Improved models of failure time for atmospheric tanks under the coupling effect of multiple pool fires

Fire accidents of chemical installations may cause domino effects in atmospheric tank farms, where a large amount of hazardous substances are stored or processed. Pool fire is a major form of fire accidents, and the thermal radiation from pool fire is the primary hazard of domino accidents. The coupling of multiple pool fires is a realistic and important accident phenomenon that enhances the propagation of domino accidents. However, previous research has mostly focused on the escalation of domino accidents induced by a single pool fire. To overcome the drawback, in this study, the failure of a storage tank under the coupling effect of multiple pool fires was studied in view of spatial and temporal synergistic process. The historical accident statistics indicated that the accident scenario of two-pool fires accounted for 30.6% in pool fires. The domino accident scenario involving three tanks is analyzed, and the typical layout of tanks is isosceles right triangle based on Chinese standard “GB50341-2014”. The thermal response and damage of a target tank heated by pool fires were numerically investigated. The volume of 500 m³, 3000 m³, 5000 m³ and 10000 m³ were selected. Flame temperature was obtained by FDS, and then was input onto the finite element model. The temperature field and stress field of target tanks were simulated by ABAQUS. The results showed that the temperature rise rate of the target tanks under multiple pool fires was higher than that under a single pool fire. The failure time of the tank under the coupling effect of multiple fires was lower than that under the superposition of multiple fires without the first stage. The stress and yield strength were compared to judge the failure of the target tank. The model of failure time for the tank under the coupling effect of pool fires was established. Through the verification, the deviation of this model is 4.02%, which is better than the deviation of 15.76% with Cozzani's model.     

化工储罐区池火灾多米诺效应风险评估

化工储罐区储罐数量较多且集中,一旦发生事故很可能诱发多米诺效应造成灾难性的后果。在分析池火灾多米诺效应作用模式的基础上,建立了池火灾多米诺效应风险评估模型,并对某化工储罐区进行了实例计算,分析了单一储罐池火灾事故引发其他储罐池火灾的风险。分析结果表明,池火灾是诱发化工储罐多米诺事故的重要因素,且会造成风险的显著增加,但并非所有的池火灾事故都会诱发多米诺效应。此外,将多米诺效应评价方法应用于化工储罐池火灾事故风险评估中可有效地预测次生事故的发生概率和后果,从而提出针对性措施。     

基于多米诺效应的定量风险评价研究

多米诺效应是引发化工重大事故的主要原因之一.本文综合国内外的研究成果,对火灾热辐射、冲击波超压等造成的多米诺效应进行了深入分析,建立基于多米诺效应的定量风险评价模型,其中包括了评价流程、传播概率、阈值距离计算、多米诺效应对事故频率的影响及后果分析的内容.最后利用Matlab7.1计算平台,以汽油储罐进行实例分析,结果表明该方法是一种适用于多米诺效应定量评价的良好方法,能够比较科学、有效的对危险单元进行风险评价,使重大事故风险评价更切合实际,为政府监管部门和化工企业进行事故的控制和预防提供决策技术.     

大型原油储罐火灾多米诺效应概率计算模型及应用

随着油品储罐区规模的不断扩大,近年来多储罐火灾事故呈上升趋势。现有的储罐防火间距是在以往事故经验的基础上设定的,通过罐组内的火灾多米诺效应概率计算,可从风险的角度为罐组内储罐防火间距的设定提供理论依据。通过综合考虑火灾环境下受辐射储罐失效时间和着火储罐火灾得到控制时间,确定了罐组内火灾多米诺效应的判定原则,并在火灾得到控制时间模型和储罐失效时间模型的基础上建立了火灾多米诺效应概率计算模型。以2万立外浮顶原油储罐为例进行模拟计算,得出在现行标准给出的防火间距下,发生罐组火灾多米诺效应的概率为3.94×10-8/a-1,属于可接受风险,为罐组内储罐的合理布局提供了理论依据。     

某储罐区火灾多米诺效应场景推演

化工园区中危险源众多,一旦发生事故很容易在整个园区内蔓延和发展.针对化工园区内储罐密集,容易引发连锁反应导致事故扩大的特点,利用FDS软件对储罐火灾场景进行数值模拟,根据储罐所受热辐射确定化工园区内储罐火灾最可能的事故发生序列,并引入基于设备失效前时间的机械设备故障概率模型对罐区内单个储罐的火灾风险进行研究,得到储罐区...     

化工储罐间距和体积对爆炸碎片多米诺效应概率的影响

化工储罐爆炸后将产生大量碎片,这些抛射碎片一旦击中相邻罐体容易引发多米诺效应。碎片的抛射方位和抛射距离具有很大的随机性,已有研究多采用概率模型来描述碎片抛射的各分过程。通过总结和发展已有的分过程模型,建立了求取多米诺效应的综合概率模型,并基于蒙特卡罗算法编制了模拟软件,可对化工储罐多米诺效应的发生概率进行预测计算。选取若干常用化工球罐为相邻目标储罐进行实例分析,计算结果表明储罐间距和体积是影响多米诺效应发生概率的两个重要影响因素：随着距离的增大,多米诺效应发生概率不断减小;目标储罐体积越大,多米诺效应发生概率将越大。其中,爆炸碎片对目标储罐的击中概率受上述因素的影响程度更大。该文工作对化工储罐区的安全评价具有一定的参考价值。     

基于蒙特卡洛法的储罐爆炸碎片冲击失效模型研究

为定量研究相邻储罐间爆炸碎片冲击的多米诺效应,基于蒙特卡洛方法建立爆炸碎片冲击失效模型。该模型共包括爆炸能量与碎片初始速度、考虑风速及碎片初始位置的碎片三维抛射轨迹、空气阻力、碎片冲击穿透等4个分步模型。基于上述模型,研究储罐爆炸后碎片的初始状态、抛射轨迹以及对相邻储罐的冲击效应。在数值模拟结果的基础上,用储罐最高允许工作压力代替泄放装置的泄压压力来计算爆炸压力,绘制碎片质量及初始速度的直方图,定量分析储罐间距对击中概率的影响。结果表明,热辐射、超压和碎片冲击3种能量作用方式均可能导致储罐间火灾爆炸事故多米诺现象发生,但爆炸碎片冲击导致相邻罐失效的概率较低。     

基于贝叶斯网络的事故多级多米诺效应计算方法研究

为了更合理地分析事故风险,提出了基于贝叶斯网络的多级多米诺效应计算方法及其计算步骤,并从个人风险和社会风险2个角度,定量分析了生产安全事故的多级多米诺效应。同时以某企业的2个汽油罐区为例,运用上述方法对其生产安全事故的多米诺效应进行定量计算,并将计算结果与未考虑多米诺效应、仅考虑一级多米诺效应时的计算结果进行比较。研究结果表明:基于贝叶斯网络的计算方法,同时考虑了多级多米诺效应和事故的协同效应,可以使计算的个人风险和社会风险更接近于实际。     

基于LOPA逻辑的罐区多米诺效应定量风险评估*

为了更好地降低化工企业罐区事故造成多米诺效应的风险,提出1种基于保护层分析（LOPA）的定量风险评估程序。首先,阐述基于保护层分析(LOPA)逻辑的多米诺定量风险评估流程,即引入包括可用性、有效性及3种逻辑门定义及量化的安全屏障定量评估;然后,利用LOPA的分析逻辑将安全屏障融入多米诺定量风险评估框架中;最后,选取2×2 000 m3苯乙烯罐区为对象,识别防火层与喷淋冷却系统2种安全屏障并开展基于LOPA逻辑的罐区多米诺效应定量风险评估,得出安全屏障能有效地降低多米诺事故发生频率及罐区个人风险的结论。研究结果表明:该分析方法可为化工企业开展多米诺效应定量风险评估提供参考。     

米诺效应中的多事故点协同作用后果研究

为了研究多米诺效应中多事故点协同作用的后果,将并联系统概率模型运用到贝叶斯概率计算过程中,体现出多事故点协同作用对多米 诺效应传播的概率影响;后果分析部分从人、物、环境3个方面出发,对事故的后果影响以及事故预防提出建议措施。最后运用模型对实例进行 了应用分析,结果表明:多事故点协同作用下储罐的多米诺失效概率增大,罐区危险性增强,可以通过对储罐设置安全屏障等措施,有效的切 断导致事故最大概率的链条。     

Study of the situation deduction of a domino accident caused by overpressure in LPG storage tank area

The production and storage of liquefied petroleum gas (LPG) is gradually becoming larger and more intensive, which greatly increases the risk of the domino effect of an explosion accident in a storage tank area while improving production and management efficiency. This paper describes the construction of the domino effect scene of an explosion accident in an LPG storage tank area, the analysis of the characteristics of the LPG tank explosion shock wave and the target storage tank failure, and the creation of an ANSYS numerical model to derive the development trend and expansion law of the domino accident in the LPG storage tank area. The research showed that: 400 m³ tank T1 explosion shock waves spread to T2, T4, T5, T3, and T6, and the tank overpressures of 303 kPa, 303 kPa, 172 kPa, 81 kPa, and 61 kPa respectively. The critical values of the target storage tank failure overpressure-range threshold were 70 kPa and 60 m. After the explosion of the initial unit T1 tank, at 38 ms, the T2 and T4 storage tanks failed and exploded; at 56 ms, the T5 storage tank exploded for the third time; at 82 ms, the T3 storage tank exploded for the fourth time; and at 102 ms, the T6 storage tank exploded for the fifth time. With the increase of explosion sources, the failure overpressure of the target storage tank increased, and the interval between explosions continuously shortened, which reflected the expansion effect of the domino accident. The domino accident situation deduction in the LPG storage tank area provided a scientific basis for the safety layout, accident prevention and control, emergency rescue, and management of a chemical industry park.     

危化品储罐区多灾种耦合效应风险分析

基于危化品储罐区内发生的多米诺效应,以单灾种引发的多米诺事故研究为基础,根据物理学中的触发器原理解释多灾种耦合引发储罐区其他罐体失效的场景,并提出基于物理学理论的多灾种耦合效应模型;基于一储罐区实例分别建立在火灾、爆炸情况下罐区的灾害扩展网络图,并通过无量纲化处理得到综合灾害扩展网络图;分析储罐区在多储罐受灾情况下的灾害扩展情形,得到当D1,D2发生灾害时,D4,D5灾害扩展概率最大;当D1,D8发生灾害时,D4灾害扩展概率最大,建立了多灾种耦合效应的关联图。研究结果对化工园区多灾种耦合的后果预测评估具有指导意义,有助于减少危化品储罐区多米诺效应的发生以及强化危化品储存的安全基础。     

The analysis of domino effect impact probability triggered by fragments

Explosion fragments are the main cause of domino effect in accidents of the chemical and process industry. A number of significant studies have been conducted to further our understanding of the mutual impact of two major hazard installations (MHIs). This work focused on the development of a new model for the impact probability of domino effect triggered by fragments. Firstly, an expression for the initial projection velocity of fragments was founded by taking the explosion moment as a polytropic process and solving energy transformation equation, then the flight trajectory and velocity were represented by some equations with the flight boundary conditions in flight process under gravity and air friction. With the obtained equations as the objective function, the projection uncertainty was analyzed through sampling of the random variables. Finally, a new systemic model for the impact probability of domino effect is put forward by integrating the flight laws and projection uncertainty of fragments, and the impact probability linear equations with the coefficient matrix of secondary effect were built up in order to calculate the impact probability of domino effect. The study on domino effect impact probability provides some useful insights into the generation mechanism, projection features, flight laws and impacts on targets of the fragments, and also lays a foundation for analysis of domino chain risk caused by explosive fragments in chemical industrial complex.     

Impact of leakage location and downwind storage tank on the gas dispersion in a typical chemical tank storage area

Toxic gas leakage in a tank area can have catastrophic consequences. Storage tank leakage location (particularly for high leakage) and downwind storage tanks potentially influence gas diffusion in tank areas. In this study, we developed a numerical and experimental method to investigate the impact of a high leakage location and downwind storage tank on gas diffusion based on three (1.05H, 0.90H, and 0.77H, H was the tank height, 22m) leakage field experiments on the leeward side of storage tank, which have been not conducted before. The experiments revealed an unexpected phenomenon: the maximum ground concentration first decreased and then increased with increasing leakage height. The simulations illustrated that the differences in micrometeorological conditions caused the maximum ground concentration of gas emitted from the roof to be higher than that emitted from the tank wall near the storage tank height. The downwind storage tank 1) had little influence on the entire diffusion direction but altered the local diffusion pattern; 2) reduced the maximum ground concentration (∼18.7%) and the distance from the emission source (approximately a storage tank diameter); and 3) had strong influences on the concentration, velocity, turbulence, and pressure on the leeward side. The concentration negatively correlated with the velocity, pressure, and turbulence in the middle of the two storage tanks on wind centerline. Our results can improve understanding of gas dispersion in tank areas and provide references for mitigating loss and protecting lives during emergency response processes.     

Influence of the source size on domino effect risk caused by fragments

We developed the movement equations for fragments with the size of the bursting vessel. The ground distributions of fragments, the probability of impact between the fragments and the target, the rupture probability of the impacted target, and the domino effect risk caused by fragments were investigated for different source types and sizes using Monte-Carlo simulations. The distribution of fragments from the lower half of the source vessels onto the ground was non-zero, that is, it is probable that the fragments would hit the target vessel close to the source. The relative difference of impact probability is larger than 10% when the target vessel is within eight times the source diameter for the three types of sources considered. The proportion of impacts of fragments from the lower part of the source to total impact decreased with distance, while that for fragments from the upper part increased. The proportion of upper and lower parts is equal for distance approximately five times the source diameter. The source size needs to be considered along with the distance from the source to the target when less than approximately 14 times the source diameter. Its effect on impact probability and domino effect risk was significant. The rupture probability of the target depended very little on the source size.     

Quantitative risk assessment of domino effect in Natech scenarios triggered by lightning

Lightning strike is the natural event more frequency causing Natech accidents involving atmospheric storage tanks. Despite the resulting fires have usually limited severity and only local effects, domino effect may cause the escalation of these primary events, possibly affecting nearby pressurized storages and process equipment, thus resulting in relevant increase in the potential area impacted. A methodology was developed for the quantitative assessment of risk due to domino effects caused by Natech accidents triggered by lightning. A comprehensive procedure was obtained, tailoring lightning risk assessment to include probabilistic models for domino escalation based on probit approach and combinatorial analysis. The methodology was applied to a case-study to evidence the shift in risk figures due to domino effect and the credibility of the secondary domino scenarios. The results of the case-study show that an increase up to two orders of magnitude with respect to risk calculated for conventional scenarios is possible when considering lightning-induced Natech primary scenarios and their escalation.     

多米诺效应下化工储罐区的脆弱性分析

为有效地减少和控制事故的多米诺效应,对影响事故扩展的关键装置,即脆弱单元的辨识及其有效控制措施进行了研究。根据具体的设计方案,依次选定不同储罐作为初始事故单元,借助ALOHA软件计算各储罐之间热辐射及冲击波相互作用强度的大小,与损伤阈值进行比较,并考虑设备间的协同作用,从而确定可能发生的多米诺事故;运用Probit模型计算事故扩展概率,根据计算结果通过Bayes Server软件建立贝叶斯网络,利用先验概率来进行整体脆弱性分析,从而确定各个方案的安全性;对优选的方案通过后验概率进行单元脆弱性分析,从而确定脆弱单元;在此基础上提出相应的控制措施。通过实例计算验证了该方法的可行性,结果表明,该方法能够在多米诺效应的预防和控制方面有效发挥作用。     

基于蒙特卡洛模拟的多米诺事故风险量化管理*

为降低危化品相关的化工事故造成的人员伤亡和财产损失,以化工多米诺事故为研究对象,探讨由初始事故引发1个或多个次生事故的连锁反应机理与风险评估方法。提出应用蒙特卡洛模拟对多米诺事故风险进行动态量化的方法,梳理化工多米诺事故风险的识别、分析、评定、处理全周期管理流程,并以1个天然气压气站为案例,验证基于蒙卡模拟的化工多米诺事故风险量化方法的有效性。结果表明:该方法可以更准确地对化工多米诺事故风险进行定量评估。多米诺事故风险全周期管理流程的梳理能够有效指导化工企业开展安全管理、事故预防等工作。     

Assessment of risks posed by chemical industries—application of a new computer automated tool maxcred-III

The paper describes the application of a new computer automated tool, developed by us, in the risk analysis of a typical chemical industry engaged in the manufacture of linear alkyl benzene. Using the tool—a comprehensive software package maxcred-III (MAXimum CREDible accident analysis)—nine different scenarios, one for each storage unit, have been studied. It is observed that the accident scenario for chlorine (instantaneous release followed by dispersion) leads to the largest area-under-lethal-impact, while the accident scenario for propylene (CVCE followed by fireball) forecasts the most intense damage per unit area. The accidents involving propylene, benzene, and fuel oil have a high possibility of causing domino/secondary accidents as their destructive impacts (shock waves, heat load) would envelope other storage and process units.Besides demonstrating the utilizability of maxcred-III, this study also focuses attention on the need to bestow greater effort towards risk assessment/crisis management. The authors hope that the study will highlight the severity of the risk posed by the industry and thus generate safety consciousness among plant managers. The study may also help in developing accident-prevention strategies and the installation of damage control devices.     

Simulating on rollover phenomenon in LNG storage tanks and determination of the rollover threshold

Rollover is a potential risk to the safety of LNG storage tanks during the LNG storage process, so study of its prevention method is very important. In this paper, rollover phenomenon in a liquefied natural gas (LNG) storage tank is modeled physically and mathematically. Its evolution is simulated using FLUENT™ software from the breakdown of stratification to the occurrence of rollover. Results show that the evolution consists of three phases: the initial phase where rollover occurs near the side wall of the storage tank; the turbulent phase where rollover transfers to the center of the tank; and the final phase where new layers evolve. Based on these phases, rollovers in 160,000, 30,000, and 5000 m³ LNG storage tanks are simulated at varying initial density differences, and a rollover coefficient is defined to describe rollover intensity. The simulations show that the rollover coefficient initially increases within a small scope and then increases rapidly with the increment of initial density difference. This turning point is chosen to be the rollover threshold, which is regarded as the critical density difference in this study. The critical density differences obtained from the simulation results of the 160,000, 30,000, and 5000 m³ LNG storage tanks are 3, 5, and 7 kg/m³, respectively, which can be used as their rollover criteria to ensure the safety of LNG storage tanks.