Electric arc clothing – testing for performance effectiveness

from ECN August 2022

GTC 400 C and 600 C Professional Thermal Camera

Peter Dumigan, Managing Director of the Hultafors Group UK, owner of Snickers Workwear and its ProtecWork range of protective wear, writes on the importance of fully tested and certified electric arc clothing.

The risk to life and limb from electric arc accidents is significant, often resulting in serious injury and sometimes death. Arcs due to electrical faults can cause severe injuries and damage – thermal injury, serious burns, electric shock, noise, UV emissions, pressure and shrapnel are commonplace, as well as the potential for toxic exposure and the impact of physical and mental shock. That’s why decisions on clothing choice have to be well-informed and carefully considered.

IEC 61482-2 specifies requirements for clothing protecting against the thermal hazards of an electric arc. This type of protective wear belongs to the Risk III category, which defines garments used in high-risk environments and certifies them to prevent second-degree burns in the event of an electric arc flash (flashover). It also certifies protection for the wearer from other serious risks such as heat, flames, and hazardous chemicals.

No type of clothing, other than Class III certified Protective Wear that is properly tested and certified, is suitable for risk environments with electric arc hazards. The wrong buying choice can be potentially catastrophic.

The developmental processes for Snickers Workwear’s Class III ProtecWork clothing therefore requires real-life product testing that replicates the risk environments and accident eventualities to ensure and certify product efficacy and performance.

Two tests – the box test and open arc – are used to measure a material and garments’ level of protection. These test methods use different test set-ups, arc configurations, test parameters, test procedures and result parameters. The results of either test method cannot be physically compared or mathematically transformed into each other. The arc rating has to be tested and assessed using either one method or the other. • Box test: The box test is carried out in accordance with EN 61482-1-2. It includes a directed electric arc in an enclosed space APC 1 or APC 2. This test was previously the most common method used to determine a material’s level of protection. • Open arc: Open arc measures protection using the 61482-1-1 test method, which is equivalent to the NFPA 70

US standard. The method uses an 8kA circular arc that strikes the test material from a distance of 30cm. The test results are presented in calories per square centimetre (cal/cm2), revealing at what calorie level the garment offers a 50% chance of protection against second-degree burns as a ATPV or

EBT50 value. The higher the value, the better the protection.

For wearers of protective clothing, it’s crucial to know what level of protection their clothing offers. The foundation of good protection is that the garments provide certified protection against electric arcs and that they do not combust. The clothing must be tested and certified against heat, flames and electric arcs. This applies not

The foundation of good protection is that the garments provide certified protection against electric arcs and that they do not combust

only to the outer garment layer, but to underwear, the base layer, mid layer and all other layers as well.

Different fabrics may have different properties and characteristics, which means the level of protection needs to be presented in two different ways. Strong fabrics may remain intact after a test procedure, yet allow enough heat to be transferred through the material that a burn still occurs. In these cases, the test results are presented as an Arc Thermal Protection Value (ATPV). The other alternative is that the fabric offers high insulation, but instead ruptures and tears so that a hole opens up in the material, causing a burn. This value is called the EBT50 (Energy Break Open Threshold).

ELIM: Whereas the ATPV or EBT50 value gives an indication of what energy level you run a 50% risk of getting a second-degree burn at, the incident energy limit (ELIM) defines the energy level at which you avoid the risk of a second-degree burn. Remember, however, that there is still a risk of getting a first-degree burn injury.

The ELIM value is calculated as the average of the three highest incident energy data points without rupture, shrink open and without reaching or exceeding the Stoll curve. The three incident energy data points are taken just below the mix zone in the test report. The Stoll curve determines the rating of the transfer of heat energy (calories) based on the time of transfer and the level of heat energy produced.

Heat Attenuation Factor – HAF: HAF is a measurement of the percentage of energy that is blocked by the material or material system. Even though a fabric may be 100% flame resistant, this does not mean it will block all of the heat it’s exposed to. A HAF of 85% means that it will block 85% of the heat the fabric is exposed to. This is in the case of a short burst of arc – flash heat – typically less than one second. In the event of prolonged heat exposure, the HAF would be much lower.