An Arc Flash Risk Assessment is an invaluable resource for electrical safety and a necessary guide to risk assessment for anyone who works on electrical systems. This assessment is also required by NFPA 70E. Properly conducted, an arc flash risk assessment contains important information: detailed one-line drawings, arc flash calculations, coordination and short circuit studies, and training. However, the final product—the arc flash label placed on the electrical equipment—is the most important component of the assessment.
The importance of the arc flash label and its role in risk assessment and electrical safety is often overlooked, so I’ve devoted this article to the arc flash label.
The arc flash label is now a vital tool for any worker conducting an electrical risk assessment, but this wasn’t the case before 2009, when the only requirement was a generic warning label stating that an arc flash and shock hazard existed.
Before 2009, only a general warning label was required.
Electrical equipment labels are to include the following information:
1. Nominal System Voltage
2. Arc Flash Boundary
3. At least one of the following:
a. Available incident energy and working distance, or the arc flash PPE category, but not both.
b. Minimum arc rating of clothing
c. Site-Specific level of PPE
Electrical equipment must now display the label pictured below or a similar label which presents the Nominal System Voltage, Arc Flash Boundary, and Available Incident Energy. Mitchell & Lindsey uses this label when we conduct an arc flash study. Let’s look at the information in more detail.
The arc flash label below is divided into 4 sections:
1. General Warning Section
2. Arc Flash Risk Information
3. Shock Risk Information
4. Equipment info and disclaimer
Section 1 – General Warning Section
Like all warning labels, this announcement section of the label is designed to get your attention, announce the nature of the risk, and warn that certain precautions are required before proceeding.
Section 2 – Arc Flash Risk Information
The arc flash information section contains three items.
• Arc flash boundary. This is the trigger point for arc flash PPE. Workers must wear arc-rated PPE when inside this boundary.
• Incident energy at working distance. This guides the worker in choosing the level and type of PPE that is required within the arc flash boundary.
• PPE level with a reference to the PPE chart found in NFPA. This is to be used as a cross reference with the second bullet point—Incident energy.
As illustrated above, the arc flash label is used to reference the arc flash PPE required to work on the electrical system in an energized state.
Section 3: Shock Risk Information
You may recall from my previous articles and videos that arc flash and shock are two different events. Section 2 of the arc flash label refers only to arc flash risk while Section 3 of the label refers only to shock risk. Like Section 2 on arc flash risk, Section 3 on shock risk also contains 3 items:
• Voltage rating of the equipment
• Limited approach boundary. This is a shock boundary only and unqualified personnel are not allowed inside its limits.
• Restricted approach boundary. This is also a shock boundary and the trigger point for shock PPE, usually consisting of voltage-rated gloves and insulated tools.
Section 4: Equipment Info and Disclaimer
This section references several important pieces of information related to the facility and specific equipment:
• Equipment name and source of the equipment feed
• Date of the evaluation
• A disclaimer stating that any changes to settings of breakers or equipment and/or faulty equipment renders the results on the label invalid. This is important to note because any change in equipment, trip settings, or condition of equipment could affect the time it takes to clear a fault, which is one of the most important factors in calculating the incident energy.
The importance of the arc flash label and its role in risk assessment and electrical safety can’t be overlooked. The label is a vital tool to evaluate risk while working on electrical equipment. Before this information was required, workers did not always understand the level of risk involved when working on energized electrical equipment. Now, with an arc flash label displayed on the equipment and the knowledge to interpret the label, workers can be properly protected from the risk of arc flash and shock.