MFL Testing Of Heat-exchange Tube Based On 3D FEM And Experimental Study

The heat-exchange tube frequently bring on the corrosion and abrasion due to corrosion medium and alternating stress among petrochemical and refining industry. Ferromagnetic heat-exchange tube is employed commonly in industries, corrosion in tube is the main failure reason of shell and tube heat exchangers and it usually cause large economic loss. Therefore, the periodic inspection of the heat-exchange tube is one of the important measures to ensure the safe operation of process units. The heat-exchange tube need inside testing method for the effect of its ferromagnetism material and structure restriction. Magnetic flux leakage(MFL) technology with its high efficiency, high reliability, etc., is currently mainly used in tank bottom scanning, oil/gas pipeline defect inspection etc., the domestic rare study and use of MFL technology to detect heat-exchange tube.This text with MFL field of the heat-exchange tube's defect for research object, use academic analysis, finite element analysis, experiment research method to carry on the analysis for MFL testing of the heat-exchange tube. The principle of MFL testing of the heat-exchange tube was introduced, and the MFL field is studied with finite element method(FEM) of electromagnetic numerical computation. The FEM is applied to establish the 3D model of MFL testing and MFL field simulation, and analyze various factors on the impact of the MFL field of the defect. Research the change of the geometry parameters of magnetic core among the magnetic structure of MFL testing of the heat-exchange tube to MFL field. After that, the laws of distribution of the MFL field are achieved with FEM numerical simulation,which are influenced by many parameters, such as geometric size(depth and diameter) and thickness of testing tube, etc. Also design two magnetic concentrating structure, and use the magnetic concentrating structure can tremendous increase the sensitivity of MFL testing.Base on the academic analysis and FEM analysis, by using plot software, the experimental system of MFL testing of heat-exchange tube is established, carry on the experimental study to theΦ38×3mm tube, and the results show that using the experimental system can realize the detection of the different defect's types of the heat-exchange tube.