Fault propagation behavior study and root cause reasoning with dynamic Bayesian network based framework

The Bhopal disaster was a gas leak incident in India, considered the world's worst industrial disaster happened around process facilities. Nowadays the process facilities in petrochemical industries have becoming increasingly large and automatic. There are many risk factors with complex relationships among them. Unfortunately, some operators have poor access to abnormal situation management experience due to the lack of knowledge. However these interdependencies are seldom accounted for in current risk and safety analyses, which also belonged to the main factor causing Bhopal tragedy. Fault propagation behavior of process system is studied in this paper, and a dynamic Bayesian network based framework for root cause reasoning is proposed to deal with abnormal situation. It will help operators to fully understand the relationships among all the risk factors, identify the causes that lead to the abnormal situations, and consider all available safety measures to cope with the situation. Examples from a case study for process facilities are included to illustrate the effectiveness of the proposed approach. It also provides a method to help us do things better in the future and to make sure that another such terrible accident never happens again.     

The bumpy road to better risk control: A Tour d'Horizon of new concepts and ideas

How can we be sure that sufficient safeguards are in place and safety level is acceptable? As we heard Prof. Nancy Leveson stating at last year's MKOPSC symposium, even with all components functioning, dysfunctional component interaction can still be a cause of mishap. Human factor expert, Prof. Erik Hollnagel, asserts it in even stronger terms: the Efficiency-Thoroughness Trade-off principle, or rather dilemma, contends that one can hardly do it perfectly well. Perfect thoroughness, certainly in complex situations, requires an amount of time with which efficiency will be in conflict. For improved situational awareness, sufficient resilience, and adequate risk control, we must adopt a top-down system approach. Hazard scenarios possible in the system, with all its entangled interactions of hardware, procedures, and humans shall be identified bottom-up and causal relations made clear. Fortunately, in recent years two potentially helpful tools have become available: Blended Hazid, a vastly improved, heavily computerized system approach making use of HazOp and FMEA, and Bayesian networks, a tool to model cause–effect structures allowing inclusion of uncertainty information. Bayesian networks as an infrastructure enable also the use of indicator values to relate the result of safety management effectiveness, which expresses itself as safety attitude of employees, competence, workload, and motivation, with their effects on error and failure probability. This paper will explain the directions these developments are advancing and the openings they provide for further process safety research and risk assessment, which when applied will result in improved process risk control.     

“Everything was fine”*: An analysis of the drill crew's situation awareness on Deepwater Horizon

PurposeInvestigation reports into the Deepwater Horizon drilling rig disaster identified issues with the drill crew's situation awareness (SA). The aim was to (1) apply the Driller's Situation Awareness (DSA) model to the cognitive data extracted from accident reports from this event to determine if it could help to explain why the crew erroneously concluded that the well was stable, which would (2) provide a preliminary evaluation of the model's validity.MethodThe DSA model was used for a content analysis of the SA components in the accounts of the crew's actions during two Negative Pressure Tests (NPT), in the hours before the blowout.ResultsThe analysis provided (1) insight into the crew's likely cognitive processes before the blowout. In particular, it revealed issues with their interpretation and mental models of the well state, as well as possible influencing factors including expectation, distraction and experience, emphasising the impact that SA can have on process safety. The categorisation has (2) initially suggested that the DSA model does contain the appropriate components.LimitationsThere are limited first hand reports of this event and thus cognitive processes have to be inferred with a degree of caution.Practical implicationsThe findings give a preliminary validation of the DSA model for further use in training and in investigation of well control events. Recommendations based on the findings are offered for assisting driller SA and consequently, for supporting safe and efficient drilling operations. There is also the opportunity to adapt the DSA model and apply the recommendations from the analysis to similar monitoring positions, where SA is essential, within the process industries.     

沙滤器回洗水薄膜过滤法

介绍了荷兰新近研究成功的适用于处理沙粒过滤器回洗水的XIGA薄膜法,及其参数、工作原理、适用条件和经济效益。     

基于生态理论的旅游产业集群发展特征研究

旅游产业集群的生态属性研究已经成为当前的热点。当前利用生态理论研究旅游产业集群的发展规律．对我国旅游产业集群的健康发展具有非常重要的意义。本文基于生态理论。从旅游产业集群的发展特征出发，认为旅游生态资源潜力、集群生态成长机制、集群生态外部环境等是影响其发展的主要因素．据此选择集群生态资源潜力、集群生态结构、集群外部环境等指标。将旅游产业集群生命周期分为旅游产业集群形成、发展、成熟、衰退——转型等四个阶段，并分析了各个发展阶段的特点。最后提出开拓旅游产业集群生态营养源泉、构建旅游产业集群与其生态环境的和谐互动机制、维护旅游产业集群内部生态平衡等相关的建议。     

Causes and consequences of thermal runaway incidents—Will they ever be avoided?

A study of runaway incidents involving thermal chemical reactions in the UK over the past 25 years (1988–2013) has been carried out. The objective of this study is to determine possible causes of thermal runaway incidents. A statistical analysis of the underlying problems that led to thermal runaway incidents has been provided. A comparison of the current study on thermal runaway incidents with those identified prior to 1988 has been carried out. This study clearly shows that lessons have not been learnt from thermal runaway incidents caused by operator errors, management failures and lack of organised operating procedures. These factors have been the possible causes of about 77% of all the thermal runaway incidents analysed in this study. The number of fatalities and injuries as a result of thermal runaway incidents has increased by ∼325% and ∼279%, respectively, in the last 25 years even though the number of incidents was significantly less. On the basis of this analysis, several recommendations have been proposed that could help to minimise the risks associated with any thermal runaway incidents in the future.     

RCNet: An optimisation software for the synthesis of resource conservation networks

RCNet is a spreadsheet-based software for the synthesis of resource conversation networks (RCNs) for planning the efficient use of material resources (e.g., water, utility gases, solvents) in industrial plants. The software is developed based on the well-established process integration tools, namely pinch analysis and mathematical programming techniques. In the first stage, pinch analysis is used to determine maximum resource conservation targets prior to detailed RCN design. In the second stage, mathematical optimisation is then used to determine the optimal flowrate allocation between process sources and sinks of the RCN, to achieve the performance targets. RCNet is applicable for various industrial applications. To date, no generic software has been developed to handle water minimisation, hydrogen recovery and property integration, which is the main subject of this work. In the developed software, same interface and platform can be used to solve abovementioned problems independently. For illustration, three literature examples on water minimisation, hydrogen recovery and property integration, as well as an industrial case study are solved using RCNet.     

The role of people and human factors in performing process hazard analysis and layers of protection analysis

Process hazard analysis (PHA) and Layers of Protection Analysis (LOPA) studies address human failures in operating and maintaining processes and the human factors that influence them, amongst other types of failures. People perform PHA and LOPA studies and, therefore, such studies themselves are subject to various possible human failures. Much less attention has been paid to the human factors that influence the performance of PHA and LOPA studies than human factors that influence hazard scenarios. Human failures in the performance of PHA and LOPA studies should be of significant concern to practitioners as such studies are difficult and time-consuming activities that place significant demands on participants, which increases the chance that errors will be made. Human factors such as willingness to rely on the unsubstantiated opinions of others, groupthink, underestimation of the frequencies of low-probability, high-consequence events, and allowing a false sense of accomplishment to distract from implementing study results must be recognized and addressed.This paper identifies and discusses various human factor issues that can influence the quality of PHA and LOPA studies covering preparing for, conducting, recording, documenting, and following-up on studies. Guidelines are provided to help minimize the extent to which these human factor issues may impair study quality.     

福建炼化生活饮用水改造总结

饮用水的安全问题日益引起重视，要加强水源保护、改进消毒工艺和净水工艺，才能保障人类健康。     

An integrated CNC accumulation system for automatic building-around-inserts

In this paper a non-layer-based additive manufacturing (AM) process named computer numerically controlled (CNC) accumulation process is presented for applications such as plastic part repairing and modification. To facilitate the CNC accumulation process, a novel three-dimensional (3D) laser scanning system based on a micro-electro-mechanical system (MEMS) device is developed for in situ scanning of inserted components. The integration of the scanning system in the CNC accumulation process enables the building-around-inserts with little human efforts. A point processing method based on the algebraic point set surface (APSS) fitting and layered depth-normal image (LDNI) representation is developed for converting the scanning points into triangular meshes. The newly developed 3D scanning system is compact and has sufficient accuracy for the CNC accumulation process. Based on the constructed surface model, data processing operations including multi-axis tool path planning and motion control are also investigated. Multiple test cases are performed to illustrate the capability of the integrated CNC accumulation process on addressing the requirements of building-around-inserts.