Analysis of Hold Time Models for Total Flooding Clean Extinguishing Agents

This study documents the experimental results of a research program designed to evaluate the validity of the widely published hold time prediction models found in NFPA 2001, Annex C and ISO 14520-1, Annex E. The models discussed in these standards obtain a measure of the equivalent leakage area, which, when coupled with ‘worst case’ assumptions, can be used to determine the minimum hold time. Three hold time prediction theories are adopted from these standards for validation; a wide descending interface model as implemented in ISO 14520-1 and two sharp descending interface models from the 2004 and 2008 publications of NFPA 2001. The experimental program is comprised of 15 tests conducted in a 103 m³ test enclosure. Three commercially available clean agents are selected to span a wide range of agent vapor densities including FK-5-1-12, HFC-125, and IG-541. A series of holes were drilled through enclosure boundaries at upper and lower elevations which were opened or closed as a means of regulating the amount of leakage area for any given test. Vertical profiles of agent concentration and ambient pressure are used to evaluate the agent concentration distribution, rates of agent draining, and the effective lower leakage fraction. A non-dimensional hold time is used to compare experimental results involving differing agent types and leakage areas. Results show that empirical values of the hold time are up to 50% longer than the theoretical hold time predictions when evaluated as the time to reduce the agent concentration to half its initial value. When evaluated as a 15% drop in concentration the model validity is significantly reduced. Under this condition, empirical hold time values are up to 50% shorter than the predictions of the sharp descending interface models and up to 100% longer than the wide descending interface model.

Hold Time Calculations for Non-Standard Enclosures

Current methods of calculating hold time for a fire fighting gas assume that the enclosure is of uniform horizontal cross-sectional area and has horizontal upper and lower boundaries (a standard enclosure). The paper shows that the hold time equation for continuous mixing in standard enclosures may also be used for non-standard enclosures, presents exact and simplified equations for descending interfaces in non-standard enclosures, and discusses the accuracy of the simplified equation. Considering the error when the simplified equation is applied to standard enclosures, and that it is always conservative for an enclosure of any shape, it is suggested that it may be used as an approximation for non-standard enclosures. The paper also presents a hold time equation for a descending interface in a standard enclosure with laminar flow in the leaks.     

Review of Fan Integrity Testing and Hold Time Standards

The paper examines the basis of the NFPA, British and ISO/CEN fan integrity testing and hold time standards. It is found that the most appropriate leakage area definition for integrity testing is Equivalent Leakage Area in CAN/CGSB-149.10-M86. Differences between the standards are discussed, an error in the NFPA standards is described, and other changes to the standards are recommended. Areas for further research are proposed to enable the errors in calculated hold times to be estimated with confidence and, if necessary, reduced.     

A modified hold time model for total flooding fire suppression

This study analyzes the validity of theoretical models used to predict the duration (hold time) for which a halon-replacement suppression agent will remain within a protected enclosure. Two current models and one new formulation are investigated: the sharp descending interface model (as applied in NFPA 2001, Annex C), the wide descending interface model (implemented in ISO 14520.1, Annex E), and the thick descending interface model (introduced herein). These three models are validated through direct comparison to the data provided by a recent experimental study. Designed to characterize full scale agent draining dynamics, the experimental phase included 34 tests using seven different clean extinguishing agents (CEA).     

一起火灾事故调查中视频分析与现场实验

在一起典型的电气火灾事故调查过程中,调查人员采用"火察"软件分析视频中的关键信息,依据弧光特征确定了电气火灾的调查方向,运用火灾视频量化数据法计算火灾视频中电弧光线的投影角度,利用光线投影的反向延长线划定了发生电弧的范围.通过现场不同位置光影轮廓线实验,缩小了调查范围,结合痕迹物证、证人证言等内容验证火灾视频分析的结论...     

气体灭火系统消防监督检查技术研究

在当下消防工作中,气体灭火系统对于大多数城市来说非常重要,尤其是在经济快速发展,建筑行业突飞猛进的时代,不少城市开始出现大量的建筑物,而这些建筑物刚好是城市发展的标志,而密集的城市建筑物也给消防安全带来了隐患,严重的火灾事故时有发生。因此,消防系统的发展开始成为社会发展的重要组成部分。而气体灭火作为其中重要的系统之一,凭借其独特的优势和广泛的使用范围赢得了社会的认同,与此同时,气体消防灭火系统的消防监督检查系统开始成为消防工作关注的重点,相关消防工作人员要注意各个消防系统的操作要点,从消防防控着手,保证气体灭火系统在消防监督检查技术的保障下,发挥出更大的作用。     

SP合成型泡沫喷淋灭火系统的应用探讨

本文简要介绍了SP合成型泡沫喷淋灭火系统的原理和特性,并且与其它灭火系统进行了比较,论述了系统的设计计算,阐明了该系统具有高效、安全、经济的特点,具有广泛的应用前景。     

高分子水凝胶灭火剂扑救建筑火灾研究

为测试高分子水凝胶灭火剂扑救建筑火灾的灭火效果,以GB 17835-2008《水系灭火剂》中A类火灭火试验相关规定为参照,搭建木垛实验平台,模拟火灾荷载密度为2 395.008 MJ/m2（相当于一家服装店的火灾荷载）的建筑火灾,且在相同条件下,对比测试高分子水凝胶与水两种灭火剂的灭火效果,并利用车泵压、流量等相关关系计算得出高分子水凝胶灭火剂在建筑火灾扑救中的灭火强度。试验对比分析结果表明,高分子水凝胶灭火剂的灭火时间比水灭火剂的灭火时间短,其灭火效果优于水;同时依据相关计算得出高分子水凝胶灭火剂扑救建筑火灾的灭火强度约为0.059 L/（s.m2）。     

水喷雾与泡沫喷雾灭油池火实验特性对比研究

通过自主搭建实验平台开展灭换流变压器油池火实验,对采集到的雾流密度、温度、热流、热成像等数据进行分析,得到水喷雾和泡沫喷雾系统的灭火特性,对比得出两灭火系统的灭火效率差异.结果表明:水喷雾与泡沫喷雾灭火所用时间为190、100 s;水喷雾灭火系统与泡沫喷雾灭火系统最终热流值分别降低至0.0059、0.0047 W/m2...     

液氮灭火装置灭火性能实验分析

以液氮作为灭火剂，对A类、B类和深位火灾进行了灭火实验，并与其它灭火剂在灭火时间和使用量方面进行比较。     

浅谈火灾自动报警及灭火系统在大型装卸机械上的应用

作者分析了集装箱桥吊电气房的火灾因素，提出了适宜桥吊电气房的火 灾报警及灭火系统类别并对具体的设置位置进行了分析。     

低压二氧化碳灭火系统及其设计计算

本文概述了低压二氧化碳灭火系统的组成和优点,详细地介绍了它的设计计算步骤,并给出了相关图表。     

有关变压器水喷雾灭火系统的探讨

本文对油浸变压器的火灾危险性进行了分析，结合工程实例，总结了水喷雾灭火系统的设计和施工要点，并对实际存在问题提出了解决方案。     

基于综合管廊火灾特性的细水雾灭火系统应用研究

综合管廊电力电缆舱室具有较高的火灾危险性,一旦发生火情,极易酿成重大火灾事故。笔者研建了综合管廊实体火灾试验平台,开展了不同工况条件下的细水雾灭火系统局部应用与全淹没应用灭火试验研究。研究表明,对于综合管廊电力舱,细水雾灭火系统宜采用全淹没灭火方式;若需采用局部应用灭火方式,应对着火分区与相邻分区同时喷射细水雾,并保证一定的灭火区间长度和喷雾强度。灭火过程中,通风排烟系统与门窗洞口严重影响细水雾灭火性能,火灾时应及时联动关闭;全淹没应用时,适当增大系统喷雾强度,是保障细水雾高效能灭火的关键。     

超微磷酸铵盐干粉灭火剂的制备

本文首次采用水相合成法制备磷酸铵盐干粉灭火剂 ,以磷酸二氢铵和硫酸铵为主料,滑石粉、云母粉、活性白土、硅油、白碳黑、硅酸钠和添加剂为辅料,成功的制备了粒径在100nm-500nm的超微磷酸铵盐干粉来火剂。     

国内外灭火药剂的发展和现状

作者按灭火剂的存在形态,将灭火剂分为气体灭火剂、固体灭火剂和液体灭火剂三大类,分别对灭火剂的发展水平、适用场所、市场情况、产品质量和开发方向等均做了简明的阐述。     

有机硅/碳氢表面活性剂对水成膜灭火剂性能的影响

针对目前水成膜灭火剂中表面活性剂存在环境危害的问题,选择性能优良、环境友好型表面活性剂,制备水成膜灭火剂,并对添加表面活性剂的灭火剂性能进行测试。结果表明,有机硅表面活性剂十二烷基二甲基甜菜碱（BS-12）与双性型碳氢表面活性剂椰油酰胺丙基甜菜碱（CAB）在复配后具有较为良好的性能,起泡能力较高,泡沫稳定,铺展迅速,灭火时间短。     

车用乙醇汽油泡沫灭火剂的研究

车用乙醇汽油的应用日益广泛,为有效处置此类特殊液体火灾,通过关键组分筛选与复配研究,研发了一种新型高效的非PFOS 类泡沫灭火剂。该产品通过了国家标准GB 15308-2006《泡沫灭火剂》的检测,灭火性能达到最高级别,且通过对比试验验证了产品的灭火性能优于国内其他产品,并进一步研究提出产品的灭火供给强度这一关键灭火应用参数。     

改性干水灭火剂灭木垛火试验研究

新型干水灭火剂因其高含水量和特殊核壳结构,具有良好的灭火效果。为探究干水对木垛火的灭火效果,自行制备磷酸二氢铵改性干水并开展小尺寸木垛火灭火试验。结果表明：干水灭火剂能够扑灭小尺寸木垛火且不发生复燃,改性干水的控火时间仅为8 s,控火过程中火焰高度持续快速下降,而干粉灭火剂的控火时间则为20 s,喷撒结束39 s后发生复燃;改性干水对火焰区及木垛的温度抑制效果均优于干粉灭火剂,控火时间内,改性干水作用下木垛表面的平均温降速率高达17.00℃/s,是干粉灭火剂作用下平均温降速率的1.94倍;改性干水能够有效降低木垛内部温度,在喷撒50 s内,木垛中心的平均温降速率为8.78℃/s,而干粉灭火剂缺乏冷却作用,木垛中心的平均温降速率仅为6.10℃/s,无法有效抑制阴燃。     

AFFF 对航空煤油油池火的抑灭有效性研究

按照国家标准灭火试验的要求,采用不同的泡沫喷射率对不同尺寸航空煤油油池火开展了灭火效果试验,分析油盘尺寸、泡沫喷射率对灭火效果的影响,验证固定喷射率条件下,能够扑救的最大尺寸的油盘。结果表明：当油盘面积为0.8 m2 时,泡沫喷射率为2.9 L/min 时的灭火时间比为1.3 L/min 时缩短近60 s;当泡沫喷射率为1.3 L/min 时,最大可控制1.0 m2 航空煤油油池火的90%燃烧,未能将其完全扑灭;当泡沫喷射率为2.9 L/min 时,可完全扑灭2.0 m2 及其以下的航空煤油油池火。