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 Post subject: Rubber Gloves IE level?
PostPosted: Tue Aug 08, 2017 7:36 am 
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Location: Rutland, VT
Attached is a pair of rubber gloves that were exposed to an arc flash. Does anyone have a feel for the incident energy level they may have been exposed to?


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 Post subject: Re: Rubber Gloves IE level?
PostPosted: Mon Aug 14, 2017 6:24 pm 
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Hi Barry

it is difficult to provide an approximate on the amount of IE that the gloves in question were exposed to. However I am attaching a PPT presentation that is a summary of some arc flash tests that were conducted up here in Toronto at Kinectrics. The tests were for WH Salisbury on arc flash testing of rubber insulating gloves with leather protectors. Tests were done on the leathers, the rubber and both combined.

hope that this is of some help

best regards


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 Post subject: Re: Rubber Gloves IE level?
PostPosted: Tue Aug 15, 2017 5:31 am 
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Leonard,
Thank you for that PPT document. I have been asked to perform an analysis to determine what the IE was at that point. When I do it, I will post what the model says for the IE.

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 Post subject: Re: Rubber Gloves IE level?
PostPosted: Tue Aug 15, 2017 7:31 pm 
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My pleasure Barry. Good luck
Thanks


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 Post subject: Re: Rubber Gloves IE level?
PostPosted: Mon Aug 21, 2017 6:41 am 
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From the modeling done, it looks to be about 53 cal/cm2 exposure. It was in a self contained 208V meter socket. The event was described as:

Meter tech had installed jumpers in a meter enclosure to remove and replace the 208V meter. In the process of removing the meter an arc flash occurred and sustained until cleared by a substation breaker. The riser fuse did not operate.

It was determined that the arc occurred in the conduit between the race and top mount of the meter enclosure. It was described as a sustained open air arc in the conduit between a conductor and the conduit inner wall.

Still evaluating so probably more to come........

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 Post subject: Re: Rubber Gloves IE level?
PostPosted: Mon Aug 21, 2017 9:10 am 
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There might be one caveat to the Salisbury PPT. Until recently (last five years) there was very little extended testing of PPE with the arc-in-the-box. I believe. the exposed electrodes in the test (PPT) transfer more heat by radiation, whereas, the arc-in-the-box, transfers most of the heat by convection. For sure, the IE versus the glove colors should change.

Perhaps, someone who has actually did glove testing with IEEE1584 box can chime in. That is a very interesting video.

Black absorbs more more heat through radiation and red emits more heat (once absorbed) than a black surface (??), does anyone have an insight into why the black glove is a far better protector??


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 Post subject: More Info
PostPosted: Mon Aug 21, 2017 10:15 am 
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Received more explaination of what happened:
The fault started out in a self-contained meter can 200 amp phase A to ground high impedance eventually burned into another phase conductor B making it a low impedance so it cleared one secondary fuse now it’s back to a high impedance fault one phase B to ground until it burns into another phase C conductor making it a low impedance clears another fuse so we are down to one fuse phase C which DOES not blow because it’s a high impedance fault.

Fault cleared by opening substation 12.5kV bkr

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 Post subject: Re: Rubber Gloves IE level?
PostPosted: Tue Aug 29, 2017 4:27 pm 
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Natural rubber is usually sort of a greyish color. Carbon black is used as a strength enhancer (filler) and improves upon UV protection among other things. The other colors are achieved by adding something else. Usually the strength does improve but the UV protection does not. I realize that for instance black means that optically it absorbs everything and reflects very little whereas the colors will absorb other parts of the visible spectrum except the color that is "seen" but we're mostly talking about broad spectrum radiation here. Furthermore, solid graphite/carbon is used as the brick of choice as refractory in protecting against exposure from liquid iron/steel. And the "char" that you get from combustion/charring of wood and other cellulose materials does a pretty good job of acting as something of a heat shield. So it's pure speculation on my part but putting this all together I would believe that somehow the carbon may slightly improve the heat resistance of the rubber.

As to the "arc-in-box" vs. other models...remember that all the surfaces are both partly absorbers and reflectors. So even if it's not a great reflector, an arc in a box is going to direct more of the thermal radiation towards the calorimeters.

I believe though what you may be referring to is that there is some kind of plasma or extremely hot gases present. In some tests this hot gas cloud (not sure if it is really plasma or not) makes direct physical contact and when it does, the incident energy measured just about doubles. Rainwear is much more resistant to this stuff and permeable workwear is much less permeable to it. I haven't seen any studies beyond studying it as something of a scientific curiosity...no definitive way to deal with it as of yet. I suspect part of this is because we're not to the point that we're applying say a radiation model to the box configuration to arrive at an incident energy value yet so something that has to consider magnetic fields, convective currents, etc., is beyond what we can model so far.


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