- Author
- Ewing, C. T. | Faith, F. R. | Romans, J. B. | Hughes, J. T. | Carhart, H. W.
- Title
- Flame Extinguishment Properties of Dry Chemicals: Extinction Weights for Small Diffusion Pan Fires and Additional Evidence for Flame Extinguishment by Thermal Mechanisms.
- Coporate
- Hughes Associates, Inc., Columbia, MD Naval Research Laboratory, Washington, DC
- Journal
- Journal of Fire Protection Engineering, Vol. 4, No. 2, 35-52, 1992
- Keywords
- dry chemicals | fleme extinguishment | extinction | diffusion flames | particle size | monnex (trademark)
- Abstract
- An experimental study was made of the extinguishment of a small n-heptane diffusion flame (25.5 cm dia. pan) by a number of dry-chemical powders - KHCO₃ NH₄H₂PO₄, Na₂B₄O₇ . 10H₂O, (NH₄)₂SO₄, K₂CO₃, K₄Fe(CN)₆ . 3H₂O, Na₂CO₃, K₂SO₄, NaCl, Na₂C₂O₄, K₂C₂O₄ . H₂O, and Monnex. The minimum weight of each required for flame extinction was determined as a function of particle size and sieve fraction. The sharp discontinuity previously observed is shown to be a common phenomenon. The experimental procedure was such that complete flame penetration was achieved for all particle sizes of each substance. Therefore, all results are latent, or maximum possible, effectiveness values. Flame extinguishment effectiveness is defined as the reciprocal of the extinction quantity. Substantial evidence, based on the new experimental data, is presented to support the propositions: (a) that particle sizes by sieve analysis below a limit size completely decompose and/or vaporize in the flame; and (b) that the observed optimum effectiveness at small particle sizes is reliably predicted by thermal mechanisms with a flame heat balance and a predictable limit temperature.