Theoretical Study On Corrosion Evaluation Of Gas Pipeline

Underground gas pipeline is an important component of urban public facilities together with power and water pipe,which constitute the city public pipe network system and bear the city gas energy transportation.Once gas pipeline corrosion failure occurs,it will inevitably lead to gas leakage.Leakage of natural gas will produce fire,explosion and other dangerous accidents under certain conditions,resulting in personnel,property damage.In addition,because of pipeline failure,the outage and post-accident repair will affect the people’s normal life.In order to ensure the safe operation of the gas pipeline,establishing the gas pipeline evaluation system is very important.The work and achievement of this dissertation mainly include:(1)The grading model of gas pipeline corrosion degree was established.The factors that affect the corrosion of gas pipeline are divided into five indicators.Adoptting the improved comprehensive analytic hierarchy process,the degree of corrosion was calculated by inputting factor levels and weight.(2)The grading model of gas pipeline corrosion accident is established.The loss radius of fireball,jet fire and cloud explosion can be calculated by inputting the corrosion size,pipe diameter,internal pressure and other parameters.The consequences of accident can be calculated based on population and property density.(3)The ripple effect model of gas pipeline corrosion accident was established.The probability of the ripple effect is calculated by entering the diameter of the corrosion source pipe,the diameter of the target pipe and the distance of the two pipes.In this paper,the influence of pipe diameter ratio and pipe clearance on the chain effect is analyzed by examples.The results show that the probability of the chain effect decreases with the increase of the distance between the two pipes.When the pipeline clearance is more than 4 times of the radius,the chain effect is obviously smaller.The chain effect is more apparent when the radius of the source pipe is smaller than the target pipe radius.(4)Compared the differences of various corrosion pipeline safety pressure calculation methods in different corrosion length,corrosion depth and pipe steel grade,the results show that DNV RP-F101 effective stress method is more stable.(5)Compiling the corrosion evaluation software.The practical software for gas pipeline evaluation system is edited based on the above research to provide efficiency of evaluation.