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Arc flashes are hands down one of the most unique hazards that anyone in our industry has to deal with. They are sudden burst of immense energy that occur without warning, and the gear needed to protect workers from this terrifying threat seems like something you would need to diffuse a bomb. In a lot of ways that’s exactly what these technicians are doing, diffusing something that could explode and hurt a lot of people.
While arc flashes are a unique hazard, they have a commonality with most other jobsite concerns. The more workers know about it and the better they are trained to deal with it, the less extreme it becomes. By understanding arc flashes, we can help to lessen the risk of injuries from arc flash incidents.
Arc Flash Explained?
An arc flash occurs when an exposed live conductor connects with another nearby conductor (phase to phase) or to ground (phase to ground) by means of an electrical arc in the air. When you boil it down like that, it doesn't sound so bad, but we are talking about hundreds of volts of electricity, and if unprepared, the nearest conductor/ground is you.
Even if the flash does not attract directly to you, a flash event is often very violent and involves a loud and powerful explosion, likely destroying and exploding equipment.
Arc flash, often called a flashover, are terms used to describe the action of a conductor making an unexpected arc through the air. Arc blast is the term used to describe the explosion that the arc flash causes.
A small-scale example that we are all familiar with is what happens when an incandescent light bulb& burns out. The filament inside the bulb breaks, but an arc is sustained across the filament. This causes a bright blue flash, often accompanied by a popping sound. If you look at the bulb after it blows out, you are likely to see black speckling on the inside of the bulb.
Arc flash incidents on the industrial or construction site are similar in theory, but they are on a much larger scale. Instead of a pop, a short blue glow, and a discolored bulb, they have much more drastic consequences.
Arc Flash Hazards
Several dangers come from an arc flash incident, which can cause short-term or long-lasting injuries to workers affected by the incident.
Temperatures in an arc flash can reach as high as 35,000 degrees Fahrenheit. These are temperatures that can cause severe burns, even if the worker is ten or more feet away from the flash itself. By comparison, the sun's surface only measures up to 9,000 degrees Fahrenheit. This is hot enough to vaporize nearby objects, humans included.
The concussion wave from the arc flash incident can expand quickly, throw workers across rooms, and knock them off ladders. Pressure from arc flash waves has been seen to produce more than 2,000 pounds per square foot of force, enough to bruise or cause disruption to body systems and damage tissue. This includes lung damage, nerve damage, and potential heartbeat disruption.
The explosion caused by an arc flash can propel shrapnel at high speeds. This can include tools and parts, but it can also include metal that has been melted by the high temperatures, with metal droplets being propelled at high speeds from the flash itself. These droplets adhere to clothing or skin and cause deep, severe burns.
A sound blast from the incident can be loud enough to cause eardrums to rupture, creating short- or long-term hearing problems.
Photokeratitis – an eye condition similar to sunburn but of the cornea – can cause temporary or long-term vision problems. Referred to as arc eye, but also sometimes called welder's flash, bake eyes, or snow blindness, this comes from seeing the flash of the arc without the proper eye covering.
What causes Arc Flashes?
Arc flash can be caused by various issues, ranging from faulty equipment to worker errors. Potential causes include:
Improper use of test equipment
Poorly maintained equipment
Insulation failure, including gaps or wear and tear
Pests such as small animals and insects entering switchgear through openings
Accumulation of dust or moisture that can weaken air-insulated bus bars
Faulty operation of a load break switch
Workers mistakenly drop tools on live electrical parts
Obstructions in disconnect panels
Exposed live parts, loose connection, and corrosion
The Best Ways To Avoid And Eliminate Arc Flash Incidents
The most effective and foolproof way to eliminate the arc flash risk is to de-energize the equipment. De-energizing is ideal, but it is not always possible to have the equipment powered down for service. Alternative ways to minimize the risk of arc flash include:
Redesigning electrical systems. If your system needs to be live for maintenance, redesign it so that the system can remain live, but individual elements can be shut off for maintenance.
Collect data about your facility’s power distribution system. This data can be used to help identify where you can use low-risk technology to reduce the chance of arc flash occurring.
Improve safety training and risk awareness. Better trained employees and personnel understand the dangers and consequences of ignoring safety procedures.
Provide suitable PPE for electrical safety. Lack of PPE or even PPE that is under-rated, or the wrong rating system will not be effective and, in some cases, can cause more harm to a worker exposed to arc flash.
Although arc flashes are, by nature, unpredictable, conducting a comprehensive risk assessment and understanding the systems that require maintenance can help you calculate the chances of an arc flash occurring.
This all sounds like fundamental, common-sense practices, and for the most part, they are. It's essential to apply thoughtful techniques when working around electrical systems. It's easy to cut corners to get the job done faster, but those corners will cost you when an entire electrical system explodes right in front of you. It's better to take the time and follow the correct safety procedures.
Arc Flash Hazard Analysis
When working on energized equipment in the U.S., you must comply with regulations set by OSHA (Occupational Safety and Health Administration) and NFPA (The National Fire Protection Association). Specifically, OSHA CFR 1910 Subpart S and NFPA 70E.
Together, both organizations outline every precaution that needs to be taken. This includes employer responsibilities, such as providing PPE and training, producing a safety procedure, posting necessary warning signage, producing circuit diagrams and specifications on equipment, etc.
One of the most significant employer responsibilities is regularly conducting a Flash Hazard Analysis. It's a comprehensive assessment conducted by an engineer to determine the risk of an arc flash.
Sometimes referred to as Arc Flash Risk Assessment, Arc Flash Hazard Study, or several other names. These are all the same thing.
All equipment at risk of creating an arc flash must have a warning label stating safety information specific to that piece of equipment. A Flash Hazard Analysis will help determine those specifics. This assessment is vital because it will dictate and inform many of the employer's safety responsibilities. The Flash Hazard Analysis will also advise what PPE is required and some procedures that will be needed to remain compliant.
A Flash Hazard Analysis will help you create and implement arc flash boundaries. These boundaries are the minimum safe distances from energized conductors or circuit parts that potentially have an arc fault. Developed by the NFPA, these are founded on research over the years.
The boundary terms you will hear are arc flash boundary, limited approach boundary, restricted boundary, and prohibited boundary.
Arc flash boundary is the furthest zone. If an arc flash occurs, workers beyond the arc flash boundary would be exposed to less than 1.2 calories per centimeters squared (cal/cm2) flash energy. 1.2 cal/cm2 is the minimum amount of hazard exposure before resulting in a second-degree burn. This is the closest any individual who is not trained or prepared to handle electrical hazards should be. Any closer would be unsafe.
The limited approach boundary is the distance from live equipment where a shock hazard exists. Standing in the limited approach boundary without the appropriate PPE can result in second-degree burns or worse if an arc flash occurs.
Restricted space and the restricted boundary is the area directly around the exposed electrical components. The boundary should only be entered by trained, qualified workers who have undergone the required training and who are equipped with the appropriate PPE. The worker should have a written plan and a work permit for the job.
The prohibited boundary is where workers come in contact with hazardous equipment. Coming in contact and working on equipment that is live or will be live should only be conducted by a qualified technician. Again, the worker must wear the PPE protection level determined by the Arc Flash Hazard Analysis.
By understanding these boundaries and explaining them to workers who may work with or be around them, you can educate everyone on where they should or should not walk. Creating these boundaries and enforcing them can keep workers safe.
Arc Flash Protection
Throughout this article, we keep saying things like "appropriate PPE level". The protective gear used for arc flash is unlike the gear you use for anything else. Due to the extreme severity of an arc flash, the gear needs to be able to withstand extreme heat while remaining non-conductive. Regular FR-rated clothing is insufficient to protect a worker from an arc flash. Read more about the different FR clothing options
Your arc flash gear needs to be all-encompassing. You will be covered from head to toe with no exposed skin. The smallest sliver of exposed skin renders all the PPE useless. This is because we work with electrical hazards, and electricity always finds the path of least resistance to ground. If you are standing near the equipment, your body is now the least resistant path, and an arc of electricity can connect with a millimeter of exposed skin between your glove and your sleeve.
It is also important to understand that not all arc-rated gear is the same. Arc-rated gear is classified into four categories, each with a maximum calorie per centimeter squared exposure limit.
Category 1 – Min rating 4 cal/cm2
Category 2 – Min rating 8 cal/cm2
Category 3 – Min rating 25 cal/cm2
Category 4 – Min rating 40 cal/cm2
Each category has specific requirements of what garments need to be included before the entire system can qualify for that category. Read our guide about FR Clothing.
So, if you are working on a machine with a category three arc flash risk, you can't just put on a 25 cal/cm2 pair of gloves and then get in there. You need the full suit; the headgear, the footwear, and everything in-between. This is why arc-rated kits are very popular.
Arc-rated gear is known to be large and cumbersome, but one added benefit is over time, as technology progresses, this gear is becoming lighter and easier to wear. This makes it easier for workers to opt for higher categories even when regulation doesn't require it.
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Here at PowerPak, we understand the potential issues that can happen with arc flash, which is why we carry a variety of highly rated visors, kits, and more. We carry various arc flash kits and protection to fit your PPE needs! From the basic arc-rated goggles and arc flash balaclava to the full Arc Flash Suit Kit.