Research On Reliability Evaluation Method For High Sulfur Natural Gas Gathering Pipeline

Natural gas is praised as the energy of the 21st century due to its advantages of cleanliness,high efficiency and low pollution.The pipeline for high sulfur in gathering and transferring system is in the influence of transmission medium,which is susceptible to corrosion,erosion damage,etc.,resulting in partial thinning of the pipe wall and causing the carrying capacity of the pipe,which becomes a hidden danger of pipeline operation safety.Therefore,it is of great practical significance to evaluate the reliability of corroded pipeline,predict the residual life and formulate appropriate maintenance strategies.The main contents in the paper and the conclutions are as follows:?1?Based on the experimental data obtained,adaptability analysis was performed for different pipeline failure pressure evaluation methods,such as ASME B31G,modified B31G,DNV-RP-F101,PCORRC,C-Fer,and API579.Studies have shown that for medium and low grade steels,the DNV-RP-F101 have good prediction results.?2?Based on the tests data and the collected pipeline corrosion data,pipeline performance data,and system operating data,SPSS and other statistical softwares were used to determine the probability distribution functions of various random variables.The reliability calculation of the corroded pipeline was completed using the calculation program,and the sensitivity analysis of the wall thickness,pipe diameter,tensile strength,corrosion depth,corrosion length,corrosion rate,and operating pressure was performed,and the main influence on the reliability of the corroded pipeline was obtained.The main factors are wall thickness,corrosion depth,operating pressure and radial corrosion rate.?3?Using ANSYS simulation software,a three-dimensional model of straight pipe with internal corrosion defects in ellipsoidal plane was established through APDL parametric design language programming instructions.Through the regulation of parameters,the equivalent stress of pipes under different defect sizes was calculated.At the same time,based on the orthogonal design test,the multi-factor significance analysis was performed.The significance sequence of the influencing factors was:pipe wall thickness,pipe diameter,corrosion depth,tensile strength,and axial corrosion length.?4?According to the corrosion depth of the pipeline,the pipeline corrosion status is divided,and the regression probability method is used to determine the transition probability matrix of Markov chain to realize the prediction of the remaining life of the pipeline.At the same time,the Markov decision process is introduced to analyze the state transition probability matrix under different maintenance strategies.And use the strategy to improve the algorithm to solve,get the optimal maintenance strategy,₇??28??1,2,3,3,4?,so as to provide theoretical guidance for on site maintenance work.