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Q. What is an Arc Flash?

A. Dangerous release of energy created by an electrical fault. Release will contain:

  • Thermal energy
  • Acoustical energy
  • Pressure wave
  • Debris

Q. What causes an Arc Flash?

A. The arc can be generated by:

  • Mechanical breakdown/failure
  • Current overload
  • Accidental contact
  • Dirt, Debris, Dust, Ionized Air

Q. What affects Arc Flash intensity?

A. Variables that affect the size and energy of an electrical Arc Flash are:

  • Clearing time
  • Available fault current
  • Amperage
  • Voltage
  • Arc Gap
  • Distance from arc
  • 3-phase v single phase
  • Confined space

Q. What type of equipment can cause an Arc Flash?

A. Typical equipment can be:

  • Motor Control Centers (MCC's)
  • Circuit Breakers
  • Disconnects
  • Metering Devices (remove-install)
  • Panel Boards
  • Switchgear (low and high voltage)
  • Transformers
  • Junction Boxes
  • Buss Way
  • Any Live Electrical Conductor

Q. What is my risk to being exposed to Arc Flash?

A. The exposure to Arc Flash depends on the following:

  • Number of times the workers perform a task involving exposed live equipment.
  • Complexity of the task performed; need to use force, available space, safety margins, reach, etc.
  • Training, skills, mental and physical agility, coordination with helper
  • Tools used
  • Condition of equipment

Q. What standards regulate Arc Flash hazards?

A. There are four main regulations governing Arc Flash. They include:

  • OSHA Standards 29-CFR, Part 1910 - Occupational Safety and Health Standards, 1910 sub part S (electrical) Standard number 1910.333 specifically addresses Standards for Work Practices and references NFPA 70E.
  • The National Fire Protection Association (NFPA) Standard 70-2009 - "The National Electrical Code" (NEC) contains requirements for warning labels.
  • NFPA 70E 2000 - Provides guidance on implementing appropriate work practices that are required to safeguard workers from injury while working on or near exposed electrical conductors or circuit parts that could become energized.
  • The Institute of Electronics and Electrical Engineers (IEEE) 1584-2002 - Guide to Performing Arc-Flash Hazard Calculations.

Q. What data is required on the new Arc Flash warning labels?

A. Labels shall include more information on the specific parameters of the hazard including:

  • Available Short-Circuit Current
  • Flash Protection Boundary
  • Incident energy at 18" expressed in cal/cm2
  • PPE required
  • Voltage shock hazard
  • Restricted shock approach boundary
  • Prohibited shock approach boundary

Q. What are the Arc Energy basics?

A. Arc Energy basics are:

  • Exposure energy expressed in cal/cm2
  • 1 cal/cm2 = hottest part of the flame from a lighter for 1 sec
  • An exposure of only 1-2 calories will cause second degree burn on human skin
  • Typical non-FR "workwear" can ignite at energies as low as 2 calories
  • Reports indicate that 80-90% of job tasks have hazards with the potential to release up to 8 cal/cm2

Q. What happens during Arc Flash events?

A. During an Arc Flash event:

  • Arc temp can reach 35,000 °F
  • Copper expands 67,000 times when vaporized
  • Fatal burns can and do occur at >10 feet
  • Per OHSA, 80% of electrically related accidents, incidents, and fatalities among qualified workers are caused by - Arc Flash


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