If you need to purchase arc flash clothing for yourself or your work team, one of the questions you will have to answer is what level of protection you need. Different arc flash suits, gloves, hoods or other clothing provide varied levels of safety protection. This level of protection relates to a measurement called Arc Thermal Performance Value (ATPV), which is measured in calories per centimetres squared, or cal/cm2.
When you see an item that is marketed as a 40 cal arc flash suit, the number actually means that the suit is rated to protect against arc flashes with an incident heat energy level of up to 40 cal/cm2. At the TEN Group, we carry arc flash clothing rated between 8 cal/cm2 on the low end and 100 cal/cm2 on the high end.
Of course, it's easy to look at numbers like this and comprehend the basics (e.g. higher numbers offer more protection, and lower numbers offer less) without necessarily understanding the specifics. For instance, you might see an arc flash hood rated to 40 cal/cm2 APTV and realise that it falls somewhere in the middle of the spectrum regarding protection. However, comprehending just how hot 40 cal/cm2 is, might be more difficult.
According to the American Transmission Company—one of the world's foremost authorities on arc energy and its dangers—one cal/cm2 in heat energy would be about the equivalent of holding your finger in the flame of a candle or a cigarette lighter. A 40 cal/cm2 arc flash suit, therefore, would be designed to absorb heat energy 40 times more intense.
An arc flash hood or arc flash suit can't always prevent an injury. APTV ratings indicate a fabric's ability to absorb heat energy but cannot neutralise it entirely. As a result, a worker wearing arc flash clothing when an arc flash heat energy incident occurs, could still potentially be burned. However, the goal with arc flash clothing is to minimise the amount of heat energy making it to the wearer's skin. Specifically, arc flash clothing is rated based on its ability to reduce the wearer's injury to a second-degree burn. In other words, a 40 cal/cm2 arc flash suit would be able to absorb the heat energy of a 40 cal/cm2 heat energy incident and protect the wearer from anything worse than a second-degree burn.
When selecting an arc flash hood, suit, gloves or any other arc flash clothing, it is important to consider the APTV ratings. You want to have a suit capable of withstanding the maximum potential incident heat energy level of the electrical system you will be using. Higher voltage systems have higher potential incident heat energy levels and therefore required suits rated with higher cal/cm2 levels.
Do you have any questions about APTV ratings or picking out the appropriately rated arc flash clothing? Click here to contact the TEN Group directly.