A quantitative study of signal characteristics of non-contact pipeline magnetic testing

Non-contact pipeline magnetic testing (NPMT) is a novel and non-destructive technology based on the metal magnetic memory (MMM) method, which can detect pipeline defects under trenchless conditions. There is a peak on the gradient modulus of the ground leakage magnetic field (GLMF), which is a signal characteristic of a defect. In this study, the physical principles of this technology were first discussed. Next, a spatial distribution model of the GLMF was built based on the theories of magnetic charge and magnetic dipole, which indicates the quantitative relationship between the defect and GLMF. The effects of the model parameter values on the gradient modulus were also discussed. The reliability of the model was verified by comparing the field testing signal with the model calculated value. Directions of further research are formulated, including factors affecting the model accuracy and the classification of defects.