Electricity is such an integral part of our lives at home and in workplace that we can tend to take its power for granted. But here’s a sobering fact.
The Bureau of Labor Statistics (BLS) in the United States of America reported that during 1999, 278 (or about five percent) of work-related deaths in the private sector in the United States resulted from electrocution. Don’t become another tragic statistic.
Electrical accidents in the workplace can, for the most part, be avoided if you use safe electrical equipment and work practices.
How Does Electricity Work?
To handle electricity safely, including working with equipment, you need to understand how electricity acts, how it can be approached, the hazards it presents, and how those hazards can be controlled.
Basically, there are two kinds of electricity:
This guidance notes is about dynamic electricity because that is the kind commonly put to use. Dynamic electricity is the flow of electrons through a conductor. An electron is a tiny particle of matter that orbits around the nucleus of an atom. Electrons of some atoms are easily moved out of their orbits. This ability of electrons to move or flow is the basis of electrical current.
When you activate a switch to turn on an electric machine or tool, you allow current to flow from the generating source through conductors (usually wires) to the area of demand.
A complete circuit is necessary for the controlled flow of electrons along a conductor. A complete circuit is made up of a source of electricity, a conductor, and a consuming device (load).
VOLTS = CURRENT X RESISTANCE
Volts = Current x Resistance, is an equation known as Ohm’s Law. The factors discussed below relate to one another as described by this equation. This relationship makes it possible to change the qualities of an electrical current but keep an equivalent amount of power.
A force or pressure must be present before water will flow through a pipeline. Similarly, electrons flow through a conductor because electromotive force (EMF) is exerted. The unit of measure for EMF is volt.
For electrons to move in a particular direction, a potential difference must exist between two points of the EMF source. For example a battery has positive and negative poles.
The continuous movement of electrons past a given point is known as Current. It is measured in amperes. The movement of electrons along a conductor meets with some opposition. This opposition is known as Resistance. Resistance to the flow of electricity is measured in ohms. The amount of resistance provided by different materials varies widely.
For example, most metals offer little resistance to the passage of electric current. However, porcelain, wood, pottery, and some other substances have a very high resistance to the flow of electricity. In fact, these substances can be used as insulators against the passage of electric current.
What are the Hazards of Electricity?
The primary hazards of electricity and its use are:
Electric currents travel in closed circuits through some kind of conducting material. You get a shock when some part of your body becomes part of an electric circuit. An electric current enter the body at one point and exits the body at another location. High-voltage shocks can cause serious injury (especially burns) or death.
You will get a shock if you touch:
Don’t take any chances with electricity. One mistake can cost you your life. The severity of the shock a person receives depends on several factors:
The effect of an electric shock on a body can range from a tingle in the part touching the circuit to immediate cardiac arrest. A severe shock can cause more damage to the body than is readily visible.
Relatively small burn marks may be all that are visible on the outside. However, a severely shocked person can suffer internal bleeding and severe destruction of tissues, muscles, and nerves. Finally, a person receiving an electric shock may suffer broken bones or other injuries that occur from falling after receiving a shock.
Burn can result when a person touches electrical wiring or equipment that is improperly used or maintained. Typically, such burn injuries occur on the hands.
Arc-blasts occur when high-amperage currents jump from one conductor to another through air, generally during opening or closing circuits, or when static electricity is discharged. Fire may occur if the arcing takes place in an atmosphere that contains an explosive mixture.
Explosions occur when electricity provides a source of ignition for an explosive mixture in the atmosphere. Ignition can be due to overheated conductors or equipment, or normal arcing (sparking) at switch contacts.
Electricity is one of the most common causes of fire both in the home and workplace. Defective or misused electrical equipment is a major cause, with high resistance connections being one of the primary sources of ignition. High resistance connections occur where wires are improperly spliced or connected to other components such as receptacle outlets and switches.
Heat develops in an electrical conductor from the flow of current. This heat raises the temperature of the conductor. As a result, resistance in the conductor increases, further raising the temperature. Thus, circuits conducting a high rate of current and generating more resistance than it can handle, may create enough heat to cause fire.
Causes of Electrical Accidents:
As a power source, electricity can create conditions resulting in bodily harm, property damage, or both. It is important to you to understand how to avoid electrical hazards when you work with electrical power tools, maintain electrical equipment, or install equipment for electrical operation.
Accidents and injuries in working with electricity are caused by one or a combination of the following factors:
Preventing Electrical Accidents:
Protection from electrical hazards is one way to prevent accidents caused by electric current. Protective methods to control electrical hazards include:
Insulators of glass, mica, rubber, or plastic are put on electrical conductors to protect you from electrical hazards. Before you begin to work on any piece of electrical equipment, take a look at the insulation (on electrical cords, for example) to be sure there are no exposed electrical wires. Also use insulated tools.
Electrical Protective Devices:
Electrical protective devices, including fuses, circuit breakers, and ground-fault circuit-interrupters (GFCIs), are critically important to electrical safety. These devices interrupt current flow when it exceeds the capacity of the conductor and should be installed where necessary.
Current can exceed the capacity of the conductor when a motor is overloaded, for example, when you ask a 10 horsepower motor to do the work of a 12 horsepower motor, or when a fault occurs, as when insulation fails in a circuit.
When a circuit is overloaded, the insulation becomes brittle over time. Eventually, it may crack and the circuit fails, or faults.
Fault occurs in two ways. Most of the time a fault will occur between a conductor and an enclosure. This is called a ground fault. Infrequently, a fault will occur between two conductors. This is called a short circuit.
A device which prevents current from exceeding the conductor’s capacity creates a weak link in the circuit. In the case of a fuse, the fuse is destroyed before another part of the system is destroyed. In the case of a circuit breaker, a set of contacts opens the circuit. Unlike a fuse, a circuit breaker can be reused by re-closing the contact. Fuses and circuit breakers are designed to protect equipment and facilities, and in so doing, they also provide considerable protection against shock.
However the only electrical protective device whose sole purpose is to protect people is the ground-fault circuit-interrupter. The GFCI is not an over current device. It senses an imbalance in current flow over the normal path and opens the circuit. GFCIs are usually installed on circuits that are operated near water.
Any “live” parts of electrical equipment operating at 50 volts or more must be guarded to avoid accidental contact. This protection can be accomplished in several different ways. The machinery or equipment can be located:
Any entrance to an area containing “live” parts of electrical equipment must be marked with conspicuous warning signs. These signs should forbid entrance except by qualified persons.
Grounding is necessary to protect you from electrical shock safeguard against fire, and protect against damage to electrical equipment. There are two kinds of grounding:
When a tool or other piece of electrical equipment is grounded, a low-resistance path is intentionally created to the earth. This path has enough current-carrying capacity to prevent any buildup of voltages in the equipment which could pose a hazard to an employee using the equipment. Therefore, never remove the ground prong from a plug because the equipment no longer protects you from short circuits. If you’re touching an ungrounded tool, you will become the path of least resistance to the ground.
Grounding does not guarantee that an employee will never receive a shock, or be injured or killed by electricity in the workplace. However, this simple procedure will substantially reduce the likelihood of such accidents. Be sure any equipment you work on is properly grounded.
Personal Protective Equipment:
If you work in an area where there are potential electrical hazards, your employer must provide you with protective equipment. You must use electrical protective equipment appropriate for the body parts that need protection and for the work to be done. Electrical protective equipment includes insulating blankets, matting, gloves, sleeves, overshoes, face protection, and hard hats among other equipment specially made to protect you from electricity.
Safe Work Practices for Handling Electricity:
If your job requires you to work with electrical equipment, you need to have a healthy respect for the power of electricity. In general, you should be sure that any tools you use are in good repair, that you use good judgment when working near electrical lines, and that you use appropriate protective equipment. Remember – if you’re not sure, don’t touch.
A word to qualified employees about de-energizing electrical equipment before you do any repairs on it or make an inspection. Common sense dictates that electrical equipment be de-energized before working on it, when feasible. (Circumstances where it might be infeasible to de-energize circuitry or equipment before working on it would include hazardous location ventilation equipment or the testing of fire alarm systems, for example, that can only be performed when the system is energized. Qualified persons are only permitted to perform this kind of work.)
Having electrical current unexpectedly present when you are working on a piece of equipment is no joke! Before any repair work or inspection of a piece of electrical equipment is begun by an authorized person, the current should be turned off at the switch box, and the switch padlocked in the OFF position.