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Unformatted text preview: at does not conduct electricity easily 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. Insulation also prevents conductors from coming in contact with people. Page 28 Section 5 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 doubleinsulated. (Double-insulated tools have two insulation barriers and no exposed metal parts.) You need to recognize that defective insulation is a hazard. A damaged live power tool that is not grounded or double-insulated is very dangerous! If you touch a damaged live power tool, you will be shocked! This extension cord is damaged and should not be used. Improper grounding hazards
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 if there is a broken ground wire or plug. If you contact a defective electrical fault current--any current that is not in its intended path ground potential--the voltage a grounded part should have; 0 volts relative to ground Section 5 Page 29 S A F E T Y M O D E L S TAG E 1 -- r E C O G N I Z I N G H A Z A r D S
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. Electrical systems are often grounded to metal water pipes that serve as a continuous path to ground. If plumbing is used as a path to ground for fault current, all pipes must be made of conductive material (a type of metal). Many electrocutions and fires occur because (during renovation or repair) parts of metal plumbing are replaced with plastic pipe, which does not conduct electricity. In these cases, the path to ground is interrupted by nonconductive material. GFCI--ground fault circuit interrupter--a device that detects current leakage from a circuit to ground and shuts the current off If you touch a defective live component that is not grounded, you will be shocked. leakage current--current that does not return through the intended path but instead "leaks" to ground ground fault--a loss of current from a circuit to a ground connection A ground fault circuit interrupter, or GFCI, is an inexpensive lifesaver. GFCIs detect any difference in current between the two circuit wires (the black wires and white wires). This difference in current could happen when electrical equipment is not working correctly, causing leakage current. If leakage current (a ground fault) is detected in a GFCI-protected circuit, GFCI receptacle. the GFCI switches off the current in the circuit, protecting you from a dangerous shock. GFCIs are set at about 5 mA and are designed to protect workers from electrocution. GFCIs are able to detect the loss of current resulting from leakage through a person who is beginning to be shocked. If this situation occurs, the GFCI switches off the current in the circuit. GFCIs are different from circuit breakers because they detect leakage currents rather than overloads. Circuits with missing, damaged, or improperly wired GFCIs may allow you to be shocked. You need to recognize that a circuit improperly protected by a GFCI is a hazard. Overload hazards overload--too much current in a circuit An overload can lead to a fire or electrical shock. Overloads in an electrical system are hazardous because they can produce heat or arcing. Wires and other components in an electrical system or circuit have a maximum amount of current they can carry safely. If too many devices are plugged into a circuit, the electrical current will heat the wires to a very high temperature. If any one tool uses too much current, the wires will heat up. Overloads are a major cause of fires. Page 30 Section 5 The temperature of the wires can be high enough to cause a fire. If their insulation melts, arcing may occur. Arcing...
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- Spring '09