September Safety Tip
Arc Flash PPE
Electricity is dangerous, as we all know. Working with live electrical wires poses an additional risk that all employers need to be aware of. The risk of arc flash is quite substantial for employees who work on live electrical wires. An arc flash is when a flashover of electric current leaves its intended path and travels through the air from one conductor to another, or to the ground. The temperature on arc flashes can reach, and in some cases exceed, 35,000°F at the arc terminals. When a human is in close proximity to an arc flash, serious injury or death can occur.
Arc flash can be caused by many things, including:
- Dust
- Dropping tools
- Accidental touching
- Condensation
- Material failure
- Corrosion
- Faulty installation
Three factors can determine the severity of an arc flash injury:
- Proximity of the worker to the hazard
- Temperature
- Time for circuit to break
Facilities are responsible for assessing their own facility for arc flash hazards because there are environmental factors that go into the arc flash calculation. The most important thing to determine is the “cal level” you are at. A hazard analysis will help you determine the flash protection boundary distance and in turn, the hazard/risk category (HRC) number. You will need to know both of these numbers before you begin shopping for PPE. Without an incident energy analysis, the table method will be necessary. An aspect of the new table method that enhances worker safety is the fact that if any of the specified conditions for normal operating conditions are not met, arc-rated clothing and PPE are mandated.
Of course the best way to protect workers from arc flash hazards is to de-energize the circuit. However, this may not always be possible, therefore the appropriate personal protective equipment must be used.
In order to determine the PPE you should use when working with live electrical wiring, you can take a look at the hazard classification table shown below from the NFPA 70E Standard for Electrical Safety in the Workplace®. This table shows you the hazard risk category associated with various tasks according to voltage level, and whether or not V-rated gloves or tools should be provided and used.
| Arc-Flash PPE Category | |
| 1. Arc-Rated Clothing, Minimum Arc Rating of 4 cal/cm2 (16.75 J/ cm2)a
Arc-rated long-sleeve shirt and pants or arc-rated coverall Arc-rated face shieldb or arc flash suit hood Arc-rated jacket, parka, rainwear, or hard hat liner (AN) Protective Equipment Hard hat Safety glasses or safety goggles (SR) Hearing protection (ear canal inserts)c Heavy-duty leather glovesd Leather footwear (AN) |
|
| 2. Arc-Rated Clothing, Minimum arc Rating of 8 cal/cm2 (33.5 J/ cm2) a
Arc-rated long-sleeve shirt and pants or arc-rated coverall Arc-rated flash suit hood or arc-rated face shieldb and arc-rated balaclava Arc-rated jacket, parka, rainwear, or hard had liner (AN) Protective Equipment Hard hat Safety glasses or safety goggles (SR) Hearing protection (ear canal inserts) c Heavy-duty leather glovesd Leather footwear |
|
| 3.Arc-Rated Clothing Selected so That the System Arc Rating Meets the Required Minimum Arc Rating of 25 cal/ cm2 (104.7 J/ cm2) a
Arc-rated long-sleeved shirt (AR) Arc-rated pants (AR) Arc-rated coverall (AR) Arc-rated arc flash suit jacket (AR) Arc-rated arc flash suit pants (AR) Arc-rated glovesd Arc-rated jacket, parka, rainwear, or hard had liner (AN) Protective Equipment Hard hat Safety glasses or safety goggles (SR) Hearing protection (ear canal inserts) c Leather footwear |
|
| 4. Arc-Rated Clothing Selected so That the System Arc Rating Meets the Required Minimum Arc Rating of 40 cal/ cm2 (167.5 J/ cm2) a
Arc-rated long-sleeved shirt (AR) Arc-rated pants (AR) Arc-rated coverall (AR) Arc-rated arc flash suit jacket (AR) Arc-rated arc flash suit pants (AR) Arc-rated arc flash suit hood Arc-rated gloves c Arc-rated jacket, parka, rainwear, or hard hat liner (AN) Protective Equipment Hard hat Safety glasses or safety goggles (SR) Hearing protection (ear canal inserts) c Leather footwear |
AN: As needed (optional). AR: As required. SR: Selection required.
aArc rating is defined in Article 100.
bFace shields are to have wrap-around guarding to protect not only the face but also the forehead, ears, and neck, or, alternatively, an arc-rated arc flash suit hood is required to be worn.
cOther types of hearing protection are permitted to be used in lieu of or in addition to ear canal inserts provided they are worn under an arc-rated arc flash suit hood.
dIf rubber insulating gloves with leather protectors are used, additional leather or arc-rated gloves are not required. The combination of rubber insulating gloves with leather protectors satisfies the arc flash protection requirement.
September 2018 Safety Tip: Arc Flash