The Basics Arc Flash Protection

Transcription

1 2008 The Basics Arc Flash Protection An arcing fault can be defined as the flow of current through a path where it is not intended to flow Rob Vajko 12/15/2008

2 What is an Arc Flash? An arc flash starts with an arcing fault. An arcing fault can be defined as the flow of current through a path where it is not intended to flow. The current creates an electric arc plasma and releases dangerous amounts of energy An electric arc is the passage of substantial electrical current through ionized air and gases. Bad things can happen. An electric arc fault is a bad thing! Page 2

3 The above photo is a still shot of a video clip of a arc flash that you can view online at Page 3

4 The above photo is a still shot of a video clip of a arc flash that you can view online at: Page 4

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6 Clothed areas can be more severely burned than exposed skin! The Costs of Burn Injury Personal Burns are one of the most painful injuries a human can experience Burn victims often seek psychological care Rehabilitation is a slow and difficult process Financial Medical costs quickly accumulate due to years of treatment Rehabilitation costs can exceed 1 million US$ per person Page 6

7 Arc Blast Hazards Up to 80% of all electrical injuries are burns resulting from an arc flash and ignition of FLAMABLE clothing Approximately 1 person dies daily in the U.S. from arc blasts, and 6 7 people are admitted to hospitals for associated injuries Pressure waves associated with Arc Blasts can: Vaporize copper, expanding it 67,000 times its initial volume Create a sonic boom condition Page 7

8 There is a known case where a utility cabinet door was blown off the hinges and embedded in a concrete wall 1.5 inches 10 feet away from the utility cabinet. Page 8

9 HOW TO PREVENT ARC FLASH Regulations and Standards Several industry standards concern the prevention of arc flash incidents: OSHA 29 Code of Federal Regulations (CFR) Part 1910 Subpart S. NFPA National Electrical Code. NFPA 70E 2000 Standard for Electrical Safety Requirements for Employee Workplaces. IEEE Standard Guide for Performing Arc Flash Hazard Calculations. Regulations for the State of Washington (Check with your own state agencies) WAC Washington State Electrical Standards for Construction WAC Washington State Electrical Construction Code WAC Washington State Electrical Work Safety Rules WISHA 6 Point Plan Compliance with the latest OSHA standards involves adherence to a six point plan: A facility must provide, and be able to demonstrate a safety program with defined responsibilities. Calculations for the degree of arc flash hazard. Correct personal protective equipment (PPE) for workers. Training for workers on the hazards of arc flash. Page 9

10 Appropriate tools for safe working. Warning labels on equipment. Companies will be cited and fined for not complying with these standards. NFPA 70E promotes establishing electrically safe work conditions by Identifying all power sources 2. Interrupting the load and disconnecting power 3. Visually verifying that a disconnect has opened the circuit 4. Locking out and tagging the circuit 5. Testing for voltage 6. Grounding all power conductors How can we prevent arc flash when we have to work on or near energized parts? Special situations: Interruption of life support equipment Deactivation of emergency alarm systems Shutdown of hazardous location ventilation equipment Removal of illumination for an area A. Use written permit system for planning & conducting work in these situations B. Use the appropriate tools for voltage and current levels when performing all electrical work NFPA 70E Key PPE Steps Page 10

11 1. Determine Arc Flash Protection Boundary 2. Conduct Arc Flash Hazard Analysis 3. Select Required FR Clothing & PPE Based on Specific Hazard Present Within Flash Protection Boundary Page 11

12 Personal Protective Equipment Select Required FR Clothing & PPE Based on Specific Hazard Present Within Flash Protection Boundary Wear the appropriate protection when working on or around energized equipment! Page 12

13 What Types Of Arc Protective Flame Resistant Garments Are Available? Basic FR Clothing Options Shirts Knit and Woven Short and Long Sleeve Pants Uniform Dress Jeans Coveralls Cold and Inclement Weather FR Clothing Options Rain wear Lined and Unlined Jackets Fleece Sweatshirts and Sweatpants Insulated Overalls and Coveralls Insulated Parkas Long Underwear and Socks Hoods/Balaclavas Vests Page 13

14 FR Garment Examples Category 1 Category 2 Category 2 Category 3 and 4 Page 14

15 FR Clothing Selection Criteria Protection Wearer Comfort Durability Cost Effectiveness Flame Resistance Durability Garment Wear Life Initial Cost Life Cycle Cost Ease of Care / Appearance In Summary Burn Injuries From Electric Arc Exposures Can Be Fatal or Can Severely Injure the Worker Based on Known Electrical Parameters and Work Practices, Arc Exposure Intensity Can Be Estimated for the Hazard, hence job tasks listed and recommendations on PPE to wear. Based On Estimated Arc Exposure Intensity, Appropriate Protective Clothing Selections Can Be Made To Minimize Worker Burn Injury Levels In The Event Of An Electric Arc Accident In Many Situations, Layering of FR Clothing Is Required to Match Electric Arc Hazard Energy Levels Page 15

16 Rain wear with Non Meltable Substrate (ASTM F 1891) Rain wear with Meltable Substrate Photo courtesy of Hugh Hoagland REMEMBER The Outermost Garment Must Be Flame and Arc Resistant Meltable Substrates Can Increase Worker Injury Other Considerations Face Shields Rated for Arc Hazard Hearing Protection Rated for Arc Hazard Hand and Foot Protection Rated for Arc Hazard Page 16

17 Exposure Energy Basics Exposure Energy is Expressed in cal/cm 2 Measured Using Thermal Sensors 1 cal/cm 2» the Exposure on the Tip of a Finger by a Cigarette Lighter in 1 Second An Exposure Energy of 1 to 2 cal/cm 2 Will Cause a 2nd Degree Burn on Human Skin Definitions ARC RATING The maximum incident energy resistance demonstrated by a material PRIOR TO BREAKOPEN OR AT THE ONSET OF A SECOND DEGREE BURN. A 1 st Degree Burn or less is the goal during an electrical arc flash. HRC Hazard Risk Category. Current categories that apply to workers are Level 0 4. Remember 4, 8, 25, 40! FLAT PANEL TESTING This is how our fabrics are tested and how the calorie rating is found (breakthrough threshold). CALORIE/CM² This is a measurement of ENERGY. A Cigarette lighter placed under your finger for 1 second equals roughly a 1 calorie burn. What is a Calorie? A Calorie is a measurement of energy, similar to labels on food products A 100 cal/cm² blast can reach temperatures of up to 35,000 degrees Fahrenheit in the center, and 11,000 degrees on the perimeter Arc Hazard Exposure Levels Category 0 N/A Category 1 4 cal/cm²* Category 2 8 cal/cm²* Category 3 25 cal/cm²* Page 17

18 z Category 4 40 cal/cm²* z Over 40 cal Recommended to re engineer system to a lower rating. z * Req'd minimum Rating of PPE. z 1.2 cal/cm² is the ONSET of a second degree burn z PPE Levels are the maximum at each exposure category Page 18