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Introduction Ever since the first discoveries of electricity were made in ancient Greece, people have looked for ways to utilize its power. Today, electricity is an essential part of our everyday life. From heating and cooling, computers, tools, televisions and more, electricity makes our world possible. Electricity is so much an integral part of everyday life that we tend to overlook its dangers. The purpose of this training program is to explain how electricity works, help you understand the hazards and dangers associated with electricity and show you can protect yourself from injury and even death. This program will cover various aspects of electrical safety but should not be considered a substitute for OSHA’s regulations. Your employer should provide additional training as necessary to ensure your safety.
Definitions Conductors - objects/materials that have very little resistance to the flow of electrical current (metal and water). Examples are electrical power lines, extension cords, and power cords. Insulators - objects/materials that resist electrical current. Not considered good conductors of electricity (plastic, glass, porcelain and dry wood). Amperes (amps) - How electrical current is measured. Voltage - The pressure that drives/pushes electrical current. Transformer - A device that increases or decreases volts of electrical current. Grounding - intentionally creating a low-resistance path to the earth for electrical current. Prevents buildup of voltages that could cause an electrical accident. Normally a secondary protective measure.
How Electricity Works A simple analogy will help explain how electricity works. Using electricity is like turning on a water faucet. There is a source of water, a way to transport it and pressure to make it flow. The faucet’s water source is a water reservoir or pump station. A pump provides pressure for the water to travel through the pipes. With electricity, there is a source of electricity, a way to transport it and pressure to make it flow. The source is a power generating plant. A transformer provides the “pressure” or voltage, for the electrical current to travel through the conductors, or electrical wires. The conductors are insulated to keep the current contained and moving to its destination and to help prevent shock, burns and fires.
How Electricity Works Electricity travels in closed circuits, normally through a conductor. Most electrical conductors are made of metal (copper) wires and cables that are then wrapped with an insulator. Electricity always attempts to travel to the ground/earth and looks for the shortest path. Electricity will take the path of least resistance to reach the ground.
OSHA Requirements OSHA has mandated certain requirements for the construction industry. Two types of grounds are required by OSHA. Grounding does not guarantee that you will not get a shock or be injured by an electrical current. It will reduce the risk, especially when used in combination with other safety measures. System or Service Ground - Designed to protect machines, tools and insulation against damage. A “neutral conductor” wire (white or gray in a low-voltage circuit) is grounded at the transformer and at the service entrance to the building. Equipment Ground - Helps protect the worker, should a malfunction cause the tool’s metal frame to become energized, by providing a second path for the current to pass through from the tool or machine to the ground.
OSHA Requirements Employers must provide either Ground Fault Circuit Interrupters (GFCIs) or a scheduled and recorded Assured Equipment Grounding Conductor Program. Ground Fault Circuit Interrupters - A fast acting circuit breaker designed to shut off electric power in the event of a ground-fault within as little as 1/40 of a second to prevent electrocution. Ground Fault - A break in the low-resistance grounding path, from a tool or electrical system, where the electrical current may take an alternate path to the ground through the user.
OSHA Requirements • A GFCI works by comparing the amount of current going to and returning from equipment along the circuit conductors. When the amount differs by approximately 5 milliamperes, the GFCI interrupt current. • Employer is required to provide approved GFCIs for all 120 -volt, single–phase, 15 - and 20 - ampere receptacle outlets on construction sites that are not a part of the permanent wiring of the building or structure and that are in use by employees. • If a receptacle or receptacles are installed as part of the permanent wiring of the building or structure and they are used temporary electrical power, GFCI protection shall be provided.
OSHA Requirements • Receptacles on the ends of extension cords are not part of the permanent wiring and, therefore the cord’s receptacle must be of the GFCI type whether or not the extension cord is plugged into permanent wiring. • GFCIs monitor the current-to-the-load for leakage to ground. • GFCIs require testing on a regular basis. Permanently wired devices test monthly and portable-type GFCIs before each use. • Ground-fault protection, such as GFCIs provide, is required by OSHA in addition to, not as a substitute for, general grounding requirements.
OSHA Requirements Assured equipment grounding conductor program - A written program, covering all cord sets, receptacles which are not part of the permanent wiring of the building or structure, and equipment connected by cord and plug which are available for used by employees. The following minimum requirements apply, though additional tests or procedures are encouraged: • A written description of the program must be kept at the jobsite outlining specific procedures for the equipment inspections, tests, and test schedule and made available to OSHA and to affected persons on demand. • Competent person(s) designated to implement the program.
OSHA Requirements Competent person - One who is qualified to identify hazards, and authorized to take prompt corrective measures. Cord sets, attachment caps, plugs and receptacles, and any equipment connected by cord and plug, must be visually inspected before use each day. Damaged equipment must be removed from use until repaired. Two OSHA-required tests must be performed on all electrical equipment. 1. Continuity Test - Ensures that the equipment grounding conductor is electrically continuous. Use a simple continuity tester, such as a lamp and battery, bell and battery, an ohmmeter or a receptacle tester.
OSHA Requirements 2. Terminal Connection Test - Ensures that the equipment grounding conductor is connected to its proper terminal. Perform this test with the same equipment used in the first test. Tests are required: • Before first use. • After any repairs, and before placing back into service. • After suspected damage, and before returning to use. • Every three (3) months. Maintain a written record of the required tests; identify all equipment that passed the tests and the last date it was tested. The written record should be made available to all affected persons and OSHA upon demand.
Static Electricity Static electricity causes a shock but is generally not as dangerous as the electrical shock discussed later. Static electricity can build up on the surface of an object and can discharge to a person, causing a shock. This occurs more frequently in the winter, when the air is dryer, and you touch a door knob or other metal object. Static electricity can have more serious consequences. Friction cause a high build-up of static electricity at a specific spot on an object. If discharged when sufficient amounts of flammable or combustible substances are present, an explosion can occur. Grounding or other measures should be taken to prevent static electricity buildup.
Electrical Shocks occur when the body becomes part of the electrical current. The current enters the body at one point and leaves at another. Shock occurs when a person contacts: • Both wires of an electric circuit. • One wire of an energized circuit and the ground. • A metal part that becomes energized while they are also in contact with the ground.
Electrical Shock Metallic parts of electrical tools and machines can become energized when a break in the insulation of their wiring occurs. A properly installed equipment grounding conductor provides protection from shock for a person touching an energized tool or machine. Electrical shock can result in a slight tingling to severe burns to immediate cardiac arrest. Wet conditions increase the chances of shock and contribute greatly to low-voltage electrocutions. Small amounts of impurities, such as salt, solvents and acid in water make it highly conductive. Objects that normally are poor conductors of electricity become good conductors when wet. Your skin and wood are good examples. Use extreme caution when working with electricity in wet or damp environments. Should you or a coworker receive a shock or other injury, seek emergency medical attention immediately even if an injury is not apparent.
Burns are the most common injury received from an electrical shock. There are different types of burns that electrical shock can cause and more than one type can occur during a single shock. Electrical burns • Causes tissue damage. • Are most serious and require immediate medical attention Arc or flash burns • Are caused by an electrical arc or explosion near an employee Thermal contact burns • Occur when body touches the hot surfaces of overheated electrical conductors, conduits or other energized equipment; or when clothing catches fire from an electrical arc
Involuntary Muscle Contraction When a person receives an electrical shock, sometimes the muscles contract and “freeze”. • Person is unable to pull away from the circuit. • Exposure to the electricity is prolonged. • Long exposures at low voltages can be just as dangerous as short exposures at higher voltages. If a person is “frozen” to an electrical circuit, do not attempt to pull him free. Turn the power off immediately or use a stick, pole or board made of dry wood or other non-conducting material to push the person free from the current. Excessive electricity flowing through the body can cause serious damage to internal organs. Internal injuries may not be immediately apparent and can be deadly.
Falls When working at elevations, workers risk a fall. Working with or near electrical lines, equipment and other energized objects at elevations creates an additional risk factor for a fall. Sometimes when a person receives a shock, the muscles will have involuntary reactions that cause an employee to be “thrown” away from the electrical circuit. This often results in a fall that can cause a variety of injuries including bruises, fractures and even death. Always use extreme caution when working with energized equipment at elevations and use appropriate fall protection when required.
Other Dangers Other dangerous situations can occur as the result of electrical accidents. • Fires from arcs • Explosions in atmospheres containing flammable gases, vapors, or combustible dusts • Equipment and machinery which “explode” sending fragmented metal in all directions
Causes of Electrical Injuries and Safety Rules The following are the most frequent causes of electrical injuries and ways to reduce the risk. Contact with power lines • Contact utilities for buried line locations. • Watch for overhead lines and buried power line indicators. Post warning signs. Unqualified employees and mechanical equipment should remain at least 10 feet away from overhead lines. • Assume all lines are energized. Lack of ground fault protection • Use Ground Fault Circuit Interrupters (GFCIs) or have an Assured Equipment Grounding Conductor Program. • Test GFCIs according to manufacturer’s guidelines. • Use double-insulated tools and equipment. • Visually inspect all equipment before use.
Causes of Electrical Injuries and Safety Rules Path to ground missing or discontinuous • Ground all power supply systems, electrical circuits and electrical equipment. • Frequently inspect electrical systems to ensure ground is continuous. • Do not remove ground prongs from cord- and plug-connected equipment or extension cords. • Ground all exposed metal parts of equipment.
Causes of Electrical Injuries and Safety Rules Equipment not used as intended Some examples of misused equipment include: • Using multi-receptacle boxes designed to be mounted by fitting them with a power cord and placing them on the floor. • Fabricating extension cords with ROMEX wire. • Using equipment outdoors that is labeled for use only in dry, indoor locations. • Using two-prong adaptor plugs on three-prong cords and tools. • Using circuit breakers or fuses with the wrong rating for overcurrent protection. • Using cords or tools with worn insulation or exposed wires. • Removing ground prongs, face plates and insulation. Always use tools, equipment and materials correctly.
Causes of Electrical Injuries and Safety Rules Improper use of extension and flexible cords Normal wear and tear on extension and flexible cords at the worksite can loosen or expose wires, creating hazardous conditions. • Use factory-assembled cord sets. • Use only extension cords that are 3 -wire type and made for hard or extra-hard usage. • Use only cords, connection devices and fittings that are equipped with strain relief. • Remove cords by pulling on the plug, not the cords. • Continually audit cords on-site. Remove unsafe cords immediately.
Generators Portable generators can also be very dangerous if used incorrectly. • Follow all manufacturers’ safety rules and guidelines. • Inspect before each use. • Keep dry. • Use only undamaged heavy-duty cords that are grounded when necessary. • Use GFCIs according to manufacturer’s guidelines. • Shut down before refueling. • Never use indoors.
Personal Protective Equipment Appropriate PPE required for the job must be provided and worn. Equipment may include: • rubber insulating gloves • hoods • sleeves • matting, blankets • line hose • industrial protective helmets designed to reduce electric shock
Lockout Tagout The proper use of lockout tagout procedures protects you from the accidental or unexpected startup of electrical equipment or machines. Your company will instruct you on the need for, and correct procedures of, lockout tagout.
Conclusion Remember to work safely around electricity. Follow your company’s safety rules and procedures and do not take chances. If and accident does occur seek medical treatment immediately. Your life may depend on it!