Unformatted text preview: icity is a familiar part of our lives, it often is not treated with enough caution. As a result, an average of one worker is electrocuted on the job every day of every year! According to the Bureau of Labor Statistics Census of Fatal Occupational Injuries Research File for 19922005, electrocution is the fifth leading cause of work-related deaths for 16- to 19-year-olds, after motor vehicle deaths, contact with objects and equipment, workplace homicide, and falls. Electrocution is the cause of 7% of all workplace deaths among young workers aged 1619, causing an average of 10 deaths per year.1
Note to the learner--This manual describes the hazards of electrical work and basic approaches to working safely. You will learn skills to help you recognize, evaluate, and control electrical hazards. This information will prepare you for additional safety training such as hands-on exercises and more detailed reviews of regulations for electrical work. Your employer, co-workers, and community will depend on your expertise. Start your career off right by learning safe practices and developing good safety habits. Safety is a very important part of any job. Do it right from the start. Electrical shock may cause injury or death! Electrical work can be deadly if not done safely. Section 1 Page 1 E L E C T r I C I T Y I S DA N G E rO U S This manual will present many topics. There are four main types of electrical injuries: electrocution (death due to electrical shock), electrical shock, burns, and falls. The dangers of electricity, electrical shock, and the resulting injuries will be discussed. The various electrical hazards will be described. You will learn about the safety model, an important tool for recognizing, evaluating, and controlling hazards. Important definitions and notes are shown in the margins. Practices that will help keep you safe and free of injury are emphasized. To give you an idea of the hazards caused by electricity, case studies about real-life deaths will be described. current--the movement of electrical charge voltage--a measure of electrical force circuit--a complete path for the flow of current You will receive a shock if you touch two wires at different voltages at the same time. How Is an Electrical Shock received?
An electrical shock is received when electrical current passes through the body. Current will pass through the body in a variety of situations. Whenever two wires are at different voltages, current will pass between them if they are connected. Your body can connect the wires if you touch both of them at the same time. Current will pass through your body. Wires carry current ground--a physical electrical connection to the earth energized (live, "hot")--similar terms meaning that a voltage is present that can cause a current, so there is a possibility of getting shocked In most household wiring, the black wires and the red wires are at 120 volts. The white wires are at 0 volts because they are connected to ground. The connection to ground is often through a conducting ground rod driven into the earth. The connection can also be made through a buried metal water pipe. If you come in contact with an Page 2 Section 1 energized black wire--and you are also in contact with the neutral white wire--current will pass through your body. You will receive an electrical shock. conductor--material in which an electrical current moves easily neutral--at ground potential (0 volts) because of a connection to ground Metal electrical boxes should be grounded to prevent shocks. Black and red wires are usually energized, and white wires are usually neutral. If you are in contact with a live wire or any live component of an energized electrical device--and also in contact with any grounded object--you will receive a shock. Plumbing is often grounded. Metal electrical boxes and conduit are grounded. Your risk of receiving a shock is greater if you stand in a puddle of water. But you don't even have to be standing in water to be at risk. Wet clothing, high humidity, and perspiration also increase your chances of being electrocuted. Of course, there is always a chance of electrocution, even in dry conditions. You will receive a shock if you touch a live wire and are grounded at the same time. When a circuit, electrical component, or equipment is energized, a potential shock hazard is present. Section 1 Page 3 E L E C T r I C I T Y I S DA N G E rO U S You can even receive a shock when you are not in contact with an electrical ground. Contact with both live wires of a 240-volt cable will deliver a shock. (This type of shock can occur because one live wire may be at +120 volts while the other is at -120 volts during an alternating current cycle--a difference of 240 volts.). You can also receive a shock from electrical components that are not grounded properly. Even contact with another person who is receiving an electrical shock may cause you to be shocked. A 30-year-old male electrical technician was helping a company service representative test the voltage-regulating unit on a new rolling mill. While the electrical technician went to...
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- Spring '09