Arc flashes are a common hazard for electrical workers. Every day in the United States, hundreds of arc flash incidents occur, with an annual average of four hundred fatalities. With this in mind, it’s critical to know what an arc flash is and how you can avoid one. Much of this comes down to a lack of awareness concerning arc flashes, what they entail, and how they can be prevented.
What is an arc flash (easy explanation)?
An arc flash is a light and heat emission associated with an electrical fault. An arc fault occurs when an electrical discharge or explosion develops from a low-impedance connection between two voltage phases or phase to ground, in an electrical system.
A popular example is when an incandescent light bulb burns out while it’s still switched on. The filament within the bulb fractures, yet an arc is maintained across it. When a light bulb burns out, it creates a blue flash and often produces a popping noise. If you inspect an extinguished lightbulb, you’ll notice black flecks on the interior of the bulb.
In theory, industrial or building site arc flashes are similar. However, instead of a pop, a brief blue halo, and a burned-out bulb, they have far more damaging effects and can be upwards of 10 feet in diameter with over 30,000 degrees Fahrenheit.
What are the risks of an arc flash?
There are many hazards that come with an arc flash, and all of them might result in temporary or permanent injuries to those exposed.
Temperature
Temperatures in an arc flash can reach thirty-five thousand degrees Fahrenheit, which is among the highest known to man. The sun’s surface, by comparison, has a temperature of roughly nine thousand degrees Fahrenheit. This is hot enough to melt anything within meters of the flash. These temperatures can result in severe burns, even if the employee is more than ten feet from the arc burst.
Concussion
Workers may be thrown across rooms and off of ladders by the arc flash’s concussion. Arc blast waves have been observed creating more than two thousand pounds per square foot of pressure. It is enough to bruise or disrupt body functions and bodily tissues, including lung and nerve damage, as well as potential heartbeat disruption.
Shrapnel
The shock wave produced by an arc flash can propel shrapnel at high velocities. Tools and components might be included, as well as metal that has been melted by the intense heat and launched ten feet or more from the arc flash. These droplets adhere to clothing or skin, resulting in deep and severe arc burns.
Sound
The sound of an explosion might be loud enough to burst eardrums, resulting in short- or long-term hearing damage.
Vision damage
The inflammation of the cornea’s epithelial layer – known as photokeratitis – is a condition that causes temporary or long-term vision issues. The term “arc eye” is used to refer to this condition, which occurs when the flash of the arc is viewed without adequate eye protection. It has different names, such as baked eyes, welder’s flash, or snow blindness.
Arc flash causes
An arc flash can occur as a result of various problems, including equipment failure (lack of maintenance) and employee mistakes. The following are some potential reasons:
- Incorrect use of testing equipment
- Equipment that has not been well maintained
- Gaps or wear and tear in the insulation
- Connections that are not firmly attached
- Accidental touch (shock)
- Small animals and insects crawling through holes into switchgear
- Accumulation of dust or moisture in the airtight busbars causing them to weaken
- A load break switch that does not operate properly (lack of maintenance/Test)
- Dropping non-insulated tools on live electrical components
- Corrosion and exposed live parts
How to prevent arc flash incidents
De-energizing the equipment is the most successful and trouble-free technique to minimize arc flash danger. This is not only a good idea, it’s also required by both OSHA and NFPA 70E unless the worker and employer can justify energized work within the guidelines outlined in the regulation and in the standard. Even when discharging equipment / shutting off, it can produce an arc explosion, and it’s not always feasible to shut down the equipment to service it. The most secure and surest method to avoid an arc flash is to de-energize, from an upstream source. The Qualified work shall evaluate the system and job planning implemented to solve these electrical safety issues.
Furthermore, there are various methods for reducing the risk of an arc flash:
- Redesigning electrical systems and controls
- Understanding the way your facility’s power distribution system works and what low risk technology is needed to reduce the risk of arc flash
- Conducting safety training and risk awareness sessions for your staff and personnel to ensure that they are aware of the hazards and consequences of disregarding safety procedures
- Through incident energy studies, determining the risks, boundaries, and appropriate PPE for electrical safety.
- Ensure that only a qualified person performs the work on the specific task
Establishing boundaries
Arc flash boundaries are one of the most effective strategies to prevent and treat arc flash injuries. They are the minimum safe distances from energized conductors or circuit components with the potential for an arc fault.
- Arc flash boundary (Arc)
According to the NFPA 70E standards, which are based on years of study, the arc flash boundary should be the furthest. If an arc flash occurs, the employee would be exposed to a maximum of 1.2 calories per centimeters squared of flash energy. The correct amount should result in no more than a curable second-degree burn to exposed skin. - Limited approach boundary (Shock)
The distance from a live part that has a shock hazard is known as the limited approach boundary. Workers should have the appropriate personal protective equipment to stay between the arc flash boundary and the limited approach boundary. A person who is not trained or qualified should not approach the possible arc flash source closer than the limited approach distance. - Restricted boundary (Shock)
The restricted area and the restricted boundary are the immediate surroundings of the exposed electrical components. The boundary should only be crossed by trained, qualified personnel who have received the necessary training and are wearing the proper PPE. For this type of work, they also need a plan and a special work permit.
By recognizing these boundaries and instructing staff who work within or around them, you can educate everyone about where they should and shouldn’t go. Establishing and enforcing these limits can keep employees safe.
Electrical safety training with Bowtie
We not only understand the dangers but also have Engineers who solve these issues for customers all over the USA and Canada at Bowtie Engineering, and this is why we offer training for electrical safety in the workplace. Contact us to learn more about the on-site training and book a call with our instructor, John Welch.