Tyndale presents Arc Week: a unique, week-long educational look at the world of arc flash hazards through the lens of Shark Week. Join Scott Margolin – our dedicated technical expert by day and passionate shark enthusiast in his free time – for engaging, memorable parallels that bring important lessons about risk protection and PPE to life.
Catch it all: Season 1, Season 2, Season 3.
We’re taking you on a journey to spend a day in the arc ratings lab, and what better way to do it than to take you to the facility that makes it all happen? Kinectrics is the world’s leader in life cycle management for the electric utility industry, and where you’ll have the opportunity to see arc ratings live on camera. Follow Brian Shiels, who serves on the ASTM International Board of Directors, through the arc rating lab and uncover exactly what it takes to test the protective qualities of arc-rated fabric.
What is an arc rating?
Simply stated, an arc rating is a direct measure of that fabric’s ability to insulate the wearer from a second-degree burn through the fabric. The higher the arc rating, the more protective the garment.
Preparing for arc flash testing at the lab.
Once the testing apparatus is set up, the first step in testing fabric at the lab is to perform a safety protocol known as “lockout/tagout” (LOTO). The LOTO process ensures nobody is within the walls of an energized station.
Testing fabric to meet the ASTM F1959 Standard.
The arc flash testing facility takes in at least seven yards of fabric at a time to be tested, weighs it, washes it in a home washing machine three times, dries the fabric once, then hands it off to be tested by the ASTM F1959 testing apparatus. ASTM F1959, Standard Test Method for Determining Arc Thermal Performance (Value) of Textile Materials for Clothing by Electric Arc and Related Thermal Hazards, is the test method used to calculate a given fabric’s arc rating—that is, to measure the thermal protection the fabric provides in an arc flash.
There are five parts to the F1959 apparatus that you should be familiar with before understanding how the testing apparatus functions:
- Vertical electrodes
- Fabric panels
- Test sensors
- Incident energy monitors
Brian explains how the F1959 testing apparatus works to conduct an arc flash stimulation by passing electricity through a non-conductive medium, air. Fabric is placed on the apparatus’ fabric panels, and a fuse wire is attached to two electrodes. The fuse wire is then blown away, leaving an opening of air. At this point, the arc flash is created, generating a plasma within the test cell. The apparatus’ test sensors monitor heat as it comes through the fabric to collect data points indicating whether a burn has occurred through the fabric panel.
Ensuring accuracy in arc flash testing.
The fabric must be tested multiple times and have at least 20 data points to establish the arc rating of a garment. For the data points to be considered complete, they must include the proper distribution of data between no burn, mix zone, and burn.
Determining the arc rating.
Once the data points have been collected and an arc rating report is created, an average is taken, and an S curve is generated through the data using logistic regression. The final arc rating is where the S curve meets 50% probability on the vertical axis, and then a line is drawn from that point to the incident rating, measured in calories on the bottom axis.
Finding the arc rating on your PPE.
ASTM F1506 specifies that the arc rating of your garment must be included on the garment label. The label is typically found on the inside of the neck of a shirt or jacket, and possibly as a pad print or sewn label on an interior fabric panel. Many manufacturers also include an external arc rating label to make spot checks easy.
Now that you know all about how arc-rated fabric is tested, did you know there are two different “species” of arc ratings?! Please join us tomorrow to catch Episode 4: Who Wins in a Dog Fight? ATPV vs. EBT Explained. “Which arc rating is better, ATPV or EBT?” ranks as one of our most frequently asked questions. And the truth is, neither one is better than the other – find out why in Episode 4.
Do you have a flash fire – rather than an arc flash – hazard? The hazards may differ, but the valuable lessons in this series are relevant to workers in oil and gas and other industries that use PPE to protect workers from thermal hazards. Tune in!