Arc flash rated clothing is personal protective equipment (PPE) designed to protect workers from the hazards of AF, which is a sudden release of energy that can occur when high voltage electricity jumps from one conductor to another or from a conductor to a ground.
Arc flash rated clothing is made of special materials that resist ignition, melting, and dripping and provide a barrier between the worker's skin and the heat. The clothing is tested and rated according to various standards, including the National Fire Protection Association (NFPA) 70E and the International Electrotechnical Commission (IEC) 61482.
The level of protection required for AF rated clothing is determined by a hazard analysis, which considers the voltage, current, fault clearing time, and other factors involved in the electrical system. Therefore, it's important to ensure that the clothing is properly maintained, clean, and in good condition to ensure its effectiveness in protecting workers from AF hazards.
Examples of arc flash rated clothing
Here are some examples of AF rated fr clothing:
Arc-rated shirts and pants - these are typically made of flame-resistant materials such as treated cotton, Nomex or other similar fabrics. They offer protection to the arms and legs from AF hazards.
Arc-rated coveralls and suits - These are one-piece garments that cover the whole body, arms, and legs. They are usually made of multi-layer materials that provide superior protection against arc flash.
Arc-rated jackets and vests - These are outerwear garments designed to protect the upper body. They can be worn alone or over other arc-rated clothing.
Arc-rated gloves and sleeves - Personal protective equipment protects the hands and arms from AF hazards. They are made of similar materials to other arc-rated clothing and come in various lengths and styles.
Arc-rated hoods and face shields - These are designed to protect the head, face, and neck from AF hazards. They come in various styles and designs, including full hoods and face shields that can be worn with hard hats.
It's important to note that the level of AF protection required can vary depending on the voltage and current levels present in the electrical system and the specific hazards associated with the work being performed. Therefore, it is recommended to conduct a hazard analysis to determine the appropriate level of protection required for a given task.
How is arc flash rated clothing rated?
Arc flash rated clothing is rated according to various standards that specify the level of protection the clothing provides against AF hazards. The two main standards used to rate PPE clothing are the National Fire Protection Association (NFPA) 70E and the International Electrotechnical Commission (IEC) 61482.
The NFPA 70E standard specifies the minimum performance requirements for arc-rated clothing, including the Arc Thermal Performance Value (ATPV) and the Energy Breakopen Threshold (EBT). The ATPV is the incident energy level at which there is a 50% probability of causing a second-degree burn. At the same time, the EBT is the energy level at which the clothing material is expected to break open or develop a hole. The higher the ATPV and the lower the EBT, the greater the level of protection the clothing provides.
The IEC 61482 standard provides two different methods of testing arc flash rated clothing: the Open Arc Test and the Box Test. The Open Arc Test measures the clothing material's ATPV and the Breakopen Threshold (BO) when exposed to an electric arc with a specific energy level. The Box Test evaluates the protective performance of the clothing ensemble when exposed to an electric arc by simulating the effect of an AF on a mannequin wearing the clothing.
Arc flash-rated clothing is also typically labelled with a rating indicating the protection level provided. The rating is usually expressed in calories per square centimetre (cal/cm2), measuring the thermal energy released during an AF event. The higher the cal/cm2 rating, the greater the level of protection the clothing provides. It's important to select the appropriate level of arc flash rated clothing for the specific hazards associated with the work performed based on a proper hazard analysis.