Research On Risk Assessment Technology Of Gas Pipeline In Upgraded District Of Regional Level

With the rapid development of the country's economy,many regions where are the gas pipelines have become densely populated but previously sparsely populated in the past.The first-class and second-class regions where the original gas pipelines were located have upgraded to the three-class and four-class regions.Namely,level of region where the gas pipelines is located upgraded.The risk of the gas pipelines is obviously increased after regional level upgrade,and how to ensure the safe operation of the gas pipelines becomes an urgent research project.To perfect the research of risk assessment technologies about gas transmission pipelines in the domestic,the paper made a study on the risk assessment of gas transmission pipelines in the regions of regional level upgrade.The main contents are as follows:(1)By comparing the difference between domestic legal norms in different periods about the parameter requirements and management of gas transmission pipelines in different regions,and analysising the field survey data of a typical gas transmission pipelines that are buried in the upgrade-risk regions in the domestic,drawing that ontology defects,mismanagement and damage of third-party are the main damage-form of gas transmission pipelines.(2)Using the fault tree to identify the main risk factors of the gas transmission pipelines in the upgrade-risk regions,and by analyzing the minimum diameter set and calculating structural importance and on-site investigation,failure probability evaluation index system is determined.Analytic hierarchy process and entropy weight method are used to determine the weight of risk factors,and fuzzy comprehensive evaluation method is used to calculate the risk factor failure probability.(3)Models for leakage,diffusion,fire and explosion of gas transmission pipelines are established in the upgrade-risk regions.Considering the impact of the gas concentration distribution after leakage for buildings in the upgrade-risk regions,and using FLUENT software to simulate.Ultimately,it is ensured that the characteristics of the gas pipeline leakage propagation and the impact of leaking gas diffusion on the distance between the buildings and the leak hole,the height of the buildings and the buildings' existence in the upgrade-risk regions.(4)Based on the natural gas concentration hazard criterion,thermal dose criterion and shock wave overpressure criterion,the failure consequences are divided into three aspects:casualties,economic losses,and intangible losses according to the fire consequence injury model and the steam cloud explosion consequence damage model,and a calculation method is proposed.Failure consequence scores are divided into different failure consequence level.Combining the failure probability level and the failure consequence level,the risk matrix method was used to classify the risk of gas pipelines in the upgrade area of the district.(5)The risk evaluation of the section called M of the gas pipeline in the upgrade pipeline of the eastern pipeline company was carried out.The evaluation results showed that the M section of the gas pipeline has a significantly higher risk level than the low risk level before the upgrade,and risk mitigation measures were proposed based on the evaluation results.The research results of this paper,to a certain extent,supplement and improve the existing risk assessment techniques for gas transmission pipelines in the regional upgrade level regions,which can provide theoretical support for the safe operation of gas transmission pipelines in the regions of regional level upgrade.