Compressed Air Foam System Research Articles

DEVELOPMENT OF A TEST SAMPLE OF A SYSTEM FOR GENERATING AND SUPPLYING COMPRESSED AIR FOAM

An effective fire extinguishing agent for class A fires is the compressed air foam formed in Compressed Air Foam Systems (СAFS). Such systems have become widespread in leading countries such as the USA, Germany, China, and others. It is worth noting that the technical parameters of CAFS (intensity and consumption of an aqueous solution of foaming agent/air), implemented in the practice of fire extinguishing in the form of industrial samples, are designed and manufactured in such a way as to ensure effective extinguishing of developed fires of a significant area. When using existing samples for obtaining compression foam, a problem arises, which lies in the limited possibilities of regulating the supply of compression foam (intensity and consumption of the aqueous solution of the foaming agent/air), under which it is possible to use it with modified additives when extinguishing laboratory fires of solid combustible materials, and the lack of a smooth regulation of its supply. As a result of the research, the authors proposed a compressed air foam system to study its properties with the content of modified additives when changing the composition of the liquid and air that make it up. The manufactured system has the following parameters: multiplicity of 4–20, working pressure of systems of 4–8 bar, smooth adjustment of the consumption of aqueous solution/foaming agent of 2–20 l/min, and smooth adjustment of gas fraction consumption of 8–450 l/min. In particular, it is possible to adjust the consumption of the aqueous solution of the foaming agent and air, to work in dependant and autonomous mode, to regulate the intensity of the foam supply using nozzles of different diameters, and to change the porosity of the porous body in the foam generator. Further, we developed a system for measuring the flow of aqueous solution and air, which is a hardware and software complex. The system allows saving the measurement results to a PC in the form of an Excel spreadsheet for further development of dependencies and simultaneously displaying the flow rate of the aqueous foaming agent solution and air on the display screen and PC in real-time. Keywords: compressed air foam, class A fires, compressed air foam systems, modified additives.

Study on Gas-Liquid Coaxial Jet Foam Generator and Its Foaming Characteristics.

In order to solve the difficulty of the existing compressed air foam system with low FER and difficult in having both the FER and range. A new type of foam generator for CAFS was designed, an air-liquid coaxial foam generator, which produces foam with high FER (the ratio of the foam volume to the volume of the foam solution) and large output momentum. In this paper, experiments on the foam production performance of a gas-liquid coaxial jet foam generator were carried out with different parameters, such as liquid flow rate, gas flow rate, and foam output end diameter. The variation of FER, foam half-life, range, foam volume, and compressed air utilization rate with the experimental parameters were analyzed. The results show that the foaming performance of the foam generator tends to rise in the range of 8-12.4 m3/h at a fixed gas flow rate, the FER and foam half-life are negatively related to it, and the foaming performance tends to decrease in the range of 12.4-18 m3/h. The best foaming performance was achieved when the liquid volume of the foam generator was 12.4 m3/h. For the liquid volume value in different intervals, the foaming performance varies with the air supply volume. When the liquid volume is higher than 12.4 m3/h, increasing the air supply volume is beneficial to improve the foaming performance, and when the liquid volume is lower than 12.4 m3/h, increasing the air volume does not improve the foaming performance. The effect of the diameter of the foaming chamber on the foaming performance is not monotonic, and an optimum value exists. Compared with similar devices, the gas-liquid coaxial jet foam generator has strong advantages in FER and range and has better application prospects for fire control in restricted spaces.

Evaluation of a compressed air foam system to clean quail rearing facilities

Evaluation of a compressed air foam system to clean quail rearing facilities

Experimental and numerical study on the pressure drop and flow pattern of liquid foam in a foam generator

In the present study, a comprehensive analysis of the pressure drop, flow pattern, and foam structural properties of vertical upward two-phase flow in a Kenics static foam generator of a compressed air foam system was carried out. A liquid with an extremely low surface tension (16.5 mN/m) was used for making the foam. The effects of the number of elements (number of individual elements combined into the mixer), aspect ratio (the ratio of length to diameter of each element), and transition angle (transition angle between elements) of the Kenics mixers on the pressure loss during foam generation were studied in detail over a wide range of Reynolds numbers through experiments and numerical simulation. A new pressure drop correlation was successfully obtained by scaling analysis and the modified Lockhart–Martinelli correlation was proposed to describe the pressure drop during foam generation. Furthermore, the experimental results validated the proposed correlation and exhibited good reliability and predictive accuracy. Finally, four flow patterns for foam generation in vertical pipes that were different from the classical gas–liquid two-phase flow patterns were proposed, and the relationships among the pressure drop, flow pattern, and foam structural properties were explored. This research expands the study of foam generation in vertical tubes containing a built-in spiral structure with low flow resistance. It provides new insights and guidance for developing continuous foam manufacturing.

Improvement of the Prototype of the Compressed Air Foam System and its Testing

The prototype of the compressed air foam system was improved based on the evaluation of the numerical parameters obtained with the help of the developed mathematical model of the foam generation process and the pneumatic-hydraulic scheme. The prototype provides the possibility of foam generation both in autonomous mode, due to the installation of cylinders with compressed gas, and in stationary mode, due to the supply of compressed air from an external source. This allows the use of an improved model of the compressed air foam system both in stationary mode (dry pipes, gas stations, etc.) and for use on heavy and light fire trucks, which is important for large cities. Testing of the improved prototype of the system for extinguishing model fires was carried out. The system provides extinguishing of model fires of class 183 B and 144 B when using both a general-purpose foaming agent and a special film-forming foaming agent. When using a film-forming foaming agent, the extinguishing time was reduced by 1.75 times, the consumption of fire extinguishing solution by 1.47 times. But at the same time, it should be taken into account that the cost of the film-forming foaming agent Sofir (sofirafff 6 %) is more than 3.2 times the cost of the general-purpose foaming agent Sofir. The effectiveness of the improved model in extinguishing class A fires was also confirmed. The autonomous compressed air foam system ensures extinguishing of a class 4 A model fire in 90 seconds. Dry foam with a factor of 14 is noted to be more effective in extinguishing solid combustible substances.

Nozzle diameter and expansion ratio of compressed air foam system

Variations of nozzles are studied for Compressed Air Foam Systems (CAFS). The CAFS is a self-contained fire suppression system with the capability of injecting compressed air into the foam solution to create a dense mist. Even though this type of foam has a tighter, denser bubble structure that allows it to adhere to vertical and horizontal surfaces and penetrate the fire more deeply before the bubbles burst, thereby making it more effective, the nozzle of CAFS is weak. The experimental study has been done in order to find the expansion ratio of the nozzle. Four sizes of diameter nozzles are 5 mm, 10 mm, and 20 mm, and three holes are 20 mm. Nozzle diameter size has a correlation with bubble size. The highest expansion ratio is found in the nozzle with three holes 20 mm in diameter. It is followed by a nozzle with a 20 mm diameter, then a 10 mm diameter. The last finding is a nozzle with five diameters. The other founding is the linear correlation between nozzle diameter size and bubble size. But it is on the other way than the correlation between nozzle diameter and bubble size. The shorter the nozzle diameter, the faster the fire extinguishing time.

Experimental and numerical investigation on optimization of foaming performance of the kenics static mixer in compressed air foam system

The current mixers in the compressed air foam system used to generate liquid foam have high flow resistance. Kenics static mixer may be a better choice for making foam because its spiral structure can lower the flow resistance. However, the effects of the structure of Kenics static mixer on the properties of liquid foam remain unclear. The primary objective of this work is to study the influences of aspect ratio, transition angle, and the number of elements of Kenics static mixer on foaming performance and make the structural design optimization. The results indicated that the aspect ratio of the Kenics static mixer had the greatest impact on the foam properties, followed by the number of elements, and the transition angle had the smallest impact. The velocity distributions were distinct at the same relative position for different aspect ratios. When the number of elements exceeded four, the increase in the number of elements hardly changed the velocity distributions. The results also emphasized the critical role of velocity distribution in improving the coefficient of variation and elucidated a strong correlation between the coefficient of variation and foaming performance. The findings can offer guidance for the optimal design of the foam generator.

Experimental investigation on the spread of aqueous foam over ethanol surface

Abstract The presence of ethanol has an adverse effect on foam spreading, and ethanol fire is difficult to extinguish with aqueous fire-fighting foams. Thus, it is necessary to explore the foam formulation suitable for ethanol fuels and study the spreading behavior of foam over ethanol surface. In the current work, stable foams based on hydrocarbon surfactant (SDS), fluorocarbon surfactant (FC1157), and polymers (XG) were prepared by using the compressed-air foam system. The spreading behaviors of foam on polar ethanol and non-polar heptane surface were observed and compared. Furthermore, the effects of stabilizer concentrations, foam flow rates and expansion ratios on foam spreading performance were investigated, respectively. The results indicate that aqueous SDS foam can spread on the heptane layer continuously, but it is difficult to cover the ethanol surface. The addition of XG and FC1157 can synergistically improve the spreading performance of aqueous foam over ethanol. Depending on stabilizer concentrations, there are remarkable differences in foam spreading behaviors. Besides, different foam application parameters including expansion ratios and foam flow rates significantly affect the foam spreading rate, despite the same foam formulation. The research methods and results guide the optimal design of foam formulations as well as the practical application of aqueous foam for ethanol fire extinguishment.

Use of Foaming Disinfectants and Cleaners to Reduce Aerobic Bacteria and Salmonella on Poultry Transport Coops

Simple SummaryChicken coops are rarely washed and can soil poultry carcasses with fecal bacteria that may make people sick. Our laboratory applied two commercially available products to experimentally contaminated coops. One product contained bleach, potassium hydroxide and a foaming agent. The other product contained vinegar and hydrogen peroxide and was mixed with a detergent. Both products were applied using a firefighting apparatus known as a compressed air foam system (CAFS). These materials were washed away using a garden hose or pressure washer as the treatments called for. Surface swabs were collected prior to and after each treatment to determine the reduction of bacteria on the surface, which would be an indicator of sanitation. We found that both treatments significantly made the surface cleaner when compared to water alone. The application of these products via a CAFS may be a practical and expedient way to clean and disinfect poultry cages.Transport coops are infrequently washed and have been demonstrated to cross-contaminate broiler carcasses. We hypothesized that peracetic acid or a chlorinated cleaner, commonly used within poultry processing plants, can also be used to disinfect transport coops when applied via a compressed air foam system (CAFS). A mixture of fresh layer manure and concentrated Salmonella Typhimurium (ST) was evenly applied to the floors of four pre-cleaned transport coops and allowed to dry for thirty minutes. Treatments consisted of a (1) water rinse only, (2) product application with a water rinse, (3) product application followed by power washing and (4) power washing followed by application of product. Each foaming treatment was applied with a compressed air foam system and allowed 10 min of contact time. Samples were aseptically collected from the transport coops prior to and following treatment using a sterile 2 × 2-inch stainless steel template and a gauze swab pre-enriched with buffered peptone water. The chlorinated cleaner significantly (p < 0.05) reduced aerobic bacteria and ST by 3.18 to 4.84 logs across application methods. The peroxyacetic acid (PAA) disinfectant significantly (p < 0.05) reduced aerobic bacteria and ST by 3.99 to 5.17 logs across application methods. These data indicate that a compressed air foam system may be used in combination with a commercially available cleaner or disinfectant to reduce aerobic bacteria and ST on the surfaces of commercial poultry transport coops.

Foam or spray application of agricultural chemicals to clean and disinfect layer cages

SUMMARY A rapid and effective means to clean and disinfect premises is needed by the poultry industry. We hypothesized that commercially available foaming disinfectants and cleaners applied via a compressed air foam system (CAFS) may be used to significantly reduce aerobic bacteria in a commercial caged layer complex. Six field trials were conducted to evaluate current industry cleaning and disinfection protocols and the proposed CAFS application. A commercially available chlorinated alkaline foaming cleaner (CHL/ALK) was applied in trials 1 and 2 by CAFS to one half of the house, and the other half of the house was not treated. The entire house was then washed with a high-pressure water rinse (HPWR). A commercially available peroxyacetic acid (PAA) in trials 3 and 4 or a 14% glutaraldehyde (HI GLUT)/2.5% quaternary ammonia (QAC) blended disinfectant in trials 5 and 6 was applied by CAFS to one half of a washed house. The remainder of the house was then treated with a 7% glutaraldehyde (LO GLUT)/26% QAC, which was spray-applied to cages by the integrator. Environmental swabs of drinker cups and cage floors were collected pre- and post-treatment to determine if aerobic bacteria were reduced. The HPWR and the CHL/ALK treatments did not consistently reduce bacteria on treated surfaces. Significant differences were observed with each of the CAFS applications of the PAA product, resulting in bacterial reductions of 1.83 to 2.27 log10 cfu/sample. Although inconsistent, differences (P

Особенности применения пеногенерирующих систем со сжатым воздухом для тушения пожаров

Проведен анализ результатов экспериментальных исследований пеногенерирующих систем со сжатым воздухом, приведен пример использования инженерной методики гидравлического расчета рукавных линий при движении компрессионной пены. По результатам теоретических и экспериментальных исследований сформулированы особенности применения пеногенерирующих систем со сжатым воздухом для тушения пожаров, которые учитывают отличие их тактико-технических характеристик от традиционных технологий пенного пожаротушения. Это позволило определить область применения пеногенерирующих систем со сжатым воздухом.

Depopulation of Caged Layer Hens with a Compressed Air Foam System.

Simple SummaryReportable diseases, such as avian influenza, spread rapidly among poultry, resulting in the death of a large number of birds. Once such a disease has been diagnosed at a farm, infected and susceptible birds are rapidly killed to prevent the spread of the disease. The methods to eliminate infected caged laying hens are limited. An experiment was conducted to study the effectiveness of foam made from compressed air, water, and soap to kill laying hens in cages. The study found that stress levels of the hens killed using compressed air foam in cages to be similar to the hens killed by carbon dioxide or the negative control. Hens exposed to carbon dioxide died earlier as compared to the foam methods. The authors conclude that application of compressed air foam in cages is an alternative to methods such as gas inhalation and ventilation shutdown to rapidly and humanely kill laying hens during epidemics.During the 2014–2015 US highly pathogenic avian influenza (HPAI) outbreak, 50.4 million commercial layers and turkeys were affected, resulting in economic losses of $3.3 billion. Rapid depopulation of infected poultry is vital to contain and eradicate reportable diseases like HPAI. The hypothesis of the experiment was that a compressed air foam (CAF) system may be used as an alternative to carbon dioxide (CO2) inhalation for depopulating caged layer hens. The objective of this study was to evaluate corticosterone (CORT) and time to cessation of movement (COM) of hens subjected to CAF, CO2 inhalation, and negative control (NEG) treatments. In Experiment 1, two independent trials were conducted using young and spent hens. Experiment 1 consisted of five treatments: NEG, CO2 added to a chamber, a CO2 pre-charged chamber, CAF in cages, and CAF in a chamber. In Experiment 2, only spent hens were randomly assigned to three treatments: CAF in cages, CO2 added to a chamber, and aspirated foam. Serum CORT levels of young hens were not significantly different among the CAF in cages, CAF in a chamber, NEG control, and CO2 inhalation treatments. However, spent hens subjected to the CAF in a chamber had significantly higher CORT levels than birds in the rest of the treatments. Times to COM of spent hens subjected to CAF in cages and aspirated foam were significantly greater than of birds exposed to the CO2 in a chamber treatment. These data suggest that applying CAF in cages is a viable alternative for layer hen depopulation during a reportable disease outbreak.

The research of press drop of compressed air foam flow through the bend

Compressed air foam system (CAFS) had obvious advantages in engineering. The flow model of compressed air foam in the pipeline was different from water flow model because the foam was the gas-liquid two phase flow with non-Newtonian fluid properties and compressibility, and, the water supply theory was not suitable for foam press pipeline transport. At present, there was little research on non-Newtonian fluid flow, especially the foam flow. This study researched the effect of foam flux, end valve and foam type on the press in the straight pipe and bend. The press drop in straight pipes and bends filled with compressed air foam was analyzed, and the result could provide experimental support for theoretical calculation of compressed air foam in bend.

Occurrence of brominated dioxins in a study using various firefighting methods

The use of different firefighting methods influences how fast a fire is extinguished and how fast the temperature drops in the area affected by the fire. These differences may also influence the formation of harmful pollutants during firefighting of an accidental fire. The aim was to study occurrence of brominated dibenzo-p-dioxins and furans (PBDD/Fs) in gas and soot during five fire scenarios resembling a small apartment fire and where different firefighting methods were used. Samples of gas and soot were taken both during the buildup of the fire and during the subsequent extinguishing of the fire while using different firefighting methods (nozzle, compressed air foam system, cutting extinguisher) and an extinguishing additive. New containers equipped with identical sets of combustible material were used for the five tests. The use of different firefighting methods and extinguishing additive induced variations in concentration and congener profiles of detected PBDD/Fs. The concentration range of ∑PBDD/Fs in gas was 4020–18,700pg/m3, and in soot 76–4092pg/m2. PBDFs were the predominant congeners and 1,2,3,4,6,7,8-HpBDF was the most abundant congener. Chlorinated dibenzo-p-dioxins and furans (PCDD/Fs) were also monitored. The PBDD/Fs contributed with in average 97% to the total (PCDD/Fs plus PBDD/Fs) toxic equivalents, in soot and gas. During extinguishing, the shorter time the temperature was around 300°C, the lower occurrence of PBDD/Fs. In the study the firefighting methods showed a difference in how effectively they induced a temperature decrease below 300°C in the fire zone during quenching, where cutting extinguishing using additive and the compressed air foam system showed the fastest drop in temperature.

Class B Fire-Extinguishing Performance Evaluation of a Compressed Air Foam System at Different Air-to-Aqueous Foam Solution Mixing Ratios

The purpose of this research is to evaluate the fire-extinguishing performance of a compressed air foam system at different mixing ratios of pressurized air. In this system, compressed air is injected into an aqueous solution of foam and then discharged. The experimental device uses an exclusive fire-extinguishing technology with compressed air foam that is produced based on the Canada National Laboratory and UL (Underwriters Laboratories) 162 standards, with a 20-unit oil fire model (Class B) applied as the fire extinguisher. Compressed air is injected through the air mixture, and results with different air-to-aqueous solution foam ratios of 1:4, 1:7, and 1:10 are studied. In addition, comparison experiments between synthetic surfactant foam and a foam type which forms an aqueous film are carried out at an air-to-aqueous solution foam ratio of 1:4. From the experimental results, at identical discharging flows, it was found that the fire-extinguishing effect of the aqueous film-forming foam is greatest at an air-to-aqueous solution foam ratio of 1:7 and weakest at 1:10. Moreover, the fire-extinguishing effect of the aqueous film-forming foam in the comparison experiments between the aqueous film-forming foam and the synthetic surfactant foam is greatest.

The Feasibility Study of Extinguishing Oil Tank Fire by Using Compressed Air Foam System

Because of the complex characteristics of oil liquid, oil tank fire is more complex, and we need to consider the performance of fire extinguishing agent and environmental factorin the process of fighting, so fire suppression of oil tank fire is hard. This page analyzed the combustion characteristic of oil tank fires and themechanism of foam loss. Based on the previous studies, this paper provides guide ides of oil tank fire by discussing the feasibility and applicability of suppressing oil tank fire by using compressed air foam system (CAFS) with different fire extinction agents and analyzing the effectiveness of different agents.

Use of a foaming disinfectant and cleaner to reduce aerobic bacteria on poultry transport coops

Poultry transportation coops are rarely washed and have been demonstrated to be a point of cross-contamination of broiler carcasses. Foaming disinfectants and cleaners, commonly used within processing plants, may be used to clean and disinfect poultry transportation coops. In this study, homogenized fecal material was evenly applied to the floors of precleaned broiler transportation coops and allowed to dry. Treatments consisted of a water rinse, a foam additive alone, foaming cleaner, and a disinfectant plus a foam additive. All foaming treatments were applied using a compressed air foam system (2,271 L/min; 600 gal/min), similar to what firefighters would use. A high-pressure water rinse (HPWR) was added prior to or following the treatments to determine whether rinsing prior to product application or rinsing after product application would improve efficacy. Based on our data, a compressed air foam system may be used in combination with a commercially available disinfectant or foam cleaner to reduce aerobic bacteria on the surfaces of commercial broiler transportation coops. Furthermore, the addition of a HPWR did not further reduce the level of aerobic bacteria on broiler transportation coop floors.

Effects Of Compressed Air Foam Application On Heat Conditions In Fire Within A Closed Space

Abstract This article evaluates the knowledge obtained in firefighting tests using compressed air foam system (CAFS) within a confined space. Six experiments were conducted for verification during the cooling of rooms and the self-extinguishing effect. The simulation was for a fully developed fire within a room. The fuel was chosen to simulate ordinary combustible materials utilized in residential areas. Mantel thermocouples were placed in the rooms to record the temperature changes. Compressed air foam was first applied with a standard fire hose nozzle to the ceiling and then to the epicenter of fire. Fire extinguishing was initiated after reaching the desired temperature in the room. The temperature for the start of fire extinguishing matched the third phase of development of a fire. Fire extinguishing was terminated after no obvious signs of fire were shown in epicenter of fire. The outputs of the experiments were evaluated on the basis of the amount of time passed for the temperature to drop below the suggested limit. Individual experiments were also conducted with various different admixing foaming agents over different locations. In the experiments, it has been verified that the application of compressed air foam has a positive effect on room cooling. Use of a compressed air foaming agent does not allow for the development of steam that can scald firefighters and reduce visibility. Furthermore, the extinguishing agent used is more efficient utilizing less water flow out of the fire area.

Experimental Research of Integrated Compressed Air Foam System of Fixed (ICAF) for Liquid Fuel

This article in view of the realistic requirement of fixed fire extinguishing system in the places of water-insoluble liquid, establishes stationary compressed air foam experiment platform in combination with the advantage of compressed air foam technology. Key component nozzle and mixing chamber of the system is designed. By cold spray test, obtains parameters of gas-liquid flow、pressure, foam mixing ratio which result in different types of foam. The division of different types of foam basis is put forward, and take drainage time as indicators, get the most stable foam parameter combination; by extinguishing experiment, get the better combination of dry foam and small nozzle whose extinguishing effect is best. The results can be guidance for production research of integrated compressed air foam and system application in combustible liquid places.

Analysis on Influencing Factors of the Gas-liquid Mixing Effect of Compressed Air Foam Systems

Abstract Compressed Air Foam System is a kind of new high efficiency firefighting systems. It produces high quality foams by injecting compressed air into foam solution. The gas-liquid mixing effect determines properties of foams. Properties of foams determine the efficiency of extinguishing. This paper introduced the status of compressed air foam system gas-liquid mixing technology, categorized and analyzed existing gas-liquid mixing modus, finally put forward factors influencing mixing effect. Stability of foams was used as criteria to evaluate the gas-liquid mixing effect. Gas-liquid mixing modus, gas-liquid mixing area and turbulence enhancer were three factors determined by mixing chamber structure. Gas-liquid flow ratio, gas-liquid mixing pressure and gas-liquid mixing speed were another three factors determined by working parameters. These factors were analyzed and corresponding optimization advices were put forward in order to better gas-liquid mixing effect. This paper could provide some guidance to the design of mixing chambers and optimization of mixing parameters.