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.     

乙二醇流淌火燃烧特性及围堵性能研究

为研究乙二醇流淌火燃烧蔓延特性,利用自行设计的流淌火试验平台,开展了乙二醇流淌火实体试验,研究了试验过程中火焰温度、前锋移动、火焰高度等典型参数变化规律。同时,为实现流淌火的有效蔓延控制,开发酚醛泡沫材料模拟乙二醇流淌火围堵处置,评价其围堵效能。结果表明:乙二醇流淌火燃烧速度缓慢,火焰温度低于池火温度;酚醛泡沫材料对可燃液体流淌火展现出较好耐火、阻隔作用,对液体危化品的泄漏围堵具有积极实践意义。     

On the thermal rupture of 1.9 m propane pressure vessels with defects in their thermal protection system

This paper describes the results from a series of fire tests that were carried out to measure the effect of defects in thermal protection systems on fire engulfed propane pressure vessels.

In North America thermal protection is used to protect dangerous goods rail tank-cars from accidental fire impingement. They are designed so that a tank-car will not rupture for 100 min in a defined engulfing fire, or 30 min in a defined torching fire. One common system includes a 13 mm blanket of high-temperature ceramic fibre thermal insulation covered with a 3 mm steel jacket. Recent inspections have shown that some tanks have significant defects in these thermal protection systems. This work was done to establish what levels of defect are acceptable from a safety standpoint.

The tests were conducted using 1890 l (500 US gallon) ASME code propane pressure vessels (commonly called tanks in the propane industry). The defects tested covered 8% and 15% of the tank surface. The tanks were 25% engulfed in a fire that simulated a hydrocarbon pool fire with an effective blackbody temperature of 870 °C.

The fire testing showed that even relatively small defects can result in tank rupture if the defect area is engulfed in a severe fire, and the defect area is not wetted by liquid from the inside. A wall failure prediction technique based on uniaxial high-temperature stress rupture test data has been developed and agrees well with the observed failure times.     

泡沫混凝土和混凝土耐火极限的比较研究

泡沫混凝土用在建筑节能保温工程中,其耐火性能对提高建筑物的抗火灾能力非常重要。在模拟火灾条件下,通过测定不同密度、不同煅烧时间、不同含水量的泡沫混凝土和混凝土的抗压强度值,比较泡沫混凝土和混凝土的耐火极限的变化规律。结果表明,在火灾条件下,泡沫混凝土和混凝土的抗压强度损失率均随密度的增大而降低;密度为300kg/m3和800kg/m3的泡沫混凝土,在800℃下煅烧20min后,其抗压强度损失率分别为66.3%和25.5%;在同样的煅烧条件下,密度为2200kg/m3和2400kg/m3混凝土的抗压强度损失率分别为18.6%和15.8%;泡沫混凝土和混凝土的含水量越高,耐火极限就越长。泡沫混凝土为具有不燃特性A级保温材料,被用于建筑外墙保温隔热材料时,其抗压强度会因火场可燃材料的高温煅烧而有所降低,但其耐火极限能完全满足《建筑防火设计规范》。     

常用聚氨酯硬泡外墙外保温系统的点燃特性研究

基于锥形量热仪实验,对常用的聚氨酯硬泡外墙外保温系统的点燃特性进行了实验研究。所研究的系统种类包括粘贴保温板薄抹灰外墙外保温系统,瓷砖饰面粘贴保温板外墙外保温系统,胶粉浆料复合保温板外墙外保温系统和保温装饰板外墙外保温系统。实验结果显示,聚氨酯硬泡保温板和聚氨酯硬泡外墙外保温系统都可由热厚型点燃描述。在防护层对点燃时间的抑制效果方面,胶粉聚苯颗粒复合保温板系统最好,瓷砖饰面系统稍差但明显好于5mm和3mm厚防护层的薄抹灰系统,铝板保温装饰板系统最差。     

空心玻璃微珠对泡沫灭火剂发泡能力和热稳定性影响研究

本文研究了空心玻璃微珠添加量及泡沫液浓度对泡沫灭火剂发泡能力和稳定性的影响,对比了热辐射条件下空心玻璃微珠添加前后泡沫的热稳定性.结果表明,添加量低于40%时,空心玻璃微珠对泡沫灭火剂发泡能力影响不大,而泡沫的稳定性显著降低,添加量为50%时,虽泡沫发泡能力降低,但泡沫的稳定性却增强.泡沫的发泡能力随蛋白泡沫浓度升高而增强.蛋白浓度为10%,空心微珠添加量为50%时,由于泡沫内部形成了稳定的三相泡沫骨架结构,泡沫热稳定性较未添加微珠之前显著增强.     

挤塑型聚苯乙烯泡沫塑料着火温度实验研究

研究了挤塑型聚苯乙烯(XPS)保温材料两种不同着火方式下的着火温度。采用南京江宁仪器分析厂生产的DW-02型点着温度测定仪对XPS的着火温度进行了测定。利用辐射引燃仪得到了2.2 cm厚挤塑型保温板在不同加热功率下的着火温度。结果表明:DW-02型点着温度测定仪测得的挤塑型聚苯乙烯保温材料的点燃温度约为355℃;热辐射引燃仪测得的2.2 cm厚保温板在不同加热功率下的着火温度是365-370℃,且引燃时间随着辐射引燃仪加热功率的增大而逐渐缩短;明火火源比热流辐射容易引燃挤塑型聚苯乙烯保温板。研究结论对FDS模拟挤塑型聚苯乙烯燃烧特性时,材料热解参数的设定有指引作用,对实际工程中遴选合适的外墙保温材料具有重要的参考价值。     

PPH (potassium polyacrylate & hectorite) composite materials – A new fire accident emergency method for thermal protection of adjacent tanks

When a chemical tank fire happens in a storage area, it is very important to protect adjacent tanks so as to decrease fire accident losses. In this paper, a new thermal protection method was put forward based on a PPH (potassium polyacrylate & hectorite) thermal insulation composite material spraying on an adjacent tank under fire. Firstly, the PPH material was prepared successfully by a polymerization reaction of potassium acrylate, hectorite, NaHSO₃ and (NH₄)₂S₂O₈. Secondly, thermal insulation performance of the PPH material was characterized by heat transfer process at high incident heat flux using cone calorimeter. The results show that thermal insulation performance of the PPH material is affected by a content change of (NH₄)₂S₂O₈, NaHSO₃ and hectorite in formulations. The content of (NH₄)₂S₂O₈ 0.14 wt%, NaHSO₃ 1.38 wt% and hectorite 1.4 wt% was an optimum formulation ratio to obtain best thermal insulation performance. Finally, possible thermal insulation mechanisms of the PPH material were presented using SEM, TG and TG-IR techniques. One of the thermal insulation mechanisms is the incident heat flux absorbed by water evaporation from the PPH material. Another is the thermal protection of the char formed from the PPH material at high incident thermal radiation, which can prevent heat and mass transfer.     

复配超细粉体三相泡沫的制备与稳定性研究

为改善泡沫灭火剂的高温稳定性和抗复燃性能,将石墨粉、膨润土和空心玻璃微珠按一定比例复配加入泡沫灭火剂中制备防灭火三相泡沫,利用自主设计的实验台架,研究其发泡、稳泡及油面热稳定性等主要性能,分析复配超细粉体对泡沫灭火剂稳定性的影响机理。实验证明,复配粉体的加入可使泡沫灭火剂在高温下的稳定时间延长10倍以上,粉体颗粒会在泡沫表面形成一层致密壳层,增强泡沫的隔热阻燃性能,石墨粉的存在使壳层更加致密且增强了泡沫的流动性,但会对泡沫的发泡性能产生较大的影响,当空心玻璃微珠和石墨粉的添加质量比为5∶2时,整体效果较好。     

基于锥形量热仪的几种防火布燃烧性能研究

生产企业常在电缆或者贵重高危机器处设置防火布来保护生产设备设施的消防安全,选取五种常用的防火布:石棉纤维防火布、陶瓷纤维防火布、硅胶防火布、涂胶防火布、碳素纤维防火布,通过锥形量热仪实验研究不同辐射强度对防火布燃烧性能的影响。结果表明:点燃时间的均方根倒数与辐射强度之间呈现线性关系;在35 kW/m~2辐射强度工况下,碳素纤维防火布的热释放速率最大,达到272.59 kW/m~2,有效燃烧热的峰值也最大,达到529.52 kJ/g;综合比较各样品的燃烧性能,防火能力强弱顺序为:硅胶防火布石棉纤维防火布陶瓷纤维防火布碳素纤维防火布涂胶防火布。     

大型浮顶油罐的危险性分析及安全对策

随着我国经济的飞速发展,国内储油罐趋向大型化发展。大型储罐具有节约钢材、占地少、投资低、便于操作管理等优点。油罐内储存的各种油品一般都具有易挥发、易流失、易燃烧、易爆炸等性质,一旦发生火灾,就会造成重大的经济损失。而且油罐火灾损失巨大,难以扑救,所以说油罐的安全已成为石油化工行业的焦点。针对大型浮顶油罐的危险性,对大量的事故案例进行了分析。在此基础上,提出了强调使用二次密封技术,设计、施工和管理上加强浮船与罐壁之间的密封,安装火灾报警和自动泡沫灭火系统,重视中央排水叠管的密封性及油罐基础的稳定性等安全对策措施。     

Study on accidental fire at a large-scale floating-roof gasoline storage tank

For an accident involving a large-scale internal floating-roof tank with 28.4 m diameter and filled with 4600 m³ gasoline, the actual behavior of the gasoline fire and the fire-fighting strategies that were applied to it were analyzed in terms of the heat release rate, burning rate, and regression rate. During the accident, the initial fire suppression strategy failed and the gasoline was moved to an external tank. A total of 2800 m³ gasoline was burned for 17 h with a resulting heat release rate of 1475 MW. The long duration of the fire burning was attributed to the burning surface of the gasoline, which was not covered with foam at the beginning of the fire using the active foam fire-extinguishing system due to damage to one of the foam chambers. The average regression rate of the gasoline was 0.16 m/h after 8 h of burning and 0.35 m/h when the fire was completely suppressed.     

高层建筑外立面U型结构火蔓延的实验研究

针对高层建筑中常见的U型外立面结构,对典型有机保温材料硬质聚氨酯泡沫(PU)进行了小尺度条件下的U型结构竖直火蔓延实验研究,分析了其区别于高层建筑普通结构的竖直火蔓延特性.实验结果表明,U型结构竖直方向火蔓延是一个非稳态的火蔓延过程,其火蔓延速度会随着时间的推进逐渐加速.在燃烧过程中U型结构会产生烟囱效应,促进火蔓延的发展,其强度随着U型结构因子的增大而增大,当结构因子大于1.2时,火蔓延加速过程趋于稳定.     

聚氨脂泡沫填缝剂生产工艺火灾危险性分析与对策

以聚氨脂泡沫填缝剂基本生产原理及其特点为基础,对生产原料进行火灾危险性分析,结果表明:该类生产场所的火灾危险等级应划分为甲类;提出聚氨酯泡沫填缝剂生产中存在的安全问题及原因;运用危险度评价法对聚氨脂泡沫填缝剂生产工艺的火灾危险性进行了定量的安全评价,得出聚氨脂泡沫填缝剂生产工艺的危险程度为高度危险;并从建筑设计、防火管理和生产工艺等方面提出了预防火灾事故发生的对策。     

防灭火泡沫流体在采空区高位倾斜裂隙通道中的扩散研究

防灭火泡沫材料是1种新型的防灭火材料,对高位倾斜裂隙火灾的降温隔热、充填加固具有很好的应用性能。为了了解高位倾斜裂隙通道中泡沫流体的扩散规律,通过理论推导得出不同裂隙倾角和方位角下浆体2端面压力差随时间的变化方程式,以理论公式为基础进行修正,提出了泡沫流体的扩散规律函数式,并通过用其他实验测点进行误差对比分析。研究结果表明:误差均在允许的范围之内,证明拟合出的函数式具有普遍适用性,可以为大采空区隐蔽高温火源点的防治提供理论支持。     

复掺轻骨料纤维喷射混凝土力学及导热性能试验研究*

为有效隔绝高地温公路隧道、深部高温巷道施工过程中的围岩散热,利用正交试验方法,以不同复合陶粒、陶砂掺量、聚丙烯纤维为影响因素,设计出1种隔热效应的轻骨料纤维喷射混凝土（Lightweight Aggregate Fiber Shotcrete,LAFS）,进行含水率、抗压、劈裂抗拉及导热性能试验,并借助X射线衍射、扫描电镜对LAFS进行机理分析。结果表明:3种因素对LAFS力学及导热性能的影响程度均为陶粒掺量>陶砂掺量>聚丙烯纤维掺量,本试验条件下,复合双掺陶粒、陶砂分别取代石子、砂子的最佳体积率为12%,6%,聚丙烯纤维的最佳掺量范围为0.2%~0.3%。建立的LAFS各性能预测模型可为工程应用LAFS确定其配比时提供试验依据。     

基于数值模拟的外墙保温体系防火问题研究

针对国内现有的外墙外保温系统的防火性较差的现状,通过分析上海公寓楼外墙保温层的火灾,得到外墙外保温防火的三种重要因素（粘结或固定方式、防火隔离带的构造、防火保护面层）。鉴于现在流行的保温材料为膨胀聚苯板（EPS）,因而选用EPS作为模拟材料,利用数值模拟计算得出以下结论：认为火灾时有空腔的保温层比无空腔的保温层更危险;设置防火隔离带能有效得阻隔火灾的蔓延,较宽的隔离带效果更好。除此之外,外保温层防火设计中还应考虑以下三方面的问题,即遴选适当的保温材料、建议保温层也使用类似于防火分区的防火措施和保证保温效果的同时增加防火隔离带的宽度。研究结论和建议对于解决外墙保温体系防火问题具有重要的参考价值和现实意义。     

Class-2 hazmat transportation consequence assessment on surrounding population

The transportation of hazardous materials by road is an utmost necessity of the world for the societal benefits, but at the same time the activity is inherently dangerous. Incidents involving hazardous material (hazmat) cargo particularly the class-2 materials can lead to severe consequences in terms of fatalities, injuries, evacuation, property damage and environmental degradation. The rationale behind considering class-2 hazmats is that they pose the greatest danger to the people and property along the transport route because of their storage condition on the transport vessel. They are stored either in pressurized vessels or in cryogenic containers. Any external impact due to collision may cause catastrophic failure of transport vessels, known as BLEVE (Boiling Liquid Expanding Vapour Explosion) with devastating consequences. Further, any continuous release from containment may cause what is known as ‘Unconfined Vapour Cloud Explosion’ (UVCE). Historically frequency of BLEVE occurrence is of the order of 1 × 10⁻⁶ per year or less, but other release scenarios e.g. a large vapour or liquid leaks are more probable and could also have devastating effects on the surrounding population. As such, the paper discussed various event scenarios and the consequences taking examples of a class-2.1 material (1,3 butadiene) and another class-2.3 (ammonia) hazmat. Comparative analysis suggests that per ton basis a rupture of ammonia tanker gives rise to larger impact areas and poses larger lethality risks compared to 1,3 butadiene as far as toxic effects are concerned. Besides, from fireball fatality on similar basis propylene causes higher consequence distance than LPG followed by ethylene oxide and 1,3 butadiene. The impact zone study results may be utilized as inputs for identifying the potential vulnerable area on a GIS enabled map, along a designated State highway route passing through an important industrial corridor in western India.     

Prediction of the self-ignition temperature in lagging fires by means of isothermal calorimetry

Under certain circumstances, contamination of a porous insulation material by a combustible liquid may result in a lagging/insulation fire. In the current study, a method based on isothermal calorimetry and modelling to estimate the risk of a lagging fire, or a maximum insulation thickness for a certain system temperature, is presented. The studied system was a combination of mineral wool and rapeseed oil. Full-scale tests were performed to determine suitable ignition criteria and to validate the results from the isothermal calorimetry tests and modelling. We contaminated the lagging using two methods – a direct method and a solvent method. These methods were evaluated in the full-scale tests. The solvent method resulted in more repeatable results than the direct method, where the contaminant was poured on the insulation. Using the calorimetric measurements, we estimated the parameters for the kinetic equation. This result was used to estimate the self-ignition temperature of contaminated lagging installed on a pipe. We found that a temperature increase of 40 °C was a reasonable ignition criterion when modelling.     

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。