Simulation Analysis Of Leakage Magnetic Field Characteristics For Tank Fillet Weld

Since entering the21st century, with the rapid economic development in ourcountry, the use of energy such as oil and gas is increased, there are a large number ofvertical storage tanks using in the petroleum and petrochemical enterprises, verticalstorage tank plays a very important role In terms of energy storage. Due to tank filletweld under corrosion medium and the action of alternating stress for long time,defects such as corrosion pits and cracks easily generated. Therefore, ascientific&reasonable testing and evaluation of the tank near the fillet weld and itsposition becomes extremely important. At present, in the field of ferromagneticmaterials nondestructive testing, magnetic flux leakage detection technology with itshigh efficiency and defect location accurate, simple operation and a series ofadvantages is widely used, but for the tank, magnetic flux leakage testing technologyresearch of fillet weld is less. Based on the tank fillet weld as the research object inthis text, we use magnetic flux leakage testing method to test the tank fillet weld andanalyze leakage magnetic field distribution under different conditions.Thinking about characteristics of tank fillet weld, the author of this papercombines theoretical analysis and finite element analysis and experiment research, ananalysis of the magnetic flux leakage testing tank fillet weld. With the basic principlefor the study of magnetic flux leakage detection as the basis. A simulation model ofmagnetic flux leakage testing about tank fillet weld was established based on ansysfinite element analysis software, to analyze leakage magnetic field distribution nearthe fillet weld and influencing factors. First of all, the paper analyzes leakagemagnetic field distribution whether there is a level plate outside the tank wall or not;the next analysis based on the fillet weld model, on the basis of specific analysis ofmagnetic flux leakage signals about the geometric parameters of magnetic structure,such as length, width, height of magnet and magnetic structure of the internal airlength; then discussing the influence of the magnetic flux leakage signal detection inthe storage tank fillet welds which is from the thickness of the steel plate (verticalwall plate and base plate), the depth of defect and distribution of defect (double defect,the distribution of up and down, the distribution of left and right) and shape of defectand so on.Under the existing conditions in the laboratory, we establish two artificialrectangular groove defect which is40%of thickness and the other is80%of thicknessunder the fillet weld toe, and obtain the magnetic flux leakage signals ofcorresponding rectangular groove defect by using tank fillet magnetic flux leakagedetection system for experimental study, can be seen from the results that magneticflux leakage signal amplitude of80%depth is significantly higher than40%defectdepth, In addition, the relative position of two defects can be determined from detection of figure. by contrastive analysis of the result of the experiment and theresult of finite element analysis, proves that magnetic flux leakage testing method canbe effectively applied to the tank fillet weld detection.