EP0855595A2
Expired / Lapsed
EP
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Method and apparatus for locating coating faults on buried pipeline
Assignee: JFE Steel Corp
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Filing: 1998-01-21
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Granted: —
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Expires: 2018-01-21
Abstract
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.
Inventors
- 👤 Toshikazu c/o Kawasaki Steel Corporation Masuda
- 👤 Toshio c/o Kawasaki Steel Corporation Osada
- 👤 Shinji Gotoh
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 21:18
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/04; G01N27/20; G01N27/205; G01N17/00
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
76 words
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.
Claim 2
Dependent Claim
166 words
The method of claim 1, wherein the detecting step includes: arranging each coil of the at least one pair of search coils so that the
axes of the search coils are spaced from each other by a distance in a direction
such that a line interconnecting the axes of the search coils crosses a plane
orthogonal to an axis of the buried pipe, the axes being arranged so as to have a
low sensitivity to a magnetic field generated by the base electric signal running in
the buried pipe; moving the at least one pair of search coils along a direction of the
buried pipe; and finding a disorder of a magnetic field generated by the leakage
current from the coating fault in the buried pipe by finding an output differential of
the at least one pair of search coils, wherein the base electric signal is used as a
reference signal to synchronously detect the output differential of the at least one
pair of search coils.
Claim 3
Dependent Claim
29 words
The method of claim 2, wherein the reference signal is transmitted
from the source via radiowaves to a unit that synchronously detects the output
differential of the search coils.
Claim 4
Dependent Claim
32 words
The method of claim 2, wherein the reference signal is generated at
a location of the search coils by detecting the base electric signal running in the
buried pipe using monitor coils.
Claim 5
Dependent Claim
32 words
The method of claim 2, wherein the reference signal is generated by
an additional electric signal generator that generates the reference signal to have a
same frequency as the base electric signal.
Claim 6
Dependent Claim
21 words
The method of claim 2, wherein the synchronous detecting uses a 90
degree phase difference between outputs of the search coils.
Claim 7
Dependent Claim
24 words
The method of claim 1, further comprising the step of identifying
locations of the coating faults on a map using a Global Positioning System.
Claim 8
Independent Claim
90 words
An apparatus for locating coating faults on a buried pipe,
comprising: 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.
Claim 9
Dependent Claim
27 words
The apparatus of claim 8, further comprising a pair of monitor coils
mounted on the movable carriage to detect the base electric signal in the buried
pipe.
Claim 10
Dependent Claim
39 words
The apparatus of claim 8, wherein axes of the at least one pair of
coils are oriented so as to have a low sensitivity to a magnetic field generated by
the base electric signal running in the buried pipe.
Claim 11
Dependent Claim
50 words
The apparatus of claim 8, further comprising: a detector coupled to the at least one pair of search coils, the
detector executing synchronous detection of an output differential of the at least
one pair of search coils by using a reference signal that is based on the base
electric signal.
Claim 12
Dependent Claim
39 words
The apparatus of claim 11, wherein the base electric signal generator
includes a radiowave emitter, the detector includes a radiowave receiver, and the
base electric signal is transmitted from the base electric signal generator to the
detector by radiowaves.
Claim 13
Dependent Claim
36 words
The apparatus of claim 11, wherein the detector includes a pair of
monitor coils that detect the base electric signal running in the buried pipe, the
reference signal being based upon the detected base electric signal.
Claim 14
Dependent Claim
31 words
The apparatus of claim 11, wherein the detector includes an
additional electric signal generator that generates the reference signal so as to have
a same frequency as the base electric signal.
Claim 15
Dependent Claim
21 words
The apparatus of claim 8, further comprising means for visually
indicating outputs of the at least one pair of search coils.
Claim 16
Dependent Claim
14 words
The apparatus of claim 15, wherein the means for visually indicating
includes an oscilloscope.
Claim 17
Dependent Claim
15 words
The apparatus of claim 15, wherein the means for visually indicating
includes a pen recorder.
Claim 18
Dependent Claim
22 words
The apparatus of claim 15, wherein the means for visually indicating
generates a map on which the detected coating faults are identified.
Claim 19
Dependent Claim
32 words
The apparatus of claim 8, further comprising a Global Positioning
System coupled to the at least one pair of search coils to generate a map on which
the coating faults are identified.
Claim 20
Independent Claim
110 words
A method of locating coating faults on a buried pipe, comprising the
steps of: 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.
Claim 21
Dependent Claim
175 words
The method of claim 20, wherein: each search coil of the at least one pair of search coils is arranged on
the movable carriage so that axes of the search coils are spaced from each other by
a distance in a direction such that a line interconnecting the axes of the search coils
crosses a plane orthogonal to an axis of the buried pipe, the axes being arranged so
as to have a low sensitivity to a magnetic field generated by the base electric signal
running in the buried pipe; the moving step includes moving the at least one pair of search coils
along a direction of the buried pipe; and the detecting step includes finding a disorder of a magnetic field
generated by the leakage current from the coating fault in the buried pipe by
finding an output differential of the at least one pair of search coils, wherein the
base electric signal is used as a reference signal to synchronously detect the output
differential of the at least one pair of search coils.
Claim 22
Dependent Claim
24 words
The method of claim 20, further comprising the step of identifying
locations of the coating faults on a map using a Global Positioning System.
Claim 23
Independent Claim
85 words
A method of locating coating faults on a buried pipe, comprising the
steps of: 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.
Claim 24
Independent Claim
86 words
An apparatus for locating coating faults on a buried pipe,
comprising: 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.
References Cited (Backward Citations)
No citation records indexed.
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