Research On In-pipeline Inspection System Based On Plane Eddy Current Sensor

The pipeline is a manifestation of a country's potential strength,and the pipeline used to transport natural gas and oil is one of the important channels for economic development.Pipes are ferromagnetic materials.Ferromagnetic materials refer to materials whose relative magnetic permeability is far greater than 1 and are easily magnetized.In the course of use,it is vulnerable to environmental impacts such as geological disasters,crustal movement,internal and external acidic media corrosion,which will cause different degrees of corrosion and damage to the internal and external pipelines and welds.These damages will cause major safety accidents such as pipeline explosions and leakage of conveying media.Therefore,the inspection and maintenance of regular safety of pipelines are extremely urgent.This paper studies the detection of internal surface defects of oil and gas pipelines based on electromagnetic eddy current detection technology.Eddy current testing is a non-destructive testing method based on the principle of electromagnetic induction.When the exciting coil generates a changing magnetic field and approaches the conductor,the magnetic flux changes to produce eddy currents.The eddy current density,signal phase and current direction in the conductor will follow the test piece.Whether there is a defect or not,the magnetic field generated by the eddy current affects the impedance of the detection coil and the induced voltage.Thus,by measuring the magnitude of the induced voltage,it can be judged whether the test piece is defective.Due to the limited inspection space in the pipeline,there are limitations to traditional eddy current inspection methods.At present,for the detection of internal defects in pipelines,the magnetic flux leakage nondestructive testing technology used in large-caliber pipelines has been mature,while magnetic flux leakage detection for small-diameter pipelines is costly and has limitations in magnetization,so it is not suitable.And because of the harsh environment inside the pipe,there are iron filings,welding heads,weld burrs,and corrosive liquids adhering to the inner surface of the pipe,so the height of the inspection is tested.Based on the planar eddy current probe,this paper studies the detection and identification of internal defects in small diameter pipelines.The research content is divided into the following three parts:(1)Based on the theory of circuit theory,electromagnetic induction theorem and wireless energy transmission theory,a double-layer differential planar eddy current sensing structure is proposed to solve the problem of lift-off detection and limited internal space of the pipeline,and the COMSOL simulation platform is used to construct the sensor Structural model.The geometric parameters of the structure are optimized by comparing the simulation results on the plane specimen to achieve the best sensitivity.(2)Process the PCB coils that have been designed and simulated,and build the hardware platform of the eddy current detection system.Including the production of excitation signal source,the design of power amplifier circuit,the adjustment of received signal preprocessing,and the design of data acquisition and storage.Obtain the experimental signal of the probe on the plane specimen and compare and analyze the simulation results to verify its correctness.(3)Construct a simulation model based on actual pipeline material parameters,and perform defect processing and experiments on pipeline specimens,including processing coils and hardware systems,processing probes and system placement supports,connecting devices between coils and systems,and completing comparisons Experimental test.The probe designed to verify its design on the completed platform can collect and identify defects on the inner surface of the pipeline.