Method and apparatus for detecting and measuring axially extending defects in ferrous tube

摘要

An apparatus for detecting and measuring axially extending defects in ferrous tube includes a magnetizing coil for inducing a longitudinal magnetic field in the ferrous tube. Linear magnetic transducers are used to detect parallel non-linking flux leakage that occurs from axially extending defects. An analog to digital converter digitizes the measured signals representing the amount of parallel non-linking flux leakage detected. A processor subtracts signals typical of ferrous tube with no axially extending defects from the measured signals. The processor further processes the resulting signals after subtraction, by separating the alternating AC components from the constant DC components to remove the effects of perpendicular flux leakage, which may exist in the measured signals. The processor then calculates the percentage of missing material due to the axially extending defects by applying a proportionality equation to the remaining DC components of the measured signals. A screen and/or printer displays to the end user the percentage of missing material detected.