Research On A Non-destructive Testing Method Based On EMAT And PECT Mechanism Composite

As a kind of transportation mode with huge traffic volume,short construction period,low operation energy consumption and long-term stable operation,pipeline transportation is an important tool to adjust the resource balance in various regions and plays an irreplaceable role in the field of resource transportation.The pipeline has been subjected to the chemical corrosion of the surrounding environment,the impact of the transport medium and the thermal expansion and contraction caused by climate change for a long time,which may cause defects such as cracks and rust on the inner and outer of the pipeline.If it is not found in time,it may lead to resource leakage and even an explosion accident.Therefore,there is an urgent need for fast and efficient pipeline integrity detection technology.As an emerging pipeline detection technology,Electromagnetic Acoustic Transducer(EMAT)technology has the advantages of non-contact,fast detection speed without using coupled medium etc.Pulsed Eddy Current Testing(PECT)is a non-contact NDT technology based on the principle of electromagnetic induction.It has the advantages of high detection efficiency and accuracy,and is suitable for defect detection on the surface and near surface of metal pipes.The two detection methods have many similarities in the detection principle and characteristics,and their combination can make up for each other in terms of detection range.Based on the problem of improving the efficient and comprehensive detection of oil and gas pipelines,this paper studies the mechanism combined detection technology of EMAT and PECT.The specific research content is as follows: 1).Based on the principle and theory of EMAT and PECT,the feasibility of composite detection was studied,and a sensor model based on mechanism composite was established.Through finite element simulation experiments,the ability of the composite model to detect various surface defects and internal defects was analyzed.The feasibility of data fusion of two detection methods is also proposed.2).Based on simulation experiments,a verification platform for composite detection systems is set up,including the design of composite sensors and composite signal separation modules.Experimental experiments were performed on flat specimens of ferromagnetic and non-ferromagnetic materials containing various types of surface-defects and bottom-thinning-defects.The experimental analysis results are consistent with the simulation results.It is verified that the EMAT signals and PECT signals can be mutually verified and data fusion.It shows that the mechanism composite detection technology proposed in this paper can correctly detect ferromagnetic and nonferromagnetic flat specimen Surface defects and thickness variations.3).An experimental study on the combined detection method of EMAT and PECT was conducted on the 813-X70 pipeline specimen from the Southwest Oil and Gas Field Company.The analysis of the experimental results proves that the combination of the two detection methods can realize the thickness change monitoring and surface defect detection of the pipeline.