If you’ve never seen an arc flash firsthand, you may not realize just how destructive they can be. An arc flash can cause significant damage to electrical systems, start fires and cause injuries or even deaths. You don’t even have to be caught by the arc itself for this to occur; damage radiates out from the arc, and the air surrounding an arc flash can become as hot as the surface of the sun!
This is obviously something to take very seriously, and you need to have a plan in place in case an arc flash occurs. If you’re not yet prepared for an arc flash incident, here are some things you should know to help protect yourself and your crew.
What Is an Arc Flash?
An arc flash occurs when a fault passes through an arc gap, resulting in all of that energy leaving the circuit it’s contained in and traveling through the air. When an arc flash occurs, not only is there a rapid energy release from the arc itself but the air around it actually becomes ionized. Temperatures surrounding an arc flash can reach as high as 35,000 degrees Fahrenheit, melting metal and setting fire to anything combustible in the surrounding area. Looking directly at an arc flash can damage your eyes, similar to the effect from staring directly at the sun.
In addition to the heat and voltage from an arc flash, the rapid expansion of air and materials cause a concussive blast as well. Even if you’re away from the arc location, this blast can knock you off your feet and the sound of it can potentially damage your hearing. If you’re close to the arc location, major burns can occur in a fraction of a second and your clothes can actually ignite. On top of all of this, the arc flash can knock loose surrounding equipment, knock over shelving units and create similar hazards in and around the arc area.
What Causes an Arc Flash?
An arc flash is essentially the combination of a short circuit and an electrical arc. A large amount of electrical energy is exposed to open air, arcing either to another object or to the ground. Though there are a number of potential causes of arc flashes, some of the most common are dust buildup, dropped tools or parts causing a circuit bridge, material failures, circuit corrosion and improperly installed components.
Of course, an arc flash can be caused by other things as well such as accidentally bumping into a component or even unexpected condensation or leaks in the area causing water to hit components. Even extraordinarily high humidity can be a contributory cause of an arc flash.
Preparing for Arc Flashes
Before performing any electrical work, the potential for arc flashes needs to be assessed during your initial inspection. High-voltage equipment needs to be inspected for damage or corrosion, and potential arc flash locations need to be properly labeled before anyone starts working in the area.
All equipment should be de-energized before work begins whenever possible, using tag lockouts so that electricity isn’t restored until all work is complete. Personal protection equipment and fire-resistant clothing should be used while in the area, even if the equipment is supposed to be depowered, and a checklist to confirm the status of the equipment should be performed by those who are actually doing the work. Because of the potential damage and injury that can occur, all OSHA and NFPA guidelines should be strictly followed when working with any high-voltage equipment.
How to Respond to an Arc Flash Event
Proper preparation goes a long way toward preventing arc flashes, but unfortunately the unexpected can still occur. In the event of an arc flash incident, there are a few things that must be done immediately:
• Cut all power to the equipment, regardless of whether circuit breakers or arc detectors are in place.
• Call emergency services to get fire and medical first responders to the site as quickly as possible.
• Put out any fires on clothing or that are endangering workers in the effected area using an approved fire extinguisher.
• Perform CPR or other necessary first aid on affected workers within 4 minutes of the incident occurring.
• Do not move affected workers unless there is an imminent danger in their current location. Internal or external injuries could be made worse if trained first responders can’t secure them before moving.
• Keep everyone except first responders out of the affected area.
OSHA requires that you have at least two individuals trained in CPR and first aid onsite whenever you have crew members working on any equipment energized at 50 volts or more, or the entire crew trained if you do not have enough workers available so that they could treat affected crew members within 4 minutes.
Training should be repeated annually to make sure that they can respond appropriately during an arc flash or similar event.
After an arc flash occurs, you’ll, of course, have to make a report with an OSHA compliance officer. Though it’s a traumatic time, there are still several things you’ll have to be able to do to aid the investigation into the incident. In addition to being able to provide sketches or descriptions of the affected circuits, you’ll also have to show that your workers were properly trained for the work they were doing.
You’ll need to explain why the circuits weren’t de-energized at the time, show whether a detailed briefing checklist was performed by the people working on the circuit and you’ll likely be asked whether NFPA annexes were followed as well.
Arc flashes can occur when least expected, but investigations into the incident will be required, in order to get to the bottom of whether the incident was a genuine accident or if it could have been prevented.