Research Of Risk Assessment On Pipelines System For Urban Gas

At present, urban gas industry has stepped into a highly developing era in China, the pipelines transmitting urban gas extends everyday, however, the safety problem of pipeline system becomes more and more important. Applying risk assessment on gas pipeline system is a effective method to acquire the safety state and provides evidences for risk management and safety management.Risk assessment includes risk identification, hazardous events probability analysis and consequence analysis and risk assessment. Applying FTA, this dissertation concludes all cause events of pipeline system faults, and by applying ETA, the 15 types of consequences caused by gas leakage are deduced. By qualitative analysis of fault tree, the failure sets are obtained, and countermeasures against pipelines leaking are presented. The methods of quantitative FTA for leaking probability of pipelines are presented in the dissertation, which include experts estimation method and historical failure data statistic method, life span statistical method according by pipeline parameters and historical life span data is also offered. According to all kinds of parameters of the pipeline, fuzzy method for pipe clustering and comprehensive assessment are presented in the dissertation, fuzzy clustering analysis can place the pipes with the same state into one cluster, and fuzzy comprehensive assessment can describe the pipe states with fuzzy language such as "good", "bad" and so on. For consequence analysis, gas leaking intensity model is deduced, and the statistical and calculated method for leaking area and leaking time are presented, and also the modeling methods for gas dispersal are summarized. By applying jet fluid model and Gauss model, the dispersal ranges of leaking gas from common pipelines are calculated, and the concentration in the trench of leaking gas is modeled by using FLUENT. The analysis methods of gas ignition, explosion and intoxication are related to in the dissertation. The model and flowchart of incorporating FTA into ETA is deduced for the pipeline risk assessment. GIS is a effective tool for risk assessment on gas pipelines, the model and methods of applying risk assessment on pipeline based on GIS are presented in the dissertation.