What Is Arc Flash?

Note: This article originally appeared on Safety.BLR.com here.

When you’re dealing with electrical hazards, there isn’t a lot of room for error. Your workers’ lives are on the line every time they head out to the jobsite. They need to be properly prepared and understand arc flash requirements, and so do you.

In a BLR webinar titled “Arc Flash Hazards and 70E: How to Protect Your Employees and Stay in Compliance,” John R. Skal outlined some basics to understand arc flash requirements.

What is Arc Flash?

Arc flash happens when an electrical arcing fault occurs. The current flows through ionized air, causing energy to be dissipated on the surrounding environment producing intense heat and light.

Arc blast comes from the air surrounding the arc that is instantly heated causing the conductors to vaporize and resulting in a pressure wave and accompanying loud sound.

Arc Flash and Blast: 5 Ws

To understand arc flash requirements, we need to look at the 5 Ws: who, what, when, where, and why.

Who is affected?

Many people could be affected by this hazard, including electricians, maintenance personnel, engineers, supervisory personnel, or others that are within the flash protection boundary. This is why understanding arc flash requirements is so critical.

Electrical equipment is also affected and serious damage can result to both people and equipment. These hazards can cause death, severe burns, hearing damage, sight damage, flying debris – causing secondary hazards, significant equipment damage, and loss of operations.

What is the cost to the business?

The average medical cost of arc flash survivor is $1.5M. Obviously this is not a small consideration. Lost work time is also a major factor, as this can total 6 to 8 months of lost work even for the fortunate victims who have relatively minor injury. Often, such a devastating injury ends a worker’s career. Skal noted during the webinar: “many times they don’t return to their previous career path. They’ll take a job as a clerk, or as a planner or something else. They’re not back on the floor with their tool belt.”

Finally, there is also the aspect of lawsuits that may follow such an accident. The average cost of litigation and settlement costs in an arc flash case is $5 to 10 million.

When do they occur?

Unfortunately, 5 to 10 arc flash explosions occur in electric equipment every day in the United States, and, Skal explaied that “this number does not reflect cases where there may be a near-miss or it’s not significant enough to be sent and held in a burn unit. That’s 5 to 10 times a day where someone is being sent to a burn unit. So each year, more than 2000 people are treated in those burn centers with pretty severe arc flash injuries.”

Where do they occur?

There are several primary locations where an arc flash or blast typically occurs:

• Main switchgear rooms
  
• Main electrical rooms
  
• Production floors
  
• Power panels
  
• Motor control centers

Anywhere you have three-phase power throughout your facility you will have the potential for an arc flash to occur.

Why do they occur?

Causes of arc flash incidents can be:

• Inadvertent contact
  
• Loose connections
  
• Insulation failure
  
• Poorly maintained equipment
  
• Voltage transients (short surges in voltage)
  
• Unsuccessful short circuit interruptions (breakers and fuses have an “interrupt rating,” which is the worst-case bolt and fault current that the device will still operate properly at; when this malfunctions, the fuse or breaker may explode instead of short-circuiting when too much current comes through)
  
• Animals such as squirrels, snakes, etc., will look for heat and get into equipment

The two largest drivers of arc flash are how much current is available and how quickly that current can be interrupted if a fault occurs.

For more information on arc flash requirements, order the webinar recording. To register for a future webinar, visit http://catalog.blr.com/audio.

John R. Skal is Project Manager of Falcon Engineering Consultants, and has more than 25 years’ engineering, operations and maintenance experience. Falcon Engineering Consultants are specialists in providing engineered Arc Flash Hazard Analysis (AFHA) solutions for NFPA-70E compliance.