A Guide To Arc Flash Testing & Certification

What is Arc Flash?

Arc flash is one of the most dangerous and least understood electrical hazards. Typically caused by short-circuiting, an arc flash is an electric discharge of high current which flows through an air gap between conductors, producing temperatures of up to 20,000°C and a very bright ultra-violet light. To put this extremely high temperature into perspective, that’s more than three times as hot as the surface of the Sun, which is around 5,500°C – meaning the electric arc is hot enough to instantly vaporise most materials it comes into contact with!

Depending on the severity, duration, and distance of the arc flash, the potential harm it can cause is considerable, including acute burns, fires, and sometimes fatalities. There is a high risk of burns to the skin and body of the worker, as well as damage to the surrounding work area, while sound blasts (up to 140dB-gun discharge level) can severely damage hearing. The ultraviolet light produced can also be very hazardous to the eyes. Arc Flash can cause numerous other dangers, including electric shock and toxic gas.

These extreme hazards illustrate why arc flashes are so dangerous, and why proper safety measures, including the wearing of the correct PPE and safety clothing is vital for personnel operating in any environment where this threat may present itself. Here, Clad Safety examine the testing procedures followed to ensure arc flash clothing and PPE is correctly tested and certified.

ATPV Testing vs ELIM Testing

Still widely used, ATPV (Arc Thermal Performance Value) has been the industry standard for many years, and is defined as the incident energy on a fabric or material that results in a 50% probability of sufficient heat transfer through the specimen to cause the onset of a second-degree burn. This testing standard has limitations in that it allows for a 50% probability of burn injury, and doesn’t account for any break-open of the safety wear fabric. Overall, it cannot guarantee fully adequate wearer protection in all scenarios.

ELIM is the new, more reliable, advanced standard introduced to address some of the limitations of ATPV. It represents the maximum incident energy exposure where the garment is expected to provide protection without break-open and with no more than a 2nd degree burn. To summarize, flash clothing conforming to ELIM standards provide the higher protection performance level.

Where ATPV certification equates to 50% probability of protection, ELIM aims for 100% probability of protection. ATPV is still widely recognised and utilized, while ELIM is gaining recognition but is not yet universally adopted. It is, however, consistently being incorporated into the latest standards, and being recommended for higher-risk scenarios. Many manufacturers still provide both ATPV and ELIM ratings for their arc-rated protective equipment, enabling users to make informed decisions based on their specific risk assessments and safety requirements.

Box Testing vs Open Testing

As with the different certification standards, there are also different testing methods. A box test is conducted in a closed, box like compartment to simulate arc flash in a confined space (such as an electrical cabinet). Thus the energy is reflected and contained within the confines of the enclosure, often resulting in higher energy readings. This configuration is more representative of indoor switchgear, motor control centres, or panel board applications, where arc flash is likely to occur in a confined space. Box testing is becoming increasingly important in arc flash hazard analysis.

An open test is performed in an open space to simulate arc flash in open air. Energy is dissipated more freely in multiple directions, resulting in lower incident energy readings. Open testing is more characteristic of outdoor equipment or open air installations, such as overhead power lines or outdoor substations. While open testing has been the traditional method for many years, and is still widely recognized, a propensity to underestimate incident energy in some scenarios renders it slightly less effective.

In practice, a comprehensive arc-flash hazard calculation study may involve both types of testing, in order to provide a more comprehensive assessment of potential hazards in various workplace scenarios. The choice between box and open tests (or the use of both) depends on the specific equipment, environment, and potential arc flash scenarios being evaluated.

Fabric Testing vs Garment Testing

There are important distinctions between testing the fabric and testing the complete garment for arc flash protection.

Fabric testing provides a baseline for material performance. It focuses on the material properties alone, evaluating the base fabric’s ability to resist heat and flame, and often uses smaller samples of material. Whilst accurately measuring properties like flame resistance, heat transfer, and break-open threshold, it does not account for garment design or construction.

Garment testing offers the most realistic assessment of worker protection, accounting for factors like fit, coverage, and layering. This method evaluates the entire assembled protective garment, including all components such as seams, closures, and layered areas. The procedure necessitates the testing of the full item of clothing and typically involves mannequin tests with sensors underneath the garment, enabling accurate assessments around overall protection, including weak points, and evaluating how the garment performs as a system. Garment testing is usually necessary for the full regulatory compliance and certification of protective clothing.

Fabric testing and garment testing are both important components in the arc flash protection development and certification process. Fabric testing provides crucial data for material selection and initial design, while garment testing ensures that the final product provides the expected level of protection in real-world scenarios. Many manufacturers use a combination of both to create and validate their arc flash protective workwear.

Cal Ratings – Meaning And Importance

Cal ratings, short for calorie ratings, are a crucial measurement in arc flash protection. The Cal rating refers to the amount of thermal energy that a fabric or garment can protect against, measured in calories per square centimetre (Cal/cm²). This measurement represents the incident energy that a worker may be exposed to during an arc flash event, specifically indicating the maximum incident energy that the protective equipment can withstand before the wearer would be likely to experience the onset of a second-degree burn. The higher the Cal rating, the higher the protection level provided by the fabric or garment.

Arc flash protection is typically categorized into different levels, often referred to as Hazard Risk Categories (HRC) or Personal Protective Equipment (PPE) categories. Arc flash incidents can vary greatly in intensity depending on factors like voltage, available fault current, and arcing time, while different electrical systems and equipment pose different levels of risk. Specific tasks also carry different levels of danger. For example, routine inspection of electrical equipment might require less protection than live electrical work. UK current practice typically uses arc flash PPE categories, or simply specifies the required Cal/cm² rating for protective equipment based on an arc flash risk assessment.

Conclusion

By carefully assessing the potential arc flash and electrical hazards in each environment and for each task, safety professionals can specify the exact rating of arc flash clothing required. This ensures that workers are fully protected without being over-encumbered, promoting safety, mobility and efficiency in electrical work environments.

At Clad, our expertise extends beyond a broad experience and knowledge of arc flash hazards and testing certifications. If you’re responsible for a large team who wear arc flash safety gear, get in touch today to find out how we can help – call us on 01423 881266 or email us at [email protected].