A protective bubble against arc flashes
20 December 2021
Arc flash-resistant clothing is critical to protect against industrial accidents, but selecting the correct level of protection for the application can be challenging says Pauline Weisser
An arc flash, also referred to as electric arc, can be defined as a non-contact short circuit taking place between two conductors such as busbars or cables. These conditions can lead to a plasma fireball that can reach extremely high temperatures of up to 20,000°C. This is enough heat to cause a worker’s clothes to catch fire, even at a distance.
Faulty electrical equipment due to incorrect installation, dust, corrosion, surface impurities, or wear and tear is a common cause of electric arcs. However, in most cases, short circuits are a result of human errors.
An arc flash can have severe consequences for workers that can range from external and internal burns to fatal injuries. There is also a risk of exposure to toxic hot gases and vaporised metal that can lead to eye injuries due to the ultraviolet light that is generated in the process.
How widespread is the risk of exposure to arc flashes?
Arc flashes continue to represent a common risk to workers across industries. The latest Eurostat data shows that over 76,000 workers in Europe suffered injuries due to “contact with electrical voltage” in 2018. These workplace accidents can have far-reaching consequences, not only for the employees involved but also for their employers. For example, in May 2021, Network Rail was fined nearly £700,000 after a worker suffered third-degree and mixed depth burns due to an electrical arc.
Arguably, the growth that the renewable energy sector is set to experience in the coming years may indirectly lead to an increase in arc flash-related incidents. The installation and maintenance of renewable energy generators such as solar panels and wind turbines inevitably present arc flash hazards, just like any other electrical application. Similarly, battery energy storage systems, the backbone of the expanding low-carbon power grid may expose workers to electric arcs.
The "4 Ps" of arc flash protection
A thorough workplace risk assessment, which is a legal requirement in the UK and other countries, is key to putting in place measures to protect workers against arc flashes. This is known as the 4P Methodology, which involves four key steps: PREDICTING the severity of the arc flash, PREVENTING damage through hazard mitigation, PROTECTING workers from any residual hazard and PUBLISHING the results.
Personal protective equipment (PPE) such as protective clothing is the last line of defense against arc flash injuries and, therefore, plays a critical role in the 4P Methodology. But not all PPE is created equal. Employers must take steps to ensure that the equipment is compliant with the latest standards is paramount.
The importance of arc flash protection standards
When it comes to specifying arc flash-protective clothing, there are different standards to consider, which vary from region to region. A fabric that complies with these minimum requirements must be flame-resistant and ensure protection against electric arcs by preventing ignition.
In Europe, there are two main standards to take into account: "IEC 61482-1-1:2019: Live working – Protective clothing against the thermal hazards of an electric arc – Part 1-1: Test methods – Method 1: Determination of the arc rating of clothing materials and protective clothing using an open arc" and "IEC 61482-2:2018: Live working – Protective clothing against the thermal hazards of an electric arc – Part 2: Requirements". "EN ISO 11612: 2015 (Protective clothing — Clothing to protect against heat and flame — Minimum performance requirements") is another important standard to consider.
Additional tests may be conducted by some manufacturers of protective clothing to guarantee an even higher level of protection. These tests are based on an instrumented manikin (as specified by ISO 13506-1:2017) and measure the amount of transferred energy. This way, the performance of protective clothing during exposure to short-duration flame engulfment can be assessed with great accuracy.
Consideration when specifying protective clothing
The single most important feature to consider when selecting arc flash protection garments is the fabric’s ability to carbonise and thicken when exposed to intense heat. This is how the fabric prevents ignition, acting as a protective barrier between the heat source and the wearer's skin.
But there are also other important factors to bear in mind. Built-in inherent thermal protection: durable fabrics that maintain their heat resistance over time – even after having been washed repeatedly – are an essential feature, especially if the clothing is used in dirty environments. Multi-hazard protection: fabrics that integrate multiple layers of protection, including resistance to heat, flame, and molten metal splashes, are the optimal choice for environments that may present multiple hazards. Comfort: selecting arc flash-protective clothing made using lightweight and highly breathable fabrics is key to ensuring a good level of comfort and preventing fatigue, which is a common cause of injuries. This is especially important in applications where workers must wear protective clothing for extended periods. Durability: some of the latest arc flash-resistant fabrics provide greater breaking strength than traditional flame-resistant-treated cotton.
The bubble effect explained
Double-faced fabrics, also known as “bubble-effect” technology, constitute one of the most recent advancements in arc flash protection. These innovative materials are designed in a way that, when they are exposed to heat, air bubbles form inside the internal layer, insulating the wearer against electric arcs. This way, it is possible to achieve best-in-class heat resistance without having to increase the weight of the material. Tests conducted by DuPont show that double-faced fabrics exhibit a higher level of electric arc flash protection than conventional fabrics with the same material composition and weight.
When tested according to IEC 61482-1-1, a double-faced fabric displays an ATPV (Arc Thermal Performance Value) between 16 and 19 cal/cm2, which is more than double the ATPV of an equivalent conventional fabric (7.2 cal/cm2).
Arc flashes continue to represent a serious risk to workers across many industries. The seemingly unstoppable trend towards electrification means that more workers than ever before will be dealing with electrical applications where they may be exposed to electric arcs.
Protective clothing is key to keeping workers safe from the risks associated with electric arcs. Double-faced fabrics are proving the optimal choice for arc flash protection. They deliver enhanced heat and flame resistance without compromising on comfort.
Pauline Weisser is application development specialist at DuPont Personal Protection