Failure Prediction And Safety Assessment Of Hydrogen-mixed Natural Gas Pipeline With Corrosion Defects

Hydrogen is a zero-carbon fuel that is burned with oxygen to produce water and is a clean secondary and renewable energy source.In the field of hydrogen production and utilization,the current technology has been relatively mature,while in the field of hydrogen storage and transportation technology is relatively weak.Usually,hydrogen transportation includes liquid hydrogen tank truck transportation,high-pressure hydrogen bottle transportation,liquid hydrogen barge transportation,etc.,but these transportation modes are too expensive and not conducive to long-distance large-scale transportation.Direct laying of hydrogen pipeline,construction cost is high.Mixing hydrogen with natural gas and transporting it in the existing natural gas pipeline is an effective method that is expected to realize long-distance large-scale transportation of hydrogen.However,both natural gas and hydrogen are corrosive,and corrosion is one of the main reasons for pipeline failure.Therefore,failure prediction and safety analysis of mixed hydrogen natural gas pipelines containing corrosion defects is the premise of ensuring the safe operation of pipelines,which is of great significance for extending the service life of pipelines and preventing pipeline safety accidents.Taking mixed hydrogen natural gas pipelines containing corrosion defects as the research object,this paper carried out researches on the failure mechanism of corroded pipelines,the blasting pressure prediction of pipelines containing single point corrosion defects and the blasting pressure prediction of pipelines containing irregular corrosion defects,etc.,specifically as follows:(1)A new multi-parameter yield criterion considering the yield ratio(Y/T)is proposed.On the basis of this criterion,the explosion pressure equation of hydrogen mixed natural gas pipeline is derived.Finally,the accuracy of the blasting pressure equation is verified by experiments and finite element method,and the effects of thickdiameter ratio,corrosion rate and bending strength ratio on the blasting pressure are analyzed.(2)The burst pressure of hydrogen mixed natural gas pipeline when single point corrosion defect occurs on outer surface of pipe wall is studied.The influence of different corrosion defect sizes(length,width and depth)on the burst pressure of corroded pipeline is analyzed.The influence of width to length ratio and length to depth ratio of corroded defect on the burst pressure of pipeline is studied by numerical simulation method.The accuracy of some existing evaluation methods is compared with the experimental data.(3)Analyze the burst pressure of pipelines with irregular corrosion defects.Firstly,the irregular defects are simplified and the model with overlapping corrosion defects is established.Then,the finite element method is used to analyze the parameters of the overlapping corrosion defect model.Finally,the overlapping defects are simplified into rectangular defects.Based on DNV evaluation method,a burst pressure equation for pipelines with overlapping defects is proposed,and the equation is verified by finite element method.