Extinguishment of Diffusion Flames of Polymeric Materials by Halon 1301

Abstract

Halon 1301 flame extinction results are discussed for the combustion of polymethylmethacrylate (PMMA), eight composite materials, and carbon in the gas phase. Two types of combustion and flame extinction experiments were performed: (1) in the Factory Mutual Research Corporation (FMRC) flammability apparatus (50 kW scale) for PMMA and composite materials, and (2) in the FMRC electrical arc apparatus for carbon in the gas phase.For char forming composite materials, mass transfer from the surface was low, turbulent diffusion flames were not generated, and flame extinction occurred between 3 to 4.5% of Halon 1301, close to the value reported for the laminar diffusion flames of polymers. For non-charring PMMA, mass transfer from the surface was high, flames were turbulent, and flame extinction was found at about 6% of Halon 1301, contrary to the accepted value of about 4% for the laminar diffusion flames of polymers. With Halon 1301 the conditions for flame instability and extinction for combustion efficiency less than about 0.40, with significant increase in the amounts of products of incomplete combustion (such as CO and hydrocarbon), were in agreement with flame instability and extinction found for fuel-rich conditions inside well-ventilated laminar and turbulent diffusion flames, in ceiling layers of combustion products, in enclosure fires, in ventilation-controlled buoyant diffusion flames of polymers, and for flame extinction of heptane flames by water.Experiments in the FMRC electrical arc apparatus showed that in the gas phase combustion of carbon vapors generated in high energy arc, chemical heat release rate and combustion efficiency decreased with increase in Halon 1301. Downloaded from 408 At about 7.5% of Halon 1301, conditions were close to flame extinction and at 9.0%, oxidative pyrolysis of carbon was indicated. Concentrations of Br-and Fions, generated from the decomposition of Halon 1301, were also measured.Concentration of Br-ions was higher than the concentration of F-ions, although there are three F atoms and only one Br atom in Halon 1301. There was brown deposit on the walls of the apparatus with extensive corrosion of rubber gaskets, electrical fan, and other components.The techniques discussed in this article appear to be attractive for the assessment of flame extinguishability and corrosive characteristics of fire suppressants to replace ozone layer depleting Halons.

Combustion Characteristics of Materials and Generation of Fire Products

“…As the equivalence ratio increases and approaches values of 4.0 and higher, the combustion efficiency approaches values less than or equal to 0.40 (see Fig. 36.33), flames are extinguished, and nonflaming conditions become important [103,104]. Thus, the upper limit for the application of the extinguishing agent working in the gas phase is dictated by the equivalence ratio !…”

“…An example of incomplete combustion is given in Table 36.9, where chemical heat of combustion and combustion efficiency decrease as CO, carbon, and ethylene are formed at the expense of CO 2 and H 2 O with reduced O 2 consumption, a typical condition found in ventilation-controlled fires [103]. The upper limit of the combustion efficiency is 1.00, corresponding to complete combustion, and the lower limit is 0.46, corresponding to unstable combustion leading to flame extinction for combustion efficiency 0.40 [103,104]. 2 and CO generated are used.…”

Clean Agent Suppression of Energized Electrical Equipment Fires

“…FM Global Electrical Arc Apparatus: In some of the first work to look at the suppression of simulated electrically-energized fires, Tewarson and Khan [52,53] describe an experiment with suppression of a fire sustained by simulated electrical arcing. The FM Global Electrical Arc Apparatus exposed burning copper-coated carbon rods, which were undergoing high-energy electrical discharge, to an atmosphere of air and Halon 1301.…”

“…Using a similar apparatus, Tewarson and Khan [52,53] determined the amount of Halon 1301 required to suppress a PMMA sample exposed to an external radiant flux of 50 kW/m 2 . Taking a different approach, but again adding controlled amounts of energy to a polymer, Niemann et al [9,[54][55][56], and Driscoll and Rivers [57], describe tests in which a polymer sample is wrapped with Nichrome wire, which adds energy while the polymer burns.…”

“…Also, the distance from the wire to the polymer sample when the suppressant is added would be helpful for characterizing the heat flux to the polymer. To some extent, the test procedure is like other polymer burning tests with radiant heat addition, with a difference here being that the radiant source is a small wire at higher temperature (rather than a cone heater [11] or quartz heaters at lower temperature [17,53]), with a radiation intensity which has not been characterized. In addition to the radiant and convective heating of the polymer, the wire also provides an ignition source.…”