Hi Martechman,
'Zone 2' is a term normally used in relation to hazardous area apparatus, as do are the terms 'Zone 1' and 'Zone 0' which indicate more stringent requirements.
Check under ATEX or hazardous area equipment for manufacturers of enclosures designed for hazardous area installation, but if you are not experienced in hazardous area design, you should seriously consider subcontracting this job out. The consequences of getting a hazardous area design wrong in a heavy process plant environment rightly make this a specialist area of design.
Check the following manufacturers:
CEAG Crouse-Hinds
Bartec
Craig & Derricott
Hope this helps
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