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A probabilistic comparison of times to flashover in a compartment with wooden and non-combustible linings considering variable fuel loadsStudhalter, Jakob January 2012 (has links)
Prescriptive fire safety codes regulate the use of combustible room linings to reduce fire risk. These regulations are based on classification systems which designate materials according to their relative hazard when exposed to a standard fire scenario. However, no quantitative data sets on the fire risk of wooden lining materials exist which take into account relevant uncertainties, such as movable fuel loads in compartments.
This work is a comparative risk analysis on the influence of wooden linings on the time to flashover in a compartment, considering uncertainties in the fuel load configuration. A risk model is set up for this purpose using B-RISK, a probabilistic fire design and research tool currently under development at BRANZ (Building Research Association of New Zealand) and the University of Canterbury. The risk model calculates fire spread in a compartment between fuel load items and from fuel load items to combustible linings. Multiple iterations are performed considering varying fuel load arrangements and input values sampled from distributions (Monte-Carlo simulation).
The functionality and applicability of the risk model is demonstrated, comparing the model with experiments from the literature. The model assumptions are described in detail. Some of the model inputs are defined as distributions in order to account for uncertainty. Parametric studies are conducted in order to analyse the sensitivity of the results to input parameters which cannot be described as distributions.
Probabilistic times to flashover are presented and discussed for an ISO 9705 compartment considering varying movable fuel loads and different lining configurations. The fuel load is typical for a hotel room occupancy. Effects of suppression measures are not considered. It is shown that flashover occurs approximately 60 seconds earlier if walls and ceiling are lined with wooden materials than if all linings are non-combustible. This value refers to the 5th percentiles of the time to flashover, i.e. in 5% of the cases flashover has occurred and in 95% of the cases flashover has not (yet) occurred. Referring to 50th percentiles (median values), the difference is approximately 180 seconds.
Furthermore it is shown that with wooden wall and ceiling linings in approximately 95% of
the iterations flashover occurs, whereas with non-combustible linings 86% of the iterations lead to flashover. After 900 seconds, in 90% of the iterations flashover occurs if walls and ceiling are lined with wooden materials, and in 77% of the iterations if the linings are non-combustible. Using different wooden lining materials (non-fire retardant plywood, fire retardant plywood, and MDF) has no significant effect on the probabilistic times to flashover. Varying the fuel load energy density has an influence only when all linings are non-combustible and when the fuel load energy density is relatively low (100–200 MJ/m2).
This work contains recommendations regarding the further development of B-RISK, the research into the fire risk connected with wooden room linings, and suggestions regarding the further development of prescriptive fire safety codes.
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Flame Spread on Composite Materials for use in High Speed CraftWright, Mark T. 05 November 1999 (has links)
"The use of advanced materials in the construction of high-speed craft is becoming more commonplace. However, there are certain requirements set in the High Speed Craft Code (published by IMO) that restrict the use of materials based on results from full scale room fire testing (ISO 9705). An obvious benefit would be gained by simulating the results of these full-scale tests using bench scale data from the Cone Calorimeter and LIFT apparatus. A flame-spread algorithm developed by Henri Mitler at the National Institute of Standards and Technology was selected for implementation into the zone fire model CFAST. This algorithm was modified from its original form, so that it could simulate flame spread on wall/ceiling lining materials for both sidewall and corner scenarios, including ISO 9705 as prescribed in the High Speed Craft Code. Changes to the algorithm included geometry of flame spread across the ceiling, flame height, radiation exchange, ignition burner heat flux maps, and multiple pyrolysis zones. The new flame spread algorithm was evaluated against room corner test data from four different marine composite materials tested per ISO 9705."
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