A criterion for developing credible accident scenarios for risk assessment

Maximum credible accident analysis is one of the most widely used concepts in risk assessment of chemical process industries. Central to this concept is the aspect of ‘credibility’ of envisaged accident scenarios. However, thus far the term credibility is mostly treated qualitatively, based on the subjective judgement of the concerned analysts. This causes wide variation in the results of the studies conducted on the same industrial unit by different analysts.

This paper presents an attempt to develop a criterion using which credible accident scenarios may be identified from among a large number of possibilities. The credible scenarios thus identified may then be processed for detailed consequence analysis. This would help in reducing the cost of the analysis and prevent undue emphasis on less credible scenarios at the expense of more credible ones.     

基于连锁效应化工储罐区火灾爆炸定量风险评价

综合考虑热辐射、爆炸冲击波和爆炸碎片引发不同类型目标装置的连锁破坏效应,建立了基于连锁效应的化工储罐区火灾爆炸定量风险评价流程.结合实例分析,证明了装置之间的连锁效应已经成为影响装置本身及区域整体风险的关键因素.     

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.     

FREEDOM II: An improved methodology to assess domino effect frequency using simulation techniques

The uncertainty and the complexity associated with the domino effect is a barrier to assessing the frequency of such accidents analytically. The use of simulation techniques, such as Monte Carlo, to examine the domino effect instead of analytical techniques has shown great promise. In this paper, a new method to assess the frequency of domino accidents is proposed—FREEDOM II—which is an improvement on the recent algorithm proposed by the authors (FREEDOM). The modifications on FREEDOM were carried out to overcome a limitation of the method and to extend its capabilities. A key shortcoming of the earlier method was its inability to handle multiple failure scenarios. This shortcoming has been overcome in FREEDOM II. A new and improved algorithm has been developed that carries out the simulation in a significantly shorter run time. The applicability of the new model is shown by performing a multi-scenario case study.     

用于工业机器设计的安全性分析模式及方法研究

工业机器也属职业事故的重要危险源之一.在其设计时,有效地进行安全性分析是消除和控制工业机器中存在的固有危险的最佳途径.为此,推荐了一种用于工业机器的安全分析模式;并对已有的安全分析方法进行了重点选择,将供设计人员使用的安全分析方法从百余种减少到11种;还对这些方法进行了分类,可供设计人员在设计工业机器时,较方便地选择和系统地应用.     

因果分析与系统安全性风险评价方法

综合了故障树分析和事件树分析的方法,提出因果分析的框架,研究了基于因果分析建立事故脚本的方法。在此基础上,还对因果分析的概率风险评价方法进行研究,并利用该评价方法,对电机过热的安全性问题进行分析,给出了分析计算的结果     

Estimation of the impact probability in domino effects due to the projection of fragments

Despite the remarkable severity of domino effects in activities at major hazard, a complete methodology analysing such events has not been developed and integrated within Quantitative Risk Analysis (QRA). Such a deficiency appears to be particularly remarkable for domino effects triggered by the projection of fragments. The aim of the present work is therefore to propose a systematic procedure for the quantification of domino effects due to fragments projection within QRA. To achieve this objective, the deterministic approach for the estimation of the realistic trajectory of fragments is entirely reviewed. In order to incorporate such a reviewed approach within the standard QRA, a probabilistic model for the impact probability of the fragments is developed by applying a Monte-Carlo method to the trajectory equations. The validation of the proposed framework is carried out by using the data related to an accident occurred in 1993 in the oil refinery of Milazzo (Italy).     

LPG罐区危险性的研究及分析

目前,绝大多数危险性评价所研究的对象是单一的危险源或危险过程.但是,在日常工业生产中,常常会出现由于初次事故能量的释放而导致的二次甚至多次事故的发生.随着工业生产的大型化,储存量的递增使得多米诺事故发生的可能性也在增加.LPG储罐区正是发生此类事故的危险区域.通过相关模型的运用评价了在LPG储罐区发生火灾爆炸后,相邻危险源发生多米诺事故的可能性,并对安全间距作了着重的分析.     

Risk assessment in support to land-use planning in Europe: Towards more consistent decisions?

Recognising the importance of establishing appropriate separation distances between hazardous installations and vulnerable residential areas for mitigating the effects of industrial accidents, the European legislation for the control of major accident hazards - the so-called Seveso II Directive - calls for procedures ensuring that technical advice is taken systematically into account for land-use planning (LUP) purposes. Due to historical, administrative, cultural and other reasons, these European Union’s Member States which have consolidated procedures for addressing this issue, have employed different approaches, methods and criteria, with a potential for great divergence in the resulting land-use planning decisions. In order to address this situation and to increase consistency and ‘defendability’ of land-use planning decisions in the EU, a European Working Group has been established and is operating under the coordination of the European Commission’s Joint Research Centre (JRC). This Group, consisting of experts from the EU Member States, the industry and the academia, is trying to understand the different approaches and their implications to LUP decision-making, to develop guidelines in support to these decisions and to examine data sources and tools for consistent application of risk assessment in support to LUP. This paper presents the activities of the Group, reviews the situation with respect to LUP in Europe and discusses whether a direction towards more consistent LUP decisions is being followed in Europe.     

RAPID-N: Rapid natech risk assessment and mapping framework

Natech accidents at industrial plants are an emerging risk with possibly serious consequences. For the mitigation of natech risk, authorities need to identify natech prone areas in a systematic manner. In order to facilitate probabilistic natech risk mapping, a unified methodology was developed that is based on the estimation of on-site natural hazard parameters, determination of damage probabilities of plant units, and assessment of probability and severity of possibly triggered natech events. The methodology was implemented as an on-line, extensible risk assessment and mapping software framework called RAPID-N, which allows rapid local and regional natech risk assessment and mapping with minimal data input. RAPID-N features an innovative data estimation framework to complete missing input data, such as on-site natural hazard parameters and plant unit characteristics. The framework is also used for damage assessment and natech consequence analysis, and allows easy modification of input parameters, dynamic generation of consequence models according to data availability, and extension of models by adding new equations or substituting existing ones with alternatives. Results are presented as summary reports and interactive risk maps, which can be used for land-use and emergency planning purposes by using scenario hazards, or for rapid natech consequence assessment following actual disasters. As proof of concept, the framework provides a custom implementation of the U.S. EPA's RMP Guidance for Offsite Consequence Analysis methodology to perform natech consequence analysis and includes comprehensive data for earthquakes. It is readily extendible to other natural hazards and more comprehensive risk assessment methods.     

化学工业重大事故的多米诺效应分析

针对化学工业重大事故多米诺效应的严重后果,进行重大事故多米诺效应发生规律的研究.在指出触发重大事故多米诺效应发生条件和发生模式的基础上,设计重大事故多米诺效应的研究程序.借助生成重大火灾爆炸事故场景和其后果分析方法,建立多米诺效应概率分析的数学模型,利用VB开发了多米诺效应计算软件DOMISOFWARE,解决较为复杂的重大事故多米诺效应概率的计算问题.研究表明,爆炸事故总是较火灾事故具有更高触发多米诺效应的可能性,并且火灾和爆炸触发加压设备发生多米诺效应的概率与常压设备相比随间距增大几乎呈线性下降;确定了爆炸和火灾触发多米诺效应的概率和临界距离.研究结果对于化工装置的安全设计和重大事故的预防控制具有重要的指导意义.     

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.     

多米诺效应阈值研究进展

多米诺效应阈值是表征破坏效应相关物理参数的限值,是判断是否会引发多米诺效应的评判准则,是多米诺效应定量评价的开端。在对国内外多米诺效应研究成果分析的基础上,介绍了多米诺效应及其阈值,综述了引发多米诺事故扩张的三种物理效应阈值（即：热辐射阈值、超压阈值和碎片阈值）的研究现状。     

道氏火灾爆炸指数法在化工品码头危险性评价中的应用

简要介绍了道氏火灾爆炸指数法（第６ 版）的评价过程,并应用该方法对某化工品码头储运生产各工艺环节的火灾爆炸危险性进行了评价。     

易燃易爆氢氧车间生产、贮气柜系统危险性评价

通过某动力公司氢氧车间生产、贮存系统危险性因素分析,对氢氧车间氢气生产、贮存各工艺环节进行了火灾爆炸危险性评价,并针对氢氧车间生产工艺系统和湿式贮气柜的火灾爆炸事故隐患,提出了事故防范的安全对策.     

Does your facility have a dust problem: Methods for evaluating dust explosion hazards

The hazards of dust explosions prevailing in plants are dependent on a large variety of factors that include process parameters, such as pressure, temperature and flow characteristics, as well as equipment properties, such as geometry layout, the presence of moving elements, dust explosion characteristics and mitigating measures. A good dust explosion risk assessment is a thorough method involving the identification of all hazards, their probability of occurrence and the severity of potential consequences. The consequences of dust explosions are described as consequences for personnel and equipment, taking into account consequences of both primary and secondary events.While certain standards cover all the basic elements of explosion prevention and protection, systematic risk assessments and area classifications are obligatory in Europe, as required by EU ATEX and Seveso II directives. In the United States, NFPA 654 requires that the design of the fire and explosion safety provisions shall be based on a process hazard analysis of the facility, process, and the associated fire or explosion hazards. In this paper, we will demonstrate how applying such techniques as SCRAM (short-cut risk analysis method) can help identify potentially hazardous conditions and provide valuable assistance in reducing high-risk areas. The likelihood of a dust explosion is based on the ignition probability and the probability of flammable dust clouds arising. While all possible ignition sources are reviewed, the most important ones include open flames, mechanical sparks, hot surfaces, electric equipment, smoldering combustion (self-ignition) and electrostatic sparks and discharges. The probability of dust clouds arising is closely related to both process and dust dispersion properties.Factors determining the consequences of dust explosions include how frequently personnel are present, the equipment strength, implemented consequence-reducing measures and housekeeping, as risk assessment techniques demonstrate the importance of good housekeeping especially due to the enormous consequences of secondary dust explosions (despite their relatively low probability). The ignitibility and explosibility of the potential dust clouds also play a crucial role in determining the overall risk.Classes describe both the likelihood of dust explosions and their consequences, ranging from low probabilities and limited local damage, to high probability of occurrence and catastrophic damage. Acceptance criteria are determined based on the likelihood and consequence of the events. The risk assessment techniques also allow for choosing adequate risk reducing measures: both preventive and protective. Techniques for mitigating identified explosions risks include the following: bursting disks and quenching tubes, explosion suppression systems, explosion isolating systems, inerting techniques and temperature control. Advanced CFD tools (DESC) can be used to not only assess dust explosion hazards, but also provide valuable insight into protective measures, including suppression and venting.