NBN EN 61241-4 : 2007

1 Scope
2 Normative references
3 Definitions
4 Pressurization principle
   4.1 Protective gas
   4.2 Automatic disconnection
   4.3 Cleaning
   4.4 Discharge of protective gas
5 General constructional requirements
   5.1 Electrical performance of apparatus
   5.2 Mechanical strength
   5.3 Apertures
   5.4 Electrical connections to enclosures
   5.5 Doors and covers
6 Temperature limits
7 Safety provisions and safety devices (except for static
   pressurization)
   7.1 General
   7.2 Pressure- or flow-activated devices
   7.3 Electrical supply
   7.4 Switching off electrical supply
   7.5 Failure of pressurization
   7.6 Level of overpressure
   7.7 Possible sources of ignition
   7.8 Enclosed components
   7.9 Separate enclosures
8 Safety provisions and safety devices for static pressurization
9 Supply of protective gas
   9.1 Type of gas
   9.2 Second source of supply
   9.3 Temperature
10 Verification and tests
   10.1 General
   10.2 Type verification and tests
   10.3 Overpressure test
   10.4 Minimum overpressure test
   10.5 Leakage test
   10.6 Impact test
   10.7 Routine tests
11 Marking
   11.1 Pressurized enclosure
   11.2 Additional marking
   11.3 Pressurized enclosures protected by static pressurization
   11.4 Any other marking required
Annex A (normative) Ducts for protective gas supply
Annex B (normative) Installation requirements for pressurization
Annex ZA (normative) Normative references to international
         publications with their corresponding European
         publications
Annex ZZ (informative) Coverage of Essential Requirements of
         EC Directives

Presents 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.