Research on the magnetic flux leakage field distribution characteristics of defect in low-frequency electromagnetic detection technique

This work aimed to investigate the distribution characteristics of low-frequency magnetic flux leakage (LF-MFL) field defect on oil and gas pipelines in electromagnetic detection technique (LFET). Taking four types crack defects (rectangular, semicircular, trapezoidal, V-shaped grooves) with equal lengths, widths different bottom shapes into consideration, specific mathematical model LF-MFL was inferred established basis dipole theory. Experimental results demonstrated that variation values tangential normal component upper-lower envelope difference curves were linearly positively correlated cross-sectional area along direction, which strictly independent shape excitation conditions (amplitude, frequency lift-off).