Risk Dynamic Evaluation Theory And Method Research And Their Application To Gas Transmission Station

Industrial system is a dynamic complex system,which is comprised of various and interrelated elements.The failure of any element may trigger chain reactions,and even result in systemic failure.Effective risk evaluation can identify hazard elements comprehensively and predict the level of risk precisely.It also provides basis for scientific risk management and decision making.Eventually,accidents can be prevented from occurring or expanding.However,most conventional risk evaluation methods are static,ignoring the dynamic characteristics of systems.Consequently,the evaluation results with conventional methods deviate from the actual risk.To overcome the shortcomings of static methods,risk dynamic evaluation theories and methodologies should be studied.Due to the difference among risk evaluation objects,risk characterization methods are different.Therefore,contributions are focused on methods for four aspects,which respectively are overall risk identification,equipment risk evaluation,process risk evaluation,and management risk evaluation.The main contents and conclusions are as follows:(1)Existing accident-causing theories and models lack completeness,consistency,and systematicness.To overcome these shortcomings,a new accident causation analysis and taxonomy(ACAT)model is proposed.Based on theories from Systems Engineering and Control Engineering,the systemic failure mode of “subject + function” is presented.The model provides a structured theoretical framework for comprehensive risk indicators identification of gas transmission station.It turns out that it can improve the completeness of risk indicators.(2)To represent the complex relationship among failure symptoms and consequences,rule-based representation and Petri net modeling are integrated and applied to compressor fault reasoning.A dynamic backward-forward reasoning strategy is presented for concurrent risks analysis.Meanwhile,dynamic risk transmission paths are obtained qualitatively and risk reachability trees are drawn.Compared with traditional fault tree analysis,Petri net has the advantages of graphical representation for complex causality and dynamic reasoning for concurrent risks.(3)Conventional fuzzy Petri net requires lacks hierarchy and the ability of local solution.A layered fuzzy reasoning Petri net is proposed to address this problem and applied to risk evaluation.Layering principles are defined to help local solution,as well as to make the model more structural and hierarchical.The operability of this method is illustrated by a case of compressor fault diagnosis.(4)Traditional job hazard analysis method ignores the correlation and propagation features of risks when decomposing a process.To address this problem,the cumulative risk theory is defined and dynamic job hazard evaluation framework is proposed.In addition,a risk assessment matrix based on consecutive rank is designed to depict dynamic risks.The effectiveness of the method is demonstrated with risk cumulative curve and actual risk situations.(5)To deal with subject and static characteristics of traditional fuzzy comprehensive evaluation,a key indicator identification method is proposed based on Spearman rank correlation analysis.Meanwhile,dynamic fuzzy theory is integrated to establish an improved dynamic fuzzy evaluation method.It is applied to the risk evaluation of health,safety,and environment management and compared with traditional fuzzy comprehensive evaluation.The results show that it has the advantages in both dynamic acquisition of risk indicators and qualitative prediction of risk level.