The Remain Life Prediction Of Wet Natural Gas Pipeline Suffering Internal Corrosion

Internal corrosion is one of the primary reasons for the failure of gas gathering pipeline.The failure of natural gas gathering pipeline has enormous impact on the safety,environment and economy of local people and property,and the safety of gathering pipeline is also the focus of local government and enterprises.How to predict the corrosion trend and how to evaluate the reliability of gathering pipelines is the key to reduce or even avert pipeline failure.There are many factors that lead to pipeline corrosion.It is difficult to consider all factors.In this paper,the corrosion is divided into uniform corrosion and local corrosion.The study provides two methods to calculate the corrosion rate,and combines the reliability analysis to predict the failure probability of the pipeline.Furthermore,the work includes the programming to evaluate the pipeline corrosion rates.As for uniform corrosion,the technical route and example analysis of phase equilibrium calculation,flow pattern judgment and corrosion rate prediction are completed,and the factors affecting the corrosion rate of the wet natural gas pipeline are quantitatively analyzed and discussed.Results show that the corrosion rate of the upward pipeline is higher than that of the downward pipeline,and that the corrosion rate increases with the water load of natural gas at the entrance of the pipeline.As for local corrosion,in combination with field data,samples of corrosion defect depth are sampled by Markov Chain Monte Carlo method.At the same time,combined with the reliability analysis of the system,Monte Carlo method is used to simulate the failure probability of pipelines under different failure modes(small leakage,large leakage and rupture).Results of parametric analysis indicate that the uncertainty of pipeline internal pressure has great influence on the probability of large leakage failure.Introducing uncertainty of the parameters is more reasonable than the traditional deterministic analysis,which will facilitate the reliability-based pipeline corrosion management programs.