Failed or Absent Defences » LTA risk assessment

41Vehicles Hitting Overhead Powerlines



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

This safety bulletin has been prompted by these recent, potentially fatal incidents:

  • A haul truck driver didn't lower his tray as he drove under the 66kV line, contacting the live conductors. The truck stopped about 20 metres past the line and two tyres blew out.
  • A dump truck brought down two 11kV powerlines when the tray was raised to tip crusher dust into a trench. The truck was then parked in an isolated area for 24 hours to reduce a possible pyrolysis hazard (fires starting inside the vehicle's tyres which could then explode some time later)
  • A rubber tyred drill rig moved toward the next drill hole position. Its mast hit and dislodged 66kV overhead powerlines from their power poles. Electrical protection circuits isolated the power.
  • An excavator being driven beneath an 11kV line contacted the 3 phases and earth wire, leaving two-phase conductors twisted together.

Identified Root Causes:

Factors that can lead to inadequate clearance between a vehicle and overhead lines include: -

  • no procedures for operation or passage of vehicles near overhead powerlines
  • lack of training, inadequate job instruction, or poor supervision
  • poor visibility, (clearances are hard to judge from the ground, the line could be obscured by the sun, etc)
  • lack of warning signs highlighting the powerlines or barriers to prevent access by unsuitable vehicles
  • poor site layout with unnecessary powerline road crossings, or operations such as stockpiling under powerlines

Energy Type(s) Involved:

Electric shock, electrocution, or severe burns, other hazards include fire, explosion, and power interruption to the site. Also be aware that electric current can arc between the vehicle and the powerline, even without actual contact.

Equipment Type(s):

Mobile machines and overhead powerlines.

Root & Contributing Cause(s):

LTA awareness

LTA competency

LTA isolation

LTA risk assessment

LTA site design

LTA Standard Work Procedures (SWP)

LTA supervision

Stated or Potential Consequence(s):

Potential Fatality

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

Possible controls may include:

  • Checking procedures for operating and travelling near powerlines, and emergency procedures for accidental contact with the lines, and maintain, review and upgrade these procedures as needed.
  • Ensuring mobile plant operators, (employees and contractors, including short term contractors) are trained in these procedures, and then adequately instructed and supervised
  • Ensuring warning signs and barriers are present to draw attention to the powerlines, and signs list the safe clearance. Inspect the worksite and maintain route maps, clearances and signage up to date - roadways do change and material can gradually build-up under the line until clearances are breached. Know the maximum height of both your own and your contractor's machines.
  • General warning signs can be used inside the vehicle cabin and as part of vehicle manuals. Also consider using audible and visual warnings to alert the operator when the tray, boom, mast, etc is raised.

Possible contact with overhead powerlines must be considered in the development of a coal mine's safety and health management system, and in the risk management practices and procedures used by metalliferous mines.

Organisation:

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


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