Resources for the Resourceful – Arc Flash

If you work on building systems, either in existing facilities or in new construction, then you likely are exposed to live electrical equipment.  As such, developing a healthy respect for live electrical equipment learning how to work safely around it should be high on your priority list.  The pictures below illustrate why.  The first shows a technician winding up the spring to rack out a breaker on a piece of switch gear.

The second is what happened about 2 and a half seconds later when something went wrong.

These pictures are extracted from a video clip captured, I suspect, by a security camera.  You can see the entire video clip of this arc flash incident along with several others on the
Easy Power website.  While  you are there, you should take advantage of a free resource they offer, Practical Solution Guide to Arc Flash Hazards.

While an effort to read the entire book  may, as one of our electrical guys said, cause you to nod off after about 2 pages, the stuff in Chapters 5, and some of the stuff  in chapter 6 is worth knowing in my opinion. 

If you are a mechanical guy like me, I think its easy to become complacent around electrical gear.  After all, the stuff is not making a loud noise or throwing off a lot of heat or anything like that when its working (vs. say a boiler or a chiller or a high pressure steam pressure reducing station).  As a result, its easy to become complacent or have less situational awareness when you are around electrical equipment.  But, as the frame captures and the linked video illustrate, just because there is not any noise or radiated energy in the form of heat that we can easily sense doesn’t mean that there is not a hazard.

I’ve been lucky and have only been exposed to a shock from 120 vac.  But let me tell you, even at that level, it will catch your attention.  And, I know a lot of others who have had a
more intense experience.  For instance, a friend of mine was blown across the room and knocked out briefly when the alligator clips on his meter, which were connected to two phases in a 480 volt circuit, accidentally touched as he attempted to install his clamp-on amp probe.  When he came too, he saw a melted mass of metal that had  previously been the panel he was testing, he was missing his eyebrows, and the emergency room doctors informed him that the intense pain he was experiencing in his eyes was due to the fact that the flash had burned a layer off of them.  

Fortunately, he is still around to tell the tale.  I know of others who are not as lucky.

I always feel like I want to be comfortably nervous around electrical stuff and if I’m not or if I’m uncomfortably nervous, then I’m dangerous. My theory is the more I know about this, the more aware I will be which will either lead to the comfortable nervousness I mention, which should keep me on my toes.  Or, I will feel the uncomfortable nervousness, which tells me I should not be thinking about doing what ever it is I am
contemplating in the first place and should get someone more qualified.

If this discussion has made you interested in learning more, you may want to consider signing up for Plant Engineering’s Arc Flash University webinar series. Its free and if you
attend three of the four sessions,  you can get some Continuing Education Units.  And more important, what you learn will make you more aware and it could save your life.
David Sellers
Senior Engineer – Facility Dynamics Engineering

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