Describe the key differences between arc-rated and non-arc-rated personal protective equipment (PPE), and why using appropriate PPE is critical for electrical safety.
The key differences between arc-rated and non-arc-rated personal protective equipment (PPE) lie in their materials, construction, and ability to protect against the specific hazards of an arc flash. Arc-rated PPE is specifically designed and tested to withstand the thermal energy of an arc flash, while non-arc-rated PPE does not offer the same level of protection and may even exacerbate injuries. Here’s a detailed breakdown:
1. Materials and Construction:
Arc-Rated PPE: Arc-rated PPE is made from specialized materials that are inherently flame resistant (FR) or have been treated to become flame resistant. These materials are designed not to ignite, melt, or continue to burn when exposed to the extreme heat of an arc flash. Examples of materials used in arc-rated PPE include Nomex, a type of aramid fiber, and FR cotton blends. These materials are constructed to minimize the possibility of the garment melting or breaking open, thereby preventing skin exposure to the thermal energy.
Non-Arc-Rated PPE: Non-arc-rated PPE, on the other hand, is made from materials that are not designed to resist the heat of an arc flash. These materials can easily ignite, melt, or continue to burn when exposed to high temperatures. Common materials used in non-arc-rated clothing include synthetic fibers like polyester and nylon, and standard cotton. For instance, a normal polyester shirt will melt and adhere to the skin, potentially exacerbating burns during an arc flash.
2. Testing and Certification:
Arc-Rated PPE: Arc-rated PPE undergoes rigorous testing to measure its ability to protect against arc flash hazards. This testing includes exposing the material to a controlled arc flash and measuring the heat transfer to the sensors placed on the mannequin behind it. Arc ratings are expressed in calories per square centimeter (cal/cm2). The higher the arc rating, the more protection the garment provides. Arc-rated PPE must meet industry standards like ASTM F1506, which specifies performance requirements for flame-resistant clothing worn by electrical workers. Certification agencies like UL (Underwriters Laboratories) also verify compliance with these standards, ensuring arc-rated PPE is fit for purpose. For example, an arc-rated jacket rated at 12 cal/cm2 has been tested and certified to protect a worker from an arc flash producing up to 12 cal/cm2 of heat energy.
Non-Arc-Rated PPE: Non-arc-rated PPE, however, does not undergo specific arc flash testing. It is designed for general safety purposes, such as protecting against cuts, abrasion, or other low-intensity hazards. Non-arc-rated clothing will burn and melt easily when exposed to the high heat from the arc flash. Items such as standard glasses, safety goggles and hard hats are not specifically designed for arc flash protection. A normal pair of safety glasses can melt during an arc flash, leaving the eyes unprotected and causing them severe injury.
3. Protective Properties:
Arc-Rated PPE: Arc-rated PPE is designed to provide a predictable level of protection against the thermal energy of an arc flash, helping to reduce burn injuries. The materials are designed to insulate the wearer and prevent heat from reaching their skin. Arc-rated face shields, for example, are designed to protect against the intense light, heat, and blast effects of an arc flash. Arc-rated gloves are designed to protect the hands from both the electrical current and the extreme heat. If a worker is wearing an 8 cal/cm2 arc-rated suit in an 8 cal/cm2 arc flash, the suit should reduce the burn injury.
Non-Arc-Rated PPE: Non-arc-rated PPE can actually increase the severity of burns during an arc flash incident. Synthetic fabrics can melt and adhere to the skin, making it difficult to remove and potentially worsening the burns. Even natural fabrics can ignite and add fuel to the fire, causing additional thermal injuries. A polyester shirt will melt onto the skin during an arc flash, causing more severe burns compared to a FR shirt that would protect the wearer.
4. Why Using Appropriate PPE is Critical:
Preventing Severe Burn Injuries: Arc flashes generate extreme heat capable of causing third-degree burns in fractions of a second. Proper arc-rated PPE is crucial to protecting skin, reducing burn severity and improving the chances of survival and recovery. When properly selected and used, arc rated PPE provides the necessary thermal protection against the arc flash energy.
Reducing the Risk of Ignition: Arc-rated PPE will not ignite, melt or continue to burn, which helps prevent clothing from contributing to burn injuries. Non-arc-rated clothing can ignite and continue to burn, increasing the severity of burns.
Protecting Against Other Hazards: While arc-rated PPE is primarily designed for thermal protection, it also provides some protection against electrical shock and the blast effects of an arc flash, especially when combined with other safety measures.
Compliance with Regulations: Standards like NFPA 70E mandate the use of arc-rated PPE for personnel working on or near energized electrical equipment where arc flash hazards exist. Adhering to these standards is not just about safety but is also a legal requirement in many jurisdictions.
Minimizing Risk and Legal Liability: Organizations and employers must ensure that employees have the proper equipment and are properly trained on how to use it. By implementing proper PPE practices organizations reduce risks and also legal liability.
In summary, arc-rated PPE and non-arc-rated PPE serve different purposes, and their suitability depends on the specific hazards present in the workplace. Arc-rated PPE offers specific and tested protection against the thermal energy from an arc flash, whereas non-arc-rated PPE will not and can actually increase the risk of harm during an arc flash event. Using appropriate arc-rated PPE is critical for electrical safety and plays a crucial role in protecting workers and preventing severe injuries.