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The most common and serious electrical injuries occur when electrical current flows between the hands and feet. This happens when a person touches an energized line. The electrical energy is looking for the shortest path to the ground, and it will pass through the body to the feet to reach it. When this occurs, a persons heart and lungs are frequently damaged by the electrical energy. Placing an insulator between the energy and the point of physical contact is one method of protection. Porcelain, rubber, pottery and dry wood offer substantial resistance to the flow of electricity, and are therefore good insulators. These materials can often protect a person from electrical shock. Precautions for avoiding electrical shocks include, but are not limited to, the following: Always make
sure electric tools are properly grounded or double insulated. The double
insulated tool must have an undamaged outer case and be clearly labeled
as "double insulated" by the manufacturer. HIGH VOLTAGE SAFETY More than 1000 employees are killed and another 30,000 injured each year from electrical shock. Hands are frequently involved in an electrical injury since they are the most common source of contact with the electrical current. However, damage to other parts of the body may be more extensive and life threatening. Severe electric shock can result in cardiac arrest due to ventricular fibrillation, massive fluid loss into swollen tissues, and kidney failure caused by an overload of muscle protein from damaged muscle and infections. Electrical injuries are often more severe than they appear to be from the outside. Injury occurs not only at the contact site, but also along the path the electricity takes, and at the exit location. Frequently, there is also extensive muscle damage that will not be evident from a visual examination of the skin. These deep tissue injuries cause severe swelling that require a deep incision extending from the hand to the shoulder to relieve the pressure. If this is not done, the mounting pressure from the swelling will shut off the blood supply by compressing the arteries, rapidly destroying any remaining healthy tissue. Extensive dead skin removal is often necessary to prevent massive infection. Deep burns result in unsightly scars that will often continue to enlarge for 12-18 months after the burn occurs. These scars are not only a cosmetic problem, but may seriously interfere with joint function because motion increases the tension across the wound, which tends to produce even more scar tissue. More than 90% of fatalities occur when contact is made with a "hot" wire, or energized equipment housing by a person who was well-grounded Most of these injuries would probably have been prevented if a GFI -- ground fault interrupter -- had been installed on the circuit. A GFI is not an overcurrent device, but is placed across the line to continuously monitor the current flowing from the source and compare it to the current returning to the source. If the difference is 6 milliamperes or more, it opens the circuit almost instantly. This is important because it has been determined that 100 milliamperes flowing through the body for only 2 seconds can cause death by electrocution. 100 milliamperes is not much current when you consider that a portable electric drill draws 30 times that much. Incidentally, the "let go" threshold that causes freezing to the circuit is about 20 milliamperes. Make sure that the equipment you are working with has a GFI -- it could save your life. To work on high voltage (over 600 volts), you must have a minimum of two years of training, experience with high voltage circuits, have demonstrated that you are familiar with the work to be performed, and the hazards involved with high voltage work according to OSHA. Other safety
requirements that must be followed include using insulated gloves for
current over 300 volts, eye protection, and lockout/tagout if working
on energized parts of equipment or systems. Conductive measuring tapes,
ropes, or similar devices obviously cannot be used around exposed conductors,
and conductive fish tapes cannot be used if they will be entering enclosures
with exposed conductors. Hazardous locations require specially designed electrical equipment to protect people and property against increased fire potential. Certain electrical components and instruments are engineered specifically for locations designated as hazardous due to the possible presence of ignitable quantities of flammable liquids, gases, vapors, combustible dusts, or ignitable fibers. Hazardous locations are classified as Class I, Class II, or Class III. The class is dependent on the physical properties of the combustible materials which may be expected to be present. Class
I locations are those in which flammable vapors or gases may be present.
Before selecting electrical equipment and the associated wiring for any hazardous location, the exact nature and concentrations of the flammable materials must be determined. An electrical fitting or device which is safe for installation in an atmosphere of combustible dust may not be safe for operation in an atmosphere containing flammable vapors or gases. These electrical fittings are specifically designed for each hazard. Class I electrical wiring applications are commonly referred to as "Explosion Proof." Properly installed and maintained class I equipment will not ignite the dangerous atmosphere surrounding it, and is approved for use in specific hazardous areas. Explosion proof fittings are designed to contain any arcing, intense heat, and explosions. These fixtures are distinctive in appearance. Class II locations may require "Dust-ignition proof" fixtures. These fixtures are designed in such a manner that their construction prohibits ignitable amounts of dust from entering the devices. Hazardous
areas that must have approved electrical installations include, but are
not limited to: locations where volatile flammable liquids are transferred
from one container to another; interiors of spray booths; in the vicinity
of spray painting operations where volatile flammable solvents are used;
locations where dangerous concentrations of suspended dust are likely,
such as in grain elevators; and gasoline fueling stations. Remember to
think electrical safety when proposing any electrical systems that will
be located in a hazardous location.
Remember,
taking the time to bond or ground when working around flammable vapors,
gases, and dusts will help prevent a serious accident. The process of forcing electrons to move through a material creates electricity. A standard generator performs this process. The best material for carrying electricity is a "conductor." Most metals are excellent conductors and the most common material used for electrical wiring is copper. In order to provide protection from direct contact with the conductor, an "insulator" is used as a cover around the conductor. Electrons will not move easily through insulators such as most plastics and rubber. Insulators and proper grounding help to prevent electrical shocks. Typically, electricity is provided to your building or facility by way of underground or overhead power lines originating from a nearby electrical power plant. The power lines feed into your electrical breaker panel(s). Each breaker in a panel represents a circuit supplying electricity to a designated area of your building. The majority of your electrical safety considerations begin at the breaker panel. Here are some basic safety considerations for all panels: > The breaker panel should be readily and easily accessible at all times. Do not store any items on the floor area directly in front of the panel. Maintain an aisle in front of the panel that is at least three feet wide. > The panel should have a closed cover. The cover should not be locked unless work is in progress requiring that the cover be locked as part of the lock out procedure. > The panel should have a directory index identifying each individual circuit breaker. It is usually found secured to the inside face of the cover. The directory should identify the various receptacles, general area, or equipment serviced by each circuit breaker. > There should not be any missing breakers or other openings in the breaker face plate that would allow you to contact the "hot" electrical bus at the back of the panel. Openings could also allow dust or dirt to accumulate inside the panel box interior. This dust may damage the breakers to the point where they will not "trip" when needed. > Breakers should never be taped or otherwise secured in the "closed" (on) position. Each circuit breaker and circuit are rated for a maximum amount of amperes. An ampere is the unit for measuring the rate of flow of electricity through the circuit. If the rate of flow in the circuit exceeds the designated maximum for the breaker, the breaker "trips" and stops the flow of electricity. If the breaker is not allowed to trip, insulators could melt from excessive conductor heat caused by electricity flowing too fast. Fires or increased exposure to shock may also occur. > Lastly, breakers should not be taped in the "open" position as a means of de-energizing the circuit during repair or maintenance activity. Open breakers should be properly tagged or locked out.
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CFR 1910 Subpart S Electrical Training Acknowledgement
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