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 Post subject: PPE
PostPosted: Wed Jan 06, 2016 8:43 am 
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If any employee put Category 3 suit on top of category 2 suit , will he can work on category 4 equipment??????Category 2 means up to 8 cal/ cm2 and category 3 means up to 25 cal/cm2. So even he wears category 2 and category 3 together, it covers 8+25= 33 cal/cm2 which is less than 40 cal/cm2. Any comments are appreciable on this topics


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 Post subject: Re: PPE
PostPosted: Wed Jan 06, 2016 8:57 am 
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The official 70E policy, I believe, is that you can't just assume PPE adds up and you have to test the PPE to get the actual value. Some manufacturers provide data as to what the total value is if you wear their clothes layered.

In practice the value is going to be greater than the sum of the individual values, the air gap between adds some value. To meet code, though, you can't assume anything, and to be conservative you have to simply go by the greater value.


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 Post subject: Re: PPE
PostPosted: Wed Jan 06, 2016 9:04 am 
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In order to layer AR PPE to increase the AR, it must be a tested combination. Manufacturers have done some testing and layering charts are available from them.

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 Post subject: Re: PPE
PostPosted: Mon Jan 11, 2016 7:54 am 
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I agree with the first two responses. Assuming these two AF suits total more than the 33 calories would be a mistake. Getting a 40 calorie rated suit or turning off the power to the equipment seem your only real options. Also, are you saying the equipment you want to work on has 40 a calorie arc flash hazard? If so, you're right at the maximum. If it's more than 40 calories, I'd advise you to not work on it energized or find a way to get the hazard below 40 calories. For example, maybe look at the upstream OCD. If it's a breaker, could you lower the instantaneous pick up settings and recalculate the calories? Or is there a way to increase the working distance, assuming the working distance is 18 inches. But like I said, to me the best option is to find a way to work it with the power off.


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 Post subject: Re: PPE
PostPosted: Mon Jan 11, 2016 10:31 am 
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Another completely separate issue you would also want to consider, is CAN your employees even PERFORM the work wearing the Cat3 PPE over the Cat 2 PPE. If the cat3 ppe is intended and sized to be normal work wear, then the answer probably is NO.

If the task at hand is TRUELY important enough that it HAS to be done, and it is SO NECESSARY that it get done without de-energizing, then it should also be worth spending the extra money and hassle on 40 Cal PPE.


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 Post subject: Re: PPE
PostPosted: Mon Jan 11, 2016 4:02 pm 
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Hi All

As previously stated we have to be cognice of the fact that when layering garments, have both garments been tested together by the manufacturer. This is information that could be obtained from the manufacturer of material- ie Westex. When layering the total incident energy protection is not additive as some may think. For example an 8 cal shirt over an 8 cal shirt does not equal 16 cal/ cm2. If anything it may be allot more due to the air gap between the garments. My advice is if you are going to start layering garments contact the manufacturer or supplier for technical information to first see if 2 choice garments have been tested together and if so what is the total cal/cm2 protection


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 Post subject: Re: PPE
PostPosted: Mon Jan 18, 2016 1:33 pm 
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We do most of the arc testing and make layered system data from multiple manufacturers which has been tested by end users available for free on our site but most of this is 2 layer data not quite 40 cal. Definitely check with the flash suit manufacturer to see if they have multilayer data. Westex by Milliken is the most common fabric in suits BUT the manufacturer may have the data and will assure you have the exact system you use.

Hugh Hoagland
ArcWear.com


Last edited by wbd on Wed Jan 20, 2016 2:11 pm, edited 1 time in total.
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 Post subject: Re: PPE
PostPosted: Wed Jan 20, 2016 12:38 pm 
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Another catch 22 in this scenario relates to face protection. Since you cannot practically place a Cat 3 hood over a Cat 2 faceshield, the resulting hood would be underrated for the requirement


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 Post subject: Re: PPE
PostPosted: Fri Jan 22, 2016 10:48 am 
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A use case for layering is for instance when workers are issued FR shirt, pants, and an FR coverall. Individually the clothing may be only say 10 ATPV but together it could be 25 ATPV and if combined with a hood it would meet ATPV 25 requirements without having to stock a 25 ATPV suit as a separate item.

It stands to reason then since a lot of winter FR clothing is getting up into the 25+ ATPV range that the supplied hood could in fact be rated for 40 ATPV and the combination of "standard" FR shirts+pants plus the winter gear could get to 40 ATPV.

Another use case is trying to achieve 12 cal/cm^2. Under OSHA 1910.269 as well as 70E Annex H wearing 12 ATPV PPE plus a face shield is acceptable but until really recently most of the shirts on the market are around 6-10 cal/cm^2. A typical knit high visibility "lineman shirt" is often only 6 ATPV while jeans are typically 12 ATPV. And speaking from experience, I'd rather be wearing that shirt all day than the more common 12 ounce cotton "welder's shirt" when working outside in the summer. So throwing a second heavier "welder's shirt" on or an FR rated rain jacket along with a face shield can be a relatively simple and comfortable solution for linemen if 12 ATPV shirts are either hard to find or not comfortable.

The "does it fit" argument doesn't really hold water. Having FR clothing loose is actually better not only from a comfort point of view but it makes it more comfortable and the extra trapped air provides additional protection, as long as the clothing is not so baggy that it becomes a work hazard by itself. In winter layering is far better than trying to get away with single layer clothing and when it gets really cold I typically wear 2-4 layers of clothing depending on the temperature. Think 1 or 2 undershirts+long sleeve (FR) shirt+FR jacket. Legs might be regular underwear+socks+long johns+FR pants+FR bib overalls for a total of 4 layers. If the underlying layers are not high visibility, this adds yet another layer.

Furthermore, I have purposely tested wearing safety glasses and full face respirator for chemical protection under a Salisbury 40 cal/cm^2 rated hood. It fits just fine and there's plenty of room for this. I have no doubts that a 10-12 cal/cm^2 face shield could actually physically fit but there are two caveats. The first is that the ears that connect the hood to the hard hat use the same holes as the face shield so the hood would just be hanging over it all loosely. The second problem is that the visibility would be seriously impeded since we're doubling up the face shield tinting in a way that I would have to believe is different from what is intended. It can still work but you'd be even more blind than the 50%+ loss in light that you get with a 40 cal/cm^2 hood.

Then we get to practicality. There's really almost no argument for having a 25 ATPV arc flash suit. Generally speaking in terms of clothing design, single layer PPE can be achieved up to around 12 cal/cm^2. Below that at some point depending on the Code being implemented there is a cutoff where face shields are no longer necessary and most shirts are only good for around 6-10 ATPV so that there are sort of 2 "levels" of PPE at that much incident energy. Above this point when the multilayer stuff becomes necessary there's little practical difference in terms of costs and ergonomics between anything in the 20-40 ATPV range. There are definitely design differences for the 60 and 100 ATPV categories mostly in terms of the fact that they get very heavy and movement and thermal insulation become much bigger factors. So for all these reasons I would argue that the 25 ATPV suit has almost no value whatsoever except that when the clothing tables were introduced into the Code, it's a big jump from 8 cal/cm^2 all the way to 40 cal/cm^2. But once you go to site-specific PPE and doing an arc flash study, you start to realize that it's better/easier to simply establish local standards based on what is available and how much coverage (how many busses) it gives you based on Annex H rather than trying to conform to a synthetic table that does not have any basis in the real world.


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 Post subject: Re: PPE
PostPosted: Tue Feb 02, 2016 7:57 pm 
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RogerF wrote:
Another catch 22 in this scenario relates to face protection. Since you cannot practically place a Cat 3 hood over a Cat 2 faceshield, the resulting hood would be underrated for the requirement


Never apply this to face protection. Use face protection rated for the hazard but layering garments is very practical.

Several face shields have greater distances off the face with adapters to allow for use of respirators etc. We have done extensive testing for the DOE on many designs for nuclear mostly but chemical works too. Use firefighter's respirators and SCBA units for the best results in a potential arc flash event. Under a hood it shouldn't be an issue but this makes it work better. Always happy to help if someone needs testing. We don't sell the PPE but happy to assist.

Hugh Hoagland
ArcWear/e-Hazard.com


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