If you thought industry standards had pretty much solved the problem of electrical injuries and fatalities in the workplace, then you should know that is not the case. Although more is now known than ever before about electricity and its effect on humans, accidents and fatalities still occur at an alarming rate.
Electricity is a silent hazard. It’s like a crouching, fire-breathing dragon—patiently waiting for a moment of carelessness or inattention—waiting, waiting, and then striking with lightning speed and terrible force. Results are then measured in overwhelming costs—not only in human suffering—but also in huge financial losses.
• Nearly 20 percent of all workplace fatalities since 1993 have occurred on construction sites, and one of the leading causes of those fatalities was electrocution. (Source: Occupational Safety and Health Administration (OSHA))
• An average of more than 4,000 nondisabling and more than 3,600 disabling electrical contact work-related injuries are recorded annually in the United States. (Source: U.S. Department of Labor)
• In addition, statistics show that one person is electrocuted in the home every 36 hours (Source: U.S. Consumer Product Safety Commission (CPSC)) and one person is electrocuted at the workplace every day. (Source: Occupational Safety and Health Administration (OSHA))
In most instances, electrical industry standards are related to equipment and installations. Employers and apprentice programs tend to teach and implement procedures and practices that rely strongly on equipment and physical circumstances. Equipment construction and installation integrity are important, since some injuries are related to equipment or installation.
However, equipment construction and installation are effective only when conditions are normal. Most injuries occur when conditions are not normal. In normal conditions, electrical equipment tends to require little people involvement. Exposure to a potential electrical hazard is also limited. When something goes wrong, exposure to potential hazards increases.
Understanding electrical hazards
In the early days, electrical energy was primarily used for lighting. Streets and buildings in the major cities in the Northeast were wired for lights. No established codes or standards existed, and electricians had virtually no training. Each installation was effectively designed as it was installed. The dragon began to breathe fire, and economic losses from fires were staggering to the expanding economy. The cost in loss of life was significant.
It was known that electrocution was possible if contact was made with an exposed energized conductor. In fact, the state of New York asked Thomas Edison to design an electric chair that would be used as a humane method of carrying out executions. Although Edison was opposed to execution, he assisted with the design and installation of the first electric chair.
The fire-breathing dragon was on the loose, but electricity’s benefits seemed to outweigh its dangers. Fire was one recognized electrical hazard; electrical shock was another.
As codes and standards developed through the years, these two hazards were the essential focus of the products. As inspection programs and training programs developed, fire and shock were the only electrical hazards that were covered. From the introduction of the National Electrical Code (NEC) in 1897 and the National Electrical Safety Code (NESC) in 1913 until the OSH Act was signed into law in 1970, few questions were asked in the consensus community about work practices.
Arc flash and arc blast—the teeth of the dragon
Several other hazards are now associated with electrical energy: arc flash, arc blast, flying parts and pieces, conducting plasma, and maybe others. Most of these hazards have only recently been recognized. But arc flash and the resulting blast are the hazards that are devastating to unprotected humans. Research has shown that temperatures near an arc can escalate rapidly to 35,000 degrees Fahrenheit. Compare this to the melting temperature of copper conductor, which is 1,981 degrees Fahrenheit.
The real concern is what arc flash energy can do to the human body. Skin tissue is very sensitive to heat. Tests indicate that after only six hours at 110 degrees Fahrenheit, cell equilibrium will start to break down. At 158 degrees Fahrenheit, cell destruction occurs in about one second. The skin’s exposure to temperatures of 200 degrees Fahrenheit for only 1/10 of one second will cause incurable second-degree burns.
An arcing fault is vastly different from a bolted fault. A bolted fault dissipates energy throughout the electrical system, since the system impedance is spread through the conductive components. On the other hand, during an arcing fault, the majority of the impedance is in the arc. Most of the available energy, then, is concentrated in the arc.
The characteristics of the electrical arc include a rapidly escalating temperature. In fact, the arc temperature can reach 35,000 degrees very quickly. The temperature in a typical arc reaches 15,000 to 20,000 degrees in just a few cycles. Most man-made fibers melt at a much lower temperature than 1,000 degrees.
Untreated cotton clothing can ignite if the temperature reaches only slightly more than 1,200 degrees. Two factors impact the amount of energy released in an arcing fault: the amount of available energy (fault current), and the duration of the arc. Current limitation has a major effect on the degree of an arc flash hazard.
An arc blast is the force from the explosion caused by the rapid expansion of air and the transition of solid conducting materials into vapor. This expansion of solid material to liquid and then into a conducting gas is significant—and potentially dangerous.
When an electrical arc occurs, the thermal energy heats the surrounding air, and the air expands. The arc melts and then vaporizes the conductor material, expanding to a volume much greater than the air. As the metal vapor and the heated air try to occupy more volume, tremendous force is generated.
Unless the electrical equipment is designed and tested to be arc resistant, the explosion will open doors and covers, even if they are closed as intended by the manufacturer. At this point, any person in front of the equipment is exposed to the thermal energy and to flying parts and pieces.
How can standards guide work practices?
OSHA defines electrical safety requirements in many different places. OSHA 29 CFR 1910, Subpart S; 29 CFR 1910.269; 29 CFR 1926, Subpart K; and 29 CFR 1926, Subpart V, all define electrical safety requirements. IEC 50110 (“Operation of Electrical Installations”), the IEEE Yellow Book, and NFPA 70E (Standard for Electrical Safety for Employee Workplaces) all address work practices. OSHA uses terms like construction and distribution without effectively defining what is really meant by those terms.
Some OSHA regulations contain sound pressure requirements. However, most are based upon standards that existed over 15 years ago. Due to the lengthy revision process and the limited personnel available, only in rare instances will OSHA regulations be up to date.
Standards such as IEC 50110 and the IEEE Yellow Book that have an international flavor tend to include more information than work practices. For instance, in addition to safety processes and work practices, the IEEE Yellow Book describes maintenance and operational requirements.
The IEC standard provides a process for exemptions based on country preferences. Although these standards are useful tools, neither should be selected as the basis for a safety program.
National Fire Protection Association (NFPA) 70E, Part I, is effectively an extraction from the NEC. There is nothing unique about Part I. Both the NEC and NFPA 70E, Part I, cover an electrical installation. They provide a safe installation when the equipment and processes are operating normally.
Doors must be opened and covers removed when things are not normal. Tests must be conducted, fuses must be changed, circuit breakers must be operated, or other troubleshooting techniques must be performed. NFPA 70E, Part II, suggests processes that will prevent injury.
The role of planning
A person might be testing for voltage when an arcing fault occurs. Among the possible reasons is that the meter is set on the incorrect scale. A meter that meets current consensus standard requirements would avoid this accident. A person might open an motor control center (MCC) door and a broken spring could cause an arcing fault.
A person might be exchanging a de-energized component and accidentally contact an energized point in the same enclosure. In each of these potential situations, the worker does not expect the situation that develops.
Adequate planning is one work process that can help to avoid an accident, and no task should be attempted without it. If the entire task/job cannot be held in memory simultaneously, a written plan should exist. On the other hand, if every step that is necessary to complete the work can be held in memory, a verbal plan is satisfactory.
The degree of formality associated with a written plan is not important. However, it is important for every person involved in executing the plan (written or verbal) to have the same understanding. An effective plan will identify all discrete steps necessary to accomplish the work. The plan will identify hazards that might be encountered as the work proceeds, as well as advise about how to avoid those hazards.
The plan will discuss any personal protective equipment (PPE) needed to avoid injury, should an accident occur. One of the most important aspects of planning is to identify the limits of the work. In other words, every person involved in the work must understand where the “safe zone” associated with the work ends. If the work requires special skills or equipment, the plan must identify them. The idea is that the plan previews the work in an effort to eliminate unexpected events.
How much training is enough?
Both qualified and unqualified persons must be trained. Their training must cover how to avoid exposure to electrical hazards. Each person should understand any electrical hazard to which he or she might be exposed in his or her job. However, perhaps the most important information is that each person understands the limits of his or her abilities. Each person must be able to recognize when to step back and ask for help.
In the past, electrical safety training was an on-the-job effort. A young person learned how to avoid injury from an experienced electrician. There is nothing wrong with on-the-job training, but the trainer must have current information about electrical safety hazards. To be a qualified person, he or she must be familiar with much more than the construction and operation of the equipment.
A qualified person knows about electrical hazards, exposure to them, and how to avoid that exposure. He or she knows how to plan a job or task. He or she also knows how to select adequate PPE and how to wear it.
All injuries can be prevented, but employers and workers must assume the attitude and armor of electrical safety. They must believe that individuals can make a difference, and they must believe that the crusade begins with them. When they do that, the fire-breathing dragon can be transformed into a manageable beast.
Ray Jones has served on several NFPA and ANSI code panels, and contributed to the National Electrical Code and NFPA’s Standard for Electrical Safety Requirements in the Workplace. Jane Jones is a technical writer, specializing in electrical safety. The Joneses work through their firm, Electrical Safety Consulting Services Inc., to help industrial companies with their electrical safety programs.Contact them at (919) 557-7711 or firstname.lastname@example.org