How Do Arc Flash Incidents Cause Damage?
By: Rich Gojdics
Despite only gaining mainstream acceptance by safety professionals and electrical contractors in the 90s, the dangers of arc flash explosions are well known. Producing some of the highest temperatures on earth (up to 35,000 degrees Fahrenheit—four times the temperature of the sun’s surface), creating a pressure wave that can throw a worker across a room, and emitting vaporized metal, these events are common in the electrical field and pose an enormous threat for electrical workers.
Arc flash incidents are unique in the electrical field as they expose workers to a completely different form of risk. However, with the dangers they pose and the commonality of such incidents, it’s important to understand what happens during an arc flash incident.
Background: Arc Flash Research
The concept of arc flash events has been around for centuries, dating back to Benjamin Franklin, who explained the practice of using lightning rods to protect buildings and vessels during storms in a series of letters throughout the 1700s.
However, this was long before the application and proliferation of electricity, and arc flash research went largely ignored for centuries, as more focus was placed on electrocution hazards until Ralph Lee published The Other Electrical Hazard: Electric Arc Blast Burns in IEEE Transactions on Industry Applications. The research was thorough and informative, exploring this deadly phenomenon, introducing calculations and equations regarding heat energy exposure, and outlining precautions and protective measures to minimize risk.
Even after this research was published, the progress made to address arc flash hazards was slow until regulators and industry organizations began to recognize the risks in the 90s and the 2000 NFPA 70E standard and IEEE 1584-2002 introduced guidelines regarding arc flash hazards. OSHA adopted definitions and PPE requirements in 2007, creating a requirement for companies to develop safety programs around arc flash safety. We will discuss the regulatory concepts in an upcoming blog, but today would like to shift our focus to answer the question, what happens in an arc flash incident?
What Happens During an Arc Flash?
As mentioned above, explosions as a result of arc flash are immensely dangerous—and extremely common. With 5-10 of these incidents taking place each day in the United States, arc flash incidents result in 7,000 burn injuries per year. Following these events, many employees fail to return to their former quality of life and often require extensive medical care exceeding $1,000,000 in cost.
In our last blog, we explored some of the common reasons that an arc flash could occur. Whether through improper care or environmental conditions, an arc flash happens when electric current flows through an air gap between ungrounded conductors as a result of a short circuit.
In turn, an arc flash can result in an arc blast, an explosion that results when metal is vaporized and expands. As the video below demonstrates, arc flash incidents occur in an instant, and cause irreparable damage to everything in the blast radius.
Temperatures Rise—Up to 35,000 Degrees Fahrenheit
The most common thing that happens during an arc flash is the extreme temperatures near the arc. In this, the arc causes surrounding air to be ionized and temperatures can reach as high as 35,000 degrees Fahrenheit—four times hotter than the surface of the sun.
These temperatures result in first-, second-, or third-degree burns while igniting or melting clothing. Depending on the magnitude of the arc flash, this does not apply only to the nearby individual—serious burns can occur ten or more feet away from an arc flash. In turn, this heat causes metal to liquify or vaporize.
High Temperatures Vaporize Metal Near the Epicenter
At 35,000 degrees F, the temperature of an arc flash greatly exceeds the melting and boiling points of every known element. When this happens, the copper, aluminum, and steel used in electrical equipment melt or are vaporized. The state change from solid to gas results in immediate and explosive expansion—vaporized copper expands 67,000 times in volume.
Workers near the arc flash are exposed not only to the high temperatures, they face additional damage when hit with metal droplets or vapor which burn clothing and can become lodged in skin.
When the metal expands, it creates large levels of outward pressure. This results in a pressure wave that can cause further damage. Ruptured panels send shrapnel flying, the pressure from the blast can knock workers off ladders or throw them across a room, and the sound from the blast can reach 170 decibels, causing acoustic injuries.
According to the arc blast pressure calculator, a 50kA arc would provide enough pressure to propel a person standing 2 feet away from the arc source and weighing 170lbs with acceleration of approximately 330 feet per second square.
Protecting Your Workers: Arc-Rated Clothing
While de-energization is always the most effective way to reduce risk when working on equipment, there are times when it is impossible or implausible to take these measures. Personal Protective Equipment (PPE) is a required component of an electrical safety program and serves as the last line of defense in protecting workers from danger when working on live equipment. In fact, even the process of voltage testing to ensure the equipment is de-energized requires the use of PPE.
Enespro PPE specializes in the design and manufacture of USA-made electrical personal protective equipment featuring advancements in performance, comfort, and functionality. Enespro PPE conducted extensive research with electricians, and electrical safety professionals to gain critical insights required to achieve breakthrough improvements in electrical safety PPE.
From our 8 CAL to our 40 CAL, we provide a complete line of PPE for working on a wide range of jobs. Watch our video below to learn more about our Enespro PPE 40 Cal AirLite Suit, browse our products here, and place your order online or by calling our dedicated line at 866-680-4950.
Additional Arc Flash Resources:
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