Avoiding arc flash
Electrical events can severely injure – or kill – workers
- Arc flash temperatures can reach 35,000° F.
- The 2015 edition of NFPA 70E has updated guidance, most notably a shift from “hazard analysis” to “risk assessment” terminology.
- The IEEE/NFPA Arc Flash Collaborative Research Project is studying arc flash and its hazards, and will possibly help develop an updated guide for calculating arc flash incident energy.
In October 2010, a wind farm technician suffered third-degree burns to his neck, chest and arms and second-degree burns to his face after energy from an arc flash struck him while working.
OSHA determined that the technician’s employer failed to ensure workers attached personal lockout/tagout devices on tower turbine switch gear at ground level. Other employees were working on the towers 350 feet off the ground. A transformer unexpectedly activated, injuring the technician. OSHA issued six citations for willful safety violations and proposed fines of $378,000.
This case is just one example of the potential health, legal and financial consequences of an arc flash incident.
During an arc flash, electric current leaves its intended path and travels to the ground, or from one conductor to another, through the air. Factors that can cause an arc flash include equipment failure, dust, dropped tools and corrosion. Injuries can be devastating, as arc flash temperatures can reach 35,000° F – which is 3 times hotter than the surface of the sun. An arc flash also can produce noise reaching 140 decibels – about as loud as a gunshot – and molten metal shrapnel.
“Arc flash is a very, very dangerous phenomenon. It is truly instantaneous. If you’re watching video of it, it would last less than a second,” said Bill Burke, division manager of electrical engineering for the Quincy, MA-based National Fire Protection Association.
Each day in the United States, an estimated five to 10 arc flash incidents occur with electrical equipment, according to NIOSH.
An arc flash injury can mean an “excruciating road to recovery, something any reasonable person would want to avoid,” said Antony Parsons, technical consultant at energy management specialist Schneider Electric. “There’s light, sound along with heat, that can cause damage to eyesight, hearing.
“It can also cause a lot of damage to equipment. It may mean main electrical equipment is not repairable. Maybe production is down in your facility for an extended period of time. Economic loss can come along with it. It can have a huge impact. If you have no protection, it’s basically a roll of the dice.”
Rules and guidance
In April 2014, OSHA issued a final rule on electric power generation, transmission and distribution; and electrical protective equipment. The rule has new or revised requirements for electrical safety – including arc-flash protection – for both construction and general industry. It affects workplaces in various industries – including manufacturing. The agency estimates the rule will help prevent about 20 deaths and 118 serious injuries per year.
Under the rule, employers must protect their workers from hazards posed by flames and electric arc in the following ways:
- Identify employees who will be working around these hazards.
- Estimate the incident heat energy of any electric-arc hazard to which a worker would be exposed.
- With certain exceptions, ensure workers exposed to such hazards wear protective clothing and other protective equipment with an arc rating equal to or greater than the estimated heat energy.
At press time, the compliance deadline for certain provisions of arc flash protection was April 1, including the requirement that employers provide workers with protective clothing and other equipment.
“The best thing employers can do is change what they put their people in,” said Jay Smith Jr., executive vice president of Indianapolis-based arc flash hazard analysis provider Lewellyn Technology. “Getting into flame-resistant clothing can drastically improve the chance of walking away from what would be considered a catastrophic event.”
Although OSHA sets the requirements for arc flash prevention and other electric safety issues in the workplace, NFPA’s standard for electrical workplace safety, 70E, aims to detail how to be safe. Originally created per OSHA’s request, 70E is intended to help employers and workers comply with OSHA 1910 Subpart S and OSHA 1926 Subpart K.
70E references the Institute of Electrical and Electronics Engineers’ IEEE 1584, a guide first published in 2002 for calculating arc flash incident energy and protection boundaries.
A new version of 70E went into effect July 29, 2014.
Although some companies might not currently have access to NFPA 70E’s new edition, David Dini – research engineer at Northbrook, IL-based safety science company UL and chair of NFPA’s 70E technical committee – encourages use of the new edition because it is meant to supersede all previous editions.
Guidance on how to protect workers will continue to evolve as more is learned about arc flash.
A special task group associated with the NFPA 70E technical committee has been exploring if the standard should include certified personal protective equipment – such as arc-rated clothing, faceshields, rubber gloves and insulated tools – for electrical workers, Dini said. This would be similar to what is in place in other NFPA standards for workers such as firefighters, who must wear turnout gear and other special protective equipment. Currently, 70E requires most PPE to meet requirements of certain ASTM standards. Certification likely would require testing to confirm a product meets the standard’s requirements.
“Most electrical workers’ PPE is self-certified to ASTM standards, and that can present issues with respect to conformity assessment, standards interpretations, testing consistency and continued compliance, not to mention counterfeit products,” Dini said.
Additionally, to better understand arc flash and its hazards and determine further safety guidance, NFPA and IEEE have been collaborating on an arc flash research project. Phases I and II of testing have been completed, and IEEE is reviewing new models for incident energy calculations, Dini said.
IEEE 1584 contains methods for calculating incident energy and arc flash boundaries based on research conducted during the 1990s, Dini said. The current project involved nearly 2,000 tests using more modern methods and equipment. Blast pressure, sound and light intensity also have been measured during the experiments.
“These results will be considered by the 70E committee, as they are responsible for the PPE requirements for both the thermal and non-thermal effects of the arc flash and the associated blast,” Dini said.
One notable change in the new version of NFPA 70E is the shift in terminology from “hazard analysis” to “risk assessment,” which is defined as a process that identifies hazards, estimates potential severity and likelihood of injury or “damage to health,” and determines if protective measures are required.
In the 2012 edition, arc flash hazard analysis was defined as “a study investigating a worker’s potential exposure to arc flash energy, conducted for the purpose of injury prevention and the determination of safe work practices, arc flash boundary, and the appropriate levels of PPE.” Risk assessment was not listed in the standard’s definitions.
In the newest version, NFPA has shifted to “risk assessment” for greater clarity, Burke said.
With risk assessment, the new edition takes more of a comprehensive approach regarding equipment history, experts say. Risk assessment asks for an understanding of the equipment, whether it has been properly maintained and if manufacturer-recommended maintenance has been performed, according to Smith. Risk assessment puts more emphasis on equipment evaluation versus simply task-based PPE selection.
“They have to really support hazard identification using concrete evaluations of their equipment and type of equipment, maintenance of equipment, upkeep,” Smith said. “It’s put more emphasis on actually calculating the hazards.”
Hugh Hoagland is senior managing partner of e-Hazard, an electric safety training and testing provider, and ArcWear, a testing specialist for protective apparel, in Louisville, KY. Hoagland said focusing on risks re-emphasizes maintenance and engineering out hazards, so PPE is no longer burdensome.
“This is the future of electrical safety,” he said.
However, some employers might believe performing a risk assessment on their own is too complicated or perilous. They may call an outside firm to evaluate hazards, train workers and recommend PPE.
“The problem with risk assessment, it’s very iffy and based on historical knowledge,” Hoagland said. “If you’re a small facility, you may struggle to know historically a piece of this equipment has had a problem. It’s probably good for you to have someone with more experience help with risk assessment.”
Regardless, NFPA hopes its national consensus standard is becoming clearer and can be used for companies’ own risk assessments.
“Rather than going out and hiring an expensive engineering firm to do all this analysis, 70E offers tables,” Burke said. “If you know four or five different things, you can figure out what your risk exposure is. A lot of big companies do engineering studies and use 70E in coordination with that. 70E is also very much for smaller companies, smaller office buildings and commercial applications where they don’t necessarily have someone on staff.”
Companies will have to continue to maintain their equipment, experts point out. Some companies might not understand what needs to be done and the importance of maintenance, or they may frown on the idea of shutting down their production for maintenance, Parsons said.
“That’s one of the biggest things many facility owners miss, doing proper periodic maintenance on electrical equipment. They don’t do it in some cases,” Parsons said. “In some cases, what they do is inadequate. The less maintained it is, the less reliable it’ll be. That doesn’t do you any favors when you talk about arc flash hazards.”
Some companies have experienced “heartburn” in response to changes in 70E, as they adjust from what they previously learned, Smith said. However, a culture change has been occurring since the 2000s, with safety awareness growing and workers realizing they have to dress appropriately for safe electrical work.
The question Hoagland’s company most frequently hears is: When are PPE and energized work permits needed?
Companies might not want to do cumbersome paperwork, but they want protective, hassle-free PPE, he said. And they want to take necessary measures.
“They want to do it when it can save a life,” Hoagland said.