The Reliability And Sensitivity Analysis Of Corroded Pipeline

Pipeline transportation is an important part of the national economic infrastructure.In the process of service,the pipeline is affected by these factors,such as operating environment,transportation medium,quality defects of the pipeline,and some other man-made or natural factors,which would cause corrosion perforations and pressure cracks in the pipeline,thus giving rise to pipe accidents.Corrosion damage is the major problem for oil and gas pipelines and it presents a significant challenge for the current pipeline business.Due to the inherent uncertainty of pipeline system,the existing methods for evaluating the residual strength and life expectancy of pipeline have great deviation.Therefore,performing study on reliability of oil and gas pipelines is bound to be a major issue in pipeline operation and maintenance.Aiming at the reliability of oil and gas pipeline,failure mechanism of pipeline corrosion,failure pressure model of corrosion pipeline,and modeling and method of corrosion pipeline are studied in this dissertation.The main researches are as follows:(1)Analysis on pipeline corrosion mechanism and failure mechanism.The corrosion form,mechanism,corrosion growth model and failure mechanism of pipeline fatigue pressure are discussed.Especially the analysis on pipeline corrosion growth model is carried out clearly.(2)Evaluation on failure pressure model of corroded pipeline.Combined with existing literature,the probability model for estimating the fracture pressure of corroded pipeline is established which includes model error factor,failure pressure of complete pipeline and residual strength factor.The validity of failure pressure model of corroded pipeline is discussed through statistical analysis.The study shows that the PCORRC model of pipeline failure tress has high confidence index and it is suitable for the reliability modeling of corroded pipeline.(3)Reliability modeling and methods for corroded pipeline.Combined with the failure pressure model of corroded pipeline,the failure mode and limit state equation are given that may be caused by pipeline corrosion.According to the high dimensional non-linearity of pipeline reliability model,The Second-Order Reliability Method with First-Order Efficiency(SORM-FOE)is proposed.(4)Reliability and sensitivity analysis on corroded pipeline.A mathematical model of rupture reliability of corroded pipeline is established and The Second-Order Reliability Method with First-Order Efficiency(SORM-FOE).On this basis,numerical derivation is used to obtain the reliability sensitivity of corroded pipeline.The results show that the average and standard deviation of pipeline wall thickness,model error factor,pipeline operating pressure and corrosion depth have significant effects on the pipeline reliability,that the average and standard deviation of model error factor and corrosion depth have critical effects on the pipeline reliability,that the wall thickness variation in the early service has great effects on the pipeline reliability and that the pipeline operating pressure in the late period counts a lot.