings, resulting in the cable supplying the light being torn from the fitting.

Incident 2

The cable supplying a flameproof light on a coal hauler was torn from the light when it contacted a rib bolt whilst the machine was in motion.

Authorised by Chris Skelding - Manager, Safety and Health, Central


Issued by Queensland Department of Mines and Energy

Placement: Place this announcement on noticeboards and ensure all relevant people in your organisation receive a copy.