Citation

Dlugogorski BZ, Hichens RK, Kennedy EM. Fire Safety J. 2002; 37(1): 53-65.

Copyright

(Copyright © 2002, Elsevier Publishing)

DOI

unavailable

PMID

unavailable

Abstract

This paper determines the flammability properties of two hydrocarbon blends, natural gas and propane-butane refrigerant, mixed with CF3I and C3F7 H inerting agents. Four flammability envelopes are obtained allowing the determination of the minimum inerting concentrations and the maximum hydrocarbon to suppressant weight ratios for formulating non-flammable hydrocarbon refrigerants. These ratios are calculated from the slopes of lines drawn from the origin and tangent to the lower branches of the flammability envelopes. The flammability measurements are conducted using a tubular flow burner. The apparatus is convenient to operate, yields reproducible results without repetitive testing necessitated by explosion vessels. More importantly, the tubular flow burner applies a clear criterion for extinction avoiding the innate problems of the explosion vessels, which relate to the strength of the ignition source and the vessel size. The results indicate that it is not possible, using CF3I or C3F7 H, to formulate a refrigerant mixture with a substantial hydrocarbon content. Specifically, inertion of the propane-butane blend considered in this study demands 87.7% and 94.2% by weight of CF3I and C3F7 H, respectively. CF3I displays similar inerting properties to those of CF3Br. The higher inerting requirement for C3F7 H stems from the nature of this agent to decrease the lower flammability limit of the hydrocarbon blends.