BS EN 61241-4 specifies the requirements for the design, construction, testing and marking of electrical apparatus for use in combustible dust atmospheres. These are 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 that 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.
Part 4 of BS EN 61241 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".
This standard does not cover the requirements for pressurized rooms with or without internal sources of dust release, nor does it apply to dusts of explosives which do not require atmospheric oxygen for combustion or to pyrophoric substances.
Requirements for pressurized enclosures with an internal source of dust release are not included in this standard. 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 IEC 61241-1-1.
Contents include
Scope Normative references Definitions Pressurization principle Protective gas Automatic disconnection Cleaning Discharge of protective gas General constructional requirements Electrical performance of apparatus Mechanical strength Apertures Electrical connections to enclosures Doors and covers Temperature limits Safety provisions and safety devices (except for static pressurization) Pressure- or flow-activated devices Electrical supply Switching off electrical supply Failure of pressurization Level of overpressure Possible sources of ignition Enclosed components Separate enclosures Safety provisions and safety devices for static pressurization Supply of protective gas Type of gas Second source of supply Temperature Verification and tests Type verification and tests Overpressure test Minimum overpressure test Leakage test Impact test Routine tests MarkingPressurized enclosure
Additional marking Pressurized enclosures protected by static pressurization Any other marking required Ducts for protective gas supply Installation requirements for pressurization Normative references to international publications with their corresponding European publications Coverage of Essential Requirements of EC Directives Examples of the static overpressure along the ducts and through a pressurized enclosure Example of the static overpressure in a pressurized electric rotating machine with fan Requirements on failure of pressurization Summary of protection requirements for enclosures
BS EN 61241-0:2006 replaces BS 6467-1:1985 an
d BS 6467-2:1988 which are withdrawn, and BS EN 50281-1-1:1999 which remains current as obsolescent until 1 October 2008.
