In addition to a standard range with 16 different enclosure dimensions, stainless steel enclosures can be made to customer specifications. The enclosures can be made of stainless steel (AISI 316L or 304) or stove-enamelled steel. Strict observation of the correct use of the levels of protection 'tb’ and 'tc’ is essential to ensure that equipment with the level of protection 'tc’ is not installed in Zone 21. IEC/EN 60079-31 'Equipment protection by enclosure t’ covers explosionproof equipment for equipment protection levels 'Db’ (Zone 21) and 'Dc’ (Zone 22) and the levels of protection 'tb’ and 'tc’. The explosionproof switchgear combinations are intended for use in Zone 21 and Zone 22 explosive dust atmospheres according to IEC/EN 60079-0 and IEC/EN 60079-31.
