Electromagnetic analysis of concrete tensioning wires
DCFirst Claim
1. An inspection apparatus for detecting discontinuities in tensioning wires of a concrete pipe, comprising:
- (i) driver means to induce a current in a metallic pre-stressing reinforcement of a concrete pipe;
(ii) detector means to produce an output responsive to magnetic flux, the detector means spacedly disposed from said driver means and adapted to be disposed proximal to a surface of the pipe and not displaced axially along the pipe from said driver means more than one pipe diameter from a plane orthogonal to the axis of the pipe and common to said driver means;
(iii) displacement sensor means to output the distance of the inspection apparatus from a known location;
(iv) means for causing the inspection apparatus to move along the concrete pipe; and
(v) means for storing outputs corresponding to detector means and the displacement sensor means.
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Abstract
Discloses methods to perform magnetic testing of tensioning elements in a pre-stressed concrete cylinder, such as a pipe or water reservoir and testing apparatus. The apparatus includes magnetic flux production means and detector means disposed proximal to a surface of the cylinder in a plane in common with the magnetic flux production means that is orthogonal to an axis of the cylinder. The apparatus operates over a range of low frequency signals, for example, between 20 and 300 hertz or a pulse. Output of the inspection apparatus includes a signal and distance plot showing the results of testing a cylinder at one or more frequencies. In accordance with another method of analysis, a characteristic of the phase of the output over distance is plotted, including the phase or representations of the in-phase or quadrature components of the received signal in relation to the driving signal.
45 Citations
53 Claims
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1. An inspection apparatus for detecting discontinuities in tensioning wires of a concrete pipe, comprising:
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(i) driver means to induce a current in a metallic pre-stressing reinforcement of a concrete pipe;
(ii) detector means to produce an output responsive to magnetic flux, the detector means spacedly disposed from said driver means and adapted to be disposed proximal to a surface of the pipe and not displaced axially along the pipe from said driver means more than one pipe diameter from a plane orthogonal to the axis of the pipe and common to said driver means;
(iii) displacement sensor means to output the distance of the inspection apparatus from a known location;
(iv) means for causing the inspection apparatus to move along the concrete pipe; and
(v) means for storing outputs corresponding to detector means and the displacement sensor means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An inspection apparatus for detecting discontinuities in tensioning wire of a concrete cylinder, comprising:
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(i) a driver coil adapted to be oriented with an axis orthogonal to an axis of a concrete cylinder to induce a current in a tensioning wire of a concrete cylinder in response to a driving signal;
(ii) means for producing, driving signal;
(iii) detector apparatus to produce an output responsive to a magnetic flux, said detector apparatus has an axis orthogonal to the axis of said driver coil and spacedly disposed there from, said detector apparatus adapted to be oriented proximal to a surface of said concrete cylinder and substantially in a plane orthogonal to an axis of the concrete pipe in common with the driver coil; and
(iv) filter means for producing an output signal representative of differences between the driving signal and the output produced by said detector apparatus. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
(i) displacement sensor means to produce an output representative of at least one distance of the detector apparatus a from a known location;
(ii) means to cause the detector apparatus to move; and
(iii) means for storing outputs derived from the output of the filter means and said displacement sensor means.
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25. The apparatus of claim 15 wherein said filter apparatus includes a multiplier and a low pass filter.
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26. The apparatus of claim 15 wherein said filter apparatus includes a lock-in amplifier.
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27. The apparatus of claim 15 mounted on a vehicle suited to movement along a pipeline.
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28. The apparatus as claimed in claim 15 wherein said driver means comprises a coil adapted to be oriented with an axis that is oriented radial to the cylinder.
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29. The apparatus as claimed in claim 28, in which the driver coil is spacedly disposed from said detector apparatus to be adapted to be positioned diametrically across the concrete cylinder from said detector apparatus.
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30. Apparatus for detecting discontinuities in spirally wound metallic pre-stressing reinforcements embedded in the wall of a concrete pipe or substantially cylindrical fluid containment structure having a longitudinal axis, comprising:
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(i) a driver coil having an axis which is radial to the longitudinal axis, for generating a periodically varying current in the spirally wound metallic prestressing reinforcements;
(ii) a detector oriented to lie along the wall surface of a concrete pipe or structure to be monitored, said detector being capable of detecting magnetic flux flowing in a direction parallel to the longitudinal axis of the pipe or structure;
(iii) means for causing the detector to move along the surface of such pipe or structure;
(iv) means for determining at least one of the location of the detector or the distance it has moved from a known original location; and
(v) means for recording the magnetic flux recorded by the detector and recording it in association with the location of the detector when such flux was detected or the distance that the detector has moved from an original known location when such flux was detected. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53)
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Specification