Do you realize that copper expands 67,000 times when it changes state from solid to vapor in an arc flash incident? This pressure wave can cause eardrum damage, concussions or consequential falls, and it can also damage surrounding equipment or tear protective clothing. This blast damage is sometimes forgotten when discussing arc flash.
There are two primary types of physical hazards from arc flash when working around electrical equipment: shock and burns. Most people can relate to an electrical shock from personal experience. When I was a child, I would receive a shock if I unplugged the household vacuum and accidentally touched the plug prongs. I didn’t get hurt, but wow! I respected the power of electricity after that. Obviously, the electrical systems that we design and work around have much higher voltages and current levels than my childhood home, so the risk for injury is far greater.
In recent years, electrical burns have received greater attention and emphasis from OSHA, NEC, insurance companies and other groups. My father-in-law is an electrician at a large extrusion company, and over the years he has helped me better understand and appreciate electrical burn hazards.
Three factors affect the severity of arc flash burns:
- Incident energy level of the arc
- Distance from the arc
- Duration of exposure
Anyone who has been through arc flash training and seen videos or pictures of victims can testify to the severity of arc flash burns. It’s not a pretty sight, but it’s an important reminder of the hazards involved that motivate us to follow needed safety measures.
Facility managers and electrical technicians need to understand the risks of arc flash and properly quantify the electrical hazards. OSHA requires equipment owners to properly label all equipment in compliance with NFPA70E, and the National Electric Code (NEC) mandates that electricians mark the highest voltage contained within the enclosure on the cover or door. This enables qualified electrical workers to calculate the magnitude of the hazard and then select the personal protective equipment (PPE), tools and procedures rated for the nominal system voltages. This process also helps in developing the complete system design needed for short-circuit/coordination studies.
Some questions you need to ask yourself, because your job and the well-being of others depend on it:
- Does your facility’s electrical distribution system have all the proper labeling?
- Do you have a properly performed short-circuit/coordination study?
- Do you have facility one-line diagrams to start the short-circuit/coordination process?
- The key to arc flash mitigation is proper setting and verification of protective devices – namely relays and circuit breakers – which ties back to proper maintenance. Do you have an electrical maintenance program that includes these features?
- If your staff is performing electrical maintenance, do you have proper PPE and training?
- Does your facility have policies and procedures to address arc flash?
Please post below and share your experiences with arc flash, and what you do to address it.
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