Study on the Distortion of Detecting Signals with the Multi-Defects in Magnetic Flux Leakage System

자기누설탐상시스템에서 밀집된 다수의 결함에 의한 탐상 신호 왜곡에 관한 연구

  • Published : 2007.05.01

Abstract

The magnetic flux leakage(MFL) type nondestructive testing(NDT) method is widely used to detect corrosion, defects and mechanical deformation of the underground gas pipelines. The object pipeline is magnetically saturated by the magnetic system with permanent magnet and yokes. Hall sensors detect the leakage fields in the region of the defect. The defects are sometimes occurred in group. The accuracy of the detecting signals in this defect cluster become lowered because of the complexity of the defect cluster. In this paper, the effects of the multi -defects are analyzed. The detecting signals are computed by 3-dimensional finite element method and compared with real measurement. The results say that, rather than the size of the defects, the effects of the relative position of the multi-defects are very important on the detecting signals.

Keywords

Nondestructive Testing(NDT);Magnetic Flux Leakage(MFL);Finite Element Method(F.E.M);Pipeline Inspection;Corrosion

References

  1. H. Haines et aI., 'Advanced MFL signal analysis aids pipe corrosion detection', Pipeline & Gas Industry, pp. 49-63, March 1999
  2. J. Bruce Nestleroth, Steven W. Rust, and David A. Burgoon, 'Determining Corrosion Defect Geometry from Magnetic Flux Leakage PIG Data', The NACE International Annual Conference and Exposition CORROSION 96, Paper No. 44, pp. 1-11, 1996
  3. S. Mandayam, L. Udpa, S. S. Udpa and W. Lord, 'Wavelet-based permeability compensation technique for characterizing magnetic flux leakage images' Data', NDT&E International, Vol. 30, No.5, pp. 297- 303, 1997 https://doi.org/10.1016/S0963-8695(96)00075-8
  4. G.S.Park, P.W.Jang, Y.W.Rho, 'Optimum Design of a Non-Destructive Testing System to Maximize Magnetic Flux Leakage', Journal of Magnetics, vol.6, no. 1, pp. 31-35, March 2001
  5. Gwan Soo Park and Eun Sik Park, 'Improvement of the Sensor System in Magnetic Flux Leakage Type Nondestructive Testing(NDT)', IEEE Trans. Magn., Vol.38, No.2, pp. 1277-1280, March 2002 https://doi.org/10.1109/20.996326