Modelling breakdown of industrial thermal insulation during fire exposure

The aging of many of the installations in the oil and gas industry may increase the likelihood of loss of containment of flammable substances, which could lead to major accidents. Flame temperatures in a typical hydrocarbon fire may reach 1100–1200 °C, which are associated with heat flux levels between 250 and 350 kW/m². To limit or delay the escalation of an initial fire, passive fire protection (PFP) can be an effective barrier. Additionally, both equipment and piping may require thermal insulation for heat or cold conservation. Previous studies have investigated whether thermal insulation alone may protect the equipment for a required time period, e.g., until adequate depressurization is achieved. The present study entails the development of a numerical model for predicting the heat transport through a multi-layer wall of a distillation column exposed to fire. The outer surface is covered by stainless-steel weather protective cladding, followed by PFP, thermal insulation, and finally an inner column of carbon steel of variable thicknesses. The model for the breakdown of thermal insulation is based on observed dimensional changes and independent measurements of the thermal conductivity of the insulation after heat treatment. The calculated temperature profiles of thermally insulated carbon steel during fire exposure are compared to fire test results for carbon steel with thicknesses of 16, 12, 6 and 3 mm. The model's predictions agree reasonably well with the experiments. The degradation of the thermal insulation at temperatures above 1100 °C limits its applicability as fire protection, especially for low carbon-steel thickness. However, the model predicts that adding a 10-mm layer of more heat-resistant insulation (PFP) inside the fire-exposed cladding may considerably extend the time to breakdown of the thermal insulation.     

On the response of 500 gal propane tanks to a 25% engulfing fire

This paper presents detailed data on the thermal response of two 500 gal ASME code propane tanks that were 25% engulfed in a hydrocarbon fire. These tests were done as part of an overall test programme to study thermal protection systems for propane-filled railway tank-cars.

The fire was generated using an array of 25 liquid propane-fuelled burners. This provided a luminous fire that engulfed 25% of the tank surface on one side. The intent of these tests was to model a severe partially engulfing fire situation.

The paper presents data on the tank wall and lading temperatures and tank internal pressure. In the first test the wind reduced the fire heating and resulted in a late failure of the tank at 46 min. This tank failed catastrophically with a powerful boiling liquid expanding vapour explosion (BLEVE). In the other test, the fire heating was very severe and steady and this tank failed very quickly in 8 min as a finite rupture with massive two-phase jet release. The reasons for these different outcomes are discussed. The different failures provide a range of realistic outcomes for the subject tank and fire condition.     

Fire protection as the underpinning of good process safety programs

This paper will provide an overview of the role of fire protection engineers in the mitigation phase of a process safety program. Fire protection engineers are involved in the assessment of hazards and the selection of fire protection strategies which can reduce the risk to an acceptable level according to the stipulated goals and objectives. Fire protection strategies may include the installation of a variety of approaches, such as passive and active fire protection systems, manual intervention and siting. Passive systems include fire rated barriers and protection of openings in those barriers, while active systems include systems such as fire detectors and sprinklers. Manual intervention may include the manual activation of fixed fire protection systems or firefighting activities by facility fire brigades or municipal fire departments. The manual firefighting activities are typically considered to be in the ‘response’ phase.     

新型气体灭火剂对飞机用橡胶材料的腐蚀性能研究

为研究氢氟烯烃(HFOs)与氢氟氯烯烃(HCFOs)灭火剂对于飞机用橡胶密封材料的腐蚀性,通过实验研究6种新型气体灭火剂(R1234yf,R1234ze,R1234ze-E,R1233xf,R1233zd,R1336mzz-E),对目前飞机用4种橡胶O型圈(硅橡胶VMQ,氟橡胶FKM,氟硅橡胶FVMQ和丁腈橡胶NBR)...     

Reliability evaluation of fire alarm systems using dynamic Bayesian networks and fuzzy fault tree analysis

In almost all industries, fire alarm systems play a vital role in the reducing the risks associated with fires and damages. Therefore, it is necessary to evaluate their reliability and performance in emergency situations. The present study aimed to use fault tree analysis (FTA) to determine the root causes involved in the failure of fire alarm systems, to use Fuzzy set theory and expert elicitation to determine relative probabilities, and finally, to evaluate the reliability of a fire alarm system using dynamic Bayesian networks (BNs) during a thirty-six months period. A total of 29 basic events were detected from the FT. The reliability of the fire alarm system was estimated at 0.954 according to the FT and 0.957 according to conventional BNs. The reliability of the fire alarm system after 36 months was estimated at 0.375 according to dynamic BNs. All the events involved in the failure of fire alarm systems were drawn in the fault tree diagram. The results indicate that remodeling of these systems and simultaneous construction activities are the most important factors in the failure of the fire alarm system. System reliability can also be increased to 0.965 by providing preventive and control measures to reduce the probability of critical events.     

新型气体灭火剂开发技术研究

为了提高哈龙替代灭火剂的灭火性能,减少其对环境的不利影响,必须加快开发新一代气体灭火剂的步伐。提出了理想哈龙替代灭火剂的筛选标准和12种主要性能的分级方法,探讨了筛选过程的设计策略和选择筛选试验方法的基本原则,通过对典型气体灭火剂主要性能的对比,揭示了气体灭火剂的发展历程。剖析了气体灭火剂的灭火浓度、大气寿命、分散性、灭火剂及其分解和燃烧产物的毒性等重要性能的筛选技术发展现状和存在问题。认为应尽快建立并完善气体灭火剂的各项主要性能筛选试验方法,构建完整的气体灭火剂替代品性质数据库,在此基础上形成科学的性能预测体系,以便更好地从大量备选化学物质中找出综合性能优异、适合面广的新一代气体灭火剂系列品种。     

应用FDS软件对零售店铺火灾的数值模拟

客运总站等大空间建筑物中的小零售店铺通常会堆放许多可燃物。在此类建筑中都安装用于整个大厅的机械排烟系统似乎不太可行。因此,在店铺中建造了包括水喷淋以及排烟等主动式消防系统的屋顶,着火时挡板将落下封闭店铺。此时应关注在封闭的小空间内发生轰燃的可能性。如果店铺没有完全封闭,烟气可能会扩散到店铺以外的空间。文中用火灾场模拟软件FDS3．1模拟了消防系统启动前店铺内的火灾环境。模拟的结果将有助于评估制定的消防安全条例以及相关的设计参数。研究结果证实了如果着火的店铺没有完全封闭,更大的烟气羽流将会在店铺以外的大空间中形成。此外,文中还对控制店铺火灾用的排烟系统及水喷淋系统的性能进行了评估。     

新型气体灭火技术在海上平台的应用可行性分析

根据海上油气生产平台的特点及灭火需求,分析了海上平台现有灭火系统及灭火剂的综合性能及缺陷,对新型灭火系统的安全性、环保特性、灭火剂的毒性及灭火效能等方面进行对比和分析,对采用新灭火技术替代平台现有灭火装置的应用可行性进行探讨,分析显示:新型灭火剂Novec1230比目前海上平台应用的其他气体灭火剂在安全环保灭火性能上更具优势。     

Study of a proposed tunnel evacuation passageway formed by opposite-double air curtain ventilation

Subway tunnel fires often result in catastrophes and heavy casualties. To help people evacuate from a tunnel fire, an opposite-double air curtain ventilation assisted tunnel evacuation system (OTES) is introduced. It can be used to create a safe evacuation passageway that is free of smoke through out the length of the tunnel. The performance of the OTES is compared with that of the traditional ventilation systems: longitudinal ventilation and natural ventilation. The effect of the heat release rate, fire source location, and fire detection time are also discussed.This study also shows that compared with natural ventilation and longitudinal ventilation, the carbon monoxide, CO, concentration with OTES is significantly lower. Given the same HRR, the CO concentration values with OTES are only 0.58–2.41% of natural ventilation or 0.52–3.12% of longitudinal ventilation at the back end of the tunnel. An obviously clear evacuation passageway is created by OTES. The effects of changes in fire source location and fire detection time on tunnel ventilation are tested. Also the effect of these changes on the formation of an evacuation passageway by OTES is reported.     

硝酸锶(钡)降低气溶胶灭火剂腐蚀性研究

研究了添加硝酸锶(钡)降低气溶胶灭火剂腐蚀性的作用,通过测试气溶胶灭火剂固体产物颗粒的生成量、吸湿性和酸碱性,分析了影响气溶胶灭火剂对金属材料腐蚀性的因素,并考察了改性配方灭火性能的变化。     

Merit pay raises and organization‐based self‐esteem

We developed and tested a theory of the relationship between merit pay raises and organization‐based self‐esteem (OBSE) in a longitudinal study of hospital employees. We predicted that the positive relationship between merit pay raise size and OBSE would be stronger when pay‐for‐performance (PFP) perceptions were high and predicted further that this interaction would be stronger among older employees. As predicted, merit pay raises were not related to OBSE levels for younger employees, but, among older employees, larger merit raises increased OBSE when PFP perceptions were high and decreased OBSE when PFP perceptions were low. Implications of the study for merit pay theory and practice are addressed. Copyright © 2008 John Wiley & Sons, Ltd.     

含硫油品储罐中硫化铁自燃引发事故原因分析

通过分析含硫油品储罐中活性硫的主要组成及对油品储罐的腐蚀方式,总结了含硫油品储罐中硫化铁的生成方式、自燃性及其主要影响因素。分析认为,尽管活性硫对设备的腐蚀形式多样,但低温湿H2S腐蚀是活性硫对油品储罐的主要腐蚀方式,腐蚀产物极易自燃而引发油品储罐发生火灾和爆炸事故。建立了含硫油品储罐硫化铁自燃事故的故障树(FTA)图并对其最小割集的分析认为:储罐防腐涂层脱落、水的存在和原油含硫是引起顶事件发生的最重要基本事件。通过故障树分析,探讨了硫化铁自燃事故的主要原因并提出相应的预防措施。     

Characteristics of large cooking oil pool fires and their extinguishment by water mist

Large cooking oil pool fires, occurring in industrial oil cookers, present a severe hazard to food processing plants due to their size and the large amount of hot oil involved. This paper reports a series of full-scale fire experiments conducted in a large industrial oil cooker mock-up. The characteristics of large cooking oil pool fires and the effect of oil depth and hood position in the oil cooker on fire growth were studied. The use of water mist for extinguishing large oil pool fires and their extinguishing performance under different discharge pressure and with different types of water mist systems were investigated. Experimental results showed that the cooking oil underwent a substantial expansion in volume during heating. The fires developed quickly once the oil auto-ignited. The fire growth rate was affected by the oil depth in the pan and the hood position in the oil cooker. The water mist fire suppression systems effectively extinguished large cooking oil fires and prevented them from re-igniting. Their extinguishing performance was determined by the type of water mist system, discharge pressure and hood position in the oil cooker.     

水添加剂作用下自动喷水灭火技术对高空间厂房火灾控火性能的影响

为研究带添加剂（浓度1%）自动喷水灭火技术对高空间厂房火灾控灭火性能的影响,采用标准燃烧物组合替代实际场所中的可燃物品,按照高空间厂房的实际火灾场景,在喷头安装高度为18m的情况下开展了高空间厂房火灾的实体灭火试验。试验结果显示,自动喷水灭火系统在高净空场所下能及时动作,在添加灭火剂后,提高了水到达可燃物表面后的粘附能力,喷头开放数量少,能够明显控制火势的增长和蔓延。系统设计喷水强度和作用面积符合该场所的设计水平。     

基于主成分分析的公路隧道消防安全系统评价研究

基于系统安全分析方法并结合数理统计理论,建立了隧道消防安全系统原理图及评估指标体系,运用多元统计理论中的主成分分析法,构造了一种基于统计基础上的综合评估函数,对近年来的典型火灾隧道的防火安全系统进行了合理评估,针对评估结果构造了分级标准,提出了公路隧道消防安全等级评估的新思路.以雪峰山隧道的实例计算表明,该评估模型具有简便性、可操作性和准确性,能全面地反映隧道消防安全系统状况,以便及时发现隐患,减少火灾的潜在危险.     

基于全尺寸火灾试验的家用喷头灭火性能研究

为研究家用喷头的灭火性能和喷头动作后对室内环境的影响,分析了住宅设置自动喷水灭火系统的必要性,并以沙发作为点火源,在相同的喷水强度下开展了不同类型家用喷头和标准喷头的灭火性能对比试验。试验结果表明,采用家用喷头和标准喷头均能有效控火,但下垂型喷头的动作时间要早于边墙型喷头。在室内环境条件变化方面,采用家用喷头时较标准喷头在CO浓度方面减少较为明显,约减少59%;在O2浓度变化方面较采用标准喷头提高了0.6%,采用家用喷头较标准喷头能为人员疏散提供更好的环境。     

Numerical simulations of heat and moisture transport in thermal protective clothing under flash fire conditions.

A numerical model of heat and moisture transport in thermal protective clothing during exposure to a flash fire was introduced. The model was developed with the assumption that textiles are treated as porous media. The numerical model predictions were compared with experimental data from different fabric systems and configurations. Additionally, with the introduction of a skin model, the parameters that affect the performance of thermal protective clothing were investigated.     

窗口火作用下建筑幕墙外保温系统防火性能的试验

建筑幕墙外保温系统火灾事故发生频率高,火灾危险性大,其防火安全性能已成为社会关注的焦点。采用大尺度实体火试验方法,选取具有代表性的金属幕墙保温系统和保温装饰板外保温系统作为试验对象,对防火隔离带和防火封堵位于墙体不同位置的4种工况,开展了一系列窗口火试验。通过采集试验表观现象、火焰蔓延特性、温度分布特性、系统损坏特征等耐火性能试验数据,综合比较分析了不同工况下不同燃烧性能等级的建筑幕墙外保温系统的耐火性能。结果表明,建筑幕墙上下贯通的空腔结构加剧了火蔓延的烟囱效应,存在较大的安全隐患。防火封堵可以阻断空腔中的热对流,防火隔离带可以阻隔材料之间的热传导,二者均可以有效抑制火焰在垂直和水平方向上的蔓延,大幅提高建筑幕墙外保温系统的防火性能。在建筑外墙窗口上方、水平线1及水平线2下方20 mm处分别设置宽度为100 mm的防火封堵和宽度为300 mm的防火隔离带时,系统具有较好的防火性能,综合考虑实际工程的应用性和经济性,可将其设为防火构造设计的基准参数。     

Resilience-based optimal firefighting to prevent domino effects in process plants

Domino effects triggered by fire can cause extremely severe damages to the chemical and process plants. In the need of a more effective prevention of fire domino effects, the present study focuses on firefighting which has received less attention compared to passive and active fire protection systems. Considering both the vulnerability and recoverability phases during fire domino effects, we have introduced a methodology for optimal identification of firefighting strategies so as to increase the resiliency of process plants in dealing with fire escalation scenarios. The area above the resilience curve (AARC), which is equal to the accumulation of loss of resilience over time, was considered as the metric to identify the optimal firefighting strategies. In other words, the strategy leading to the lowest AARC can be selected as the optimal strategy from a resiliency perspective.     

基于热重分析的硫化亚铁氧化倾向性研究

含硫油品储罐内壁腐蚀产物硫化亚铁在空气中有很高的氧化性,很容易引起储罐火灾爆炸事故.用美国TA公司生产的SDT-Q600同步热分析仪在30～1 000 ℃范围内对硫化亚铁进行热重分析,从物理吸附、化学吸附和化学反应的角度分析了硫化亚铁氧化过程,讨论了粒径和升温速率对硫化亚铁TG曲线的影响.结果表明,硫化亚铁经物理吸附和化学吸附,发生了剧烈的化学反应,并放出大量热;粒径和升温速率对TG曲线有明显的影响,粒径减小,TG曲线向低温方向移动,氧化起始温度和氧化终止温度降低;升温速率增大,TG曲线向高温方向移动,氧化速度减小.