Dynamic Risk Analysis Of Urban Underground Gas Pipeline Leakage Based On Bayesian Network

Urban gas pipelines are an important infrastructure and lifeline of the city,and are affected by factors such as complex environment and quality defects leads to frequent accidents.Urban gas pipelines are mostly placed in densely populated areas,and the conveying medium is inflammable and explosive,so its safety issues be ignored.Traditional risk analysis methods cannot effectively analysis and real time judgment the risk of gas pipelines,resulting in easy deviation of results.Therefore,dynamic risk analysis of urban gas pipelines accidents are necessary to prevent and reduce pipeline accidents and ensure safe operation of pipelines.Based on the actual situation of urban gas pipelines,this paper studies the real-time risks in the operation of urban gas pipelines.by BN and reliability engineering theory and proposes a dynamic risk analysis method of gas pipeline based on BN,which aims to provide a basis for timely and effective risk control and emergency measures.The main research contents and results are as follows:（1）Through the statistical analysis of urban gas pipelines leakage accidents,the main reason of gas pipelines leakage accidents are third-party damage,corrosion,defects,misoperation and natural disasters.Using the BT model to systematically identify the dynamic and static risk factors of gas pipelines,and dynamic risk factors such as cathodic protection failure(X₁₄),external coating failure(X₁₅),illegal construction(X₃₇)and Static risk factors such as high impurity content(X₂₁),uneven wall thickness(X₂₅)areobtained.（2）The Urban gas pipelines leakage risk BT model is transformed into BN model by mapping algorithm,and the failure probability of basic events are determined by reference gas pipelines accident database,related literature and expert scoring method.Using the analysis results of minimum cut set,structural importance,sensitivity and the failure probability of basic events,combined with the dynamic and static classification results of basic events,the top 15 key dynamic basic events such as illegal construction(X₃₇)and sabotage(X₄₆)are obtained.（3）The failure probability of basic events are corrected by combining the occurrence times of basic events with Bayesian theory and the physical reliability model.The failure probability of safety barriers are updated by combining the accident precursor data with the bayesian theory.So as to obtain the real time failure probability of dynamic basic events and safety barriers.The dynamic failure probability of the gas pipelines and each accident are obtained by using the reasoning function of BN.（4）The leakage model of urban gas pipelines leakage is analyzed,and the dynamic leakage diffusion model of gas pipeline is improved.Using MATLAB software simulate the accidental consequences of jet fire,vapor cloud explosion and fireball,the effects of dynamic factors such as pressure,pipe diameter,crack area and wind speed on the consequences of gas pipeline accidents are studied,it is found that the pressure,the area of the fracture and the diameter of the pipe are directly proportional to the radius of the accident,while the wind speed is inversely proportional to the curve.（5）The quantitative risk analysis model of urban gas pipelines is analyzed,a multi-effect urban gas pipelines accident dynamic risk analysis model is proposed,and the risk tolerable standard and obtains the risk tolerable standard applicable to urban gas pipelines is analyzed.Finally,urban underground gas pipelineis taken as an example to apply the engineering example.The dynamic risk of urban underground gas pipeline leakage accident is analyzed and calculated,and the rationality and applicability of the urban underground gas pipeline dynamic risk analysis method established by the article are verified.