Causes of arc flash and arc flash blast incidents

Arc flash incidents are common causes of injury in a facility and knowing how and why they occur is a good strategy to prevent them from occurring in the first place.

By David Manney, L&S Electric March 21, 2017

Arc flash incidents are, unfortunately, common causes of electrical injuries in a facility. These events result from a combination of heat and light emitted during a dangerous electrical explosion. With hot gasses released into the air by an arc flash, they immediately melt metals and similar materials. Copper and other metals also tend to vaporize in an explosive manner because of the high temperature. The plasma arc becomes even more powerful as vaporized metal provides this effect.

Moreover, fatalities can occur from arc flash incidents. Severe injuries include eyesight damage and radiation burns. When pressure waves accompany the arc flash, individuals near the incident may suffer brain function and hearing issues. Further accidents are also bound to happen once free tools, debris, and machinery get in the way. Downtime is another problem caused by arc flash once pieces of equipment and tools in the facility fail to function because of massive damages.

Causes of arc flash incidents

Spikes or voltage transients often cause arc flash. When lightning strikes, or upon switching reactive loads, such voltage transients occur. Although it takes only a few microseconds for the transient to last, this comes with thousands of enormous amps of energy and plasma arcs.

Other causes include installation gaps or resistance heating arises because of corrosion and dust. Other arc flash triggers include worn connections, equipment not properly installed, and failure to handle the test probe to the right surface.

Then there is the human element. For the most part, carelessness and poor safety practices result to arc flashes and several other types of electrical accidents. Your staff may be well-trained, but there is always the chance that their inability to perform safety procedures or maintain focus on their tasks, hazards in the facility occur.

A lack of compliance with safety precautions and guidelines combined with faulty electrical equipment in the building all lead to electrical issues, including an arc flash.

Other causes that contribute to an arc flash incident include: 

  • Exposed live parts
  • High voltage cables
  • Damaged equipment
  • Circuit breakers not maintained
  • Broken conductor insulation
  • Static electricity
  • Blocked disconnect panels.

Injuries caused by an arc flash

Any individual within the area of the arc flash incident may suffer from injuries and fatalities. An arc flash is hot, which can cause massive burns to one’s skin. Even if the person is several feet away from the incident, he or she is still at risk of burns. The clothing ignites right away upon exposure to an arc flash. While there is a treatment for burns caused by an arc flash, there still may be years of recovery.

Eye damage also arises from arc flash incidents. If the personnel does not wear the required eye protection, molten debris and projectiles may hit them in the eyes. Damages to the retina result from the harsh UV radiation that accompanies the arc flash.

Respiratory problems, such as breathing impairment and lung injury, impacts an individual near an arc flash. Massive heated vapors make it difficult to breathe, which leads to serious lung damage. Other internal organs may also be susceptible to injuries because of the thermoacoustic blast. The powerful blast can knock people off their feet. This explosion increases the chances of a fatality from falls or electrocution.

  • Many types of injuries result from an arc blast include:
  • Memory loss due to a concussion
  • Shock hazard from touching an energized conductor
  • Hearing loss from the explosion sound
  • Shrapnel wounds resulting from flying debris.

More facts on arc flash, arc flash blast

Arc flash occurs when there is an uncontrolled conduction of the electrical current from various scenarios, such as phase to neutral, phase to phase, or phase to ground, combined with ionization of the air outside. A three-phase arcing fault may even arise as the conductive metal vaporizes. This fault happens as quick as 1/1000th of a second, which leads to widespread damages in an instant.

Any personnel situated nearby or even a few feet away from the incident become exposed to fatalities and injuries caused by arc faults. Expect several injuries as powerful energy in various form escapes into the air due to arc fault current. These include massive burns and damages of one’s vision.

It is also worth noting that conductors vaporize faster because of a high arc temperature. When copper vapor, for instance, expands to as much as 67,000 times the typical volume of solid copper, a pressure wave or arc blast occurs. This pressure wave is capable of knocking over construction walls or snapping the heads of steel bolts as thick as 3/8-in.

Both an arc flash and an arc blast pose serious hazards in an electrical or industrial facility. But, it is possible to prevent these by following proper safety practices and utilizing the right equipment for the best protection. Avoiding energized components in the workplace also spares anyone from fatalities due to these jeopardizing incidents. 

David Manney is a marketing administrator at L&S Electric. This article originally appeared on L&S Electric Watts New Blog. L&S Electric is a CFE Media content partner.

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