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ELECTRICAL SAFETY LECTRICAL SAFETY IN MINING One flash and you’re ash All incidents are preventable, but only if they can be predicted and someone or something intervenes, writes Chris Towsey. Yet another Queenslander died on the job following an electrocution incident on 12 February 2011. Peter Lamont, Executive Director of the Queensland Electrical Safety Office issued a safety alert, with a terse and concise analysis – “Initial findings indicate that while performing electrical work on a lighting circuit the worker came into contact with live parts. The purpose of this alert is to remind electrical workers of the fundamental safety principles where electrical work is being carried out: Don’t work live; identify, isolate and lock out circuits. Test before you touch to ensure effective isolation. Stay safe. Turn the power off and test before you touch any electrical equipment you intend working on.” Words we all agree with, but unfortunately words we’ve all heard before and will continue to hear, as electrocutions continue in industry in general and the mining industry as well. Without implying any criticism of either Peter or the ESO, is this the best we as an industry can do in 2011? Surely we can go further than just reiterating standard procedures and telling people something they already know. Where is our focus on predicting events before they happen, and on warning devices to pick up nearby electric fields? Every fatality I’ve investigated, I’ve asked “why did they do that?” – actions that the worker knew he shouldn’t be doing. All incidents are preventable, but only if they can be predicted and someone or something intervenes. Australia generally has an ongoing issue with electrocutions, whether these relate to a teenage girl stepping on a fallen power line walking home from a night out (Geraldton, WA, Jan 2011), her two friends who suffered shocks and burns trying to roll her away from the hazard, or a young ceiling insulator firing a staple through a live cable. In 1998-2003, over 30 people a year died from electrocutions, with Queensland and NSW having the highest numbers. 42 AUSTRALASIAN MINE SAFETY JOURNAL The deaths of insulation workers from electrocution was seized upon and used as a political weapon to berate various Federal Government ministers on range of issues ranging from incompetence to financial maladministration. It seems a shame that the media were more interested in the politics than in preventing further deaths from electrocution. In the last 15 years considerable progress and improvement has been made through government interventions. Legislation and regulations have been introduced to mandate the use of safety switches and retro-fitting these to buildings, temporary accommodation and portable equipment. A ‘safety switch’, also known as a Residual Current Device (RCD) or Earth Leakage Switch, is an electrical device that monitors electrical current flowing in the active and neutral conductors of a circuit. The safety switch’s earth leakage sensor responds to any imbalance detected in the circuit and cuts the power in less than 40 milliseconds (under 1/25th of a second). For example, when an appliance has a broken or exposed wire, and electricity passes through this wire to earth, either through the metal body of the appliance that has an earth wire attached to it or because a person acts as the contact to earth, the safety switch recognises this fault and operates instantaneously. In the case of a double-insulated appliance where there is no metal body or exposed metal (and no earth wire), electricity that escapes may pass to earth through a person, e.g. as a result of an exposed wire from a damaged appliance. A safety switch will also operate in such circumstances. Thus, safety switches protect people from earth leakage, regardless of whether or not an earth wire is attached. Section 77 of the Queensland Electrical Safety Regulation 2002 defines an approved safety switch as a RCD that has a Queensland or external approval and a rated residual current of not more than 30mA. The cost of installation of a safety switch on a typical domestic switchboard is estimated by industry sources as between $200 to $250 inclusive of materials, call-out and fitting charges. Why the focus on electrical incidents? What is electricity capable of? Electricity can shock, burn, damage nerves and internal organs and kill people and animals. Due to the nature of electricity, injury can be almost instantaneous and without warning. Depending on current and time, the effects on the human body can range from no effect to ventricular fibrillation, cardiac arrest, breathing arrest and heavy burns. Ventricular fibrillation is the usual cause of death from contact with Australia’s 230/240 volt electricity supply. Recovery from electrocution can be very difficult, with permanent scarring, nerve damage or interference with the functioning of the heart. Electricity can also cause immense damage to property. The release of energy from major faults can be very large and create an explosion or fire. Even minor faults can be a source of fire that can go on to cause serious property damage and risk to life. The difference between an electric shock and a fatal electrocution is merely a matter of current and the degree of insulation. Common causes of electrical shocks and electrocution in Australia There are many factors that can contribute to electrical shock and electrocution incidents, however an analysis of events reported in South Australia in the period from 1994-2003 indicate that about 50 per cent of shocks were due to problems on the distribution network and 50 per cent were due to problems in consumer’s installations. The major causes of electrical shock and electrocution incidents in studies in South Australia were found to be: • 41% exposed metal raised to shock voltages because of electrical faults • 18% contact with live parts • 10% exposed metal raised to shock voltages because of inadequate circuit design • • • • 9% defective insulation 3% electrostatic phenomena 2% loss of earthing 1% lack of earthing • 16% other In Queensland, a series of fatalities in the late 1990s with complaints from relatives of the deceased to the Ombudsman led to a major investigation, and recommendations produced changes that made a dramatic difference to the fatality rate from 2001, as shown below in Figure 4. The Report of the Queensland Ombudsman, The Workplace Electrocution Project - a report on investigations into the adequacy of the responses of government agencies to nine fatal electrical incidents and an analysis of the effectiveness of changes made to