Avoiding arc flashes
The injuries can be catastrophic. Experts say they’re preventable.
In mere seconds, an arc flash incident can wreak havoc and change lives forever.
If they don’t prove fatal, arc flash injuries can result in severe burns, loss of hearing and/or sight, and concussions, as well as other medical problems stemming from flying shrapnel and getting knocked to the ground.
“Simply put,” OSHA states, “an arc flash is a phenomenon where a flashover of electric current leaves its intended path and travels through the air from one conductor to another, or to ground.” The electrical explosion caused by the event can reach temperatures as high as 10,000° F. It also can register sound levels as high as 140 to 160 decibels – roughly the equivalent of standing 100 feet from a jet taking off.
In 2018, the most recent year for which Bureau of Labor Statistics data is available, more than 160 deaths resulting from exposure to electricity, as well as 2,000 lost-time injuries and illnesses, were recorded.
Here are some reasons why, as told by experts, arc flash incidents happen and their advice on how to avoid them.
Lack of maintenance is a major reason why arc flash incidents occur. If not properly removed, for instance, dust or other materials can build up and create a path for electricity to travel.
Corrosion of electrical equipment is another issue, according to Thomas Domitrovich, vice president of technical sales at power management company Eaton Corp. and member of multiple National Fire Protection Association standards committees.
“There are many different maintenance items that, if not addressed, could result in equipment failure,” Domitrovich said. He pointed to OSHA regulations that call for equipment such as pull boxes, junction boxes and fittings to have covers. These regulations also require each outlet box to have “a cover, faceplate or fixture canopy” in completed installations. These are especially important in businesses where work activities generate airborne powders or other fine materials, including food processing factories.
Associate Editor Alan Ferguson discusses this article in the June 2020 episode of Safety+Health's “On the Safe Side” podcast.
“When you remove a circuit breaker, there’ll be a hole there where the breaker was,” Domitrovich said. “You need to plug all of those holes. So it’s a lot of, you would think, commonsense stuff that people just don’t do, unfortunately, because, for whatever reason, they didn’t have the mechanism to block that hole. So they just said, ‘I will get it later.’ And then later never comes.”
Water and intrusions from animals into an electrical system, including rats, snakes and even armadillos, are among the other causes of arc flashes. Lack of maintenance can also cause components to falter when an employee tries to work on them.
“Sometimes things don’t break until someone starts interacting with them,” Domitrovich said. Recommended electrical maintenance practices are detailed in the NFPA 70B standard.
“Poorly designed or cheaped-out equipment that just barely meets the [National Electrical Code] standard,” is another cause of arc flash, said Hugh Hoagland, senior partner and co-founder of e-Hazard, an electrical/arc flash training and consulting services company.
Hoagland and Domitrovich advocate safety by design. Examples of this concept include remote racking systems, which let operators install and remove electrical devices while remaining outside the flash protection boundary.
NFPA’s 70E standard on electrical safety in the workplace – which is the basis of part of OSHA’s electrical standards and provides guidelines on how to comply with its regulations – has charts (Tables 130.7(C)(15)(a) and (b)) on boundary distances depending on the equipment involved.
“OSHA is the ‘shall’ and 70E is the ‘how,’” Domitrovich said.
Other examples of safety by design include voltage presence indicators, visible blades on safety switches and arc-quenching switchgear. Domitrovich also noted the use of computers or mobile devices to turn off electrical components.
Another issue is look-alike equipment, which the 70E standard defines as equipment “similar in size, shape and construction.” Under the standard, employers must use one of three alerting techniques: safety signs and tags, barricades, or an attendant who is “stationed to warn and protect employees.”
Allowing work on energized equipment is another potential contributor to arc flash, said Christopher Coache, senior electrical engineer at NFPA. The 70E standard states that equipment operating at 50 volts or more must remain in “an electrically safe work condition,” meaning that it’s verified as de-energized, locked out and tagged out. If necessary, workers may need to ground the equipment temporarily for “personnel protection.”
“For equipment meeting normal operating conditions, an arc flash is extremely rare when establishing an electrically safe work condition,” Coache said.
Domitrovich said financial concerns or time pressures may compel employers or employees to permit energized work when, “in reality, it could have been performed after establishing an electrically safe working condition.”
He added: “An event can cost a lot more than the downtime needed to perform the work.”
Wearing proper PPE
Domitrovich compared electrical protections such as safety by design to layers of an onion. The final layer is personal protective equipment, and the key term is “arc-rated” clothing. Table H.2 in the 70E standard provides a “simplified” system for arc-rated clothing.
“The biggest challenge we have is getting our electrical workers to wear it,” Domitrovich said. “All too often they had the gloves and shirt (on) but not the pants. They didn’t have all of their PPE on. When leveraged, it saves lives.”
Arc-rated clothing is flame resistant, but not all FR clothing is arc-rated. A list of which AR clothing is needed, depending on the potential incident energy exposure, is available in the 70E standard, along with relevant ASTM and ANSI/ISEA standards for types of clothing.
OSHA’s Electric Power Generation, Transmission, and Distribution Standard (1910.269) states that employers must ensure all workers who are exposed to electrical-arc or fire hazards don’t wear clothing that could melt onto their skin or ignite.
This is important, Hoagland said, because most people aren’t fatally injured directly as a result of an arc-flash incident, but rather from burns resulting from flammable clothing or electric shock.
“That’s one of the things a lot of people don’t understand,” Hoagland said.
Miscommunication between a work crew and managers led to an incident at the Los Alamos (NM) National Laboratory in May 2015. According to a Department of Energy Construction Safety Advisory Committee report issued in September 2016, the crew was conducting maintenance and cleaning operations when one member of the team entered a cubicle he thought was de-energized. Two of three buses were turned on to power equipment and systems.
The worker sprayed a cleaning solution that ignited an arc flash that left him with substantial burns and a head injury. He survived, in large part, because he was wearing AR clothing.
“Visual and physical indications of power were misleading, at best,” the report states. It also was determined that there was inconsistent zero energy verification during the job and no “meeting of the minds” occurred between the crew and managers. “This resulted in uncertainty of zero voltage checks required for each cubicle, no consideration of look-alike equipment (and) inadequate consideration of workflow during concurrent tasks,” the report states.
Part of good jobsite communication is making sure all electrical diagrams are current, said Domitrovich, who compared using old diagrams to relying on a map from the 1800s instead of GPS. Up-to-date drawings are necessary for electrical workers to determine what needs to be locked out and tagged.
“Documentation is really critical,” he said. “I’ve been in facilities to do a short circuit study, grabbed the one-line diagram and it’s 30 years old. Equipment has been moved and relocated. So a lot of that stuff isn’t kept up to date. That could help prevent an arc flash event.”
Having training and procedures in place can go a long way to preventing arc flash incidents, Domitrovich said. Part of the training, Hoagland noted, should focus on the use of insulated tools.
“A lot of companies either don’t provide the tools or the workers just skip the step of going and getting the insulated tool and using an uninsulated tool in an energized state,” Domitrovich said.
A key piece of proper procedures is ensuring only qualified employees perform electrical work, Coache said. The 70E standard defines a “qualified person” as someone who has “demonstrated skills and knowledge related to the construction and operation of electrical equipment and installations and has received safety training to identify the hazards and reduce the associated risk.”
Another key point? Don’t work distracted.
“The [mistakes] that I’m most familiar with are the ones that happened on a Friday afternoon,” Domitrovich said. “‘It’s beer-30, I want to get out of here. This is the last step of the job.’ And your brain goes south at that point. You’re thinking about other things.”