|
F.A.Q.
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
|
