ASSESSING THE ARC FLASH RISK
Causes of Electric Arcs Dust and impurities Corrosion Condensation of vapor and water dripping Accidental touching Dropping tools Failure of Insulating Material Improper Design or Utilization Equipment Improper Work Procedures
Intense Heat Cause Sudden Expansion of Air. Lightning is a Natural Arc.
Hazards of Arc Flash Serious Burns occur when victim is several feet from arc. Spraying of molten metal at high pressure Blast pressure waves have thrown workers across rooms or off ladders. Pressure on the chest can be higher than 2000 lbs./sq. ft. Clothing can be ignited and burn more severely than unclothed areas. Hearing loss can occur where a blast can have a magnitude as high as 140 dB at 2 feet from arc.
The Nature of Arc Flash 35,000 ˚F Four Times The Surface Temperature of the Sun
The Nature of Arc Flash Energy of an Arc Flash is a Function of System Voltage, Fault Current Magnitude, and Fault Duration.
Arcs in Enclosures Magnify the Blast and Energy Toward Open Side of the Enclosure and Toward the Worker.
The Nature of Arc Flash Copper Expands in Volume by 67,000Times Water Expands in Volume by 1670 Times
Probability of Survival Decreases With Age Burn Injury Statistics – Probability of Survival (Source: American Burn Association, 1991-1993 Study; Revised March 2002)
Addressing Arc Flash Hazard Past National Electric Code (NEC) and other safety codes primarily concerned with protection from fire, electrocution, and shock hazard. The 2005 NEC now has requirements for warning labels in conjunction with a new standard, NFPA 70E-2004, Standard for Electrical Safety in the Workplace. NFPA 70E-2004 is intended for use by employers, employees, and OSHA.
Addressing Arc Flash Hazard
Addressing Arc Flash Hazard
Addressing Arc Flash Hazard NFPA 70E-2004 and IEEE Std 1584-2002 provide guidance on implementing appropriate safety procedures and arc flash calculations. Although OSHA doesn't directly state what to do about arc-flash hazards, OSHA 29 CFR1910.132(d)(1) requires employers to evaluate the workplace for hazards. And based on these assessments, the employer must select and require the use of appropriate personal protective equipment (PPE) for its employees. NFPA 70E-2004 requires a flash hazard analysis be performed in order to determine the Flash Protection Boundary and PPE required within that boundary.
NFPA 70E Protection Boundaries Only “qualified” people can enter these boundaries wearing appropriate PPE.
Flash Protection Boundary Distance from arc source where potential incident heat energy on skin is 1.2 calories/cm² . An skin exposure would normally result in a curable 2 nd degree burn. Within this boundary protective clothing such as fire resistant shirts and pants and other equipment is required (PPE).
Working Distance – The distance between arc source and the worker’s face or chest. Approach Boundary - The approach working distance for a qualified personnel. Limited Approach Boundary – An approach limit at a distance from an exposed live part within which a shock hazard exists. Restricted Approach Boundary – An approach boundary limit at a distance from an exposed live part within which there is an increased risk of shock, due to electrical arc over combined with inadvertent movement, for personnel working in close proximity to the live part. Prohibited Approach Boundary – An approach limit at a distance from an exposed live part within which work is considered the same as making contact with the live part.
Rubber Glove Class Color Maximum Usage 00 Beige, Red 500 VAC or Blue 0 Red or 1,000 VAC Blue 1 White 7,500 VAC 2 Yellow 17,000 VAC 3 Green 26,500 VAC 4 Orange 36,000 VAC Leather Protector Grove - Always worn over rubber glove to provide needed mechanical protection against cuts, abrasions and punctures and alone do not provide any protection from electrical shock.
Personal Protective Equipment
Personal Protective Equipment
Hazard/Risk Classification per NFPA 70E-2004 Table 130.7(C)(11) & modified to MOM standards Additional PPE is required other than examples above that cover the torso.
Assessing Flash Protection Boundary & Hazard Category MOM Policy is to have Arc Flash Protection Boundary and PPE requirements calculated under engineer supervision using either the NFPA 70E or IEEE Std. 1584 methods of analysis.
Limitations of Assessment Equations used are based on test performed in laboratory and may differ at the facility in question. Equations based on range of test values which should be cross-reference to the facility’s electrical system parameters. Random nature of arcs make it difficult to model precisely. The estimates provided by the equations are “average” values.
NFPA 70E and IEEE 1584 NFPA 70E method is believed to be generally conservative. IEEE 1584 method is more realistic and aims to avoid accidents due to limitations provided by over-protection to workers. Over-protection can also lead to the restriction of visibility and movement, discomfort and reduces worker productivity.
Is Your Facility at Risk?
Reasons for Risk Analysis Determine the incident energy for each electrical distribution path to each piece of electrical equipment. Determine the level of PPE required when working on energized circuitry Determine labeling requirements Comply with OSHA regulations through standards determined by NFPA and IEEE.
Reasons for Risk Analysis Minimize The Risk of Personal Injury or Death
Reasons for Risk Analysis Minimize a Facility’s Vulnerability to Insurance and Legal Issues
Documentation is Key The facility one-line diagram is the summary of all electrical documentation. If the one-line diagram is not accurate, further efforts toward analyzing arc flash are futile.
Documentation is Key Once electrical documentation is in order, you can proceed to analyze the facility. Identification of locations/equipment Collecting Data Short Circuit Analysis Protective Device Coordination Actual Arc Flash Analysis Arcing Current Arcing Times Determine Incident Energy Determine Flash Protection Boundary Determine Personal Protective Equipment (PPE) Category Documentation
Continuous Compliance Once your facility is compliant, you can relax?
WRONG !!!!
Electrical Distribution System Changes Additions or deletions to a electrical distribution system will alter the energy paths and incident energy across the system. CHANGE THE SYSTEM AND YOU MUST CHANGE YOUR DOCUMENTATION, AND YOU MUST RECALCULATE ALL AFFECTED ENGERY PATHS.
Training & Work Procedures Work Permits Lockout/Tagout
QUESTIONS ??? Thank You for Your Time !
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