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An Update on Arc Flash: Revised Regulations and Best Practices Help Keep Workers Safe

Troy A. Miesse, Strategic Marketing, Industrial Enclosures
Rittal Corp.

The National Fire Protection Association (NFPA) 70E, Electrical Standards for Safety in the Workplace describes arc flash as a dangerous condition. According to the National Institute for Occupational Safety and Health (NIOSH), during an arc flash temperatures as high as 35,000°F have been recorded. In fact, a NIOSH study estimates five to 10 arc flash explosions occur every day in the US. In addition, injury can occur within a few milliseconds according to the National Electrical Contractors Association.

Given the most recent change reflected in the 2011 National Electrical Code (NEC) and the fact that the Occupational Safety and Health Administration (OSHA) has started fining companies, arc flash continues to be in the forefront of our industry as a serious issue.
The article proposes to 1) define arc flash, 2) provide an update on the applicable safety codes and standards, 3) outline best practices to keep workers safe and companies compliant, and 4) outline product solutions to prevent arc flash.

What is an Arc Flash?
An arc flash is the explosive release of energy that occurs when there is a phase-to-phase or phase-to-ground arc fault. The arc fault may be the result of unsafe work procedures such as a dropped tool or accidental human contact. Additionally, an arc fault may be caused by corrosion, insulation failure, conductive dust and contact by animals.
Workers who are exposed to an arc flash sustain injuries typical to an explosion such as: burns, loss of sight, loss of hearing, broken bones, head injuries and shrapnel injuries.

What are the Applicable Codes and Standards?
While little has changed in the past couple of years regarding regulations, the NEC is revised every three years. The 2011 revisions include an additional change to the wording regarding warning labels. While a change in wording seems minor, it does give reinforcement to the importance of arc flash hazards.

NEC 110.16 Arc-Flash Hazard Warning (REVISED)
The title was changed from simply “flash protection” to “arc flash hazard warning” because arc flash protection was not addressed in the previous requirement. The required field marking relates to a warning of potential arc flash hazards. This rule does not apply to individual dwelling units, but usually applies to equipment in a large building that contains multiple individual dwelling units. Service equipment is to be field-marked with the maximum available fault current and dated. Modifications that change the available fault current (AFC) require updated available AFC marking as well as the date the calculations were performed.

There are five main codes, standards and regulations that address arc flash prevention and safety. They were developed through the National Fire Protection Association (NFPA), OSHA and the Institute of Electronics and Electrical Engineers (IEEE):
• NFPA 70 (the NEC) – deals with labels for hazard awareness
• NFPA 70B “Recommended practice for Electrical Equipment Maintenance” outlines the procedures and practices to be followed for OSHA compliance and safety when working on live equipment
• NFPA 70E “Standard for Electrical Safety Requirements for Employee Workplaces” discusses a variety of issues, including personal protective equipment (PPE), safety programs, worker training calculating the degree of hazard and warning labels for equipment
• OSHA Standards 29-CFR 1910-S, number 1910.333 focuses on the legal requirements of which employers need to be aware to guard against arc flash hazards. It sets general requirements for safe work practices, PPE and hazard analysis
• IEEE 1584 “Guide to Performing Arc Flash Hazard Calculations” deals with calculating the size of the potential fault. These calculations provide a basis for the level of PPE that is required when examining or servicing equipment

What are Best Practices When Dealing with the Potential for an Arc Flash?
The only true way to prevent arc flash and protect your workers is to de-energize circuits before working on them. If it is not possible to de-energize, or if de-energizing introduces additional or increased hazards, such as stopping ventilation to a hazardous location, the following practices are critical to maintaining a safe and productive environment on the shop floor and in the field.

Analyze the workplace for arc flash hazards by trained electrical safety professionals and perform a detailed hazard analysis.
Ultimately, the employer is responsible for its employees’ actions and should know what they do and don’t do regarding safety procedures.
OSHA 29 CFR 1910.269(a)(2)(iii) states: “The employer shall determine, through regular supervision and through inspections conducted on at least an annual basis, that each employee is complying with the safety-related work practices required by this section:”
“Note: OSHA would consider that tasks that are performed less often than once per year to necessitate retraining before the performance of the work practices involved.”

IEEE 1584 and NFPA 70E are the guidelines for conducting an arc flash hazard analysis and safety initiatives.

Label all field enclosures to warn of arc flash hazards. The NEC requires warning labels to be placed on the outside of electrical enclosures to alert engineers and other personnel of the arc flash hazard inside the control panels. These warning labels need to be an industry standard symbol, at a minimum.

A better option is to include the results from the arc hazard analysis on the label. For instance, a more detailed label could include specific information about the following:
• Incident Energy – The amount of energy produced during an arc flash.
• Flash Protection Boundary – The safe approach distance from energized equipment or parts where a person has a 50 percent chance of receiving a second degree burn from the arc flash.
• Limited Approach – The shock protection boundary where only qualified personnel should approach.
• Required PPE Level – The service level rating for the type of protective clothing and apparatus is required when servicing a panel (i.e. opening the panel door) to protect against arc flash.

In addition, article 409 of the NEC includes the requirement that all industrial control panels must be marked with a short circuit current rating (SCCR). An SCCR is the maximum current a device can safely withstand for three AC electrical cycles (50 m/s) or while an over-current protective device operates. SCCRs enable on-site engineers to understand the capabilities of their control panels and the amount of short-circuit current available at each control panel connection point. The control panel SCCR provides the on-site engineer with the system data needed to maintain a safe system installation.

Establish safe protection boundaries within the flash protection boundary, there are three shock approach boundaries (limited, restricted and prohibited) required to be observed in NFPA 70E 2000 and all are based on the voltage of the energized equipment. NFPA 70E 2000 requires a flash hazard assessment must be performed before an employee approaches exposed electric conductors or circuit parts that have not been placed in a safe work condition. Until equipment is placed in a safe work condition, it is considered live.

IEEE 1584, Guide to Performing Arc Flash Hazardous Calculations provides the necessary guidance on how to calculate the flash protection and limited approach boundaries.

Define what PPE must be used or excluded within these boundaries.

PPE, including clothing and tools, is one of the most crucial elements to minimizing injuries to workers from arc flash hazards and OSHA mandates employers are responsible to pay for most PPE used on the job by its employees.
Clothing - OSHA regulation 1910.269(l)(6)(iii) deals with protective equipment.

“The employer shall ensure that each employee who is exposed to the hazards of flames or electric arcs does not wear clothing that, when exposed to flames or electric arcs, could increase the extent of injury that would be sustained by the employee.”

“Note, clothing made from the following types of fabrics, either alone or in blends, is prohibited by this paragraph, unless the employer can demonstrate that the fabric has been treated to withstand the conditions that may be encountered or that the clothing is worn in such a manner as to eliminate the hazard involved: acetate, nylon, polyester, rayon.”

Selecting the proper PPE is critical, so choose flame retardant (FR) clothing that is rated appropriate for the particular arc heat exposure. Guidance for calculating an arc’s heat energy can be found in NFPA 70E. Usually, FR clothing made from 100 percent natural fibers are acceptable if they are weight-appropriate for the conditions in which employees will be working.
Tools again, it is mandated to use the properly-rated insulated tools when working on exposed part energized at 50 volts or greater. According to 1910.269(l)(7):

“Fuse handling.” When fuses must be installed or removed with one or both terminals energized at more than 300 volts or with exposed parts energized at more than 50 volts, the employer shall ensure that tools or gloves rated for the voltage are used.
When expulsion-type fuses are installed with one or both terminals energized at more than 300 volts, the employer shall ensure that each employee wears eye protection meeting the requirements of Subpart I of this Part, uses a tool rated for the voltage, and is clear of the exhaust path of the fuse barrel.”

Develop ongoing safety programs, including worker training and retraining. More than one study has concluded that the majority of injuries and citations occur because of unsafe worker practices. That’s why a proactive and continuous safety program is important to protect both the workers from injuring themselves and your organization from fines and litigation. Only properly trained and qualified employees should be working around exposed and energized lines or parts.

OSHA 1910.269(l)(1) “General.” Only qualified employees may work on or with exposed energized lines or parts of equipment. Only qualified employees may work in areas containing unguarded, uninsulated energized lines or parts of equipment operating at 50 volts or more. Electric lines and equipment shall be considered and treated as energized unless the provisions of paragraph (d) or paragraph (m) of this section have been followed.”

Utilize product design strategies and enclosure systems to minimize or eliminate the potential for an arc flash.
In addition to employee training, protective boundaries, label warnings and PPE, arc flash hazards can be prevented by electrical product solutions and design strategies.

An enclosure forms a barrier between the maintenance personnel and the live electrical circuit, providing the touch safety required. But, when the door to the enclosure is opened, live circuits are accessible and the safety provided by the enclosure is completely forfeited.
To minimize the need for the maintenance personnel to go inside the enclosure, test points and network connections as well as programming interfaces should be provided on the exterior of the enclosure, thus keeping it sealed during routine maintenance. This can be accomplished through:

• Service Covers and Access Flaps – These accessories provide access to data ports and connections without opening the enclosure door. Because of this, the enclosure’s protective barrier is maintained.
• Viewing Windows – Using viewing windows, allows maintenance personnel to view interior instruments without opening the enclosure door.
Two additional approaches most commonly used to solve this problem are the box-in-box and box-on-box methods.
• Box-in-Box – Using a box-in-box approach, the disconnect is housed within a second, smaller enclosure placed inside the larger enclosure. Using the box-in-box method, the live line side of the disconnect is housed inside of the inner enclosure and touch safety remains in place.
• Box-on-Box – Using the box-on-box method, the disconnect is housed in a separate enclosure mounted on the outside of the larger enclosure. In this way, the live line side of the disconnect is not located inside of the main enclosure and touch safety is insured. The drawback of the box-on-box method is attaching a smaller enclosure on the outside of the larger enclosure.

Stay Safe. Stay Compliant
Arc Flash is a serious, but preventable hazard. While protecting workers is paramount, the penultimate goal is protecting your company. Both can be accomplished with a five-step approach:
• Analyze the workplace for arc flash hazards with trained electrical safety professionals and perform a detailed hazard analysis.
• Label all field enclosures to warn of arc flash hazards
• Establish safe protection boundaries.
• Define what Personal Protection Equipemnt (PPE) must be used or excluded within these boundaries.
• Utilize product design strategies and enclosure systems to minimize or eliminate the potential for an arc flash.

The Rittal Corp. is the US subsidiary of Rittal GmbH & Co. KG and manufactures industrial and IT enclosures, racks and accessories, including climate control and power management systems for industrial, data center, outdoor and hybrid applications. Rittal’s off-the-shelf standard, modified standard and custom-engineered products are recognized throughout the world as innovative, high quality solutions for practically any industrial or IT infrastructure application from single enclosures to comprehensive, mission critical systems.

For more information please visit www.rittal-corp.com.