Fractional Vaporization of Ignitable Liquids: Flash Point and Ignitability Issues
P. Kennedy, A. Armstrong, 2016
Flashpoint, Flammability Testing, MSDS, Flammable Liquids, Paints, Solvents, Chemicals
Explosions or flash fires have occurred under circumstances in which suspected liquid fuel doesnot appear to explain the fuel source because of its high reported flash point. In some cases, science can explain the fuel source by the application of the principal of fractional distillation. Test can reveal that perceived ignitability of the original liquid is masked or underreported in material safety data sheets, labels, warnings, and product use instructions.
ABSTRACT
Explosions or flash fires have occurred under circumstances in which suspected liquid fuel does not appear to explain the fuel source because of its high reported flash point. These instances have posed a conundrum to the fire investigation profession. In some cases, science can explain the fuel source by the application of the principal of fractional distillation.
Commercial ignitable liquid products that are mixtures of various ignitable liquid components or ignitable and non-ignitable liquid components, with varying vapor pressures, can undergo fractional vaporization. In this process normal evaporation can separate the various ignitable or non-ignitable components, with the lighter end fraction (high vapor pressure) compounds evaporating first. When applied to flammable and combustible liquids, this process is sometimes referred to in the fire and explosion investigation profession as “weathering.” In these situations, the flash point of the remaining (not yet vaporized) liquid will be higher than the measured flash point of the “non-weathered” original liquid. It is possible for such mixtures to evolve concentrated vapors and be ignited even when the parent liquid is at a temperature below its reported flash point.
When applied to mixtures of ignitable and non-ignitable components in which the non-flammable component(s) evolve first, the process is referred to as “outgassing.” When the earlier evolving volatile compounds are generally considered “non-combustible,” such as halogenated hydrocarbons like methylene chloride, the flash point of the original liquid can actually initially increase and then decrease as vaporization continues.
In both situations, fractional vaporization can be extremely dangerous in that the perceived ignitability of the original liquid is masked or underreported in material safety data sheets, labels, warnings, and product use instructions.
In general, the process is observed more frequently in products that are designed to be used in coatings where the distribution or spreading over large surface areas is expected. Evaporation is an intended part of their application. These dangerous situations have been observed in products such as paints, stains, other surface coating materials, cleaning products, and strippers/removers.