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Unformatted text preview: stay inside. Always be aware of what is going on around you. Use proper wiring and connectors Avoid overloads--Do not overload circuits. Test GFCIs--Test GFCIs monthly using the "test" button. Portable GFCI. Section 8 Page 65 S A F E T Y M O D E L S TAG E 3 -- C O N T r O L L I N G H A Z A r D S : S A F E W O r K P r AC T I C E S worker from an electrical service company was changing bulbs in pole-mounted light fixtures in a shopping center parking lot. The procedure for installing the bulbs was as follows: The worker would park the truck near the first light pole. The truck was equipped with a roof-mounted ladder. The worker would extend the ladder high enough to change the bulb, then drive to the next pole without lowering the ladder. A After the worker replaced the first bulb, he got back in the truck and drove toward the next light pole. As the truck moved along, a steel cable attached to the top of the ladder contacted an overhead powerline. The worker realized something was wrong, stopped the truck, and stepped onto the pavement while still holding onto the door of the truck. By doing this, he completed the path to ground for the current in the truck. Because the ladder was still in contact with the powerline, the entire truck was now energized. He was engulfed in flames as the truck caught fire. Fire, police, and paramedic units arrived within 5 minutes. Utility workers arrived in about 10 minutes and de-energized (shut off) the powerline. The victim burned to death at the scene. Below are some ways to prevent contact with overhead powerlines. A safe distance must be maintained between ladders (and other equipment) and overhead lines. OSHA requires that a clearance of at least 10 feet be maintained between aerial ladders and overhead powerlines of up to 50,000 volts. Moving a truck with the ladder extended is a dangerous practice. One way to control this hazard is to install an engine lock that prevents a truck's engine from starting unless the ladder is fully retracted. If there are overhead powerlines in the immediate area, lighting systems that can be serviced from ground level are recommended for safety. If the worker had been trained properly, he may have known to stay inside the truck. Job hazard analysis should always be performed to identify and control hazards. In this case, a survey would have identified the powerlines as a possible hazard, and appropriate hazard control measures (such as lowering the ladder between installations) could have been taken. Check switches and insulation--Tools and other equipment must operate properly. Make sure that switches and insulating parts are in good condition. Use three-prong plugs--Never use a three-prong grounding plug with the ground prong broken-off. When using tools that require a third-wire ground, use only three-wire extension cords with three-prong grounding plugs and three-hole electrical outlets. Never remove the grounding prong from a plug! You could be shocked or expose someone else to a hazard. If you see a cord without a grounding prong in the plug, remove the cord from service immediately. Use extension cords properly--If an extension cord must be used, choose one with sufficient ampacity for the tool being used. An undersized cord can overheat and cause a drop in voltage and tool power. Check the tool manufacturer's recommendations for the required wire gauge and cord length. Make sure the insulation is intact. To reduce the risk of damage to a cord's insulation, use cords with insulation marked "S" (hard Never use a three-prong grounding plug with the ground prong broken off. Page 66 Section 8 service) rather than cords marked "SJ" (junior hard service). Make sure the grounding prong is intact. In damp locations, make sure wires and connectors are waterproof and approved for such locations. Do not create a tripping hazard. Check power cords and extensions--Electrical cords should be inspected regularly using the following procedure: 1. Remove the cord from the electrical power source before inspecting. 2. Make sure the grounding prong is present in the plug. 3. Make sure the plug and receptacle are not damaged. 4. Wipe the cord clean with a diluted detergent and examine for cuts, breaks, abrasions, and defects in the insulation. 5. Coil or hang the cord for storage. Do not use any other methods. Coiling or hanging is the best way to avoid tight kinks, cuts, and scrapes that can damage insulation or conductors. You should also test electrical cords regularly for ground continuity using a continuity tester as follows: 1. Connect one lead of the tester to the ground prong at one end of the cord. 2. Connect the second lead to the ground wire hole at the other end of the cord. 3. If the tester lights up or beeps (depending on design), the cord's ground wire is okay. If not, the cord is damaged and should not be used. Do not pull on cords--Always disconnect a cord by the plug. Use correct connectors--Use electrical plugs and receptac...
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This document was uploaded on 03/14/2014 for the course ECE 482 at University of Tennessee.
- Spring '09