An
Arc Flash
is an electrical explosion due to a fault condition or short circuit when
either a phase to ground or phase to phase conductor is connected and current
flows through the air.Arc flashes cause electrical equipment to explode,
resulting in an arc-plasma fireball.
Temperatures
may exceed 35,000° F (the surface of the sun is 9000° F). These high
temperatures cause rapid heating of surrounding air and extreme pressures,
resulting in an arc blast. The arc flash / blast will likely vaporize all solid
copper conductors which will expand up to 67,000 times its original volume when
it is vaporized. The arc flash / blast produces fire, intense light, pressure
waves and produces flying shrapnel.
When
an arc flash happens, it does so without warning and is lightning quick. The
result of this violent event is usually destruction of the equipment involved,
fire, and severe injury or death to any nearby people. Proper safety and
protection measures must be taken to limit the damage from an arc flash which
include conducting an arc flash study, short circuit study, and NFPA 70E
electrical safety training.
ARC
FLASH COMPLIANCE
Summary:
OSHA mandates that employers identify electrical hazards, warn employees about
the hazards and provide them proper protection and training regarding the
hazards. Compliance with OSHA is mandatory for all US companies. While OSHA
tells you “what to do” for arc flash, they don’t tell you how to do it. The
role of NFPA 70E, IEEE 1584 and NEC is to provide guidance on “how” to properly
implement the OSHA regulations.
The
regulations that govern Arc Flash Analysis and labeling are:
- OSHA Standards 29-CFR, 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.
- 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 Study / Analysis states that an ” Arc 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 / Study must be done to determine the level of PPE safety equipment 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 Hazard Warning Label according to NFPA 70E.
- The National Fire Protection Association ( NFPA ) Standard 70 – “The National Electrical Code” (NEC) contains requirements for warning labels, including ANSI compliance.
- The Institute of Electronics and Electrical Engineers (IEEE) 1584 – Provides the Guide to Performing Arc Flash Hazard Study and Analysis Calculations.
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