ARC FLASH HAZARDS
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Transcript of ARC FLASH HAZARDS
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ARC FLASH HAZARDS
Construction SafetyAssociation of Ontario
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Purpose of this Presentation
Introduction to:
– Hazard of arc flash
– New CSA Standard on electrical safety
– Arc flash prevention and protection
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Five Main Topics
1. Introduction to arc flash
2. Arc flash injuries
3. Codes and standards
4. Protective clothing and equipment
5. Prevention
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Topic 1 – Topic 1 – Introduction to Arc FlashIntroduction to Arc Flash
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What is an Arc Flash Hazard?
“. . . a dangerous condition associated with the release of energy caused by an electric arc.”
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What is an Electric Arc?
An electric arc is a short circuit through the air.
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An electric arc will oscillate and escalate if not constrained.
A single-phase electric arc can engulf a second or third conductor in only two cycles.
An electric arc’s current propels the arc away from the power source.
Characteristics of an Electric Arc
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What Causes Arc Flash?
Dust, impurities, corrosion, condensation, animals
Spark discharge from:
– Accidental touching
– Dropping tools
Over-voltages across narrow gaps
Failure of insulating materials
Equipment failure
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What is Arc Blast?
1. The flash causes an explosive expansionof air and metal.
– For example: When copper vapourizes it expands by a factor of 67,000.
2. The blast produces dangerous:
– Pressure waves
– Sound waves
– Molten steel and shrapnel.
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Video Clip 1 – Arc Flash DemoVideo Clip 1 – Arc Flash Demo
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Electric arc Arc flash Arc blast
Arc Flash Events
Compliments of Salisbury Electrical Safety L.L.C.
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Forms of Arc Flash Energy
Noise
Expansion
Vaporization
Thermal radiation
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Topic 2 – Arc Flash InjuriesTopic 2 – Arc Flash Injuries
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Arc Flash Injuries
Electric shock
Severe burns
Blindness
Blast injuries
– Shrapnel wounds
– Lung blast injuries
– Ruptured eardrums
– Pressure wave injuries
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1. Power – amount of energy at the arc
2. Distance – of the worker to the arc
3. Time – duration of the arc exposure
Severity Factors
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Video Clip 2 – “Not Safe at 18 inches”
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Video Clip 3 – “Not Safe Working Near”
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Electric Shock Injury – Burn
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Severe Burns from Arc Flash
Arc flash up to 35,000°F
Sun 9,900°F
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Probability of Surviving Burns
0
20
40
60
80
100
20+ 30+ 40+ 50+
25% Body Burn
50% Body Burn
75% Body Burn
% S
urv
ival
Age Range, Years
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Blindness
Flash of light is so intense it can damage vision.
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Shrapnel Wounds
Material and molten metal can hit the body at over
700 miles per hour.
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Blast Lung Injury (BLI)
Arc blast can cause inhalation injuries.For example:– Inhaling high temperature
copper vapour.– More than 100 toxic
substances can be foundin the fumes.
BLI + Burns = Greater chance of death
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Hearing Damage
Arc blast at 2 feet 145 decibels
Jet engine at 200 feet 132 decibels
Pain threshold 130 decibels
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Pressure Wave Injuries
Arc blast can throw a worker:– Off a ladder– Into nearby walls or equipment.
2000 lbs/ft2 pressure on the body can cause:– Concussion– Collapsed lungs– Other internal injuries
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Topic 3 – Topic 3 – Codes and StandardsCodes and Standards
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Standards
US Occupational Safety & Health Administration
US National Fire Protection Association -Standard NFPA 70E
Institute of Electrical & Electronics Engineers -Standard 1584
Canadian Standards Association -Standard Z-462
Occupational Health & Safety Act -Applicable regulations
Canadian Electrical Code -Rule 2-306
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What is NFPA 70E?
National Fire Protection Association
“Standard for Electrical Safety in the Workplace”
• Standard for electrical safety in United Sates
• “Harmonized” with CSA Z462
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What is CSA Standard Z462?
The standard for workplace electrical safety in Canada.
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Electrical Safety Program
Arc Flash Hazard Analysis
– Flash Protection Boundary
– Fault Current Calculations
– Arc Fault Clearing Time
– Incident Energy Exposure
Required PPE
CSA Standard Z462 addresses:
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Institute of Electrical and Electronics Engineers
Offers a method for performing arc flash hazard calculations.
What is IEEE Standard 1584?
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What is CEC Rule 2-306?
Canadian Electrical Code
“Rule 2-306 Shock and Flash Protection” A requirement for field-marking electrical
equipment to warn persons of potential electric shock and arc flash hazards.
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Sample label that complies with CEC Rule 2-306.
Required Warning Label
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Optional Warning Label
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Topic 4 – Protective ClothingTopic 4 – Protective Clothingand Equipmentand Equipment
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Flame-Resistant (FR) Clothing
Protects a worker from receiving severe burns if the worker is exposed to a flame.
Is self-extinguishing when the source of the flame is removed.
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What is a Calorie?
A calorie is the amount of heat needed to raise the temperature of one gram of water by 1°C.
Thermal energy is measured in calories/cm².
1.2 calories/cm² = Holding your finger
in the blue part of the
flame for one second.
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Limit the ‘Incident Energy’ level of the
arc flash to 1.2 cal/cm² against the
worker’s chest. Look for a label that states:
– 1506 approval (ASTM F1506)
– Arc rating of the garment. All materials in the garment
should be FR Rated:
– Thread
– Buttons
– Insulation
– Zippers, etc.
FR Rated Clothing
Photo compliments ofSalisbury Electrical Safety L.L.C.
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Typical PPE Requirements
Hazard/RiskCategory
Eye protection, ear canal inserts, long sleeve shirt
and pants
Arc rated clothing
Face & Head Protection
Flash Suit Hood
0 1 2 3 4
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Typical Protective Clothing
Hazard/Risk Category Clothing Description Required Minimum
Clothing Arc Rating
0 Non-melting, flammable materialwith fabric weight of at least 4.5 oz/yd2
Not applicable
1 Arc-rated FR shirt + FR pants or FR coveralls 4 calories/cm²
2 Arc-rated FR shirt + FR pants or FR coveralls 8 calories/cm²
3 Arc-rated FR shirt + FR pants or FR coveralls, and Arc-rated flash suit, the layered system must meet the required minimum rating.
25 calories/cm²
4 Arc-rated FR shirt + FR pants or FR coveralls, and Arc-rated flash suit, the layered system must meet the required minimum rating.
40 calories/cm²
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Synthetic Clothing
Synthetic clothing that melts shall not be worn, such as:– Acetate– Nylon– Polyester– Polypropylene– Spandex.
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Arc Flash Rated PPE
Required minimum clothing:– Non-melting, flammable material,
– Fabric weight of at least 4.5 oz/yd.
PPE must also providearc flash protection:– Face shield
– Gloves, etc.
Photo compliments ofSalisbury Electrical Safety L.L.C.
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Video Clip 4 – 100% Cotton Clothing
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Video Clip 5 – Polyester/Cotton Clothing
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Video Clip 6 – FR Clothing
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Increases level of protection.
May be lighter than a singleheavy garment.
Manufacturer must providethe new combined arc ratingafforded by layering.
FR Clothing Can Be Layered
Photo compliments ofSalisbury Electrical Safety L.L.C.
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Tell the supplier that you needarc flash rated PPE and clothing.
PPE must have some resistance to:– Flame– Ignition– Melting.
obtain PPE from a known and
trusted supplier.
When Purchasing PPE
Not all FR clothing is tested to ASTM F1506
Photo compliments ofSalisbury Electrical Safety L.L.C.
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Topic 5 – PreventionTopic 5 – Prevention
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Tasks with Potential for Arc Flash
Operating a switch or circuit breaker
Inserting or removing a circuit breaker
Opening an enclosure door
Removing a cover (bolted or hinged)
Testing for voltage
In each task:
Worker is interacting with energized equipment.
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Conduct a Flash Hazard Analysis to determine the
Flash Protection Boundary Incident Energy exposure Type and arc rating of PPE
If work must be done on or near energized electrical equipment,
identify the potential for arc flash.
Arc Flash Hazard Analysis
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Reduce the fault clearing time.
Reduce the short-circuit current.
Improve equipment maintenance.
CONTROLLING ARC FLASH HAZARDS
At the Source
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Use flash-resistant equipment.
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CONTROLLING ARC FLASH HAZARDS
At the Source
These disconnect switch-plugs have beendesigned with built-in flash-protection.
Photos courtesy of Meltric Corporation
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Increase the working distance.
Reduce the energy exposure.
Use hinged doors instead of bolted doors to eliminate the risk of bolts falling into the panel.
Work de-energized.
CONTROLLING ARC FLASH HAZARDS
Along the Path
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Energized electrical work permit
Barriers
Training and skills
Job briefings
PPE
Tools
CONTROLLING ARC FLASH HAZARDS
At the Worker
Photo compliments ofSalisbury Electrical Safety L.L.C.
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Prevention Summary
1. Include Electrical Safety in your Occupational Health and Safety Management Program.
2. Use an electrical work permit system.
3. Conduct regular equipment maintenance and label equipment that poses a flash hazard.
4. Confirm single-line diagrams for accuracy and available fault current.
5. Maintain documentation process.
6. Provide training and job briefings.
7. Conduct periodic safety audits.
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ARC FLASH HAZARDSARC FLASH HAZARDS
It is ALWAYS
preferable to work on
de-energized equipment.
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