Finite Element Analysis And Safety Assessment Of Pressure Pipelines With Defects Based On Ultrasonic Phased Array Inspection

As a typical special equipment,Pressure pipelines are widely used in industries such as petrochemical,food,electric power,and medicine.In the process of pressure pipeline installation and welding,affected by factors such as the technical level of welding personnel and welding environment,some defects such as incomplete fusions,incomplete penetrations,cracks,slag inclusions and gas porosity often occur which bring huge hidden dangers to the safe operation of pressure pipelines.If these defects are not timely detected and dealt with,it is easy to appear the phenomenon of expansion,resulting in immeasurable security accidents.Therefore,it is particularly important to detect defects and assess the safety of pressure pipes containing defects.In this paper,a petrochemical enterprise normal depressurization device containing defects in the pressure pipe as the object of study,in order to facilitate experimental research,the production of the same specifications of the same material containing the same type of artificial defects in the pipe.The pipeline was inspected by ultrasonic phased array inspection method,finite element analysis of pipeline defects was performed by Workbench module of ANSYS software,safety assessment of pipeline was performed according to the method recommended by GB/T 19624-2019 " Safety assessment of in-service pressure vessels containing defects ",and a software named "Safety Assessment System for Straight Pipe Sections of Pressure Pipelines" was developed by Visual Basic 6.0 programming language.The main research contents are as follows:(1)Ultrasonic phased array inspection method was used for nondestructive testing of defective pipelines.In order to prevent missing inspections during the inspection process,ultrasonic phased array inspections were conducted on the left and right sides of the pipeline welds by changing the probe position and using the single face and bilateral scanning method of the weld for three times on one side,a total of six times.From the test results,it can be seen that the pipe has 2 defects at the welded joint,namely a crack defect of 34.7mm in length and 3.0mm in height,and an incomplete penetration defect of 30.8mm in length and 3.1mm in height.(2)The ANSYS software Workbench module is applied to finite element analysis of pipe defects to derive the stress data of defects in the pipe,and the effect of defect size and location on stress results is studied by changing the size and spacing of defects based on the defect data obtained from detection.The results show that: Ⅰ)the maximum combined stress(Sum of axial film stress and bending stress)of the crack is 145.302 MPa and the maximum stress of the incomplete penetration defect is 27.499 MPa;Ⅱ)in terms of size,the defect height has the greatest effect on the stress results;Ⅲ)in terms of location,the stress increases,then decreases and finally stabilizes as the defect spacing increases.(3)The safety assessment of the pipeline with defects was carried out according to the method recommended in GB/T 19624-2019 " Safety assessment of in-service pressure vessels containing defects",and the influence of the defect size and location on the safety assessment of the pipeline was studied by changing the size and spacing of the defects.The results show that: Ⅰ)the pipe crack defect can meet the assessment requirements,the pipe incomplete penetration defect can not meet the assessment requirements;Ⅱ)in terms of size,the height of crack defects has the greatest impact on safety assessment,and the length of incomplete penetration defects has the greatest impact on safety assessment;Ⅲ)in terms of location,the coexistence of two defects of the same type(crack defect and crack defect,or incomplete penetration defect and incomplete penetration defect)that are safe alone may lead to their unsafety as the defect spacing increases and the location of the two defects of the same type changes.(4)The Visual Basic 6.0 programming language was used to develop a software called "Safety Assessment System for Straight Pipe Sections of Pressure Pipelines",which was applied to the defective pressure pipelines in this paper.The results show that the safety assessment software is convenient and the assessment results are reliable,which has good engineering practical application and promotion value.