Axial Load Research Based On Collision Traces After Fracture Of Accidental Pipeline

The investigation of the pipeline accident found that when the pipeline rupture is located near the elbow,a collision gap will appear after the pipeline is disconnected,indicating that the pipeline has been subjected to a large axial load before the disconnection.There is no more precise calculation method and conclusion for the range.Therefore,based on the characteristics of the accident fracture,this thesis proposes a calculation method for estimating the determination of the axial load before the failure of the girth weld.Firstly,a three-dimensional model of the accident fracture was established,and a handheld three-dimensional scanner was used to scan and model the contact traces at the fractured ring weld of the high-grade steel pipeline,and the digital characteristics of the contact traces were obtained by calculation.The motion analysis of the accident pipeline was carried out,and the range of the axial load that the accident pipeline might be subjected to before the fracture was obtained by reverse inference.The movement process and the instantaneous state of the collision after the accident pipeline was broken by the tensile action were explained and analyzed in detail.And make an extension based on this,change the angle of the elbow and the length of the straight pipe section,continue to calculate the collision after the pipe is broken,and summarize the collision law.The research results show that: in this accident,the axial load range of the pipeline before fracture is about 590MPa-640 MPa.At this time,the axial stress of the welded joint of the fractured ring of the pipeline has exceeded the yield strength of the pipeline itself.When the axial load range is between 400 MP and 655 MPa,the pipeline will collide during the movement process after disconnection;during the pipeline stretching process,the inner wall of the elbow will generate relatively large stress,when the pipeline elbow angle is between 13° and 29°,the pipe will collide.When the angle of the pipe elbow is between 0° and 13°,the pipe will not collide after it is disconnected;during the collision process of the pipe,the angle between the two gaps and the center of the pipe will increases and then decreases with the increase of the displacement of the straight pipe,and the notch depth presents a bimodal curve trend with the increase of the axial displacement of the pipe.