There are many arc flash terms, standards and requirements that they overwhelm the senses but it is important to understand each one so that you can comply with these standards and most importantly – keep your employees safe.
1.) What exactly is an arc flash?
An arc flash is:
• Caused by an arcing fault - an electrical explosion due to a rapid release of energy
What happens when an Arc flash occurs:
• Pressures generated 100's - 1,000's lb./ft2
• Sounds due to pressure waves can exceed 160 dB
• Debris & molten metal can reach speeds that exceed 700 mph
• The flash can reach temperatures in excess of 30,000 degrees Fahrenheit
• Extreme temperatures can vaporize copper wires with an estimated expansion of 67,000:1
2.) Why Arc Flashes happen?
There are a variety of reasons why an Arc Flash can occur, but most of them are preventable. Most arc flashes occur when maintenance workers are manipulating live equipment for testing or repair and accidentally cause a fault. Improper tools, improper electrical equipment, corrosion of equipment, improper work techniques and lack of training are just some of the events that can lead to a devastating arc flash or arc blast.
3.) What standards or codes govern compliance?
There are 4 main regulations that govern electrical safety & arc flash:
1. OSHA Standards 29CFR, Part 1910. Occupational Safety and Health Standards. 1910 sub part S (electrical) Standard number 1910.333 specifically addresses Standards for Work Practices and references NFPA 70E. OSHA 29CFR 1910.335 (a) (1)(i) requires the use of protective equipment when working where a potential electrical hazard exists and 29CFR 1910.132(d)(1) which requires the employer assess the workplace for hazards and the need for personal protective equipment. OSHA compliance is required by any plant building or facility.
2. The National Fire Protection Association (NFPA) Standard 70 – 2002 “The National Electrical Code” (NEC) contains requirements for warning labels.
3. NFPA 70E provides guidance on implementing appropriate work practices that are required to safeguard workers from injury while working on or near exposed electrical conductors or circuit parts that could become energized. Part II 2-1.3.3 regarding Arc Flash Analysis states that a “Flash Hazard Analysis shall be done before a person approaches any exposed electrical conductor or circuit part that has not been placed in an electrical safe work condition”. This Arc Flash Hazard Analysis must be done to determine the level of Personal Protection Equipment PPE that a worker must use, and the Arc Flash Boundary in inches along with the incident energy found at each location. Each panel must be marked with an ANSI z535 approved Arc Flash Warning Label.
4. The Institute of Electronics and Electrical Engineers (IEEE) 1584 – 2002 Guide to Performing Arc-Flash Hazard Calculations.
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JD McCullough, P.E.