Junction Boxes for zone 0

  • Thread starter Ibrahim Abdelmohsen
  • Start date
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Thread Starter

Ibrahim Abdelmohsen

I have IS circuit connected to field Junction box with blue terminals (IS). this JB is broken and I have to replace it but the old one does not have any label. so what the minimum EX requirements for that junction box to be installed in this zone 0 with this IS circuits?
 
Ibrahim,

The easiest way to answer this is to replace like for like. Equipment ratings should be displayed on the nameplate, along with information regarding the certification. I would suggest using this information to trace an exact replacement.

Further to that does the site have a record of the hazardous area equipment installed? If so this should also be able guide you for a replacement.

If you have neither, then it will be necessary to understand what are the associated hazards etc in that area. What equipment it is being used with and then selecting the correct equipment based upon this information.

M
 
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Bruce Durdle

The only requirements in IEC60079.11 relating to enclosure design refer to Ingress Protection. As long as specified minimum clearance and creepage distances are exceeded, IP54 or better enclosures can be used. In general, this requirement can probably be met by an Ex e enclosure. (Since the circuits inside the box are already protected to Zone 0 requirements by the Ex i system, the actual rating of the enclosure is irrelevant).
 
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Asok Kumar Hait

1st of all you haven't indicated correctly the hazardous rating of the area where the junction box is installed. You are using an IS circuit which is suitable for Zone-0 (if it is Ex ia, Zone-1 only for Ex ib), but that doesn't mean that the junction box is installed in Zone-0 area. Most probably the junction box will be installed in Zone-2 or in safe area.

Anyway, this doesn't matter. Junction box in IS circuit is considered as "simple apparatus" and doesn't need any Ex-certification. A simple weatherproof junction box will be good enough. However, if the JB is installed in hazardous area you need to meet the minimum requirement of any enclosure in hazardous area e.g. material requirement for metallic or non-metallic material as per IEC-60079-0 etc. To avoid any unexpected problem and reduce the spare inventory, many users just specifies Exe JBs to be installed in hazardous area. For further information you may look into the following article from MTL:
http://www.mtl-inst.com/images/uploads/datasheets/App_Notes/AN9003.pdf
 
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