Method and apparatus for locating coating faults on buried pipelines
First Claim
1. A method of locating coating faults on a buried pipe, comprising the steps of:
- transmitting a base electric signal from a source to the buried pipe; and
detecting a location of coating faults on the buried pipe by detecting a gradient of a changing magnetic field between two points along the buried pipe caused by a leakage of current from the coating faults based upon an output differential of at least one pair of search coils, each coil of the at least one pair of search coils arranged so that axes of the search coils are spaced from each other by a distance in a direction along a length of the buried pipe such that a line interconnecting the axes of the search coils crosses a plane orthogonal to an axis of the buried pipe.
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Accused Products
Abstract
A coating fault locating technique transmits a base electric signal from a power source to a buried metal pipe. A location of a coating fault in the buried pipe is detected by detecting a gradient of a changing magnetic field between two points spaced along the buried pipe. The gradient is detected based upon the output differential of at least one pair of search coils. The gradient is caused by a leakage of current that occurs at the coating fault. In particular, the at least one pair of search coils are provided in a mobile unit that is located above ground. The at least one pair of search coils are spaced apart from one another and have their axes arranged so as to have a low sensitivity to a magnetic field generated by the base electric signal running through the buried pipe. The at least one pair of coils are spaced apart from each other such that a line drawn between midpoints of the search coils'"'"' axes crosses a plane normal to the axis of the buried pipe. For example, the at least one pair of search coils are spaced from each other horizontally, with each coil arranged with its axis extending in a vertical plane. The data detected by the search coils in the mobile unit can be transmitted to a GPS system, which then generates a map identifying the locations of any detected coating faults.
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Citations
24 Claims
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1. A method of locating coating faults on a buried pipe, comprising the steps of:
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transmitting a base electric signal from a source to the buried pipe; and detecting a location of coating faults on the buried pipe by detecting a gradient of a changing magnetic field between two points along the buried pipe caused by a leakage of current from the coating faults based upon an output differential of at least one pair of search coils, each coil of the at least one pair of search coils arranged so that axes of the search coils are spaced from each other by a distance in a direction along a length of the buried pipe such that a line interconnecting the axes of the search coils crosses a plane orthogonal to an axis of the buried pipe. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An apparatus for locating coating faults on a buried pipe, comprising:
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a movable carriage, at least one pair of search coils mounted on the movable carriage, the at least one pair of search coils spaced from each other in a moving direction of the movable carriage; and a base electric signal generator that applies a base electric signal to a buried pipe, wherein the at least one pair of search coils detects a gradient of a magnetic field resulting from leakage of current through coating faults in the buried pipe. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method of locating coating faults on a buried pipe, comprising the steps of:
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supplying a base electric signal from a source to the buried pipe; moving a movable carriage above ground in a vicinity of the buried pipe, the movable carriage including at least one pair of search coils that are spaced from each other in a movement direction of the movable carriage; and detecting a location of coating faults on the buried pipe based on currents induced in the at least one pair of search coils by a changing magnetic field caused by a leakage of current, caused by the supplied base electric signal, from the coating faults. - View Dependent Claims (21, 22)
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23. A method of locating coating faults on a buried pipe, comprising the steps of:
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detecting at least one coating fault on a buried pipe by moving a movable carriage containing a coating fault detector above ground in the vicinity of the buried pipe; transmitting position data of a position where the at least one coating fault was located to a Global Positioning System; and generating a map that indicates the position of the at least one coating fault using data from the Global Positioning System.
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24. An apparatus for locating coating faults on a buried pipe, comprising:
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a movable carriage containing a coating fault detector, the movable carriage being movable above ground in the vicinity of the buried pipe to detect coating faults in buried pipe; means for transmitting position data of a position where the at least one coating fault was located to a Global Positioning System; and means for generating a map that indicates the position of the at least one coating fault using data from the Global Positioning System.
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Specification