In magnetic flux leakage (MFL)-type nondestructive testing (NDT) system, the sensitivity of MFL sensor depends on the change of the magnetic field, not just on the magnitude of the field. In this paper, the leakage parameter was defined to determine the operating point in saturation curves, and an optimum design method to determine the size of the magnet to maximize the MFL signals in NDT is described. For detecting the small depth defect, we also developed the back yoke sensor system. The sensitivity of the optimum sensor system is increased up to 200%. The computed MFL signals in the optimally designed system are verified by measurement using Hall sensors mounted on the six-legged PIG in an 8-in test pipe with defects. The rhombic defects could be successfully measured and identified from the weak defect signals.
[1]
David L. Atherton,et al.
Finite element calculation of magnetic flux leakage detector signals
,
1987
.
[2]
Song-Yop Hahn,et al.
Implementation of hysteresis characteristics using the Preisach model with M-B variables
,
1992
.
[3]
A E Crouch.
IN-LINE INSPECTION OF NATURAL GAS PIPELINES.
,
1993
.
[4]
J. B. Nestleroth,et al.
Determining corrosion defect geometry from magnetic flux leakage pig data
,
1996
.
[5]
K. K. Tandon.
MFL tool hardware for pipeline inspection
,
1997
.
[6]
Y. W. Rho,et al.
Optimum Design of a Non-Destructive Testing System to Maximize Magnetic Flux Leakage
,
2001
.