The hazards associated with working on live electrical equipment were discussed in our previous articles. Shock and arc flash are the major hazards to avoid in the electrical environment. Obviously, the goal of every worker is to avoid being shocked, burned, or blown up. We’ve also discussed the differences in a shock event and an arc flash event and why both events require separate risk assessments and PPE. Shock PPE consists of insulating equipment such as voltage-rated gloves and insulated tools. Arc flash PPE is different, so the focus of this article is choosing the right PPE for arc flash protection.
With a shock event, voltage determines risk. The higher the voltage, the higher the risk. With arc flash, incident energy determines risk. Incident energy is to arc flash as voltage is to shock. A discussion about PPE needs to begin with an understanding of the term “Incident Energy”. Incident energy represents the risk level of an arc flash event. It is measured in calories/cm2 where calories are a unit of heat and cal/cm2 is the energy level in the form of heat that can be produced during an arc flash event. The higher the calories, the higher the risk.
As in shock, the protection boundaries for arc flash can be found on the arc flash label of the equipment.
The highlighted area of the arc flash label shows the Incident Energy and Flash Hazard Boundary. The calorie rating on the arc flash label helps determine the Flash Hazard Boundary. Anytime a worker is within the arc flash boundary while exposed to live electrical parts, arc rated PPE is required. The arc rating of the PPE being utilized must match or exceed the calorie rating on the label.
The higher the calories or arc rating, the higher the risk and, therefore, the more robust the PPE requirement. All arc flash PPE is required to contain an arc rating measured in cal/cm2. If PPE doesn’t exhibit this rating, then it is not arc rated and is not designed to be used as arc flash PPE.
Arc Flash PPE consists of more than just clothing because all parts of the body are to be protected when inside the flash hazard boundary and exposed to live electrical parts, including the face, neck, head, and hands. Arc rated clothing such as a shirt/pants combo or a coverall provides protection for the body, arms, and legs; however, an arc flash event can encompass the entire area, so the entire body must be protected. For this reason, face shields and balaclavas or an arc flash hood are required when the face and head are within the flash hazard boundary. Like arc flash clothing, these items must exhibit an arc rating.
Utilize Arc Rated PPE to protect all areas of the body that might be within the flash hazard boundary.
The calorie rating also provides guidance on the type of arc rated PPE required.
Protecting ourselves from arc flash is more involved than shock protection in many ways. In most situations, voltage-rated gloves and insulated tools meet the requirements for shock protection. However, arc flash protection involves clothing, head and neck protection, face protection, eye protection, hand protection, and hearing protection. All parts of the body must be protected.
In addition, the incident energy determines the level of risk in an arc flash, whereas voltage determines the risk for shock. Incident energy is not as straight forward as voltage. A typical facility might only have two voltage systems: 120/208 and 277/480. This means that the shock hazard boundaries are straight forward.
With incident energy, however, the numbers involve a much wider range. A typical facility might contain equipment with incident energy calorie levels between .1 and 100 and anywhere in between.
So how do we keep it simple and easy to follow?
Keeping it Simple
A simple and easy-to-follow PPE program depends on several variables:
• The frequency of live electrical work in which your workers are engaged
• The qualifications of the maintenance team
• The incident energy levels and flash hazard boundary range. What do the arc flash labels say?
• The condition and age of the equipment and robustness of the PM program
• The conditions that exist in the facility such as dust, corrosion, heat, and humidity
All the factors above must be taken into consideration before designing an arc flash PPE program. No cookie cutter approach exists, but there a few common considerations:
• Arc Rated Uniforms – If your team conducts live electrical work every day, a uniform system might make the most sense. The worker wears arc rated clothing full time and utilizes the head, neck, and hand protection as needed. In this case, answers to the following questions are necessary:
1. What should be the arc rating of the purchased PPE?
2. What is the plan for head, neck, face, and hand protection?
3. What is the plan when the arc rating of the equipment exceeds the arc rating of the PPE?
• Wear Arc Flash PPE only while performing live electrical work – If your team does not work on live electrical equipment regularly, this program might work for you. With this system, rather than working full time in the arc rated clothing, the work would put on the PPE only while engaging in live electrical work. The most common form of this method is to have coveralls at the ready to be utilized when necessary. With this approach, the following questions should be considered:
1. What should be the arc rating of the purchased PPE?
2. Where will it be stored for convenient access?
3. Will this PPE be shared or will everyone have their own equipment?
Arc Flash PPE programs are part of an overall electrical safety and PPE program, which also takes shock protection into consideration. Shock protection is much more straight forward and easier to implement than arc flash protection. However, arc flash protection can be made less complicated by carefully considering the workplace in advance. As with most things, the more effort expended on the front end, the more benefit on the back end.
Thank you and be safe,
Bobby Lindsey – CESCP
Mitchell & Lindsey – President
M: (502) 836-4217