Arc flash, a type of electrical explosion, is one of the most complex workplace risks that exists. It is often described using technical terminology and several acronyms. But beneath the alphabet soup of letters and numbers associated with workplace electrical safety, there is a simple explanation for arc flash.
Firstly, it’s important to understand arc flash has nothing to do with welding; it’s an electrical hazard. There are three general categories of electrical hazards defined within the applicable standards: shock, arc flash and arc blast. Within a millisecond, the temperature produced by an arc flash, at its core, can be up to four times hotter than the surface of the sun. Other secondary hazards related to an arc flash include intense light emissions, pressure wave (arc blast), flying debris, toxic fumes and damaging sound levels.
Workers perform tasks that put them at risk for exposure to an arc flash every day, including voltage testing, removing bolted-on panel covers and inserting or removing circuit breakers.
An arc flash hazard can be an extremely violent event that may result in worker fatalities. Workplace injuries and fatalities resulting from electrical hazards, including arc flash and shock, are considered low frequency, high severity events. Arc flash accidents are rare, but they do happen — and often with catastrophic results if workers are not wearing arc flash personal protective equipment (PPE). Specific to arc flash and shock, the electrical safety industry reports the ratio of deaths to incidents as being about one in 10.
A typical arc flash is caused when a conductive object gets too close to an energized conductor or circuit part and ground. An electric arc super heats and ionizes the air, allowing for a path for electrical current to flow. Provided there is sufficient voltage, usually above 208 V, the arc can sustain itself and transform into an arc flash.
An arc flash can be caused by equipment failure and human interaction. However, under normal operating conditions, enclosed energized electrical equipment that has been properly installed and maintained poses a negligible risk of an arc flash hazard. Anyone working with energized electrical equipment should be knowledgeable and competent to assess normal versus abnormal conditions to be permitted to perform any routine operation of that equipment.
The acceptable occupational health and safety hierarchal approach to eliminate or reduce risk related to an arc flash hazard is similar to any other workplace hazard. Within the context of electrical safety, these steps include:
• de-energize, isolation and lockout/tagout
• substitution with safer systems or processes
• engineering “safety by design” including effective equipment maintenance
• warning signs and barricading
• administrative controls, training and procedures
• electrical specific PPE, tools and equipment with proper care, use and maintenance.
The most effective way to manage electrical hazards, including arc flash, is to implement an electrical safety program as part of an overall occupational health and safety management system. An electrical safety program will provide the rules and tools for energized electrical equipment. Even the most robust corporate safety management systems may not effectively cover off arc flash and electrical hazards. Electrical safety auditing on both an employer’s electrical safety program and fieldwork is a strict requirement of CSA Z462 Workplace Electrical Safety and shall be documented.
Assessing the hazard
The latest edition of CSA Z462, published in January, requires an arc flash risk assessment. This process is used to determine if an arc flash hazard exists (hazard identification), estimating the potential severity of injury or damage to health and estimating the likelihood of the occurrence. Risk is defined as being a combination of the severity and likelihood. The requirement to perform an arc flash risk assessment is a fundamental part of any comprehensive electrical safety program. Different types of risk assessment processes can be used including the arc flash PPE category method within the CSA Z462-15 standard.
The arc flash PPE category method requires the use of tables from within the CSA Z462-15 standard. The following steps are completed when using this method:
• Determine if arc flash PPE is required through arc flash hazard identification (work task and equipment condition).
• Determine arc flash PPE categories for AC and DC systems (equipment types, voltage levels and specific electrical parameters).
• Outline arc flash PPE and other personal protective equipment requirements for each of the arc flash PPE categories (1-4).
The incident energy analysis method requires the use of engineering based calculations using the IEEE 1584 standard to estimate the incident energy exposure level. Arc flash PPE is then selected based on the incident energy so the arc rating matches or exceeds the incident energy calculated.
PPE is one of the most readily available solutions to protect workers; however, it should be used as a last line of defense.
Arc flash PPE consists of specially designed and appropriately tested products suitable for use by workers that need protection from the heat of an arc flash hazard. Employers are required to ensure workers within the arc flash boundary wear appropriate full body protection when it is determined that arc flash PPE is necessary based on an arc flash risk assessment.
There are hundreds, if not thousands, of different arc flash PPE products available on the market. Arc-rated PPE product segments include clothing, face shields, arc flash suits, outerwear and specialized equipment. All arc-rated PPE is available with the associated laboratory testing documentation — employers just need to ask for it. Unlike shock protective PPE, arc flash PPE doesn’t require recertification. At the very least, all arc-rated PPE shall indicate compliance with ASTM F1506, which outlines performance specification for flame resistant and arc flash textiles specifically for electrical workers.
The product label is the best indication of its compliance, but only destructive testing can verify a manufacturer’s claims.
Training is also an important component and there are several formats available, including on-the-job, e-learning, instructor-led and blended learning (e-learning and instructor-led training). Both e-learning and instructor-led training formats can be considered classroom training, either in the traditional sense or virtual. Any worker exposed to electrical hazards in the workplace requires adequate training suitable for their role and appropriate for the risk of their exposure. This includes both electrical and non-electrical workers.
[em]Jim Pollard is a member of several technical committees, including CSA Z462. He is the owner of Unlimited PPE in Stoney Creek, Ont., and he can be reached at firstname.lastname@example.org or (905) 573-0300.
This article originally appeared in the April/May 2015 issue of COS.
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