All ICAM Categories » LTA equipment integrity » LTA design

94Electric Shock From Mobile Lighting Plant #2



Click to view link.

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

INCIDENT

A mine technician received an electric shock from a mobile lighting tower in an open cut mine. The technician was adjusting wiring in an electrical enclosure when he contacted a 240 V conductor.

CIRCUMSTANCES

Mobile lighting towers are used extensively in open cut operations to provide area lighting for night time operation. These may be wheel or skid mounted, and are powered by a diesel engine driving a 415 V three phase alternator. Two electrical enclosures, similar in appearance, contained the electrical control equipment. One was for 415 / 240 V circuits, the other was for 12 V DC (extra low voltage[ELV]) circuits. The 12 V DC circuits were for engine management and monitoring, and included a 12 V powered programmable logic controller (PLC). The mine technician was a mechanical tradesperson with auto-electrical skills, and authorised to work on ELV circuits only. He was trying to diagnose a fuel level monitoring fault, and attempted to re-seat the input plug to the PLC.

Unknown to him, a 240 V conductor had been wired to the PLC to notify the PLC that the alternator had built up voltage. This conductor was exposed for a short length at the back of the plug, allowing the technician to make inadvertent direct contact with his thumb. His other hand was on the door of the enclosure, completing a circuit across his chest.

Identified Root Causes:

INVESTIGATION

The 12 V DC enclosure was not lockable, did not require special tools for access, and was not fitted with signage warning of electricity. The 12 V DC enclosure is regarded as an operating area as defined in AS 3007, and as such it is not permissible to have exposed conductors at a voltage above ELV inside the enclosure.

Energy Type(s) Involved:

Direct contact with live electrical conductors

Equipment Type(s):

Lighting Plant

Root & Contributing Cause(s):

LTA design

LTA equipment modification

Stated or Potential Consequence(s):

Potential Fatality

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

· Owners of the same or similar apparatus should immediately determine whether exposed or unprotected conductors above ELV are present in enclosures that are regarded as “operating areas”.

· Mines should check that electrical apparatus complies with AS 3007 where appropriate. Regard must be had for the classification of operating areas, including enclosures of electrical equipment.

· Where complete protection by insulation or barriers cannot be achieved, enclosures must be secured by a key or special tool, and accessed only by skilled persons. Signs warning of the danger of electricity must be fitted to such enclosures.

Organisation:

New South Wales Department of Primary Industries, Minerals and Petroleum


Results

Here are the results.


Information

Reference Type:

Mine Safety Report #SA00-07

Mine Type:

Surface Mine

Energy:

Electrical

Equipment:

Published:

2000

Region:

Australia, New South Wales

ICAM Categories

Organisational Factors

• LTA adherence to safe system of work

• LTA commissioning procedures

• LTA compliance with electrical standards

• LTA equipment

• LTA equipment integrity

• LTA maintenance

Task or Environmental Conditions

-

Individual or Team Actions

-

Failed or Absent Defences

-



©2019 ISOLgate