Comparing safety analysis techniques

In process industry Safety Instrumented Systems (SIS) and Emergency Shutdown Systems (ESD) are very important for the management/reduction of risk. In new standards (e.g. Ref. [1]) on functional safety of electrical/electronic/programmable electronic safety-related systems a quantification of the achieved safety is often required. These new standards do not prescribe how to calculate the achieved safety. Only guidelines and recommendations are given. The problem with this approach is that all kinds of different analysis techniques will be used and in industry the results of the analysis will be compared. These different analysis techniques all use different methodologies and assumptions, which implies that the results may not be comparable. In this paper an approach for comparing different analysis techniques and the qualitative and quantitative results from this comparison are described. The author suggests that, because of the differences in the analysis techniques, one analysis technique is to be preferred. The Enhanced Markov Analysis technique, described in this paper, could be used for this purpose because it covers most aspects relevant for quantification of safety.     

Reducing medication errors in hospitals: a peer review organization collaboration

BACKGROUND: Motivated by published reports of the incidence, costs, causes, and nature of adverse drug events (ADEs) in hospitalized patients, in 1997 the Medicare peer review organization for Nevada and Utah initiated a voluntary project of medication error reduction for Utah hospitals. METHODS: Through project activities, hospital teams were encouraged to make changes to their medication processes based on direct evaluation of medication systems characteristics, informed by ergonomic principles and published studies of medication errors. Assessment of project effects included an evaluation of the changes implemented and results from an anonymous medication errors survey of clinical staff from participating organizations. RESULTS: Thirteen of the 39 acute care hospitals in Utah participated in 1997-1998 in the collaborative project. Participants reported substantive medication system changes that were expected to result in improved patient safety. Baseline and follow-up survey data were available for 8 of the participating hospitals. Analysis of 560 responses showed a 26.9% decrease in overall error frequency, a 12.5% increase in error detection and prevention, and a 24.1% increase in formal written reporting of errors that reached the patient. CONCLUSIONS: This project demonstrated community interest in a proactive and collaborative approach to improving patient safety. The improvement efforts were substantive and sustainable. Survey results suggest that the changes implemented in participating organizations may have reduced medication errors and improved capacity for error detection and prevention.     

New quantitative safety standards: different techniques, different results?

Safety Instrumented Systems (SIS) are used in the process industry to perform safety functions. Many factors can influence the safety of a SIS like system layout, diagnostics, testing and repair. In standards like the German DIN no quantitative analysis is demanded (DIN V 19250 Grundlegende Sicherheitsbetrachtungen für MSR-Schutzeinrichtungen, Berlin, 1994; DIN/VDE 0801 Grundsätze für Rechner in Systemen mit Sicherheitsaufgaben, Berlin, 1990). The analysis according to these standards is based on expert opinion and qualitative analysis techniques. New standards like the IEC 61508 (IEC 61508 Functional safety of electrical/electronic/programmable electronic safety-related systems, IEC, Genève, 1997) and the ISA-S84.01 (ISA-S84.01.1996 Application of Safety Instrumented Systems for the Process Industries, Instrument Society of America, Research Triangle Park, 1996) require quantitative risk analysis but do not prescribe how to perform the analysis. Earlier publications of the authors (Rouvroye et al., Uncertainty in safety, new techniques for the assessment and optimisation of safety in process industry, D W. Pyatt (ed), SERA-Vol. 4, Safety engineering and risk analysis, ASME, New York 1995; Rouvroye et al., A comparison study of qualitative and quantitative analysis techniques for the assessment of safety in industry, P.C. Cacciabue, I.A. Papazoglou (eds), Proceedings PSAM III conference, Crete, Greece, June 1996) have shown that different analysis techniques cover different aspects of system behaviour.This paper shows by means of a case study, that different (quantitative) analysis techniques may lead to different results. The consequence is that the application of the standards to practical systems will not always lead to unambiguous results. The authors therefore propose a technique to overcome this major disadvantage.     

Do you see what I see? Effects of national culture on employees’ safety-related perceptions and behavior

Growing international trade and globalization are increasing the cultural diversity of the modern workforce, which often results in migrants working under the management of foreign leadership. This change in work arrangements has important implications for occupational health and safety, as migrant workers have been found to be at an increased risk of injuries compared to their domestic counterparts. While some explanations for this discrepancy have been proposed (e.g., job differences, safety knowledge, and communication difficulties), differences in injury involvement have been found to persist even when these contextual factors are controlled for. We argue that employees’ national culture may explain further variance in their safety-related perceptions and safety compliance, and investigate this through comparing the survey responses of 562 Anglo and Southern Asian workers at a multinational oil and gas company. Using structural equation modeling, we firstly established partial measurement invariance of our measures across cultural groups. Estimation of the combined sample structural model revealed that supervisor production pressure was negatively related to willingness to report errors and supervisor support, but did not predict safety compliance behavior. Supervisor safety support was positively related to both willingness to report errors and safety compliance. Next, we uncovered evidence of cultural differences in the relationships between supervisor production pressure, supervisor safety support, and willingness to report errors; of note, among Southern Asian employees the negative relationship between supervisor production pressure and willingness to report errors was stronger, and for supervisor safety support, weaker as compared to the model estimated with Anglo employees. Implications of these findings for safety management in multicultural teams within the oil and gas industry are discussed.     

Core safety of Indian nuclear power plants (NPPs) under extreme conditions

Nuclear power is currently the fourth largest source of electricity production in India after thermal, hydro and renewable sources of electricity. Currently, India has 20 nuclear reactors in operation and seven other reactors are under construction. Most of these reactors are indigenously designed and built Heavy Water Reactors. In addition, a 300 MWe Advanced Heavy Water Reactor has already been designed and in the process of deployment in near future for demonstration of power production from Thorium apart from enhanced safety features by passive means. India has ambitious plans to enhance the share of electricity production from nuclear. The recent Fukushima accident has raised concerns of safety of Nuclear Power Plants worldwide. The Fukushima accident was caused by extreme events, i.e., large earthquake followed by gigantic Tsunami which are not expected to hit India’s coast considering the geography of India and historical records. Nevertheless, systematic investigations have been conducted by nuclear scientists in India to evaluate the safety of the current Nuclear Power Plants in case of occurrence of such extreme events in any nuclear site. This paper gives a brief outline of the safety features of Indian Heavy Water Reactors for prevention and mitigation of such extreme events. The probabilistic safety analysis revealed that the risk from Indian Heavy Water Reactors are negligibly small.     

Analysis of human error in nursing care

Analysis of reports about incidental and accidental events in nursing care were made using a reliability engineering method. Unnatural working hours, such as evening duty, night duty falling next to a holiday, two consecutive night-duty shifts, and two consecutive evening-duty shifts were major factors in the occurrence of errors. In a mixed-division ward (a ward containing patients belonging to different divisions), rule-based errors happened more frequently than in a single-division ward. Also, less experienced nursing staffs made errors more frequently than experienced nursing staffs.     

基于小波能谱和小波信息熵的管道异常振动事件识别方法

提出了基于小波能谱和小波信息熵的油气管道异常振动事件识别方法。基于Mach-Zehnder光纤干涉仪原理的分布式光纤油气管道安全监测系统实时检测管道沿途振动信号,对测量的时间序列进行小波变换,根据小波系数计算小波能谱与小波信息熵,通过小波能谱和小波信息熵值两种测度识别不同的管道安全异常事件。港枣线成品油管道的现场实验结果表明,该方法可以快速有效地识别管道周围发生的泄漏及其他异常情况,其总体识别准确率达到98.5%,有效降低了误报警率,具有较强的在线工况识别能力。     

Cognitive functioning differentially predicts different dimensions of older drivers’ on-road safety

The extent to which deficits in specific cognitive domains contribute to older drivers’ safety risk in complex real-world driving tasks is not well understood. We selected 148 drivers older than 70 years of age both with and without neurodegenerative diseases (Alzheimer disease–AD and Parkinson disease–PD) from an existing driving database of older adults. Participant assessments included on-road driving safety and cognitive functioning in visuospatial construction, speed of processing, memory, and executive functioning. The standardized on-road drive test was designed to examine multiple facets of older driver safety including navigation performance (e.g., following a route, identifying landmarks), safety errors while concurrently performing secondary navigation tasks (“on-task” safety errors), and safety errors in the absence of any secondary navigation tasks (“baseline” safety errors). The inter-correlations of these outcome measures were fair to moderate supporting their distinctiveness. Participants with diseases performed worse than the healthy aging group on all driving measures and differences between those with AD and PD were minimal. In multivariate analyses, different domains of cognitive functioning predicted distinct facets of driver safety on road. Memory and set-shifting predicted performance in navigation-related secondary tasks, speed of processing predicted on-task safety errors, and visuospatial construction predicted baseline safety errors. These findings support broad assessments of cognitive functioning to inform decisions regarding older driver safety on the road and suggest navigation performance may be useful in evaluating older driver fitness and restrictions in licensing.     

我国与印尼民用爆炸物品储存库标准对比分析

民用爆炸物品使用属于特殊行业的行为,涉及爆炸物品的购买、运输、储存和操作等环节,是构成本质安全和社会公共安全的重要因素。为比较我国与印尼民用爆炸物品储存库标准的不同,更好地指导工程实践,以我国和印尼合作的某铅锌矿项目民用爆炸物品储存库建设工程为背景,通过对比分析两国民用爆炸物品储存库相关标准,发现在储存库标准体系、分类方法以及安全距离设置等方面均存在不同之处。相较印尼标准,我国标准体系更为健全完善,分类方法更为合理实用,技术指标更为科学严谨。其对比分析结论,有助于项目部积极采用我国民用爆炸物品储存库标准,提高工程本质安全和社会公共安全水平,并助力我国矿山企业"走出去",我国标准"走出去",进一步提升我国在国际合作中的话语权。     

Monte Carlo simulation of the movement and detection efficiency of a whole-body counting system using a BOMAB phantom

This study reports on the computational analysis and experimental calibration of the whole-body counting detection equipment at the Nuclear and Technological Institute (ITN) in Portugal. Two state-of-the-art Monte Carlo simulation programmes were used for this purpose: PENELOPE and MCNPX. This computational work was undertaken as part of a new set of experimental calibrations, which improved the quality standards of this study's WBC system. In these calibrations, a BOMAB phantom, one of the industry standards phantoms for WBC calibrations in internal dosimetry applications, was used. Both the BOMAB phantom and the detection system were accurately implemented in the Monte Carlo codes. The whole-body counter at ITN possesses a moving detector system, which poses a challenge for Monte Carlo simulations, as most codes only accept static configurations. The continuous detector movement was approximately described in the simulations by averaging several discrete positions of the detector throughout the movement. The computational efficiency values obtained with the two Monte Carlos codes have deviations of less than 3.2 %, and the obtained deviations between experimental and computational efficiencies are less than 5 %. This work contributes to demonstrate the great effectiveness of using computational tools for understanding the calibration of radiation detection systems used for in vivo monitoring.     

INTENT: a method for estimating human error probabilities for decisionbased errors

The development of a method, INTENT, for estimating probabilities associated with decisionbased errors is presented. These errors are not ordinarily incorporated into probabilistic risk assessments (PRAs) due to both the difficulty in postulating such errors and to the lack of a method for estimating their probabilities from existing data. By failing to include decisionbased errors in their analyses, most PRA practitioners seriously underestimate the true contribution of human actions to systems failure. This paper attempts to extend the identification of such errors and to quantify them. Two sources, Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR) and licensee event reports (LERs) were reviewed and two methods, HSYS and SNEAK, were used to identify a generic list of twenty potential errors which may be manifest as erroneous acts. Four categories of influence emerged from the data: consequence, attitudes, response set, and dependency. Corresponding human error probabilities (HEPs) for each error were generated by expert judgment methods. Lower and upper bounds for the HEPs for each error were determined by positing a situation reflecting optimized and degraded performance shaping factors, respectively. To allow analysts the opportunity to refine these extreme HEP values when evaluating a particular scenario of interest, normalization procedures were conducted and generic importance weights were computed for each of 11 performance shaping factors (PSFs) believed to affect the 20 decisionbased errors. It is believed by the authors that PSFs constitute a performance influence which, in some cases, such as in that for training, can serve to either augment or reduce the intellectual resources used by people to successfully accomplish tasks. These derived importance weights are used in conjunction with situation specific PSF ratings to compute a composite PSF score which, in turn, is mapped onto an HEP distribution. Distribution assumptions are presented and a function defining the relationship between composite PSF scores and HEPs is presented for use by the analyst.     

Operator error and system deficiencies: Analysis of 508 mining incidents and accidents from Queensland, Australia using HFACS

Historically, mining has been viewed as an inherently high-risk industry. Nevertheless, the introduction of new technology and a heightened concern for safety has yielded marked reductions in accident and injury rates over the last several decades. In an effort to further reduce these rates, the human factors associated with incidents/accidents needs to be addressed. A modified version of the Human Factors Analysis and Classification System was used to analyze incident and accident cases from across the state of Queensland to identify human factor trends and system deficiencies within mining. An analysis of the data revealed that skill-based errors were the most common unsafe act and showed no significant differences across mine types. However, decision errors did vary across mine types. Findings for unsafe acts were consistent across the time period examined. By illuminating human causal factors in a systematic fashion, this study has provided mine safety professionals the information necessary to reduce mine incidents/accidents further.     

Risk implications of digital reactor protection system operating experience

This paper summarizes an in-depth review of the US nuclear operating experience with the first generation of digital reactor protection systems. The accumulated operating experience from 1984 to 2006 on these first generation digital reactor protection system functions exceeds 1.27 million hours (145.5 yr). A review of failure event reports identified 141 specific events associated with these systems on seven US nuclear power plants. Twenty-six of these events involved some type of common cause failure mechanism (predominantly redundant sensors/channels being out of calibration), which temporarily rendered redundant portions of the overall trip function degraded. Most of these failures were found not to be unique to digital systems. Six of the common cause failure events were more severe and involved situations where incorrect addressable constant data sets were systematically loaded into all redundant computer channels due to personnel errors. One of these events involved a latent software design change error introduced during a software update, which would prevent proper operation, given an unlikely event involving failure of three out of four sensors of one type.Based upon this review of digital system operating experience, a series of risk assessment calculations were performed to evaluate the safety significance of the observed failure events. From the insights gained in this work, it is possible to develop a framework for establishing digital reactor protection system reliability requirements that can be related back to regulatory safety goal objectives and operating experience.     

核电站安全分析方法与安全评价标准初探

文章首先陈述了核电站的安全性与安全分析的任务；其次，论文阐述了核电站２种分析方法，即确定论与概率风险分析法，后者是前者的发展，而两者的结合与优化构成了核电安全分析的完整体系；最后文章探讨了核电站的定量评价标准，包括个人、社会和经济的评价目标。     

Understanding the human factors contribution to railway accidents and incidents in Australia

Forty rail safety investigation reports were reviewed and a theoretical framework (the Human Factors Analysis and Classification System; HFACS) adopted as a means of identifying errors associated with rail accidents/incidents in Australia. Overall, HFACS proved useful in categorising errors from existing investigation reports and in capturing the full range of relevant rail human factors data. It was revealed that nearly half the incidents resulted from an equipment failure, most of these the product of inadequate maintenance or monitoring programs. In the remaining cases, slips of attention (i.e. skilled-based errors), associated with decreased alertness and physical fatigue, were the most common unsafe acts leading to accidents and incidents. Inadequate equipment design (e.g. driver safety systems) was frequently identified as an organisational influence and possibly contributed to the relatively large number of incidents/accidents resulting from attention failures. Nearly all incidents were associated with at least one organisational influence, suggesting that improvements to resource management, organisational climate and organisational processes are critical for Australian accident and incident reduction. Future work will aim to modify HFACS to generate a rail-specific framework for future error identification, accident analysis and accident investigation.     

Human factors, human reliability and risk assessment in license renewal of a nuclear power plant

This paper describes human factors and human reliability assessments carried out as a part of operating license renewal of a nuclear power plant. The structure and contents of human factors assessments, the source material and the role of probabilistic safety assessment are described. Similar evaluations are recommended as an integral part of periodic safety reviews of regulated industrial facilities.The qualitative part of the human factors review is structured according to an international guide. The assessments are here enhanced with operating experience evaluations, measured by quantitative statistical data obtained from inspections and assessments made by plant safety and quality assurance personnel, by regulatory authorities and by peer reviews.The quantitative assessment is based on the roles and contributions of human errors in the accident risk of the target plant. The assessment uses importance measures quantified in probabilistic risk assessment. The scope and the quality of the risk assessment and the scope and the quality of human reliability assessments are also taken into account. Furthermore, the assessment describes how risk assessment can be used to reduce errors and improve human factors. The results tend to be very plant-specific, and the errors have very different importances in different operating states and for different initiating event categories. The results are useful for planning preventive actions, i.e. for preventing errors by developing and prioritizing human factors improvement activities.     

Cabin safety and emergency evacuation: passenger experience of flight CI-120 accident

Aircraft evacuation effectiveness is a critical but challenging issue in the civil aviation industry. This paper explores the cabin safety perceptions of passengers from their emergency evacuation experiences in an actual aviation accident. A questionnaire survey and in-depth interviews were conducted with China Airlines flight CI-120 passengers. The qualitative and quantitative results provide insights into passengers’ views of cabin safety. The in-depth interview results show that passenger safety education requires more instructions about the use of emergency equipment. The data from the passenger perception questionnaire were analyzed using the factor analysis method; the findings indicate that crew assistance and emergency procedures are the most important factors. The results are likely to be of value to the aviation industry when taking into account passenger perceptions in implementing safety programs.     

工商制冷设备可燃性制冷剂相关安全标准的研究动态

简述了现有各类可燃性制冷剂相关安全标准,着重介绍了与工商制冷设备相关的可燃性制冷剂标准,分析并比较了这些标准中制冷剂命名、安全性分类以及制冷系统安全要求等差异,以期为制修订我国工商制冷空调设备使用可燃性制冷剂标准提供技术支持。     

国家标准在制图教材中的贯彻

从制图教材中所涉及到的制图国家标准中有关通用规定、图样画法、图样注法3个方面,论述了在所审核的5家出版社的16套教材中有关通用规定、图样画法、图样注法国家标准的常见问题,指出了在编写教材中对这些问题的理解差异和认识程度的有误对教材质量及至工程制图教学中正确贯彻国家标准的影响,对课程和教材质量和水平的提高有一定益处。     

Analysis of tomato microRNAs expression profile induced by Cucumovirus and Tobamovirus infections

MicroRNAs (miRNAs) are a class of small RNAs that affect the morphological and physiological development of plants. In recent years, there is accumulating evidence that miRNAs are involved in defense mechanism of host plants. Therefore, investigating the alteration of miRNAs expression profiles after virus infection will provide new insights for understanding the sophisticated virus-host plant interaction. The current miRNA sequence database (miRBase) contains more than 1669 mature plant miRNAs across 25 species, but few tomato miRNAs are reported. Here we created a microarray suitable for detection of plant miRNAs based on the conservative character of miRNAs, and a total of 105 conserved plant miRNAs were detected from tomato leaf tissues. Among them, 85% of the detected miRNAs showed significant expression alterations when infected by different strains of cucumber mosaic virus (CMV) and N5 strain of tomato mosaic virus (ToMV). Combination with their symptoms development, interferences of CMV 2b protein and alleviated/aggravated satellite RNA on host miRNA pathway were discussed, and the differences in interference mechanisms between CMV and ToMV on host miRNA pathway were compared. Our results represent the comprehensive investigation of tomato miRNAs on a genome scale thus far and provide information to study the interaction between plant viruses and host plants.