Flame extinguishment properties of dry chemicals: Extinction concentrations for small diffusion pan fires

Ewing, C. T.; Faith, Francis R.; Hughes, J. Thomas; Carhart, Homer W.

doi:10.1007/bf01041422

Cited by 54 publications

(26 citation statements)

References 4 publications

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“…The optimal small-particle fraction we observed behaved as it should for an aerodynamic effect and acted independently of the chemical type and density of the cartier and of both the type and physical size--if below 38 p m --o f the transported particles. As shown in Figure 4, the optimal proportion of any combination of can-ier and extinguishant substances included in this study (except for a Monnex carrier with reactive particle sizes above 38 pm) can be estimated from: (2) where X A is the optimal small-particle fraction for any extinguishant powder (0 to 38, 0 to 30, or 0 to 20 pm); S is the weight-mean particle size of the carrier powder, SA= J S dX; X is the weight fraction of the carrier particle at each particle size; and S is sieve size of particles. Monnex.…”

Section: Aerodynamic Drag and Optimal Flame Extingui Hing Effectivenessmentioning

confidence: 99%

Extinguishing class B fires with dry chemicals: Scaling studies

et al. 1995

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In a continuing study of flame extinguishment, ~, 2, 3, 4 we report on scaling studies for dry chemicals on larger heptane diffusion flames (0.29 m 2 and 2.32 m 2 pans). We demonstrate again that small particle sizes extinguish most effectively. Extinguishment is related to heat absorption by decomposing or vaporizing particles. We show that the limiting particle size for each dry chemical--that is, the maximum size which completely decomposes or vaporizes in the flame--is independent of flame size for the systems studied. We broaden and apply the concept of latent or maximum effectiveness 2,3 to pan fires of all sizes. Finally, we describe and characterize an aerodynamic effect in the transport of powders, where large particles with their higher momenturn entrain and drag smaller, more effective particles into the flame.We also show that extinction curves, involving the ratio of real-to-latent extinction weight and the proportion of small to large particles, have predictable shapes and predictable quantitative levels for most dry chemicals. We have developed the real-to-latent concept along with scaling equations for agent mixtures and for a wide spectrum of agents and particle sizes.

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Section: Aerodynamic Drag and Optimal Flame Extingui Hing Effectivenessmentioning

confidence: 99%

Extinguishing class B fires with dry chemicals: Scaling studies

et al. 1995

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“…However, the study did not report the ranges of particle sizes present in the Purple-K employed in these experiments and the powder-delivery system did not perform satisfactorily. The studies of Birchall (1970), Ewing et al (1989b), Ewing et al (1992), Beda et al (1993), and Mitani (1983 have concluded that initial particle size is a key parameter influencing the critical conditions of extinction of laminar premixed flames, turbulent premixed flames and turbulent diffusion flames. Dodding et al (1970) have reported on the amount of NaHCO J required in the oxidizer stream to extinguish counterflow methane-air diffusion flames.…”

Section: Introductionmentioning

confidence: 96%

“…ders may be suitable replacements for halons. Very few well-controlled laboratory experiments have been conducted previously to evaluate the effectiveness of dry powders in extinguishing flames (Ewing et al, 1989b;Ewing et al, 1992;Birchall 1970;Dodding et al, 1970;Milne et al, 1970). Milne et al (1970) compared the effectiveness of Purple-K (KHCO J powder) in extinguishing counterflow methane-air diffusion flames with that of CFJBr.…”

Section: Introductionmentioning

confidence: 99%

Experimental Studies of Flame Extinction by Sodium Bicarbonate (NaHC0₃) Powder

Trees

Seshadri

1997

Combustion Science and Technology

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An experimental study is conducted to evaluate the effectiveness of sodium bicarbonate (NaHCO,) powder in extinguishing flames burning hydrocarbon fuels. Experiments are performed on flames stabilized in a counterflow burner. Powders with various particle sizes are used. The minimum amount of NaHC0 3 powder required to extinguish these flames is rneasured and compared with previous measurements using CF 3Br and N 2 . The results show NaHCO, to be much more effective than CF,Br and N, in extinguishing the flames. The calculated equilibrium temperatures of NaHCOJ inhibited flames close to extinction show that NaHCO, inhibits the flame by chemical mechanisms.

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“…An experiment has been conducted by Curtis T. Ewing, the leading author, to study the relations between the particle size of dry chemicals and the extinguishment of Class B n‐heptane fire by K 3 HCO 3 , NH 4 H 2 PO 4 , Na 2 B 4 O 7 ·10H 2 O, (NH 4 ) 2 SO 4 , K 2 CO 3 , K 4 Fe(CN) 6 ·3H 2 O, Na 2 CO 3 , K 2 SO 4 , NaCl, Na 2 C 2 O 4 , K 2 C 2 O 4 ·H 2 O, and Monnex . It finds out that the smaller the sizes of the particles are, the more effective they will be in fire extinguishment.…”

Section: Introductionmentioning

confidence: 99%

Study on the relationship between the particle size distribution and the effectiveness of the K‐powder fire extinguishing agent

et al. 2018

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Summary The relationship between the particle size distribution and the extinguishing effectiveness of the new K‐powder fire extinguishing agent has been studied experimentally, to explore the reason of the great extinguishing efficiency exhibited by the new K‐powder fire extinguishing agent on Class B fire (liquid fuel fire). The results of the experiment showed that the extinguishing effectiveness increased along with the decrease of the particle size distribution. In addition, a sharp discontinuity appeared around the limiting size, about 40 μm. The powder with the particle size below 40 μm exhibited highly effective extinguishing with the minimum effective extinguishing concentration Cxr = 23 g·m−3, while the powder with the particle size above 40 μm exhibited little fire extinguishing efficiency. Compared with other fire extinguishing agents produced by different substances, the new K‐powder fire extinguishing has the bigger limiting size. That means, in the same particle size distribution, the new K‐powder fire extinguishing agent contains more highly effective powder than others contain, and is more effective.

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Flame extinguishment properties of dry chemicals: Extinction concentrations for small diffusion pan fires

Cited by 54 publications

References 4 publications

Extinguishing class B fires with dry chemicals: Scaling studies

Extinguishing class B fires with dry chemicals: Scaling studies

Experimental Studies of Flame Extinction by Sodium Bicarbonate (NaHC0₃) Powder

Study on the relationship between the particle size distribution and the effectiveness of the K‐powder fire extinguishing agent

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Flame extinguishment properties of dry chemicals: Extinction concentrations for small diffusion pan fires

Cited by 54 publications

References 4 publications

Extinguishing class B fires with dry chemicals: Scaling studies

Extinguishing class B fires with dry chemicals: Scaling studies

Experimental Studies of Flame Extinction by Sodium Bicarbonate (NaHC03) Powder

Study on the relationship between the particle size distribution and the effectiveness of the K‐powder fire extinguishing agent

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Product

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Experimental Studies of Flame Extinction by Sodium Bicarbonate (NaHC0₃) Powder