Citation

Babrauskas V, Britton LG. Fire Technol. 2018; 54(1): 37-55.

Copyright

(Copyright © 2018, Holtzbrinck Springer Nature Publishing Group)

DOI

10.1007/s10694-017-0671-1

PMID

unavailable

Abstract

Database tabulations of minimum explosion concentration MEC for dust clouds often contain data values that are extremely low, i.e., 30 g m−3, or lower. Such values invariably represent measurement or analysis errors, often due to inadequate dust uniformity in the test vessel. There are only two organic vapors with MEC values below 30 g m−3, and it is physically implausible that either stationary or randomly moving dust clouds would be more efficient in combustion than vapors. Combustion of dust clouds will have all of the types of heat losses that occur with burning of vapor clouds, but have additional sources of heat losses, particulate radiation and endothermic pyrolysis, not present for vapors (dusts of unstable chemicals are not considered in this paper). Thus, MEC values for dust clouds necessarily have to be higher than for vapors. Other sources of error for dust cloud MEC values have also been identified. These include incorrect data analysis, unrealistic pressure-rise criteria for what constitutes an explosion, and excessive igniter energies used in some apparatuses. German data based on VDI 2263-1 should be post-corrected for statistical treatment errors. But no specific correction exists for low reported MEC values due to mixture nonuniformity or inappropriate pressure criteria. It is recommended that any reported MEC values below 65 g m−3 for cellulosic agricultural dusts, below 35 g m−3 for any other organic dusts, and below 55 g m−3 for dusts of metals or non-metallic elements be expunged as likely to be incorrect. Even at higher MEC values, there is likely to be a systematic bias in the data and this needs to be considered in longer-range research. ASTM E1515 offers more reliable testing and data analysis procedures than does VDI 2263-1 and is preferred.

Language: en

Keywords

Dust clouds; Dust explosions; Experimental errors; Minimum explosible concentration (MEC); NFPA 68; Test errors