Mine Safety Report No: SA05-12
File No:05/4589
Comet ID:317523671001
Prepared by: Bob Kennedy IEE Wollongong
Phone: 0438467992
Date Created: 3 September 2005
SAFETY ALERT
Electric shock from a light fitting.
INCIDENT
A mineworker received an electric shock when his forearm made contact with a
flameproof Burn Brite fluorescent light fitting (Certificate No AUS EX 424X) on a
continuous miner in the hazardous zone of a coal mine. The victim was
transported to hospital in accordance with the mine’s electric shock protocol and
was allowed to leave after medical tests and examination determined that no
permanent injury had occurred as a result of the shock and there was minimal
risk of delayed arrhythmia.
The presence of electricity external to the flameproof enclosure also presented a
potential ignition source of methane
CIRCUMSTANCES
The source of voltage was from a 110 volt power supply located in the master
control enclosure on the continuous miner. The Burn Brite light fitting case was
plastic; however three brass threaded inserts are embedded in the boss
assembly to enable cable glands to be fitted. These metal inserts are not
connected to earth, and any metal gland screwed in may not be earthed (see
photograph below)
The light fitting was mounted vertically which allowed water to enter and
accumulate as a result of a missing “O” ring between the boss and nut assembly
of the light fitting. The missing “O” ring constitutes a failure of the IngressMine Safety Report No: SA05-12
File No:05/4589
Comet ID:317523671001
Prepared by: Bob Kennedy IEE Wollongong
Phone: 0438467992
Date Created: 3 September 2005
he presence of water in the light fitting caused a fault current to flow to the
VESTIGATION
ingress protection,
rn Brite light fitting, and
com e of the coal
hazards were;
was able to deliver an electric shock to a mineworker,
2. xplosion-protected equipment failed to contain the electrical energy
ECOMMENDATIONS
ay also apply to other light fittings and on other
Protection (IP). (Note: The “O” ring may become dislodged during re-assembly of
the light fitting after maintenance). The outer case collar (flamepath) was
cracked (see photograph below) and the poly-carbonate case was also cracked.
T
earth screen of its supply cable. This imposed a touch voltage onto the
unearthed external cable gland. The fault current was below the magnitude
necessary to cause the electrical protection to operate. The circuit protection is a
10-ampere fuse and a toroidal earth-leakage relay set to trip at 500 milliamps,
within 250 milliseconds. The light fitting continued to operate with the water
present.
IN
The three factors of:
1. A failure of the
2. Unearthed external metal on the Bu
3. The 500 mA/250 ms setting of the earth leakage protection,
bined to present two separate hazards in the hazardous zon
mine.
These
1. A touch voltage
AND
The e
within the enclosure under fault conditions creating a potential source of
ignition of methane.
R
The issues raised herein m
machinery at NSW mines. Mine Safety Report No: SA05-12
File No:05/4589
Comet ID:317523671001
Prepared by: Bob Kennedy IEE Wollongong
Phone: 0438467992
Date Created: 3 September 2005
Manufacturers of light fittings and continuous miners, should review the risks to
safety from their products and to promptly stipulate earthing, protection,
maintenance and inspection requirements to their customers as required by the
NSW OHS Act.
All mines should assess the risks to safety of the Burn Brite light fitting in a
manner consistent with clause 6 of the Coal Mines (General) Regulation to
decide if continued use is appropriate, and if so, under what conditions of use,
including inspection, environment, earth leakage protection settings and
inspection and overhaul schedules.
All mines should review the training and competence requirements of persons
responsible for maintenance of the light fitting to:
• Prevent mistaken assembly,
• Identify cracks in the flameproof assembly.
• Ensure adequate earthing
All mines should review the inspection, testing and maintenance of all electrical
equipment to include the checking of the integrity of earthing of exposed metal
parts and earth continuity testing.
Rob Regan
DIRECTOR
MINE SAFETY OPERATIONS BRANCH
NSW DEPARTMENT OF PRIMARY INDUSTRIES
View more safety alerts at www.minerals.nsw.gov.au. If you would like to receive safety alerts by email, send your details
to safetyalert@minerals.nsw.gov.au .
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