INSTRUCTOR’S NOTES: Insulation that is defective or inadequate is an electrical hazard. Usually, a plastic or rubber covering insulates wires. Insulation prevents conductors from coming in contact with each other or with people. Extension cords may have damaged insulation. Sometimes the insulation inside an electrical tool or appliance is damaged. When insulation is damaged, exposed metal parts may become energized if a live wire inside touches them. Electric hand tools that are old, damaged, or misused may have damaged insulation inside. If you touch damaged power tools or other equipment, you will receive a shock. You are more likely to receive a shock if the tool is not grounded or double-insulated. (Double-insulated tools have two insulation barriers and no exposed metal parts.) You need to recognize that defective insulation is a hazard.
INSTRUCTOR’S NOTES: When an electrical system is not grounded properly, a hazard exists. The most common OSHA electrical violation is improper grounding of equipment and circuitry. The metal parts of an electrical wiring system that we touch (switch plates, ceiling light fixtures, conduit, etc.) should be grounded and at 0 volts. If the system is not grounded properly, these parts may become energized. Metal parts of motors, appliances, or electronics that are plugged into improperly grounded circuits may be energized. When a circuit is not grounded properly, a hazard exists because unwanted voltage cannot be safely eliminated. If there is no safe path to ground for fault currents, exposed metal parts in damaged appliances can become energized. Extension cords may not provide a continuous path to ground because of a broken ground wire or plug. If you contact a defective electrical device that is not grounded (or grounded improperly), you will be shocked. You need to recognize that an improperly grounded electrical system is a hazard. 1910.304 (f) Grounding. Paragraphs (f)(1) through (f)(7) of this section contain grounding requirements for systems, circuits, and equipment. (4) Grounding path. The path to ground from circuits, equipment, and enclosures shall be permanent and continuous.
INSTRUCTOR’S NOTES: Hand-held electric tools present a potential danger because they make continuous good contact with the hand(s). Metallic parts of electric tools and machines can become energized if there is a break in the insulation of their wiring. A low-resistance wire between the metallic case of the tool/machine and the ground – an equipment grounding conductor – provides a path for the unwanted current to pass directly to the ground. This greatly reduces the amount of current passing through the body of the person in contact with the tool or machine. Properly installed, the grounding conductor provides protection from electric shock.
INSTRUCTOR’S NOTES: 1910.304 Wiring design and protection (f)(5)(v)(C)(3) (f) Grounding. Paragraphs (f)(1) through (f)(7) of this section contain grounding requirements for systems, circuits, and equipment. (5) Supports, enclosures, and equipment to be grounded (v) Equipment connected by cord and plug. Under any of the conditions described in paragraphs (f)(5)(v)(A) through (f)(5)(v)(C) of this section, exposed non-current-carrying metal parts of cord - and plug-connected equipment which may become energized shall be grounded. [A] If in hazardous (classified) locations (see §1910.307). [B] If operated at over 150 volts to ground, except for guarded motors and metal frames of electrically heated appliances if the appliance frames are permanently and effectively insulated from ground. [C] If the equipment is of the following types:  Refrigerators, freezers, and air conditioners  Clothes-washing, clothes-drying and dishwashing machines, sump pumps, and electrical aquarium equipment  Hand-held motor-operated tools  Motor-operated appliances of the following types: hedge clippers, lawn mowers, snow blowers, and wet scrubbers  Cord- and plug-connected appliances used in damp or wet locations or by employees standing on the ground or on metal floors or working inside of metal tanks or boilers  Portable and mobile X-ray and associated equipment  Tools likely to be used in wet and conductive locations and  Portable hand lamps. Tools likely to be used in wet and conductive locations need not be grounded if supplied through an isolating transformer with an ungrounded secondary of not over 50 volts. Listed or labeled portable tools and appliances protected by an approved system of double insulation, or its equivalent, need not be grounded. If such a system is employed, the equipment shall be distinctively marked to indicate that the tool or appliance utilizes an approved system of double insulation. (vi) Nonelectrical equipment. The metal parts of the following nonelectrical equipment shall be grounded: frames and tracks of electrically operated cranes; frames of nonelectrically driven elevator cars to which electric conductors are attached; hand operated metal shifting ropes or cables of electric elevators, and metal partitions, grill work, and similar metal enclosures around equipment of over 750 volts between conductors. Hazards of portable electric tools: Currents as small as 10 mA can paralyze, or “freeze” muscles - Person cannot release tool - Tool is held even more tightly, resulting in longer exposure to shocking current Power drills use 30 times as much current as what will kill. Double-insulated equipment must be distinctly marked to indicate that the equipment utilizes an approved system of double insulation.
INSTRUCTOR’S NOTES: Most people do not realize that overhead power lines are usually not insulated. More than half of all electrocutions are caused by direct worker contact with energized power lines. Power line workers must be especially aware of the dangers of overhead lines. In the past, 80% of all lineman deaths were caused by contacting a live wire with a bare hand. Due to such incidents, all linemen now wear special rubber gloves that protect them up to 34,500 volts. Today, most electrocutions involving overhead power lines are caused by failure to maintain proper work distances. 1910.333(c)(3). (c) Working on or near exposed energized parts. (3) Overhead lines. If work is to be performed near overhead lines, the lines shall be deenergized and grounded, or other protective measures shall be provided before work is started. If the lines are to be deenergized, arrangements shall be made with the person or organization that operates or controls the electric circuits involved to deenergize and ground them. If protective measures, such as guarding, isolating, or insulating, are provided, these precautions shall prevent employees from contacting such lines directly with any part of their body or indirectly through conductive materials, tools, or equipment. Note: The work practices used by qualified persons installing insulating devices on overhead power transmission or distribution lines are covered by §1910.269 of this Part, not by §§1910.332 through 1910.335 of this Part. Under paragraph (c)(2) of this section, unqualified persons are prohibited from performing this type of work. (i) Unqualified persons. [A] When an unqualified person is working in an elevated position near overhead lines, the location shall be such that the person and the longest conductive object he or she may contact cannot come closer to any unguarded, energized overhead line than the following distances:  For voltages to ground 50kV or below - 10 feet (305 cm)  10 feet (305 cm) plus 4 inches (10 cm) for every 10kV over 50kV. [B] When an unqualified person is working on the ground in the vicinity of overhead lines, the person may not bring any conductive object closer to unguarded, energized overhead lines than the distances given in paragraph (c)(3)(i)(A) of this section. Note: For voltages normally encountered with overhead power line, objects which do not have an insulating rating for the voltage involved are considered to be conductive. (ii) Qualified persons. When a qualified person is working in the vicinity of overhead lines, whether in an elevated position or on the ground, the person may not approach or take any conductive object without an approved insulating handle closer to exposed energized parts than shown in Table S-5 unless: [A] The person is insulated from the energized part (gloves, with sleeves if necessary, rated for the voltage involved are considered to be insulation of the person from the energized part on which work is performed) or [B] The energized part is insulated both from all other conductive objects at a different potential and from the person or [C] The person is insulated from all conductive objects at a potential different from that of the energized part.
INSTRUCTOR’S NOTES: Working in wet conditions is hazardous because you may become an easy path for electrical current. If you touch a live wire or other electrical component-and you are well-grounded because you are standing in even a small puddle of water, you will receive a shock. Damaged insulation, equipment, or tools can expose you to live electrical parts. A damaged tool may not be grounded properly, so the housing of the tool may be energized, causing you to receive a shock. Improperly grounded metal switch plates and ceiling lights are especially hazardous in wet conditions. If you touch a live electrical component with an uninsulated hand tool, you are more likely to receive a shock when standing in water. But remember, you don't have to be standing in water to be electrocuted. Wet clothing, high humidity, and perspiration also increase your chances of being electrocuted. You need to recognize that all wet conditions are hazards.
INSTRUCTOR’S NOTES: OSHA’s electrical safety-related work practice requirements are contained in 29 CFR 1910.331-.335. Electrical accidents are largely preventable through safe work practices. As the instructor you may, at your discretion, include the following safe work practices: Know Where The Hazards Are Properly Maintain Equipment No Exposed Parts Or Energized Surfaces Use Barriers And Devices Where Appropriate No Conductors To Walk On Or Trip On Never Use Plugs Or Receptacles That Can Alter Polarity Properly Plug All Connecting Plug-Ins Install And Use Protective Devices Stay Away From All Unguarded Conductors Never Overload A Circuit Or A Conductor Be Sure Plug And Receptacle Have Proper Mating Configuration Don’t Use Nails, Staples, Screws, Etc, To Attach Or Fasten A Cord Or Plug Two Conductor Cords Are Illegal Damaged Cords Should Never Be Used Ensure Enough Slack To Prevent Strain On Plug Or Receptacle A Plug-Receptacle Should Have At Least 8 Ounces Of Contact Tension Cords Should Be Kept Clean And Free Of Kinks And Insulation Breaks Cords Crossing Vehicular Or Personnel Passageways Should Be Protected, Sign Posted, And Used Temporarily Or In An Emergency Cords Should Be Of Continuous Length And Without Splices
INSTRUCTOR’S NOTES; OSHA’s electrical safety-related work practice requirements are contained in 29 CFR 1910.331-.335. All employees should be trained to be thoroughly familiar with the safety procedures for their particular jobs. Moreover, good judgment and common sense are integral to preventing electrical accidents. When working on electrical equipment, for example, some basic procedures to follow are: • de-energize the equipment, • use lockout and tag procedures to ensure that the equipment remains de-energized, • use insulating protective equipment • maintain a safe distance from energized parts
INSTRUCTOR’S NOTES: Emphasize to students the need for training before doing any work. Lock-out/tag-out is an essential safety procedure that protects workers from injury while working on or near electrical circuits and equipment. Lock-out involves applying a physical lock to the power source(s) of circuits and equipment after they have been shut off and de-energized. The source is then tagged out with an easy-to-read tag that alerts other workers in the area that a lock has been applied. Also, lock-out/tag-out prevents the unexpected release of hazardous gasses, fluids, or solid matter in areas where workers are present. Deenergizing Electrical Equipment The accidental or unexpected sudden starting of electrical equipment can cause severe injury or death. Before ANY inspections or repairs are made, the current must be turned off at the switch box and the switch padlocked in the OFF position. At the same time, the switch or controls of the machine or other equipment being locked out of service must be securely tagged to show which equipment or circuits are being worked on. For more information on the Lockout/Tagout (LOTO) standard, 1910.147, see the Lockout/Tagout Interactive Training Program at the osha web site, www.osha.gov and find this reference under “OSHA Advisors”.
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Electrical Safety www.Career Safe Online.com Electricity is an important part of our modern world and sometimes it is easy to forget just how dangerous it can be. Given the correct circumstances, electricity can cause serious injuries or even death.
Thermal contact burns can occur when electricity ignites combustible material.
Thermal contact burns
Falls www.Career Safe Online.com Another common type of electrical injury is falling. Workers who experience a shock on elevated work surfaces such as platforms, ladders or scaffolds can fall resulting in serious injury or death.
A ground fault circuit interrupter (GFCI) detects current leaking from a circuit to ground and shuts the current off.
Ground fault circuit interrupters
Defective Insulation www.Career Safe Online.com To protect you, electrical wires are insulated by a plastic or rubber covering. Insulation prevents conductors from coming in contact with each other and with people. Make sure the insulation of tools and cords you are using is not damaged.
Grounding www.Career Safe Online.com When an electrical system is properly grounded, there is a path that allows the current to travel to the earth (the ground). When any electrical system is not properly grounded, a hazard exists.
Power Tools www.Career Safe Online.com Power tools that are damaged or not properly maintained can cause you to be seriously injured. If you touch a metallic part of a power tool that is energized because of damaged insulation or improper grounding, you could be shocked.