Research On Automatic Magnetic Flux Leakage Detection Technology For The Wall Of Tank

Storage tanks are affected by environmental factors and corrosive chemicals in the medium.Wall corrosion often occurs.If an incident occurs in the storage tank,it will have a serious impact on the economy and the environment,and even directly endanger people's life safety.Inspection of the tank wall has become inevitable.Magnetic flux leakage detection holds high detection reliability.In particular,the application of automated detection can obtain higher detection efficiency.Based on the principle of magnetic flux leakage detection,this paper uses the finite element simulation analysis to simulate leakage magnetic field signals under two modes of the circumferential magnetization and axial magnetization about the internal and external wall corrosion defects and different types of defect,including cylindrical,hemispherical and conical defects.The results show that the leakage magnetic field strength of the cylindrical defect is stronger than that of the hemisphere,and the leakage magnetic field strength of the hemispherical defect is stronger than that of the cone,and the leakage magnetic field strength of the outer wall defect is stronger than that of the inner wall.Under the axial magnetization,the lift off values of each channel are not consistent,and the change of the diameter of the wall has a direct influence on the lift off value.Therefore,the effect of defect magnetic flux leakage signal on each channel is studied under the diameter change of the wall.In view of the difference of the amplitude between the middle channel and the edge channel,the relationship between the diameter and the channel is established by introducing the amplitude correction coefficient.The multi-channel magnetic flux leakage signal preprocessing model is obtained.The preprocessing model can be used to know the leakage magnetic field amplitude of each channel after pretreatment,so as to achieve uniform distribution of leakage magnetic field in each channel of axial magnetization.The experimental study was carried out using the magnetic flux leakage detection system of the tank wall and the defects were artificially pre-manufactured on the test piece.In the analysis of experimental data processing,the law of leakage magnetic field is analyzed by using the best channel data collected above the defect.The experimental results are consistent with the simulation analysis.Considering the safety and detection efficiency,the automatic detection device is designed to replace the manual operation.The magnetic leakage detection technology and the automation technology are combined organically to design magnetic flux leakage detection device.It owns the wheel self-driving and the 180 degree steering mechanism.Because commonly used tank surface are variable cross sections,the lifting mechanism of magnetized structure crossing weld is designed.The system realizes the acquisition of magnetic flux leakage signals by wireless transmission.