Employees who work with electricity and/or energised equipment are au fait with the risks of an arc flash. Many of the same people, however, know little about what an arc flash is or how its risks can be mitigated. One way to mitigate the risk of occupational injury is to ensure the employees have a good understanding of the dangers of their job, and that they are wearing PPE suitable to the hazards they face. The term ‘personal protective equipment’ covers a very wide range of items, including garments specifically designed for protection against the hazards of an arc flash. As arc wear specialists, CHARNAUD® supplies the SURVIVE-ARC® range and various components to multiple industries where the threat of arc flash is real and ever-present.
What Is An Arc Flash?
An arc flash happens when an electric current leaves its path, likely due to a fault, and makes contact with external conductors. In this case, normally non-conductive gases like air now become conductive, and the electrical breakdown of the gas produces a continuous discharge of plasma. It is the plasma which is highly dangerous and can reach temperatures of up to 5537,778° C/ 10,000° F.
The arc flash is not only a threat to those in close proximity – it can also fatally burn people who are as much as 3 metres/ 10 feet away. A large proportion of arc flashes happen at 277 volts, which is much more than any human can withstand. For illustrative purposes, a human can die from exposure to 47 volts for as little as 2 seconds. In an arc flash, the exposure to high volts, extremely hot plasma discharge, exposure to intense radiant heat as well as resultant bodily burns is what kills people. The term ‘arc flash’ covers a range of different kinds of arc flash; all of which have the same aggravating factors and the same result.
What is an Arc Blast?
In an arc blast, air heats up very quickly which in turn causes a wave of pressure, or a supersonic shockwave due to the arc vaporising the metal conductors. The intense pressure wave then forces the outer shell of metal to vaporise, which blasts vaporised metal and dangerous plasma outwards. The plasma causes an explosion and burns any people and materials in its wake. An arc blast happens because of a current fault, however data from recent studies indicates that arc containment plays a critical role in terms of injuries.
Hazards Associated with Different Types of Arc Flashes
Open-Air Arc: This kind of arc flash is the most commonly known and is often used in testing, as is Arc-in-a-box. An Open-Air arc produces infrared radiation and hot gases. At higher than 480 volts, an open-air arc can become an ejected arc or a tracking arc.
Ejected Arc: An Ejected Arc is when dangerous plasma is ejected and makes contact with the person or worker.
Arc-in-a-Box: This is an ‘equipment focused’ arc flash, which is arguably more hazardous than an open-air arc because the energy released can potentially be two to twelve times greater. In this scenario, the energy is forced towards the direction of the opening which is where the worker is situated.
‘Tracking’ Arc: This normally occurs at a higher voltage or during electrical contact. A ‘tracking’ arc conducts through skin or clothing, potentially causing unrated clothing fibres to ignite.
Stay as Safe as Possible with CHARNAUD®
While it may be possible to prevent injury or death from an arc flash, it’s almost impossible to predict when it may occur and that is why wearing the correct PPE is crucial. All arc-rated clothing should be backed by safety certification in accordance with national and/or regional safety requirements for its industry.
Get in touch with CHARNAUD® to find out more about their arc-rated personal protective equipment and clothing.