Simulation And Experimental Study On Corrosion Detection Of Buried Pipeline By Magnetic Gradient Method

Metal pipeline is the most economical way to transport oil and gas,which is basically buried in the ground and its burial depth is generally 0.5-2m underground.With the growth of service time,the buried metal pipeline will be corroded,deformed and even broken under the influence of external forces,internal medium corrosion and external electrochemical corrosion,which will seriously threaten the operation safety of the pipeline and cause serious economic losses and environmental pollution.Timely and effective detection of in-service pipeline operation status is one of the important links to ensure energy safety transportation,among which detection of corrosion status of buried metal pipeline is the key basis for pipeline safety evaluation,so it is particularly important to find effective trenchless detection technology of buried pipeline.In this paper,a weak magnetic detection technique for buried pipeline based on magnetic gradient method is proposed to effectively detect the corrosion of buried pipeline.Firstly,the composition and spatial distribution of geomagnetic field are introduced.The magnetic properties and magnetization characteristics of materials are explained from the microscopic perspective,and combined with the basic theory,the principle of weak magnetic detection of buried pipeline is expounded.The theory of magnetic gradient method is explained mathematically,which combined with the weak magnetic detection of buried pipelines to obtain a new weak magnetic detection technology;Secondly,this paper simulates different types of corrosion defects of buried pipelines and analyzes the influence of various factors on magnetic field signals of buried pipelines;Then,according to the simulation results,a similar test scheme is designed,and different types of corrosion defects are prefabricated on the buried pipeline respectively.After data processing and analysis,the accuracy of the simulation results is verified according to the test results.The results show that the experimental results are basically consistent with the simulation results.The larger the width of the annular groove,the smaller the magnetic gradient anomaly;The deeper the depth of the annular groove,the smaller the magnetic gradient anomaly;The larger the aperture is,the smaller the magnetic gradient anomaly is,but the overall anomaly is smaller than the annular groove;When perforating at different angles except 90°,the anomaly cannot be judged.When the Angle is from30° to 60°,the magnetic gradient anomaly is basically the same,which is contrary to the anomaly trend at 0°;The larger the pipe diameter,the larger the magnetic gradient amplitude,but the abnormal trend is basically the same;Finally,the detection method is applied to engineering practice,and the abnormal signals found in two cases are given a basic judgment,and the results are verified by excavation.The results of excavation verification are consistent with the results of detection,which proves the feasibility and effectiveness of the detection method.