Fire-extinguishing Powders Research Articles

Thermotechnical properties of the fire-extinguishing powder for extinguishing materials based on magnesium alloy chips

The article addresses the relevant issue of determining the thermotechnical characteristics of the fire-extinguishing powder for thermal insulation of the fire center of materials based on magnesium alloy chips to prevent fire development and propagation and its effective extinguishing. To solve this problem, laboratory and field experimental studies of the heat-insulating ability of the fire-extinguishing powder of combined effect were conducted. As a result, we obtained the data on the temperature in the center of the fire of materials based on magnesium alloy chips and outside during their suppressing by the fire-extinguishing powder with a combined effect. In this case, the temperature of the non-heated side of the fire-extinguishing powder layer does not exceed 170 °C at the average temperature of the fire center of 740 °C, which indicates high insulation capacity of the powder and, consequently, its high fire-fighting efficiency in extinguishing the fires of materials based on magnesium alloy chips. The obtained temperature data were used to determine the thermophysical parameters of the layer of the fire-fighting powder using the created mathematical model of the heat transfer process in the powder layer at the heat insulation of the fire center. To create a mathematical model of the heat transfer process, the main provisions during consecutive consideration of several experimental situations were stated. The first experimental situation meets the conditions of the stationary thermal process, and other experimental situations meet the conditions of the non-stationary thermal process. These experimental situations were created with the help of changing the thickness of the fire-fighting powder layer at different parameters of its feeding to the fire center. The mathematical model of the process is based on the use of the differential equation of heat transfer at its approximation by the method of finite differences. At the same time, it is believed that the heat transfer conditions at the boundary between the non-heated side of the insulating layer of the fire-extinguishing powder and the environment in each experimental situation are the same. Using the created model, the coefficient of heat transfer between the non-heated side of the insulating layer of the fire-extinguishing powder and the environment was determined. It amounted to 395.7 W(m 2 ×°С). The dependence of the effective thermal conductivity coefficient on the thickness of the insulating layer was explored. It was shown that this dependence can be approximated by linear dependence l(d)=–0.016+93.907×d (d is the thickness of the layer of the fire-extinguishing powder in meters). After conducting the necessary calculations, we obtained the value of the required thickness of the layer of fire-extinguishing powder d=45.2 mm

Research on Vehicle Exterior Fire Suppression Techniques

This paper studies automatic vehicle exterior fire detection and suppression techniques. The main difficulties include: 1) complex and changeable environment outside the vehicle; 2) low sensitivity of the fire detector; 3) quick dissipation of fire extinguishing agent in the open space outside the vehicle; 4) extinguishing agent nozzle blocking due to dust and sand. This paper selects a special ultra-fine dry powder fire extinguishing agent for automobiles to design the protective nozzle and to study the automatic detection controller with the functions of condition monitoring and fault diagnosis, with an aim to improve fire suppression reliability. Based on the virtual and real vehicle tests, it is verified that the fire extinguishing effect of the designed system meets the design requirements.

Experimental study on the thermal flow characteristics of a columnar sodium fire affected by a small amount of fire extinguishing powder in a cylindrical confined space

Liquid sodium, as a special form of metal has unique combustion characteristics and is difficult to extinguish quickly. To obtain a deeper understanding of the combustion and suppression characteristics of a columnar sodium fire affected by fire extinguishing powder in a confined space, investigative experiments were conducted in a cylindrical test chamber. The temperature of the space and the bottom surface were measured and analysed, and the effects on the suppression of combustion and the spatial heat flow field when different amounts of Class D fire extinguishing powder were sprayed into the space in the early and late combustion stages were compared. A local high temperature easily formed near the columnar sodium flow zone, because the sodium is more likely to adhere to the sensor at that measurement point. For a space heat flow field formed by a sodium fire in a confined space, the lateral temperature distribution at each height of the space is approximately linear. The overall temperature distribution at the upper space is relatively uniform, and the temperature near the fire source in the lower part of the space varies exponentially along the height. Compared with the spraying of fire extinguishing powder in the late stage of a sodium fire, spraying at the initial stage is more effective in suppressing the combustion of liquid sodium, the flow of liquid sodium and the disturbance of the space heat flow field. Further, the reignition hazard that may occur when spraying fire extinguishing powder to suppress a sodium fire should be given sufficient attention.

Distribution of fire extinguishing powder fractions in simulated non-stationary gas stream

Introduction. The article presents the regularities of particles distribution of fire extinguishing powder fractions in the cross sections of the simulated unregulated non-stationary gas stream. The distance from the fire extinguisher cut which the stream is most stable in terms of the content of fire extinguishing powder particles is determined. There are works in which the physical and chemical properties of fire-extinguishing powders are considered, the movement of powder particles in the stream is modeled, the influence of the fractional composition of the powder on its fire-extinguishing capacity is determined. At the same time distribution of powder fractions during its movement in gas-powder stream is not considered. The purpose of the present work is to find ways to improve the efficiency of powder extinguishers by controlling the distribution of powder fractions in a non-stationary gas stream.Materials and methods. Experimental study installation consists of coordinate table oriented perpendicular to gas-powder stream direction. The table is equipped with collectors that allow to collect powder samples at control points of flow cross-section. Food sodium chloride (further — salt) was used in the experiment. Its characteristics correspond to GOST R 53280.4–2009 and allow to apply it as a model. The coordinate table was installed sequentially at a distance of 500, 750, 1000 and 1250 mm from the fire extinguisher cut. Next, a shot of salt with a known fractional composition was supplied with a fire extinguisher model to a coordinate table and the retained powder samples were taken. The mass and fractional composition of the samples collected by each collector were then determined. Stability of the particle distribution in the gas stream by statistical analysis (by Fischer’s criterion) was measured for their content.Conclusions. Regularities of different fire extinguishing powder fractions distribution in cross section of non-regulated non-stationary gas stream are established and analytically described. These regularities can be used in finding ways to regulate fire extinguishing powder fractions during fire extinguishing. The most representative and stable in accuracy (correctness and precision) results of powder fractions content in the section of non-stationary gas stream at a distance of 1000 mm from the fire extinguisher cut. This should be taken into account in further research.

Model of Thermal Mechanism of Subclass A1 Fire Extinguishing with General Purpose Fire Extinguishing Powder in Non-Stationary Heat Exchange Conditions

The aim of the paper was to develop a model of thermal extinguishing mechanism using dry chemical powder taking into account the inertia of heat transfer to powder particles during unsteady heat exchange to identify the optimal conditions for extinguishing of A1 class fires with powders.The method of experimental and mathematical modelling of fire extinguishing process using dry chemical powder with short-term effect on the fire was used to achieve the goal. The experimental dependences of the extinguishing time and unit consumption of the extinguishing powder on the intensity of the powder supply to the combustion zone in extinguishing of subclass A1 fire in same area and in a limited volume were obtained. The mathematical model of a thermal extinguishing mechanism using dry chemical powder has been developed, taking into account the inertia of heat transfer to powder particles during unsteady heat exchange.Analysis of the regularities of extinguishing the subclass A1 fire using powder with a short feeding it into the fire indicates the presence of optimum values of unity consumption of powder on the fire from the intensity of feeding it into the fire. The presence of this optimum is due to the inertia of extinguishing the subclass A1 fire using powder due to the finiteness of the heat transfer time to the particles of the extinguishing powder and the limited time of interaction of particles with the combustible material.The theoretical analysis of the fire extinguishing process over the area taking into account the inertia of heat transfer to the powder particles at non-stationary heat exchange are carried out. The results of the analysis are in qualitative agreement with the results of the experimental study of the regularities of extinguishing of model fire foci of subclass A1 with General-purpose fire extinguishing powder.

Оптимизация конструкции порошкового огнетушителя и исследование параметров подачи огнетушащего порошка

Цель. Оптимизировать конструкцию порошкового огнетушителя, исследовать параметры подачи огнетушащего порошка, провести натурные испытания.
 Методы. Экспериментальное определение текучести и остатка огнетушащего порошка в баллоне огнетушителя после его использования. Теоретические исследования значения потерь давления перед насадком-распылителем и дальности струи порошка.
 Результаты. Получены зависимости текучести огнетушащего порошка и давления перед насадком-распылителем от времени истечения огнетушащего заряда. Установлены средние значения текучести огнетушащего порошка и давления перед насадком-распылителем для исходной и оптимизированной конструкции порошкового огнетушителя. Предложена конструкция огнетушителя, которая позволяет эффективно использовать весь огнетушащий порошок, рассчитаны потери давления в конструкции с сифонной трубкой. По функциям давления и текучести перед насадком-распылителем установлено, что в предлагаемой конструкции огнетушителя без увеличения исходного рабочего давления в баллоне при увеличении подачи огнетушащего порошка дальность его струи также увеличивается. Рассчитаны значения потерь давления в сифонной трубке. Практически доказана эффективность предлагаемой конструкции порошкового огнетушителя.
 Область применения исследований. Результаты исследования могут быть использованы для оптимизации конструкции порошкового огнетушителя.

ПРОБЛЕМНІ ПИТАННЯ НАДІЙНОСТІ ПОРОШКОВИХ ЗАСОБІВ ПОЖЕЖОГАСІННЯ І ШЛЯХИ ЇХ ВИРІШЕННЯ

Проведено аналіз проблемних питань забезпечення надійності порошкових засобів пожежогасіння: забезпечення надійності якості вогнегасних порошків під час їхнього виготовлення, зберігання і застосування, забезпечення якості, надійності використання, безпеки використання порошкових вогнегасників. Проаналізовано вплив на якість вогнегасних порошків хімічного складу, встановлено оптимальні концентрації компонентів вогнегасного складу, які забезпечують якість вогнегасних порошків. Проаналізовано вплив введення у дію Закону України "Про стандартизацію" (2014 рік), яким відмінено обов’язкову державну реєстрацію стандартів і ТУ, а також запровадження добровільності їх застосування, на якість і надійність застосування порошкових засобів пожежогасіння. Запропоновано шляхи покращення якості вогнегасних порошків і порошкових вогнегасників і підвищення надійності гасіння ними пожеж.

Increasing fire retardancy of wood by impregnation with inorganic salts recovered from exhausted fire extinguishing powder

The fire retardancy of wood impregnated with a mixture of ammonium dihydrogen phosphate and ammonium sulfate recovered from exhausted fire extinguishing powder was assessed. Impregnated specimens recorded a 14.3% total weight loss due to combustion, as opposed to 93.8% for the untreated ones. Treated specimens also showed a significantly lower burning time and maximum burning rate as well as higher sustainable ignition time than untreated ones.

On unmanned aircraft systems application for fire extinguishing in high-rise buildings

Introduction. The purpose of the study is to formulate and analyze problems that should be solved before implementing the ideas of fire fighting in high-rise buildings by using unmanned aircraft systems (UAS). To achieve this purpose, the following concepts were considered and assessed: the possibilities of water and water-based fireextinguishing solutions delivery to the fire source from a ground pumping station using a hose line; delivering compression foam along a vertically positioned hose line; and, the possibilities of UAS for fire extinguishing; supply of fire extinguishing powders and aerosols placed on the UAS to the center of fire. Methods. The adopted in Russia hydraulic calculation methods, the results of the experimental studies on the compression foam, the existing theoretical and practical advances in the field of fire-extinguishing by jet delivering fire-extinguishing substances. Conclusions. The results achieved show that one of the ways to increase fire extinguishing capability in high-rise buildings can be provided by applying UAS for continuous horizontal supply of water based solution or compression foam to the center of fire, as well as supply of fire extinguishing powders and aerosols using powder fire barrels and pyrotechnic cartridges. However, to implement each of these methods, certain problems need to be solved. They are: the fire extinguishing height limitations a large capacity of UAS needed; a hydraulic calculation methodology for compression foam supply systems; safe use of UAS under the conditions of compression foam separation; the possibilities for developing supply equipment, which can be utilized by the UAS.

The role of powder physicochemical properties on the extinction performance of an extinguishing powder for sodium fires

The French Atomic and alternative Energy Commission (CEA) aims to reuse its sodium fire (carbonate base) extinguishing powder after long term storage (stock from the dismantlement of its old sodium facilities). As the composition of the powder appears to change during the storage, the efficiency on the extinction as a function of the physicochemical properties was questioned. Small sodium fire extinction experiments were carried out with powders of different compositions. The results demonstrated a dominant role of water of crystallization on the extinction. Two steps are proposed for the extinction mechanism that includes: (1) the formation of liquid sodium hydroxide and (2) the melting of carbonate mixture at eutectic composition. The sodium hydroxide behaves as a protective layer and insulates the sodium surface from prolonged contact with oxygen. Consequently, it provides rapid decrease of temperature, unlike the slow melting of carbonates eutectic and its porous layer formed due to its higher viscosity. The presence of trona (aging product) does not alter the extinction capacity of the powder. To extrapolate the results to large fires, 35 g of water of crystallization are necessary to extinguish 1 m2 of sodium pool fire. Finally, the particle size appears to be a non-significant parameter to the quality of extinction except for the spreading performance.

Effects of Fire on the Strength of Reinforced Concrete Structural Members

This multidisciplinary research focuses on the effect of fire on structures due to the Boko Haram insurgency in Maiduguri, Northern Nigeria. It is aimed at giving a further contribution to understand the effect of fire with respect to the local aggregates, quenching methods and proposing an assessment methodology based on a suitable analytical procedure applied to reinforced concrete subjected to sustained fire. Cement, river sand, Bama gravel and water in standard proportion in accordance to BS1881 Part 101 were mixed to produce beams, slabs and cubes of different sizes and cured for 28 days. The samples were burnt in a designed fire simulation furnace using sugarcane bagasse as fuel with varying air velocities for 2 hours. Cooling of samples was carried out using water splashing, CO2 powder fire extinguisher and air cooling methods before the compressive strength tests using a Seidner Compressive Testing Machine and Non-destructive test with Rebound Hammer. The scanning electron microscopy tests were carried out using a Phenom ProX scanning electron microscope for imaging and analysis to physically examine and determine the elemental micro structural redistribution and influence on the tested samples. As the temperature within the experimental set-up reaches 900°C, the temperature around the vicinity of slab, beam or cube reached an average of 500°C. The results of the investigations show that different cooling methods induce varying levels of deteriorating and significant effects on the final internal micro-structures as well as physical, mechanical and thermal characteristics of concrete. Results from the destructive and non-destructive tests show that losses of strength vary from a minimum of 37.73% to a maximum of 86.67 % in the samples investigated. The local aggregates used namely the river sand and the Bama gravel surely influenced the medium grade reinforced concrete behaviour when subjected to fire.

Improvement of a discharge nozzle damping attachment to suppress fires of class D

The software package COSMOSFloWorks has been used to study a discharge nozzle damping attachment. A procedure has been proposed to estimate the covering of surface with dimensions of 0.4×0.4 m by a fire-extinguishing powder. It was established that existing discharge nozzle damping attachments are not efficient because at extinguishing light metals they do not effectively reduce the speed of powder supply onto a flammable surface and fan the fire, not being able to cover the burning surface by a fire-extinguishing powder. After putting out the fire the surface that was covered with powder reveals the burnouts. We have modeled the optimal structural parameters for a discharge nozzle damping attachment in order to extinguish fires of class D in the form of a discharge nozzle damping attachment with an elliptical top and a parabolic reflector. It has been proven that a damping attachment with two working surfaces outperforms the previous damping attachment with a single working surface by 30 %. Given this, the fire-extinguishing powder covers the burning surface by a larger layer, preventing the fanning of chips from the surface of a burning metal, thereby shortening the duration of burning and improving the efficiency of a fire-extinguishing powder supply. Experimental study has confirmed that the use of a damping attachment that supplies a fire-extinguishing powder with two working surfaces in order to extinguish fires of class D increases the powder feed to a fire site, reaching above 90 %. The diameter and the shape of the attachment have been determined. The attachment must acquire the form of a diffuser with a diameter of 16 mm. Our development could be used when designing the stationary and portable fire extinguishing systems for light metals and alloys, including incendiary grenades under condition of proper selection of the powder. We have achieved positive results during field tests of the discharge nozzle damping attachment using a make-up fire to burn the shavings of magnesium alloys

Hydrophobized Silicas as Functional Fillers of Fire-Extinguishing Powders

This paper presents a comparative evaluation of the use of hydrophobized silica materials as functional fillers in ammonium phosphate-based fire-extinguishing powders (FEPs). To this end, we have hydrophobized the surface of different silicas: commercially available fumed silica and Aerosil and monodisperse silica prepared by the Stober method under laboratory conditions. We have optimized the content of hydrophobized silica fillers in FEPs so that the powder materials exhibit superhydrophobic properties and the lowest flow resistance.

Lebensbedrohliche Acidose nach Ingestion von ABC-Löschpulver

We present the case of a31-year old male with ingestion of fire extinguisher powder in an attempted suicide. After consulting several poison information centres, the intoxication was initially classified as harmless; nevertheless, the patient was admitted to our intensive care unit for cardiopulmonary monitoring. Subsequently, due to the ingestion of ammonium sulphate and ammonium dihydrogen phosphate containing powder the patient developed severe metabolic acidosis with distinct electrolyte imbalance that required temporary haemodialysis.

Efficiency characterization of fire extinguishing compound superfine powder containing Mg(OH)2

To improve the fire extinguishing efficiency of existing dry powders, a new type of superfine dry powder was prepared using magnesium hydroxide as an additive. In our study, a thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to analyze the thermal decomposition of the synthesized powders. The temperature of thermal decomposition, weight loss, and other thermodynamic parameters of the fire extinguishing powders were analyzed to explain the performance advantages of the compound superfine powder. Through a small-scale fire experiment, the physical parameters of the extinguishing process—such as extinguish time, powder dosage, smoke concentration, and minimum extinguishing concentration—were quantified for the suppression of a diesel fire using the different powders; these parameters were used to evaluate the fire extinguishing capacity and toxic gas suppression ability of the powders. TGA demonstrated that the compound superfine powder decomposed more quickly and its thermal decomposition process was much shorter than those of the other powders. The DSC data indicated that the compound superfine powder could decrease the characteristic temperature at each stage and thus the powder absorbed the flame's heat more quickly and suppressed flame propagation. The fire extinguishing test demonstrated that the consumption of the three types of fire extinguishing powder decreased with an increase in the driving pressure, and the order of powder dosage was as follows: commercial dry powder > superfine powder > compound superfine powder. Similarly, the order of minimum extinguishing concentration was as follows: commercial dry powder > superfine powder > compound superfine powder. Furthermore, the compound superfine powder exhibited a greater capacity for controlling toxic and harmful gas emissions.

OPTIMIZATION OF THE DRY CHEMICAL POWDERS’ COMPOSITION FOR CLASS D1 FIRES EXTINGUISHING

During the researches, carried out in the article, sodium chloride recommended itself as the best fire-extinguishing substance. In order to give it the properties of a fire extinguishing powder, two more components were added to it, namely ground slag and aerosil. These components were chosen according to their physical and chemical properties. As evidenced by the corresponding quenching parameters, the optimal composition of the fire extinguishing powder was established on the basis of performed experiments and obtained dependences. The properties of the fire extinguishing powder were improved by adding ground slag and aerosil. These additives increase the heat resistance, insulating and anti-caking ability, fluidity and fire-extinguishing efficiency of the powder. The best results were obtained after using the extinguishing powder of such composition: sodium chloride - 73.5%, ground slag - 25%, aerosil - 1.5%. Experimental-empirical dependence for determination the extinguishing intensity according to the extinguishing parameters and the fire-extinguishing composition was developed.

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

SummaryThe 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.

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.

Analysis of minimum ignition temperature of pellet dust layer and cloud due to adding BC and ABC fire extinguishing powders

The paper describes the impact of adding fire extinguishing powders acting based on oxygen or flame on values of minimum ignition temperatures of the layer and cloud of pellet dust, and as a consequence the impact or lack of impact on values of maximum admissible temperature on external surfaces of electrical appliances working in their atmospheres. Tests were conducted of the minimum ignition temperature of layer and cloud of the agro armakow pellet dust and the agro jesień pellet dust, with and without additives of fire extinguishing powders BC Jet, BC LB2, ABC 90 and Ogniotex 103 at concentrations ranging from 5 to 70% by weight of powder contents in the mixture. Based on obtained test results it has been ascertained that type ABC powders appear to be much more effective than those type BC, because they have a much bigger impact on increasing the minimum ignition temperature of the layer and the cloud of analysed dust types. Adding only 15% of ABC 90 extinguishing powder to the agro jesień pellet has caused an increase in the minimum ignition temperature of dust layer by 80°C. The BC LB2 powder with agro armakow pellet dust has not been found to cause any changes, even at its concentration as high as 70%. The most optimum additive of powder to the biomass dust was 10% by weight of ABC powder in the mixture. At this concentration the highest increase was recorded in the maximum admissible temperature on the outer surface of electrical appliances from 235°C to 273°C.

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.