Extinguishment of Class B Flames by Thermal Mechanisms;Principles Underlying a Comprehensive Theory;Prediction of Flame Extinguishing Effectiveness

Abstract

Flame quenching by condensed or gaseous extinguishants and by external sources is exam ined. The quenching by extinguishants is due to heat-absorption sinks—dissociation, decompo sition, vaporization, and heat capacity. External quenching by water-cooled metal surfaces or by radiation to surroundings is shown to have common properties with internal quenching by extinguishant particles or molecules.

Flame-extinguishing mechanisms are effectively explained with thermal quenching concepts and a flame heat balance. New criteria for the extinguishment of Class B flames are postulated and, then, substantiated by a comprehensive analysis of extinguishment data for a large number of agents. Adiabatic limit temperatures were initially computed with the flame heat balance (Equation 1) using quenching quantities based on heats of formation of extinguishing sub stances at 298 K, but such limits and quenching quantities exhibited no systematic character. However, alternate limits and quenching quantities based on heats of formation of molecular parts (of extinguishing substances) exhibited exceptional ordering and internal consistency. This alternate analysis contributed to increased understanding of thermal mechanisms, concur rent exothermic reactions, and other processes involved in flame extinction. It is further demonstrated that the flame extinguishing effectiveness of dry chemicals and most gaseous halocarbons (agents containing C, H, F, CI, Br or I) can be reliably predicted from the additive properties of enthalpy, temperature, and quenching quantities. The flame-extinguishment model provides definitive criteria for selecting alternate agents with superior flame extinguishing

properties.

Get full access to this article

View all access options for this article.

References

Ewing, C.T. , Hughes, J.T. , & Carhart, H.W. , "The Extinction of Hydrocarbon Flames Based on the Heat-absorption Processes Which Occur in Them," Fire and Materials, 8, 1984, p. 148.

Ewing, C.T. , Faith, F.R. , Hughes, J.T. , & Carhart, H.W. , "Flame Extinguishing Properties of Dry Chemical: Extinction Concentrations for Small Diffusion Pan Fires," Fire Technology, 25, 1989, p. 134.

Ewing, C.T. , Faith, F.R. , Hughes, J.T. , adiabatic premixed flames," National Bureau of Standards , Special Publication 561, 1979, p. 1281.

Dewitte, M. , Vrebosch, J. and Van Tiggelen , A. , "Inhibition and Extinction of Premixed Flames by Dust Particles," Combustion and Flame , 8, 1964, p. 257

Dodding, R.A. , Simmons, R.F. and Stephens, A.J. , "The Extinction of Methane-Air Diffusion Flames by Sodium Bicarbonate Powders," Combustion and Flame ,, 15, 1970, p. 313.

Bulewicz, E.M. and Kucnerocwicz, B.J. , "The Action of Sodium Bicarbonate and of Silica Powder on Upward Propagating Flames in a Vertical Duct," Journal ofApplied Chemistry, 5, 1955, p. 510.

Lerner, W.R. and Cugliostro, D.E. , "Flame Inhibition by Halogen Halides; Some Spectroscopic Measurements," Combustion and Flame, 21, 1973, p. 315.

Holmsted, G.S. , Persson, H. , and Sawemark, G. , "Extinguishing Diffusion Flames with Dry Powder and Halon at Low Froude Numbers," Technical Report 1986: 24, PB 86-11365 , Statens Provningsanstdt, Boras, Sweden, 1986.

Botha, J.P. & Spalding, O.B. , "The Laminar Flame Speed of Propane/Air Mixtures with Heat Extraction from Flames," Proceedings of the Royal Society, A225, 1954, p. 71.

10.

Hertzberg, M. , Zlochower, I.A. , & Cashdollar , K.L. , "Volatility Model for Coal Dust Flame Propagation and Extinguishment," Twenty-first Symposium (Int.) on Combustion, Munich, West Germany, 1986, p. 325.

11.

Gaydon, A.G. and Wolfhard, H.G. , "Flames, Their Structure, Radiation, and Temperature," Chapman and Hall, LTD, London, 1970 , p. 87.

12.

Zeldovich, Ia. B. , "Theory of Flame Propagation," English Translation, N.A.C.A. Technical Memo 1282, 1948.

13.

Jarosinski, J. , "A survey of Recent Studies on Flame Extinction," Prog. Energy Combustion Sci., 12, 1968, p. 81.

14.

Hirst, R. & Booth, K. , "Measurement of Flame- Extinguishing Concentrations," Fire Technology, 13, 1977, p. 13.

15.

Miller, M.T. , "The Relevance of Fundamental Studies of Flame Inhibition to the Development of Standards for the Halogenated ExtinguishmentAgent Systems," American Chem. ical Society Symposium Series, 16, 1975, p. 64.

16.

Benson, S.W. , Thermochemical Kinetics ; Methods for the Estimation of Thermochemical data and Rate Parameters,_ Second Ed., John Wiley & Sons , New York, 1972.

17.

Davies, C.A. , Freedman, E. , Frurip, D.J. , Hertel, G.R. , Seaton, W.H. , & Treweek, D.N. , CHETAH; The ASTM Chemical Thermodynamic and Energy Release Evaluation Program , American Society for Testing and Materials, 1990.

18.

Lugar, J.R. , Private Communication, David Taylor Navy Ship R and D Center , 1981.

19.

Fire Master 100 Property Comparison, Great Lakes Chemical Corporation, P. O. Box 2200, Highway 52, N.W., West Lafayette, Indiana, 47906.

20.

Sheinson, R.S. , Penner-Hahn, J.E. & Indritz , D. , "The Physical and Chemical Actions of Fire Suppressants," Fire Safety Journal, 15, 1989, p.437.

21.

Robin , " Evaluation of Halon Alternatives," Proceedings of the Halon Alternatives Technical Working Conference, April 30-May 1, Albuquerque, New Mexico, 1991, p. 16.

22.

Heinonen, E.W. and Skaggs, S.R. , "Fire Suppression and Inertia Testing of Halon 1301 Replacement Agents ," Proceedings of the Halon Alternatives Technical Conference, May 12-14, Albuquerque, New Mexico, 1992, p. 213.

23.

Adcock. J.L. , Mathur, S.B. , Huang, H-Q. , Mukhopadhyay, P. , and Wang, B-H. , "Fluorinated Ethers; A New Family of Halons," International CFC and Halon Alternatives Conference, Baltimore, MD, Dec 3-5, 1991, p. 642.

24.

Fernandez, R.E. , "Dupont's Halon Alternatives Program," Proceedings of the Halon Alternatives Technical Working Conference, April 30-May 1, Albuquerque, New Mexico, 1991, p. 39.

25.

Sheinson, R.S. and Baldwin, S.P. , "Halon Replacement Extinguishant Concentration Requirements," Annual Conference on Fire Research, NIST 4924, Oct 13-15, Rockville, Md., 1992.

26.

Ford, C.L. , "An Overview of Halon 1301 Systems," American Chemical Society Symposium Series 16, 1975, p. 13.

27.

Nimitz, J.S. , Skaggs, S.R. , and Tapscott, R.E. , "Next-generation High-efficiency Halon Alternative," International CFG and Halon Alternative Conference, Baltimore, Maryland, 2-5 Dec., 1991, p. 632.

28.

"FE-232 Streaming Agent for Portable Applications," Dupont, Wilmington, Delaware.

29.

Friedman, R. and Levy, J.B. , "Inhibition of Opposed-jet Methane-Air Diffusion Flame. The Effects of Alkali Metal Vapours and Organic Halides," Combustion and Flame, 7, 1963, p. 195.

30.

Friedman, R. and Levy, J.B. , "Mechanisms of Fire Extinguishment of Alkali Metal Salts," Tech. Report No. 1, Proj. NR051-421, ASTM Doc. Nr. 260726, July, 1961.

31.

Skinner, G.B. , "Survey of Recent Research on Flame Extinguishment ," Monsanto Chemical Co., Dayton, Ohio, Tech. Doc. Report No. ASO-TR-61-408, Suppl. 1, Dec.,1962.

32.

Ewing, C.T. and Carhart, H.W. , "Effectiveness of Water Mist on the Extinguishment of Class B Flames ," In Publication.

33.

Hanauska, C. and Back, G. , "State-of-Art of Water Mist Fire Suppression," International CFC and Halon Alternatives Conference, Washington, D.C., 1993

34.

Holmstedt, G. , "Extinction Mechanisms of Water Mist," International Conference on Water Mist Fire Suppression

35.

Rosser, W.A. , Jr., Inami, S.H. , & Wise, H. , "The Effect of Metal Salts on Premixed Hydrocarbon-Air Flames,"Combustion and Flame, 7, 1963, p. 107.

36.

Ronney, P.D. , "Effect of Gravity on Hydrocarbon Flame Retardant Effectiveness, " Acta Astronautica, 12, 1985, p. 915.

37.

Simmons, R.F. and Wolfhard, H.G. , Transactions of the Faraday Society 51, 1955, p. 1211.

38.

Kucnerowicz-Polak, "The Behavior of some Extinguishing Powders under Different Experimental Conditions," Fire and Materials , 13, 1988, p. 303.