Posted by Nick Bloom on Friday, December 2, 2022
Your electrician is troubleshooting at your facility. As they open the panel cover, something falls inside. Within a split second, the area is engulfed in a momentary fireball, stunning and injuring the electrician. After a day of 911, ambulances and Emergency Rooms, you learn that they’ve got 2nd degree burns on their hands and one forearm and temporary hearing loss. Thankfully, the electrician’s injuries are expected to heal, though they will be off work for a few weeks.
Even though they weren’t wearing proper arc flash PPE, the panel cover and their work gloves shielded them from the worst of the arc flash, but you don’t want to count on that providential arrangement next time. After making an incident report, your liability insurance carrier and OSHA initiate investigations. You receive a fine from OSHA because you failed to protect the electrician from arc flash hazards and your liability insurance carrier refuses to renew your coverage unless you implement an electrical safety program. So, what happened and how do you prevent it happening again?
What is electrical arc flash?
This story is an example of arc flash hazards. Arc flash is a dangerous release of energy due to flash-over between electrical conductors. It can be initiated by a dropped or forgotten tool or scrap of wire, dirt or dust, corrosion, loose connections, or even animals. Once initiated, the arcing produces a plasma-bridge in the air that continues to conduct even after the initiating source is vaporized. The arcing stops when an upstream protective device trips, isolating the arcing fault from its energy source. Depending on the system, the energy release can be extremely powerful, producing intense heat, light, and a pressure blast strong enough to throw people across the room. The arc flash can cause life-threatening burns and impact injuries as well as vision and hearing loss.
How can you protect yourself from electrical arc flash?
The best way to avoid exposure to arc flash hazards is to avoid working on live electrical equipment. However, certain tasks cannot be performed with the equipment de-energized whether due to the safety hazard created by de-energization, such as hazardous area ventilation equipment, or because the task itself is impossible without the equipment energized, such as troubleshooting a control circuit. So, when de-energization is not possible, it is imperative to protect yourself with the proper PPE (Personal Protective Equipment).
What is the right level of PPE to protect from arc flash?
Electrical PPE levels vary in the amount of protection they offer, just like say, footwear. Steel-toed boots protect your feet better than sandals, but they might not be the most practical and efficient to walk along the beach. So, you want to know the right protective tools for the task at hand – which in a nutshell is exactly what electrical arc flash studies deliver. At the conclusion of the study, each potential arc flash source is clearly labeled with the PPE required to work on that source.
Arc flash studies calculate the expected incident energy if an arc flash event were to occur, given the available arcing current (calculated from the available fault current established by a short circuit study) and arcing time (calculated from the protective device time-current curves evaluated in a coordination study). Knowledge of the incident energy allows for selection of appropriately rated PPE, as well as identifying locations in the electrical system for which no amount of PPE will adequately protect against the hazards and live work cannot be safely performed.
Performing an arc flash study and using PPE are part of an effective electrical safety program; other components include processes such as lock-out/tag-out and energized work permits. NFPA 70E, Standard for Electrical Safety in the Workplace, is the industry consensus standard for electrical safety programs and it contains best practices to ensure the safety of employees from electrical hazards. OSHA requires employers to protect their employees against electrical hazards, and implementation of an NFPA 70E electrical safety program is an acceptable and industry-standard way to do just that. Besides OSHA requirements, protecting the health and safety of employees from known hazards is simply responsible practice and the right thing to do.
You can learn more about our electrical studies webpage, including arc flash studies, or if you have questions or want to discuss further, reach out to me!
Categories: Buildings & Campus
Tagged: Electrical | Health & Safety