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.     

Extensions To Standard Hold Time Calculations

The paper extends existing methods of calculating the hold time for a fire extinguishing gas in an enclosure to cover mechanical HVAC systems and wide descending interfaces, and compares the wide descending interface model's predictions with some experimental data. A simple approximation to the measured wide descending interface gives conservative hold time predictions, while the sharp descending interface model used in current standards gives optimistic predictions.     

AP1000核电厂常规岛消火栓和灭火器设计标准分析

随着国内AP1000核电厂的陆续兴建,尽快掌握国际通用的相关标准已经迫在眉睫。消防系统是电厂设计中的重要系统之一,美国NFPA(National Fire Protection Association)标准作为国际通用的消防设计标准,与中国标准存在一定的差异。对比分析了中国标准和美国NFPA标准在消火栓和移动式灭火器系统方面的差异,以期为消防系统设计人员提供参考。     

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.

Fire Safety Code for Historic Structures

The National Fire Protection Association (NFPA) periodically updates each fire safety code and standard that it develops. Acknowledging the need for a document to prescribe fire safety for historic buildings, a complete and thorough rewrite of NFPA 914 was undertaken. The former recommended practice has now been issued as the Code for Fire Protection in Historic Structures. The 2001 edition identifies a process for analyzing fire safety needs in historic buildings, outlines generic approaches to dealing with specific provisions of other codes that may endanger historic integrity, and includes a performance-based approach to fire safety in historic buildings. This paper describes the background, revision process, and current proposed content NFPA 914.     

空气预热器消防装置的研制与应用

介绍了空气预热器的用途与原理,给出了预热器的火灾安全分析,根据安全分析结果,参照NFPA 850标准要求设计了一种空气预热器专用消防装置,给出了装置满足标准要求的实验验证方法和结果,并将本消防装置进行了实际工程设计。装置具有结构简单紧凑、安装维护简便等优点。     

特高压变压器水喷雾消防管网耐火能力提升措施研究

特高压变电站的固定灭火系统完好是实现其灭火能力的重要前提。首先,通过对现有标准中消防管网耐火能力试验方法进行对比,结合特高压变压器实体火灭火试验数据,明确了特高压变电站水喷雾灭火系统消防管网耐火能力现状。其次,利用气体燃烧器原理设计试验火源,测试结果显示试验火源温度与全尺寸特高压变压器实体火灭火试验中测到的温度较一致,利用该试验火源开展试验能符合实际工况。最后,通过对比试验给出了水喷雾消防管网耐火能力提升建议,为实际工程改造与建设提供参考。     

Standardizing the Measurement of Minimum Extinguishing Concentrations of Gaseous Agents

The cup-burner test method has had a long history as a tool for measuring the minimum flame extinguishing concentrations (MEC) of gaseous fire-extinguishing agents for flammable and combustible liquid fuels. The pioneering work by Hirst and Booth (1977) set out the basic principles of the cup-burner and its use. Saso et al. (1993) reported on scale effects on MEC measurement. Preece et al. (2003) reported on parametric effects on MEC measurement. A number of investigators have provided determined values of MEC for a number of inert gas and fluorocarbon agents. See Dlugogorski et al. (1996); Saito et al. (1996); Moore et al. (1998); Sheinson et al. (1998). Takahashi et al. have reported on several investigations of flame extinguishment in the cup-burner including conducting a detailed computational fluid dynamic modeling including reaction kinetics and mass and heat transfer (2003); physical and chemical aspects of flame extinguishment (May 2005); and evaluation of flame extinguishment in low gravity (January 2005). Application of the cup-burner method has, in some instances, produced inconsistent results. MEC values reported by several investigators for the same inert gas agents have exhibited differences that are significant with respect to the way in which they are used (Senecal 2005). Thermochemical analysis and data obtained in a consistent manner suggested that there is a reasonable basis to expect highly consistent, and even predictable, MEC values for inert gas agents. It appeared that the likely source of measurement variation was due to procedural and mechanical differences in the conduct of the cup-burner test among various laboratories. A Task Group, appointed by the NFPA GFE-AAA technical committee on gaseous fire-extinguishing systems, revised the cup-burner test procedure including the specification of a standardized test apparatus. This article describes an inter-laboratory study conducted in 2006 to (1) determine consensus value benchmark minimum extinguishing concentrations (MEC) of an inert gas agent and a halocarbon agent; (2) evaluate the reproducibility of the revised test method; and (3) evaluate the day-to-day consistency (repeatability) of the test method. The results of an inter-laboratory (round robin) study have established benchmark MEC values for nitrogen and HFC-227ea with excellent reproducibility. The results show that MEC values reported by most laboratories were in very good agreement, i.e., exhibited good reproducibility based on averages of three replicate determinations on different days. Analysis of the replicate data revealed a variable degree of repeatability, suggesting that a laboratory will need to review key procedural details in some cases.

国内某地铁加装细水雾灭火系统方案

对行业内自动灭火系统进行对比,提出细水雾灭火系统在城市轨道交通车辆上应用的优势。通过在国内某地铁加装细水雾灭火系统的实例,介绍了细水雾灭火系统的方案、系统组成及细水雾装置的配置方案,依据地方标准的要求,通过对灭火时环境参数的分析,验证了加装的细水雾灭火系统达到了设计要求,起到了灭控火的目的。     

竹结构轻型框架房屋火灾安全性能试验研究

采用欧洲规范确定房屋的火灾荷载后,使用木垛火作为火源,对一足尺竹结构轻型框架房屋进行火灾模拟试验,研究了此类型房屋的火灾安全性能。历时1h的火灾作用后,墙体骨柱在9.5mm厚普通石膏板的保护下,平均炭化深度仅为截面尺寸的1/3,而楼盖格栅在19mm厚防火石膏板的保护下几乎没有火灾损伤,房屋最终保持了良好的结构整体性,表明此类竹结构房屋耐火时间可以达到1.0h以上,具有良好的火灾安全性能;墙体和楼板内外表面的热电偶数据显示迎火面墙体最高温度达到686℃的情况下,背火面温度维持在一个较低的温度水平(最高温度仅为46～84℃),表明采用石膏板和岩棉的房屋墙体和楼板具有良好的保温隔热性能;在试验研究的基础上,对竹结构轻型框架房屋的构造措施提出了设计建议。     

可燃液体火灾危险场所细水雾灭火系统的试验研究

针对可燃液体火灾危险场所中不同燃烧功率、火灾类型、障碍物特征、燃烧物质情况进行了细水雾灭火试验，给出了部分试验结果。针对试验数据进行分析总结，提出了火灾规模、空间通风率等是实体火灾试验中必须关注的问题，给出了细水雾系统在可燃液体火灾危险场所使用的基本要求。指出细水雾灭火系统按实体火灾试验规约进行产品检验的重要性，为今后我国细水雾灭火系统的研究和工程应用提供借鉴。     

住宅小区消防给水设计体会

依据现行消防设计规范，结合某居住区的规划设计论证，论述了居住区的消防设计标准、市政条件和消防供水方式的确立，提出了消防系统的安全性保障措施。     

细水雾灭火系统在电厂电缆大厅中的应用

细水雾灭火系统是一种新兴的灭火技术，它在灭火效果、工程造价、环境保护、二次灾害损失等方面都有较大的应用空间。介绍了细水雾灭火系统在电厂电缆大厅中的应用及灭火试验。     

福州市档案馆消防设计

本文介绍了甲级档案馆消防设计,探讨了在我国目前档案馆建设中如何选择经济适用的灭火系统,并提出了有关设计规范间存在互为矛盾的问题。     

对消防安全技术应用和研究的思考

分析了增强城市人员密集场所火灾防控能力的必要性，介绍了安防报警与消防逃生门锁系统、城市火灾自动报警网络系统、简易喷水灭火系统、自动控制排烟窗及单点式火灾探测报警器等技术，讨论了制、修订消防技术规范标准的相关问题。     

消防用电设备配电线缆现状分析

文章通过介绍国内外配电线缆耐火性能的试验标准，分析了目前消防用电设备配电线缆应用和模拟实体火灾的试验。对现行规范的相关内容提出了修改建议。     

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).     

酒厂防火防爆关键技术研究及应用

论述饮料酒的火灾危险性属类、适用于酒库的灭火系统和关键设计参数、酒厂灭火器配置场所的危险等级、电气防爆和生产工艺装置防静电、陶坛酒库的建筑防火设计参数以及酒厂消防站和消防装备的配置等关键技术,对比分析主要技术参数与相关国家标准同类技术之间的先进性,并简介研究成果的推广应用概况。     

灭火器的定位和有效性辨识研究

智慧消防是智慧城市建设的重要组成部分，在消防工作创新发展中发挥重要作用。灭火器作为扑救初期火灾的最普遍、最便捷和最广泛使用的灭火设施，在初期火灾的扑救和火灾防控中发挥重要的作用，其有效性和完好性是扑救初期火灾的必要条件。基于物联网及大数据的优势，建立消防灭火设施的定位与有效性辨识系统，并介绍系统的关键技术、网络架构、技术特征。此系统可对灭火器等消防灭火设施的伺应状态、完好性、有效性等功能特性进行跟踪巡检和辨识，以实现对灭火器的实时监控和智能化管理，促进消防设施建设的完善和优化，增强灭火系统的可靠性，充分发挥智慧消防技术在智慧城市建设中的优势。     

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...