Risk-based Decision-making On The Maintenance Of Urban Gas Pipeline Ontology Defects

Urban gas pipelines are one of the lifelines of the city,but pipelines are often subject to internal and external interference factors that cause pipelines to fail,which seriously threatens urban public safety,and gas companies need to take necessary maintenance measures to reduce pipeline risks.In order to avoid relying only on experience and inference and regulations to determine maintenance measures and improve the effectiveness of pipeline maintenance,this thesis takes the pipeline of a gas company as the research object,establishes a risk assessment model of urban gas pipelines based on Bayesian network,and proposes a decision-making method for maintenance of urban gas pipeline body defects based on utility.The main research contents and conclusions are as follows:(1)An urban gas pipeline risk assessment model based on Bayesian network is constructed.Through the statistics of pipeline accidents at home and abroad,the safety barriers set by gas companies on the pipeline system were investigated,and the gas pipeline accident scenes were established,so that 42 model nodes were obtained.Based on the Bayesian network model,the urban gas pipeline risk assessment model is constructed on Ge NIe software.Taking the Shiyan gas pipeline explosion accident as a case,the evidence information in the accident report is extracted and summarized,and input is entered into the model to verify the logic of the model structure.The results show that the accident scenarios and consequences calculated by the model are consistent with the accident report,and the logic of the model structure is reasonable.(2)Simplify the structure of the urban gas pipeline risk assessment model based on Bayesian network.Using expert opinions and D-S theory,the conditional probability of the simplified model node is calculated;the gas pipeline explosion accident is used as a case to verify the applicability of the simplified model structure and the accuracy of the parameters;through the influence analysis of the Bayesian network,four paths for the occurrence of the gas explosion accident are determined;the pipeline risk of five pipeline ontology defect scenarios is quantitatively evaluated,and the risk values of scenarios 2,3,4 and 5 are increased by 62.7%,48.1%,53.1% and 75.4% respectively compared with Scenario 1.The results show that the body defect is a key part of the gas pipeline accident path,and whether there is a serious defect in the pipeline body has a huge impact on the pipeline risk,which needs to be checked and repaired.(3)This paper proposes a decision-making method for the maintenance of urban gas pipeline body defects based on utility.Taking the sub-high-voltage pipeline of the gas company as an example,the simplified model of urban gas risk assessment is used to risk assess the risk,and the probability distribution of the pipeline state is calculated;the ontological defects of different types of pipelines in different regions are discussed separately,and the utility value of each consequence is calculated based on the utility theory;the expected utility value is calculated according to the probability distribution and utility value,which is used as the basis for decision-making,and the maintenance measure with the greatest utility is decided.The decision-making results are: for metal loss defects in the third and fourth level areas and the first and second level areas,the maintenance measures for installing the B-type sleeve and welding repair are selected respectively;for the depression defects in the third and fourth level areas and the first and second level areas,the maintenance measures for installing the steel epoxy sleeve and the A-type sleeve are selected.The results show that for different types of gas pipeline body defects in different regions,different maintenance measures need to be used to maximize the effectiveness of maintenance measures.