Research On Pipeline Inspection Based On Emat And Pulsed Eddy Current Technology

Safety of pipeline transportation is crucial.Though piezoelectricity ultrasonic transducers are widely applied in the inspection of pipelines,they rely on couplant.Thus piezoelectric transducers are not available for the inspection of gas pipelines since coulant cannot be used.Electromagnetic acoustic transducer(EMAT)is couplant free and of high efficiency.However,design of EMAT coil's parameters are mostly based on engineering experience and lack of theoretical support at present.Meanwhile,EMAT is unable to inspect inner-surface defects caused by pipeline corrosion.To depote a solution to the problems above,a pipeline corrosion inspection method based on EMAT and eddy current is studied in this article.At present,most finite element methods ignore the impact of circuit parameters on the signal received in EMAT.Thus limits guidance function of simulation results on EMAT design.To solve this problem,by analysying the mechanism of EMAT bulk wave and studying the imact of transmission and receiving stage,a full modeling method including transmission and receiving process is proposed.During the inspection of long-distance pipeline,vertical magnetic field EMAT suffer serious abrasion with the stress to the wall.To solve this problem,an horizontal EMAT based on full modeling method is designed.EMAT coil is designe in the method of full modeling.By analysing the impact of coil parameters on the EMAT performance,parameters of EMAT coil are designed.Magnetic field of EMAT is designed by testing.By detemining the rule between magnetic field and echo signal amplitude,the magnetic filed of EMAT is designed.By establising experimental platform,the full modeling method and the design result are proved.EMAT is unable to inspect inner-surface defects caused by pipeline corrosion,and its own inspection result is influnced by the defcts.To solve this problem,ultrasonic is united with the eddy current stimulated by EMAT.By studying the mechanism of eddy current,a finite element model is established to analys the feasibility of eddy current detection and the features of defect signals.With the EMAT designed above,eddy current is stimulated in the pipeline to inspect the defetcs.Then the finite element model is proved and EMAT and eddy current inspection methods are united.A inspection system based on EMAT and eddy current methods is designed to inspect the pipeline corrosion.Through experiment the performance of the system is tested.The reults indicate that the system's thickness gauging accuracy is under ±0.2mm.Meanwhile the system is able to inspect defects of size minimum to 0.5mm.The system is efficient in the inspection of pipelin corrosion.