Article,
Minimum ignition energy (MIE) -- a basic ignition sensitivity parameter in design of intrinsically safe electrical apparatus for explosive dust clouds
Journal of Loss Prevention in the Process Industries, 15 (4): 305--310 (July 2002)
DOI: http://dx.doi.org/10.1016/S0950-4230(02)00003-7
Abstract
In general terms, the purpose of any safety standard is to define
borderlines between safe and unsafe conditions, with reasonable safety
margins. The electrical spark ignition sensitivity of dust clouds
(MIE) varies over at least eight orders of magnitude. Therefore,
in the case of intrinsically safe electrical apparatus to be used
in the presence of explosive dust clouds, substantial differentiation
of the minimum requirements to prevent ignition by electrical sparks
is needed. The present paper proposes a method by which adequate
differentiation of required maximum permissible currents and/or voltages
in intrinsically safe electrical circuits to be used in explosive
dust clouds can be achieved. In essence, the concept is to use conservative
first-order ignition curves, calculated or estimated from the experimental
MIE value of clouds in air of the actual dust. Charts to be used
for design purposes are given in the paper. Internationally standardised
test methods allow MIE for clouds of any dust to be determined, at
least down to the range of a few mJ. There is, however, a need for
a supplementary method covering the range of lower energies, down
to 0.01 mJ.
