Extinguishing Time Research Articles

Fire-extinguishing performance and mechanism of aqueous film-forming foam in diesel pool fire

A laboratory fire-extinguishing system was applied to investigate the effect of gas-liquid ratio on the fire-extinguishing performance of aqueous film-forming foam (AFFF) in diesel pool fire, and the proposed fire-extinguishing mechanism of AFFF is carefully analyzed. The results show that the AFFF foam possesses the shortest extinguishing time of 42s and lowest foam liquid consumption of 210 g at a gas-liquid ratio of 16, exhibiting the best fire-extinguishing performance. Chemical analysis of AFFF indicates that a proper gas-liquid ratio is beneficial to enhance the expansion ratio and drainage rate of AFFF that affect the cooling and covering effects of foam, thus achieving the optimum fire-extinguishing efficiency. Infrared thermal imaging analysis indicates that the main fire-extinguishing mechanism of AFFF is mainly ascribed to the superior cooling, covering and suffocating effects of foam against the transfer of heat and oxygen, thus effectively preventing the underlying fuel from further combustion.

Assessment of the Fire Dynamics Simulator for Modeling Fire Suppression in Engine Rooms of Ships with Low-Pressure Water Mist

Water mist-based fire-extinguishing systems are gaining acceptance for the protection of ship machinery spaces. The use of simulation tools presents a great potential for taking a performance-based design (PBD) approach to these fire scenarios. The Fire Dynamics Simulator (FDS) is the most frequently used and validated fire modeling software; however, studies of low-pressure water mist fire suppression modeling in ship engine rooms are rare. This paper contributes to the current literature by using the FDS to model a series of fire suppression scenarios defined by the International Maritime Organization (IMO) Circulars, including spray and pool fires with heptane and diesel oil, as well as exposed and obstructed fires. The simulation results are compared to data from full-scale tests conducted at recognized fire testing laboratories. Furthermore, an analysis of both the experimental and model uncertainties is carried out to assess the simulations performance. In general, a good agreement in compartment temperature evolution and fire extinguishing time is found for the modeled fire scenarios. The results support the application of FDS in a PBD approach for the design of water mist fire extinguishing systems for machinery spaces in ships. In this way, designers and engineers could model different machinery volumes and nozzles spacings that differ from those prescribed for a one story square engine room of the IMO, and, thus, predict the evolution of temperatures and extinguishing times for get the authorities approval.

Experimental study on fire-extinguishing efficiency of protein foam in diesel pool fire

In order to improve the fire-extinguishing performance of protein foam (PF) in diesel pool fire, a self-built foam extinguishing device was used to explore the influence of gas-liquid ratio, injection angle, driving pressure and liquid flow rate on the fire-extinguishing efficiency of PF. When the gas-liquid ratio is 20, the foam possesses the shortest extinguishing time of 200s and lowest extinguishing agent dosage of 260 g among the samples. Besides, the fire-extinguishing efficiency of PF varies with the change of injection angle and the order is 90° (vertical injection) > 45° (overlooking injection)> −45° (upward injection)> 0° (horizontal injection). In addition, as the increase of liquid flow rate and driving pressure, the fire-extinguishing efficiency of PF increases. In particular, the extinguishing time and the extinguishing dosage agent are reduced by 35.0% and 11.5%, respectively, with the PF flow rate of 50 L/h compared to the case of 20 L/h, which are reduced by 25.0% and 24.6%, respectively, with the driving pressure of 0.5 MPa compared to the case of 0.3 MPa. The factor of fire-extinguishing efficiency of PF was investigated from the experimental aspects, which provided a basis for the application of PF in firefighting.

Experimental study on vertical rigid and flexible polyurethane fire suppression using water spray

A series of vertical fire suppression experiments on rigid polyurethane (RPU) and flexible polyurethane (FPU) with/without water spray were conducted in a standard chamber. A new video processing method was developed to determine the pyrolysis front position of wind-aided flame. Averaged flame height, carbon monoxide/hydrogen cyanide concentration, view factors, and extinguishing time were determined with operating pressure varying from 0.15 MPa to 0.4 MPa. The experimental study showed that water spray would suppress RPU/FPU fire mainly by fuel surface cooling. Furthermore, the perfect water spray pressure for RPU/FPU fire suppression was 0.3 MPa and the corresponding water application rate was 0.7511 mg/(cm2·s).

Fire suppression efficiency of water mists containing organic solvents

This paper investigates the fire-suppression ability of water mists containing various organic solvents—ethanol, 1-propanol, tetrahydrofuran, methyl acetate, and 1,2-dimethyoxyethane—which form minimum-boiling azeotropic mixtures with water. The key factors influencing the suppression efficiencies of the solvent-containing water mists were elucidated by measuring the evaporation rates, flash points, extinguishing times, and spray properties (droplet-size distribution, spray mass-flux density, and droplet velocity) of the mists. Suppression trials indicated that (i) heptane pool fires can be extinguished by aqueous solutions of ethanol and 1-propanol at solvent concentrations of 1.0–20.0 vol%, but are not consistently extinguished by the other three solvents, and (ii) the extinguishing times of aqueous ethanol and 1-propanol (despite their high flammability) are significantly shorter than those of a wet chemical (i.e., conventional fire-extinguishing agent). In a stepwise regression analysis, the fire-suppression abilities of water mists containing ethanol and 1-propanol were positively related to the spray flux density, spray velocity, and flash point, enabling an estimation of the extinguishing times. A correlation analysis demonstrated that a faster evaporation rate improves the fire-suppression ability. The results confirmed that ethanol and 1-propanol are effective additives to fire-extinguishing water mists. The study findings provide useful insights into the development of new water-mist fire suppressants, potentially making a large contribution to the reduction of fire-related fatalities and economic losses in industries.

Investigation on characteristics of arc extinguishing time of a new lighting protection gap for transmission lines

The present research envisages the development of a novel arc extinguishing lightning protection gap in pursuit of reducing the lightning trip-out rate and accident rate. In the developed setup, the jetting stream arc extinction lightning protection gap device was used for transmission line. When this transmission line was struck by lightning and the lightning surge was going to break down the gap, the arc extinguishing lightning protection gap immediately jetted out sufficient electronegative gas flow that quickly cut off the arc and effectively prevented the insulator from being damaged by the arc. Furthermore, when the line was attacked by lightning, the generated overvoltage instantaneously broke the gap that was parallel to the insulator string, so that the lightning current was oriented to the earth from the gap. Simultaneously, it triggered the gas generator and generated a high speed stream, then extinguished the frequency continuous current arc rapidly, thus effectively reducing the rate of line trip to ensure the reliability of power supply. We used a high-speed camera and ordinary camera that automatically captured the process of the jetting stream arc in the extinction lightning protection gap device, while extinguishing the 1kA power frequency arc. The image of the high-speed camera indicated that the power frequency arc of 1kA was quenched in 10 ms before the relay protection action of the test loop, which made that the overhead line lightning flashover but the circuit breaker did not trip. Thus, a reduction in the rate of lightning trip was observed by the developed setup, and it has an immense potential for application at the transmission lines of China.

Fire suppression performance of a new type of composite superfine dry powder

SummaryTo enhance the performance of existing dry powders and ensure process security, a new type of dry powder based on ammonium dihydrogen phosphate (NH4H2PO4) was prepared. The prepared composite superfine dry powder was denoted as NH4H2PO4/zeolite composite in this paper. The effectiveness of commercial ABC dry powder, superfine dry powder, and the NH4H2PO4/zeolite composite in fire suppression were compared in a small‐sized fire‐extinguishing chamber. Laboratory‐scale tests showed that the NH4H2PO4/zeolite composite had considerably superior fire‐extinguishing efficiency to that of commercial ABC dry powder and superfine dry powder, along with shorter average extinguishing time and less average mass of powders consumed. In addition, the NH4H2PO4/zeolite composite also displayed much improved toxic gas suppression ability. The physical and chemical characteristics of commercial ABC dry powder, superfine dry powder, and the NH4H2PO4/zeolite composite were characterized using a range of techniques of laser particle size analysis, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. Based on the analysis results, the improved fire suppression performance of the NH4H2PO4/zeolite composite can be ascribed to smaller particle size, larger surface area, and a special chemical decomposition process.

Gasoline fire extinguishing by 0.7 MPa water mist with multicomponent additives driven by CO2

Water mist has a good three-dimensional cooling effect; however, its extinguishing effect on oil fires is less than that of foam extinguishing agents. This study aimed to enhance the gasoline fire extinguishing efficiency of water mist by adding KBr, Tween-80, and a dissolved CO2 solution as multicomponent additives with different suppression mechanisms. The fire extinguishing time was measured to evaluate the extinguishing efficiency of different additives. The test showed that KBr mainly works near the flame base and makes an unstable gap between the flame base and the gasoline surface; the Tween-80 mist and dissolved CO2 mist make the flame height lower under the test conditions. By analyzing the different extinguishing phenomena, temperature and efficiency of each additive, the multicomponent additives were proposed to enhance the extinguishing efficiency based on different mechanisms. The results showed the water mist with KBr, Tween-80 and dissolved CO2 resulted in a remarkable improvement in the ability to extinguish a gasoline fire compared with pure water mist.

Fire-Extinguishing Efficiency of Superfine Powders under Different Injection Pressures

Ammonium phosphate fire-extinguishing agents are one of the best substitutes for halon in many powder media. Here, 11 μm median diameter ammonium phosphate ultrafine dry powder was used as a fire-extinguishing medium. The fire-extinguishing performance of ultrafine powder under different pressures was studied by analyzing fire-extinguishing time, amount of extinguishing agent, and temperature during the fire-extinguishing process. The results show that the fire-extinguishing performance of the ultrafine powder is improved with increasing injection pressure. Finally, we used FDS software for fire simulation to study the influence of injection pressure on the extinguishing agent. The results show that the extinguishing time is shortened with increasing injection pressure. From 0.2 MPa to 1.0 MPa, the extinguishing time decreases from 34 seconds to 4 seconds.

Analysis of the fire-extinguishing effect and the weakening of flame intensification of nonionic liquid water mist*

ABSTRACTThe determination of a water mist additive is important to weaken the flame enhanced by water mist, which affects the safety and applicability of the water mist fire-fighting technology to a certain extent. Based on the theory of physical chemistry, in this study, a water mist additive, that is, a nonionic liquid alkyl phenol epoxide (APE) condensate to weaken the flame intensification and systematically perform an experimental study on extinguishing the fire in oil pool with nonionic liquid water mist. The results show that the nonionic liquid water mist has better atomization parameters. The extinguishing time and the maximum temperature are all decreased with the increase of nonionic liquid mass fraction under the action of nonionic liquid water mist. The maximum CO volume fraction and the time to maintain a high CO volume fraction in fire flue gas decreases with the increasing nonionic liquid mass fraction. The minimum O2 volume fraction and the recovery rate from this minimum value to the normal value increases with increasing nonionic liquid mass fraction. The nonionic liquid water mist can weaken the flame intensification and extinguish the oil pool fire better than pure water mist. This is because the suspended air and water bubbles formed after the spraying of the nonionic liquid water mist can block heat radiation, cutting off the oxygen supply and isolating the contact of combustibles with oxygen. In addition, owing to high temperature, surfactant and water molecules linked by hydrogen bond ether group rupture, resulting in reduced HLB, thus enhancing the ability to trap hydrocarbon molecules and capture H• and OH• radicals in the chain reaction.

Synthesis and characterization of a novel surfactant used for aqueous film-forming foam extinguishing agent

Fluorocarbon surfactants are a key ingredient of aqueous film-forming foam (AFFF) extinguishing agent. As is well known, the most widely used fluorocarbon surfactants are perfluorooctane sulfonates (PFOS) and theirs derivatives. However, PFOS has been restricted due to its drawbacks such as toxicity, bio-accumulation and resistance to biodegradation, etc. Fortunately, the toxicity and bio-accumulation can be neglected if the fluorocarbon chain contained in the surfactants is less than or equal to 4. Therefore, synthesis of novel short fluorocarbon chain (≤ C4) surfactants has become a very important way to solve this problem. A novel fluorocarbon surfactant based on perfluorobutyl had been synthesized and its chemical structure had been confirmed by Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance (NMR) and 19F NMR measurements in this work. Since the fluorocarbon surfactant mixed with appropriate hydrocarbon surfactant can reduce its dosage and cutting production costs, the surface tension and the critical micelle concentration (CMC) of the synthesized fluorocarbon surfactant and its equimolar mixtures with CH3(CH2)5NaO3S had been studied. The results show that CMC and the surface tension at CMC (γCMC) of the pure surfactant were 21.68 mmol/L and 17.08 mN/m, while the minimum surface tension and CMC could reach to 16.58 mN/m and 7.72 mmol/L for the mixed system, respectively. In addition, the foamability, spreadability and extinguishing performance of the equimolar mixed system has also been investigated. The foam expansion and the 25% drainage time are 9.8 and 313 s, respectively, and the extinguishing times are less than 65 s while the burnback times are more than 14.50 min for all the hydrocarbon oils studied in this work, indicating a great application prospect in AFFF.

Castor‐oil derived nonhalogenated reactive flame‐retardant‐based polyurethane foams with significant reduced heat release rate

ABSTRACTNational Fire Protection Association encounters one structural fire every 66 s. Rigid polyurethane foam is one of the principal components used in constructional and household applications. In this work, a reactive flame retardant (FR) was synthesized using a facile one‐step thiol–ene reaction by reacting mercaptenized castor oil (MCO) and diethyl allyl phosphonate (DEAP). The obtained MCO–DEAP polyol was used for the preparation of polyurethanes having different weight percentages of phosphorus (P). Addition of FR polyol showed no adverse effect on the cellular structure of the foams and maintained the compressive strength. All the foams showed closed cell content greater than 95%. Horizontal burning test (HBT) was performed before and after the migration test to understand the stability of the FR within the foams. Foams showed no relative weight loss before and after the migration test and maintained equivalent results for HBT. For 1.5 wt % P foams, low extinguishing time of 3 s and weight loss of 4% was observed. The cone calorimeter test showed a reduction in the peak heat release rate from 313 to 158 kW m−3, the total heat release from 18 to 8 MJ m−2, and O2 consumption from 12 to 6 g. Our results suggest that MCO–DEAP polyol could act as an essential FR for rigid PU foam ensuring fire safety. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47276.

PROPERTIES OF COMPOSITE BASED ON HIGH DENSITY POLYETHYLENE/ETHYLENE VINYL ACETATE BLEND AND A NOVEL ORGANIC MODIFIED WASTE GYPSUM

In this study, waste gypsum (WGS) was used as the filler in blend of high density polyethylene (HDPE) and ethylene vinyl acetate copolymer (EVA) in order to improve the flame resistance of this composite. After modification by ethylene bis stearamide (EBS), modified gypsum (EGS) at various contents was dispersed into HDPE/EVA blend by melt-mixing method to obtain EGS/HDPE/EVA composites. The IR analysis of the EGS showed the interaction between EBS and gypsum. The difference in morphology of HDPE/EVA/EGS and HDPE/EVA/OGS composites was also observed in SEM images. By adding EGS and small amounts of flame retardant additives such as ammonia polyphosphate and zinc borate, the thermal stability and the flame resistance of HDPE/EVA/EGS composites have improved and classified at V2 grade of UL94 standard. Moreover, the second self extinguishing time (t2) of EGS composite is shorter than that of unmodified gypsum (OGS) composite because of the quality char forming after the fist burning and it plays a role as thermal barriers to protect material from heat of the second ignition. About mechanical properties, both tensile strength and elongation at break of the composite decreased with increasing the gypsum content and flame retardant additives because of filler aggregation.

Assessment of a clean and efficient fire-extinguishing technique: Continuous and cycling discharge water mist system

Abstract As the succedaneum of halon extinguishing agent, water mist is absolutely green, harmless, and sustainable which does not cause the ozone depletion. In order to investigate the fire extinguishment performance of water mist system with both continuous and cycling discharge modes, a series of full-scale pool fire suppression experiments (including gasoline and diesel) with the two discharge modes were conducted in a confined compartment (3 m × 3 m × 3 m) under different mechanical exhaust rates. Some characteristic parameters, such as the smoke temperature, radiative and total heat flux, fire-extinguishing time, and carbon monoxide and oxygen concentration under the influences of both water mist and mechanical ventilation, were obtained, and their variation mechanisms were analyzed in detail. The experimental results show that pool fires could be extinguished more quickly using cycling water mist with shorter turn-off time. The reduction coefficient of carbon monoxide concentration increases exponentially, while the extinguishing time of both gasoline and diesel pool fires decreases first and then increases with the ventilation rate. With cycling discharge mode, the smoke temperature and heat flux both fluctuate with alternate activation of water mist. The application of cycling discharge mode substantially improves the fire suppression efficiency, especially in the condition that the pool fire is difficult to extinguish utilizing continuous discharge mode. The cycling discharge water mist system can be applied in some ventilated spaces when mechanical ventilation is unavoidable, and is helpful for personnel security and evacuation.

Cable Insulation Failure Probability Analysis in Nuclear Power Plant Distribution Cabinet Fire

This paper takes the nuclear power plant power distribution cabinet fire as example and adopts FPRA methodology to analyse the failure probability of cable insulation at contiguous region among distribution cabinet. The influential factor that fire brigade dealt with the fire in the spot is considered in this research. The cumulative distribution function of fire brigade’s arriving and extinguishing time is conducted discretization, confirming the sample statistics of areas and establishing the numbers of cable insulation failure events of distribution cabinet fire. Combining failure predicted model of cable insulation and calculating the failure situation of cable insulation under each of fire background, obtaining the probability that cable insulation failure events among the distribution cabinet fires. The results show that the HRRmax of distribution cabinet fire in term of case scenario is 750 kW, the cable never happens the insulation failure; when the distribution cabinet fire is 1000 kW, the possibility of cable insulation failure is 12.6%.

Experimental Study on Fire Extinguishing Properties of Compound Superfine Powder

Abstract In this paper, the existing fire extinguishing powder was improved with magnesium hydroxide as additive to prepare the compound superfine powder. And the fire extinguishing performance of the compound powder was tested by the modified cup-burner, being compared with the commercial dry powder and the superfine powder. The advantages of the compound superfine powder were explained from the aspects of minimum extinguishing concentration, temperature and extinguishing time. The experimental results showed that the minimum extinguishing concentration of compound superfine powder was much lower than the other two, and the temperature drop rate was greater in the process of suppressing flame. Although the compound superfine powder was slightly lower than the superfine powder in the average extinguishing time, the standard deviation results showed that the composite powder had better stability. In addition, the experimental results showed that the fray-out of flame was very fast and the time only accounted for 17.5% in the fire extinguishing process.

Production of charcoal briquettes from biomass for community use

This article reports of a study on the production of charcoal briquettes from biomass for community use. Manufacture of charcoal briquettes was done using a briquette machine with a screw compressor. The aim of this research was to investigate the effects of biomass type upon the properties and performance of charcoal briquettes. The biomass samples used in this work were sugarcane bagasse (SB), cassava rhizomes (CR) and water hyacinth (WH) harvested in Udon Thani, Thailand. The char from biomass samples was produced in a 200-liter biomass incinerator. The resulting charcoal briquettes were characterized by measuring their properties and performance including moisture content, volatile matter, fixed carbon and ash contents, elemental composition, heating value, density, compressive strength and extinguishing time. The results showed that the charcoal briquettes from CR had more favorable properties and performance than charcoal briquettes from either SB or WH. The lower heating values (LHV) of the charcoal briquettes from SB, CR and WH were 26.67, 26.84 and 16.76 MJ/kg, respectively. The compressive strengths of charcoal briquettes from SB, CR and WH were 54.74, 80.84 and 40.99 kg/cm2, respectively. The results of this research can contribute to the promotion and development of cost-effective uses of agricultural residues. Additionally, it can assist communities in achieving sustainable self-sufficiency, which is in line with our late King Bhumibol’s economic sufficiency philosophy.

Assessment of extinguishing efficiency of hybrid system using water mist and inert gas during class A fires

Fixed hybrid fire extinguishing system, a new technology used in fire protection all over the world in the last years, was discussed. A four-head twin pipe system supplied with water mist and inert gas (air or nitrogen) was applied. A pile of 50 pine wood boards was used as a combustible material (class A fire). It was located in the corner of the compartment while the nozzles were mounted symmetrically in the centre (volume suppression). The extinguishing processes differing in the proportion of water mist to gas were analysed. The extinguishing time was taken as the most important parameter indicating the extinguishing efficiency. The impact of water flow on extinguishing process was discussed. The clear dependence of extinguishing time on the water/gas ratio was proven. The best performance of the hybrid system at water flow 3 dm3/min and nitrogen as inert gas was observed. The results obtained during experiments can be useful in developing new international standards e.g. NFPA.

Elaboration of New Types, Environmentally Safe Fire- Extinguishing Powders and Establish the Conditions of Extinguish Optimum and Effective Use of Such Powders

The aim of the presented investigation is the development of technology for production of novel, halogen-free, environmentally safe, highly efficient fire-extinguishing powders based on local mineral raw materials, which does not require modification with expensive, halogen-inclusive, hydrofobizing additives, providing low-cost production of fire-extinguishing powders in comparison with imported analogues. The optimal dispersity was selected in such way, that caking capacity be minimal and a homogeneous action of combustion products on the flame as well as a heterogeneous inhibition of combustion process must take place. The evaluation of powder efficiency is carried out with consideration of the both effects. Experimental data confirm that the developed fire-extinguishing powders are characterized with high performance characteristics, as well as high fire-extinguishing capacity. At the same time, it should be noted, that the efficiency of the obtained powders is practically the same as of standard imported powders, but do not contain any halogens, is environmentally safe and 1.5-2 times cheaper than the imported analogues. For obtained powders, the conditions of extinguish optimum and effective use of powder are stated. Optimum extinguishing condition means the selection of optimum intensity of powder supply into seat of fire when minimum consumption of powder provides fire extinguishing in minimum time. Thus, in order to determine optimum conditions of extinguishing it is necessary to study the dependence of powder specific consumption and extinguishing time to supply intensity. For our powders optimum condition of extinguish is: powder supply intensity I-0.6-1.0 kg/m2sec to fire center when powder specific consumption does not exceed G=0.8-1.2 kg/m2. Therefore, we can assume that the use of fire-extinguishing powders of our preparation is possible at extinguishing all types of fires over ground, as well as, underground constructions and does not need additional antiseptic measures.

New classification of foaming agents for fire extinguishing

Extinguishing fires of petroleum products during emergency spill at industrial facilities of capital construction, transport, gas stations and the destruction of oil tanks is most effective when using foamers. Classification of foaming agents intended for extinguishing of fires of oil products, which is based on the structure of spreading coefficient of water foam-forming solution over hydrocarbon surface is presented. Results of experimental studies using various foaming agents with different structure of spreading coefficient are given. It is determined which of homologs of a number of sodium primary alkylsulfates differ in foaming capacity and fire extinguishing efficiency. It is revealed that decrease of interfacial tension value leads to reduction of extinguishing time of a heptane flame.