Electrical Safety II- Arc Flash Safety

In our previous article, Electrical Safety I: The Importance of Proper Lockout-Tagout Procedures, we helped identify what sources need to be locked out, offered examples and a starting point for proper LOTO procedures, and provided OSHA standards for specific industries.

Arc Flashes occur 5-10 times every day throughout the United States.  This article will discuss several different aspects of arc flashes, including a definition of what an arc flash is; what type of injuries it can cause; and a better understanding of applicable standards and safety measures you can implement to help prevent these dangerous (and sometimes deadly) accidents.

In the next article in this series, learn about the three-step process to  prevent electrical fires- one of the leading causes of fires in the workplace every year. 

NOTE: The information presented in this article is gathered from multiple sources cited below and is intended for general discussion only.  Information contained in this article should not be used for compliance purposes.

Use these links to jump to the information you are interested in:

What Causes an Arc Flash?
Potential Injuries
Applicable Standards
Safety and Prevention

What Causes an Arc Flash?
 

Wikipedia defines an arc flash as "an electrical breakdown of the resistance of air resulting in an electric arc which can occur where there is sufficient voltage in an electrical system and a path to ground or lower voltage."

The massive energy released in the fault rapidly vaporizes the metal conductors involved, blasting molten metal, and expanding plasma outward with extreme force.  An arc flash with 1000 amperes or more can cause substantial damage, fire, or injury, and temperatures can reach or exceed 35,000 degrees Fahrenheit at the arc terminals.

A high-energy arcing fault can also produce a considerable pressure wave and sound blast.  The intense heat from an arc causes the sudden expansion of air, resulting in a blast.  Pressure on the chest can be as high as 2000 lbs/sq foot.  In some cases, the pressure wave has sufficient energy to snap the heads of 3/8-inch steel bolts and to knock over construction walls.  Moreover, it can send metal parts flying at speeds over 700 miles per hour.

Source: Wikipedia

This video is of an arc flash explosion that occurs when faulty switchgear (which is used to isolate electrical equipment) is turned on.  The force from the explosion is so powerful it shakes the camera!

In this video, no one was injured- but when an arc flash explosion happens, not everyone is so lucky. 

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Potential Injuries

Hundreds of deaths and thousands of disabling injuries occur each year due to shock, electrocution, arc flash, and arc blast.  We have listed some of the more common injuries below.

Injuries associated with an arc flash include:

• Fatal burns can occur when the victim is several feet from the arc. Serious burns are not uncommon even at a distance of 10 feet. Arc flash can cause skin burns by direct heat exposure.
   
• Clothing can start on fire from the arc flash.
   
• Synthetic fabrics can melt and stick to the wearer.
   
• Metal is vaporized at this temperature. If the vaporized metal is inhaled, serious lung damage occurs when the vapor cools and solidifies in the respiratory system.
   
• Droplets of molten metal can be propelled over great distances, causing serious burns or igniting clothing.
   
• High-intensity flash can also cause damage to eyesight secondary to the intense light it produces.

Injuries associated with an arc blast include:

• Lung collapse from the pressure on the chest.
   
• Shrapnel wounds from flying debris propelled at high speeds.
   
• Loss of memory or brain functions from concussion.
   
• Hearing loss from ruptured eardrums. The sound associated with blast can exceed 160 dB. The sound of jet engine is only 145 db!
   
• Other physical injuries from being blown off ladders or into walls or from wall collapse.

Source: Arc Flash Electrical Safety

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Applicable Standards
 

Every industry has organizations that provide standards, guidelines, and documentation to protect workers from hazards.  Each of the standards mentioned below offer guidance for safely working on and installing de-energized equipment in the United States.

OSHA

The Occupational Safety and Health Administration (OSHA) has defined several different instances where a lockout/tagout procedure is required or necessary.  OSHA's mission is to ensure safe and healthful working conditions for working men and women. 

The links in this section will take you directly to OSHA's website for more details.

NOTE: The information presented in this section is intended for general discussion only and should not be used for compliance purposes.  For more detailed information on OSHA standards and their application to specific situations, please visit the Occupational Health and Safety Administration's website, or contact OSHA directly.

29 CFR 1910.333: Selection and use of work practices

Safety-related work practices shall be employed to prevent electric shock or other injuries resulting from either direct or indirect electrical contacts, when work is performed near or on equipment or circuits that are or may be energized.  The specific safety-related work practices shall be consistent with the nature and extent of the associated electrical hazards.

1910.333(b) covers these OSHA requirements:

• Working on or Near Deenergized Parts
• Lockout and Tagging Procedures and Proper Applications
• De-Energizing Equipment Procedures
• Verification of Deenergized Conditions
• Proper procedures for removing a lock and tag when an employee is not present.

29 CFR 1910.335 Safeguards for personnel protection

1910.335(a)(1), sections i-v covers the requirements and procedures for personal protective equipment required to perform electrical work.  It includes:

• Maintaining protective equipment in a safe, reliable condition. along with periodically inspecting or testing protective equipment.
   
• If the insulating capability of protective equipment may be subject to damage during use, the insulating material shall be protected (i.e. an outer covering of leather on top of rubber insulating material).
   
• Wearing non-conductive head protection wherever there is a danger of head injury from electric shock or burns due to contact with exposed energized parts.
   
• Wearing protective equipment for the eyes or face wherever there is danger of injury to the eyes or face from electric arcs or flashes or from flying objects resulting from electrical explosion.

1910.335(a)(2)- General Protective Equipment and Tools describes the items that need to be provided when working near exposed conductors or circuit parts.  This includes:

• Insulated tools or handling equipment if the tools or handling equipment might make contact with such conductors or parts.
   
• Fuse handling equipment, insulated for the circuit voltage, shall be used to remove or install fuses when the fuse terminals are energized.
   
• Non-conductive ropes and handlines.
   
• Protective shields, protective barriers, or insulating materials used to protect each employee from shock, burns, or other electrically related injuries while that employee is working near exposed energized parts which might be accidentally contacted or where dangerous electric heating or arcing might occur.

1910.335(b)- Alerting Techniques identifies the techniques that should be used to warn employees about electrical hazards that may enganger them.   It Includes:

• Safety signs and tags. Safety signs, safety symbols, or accident prevention tags shall be used where necessary to warn employees about electrical hazards that may endanger them.
   
• Barricades used in conjunction with safety signs where it is necessary to prevent or limit employee access to work areas exposing employees to uninsulated energized conductors or circuit parts. Conductive barricades may not be used where they might cause an electrical contact hazard.
   
• If signs and barricades do not provide sufficient warning and protection from electrical hazards, an attendant shall be stationed to warn and protect employees.

NFPA
 

The National Fire Protection Association (NFPA) attempts to reduce the worldwide burden of fire and other hazards on the quality of life by providing and advocating consensus codes and standards, research, training, and education.

The world's leading advocate of fire prevention and an authoritative source on public safety, NFPA develops, publishes, and disseminates more than 300 consensus codes and standards intended to minimize the possibility and effects of fire and other risks.

NFPA70- National Electric Code (NEC)*

The National Electric Code is updated every three years.  It covers the installation of electrical conductors, equipment, and raceways; signaling and communications conductors, equipment, and raceways; and optical fiber cables and raceways for the following:

• Public and private premises, including buildings, structures, mobile homes, recreational vehicles, and floating buildings
• Yards, lots, parking lots, carnivals, and industrial substations
• Installations of conductors and equipment that connect to the supply of electricity
• Installations used by the electric utility, such as office buildings, warehouses, garages, machine shops, and recreational buildings, that are not an integral part of a generating plant, substation, or control center.

NFPA70E-2012- Standard for Electrical Safety in the Workplace (2012 Edition)*

This standard addresses electrical safety requirements for employee workplaces that are necessary for the practical safeguarding of employees during activities such as the installation, operation, maintenance, and demolition of electric conductors, electric equipment, signaling and communications conductors and equipment, and raceways.

The 2012 edition has incorporated a multitude of changes from the previous version- Jim Phillips from Electrical Contractor Magazine covers the more significant changes in this article:

It's Almost Here: Changes in the 2012 edition of NFPA 70E

* Register on NFPA’s site for free to view this entire document online

IEEE 1584- Guide for Performing Arc-Flash Hazard Calculations

The Institute of Electrical and Electronics Enginees (IEEE) is "The world’s largest professional association dedicated to advancing technological innovation and excellence for the benefit of humanity".  This guide defines the practice for performing detailed arc flash calculations.  This method has become the currently accepted industry practice used for calculating the prospective incident energy that could be available at a given location which can be used to determine the PPE requirements. 

For an overview and extensive discussion about these calculations, please visit the IEEE 1584 Forum.
 

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Safety and Prevention

There are several steps that a company can take to provide the best safety and protection for their workers or potentially prevent arc flashes.  These four items are just the first steps to help protect workers and prevent injuries involving arc flash.

• Arc Flash Analysis
  
  Performing an Arc Flash Analysis to determine where a system might have faults that could cause an arc flash is the first critical step in electrical repair and maintenance.  This analysis can be performed using calculations from IEEE 1584.
  
  By using a company that specializes in this type of analysis or by utilizing specialized software, you can help determine where an arc flash might occur before it causes an accident or an injury.

• Proper Lockout/Tagout Procedures
  
  After a proper Arc Flash Analysis is performed, the next line of defense is ensuring that your company has established lockout/tagout procedures to control hazardous energy when a machine or electrical system is being serviced or repaired.
  
  If proper lockout/tagout procedures are followed in combination with the appropriate personal protective equipment, you have provided the protection necessary to save lives.
   

• Appropriate Personal Protective Equipment (PPE)
  
  Ensuring that employees have and maintain the appropriate PPE to protect themselves from hazards is vital to the safety and well-being of your employees.  NFPA70 and 29 CFR 1910.335 are good places to start to determine what equipment is necessary for your particular application.
  
  Stonehouse Signs also offers a full line of safety signs and lockout/tagout accident prevention tags to help warn and inform your employees of the proper equipment required before performing maintenance or installation of electrical equipment.

• Training and Education
  
  Providing training and education is always vital for the safety of your employees. By   scheduling regular training sessions, advising your employees on appropriate PPE equipment and how to use it, and ensuring that all safety procedures are universally  understood will help minimize an injury if an accident occurs- or it could prevent the accident altogether.

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Stay tuned for Electrical Safety Part III, where we discuss Electrical Fires- What they are, and how to stop them.