In an article found at Safety.BLR.com, Ana Ellington does an excellent job in describing arc flash hazards. (Emphasis mine in bold).
An arc flash is an undesired electric discharge that travels through the air between conductors or from a conductor to a ground. The flash is immediate, but the result of these incidents can damage equipment and cause severe injury, including burns.
According to the National Fire Protection Association (NFPA) 70E (2012), more than 2,000 people are admitted to intensive care burn units each year as a result of severe arc flash burns they received during an arc flash incident. Fatalities occur at a rate of approximately one per day in the United States, with nonfatal arc flash incidents occurring approximately 5 to 10 times per day. Even these nonfatal arc flash incidents consistently result in many serious burns and injuries requiring weeks to months of intensive care hospital stays and many months of painful rehabilitation.
How sudden are these “undesired electric discharges,” watch this brief video:
Culprits Behind Arc Flash Events
Ellington provides several reasons behind an arc flash event.
- Workers mistakenly dropping tools on live parts
- Pests entering switchgear through openings
- Faulty operation of a load break switch
- Dust or moisture accumulating to weaken air insulated bus bars
- Improper use of test equipment
Electrical arc flashes produce some of the highest temperatures known to occur on earth, up to 35,000 °F (19,426 °C). This is four times the temperature of the surface of the sun, which is 9,000 °F (4,982 °C). This intense heat causes a sudden expansion of air, which results in a blast with very high air pressure.
The NFPA developed four boundaries near electrical equipment to protect people as they work on the equipment.
- Prohibited Approach Boundary: closes distance, essentially touching the live part
- Restricted Approach Boundary: area crossed only by qualified workers in appropriate personal protective equipment (PPE).
- Limited Approach Boundary: where an unqualified person may safely stand from the live part
- Flash Protection Boundary: the furthest established boundary from the live part.
If, Ellington writes, employers require electrical work performed while the equipment is live, they must provide the following:
- A written safety program with defined responsibilities
- Calculations for the degree of arc flash hazard
- PPE for workers
- Training for workers
- Tools for safe work
- Warning labels on equipment
Safe Workplace Regarding Arc Flash
Ellington provides some common sense and rules to follow when working on energized electrical equipment.
The most effective and foolproof way to eliminate the risk of electrical shock or arc flash is to simply de-energize the equipment. But, in some cases, turning off the power is just not possible. Understanding arc flash and its potential hazards, calculating risk, knowing the importance of labeling, and the proper use of PPE can maintain the effective use of live electrical equipment and parts. Essentially, OSHA and NFPA requirements should be followed to develop and implement an effective electrical safety program—and ultimately save lives.
OSHA Citations as Result of Arc Flash Explosion
Unfortunately, some companies still cut corners regarding #ArcFlash and it results in injury and fines. From the EHS Today website. (Emphasis mine in bold).
The Iowa Division of Labor Services Occupational Safety and Health Bureau has issued citations to three employers – the city of Sibley Electric Department, Timewell and Current Electric – in an arc flash explosion last July in Sibley, Iowa, that sent five employees to the hospital. According to I-OSHA, employees did not receive training regarding the hazards of arc flash and were not wearing appropriate personal protective equipment.