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Page Title:
Table 5-6. Summary of typical combustible dust hazardous atmospheres |
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|  Table 5-6. Summary of typical combustible dust hazardous atmospheres.a
Class
Division
Group Temperature, atmosphere
Covered
Measured
Limiting value
Eb
II Combustible 1 (Normally
Atmospheres containing
Devices not
Maximum external
Shall be less than
temperature in 40C
dust
hazardous)
combustible dusts regardless
subject to
ignition-temperature
of resistivity, or other combustible
ambient with a dust
dust but not more
dusts of similarly hazardous
(switches,
blanket
than:
characteristics having resistivity
meters)
of less than 102 ohm-centimeter
No overload:
E--200C (392F)
Fb
Atmospheres containing
Devices subject to
F--200C (392F)
carbonaceous dusts having
overload (motors,
G--165C (329F)
ohm-centimeter
Gb
Atmospheres containing dusts
Possible overload in
having resistivity of 108
operation:
ohm-centimeter
Normal:
E--200C (392F)
F--150C (302F)
G--120C (248F)
Abnormal
E--200C (392F)
F--200C (392F)
G--165C (329F)
2 (Not
F
Atmospheres containing
Lighting fixtures
Maximum external
normally
carbonaceous dusts having
temperature under
hazardous)
resistivity of 105 ohm-centimeter
conditions of use
G
Same as Division 1
a. Chart from Crouse-Hinds ECM Code Digest, 1990.
b. NEMA Enclosures Type 9 shall be used for Class II Groups E, F, or G.
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