When arc flashes occur, the most severe injuries often are the result of non-flame-resistant clothing igniting and continuing to burn, causing far more severe burn injuries than the arc flash itself. The use of appropriate arc-rated (AR), flame-resistant (FR) clothing has a proven track record of protecting workers and saving lives.
Let's examine the three situations that are common causes of hazardous arc flash:
- Energized work that should have been de-energized
- Operator error
- Poorly maintained equipment.
NFPA 70E strongly encourages electrical workers to de-energize equipment – and potentially utilize an energized electrical work permit – to help determine if the work safely can be done energized. Energized work only should be done when de-energized work is deemed infeasible (infeasible, not inconvenient) based on equipment design and operational limitations or when de-energized work creates additional hazards or increases risk. For example, at hospitals, removing power to conduct electrical work would create an adverse situation for patients.
Causes of unnecessary energized work include situations where the electrical worker believes that he has the expertise to work on "hot" equipment or he is pushed for time. He may choose to not de-energize equipment since de-energizing will halt plant operations, inconvenience clients and cost money. While working hot may keep the system operational or allow for troubleshooting, it presents an environment for arc flash.
Electrical worker error is another cause of catastrophic arc flash incidents. Failure to verify absence of voltage, utilizing incorrect testing equipment (i.e. voltage testers), overconfidence, complacency and poor co-worker communication and lack of lockout/tagout procedures have all been underlying root causes of arc flash incidents.
Improper communication with the utility may allow for the system to be reenergized upstream. Or, some feeds may be disconnected, but additional feeds may be hidden or non-obvious due to equipment/system design.
Some workers and employers claim they don't need personal protective equipment (PPE), since they de-energize all their equipment, thus eliminating the hazard. This line of thinking is erroneous; the act of de-energizing equipment is considered energized work and requires AR/FR PPE. You must verify with a voltage meter that there is indeed an absence of voltage before it is safe to remove AR/FR PPE.
Poor Equipment Maintenance
All equipment has an expectation for routine ongoing maintenance. However, in cost-cutting circumstances, sometimes maintenance is skipped or done incorrectly, jeopardizing the long-term safety of the system.
The lack of housekeeping and maintenance causes corrosion, which leads to increasing resistance and unwanted heat. This is the primary culprit in electrical system breakdown and potential causes of arc flash events. Other equipment, when not properly exercised, either can delay or not trip when expected. Arc flashes due to poor equipment maintenance damage equipment and property, as well as injure workers interacting on or around the equipment.
Industry Regulations & Consensus Standards
OSHA, NESC and NFPA mandate the use of AR/FR clothing for safe electrical workplace practices.
OSHA regulations state that companies must prioritize safety and provide a workplace that is free of recognized hazards that could cause harm. The regulations provide actionable steps for organizations:
- Conduct a hazard assessment of the workplace
- Provide adequate protection, such as AR/FR PPE for identified hazards
- Educate employees on dangers present and the use of PPE to create a safer workplace.
NESC and the NFPA 70E standard also mandate the use of appropriate AR/FR apparel wherever arc flash hazards exist.
These confounding factors as well as industry regulations and standards surrounding electrical safety demonstrate the ongoing need for electrical workers to protect themselves daily against arc flash.
A Solution: FR Daily Wear
While no one plans for an arc flash incident to occur, there are ways to prepare for the dangers it presents. Creating a safe workplace means allowing the downtime required to de-energize equipment for safe handling, despite the inconvenience to operations. It also means supplying workers with appropriate AR/FR apparel.
When electrical workers experience an arc flash, the arc flash itself often is not what causes significant burn injury. Injuries occur when non-FR clothing ignites and fuels the flame, thereby increasing the extent of the injury. AR/FR clothing plays two key roles in protecting electrical workers against burns:
- Self-extinguishes to mitigate burn injury when the source of ignition is removed.
- Provides insulation to reduce probability of a second-degree burn.
For common lower energy, PPE Category 1 and 2 tasks, wearing AR/FR daily wear is the simplest, most effective solution. It removes the guess work of determining if a task requires arc-rated clothing. By doing this, workers avoid the extra step of donning task-based PPE and it can be as simple as choosing to wear one work shirt over another. AR/FR daily wear also eliminates employer safety concerns that employees aren't properly wearing AR/FR for every task, including verifying that natural fiber-based clothing is worn underneath task-based gear to be in compliance. For higher energy tasks (PPE Categories 3 and 4), the extra step of donning appropriate task-based PPE is common, due to the high PPE arc-rating requirements.
Match AR/FR Clothing with Hazard Levels
NESC requires utilities to assess hazards for employees that work near or on energized equipment. If energies present exceed 2 cal/cm2, workers must wear AR/FR clothing with an arc-rating equal to or greater than the energies of the electrified equipment with which they work.
To comply with NFPA 70E, employers also are required to perform an arc flash risk assessment to determine the potential energy level of the hazard and the flash protection boundary, or the total area in which the hazard exists. Where required, employees must wear AR/FR protective clothing that meets ASTM F1506, the minimum performance specifications for protective clothing for workers exposed to the risk of electrical arc flash.
To anticipate energy levels, NFPA 70E denotes two main incident energy analysis schemes: the calculation method and the table method. It's critical to note these procedures cannot be combined on the same piece of equipment.
For the calculation method, the potential incident energies of various equipment are calculated using formulas and/or commercially available software. The difficulty of the calculation method is relative to the complexity of the electrical system. The table method characterizes AR/FR garments and garment systems by PPE categories. In the table, the NFPA 70E standard lists typical pieces of equipment, their operating conditions and the required PPE category for each energy level.
Specify the Fabric
Once the energy level and arc-rating are determined, you'll be able to move forward in selecting the best AR/FR clothing. Start with selecting the fabric first: it's important to understand the FR fabric manufacturer – history, experience, product line and capabilities – and look for brands that provide the comfort and performance that meet the needs of your workplace and job tasks.
AR/FR daily wear also must be comfortable while working. Conduct a wear trial of various garments to assess movement and breathability to ensure workers will be able to work effectively and comfortably.
External work conditions should be considered. The fabric and fabric system needs in diverse climates can are different, such as insulated products for northern climates and lightweight, single-layer constructions for hot and humid conditions.
Arc flashes are unexpected and dangerous and can occur during various points of electrical workers' daily operations. By wearing AR/FR, workers can equip themselves to perform their jobs safely, efficiently and comfortably, all of which help them concentrate on the task at hand: getting the job done right and going home to their families.
Scott Francis is the midwest regional market manager for Westex by Milliken. Francis has been involved with the safety industry since 1991 and has extensive experience with protective apparel fabrics and programs.