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Jim Phillips (brainfiller)
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Post subject: Have you/client had a DC arc flash?  Posted: Sun Jan 21, 2018 10:39 am |
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Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1727
Location: Scottsdale, Arizona
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This is the last question in the series about DC arc flash.
Have you/your client ever had a "significant" DC arc flash
No
Yes – equipment damage
Yes – injury
Yes - equipment damage and injury
*significant refers to equipment damage and/or injury
Stories are always welcome.
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bbaumer
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Post subject: Re: Have you/client had a DC arc flash? Posted: Mon Jan 22, 2018 4:18 am |
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Joined: Fri Jul 08, 2016 10:01 am
Posts: 443
Location: Indiana
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Not that I know of.
I've stupidly reconnected the - terminal first on a car battery and then shorted the + terminal to the body via a wrench before. Does that count?
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SKM jockey for hire
PE in 17 states
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bbaumer
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Post subject: Re: Have you/client had a DC arc flash? Posted: Mon Jan 22, 2018 7:31 am |
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Joined: Fri Jul 08, 2016 10:01 am
Posts: 443
Location: Indiana
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Oh, and no injury to speak of other than my pride was a little hurt.
_________________
SKM jockey for hire
PE in 17 states
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rmgbob
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Post subject: Re: Have you/client had a DC arc flash? Posted: Mon Jan 22, 2018 9:49 am |
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Joined: Wed Nov 11, 2015 9:18 am
Posts: 9
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The manufacturers technician doing start-up on a newly installed unit set his wrench down across the lugs of the battery breaker.
Nothing left of the wrench, equipment damage and soiled pants.
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ivanpulido92
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Post subject: Re: Have you/client had a DC arc flash? Posted: Tue Jan 23, 2018 1:20 pm |
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Joined: Thu Mar 09, 2017 8:16 am
Posts: 2
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Yes... Once a technician was connecting the battery bank for a solar power plant´s protection system (relays) , then when He tried to make the last connection He shorted all the batteries so it was a pretty good flash. The worker had no injury so, it was an economic experience.
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PaulEngr
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Post subject: Re: Have you/client had a DC arc flash? Posted: Thu Jan 25, 2018 3:18 pm |
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Joined: Tue Oct 26, 2010 9:08 am
Posts: 2178
Location: North Carolina
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Isn't half the fun of working on DC flashing over a motor/generator and removing all the hair on your arms?
I've seen plenty of "aftermath" and even had a few buddies who got a "summer hair cut" (hair burned off their arms and maybe their face) from flashovers but I have not seen any injuries yet. In the mining industry commonly the largest DC motor they use is a GE MD824 and the associated generator which has a stall current of around 6000 A but at something like 12 VDC, and a name plate voltage of 90 VDC.
When it comes to DC generators and motors, it seems like nobody ever wants to take the time to blow the carbon dust out or tries to see how long they can go before something flashes over. It can get ugly but usually the damage is relatively minor.
When it comes to DC motors ang generators as far as I've seen the biggest hazard seems to be the danger of failure of the banding on the commutator. When this fails, the commutator flies apart and the level of destruction is scary. A single motor or generator can destroy multiple others around it in a larger MG set.
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