To prevent an arc flash from occurring, the electrical systems of every workplace facility need to be thoroughly evaluated. This process is known as the arc flash study.
Arc flashes permanently injure and even kill many workers around the world every year. These fiery explosions can also cause financial chaos in the form of lawsuits, fines, and severe damage to costly equipment.
How are these studies conducted? Who can perform them? If you’re looking for answers to these questions, you’re in the right place.
- 1 What’s an Arc Flash?
- 2 What Happens During an Arc Flash?
- 3 Which Factors Determine the Severity of an Arc Flash?
- 4 What Is An Arc Flash Study?
- 5 Who Can Perform an Arc Flash Study?
- 6 Putting Results into Action
- 7 Conclusion
What’s an Arc Flash?
To put it simply, this would be an explosive burst of light and heat. It is caused by an uncontrolled current passing through the air between two conductors, thus forming an “arc”.
In just a fraction of a second, the temperature can go as high as 35,000°F. A heat burst of this magnitude vaporizes metal and causes deadly burns.
The blast wave caused by an arc flash can collapse lungs and rupture eardrums. Additional injuries can be caused by intense UV rays, toxic gasses, and shrapnel.
Arc flash can cause a slow, painful death, but also kill in an instant. Even if you don’t die immediately, your injuries may require years of therapy and medical care.
What Happens During an Arc Flash?
This complex phenomenon can take place in cases of close proximity between an exposed current source and a conductive object. Some of the opportunities for the arc flash to take place include removing or inserting components from an energized system, opening panels on decayed equipment, and even dropping tools. (This is why lockout tagout is important)
An arc can continue to ionize the surrounding air if it has enough energy. This process allows the arc to draw even more current, and the buildup of energy leads to an arc flash.
When it comes to injuries, the primary source is the sudden burst of heat. In a short amount of time, a tremendous amount of heat energy is released. By drastically raising the temperature of the surrounding air, an arc flash vaporizes and melts everything in the vicinity. Moreover, melted materials can quickly form clouds of toxic dust, mist, and vapor.
It’s pretty safe to say that the arc flash is among the more dramatic electrical accidents. Without proper safety precautions, it can be lethal.
Which Factors Determine the Severity of an Arc Flash?
Proximity to the Arc Flash
The closer an employee is to the equipment, the greater the risk of an arc flash accident. For that matter, employees should always stand as far away from the equipment as they can.
The quantity of electricity consumed by the arc is what determines its temperature. This quantity is usually measured in megawatts, which means that this phenomenon conveys a high volume of energy.
The Presence of Protective Devices
Overcurrent protective devices can minimize the duration of the arc flash. They, however, need to be well-maintained to function properly. If such a device malfunctions, extinguishing the fault will take more time, increasing the chance of an injury.
The Type of Clothes Worn
A factor that determines the quantity of transferred heat is the type of clothes an employee is wearing. Each layer of clothes worn under the protective equipment reduces the amount of received heat by approximately 50%.
What Is An Arc Flash Study?
As mentioned in the intro, an arc flash study is the on-site evaluation of a workplace facility, whose goal is to determine potential hazards related to the arc flash. These studies are crucial to minimizing hazards.
By conducting an arc flash study, it is possible to identify the facility’s electrical risk levels. This allows the owner of the facility to apply the needed safety practices. In that way, the risk of injuries to vendors, contractors, and employees is minimized.
The arc flash study is required for all commercial, industrial, and manufacturing facilities. It must be performed in all facilities with meter socket enclosures, industrial control panels, switchboards, panel-boards, electrical transformers, motor control centers, electrical disconnects, etc. This analysis is required by NESC, IEEE1584, NFPA, and OSHA.
The NEC standards which apply for arc flash are:
- Article 110.16(B)
- Article 110.16(A)
The NFPA 70E codes which apply for arc flash are:
- Article 130.7
- Article 130.5
The OSHA standards which apply for arc flash are:
- OSHA 29 CFR 1910.335(a)(1)(iv)
- OSHA 29 CFR 1910.335(a)(1)(i)
- OSHA 29 CFR 1910.333(b)(2)(iv)(B)
- OSHA 29 CFR 1910.332(b)(1)
- OSHA 29 CFR 1910.132(d)(1)
Failure to comply with these standards can result in severe injuries, loss of life, fines, litigation, company downtime, lost production, and large medical claims.
Who Can Perform an Arc Flash Study?
This type of assessment should be conducted by qualified electrical personnel, such as professional electrical engineers. These individuals need to be registered in the same state where the facility in question is located. They also need to be experienced in conducting an electrical system assessment.
Before the actual analysis, qualified personnel has to collect all information on the facility’s power distribution system.
They need to obtain an up-to-date diagram of the facility’s power distribution system, as well as the cross-section of all cables with their lengths. The entire study depends on the data collected, which is why it needs to be accurate and collected from all equipment in need of evaluation.
Once all necessary data is collected, the arc flash study commences. It may take four to six weeks for this analysis to be completed, depending on the facility’s size. Fortunately, there’s one thing that makes the job easier – specialized, commercially available software. With it, analyzing the study data and performing calculations is faster and easier.
The actual arc flash study is typically broken down into several steps. The engineers have to assess a number of things, such as incident energy calculations or short circuit study. Each significant point in the system needs to be thoroughly evaluated.
Putting Results into Action
The professional electrical engineers who have conducted the study will provide a summary of their findings, along with their recommendations for the needed corrective actions.
The most important result of this evaluation is the identification of the arc flash protective boundary (AFPB). The AFPB determines the closest approach allowed before an employee needs to wear personal protective equipment (PPE).
Inside AFPB, an employee has to wear adequate PPE. The hazard category of the required PPE is also determined by the qualified personnel who have conducted the arc flash study.
The owner of the facility needs to incorporate the study results into practice. Employees need to be trained and wear proper PPE. All potentially dangerous equipment needs to be properly labeled. Furthermore, all documentation needs to be updated for future reference.
Although it’s been around for quite a while, arc flash was only recently addressed in national standards. It’s a complex, extremely dangerous phenomenon, capable of causing serious injuries and even death.
For that matter, an arc flash study needs to be performed every five years, or after every major alteration of the facility’s power distribution system. Once it identifies arc flash hazards and estimates the potential severity of injuries, this analysis will determine which protective measures are required.