Research Of Inner And Outer Surface Defect Identification Technology Via Eddy Current Pipeline Internal Inspection

In recent decades, the pipeline has become the main method of transporting in the oiland gas transportation process because of its advantages. The security of the pipeline needsto be periodically checked in order to safeguard the security of oil and gas transportation.The eddy current testing technology has been widely used in the detection of the pipeline,and eddy current testing for the pipeline surface defects has high detection sensitivity andresolution. The research of eddy current sensor is playing an important role in the pipelinedaily maintenance and safety testing.This paper mainly talks about the oil and gas pipelines. Aiming at the difficulty ofdefect between the inner and outer wall distinguish of the pipeline inspection, the eddycurrent detection method of improving the detection coil resolution is adapt. The solidmodel of the coil probe and the test section of pipeline are built using the ANSYSsimulation software. The parameters that influence the change of the magnetic inductioncaused by coil probe are simulated. The law of geometry defect influences the magneticfield caused by the coil probe is obtained. The characteristic of the magnetic inductionintensity of the axial direction is analyzed by changing the number of turns of the coilprobe, defect depth and other conditions in the simulation. At the same time, the simulationresults are combined to design the eddy coil probe experimental device and then the eddycurrent testing system is developed. The detection system consists mainly of the excitationsignal source, the power amplifier circuit, bridge eddy current probe, the detection circuitof output signal and data acquisition system etc. During the experiment, on the basis ofinfluence characteristics of the output voltage signal caused by the probe with differentnumber of coil turns and the defects with different depths, the method of contrasting theamplitude of output voltage signal is adopted to realize the distinguish of inner and outerwall defects.The steel sheet with different depths of rectangular groove defects laying on itssurface and back is detected by using the eddy current testing system. The defects on the surface and back of the steel sheet represent the inner and outer defects of pipeline wall.Experimental results show that the peak difference of the output voltage signal in thesurface defects of the steel sheet is accurate to millvolt level. The level of precision isenough to realize the detection of the pipeline wall defects. The peak of output voltagesignals has not changed in the back defects of the steel plate. Thus, the system realizes theidentification of the pipe wall defects and solves the distinguish problems of the inner andouter wall defects.