What is Arc Flash?
About Arc Flash
What is Arc Flash?
Arc Flash is a short circuit that passes through air between two live conductors, or between a live conductor and ground (lightning are natural arcs). The massive energy discharge causes an immediate flash- a blast with very high air pressure capable of devastating everything in its path and creating deadly shrapnel as it dissipates. In addition to the explosive blast of such a fault, destruction also arises from the intense radiant heat produced by the arc, which can melt metal, cause severe burns and result in death.
The Causes
Causes of an arc flash incident can vary and may include:
- Accidental contact with energized components by a human, animal, tool, etc.
- Dropping a tool or otherwise creating a spark can ignite an arc flash.
- Overload of current in a given circuit.
- Equipment failure due to use of substandard parts, poor maintenance, improper installation, or even normal wear and tear.
- Breaks or gaps in insulation.
- Dust, corrosion or other impurities on the surface of the conductor.
The Dangers
- An arc flash can cause anything from minor injuries to third degree burns, blindness, hearing loss, nerve damage, cardiac arrest, and death.
- Fatal burns can occur when the victim is several feet from the arc. Serious burns are common at a distance of 10 feet. Staged tests have shown temperatures greater than 437°F (225°C) on the neck and hands of a person standing close to an arc blast.
- Arcs spray droplets of molten metal at a high speed. Molten metal from an arc can be propelled for distances up to 10 feet and blast shrapnel can penetrate the body.
- Blast pressure waves have thrown workers across rooms and knocked them off ladders. Pressure on the chest can be higher than 2000 lbs/sq. ft.
- Clothing can be ignited several feet away. Clothed areas can be burned more severely than exposed skin.
These dangers and the escalation of associated injuries have highlighted the issue of Arc Flash and caused OSHA to take considerable notice.
