Embedding the human factor in road tunnel risk analysis

The paper is focusing on road tunnel safety and builds upon the Directive 2004/54/EC launched by the European Commission; the latter sets basic requirements and suggests the implementation of risk assessment in several tunnel cases apart from technical measures imposed on the basis of tunnel structural and operational characteristics. Since the EU Directive does not indicate the method for performing risk assessment, a wide range of methods have been proposed, most of them based on quantitative risk assessment (QRA). Although the majority of current road tunnel QRAs assess physical aspects of the tunnel system and consider several hazards concerning the transportation of dangerous goods through a tunnel, they do not take into account, sufficiently, several organizational and human-related factors that can greatly affect the overall safety level of these critical infrastructures. To cope with this limitation this paper proposes a fuzzy logic system based on CREAM method for human reliability analysis (Hollnagel, 1998) in order to provide more sophisticated estimations of the tunnel operator's performance in safety critical situations. It is deduced that a human reliability analysis component to analyze operator performance, like the fuzzy system proposed here, is important for risk analysts. Consideration of organizational and human factors will enhance risk analysts’ studies and highlight the uncertainty related to human performance variability.     

考虑人为因素的可靠性评估

统计数据表明,系统的可靠运行不可忽略人为误操作造成的故障,该故障发生率有时甚至超过设备本身导致的系统故障发生率。将人为因素与设备自身因素造成的系统故障进行对比,分析人为因素造成系统故障后的特点,可得出人为因素的可靠性参数。根据解析法和模拟法的相关理论计算考虑人为因素的可靠性指标,可以看出考虑人为因素的计算结果更加符合实际运行特点,便于相关人员采取对策,保障系统的安全运行。     

功能安全评估在安全评价中的应用体系研究

在工业过程控制领域,安全仪表系统监视生产过程的状态,在危险条件出现时采取相应的措施,防止危险发生,避免潜在危险对人身、设备、环境造成伤害或减轻造成的损失,是保障生产安全的重要措施。安全仪表系统应能在危险发生时正确的执行其安全功能,因而其自身的功能安全成为关注的焦点。作为安全评价的延伸,应将功能安全评估引入,从而完善安全评价体系。本文以功能安全国际标准为基础,讨论建立我国功能安全评估机构的运作模型及功能安全评估在安全评价中的应用体系。     

基于模糊评判和RCM的CTCS-3级车地通信子系统维修决策

CTCS-3级车地通信子系统是列控系统的重要组成部分之一,且列控系统需求的列车位置、行车许可、临时限速等安全信息都由其提供,因此,对其进行可靠性分析具有十分重要的意义。采用贝叶斯网络对系统进行可靠性分析,并对维修方式进行了讨论。首先,根据车地通信子系统的功能与结构构建其贝叶斯网络模型。然后,综合考虑维修性、共因失效等因素,对车地通信子系统进行可靠性分析。最后,在可靠性分析的基础上运用模糊综合评判法对其进行维修决策。结果表明:利用贝叶斯网络的双向推理,不仅可以计算出车地通信子系统的可靠度,还可以有效识别系统的薄弱环节;若不考虑车地通信系统冗余结构中的共因失效,则得到的可靠性指标会偏于乐观。地面GSM-R单元失效是引起车地通信子系统失效的关键事件,因此针对此薄弱环节进行状态维修检查能够有效降低事故的发生概率。     

火灾自动报警系统可靠性研究

火灾自动报警系统主要包括火灾探测器、火灾报警控制器、减灾装置和灭火装置4部分,从这4部分分析了其工作原理。在此基础上,着重分析了误报、漏报概率较高的火灾探测系统(包括火灾探测器和火灾报警控制器)在使用过程中可能出现的失效状态。其失效的根本原因是在探测器的设计、选型与安装中出现的问题以及各类控制器和控制软件出现的问题。火灾自动报警系统在设计、安装和使用过程中出现的一些问题可能导致整个系统失效,主要包括硬件故障、系统失误和管理缺陷3类。因此,从火灾自动报警系统设计、软硬件产品质量、选型与安装及维护保养等方面给出了提高火灾自动报警系统可靠性的措施。最后应用系统安全及可靠性理论建立了包括电源系统、触发装置、报警控制装置和警报装置4个指标的火灾自动报警系统可靠度计算模型。     

信息可视化在化工企业大气环境影响评价中的研究及应用

运用data system.exe技术,提出大气环境影响评价信息可视化软件的设计方法,建立了大气环境污染因子数据信息可视化模型,应用该成果对某石油化工企业大气环境进行初步风险评价,结果表明:通过输入大气环境污染因子监测值,系统可自动判定大气环境的污染程度,并把对应环境质量的级别、环境的安全程度以及污染对人体与生物的影响程度在图中显示出来,能有效地提高环境影响评价的可靠度。该软件能在识别污染因子数据信息的同时生成与之相匹配的直观的模拟环境图像,有助于管理者进行及时分析与决策,建立的环境污染因子数据信息可视化软件具有很强的适用性。同时对政府部门制定环保工作决策具有重要的参考价值。     

基于马尔可夫方法的水下防喷器可靠性研究

水下防喷器是保障海上钻井安全的关键设备,对其可靠性进行定量评价对井控作业有重要的指导意义.为了弥补现有水下防喷器可靠性评价方法的不足,将水下防喷器的工作状态分为四种,包括无故障可用、关井、井控关键失效及关井时失效.利用Markov方法建立了水下防喷器的Markov模型.通过水下防喷器系统的状态转换图找出了各工作状态的转换关系.通过分析墨西哥湾83口深水井水下防喷器的失效数据,定义了影响水下防喷器可靠性的井控关键失效,并对深水钻井水下防喷器防喷功能的可靠性进行了定量计算.将计算结果与不考虑关井期间的井控关键失效相比较发现,防喷器的防喷失效概率增加了65％.因此传统的定量评价方法可能会得出相对乐观的结论,应在实际生产中给予重视.     

基于多故障冲击模型和故障树的PFDavg计算方法研究*

为提高安全仪表功能（SIF）要求时危险失效平均概率（PFDavg）计算结果的精确度,提出1种能准确计算SIF在多重共因失效影响下的PFDavg的数学模型。建立包含多重共因失效的系统失效故障树,然后利用多故障冲击模型区分普通失效率和多重共因失效率,根据瞬时不可用率的定义和故障树的逻辑关系计算出SIF的瞬时不可用率;基于PFDavg的定义,计算出SIF的PFDavg,以某化工企业SIF为例进行验证。结果表明:方法有效考虑了多重共因失效对SIF的影响,通过模型计算出SIF的PFDavg大于基于马尔可夫（Markov）方法的软件计算结果,但二者处于相同的数量级。模型在评估SIF的PFDavg时比传统方法偏保守,能提高安全仪表功能的安全性。     

Mitigation performance of the process protection system on the accident consequences of H2S-containing natural gas release and explosion

Toxic loads and explosion overpressure loads pose grave threats to the offshore oil and gas industry. Many safety measures are adopted to prevent and mitigate the adverse impacts caused by toxic loads and explosion overpressure loads. As a general safety barrier, the process protection system has been widely used but rarely evaluated. In order to assess the barrier ability, the mitigation performance of the process protection system is concerned in this study. Firstly, several chain accidents of H₂S-containing natural gas leakage and explosion are simulated by varying the response time of the process protection system with CFD code FLACS. Qualitative assessment is conducted based on the variation of the dangerous load profiles. Furthermore, the quantitative assessment of the mitigation performance is accomplished by considering its ability in reducing the probability of fatality. Emergency evacuation and no emergency evacuation are considered respectively in the quantitative assessment. The results prove that the process protection system takes effect on mitigating the toxic impact and explosion overpressure impact. The results also demonstrate that although the emergency evacuation may result in a severer explosion load to the operator, the process protection system can mitigate the adverse impacts regardless of whether the emergency evacuation is conducted or not.     

Reliability-based optimisation of a mine production system using genetic algorithms

In this research, a safety management system is planned for a mine operation. The objective is to develop a mine production design that will achieve the desired reliability and variance of reliability estimation of system while performing all sub-system functions at a minimum cost. The problem was formulated in an underground mine system containing five sub-systems with varying reliability estimates, estimation variances and feasibilities and solved by genetic algorithms (GA).     

安全系统的故障分析

以可靠性研究为基础,分析独立和冗余配置的安全系统的故障状态,给出独立配置和冗余配置时安全系统的显性故障率、隐性故障率以及系统可用度的定量模型。以该模型对以紧急停车系统(ESD)和生产监控系统(DCS)构成的组合安全系统进行了比较和分析。笔者认为:ESD单独设置时,应注意降低隐性故障率、提高其修复率;ESD与DCS冗余配置时,无论是并联冗余还是串联冗余,安全保护功能都是增加的,但同时显性故障率有所增加,隐形故障率大大减少。因此,用ESD补充DCS的安全保护功能而不是简单的重复其功能,对提高系统的整体安全水平将是十分明显的。     

机场货站易爆危险品存储区外部安全防护距离研究*

为合理设定机场货站易爆危险品存储区外部安全防护距离,基于爆炸威力计算模型,利用有限元分析软件AUTODYN模拟包装约束下爆炸品爆炸冲击波特性,通过引入包装约束系数,描述包装材料对爆炸威力影响,计算航空运输易爆危险品存储区外部安全防护距离。结果表明:1 mm厚度聚碳酸酯、钢和铝材质外包装的包装约束系数分别为0.904 7,0.860 1,0.870 6,相较于聚碳酸酯和铝材质,钢材质外包装对易爆危险品爆炸威力削弱程度较大。研究结果可为机场货站外部安全防护距离规划设置提供参考。     

危险化学品道路运输系统危险性分析

针对危险化学品道路运输中的安全问题 ,建立了危化品道路运输系统模式和系统危险性评价程序。应用所开发的ACES软件系统对汽车燃料汽油的替代品LPG的道路运输进行了最大事故后果分析评价 ,并提出了建议和对策。研究结果不仅能够为危化品道路运输系统危险性的控制和预防提供科学指导 ,还能为减少系统事故损失及事故时的应急疏散等提供参考数据 ,具有潜在的经济效益和社会效益。     

Planning protection measures against runaway reactions using criticality classes

A systematic approach to the assessment of thermal risks linked with the performance of exothermal reactions at industrial scale was proposed a long time ago. The approach consisted of a runaway scenario starting from a cooling failure and a classification of these scenarios into criticality classes. In the mean time these tools became quite popular and many chemical companies use them. Recently, the international standard IEC 61511 required the use of protection systems with reliability depending on the risk level. Since the criticality classes were developed as a tool for the choice of risk reducing measures as a function of the criticality, it seems obvious that the criticality classes may be used in the context of the standard IEC 61511, which provides a relation between the risk level and the reliability of protection systems.Firstly, the runaway scenario and the criticality classes will be shortly described. Secondly, the assessment criteria for severity and probability of occurrence of a runaway scenario will be described together with the required data and their interpretation in terms of risk. Thirdly, the assessment procedure is exemplified for the different criticality classes. Finally, the design of protection measures against runaway and the required IPL and SIL are based on the risk assessment obtained from the criticality classes. This approach allows minimising the required data set for the safety assessment and for the definition of the protection system designed in order to avoid the development of the runaway.     

Improving safety and availability of complex systems using a risk-based failure assessment approach

This paper presents a structured risk-based failure assessment (RBFA) approach, which provides a complete solution to avoid repeated and potential failures to improve overall plant safety and availability. Technological advancements and high product demand have encouraged designers to design mega-capacity systems to enhance system utilization and improve revenues. However, these benefits make the systems more complex and thus prone to unnoticed failure. It is an overwhelming task to address all the failures due to the limited resources and time constraints. This leads to substandard and poor quality failure assessments, which cause repeated failures. To address this common industry concern, a four phase RBFA framework is proposed which is not limited to the identification of root cause(s) but also includes other actions such as failure monitoring. The four phases include the plan phase, the assessment phase, the analysis phase and the implementation-tracking phase. These phases cover identification of failure, failure analysis, root cause(s) analysis, and failure monitoring. In this paper, the applicability and advantages of the proposed approach are examined through two real case studies pertaining to bearing failure and drive coupling failure. By implementing the proposed approach, significant improvements have been experienced in the system availability in both the cases.     

加油站安全监测系统研究

随着加油站数量的猛增,加油站安全问题已经越来越受到社会各界的关注,但目前对加油站整体监测系统的研究很少,而且没有相关产品.从加油站组成结构出发,分析了加油站危险化学品的理化性质,考虑了硬件和软件2部分,提出了加油站综合安全监测系统的研究方案.     

Learning from the application of nuclear probabilistic safety assessment to the chemical industry

This paper introduces the new approach of risk analysis established by the French Ministry of the Environment and develops the benefits of applying nuclear probabilistic safety assessment approaches to the chemical industry.In the aftermath of the AZF disaster in Toulouse on 21 September 2001, a new law was proposed by the French government asking for the investigation of all representative scenarios and the assessment of the probability of the resulting dangerous phenomena to demonstrate an acceptable level of safety. Therefore, any accident is investigated from a global point of view, according to its gravity and its probability.In 2000, the French Ministry of the Environment asked the Institute for Radiological Protection and Nuclear Safety (IRSN), and in particular its Systems and Risk Protection Assessment (SESPRI) and its Industrial Risks, Fire and Containment Assessment and Study (SERIC) departments, to conduct a Probabilistic Safety Assessment (PSA) study of an LPG distribution facility, specially for the BLEVE scenario. This study has showed the power of PSA for defining and prioritizing actions to be carried out to improve safety of facilities; however, it requires credible data for reliability and failure of the equipment, not available in generic failure databases.Since 2007, IRSN has taken several initiatives in collaboration with operators in order to provide more precise and representative failure rates for main safety equipment, ready to use in future PSA relative to LPG plants.     

一种高安全、容错控制计算机的设计与实现

在许多工业领域中 ,其控制系统必须是高可靠、高可用和高安全的。根据IEC 6 15 0 8标准 ,1oo2D(oneoutoftwowithdiagnostics)结构满足这些要求。实现 1oo2D结构时 ,每个通道采用双CPU结构 ,通道间同步采用软硬件结合方式 ,硬件数据比较器具备强故障安全特性 ,通道间通信采用高速并行方式 ,自诊断包括内嵌诊断设备、自诊断程序和看门狗。研制了实验原型机 ,进行的功能测试和错误注入测试表明 :其控制功能正常 ,容错性能和安全性能满足工业控制要求     

高要求模式SIS异型冗余结构PFH计算模型*

为了满足石油化工生产中对高要求操作模式下采用异型设备的安全联锁回路进行SIL定级的需求,避免因误用同型PFH公式导致SIL等级评估误差。考虑各通道差异性及其失效顺序的遍历性,以MonteCarlo仿真值为多元线性回归模型观察样本,以改进共因失效部分多样性修正因子确定方法,提出异型KooN冗余结构每小时危险失效平均频率(PFH)的计算公式;比较该模型独立失效部分与异型1oo2结构Markov模型PFH结果,并分别将该模型和传统同型PFH公式应用于海上采油平台高完整性压力保护系统(HIPPS)异型关断阀子系统的比较分析。研究结果表明:在不同检测周期内,所提出的PFH计算模型与Markov模型PFH计算结果相对误差均保持在10-3数量级;但当检测周期大于3 a时,使用同型PFH公式会出现对HIPPS子系统SIL等级的误判,造成井口压力联锁保护功能过保护或欠保护。研究结果有助于生产单位准确评估联锁保护风险和设备维护投入。     

Dynamic failure assessment of an ammonia storage unit: A case study

Chemical Process Industries usually contain a diverse inventory of hazardous chemicals and complex systems required to perform process operations such as storage, separation, reaction, compression etc. The complex interactions between the equipment make them vulnerable to catastrophic accidents. Risk and failure assessment provide engineers with an intuitive tool for decision making in the operation of such plants. Abnormal events and near-miss situations occur regularly during the operation of a system. Accident Sequence Precursors (ASP) can be used to demonstrate the real-time operating condition of a plant. Dynamic Failure Assessment (DFA) methodology is based on Bayesian statistical methods incorporates ASP data to revise the generic failure probabilities of the systems during its operational lifetime.In this paper, DFA methodology is applied on an ammonia storage unit in a specialized chemical industry. Ammonia is stored in cold storage tanks as liquefied gas at atmospheric pressure. These tanks are susceptible to failures due to various abnormal conditions arising due process failures.Tank failures due to three such abnormal conditions are considered. Variation of the failure probability of the safety systems is demonstrated. The authors use ASP data collected from plant specific sources and safety expert judgement. The failure probabilities of some safety systems concerned show considerable deviation from the generic values. The method helps to locate the components which have undergone more degradation over the period and hence must be paid attention to. In addition, a Bayesian predictive model has been used to predict the number of abnormal events in the next time interval. The user-friendly and intuitive nature of the tool makes it appropriate for application in safety assessment reports in process industries.