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Understanding Arc Flash and the Requirements of NFPA 70E

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By Steve Bowers, CSP
President of Global Safety Management
ClickSafety Safety Content Consultant

This year marks 34 years since the National Fire Protection Association (NFPA) developed the first edition of NFPA 70E. The most recent version, the ninth edition, which was published in 2011, represents the best known policies and procedures for protecting personnel from energized electrical hazards, such as electrocution and arc flash hazards in the workplace.

Electrocution, or death by electricity, is a well-known hazard associated with the direct contact of humans with electrical energy. Arc flash however, is not as well-known and based on the statistics discussed below, is definitely not as understood or respected.

Photos courtesy of Salisbury by HoneywellAn arc flash is the sudden release of electrical energy that jumps through the air, and is caused when a high-voltage gap exists during a breakdown between conductors. During an arc flash incident, tremendous amounts of heat, and bright, intense light are released that reach temperatures as high as 35,000 degrees Fahrenheit (ºF).

OSHA authorized NFPA to develop the 70E standard in 1976 due to the sheer number of lives lost due to electrocution and arc flash incidents. Though the exact numbers of injuries and deaths from electrocution and arc flash are unknown due to inconsistencies in reporting, the US Department of Labor estimates that combined, they result in over 400 fatalities and nearly 10,000 serious injuries each year. Arc flash incidents alone are estimated to occur five to 10 times each day resulting in a fatality every workday. Contact with energized electrical components is the fourth leading cause of death in construction and represents 9 percent of all construction-related fatalities.

With so many deaths occurring annually, it would appear that the estimated 10,000 or more survivors of electrical shock and arc flash incidents represent the “lucky ones”… that’s if you consider living with severe scaring, disfigurement, dismemberment, blindness, hearing loss and a host of other permanently disabling injuries, lucky.

Few would disagree that the statistics above are unacceptable and that improvements must be made. But what can we do to change this trend? Root Cause Analysis¹ has shown that the most common cause of electrical incidents is the failure to understand, train, implement, comply with and/or enforce the safe work procedures detailed in 70E.

Though 70E is designed in its entirety to protect personnel that work in and around electrical systems and equipment, it can only be effective when programs are implemented and employees are trained and audited for compliance. Below is a short overview of some of the critical components and requirements of 70E and some best practices that industry leaders utilize to protect both their employees and contractors.

Electrical Safety Program: 

  • Ensure you have an effective electrical safety program that meets or exceeds NFPA 70E requirements.

Ensure Electrically Safe Work Conditions:

  • Perform all work de-energized by following control of hazardous energy procedures such as lockout/tagout; 
  • Identify all possible sources of electrical supply to the equipment by checking up-to-date drawings, diagrams, and identification tags; 
  • Use an adequately rated voltage detector to verify zero energy.

Work Involving Energized Electrical Hazards:

  • Energized electrical work requires a documented justification from management that details a “compelling reason” why the work must be done energized.
  • Compelling reasons fall into the following three categories:
    1. Greater Hazards - Those hazards where the employer can demonstrate that de-energizing the electrical systems will produce increased risks and/or hazards. Examples could include power to hospitals, life support systems or other examples where life or safety depends on uninterrupted electrical power.
    2. Infeasibility - Those situations where an employer can demonstrate that the task to be performed is infeasible in a de-energized state due to equipment design or operational limitations.
    3. Less than 50 Volts - Where energized work would be performed on systems that operate at less than 50 volts.

Even with safeguards in place, energized electrical work puts workers at risk and the decision to perform electrical work “energized” should always be the last option on the table. Many companies utilize a policy that requires executive management to approve energized electrical work and puts the responsibility for such a critical decision at the right level in the organization.

Hazard Identification and Risk Assessment
Safe work practices must be designed for the work to be performed with the intent of safeguarding all employees exposed to energized electrical hazards. Work practices that are used shall be suitable for the conditions under which the work is to be performed and for the voltage level of the energized electrical conductors. NFPA 70E requires that these safe work practices be effective and determined before anyone is exposed to the electrical hazards. The tools used to develop these safe work practices and controls are called the Shock Hazard Analysis and Arc Flash Hazard Analysis.

Shock Hazard Analysis
The Shock Hazard Analysis is a process in which the Limited Approach Boundary, the Restricted Approach Boundary, and the Prohibited Approach Boundary are identified. The size and distance of each approach boundary is 100 percent dependent on the voltage levels of the exposed electrical components.

The Limited Approach Boundary is the distance from an exposed energized electrical conductor or circuit part within which a shock hazard exists. Only qualified persons² and escorted unqualified persons are allowed within the Limited Approach Boundary.

The Restricted Approach Boundary is the distance from an exposed energized electrical conductor or circuit part within which there is an increased risk of shock for personnel working in close proximity to the energized electrical conductor or circuit part.

The most dangerous and highest hazard of all approach boundaries is the Prohibited Approach Boundary and is considered the distance from an exposed energized electrical conductor or circuit part within which work is considered the same as making actual contact with the electrical conductor.

Arc Flash Analysis
An arc flash hazard analysis is used to determine:

  • The Arc Flash Boundary
  • The Incident Energy at the Working Distance, and
  • The required PPE to protect personnel from the identified hazards

Annex D of NFPA 70E contains the calculation methods for determining incident energy and arc flash boundaries. It is recommended that an experienced electrical engineer, electrical safety consultant or other qualified entity conduct the Arc Flash Analysis for your equipment. The safety of your personnel or facility is dependent on the results of the analysis being accurate.

Equipment Labeling
Electrical equipment must contain labels that clearly state one of the following:

  • The Available Incident Energy and the corresponding working distance, or
  • The minimum rating of clothing required, or
  • The required level of PPE required, or
  • The highest hazard/risk category for that specific piece of equipment.

In addition, the label must include the nominal system voltage and arc flash boundaries. Labels applied before Sept. 30, 2011, are acceptable only if they contain the available incident energy or required PPE.

NFPA 70E provides industry-proven safety systems and processes that help companies protect their employees from arc flash hazards and if followed completely, compliance with OSHA requirements. Implementation, training, enforcement and auditing for compliance are all equally important and required components of an effective electrical safety program. Though OSHA does not dictate the use of NFPA 70E specifically, it does require employers to use industry standards and practices that will protect their workforce from harm, and NFPA 70E is recognized as the reference document for workplace electrical safety.

By taking the time to understand, train, implement and enforce the requirements of NFPA 70E in the workplace, we can all help protect our most valuable asset, our employees.

1 Root Cause Analysis (RCA) is a structured method used to analyze serious adverse events. A central tenet of RCA is to identify underlying problems that increase the likelihood of errors while avoiding the trap of focusing on mistakes by individuals. (U.S. Dept. of Health and Human Services)

2 OSHA defines "qualified" as meaning one who, by possession of a recognized degree, certificate, or professional standing, or who by extensive knowledge, training and experience, has successfully demonstrated his ability to solve or resolve problems relating to the subject matter, the work, or the project.

Photos courtesy of Salisbury of Honeywell


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