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 Post subject: Unrated Underlayers
PostPosted: Wed Dec 17, 2014 9:29 am 
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Location: Toronto
I'm looking to up the level of sophistication on our underlayer policy. Right now we have a general statement that "clothing worn in conjuction with arc rated clothing shall not contribute to worker injury." I'd love to hear people's experiences related to this and I'll provide some when, uh, the report comes out.

We've basically said that underlayers have to be non-melting natural fibres, and all unrated clothing must be covered by FR. On those two points:

Is the problem with synthetic material that it melts at a temperature that is expected below the rating limit of the arc-rated outer layer? If so, how *much* synthetic fibre is acceptable in a blended fabric? How much poly in poly-cotton? What about spandex mixed with cotton or wool?

How much exposure of unrated clothing is likely to be a problem? I expect that if a big cotton or poly-cotton hoodie hood ignites that it will spread to the rest of the sweatshirt underneath the FR jacket. But what about the triangle of exposed unrated t-shirt underneath the open collar of a work shirt? An inch at the bottom of an unrated t-shirt sticking out of an FR sweatshirt? Unrated sweatshirt sleeve cuff sticking out beyond an FR parka? Before anyone says they should be wearing flash hoods, gloves, etc., I'm talking about the basic arc-flash wear the utility guys have on all the time (designed to protect them from exposure to arc they're not expecting at all) as opposed to full gear they don to address an identified arc flash hazard.

Has anyone banned the use of unrated underlayers? Did anyone manage to do it without imposing (and buying everyone) unrated underwear?

Any thoughts or experiences much appreaciated.

Jody


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 Post subject: Re: Unrated Underlayers
PostPosted: Wed Dec 17, 2014 9:40 am 
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Location: Port Huron, Michigan
jody wrote:
I'm looking to up the level of sophistication on our underlayer policy. Right now we have a general statement that "clothing worn in conjuction with arc rated clothing shall not contribute to worker injury." I'd love to hear people's experiences related to this and I'll provide some when, uh, the report comes out.

We've basically said that underlayers have to be non-melting natural fibres, and all unrated clothing must be covered by FR. On those two points:

Is the problem with synthetic material that it melts at a temperature that is expected below the rating limit of the arc-rated outer layer? If so, how *much* synthetic fibre is acceptable in a blended fabric? How much poly in poly-cotton? What about spandex mixed with cotton or wool?

How much exposure of unrated clothing is likely to be a problem? I expect that if a big cotton or poly-cotton hoodie hood ignites that it will spread to the rest of the sweatshirt underneath the FR jacket. But what about the triangle of exposed unrated t-shirt underneath the open collar of a work shirt? An inch at the bottom of an unrated t-shirt sticking out of an FR sweatshirt? Unrated sweatshirt sleeve cuff sticking out beyond an FR parka? Before anyone says they should be wearing flash hoods, gloves, etc., I'm talking about the basic arc-flash wear the utility guys have on all the time (designed to protect them from exposure to arc they're not expecting at all) as opposed to full gear they don to address an identified arc flash hazard.

Has anyone banned the use of unrated underlayers? Did anyone manage to do it without imposing (and buying everyone) unrated underwear?

Any thoughts or experiences much appreaciated.

Jody


Have everyone wear cotton or wool underwear, socks, and T-shirts (and bras) is the easy answer. "Natural fibers" is I believe the term used.


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 Post subject: Re: Unrated Underlayers
PostPosted: Wed Dec 17, 2014 11:29 am 
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Location: Rutland, VT
I think NFPA 70E-2015 is pretty clear on this.
1. Clothing that is not in accordance with 130.7(C)(11) shall not be worn
2. 130.7(C)(9) states if arc rated clothing is required it shall cover all associated parts of the body as well as all flammable material. Shirt and coverall sleeves shall be fastened at wrists, shirts shall be tucked into the pants, shirts shall be closed at the neck. Tight fitting clothing shall be avoided.

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Barry Donovan, P.E.
www.workplacesafetysolutions.com


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 Post subject: Re: Unrated Underlayers
PostPosted: Fri Dec 19, 2014 6:52 am 
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1. Understand first the physics. "Natural fibers" (wool, cotton, silk) do not melt, they char. As long as they do not ignite once the heat source is removed, the effects of combustion stop immediately. With synthetic materials, they melt and continue to conduct heat to the skin. That is the basic problem with synthetics.

2. With blends, there are two issues. First, it is definitely not only possible but there is actually arc rated apparel that uses synthetic fibers. Certain fibers (aramids such as Nomex in particular) are fire retardant in and of themselves. Others don't pose a problem either because of the blend or because for instance the meltable fiber is positioned in an outer weave where the lower layer is nonmelting in nature and it passes the ASTM tests. None of this is the case with the various polycotton shirts and so forth unless they are actually purposely designed and tested to meet ASTM tests for arc rating. So there are no shirts, winter linings, etc., that are "nonrated" and acceptable.

3. The synthetics can definitely melt right under the arc rated clothing and this has happened in several documented cases. A lot of synthetics melt at a temperature of around 130-160 F. Contrary to popular belief, the ASTM 1959 test for arc rated clothing doesn't stop at 1.2 cal/cm^2. In fact it follows the profile of human skin and as the time increases, higher incident energy ratings are considered acceptable (up to a little over 2 cal/cm^2). Temperatures don't equate directly to energy, so we can't say what energy (cal/cm^2) is acceptable for synthetic fiber clothing. Suffice to say basically, don't do it. A second problem with synthetics is that for instance cotton ignites at over 600 F. Synthetics ignite at a much lower temperature and give off a lot of toxic smoke even before that point. So again, don't do it.

4. Currently NFPA 70E states that an "incidental" amount of meltable material is acceptable but does not clarify this. It has been taken to mean for instance nylon bands on the top of socks and underwear. Some have taken it to mean name tags but others have not. This is definitely a "your mileage may vary" territory. I submitted a public comment on the last 70E Code cycle to give a specific dimension (square meters) with substantiation for the amount and it was rejected so I guess the 70E Committee likes vagueness.

5. The PPE manufacturers are very clear on material "sticking out". 100% coverage is required. The upper button on the collar is supposed to be buttoned. Yes, many workers don't do this. I hate the velcro collar on 40 cal jackets and I don't actually close it until I put the hood on and as soon as the hood comes off, so does the velcro closure at the neck. I also don't like turtlenecks. But there are documented cases of a shirt "sticking out" and causing injury by "wicking" up under the AR clothing. E-Hazard has a video on this. Just because the guys like to wear Henley shirts with the collar unbuttoned and not tucked in doesn't make it right. There is even a case documented by Doan where a person cut the sleeves off a long sleeve shirt and was not burned under the shirt or gloves but was severely burned only on the arms.


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 Post subject: Re: Unrated Underlayers
PostPosted: Mon Dec 22, 2014 9:04 am 
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To add to PaulEngr comments - NFPA 70E section 130.7 (C)(9)(d) specifically states "Coverage. Clothing shall cover potentially exposed areas as completely as possible. Shirt and coverall sleeves shall be fastened at the wrist, shirts shall be tucked into pants, and shirt, coverall, and jackets shall be closed at the neck."


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 Post subject: Re: Unrated Underlayers
PostPosted: Mon Jan 05, 2015 1:19 pm 
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Location: Toronto
Thank you all, particularly to the detail from PaulEngr. I'll post more as it becomes available.

Happy New Year!


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