This training session covers electrical safety for unqualified persons. Unqualified persons are machine operators, operators of powered industrial

Transcription

1 This training session covers electrical safety for unqualified persons. Unqualified persons are machine operators, operators of powered industrial trucks, construction workers, and others who are not qualified to perform electrical work, but who need to know important information about the hazards of electricity and how to prevent serious injury. Additional training is required for workers who are qualified to work on exposed electrical equipment and wiring. 1

2 The objectives of this session are to inform unqualified people about the basic points of electrical safety. By the end of the session, you will be able to: Describe the hazards of electricity; Identify and avoid common electrical hazards; and Follow safe work practices around electrical equipment. 2

3 How does electricity work? In order to recognize and avoid the hazards, it s important to understand the basics of electricity. Electricity is the flow of electrons, similar to the flow of water through a pipe. All electricity follows what s known as Ohm s Law : V, or voltage, equals I, or amperage, times R, or resistance. Let s compare electricity to the flow of water in a pipe to explain the relationship between voltage, amperage, and resistance. Voltage can be compared to pressure or force. The higher the voltage, the more likely it is to cause injury, just like the difference in force between high and low water pressure. Amperage can be compared to flow. Higher amperage means a higher volume of electricity, in much the same way as a largediameter pipe will allow a greater flow of water than a small-diameter pipe. (Higher amperage means higher risk of injury.) Finally, resistance can be compared to restrictions in a water pipe. When the flow of electricity has resistance, this generates heat, which can result in fires, burns, or damaged equipment. 3

4 Here are some of the more common electrical hazards that you might encounter: Contact with power lines, either overhead or buried in the ground, or contact with equipment that is touching these lines; Contact with electrical equipment or tools that are damaged or have damaged insulation; Improper wiring or repairs or loose connectors that can cause a short circuit; Overloading of circuits or wiring; or Unsafe work practices, such as using a metal ladder near or against power lines. Take a moment to think about some of the potential electrical hazards you might encounter in your workplace. 4

5 Electrical injuries can be very serious and sometimes even fatal. Electrical injury for the purpose of this discussion is the passing of electrical current through a portion of the body, thereby using the body as an alternate conductor of the current. Here are some common types of electrical injuries: Cardiac arrest and respiratory failure resulting from electrical shock or electrocution; Muscle, nerve, and tissue destruction from electrical current passing through the body; Burns from arc flash and arc blast; Thermal burns from contact with sources of electricity; and Secondary injuries, such as falling from a ladder after receiving an electrical shock. 5

6 In basic terms, here is how electrical shock occurs: Fundamentally, a shock occurs when electrical energy contacts your body. A shock can occur when you contact two exposed currentconducting wires and your body becomes part of the electrical circuit pathway. An example would be touching the hot and neutral wires of a standard 120-volt system. Another example is touching different phases in a 480-volt, three-phase system. If there is contact with live wires or other electrical components, this suggests that they are not insulated or enclosed properly. Another way to get shocked is for you to become a part of the path between a live wire and the ground. Electricity always takes the path of least resistance, and your body can become part of the path because it is a good electrical conductor. If you touch a live wire with your hand, electricity can travel through your body and exit through your foot. This kind of electrical shock is, unfortunately, very common. 6

7 The severity of an electrical shock depends on three primary factors: First, the amount of electrical current or amperage the more current, the more dangerous it is. Amperage is like the volume of water flowing through it the greater the volume, the greater the hazard. Second, the duration, or length of time, the current passes through the body. The longer the duration, the more dangerous it is. Finally, the specific path the current takes through the body; it is most dangerous when it travels through the chest, affecting the heart, lungs, or the brain. Note that you cannot know the path the current might take through your body once it enters, but it may enter at one location and exit at another. 7

8 This slide shows the effects of different flows of electrical currents or amperage on the body when the current flows for 1 second. Note that the designation ma means milliamp, or one one-thousandth of an amp. You ll see that a small fraction of 1 amp of electricity is enough to cause a painful shock, respiratory arrest, and even death. At more than 1 amp, cardiac arrest and death are likely. According to the slide, a shock of 0.5 to 3 milliamps will cause you to feel a faint, tingling sensation. At 6 to 30 milliamps, you will feel a painful shock and experience severe muscle contractions to the point where you cannot control your muscles. At 50 to150 milliamps, you will experience an extremely painful shock, along with respiratory arrest, severe muscle contractions and, possibly even death. A shock of 1 to 4 amps, or A, will cause ventricular fibrillation and nerve damage. You are likely to die from a shock of this magnitude. And finally, at 10 amps, you will experience cardiac arrest, severe burns, and probably death. Now think about common everyday electrical equipment and appliances. For example, a 100-watt lightbulb has 833 milliamps of electricity flowing through it, which could be enough to kill you. A typical kitchen toaster has more than 9 amps of current, which is certainly enough to kill you. So remember, the electrical equipment we use every day has enough current to cause serious injury and death if we re not careful. 8

9 Electrical shock causes many kinds of serious injuries. Electrocution simply means that the shock is powerful enough to cause death. Hand-held power tools typically carry more than enough current to cause electrocution. Injuries from electrical shock happen because electricity follows the path of least resistance which, in the body, means your blood, organs, and tissue. Electrical current can damage nerves and body organs. Burns occur because of the resistance of the skin and body as electricity flows through it. And, secondary injuries occur when someone receives an electrical shock and as a result has another type of accident. An example would be someone on a ladder with an electric drill, who receives a shock and falls off the ladder. Another example would be someone working on a machine who gets a small shock that causes him to pull his or her hand or arm back quickly, striking a piece of metal and causing serious trauma to the hand or arm. 9

10 Arc flash and arc blast are types of electrical accidents that are extremely dangerous. An arc flash occurs when electricity travels through the air. This can happen when electrical devices such as circuit breakers and disconnects are opened and closed, when energized equipment is touched with a tool, or when equipment fails. An arc flash lasts only a fraction of a second, but it can create temperatures of up to 35,000 degrees, which is enough to vaporize metal. Needless to say, an arc flash causes severe skin burns. An arc flash can also travel consider it a lightning bolt of sorts. Being in the path of the arc flash can cause traumatic injury. Therefore, always position yourself so that you are not in the pathway in the event of an arc flash. An arc blast is a pressure wave from an arc flash it is essentially an electrical explosion that causes severe injuries and death, as well as major damage to facilities and equipment. 10

11 Electrical burns are a very common and serious injury related to electrical shock. Electricity in the body generates heat because the body produces resistance. The heating of body tissues results in electrical burns. Second-degree and third-degree burns can occur on the skin, or they may be internal, so that the person may not look seriously injured. While electrical burns may look minor from the outside, they might be severe on the inside because of the damage they have caused to internal organs and tissues. Thermal burns also can occur from contacting surfaces that are extremely hot because of electricity, or when clothing or equipment catches fire. 11

12 It s time for an exercise. On this screen, you ll see various amperage amounts on the left, followed by effects on the body on the right but these are not matched correctly. Can you match them correctly? Here are the answers how did you do? 0.5 to 3 milliamps Faint, tingling sensation 6 to 30 milliamps Painful shock; muscle contractions severe; cannot control muscles 50 to 150 milliamps Extremely painful shock; respiratory arrest; severe muscle contractions; death may occur 1 to 4 amps Ventricular fibrillation; nerve damage; death is likely Greater than 4 amps Cardiac arrest; severe burns; death is probable 12

13 Do you understand the hazards of electricity and the injuries it can cause in the workplace? Now it s time to ask yourself if you understand the information presented so far. It is important for your safety that you understand the hazards of electricity and the injuries it can cause. 13

14 Now we ll discuss what to do in the event of an electrical shock and review the safe practices and procedures that will help make sure an electrical shock doesn t happen in the first place. Proper emergency response and first aid can be a lifesaver in the event of an electrical shock. If a person is shocked: Do not touch the person if he or she is still being shocked. This is very important! The electrical charge could pass through to you. Shut off the electrical equipment that is causing the shock, if the shock is continuing. Call for trained first-aid personnel immediately; or If you are appropriately trained, administer first aid and cardiopulmonary resuscitation, or CPR, as necessary. 14

15 Electrical shock often causes ventricular fibrillation, or not producing a proper heartbeat. If that happens, you may need to use an automated external defibrillator, or AED, to monitor the situation and help start the heart beating properly again. Be sure you have been trained to use an AED correctly before you attempt to use it. If a person has no pulse, it may be advisable to use an automated external defibrillator (AED). A person is said to have ventricular fibrillation when the brain is sending signals to the heart but the heart is not able to produce a beat. An AED can help in these situations, even if CPR is not effective. An AED works by shocking the heart so it can restore a normal beating rhythm. AEDs can dramatically increase survival rate when used properly and in the first few minutes of when a person is suffering a cardiac arrest. Many AEDs have a built-in system that talks the user through the instructions. However, if your organization has an AED on-site, you should be trained to use it properly. 15

16 Now let s go on to discuss ways to avoid electrical shock in the first place. One very good rule is to stay away from power lines. Stay at least 10 feet away. Keep equipment at least 10 feet away. Add 4 inches to the 10-foot distance for every 10 kilovolts, or kv, over 50 kilovolts. That means that if the voltage of the power line is 138 kilovolts, the minimum safe distance is 13 feet instead of 10 feet. Don t dig any holes or trenches in the ground until you have confirmed that there are no buried power lines or other utilities in the area. This is often known as Call before you dig. Also, many buried utility lines have induced electrical currents applied as corrosion protection. Under certain circumstances, these can have the potential of creating injuries if the conduit is contacted. 16

17 Damaged equipment and insulation, loose connectors, or lack of grounding can result in serious electrical hazards. Stop using, and report to your supervisor: Any damaged electrical covers on electrical panels, junction boxes, and other equipment where live electrical parts and wiring may be exposed. Damaged tools that may expose live electrical parts and wiring to a person. Report the damage to your supervisor. Electrical cords, which are easily damaged, exposing live wires; and Damaged equipment. 17

18 Ensuring that all electric-powered tools and equipment are properly grounded is another good way to prevent an electrical shock. Remember that electricity always takes the path of least resistance to the earth or ground If there is no safe path to the ground, exposed parts can become energized. The purpose of grounding is to provide a safe path for electricity to travel to the ground. If the grounding path is broken for instance, by not having a ground prong on a plug electricity will take the path of least resistance, which may be through your body. Electric power tools and equipment must be grounded or double insulated. Double-insulated tools do not have to be grounded because they are designed not to have electrical hazards as long as their insulation has not been damaged. This kind of tool will be marked with a symbol of a square within a square or will bear the words Double Insulated. If these designations aren t there, the equipment should be grounded. 18

19 Circuit protective devices are designed to protect wiring and equipment in the system from being damaged by too much current, so it s important to understand their purpose and to know what to do if they trip. Devices such as circuit breakers and fuses are intended to allow a certain amount of amperage into the circuit before tripping, blowing, or otherwise breaking the circuit. Don t reset a circuit breaker or fuse unless you are qualified to do so. If something trips or blows, that may be a sign of a problem, such as a short or some other hazard. A qualified employee should inspect the system before it is reset. Finally, for any problem involving a circuit protective device, call a qualified person to investigate rather than taking chances with a potential electrical hazard. 19

20 A ground-fault circuit interrupter, or GFCI, provides excellent protection against electrical shock. A GFCI detects the amount of current going to and flowing from equipment along the conductors or wires plugged in through the outlet. When the amount of current going to equipment differs from the amount returning because of a malfunction or ground-fault, the GFCI will trip, or shut off the current, before a serious shock can occur. GFCIs trip at about 5 milliamps in a fraction of a second. It is still possible to receive a brief shock before the GFCI trips, but it trips so quickly that the shock won t be harmful. If a GFCI keeps tripping, a serious problem may exist. Don t assume that the GFCI is defective and substitute a non-gfci outlet. Instead, have a qualified person check for the cause of the tripping. Finally, GFCIs need to be tested periodically. The test button should be pushed according to the manufacturer s instructions. 20

21 Following lockout/tagout procedures is an essential way to prevent serious electrical shock. These procedures lock, block access to, or warn people away from sources of electricity and other hazardous energy used by machines and equipment while they are shut down and repaired or serviced. Devices that prevent access to hazardous energy, or that clearly warn people to stay away from hazardous energy, are known as lockout/tagout. Lockout ensures that equipment is not accidentally restarted by making sure that it is shut down, de-energized, and locked. Tagout is used where lockout is not feasible and only if the tags provide protection that is equal to the protection of a lockout program. It involves placing warning tags on the equipment. Always follow the requirements of the lockout/tagout program and procedures in your workplace. 21

22 Follow safe work practices for working around electricity. Most such practices are simply commonsense rules to keep you from being shocked. Only qualified persons are allowed to work on exposed electrical equipment or wiring; Always wear proper safety equipment, such as insulating gloves, rubber boots, and insulating sleeves; The work area should be well-illuminated so that you can see if there are any electrical hazards present; and Use nonconductive ladders for working anywhere near electrical equipment. Examples are wooden and fiberglass ladders. 22

23 Don t wear clothing that can conduct electricity when working with electric-powered equipment. This includes clothing with exposed metal, such as snaps and zippers, metal hard hats, or wire-mesh gloves; Don t use conductive liquids such as water or for that matter, any conductive items anywhere near exposed electrical equipment; and Do not defeat or try to circumvent electrical interlock devices. 23

24 Make sure you know how to use portable electrical equipment, such as power tools, safely. Before you use such equipment: Inspect it for damage. Never use it if it smokes or sparks. In particular, make sure the cord is not damaged and that the ground prong is present, unless it is a double-insulated tool. If it is double insulated, make sure there is no damage and the insulation properties are not compromised. Don t lift portable electrical equipment by the cord, or pull the plug by tugging on the cord. This could damage the connection from the cord to the equipment. Make sure your hands are dry before plugging or unplugging electrical equipment. Finally, always plug the equipment into a GFCI outlet if the work area is wet or has moisture present and when working at construction sites. 24

25 It s extremely important to stay away from electrical work areas that is, areas where qualified personnel are working on energized electrical equipment. These areas need to be isolated so that unqualified personnel are not exposed to electrical hazards. Alerting techniques used to keep these areas isolated include safety signs and tags, barricades, and attendants guarding the area. Never try to go around or ignore these warning methods. 25

26 Always follow the rules and guidelines of our electrical safety program. This written program includes: Responsibilities; Procedures; Safe work practices; and Personal protective equipment, or PPE, for work that may involve electrical hazards. And remember that only qualified personnel may work on exposed, energized electrical equipment. 26

27 It s time for another exercise. You will see a series of six statements appear on the screen. Decide if they are safe practices or unsafe practices. Work on electrical equipment if qualified this is a safe practice. Illuminate work area this is a safe practice. Wear conductive apparel this is an unsafe practice. Use nonconductive ladders this is a safe practice. Use conductive liquids near electricity this is an unsafe practice. Defeat electrical interlocks this is an unsafe practice. 27

28 Now it s time to ask yourself if you understand the information presented so far on electrical safety practices. In the previous slides, we ve covered: First aid; Electrical equipment; Electrical circuits; Lockout/tagout; Safe work practices; and Our electrical safety program. It is important for your safety that you understand these topics. 28

29 The key things to remember about electrical safety include the following: Exposure to electricity is dangerous it can cause electrocution, shock, electric and thermal burns, arc flash and arc blast burns, and secondary injuries such as falls. Watch carefully for possible electrical hazards for instance, never use damaged tools, cords, or electrical equipment. Always follow safe work practices, including proper emergency response procedures. Always follow our electrical safety program, which is designed to protect you and other workers from electrical hazards. And finally, seek assistance from a qualified person whenever you have any doubt about electrical safety or think there might be an electrical hazard. Too many things can go wrong with electricity for you to take risks. 29