Patent ID: 6239593
Filing Date: 2001-05-29
Classification: G01B,G01N

Abstract:
A system for nondestructive testing utilizing nonlinear harmonic techniques to determine mechanical damage within ferromagnetic material of a pipeline, comprising:a. means for supplying a time varying current at a fundamental frequency to a nonlinear harmonic sensor and for outputting a phase reference signal contained within a pigging device for passing through a pipeline;b. the nonlinear harmonic sensor attached to a pigging device for passage through a pipeline comprising:i. an excitation coil for generating a magnetic field within a pipeline when supplied with the time varying current as the pigging device passes through the pipeline;ii. a sensing coil for detecting a signal caused by induced magnetic field in the pipeline;c. means for amplifying and selecting a portion of the signal of step b. ii. that represents a harmonic frequency component of the signal and generating an output signal using the phase reference signal;d. means connected to the pigging device for converting the output signal to a digital harmonic signal;e. means connected to the pigging device for storing the digital harmonic signal; andf. computer means for removing probe liftoff signal components and analyzing the digital harmonic signal to detect areas of stress and plastic deformation within the pipe.