Study On The Influence Of Boiler Water-cooled Wall Tube Fins On Magnetic Leakage Detection

At present,boiler units are still the basic energy equipment of thermal power plants in China,and they are prone to failure.according to the relevant national regulations,boiler water wall tube to carry out regular maintenance and repair,magnetic leakage detection technology because of its unique advantages,can be applied in the boiler water wall tube non-destructive testing,the current more common boiler water wall tube for finned membrane water wall tube,but in the actual testing process,we found that the fin will have an impact on magnetic flux leakage detection,resulting in reduced detection accuracy,Therefore,it is very important to study the influence of boiler water-wall tube fins on magnetic leakage detection.This paper,based on magnetic flux emission detection technology,combines simulation analysis of limited elements and an experimental basis.For the first time,simulation analysis of limited elements is used to study the distribution of space of magnetic flux density of leakage magnetic field during magnetic flux leakage detection of water-walled tubes in boilers with or without fins,and sets two defect variables,namely different sizes of defects and different positions of defects,and the larger the size of the defect,the greater the density component of the magnetic flux density of the leakage magnetic field,and the change of defect position has little effect on the spatial distribution of the leakage magnetic field.Comparative analysis of leakage magnetic field data with and without fins.It is concluded that the fin will cause the magnetic flux leakage detection signal to become smaller,and in the case of fins,the Xdirection component of the leakage magnetic flux density decreases as a whole,and the fluctuation amplitude of the Y-direction component of the leakage magnetic flux density decreases.Set up an experimental platform in the laboratory,set defects of different sizes and positions on the fin free boiler water wall tube and the water wall tube of the fin boiler,design a magnetic leakage detector to detect it,and compare and analyze the magnetic leakage data obtained,and the experimental and simulation results are consistent.In order to reduce the influence and improve the accuracy of magnetic leakage detection,this paper attempts to reduce the influence by two methods,the first method is to add a magnetization head on the left and right sides of the target pipeline to enhance the magnetization strength,so as to enhance the magnetic leakage signal,perform finite element simulation analysis of the new structure,and extract the leakage magnetic field data,and compare and analyze the magnetization of a single magnetization head of the finless water-walled tube and the finless water-walled tube.The second method is to curve fit the X and Y direction component data of the magnetic flux density of the leakage magnetic field with or without fins,calculate the correction formula,and bring the leakage magnetic field data of different size defects into the correction formula for verification,and it is concluded that the correction formula is suitable for defects of different sizes.After experimental verification of the two methods,it is concluded that both methods can reduce the influence of fins on magnetic leakage detection.And it can improve the accuracy of magnetic flux leakage detection by more than 25%.