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An Intro to Arc Flash: Dangerous, Misunderstood, Overlooked, Preventable

By Chris Falzarano on 8/27/2014

Due to the nature of their work, water and wastewater treatment plant operators are potentially at a higher risk for accidents and injury. They use chemicals, are exposed to hazardous energy sources, work in or around confined spaces, and face various environmental and health hazards. A safe work environment will promote practices that safeguard employees and enhance public health protection. Another safety hazard that can be encountered in the workplace, which you may or not be familiar with, is Arc Flash. Due to an increase in documented incidents resulting in serious injuries or death, Arc Flash awareness and concerns have recently been heightened throughout the industry. The following will provide you with a better understanding of Arc Flash, the safety concerns involved with Arc Flash, and the measures that can be undertaken to mitigate the potential for incidents. What is Arc Flash? Arc Flash, not to be confused with electric shock, is a rapid release of energy due to an arcing fault, where current leaves its normal path and travels through the air from one conductor to another, or to ground.

The consequences are often severe, frequently resulting in serious injury and sometimes death.  How can I be exposed to Arc Flash? Common sources of exposure are motor control centers, switchgears, panel boards, disconnect switches, transformers and control panels. Why is it important to understand Arc Flash? Arc Flash is a dangerous, complex, and misunderstood occurrence, as is anything accompanying the flow of current. For this reason, Arc Flash awareness is critical to anyone involved with electrical equipment. This holds especially true for water and wastewater operators. What are the causes of Arc Flash? Arc Flash can be caused by one or a combination of several reasons. Some causes include: dust; dropping tools; accidental touching; condensation; material failure; corrosion; faulty installation; or improperly rated equipment. What are the dangers involved with Arc Flash? There are many factors to consider if an Arc Flash were to occur. The consequences to the worker involved are connected to three elements: The worker’s distance from the source of the arc; the time required for circuit breakers to interrupt the fault; and the intensity of the heat produced by the Arc Flash. Some dangerous conditions resulting from Arc Flash include: extreme heat up to 35,000 degrees Fahrenheit; sound waves over 150 decibels; shrapnel that travels at speeds in excess of 700 miles per hour; intense light; molten metal; pressure waves, also known as arc blast; and copper vapor that expands at a rate of 67,000:1 (water boils at a rate of 1,670:1).

What regulatory organizations oversee Arc Flash compliance? There are three organizations that oversee Arc Flash compliance. They are the Occupational Safety & Health Association (OSHA), the Public Employee Safety & Health Bureau (PESH), and the National Fire Protection Association (NFPA). With a mission to “assure safe and healthful working conditions,” OSHA, which operates under the umbrella of the United States Department of Labor, enforces their regulations and ensures compliance by all private sector employers and employees. PESH is an OSHA-approved state program administered by the New York State Department of Labor. It applies to all public sector employees throughout the state and sets job safety and health standards that are “at least as effective” as OSHA standards. They have also adopted all OSHA standards. NFPA created the standard NFPA 70E, which serves as one of OSHA’s reference documents as it relates to electrical safety in the workplace.

How can you comply with Arc Flash safety regulations? There are two methods that the technical committee to NFPA 70E consider equally applicable. The first method, which is typically referred to as the incident energy method, is applied through the Institute of Electrical and Electronics Engineers (IEEE 1584) method of Arc Flash analysis. The preferred and most accurate approach, it is a systematic, computer-aided approach that calculates exact Arc Flash energies at each equipment location. Using this approach provides the ability to perform equipment evaluation and circuit breaker coordination studies. The other way to comply is through the NFPA 70E table method, which is a generalized approach that provides appropriate personal protective equipment (PPE) for a given task. This method may be used only if the system meets the parameters set by the NFPA 70E.

The table method does not provide the ability to perform equipment evaluation or coordination studies. What are the costs associated with an Arc Flash occurrence? Arc Flash incidents involving bodily harm or death have the potential to lead to very high costs for the employer. The employer could be responsible for medical bills and workers compensation claims, and will likely be fined by OSHA or PESH, on top of having to repair or replace the electrical equipment involved. They also face the risk of litigation, increased insurance premiums and decreased morale among the entire company. What steps can be taken to protect against Arc Flash? For starters, follow the “Don’t work it hot” rule of thumb, which means shut down all equipment before performing any type of work and confirm that it is de-energized, unless it is not feasible to do so.  Also, comply with OSHA’s federal guidelines, as well as their approved state programs, as they help ensure safe and hazard-free work environments.

Employers can perform an electrical hazard assessment in accordance with NFPA 70E, short circuit, coordination and equipment evaluation studies. They can also develop and enforce safety-related work practices, provide employee training, and provide employees with the proper personal protective equipment. While Arc Flash can’t be eliminated completely, there are many steps that we can take to minimize risk. When it comes to electrical safety, it is an employer’s duty to provide a safe work environment. Providing an electrically safe work environment will improve system reliability, reduce costs and, most importantly, save lives. Tvrtko Stigler is a Project Engineer supporting the Electrical Engineering department in arc flash assessment, short circuit analysis and overcurrent protective device coordination. He can be reached at tstigler@h2m.com.

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