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 something
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 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.

Senior Engineer -
Facility Dynamics Engineering 
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