PR0535342 - Laserfiche WebLink

Home Browse Search

SCIENTIFICALLY EVALUATING CODE REQUIREMENTS A great part of our knowledge concerning Medium Scale Test fire prevention in tire piles is based on the fire protection engineers' mathematical The medium scale test burn was formulas derived from their understandiny, conducted in a combustion chamber. This of burning structures. For example, the series of experiments was accomplished in separation distances in the table included a gas burner which measured 8' wide by in NFPA 231D is based upon separation 12' long by 6' 8" high. The combustion distances between buildings and other chamber was constructed of porus mineral exposures. fiber so that the propane gas could diffuse through the top surface. This feature of A fundamental question of validity arises. the combustion chamber reduced, but did A pile of scrap tires is completely not completely eliminate the convective different in chemistry, composition, build-up of heat from the propane burner density, geometry, heat content, ignition in the chamber itself. Heat flux characteristics, flame spread, and other transducers (gardon type) were placed features than buildings. How valid then above and below the tire. A controlled are these separation distances? That is temperature was provided by a gas burner the topic of research in progress at the placed one foot from the surface of the Fire Research Laboratory at the tire. Radiant heat was transferred to the University of California, Berkeley under tire until ignition took place. direction of Professor Brady Williamson. Preliminary test show that the tire ignited The character of burning scrap tires in ten minutes with a radiant heat flux of depends on many factors, but among the 35KW/m2. At a higher heat flux of most important are the ignition 43KW/m2, the tire ignited in about eight characteristics of tires in various physical minutes. The trend of the data suggests arrangements and geometries. The task of that as the heat flux is increased to 50 Dr. Williamson is to measure the KW/m2 the ignition time would be less temperature and heat flux necessary to than one minute. Professor Williamson both ignite and sustain ignition of a scrap estimates that the heat flux in these tire within a given amount of time. experiments is twice that necessary to ignite wood in the same time frame. Heat flux measures the rate of energy radiated from burning objects. The value of heat flux is expressed as kilowatts per meter squared. The experiments measure the amount of energy (kilowatts) radiated against the surface area (m2) of an object over a period of time. These experiments are accomplished through a series of medium and large scale test burns. 31