Research On The Key Technology Of Pipeline Crack Detection Based On Eddy Current Sensor

With the explosive growth of China natural gas market,the explosion accidents of domestic gas pipeline are also increasing.In order to avoid unnecessary losses caused by aging of pipeline network and geological settlement of buried pipeline,it is necessary to regularly detect the service pipeline.Eddy current nondestructive testing technology is a kind of nondestructive testing technology with high reliability and strong visualization ability.It has great advantages for the detection of micro cracks.However,there is still a large room for improvement in the detection efficiency and quantitative characterization of the technology.Therefore,this paper studies the key problems of pipeline crack detection based on eddy current sensor,and the specific work is as follows:(1)Aiming at the calibration problem of the optimal parameters of different materials in eddy current testing,the influence of excitation frequency and lift off value on the testing quality is simulated and analyzed,and the results of simulation,testing experiment data and theoretical derivation calculation are compared and analyzed.It is concluded that the optimal lift off value of 4340 steel pipe detection is 0.5mm,and the optimal excitation frequency is 100 Hz.Using this parameter to test effectively improves the quality of eddy current testing.(2)Aiming at the problem of quantitative characterization of C-scan cracks in eddy current testing,based on the region extraction and feature enhancement of C-scan image,a quantitative characterization method of defects in eddy current testing based on improved Sobel operator is proposed to realize the characterization of pipeline cracks.(3)In view of the problems of low efficiency and poor stability of eddy current inspection,the method of mutual cooperation between axial sliding table and rotary gear ring is adopted,and the automatic inspection of pipeline cracks is realized by using electrical control technology and two AC servo motors,which greatly improves the inspection efficiency.The method of speed and position control of servo motor by PLC avoids heavy equipment The speed fluctuation caused by force improves the stability of scanning.(4)In order to improve the quality of pipeline crack scanning and whether the performance of the equipment is up to the standard,the experimental research is carried out,including the axial scanning speed experiment under different angles,the circumferential velocity experiment under different pipe diameters and the movement stability experiment of the device.The experimental results of scanning speed show that the average speed of axial scanning is 16.65mm/s and that of circumferential scanning is 1.59mm/s,which meets the requirements of technical parameters of the equipment.The results of the movement stability experiment show that: in the long running process after the equipment is started,the full coverage of the pipeline external wall scanning is realized efficiently and stably,which meets the design requirements.The research content of this paper provides theoretical and experimental support for the quantitative characterization and improvement of detection efficiency of eddy current detection of pipeline cracks,which is helpful to the further development of eddy current detection technology.