A new foam rheometer for studying fire fighting foams

A new foam rheometer has been developed to study the yield stress and rheological properties of fire fighting foams. The instrument applies a constant stress to the foam, which enables direct comparison of different types of foam.     

Hangar fire protection with automatic AFFF systems

The control and extinguishment times of fuel fires using aqueous film-forming foams as the suppressant have been found to depend not only on application rate, but also on the type of discharging device. It is more effective to apply the suppressant directly to the burning fuel surface than to depend on flow of a foam blanket into the fire from the perimeter. Note: The aqueous film-forming foam discussed in this paper is Light Water, a registered trademark product of the 3M Company. Specifically, tests reported here were made with Light Water FC-200.     

Fighting fires in oil storage tanks using base injection of foam — Part I

This paper compares the characteristics of protein and fluoroprotein foams for base injected application to fires in oil storage tanks. Part I discusses foam flow and distribution and fuel pickup characteristics. Note: This paper was presented at the 81st Annual Meeting of the National Fire Protection Association in Washington, DC on May 17, 1977.     

Steel foam for structures: A review of applications,manufacturing and material properties

The objective of this paper is to provide a state-of-the-art review for the structural application, manufacturing, material properties, and modeling of a new material: steel foam. Foamed steel includes air voids in the material microstructure and as a result introduces density as a new design variable in steel material selection. By controlling density the engineering properties of steel components may be altered significantly: improvement in the weight-to-stiffness ratio is particularly pronounced, as is the available energy dissipation and thermal resistivity. Full-scale applications of steel foams in civil structures have not yet been demonstrated. Therefore, existing applications demonstrating either proof-of-concept for steel foam, or full-scale use of aluminum foams in situations with clear civil/structural analogs are highlighted. Adoption of steel foam relies on the manufacturing method, particularly its cost, and the resulting properties of the steel foam. Therefore, published methods for producing steel foam are summarized, along with measurements of steel foam structural (modulus, yield stress, etc.) and non-structural (thermal conductivity, acoustic absorption, etc.) properties. Finally, existing models for predicting foamed steel material properties are summarized to highlight the central role of material density. Taken in total the existing research demonstrates the viability of steel foams for use in civil/structural applications, while also pointing to areas where further research work is required.     

泡沫钢的应用、制作及属性

对泡沫钢的结构应用、制作、属性及模拟方法进行说明。泡沫钢内部含有许多微小空隙,故提出紧密度,作为泡沫钢的设计变量。改变紧密度,泡沫钢结构的工程特性可能发生重大变化:质量与刚度之比显著提高,有效能耗和热电阻也发生较大变化。在土木工程领域中,泡沫钢的实际应用尚未见报道。因此,在类似结构研究比较充分的前提下,着重研究现有泡沫钢的理论或泡沫铝的实际应用。泡沫钢的应用取决于制作方法,特别是成本费用及泡沫钢的性能。总结了已公开的泡沫钢生产方法、结构属性(模态、屈服应力等)或非结构属性(导热性、隔音性)。总结了泡沫钢属性的现有测量模型,突出了材料紧密度的重要作用。现有研究证明了泡沫钢在结构工程应用中的有效性,并指出进一步的研究方向。     

Suppression Performance Comparison for Aspirated,Compressed-Air and In Situ Chemically Generated Class B Foams

This contribution describes the experimental program undertaken to test the performance of a novel firefighting foam against the current Class B foam technology. The novel foam involved the use of a chemical reaction between dissolved species to generate inert nitrogen gas in situ; hence in situ generated nitrogen foams (ISNF). The experimental program encompassed the utilisation of the DEF(AUST)5706 test standard for measuring the suppression and burnback performance of the ISNF as well as that of compressed air foams (CAF). All tests were performed using the same two types of surfactant concentrates (one telomer and one PFOS-based) in order to accurately determine the effect of the generation technology on the foam performance. The three kinds of foams (i.e., aspirated, CAF and ISNF) were characterised in terms of their bubble size distributions and drainage rates. Bubble size analysis placed the size distribution of the ISNF midway between those of aspirated and compressed air foams, whilst drainage performance was found to be only slightly superior to the aspirated foam. The results of the experiments showed that in situ nitrogen foams are able to achieve good performance, similar to that of aspirated and CAF technologies. Further work is needed to optimise foam formulations for ISNF so that surfactants are not affected by the chemistry of nitrogen generation and by the presence of salts formed during chemical reactions.     

The use of light water for major aircraft fires

When a new extinguishing agent appears on the scene, existing agents become the yardsticks by which its performance is measured. The authors compared the relatively new Light Water foam with conventional protein foam and protein foam to which surface-active fluorocarbons had been added. Fire Research Station (JFRO) Note: Mr. Nash presented this paper at the 73rd Annual Meeting of the National Fire Protection Association on May 12, 1969 in New York City.     

Axial crushing of metal foam-filled square columns: Foam density distribution and impactor inclination effects

In this paper, the effects of foam density distribution and initial impactor inclination angle on crushing behaviour of metal foam-filled thin-walled square columns have been investigated. The simplified version of an existing pressure dependent self-similar constitutive model with tensile failure for metal foam has been implemented in ABAQUS/Explicit code. Random distribution of cubic regions with normal distribution of density has been created. The analyses have been accomplished for three distinct foam densities, two extreme random distributions (fine and coarse), and five different impactor inclination angles. A local effect on folding patterns of columns filled with low-density foam has been identified. Furthermore, unstable bending mode of collapse appears in the case of slightly inclined impactor and medium and high-density foams. In addition, for high-density foam-filled specimens global buckling can initiate by just letting the density of foam vary inside the sample.     

A comparative study of drainage characteristics in AFFF and FFFP compressed-air fire-fighting foams

Drainage measurements are commonly used for assessing the quality, water-retention ability and stability of aqueous foams used in fire-fighting applications. A new experimental technique is proposed in this paper, for measuring the drainage rate of liquid from compressed-air fire-fighting foams. The procedure outlined here provides advancement in precision over that prescribed by the standard for low expansion foams (NFPA 11, Standard for evaluating low expansion foams, NFPA, Quincy, MA, 1998). A comparative analysis of drainage characteristics in two commonly used Class B fire-fighting foams was undertaken, from theoretical and experimental perspectives: (i) aqueous film forming foam and (ii) film forming fluoroprotein foam. It is demonstrated that even though both the foam solutions exhibited similar fundamental physical properties, the disparities in surface rheological properties cause the resulting foams to have remarkably distinct drainage and coarsening characteristics. In addition, a drainage model is outlined, which allows the explicit prediction of the time evolution of liquid holdup profiles and drainage rates in fire-fighting foams. The existing drainage model is extended to simulate fire-fighting foams made from protein based and synthetically produced surfactants.     

Rheology of fire-fighting foams

This paper examines the rheological properties of compressed-air foams and contains velocity profiles of foams flowing through straight horizontal tubes. It is shown that a master equation can be derived from the experimental data to account for a range of expansion ratios and pressures normally encountered during pumping of polyhedral-in-structure fire-fighting foams. The experimental data come from a Poiseuille-flow rheometer consisting of three stainless steel tubes 6.95, 9.9, 15.8 mm in diameter, with foam generated by mixing a pressurised solution of Class A foam with compressed air. Results are corrected for wall slip following the method of Oldroyd-Jastrzebski, which implies the dependence of slip coefficients on the curvature of the tube wall. The experimental results demonstrate the applicability of the volume equalisation method to the more expanded, polyhedral (ε>5) and transition, bubbly-to-polyhedral (5⩾ε⩾4) foams. (The method of volume equalisation was introduced by Valkó and Economides to correlate the viscosity of low expansion foams (ε<4), characterised by spherical bubbles.) The present results indicate that all data points align themselves along two master curves, depending on whether the foam consists of bubbles or polyhedral cells.     

Foam — Its efficiency in tank fires

The increasing use of floating roof tanks for the storage of flammable liquids has given rise to a tendnecy toward using foam monitors for fire protection instead of fixed applicators. The authors studied the effect of application methods on foam efficiency and compared the effectiveness of two protein-based foams, Light Water, and a fluoroprotein foam known as F.P. 70.     

Polyurethane foam: Some studies relating to its behavior in fires

According to one test, polyurethane foam is “self-extinguishing,” while another classifies it as a “surface of rapid flame spread.” The author has found that its burning rate is sensitive to the applied heat flux and suggests that the fire resistance of polyurethane foam be assessed in tests using more realistic heat flux levels. Note: This paper is Crown Copyright 1971.     

Three-dimensional gaseous transfer within cellular plastic insulation and its consequences

The authors present a 3D gaseous transfer model and a simplified mechanical model. Thermal ageing and average volume change of ozone depletion potential foams with different facings are addressed. A formula has been suggested to correlate the elastic modulus and the reduced density of rigid foams over the whole foam density range. Les auteurs presentent un modele tridimensionnel de transfert gazeux et un modele mecanique simplifie. Ils traitent du vieillissement thermique et de la modification volumique moyenne de produits mousse a pouvoir d'appauvrissement de la couche d'ozone, en fonction de leur revetement; et proposent une formule permettant d'etablir une correlation entre le module elastique et la densite reduite des mousses rigides sur la plage complete de densite de mousse.     

An experimental study of the use of liquid argon and argon-filled aqueous foams for the extinction of lithium fires

The lithium pool temperatures of a 10-g lithium fire in an insulated container approximate the lithium pool temperature (above 1000°C) of a large-scale lithium fire. Addition of water or air-filled aqueous foam to a large-scale lithium fire generally results in a violent reaction. This violent reaction was observed when water or air-filled aqueous foam was added to an insulated 10-g size lithium fire.The use of a liquid argon spray against an insulated 10-g lithium fire resulted in substantial spattering of the hot, molten lithium. Consequently, a liquid argon spray is not recommended against a large-scale lithium fire.Although an argon-filled aqueous foam directed onto an insulated 10-g lithium fire resulted in an increase of the lithium pool temperature, in every experiment conducted in this effort the lithium fire was extinguished. The extinguishing action of the argon-filled foam is positively correlated to the foam flow rate directed to the fire. Aqueous argon-filled foams from concentrated sodium silicate solution or cupric chloride solution did not appear to enhance the extinguishing action of the foam, compared to argon-filled water (only) foams.     

压缩空气泡沫灭火抗烧效能试验研究

为进一步量化压缩空气泡沫介质的性能特征优势,采用固定式压缩空气泡沫灭火系统,通过标准油盘火对比试验,分别考察压缩空气泡沫和常规吸气泡沫控火、灭火、防复燃、抗烧效能,并测试两种特征泡沫多项性能指标。结果表明：基于相同火灾试验模型和测试方法,两种特征泡沫均可扑灭92#汽油火,火焰均未复燃,但压缩空气泡沫在低灭火强度条件下的控火、降温、灭火、抗烧效能明显优于高灭火强度常规吸气泡沫;由基本性能指标表征出压缩空气泡沫具有更为稳固均细的膜状组织,并且低温环境对压缩空气泡沫结构群体具有维护作用,不会发生冰冻现象;采用压缩空气泡沫离散型喷头既可生成高质量泡沫灭火介质,又可对保护区域进行无盲点均匀覆盖,拓宽了压缩空气泡沫应用方式,对于后续重点开展压缩空气泡沫应用于高层、高大、高危建筑体室内消防安全论证工作具有一定的借鉴作用。     

Design of protective structures with aluminum foam panels

Design of protective structures requires multiple functions and reasonable safety criteria according to target structures. Hardening is one of the common concept to protect facilities and people. A general concept of blast pressure mitigation by metal foams was proposed. In this paper, a composite panel with aluminum foams and steel skins is introduced. Aluminum foams have low density and are attractive materials to mitigate high-speed pressure by blast loads due to high-energy absorption capabilities. A steel skin with high energy absorption capacity can be effectively used to resist penetration at front surface of the barrier and debris risk at rear surface. Mechanical properties of the aluminum foam according to different densities were obtained by material tests. Three material models for concrete, steel and aluminum foam were utilized considering strain-rate effects. Using the derived material models, explicit analyses of the composite panels were performed and their performance was evaluated. The newly developed high strength foam showed higher yield strength and better energy absorption capacity resulting in lightweight protective panels. For high blast pressure, the combination of energy absorbing steel skin and relatively dense foam or thicker foam is more effective.     

LNG facilities — Engineered fire protection systems

Dry chemical fire extinguishers used in conjunction with high expansion foam have been used successfully in tests to extinguish LNG spill fires. Note: This paper was presented at the 79th Annual Meeting of the National Fire Protection Association, May 1975, Chicago, Illinois.     

改性酚醛保温板研究与应用

酚醛泡沫以甲阶酚醛树脂为主要原料,由于其优异的保温和阻燃性能在保温领域具有广阔的应用前景.但是,酚醛泡沫在成型过程中通过酸性(催化)固化剂固化成型,金属材料与泡沫体接触时容易受到腐蚀.为了降低金属被腐蚀的可能性,在不影响酚醛泡沫其他优良性能的前提下,通过选择合适的碱性填料、用酯固化作用取代酸固化剂、合成吸酸剂等方法降低...     

聚氨酯泡沫热解产物对可燃液体物证鉴定的干扰性研究

摘 要：以不同密度聚氨酯泡沫为研究对象,采用同步热分析（STA）和气相色谱-质谱联用技术（GC-MS）,分析了聚氨酯泡沫塑料热解产物对汽油鉴定干扰性的影响。试验表明,聚氨酯泡沫塑料热解过程可分为两个阶段,80 kg/m3聚氨酯泡沫塑料第一阶段热解初始温度略低,质量损失率略大。聚氨酯泡沫塑料燃烧残留物中可检测到芳香烃、稠环芳烃和茚满类特征组分,但40 kg/m3聚氨酯泡沫塑料燃烧残留物检出的相似特征组分数量明显较多,因此,40 kg/m3聚氨酯泡沫塑料对汽油鉴定的干扰性高于80 mg/m3。     

Development and characterization of an inorganic foam obtained by using sodium bicarbonate as a gas generator

In the construction industry almost all of the insulating and expansive materials are organic foams. In this work, the production of an inorganic foam is described. Sodium bicarbonate is used as a gas generator. CO₂ gas is released when water is added to the mixture of sodium bicarbonate and β-hemihydrate gypsum powder (CaSO₄ · 1/2H₂O). Hence, stabilization of the foam is achieved when CO₂ gas is released and water is absorbed by β-hemihydrate gypsum powder, which subsequently is converted into calcium sulphate dihydrate (gypsum matrix). The bulk density and mechanical properties (compressive and flexural strength) of the inorganic foam and gypsum were determined. Microstructural characterization has been carried out by SEM and XRD, and a new sodium sulphate phase was identified in the gypsum foam due to this chemical reaction. Finally, thermal properties such as thermal conductivity and diffusivity were measured and it was observed how for the same heat flux, the thickness of an inorganic foam slab is 73.4% less than that of a concrete slab.