Protective clothing against the thermal hazard of an Electric Arc
This standard specifies PPE Clothing when there is a risk of an Electric Arc – for instance when working with electricity on open equipment or maintenance / switching work. Electric Arc garments come under PPE Regulation Category III. Fabric properties and garment design are important parameters in the certification process of Electric Arc garments.
ELIM: 8,1 cal/cm²
EBT: 8,7 cal/cm²
During the transition period, Tranemo will have garments with both types of marking.
Tranemo Electric Arc garments are marked with IEC 61482-2 which includes both test methods for Electric Arc: EN 61482-1-1 “Open Arc test” which involves a medium voltage range (>1 000V) and EN 61482-1-2 “Box test” which involves a low voltage range (400V). Both tests simulate different levels of risks.
EN 61482-1-1 Open Arc test - This standard tests the protection level of the garment by using an Open Arc. The test method is similar to the American Electric Arc Standard ASTM F1959 and results in an Arc Rating which includes ATPV (Arc Thermal Performance Value) and/or EBT (Energy Break Open Threshold). Both ATPV and EBT is based on a 50% probability of second degree burn and the Americans use NFPA 70E to handle the Risk Assessment around Electric Arc. NFPA 70E is also noted in the updated IEC 61482-2 as a help in the Risk Assessment. To be able to publish the European version of this standard and to follow the EU Regulation that demands a 0% probability of injury/second degree burn, the European Open Arc test will include the new value: ELIM (Incident Energy Limit). The idea of ELIM is to remove the risk of second degree burn and to help protect workers in a safe way without increasing other risks and preventing work.
All three values (ATPV/EBT/ELIM) are based on the Stoll Curve and a number of tests are performed on the fabric/fabric layers to determine an Arc Rating. The result is given in cal/cm² and shows the incident energy level where the garment is predicted to protect from a second-degree skin burn. The value helps you to chose the right level of protection. The new marking can include ELIM and ATPV or EBT as noted above. Tranemo will have both values in the marking : ELIM to show at what Arc Rating you have 0% probability for a second degree burn and ATPV/EBT to be able to relate to the American Risk Assessment standard NFPA 70E (that only refers to ATPV and EBT based on a 50% probability of second degree burn) in its PPE categories for different risk levels. Over time, Tranemo will re-test all fabrics and due to the changes in the standard, we will see differences in the ATPV/EBT result compared to before on single fabric and also on Tranemo Skinsafe™ combinations.
Like noted in NFPA 70E, and from experience of Tranemo Skinsafe™ tests, layers of Arc rated clothing is an effective approach to achieve the required Arc Rating with the lowest number of layers and clothing system combined weight. This provides the required protection at a higher level of worker comfort and increases the probability that the Electric Arc PPE will be worn. The differences in the values between ELIM and ATPV/EBT will also highlight the importance of wearing several layers in your Tranemo Skinsafe™ system to ensure you are fully protected. The air gaps created between the layers will provide extra protection and very often will have an increase Arc Rating in combination than the sum of the individual layers.
It is important to understand that the Arc Rating of the total system CANNOT be calculated by simply adding the Arc Ratings of the individual layers. The only way to determine the Arc Rating of the total system is to conduct a multi-layer Arc test assembled as the garments would be worn in reality. This is what we call Tranemo Skinsafe™ - multi-layer tests that gives a best opportunity to choose the correct PPE combination that matches to the Risk Assessment.
The American performance standard for Electric Arc fabrics is called ASTM F1506 where fabric specifications also include the Open Arc test ASTM F1959. This standard is similar to the European IEC 61482-2 standard for fabric and garments. The biggest difference of the American demand compared to the European demand is the Char Length test - where a maximum char length is determined. The test is done after 25 washes and to pass, the maximum char length it is allowed to be maximum 152 mm after 12 s exposure. Tranemo has tested the fabrics that are developed for Electricians; Tera TX and Aramid 6.4FC. The test provides a useful indication of the fabrics Flame Retardant properties in an Electric Arc accident.
(Electrical insulating protective clothing against Electric shock or clothing for work intentionally using an Electric Arc (such as arc welding and plasma torch cutting) IS NOT covered by the European IEC 61482-2 standard.)
Risk Assessment Electric Arc hazard
Documents like NFPA 70E and ISSA Guidelines helps to assess hazards from a practical perspective. The hazards of an Electric Arc includes thermal effects, noise, pressure wave effect, shrapnel and flying debris, molten metal, optical and other effects and it is important that the risk assessment considers all the potential effects. To achieve enough protection, it is important that the whole body is protected with supporting arc PPE, e.g. helmet with protective screen, ear protection, gloves and safety shoes together with Tranemo protective clothing.
The American NFPA 70E Standard for electrical safety in the workplace is a consensus standard on how to protect workers from the hazards of an Electric Arc. NFPA is designed to help employees and workers to understand electrical hazards, it helps with: risk assessment, arc rated PPE selection and electrical safe work practices.
The Arc Rating (ATPV/EBT) is divided into four PPE Categories, PPE stands for Personal Protective Equipment. Tranemo normally recommends that the outer layer reaches 8 cal/cm² (i.e. PPE 2/CAT 2).
PPE 1 / CAT 1 – 4-8 cal/cm²
PPE 2 / CAT 2 – 8-25 cal/cm²
PPE 3 / CAT 3 – 25-40 cal/cm²
PPE 4 / CAT 4 – >40 cal/cm²
EN 61482-1-2 Box test - tests the APC (Arc Protection Class) of the garments by using a constrained and direct arc.
APC 1(former Class 1) – 168kJ (4kA, 400V)
APC 2(former Class 2) – 320kJ (7kA, 400V)
A single layer garment will in most cases pass APC 1. To reach APC 2, a two or three-layer system (or a thicker garment such as a winter garment) is needed.