JP2005134159A - Metal touch portion detecting method for buried metal tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for locating a metal touch portion when a buried metal tube is in metal-touch with another metal tube buried in parallel therewith. <P>SOLUTION: This method is for detecting the metal touch portion of the buried metal tube with an anticorrosive coating with the other metal tube close-buried in parallel therewith. AC signals of different frequencies are applied to the buried metal tube and to the ground from both the sides of an objective zone of detection. The intensity of a magnetic field is measured by moving magnetometric sensors disposed on a ground surface to each of measurement points placed at prescribed intervals in the extension direction of the buried metal tube while scanning in the orthogonal direction. By signal-processing obtained data, changes in the intensity of the magnetic field are compared with each other at respective measurement points corresponding to the signals of different frequencies, thereby determining whether there is a metal touch portion, and its location. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for identifying the presence and position of a metal touch in which a buried metal pipe is in contact with another metal pipe and a base metal, and in particular, buried in parallel with a buried metal pipe to be investigated. The present invention relates to a method for detecting a metal touch portion of another metal tube.

(1)
ここで、μ_０は真空の透磁率（Ｈ／ｍ）、μ_Ｓは媒質の比透磁率である。
磁界Ｂは、指向性を持つ磁気センサ５を用いて水平成分ｘの磁界強度Ｂｘと鉛直成分ｚの磁界強度Ｂｚとに分離して測定することが出来る。例えば、図１０において磁気センサ５が埋設金属管の管軸方向と直交する方向にＰ１からＰ３まで地表面を走査すると、ＢｘはＰ２の地点、すなわち埋設金属管１の直上で極大となり左右に離れるに従い減少する。また、Ｂｚ埋設金属管１の直上に接近するに従って減少し、直上で零となりその後極性が反転して埋設金属管から離れるに従って大きくなる。これらの結果から埋設金属管の位置を知ることが出来るためパイプロケータとしても用いられる。
上記測定手段を用いてメタルタッチ部を検出する場合、磁気センサ５を金属管１の直上の地表面を管軸方向に沿ってＰ２からＰ５に走査させると、図１１に示すように他の金属管２が交差状にメタルタッチしている場所３の直上Ｐ７で信号電流の流入状態が変化するため磁界強度Ｂｘが大きく変化するため、この点をメタルタッチ部３であると判定できる。 When the buried metal pipe with the anticorrosion coating comes into contact with another metal pipe (buried object) by piping work or the like and damages the anticorrosion coating and makes a metal touch with the base metal, corrosion of the buried metal pipe proceeds from that portion. In addition, a buried metal pipe that has been subjected to electrocorrosion has an adverse effect that the designed anticorrosion current cannot be maintained and the effect of electrocorrosion cannot be exhibited normally. For this reason, it is necessary to identify the presence and position of the metal touch from the viewpoint of good maintenance of the buried metal pipe, and to take immediate measures if the metal touch is recognized.
As a method of specifying the metal touch position 3 of the metal pipe 1 buried in the ground, as shown in FIG. 10, a signal current is passed from the signal transmitter 6 to the buried metal pipe 1 to be investigated, and the buried metal pipe 1 There is a method of detecting the magnetic field generated around by the current flowing through the magnetic sensor 5 using the magnetic sensor 5 using a probe coil, a Hall element, etc., and identifying the change point of the detection signal to identify the metal touch position 3. (Nick J. Frost: “Electromagnetic techniques to monitor pipe line coatings”, “PIPE LINE INDUSTRY” September 1988, p33-35)
According to this document, a magnetic field B (T) expressed by the equation (1) is generated at a distance r from the center of the buried metal tube 1 by the current I flowing through the buried metal tube 1.

(1)
Here, μ ₀ is the vacuum magnetic permeability (H / m), and μ _S is the relative magnetic permeability of the medium.
The magnetic field B can be measured by separating the magnetic field strength Bx of the horizontal component x and the magnetic field strength Bz of the vertical component z using the magnetic sensor 5 having directivity. For example, in FIG. 10, when the magnetic sensor 5 scans the ground surface from P1 to P3 in a direction perpendicular to the tube axis direction of the buried metal tube, Bx becomes a maximum at the point P2, that is, directly above the buried metal tube 1, and moves left and right. It decreases according to. Moreover, it decreases as it approaches directly above the Bz buried metal tube 1, becomes zero immediately above, and then increases as the polarity reverses and moves away from the buried metal tube. Since the position of the buried metal pipe can be known from these results, it is also used as a pipe locator.
When the metal touch part is detected using the measuring means, when the magnetic sensor 5 scans the ground surface immediately above the metal tube 1 from P2 to P5 along the tube axis direction, another metal as shown in FIG. Since the inflow state of the signal current changes at the position P7 directly above the place 3 where the tube 2 is metal touching in an intersecting manner, the magnetic field strength Bx changes greatly, so that this point can be determined to be the metal touch part 3.

Japanese Patent Laid-Open No. 2001-215204 discloses a metal touch investigation method for buried metal pipes. This investigation method digs holes 3a to 3e of about 8 to 10 mm at a plurality of locations above the buried pipe 1 around an area where metal touch is suspected as shown in FIG. 12, and the tip of the casing 101 as shown in FIG. A pin terminal 103 having a tapered electrode 102 with a built-in heater attached thereto is brought into contact with the buried pipe 1 and heated to dissolve the coating so that the electrode is brought into contact with the metal substrate of the buried pipe. The metal touch position is specified by measuring a voltage drop between adjacent pin terminals 103 while flowing a constant current.
In addition, by providing energization points upstream and downstream of the buried pipe to which a plurality of pin terminals 103 are connected, and measuring the voltage drop between the pin terminals 103 by alternately passing a direct current 104, the other metal pipes 2 of the metal touch The position can be specified. Note that the repaired cap is repaired by using the heater of the tapered electrode 102 at the peeling part of the coating covering damaged after the investigation.
“PIPE LINE INDUSTRY” September 1988, p33-35) JP 2001-215204 A

However, in the method according to Non-Patent Document 1, when the buried metal pipe to be investigated and another metal pipe buried in parallel are in metal touch as shown in FIG. Identification becomes difficult. This is because when the magnetic sensor 5 scans the ground surface from P1 to P3 in a direction orthogonal to the tube axis direction of the buried metal tube as described above, the magnetic field strength is generated from the buried metal tube 1 to be investigated and the other metal tube 2. A combined magnetic field is detected, and a Bx maximum appears at an intermediate position between the buried pipes 1 and 2, and the polarity of Bz is reversed, and the change in the magnetic field strength B due to the presence of the metal touch 3 does not appear.
When the magnetic sensor 5 is scanned from P2 to P5 along the tube axis direction on the ground surface immediately above the metal tube 1, the value of the combined current I flowing through the buried metal tube 1 and the other metal tube 2 does not change. Therefore, the metal touch part 3 cannot be detected.
In addition, the metal touch investigation method according to Patent Document 1 is an improvement of the conventional method for measuring the in-tube current. However, in the case of concrete implementation, when the pin terminal 103 of the measurement point is provided, The buried metal tube 1 is previously embedded in order to dig down the holes 3a to 3e of about 10 mm from directly above the tube 1 to the upper surface of the buried metal tube 1 to remove the earth and sand in the hole and bring the special electrode 102 into contact with the metal substrate of the buried metal tube. It is necessary to obtain the exact position of the pin terminal 103, and the installation work of the pin terminal 103 is complicated.
Further, since the pin terminal 103 melts the coating of the buried metal tube 1 and contacts the special electrode 102 to the metal substrate, there is a concern that the anticorrosion performance is deteriorated even if the pin terminal 103 is repaired after the investigation. Moreover, when the coating of the buried metal pipe 1 is a hard polyethylene coating, a high temperature is required to melt the coating and expose the metal substrate, and there is a problem that it is difficult to melt.

The gist of the present invention is as follows.
(1) A method of detecting a metal touch part between a buried metal pipe coated with anti-corrosion and another metal pipe buried in close proximity in parallel to the buried metal pipe and the ground from both sides of the detection target section. Obtained by measuring the magnetic field intensity by applying a first signal current and a second signal current and scanning a magnetic sensor that scans the ground surface in the direction perpendicular to the tube axis at each measurement point in the extension direction of the buried metal tube. The data processing is performed to compare the change in the magnetic field strength at each measurement location corresponding to the first signal current and the second signal current, and the presence / absence of the metal touch part and the position of the metal touch part are specified. It is a metal touch part detection method of a buried metal pipe.
(2) In the metal touch part detection method of another metal pipe parallel to the buried metal pipe in the invention of (1) above, the magnetic sensor is arranged to detect a horizontal component magnetic field in the direction perpendicular to the pipe axis. The position of occurrence of the maximum value of the magnetic field strength corresponding to the first signal current and the second signal current is compared from the measurement data of the magnetic field strength when scanned in the direction perpendicular to the tube axis at each measurement location, and the presence or absence of the metal touch portion And the metal touch part position is specified.
(3) In the metal touch part detection method of another metal pipe parallel to the buried metal pipe in the invention of (1) above, a magnetic sensor is arranged so as to detect a vertical component magnetic field, and Compare the occurrence position of the minimum value of the magnetic field intensity corresponding to the first signal current and the second signal current from the measurement data of the magnetic field intensity when scanned in the direction perpendicular to the tube axis, and the presence or absence of the metal touch part and the position of the metal touch part Is identified.
(4) In the metal touch part detection method of another metal pipe parallel to the upper or lower side with respect to the buried metal pipe in the invention of (1) above, the magnetic sensor detects the horizontal component magnetic field in the direction perpendicular to the pipe axis. The first signal current and the first signal current are obtained from the measurement data of the maximum value of the magnetic field intensity when two stages are arranged at a predetermined interval and scanned in the direction perpendicular to the tube axis of the two-stage magnetic sensor at each measurement point. The apparent depth of the buried metal pipe corresponding to the two-signal current is calculated, and the value is compared to specify the presence / absence of the metal touch part and the metal touch part position.
(5) In the metal touch detection method of another metal pipe parallel to the oblique position with respect to the buried metal pipe in the invention of (1) above, the magnetic sensor detects a horizontal component magnetic field in the direction perpendicular to the pipe axis of the buried metal pipe. The first signal is obtained from the measurement data of the magnetic field intensity when scanning in the orthogonal direction of one or both of the magnetic sensors at each measurement location. The position of occurrence of the maximum value of the magnetic field strength corresponding to the current and the second signal current is obtained, and from the measurement data of the maximum value of the magnetic field strength when scanned in the direction perpendicular to the tube axis of the two-stage magnetic sensor, The depth is calculated, the presence / absence of the metal touch part and the metal touch part position are specified by comparing the generation position of the maximum value of the magnetic field strength and the calculation depth of the buried metal pipe.
(6) A method of detecting a metal touch part between a buried metal pipe coated with anti-corrosion and another metal pipe buried in close proximity in parallel to the buried metal pipe and the ground from both sides of the detection target section. A magnetic sensor that applies the first signal current and the second signal current and scans the ground surface is arranged so as to detect the magnetic field of the vertical component, and the minimum value of the magnetic field strength of the vertical component corresponding to the first signal current The change in the magnetic field strength of the vertical component corresponding to the second signal current is measured while tracking the extending direction of the buried metal tube along the position of the position, or the magnetic field strength of the vertical component corresponding to the second signal current is minimized. The change in the magnetic field strength of the vertical component corresponding to the first signal current is measured while tracing the extension direction of the buried metal tube along the position of the value, and the obtained data is subjected to signal processing to obtain the second signal current. Or change in magnetic field intensity corresponding to the first signal current. Compared to identify the presence and metal touch portion position of the metal touch portion.
(7) In the above (1) to (6), the first signal current and the second signal current applied to the buried metal pipe and the ground from both sides of the detection target section are simultaneously energized with AC signals having different frequencies. It is desirable to do.
(8) In the above (1) to (6), the data obtained by the magnetic sensor is signal-processed to obtain a magnetic field intensity corresponding to a different frequency signal, and is applied to the buried metal tube and the ground. It is desirable to use a lock-in amplifier that uses a reference signal having the same frequency as the signal frequency to be transmitted.

According to the present invention, a magnetic sensor that scans the ground surface at a metal touch position with another metal pipe that is close to the buried metal pipe in parallel with the buried metal pipe, which has been difficult in the past, can be obtained without damaging the buried metal pipe. It is possible to identify well.
That is, in this invention, a 1st signal transmitter and a 2nd signal transmitter are installed in the both sides of the investigation range of the buried metal pipe used as investigation object, and two signal currents are supplied with electricity between the buried metal pipe and the ground. This signal current flows out from the grounding poles of two transmitters to the ground, forms a closed loop that flows from the ground into the buried metal pipe and returns to the transmitter. If a metal touch part exists in the buried metal pipe and other metal pipes to be investigated, the magnetic field strength generated around both buried pipes (buried metal pipe and other metal pipes) is changed by two signal currents. It is possible to determine the presence and position of the metal touch portion by measuring the change in strength by a magnetic sensor that scans in the direction perpendicular to the tube axis at each measurement location in the extending direction of the buried metal tube.
In order to detect the metal touch part of another metal pipe that is parallel to the buried metal pipe, the magnetic sensor is scanned in the direction perpendicular to the pipe axis, and the magnetic component of the horizontal component (x) is detected. The intensity is measured to compare the occurrence position of the minimum value of the magnetic field intensity corresponding to the first signal current and the second signal current, and the presence / absence of the metal touch part and the metal touch part position are specified.
According to a third aspect of the present invention, the magnetic sensor is disposed so as to detect the magnetic field of the vertical component (z), and the generation position of the minimum value of the magnetic field intensity corresponding to the first signal current and the second signal current is compared. The presence or absence of the metal touch part and the position of the metal touch part may be specified.
Further, in order to detect the metal touch part of another metal pipe parallel to the upper side or the lower side with respect to the buried metal pipe to be investigated, as shown in claim 4, the magnetic sensor has a horizontal component magnetic field in the direction perpendicular to the pipe axis. From the measurement data of the maximum value of the magnetic field strength when scanning in the direction perpendicular to the tube axis of the two-stage magnetic sensor at each measurement location. The apparent depth of the buried metal pipe corresponding to the signal current and the second signal current is calculated, and the value is compared to specify the presence / absence of the metal touch portion and the position of the metal touch portion.
In order to detect the metal touch part of another metal pipe parallel to the oblique position with respect to the buried metal pipe, as shown in claim 5, the magnetic sensor detects a horizontal component magnetic field in the direction perpendicular to the pipe axis of the buried metal pipe. The first signal is obtained from the measurement data of the magnetic field intensity when scanning in the orthogonal direction of one or both of the magnetic sensors at each measurement location. The position of occurrence of the maximum value of the magnetic field strength corresponding to the current and the second signal current is obtained, and from the measurement data of the maximum value of the magnetic field strength when scanned in the direction perpendicular to the tube axis of the two-stage magnetic sensor, The depth is calculated, the presence / absence of the metal touch part and the metal touch part position can be specified by comparing the generation position of the maximum value of the magnetic field intensity and the calculation depth of the buried metal pipe.
In addition, in the method of detecting a metal touch part with another metal pipe embedded in close proximity in parallel, a first signal current and a second signal current are applied to the embedded metal pipe and the ground from both sides of the detection target section. A magnetic sensor that scans the ground surface is arranged so as to detect the magnetic field of the vertical component, and extends in the extending direction of the buried metal tube along the position of the minimum value of the magnetic field strength of the vertical component corresponding to the first signal current. Measure the change in the magnetic field strength of the vertical component corresponding to the second signal current while tracking, or extend the buried metal tube along the position of the minimum value of the magnetic field strength of the vertical component corresponding to the second signal current The change in the magnetic field strength of the vertical component corresponding to the first signal current is measured while tracking, and the obtained data is subjected to signal processing to change the magnetic field strength corresponding to the second signal current or the first signal current. Compare the metal touch part There free and also a method for identifying a metal touch portion position.
In the present invention, as described above, when the metal touch portion exists, the change in the magnetic field strength Bx corresponding to the first signal current and the second signal current, that is, the maximum position of the horizontal magnetic field strength Bx or the vertical magnetic field strength Bz. Since the relative shift of the zero point position is reversed with the metal touch part as a boundary, the inverted intersection part can be specified as the metal touch part. (When there is no metal touch, the peak position or zero point position of the magnetic field intensity corresponding to the first signal current and the second signal current does not change, and can be determined)
In the present invention, since the two signal currents of the first signal current and the second signal current are used to specify the presence and position of the metal touch part, the maximum position of the magnetic field strength Bx or the zero point of the magnetic field strength Bz of the vertical component It is possible to accurately determine whether the change in the relative displacement of the position is due to the metal touch or the bending of the buried metal pipe.

Hereinafter, a method for detecting a metal touch part of a buried metal pipe according to the present invention will be described with reference to the drawings.
FIG. 1 is an example showing an embodiment of the present invention, and shows an overall configuration for detecting a metal touch position of another metal tube 2 that is embedded in parallel with the buried metal tube 1 to be investigated. .
The first signal transmitter 6 and the second signal transmitter 8 are installed on both sides of the investigation range of the buried metal pipe 1 to be investigated, and signal currents Ia and Ib are energized between the buried metal pipe 1 and the ground. This signal current flows out from the ground electrodes 7 and 9 of the transmitters 6 and 8 to the ground, forms a closed loop that flows from the ground into the buried metal tube 1 and returns to the transmitters 6 and 8. In this embodiment, the magnetic field strength of the magnetic field generated around the signal currents Ia and Ib flowing in the buried metal tube 1 is measured by the magnetic sensor 5 that scans the ground surface in the direction orthogonal to the tube axis, and is parallel to the buried metal tube 1. Thus, the presence and position of the metal touch part 3 of another metal tube 2 embedded in the metal pipe 2 are detected.

The signal currents Ia and Ib applied to the buried metal pipe 1 are energized from the first signal transmitter 6 and the second signal transmitter 8 installed on both sides of the survey range. This signal current is preferably supplied with alternating currents of different frequencies at the same time. However, the alternating current of the same frequency may be supplied by switching the timing, or a single signal transmitter may be moved. You may make it energize from one place.
In the case where alternating currents of different frequencies are simultaneously applied, the magnetic sensor 5 needs to be measured only once for each measurement location, and there is an advantage that highly accurate measurement data under the same conditions can be obtained.
When the signal current of the same frequency is switched or moved and energized, the magnetic sensor 5 makes the tube axis orthogonal at the same measurement location each time the first signal transmitter 6 side and the second signal transmitter 8 side are energized. It is necessary to measure the magnetic field strength in the direction.

FIG. 1 shows an embodiment in which alternating currents Ia and Ib having different frequencies are used for the first signal transmitter 6 and the second signal transmitter 8. When the signal currents Ia and Ib having two different frequencies are used, it is necessary to separate the magnetic field intensity corresponding to the signal current of each frequency. Therefore, the signal corresponding to the first signal current Ia that processes the signal of the magnetic sensor 5 The first signal processing device 12 for processing the signal and the second signal processing device 13 for processing the signal corresponding to the second signal current Ib.
The first signal processing device 12 and the second signal processing device 13 desirably use a lock-in amplifier provided with a reference signal transmitter. When a lock-in amplifier is used, the output of the magnetic sensor 5 is input in parallel to the first lock-in amplifier and the second lock-in amplifier, and each frequency of the reference signal transmitter of each lock-in amplifier is set to the first signal transmitter 6. And the frequency of the second signal transmitter 8 and the magnetic field strength of only the frequency component corresponding to the first signal transmitter 6 and the second signal transmitter 8 from the magnetic field strength data input from the magnetic sensor with high accuracy. Can be separated and output to the display device 14.
Further, the display device 14 includes a distance measuring circuit 15 for calculating a distance by a wheel 11 to which a rotation signal generator such as an encoder is attached in order to display a scanning distance of the magnetic sensor 5.
The magnetic sensor 5, the signal processing device (12, 13), the distance measuring circuit 15, the display device 14, etc. are mounted on a measuring carriage 10 with wheels, and a tube axis for each measuring point in the extending direction of the buried metal tube 1. Travel in the orthogonal direction and measure the magnetic field strength and travel distance.
The dotted line shown in the orthogonal direction on the buried metal tube 1 in FIG. 1 is the measurement scanning line of the magnetic sensor. The frequency of the alternating current IaIb used in the first signal oscillator 6 and the second signal generator 8 is several tens Hz to 750 Hz. Use different frequencies selected from a range of frequencies. However, if a frequency multiplied by 50 Hz and 60 Hz of the commercial frequency is used, noise is superposed, so the use of this frequency must be avoided.
Note that if the difference between the two frequencies used is too small, the signal of the other frequency may be detected. Therefore, the frequencies of the two signal currents Ia and Ib to be used are frequencies separated by several tens of Hz or more. There is a need. For example, when the frequency of the first signal oscillator 6 is 220 Hz and the frequency of the second signal generator 8 is 320 Hz, preferable results are obtained.

FIG. 2 shows the metal of another metal tube 2 in the vicinity when the signal currents Ia and Ib flow from the first signal transmitter 6 and the second signal transmitter 8 installed on both sides of the investigation target range to the buried metal tube 1. The magnitudes of currents at various places when the touch unit 3 is present are shown. Assuming that the first signal oscillator 6 side is A and the second signal generator 8 side is B at the metal touch position 3, the signal current corresponding to the first signal current is on the A side of the buried metal pipe 1 to be measured. Ia1 + Ia2 + Ia3 flows toward the first signal oscillator, and a signal current Ib1 corresponding to the second signal current flows toward the second signal generator. On the B side, a signal current Ib1 + Ib2 + Ib3 corresponding to the second signal current flows toward the second signal generator, and Ia1 corresponding to the first signal current flows toward the first signal oscillator.
Further, the signal currents Ia3 and Ib3 corresponding to the first and second signal currents flow toward the metal touch portion 3 on the A side of the other parallel metal pipe 2 and the Ia2 and Ib2 corresponding to the first and second signal currents, respectively.
In the present invention, the change in the magnetic field strength generated around both buried pipes (buried metal pipe 1 and other metal pipe 2) by these signal currents is perpendicular to the tube axis at each measurement point in the extending direction of the buried metal pipe 1. The presence and the position of the metal touch part are specified by measuring with the magnetic sensor 5 that scans at the same time.

  In addition, when the other metal pipes 2 in parallel are not in metal touch, the current from the other metal pipes 2 does not flow into the buried metal pipe 1 to be investigated. Only the signal current Ia of the signal oscillator and the signal current Ib of the second signal oscillator flow, and the magnetic field strength generated around the buried metal tube 1 does not change. For this reason, when there is no change in magnetic field strength, it can be determined that there is no metal touch.

(Example 1)
FIG. 3 is an embodiment of the invention according to claims 1 to 3 and shows a method of detecting a case where another metal pipe 2 parallel to the buried metal pipe 1 to be investigated is in metal touch. is there. When other metal pipes 2 are buried at the same depth as the buried metal pipe 1 to be investigated, if there is an obstacle such as a manhole 29 on the way, the piping route is bent and the adjacent buried metal pipe 1 There is a case where it touches and makes a metal touch.
In the metal touch investigation, first, the first signal oscillator 6 and the second signal generator 8 are connected to the buried metal pipe 1 and the ground between both ends of the investigation target section, and signal currents having different frequencies are energized. Then, a measurement carriage (shown in FIG. 1) equipped with a magnetic sensor 5 arranged in a predetermined detection direction is scanned in the direction perpendicular to the tube axis on the ground surface to acquire magnetic field strength data together with distance measurement circuit data. The detection direction of the magnetic sensor 5 is a horizontal component (x) in the direction perpendicular to the tube axis of the buried metal tube, or a vertical component (z) or both horizontal and vertical components (x, z).
The measurement operation is performed by moving the measurement carriage 10 (not shown) for each measurement location and scanning in the direction perpendicular to the tube axis, and the magnetic sensor 5 (P1-P3, P4-P6) data on the surface magnetic field strength is scanned. Get along with the data. The range in which the measurement carriage 10 scans in the direction perpendicular to the tube axis needs to be increased as the covering of the metal tube 2 is deeper, but it may be approximately 2 to 3 m on the left and right with the buried metal tube as the center.

FIG. 4 is an embodiment according to the invention of claim 2, and shows the magnetic field strength data at a certain measurement location when there is a metal touch part of another metal tube 2 parallel to the middle of the buried metal tube 1. (A) shows the magnetic field intensity in the direction perpendicular to the tube axis on the B side corresponding to the first signal current obtained by measuring the magnetic sensor 5 in the horizontal direction (x) perpendicular to the tube axis. This is magnetic field strength change data in the direction orthogonal to the tube axis on the A side corresponding to the change and the second signal current. (B) is data on the magnetic field strength change in the direction perpendicular to the tube axis on the A side corresponding to the first signal current and the magnetic field strength in the direction perpendicular to the tube axis on the B side corresponding to the second signal current.
The magnetic field intensity (Bx and Bz described later) shown on the vertical axis in the figure is the magnetic flux density: (× 10 ⁻⁷ T).
Reference numerals 16 of the magnetic field strength curves shown in FIGS. 4A and 4B are the magnetic field strength generated from the signal current flowing through the buried metal tube 1, 17 is the magnetic field strength generated from the signal current flowing through the other metal tube 2, and 18 is 16 17 and the combined magnetic field strength (Bx) measured by the magnetic sensor 5.

  According to FIGS. 4A and 4B, on the A side, the peak of the combined magnetic field strength 18 (Bx) corresponding to the first signal current appears outside the buried metal tube 1, and the combined corresponding to the second signal current. The peak of the magnetic field strength 18 (Bx) appears between the buried metal tube 1 and the other metal tube 2. On the other hand, on the B side, the peak of the composite magnetic field strength 18 (Bx) corresponding to the first signal current appears between the buried metal tube 1 and the other metal tube 2, and the composite magnetic field strength corresponding to the second signal current. The 18 (Bx) peak appears outside the buried metal tube 1.

FIG. 5 shows an embodiment of the invention according to claim 3, wherein (a) shows a B-side tube axis corresponding to a first signal current obtained by measuring the magnetic sensor 5 in the vertical direction (z). This is magnetic field strength change data in the direction orthogonal to the tube axis on the A side corresponding to the magnetic field strength change in the orthogonal direction and the second signal current. (B) is data on the magnetic field strength change in the direction perpendicular to the tube axis on the A side corresponding to the first signal current and the magnetic field strength in the direction perpendicular to the tube axis on the B side corresponding to the second signal current.
When scanning in the direction perpendicular to the tube axis, the absolute value of the magnetic field strength Bz in the vertical direction decreases as it approaches the buried metal tube 1 and the other metal tube 2 in parallel, and becomes zero near the buried metal tube and becomes polar when it passes. Invert. Reference numeral 16 in the figure indicates the magnetic field strength generated from the signal current flowing through the buried metal tube 1, and 17 indicates the magnetic field strength generated from the signal current flowing through the other metal tube 2, which is measured by the magnetic sensor 5. This is the magnetic field strength (Bz) indicated by reference numeral 18 that combines 16 and 17.

  5A and 5B, on the A side, the zero point of the combined magnetic field strength 18 (Bz) corresponding to the first signal current appears outside the buried metal tube 1 and the combined magnetic field corresponding to the second signal current. A zero point of strength 18 (Bz) appears between the buried metal tube 1 and the other metal tube 2. On the contrary, on the B side, the zero point of the combined magnetic field strength 18 (Bz) corresponding to the first signal current appears between the buried metal tube 1 and the other metal tube 2, and the combined magnetic field strength corresponding to the second signal current. A zero point of 18 (Bz) appears outside the buried metal tube 1.

FIG. 6 shows the peak of the combined magnetic field strength Bx corresponding to the first signal current from the horizontal component magnetic field strength data obtained by measuring the magnetic field strength in the direction perpendicular to the tube axis at each measurement location in the extending direction of the buried metal tube 1. The line 20 which connected the line 19 and the peak of the synthetic | combination magnetic field intensity | strength Bx corresponding to a 2nd signal current is shown. Since the line 19 connecting the peaks of the combined magnetic field intensity Bx corresponding to the first signal current and the line 20 connecting the peaks of the combined magnetic field intensity Bx corresponding to the second signal current intersect at the metal touch part 3, this point Can be identified as the metal touch part 3.
Note that the zero point of the vertical component magnetic field strength (Bz) is also drawn in the same manner as the peak lines 19 and 20 of Bx, and the metal touch part 3 can be specified.
Thus, if the metal touch part 3 exists, since the peak position of the magnetic field intensity Bx or the zero point position of Bz corresponding to the first signal current and the second signal current is relatively shifted, the presence or absence of the metal touch part can be determined. When there is no metal touch, the peak position or zero point position of the magnetic field intensity corresponding to the first signal current and the second signal current does not change. The relative shift between the peak position of the horizontal magnetic field strength Bx or the zero point position of the vertical magnetic field strength Bz is reversed with the metal touch portion as a boundary, so that this reversed intersection can be identified as the metal touch portion. .
The reason for using the two signal currents of the first signal current and the second signal current in the present invention is as follows. If a single signal current is used and the peak position or zero point position of the magnetic field strength changes, it cannot be determined whether it is due to a metal touch or a bent pipe of an embedded metal tube, but the first signal current and the second signal When two signal currents of current are used, the presence of the metal touch part is detected from the relative shift and the reversal of the peak position of the magnetic field strength (Bx) corresponding to the two signal currents or the zero point position of the magnetic field strength strength Bz as described above. And position can be specified. If the magnetic field strength Bx or Bz corresponding to the two signal currents does not invert and intersect, it can be determined that there is no metal touch part.

  When practicing the present invention, the magnetic sensor 5 is scanned in the direction perpendicular to the tube axis in the horizontal direction (x) or the vertical direction (z) perpendicular to the tube axis, and data on the magnetic field strength of either Bx or Bz is acquired. Thus, the metal touch portion can be detected. Also, if two magnetic sensors are used simultaneously in the horizontal direction (x) and vertical direction (z) perpendicular to the tube axis, and the metal touch part is detected from both Bx and Bz magnetic field strength data, the number of determination factors increases. Accuracy can be increased.

(Example 2)
Next, an invention according to claim 4, that is, a method for detecting a metal touch portion of another metal tube 2 embedded in parallel above or below the embedded metal tube 1 to be measured will be described. FIG. 7 shows that another metal pipe 2 buried in parallel under the buried metal pipe 1 is further bent in order to avoid interference with the buried pipe 30 or the like intersecting therebelow. It is a case that touches the metal and makes a metal touch.
In the investigation of the metal touch part in such a case, the first signal oscillator 6 and the second signal generator 8 described above are embedded between the buried metal pipe 1 at both ends of the investigation target section and the ground in the same manner as in the first embodiment. Are connected, and a measurement carriage 10 equipped with a magnetic sensor 5 arranged in a predetermined detection direction in a state where the first signal current and the second signal current are supplied from two places is scanned in a direction perpendicular to the tube axis on the ground surface. The magnetic field strength data is acquired together with the distance meter data. In the present invention, the difference from the first embodiment is that two magnetic sensors 5 and 26 for detecting the orthogonal horizontal component (x) are arranged on the ground surface at a height with a predetermined interval (dz).
And like the said Example 1, it scans to a pipe-axis orthogonal direction (P1-P3, P4-P6) for every measurement location of the extension direction of the buried metal pipe 1 over the measurement object range, and a 1st signal current and 2nd The peak values of the two-step ground magnetic field strengths Bx1 and Bx2 at each measurement location corresponding to the signal current are acquired.

(2)
一方、他の金属管２とメタルタッチして電流が流れ込んでいる場合、他の金属管２からの信号電流の影響により、（２）式で得られる距離ｚ_１は金属管１の中心までの真の距離ｚ_０と異なった値を示す。 When there is no metal touch part and a signal current flows only in the buried metal tube 1, the peak values of the horizontal components Bx1 and Bx2 of the magnetic field intensity measured by the two magnetic sensors 5 and 26 arranged at the vertical interval dz from the apparent distance z ₁ to the center of the metal tube 1 can be obtained from equation (2).

(2)
On the other hand, when a current is flowing in by metal touch with another metal tube 2, the distance z ₁ obtained by the expression (2) is reduced to the center of the metal tube 1 due to the influence of the signal current from the other metal tube 2. A value different from the true distance z ₀ is shown.

(3)
となり真の距離１ｍより見掛け上大きく現れる。（電流符号は図２参照、以下同じ）
一方、第１信号電流に対応する磁界強度をＡ側において測定すると、（Ｉａ１＋Ｉａ２＋Ｉａ３）とＩａ３の電流の方向が異なり、磁気センサ５で測定される磁界Ｂｘ１のピーク値はＢｘ１＝３．３３×１０-７（Ｔ）となり、金属管１に遠い方の磁気センサ２６で測定される磁界Ｂｘ２のピーク値はＢｘ２＝２．１７×１０^−７（Ｔ）となる。従って、このＢｘ１、Ｂｘ２の値を用いて、金属管１までの距離z_１aを求めると、

(4)
となり実際の距離１ｍより小さく現れる。 For example, the true distance z ₀ between the buried metal pipe 1 to be investigated and the magnetic sensor 5 is 1 (m), the distance z ₂ between the other metal pipe 2 and the magnetic sensor 5 is 1.5 (m), and two pieces. Let us consider a case where the distance dz between the magnetic sensors 5 and 26 is 0.5 (m).
At this time, in the signal current shown in FIG. 2, the first signal current flowing through the buried metal tube 1 is Ia1 = 1A on the B side, the first signal current Ia2 = 0.5A flowing through the other metal tube 2, and the buried metal is on the A side. When the first signal current flowing through the tube 1 is (Ia + Ia2 + Ia3) = 2A, and the first signal current Ia3 flowing through the other metal tube 2 is 0.5A,
When the magnetic field intensity corresponding to the first signal current is measured on the B side, the current directions of Ia1 and Ia2 are the same, so the peak value of the magnetic field Bx1 measured by the magnetic sensor 5 is Bx1 = 2.67 × 10 ^{− 7} (T), and the peak value of the magnetic field Bx2 measured by the magnetic sensor 26 far from the metal tube 1 is Bx2 = 1.83 × 10 ⁻⁷ (T). Therefore, when the apparent distance z _1a to the metal tube 1 is obtained using the values of Bx1 and Bx2,

(3)
It appears larger than the true distance of 1m. (Refer to FIG. 2 for the current sign, and the same applies hereinafter)
On the other hand, when the magnetic field intensity corresponding to the first signal current is measured on the A side, the current directions of (Ia1 + Ia2 + Ia3) and Ia3 are different, and the peak value of the magnetic field Bx1 measured by the magnetic sensor 5 is Bx1 = 3.33 × 10. −7 (T), and the peak value of the magnetic field Bx2 measured by the magnetic sensor 26 far from the metal tube 1 is Bx2 = 2.17 × 10 ⁻⁷ (T). Therefore, when the distance z _1a to the metal tube 1 is obtained using the values of Bx1 and Bx2,

(Four)
And appears smaller than the actual distance of 1 m.

From the above results, the apparent distance z _1a between the magnetic sensor 5 and the buried metal tube 1 is true on the B side where the signal current flowing through the other metal tube 2 is in the same direction as the first signal current Ia. It can be seen that the apparent distance z _1a between the magnetic sensor 5 and the metal tube 1 appears to be smaller on the side A where the current appears larger than the distance and the current is in the opposite direction.
Similarly, when the apparent distance z _1b of the buried metal tube is calculated from the peak values of Bxb1 and Bxb2 corresponding to the second signal current Ib, it is 1.09 (m) on the A side and 0.94 (m) on the B side. Thus, the value corresponds to the value corresponding to the first signal current.

FIG. 8 shows a line 27 connecting plot points of the apparent distance z _1a corresponding to the first signal current at each measurement point in the extending direction of the buried metal tube 1, and an apparent distance z _1b corresponding to the second signal current. The line 28 connecting the plot points is shown, and the intersection 3 (P7) can be specified as the metal touch part point.

(Example 3)
The invention of claim 5 is a method for detecting a metal touch part of another metal tube 2 embedded in parallel to the oblique direction of the embedded metal tube 1 to be measured. The metal touch part 3 in this case can be detected by the detection method described in the first and second embodiments, but it is preferable to make a comprehensive judgment by using both.
That is, the two magnetic sensors 5 are arranged in two steps at a predetermined interval on the ground surface with the magnetic sensor 5 in the direction in which the orthogonal horizontal component (x) is detected and disposed at a distance dz on the ground surface. , 26 from the peak values of the magnetic field strengths Bx1 and Bx2 measured by scanning in the direction perpendicular to the tube axis at each measurement point in the extending direction of the buried metal tube, the buried metal tube corresponding to the first signal current and the second signal current The apparent distance z1 to the center of ₁ is obtained, and the intersection of the lines connecting the plot points in the tube axis direction is specified as the metal touch part.
Further, the metal touch portion can be specified from the intersection of the peak positions of the magnetic field strength of any one of the magnetic sensors 5 and 26.
Further, the magnetic sensor 5 is arranged also in the vertical direction (z), and a method of specifying the metal touch part from the change of the zero point position of the magnetic field intensity is combined, and these data are comprehensively judged to determine the metal touch part. The detection accuracy can be further improved by specifying.

Example 4
Next, an embodiment of the invention according to claim 6 will be described. In the inventions of the first to fifth aspects, the magnetic sensor 5 is scanned in the direction perpendicular to the tube axis of the buried metal tube 1. In this invention, the magnetic sensor 5 is scanned in the tube axis direction of the buried metal tube 1. Is different from the inventions of claims 1 to 5 described above.
The configuration of the measuring apparatus of the present invention is the same as that shown in FIG. 1. The first signal transmitter 6 and the second signal apply signal currents of two different frequencies to both sides of the investigation range of the buried metal pipe 1 to be investigated. A transmitter 8 is installed, and a signal current is applied to the buried metal pipe 1 and the ground.
The magnetic sensor 5 for measuring the magnetic field intensity, the first signal processing device 12 for processing the measurement signal, the measurement carriage 10 equipped with the second signal generator 8 and the distance measuring circuit 15 move in the tube axis direction of the buried metal pipe. Arrange as follows. The magnetic sensor 5 is arranged so as to detect the magnetic field component of the vertical component (z), and the rotation signal generator for distance measurement aligns the rotation direction of the wheel 11 with the tube axis direction.

  The method of detecting the metal touch portion using the measurement carriage described above is performed by adjusting the position of the magnetic sensor 5 so as to match the position of the minimum value of the magnetic field intensity of the vertical component corresponding to the first signal current. 10 is moved in the extending direction of the buried metal tube 1, and the change in the magnetic field strength of the vertical component (z) corresponding to the second signal current is measured. Alternatively, while adjusting the position of the magnetic sensor so as to match the position of the minimum value of the magnetic field intensity of the vertical direction component (z) corresponding to the second signal current, the measurement carriage is moved in the extending direction of the metal tube, and the first signal The change in the magnetic field strength of the vertical component corresponding to the current is measured. Then, the obtained data is subjected to signal processing to compare the change in magnetic field intensity corresponding to the second signal current or the first signal current.

The dotted line 24 in FIG. 10 is a change in the tube axis direction of the magnetic field strength of the vertical component corresponding to the former second signal current, and the solid line 25 is the tube axis direction of the magnetic field strength of the vertical component corresponding to the latter first signal current. It is a change.
In any case, the point 3 where the polarity of the magnetic field strength is reversed can be specified as the metal touch portion.
When the polarity of the magnetic field strength does not reverse in the tube axis direction, it is determined that there is no metal touch part.
When implementing the present invention, when adjusting the position of the magnetic sensor so as to match the position of the minimum value of the magnetic field strength of the vertical component corresponding to the first signal current or the second signal current, scanning is performed in the direction perpendicular to the tube axis at the start point. Then, it is better to detect the position of the minimum point, and then to move in a zigzag direction along the tube axis while finding the minimum point.

The whole block diagram of the Example of the metal touch part detection method of the buried metal pipe which concerns on this invention. Current flowing in buried metal pipes and other parallel metal pipes. The metal touch part detection block diagram of Example 1 in which the other metal pipe which adjoins the buried metal pipe of investigation object, and exists in parallel horizontally exists. (A), (b) The example of distribution which showed the measurement data of the horizontal direction component Bx of the magnetic field intensity in Example 1 by taking the scanning distance of the pipe axis orthogonal direction on the horizontal axis. (A), (b) The example of distribution which showed the measurement data of the vertical component Bz of the magnetic field intensity in Example 1 by taking the scanning distance of the orthogonal direction of a pipe axis on the horizontal axis. In Example 1, the top view which tied the peak position of Bx obtained by the signal current of the 1st signal transmitter and the 2nd signal transmitter, and the zero point of Bz. The metal touch part detection block diagram of Example 2 in which the other metal pipe which adjoins the buried metal pipe of investigation object, and exists below exists. Sectional view connecting apparent distance z ₁ which corresponds to the apparent distance z ₁ and the second signal current corresponding to the first signal current obtained in Example 2. The change in the tube axis direction of the magnetic field intensity of the vertical component corresponding to the two signal currents obtained by moving the magnetic sensor in the tube axis direction in Example 4. Example of conventional technology Example of conventional technology Example of conventional technology Example of conventional technology

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Buried metal pipe of investigation object 2 Other metal pipe 3 Metal touch part 4 Ground 5 Magnetic sensor 6 1st signal transmitter 7 Counter electrode 8 2nd signal transmitter 9 Counter electrode
10 Measuring cart
11 wheels
12 First signal processor
13 Second signal processor
14 Display device
15 Distance measurement circuit
16 Magnetic field generated from the signal current flowing through the buried metal tube 1
17 Magnetic field generated from the signal current flowing through another metal tube 2
18 16 and 17 combined magnetic field
19 Line connecting peaks of the combined magnetic field strength Bx corresponding to the first signal current
20 Line connecting peaks of the combined magnetic field strength Bx corresponding to the second signal current
21 Magnetic field generated from the first signal current
22 Magnetic field generated from the second signal current
23 Position at which the absolute value of the magnetic field intensity generated from the first signal current is minimal
24 Magnetic field composed of the second signal current measured when the position where the absolute value of the magnetic field intensity generated from the first signal current is minimized is traced in the extending direction of the metal tube.
25 Magnetic field composed of the first signal current measured when the position where the absolute value of the magnetic field intensity generated from the second signal current is minimized is traced in the extending direction of the metal tube.
26 Magnetic sensor farther away from the metal tube 1 used in calculating the separation z _{1 of} Example 2
27 Line connecting plot points of apparent distance z ₁ corresponding to the first signal current
28 Line connecting plot points of apparent distance z ₁ corresponding to the second signal current
29 Manholes and other structures
30 Structures such as other buried pipes

Claims (8)

A method of detecting a metal touch part between a buried metal pipe coated with anticorrosion and another metal pipe buried in close proximity in parallel, which is the first to the buried metal pipe and the ground from both sides of the detection target section. Applying the signal current and the second signal current, the magnetic sensor that scans the ground surface is scanned in the direction perpendicular to the tube axis at each measurement point in the extension direction of the buried metal tube, and the magnetic field strength is measured. A buried metal tube characterized in that the presence or absence of a metal touch part and the position of the metal touch part are specified by performing signal processing and comparing changes in the magnetic field strength at each measurement location corresponding to the first signal current and the second signal current. Metal touch detection method. In the metal touch part detection method for other metal pipes parallel to the buried metal pipe, the magnetic sensor is arranged to detect the horizontal component magnetic field in the direction perpendicular to the pipe axis, and in the direction perpendicular to the pipe axis at each measurement location. Comparing the occurrence position of the maximum value of the magnetic field intensity corresponding to the first signal current and the second signal current from the measurement data of the magnetic field intensity at the time of scanning, and specifying the presence / absence of the metal touch part and the metal touch part position The method for detecting a metal touch part of an embedded metal pipe according to claim 1, wherein: In the metal touch part detection method of other metal pipes that are parallel to the buried metal pipe, the magnetic sensor is arranged to detect the vertical component magnetic field, and when each of the measurement points is scanned in the direction perpendicular to the pipe axis , The presence / absence of a metal touch part and the position of the metal touch part are specified by comparing the occurrence positions of the minimum values of the magnetic field intensity corresponding to the first signal current and the second signal current from the measurement data of the magnetic field intensity. The metal touch part detection method of the buried metal pipe of 1. In the metal touch part detection method of another metal pipe parallel to the upper or lower side with respect to the buried metal pipe, the magnetic sensor is set to a direction to detect a horizontal component magnetic field in the direction perpendicular to the pipe axis and at a predetermined interval. Apparent appearance corresponding to the first signal current and the second signal current from the measurement data of the maximum value of the magnetic field intensity when two stages are arranged and scanned in the direction perpendicular to the tube axis of the two-stage magnetic sensor at each measurement location. 2. The method for detecting a metal touch part of a buried metal pipe according to claim 1, wherein the depth of the buried metal pipe is calculated, and the value is compared to identify the presence / absence of the metal touch part and the position of the metal touch part. In a method for detecting a metal touch part of another metal pipe parallel to an oblique position with respect to the buried metal pipe, the magnetic sensor is set to a direction to detect a horizontal component magnetic field in a direction perpendicular to the pipe axis of the buried metal pipe, and has a predetermined interval. In addition, the magnetic field corresponding to the first signal current and the second signal current is measured from the measurement data of the magnetic field intensity when two stages are arranged and scanned in the orthogonal direction of one or both of the magnetic sensors at each measurement location. The position of occurrence of the maximum value of the strength is obtained, and the depth of the buried metal tube is calculated from the measurement data of the maximum value of the magnetic field strength when scanning in the direction perpendicular to the tube axis of the two-stage magnetic sensor. 2. The method of detecting a metal touch part in an embedded metal pipe according to claim 1, wherein the presence of the metal touch part and the position of the metal touch part are specified by comparing the generation position of the maximum value and the calculation depth of the embedded metal pipe. A method of detecting a metal touch part between a buried metal pipe coated with anticorrosion and another metal pipe buried in close proximity in parallel, which is the first to the buried metal pipe and the ground from both sides of the detection target section. A magnetic sensor that applies a signal current and a second signal current and scans the ground surface is arranged so as to detect a vertical component magnetic field, and is positioned at the position of the minimum value of the magnetic field strength of the vertical component corresponding to the first signal current. Measure the change in the magnetic field strength of the vertical component corresponding to the second signal current while tracking the extension direction of the buried metal pipe along the position, or the position of the minimum value of the magnetic field strength of the vertical component corresponding to the second signal current The change in the magnetic field strength of the vertical component corresponding to the first signal current is measured while tracking the extension direction of the buried metal pipe along the first and second signals. Ratio of change in magnetic field strength corresponding to signal current Metal touch portion detection method of the buried metal tube and identifies the presence and metal touch portion position of the metal-touch portion is. The first signal current and the second signal current applied to the buried metal pipe and the ground from both sides of the detection target section are configured to simultaneously pass alternating signals having different frequencies, respectively. The method for detecting a metal touch part of an embedded metal pipe according to claim 6. A lock that uses a reference signal with the same frequency as the signal frequency applied to the buried metal pipe and the ground as a signal processing device that obtains magnetic field strength corresponding to different frequency signals by processing the data obtained by the magnetic sensor 8. The method for detecting a metal touch part of a buried metal pipe according to claim 7, wherein an in-amplifier is used.

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