Test Method for Determining the Arc Rating of Materials for Clothing
ASTM F1959/F1959M is an internationally recognised test method for determining an 'arc rating' or 'Arc Thermal Performance Value' (ATPV) of a material, or combination of materials, intended to construct a flame-resistant garment.
The results from the ASTM F1959/F1959M test method will detail the fabric samples material proprieties when exposed to convective and radiant energy generated by an electric arc.
The Test Method
The ASTM F1959/F1959M test method takes a fabric sample, placing it vertically while remaining flat with no other movements.
The sample is exposed to convective and radiant energy generated by an electric arc. A heat-sensitive sensor is set to specified exposure conditions.
These conditions may produce different results. Additionally, the test sample may be tested to other conditions representative of expected onsite hazards. If these tests are conducted they will be recorded on the products test report, detailing the performance results.
For the material to be tested using the ASTM F1959/F1959M test method, it must:
- be intended to be worn as protective workwear against arc flash
- less than 150mm (6 inches) char length
- burn for less than 2 seconds after flame is extinguished when tested in accordance with test method D6413 Method for Flame Resistance of Textiles
The results of this test method produce an arc rating either expressed as an Arc Thermal Performance Value (ATPV) or Energy Breakopen Threshold (EBT) or both. Which test method used will be indicated in brackets next to arc rating indication, e.g. arc rating (ATPV) = X cal/cm2. Both ratings can appear on the report, but only the lowest value is accepted as the arc rating, according to ASTM F1506 specifications.
Arc Rating (ATPV)
The Arc Thermal Performance Value (ATPV) is an arc rating and is expressed in kW.s/m2 or cal/cm2. An ATPV value is an important indication of a fabrics ability to protect an individual from a second-degree burn due to incident energy from an arc flash event. The ATPV records the point at which there is a 50% chance of heat transferring through the garment's fabric, reaching the temperature required for the onset of second-degree burns (based on the Stoll Curve). The fabric must not break open before reaching this threshold.
Arc Rating (EBT)
Instead of reaching the threshold of onset second-degree burns with the fabric intact, particular test fabrics will develop breakopens or holes. A breakopen is defined by an open area of at least 1.6 cm2 (0.5 in2). If the test fabric is recorded as Energy Breakopen Threshold (EBT), the fabric breaks open before the wearer begins to develop second-degree burns. Therefore, arc rated fabrics with an ATPV value will allow burns before the fabric will break open.
Heat Attentuation Factor (HAF)
Furthermore, the test method is used to determine a Heat Attenuation Factor (HAF), the percentage of total heat blocked by the fabric from reaching the sensor. In electric arc fault testing, this is the percentage of incident energy that is blocked by a material at an incident energy level equal to the ATPV. The test method is limited to electric arc flash that would generate incident energy or heat flux rates from 84 to 3,505 kW/m2 [2 to 600 cal/cm2]. The test is not used to assess non-flame resistant materials. However, layers of a multi-layered flame resistant fabric sample can be tested using this standard. The method also excludes electrical contact or electrical shock hazards.