The Capabilities and Limitations of Total Flooding, Water Mist Fire Suppression Systems in Machinery Space Applications

Water mist fire suppression systems are being seriously considered as replacements for Halon 1301 total flooding systems in machinery space applications. A total flooding water mist system is designed to discharge mist uniformly throughout the entire enclosure/compartment. The tests conducted to date form a substantial database for water mist systems installed in machinery spaces with volumes from 100 m³ to 1,000 m³ and varying degrees of ventilation. These tests have also identified the strengths and limitations of water mist in these applications. This report describes the capabilities of total flooding water mist fire suppression systems in machinery space applications.     

高压细水雾灭火系统用于绍兴市档案馆库房

细水雾灭火系统是一种灭火效率高、耗水量少、绿色环保的新型灭火系统。结合绍兴市综合档案馆大型库房消防设计实例,介绍了高压细水雾灭火系统的组成、工作原理、设计参数、计算公式、控制方式等,提出了高压细水雾灭火系统在实际应用中存在的问题和相关建议。     

Extinguishment of Cooking Oil Fires by Water Mist Fire Suppression Systems

A series of full-scale experiments were conducted in a mock-up commercial cooking area to study extinguishing mechanisms and effectiveness of water mist against cooking oil fires. The impact of water mist characteristics, such as spray angle, droplet size, flow rate, discharge pressure and type of nozzle, on the effectiveness of water mist against cooking oil fires was investigated. A series of oil splash experiments were also conducted to determine if the oil was splashed by water mist. In addition, the change in oil composition during heating and fire suppression was determined using Fourier Transform Infrared (FTIR) technique.The study showed that cooking oil fires were very difficult to extinguish, because they burned at high temperature and re-ignited easily due to changes in oil composition during heating and fire suppression. The water mist systems developed in the present work effectively extinguished cooking oil fires and prevented them from re-ignition. The spray angle, discharge pressure, and water flow rate were important factors to determine the effectiveness of water mist in extinguishing cooking oil fires.     

Evaluation of Surfactant Enhanced Water Mist Performance

Water-mist technology provides efficient fire suppression for compartments while minimizing water usage. Even with the many advantages of water mist systems, there is still room for improvement. Water mist systems have demonstrated effectiveness at suppressing flammable liquids (Class B) fires in compartments. However, an especially challenging fire suppression scenario for water mist systems is the small Class B fire. This scenario is often realized after a large fire has been reduced in size or ‘controlled’ by water mist. The small fire scenario is challenging because a small fire may not be able to generate enough vaporized water to displace sufficient oxygen for complete extinction. It should also be noted that even if the Class B fire is extinguished with a water mist system, re-ignition from the hot surrounding surfaces may occur at any time. In the present work, an additive is introduced into the water supply and its effect on the water mist suppression performance is studied. This Forafac^TM additive is a specific formulation, which includes fluorinated surfactants for creating a robust fire suppression foam. The enhanced suppressant exiting the mist nozzle is dispersed in the form of small droplets (not as a continuous foam) similar to a pure water mist spray. However, these droplets create a foam blanket on the surface of the fire, which acts to isolate the fuel from the air. With this formulation, the efficiency of the water mist system is improved even on small fires and most importantly the re-ignition of class B fires is prevented.

细水雾灭火机理探讨

本文研究了细水雾水滴直径与蒸发时间的关系,不同可燃物燃耗氧量的关系,并分析了水滴蒸发吸热量和水蒸汽分压增加对灭火效果的贡献,结合实验研究结果提出细水雾灭火的机理主要是水滴迅速汽化形成的水蒸气层阻碍了氧气向燃烧区域的扩散,而使可燃物燃烧耗尽局部区域氧气窒息熄灭。     

高压细水雾灭火系统在南宁市城建档案馆中的应用

简述高压细水雾灭火系统在国内外的发展概况,通过与几种常用气体灭火系统的对比,总结出高压细水雾灭火系统的特点。同时,以南宁市城建档案馆为例,介绍了该系统在实际项目中的设计应用。     

Examination of the Extinguishment Performance of a Water Mist System Using Continuous and Cycling Discharges

We conducted a series of full-scale fire tests of a twin-fluid water mist system in an empty enclosure and in a simulated machinery space. During the tests, two water mist discharge modes, continuous and cycling, were used. We investigated the extinguishment performance of the water mist system using these two discharge modes under various fire scenarios, including different fire sizes, types, and locations, and different ventilation conditions. Test results showed that use of the cycling discharge substantially improved the effectiveness of the water mist system for fire suppression, in comparison to the continuous discharge. The corresponding extinguishing time and water requirement for fire suppression were significantly reduced, and some fires that could not be extinguished with the continuous discharge were extinguished with the cycling discharge. The improvement in fire suppression was attributed to high depletion and dilution rate of oxygen and the recurrent dynamic mixing generated by the cycling water mist discharge in the compartment.     

Water Spray Protection of Machinery Spaces

This report provides an evaluation of the firefighting capabilities of fixed pressure water spray systems for machinery spaces as described in Regulation 10 of Safety of Life at Sea (SOLAS). The objective of this evaluation was to determine if a system meeting the minimum SOLAS requirement can provide adequate protection of shipboard machinery spaces. To meet this objective, the capabilities and limitations of twelve water spray systems were determined using the International Maritime Organization (IMO) test protocol for water mist systems (MSC 668 and 728) as the basis for this analysis. The tests were conducted in a simulated 500-m³ machinery space onboard the U.S. Coast Guard's test vessel STATE OF MAINE. Generally speaking, the trends in performance of water spray systems were similar to those observed for water mist systems. All systems were capable of extinguishing larger fires (4 kW/m³ and greater) with variations in system capabilities becoming apparent as the fire size was reduced (2 kW/m³ and below). Only about half of the systems were capable of extinguishing the 1.0 MW obstructed spray fire located on the side of the engine mock-up (similar to IMO-6). Water mist systems typically exhibit slightly better capabilities primarily against the smaller fires. It was concluded that the capabilities of these systems cannot be associated with a single parameter such as application rate and must be determined empirically. As a result, the approval of these systems needs to be performance based as with all other fire suppression systems required by SOLAS. It was recommended that SOLAS Regulation 10 be re-written to cover all water based machinery space systems with the caveat that they pass a modified IMO test protocol based on the one currently used for approving water mist systems [MSC 668 and 728].     

浅谈高压细水雾灭火系统在某档案馆中的应用

简述了档案馆的特点和灭火要求,并结合消防工程设计实例介绍了高压细水雾灭火系统的构成、工作原理及在档案馆中的设计原则、设计参数、喷头布置及控制方式等,认为该系统不仅可避免环境污染及水渍损害,还具有多种应用优势,供建筑消防设计参考。     

An Evaluation of Total Flooding High Expansion Foam Fire Suppression Systems for Machinery Space Applications

Full-scale fire tests were conducted to identify the fire extinguishing capabilities and limitations of High Expansion Foam Fire Suppression Systems (HEFFSS) in shipboard machinery space applications. A total of 35 tests were conducted in this evaluation utilizing the equipment and foam concentrates from three manufacturers. Each manufacturer was responsible for the design of their respective system. These designs were based on the minimum SOLAS/FSS Code requirements plus some additional capacity to provide a factor of safety for these tests. Each system was evaluated against the three large fire scenarios described in the International Maritime Organization's (IMO) gaseous agent test protocol (MSC/Circ. 848). The reason the HEFFSS test protocol (MSC/Circ. 670) was not used is discussed in the article. In addition to the tests in MSC/Circ. 848, parametric assessments of fill rate, fire size and type, and the use of inside air (the products of combustions) to make the foam were also conducted (one parameter for each of the three systems). In summary, there were significant differences in capabilities between the three systems. All three systems easily extinguished the pan fires included in this evaluation independent of the type of fuel (heptane or diesel). The differences in system capabilities were observed during the extinguishment of the spray fires (namely the heptane spray fires). The heptane spray fires presented a major challenge to the HEFFSS and in some cases, were not extinguished.     

A Water Requirements Estimation Model for Fire Suppression: A Study Based on Integrated Uncertainty Analysis

Rescue work is one of the main objectives of firefighting. To minimize casualties and financial losses, fire service agencies consider sufficient water supply for fire suppression to be the key among the many factors affecting firefighting. The difficulty of collecting water usage data from actual fire scenes has confined the research on water allocation for firefighting in either domestic or international arena mostly to theoretical studies. Consequently, the use of firefighting water resources often follows empirical methods or related government legislation, rather than being an effective practice verified by in-depth field investigation. This study, based on fire engineering theory, employs heat release rate combined with uncertainty analysis to develop a model for estimating water requirements for firefighting. Using firefighting cases at Taoyuan County in Taiwan, R.O.C., a quantitative analysis of the field data was integrated with uncertainty analysis to evaluate the suitability and uncertainty of the proposed firefighting water supply model. The result indicates that the proposed model of firefighting water requirements can effectively reflect water demand in an actual fire incident. Among the 100 cases tested, the actual firefighting water consumptions are averaged as 44.2 metric tons whereas the mean difference between the derived water requirements and the actual amount is approximately ±15 metric tons.     

关于居住小区加压泵房贮水池贮存消防用水的思考

本文针对《建筑给水排水设计规范》GB50015—2003第3.2.8条与第3.7.2条规定展开讨论,指出这两条规定并不矛盾,对规范条文的适用性应有正确的理解和掌握,并根据实际工程的问题加以分析,确保居住小区加压泵房贮水池的贮水符合卫生、安全等方面的要求。     

大空间建筑消防给水系统的优化研究

大空间建筑具有灭火困难、发生火灾危险性大以及面积大、层数高的特点。因此,在设计大空间建筑消防给水系统时,要综合多方面因素,保证其安全性和可靠性。本文针对大空间建筑的消防给水系统优化进行了详细的分析。     

大空间建筑消防给水系统的优化研究

大空间建筑具有灭火困难、发生火灾危险性大以及面积大、层数高的特点。因此,在设计大空间建筑消防给水系统时,要综合多方面因素,保证其安全性和可靠性。本文针对大空间建筑的消防给水系统优化进行了详细的分析。     

A computational and experimental study of ultra fine water mist as a total flooding agent

Computational fluid dynamics (CFD) calculations were carried out to design total flooding fire tests in a 28 m³ compartment for an ultra fine water mist (<10 μm). The exit momentum of the mist produced by a proprietary ultrasonic generator technology was extremely low with a mist discharge velocity below 1 m/s. The mist was discharged with multiple floor outlets equally spaced around the centrally located 120 kW pool-like gas fire. The transport of mist and its interaction with the fire was simulated by Fluent, a commercial CFD model. Lagrangian Discrete Phase Model (DPM) was used for droplets. Simulation predicted extinguishment within 10 s with a mist delivery rate of 1 l/min. However, in total flooding fire tests conducted, extinction times were more than 5 min. Additional computations approximating the ultra fine mist (UFM) as a dense gas agreed well with the observed transport timescales of minutes indicating that UFM behaves like a gas. Further, the mist–fire interaction needs a multi-phase Euler–Euler approach with a droplet vaporization model.     

A Study on the Reliability of Fire Water Supply System in High-rise Buildings

This paper puts forward the significance of study for the reliability of fire water supply system in high-rise buildings, as an exploration for the reliability of fire water supply system to attract the attention from experts on this issue. It briefly introduces the reliability model and calculation of the system, and analyses functional application process and probability features of the system. It raises the principles of reliability design and the method of improving reliability to benefit the optimization of fire water supply system design. Moreover, the development of reliability study has been looked ahead in the paper.     

Water Treatment Using Magnetite: A Study of a Sirofloc Pilot Plant

T he S irofloc PROCESS uses magnetite to remove colour, turbidity, iron, and aluminium from water. Subsequent filtration removes manganese and traces of magnetite. Trials with a 0.45 MI/d pilot plant at Morehall Water Treatment Works (WTW), Yorkshire Water Authority (YWA), have shown that this process can produce water which complies with the EC Drinking Water Directive. Two full-size plants exist in Australia, and a 20/Ml/d plant is being commissioned at Redmires (YWA).     

基于水安全目标的城市绿地水体设计方法研究——以第二届河北省园林博览会（秦皇岛）园区为例

城市绿地水系作为影响城市绿地生态稳定的主要因素,在雨洪管理中承担着重要角色,总结具有普遍指导意义的设计方法可以为海绵城市的理论研究和建设提供参考。以第二届河北省园林博览会（秦皇岛）园区为研究对象,通过分析和解决场地面临的雨水安全问题,提出基于水安全目标的城市绿地水体设计方法：1）确定雨水径流控制目标;2）计算场地内外源径流消减总量并确定水体调蓄容积;3）利用SWMM软件建立动态管理模型,对比分析场地开发前后雨洪调蓄能力;4）结合水体设计的景观化策略,通过水利分析模型（MIKE21）对水景面积进行模拟。结果表明：1）通过合理的水体设计,城市绿地可以有效调蓄场地及周边区域地表径流;2）基于水安全目标的城市绿地水体在设计时需综合考虑现状条件、海绵城市区域建设要求与控制目标,并利用情景模拟的方法结合定量与定性分析,最终确定设计方案。