Bench‐scale studies of poly(vinyl chloride) fires with water mist

Bench‐scale tests to study the effect of water mist on burning solid poly(vinyl chloride) (PVC) were carried out with a cone calorimeter. Water mist was discharged from a small nozzle under two operating pressures, 0.4 and 0.7 MPa. The corresponding water flow rates were 103.5 and 134 mL/min, respectively. The cone angle of the discharged water spray was 90°, and the volume mean diameter of the mist was about 90 μm. The results were useful in understanding the effects of discharging water mist to suppress the diffusion flame from burning PVC. The reignition process also was studied. The testing method was appropriate for studying the interaction between water mist with smaller droplets and the diffusion flame in a confined space. There, the combined effects of oxygen displacement, gas phase, and fuel surface cooling were the key extinguishing mechanisms. The critical water mist application rate on burning PVC under different thermal radiative heat fluxes was able to be determined. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2520–2527, 2006     

Improving the performance of fluoroprotein foam in extinguishing gasoline pool fires with addition of bromofluoropropene

The fluoroprotein foam is one of the most widely used fire suppressants for its low cost, low toxicity and biodegradability. However, its fire extinguishing performance is limited. In this article, fluoroprotein foam was combined with a clean and degradable fire suppressant of 2‐bromo‐3,3,3‐trifluoropropene (BTP) to improve its fire extinguishing efficiency. Laboratory scale suppression experiments on gasoline pool fires were conducted in a 27 m³ confined space. An optimized volume flow ratio of air to foam solution was found out first to acquire fluoroprotein foam with best fire extinguishing efficiency; then varied amounts of BTP were added to the foam at the optimal flow ratio for performance examination. Results demonstrated: at the optimized volume flow ratio of air to foam solution of 9 and the volume flow ratio of BTP to foam solution of 3.75%, a superior fire extinguishing performance was achieved with the fire extinguishing time reduced by 43% in comparison to that without any BTP added. The fire suppression mechanism of the foam with BTP additive was discussed based on established fire suppression theories and experimental results. Copyright © 2014 John Wiley & Sons, Ltd.     

Assessment of fire protection performance of water mist applied in exhaust ducts for semiconductor fabrication process

Fume exhaust pipes used in semiconductor facilities underwent a series of fire tests to evaluate the performance of a water mist system. The parameters considered were the amount of water that the mist nozzles used, the air flow velocity, the fire intensity and the water mist system operating pressure. In order to make a performance comparison, tests were also performed with a standard sprinkler system. The base case served as a reference and applied a single water mist nozzle (100 bar operating pressure, 7.3 l/min water volume flux and 200 µm mean droplet size) installed in the pipe (60 cm in diameter) subjected to a 350°C air flow with an average velocity of 2 m/s. In such a case, the temperature in the hot flow dropped sharply as the water mist nozzle was activated and reached a 60°C saturation point. Under the same operating conditions, four mist nozzles were applied, and made no further contribution to reducing the fire temperature compared with the case using only a single nozzle. Similar fire protection performances to that in the base case were still retained when the exhaust flow velocity increased to 3 m/s and the inlet air temperature was increased to 500°C due to a stronger input fire scenario, respectively. Changing to a water mist system produced a better performance than a standard sprinkler. With regard to the effect of operating pressure of water mist system, a higher operating pressure can have a better performance. The results above indicate that the droplet size in a water‐related fire protection system plays a critical role. Copyright © 2005 John Wiley & Sons, Ltd.     

Heat sensing manikin test probe

A manikin test probe has been developed to simulate the thermal behaviour of human skin when exposed to thermal conditions likely to occur in fires. The threshold for second‐degree burn injuries is evaluated from the temperature readings using a damage integral. The probe has been exposed to different radiation fluxes and the calculated damage criterion for second‐degree burn injuries is in agreement with data from the literature on human skin and pig skin. Probes mounted on a manikin have been used to assess how the extent of burn injuries develop as a function of time on a fully dressed pilot inside a military aeroplane surrounded by a large pool fire. In another scenario burn injuries for humans inside a fire room are assessed when a super‐heated water mist extinguishing system is activated. Copyright © 2000 John Wiley & Sons Ltd.     

Performance evaluation of bromofluoropropene in extinguishing liquid fuel spray fires

Liquid fuel spray fires emit high radiation heat fluxes, posing great threat to humans. The study of suitable agents and techniques for extinguishing this particular type of fire is of great importance. In this study, degradable 2‐bromo‐3,3,3‐trifluoropropene (BTP), a new clean fire extinguishing agent, was tested for its effectiveness in extinguishing three types of liquid fuel spray fires, namely diesel, gasoline, and ethanol. Bench‐scale experiments were conducted in a 6 × 5 × 3 m compartment with natural ventilation. The liquid fuels sprayed at varying pressures were ignited by a small open flame and then extinguished by a portable BTP extinguisher. Results showed that BTP of less than 60.0 g could extinguish all liquid fuel spray fires of 0.20 to 1.0 MPa in less than 2.0 s. The results also showed that when compared with fire sparked by gasoline and diesel, it is significantly easier to put out ethanol spray fires because of its high flame temperature and low flame power. Based on well‐established fire suppression theories and experimental results, the detailed mechanism of how BTP functions as an extinguishing agent in the suppression of liquid fuel spray fires will be discussed. Copyright © 2013 John Wiley & Sons, Ltd.     

Study on the suppression mechanism of water mist on poly(methyl methacrylate) and poly(vinyl chloride) flames

In this study, the action of water mists on poly(methyl methacrylate) (PMMA) and poly(vinyl chloride) (PVC) in a confined space under different external radiant heat fluxes was studied. Water mist was generated by a downward‐directed single pressure nozzle. Physical characteristics of the water mist were measured by laser doppler velocimetry and the adaptive phase doppler velocimetry system. The heat release rate, oxygen, carbon dioxide, and carbon monoxide concentrations, and other important parameters of the interaction under various experimental conditions were measured with cone calorimeter. To explain experimental results, the chemical suppression mechanisms of water mist extinguishing PMMA and PVC flames are investigated from literatures, and the corresponding proposed chemical reactions with water mist are presented. The investigation shows that aromatic compounds are formed by light hydrocarbon products with water mist for PMMA flame. Otherwise, for PVC flame, the decrease of temperature with water mist prevents aromatic compounds from oxidation and degradation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1130–1139, 2006     

室外油浸式变压器灭火系统设计研析

大型油浸式变压器作为工矿企业、电厂和重特大试验厂房等能源动力系统关键部位,发生火灾后会给生活、生产和科研试验造成极其严重的后果.结合现行标准规范,研析现有油浸式变压器各类灭火系统形式,应优先采用水喷雾灭火系统.通过具体工程实例,重点就水喷雾灭火系统设计、计算和注意事项进行了探讨,针对新修订的GB 50219—2014《...     

基于cup burner的含铁基添加剂超细水雾灭火有效性分析

针对典型的液体燃料（乙醇和正庚烷）油池火焰，在自行搭建的实验台上对含铁基添加剂的超细水雾的临界灭火浓度进行测量，定量评价其灭火性能。为深入分析铁基添加剂的灭火机理，基于密度泛函理论，对铁氧化物与H自由基反应产物的结构进行优化计算。研究表明：二茂铁与硫酸亚铁添加剂均能使超细水雾的临界灭火浓度呈现不同程度的降低，并且存在最佳浓度。二茂铁与硫酸亚铁的质量分数分别为0.01%和1%时，灭火效果最好；含铁基添加剂细水雾灭乙醇火的效果好于正庚烷火。铁氧化物与H自由基反应生成的Fe(OH)₂是一种活性催化物质，能够通过链式反应消去H自由基。     

An efficient methodology for evaluating the nozzle performance of water-based automatic fire extinguishers

The performance of automatic fire extinguishers (AFE) was tested using a novel nozzle distribution test in relation to a point of visual approach. The visual nozzle distribution data was obtained from the mapping of the amount of the collected fire extinguishing agent to each position and the gradient was given in accordance with the visually collected amount. The results showed that the effective discharge time was determined by the nozzle structure and its size. The visual nozzle distribution test (VNDT) provided relevant information regarding the performance efficiency of AFE, including the nozzle coverage area, the effective amount of the fire extinguishing agent and the distribution uniformity of fire extinguishing agents, and calculations for the proper amount of a fire extinguishing agent to extinguish a fire. Consequently, the results indicate the VNDT is an excellent method for analyzing the performance efficiency of AFE.     

Bench Scale Tests on Controlling Plastic Fires with Water Mists

Bench scale tests are proposed to study the performance of a water mist fire suppression system on plastic fires. The effects of water mist on burning solid polymethylmethacrylate (PMMA) and polyvinylchloride (PVC) are compared with a cone calorimeter. A scaled nozzle developed earlier for discharging water mist in a cone calorimeter was used. Operating pressures of 0.2–0.7 MPa, corresponding to water flow rates of 68 mL/min and 134 mL/min, were used. It was observed that PMMA samples could be ignited easily and liberated significant amounts of heat at high release rates. PVC was more difficult to ignite, but gave out large quantities of smoke. Discharging water to both did not increase the heat release rate significantly. However, both smoke quantity and carbon monoxide concentration increased. This was more obvious for PMMA fires. Hazard assessment parameters for thermal aspects and smoke were measured and presented as a ‘hazard diagram' to understand the action of water mist and the potential for re‐ignition. It is suggested that bench scale tests can also give useful results for designing water mist systems. The discharging time of water mist is a key factor in controlling PMMA fires. If the discharging time is not long enough, re‐ignition might occur once the discharging of water stops.     

油浸变压器水喷雾灭火系统的设计探讨

通过分析室外大型油浸变压器的火灾危险性和相关防火规范的要求,介绍日前常用的保护各类油浸变压器的灭火系统,描述了水喷雾灭火系统的灭火原理及其系统组成,并以某化工项目变电所室外油浸变压器的水喷雾灭火系统设计为例,介绍该系统的设计流程及应注意的问题。     

化工建设项目初期污染雨水及消防事故废水收集系统

化工企业在火灾事故时,经常会由于设施缺失或设置不合理而外排废水,从而造成了大量水体污染事件。对设计过程中如何设置收集初期污染雨水及消防事故废水的设施进行了简要介绍,重点介绍了收集系统的分类及特点、废水储存设施有效容积的确定,及设计过程中应注意的问题。     

An instrument for determining the total water content in air when extinguishing fires

An instrument suitable for measuring the total water content both as small liquid droplets and as vapour in the air, in water mist total flooding extinguishing tests, is presented. The instrument consists of a heater and a Vaisala humidity meter. The Vaisala humidity meter is capable of measuring relative humidity at temperatures up to 180°C. The instrument has a measuring range of 0–600g/m³, a sample rate of 1 L/min, a time constant of 5–10 s and an accuracy of ±40 g/m³. Accurate results are obtained when used outside the direct spray from a nozzle. If the instrument is placed in the spray the total water content can be either over‐ or underdetermined, depending on which part of the instrument faces the spray. Copyright © 1999 John Wiley & Sons, Ltd.     

Design and testing of a new smoke concentration meter

The design of a new smoke concentration meter based on light‐extinction measurements with a He‐Ne laser is described. The measurement allows the determination of the mass‐generation rate of smoke and smoke yield during a fire test with little more time or labour than is required for performing heat‐release‐rate and mass‐loss‐rate measurements. The new smoke concentration meter was motivated by the finding from several studies of a nearly universal value of the specific extinction coefficient of post‐flame smoke produced by over ventilated fires. Key design features include the use of a stabilized laser, purge flow to eliminate smoke deposition on the optics, U channel construction to minimize the effect of heating on the optical alignment and beam correction optics. The facility was fabricated almost entirely from commercially available components to allow this design to be easily reproduced by fire research and testing laboratories. The smoke concentration meter was able to measure a smoke yield as small as 0.005 for a propane fire to as large as 0.10 for a toluene pool fire. A detailed uncertainty assessment was made. The result for a 50cm diameter heptane pool fire agrees well with previous smoke yield measurements made for the same fuel and pool diameter based on filter collection and weighing. Copyright © 2000 John Wiley & Sons, Ltd.     

The effects of transient heat release rate and crosswind on flame length and tilt angle of flames at different positions in the spread of fire over a diesel pool

The spread of fire over liquid fuel is a common phenomenon, and it has been demonstrated experimentally that the flame length and tilt angle change with the transient heat release rate and different positions of the flame. The coupling relationship between these factors is studied in this paper. The experiments are composed of a rectangular pool with dimensions of 80 cm × 6 cm × 5 cm and crosswind with speeds of 0.8 to 2.4 m/s. Diesel is used as the fuel, and a new method is applied to ensure that the initial temperature of the diesel is constant during ignition. The results show that the traditional method of luminous flame intermittency may not be suitable for studying the geometric characteristics of the spread of fire over a pool, and a new method is proposed. In addition, the transient variation of flame length in different positions of the pool is shown to fluctuate around a mean flame length. The evolution of flame tilt angle along the longitudinal direction of the pool exhibits a U‐shaped curve. Moreover, the multivariate nonlinear relationships of mean flame length and tilt angle among the heat release rate, fire position, and wind speed are established, and relevant coefficients are determined.     

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

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 C_xr = 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.     

Ghosting flame mechanism under different extinctions modes in ceiling vent cabin

In this paper, large eddy simulation coupled with a low Mach number compressible thermal-drive flow model had been utilized to investigate the development of large-scale engine room fire, and the characteristics of engine room fire were analyzed through based upon the distinctive fire extinction behavior. Results indicated that extinction modes of engine room fire could be divided into oxygen control type and fuel control type. And the flame morphology could be divided into four stages: conical flame, pulsating flame, column flame, and ghosting flame. The appearance of the ghosting flame was affected by the extinction mode, but there were obvious differences in the causes of ghosting flame between the two modes. The cause of ghosting flame was related to the distribution of temperature field under the fuel control type, while the occurrence of ghosting flame in oxygen control type was mainly affected by oxygen concentration. Deflagration should be avoided when extinguishing fire by sealing the cabin.     

Studies of fundamental physical–chemical mechanisms and processes of flame extinguishing by powder aerosols

Theoretical and experimental studies on mechanisms of interaction of the fire‐extinguishing aerosol with flame are carried out. The factors of heterogeneous inhibition of flame free radicals (O, OH, H, CH_x) on a crystal surface of inorganic salts being the basic components of fire‐extinguishing powders and aerosols are measured using laboratory equipment. The semi‐empirical calculations by methods of quantum chemistry for heterogeneous and homogeneous inhibition reactions of burning are executed. The thermal mechanism for fire extinguishing is evaluated. The universal mechanism of influence on flame of a crystal surface of a fire‐extinguishing powder particle is offered. Copyright © 2007 John Wiley & Sons, Ltd.     

Remote extinguishing of large fires with powder aerosols

A new method for distant extinguishing of fire spreading in an extended closed volume such as a mine working, storehouse, subway tunnel, electric cable channels, etc. is proposed. A novel extinguishing agent based on a stable mixture of superfine ammonium phosphate [NH₄H₂PO₄] and modified fumed silica [SiO₂–CH₃] is supplied to the fire by a powerful ventilator. The properties of the extinguishing agent (average particle size, airborne residence time, distance of transfer by the air stream) have been studied in an experimental chamber (100 m³). A test extinguishing of a large‐scale fire has been performed in an experimental tunnel 180 m in length. Extinguishing agent consumption, dynamics of temperature change over the tunnel length and composition of fire gases were recorded in this test. The influence of foam concentration, addition of nitrogen and halons to aerosol, were also studied. Copyright © 2006 John Wiley & Sons, Ltd.     

某立式可燃液体储罐区消防灭火及冷却用水系统的设计

根据相关规范和业主要求,某立式可燃液体罐区采用固定式消防冷却水系统和低倍数泡沫灭火系统相结合的灭火系统。本设计通过对市场上实际灭火设备参数的选取,确定了泡沫比例混合装置的参数：并通过对罐区环状消防冷却水管分区布管的比较,选择最优的布管方式,该布管方式不仅避免了因设计取值较小造成消防储水量的不足而且减少了消防用水量。