Arc Flash Boundaries

There are many possible hazards within industrial work environments; however, an arc flash is potentially one of the most deadly and debilitating dangers. An arc flash can be described as an arc-shaped electrical current that leaves its intended path and travels through the air to the ground or another conductor point. The heat and light given off by an arc flash are capable of causing extensive damage and/or harm to anything or anyone in the vicinity. In order to help provide protection against the possibility of an arc flash, the National Fire Protection Agency or NFPA created protection boundaries to help ensure the safety of employees working around equipment capable of producing an arc flash.

NFPA Arc Flash Boundaries

There are three different boundaries identified by the NFPA. The boundaries are labeled as limited, restricted, and prohibited. In order to visualize the boundary set-up, imagine the boundaries as a circular target shape with the energized equipment in the center and three rings moving outwards from the center.

  • Prohibited: This is the ring closest to the center or energized equipment. Only qualified employees who have been properly trained and who are wearing appropriate personal protection equipment (PPE) are allowed to cross into the prohibited area. Trained employees must utilize high levels of PPE when working within the prohibited area, as working in this boundary carries the same dangerous repercussions of actually touching the electrically charged parts.
  • Restricted: This is the second closest ring to the energized equipment. Just has the prohibited area, the restricted area also only warrants employees who have been properly trained to enter the restricted zone. Any employee who enters this area must also utilize the assistance of PPE for bodily protection but must also use shock protection equipment and techniques to limit the risk of harm.
  • Limited: This area is the third ring from the center and is generally safer than both the prohibited and restricted areas. However, even though this area is safer, it is never okay to neglect safety practices. Only qualified employees are able to utilize this space as well, however, in some situations an unqualified employee may enter this space if escorted by a qualified person.

Calculate your minimum approach distance (MADs)  

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Added Protection

Even though NFPA’s boundary system works well to provide protection, there are also some added practices and tactics that can help further improve the safety and well-being of employees. Some helpful practices are as follows:

  • Barricades – Barricades serve as both a visual and physical reminder about the dangerousness of a specific area so there is not any confusion related to the potential hazard.
  • Ground Fault Circuit Interrupters (GFCI) – This type of protection disconnects the live circuit when it detects an imbalance.
  • Training – Provide adequate safety training to all employees so there isn’t any confusion regarding the boundaries related to arc flash protection, and so employees are aware of how dangerous an arc flash can be.

The possibility of injury from an arc flash is traumatic and often times fatal when certain safety precautions are not taken. The heat from an arc flash can reach 35,000 degrees Fahrenheit which is nearly four times hotter than the sun’s surface. The incorporation of arc flash boundaries is crucial when energized electrical equipment is utilized. In order to make your industrial facility safer for all employees, make sure you have created appropriate arc flash boundaries as needed.

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