Method and apparatus for estimating the condition of a coating on an underground pipeline
First Claim
1. A method for estimating a condition of a coating on a pipeline buried in soil using a magnetometer, comprising:
- conducting a magnetically-detected electrochemical impedance spectroscopy (MEIS) test over a plurality of locations along one or more segments of the buried pipeline; and
compensating for undesirable interfering and/or stray current signals flowing through at least one of the plurality of locations along a segment of the pipeline by providing at least one sinusoidal signal having a predominant amplitude and frequency to an output signal from the magnetometer.
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Accused Products
Abstract
Methods are provided for reducing interference from stray currents in buried pipelines/metal structures during MEIS testing or other current-sensing applications in the pipeline. Methods are also provided for measuring bulk complex electrical impedance between a buried pipe and the soil, thereby rendering an indication of the quality of the anti-corrosive coating. Methods are also provided for measuring the complex propagation constant of AC voltages propagating along an attenuative pipeline. This information is useful for assessing the general condition of the anti-corrosive coating involved, or to enhance MEIS inspection of the pipeline. Methods are also provided for enhancements to MEIS testing, including (a) canceling magnetometer offset effects associated with the Earth'"'"'s magnetic field after the magnetometer is positioned for measurement, (b) implementing a separate sensing connection to the pipe so as to avoid interference from voltage loss in the pipe feed-line connection, (c) providing a power amplifier to excite the pipe with large-amplitude signals.
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Citations
27 Claims
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1. A method for estimating a condition of a coating on a pipeline buried in soil using a magnetometer, comprising:
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conducting a magnetically-detected electrochemical impedance spectroscopy (MEIS) test over a plurality of locations along one or more segments of the buried pipeline; and compensating for undesirable interfering and/or stray current signals flowing through at least one of the plurality of locations along a segment of the pipeline by providing at least one sinusoidal signal having a predominant amplitude and frequency to an output signal from the magnetometer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. Apparatus for estimating a condition of a coating on a pipeline buried in soil using a magnetometer, comprising:
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means for conducting a magnetically-detected electrochemical impedance spectroscopy (MEIS) test over a plurality of locations along one or more segments of the buried pipeline; and means for compensating for undesirable interfering and/or stray current signals flowing through at least one of the plurality of locations along a segment of the pipeline by providing at least one sinusoidal signal having a predominant amplitude and frequency to an output signal from the magnetometer. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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22. Method for estimating a condition of a coating on an underground metal structure using bulk structure-to-soil spectroscopy, comprising:
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providing an AC voltage between a ground-return electrode and an injection end point of the structure via a feed line at a plurality of test frequencies; positioning a reference electrode proximate said structure; positioning a magnetometer adjacent to the feed line to sense all currents being provided to the structure; calibrating the magnetometer at a predetermined number of the test frequencies; receiving a first voltage potential value representing a difference between the voltage at the injection end point and the reference electrode; receiving a second voltage potential representing a difference between a voltage sensed by the magnetometer and the reference electrode; and computing, from the first voltage potential and the magnetometer-measured currents, a first net impedance between the structure and soil at the plurality of frequencies, thereby defining a first impedance spectrum; computing, from the second voltage potential and magnetometer measured currents, a second net impedance between the structure and the ground-return electrode at the plurality of frequencies, thereby defining a second impedance spectrum; determining the difference between the first and second net impedances and/or first or second impedance spectra, said differences providing indicia of the earthing resistance of the ground-return electrode; and analyzing the first and second impedance spectra to assess the condition of the coating on the structure under test. - View Dependent Claims (23, 24, 25, 26, 27)
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Specification