Transient electromagnetic method for detecting irregularies on conductive containers having variations in jacket thickness
First Claim
1. A method for detecting irregularities on electrically conductive walls of container means, comprising the steps of:
- (a) providing transmitting antenna means and transmitter means connected with said transmitting antenna means;
(b) providing receiving antenna means and receiver means connected with said receiving antenna means;
(c) placing said transmitting antenna means in proximity to that portion of the container means wall which is to be investigated;
(d) placing said receiving antenna means in proximity to the container means wall portion and in proximity to said transmitting antenna means, said receiving antenna means being separated from said transmitting antenna means;
(e) providing an abruptly changing current to said transmitting antenna means from said transmitter means so as to induce current into the container means wall portion;
(f) detecting the presence of and the decay of said induced current in said container means wall portion with said receiving antenna means to produce a received signal, said received signal having an intermediate time range and a late time range, said received signal having a maximum occurring in the intermediate or late time ranges, said received signal having an arrival time which is the time when said maximum occurs;
(g) examining said received signal to determine the maximum of said received signal and examining the received signal to determine the arrival time of said maximum, said maximum and said arrival time providing an indication of the presence or absence of irregularities in said container means wall portion, wherein the presence of irregularities is indicated by a maximum which is greater than a maximum obtained from an irregularity-free container means wall portion.
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Abstract
A transient electromagnetic method for detecting irregularities on container walls by measuring wall thickness. The method utilizes a transmitting antenna and separate receiving antennas so as to form a loop-loop configuration. The transmitting antenna induces current into the container wall and the receiving antennas detect the induced current and produce received signals. The distance between the antennas and the container wall can vary, particularly where insulation is interposed therebetween. The variations in antenna distance affects the received signals. The affects are corrected by determining the maximum of the respective received signal and determining the arrival time of the maximum. The maximum and the arrival time are used to determine the thickness of the wall.
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Citations
29 Claims
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1. A method for detecting irregularities on electrically conductive walls of container means, comprising the steps of:
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(a) providing transmitting antenna means and transmitter means connected with said transmitting antenna means; (b) providing receiving antenna means and receiver means connected with said receiving antenna means; (c) placing said transmitting antenna means in proximity to that portion of the container means wall which is to be investigated; (d) placing said receiving antenna means in proximity to the container means wall portion and in proximity to said transmitting antenna means, said receiving antenna means being separated from said transmitting antenna means; (e) providing an abruptly changing current to said transmitting antenna means from said transmitter means so as to induce current into the container means wall portion; (f) detecting the presence of and the decay of said induced current in said container means wall portion with said receiving antenna means to produce a received signal, said received signal having an intermediate time range and a late time range, said received signal having a maximum occurring in the intermediate or late time ranges, said received signal having an arrival time which is the time when said maximum occurs; (g) examining said received signal to determine the maximum of said received signal and examining the received signal to determine the arrival time of said maximum, said maximum and said arrival time providing an indication of the presence or absence of irregularities in said container means wall portion, wherein the presence of irregularities is indicated by a maximum which is greater than a maximum obtained from an irregularity-free container means wall portion. - View Dependent Claims (2, 3, 4)
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5. A method for detecting irregularities on electrically conductive walls of container means, comprising the steps of:
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(a) providing transmitting antenna means and transmitter means connected with said transmitting antenna means; (b) providing receiving antenna means and receiver means connected with said receiving antenna means; (c) placing said transmitting antenna means in proximity to that portion of the container means wall which is to be investigated; (d) placing said receiving antenna means in proximity to the container means wall portion and in proximity to said transmitting antenna means, said receiving antenna means being separated from said transmitting antenna means; (e) providing an abruptly changing current to said transmitting antenna means from said transmitter means so as to induce current into the container means wall portion; (f) detecting the presence of and the decay of said induced current in said container means wall portion with said receiving antenna means to produce a received signal, said received signal having an intermediate time range and a late time range, said received signal having a maximum occurring in the intermediate or late time ranges, said received signal having an arrival time which is the time when said maximum occurs; (g) examining said received signal to determine the maximum of said received signal and examining the received signal to determine the arrival time of said maximum; (h) comparing said arrival time of said maximum to the arrival times of other maximums of other received signals obtained from other portions of the container means wall; (i) selecting the maximums of said other received signals that have arrival times similar to said maximum of said investigated container means wall portion, and comparing said maximum of said investigated container means wall portion to the selected maximums of said other portions of the container means wall. - View Dependent Claims (6, 7, 8)
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9. A method for detecting irregularities on electrically conductive walls of container means, comprising the steps of:
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(a) providing transmitting antenna means and antenna means; (b) providing receiving antenna means and receiver means connected with said receiving antenna means; (c) placing said transmitting antenna means in proximity to that portion of the container means wall which is to be investigated; (d) placing said receiving antenna means in proximity to the container means wall portion and in proximity to said transmitting antenna means, said receiving antenna means being separated from said transmitting antenna means; (e) providing an abruptly changing current to said transmitting antenna means from said transmitter means so as to induce current into the container means wall portion; (f) detecting the presence of and the decay of said induced current in said container means wall portion with said receiving antenna means to produce a received signal, said received signal having an intermediate time range and a late time range, said received signal having a maximum occurring in the intermediate or late time ranges, said received signal having an arrival time which is the time when said maximum occurs; (g) determining the maximum and the arrival time of the received signal and comparing the maximum and the arrival time of the received signal to reference maximums and reference arrival times to determine the wall thickness of said container means wall portion, said reference maximums and reference arrival times obtained from reference container means with known wall thicknesses. - View Dependent Claims (10, 11, 12, 13)
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14. A method for detecting irregularities on electrically conductive walls of container means, comprising the steps of:
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(a) providing transmitting antenna means and transmitter means connected with said transmitting antenna means; (b) providing receiving antenna means and receiver means connected with said receiving antenna means; (c) placing said transmitting antenna means in proximity to that portion of the container means wall which is to be investigated; (d) placing said receiving antenna means in proximity to the container means wall portion and in proximity to said transmitting antenna means, said receiving antenna means being separated from said transmitting antenna means; (e) providing an abruptly changing current to said transmitting antenna means from said transmitter means so as to induce current into the container means wall portion; (f) detecting the presence of and the decay of said induced current in said container means wall portion with said receiving antenna means to produce a received signal, said received signal having an initial portion occurring immediately after said abruptly changing current is provided to said transmitting antenna means, said received signal also having a maximum occurring after said initial portion, said received signal having an arrival time which is the time when said maximum occurs; (g) determining the maximum and the arrival time of said received signal and comparing the maximum and the arrival time of said received signal to a maximum and its respective arrival time of a reference signal, said reference signal being obtained from a reference container means. - View Dependent Claims (15, 16, 17)
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18. A method for detecting irregularities on electrically conductive walls of container means, comprising the steps of:
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(a) providing transmitting antenna means and transmitter means connected with said transmitting antenna means; (b) providing receiving antenna means and receiver means connected with said receiving antenna means; (c) placing said transmitting antenna means and said receiving antenna means in proximity to that portion of the container means wall which is to be investigated such that said transmitting antenna means and said receiving antenna means are separated from said container means wall portion, said receiving antenna means being separated from said transmitting antenna means; (d) providing an abruptly changing current to said transmitting antenna means from said transmitter means so as to induce current into the current means wall portion; (e) detecting the presence of and the decay of said induced current in said container means wall portion with said receiving antenna means to produce a received signal, said received signal having an initial portion occurring immediately after said abruptly changing current is provided to said transmitting antenna means, said received signal also having a maximum occurring after said initial portion, said received signal having an arrival time which is the time when said maximum occurs; (f) determining the maximum and the arrival time of said received signal and comparing the maximum and the arrival time of said received signal to a maximum and its respective arrival time of a reference signal, said reference signal being obtained from a reference container means. - View Dependent Claims (19)
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20. A method for detecting irregularities on electrically conductive walls of container means, comprising the steps of:
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(a) providing transmitting antenna means and transmitter means connected with said transmitting antenna means; (b) providing receiving antenna means and receiver means connected with said receiving antenna means; (c) placing said transmitting antenna means in proximity to that portion of the container means wall which is to be investigated; (d) placing said receiving antenna means in proximity to the container means wall portion and in proximity to said transmitting antenna means, said receiving antenna means being separated from said transmitting antenna means; (e) energizing said transmitting antenna means with current for a sufficient period of time to stabilize the magnitude of the current in said transmitting antenna means, and then abruptly deenergizing said transmitting antenna means so as to induce current into the container means wall portion; (f) detecting the presence of and the decay of said induced current in said container means wall portion with said receiving antenna means to produce a received signal, said received signal having an initial portion occurring immediately after said transmitting antenna means is abruptly deenergized, said received signal also having a maximum occurring after said initial portion, said received signal having an arrival time which is the time when said maximum occurs; (g) determining the maximum and the arrival time of said received signal and comparing the maximum and the arrival time of said received signal to a maximum and its respective arrival time of a reference signal, said reference signal being obtained from a reference container means. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28)
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29. A method for detecting corrosion on electrically conductive walls of container means, said corrosion acting to reduce the wall thickness of said conductive wall, comprising the steps of:
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(a) providing transmitting antenna means and transmitter means connected with said transmitting antenna means; (b) providing receiving antenna means and receiver means connected with said receiving antenna means; (c) placing said transmitting antenna means in proximity to that portion of the container means wall which is to be investigated; (d) placing said receiving antenna means in proximity to the container means wall portion and in proximity to said transmitting antenna means, said receiving antenna means being separated from said transmitting antenna means; (e) providing an abruptly changing current to said transmitting antenna means from said transmitter means so as to induce current into the container means wall portion; (f) detecting the presence of and the decay of said induced current in said container means wall portion with said receiving antenna means to produce a received signal, said received signal having an initial portion occurring immediately after said abruptly changing current is provided to said transmitting antenna means, said received signal also having a maximum occurring after said initial portion, said received signal having an arrival time which is the time when said maximum occurs; (g) determining the maximum and the arrival time of the received signal and comparing the maximum and the arrival time of the received signal to reference maximums and reference arrival times to determine the wall thickness of said container means wall portion, said reference maximums and reference arrival times obtained from reference container means with known wall thicknesses.
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Specification