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Posted By Topic: Barrier Gland requirements in Hazardous Area

Albajohn
Jul 10 2016 15:01

I know the requirements for a barrier gland to be fitted on the cable for entry to Exd equipment with regards to the flow chart in AS/NZS 60079-14:2009, 10.4.2. and also the requirement for a barrier gland to be fitted on the cable for entry to ANY Exd enclosure if the cable is not compact, circular and with extruded bedding and non hygroscopic fillers.

But what about the requirement for a barrier gland to be fitted to the cable for entry into any other Ex concepts i.e Exe, Exi, etc where the cable is also not compact, circular and with extruded bedding and non hygroscopic fillers.
Just about all instrument cable with twisted pairs would fit into that category.

If you look at AS/NZS 60079.14:2009, Section 9, Wiring Systems, on page 42, Under table 6, Note 1, you will see that a barrier gland is required for ANY ex concept as described below:
NOTE 1 - Where enclosures are likely to be subjected to large variations in ambient and/or service temperature conditions, a ‘pumping’ action can transfer the fluids from the hazardous atmosphere through cables which are not substantially compact. Similarly cables with non-filled interstices or with hygroscopic fillers (eg. fibre fillers), may transmit flammable fluids through the interstitial spaces of the cable under capillary or hygroscopic action with
sufficient partial pressure to exit the cable termination at the extremities of the cable. Particular caution is drawn to the use of electro-pneumatic transducers and the like which employ natural gas as their pneumatic medium. When such cables link between a hazardous and non-hazardous area this may result in a flammable atmosphere being transported to the inside of, for example, control room equipment. The situation is likely to be most acute with
equipment installed in a Zone 0 or Zone 1 location (where the presence of a hazardous atmosphere has a greater likelihood and duration). If these conditions are likely to apply, a cable sealing device (which seals between the inner sheath and the individual conductors) should be used. The application of a cable sealing device may only mitigate the rate of vapour transmission and additional attenuation measures may be necessary.

Conclusion:
If the cable used can be confirmed to be suitable for use in a Hazardous Area and is compact, circular and with extruded bedding and non hygroscopic fillers then use the following guide:
For Exd equipment: Use the flow chart in AS/NZS 60079-14:2009, 10.4.2 to see whether or not a barrier gland is required.
For Exe, Exi use normal Exd E1FW Gland.

If the cable cannot be confirmed to be suitable for use in a Hazardous Area use and is not compact, circular and with extruded bedding and non hygroscopic fillers then use the following guide:
Zone 1: Cables leaving hazardous area, Exd, Exe and Exi use barrier gland
Zone 2: Cables leaving the hazardous area, Exd only need to use barrier gland.

Please advise if I am on the right track here as this is a source of confusion with most of the Hazardous Area Inspectors I have spoken to.





   

Aza1402
Oct 10 2016 19:30

there a few factors to this
- Hazardous area classification of the location of your instrument
- Protection method for your instrument (Is or non IS)
- is there a spark potential in the instrument(IS or Non IS)
- if so is the volume over 2 ltrs
   

HazInspector
Oct 11 2016 08:28

The next edition of AS/NZS60079.14 will clarify this requirement.

Currently the wording in edition 5.0 of IEC60079.14 is that selection of cable glands (for Exd) shall be either;

barrier cable glands, or

standard Exd where cables are circular, compact etc and less than 3m, or

indirect cable entry, or

MIMS with Exd rated pot end, or

with a flameproof sealing device.


Note that the full wording will be available when AS/NZS60079.14 is re issued.