Arc Flash Safety

NFPA 70E Electrical Safety – Arc Flash Safety for Employees

• An arc occurs when electric current flows between two or more separated energized conducting surfaces
• Insulation failure is a common cause of arcs
• Temperatures at the arc terminals can reach or exceed 35,000
• Arc flash is heat energy and intense light at the point of the arc
• Arc blast is air surrounding the arc instantly heated and conductors vaporized causing a pressure wave
• Anything that produces an electrical current has the potential to produce an arc
• Anything that produces electrical current has the potential to produce an arc.
• Exposure to an arc flash frequently results in serious injury and sometimes death.
• Arc blast can cause equipment to explode with life threatening force.
• Flashes and blasts can be life threatening and require special training.

Arc-flash injuries occur in 77% of recorded electrical injuries!

What About Arc-Flash Study – What does it Do? It provides the following:

• An up-to-date facility one-line diagram: To accurately document the facility power system
• An up-to-date short-circuit study: To determine fault current levels at each node
• An up-to-date coordination study: To ensure that only the closest protective device
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From the above data, flash energy is determined so PPE and flash boundaries can be selected. The organization needs to develop boundaries for all electric equipment. Boundaries are:

• up to 750 volts – 3’ boundary
• 750 volts to 2,000 volts – 4’ boundary
• 2,000 to 15,000 volts – 16’ boundary
• 15,000 to 36,000 volts – 19’ boundary
• Over 36,000 volts – must be independently calculated

Workers entering a flash protection boundary must be qualified and wearing appropriate PPE. Boundaries must be calculated by determining the incident energy. There is software available for developing arc flash assessments. PPE, as it applies to arc flash and boundary assessments, should include:

• Hard hat
• Face shield
• Flame-resistant neck protection
• Ear protection
• Nomex suit
• Insulated rubber gloves with leather protectors
• Insulated leather footwear

It is important to establish the boundaries in order to select the appropriate PPE in the event of a flash. If a person is closer than 18”, the higher the incident energy and blast hazard will be.

Arc Flash Hazards:

• panelboards and switchboards
• motor control centers
• metal clad switchgear
• transformers
• motor starters
• high voltage switching and grounding
• pad mount switching
• meter bases and banks

The best way to prevent an arch flash is to de-energize electrical circuits when equipment is being prepared for maintenance. NFPA 70E requirements apply to new and old equipment and include coordination and short circuit studies and arc flash analysis must be developed. Make sure your operation meets NFPA 70E and OSHA requirement