基于不可用性及表决机制的探测器优化布置

在化工工业中,危险气体探测系统的表决机制以及失效问题对于探测器的网络布设至关重要。本文通过引入表决系统需求失效概率以及对探测系统表决逻辑进行分析,提出了一种基于不可用性及表决机制的探测器优化布置方法。首先对探测系统表决逻辑进行分析获得各逻辑回路参与表决的探测时间及需求失效概率,以所有泄漏扩散场景各级探测器的总探测时间最小化为目标函数,结合探测器数量和位置约束构建数学优化模型。其次以各候选探测器监测点为基因,基于遗传算法编写优化模型求解程序。最后利用泄漏扩散场景模拟数据作为输入值,求解得到不同探测器数量条件下的布置方案。通过对各布置方案的场景探测结果进行分析,验证了该方法在不同需求条件下的实用性。     

油田中心处理站火灾和气体监测报警系统设计

针对伊朗雅达瓦兰油田中心处理站生产工艺的特殊环境情况,阐述设计火灾和气体监测报警系统的重要意义,介绍火气系统的构成及应达到的功能,并以IEC61508和IEC61511为依据,总结出了火气系统在设计过程中需要遵循的几个指导性原则。从探测器的选型布置和表决原则、控制器硬件选型及软件逻辑设计等方面对火气系统做了详细介绍。该系统可靠性好、安全性高、可用率高、误动作少,能满足SIL3安全等级。     

基于控制室爆炸载荷的可燃气云等价尺寸阈值

火气系统是防控气体泄漏灾害的重要安全屏障。可燃气体泄漏后与空气混合形成可燃气云,其爆炸属于体积爆炸,具有复杂性和多变性,因此将其折算为等价气云并提出阈值尺寸计算方法,是实现火气系统探测器网络量化布设的关键输入指标。选取控制室为受体,以载荷作为爆炸冲击波超压的临界值,运用多能法倒序计算,逆推得到对应的等价气云尺寸作为探测阈值,进而利用等价气云方法与高斯扩散模型得到火气系统探测临界时间。通过某LNG罐区案例分析,定量确定了该罐区可承载的气云尺寸最大值及扩散临界时间。数值计算表明,等价气云尺寸阈值不仅可以作为火气系统探测设计的量化输入指标依据,并可对探测时间设置以及气体泄漏及爆炸的防控措施提供理论支持。     

基于控制室爆炸载荷的可燃气云等价尺寸阈值

火气系统是防控气体泄漏灾害的重要安全屏障。可燃气体泄漏后与空气混合形成可燃气云,其爆炸属于体积爆炸,具有复杂性和多变性,因此将其折算为等价气云并提出阈值尺寸计算方法,是实现火气系统探测器网络量化布设的关键输入指标。选取控制室为受体,以载荷作为爆炸冲击波超压的临界值,运用多能法倒序计算,逆推得到对应的等价气云尺寸作为探测阈值,进而利用等价气云方法与高斯扩散模型得到火气系统探测临界时间。通过某LNG罐区案例分析,定量确定了该罐区可承载的气云尺寸最大值及扩散临界时间。数值计算表明,等价气云尺寸阈值不仅可以作为火气系统探测设计的量化输入指标依据,并可对探测时间设置以及气体泄漏及爆炸的防控措施提供理论支持。     

海洋平台火气探测系统浅析

火气探测系统用于对整个平台的易燃易爆气体、有毒气体或火灾情况进行连续监测,通过早期报警,防止可燃气体大面积泄露或者火势蔓延,有效保证平台设备和人员安全。火气探测设备探测效果除与探测器本身灵敏度及性能相关外,还受整个火气系统规划、探头布局及逻辑组态等因素影响。文章结合作者多年工作经验,对海洋平台火气探测系统在设计过程中需要考虑的一些问题做简要的分析阐述。     

考虑多因素的危险气体探测器选址优化方法

危险气体探测器是炼化装置安全的重要保护层,合理的选址可大幅提高检测效率,降低泄漏事故损失。本文从削减气体泄漏风险的角度提出了一种危险气体探测器选址的定量优化方法。基于多种影响危险气体泄漏扩散的外界因素,确定了危险气体泄漏场景发生概率、泄漏后果以及泄漏风险的定量表征方法。以累积泄漏风险最小化为优化目标,针对气体探测器的工作失效模式和冗余结构等内部因素,建立了考虑气体探测器不可用性、表决逻辑和条件风险值约束的选址优化模型,并提出求解优化方案的粒子群算法。以某柴油加氢装置为例进行算例研究,结果表明优化方案可有效削减气体泄漏风险,且效果明显优于原布设方案。后继还将开展优化模型的验证试验及多目标优化研究,以进一步提高优化模型的实用性。     

浅谈海上油气平台火气探测设备的选择及布置

火气探测设备是海上油气平台火气系统的重要组成部分,是保证人身安全和油气生产的重要一环,通过对火气探测设备的类型及性能进行分析,并根据在海上平台的使用经验对探测器的选择及布置进行总结,为以后火气探测设备的选择和布置更合理、更经济提供参考。     

南海地区FPSO高温烟气排放对直升机起降影响的数值分析

以南海某FPSO直升机甲板为研究对象,通过KFX软件模拟不同工况、不同风况参数条件下直升机甲板起降区域高温烟气的空间运移、湍流和温升变化规律。参考CAP437对环境条件的安全判定标准,计算了采取优化方案前后的直升机甲板的年不可用概率值。结果表明,采取的联合优化方案能够显著降低FPSO的直升机甲板的年不可用率。为FPSO直升机甲板安全设计提供了工程指导和借鉴。     

基于等价气云爆炸风险评估的气体防护区域定量划分

目前对危险气体泄漏防护区域的划分方法主要为定性方法,难以对具体场景定量表征,进而无法用于风险防控系统的设计规划。本文在等价气云理论的基础上,基于爆炸事故后果风险评估,提出一种定量划分气体防护区域的方法。综合考虑气体泄漏概率、风速风向联合分布概率等现场特征要素,运用高斯扩散模型,得到气体泄漏扩散的等价气云体积以及气体泄漏扩散风险集合,并进行泄漏场景筛选。针对扩散风险较大的场景进行点火概率分析,利用多能法计算气云爆炸影响范围,对气云爆炸事故进行风险评估得到爆炸事故后果风险集合。在ALARP标准与火气系统探测器场景覆盖率的指导下,依据不同装置区域的风险值确定气体防护区域等级定量划分标准。通过某LNG接收站案例分析,可定量得到不同装置的防护区域等级,实现针对具体泄漏场景的气体防护区域等级定量划分。数值计算表明,气体防护区域定量划分可为火气系统探测器布设提供理论支持。     

激光对射式可燃气体探测器在压气站工艺区布置方案研究

为进一步提升压气站场的安全性,拟在站场露天工艺区域布置可燃气体探测器。由于工艺区为敞开区域,常规的点式探测器难以发挥效用,因此拟采用激光对射式探测器。本文对该区域内的微量泄漏进行了数值模拟分析,得出了量程、报警浓度以及布置高度对可燃气体探测器布置的影响,提出露天工艺区域激光对射式探测器的布置建议,为压气站露天工艺区域可燃气体探测器的选型和布置方案提供指导。     

浅谈水泥工厂建(构)筑物防火设计

随着我国经济建设快速发展，国家对建筑物的防火要求越来越高。结合建筑设计防火规范和水泥工厂设计规范,针对其中条文相互补充互为关联的部分，结合设计实际，分析讨论水泥厂建（构）筑物生产的防火设计的防火分区、耐火等级及防火间距问题。     

Investigation of a combustible material in the fire of Hengyang merchant's building

Agaric, a kind of important combustible material in the fire of Hengyang merchant's building, was investigated using different experiment equipments. Its degradation and pyrolysis behavior were studied by means of thermogravimetric and kinetic analysis and pyrolysis gas chromatography–mass spectroscopy analysis. External radiation heat and internal heat were used to ignite the agaric. For external radiation ignition, a series of bench‐scale fire tests were done in cone calorimeter in accordance with ISO 5660. As for the internal heat ignition, a fire test was carried out in a full‐scale room in accordance with ISO 9705. Multi‐parameter measurement, including heat release rate (HRR), mass loss rate (MLR), temperature field and species concentration, has been accomplished. Meanwhile, the process of a full‐scale fire test was numerically simulated. The computational results were consistent with experiment data, which will lay down a good foundation for further study in fire reconstruction of the whole fire. Copyright © 2008 John Wiley & Sons, Ltd.     

Highway vehicle fire data based on the experiences of US fire departments

In 2003–2007, US fire departments responded to an average of 267 600 highway vehicle fires per year. These fires caused an average of 441 civilian deaths, 1326 civilian injuries, and $1.0bn (in US dollars) in direct property damage annually. Highway vehicles include cars, trucks, and other vehicles designed for highway use; highway vehicle fires can occur anywhere, not just on a highway. While these fires and associated losses have been falling in recent years, highway vehicles fires accounted for 17% of reported US fires, 12% of US fire deaths, 8% of US civilian fire injuries, and 9% of the direct property damage from reported fires. Data from the US Fire Administration's National Fire Incident Reporting System and the National Fire Protection Association's fire department survey were used to provide details about the circumstances of highway vehicle fires. Mechanical or electrical failures caused roughly three‐quarters of the highway vehicle fires but only 11% of the deaths. Collisions and overturns were factors contributing to the ignition in only 3% of the fires, but fires resulting from these incidents caused 58% of these vehicle fire deaths. The rate of bus fires per billion miles driven was 3.5 times that for highway vehicle fires overall. Copyright © 2012 John Wiley & Sons, Ltd.     

A new test methodology for studying the response of walls to real fire environments

A new test methodology was developed to investigate the response of walls, partitions, and in-wall systems exposed to real fires. The apparatus includes a 3.5 m long, 2.3 m wide, and 2.3 m high fire compartment within a standard sea container. A wall specimen measuring up to 1.8 m wide, 1.8 m tall, and 0.3 m deep is mounted in a steel frame at one end of the fire compartment. Fire exposures to the wall specimen evolve over time depending on the fuel load and ventilation configuration. Gas temperatures and heat flux were characterized for five different fuel and ventilation configurations. Peak exposures ranged from 30 to 75 kW/m² for about 20 minutes. Five additional tests were conducted using a single fuel and ventilation configuration to assess the repeatability of the test methodology. It was found that a 19.3 minute growth period occurred plateauing at a ceiling temperature of 708°C for 8.4 minutes, on average. Compartment gas temperatures were found to be repeatable, having a sample standard deviation less than 32°C for symmetric data. Repeatability improved when account was taken for the rapid fire growth inflection point. The utility of the approach for studying fire performance of building elements was demonstrated.     

CFD modeling approach of smoke toxicity and opacity for flaming and non‐flaming combustion processes

Current engineer's methods of fire safety design include various approaches to calculate the fire propagation and smoke spread in buildings by means of computational fluid dynamics (CFD). Because of the increased computational capacity, CFD is commonly used for prediction of time‐dependent safety parameters such as critical temperature, smoke layer height, rescue times, distributions of chemical products, and smoke toxicity and visibility. The analysis of smoke components with CFD is particularly complex, because the composition of the fire gases and also the smoke quantities depends on material properties and also on ambient and burning conditions. Oxygen concentrations and the temperature distribution in the compartment affect smoke production and smoke gas toxicity qualitatively and quantitatively. For safety designs, it can be necessary to take these influences into account. Current smoke models in CFD often use a constant smoke yield that does not vary with different fire conditions. If smoke gas toxicity is considered, a simple approach with the focus on carbon monoxide is often used. On the basis of a large set of experimental data, a numerical smoke model has been developed. The developed numerical smoke model includes optical properties, production, and toxic potential of smoke under different conditions. For the setup of the numerical model, experimental data were used for calculation of chemical components and evaluation of smoke toxicity under different combustion conditions. Therefore, averaged reaction equations were developed from experimental measurements and implemented in ANSYS CFX 14.0. Copyright © 2015 John Wiley & Sons, Ltd.     

Experimental study of smoke effects on energized electrical cabinets located nearby a lubricant oil pool fire

This paper presents an experimental study of smoke exposure effects on potential malfunction of three electrical cabinets located nearby an oil pool fire. This study was performed as part of the PRISME‐2 international OECD project. Lubricant oil was used as fire source, and three real energized electrical cabinets were used as targets exposed to smoke in the adjacent room to the fire room. The main fire properties, as well as the fire consequences, such as gas temperatures and smoke concentrations in the rooms, and the cabinets are presented in detail. The heat release rate was thus assessed at around 500 kW for nearly all the fire duration, and maximum gas temperatures reached 300°C in the fire room, and 120°C in the adjacent room. Moreover, the maximum gas temperatures and soot mass concentrations inside the cabinets ranged from 90 to 120°C and from 0.3 to 1 g/m³, respectively. Nevertheless, continuous electrical monitoring of the three cabinets did not highlight malfunction. After the experiment, monitoring test of the cabinets was conducted to investigate the potential effects. The isolation resistance of electrical circuits on the most severe smoke exposed cabinet reduced during the monitoring test. It seemed the soot deposition have caused it.     

An experimental investigation on char pattern and depth at postflashover compartments using medium‐density fibreboard (MDF)

To determine the fire origins for postflashover compartments, the char pattern and depth are investigated. A set of experiments was carried out using large‐scale compartments made of medium‐density fibreboard. A liquefied petroleum gas burner was used as the ignition source to mimic the fire origin. The burner was set at different locations in different experiments. It is found that time to flashover, intermittent flame of gas burner and ventilation condition have effects on the char patterns. The ‘ventilation patterns’ are likely to confuse the fire investigators; therefore, it needs to be identified from the ‘flame patterns’. In general, the ventilation patterns at the floor would initiate directly from the compartment opening. CFD simulations is used to reflect the ventilation conditions during fires thus assisting the identification of ventilation patterns. For those cases with less distinguishable char patterns, the profiles of total leftover material thickness and char depth were used to determine the fire origin. The char layer and total thickness in the flame regions were found to be respectively deeper and thinner than the rest parts of the compartment. The ventilation condition also affects the char depth profile; therefore, it cannot be ignored from analysis. At the end, a strategy of fire origin determination is proposed. Copyright © 2014 John Wiley & Sons, Ltd.     

Experimental studies on the effect of fire accelerants during living room fires and detection of ignitable liquids in fire debris

Reconstructing the course of a fire and performing chemical analysis of ignitable liquids in fire debris is an important tool to conduct fire investigations in suspected arson cases. Here, a total of five fire tests has been performed to investigate the effect of fire accelerants on the fire development of a room fire and to prove the capability of analytical methods. Different experimental scenarios have been realized (no accelerant, accelerant applied at different positions, and different amounts of fire accelerant). Each test room was equipped with an identical set of living room furnishing. The location and amount of the fire accelerant applied löschen varied in four of five tests. One experiment was carried out without fire accelerant. Fire quantities such as mass loss (of the entire room), gas temperatures (at several locations in the room), and heat release were determined during the experiments, and chemical‐analytical studies were carried out. A headspace solid phase micro extraction procedure, using gas chromatography–mass spectrometry, was used to analyze fire debris samples to potentially detect ignitable liquids. Beside the analysis of fire debris samples, swipe soot samples were analyzed and the detectability of the fire accelerant used was demonstrated. Results show that it is possible to provide evidence of ignitable liquids in soot samples collected from walls. This allows an additional sampling strategy at potential crime scenes, besides taking fire debris samples. Copyright © 2014 John Wiley & Sons, Ltd.     

Investigation of smoke gases and temperatures during car fire – large‐scale and small‐scale tests and numerical investigations

The hazards for passengers during vehicle fires result from the increasing temperature and the emitted smoke gases. A fire was set on a car to investigate the development of temperature and of gaseous fire products in the passenger compartment. The study was based on a full‐scale test with a reconstructed scene of a serious car fire. The aim of this work was to identify the conditions for self‐rescuing of passengers during a car fire. A dummy, equipped with several thermocouples, was placed on the driver's seat. Also, the smoke gases were continuously collected through a removable probe sensor corresponding to the nose of the dummy in the passenger compartment and analyzed using Fourier transform infrared spectroscopy. Additionally, several car components were investigated in the smoke density chamber (smoke emission and smoke gas composition). It was found that the toxic gases already reached hazardous levels by 5 min, while the temperatures at the dummy were at that time less than 80 °C. The toxicity of smoke gases was assessed using the fractional effective dose concept. The various experimentally parameters (temperature and smoke gas composition) were implemented into numerical simulations with fire dynamics simulator. Both the experimental data and the numerical simulations are presented and discussed. Copyright © 2015 John Wiley & Sons, Ltd.