The Research Of Pipeline Weld Area Of Defect Magnetic Flux Leakage Detection Method

In order to ensure pipeline safety, reliability, proper functioning, the issue of changing thethickness of the pipeline becomes very important. Piping not testing before use, unable to graspits damage degree, can’t guarantee quality. In the pipeline to use, pipe wall thickness changes arerelationship between the safety factor of piping system. Timing measurement pipeline thicknesscan reflect the health condition of pipeline in time, eliminate the hidden danger, ensure thenormal operation of pipeline and unexpected accidents during the operation, increased the safetyof life and property security. At the same time, detecting the thickness of the pipes is also provideresources for pipeline maintenance, Reduces the maintenance cost, Reduce the unnecessaryhuman consumption, avoid the cost of pipeline changed frequently, Save the money, improve theeconomic benefits of the pipeline, to promote the vigorous development of the oil pipeline in ourcountry.Pipeline weld as a special case of pipeline thickness change, in the actual detection, in theactual detection, ignore the pipe welding seam and the weld area of defect magnetic flux leakagesignals, is easy to be confused with defect leakage magnetic field, often can cause misjudgment,Affect the accuracy of the test results. Therefore, for pipeline weld area namely thickeningspecial part of the study of the magnetic flux leakage signals has an important significance.Onecoil dc excitation was studied through the type of magnetic flux leakage thickness method. Inorder to reduce the measurement error, and puts forward the double probe test method thatincreases the vertical space point measurement, based on the two measured values for calibration,make the value more accurate measurement results. Through the analysis of the current size ofcoil influence on magnetize properties, determines the optimum excitation dc coil excitationintensity, It is concluded that the pipeline magnetic flux leakage strength and the relationshipbetween the pipe thickness changes. Using COMSOL software for finite element simulation, andhas set up a test platform, for working principle and testing method of demonstrates the feasibility.Results show that the wall thickness and the sensor output voltage has certain relationcurve, which does not directly measure of pipe wall thickness, by means of the pipe wallthickness change and cause of pipeline surface leakage magnetic field variations to indirectlymeasure the thickness of the pipes, The magnetic flux leakage testing technique in engineeringoptimization design provides a theoretical basis and theoretical reference.Using Comsol Multiphysics finite element simulation, get the pipe weld area defects ofleakage magnetic field of the axial, radial and circumferentialgraph, cloud, highly expression, as well as wall thickness and pipe surface curve of the relationship between the magnetic inductionintensity. Respectively compared with the pipe, weld defects and weld area with and withoutdefects of three axis component curve, under the condition of different pipe thickness anddifferent exciting current, the leakage magnetic field on the surface of the pipe size changes.