Electrical equipment is used virtually on every site. Everyone is aware with the fact, but unlike most other hazards, which can be seen, felt or heard, there is no advance warning of danger from electricity, and electricity can kill.
Electrical systems and equipment must be properly selected, installed, used and maintained. Hazards arise through faulty installations, lack of maintenance and abuse of equipment. Accidents happen because people are working on or close to equipment which is either:
- Assumed to be dead, but is in fact live; or
- Known to be live, but workers have not received adequate training or adequate precautions have not been taken.
Injuries or death arising from the use of electricity or electrical appliances at construction site is common. Every year, the use of electricity on construction sites results in a number of accidents. People suffer with electric shocks and burns which can in themselves cause serious and fatal injuries. People may also fall from ladders, scaffolds and other equipment as a consequence to the shock, which can result in further injury. Also, those using the electricity may not be the only ones at risk, for example faulty equipment may lead to a scaffold becoming live or short circuits can result in fires. To prevent such accidents, workers must pay attention to safety in using electricity.
Electricity is a form of energy resulting from the existence of charged particles (such as electrons or protons), either statically as an accumulation of charge or dynamically as a current.
Electrical Hazard is a dangerous condition where a worker could make electrical contact with energized equipment or a conductor, and from which the person may sustain an injury.
Electrical hazards can be classified in five categories.
- Electric Shock or Electrocution: It occurs when current flows through the body which results in physical damages in a worker.
- Electrical Burns: They are caused by arc blast or hot conductors.
- Fire: It occurs by overloading a circuit or appliance or by current flowing through high resistance due to faulty wiring.
- Indirect Falls: Falls can also occur from ladders, scaffolds, or other walking and working surfaces due to electric shock.
- Explosions: It can be caused when electricity provides a source of ignition for an explosive mixture in the atmosphere.
Preventive measures that can be considered to reduce the risks of electrical accidents at construction site are as follows:
- Always make sure electric tools are properly grounded or double insulated. The double-insulated tool must have an undamaged outer case.
- Keep ladders, poles, cranes and similar objects that could serve as grounding devices at least 10 feet away from overhead power lines. Electricity is always looking to ground itself, so, does not become a conductor of electricity.
- Inspect electrical cords for all types of exposed or frayed wiring. Use heavy-duty grounded extension cords.
- Cordless equipment or tools which operate from a 110V supply system, which is center-tapped to earth so that the maximum voltage to earth should not exceed 55V, will drastically reduce the risk of death and greatly subdue the rate of injuries in the event of an electrical accident. For other purposes such as lighting, specifically in confined and wet locations, lower voltages can be used which are much safer .
- Ensure that electric plugs are properly grounded and they are completely encased in the shroud. Do not overload circuits, Overloading can lead to overheated wires and arcing, which can cause fires and electrical shock injuries. Use a single plug for each electrical connection; multiple plugs for additional connections should be avoided.
- If performing work in or around electrical panels and generators, wear Electrical rated PPE, including rubber soled shoes and mats, shirts and protective helmets. Watch for identified arc flash hazards in the workplace.
- Avoid mixing water and electricity. Do not stand in water while operating electrical equipment. Keep not only cords, tools and working or walking surfaces dry, but also keep your hands and feet dry.
- Workers should always use plugs to connect equipment to the electricity power. Never insert electric wires directly into sockets otherwise it can cause shock to the workers.
- Electricity together with flammable substances can create severe fire and damages to the workers and workplace. So always avoid leaving flammable substances near switches.
- Installation of electrical appliances, connection of electric wires and repair & maintenance of electrical equipment must be conducted by qualified and trained electrician. Remember to isolate the electricity supply before work.
- Prior to excavation in the vicinity of underground cables, determine the alignment and depth of the cable. Adopt safe excavation practices to prevent damaging of cables.
- Ensure that circuits at construction site are protected by appropriate RCDs, specially the circuits where portable electrical equipment can be connected. They must be tested by operating the test button after connection to a socket or before connecting equipment.
- Tools and equipment must be chosen according to site conditions. DIY tools and domestic plugs and cables are not designed to stand up to everyday construction work. Other restrictions imposed on use of certain equipment by manufacturers must be known to the working personnel to maintain safe working conditions
- If work is to be done in areas where there is a risk of flammable vapours (such as in a petrochemical works), it will be necessary to select specially designed electrical equipment to prevent it acting as a source of ignition due to sparks and overheating. Precautions should be covered in the project health and safety plan and the operator of the premises should be able to provide advice. Specialist advice may also be needed.
Overhead Power Lines
Contact with overhead power lines is one of the most common causes of death and injury. Any work near electric distribution cables or railway power lines must be carefully planned to avoid accidental or unintentional contact. The following steps must be followed so that this aspect can be managed easily with caution: The most common operations leading to contact with overhead lines are:
- Operating cranes and other lifting equipment;
- Raising the body or inclined container of tipper lorries;
- Operating excavators and other earth-moving equipment;
- Handling long items such as scaffold tubes, metal roof sheets, ladders etc.;
- Using MEWPs. (Mobile Elevated Work Platforms)
If contact with the overhead line is likely possible then work must be carried in an area well clear of the line itself. Places where it is not feasible then either the power line must be made dead or suitable precautions must be taken to prevent any danger. For some jobs, it may be necessary for the electricity supplier to isolate or re-route overhead lines to enable work to proceed.
In some cases it may be possible to eliminate the risk involved by altering the work to be carried out, for example by reducing the length of scaffold tubes, ladders or roof sheets to ensure that the line cannot be contacted accidentally.
If plant is operating in the vicinity of an overhead power line then care must be observed and it should be seen that the distance between the plant and the overhead line is at least: 15 m (exclusive of the length of the jib) if the lines are suspended from steel towers; 9 m (exclusive of the length of the jib) if the lines are supported on wooden poles.
In cases where approach is likely, stout, distinctive barriers should be erected at ground level to prevent access Where work is to take place close to overhead lines, detailed precautions should be discussed with the owner of the lines (any work next to any railway where the work is likely to encroach onto railway land should in any case be discussed with the railway operator before work begins). However, the responsibility for ensuring that precautions are adequate remains with the contractors undertaking the work, not with the owner of the power lines.
In addition to the precautions required when working in the vicinity of overhead power lines, Some useful measures can be practiced to avoid accidents caused by overhead lines which are as follows:
- Erect high-visibility barriers at least 6 m away, to prevent inadvertent approach by other site vehicles
- Install clearly marked crossing points beneath the lines at a height specified by the electricity supplier;
- Do not practice storage of materials in the area between the overhead lines and the ground-level barriers.
If a worker comes in contact with electricity, he will suffer from electric shock. The first aid treatment should be given to the casualty.
- The first priority for the rescuer is to avoid becoming a casualty. The rescuer should not touch the casualty with unprotected hands.
- If casualty is still connected to the electrical current, then break the contact by switching off the current, removing the plug, or wrenching the cable free. The rescuer should stand on dry insulating material such as wooden box, clean rubber or plastic mats etc.
- Check breathing and pulse circulation of the casualty. The unconscious casualty, who is breathing and has a pulse, should be placed in the recovery position and monitored until medical assistance arrives.
- If there is a pulse and casualty is not breathing, provide him mouth to mouth ventilation. And if casualty is not breathing and there is no pulse, then cardiopulmonary resuscitation that is CPR must be given to the casualty.