Judgment of protective performance of arc protective clothing

The common problem in the field of arc protective clothing is: whether the arc-level ATPV value or the arc-level EBT value can better reflect the protective performance of clothing. In the field of arc protection, the United States has decades of experience in protection. Therefore, some brief introduction and analysis of the ATPV value and EBT value are made with reference to relevant standards of the American Standard and foreign language data.

When the method of testing the arc rating of garment materials is still in its infancy, the ASTM F18 Committee (American Society of Experimental Materials Workers' Electrical Protection Equipment Committee) recognizes that some materials can cause the skin to sense burning warnings before the material breaks, while other materials Can't. Therefore, two rating criteria were initially generated: one was ATPV, the arc thermal performance value; the other was EBT, the material rupture threshold energy value.

A company once had a difference between the two in the early stages of its market, on the grounds that the materials they tested did not have a “burst” phenomenon. This conclusion is arbitrary because subsequent experiments have shown that each fiber will break before it reaches the combustion forecasting level. Now, we find that knitted fabrics usually break before the burning point and woven fabrics burn before the breaking point. Each fabric structure and all types of fibers have their own advantages and disadvantages.

There are two reasons why the committee has renamed the arc rating: First, simplify the terminology on the label so that end users can better understand it, and second, to eliminate everyone's misunderstandings about EBT. In many respects, the Commission retained the EBT and ATPV values ​​as a mark or appendix in the arc rating, which is of great significance for more professional and safe use of arc-protection clothing. So now we can see that the arc protection suit label is marked with ATPV=Xcal/cm2 or EBT=Xcal/cm2.

Fabrics marked with EBT values ​​do not exhibit secondary burns on the calorimetric sensor in most cases because the tiny cracks on the fabric are not directly on the sensor. Theoretically, if these fracture holes are located directly on the sensor, then there will be a burn site predicted in the crack hole, so it can be directly rated. Both arc ratings are in cal/cm2 and the minimum is usually recorded. That is, EBT values ​​or ATPV values ​​can all be recorded, but only one of the arc ratings for the fabric is ultimately selected. According to the provisions of arc rating in ASTM F1506 (Standard Performance Specification for Textile Materials Used in Protective Clothing for Electrical Workers Exposed to Instantaneous Arc and Related Thermal Hazards), only the minimum value can be written on the clothing label.

If the clothing arc rating is assessed according to the ASTM F1506 standard, the fabric undergoes several tests. For example, the fabric must be subjected to a water wash test and the ASTM D6413 vertical combustion test. That is, fabrics that are truly flame retardant under arc, flash fire, or any flame conditions must meet a series or more comprehensive tests.

According to the ASTM standard, the two indicators of the arc rating are as follows:

The ATPV value is based on the Stortor curve. There is a 50% chance that the energy incident on the material will allow enough heat to penetrate the specimen to cause a secondary burn.

The EBT value is a 50% chance that the energy incident on the material breaks the sample. When the total area of ​​holes on the fabric exceeds 1.6cm2, we see it as broken.

Both ATPV and EBT were evaluated using the same test method (ASTM F 1959), but the arc level was recorded using the first achieved value. If the thermal insulation value of the material is greater than the tensile strength of the arc, the material will first break; otherwise it will burn before it breaks.

If the EBT value is equal to or less than the ATPV value, then "EBT" will be used as the arc rating value and marked as the arc rating (EBT); if the EBT value is greater than the ATPV value, "ATPV" will be treated as the arc rating value and marked as the arc rating .

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