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Preventing and Minimizing Arc Flash Risk

Following OSHA regulations and using good design can reduce the risk of damage to workers and equipment from arc flashes.

Arc flashes present a serious hazard involving electrical equipment that is more common than many would believe. Due to OSHA’s reporting requirements for arc flashes, they are under-reported or not reported at all. No one is certain how frequently they occur, but some sources estimate there are five to 10 electrical equipment explosions (aka arc flashes) each day in the U.S.

Most reports on electrical-related injuries focus on shock and electrocution, rather than arc flashes in which explosive forces, heat, and gasses cause the injuries and deaths, according to the National Fire Prevention Assoc. But research conducted across burn centers show arc flashes cause 34% to 55% of all the electrical burns received on the job.

It has been estimated that more than 2,000 workers are admitted to burn centers annually to be treated for severe arc-flash burns, and arc flash incidents kill one to two people every day. In addition to injuries and fatalities, arc flash also carries significant financial costs. Medical treatment for arc-flash injuries costs an average of $1.5 million per incident, which is borne by the factory owner. This makes arc-flash prevention and risk reduction a high priority when designing electrified equipment.

Labels indicate boundaries around electric enclosures and levels of personal protective equipment  for working inside it.

Arc Flashes vs. Arc Faults

An arc flash is the explosion caused by a phase-to-phase or phase-to-ground short circuit. Arc flashes emit extreme heat, intense light, and violent pressure blasts. In comparison, an arc fault is the high-power discharge that causes the short and triggers an arc flash. Arc faults can be caused by several different conditions, including a faulty wire, a loose fuse, a tool dropped into a live cabinet, or even personal contact with live components.

Arc flashes pose a significant risk for bodily harm from the force of the explosion, heat of the blast, and the corrosiveness of the gasses. Physically, the pressure of the explosion can be as much as 10,000 psi, which compares to the force of a high-speed collision.

In addition to its explosive force, arc flashes carry high temperatures and can reach up to 35,000°F, which is hotter than the surface of the sun. Arc events also create noxious and corrosive gasses that, if inhaled, increase the chances of catastrophic injury or death.

Arc-Flash Regulations and Standards

The Occupation Safety & Health Administration (OSHA) is the governing body that regulates workplace safety, including arc flash prevention, equipment labeling, and use of personal protection equipment (PPE). Specific standards related to arc flash include OSHA 1910.137 for electrical protective equipment and OSHA 1910.269 App E on protection from flames and electric arcs.

 The National Fire Prevention Association’s standard NFPA 70E covers safety-related work practices, maintenance requirements, and special equipment requirements. Companies that comply with NFPA 70E must conduct an Arc Flash Risk Asessment, sometimes called an Arc Flash Study or Arc Flash HazardAnalysis. The review determines safe work practices, arc-flash boundaries, and appropriate levels of PPE to be used.

Underwriters Laboratory also has a standard specifically for industrial control panels and switchgear (manufactured and modified). It covers control panels intended for general industrial use and operating at 600 V or less. Equipment meeting this standard is installed in “ordinary” locations in accordance with the National Electrical Code, ANSI/NFPA 70.

As the governing body for workplace safety, OSHA regs are the driving force for compliance in the U.S. Manufacturers that do not meet the regs can be fined by OSHA and lose their insurance. With OSHA issuing fines and penalties when workers are put at risk for arc flash injuries, a common misconception arose that the agency enforces NFPA 70E. Although companies are not specifically required to comply with NFPA 70E, it acts as an outline on how to ensure compliance with OSHA’s arc flash safety regulations.

A Closer Look at NFPA 70E

NFPA 70E sets arc flash boundaries for organizations, including keeping 3 ft away from cabinets with electrical circuits running at less than 750 V and keeping 19 feet away from cabinets holding circuits running at 15,000 to 36,000 V. Boundaries are delineated by tape or a chain and show the safe distance from cabinets for workers without PPE.

Arc flash boundaries vary with the risk level and the voltage of the equipment. For instance, a “limited” range is for minimal shock hazards from electrical overarcs; a “restricted” range is for increased shock risks; and a “prohibited” range entails significant risks of direct contact with electrified components. Ranges for these boundaries are outlined in NFPA 70E table 2-1.3.4. and OSHA 29 CFR,1910.269 table R6.

Energized panels or boards must be marked with a danger or warning label that indicates the potential hazard and the level of PPE required (from 0 to 4). Category 0 PPE requires cotton, untreated fiber shirts and pants, safety glasses, and hearing protection. It warns against wearing polyester or synthetic fabrics near the equipment that could melt This category is for areas with the lowest potential for an arc flash event, but the standard warns against wearing polyester or synthetic fabrics that could melt near the equipment. At the other end of the spectrum, Category 4 protection includes an arc-rated suit, along with protection for face and head, hands, eyes, and hearing, as well as a hard hat and appropriate footwear.

Reducing the Risks

To minimize the possibility risk of an arc flash, follow OSHA’s lockout/tagout procedures. When followed closely, they can protect workers from hazardous energy release and from the unexpected energization or startup of machinery and equipment.

Lockout/tagout requires that machinery be turned off and disconnected from its energy source before anyone performs maintenance on it. It mandates that authorized individuals either lock or tag the energy isolating device(s) to prevent the release of hazardous energy. An authorized person must also take the required steps to verify energy has been isolated effectively. Lockout devices hold energy-isolation equipment in a safe or off position. They prevent equipment from being energized and can only be unlocked with a key. Tagout devices feature prominent warnings that are fastened to energy-isolating equipment to warn workers not to reenergize the equipment while it is being serviced. Details for using tagout devices are listed in the OSHA standard, The Control of Hazardous Energy (Lockout/Tagout), Title 29 Code of Federal Regulations Part 1910.147.

 The safest way to work on any panel is when the panel is turned off. If lockout/tagout is done correctly, maintenance staff can safely work on electric panels without risking exposure to arc flash.

An arc flash assessment, another required safety measure, determines both the potential and intensity of an arc flash. Calculations done in these assessments (found in IEEE 1584, Guide for Performing Arc-Flash Hazard Calculations) helps in creating appropriate training and procedures for anyone working with energized electrical parts, switches, breakers, or other equipment.

To minimize arc flash risks, it is critical to understand that NFPA 70E standards make it easier to comply with OSHA regulations. NFPA 70E outlines proper training and  procedures and PPE standards for manufacturers and their maintenance staff. In addition, engineers can design arc-flash prevention into enclosures so that they serve as the first line of defense. Using the isolated box approach, customized with appropriate accessories, manufacturers can prevent unsafe access inside enclosures. As manufacturers look to improve efficiency and safety of their operations, developing and executing proper arc flash prevention standards will ensure the health of their staff and their bottom line.

 

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Lockout/Tagout (LOTO): Electrical Safety Simplified

This article is from the March 2019 issue of Occupational Health & Safety Magazine and written by our Executive Vice President:

Lockout/Tagout (LOTO): Electrical Safety Simplified

LOTO is an integral part of the electrical safety requirements contained in the NFPA 70E Standard for Electrical Safety in the Workplace.


OSHA Mandate: The Law
The Occupational Safety and Health Administration, OSHA, has some minimum requirements that are invoked whenever employees are going to perform installation, maintenance, or repair on equipment. There are three major sections that apply when this occurs:

  • CFR 1910.147, which applies for General Industry applications
  • CFR 1926.147, applicable to Construction
  • CFR 1910.133 Subpart S, which directly involves electrical hazards

NFPA 70E: Industry Best Practice
The NFPA 70E standard is produced by the National Fire Protection Association, they are one of the major players when it comes to producing standards that are used for various applications in the modern world. One of their standards that is used worldwide is NFPA 70, or the National Electrical Code, more commonly referred to as the NEC. There is also NFPA 70B, which applies to maintenance standards for electrical equipment that are also interwoven into the NFPA 70E standard. The final piece is NFPA 70E, which is the commonly used standard in the United States for electrical safety, as well as being applied worldwide within certain industries. These include oil and gas production as well as paper production.

OSHA vs. 70E: Why the Two?
Although the OSHA regulations are the minimum standards for encompassing, among other things, lockout/tagout (LOTO) for electrical safety, there are several reasons why the 70E is commonly used. Historically, the NFPA appointed a new electrical safety committee in 1976 to help OSHA implement an electrical safety standard that could be quickly used as an extension of the OSH Act. Some of the requirements involved having the public involved in the adoption and modifications in the form of notice, comments, and hearings.

The standard then in common use was the NEC, and it was thought that reworking this document in this manner would entail excessive effort and might result in a document that would differ excessively from what the NEC would otherwise contain. Additionally, the NEC in its current form is used basically for electrical installations and is not directly applicable to personnel safety. The NFPA realized that a need existed for a safety standard that OSHA could promulgate and still coordinate with the NEC.

This concept and offer of cooperation was proposed to OSHA and in May 1975 OSHA responded in a positive manner, so the concept of an electrical safety standard was born.

NFPA 70E: LOTO Requirements
The terminology that is commonly used within the safety community for LOTO is an “electrically safe work condition.” This refers to an area that has been deemed “safe” from electrical hazards. Some common terms that are used for both OSHA and 70E purposes are the following:

Authorized person: Someone who is permitted due to knowledge of equipment or system to lock/tag the system in a safe and controlled manner, typically equipment operators.

Qualified person: Someone who is knowledgeable of the system enough to be able not only to lock/tag the system, but also troubleshoot, repair, or maintain the system again in a safe and controlled manner, typically technicians, electricians, etc.

Affected person: Person who may be exposed to the hazards of energizing or de-energizing the equipment or system.

PPE: Personal protective equipment for electrical hazards: rubber insulating gloves for shock hazard and arc flash-rated clothing for arc flash hazards.

LOTO: Lockout/tagout, when an electrical system or equipment has been disabled to such an extent as to render the system safe from electrical hazards for interaction with personnel.

General LOTO requirements for the employer consist of the following:

1. Shall implement a LOTO program that will include written procedures for their electrical systems.

2. Provide necessary equipment for LOTO program (locks, tags, diagrams, etc.).

3. Provide documented LOTO training to all workers exposed to the hazards.

4. Should audit the LOTO program as a whole to ensure compliance with the written program.

5. Also should audit individual personnel who implement the LOTO procedure to ensure compliance and maintain documentation of the audit.

LOTO preparations should include the following:

1. Any person who may be exposed to the electrical energy should be party to the LOTO procedure.

2. A written LOTO procedure should be developed for each system or piece of electrical equipment.

3. Up-to-date and accurate documentation should be referenced when developing the LOTO process. This will address all forms of energy and ensure that hazard exposure is minimized (eliminated).

4. LOTO is applied only to power sources, not controls. (LOTO breaker, not on/off switch).

5. LOTO equipment unique (don’t use LOTO locks for lockers, etc.).

Up-to-date and accurate schematics are required for LOTO.

LOTO equipment shall consist of the following: Any equipment installed/updated/replaced/modified after January 1990 should accept a lock in the open (off) position. The employer provides the lock, but the employee has the responsibility to use the lock when working on equipment. The lock should have only one key, its combination known to only one person, and identify who placed the lock on equipment (name, face, department, phone number, etc.). It should prevent operation of equipment without undue force or tools (using a crowbar or grinder to bypass). Equipment should have a tag that displays “Do not use, Do not operate, etc.” Equipment should be suitable for the environment (paper tag inside a water tank not permitted). Use tagout only if it is not possible to apply a lock, and this must use two isolation means (open breaker and remove cable from lug).

LOTO procedure will include the following: Locating sources of energy on up-to-date, accurate single line diagrams and also identifying any personnel that are in hazardous positions for the purpose of LOTO and any PPE required for their location. Also identify the person who is responsible for the LOTO. This will provide for types of LOTO: Simple LOTO only has one source of energy and involves only qualified personnel. Complex LOTO involves multiple power sources, crafts, departments, etc.

Exception: A written procedure is not required if there is only a single source of energy, one single LOTO will isolate all energy to said equipment, the LOTO is under exclusive control of a single qualified person.

LOTO control elements shall consist of the following:

1. The shutdown procedure and the qualified person responsible.

2. Shall include methods for removal of all stored energy from equipment/system.

3. Shall include disconnecting means verification. Ensure that the equipment is turned off.

4. Identify the responsible qualified person charged with coordinating LOTO as a whole.

5. Verify that the equipment/system cannot be restarted or energized. Attempt to start system, depress on button, attempt to close disconnect, etc.

6. Test target circuit/equipment to verify lack of energy. This process will consist of the following steps:

a) Verify test instrument on known good live source to verify test equipment is working properly.

b) Measure test circuit/equipment to verify no energy is present. Two steps are required:

1. Check zero energy on phase to phase measurement. Test each of the 1ɸ/3ɸ.

2. Check zero energy on phase to ground measurement. Test each of the 1ɸ/3ɸ.

c) Re-verify test instrument on known good live source to verify test equipment is still working properly.

7. Grounding requirements shall be examined. Generally, if there is danger of backfeed or the circuit is rated over 600V, then personnel safety grounding should be implemented.

These are some of the major points to take into account when realizing an electrical LOTO program.

Conclusions for LOTO
These are general guidelines, and anyone implementing or designing a LOTO program should reference the OSHA regulations as well as the NFPA 70E for further guidance.

At the end of the day, everyone’s goal is to return home safely to their loved ones, without injury. Implementing and following through with a sound electrical safety program and proper electrical safety training, including LOTO, is a giant step toward reaching that goal.


About the Author

Robert J. St. Pierre is the Executive Vice President of The Jacman Group, industry leaders in arc flash/electrical safety training (www.JacmanGroupSafety.com). He may be reached personally by phone 877-252-2626, ext. 2069 or by email, bobs@jacmangroupsafety.com.

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