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Understanding Arc Flash Hazards: Prevention and Safety Measures

Learn about arc flash hazards, causes, and prevention methods, including the importance of safety training, OSHA regulations, and conducting an arc flash study before working around electrical systems.

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Understanding Arc Flash Hazards: Prevention and Safety Measures

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  1. ARC FLASH SAFETY Bureau of Workers’ Comp PA Training for Health & Safety (PATHS) 29 CFR 1910.303 29 CFR 1910.305 29 CFR 1926.400-449,Subpart K NFPA 70E PPT- 054-01 1

  2. OSHA Cited Violations: FY 2010 • OSHA has long understood the importance of safety in this area and tracks electrical violations • OSHA Most Cited Violations (2010) • Electrical-General Requirements (1910.303): 2,770 • Lock-out/Tag-out (1910.147): 3,531 PPT- 054-01 2

  3. OSHA Violations FY 2010 1926.400-449, Subpart K • 404(f)(6) Grounding path 473 • 404(b)(1)(i) Ground fault protection 338 • 405(g)(2)(iv) Flexible cords-strain relief 277 • 416(e)(1) Worn/frayed cords or cables 256 • 403(b)(2) Equipment installation and use 241 PPT- 054-01 3

  4. OSHA Violations FY 2011 • 1910.147 Lock-out/Tag-out 3,639 • 1910.305 Electrical-Wiring Methods 3,584 • 1910.303 Electrical-General Requirements 2,863 PPT- 054-01 4

  5. Electrical Hazards • Shock • Electrocution: 4th leading cause of industrial fatalities • Fires • Burns • Arc Flash • Arc Blast PPT- 054-01 5

  6. Arc Flash Defined • Electrical work may cause injury or death • One severe occurrence is the Arc Flash event “Arc Flash: an electrical discharge that uses the air as a conductor, exploding from a high voltage source to another conductor or ground nearby. The release can be 5,000oF or hotter, melting nearby metals and damaging the electric circuits involved. The brightness, heat and force of the arc flash can cause damage to the human body.” Tyler Lacoma, eHow Contributor, http://www.ehow.com/about_5110071_definition-arc-flash.html PPT- 054-01 6

  7. Arc Flash Hazards resulting from arch flash: • Heat • Shrapnel • Pressure • Sound • Intense light • UV • IR PPT- 054-01 7

  8. Arc Flash Hazards Statistics:* 5 to 10 such serious arc flashes a day occur in the United States Result: 1 to 2 fatalities Although protective clothing exists, there is no guarantee against such severe energy releases. *Dr. Mary Capelli-Schellpfeffer, “Arc Flash Presentation,” as quoted in eHow.com facts, May 30, 2012 PPT- 054-01 8

  9. Causes of Arc Flash • Overloading/overheating of circuits • Damaged circuit breakers • Over-fusing • Wiring in a non workman -like manner • Faulty electrical panels PPT- 054-01 9

  10. Causes of Arc Flash • System overload • Incorrect wire gauge for system requirements PPT- 054-01 10

  11. Causes of Arc Flash Faulty panels or overloading panels PPT- 054-01 11

  12. Arc Blast • Accompanies the flash • Intense radiant heat released • Nearby surfaces (persons and objects) absorb and are instantly heated to vaporizing temperatures PPT- 054-01 12

  13. Arc Blast Hazards Serious situations!! PPT- 054-01 13

  14. Electrical System Susceptibility SystemHazard Less then 120V Arc flash highly improbable 480V electrical Sufficient capacity to cause services Above 600V Medium-voltage with higher energy/potential for an arc flash event http://en.wikipedia.org/wiki/Arc_flash PPT- 054-01 14

  15. Arc Flash Energy Released Per Wikipedia Example: single phase-to-phase fault on 480V system with 20,000 amps of fault current Resulting power is 9.6 MW If fault lasts 10 cycles at 60Hz, resulting energy would be 1.6 megajoules Comparison: TNT releases 2,175 J/g or more when detonated. This fault is equal to 380 grams (about 0.8 pounds) of TNT !!! http://en.wikipedia.org/wiki/Arc_flash PPT- 054-01 15

  16. Possible “Traps” Beware of a “profusion of electrical confusion” PPT- 054-01 16

  17. Current/Reaction Chart CurrentReaction Below 1 milliampere Generally not perceptible. 1 milliampere Faint tingle. 5 milliampere Slight shock. Not painful-disturbing. Average person can let go. Strong involuntary reactions can lead to other injuries. 6-25 milliamperes Painful shock. Loss of muscular control. (women) 9-30 milliamperes Freezing current (“let-go” range). Person can not let go but can be thrown from the current if extensor muscles are stimulated. 50-150 milliamperes Extreme pain, respiratory arrest, severe muscular contractions. Death is possible 1,000-4,300 Rhythmic pumping action of heart ceases. Muscular milliamperes contraction and nerve damage occur; death likely. 10,000 milliamperes Cardiac arrest, severe burns; death probable. OSHA Training Institute, “Construction Focus Four: Electrocution Hazards,” April, 2011 PPT- 054-01 17

  18. Need for an Arc Flash Study • Numerous inherent dangers when working around electrical systems • Safety from arc flash should include an Arc Flash Study • Done prior to conducting work on hazardous locations PPT- 054-01 18

  19. Arc Flash Study Study components per IEEE 1584: Data Collection (steps 1 & 2) System diagrams Modes of operation scenarios Analysis (steps 3-7) Determination of bolted fault currents Protective devices recommended Document system voltages & classes of equipment Determine working distance from arc flash source PPT- 054-01 19

  20. Arc Flash Study Arc Flash Hazard Analysis (Steps 8 & 9) Incident energy determination (Energy needed for an arc flash to cause second-degree burns) Flash protection boundaries (Distance where the second-degree burns are caused, or where the incident energy is 1.2 calories per centimeter squared or 1.2 cal/cm2) Both may be calculated using NFPA or IEEE equations Diane Bonder, eHow Contributor PPT- 054-01 20

  21. Aids to Safe Operations • NFPA 70E-2004 Standard for Electrical Safety Requirements for Employee Workplaces • IEEE 1584 Guide for Arc Flash Hazard Calculations PPT- 054-01 21

  22. Arc Flash Hazard Analysis Results aid in determining: Proper PPE, distance-dependent from possible threat: - Shirts - Pants - Underwear - Goggles - Gloves - Hard hats - Shields, face and neck - Heating protection - Shoes PPT- 054-01 22

  23. Safe Distance Calculations Used to determine safe distances and PPE Variables taken into account: • Voltage • Working distance • Clearing time • Grounding • Gap between conductors • Bolted fault current PPT- 054-01 23

  24. Arc Flash Boundaries “Distance from an arc flash within which an unprotected person has a 50% chance of receiving a second degree burn” PPT- 054-01 24

  25. Flash Protection Boundary Arc flash hazard is based on: • Fault current • Arcing time • Distance Preplanning your facility will enhance the safety of your staff PPT- 054-01 25

  26. PPE Based on Incident Energy Preplan PPT- 054-01 26

  27. PPE by Hazard Risk Category Findings compared to table which indicates arc thermal performance of clothing Dangers above a 4 is prohibited “No Safe PPE Exists Energized Work Prohibited” PPT- 054-01 27

  28. Definitions • Voltage (E): electromotive force (emf) that forces electrons to flow through a circuit measured in Volts (V) • Current (I): the number of electrons that flow past a point in a circuit in one second measured in Amperes or Amps (A) • Resistance (R): the opposition to current flow in a circuit that contains only resistance and is measured in ohms PPT- 054-01 28

  29. Ohm’s Law • Relationship between E, I, R • “One volt of electromotive force will force one ampere of current to flow through one ohm of resistance” E By knowing 2 of these variables, the other can be calculated! I R PPT- 054-01 29

  30. Power Formula • Power: the rate at which work is done and is measured in Watts (W) (E x I)=Watts • So Power is equal to P= E x I • Power can be measured in the thousands of watts per hour and reads as KWH or kilowatthours PPT- 054-01 30

  31. Horsepower and Watts • Horsepower is the unit of measure for mechanical energy • 746 Watts = 1 Horsepower (hp) or P = E x I • Flow of Amps= E/R • Additional information PPT- 054-01 31

  32. Qualified Person • Qualified Person: One who has received training in and has demonstrated skills and knowledge in the construction and operation of electric equipment and installations and the hazards involved • OSHA defines these as specially trained to work on live electrical equipment • Unqualified Person: per 1910.332(b)(2) must still be trained in safe electrical practices for their support jobs (painters, cleaners as examples) PPT- 054-01 32

  33. Types of Damage Fully understand the hazards related to these activities If possible, review case histories of your industry to devise safe operations PPT- 054-01 33

  34. Caution!! Abide by distances determined by NFPA or IEEE NO SHORT CUTS!!! PPT- 054-01 34

  35. Signage Ensure signage fits hazard and conforms to regulatory requirements PPT- 054-01 35

  36. Hazard Preplan • Use checklists to preplan equipment needs when performing service or maintenance • Label systems for future maintenance and arc flash studies PPT- 054-01 36

  37. Safety Precautions: PPE • PPE should fit the requirements of the job • Specific level of PPE is required PPT- 054-01 37

  38. PPE Tests for arc rating of PPE Found in ASTM F1506 “Standard Performance Specifications for Flame Resistant Textile Materials for Wearing Apparel for Use by Electrical Workers Exposed to Momentary Electric Arc and Related Thermal Hazards” PPT- 054-01 38

  39. Match PPE to Task Level 2 Protective Coverall PPT- 054-01 39

  40. Match PPE to Task PPT- 054-01 40

  41. Match PPE to Task Prepare for the possible! PPT- 054-01 41

  42. Tools • Support equipment rated for the task • Tools properly insulated • Correct support equipment for the job PPT- 054-01 42

  43. Safety Robotic removal or disengagement devices can do much to maximize personnel safety Also: • Draw-out circuit breakers on a life bus • Remote racking PPT- 054-01 43

  44. Safe Work Practices Lock-out/Tag-out: Make sure you’re wearing the proper PPE for this job also PPT- 054-01 44

  45. Avoiding Arc Flash Assign qualified person • Conduct system analysis to determine arc flash hazard • When working, secure all power and enact Lock- out/Tag-out • Proper tools and PPE rated for the job • Assign electrical safety program manager familiar with codes • Properly maintain system and components • Apply warning labels PPT- 054-01 45

  46. Some Questions OSHA will Ask From EHSToday, March 13, 2008 (and still timely), Kenneth Cybart: OSHA’s goal: for employers to identify all electrical hazards, potential and actual Analyze workplace for shock and arc flash hazards, set safe protection boundaries and define required PPE Circuit or equipment description at job location? Written description, drawing Detailed job description of work? PPT- 054-01 46

  47. Some Questions OSHA will Ask Can the fact that the equipment cannot be de-energized or job be deferred be justified? 1910.333(a)(1) Live parts must be de-energized before employee works on/near them Less than 50 volts to ground need not be de-energized if there will be no increased exposure to electrical burns or to explosion due to electric arcs However, never work on live circuits unless absolutely necessary PPT- 054-01 47

  48. Some Questions OSHA will Ask Live circuit work necessary? OSHA 1910.33(a)(2): Safety-related work practices required NFPA 70E Article 110.8(B)(1): Electrical Hazard Analysis required before work performed on live equipment operating at 50 volts and higher Other questions to ask: - Safe work procedures? -Detailed work procedure established? Will it be used? -Job briefing checklist performed? PPT- 054-01 48

  49. Some Questions OSHA will Ask Was job briefing given to those doing the job? Proper management approval obtained? NFPA 70E annexes to assist your program: AnnexTopic E Electrical Safety Programs F Hazard Risk Evaluation Procedures I Job Briefing Checklists J Energized Work Permits PPT- 054-01 49

  50. Some Questions OSHA will Ask Electrical safety analyses performed? Arc flash hazard analysis performed? Flash protection boundaries established? Other potential electrical hazards identified? Proper insulated tools and equipment used? Necessary PPE determined? Insulated blankets/sheeting used to cover all liveparts? PPT- 054-01 50

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