Research On Integrity Evaluation Technology Of Gas Transmission Pipeline Based On Internal And External Inspection Data

Due to internal and external environment,transportation medium and other factors,the wall of natural gas pipeline will reveal its defects after long-term operation,so that the pipeline cannot operate safely under the current operating pressure,and even cause pipeline leakage and cracking.The integrity evaluation of the pipeline is an effective technical means to ensure the safe operation of the pipeline.In view of this,based on the actual data of gas pipeline defects,this paper not only effectively analyzes and distinguishes the causes and types of gas pipeline defects,but also analyzes and studies the integrity evaluation technology of the defective pipelines.The specific work is summarized as follows:Firstly,the key point alignment steps and comparative analysis method of internal and external pipeline inspection data are proposed.By integrating and aligning the inspection data in the same coordinate system,the defect types,distribution rules and causes are explored.The results show that the distribution of internal defects is regular,and the correlation between external defects and various external inspection data is small.Secondly,the theoretical basis of various evaluation standards for residual strength of pipelines with defects is analyzed,and the evaluation process and application scope are clarified.Based on the defect measured data and different residual strength evaluation standards,the evaluation results of pipeline residual strength are compared by collecting the blasting test data of pipeline with defects;the applicability of different evaluation standards is determined.Besides,the defect evaluation results are acceptable,and the pipeline can operate safely under the current pressure.By establishing a three-dimensional solid model of pipeline with defects and using ANSYS finite element simulation method,the strain situation of pipeline defects is analyzed,and the variation law of residual strength of pipeline defects with defect size is studied;for the measured data of defects,the finite element calculation results verify the accuracy of the standard evaluation results of residual strength.Based on the strain results of finite element calculation of pipeline defects,the strain formula fitting is carried out,and the average error is smaller when the fitting strain formula calculation results are compared with the finite element simulation results.Finally,the remaining life prediction method of pipeline with defects is studied,the conservatism of various remaining life prediction methods under different corrosion rates is analyzed,and the remaining life prediction of measured pipeline defects is carried out.Based on the prediction results of various standards and defects life,the pipeline re-inspection interval and repair suggestions are put forward.