Mechanics of Arc Flash

Mechanics of Arc Flash

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Join HSI Chief Safety Officer Jill James as she visits environmental health and safety professionals in their workplaces to explore important workplace safety topics. This video explains the mechanics of what causes an arc flash and how to reduce the likelihood of an arc flash occurring.

Video Transcript:

Hi. I'm Jill, Chief Safety Officer with HSI. I'm a former OSHA inspector, and I'm here to help you identify and correct workplace safety hazards. For this series, we're at Southern Minnesota Beet Sugar Cooperative in the heart of the upper Midwest to show you, no matter where you work, safety training is for everyone.

Many of us have heard the term arc flash, yet how many of us understand the mechanics of what really causes an arc flash, and how can we avoid the probability of it happening? To unwind the mystery of arc flash, I'm joined today by Phil, Vice President of Operations for EPSCO. EPSCO is a electrical engineering company that specializes in safety.

Phil, can you explain, kind of set the stage for us, what is an arc flash?

Thanks, Jill. An arc flash is a release of energy. It's almost like an electrical explosion. It starts inside of electrical gear. A lot of times, when it happens, it'll blow the covers off, huge noise, a lot of sound, and a lot of times very destructive to the environment or to the people that's working in the area.

Yeah. What sort of devices can an arc flash happen in?

Arc flash happens in electrical panels. It can be inside a switchgear, like what we're next to right here, an MCC. They can happen in those type of situations, or in a common, just an electrical panel situation as well.

What causes it to happen? What are the mechanics of getting something to arc inside of one?

A lot of times, the most common actually, the most common cause of an arc flash incident is a careless removal of a cover. Actually, these devices are all covered. Inside of there is high voltage equipment. When somebody takes that cover off, if they're not doing it properly, they can drop a screw, or the cover can be a little bit tweaked and can end up contacting the high voltage that's inside of there. When that happens, it instigates that arc flash event. It all happens in a blink of an eye.

Can it happen with dust and materials inside of a panel as well?

Yup, absolutely. Poor maintenance will also contribute to that problem. Manufacturing plants have a lot of airborne debris that finds its way into electrical gear. When it builds up, it creates a pathway for that arcing to happen. Once it happens, it just keeps happening until something blows itself apart so it stops.

You could change the environment by maybe removing a panel, and you've got some of that atmosphere in there, is that when it can happen too or no?

More so when the debris is built up.



It creates the right atmosphere, like the fire tetrahedron or something.


Yeah, okay.



Another cause of it happening is actually using the device itself. As the equipment ages, and if it's not maintained properly, you can end up having that problem occurring actually just from physically switching it on or off. You're actually changing the state of the electrical device itself.

So it can happen with a knife switch. It can happen in a breaker panel.


It can happen on a control on an actual piece of equipment?



We do a lot of training. I had a customer, during a training class, tell me a story, a situation that happened to him. A lot of times it's really interesting to have people actually tell the story, because they don't necessarily want to admit it happened to them.

Right, because it's really scary.

It is, and there's a stigma that goes with it.


We want to break that stigma. We don't want people to be nervous about talking about it. It's a real problem. In that person's situation, it was like here, a different type of configuration, with an MCC, but he had done some troubleshooting on a circuit, and he had replaced some parts inside of one of these type of devices. When he got all the parts back together, he closed the door and restarted it without actually bolting the cover shut. The situation that happened, there was a fault out in the field, so when he turned it back on, the whole device blew up.


The door of the panel came and hit him upside of the head. He said he couldn't hear anything for many, many hours after it happened. The fireball came out. It was probably eight feet of fireball that actually came out of the equipment. It was really a serious situation.

Wow. The fault in that one happened way downline.


Or upline.

Yeah, well actually yeah, downstream of the actual device, yeah.

Downstream. Right. He wouldn't have known that, and so needed to know the right precautions, including bolting it shut nice and tight, so if it was going to happen, it'd be contained in that unit?


That would've prevented that kind of-

It could've. Absolutely.

It could've, or at least not made it as dramatic as what he experienced.

He actually violated one of the rules of electrical. We need to have all the covers in place, and fastened in place when you're actually using-

And all the screws, not three of them or two of them.

Right, absolutely.


Yeah, there was another situation where a lineman that I know was putting a new service into a manufacturing plant. They got all the service in, and when the electrician turned on the main disconnect for this new panel, the whole works blew up.


The electrician, there was three electricians involved, and one of them really, really was hurt bad. In fact, the lineman that I know, when they hauled the electrician out of that situation, he said his eyeballs looked like little dried up white raisins.

Because of the-

The man on the stretcher.

Yeah, because of the blast.

The blast, yeah.

Yeah, the blast.

Such a violent explosion. It could've possibly have been prevented. The electrician wasn't wearing any gear, no safety glasses, no arc flash rated equipment.


Clothing, none of that. Actually had short sleeve shirt on. Also, when they turned the power on, they didn't have the panels in place.

So nothing was fastened down and covered. Right, right.

Yeah. Those folks, if they would've been following safe work practices, they probably could've avoided that whole situation.

Arc flashes can happen in bigger devices, like what we're near today, but it can also happen in simple breaker panels too, right?

Oh, sure.

Oh, sure.


What's the difference between a bigger service and a smaller service? Is it the amount of energy that comes out?



When you have a huge industrial plant, they have a lot more energy available just for processing in that building than a small, like in the case of a home, for example.


We teach, in safety training class, even at home, if we're switching actual breaker, to stand to the side.

Not right in front of the panel, where a blast can happen.



Even in our own homes, we recognize that danger, but sometimes in an industrial environment, we find that people don't observe that same safety type of situation that maybe they would at home.

The safe practice, if you don't know anything today, if you need to disconnect or turn off power, you physically put your body to the side, so if a blast is going to happen, it's going to happen over your shoulder.

Yeah. Right. The best case scenario on that instance would be to have a qualified electrical worker for that actual facility-


... that has been through all of the safety training protocol that that facility has, do that work for you.

Mm-hmm (affirmative).

We sometimes ... I visit with firefighters a lot, because firefighters often have to go in and work inside of a building, and they don't understand the power system.

Of course.

They often are called upon to shut power off.

But they may, they don't know ...

They put themselves in harm's way. It's bad enough when we understand the risk that firefighters put themselves into just to save our property, right? We, a lot of times, we overlook the extra risk that they put themselves in just to control the electric hazard, and they may not necessarily know the hazard involved there.

Because that's not their day to day life.

It's not their thing.

They don't know. When employers are doing emergency action planning, and they're working with their local response teams, they can involve that piece to say, "Hey, if you're responding to our facility, we've got someone qualified to go and accompany you to turn power off."

Yes, absolutely.

To restore power to things. That's a really great tip.

It really helps with the firefighters' comfort level with the facility, because a lot of times at an industrial facility, they'll have specialized training for the firefighters for ammonia or for some of those other gases.

But electrical too.

We don't see it as often with electrical, but it's every bit as important.

Yeah. Right. When it comes to arc flash, and the people who are listening to this safety tip, they might be thinking, "Yeah, but maybe this doesn't apply in my facility." I'm guessing arc flash can happen anywhere you work.

It really does apply in almost every commercial facility. The arc flash standards that we work with in a general plant environment all relate back to NFPA 70E. That's the standard that's used for industrial environments. It doesn't apply to ships, or rolling railroad stock, those kind of things. They're specialized equipment, and there's specialized safety standards for that equipment, but in a general sense, NFPA 70E applies to us here.

There's a couple of tracks a person can use. Having an arc flash analysis done helps build an understanding of the danger, so the qualified electrical worker, when they come to the location of the equipment, they can understand what they're dealing with.

If an employer is listening, and they're thinking, "Well, we don't have qualified electricians where we work," but everybody has electricity. If they have lights on, they have electricity. That doesn't necessarily mean you shouldn't be teaching and training your employees on what the limits of what they can do, and how to avoid arc flash, correct?

Yes, absolutely. The other part of that equation is, if we have a building where we don't have any electricians, we still have equipment that needs to be serviced. If I'm going to hire a fitter, for example, and the fitter has to come and work on a 500 ton chiller, that 500 ton chiller is going to have huge electric service coming to it. That fitter is going to have to understand the dangers that are involved if they're going to be interfacing with the power system.

Just to lock it out.

Just to lock it out, absolutely.

I mean, simple lock out procedures can put you at risk for an arc flash.


Yeah, right, right.

In NFPA 70E, the lock out tag out process is actually step number six in an eight step process for creating an electrically safe work condition. Those fitters, when they come and work in that environment, a lot of times when we start to work with them, they see lock out tag out as an electrical safety program, but it's not. It's a component.

It's a component of it.

It's a vital component, but the safety program is actually a bigger picture.

Right. Are there any myths that you think people believe about arc flash, or any specific tips that you can think of that you'd like to make sure ... If you wish everybody knew this, a couple of things, what would that be?

When we do training, I hear a lot of times people think that it's only going to happen to somebody else. It's not going to happen to me. Last summer, I was doing a research project, and there was an article that talked about how our brains think of electrical safety. A lot of times, we'll have people, they use a story of getting shocked, and so they've been involved in some kind of electrical incident. They've been shocked. They're talking to their buddy about it, and they use kind of a funny connotation that goes with it.


It forces our brains to not recognize the danger that somebody was really in. The author of that research paper actually maintained that we should talk about electrical shock incidents as either fatal or nonfatal.


It really sounds, on the surface, like an extreme condition.

But ... Yes.

When you look at, there's not a lot of middle ground.


When somebody's not hurt, they're not hurt, but when they're hurt, it's usually so bad, or they're killed.

Yeah. It's debilitating, life altering, or a death.

Yes. Our mission, when we do training, is to talk about that. We try to get people to think about that shock hazard or the shock situation, it's either fatal or nonfatal. I guarantee you, when we go home to our loved ones, if I went home and told my family that I was shocked at work, it probably would go in one ear and out the other. Not for me, because we're electrical safety. It's going to be a little bit different situation. But if I go home and tell my family that I was involved in a nonfatal incident, it will get the due attention that it deserves.

That's right.

It's a focus we try and make. We think it's important.

It is.

To get our mindset to change on it. When that mindset changes, people are able to give it the attention that it deserves, and be able to treat it with the respect that they should.

So true. It's not something to laugh off or shrug off. "Oh, I got a little shock today."


You avoided not dying, and you're lucky for it.



The amount of current that is required to really cause significant damage ...


For instance, I used to work, many years ago, in a manufacturing plant. The service into that building could deliver, in a worst case scenario, maybe 30,000 amps, 40,000 amps.

Amps, mm-hmm (affirmative).

40,000 amps is a lot when you think of, a quarter to a half an amp can kill you.

Yeah, a quarter to a half an amp crossing your heart in just the right way can kill you.


Yeah, so people think, "Oh, it's low voltage." Well, what is low voltage mean? You're really looking at the amps.


Knowing that half ... What'd you say, a quarter to a half an amp?

Of an amp can kill you.

Right. Pretty dramatic.

When people have been shocked, oftentimes I'll ask them, "Well, did you feel like you were being tased?" They look at me like, "What are you talking about being tased? That doesn't make any sense," but a taser, the amount of current that's available on a taser is in that 10 to 20 or 30 milliamps or whatever it is, milliamps.

Milliamps. We were just talking about amps, right.

Yeah, so if you didn't feel like you were getting tased, then you really got lucky when you got shocked. You really didn't get the full effect of what was available.

Yeah, yeah, very lucky. Thank you so much, Phil, for this really valuable information.

Oh, thanks for having me.

Really appreciate it. Really appreciate it.

Hopefully, some of you have picked up some tips today in understanding what an arc flash really is, and some basic precautions you can start taking today.

I hope you gained a safety skill today. If you know someone who needs this, go ahead and pass it on. Safety is everyone's business.

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