事故树分析法在LPG储罐火灾爆炸事故中的应用

LPG(液化石油气)属于危险化学品之一,LPG储罐发生火灾爆炸的机率大,造成的损失比较严重,故对其火灾爆炸事故进行研究具有重要意义。LPG储罐爆炸根据其发生机理分为化学爆炸(燃爆)和物理爆炸两种模式。本文通过对LPG储罐燃爆﹑物理爆炸两类事故进行系统分析,建立了以LPG储罐燃爆、物理爆炸为顶事件的事故树。通过对其事故树的定性分析,得到了影响顶事件的各个最小割(径)集。通过计算底事件的结构重要度,确定了影响LPG储罐火灾爆炸事故的主要因素,并提出了相应的改进措施,进而提高LPG储罐的安全性和运行可靠性。     

A new look at release event frequencies

Within the context of a quantitative risk analysis (QRA), the two main constituents used to describe petrochemical risks are, and have always been, consequence and probability. The consequences of hazardous material accidents are easy to apprehend – if a hazard is realized it can injure people or cause fatalities, damage equipment or other assets, or cause environmental damage. Frequencies for these consequences, on the other hand, are not as easy to understand. Process safety professionals develop event frequencies by evaluating historical data and calculating incident rates, which represent, in the QRA context, how often a release of a hazardous material has occurred. Incident rates are further modified by probabilities for various hole sizes, release orientations, weather conditions, ignition timing, and other factors, to arrive at unique event probabilities that are applied in the QRA. This paper describes the development of incident rates from historical database information for various equipment types, as well as defining a methodology for assigning hole size probabilities from the same data, such that a hole size distribution can be assigned within each QRA study. The combination of total incident rates and a hole size distribution relationship can then serve as a foundation within the frequency side of many QRA studies.     

A method for determining critical events during large disasters of production platforms

This article presents a calculation-based methodology to determine the dominant event class in each of the phases of disasters being analysed, and to address the question of whether different disasters have similarities at crucial times in each phase of the disaster. Our approach is based on event network analysis. Disasters can be modelled using block diagrams and multiphase process trees. We propose trees in this article can be used as a tool for modelling phases of a disaster. The starting point for developing these models was fault tree analysis used for modelling the reliability structure of complex systems. This study demonstrates the possibility of using dual fault trees to describe the process as opposed to the structure. In our analyses, we examined four major disasters of production platforms that occurred in the last 50 years: Ixtoc I, Piper Alpha, Petrobras 36 and Deep Water Horizon. The course of each of these disasters has been described, the basic events of these disasters have been isolated, and assigned to event classes. The hierarchical importance of events was determined using the Birnbaum reliability measure, Birnbaum structural measure, Fussell-Vesely measure, criticality measure and improvement potential. For each phase of the analysed disasters, event importance is ranked, and the most important events that contributed to the phase are identified. General principles on the analysed disasters and the methodology used are also discussed.     

An Analysis of Accidents Caused by Improper Functioning of Machine Control Systems

The scope of this study covers events resulting from improper functioning of machine control systems. An accident model providing a basis for formulating a checklist for accident analysis has been developed. Data about 700 accidents were collected. An analysis has proved that in the group of accidents caused by improper functioning of machine control systems, serious accidents happened much more frequently as compared to the group of accidents with no relation to the control system. The reasons for the majority of incidents caused by improper performance of safety functions consist in the errors made by designers. In view of that, incorrect behaviour of a worker should be treated as a normal event instead of a deviation causing an accident.     

The application of reliability models in traffic accident frequency analysis

Analysis of traffic accident frequency represents an important subject of research of many authors. From the aspect of temporal analysis of traffic accident occurrence, two approaches have been singled out in previous practice: the collective (analyzes traffic accidents over a longer period of time) and individual (analyzes traffic accidents in real time). The paper shows that the system reliability theory, with certain adjustments, can be largely used to analyze traffic accident frequency based on the individual approach. A certain similarity has been observed between the system reliability theory and the traffic safety theory, and conceptual adjustment of equivalent terms and states has been performed based on this. A model has been successfully tested on the basis of which, for the road and sections, we have determined the traffic accident frequency, the probability of the occurrence of a certain number of traffic accidents and the mean time between two consecutive traffic accidents.     

LNG储罐火灾和爆炸事故树分析

对引起液化天然气储罐发生火灾、爆炸的因素进行系统分析,建立以LNG储罐火灾、爆炸为顶事件的事故树,并进行事故树分析,得到影响顶事件的各阶最小割集。利用二次计算的方法,更加精确地计算底事件的结构重要度系数,确定了影响储罐事故的主要因素,为提高LNG储罐的安全性和运行可靠性,提出相应的改进措施。     

跨界水污染事故危害实时判定方法的建立

针对跨界突发性水污染事故特点,基于压力-状态-响应模型(PSR)构建了跨界水污染事故预警指标体系,并确立了各指标的分级标准。采用AHP(层次分析法)-综合模糊评价法建立了事故危害实时判定方法。     

基于HFACS的中国特别重大煤矿事故研究

特别重大煤矿事故一直被认为是中国最严重的社会问题之一。本论文的研究目标有两个。首先,分析中国特别重大煤矿事故的致因因素;其次,定量考察事故致因因素间的相互作用关系。基于HFACS模型,在层级层面上,94起特别重大煤矿事故的实证表明:"不安全行为"的发生频率最高;在类别层面上,"监管不力"的发生频率最高;在指标层面上,"对违法行为失察或制止不力"的发生频率最高。借助OR技术,计算得出上一层级对下一层级指标的影响关系,并得到了一系列致因因素间的影响路径,这为遏制和预防特别重大煤矿事故提供了"路线图"。     

Consequence risk analysis using operating procedure event trees and dynamic simulation

Faults due to human errors cost the petrochemical industry billions of dollars every year and can have adverse environmental consequences. Unquantified human error probabilities exist during process state transitions performed each day by process operators using standard operating procedures. Managing the risks associated with operating procedures is an essential part of managing the overall safety risk. Additional operator training and safety education cannot eliminate all such faults due to human errors; therefore, we propose an operating procedure event tree (OPET) like analysis with branches and events specifically designed to perform risk analysis on operating procedures. The OPET method adapts event trees to analyze the risk due to human error while performing operating procedures. We consider human error scenarios during the procedure and determine the likely consequences by applying dynamic simulation. The modified event tree provides an estimate of the error frequencies.Operating procedure steps were developed, and potential operator faults were determined for two typical equipment switching procedures found in chemical plant operations. Then, dynamic simulation using Aspen HYSYS software was applied to determine the overpressure related consequences of each fault. Finally, the error frequencies resulting from those scenarios were analyzed using operating procedure event trees. We found that a typical ethylene plant gas header would overpressure with 0.6% frequency per manual dryer switch. Since dryer switches occur from every few days up to once per shift, these results suggest that dryer switching should be automated to ensure safe and environmentally friendly operation. Process dryer switching performed manually by operators opening and closing gate valves can be automated with control valves and a distributed control system. A sample distillation column was found to overpressure with 0.85% frequency per manual reflux pump switch.     

煤矿本质安全化管理体系建立及其应用的探讨

运用安全系统工程中的事故树理论,以瓦斯爆炸事故为例分析了煤矿中的7类主要事故,并得出相应的事故树。通过对事故树的定性分析,得出事故树的最小径集和基本事件重要度排序。进而可预测基本事件的发生所能够导致的结果,可根据各基本事件的重要度排序,确定避免发生事故应采取的基本措施,并建立了煤矿本质安全化管理体系。设计出煤矿本质安全化管理体系的软件,并以瓦斯爆炸事故为例,分析了该管理体系在实际中的应用效果。     

基于FTA-IOT的高校校园安全系统性分析

为了更好的预防校园安全事故的发生,利用事故树方法研究了校园安全中的住宿安全、交通安全和饮食安全问题。论文通过计算事故树的最小径集对三类安全所有基本事件的结构重要性进行了分析,得出了对三类安全影响最大的因素。结果显示,财产丢失、火灾初期的控制是影响住宿安全的主要因素;校园车辆管理和人的行为是影响校园交通安全的主要因素;学生的不良饮水习惯、食堂卫生管理是影响饮食安全的主要因素。基于此,论文提出了基于物联网以RFID技术来提升校园的安全水平的措施。     

Fatal accidents in Swedish farming and forestry, 1988–1997

It has long been acknowledged that farm work is associated with accident risks. In this investigation it has been determined how these risks have changed over the past 10-year period, and how different factors have affected the risk pattern. All the registered accidents forming the basis for this study (ISA, The Occupational Safety and Health Administration) were supplemented with information obtained from the Labor Inspectorate, police, Occupational Health Services, and in many cases, persons from the district having information about the accident. The number of fatal accidents occurring at work is decreasing in Sweden and in many other countries. This, however, is not true for Swedish farm and forestry operations. The frequency of fatal accidents is 11.6 per year per 100,000 persons among those with farming as a main occupation, and 13.6 among those with forestry as a main occupation, and the trend appears to be on the increase. In addition, a number of farmers, persons with other occupations, or senior citizens (mostly retired farmers) also meet with fatal accidents, primarily in forestry. Access or membership in occupational health schemes was lower than expected among the victims. Even among the employed forestry workers, only a minority had access. More than half of the accidents were due to either the victim or a fellow worker not following generally known rules or recommendations.     

Historical analysis of accidents in seaports

A study has been carried out of accidents occurring in seaports. A total of 471 accidents occurring between the beginning of the twentieth century and October 2002 have been analysed. The results obtained show a significant increase in the frequency of accidents over time: 83% of the accidents occurred in the last 20 years and 59% in the past decade. The most frequent accidents were releases (51%), followed by fires (29%), explosions (17%) and gas clouds (3%). More than half the accidents occurred during transport: loading/unloading operations, storage and process plants also make a large contribution to the total. The various causes of the accidents have also been analysed, as have the type of substance involved and the consequences for the population (number of people killed, injured and evacuated). Finally, some conclusions are drawn concerning the need to improve certain safety measures in ports.     

Generic event trees and probabilities for the release of different types of hazardous materials

To simplify quantitative risk analysis, the initiating events leading to loss of containment are normally described using generic hypotheses. For example, the following hypothesis is applied to the loss of containment from a storage tank: instantaneous release of the complete inventory, continuous release of the complete inventory in 10 min, and continuous release from a hole with a diameter of 10 mm. Once the initiating events have been specified, the corresponding event trees must be drawn to establish the sequences from each initiating event to the diverse final outcomes or accident scenarios, which will depend on the properties of the released material or on other specific factors. In this paper we propose, in a systematic way, a set of short generic event trees for the main loss of containment scenarios involving different types of hazardous materials. Even though most of them have been taken from the literature (BEVI Reference Manual), we have modified some of them, added the corresponding intermediate probabilities (immediate ignition, delayed ignition, flame front acceleration, etc.) obtained from a literature review and expert judgment, and associated the use of each event tree to the hazardous properties of the material (flammability, volatility and toxicity) and to its category according to EC labeling directives.     

ATA方法在交通事故分析中的应用

从系统工程学的角度出发,将广泛应用于系统安全研究中的事故树分析方法(ATA)应用到交通事故的分析。根据组成交通系统的四大因素(人、车、路和环境因素),总结和归纳了引起交通事故的原因。运用Fault Tree绘制软件,绘制了交通事故的事故树图。对交通事故基本事件概率的算法进行分析,提出用以平衡样本局限性的误差修正系数。并根据事故树基本原理和算法,对交通事故事故树进行最小割集分析、基本事件重要度分析和顶上事件发生概率的定性定量分析。     

GAP—a fault-tree based methodology for analyzing occupational hazards

Occupational accidents are stochastic events. The moment of their occurrence cannot be predicted. However, their rate of occurrence may be reduced, albeit not to zero. Considerable effort has been invested into this objective. This led to decreasing numbers of accidents over the years, a tendency which seems, however, to have come to a standstill since approximately 1998. The potential of presently used methods like check lists or HAZOP-based approaches for evaluating and producing recommendations for reducing occupational hazards has apparently been exhausted. Hence, further improvement of the injury rates is expected only from the use of in-depth analysis methods. Therefore, fault tree analysis is applied to occupational safety. This leads to the formulation of the hazard base model and its representation by means of an occupational hazard tree. This tree serves as an example for the assessment of occupational hazards of work places and activities. The characteristic feature of the occupational hazard tree is the decomposition of the undesired event ‘injury’ into basic events. These are qualified verbally using the expressions ‘certain/permanently’, ‘impossible/never’, ‘probable/frequently’, ‘possible/occasionally’, ‘improbable/rarely’. The procedure is implemented in the program GAP (HazardAnalysisProgram), which enables one to generate and evaluate occupational hazard trees. A global verbal assessment of a workplace or an activity is then obtained. On its basis weaknesses of the occupational safety concept are identified, appropriate countermeasures are devised, they are prioritized and their efficiency is valuated. The procedure was successfully tested by analyzing two accidents and assessing a workplace at a major industrial firm.     

Evaluation of the Risk OMT model for maintenance work on major offshore process equipment

Operational safety is receiving more and more attention in the Norwegian offshore industry. Almost two thirds of all leaks on offshore installations in the period 2001–2005, according to the Risk Level Project by the Petroleum Safety Authority in Norway, resulted from manual operations and interventions, as well as shut-down and start-up. The intention with the Risk OMT (risk modelling – integration of organisational, human and technical factors) program has been to develop more representative models for calculation of leak frequencies as a function of the volume of manual operations and interventions. In the Risk OMT project a generic risk model has been developed and is adapted to use for specific failure scenarios. The model considers the operational barriers in event trees and fault trees, as well as risk influencing factors that determine the basic event probabilities in the fault trees. The full model, which applies Bayesian belief networks, is presented more thoroughly in a separate paper. This paper presents the evaluation of the model. The model has been evaluated through some case studies, and one important aspect is the evaluation of the importance of each risk influencing factor. In addition some risk-reducing measures have been proposed, and the paper presents how the effect of these measures has been evaluated by using the model. Finally, possible applications and recommendations for further work are discussed.     

An analysis of accidents caused by improper functioning of machine control systems.

The scope of this study covers events resulting from improper functioning of machine control systems. An accident model providing a basis for formulating a checklist for accident analysis has been developed. Data about 700 accidents were collected. An analysis has proved that in the group of accidents caused by improper functioning of machine control systems, serious accidents happened much more frequently as compared to the group of accidents with no relation to the control system. The reasons for the majority of incidents caused by improper performance of safety functions consist in the errors made by designers. In view of that, incorrect behaviour of a worker should be treated as a normal event instead of a deviation causing an accident.     

价格对中国煤矿事故的影响分析

针对我国目前煤炭产业严峻的安全形势，本文采用、统计的方法，分析了煤炭价格和产量与煤矿安全生产事故之间的相关关系，验证煤炭价格与煤矿安全生产事故的发生存在协整关系，而且煤价是煤矿伤亡事故的致因，并进一步做回归分析，并尝试从价格的角度揭示煤矿安全生产事故发生的规律。