Research On Risk Appraisal Of Urban Gas Pipelines

The urban gas pipeline is buried underground. Its medium is flammable and explosive easily and it is in a certain pressure. So there exists big risk in urban gas pipeline. In our country the pipeline has 20 years history. With the aging of pipeline, the aggravating corrosion, the growth of the transportation ways and the increase of population lives around the pipeline, the pipeline problems become more and more vital to public. Therefore, risk assessment on duty pipeline is significant practically.Risk assessment is made up of risk identification, risk probability analysis, risk consequence analysis and risk evaluation. In the thesis, the risk of gas pipeline is identified by using fault tree analysis theory. Attribute reduction is carried on the basic events of the fault tree of urban gas pipeline using rough sets theory to get the risk factors. And then experts carry on analysis on the risk factors and give the happening probability of them according to the data materials and their decisions. The experts' ideas are turned into fuzzy failure probability according to fuzzy sets theory. And the quantitative model to determine the failure probability of pipeline and the risk factors is formed. In failure result analysis the personnel casualty radius and the direct loss radius of jet fire, vapor cloud explosion and flame accidents are estimated by the calculating model of heat radiation intensity and leakage. And the personnel casualty number and the direct property damage which accident creaked are estimated after knowing the average density of population and property. The F-N curve of gas pipeline risk is given, and then the risk acceptance criterion of gas pipeline engineering is estimated. According to this criterion the risk assessment can be carried on to estimate the risk degree of the urban gas pipeline. Finally the decision support system and geographic information system are used in risk assessment to make foundation to realize dynamic risk assessment.The thesis can establish standards on risk assessment of urban gas pipeline and it can provide decision-making basis for controlling risk and making risk management measures, and it is significant to insure public safety and promote society development.