Page 607 - Dust Explosions in the Process Industries

574 Dust Explosions in the Process Industries

Figure 8.10 Theoretical resistive ignition curves
based on the empirical equation I = 75,000
MIEo45 1/U2obtained by correlating resistive igni-
tion data for combustible gases and lycopodium
)o dust. The numbers attached to the straight lines
Voltage (V) are the respective MIE values in J.

8.6
SUMMARY AND CONCLUSIONS

8.6.1
”ATEX 1OOa” DIRECTIVE

Revision of the currentEuropean “Atex lOOa” Directive constitutes a first important step
toward an improved approach for the standardizationof electrical apparatusesto be used
in areas containing combustible dusts. The revised directive must differentiate clearly
between the way in which gas clouds, on the one hand, and dust clouds, on the other,
are generated and sustained in industrial practice; and it must include open and smol-
dering dust fires as hazards in their own right, in addition to dust explosions.
A revised “Atex 1OOa”Directivewill prevent excessive“harmonization”of standardsfor
electrical apparatusesfor combustibledusts, with establishedstandardsfor gases and vapors.

8.6.2
AREA CLASS1FICATION

International and European area classificationstandards, as well as the European “Atex
118a” Directive,must be revised to include combustibledust layers and deposits that can
give rise to open OF smolderingfires in the definitionof hazardous areas, irrespective of
whether the layers or deposits may become dispersed into explosive dust clouds.