Failed or Absent Defences » LTA isolation hardware » LTA safety device operation

22Failure Of An Isolation Device

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Brief Description of Incident/Accident & Description of Consequences/Outcomes:

A plant operator isolated the energy source to a pug mill to carry out the daily cleaning task. After attaching his pad lock and personal danger tag to the isolator he tested the effectiveness of the isolation by pressing the start push button. Unexpectedly the pug mill started up. This indicated that the isolation was ineffective and therefore the equipment was unsafe.

Identified Root Causes:

The internal aluminium shaft of the isolator had broken allowing the handle of the switch to rotate to the off position without isolating the energy source.

Energy Type(s) Involved:

Uncontrolled release of energy

Equipment Type(s):

Pug mill and electrical isolator

Root & Contributing Cause(s):

LTA isolation

LTA safety device operation

Stated or Potential Consequence(s):

Potential Fatality

Preventative/Recommended/Accepted Steps of Risk Mitigation, Points of Interest:

Always ensure when isolating an energy source that the isolation is effective by testing the plant and its energy source for zero potential.

All safety isolation or lock-out devices must be properly selected, installed and maintained according to the expected duty cycle.


Queensland Government Department of Employment, Economic Development and Innovation (DEEDI)


Here are the results.


Reference Type:

Safety Alert #82

Mine Type:

Surface Mine







Australia, Queensland

ICAM Categories

Organisational Factors

• LTA commissioning procedures

• LTA equipment integrity

Task or Environmental Conditions


Individual or Team Actions


Failed or Absent Defences

• LTA isolation hardware

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