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Abstract
A dimensionless "flame acceleration factor" (FAF) based on an existing concurrent flame spread model that includes consideration of fuel burnout, has been used to evaluate the flame spread on thin rooflight (or skylight) materials. The FAF is a function of ignition time, buring duration and chemical heat release rate obtained from bench-scale tests in the ASTM E-2058 Fire Propagation Apparatus (FPA). A direct correlation between the FAF values and the extent of flame spread over eighteen thin polymeric rooflight materials (1.0 - 3.3 mm thick and and 1.4 - 4.0 kg/m sq areal density) measured in large-scale tests in te ASTM E108 Test Apparatus has been presented in this paper. In accordance with the model prediction, the flame spread remains within the proprane burner flame exposure region in E-108 tests when FAF <0. Flame spread is distinctly beyond the exposure source when the FAF >0, except for the case of some extensive melting thermoplastics. This model does not take the melting phenomenon into account. A calculation procedure for safe separation distance for rooflights that support flame spread has been developed. These separation distances are based on chemical heat release rate, critical heat flux for ignition and smoke yield of the material as measured in the FPA, the length of rooflight that is burnint at any given time and the flame height, and overall dimensions and orientation on potential rooflight targets. The calculated safe separation distance is found to be greater than one-half of the total flame height.
A dimensionless "flame acceleration factor" (FAF) based on an existing concurrent flame spread model that includes consideration of fuel burnout, has been used to evaluate the flame spread on thin rooflight (or skylight) materials. The FAF is a function of ignition time, buring duration and chemical heat release rate obtained from bench-scale tests in the ASTM E-2058 Fire Propagation Apparatus (FPA). A direct correlation between the FAF values and the extent of flame spread over eighteen thin polymeric rooflight materials (1.0 - 3.3 mm thick and and 1.4 - 4.0 kg/m sq areal density) measured in large-scale tests in te ASTM E108 Test Apparatus has been presented in this paper. In accordance with the model prediction, the flame spread remains within the proprane burner flame exposure region in E-108 tests when FAF <0. Flame spread is distinctly beyond the exposure source when the FAF >0, except for the case of some extensive melting thermoplastics. This model does not take the melting phenomenon into account. A calculation procedure for safe separation distance for rooflights that support flame spread has been developed. These separation distances are based on chemical heat release rate, critical heat flux for ignition and smoke yield of the material as measured in the FPA, the length of rooflight that is burnint at any given time and the flame height, and overall dimensions and orientation on potential rooflight targets. The calculated safe separation distance is found to be greater than one-half of the total flame height.
Date
8/2003
8/2003
Author(s)
M Khan; R Alpert; G Smith
M Khan; R Alpert; G Smith
Page(s)
37-46
37-46
Keyword(s)
plastic rooflight; flame spread; fire test; heat release; separation distance
plastic rooflight; flame spread; fire test; heat release; separation distance