Research On Inner Detection Technology Of Pipeline Defects Based On Differential Planar Eddy Current Sensors

Pipelines transport is a critical transport mode for oil,gas,and other vital resources.Pipelines are installed in different environments.As the service life of the pipeline continues to increase,problems such as corrosion,cracks,deformation,and external force damage are prone to occur.These defects will destroy the integrity of the pipeline and lead to major safety accidents.Therefore,pipeline safety detection has practical significance.In recent years,the state has attached great importance to the development of pipeline detection technology.The pipeline detection technology is generally divided into inner pipe detection and outer pipe detection: the outer pipe detection is mainly to detect the exposed part of the pipe by using the instrument;the inner pipe detection is to use the inner detector to perform online detection of the pipeline when the pipeline is running online.Since the internal situation of the pipeline is difficult to be controlled,it is difficult to realize detection.Given the lack of mature domestic detection methods for the inner surface defects of small-diameter long-distance pipelines,an in-pipe detector based on the planar coil eddy current detection method was proposed to detect the inner surface defects of smalldiameter pipelines.Conventional internal detection tools are relatively complex in structure and large in size and are not suitable for the detection of small-diameter pipes.Based on the research of wireless energy transmission theory and planar coil eddy current detection technology,this thesis innovatively proposes a differential coupling planar eddy current sensor based on passive resonance enhancement.Through finite element simulation,artificial test pieces,and field pipelines for verification,and integration and development of a commercial pipeline eddy current detector,it has realized the detection and excavation verification of domestic small-diameter oil and gas pipelines.The main research work of this thesis is illustrated as follows:（1）Based on the theory of wireless energy transmission and the law of electromagnetic induction,a pipeline eddy current detector based on a differential planar eddy current sensing structure enhanced by passive resonance is designed to solve the problems of limited internal space and complicated pipeline conditions in small-diameter pipelines and use the COMSOL finite element simulation software to build the structural model of the pipeline-planar eddy current coil,optimize sensor structure parameters,and achieve the best sensitivity for detection.Through the comparative analysis of the simulation results of different structural sensors for different types of defects,the sensor is superior to other sensors in defect detection and establishes a relationship between sensor detection signals and defect parameters.（2）Design and process the proposed sensor and build a hardware platform for the laboratory system.By comparing the test results of the sensor and sensors with different structures for different types of defects,combined with the simulation results,it is effectively verified that the passive resonance enhancement effect improves the defect detection capability of the sensor.And the conclusions obtained are used for subsequent identification and quantitative detection of pipeline defects.（3）Integrated development of an eddy current detector suitable for 219 mm diameter pipelines,including excitation signal source design,power amplifier circuit design,data acquisition,storage design,and mechanical structure,and carried out pipeline artificial defect and weld defect detection experiments.The detection of defects has realized the identification and size analysis of natural pipeline inner surface defects at high speed and verified its reliability through field excavation,which meets national commercial internal detector standards.