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|Arc Flash Safety|
Inform all employees, including apprentices, machine operators, technical assistants, and others who will or may work near energized electrical equipment about the hazards of electrical arc flash and arc blast, the safety rules and industry standards that apply to energized electrical equipment, and how to protect themselves from serious or fatal injuries when working near such equipment.
Suggested Materials to Have on Hand
• OSHA Standard 29 CFR 1910, Subpart S, Electrical
• The National Fire Protection Association (NFPA) 70E: Standard for Electrical Safety in the Workplace® consensus standard
• The NFPA 70: National Electrical Code (NEC)® consensus standard
• The Institute of Electrical and Electronics Engineers (IEEE) Standard 1584, Guide for Performing Arc-Flash Hazard Calculations consensus standard
• Your organization’s written electrical safety program
• Your organization’s written lockout/tagout program
• Copies of your organization’s arc flash risk assessment
An arc flash is as a short circuit, or electric arc, through the air. It occurs when an electric current flows between separate energized conducting surfaces, such as when circuit breakers and disconnects are opened and closed, when energized equipment is touched with a tool, or when electrical equipment fails. In many cases, an instantaneous and powerful pressure wave called an arc blast radiates from the source of the arc flash.
In an arc flash incident, an enormous amount of concentrated radiant energy explodes outward from electrical equipment, creating:
• Pressure waves that can damage your hearing;
• Pressure waves that send pieces of damaged equipment, tools, and other objects flying through the air at high speed;
• A high-intensity flash that can damage your eyesight; and
• A superheated ball of gas that can severely burn your body and can melt metal.
According to the National Institute for Occupational Safety and Health (NIOSH), it is estimated that 5 to 10 arc flash incidents with the potential to cause serious injury or death occur in electrical equipment every day in the United States.
Many workers are unaware of the potential hazards associated with the possibility of an electrical arc flash.
Arc flash is a recognized hazard for many industrial applications. Electrical arc flash hazards are not only present at high voltage industrial facilities. Locations consisting of many relatively low voltage equipment sources (under 600 volts) account for the most electrical arc flash occurrences. Electrical arc flashes have become more of a concern through the requirement of increased power consumption for industrial applications.
Topics for the Arc Flash Meeting
Before employees perform work near live electrical systems or systems where arc flash is a risk, a meeting or job briefing should take place to go over the following items:
• Review the work operation and procedures.
• Identify and review the electrical and other hazards of the job.
• Review energy source controls.
• Determine and implement special precautions and protective measures.
• Determine appropriate personal protective equipment (PPE) to wear.
• Know how to respond to an arc flash incident.
• Review the information on the electrical work permit, if applicable.
Although OSHA does not have a regulation specific to arc flash, there are several OSHA rules that address safe work practices around electrical equipment with arc flash hazards, and the qualifications of workers who are allowed to work on or near energized electrical equipment or parts.
According to OSHA rules (29 CFR 1910.333), only a qualified person is allowed to work directly on energized electrical equipment.
OSHA defines a qualified person (29 CFR 1910.399) as someone who has demonstrated skills and knowledge related to the construction and operation of electrical equipment and installations, has received safety training to identify and avoid the hazards involved, and is aware of the use and proper application of PPE.
OSHA defines an unqualified person (29 CFR 1910.399) as someone who has no familiarization with or training in the construction and operation of the electrical equipment and hazards involved.
An unqualified person is not allowed to work directly on energized electrical equipment and parts.
Electrical Safe Work Practices
OSHA’s work practices rule generally requires that live parts be de-energized before an employee works on or near them. The electrical regulation addresses selection and use of safe electrical work practices (29 CFR 1910.333). The rule states, in part, “[s]afety-related work practices must be employed to prevent electric shock or other injuries resulting from either direct or indirect electrical contacts ...” Arc flash doesn’t require an electrical worker to touch a piece of energized equipment in order to be harmed; it is an example of the “other injuries” described in the standard. Therefore, with respect to arc-flash burn hazard prevention, the work practices rule requires that live parts be de-energized before an employee works on or near them; that is, employees must first render electrical equipment safe by completely de-energizing it by means of lockout and tagout procedures.
Work on Energized, or ‘Live,’ Equipment
OSHA regulations state in 1910.333(a) that workers should not work on energized or live equipment greater than 50 volts, unless:
1. De-energizing introduces additional or increased hazards such as cutting ventilation to a hazardous location, or
2. It is infeasible because of equipment design or operational limitations such as when voltage testing is required for diagnostic purposes.
When it is necessary to work on energized equipment, the employer and its workers must follow safe work practices, assess the hazards and risks, wear proper PPE, and use the proper tools.
Arc flash hazards are also addressed in OSHA’s rule, Safeguards for Personnel Protection (29 CFR 1910.335(a)(1)(v)), which requires that PPE for the eyes and face be worn whenever there is danger of injury to the eyes or face from electric arcs, flashes, or from flying objects resulting from an electrical explosion. The rule requires the use of protective shields, barriers, or insulating equipment “to protect each employee from shocks, burns, or other electrically related injuries while that employee is working ... where dangerous electric heating or arcing might occur.”
OSHA’s general rule for PPE (29 CFR 1910.132(d)) states that the employer is responsible for assessing the hazards in the workplace; selecting, having, and using the correct PPE; and documenting the assessment.
General Duty Clause (GDC) and Industry Consensus Standards
OSHA has used the GDC statute (29 US Code 654) to link the requirement to provide a workplace free from recognized hazards to the hazard assessments conducted under the general PPE rule (29 CFR 1910.132(d)) and compliance with the NFPA 70E consensus standard concerning arc flash protection.
In a letter of interpretation (Dolin, 2/29/08), OSHA states:
“Industry consensus standards can be evidence that there is a hazard for which that PPE is ‘necessary.’ While the NFPA 70E consensus standard has not been adopted as an OSHA standard, it is relevant as evidence that arc flash is a recognized hazard and that PPE is necessary to protect against that hazard.”
OSHA also stated that the NFPA 70E document is evidence of the recognition of arc flash hazards in the electrical industry, and that employers that use 70E to conduct hazard assessments under the PPE rule should also comply with the worker protection provisions of 70E, including PPE requirements.
Industry Consensus Standards
There are several nonmandatory electrical industry codes and guidelines referenced in the OSHA regulations that can be helpful in understanding and complying with electrical safety requirements:
NFPA 70E. NFPA 70E provides guidance on implementing appropriate work practices and maintenance requirements that are required to safeguard workers from injury while working on or near exposed electrical conductors or circuit parts that are or could become energized. Though OSHA does not formally enforce the 70E standard, the agency considers it a recognized industry practice, and OSHA’s field inspectors may use a current version as a reference when inspecting a workplace.
NFPA 70: NEC. This standard covers installation of electrical conductors, equipment, and raceways; signaling and communications conductors, equipment, and raceways; and optical fiber cables and raceways in commercial, residential, and industrial occupancies. NFPA 70: NEC contains requirements for electrical warning labels, but not at the level of detail required in NFPA 70E for arc flash.
American National Standards Institute (ANSI)/ Institute of Electrical and Electronics Engineers, Inc. (IEEE) C2, National Electric Safety Code (NESC). This standard covers installations at electric utilities. It contains guidance for a protective clothing system.
IEEE 1584. The guidelines published by the IEEE in Standard 1584, Guide for Performing Arc Flash Hazard Calculations, help facility personnel calculate the hazards of arc flash in different types of equipment in various power systems.
NFPA 70E General Requirements
70E includes procedures to protect workers from energized electrical equipment or systems where turning off the power could create a greater hazard to people or processes than leaving it on. These standards place responsibility on employers and facility owners for establishing safe practices to protect their workers against arc flash incidents. NFPA 70E states that facilities must provide, among other requirements:
• An Electrical Safety Program that directs activity appropriate to the electrical hazard risks before any work is started by employees;
• Risk assessments that address employee exposure to electrical hazards;
• Safety-related work practices;
• Maintenance condition of electrical equipment and systems;
• PPE for workers;
• Classroom and/or on-the-job training and job briefings for workers in safety-related work practices and emergency response;
• Tools for safe work; and
• Warning labels on equipment.
Risk assessments. NFPA 70E requires employers to perform a risk assessment before allowing a worker to work on energized equipment and implement risk control according to a hierarchy of methods. The assessment is necessary to identify hazards, to estimate the potential severity of injury or effect on health, to estimate the likelihood of occurrence of injury or damage to health, and to determine if protective measures are required.
There are two types of assessments associated with arc flash:
• Arc flash risk assessment
• Shock risk assessment
The assessments are used for determining the flash protection boundary, shock protection boundaries, and the type of PPE required. To establish this information, an incident, or thermal, energy calculation is generally necessary. The NFPA 70E standard has information about incident energy level, incident energy calculations, and hazard/risk categories. The IEEE 1584 standard contains detailed incident energy calculation procedures, as well as a number of shortcuts for low voltage circuit breakers.
Safety Meeting Session
What Is an Arc Flash?
An arc flash is a short circuit that sends a powerful, high-amperage electric current through the air as an electric arc. The arc occurs when an electric current flows between separate electrified surfaces, such as when circuit breakers and disconnects are opened and closed, when energized equipment is touched with a tool, or when electrical equipment fails. Low-voltage (under 600 volts) equipment sources account for most electrical arc flash occurrences. However, high-voltage (above 600 volts) incidents can be the most catastrophic.
In an arc flash incident, an enormous amount of concentrated radiant energy flows outward from the source of the arc, along with extremely hot gases (arc plasma).
A high-intensity flash is produced that can be bright enough to damage your eyesight.
There is an instantaneous and powerful pressure wave, or arc blast, that radiates from the source of the arc flash. The wave can cover several feet in half a second.
The arc blast can send loose material like pieces of damaged equipment, tools, molten metal, and other objects flying through the air at high speed.
The thermal blast generates a superheated ball of gas that can severely burn the human body and can even melt metal.
Hazards and Effects of Arc Flash
Electrical burns, often severe, are a common injury from arc flash incidents.
The flash itself can reach 35,000° Fahrenheit (°F), and the resultant fireball will severely burn skin and underlying tissue. You can be severely injured from an arc flash without touching the energized equipment! And, the heat blast can cause severe burns several feet from the source.
Severe burns can also occur from contacting surfaces, being hit by super-heated projectiles, or when clothing or equipment catches fire from the thermal blast.
The arc blast pressure wave can damage your hearing.
Equipment that is part of or that is exposed to the arc blast is often severely damaged.
Also, flying debris can puncture or lacerate the skin.
Causes an Electric Arc
As already mentioned, an arc flash is generated during an electric arc through the air. Common causes of an electric arc include:
• Tools dropped on conductors, circuit breakers, or other energized parts, which can cause a short-circuit;
• Improper work procedures, such as working on energized equipment when it should have been de-energized or locked out;
• Insulation failure where the fault current’s magnetic effect causes conductors to separate, producing an arc;
• Testing electrical equipment with inappropriate instruments;
• Buildup of dust, impurities, and corrosion on insulating surfaces, which can provide a path for current;
• Sparks produced during racking of breakers, replacement of fuses, and closing into faulted lines; and
• Birds or rodents that snap leads at connections.
Risk of Exposure to Arc Flash
The risk of an arc flash—and your exposure to it—depends on many factors.
There is a higher risk of an arc flash incident when workers are:
• Exposed to energized parts repeatedly or for extended periods;
• Exposed to poorly maintained or defective electrical equipment;
• Required to perform several tasks in the same work area during the same operation;
• Poorly trained in the specific tasks they must perform; or
• Diverted from paying attention to the task at hand.
The risk of an arc flash from energized equipment is lower when:
• Clear work practices are established, such as written safe work practices and procedures and energized electrical work permits.
• Training is thorough and up to date.
• The right PPE is worn at all times near energized parts.
• Electrical equipment is routinely maintained and inspected.
• Workers are alert to the risks of their tasks.
Arc Flash Prevention
The best way to prevent arc flash incidents is to:
• Follow all electrical safety program requirements and safe work practices learned during training.
• Create an electrically safe work condition by de-energizing and lock out all equipment whenever possible, and verify the condition before beginning work.
• Enclose or otherwise block unauthorized access to energized equipment to prevent unintentional or accidental contact.
• Allow only qualified persons to work on energized electrical equipment.
• Ensure all workers observe the protection boundaries from energized equipment.
• Implement safe work practices designed for the specific hazards and risks of the job.
• Use only testing equipment and work tools that have been designed and certified for the task.
Electrically Safe Work Condition—De-Energize and Lock Out
With careful planning, work can almost always be done with equipment de-energized. Placing equipment in a de-energized or electrically safe work condition involves a number of steps that have to be taken before the equipment is in a safe condition. Appropriate protective precautions, including the use of PPE, are necessary during the de-energizing process.
Anyone who could be exposed or affected by the lockout/tagout has to be trained to understand the established procedure to control the energy and their responsibility in the procedure. The following steps performed by someone trained and authorized to do so will ensure that an electrically safe work condition exists:
• Find all possible sources of supply.
• Open disconnecting device(s) for each source.
• Where possible, visually verify device is open.
• Apply lockout/tagout devices.
• Test voltage on each conductor to verify that it has been de-energized.
• Apply grounding devices where stored energy or induced voltage could exist or where de-energized conductors could contact live parts.
Exceptions. Procedures for electrically safe work conditions have to be used for electrical equipment 50 volts or greater, except when:
• De-energizing or shutdown introduces additional or increased hazards, such as cutting ventilation to a workplace with a hazardous atmosphere; or
• It is not feasible to de-energize because of equipment design or operational limitations, such as when voltage testing is required for diagnostic purposes.
Arc Flash Assessment and Shock Risk Assessment
If energized equipment cannot be de-energized and locked out because increased hazards would be created or it is infeasible to do so, NFPA 70E calls for the employer to conduct a shock risk assessment of energized equipment that addresses the voltage to which employees will be exposed, the shock protection boundaries, and PPE required.
An arc flash risk assessment must also be done to determine if an arc flash hazard exists, to establish safe work practices and the arc flash boundary, and to determine the PPE required within the arc flash boundary.
Safety-Related Work Practices
Before starting any work in areas with energized parts, make sure you understand and follow safety-related work practices. Every electrical operation is different. Even if you work in a familiar area, someone else working in the same area may have changed something that affects your safety. Before performing or working near electrical equipment, make sure you:
• Read all the warning signs in the work area about electrical hazards and the instructions for protecting yourself from them.
• Read all the requirements of any electrical work permit issued for your work around live electrical parts and equipment. It may seem tedious, but it could save you many years of pain and suffering—or even your life.
• Do an inventory of all tools that will be needed for each operation, and ensure that they are rated for the specified use and are in good working condition.
• Take whatever measures are necessary to ensure the system is operating normally before working near an energized system.
• Identify and inspect all of the energized parts and equipment in your work area, regardless of whether you plan to work on them. Many arc flash incidents occur when tools touch or fall on live electrical equipment adjacent to or below the parts being serviced. In other cases, the cause is faulty or old circuits and connections that were not inspected.
• Do not cross an arc flash boundary without wearing all appropriate PPE.
• Never cross the limited approach boundary unless escorted by a qualified person and wearing all appropriate PPE.
• Never cross the restricted approach boundary under any conditions.
• Never reach blindly into areas that may contain energized parts.
• Do not wear any clothing that can conduct electricity.
• Check your work area for sharp objects and other obstructions that could cause injury or that could hinder escape and rescue if an arc flash or other electrical accident takes place.
• Identify all environmental hazards, such as water on the floor, which can create a ground; or oil on the floor, which can ignite or can indicate a leak in an oil-filled breaker or transformer.
• Ensure that the work area is well-lit so that you can see if there are any electrical hazards present.
• Do not use conductive liquids, such as water—or, for that matter, any conductive items—anywhere near exposed electrical equipment.
• Do not defeat or try to circumvent electrical interlock devices.
• Double-check to make sure you are using the right tools rated for the job you are doing.
Flash Protection Boundary
The flash protection boundary is the distance from the arc source where the potential incident (or thermal) energy could cause a second-degree burn. This boundary is established separately from the shock protection boundaries.
The “incident energy” is the amount of thermal or heat energy that reaches a surface (e.g., skin) a certain distance from the energy source generated during an electrical arc event. The incident energy level is commonly shown on warning labels in calories per square centimeter (cal/cm2) at a certain distance. For example, incident energy expressed as 1.2 cal/cm2 at 18 inches means a second-degree burn would occur 18 inches from the source of the arc event. A more intense burn would occur less than 18 inches from the arc source.
Never wear jewelry or any other conductive material within a flash protection boundary.
Shock Protection Boundaries
• The limited approach boundary is the distance from an exposed energized electrical conductor or circuit part within which a shock hazard exists and that may not be crossed by “unqualified” persons unless accompanied by “qualified” persons.
• The restricted approach boundary is distance from an exposed energized electrical conductor or circuit part within which a shock hazard exists and that may be crossed only by “qualified” persons using appropriate shock prevention techniques and equipment.
Wear PPE that is rated for the electrical protection level required for the particular part of the body and the work to be performed. Common types of PPE used for arc flash or shock protection include:
• Arc-rated clothing wherever there is a chance of exposure to an arc flash that could cause a second degree burn or greater;
• Nonconductive helmet or headgear;
• Face shield that is rated for the type of operation;
• Safety glasses;
• Rated gloves and insulated rubber gloves and leather protectors where there is an electric shock hazard;
• Rated shoes or boots; and
• Rated flame-resistant clothing.
Don’t wear outer clothing made of cotton or synthetic materials (such as nylon, acetate, or rayon) because it can burn or melt onto skin. Use cotton for undergarments only underneath arc-rated garments. The cotton fabric must not be made with fabrics that melt.
Remember, do not wear metal buttons, clasps, or zippers—they will create additional risks. This includes anything with metal, such as metal-rimmed glasses, jewelry, or wire-mesh gloves.
Warning labels are placed on all electrical equipment that poses a potential arc flash hazard. Labels should include at least the nominal system voltage, arc flash boundary, and the available incident energy or required level of PPE. Newer labels will include the corresponding working distance, or arc flash PPE category for the equipment. Always follow the instructions on warning labels.
Only qualified persons are allowed to perform preventive maintenance on energized electrical equipment in order to preserve or restore the condition of electrical equipment for the safety of employees exposed to electrical hazards.
Housekeeping duties are not allowed within the limited approach shock boundary unless adequate safeguards (e.g., barriers, insulating equipment) are available to prevent contact with energized equipment or parts. Do not use conductive cleaning materials (e.g., steel wool, conductive liquids) inside the boundary unless procedures are in place and followed to prevent electrical contact.
Report Damaged Electrical Equipment
Damaged equipment can result in serious electrical hazards. Report to your supervisor:
• Any damaged electrical covers on electrical panels, junction boxes, and other equipment where live electrical parts and wiring may be exposed
• Damaged tools that may expose live electrical parts and wiring to a person
• Damaged equipment, such as circuit breakers, connectors, and switches
• Improper equipment placement such as an extension cord over energized equipment
If there is an arc flash incident and you are uninjured and able to respond, take the following measures to minimize further injury to an injured person:
• Turn off the power supply only if you are trained and able to do so.
• Extinguish flames on a person first, then those on equipment if the fire is incipient (early stages and small).
• Call for help—sound the alarm.
• Once it is clear the injured person is not still connected to energized equipment or parts, begin cardiopulmonary resuscitation (CPR) immediately if the person is not breathing, and administer first aid if you are trained to do so. Before beginning CPR, be sure there are no serious burn injuries to the chest region.
Suggested Discussion Questions
1. What are the hazards of an electrical arc flash?
2. What are some of the potential causes of an electrical arc?
3. What are the primary OSHA regulations and consensus standards that cover arc flash?
4. What is an electrically safe work condition?
5. What is the flash protection boundary?
6. What PPE should be worn to protect against arc flash?
7. What do arc flash warning labels look like?
8. What preventive maintenance tasks can help prevent arc flash?
9. What engineering controls can reduce the risk of arc flash?
10. Do you have any other questions?
Never underestimate the risks and hazards of an arc flash associated with working on energized equipment. The long-term physical and emotional costs of ignoring the hazards and not following safe work practices are high and often permanent.
Here are a few key points to remember when working with energized electrical equipment.
• Always inspect equipment and work areas for arc flash hazards and risks each time you enter an area with live electrical equipment. Keep an eye out for arc flash warning labels.
• Human error is a major cause of arc flash incidents, such as dropped tools, contact with an electrical part, wrong test equipment, and improper work practices.
• To prevent arc flash, always de-energize and lock out equipment whenever possible.
• Follow safe work practices without fail, and do not deviate from them at all. They could save your life, and years of pain and suffering.
• Wear all required PPE—make sure it is in excellent working condition and rated for the specific use that your work calls for.
• And finally, always report—and don’t use—damaged electrical equipment, testing equipment, and other tools.
Sample Handout # 1
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