Research On Stress Of Overhead Gas Pipelines In The Condition Of Leakage

With the advancement of society and economic development,overuse of natural resources such as coal and petroleum and depletion of resources,people increasingly prefer clean energy-natural gas,which has the advantages of cleanliness,high efficiency,and high calorific value.The pipeline industry supporting natural gas transportation also has been rapidly developed.At present,China's pipeline project has the characteristics of long distance,wide coverage,and being easily affected by environmental.Due to defects in the pipeline itself,China's natural gas pipelines are prone to leakage.The leakage forms are mainly divided into rounds caused by single-point corrosion and cracks due to factors such as welds.When the pipeline leaks,the normal operation of the pipeline is damaged due to the uneven stress distribution and stress concentration at the leaking hole or crack.Therefore,it is important to study the stress and strain laws of pipeline leakage under internal pressure and the specific influence of the pipeline internal pressure and crack stress intensity factor with different pipe sizes,and then to take effective rescue measures and reduce the accident losses.This paper intends to use finite element software ANSYS to establish the finite element analysis model of two different leakage situations of natural gas pipelines under internal pressure,and study the stress variation law of pipelines with leakage holes and cracked pipelines,and finally analyze and evaluate the pipeline leakage hazard consequences.The specific research content is as follows:1.At first,this paper intends to establish a finite element analysis model for the leakage of circular holes,considering the factors such as wall thickness,leakage aperture,and pipe diameter,than studies the stress distribution and distribution around the leak hole.And by calculating the stress concentration factor method to verify,so as to prove the effectiveness of numerical modeling methods.2.Pipelines containing leaky holes were researched by using the stress failure criteria,though defining the reference stress value to determine the internal pressure of the leaky pipeline,and than the paper studied the influencing factors of the pipeline's limit internal pressure.Including studying the different internal pressures,different pipe diameters,and different wall thicknesses,this paper researched the influence of different leakage aperture influence factors on the limit internal pressure of the pipeline.3.The finite element analysis model of cracked pipelines was established and the stress magnitude and distribution of crack tip were studied and analyzed.This paper solved the stress intensity factor of the pipeline and compared it with the theoretical value to verify itscorrectness.Considering the influence factors of different internal pressures,pipe diameters,pipe wall thickness,leakage aperture,this paper intended to Analyze and study the influencing of the cracked pipeline,and simultaneously using the method of CEDG R6 to evaluate the cracked pipeline for failure assessment.Finally the results show that with the increase of internal pressure,the internal pressure values of crack half-length out of the safety zone are not the same.With the increase of crack half length,the internal pressure of the crack pipe when it breaks out of the safety zone decreases.