Arc flash ATPV vs. ATPV 20%
Understanding the Open Arc Test Method
During testing, 4 glove samples in each test shot are exposed to a controlled electric arc. The resulting heat transfer through each glove, as well as the incident heat received by separate monitor sensors, is recorded. The heat exposure to each glove is considered to be equal to the average exposure measured by the 2 neighbouring monitor sensors.
Based on this data, the heat energy transferred through the glove versus time is measured. The Stoll curve defines the relationship between heat energy exposure and time that leads to the onset of a second-degree skin burn. By comparing the glove’s heat transfer data to this curve, each test point is classified as either below the Stoll curve or as causing a predicted second-degree burn. An arc test has a minimum of 20 valid test points, and typically around 24 test points. All of these are then used to calculate the arc incident energy that results in a 50% probability of a second-degree burn (skin blister).
ATPV values for protective gloves exposed to Electric Arc Flashes
The following Eureka safety gloves have been tested for resistance to electric arc flashes according to ASTM F2675:
- 18-2 Heat ArcDot-8
- 18-2 Heat AF-10
- 15-4 Heat AF-11
- 13-4 Heat AF-17
- 13-4 Heat AF-29
- 13-4 Heat AF-50
Arc Thermal Performance Values (ATPV)
When evaluating gloves for arc flash protection, the Arc Thermal Performance Value (ATPV) is the key indicator of performance.
The ATPV value represents the incident energy (in cal/cm2) at which there is a 50% probability of crossing the Stoll curve, indicating the onset of a second-degree burn through the material.
Energy Limit Value (ELIM)
The ELIM calculation uses the same open-arc test data. ELIM is calculated as the average of the 3 highest incident-energy test points below the first failed test point. The value is therefore more conservative than ATPV, but the final ELIM calculation is initiated by the first failure and is hence more sensitive to random variations.
ATPV 20%
The ATPV20 is a Eureka in-house calculation method that uses the same large sample set generated for the standard ATPV calculation. It is therefore less sensitive to individual random test variations while still providing a more conservative value than the traditional ATPV. ATPV20 represents the incident energy at which the calculated probability of crossing the Stoll curve is 20%, compared with 50% for the traditional ATPV.
Using the ATPV20 value in engineering risk assessments provides an extra safety margin, especially in higher-risk or uncertain environments.
| Value | Meaning | Description | Typical Use |
|---|---|---|---|
| ATPV | Energy at 50% chance of 2nd-degree burn | Values from certification test reports | ASTM / NFPA certification |
| ATPV20 | Energy at 20% chance of 2nd-degree burn | Eureka in-house calculation | More conservative PPE selection |
Test Results
The following table and chart present the ATPV and ATPV20 values obtained from the arc flash tests for each glove model.
| Glove model | ATPV | ATPV20 |
|---|---|---|
| 18-2HAD-8 | 7,9 cal/cm2 | 5,9 cal/cm2 |
| 18-2HAF-10 | 9,7 cal/cm2 | 7,8 cal/cm2 |
| 15-4HAF-11 | 11,1 cal/cm2 | 9,8 cal/cm2 |
| 13-4HAF-17 | 17,1 cal/cm2 | 14,6 cal/cm2 |
| 13-4HAF-29 | 28,8 cal/cm2 | 25,4 cal/cm2 |
| 13-4HAF-50 | 42 cal/cm2 | 30,9 cal/cm2 |
Summary
Using ATPV20 in risk assessment could allow for a more conservative, lower-risk PPE selection, improving protection reliability in environments where arc conditions or exposure uncertainties are higher than predicted.