1
3/15/2016

Raise awareness about:
– the hazards of arc flash
– new NFPA 70E code standard on electrical safety
– arc flash prevention and protection

“. . . a dangerous condition associated with the release of energy caused by an electric arc.”

An electric arc is a short circuit through the air.

 An electric arc will oscillate and escalate if not constrained.
 A single conductor can engulf a second or third conductor in only two cycles.
 An electric arc’s current propels the arc away from the power source.

 Dust, impurities, corrosion, loose connections, condensation, animals
 Spark discharge from:
– Touching
– Dropping tools or materials
– Opening and closing panels, breakers and disconnects
 Over-voltages across narrow gaps
 Failure of insulating materials
 Equipment failure

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.

1.
Arc Blast is when the flash causes an explosive expansion of air and metal.
– For example: When copper vaporizes it expands by a factor of 67,000.
2.
The blast produces dangerous:
– Pressure waves
– Sound waves
– Molten steel and shrapnel.

Electric arc Arc flash Arc blast

 Electric shock
 Severe burns
Arc flash up to 35,000°F
 Blindness
Sun 9,900°F

 Blast injuries
– Shrapnel wounds
– Lung blast injuries
– Ruptured eardrums
– Pressure wave injuries
Material and molten metal can hit the body at over
700 miles per hour.
Arc blast at 2 feet
Jet engine at 200 feet
Pain threshold
145 decibels
132 decibels
130 decibels

1.
Power – amount of energy at the arc
2.
Distance – of the worker to the arc
3.
Time – duration of the arc exposure

US National Fire Protection
Association
NFPA 70E
-Standard for Electrical
Safety in the Workplace
Occupational Health & Safety Act
-Applicable regulations
Institute of Electrical &
Electronics Engineers
-Standard 1584
Offers a method for performing arc flash hazard calculations.
US Occupational Safety &
Health Administration

NFPA 70E addresses:
Article 130.3(2)(B)(1)
 Employers must conduct an arc flash hazard analysis and place a label on an external surface of equipment that indicates the degree of existing thermal hazard. The
NEC requires a label that warns employees of a potential thermal hazard .

 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.

Hazard/Risk
Category
0
1
2
3
4
Clothing Description
Non-melting, flammable material with fabric weight of at least 4.5 oz/yd 2
Arc-rated FR shirt + FR pants or FR coveralls
Arc-rated FR shirt + FR pants or FR coveralls
Arc-rated FR shirt + FR pants or FR coveralls,
and Arc-rated flash suit, the layered system must meet the required minimum rating.
Arc-rated FR shirt + FR pants or FR coveralls,
and Arc-rated flash suit, the layered system must meet the required minimum rating.
Required Minimum
Clothing Arc Rating
Not applicable
4 calories/cm²
8 calories/cm²
25 calories/cm²
40 calories/cm²

 Synthetic clothing that melts shall not be worn, such as:
– Acetate
– Nylon
– Polyester
– Polypropylene
– Spandex.

1.
Have a Electrical Safety in your Occupational
Health and Safety Management Program.
2.
Have a Arc Flash Analysis performed every three years and update when changes are made in the electrical system.
3.
Conduct regular equipment maintenance with annual IR Scan.
4.
Conduct periodic safety audits.
5.
Provide a safe working environment for your employees.

It is ALWAYS preferable to work on de-energized equipment.
1601 Cross Beam Drive
Charlotte NC 28217