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Topic Title: Wiring through an Atex Space
Topic Summary: Atex Wiring
Created On: 12 October 2012 04:32 PM
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 12 October 2012 04:32 PM
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Mattysmith1983

Posts: 62
Joined: 25 July 2008

Please can someone give me some advice on this subject. I'm looking at a scheme where the electrical wiring will pass through a zone 1 Atex space. The distribution board itself and final outlets are with areas that are not Atex rated, however to get to final outlets the cables need to pass through this Atex Space. Do I need to use Atex graded cable and because of this would the distribution board need upgrading to an Atex rated one.

What are the regulations on this i just cant find any answers.
 12 October 2012 07:39 PM
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weirdbeard

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Sorry to be of no constructive help, I know sweet FA about atex requirements, but is there any reason you can't just take an alternative route that avoids the atex issues?
 12 October 2012 07:57 PM
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daveparry1

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I'm going to display my ignorance here, what is Atex?

Dave.
 12 October 2012 08:03 PM
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bak1950

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google.

ATEX is the name commonly given to the legal requirements for controlling explosive atmospheres and the suitability of equipment and protective systems
 12 October 2012 08:12 PM
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daveparry1

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Thanks bak, Google is usualy my first place to look for something i'd not heard of before!
 12 October 2012 08:30 PM
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weirdbeard

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Originally posted by: daveparry1

I'm going to display my ignorance here, what is Atex?



Bon soir dave, nous sommes dans un similar boat. Je suis only know le name comes from the french "ATmosphères EXplosives."

Though from a brief bit of googling it seems the method of glanding cables within atex zones is the most important thing, so I would hazard a guess that say an unbroken length of swa passing through a zone itself isn't going to cause a great hazard, but the actual installing such as drilling holes, etc, and sealing of the entry and exit wounds in the zones fabrics would be more problematic???
 12 October 2012 08:43 PM
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daveparry1

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Seems that way doesn't it.
 12 October 2012 11:35 PM
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Legh

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Welcome to electrical sanatorium.
Not being ATEX certified my opinion is probably worth a 'Friday' answer...
However, since everybody's recovering from a Thursday 'hangover' I'll start the ball rolling....
So, IMO if a cable passes through an area subject to likely fire or explosion then the cable must be rated for that area such as pyro/mims. However, saying that there maybe certain regulations that prohibit cables destined for one area to pass through another; the cable runs passing from a non-rated area to one that's potentially dangerous, via a duct or hole, must be sealed to the same degree as the area in which it passes through. Equipment installed in a non-rated area doesn't require any special treatment so I would consider nothing needs to be up-rated.

Fire away chaps

Legh

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 13 October 2012 12:28 AM
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alancapon

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You should also check your PL insurance. There is a strong possibility that it does not cover any work in an ATEX classified zone, as it is seen as a higher risk (for obvious reasons).

Regards,

Alan.
 13 October 2012 11:34 AM
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dlane

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For installations within a hazardous zone we work to the BS60079 series of standards. (Correction): The regulation you require is 9.1.7 of Part 14.

9.1.7 Circuits traversing a hazardous area
Where circuits traverse a hazardous area in passing from one non-hazardous area to another,the wiring system in the hazardous area shall be appropriate to the zone(s).

The rest of section 9 details the aspects of installing cabling within the hazardous zone.

There is also an umbrella standard EN1127-1 that deals with the concepts of protecting against ignition of hazardous substances that adopts a risk based approach to the installation, which you are probably going to have to apply to your scenario. The standard prohibits the introduction of electrical equipment that could cause a spark or heat that would ignite the gas so you will need to assess the likelihood of the cable causing a spark or heat under normal and fault conditions.

You say it is a zone 1 which isn't the most onerous zone. In general these are usually fairly small zones, such as around fan shaft seals, safety vent outlets ets and can be bypassed, which would be the preferred option based on EN1127-1. Is the gas lighter or heavier than air? If heavier you can run cables above the zone to reduce risks and vice versa. Is the zone indoors or outdoors?

Officially there is no such thing as an ATEX approved cable as they are considered passive devices and do not store energy, it is going to be more about the mechanical protection of the cable and reducing the risk of damage leading to a fault that causes a spark. The comments in other posts regarding sealing ducts etc will need to be observed.

If there is already an existing cable tray with cables on it feeding apparatus already in the zone then the addition of an extra cable isn't going to increase the risk in my opinion, as long as it doesn't introduce circulating earth currents or different potentials into the zone. If there is no other cabling in the area and you are adding your own traywork etc then that is a different proposal that does potentially introduce a risk that wasn't previously there.

For the board and outlets outside of the zone, standard apparatus can be fitted and no upgrades will be required. The only thing that has been said to me regarding outlets is if they are close to the hazardous zone they may encourage someone to use a portable appliance within the zone, but that probably isn't your issue.

As already pointed out, you will need the appropriate insurance for working in hazardous areas. If it is yourself that has specified that the cable will run through the zone then you will also need insurance to cover the design aspect as well. Zone 1 will have a minimum requirement for anti-static footwear when working in there along with the appropriate anti-static tools unless the process has been purged and the area made safe.

Without any more details of the nature of the installation I can't give any more advice.

Kind regards

Donald Lane

Edited: 13 October 2012 at 12:02 PM by dlane
 14 October 2012 09:15 PM
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Mattysmith1983

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Thanks for this everyone, its of great help. In regards to the Atex Zone 1 space, its for a distrillery for the making of gin and therefore has an explosive atmosphere. The problem i have is that the plant room adjacent to the Atex space is where the local distribution board is located and then the room the other side of the atex space is where the final outlets are required. So even though no connections are to be made in the Atex space would an SWA, MICC or an SY cable be needed, i take it twin and earth would not be permitted even if all the builders work in making any holes good were carried out. Your comments are gratefully received.

Many thanks

Matt
 14 October 2012 09:28 PM
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Mattysmith1983

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Also in regards to your comments Donald therre is a need for a new containment system i.e cable tray would be needed, presuming this is earthed correctly to remove earth currents or different potentials and is not continuous from a non Atex rated space to a Atex rated space would this be acceptable?
 14 October 2012 11:07 PM
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dlane

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Generally all the metal work within the hazardous area is cross bonded to prevent potential differences arising. Without knowing anything about the installation I can't comment on the affect of linking metalwork into other areas.

Twin and Earth would not be acceptable in a hazardous area unless it was contained within some form of mechanical protection. MICC or SWA would be acceptable but unless the MICC was sheathed you would be bringing an earth potential into the zone which may or may not be an issue.

Is the whole of the room a zone 1 area? Or can you install the cabling away from the equipment generating the zone 1 area?

Kind regards

Donald Lane
 15 October 2012 08:21 AM
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Mattysmith1983

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The whole of the space is classed as a zone 1 area due to the potential flammable fumes from the alcohol within the gin. So all the lighting etc is all rated to a Zone 1 level. The cable will be installed around the perimeter of the Atex space way from the actual equipment but as the whole area as been deemed a zone 1 it must comply to the Atex regulations.

Speaking with a Victor lighting (Atex lighting manufacturer) the use of SY cable is permitted due to its Galvanised Steel Wire Braid but in regards to containment i think the best option would be to break the containment run so it does not continue into the Atex zone, then ensure each section of containment is earthed correctly to remove and potential differences.

What are your thoughts?

Cheers

Matt
 15 October 2012 03:12 PM
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OMS

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If it were me Matty, and given the Zone 1 nature of the space, I wouldn't even go in there with cabling not required (and designed, installed and certified) for Zone 1.

If you look at this from an ATEX/DSEAR perspective, how are you going to certify your install ?

Go around, outside, above, over or under - but don't take your cabling through there - if I were the design authority for this client, I'd have you going through hoops to prove this to me -and even then I wouldn't generally be prepared to believe you without compex etc and very robust design documentation

Regards

OMS

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 16 October 2012 12:14 PM
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MAXMIRA

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Hi Matty,

I am a Electrical designer within the Hazardous area industry so i may be able to help you here.

Firstly it is only equipment within the hazardous area that requires Atex approval.

I would suggest using BS5467 cable to pass through a hazardous area as this will give sufficient mechanical protection.

No cable joints or junction boxes must be made within the hazardous area.

Last thing to note would be that if the hazardous area is within an enclosed room all cable transits to and from the room must be suitable for sealing the hazardous area.

Regards,
Dave
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