Study On Spatial Distribution Characteristics Of Leakage Magnetic Field In Tank Floor

Storage tank is one of the most common pressure vessels in the petrochemical industry.In the long run,the storage tank is prone to corrosion.It is not easy to detect the characteristics of repair and easy to aggravate the corrosion.The corrosion defects will caused the failure of the tank and it will be a threat to production safety.Therefore,it is very important to use an efficient detection method to detect the storage tank in time.In the conventional detection methods,magnetic flux leakage detection is widely used because of its advantages such as high scanning efficiency,portable detection equipment and accurate detection results.The quantification of MFL signals are only for general defects in length and breadth,and the study of geometry and spatial distribution characteristics of defects is less.Therefore,during quantitative process of defects,there is still a large exploration of space on the specific shape and influence on the missing factors of spatial distribution characteristics of the magnetic field.This paper focuses on the tank bottom defect on the three-dimensional simulation using the finite element method according to the depth and the width of the defect,defect geometry,defect overlay,defect position,detection of air gap and plate deformation,the backing plate and the corrosion product of the modeling and analysis.The control variables are used to simulate the different defects to obtain the magnetic flux leakage signal and extract the amplitude of each curve.Finally,the spatial distribution curve of magnetic flux leakage signal is obtained by summarizing the MFL signals of channels.On the basis of the finite element analysis,the whole scheme of MFL testing for the corrosion defects of the tank floor is developed.Under the condition of laboratory,the steel plate is used to simulate the bottom plate of the tank,and a set of magnetic flux leakage detection device for the corrosion of the bottom plate of the tank is set up.In the experiment,different types of defects corresponding to the simulation are obtained,and several factors affecting the spatial distribution of the leakage magnetic field are set up.Finally,the experimental results are in agreement with the finite element simulation results.