Development Of Pipeline Outer Detector With Three Magnetization Units And Numerical Simulation Of Magnetic Field

As the rapid development of China's long-distance oil and gas pipeline construction, it is directing to the way of large diameter, high pressure and long-range. Because most of them are made of iron magnetic material, buried long enough and operated under the conditions of pressure or high temperature, a variety of corrosion damage or injury can be generated easily. At present, magnetic flux leakage (MFL) inspection technology are widely used in storage tank floor and pipeline internal testing for its high efficiency, high reliability, etc., the MFL inspection technology of pipeline external are in the process of development and perfection at home and abroad. This thesis will design and manufacture a MFL detector prototype outside pipeline. Improved through structural optimization, the MFL technology will be applied to oil and gas pipeline inspection better, which will narrow the gap between China and foreign countries.The research project is involved in the use of theoretical analysis and experimental study. First of all, the leakage magnetic field theory such as magnetic dipole model is used to study the leakage magnetic field of defects, analyze the different effects to the leakage magnetic field by different defect parameters. In the use of SolidWorks and Auto CAD software to design the structure of the prototype, at the same time, the stacking interaction between the magnetic field and the leakage magnetic field distribution characteristics of pipeline corrosion defects of different sizes are analyzed using ANSYS finite element method. Through a series of improvement and development, the prototype size is determined ultimately and the parts are fabricated, and then assembled. Under laboratory conditions, the experimental inspection device of simulated pipeline corrosion defects is established. After debugging the prototype inspection system, the experimental study on the magnetic interaction between units, detection of corrosion defects in different location or size, leakage magnetic field characteristics of weld part and inspection of inner pipeline wall defects. Some experimental data is compared with the numerical simulation results, thus the reliability of the equipment is tested.In the end of this research, a pipeline MFL detector prototype has been designed and processed, the detector structure is compact, light weight and has good reliability, it's able to detect the cylindrical corrosion defects that exist in the inner or outer wall of pipeline above a certain size.ANSYS finite element analysis software is applied to research the leakage magnetic field of pipeline defects and superposition of magnetic fields analysis. It provides a theoretical reference to pipeline inspection using the MFL technology. If the detector prototype designed by this research can be optimized and improved more, it will be applied to pipe-line detection at the scene with considerable economic value and a certain degree of social value.