MFLThe current magnetic flux leakage (MFL) inspection technique can detect and locate defects on both the internal and external walls of drill pipe, but is generally unable to differentiate between internal and external defects. This paper presents a new method to distinguish between internal and external defects based on weak magnetic inspection. The study is undertaken using extensive finite element analysis (FEA), focusing on the 3D magnetic field distribution of internal and external defects in both strong and weak magnetic regions. Through the 3D magnetic flux density vector diagram and the axial and radial component diagram of the magnetic leakage field of the defects, the characteristics of the magnetic leakage field around defects are obtained intuitively, which demonstrates that weak magnetic inspection can be used as a method for internal and external defect recognition. The experimental test results show that such discrimination is viable using weak magnetic inspection.Keywords: 3D FEM, magnetic flux leakage testing, weak magnetic inspection, internal and external defect identification.
MFLThe magnetic flux leakage (MFL) technique is generally considered to be an efficient and effective non-destructive testing (NDT) method and has been widely used in the oil field inspection industry for the examination of drill pipe. This paper studies the resistance distribution in the magnetic circuit of magnetic flux leakage detection probes and proposes the method of adding a pole piece to reduce magnetic resistance. The magnetic circuit model is simulated by using finite element analysis and the results show that the detection probe with a pole piece can strengthen the magnetic leakage signal for a drill pipe defect, and pole pieces with different thicknesses have little influence on the defect magnetic leakage signal in the circuit. Practical testing confirms that the probe with a pole piece can clearly improve the SNR of the MFL signal. The analysis results are of great value for improving defect identification rates and for the precise detection of defects.This book will provide guidance on the subject of Infrared Thermography (IRT), namely heat transfer theory, equipment selection, applications and operational factors; and as such can be used as an information source to support IRT operations. Volume 2: Applications by A N NowickiThis book is aimed at thermographers who have attained at least Level 1 accreditation in IRT. It is recommended that the reader also has some operational experience in order to have the required level of knowledge to understand the terminology and diagnostic descriptions included.
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