Common Causes of Arc Flash
Occurring 5-10 times per day in the United States and resulting in over 600 fatalities and 30,000 injuries a year, arc flash occurrences are common, dangerous, and often deadly incidents.
Arc flash injuries are different than common electrical shock injuries; while electrical shock injuries occurs when current passes through the body, the risk from an arc flash comes from concentrated energy during an arcing fault. The energy of an arc flash has the power to instantly vaporize metal including copper and steel, exposing a worker to temperatures that can reach or exceed 35,000 °F, blast pressures that could destroy concrete, and shrapnel from an arc blast.
Arc flash incidents can occur in an instant, with a line-to-line or line-to-ground arcing fault can escalate into a three phase arcing fault in less than a 1/1000 of a second. Whether these incidents result in severe burns (the most serious burns are usually the result of clothing ignition), blindness, loss of hearing, or one of the many other injuries that could occur, these injuries are absolutely debilitating, and it’s common that an injured employee never regains past quality of life.
Causes of Arc Flash Hazards
While human error or carelessness of a worker account for the majority of incidents, arc flash can be the result of a wide variety of causes—static electricity, loose connections, or even a rodent in the vicinity that compromises the distance between energized components.
Human Error and Carelessness
No matter how well trained a worker is, accidents happen and are often the result of operator error. Distractions, weariness, pressure to get the job done quickly, or simply overconfidence can cause a worker to move too fast, fail to don protective equipment, or bypass other safety procedures. It’s estimated that two out of every three arc flash incidents occur as a result of human error and carelessness.
Often is the case, a worker will complete the same task many times over the course of a year, a decade, or a career without incident, developing bad habits while trying to save time. It only takes one mistake to cause the electrical current to become uncontrolled, even something as routine as a control panel adjustment could end up with deadly consequences.
Additionally, failure to verify absence of voltage, utilizing incorrect testing equipment (i.e. voltage testers), overconfidence, complacency and poor co-worker communication and lack of lockout/tagout procedures have all been underlying root causes of arc flash incidents
A dropped screw or bolt, a tool slipping when he or she applies torque, or a distraction during a critical moment could result in a mistake that leads to the flash.
Failure to Use an Insulated Tool
While this may fall into the carelessness category, many arc flash explosions occur when an employee uses a non-insulated tool that is not designed for the job. A tool slips or gets dropped and without the proper insulation it immediately becomes a conductor for electricity.
The result of negligence over the course of months or years, dust buildup can result in a faulted path in the electrical current. This faulted path causes the current to be drawn to another conductor, creating an environment in which arc flash incidents occur.
All equipment has an expectation for routine ongoing maintenance. However, in cost-cutting circumstances, sometimes maintenance is skipped or done incorrectly, jeopardizing the long-term safety of the system. This failure to maintain leads to corrosion, exposing conductive surfaces creating resistance and heat—two of the primary culprits in arc flash events.
Improperly Maintained or Installed Switches and Circuit Breakers
Sometimes negligence isn’t the culprit—sometimes normal wear and tear could result in environment ripe for an arc flash incident. Other times, proper installation procedures may not have been followed. Both instances create an unsafe environment for workers operating on an energized environment, as improper installation can make it difficult or impossible for electricity to follow the intended path, which can cause an arc flash.
Use of Substandard Parts
One of the most avoidable mistakes that could lead to an arc flash injury is the failure to use parts that are rated for the equipment on which they are being used. Because electrical equipment parts are rated for certain levels of current, using a part that is not appropriately rated for its application can lead to an arc flash situation.
Condensation, Water, or Other Liquid near Electrical Equipment
If condensation or other liquid is near a conductive surface, electricity may escape the wiring through the water, and then the arc flash will occur as the electricity seeks its destination.
Minimizing Risk of Injuries from Arc Flash
There are many ways to minimize arc flash risk when it’s not possible to deenergize the source, and many of them rely on following safety standards set by OSHA, NFPA, and more including basic features like lockout/tagout, approach boundaries, and labeling needed to avoid injury risk in the event of an arc flash.
Knowing this, one of the most important parts of safely working on equipment in which an arc flash may occur is to take necessary steps to protect yourself or your people. Training and retraining employees, deenergizing equipment, and suppling workers with effective and compliant personal protective equipment (PPE) are all necessary parts of an effective risk avoidance strategy as it pertains to arc flash hazards.
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