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PostPosted: Thu Apr 24, 2014 10:15 am 
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Voltrael wrote:
It's probably more important, from the emphasis of 70E, to have a higher AR in the trunk and head, but we still need to make sure that all areas of the body meet the minimum value called for for the task being performed. I tend to wear an arc rated reflective vest most of the time when I am needing protection. It gives part of my body extra protection, but since it doesn't cover my arms, I don't count it toward my AR total.


Hmm...this contradicts the second paragraph. The emphasis is on the face/chest area. Although the various manufacturers test clothing and there is a published information demonstrating that "head-to-foot" coverage is necessary (employees burned at wrists where gloves did not overlap PPE, examples of hot vapors blowing "up" into smock/switching coats that were popular a few years back). And I highly question any claim that there is an effort to improve arc rating anywhere.

The ASTM test is actually applied to sample pieces of material. It is held vertically perpendicular to the source of an arc. All PPE material testing these days is done by just one lab (Kinetrics) as far as I know. The various ASTM standards are for the material itself, not the clothing or ensemble. Dupont used to do testing of the entire PPE in the past. Although PPE tests are still done, I don't believe there is an ASTM standard addressing the actual PPE. I'm going out on a limb here so if I screw it up, elihuiv will correct me.

So it is not necessarily true that PPE has a "higher" AR rating for the face/chest area or even that the AR rating of the arms, legs, or hands is treated any differently. The only reason that there is an "increase" in protection in the head/chest area is by virtue of distance. Although the exponent is not exactly 2, doubling the distance is close to cutting the incident energy by a factor of 4. So if the working distance (to head/chest) is 18", hands that are only 1" away should logically see nearly 300 times the incident energy. There is a practical issue with this grossly oversimplied point of view though because arcs are not point sources of radiation so geometric issues can significantly change the result. But the result still stands that the incident energy at the hands if an electrical worker is currently working on equipment at the time of an arc flash, the incident energy at the hands will be much higher than at the chest and head areas. The arc rated material could be the same but simply geometry means that the exposure will be less at the head/chest.

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Hands and feet don't really even have ratings as of 70E right now (although I believe you can purchase rated items), you just wear thick leather gloves or rubber gloves with covers for hands, and leather boots for feet.


Not entirely true. It's not listed in 70E but there are some published articles where rubber gloves and leather gloves have been "type tested" (a large sample size was tested) and passed with the ratings given in the text in 70E. So they are not rated because they don't have to be. Boots have been tested by elihuiv's company but I don't know of any publications describing the results.


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PostPosted: Thu May 29, 2014 6:55 am 
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elihuiv wrote:
I don't know of any non-FR cotton that meets the ANSI 107 High Visibility Standard. Polyester and Modacrylic are the only materials which do to date. Modacrylic is non-melting and can be arc rated. Polyester cannot.


Why would your T shirt have to be high visibility or anything other than cotton if you are wearing it under a HRC 2 shirt?


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PostPosted: Thu May 29, 2014 12:00 pm 
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Voltrael wrote:
Hands and feet don't really even have ratings as of 70E right now (although I believe you can purchase rated items), you just wear thick leather gloves or rubber gloves with covers for hands, and leather boots for feet.


It does cover this in quite a bit of detail. See 130.7(xxx). It just so happens that leather gloves give you roughly the same proteciton as 8 ATPV and rubber voltage rated gloves exceed 40 ATPV. These were tested as a group and that's why 70E lists these rather than requiring an actual arc flash rating.

Also, done quite a bit of research further on the subject of high visibility + arc flash clothing.

Fluorescent dyes wash right out of cotton so cotton cannot be used as part of the "high visibility" standard under ANSI 107 which includes a wash test. Other standards are weaker and could potentially allow it. The number of square inches of fluorescent and retroreflective material though definitely does not mean that the entire piece of clothing has to be high visibility. One can easily sew on stripes that meet the requirement to a shirt or jacket.

There are a few all-lime green high visibility shirts that are also arc rated on the market. Three manufacturers are Carhartt, Dragonwear, and Radians but there are others. Dragonwear runs around $150, Carhartt around $100, and Radians around $55. The basic material is mostly made of modacrylic and since there is a lot of it and the material appeas to be patented, the price is very high. I'm not 100% sure but according to Radians web site the FR/high visibility material that they use is Glengard. I don't know who the others are using.

The second option is to take a standard fire retardant shirt and sew fire retardant stripes onto it. This drops the price of the shirt itself down to a more reasonable $30-$45 price range, and the stripes are relatively inexpensive to add to it. Workrite does this. Cintas (major national rental company) simply sells/uses Workrite shirts even though they are competitors.

The third option is to use a high visibility and FR rated vest. These are usually modacrylic material again. It adds a layer of clothing so it is hotter in the summer and they tend to get hung up on everything but since there is less physical material the cost is mid range, about $40 seems to be the low end of the pricing. You can't get a size "small" vest in ANSI 107 level 2, and the smallest sleeveless vest that meets level 3 is size 4XL so for all practical purposes they don't exist.


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