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ATPV / Ebt

The Arc Thermal Performance Value (ATPV) is the incident energy that results in a 50% probability that sufficient heat transfer through a material is predicted to cause the onset of second-degree burn injury. The Energy Break-open Threshold (Ebt) is the incident energy that results in a 50% probability of material break-open.

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Shutterstock 437750431

ATPV EXPLAINED

Arc Thermal Performance Value (ATPV) as defined by ASTM Standards, is the incident energy on a material that results in a 50% probability of sufficient heat transfer through a specimen to cause the onset of a second-degree burn based on the Stoll Curve. The ATPV is reported in calories per centimetre squared (cal/cm2).

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Shutterstock 130698689

Ebt EXPLAINED

The Energy Break-open Threshold (Ebt) as defined by ASTM Standards, is the incident energy that results in a 50% probability of a material breaking open, defined as an open area of at least 1.6 cm2, when exposed to an arc. The Ebt is reported in calories per centimetre squared (cal/cm2).

ATPV / Ebt OVERVIEW

  1. The ATPV and Ebt are evaluated in the same test.
  2. The first point to be reached, either the ATPV or Ebt, is the reported arc rating.
  3. If an Ebt value is determined and found to be equal to or below a determined ATPV, then the Ebt value is reported as the arc rating value and noted as Arc Rating (Ebt).
  4. If an Ebt value is found to be above a determined ATPV, then the ATPV value is reported as the arc rating value and noted as Arc Rating (ATPV).
  5. ATPV and Ebt arc ratings are expressed in calories per centimetre squared (cal/cm2). For example, a material with a determined ATPV of 12 would have an arc rating of 12 cal/cm2.
  6. A calorie is defined as a unit of energy equivalent to the heat energy needed to raise the temperature of 1 gram of water by 1 degree Celsius (now often defined as equal to 4.1868 joules). 

Neither measurement is better. Essentially Ebt fabrics are typically more insulative than they are strong and ATPV materials are stronger than they are insulative. 

Usually Ebt indicates the garment is a knit and is more comfortable but essentially no less protective to the user.  

TESTING FOR ATPV AND Ebt - DUPONT™ ARC-MAN® 

The open arc test determines the limit of the incident energy to which a material or material assembly will provide protection against the thermal effects of an electric arc. The electric arc testing system developed by DuPont™ measures the Arc Thermal Performance Value (ATPV) and Energy Break-open Threshold (Ebt) values of protective fabrics and garments in simulated open electric arc incidents according to IEC/EN 61482-1-1.