What Do the Labels Say? What Do They Mean?Īrc Flash labels must include the following information according to NFPA 70E. NFPA 70E Table 130.7(C)(14) lists the ASTM and ANSI standards to which PPE must adhere, but labeling in accordance with NFPA 70E alone is irrelevant because the NFPA doesn’t approve equipment/clothing.Īs with FR clothing, launder arc-rated clothing in accordance with labels. (Material must be flame-resistant before it can even be tested to determine its arc-rating.)Īrc-rated clothing will carry an Arc Thermal Performance Value (ATPV) rating, which is the maximum performance capability in cal/cm2.Ĭlothing must not only carry an arc rating but also be labeled correctly, to indicate compliance with national standards – ASTM F1506 (material) and ASTM F1959 (test method). Arc-rated clothing is FR rated, but not the other way around. PPE CATEGORIES – based on 2012 NFPA 70E (no Cat 0 in 2015)Arc-rated (AR) clothing is tested for exposure to an electric arc, which is different than how flame-resistant (FR) clothing is tested. The amount of absorbed heat (incident energy) is directly related to how close your hand is (working distance), how big the flame is (arcing fault current), and how long you hold your hand over it (arcing time). In practical terms, it’s similar to holding your hand over an open flame. The thermal energy is a function of a) the amount of current associated with the arcing fault and b) the time it takes protective relaying to open breakers and remove the fault. The incident energy associated with an Arc Flash event is the thermal energy (measured in cal/cm2) at a working distance from the arc fault. It’s noted that equipment that needs trouble shooting is no longer “normally operating”. Under normal operating conditions, enclosed energized equipment that has been properly installed and maintained is not likely to pose an arc flash hazard.” “An Arc Flash hazard may exist when energized electrical conductors or circuit parts are exposed or when they are within equipment in a guarded or enclosed condition, provided a person is interacting with the equipment in such a manner that could cause an electric arc. Light intensity as much as 2000 times normal office lighting. Temperatures can reach as great as 20,000-35,000˚C, with volumetric expansion as great as 40,000-67,000 times. An Arc Flash can occur because of environmental conditions (dust, condensation), normal/abnormal wear-and-tear (material failure, corrosion), or personnel (dropping tools, accidental touching). The ways in which workers and equipment can be protected from Arc Flashes are specified below.Ī flashover event where electric current leaves its intended path and travels through the air from one conductor to another, or to ground. Because Arc Flashes create such hazardous conditions, warning labels, protective clothing, and special field measures have to be taken to mitigate risk. It also outlines best practices for limiting the probability of Arc Flashes occurring and harming workers interacting with the equipment. The following Arc Flash study defines what an arc flash is and why it is dangerous.
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