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ANSI/ISA 61241-2 (12.10.06)-2006 (R2015)
Electrical Apparatus for Use in Zone 21 and Zone 22 Hazardous (Classified) Locations - Protection by Pressurization "pD"
This standard gives requirements on the design, construction, testing and marking of electrical apparatus for use in combustible dust atmospheres in which a protective gas (air or inert gas), maintained at a pressure above that of the external atmosphere, is used to prevent the entry of dust which might otherwise lead to the formation of a combustible mixture within enclosures which do not contain a source of combustible dust. This standard contains the specific requirements for construction and testing, including protective requirements that apply to electrical apparatus with type of protection pressurization "pD" intended for use in potentially combustible dust atmospheres. This standard includes the requirements for the construction of the enclosure and its associated components, including, if any, the inlet and outlet ducts for the protective gas, and for the safety provisions and devices necessary to ensure that pressurization is established and maintained for type of protection pressurization "pD". Requirements for pressurized enclosures with an internal source of dust release are not included in this standard. This standard does not cover the requirements for pressurized rooms with or without internal sources of dust release. This standard does not apply to dusts of explosives which do not require atmospheric oxygen for combustion or to pyrophoric substances. This standard does not cover combined gas and dust hazard. Those requirements are under consideration. The requirements contained in this standard are supplementary to those in ANSI/ISA-61241-0.
The International Society of Automation [isa]