The basics of arc flash

The Basics of Arc Flash Protection

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.

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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 processFinancial•Medical costs quickly accumulate due to years of treatment•Rehabilitation costs can exceed 1 million US$ per person



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• 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.



HOW TO PREVENT ARC FLASH

Regulations and StandardsSeveral industry standards concern the prevention of arc flash incidents: •OSHA 29 - Code of Federal Regulations (CFR) Part 1910 Subpart S. •NFPA 70-2002 - National Electrical Code. •NFPA 70E-2000 - Standard for Electrical Safety Requirements for Employee Workplaces. •IEEE Standard 1584-2002 - Guide for Performing Arc Flash Hazard Calculations.


WISHA 6 Point PlanCompliance 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. •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...

• 1. 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 situationsB. Use the appropriate tools for voltage and current levels when performing all electrical work


NFPA 70E - Key PPE Steps

• Determine Arc Flash Protection Boundary • Conduct Arc Flash Hazard Analysis• Select Required “FR Clothing” & “PPE” Based

on Specific Hazard Present Within Flash Protection Boundary


Personal Protective EquipmentSelect Required “FR Clothing” & “PPE” Based on Specific Hazard Present

Within Flash Protection Boundary


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


FR Garment Examples

Category 1


FR Garment Examples Category 2


FR Garment Examples Category 3 and 4


FR Clothing Selection Criteria• Protection• Wearer Comfort• Durability

• Flame Resistance Durability• Garment Wear Life

• Cost Effectiveness• 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


Rain wear with Non-Meltable Substrate Rain wear with Meltable Substrate (ASTM F-1891)


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


Exposure Energy Basics

• Exposure Energy is Expressed in cal/cm2

• Measured Using Thermal Sensors• 1 cal/cm2 » the Exposure on the Tip of a

Finger by a Cigarette Lighter in 1 Second

An Exposure Energy of 1 to 2 cal/cm2 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 1st 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*• Category 4 – 40 cal/cm²*• Over 40 cal – Recommended to re-engineer system to a lower

rating. • * Req'd minimum Rating of PPE.• 1.2 cal/cm² is the ONSET of a second degree burn• PPE Levels are the maximum at each exposure category



Health & Medicine

The basics of arc flash