A major improvement in ASTM F2178 for end users and manufacturers has been published. The 2020 version recognizes that hoods are limited by the rating of the fabric and that 20 minimum samples tested to levels much higher than the final rating provide no value to end users or manufacturers. ArcWear and Kinectrics took the lead to fix this issue in the newest version. To make hoods even safer, the standard now has an after flame failure if there is any after-flaming visible inside a hood (something that our lab did but was not a standard requirement) and a total limit on afterflame time on hoods in testing to make the hoods even safer. Hoods also will receive testing above the rating to ensure that they do not ignite or melt in any way that would endanger a worker. Before some face shields could have issues above the rating, but that was not captured as the rating might end as low as 12 cal/cm². Not every shield will receive a higher level test to ensure no catastrophic failure will happen in arc flash events near the arc rating of the product.
The new changes do not negate older reports, but as manufacturers move forward the cost of testing should be lowered and fewer samples will be needed for arc flash hoods. This testing change is unlikely to affect shields, but hoods were often tested to 2-4 times higher than their final rating resulting in added cost and damage to lab equipment with no value for end users or manufacturers.
Procedure B, which includes the new term “Arc Rating Limit” was the new path added for systems containing fabric components that have been tested for an arc rating to ASTM F1959. This procedure allows manufacturers to designate a rating lower than the fabric rating, or to use the fabric rating for evaluation of the hood. Often, hood systems are de-rated to the rating of the fabric composite used in the design; procedure B creates a path for an expedited test to complete the rating at the level of the fabric rating (or other, lower, assigned value). Procedure B also covers systems with fabric ratings of 100 cal/cm², as this is the capacity of the equipment. In the new Procedure B to determine the “Arc Rating Limit”, 6 specimens are evaluated at the arc rating of the fabric used in the system for verification.
If the system fails any evaluation, exhibits breakopen, or any of the four sensors in the hood design exceeds the Stoll Curve within 10 cal/cm² of the rating of the fabric or designated rating below the fabric rating, the testing must be reverted to Procedure A for a full analysis.
There are a few additional items that were added to the 2020 edition of ASTM F2178:
- A requirement to evaluate products arc rated < 20 cal/cm² for ignition, melting and dripping at a minimum of a 20 cal/cm² exposure
- Afterflame Requirements*: No single specimen can afterflame for more than 60s, the average cannot exceed 30 seconds, and any flaming visible inside the headspace of the hood shall constitute a failure. *there are afterflame exceptions for small pieces and candle-like flames that do not pose a risk of ignition to the facepiece, brackets, etc., like small labels.
- The maximum arc rating of the standard is 100 cal/cm²