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Topic Title: Arc Protective Clothing - Aramid Fibers vs Cotton clothing
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Created On: 01 June 2010 09:39 PM
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 01 June 2010 09:39 PM
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Badshah

Posts: 38
Joined: 22 July 2009

Recently while browsing the internet, i found aramid fibers are more effective in protecting from arc-flashover compared to cotton clothings. But how much will be the weight of the aramid fiber clothing? Is the fiber comfortable to wear in hot & humid or extreme climate temperatures?

If anybody using it, is the fiber more comfortable and safer compared to Cotton protective clothing?
 01 June 2010 11:14 PM
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simongallagher

Posts: 148
Joined: 28 July 2005

Hi,

The overalls we wear while working/switching/in a substation/digging are made from aramid (Nomex). I don't think all the UK DNO's have went down the route (yet).

I have seen a few photographs of people who have been burned from a flash-over, and it's amazing the difference that the overalls make. They are more expensive than cotton, but offer much higher levels of protection.

The overalls themselves feel like heavy cotton, although ours have extra cotton lining in the sleeves to bring them up to a specific standard. They are good in the winter, but in the summer the craftsmen really do suffer in them (although not as much as they would do from a bad burn.....).

Some other differences the overalls have to bring them up to the required standard are a higher neck, no slits for pockets and zip closing (no gaps from poppers)
 05 June 2010 08:47 PM
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dlane

Posts: 690
Joined: 28 September 2007

There are basically 2 kinds of FR fabrics to provide protection against arc flash burns, the inherently flame resistant aramid fibres such as Nomex and Kermel and the treated cotton blends such as Proban and Indurasoft.

Both types of fabrics will provide a much greater level of protection than basic untreated cotton clothing during arc and flash fire incidents.

They both have their own advantages and disadvantages and you have to look at all your risks and decide which fabric provides the best solution. I know a lot of companies that go straight for an aramid fibre on the asumption that it is better but this is not always the case. There are several companies that all use Proban and Indurasoft and are happy with them.

With garments of the same fabric weight you will usually find that Indurasoft will out perform the aramid fabrics under arc flash incidents but that the aramid fibres will out perform the treated fabrics under flash fire incidents especially when exposure exceeds 3 to 4 seconds.

As Simon has already said, aramid fibres are much warmer to wear and that will probably be the biggest moan you will get about them during summer.

Remember that if you do wear flame resistant overalls then any garments worn over the top must also be flame resistant otherwise the overalls will not protect correctly. Any clothing worn underneath must be off natural fibres that will not melt with heat, or again you can be burnt underneath the flame resistant overalls. You will also ned to provide protection for the face and hands for certain activities.

Kind regards

Donald Lane
 06 June 2010 03:24 PM
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alancapon

Posts: 5840
Joined: 27 December 2005

You will also have to do a study of your fault current / fault clearance times in order to come up with the specific material rating for arc flash that you will require. There is software around that is able to calculate values, or you can do the calculations manually.

Regards,

Alan.
 08 June 2010 06:28 PM
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ArthurHall

Posts: 737
Joined: 25 July 2008

I concur with all of the above statements but would add that I have been using a Nomex overall for the last couple of years. It is light weight and very comftable. The arc rating is obviously fairly low but it was speced by a large DNO for substation staff. I work mainly on protection and control circuits so am happy that it provides better protection than a cotton suit.
Anything is better than nothing, its not that long ago that the standard PPE for DNO engineers switching was a collar and tie.
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