“An employee is connecting an exit sign to an energized, 220-volt emergency lighting circuit. While stripping insulation from a hot lead; the lead shorts out, knocking him backward off the sixth step of an eight-foot wooden stepladder. He lands on the back of his head on the cement floor and dies as a result of both the electric shock and his fall”.
This hypothetical accident is exactly the type of scenario that can be prevented by meeting all safety requirements.
Electric shock has three manifestations:
- Burns: Result from electric current traveling through body tissues.
- Muscular contractions: Result when electric current overwhelms the voluntary muscles, which can cause a person to be thrown from or become fixed to the circuit. Remember this rhyme: “AC throws me, DC holds me”.
- Cardiac fibrillation: Results when electric current overwhelms the involuntary muscles, which can cause the heart to beat erratically. At 120-volt and 60-hertz cycles, as little as 50 milliamps of current can cause fibrillation.
The following list provides a general overview of certain electrical safety requirements. For more specific information, refer to OSHA standard 29 CFR 1910.301 through 399 and other specific procedures such as LOTO. Some of the requirements and voltage settings may differ country to country. Please abide by the rules specific to your country, whereas, the OSHA standards cited above could be used as general guidelines.
Much of the guidelines is common sense, balance comes from training and self-discipline.
- As in any other field of work, only trained and authorised personnel are to be permitted to perform electrical work.
- For all contracted electrical work, compliance with OSHA standards, the NEC (National Electric Code, published by the NFPA) or country specific standards are to be followed.
- Employees must be instructed and encouraged to report any obvious hazards to life or property observed in connection with electrical equipment or lines as and when they observe them.
- All employees should be instructed to do a complete visual and practical checks of the equipment and systems before starting actual work.
- Switches must be opened, locked out, and tagged when electrical equipment or lines need to be serviced.
- Portable electrical tools must be grounded or double insulated.
- Electrical appliances such as vending machines, coffee makers, vacuum cleaners, and floor polishers must be grounded.
- Extension cords used in the workplace should have a grounding conductor.
- Extension cords must be inspected and their condition recorded in a written inspection log. OSHA’s electrical standard 29 CFR 1910.305(g) prohibits use of flexible cords in lieu of permanent wiring.
- Permanent extension cords must be inspected every six months for all types of defects. Repairs should be effected immediately on detection of defect.
- Movable extension cords must be inspected every three months for all types of defects. Repairs should be effected immediately on detection of defect.
- According to the NEC, extension cords longer than 150 feet should never be used. Multi-plug adapters should not be used in such operations.
- GFCIs (Ground Fault Circuit Interrupter) must be installed on each temporary 15 or 20-ampere, 220-volt AC circuit at locations undergoing construction, demolition, modification, alteration, or excavation. A GFCI is a device that stops the flow of electricity by opening (or breaking) the circuit when a flow of current to ground is detected. These devices should, obviously, also be installed in locations that are usually wet, such as fountains, rest rooms, and swimming pools. OSHA’s standard 29 CFR 1910.306(j)(s) specifically addresses the use of GFCIs.
- Temporary circuits must be protected by suitable disconnecting switches or plug connectors at the junction with permanent wiring.
- All electrical installations in hazardous dust or vapor areas must meet NEC requirements for hazardous locations.
- Exposed wiring and cords with frayed or deteriorated insulation must be replaced or repaired promptly.
- Flexible cords and cables must be free of splices or taps (splices in a cord used to add another outlet).
- Clamps or other securing means must be used for flexible cords or cables at plugs, receptacles, tools, and equipment, for example, and the cord jacket must be securely held in place.
- All cord cable and raceway connections must be intact and secure.
- For wet or damp applications, electrical tools and equipment must be the appropriate type, or otherwise protected, for such use.
- The location of electrical power lines and cables (overhead, underground, under floor, or other sides of walls) must be determined before digging or similar work begins.
- Use of all metallic measuring tapes, ropes, hand lines, or similar devices with metallic thread woven into the fabric is prohibited when these items may contact energized parts of equipment or circuit conductors.
- Use only wooden or FRP ladders when a ladder or the person using that ladder could contact energized parts of equipment, fixtures, or circuit conductors.
- While disconnecting switches or circuit breakers, label the same to indicate their use or the equipment being served.
- All disconnecting means must be opened before fuses are replaced
- All interior wiring systems must include provisions for grounding metal parts of electrical raceways, equipment, and enclosures.
- All electrical raceways and enclosures must be securely fastened in place.
- Approved cabinets or enclosures must be used to guard against accidental contact with energized parts of electrical circuits and equipment.
- Provide sufficient access and working space around all electrical equipment to permit safe operations and maintenance.
- All unused openings (including conduit knockouts) in electrical enclosures and fittings must be closed with appropriate covers, plugs, or plates.
- All electrical enclosures such as switches, receptacles, and junction boxes must be provided with tight-fitting covers or plates.
- All disconnecting switches for electric motors larger than two horsepower must be capable of opening the circuit without exploding, in the event of the motor stalling. Switches must be rated equal to or greater than the horsepower of the motor.
- Low-voltage protection must be provided in the control device of motors driving machines or equipment that could cause probable injury from inadvertent starting.
- Each motor disconnecting switch or circuit breaker must be located within sight of the motor control device.
- There should be provision for applying LOTO devices to each motor, close to the controller, or a separate disconnecting means must be installed in the circuit within sight of the motor.
- Use a “Buddy” system (using authorised personnel in pairs) while employing personnel on energized lines or equipment over 600 volts.
- Employees who regularly work on or around energized electrical equipment or lines must receive appropriate training on the risks and hazards present and the safety measures to be practiced by them in all their functions.
This article is adapted from BOMI International’s Environmental Health and Safety Issues. More information regarding this is available by visiting www.bomi.org.