JP2000019159A - Method and device for detecting paint film damaged position of buried steel pipe - Google Patents
Method and device for detecting paint film damaged position of buried steel pipeInfo
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- JP2000019159A JP2000019159A JP10183841A JP18384198A JP2000019159A JP 2000019159 A JP2000019159 A JP 2000019159A JP 10183841 A JP10183841 A JP 10183841A JP 18384198 A JP18384198 A JP 18384198A JP 2000019159 A JP2000019159 A JP 2000019159A
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- Prior art keywords
- steel pipe
- buried steel
- potential difference
- voltage
- distribution
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- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は埋設された塗覆装鋼
管の塗膜損傷部位を、地上にて非接触で検出する塗膜損
傷位置検出方法及び装置に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting a damaged position of a coating film on a grounded surface of a coated steel pipe in a non-contact manner.
【０００２】[0002]
【従来の技術】一般に、地中に埋設される鋼管には、腐
食を防止するために塗覆装がその周囲に施されている。
しかしながら、何らかの原因により塗覆装による塗膜が
損傷すると、その損傷部位から腐食が進行し、やがて鋼
管に腐食孔が生じるようになる。このため、埋設鋼管の
保全上、塗膜損傷の有無とその位置を早期に発見するこ
とが重要である。2. Description of the Related Art Generally, steel pipes buried underground are provided with a coating to prevent corrosion.
However, if the coating film by the coating and covering is damaged for some reason, corrosion progresses from the damaged portion, and eventually a corrosion hole is formed in the steel pipe. For this reason, it is important to detect the presence and location of paint film damage at an early stage in the maintenance of buried steel pipes.
【０００３】これに応えるものとして、従来から種々の
塗膜損傷位置検出方法が提案されている。これらの方法
のうち、作業性及び測定精度の面で優れた方法として、
電位差法が周知である。In order to respond to this, various methods for detecting a damaged position of a coating film have been proposed. Among these methods, as methods excellent in terms of workability and measurement accuracy,
Potentiometric methods are well known.
【０００４】図３は電位差法を実現するためのシステム
構成を表す図である。図３において、１は埋設鋼管、２
は交流電源、３は電力増幅器、４は接地電極、５は埋設
鋼管の塗膜損傷部、６は探査機、６ａ及び６ｂは探査機
の車輪電極、７はフィルタ、８は電位差検出器である。FIG. 3 is a diagram showing a system configuration for realizing the potential difference method. In FIG. 3, 1 is a buried steel pipe, 2
Is an AC power supply, 3 is a power amplifier, 4 is a ground electrode, 5 is a damaged portion of a coating of a buried steel pipe, 6 is a probe, 6a and 6b are wheel electrodes of the probe, 7 is a filter, and 8 is a potential difference detector. .
【０００５】交流電源２から電力増幅器３を介して、埋
設鋼管１と接地電極４との間に電圧を印加すると、埋設
鋼管１に沿って（以下、管軸方向という）電流が流れ
る。一方、探査機６は地表面上を埋設鋼管の管軸方向に
沿って移動する。その際、探査機６に設けられた車輪電
極６ａ及び６ｂが、接触している地面の電位をそれぞれ
検出する。それぞれが検出した電位に対し、フィルタ７
及び電位差検出器８により、電位差を検出する。When a voltage is applied between the buried steel pipe 1 and the ground electrode 4 from the AC power supply 2 via the power amplifier 3, a current flows along the buried steel pipe 1 (hereinafter, referred to as a pipe axis direction). On the other hand, the spacecraft 6 moves on the ground surface along the pipe axis direction of the buried steel pipe. At this time, the wheel electrodes 6a and 6b provided on the probe 6 detect the potential of the ground in contact with each other. Filter 7 is applied to each detected potential.
And the potential difference detector 8 detects the potential difference.
【０００６】通常、埋設鋼管１に塗膜損傷がない場合、
埋設鋼管１に流れる電流からの電流漏れはほとんどない
と考えられる。しかし、埋設鋼管１の塗膜に塗膜損傷部
５がある場合、印加した電圧に応じて塗膜損傷部５より
電流漏れが起こる。この電流漏れによって付近の土壌に
電位が生じる。ここで、この土壌付近の地表面における
電位は次式（１）で表される。 Ｖ＝ρｉ／｛２π（ｘ2 ＋Ｚ0 2 ）1/2 ｝ （ｖ） …（１） ここで、Ｖは電位、ρは土壌の平均比抵抗、ｉは通電電
流、Ｚ0 は地表から塗膜損傷部５までの距離を表してい
る。ここで、管軸方向をｘ軸とし、塗膜損傷部５の位置
をｘ＝０としている。Normally, when there is no paint film damage on the buried steel pipe 1,
It is considered that there is almost no current leakage from the current flowing through the buried steel pipe 1. However, when the coating film of the buried steel pipe 1 has a coating film damaged portion 5, current leaks from the coating film damaged portion 5 according to the applied voltage. This current leakage creates a potential in nearby soil. Here, the potential on the ground surface near the soil is expressed by the following equation (1). V = ρi / ｛2π (x 2 + Z 0 2 ) 1/2 ｝ (v) (1) where V is the potential, ρ is the average specific resistance of the soil, i is the conduction current, and Z 0 is the painting from the ground surface. The distance to the film damaged part 5 is shown. Here, the pipe axis direction is the x axis, and the position of the coating film damaged part 5 is x = 0.
【０００７】ここで、電位の勾配の符号は、塗膜損傷部
５の真上の位置（ｘ＝０）を境にして反転する。したが
って、探査機６を埋設鋼管の管軸方向に沿って走行させ
たときの走行距離を横軸に、車輪電極６ａ及び６ｂによ
り検出された電位の電位差を縦軸にとったグラフを作成
すると、理想的には、ｘ＝０（塗膜損傷部５の真上）を
中心としたＳ字型のカーブを描く。この電位差を表す式
を次式（２）に示す。式（２）により算出される電位差
の理論値は、式（１）を微分することによって得られ
る。ここで、Ｖ’は電位差である。これは電極の間隔が
十分小さいときには成り立つ。 Ｖ’＝ρｉｘ／｛２π（ｘ2 ＋Ｚ0 2 ）3/2 ｝ （ｖ／ｍ） …（２）Here, the sign of the gradient of the potential is reversed at a position immediately above the damaged portion 5 (x = 0). Therefore, when a graph in which the traveling distance when the probe 6 travels along the tube axis direction of the buried steel pipe is plotted on the abscissa and the potential difference between the potentials detected by the wheel electrodes 6a and 6b is plotted on the ordinate, Ideally, an S-shaped curve centered on x = 0 (directly above the damaged portion 5 of the coating film) is drawn. An equation representing this potential difference is shown in the following equation (2). The theoretical value of the potential difference calculated by Expression (2) can be obtained by differentiating Expression (1). Here, V 'is a potential difference. This is true when the distance between the electrodes is sufficiently small. V ′ = ρix / {2π (x 2 + Z 0 2 ) 3/2 } (v / m) (2)
【０００８】したがって、このＳ字型のカーブの中央の
位置（ゼロクロス点）を検出し、塗膜損傷部５の真上の
位置（ｘ＝０）を特定することにより、塗膜損傷部５の
位置を地上において非接触で検出することができる。Therefore, by detecting the center position (zero cross point) of the S-shaped curve and specifying the position (x = 0) immediately above the damaged portion 5 of the coating film, the position of the damaged portion 5 of the coating film is determined. The position can be detected on the ground without contact.
【０００９】図４は塗膜損傷部を検出したときの電位分
布と距離及び車輪電極６ａ及び６ｂにより測定された電
位の電位差と距離との関係を表す図である。図４（ａ）
は電位分布を表している。また、図４（ｂ）は電位差を
表している。ここで、図４（ｂ）について、電位差の左
半分の符号は正であり、右半分の符号は負となってい
る。これは塗膜損傷部５の真上の位置（ｘ＝０）を境に
して、左半分の位置と右半分の位置では、電位分布の勾
配の符号が反転している（勾配の方向が上昇から下降に
なっている）ことを示す。そして前述したように、図４
（ｂ）におけるＳ字型カーブの中心、すなわち、電位差
が０となる位置を塗膜損傷位置の真上であると判定す
る。FIG. 4 is a diagram showing the relationship between the potential distribution and the distance when a damaged portion of the coating film is detected and the potential difference between the potential measured by the wheel electrodes 6a and 6b and the distance. FIG. 4 (a)
Represents a potential distribution. FIG. 4B shows a potential difference. Here, in FIG. 4B, the sign of the left half of the potential difference is positive and the sign of the right half is negative. The sign of the gradient of the potential distribution is reversed at the left half position and the right half position with respect to the position (x = 0) immediately above the coating film damaged portion 5 (the direction of the gradient is rising). From). And, as described above, FIG.
The center of the S-shaped curve in (b), that is, the position where the potential difference becomes 0, is determined to be right above the coating film damage position.
【００１０】[0010]
【発明が解決しようとする課題】しかしながら、前記の
電位差法は、次に示すような問題点を有する。１つの問
題点は、２点の車輪電極により測定された電位差を検出
するので、電極の間隔（つまり車輪の間隔）によって電
位差の距離分解能が決まってしまう。したがって、電極
の間隔に比べ、２つ以上の塗膜損傷部が互いに近接した
位置にあった場合には、弁別することが困難である。そ
こで、電極間隔を狭くすることを考えると、損傷位置の
分解能は向上するが、逆に２つの車輪電極により検出す
る電位の差が小さくなる。したがって、あまりに電極の
間隔を狭くすると、電位差として検出した検出信号自身
のＳ／Ｎ比が悪化し、塗膜損傷部の有無を検出すること
も困難となる。However, the above-mentioned potential difference method has the following problems. One problem is that since the potential difference measured by the two wheel electrodes is detected, the distance resolution of the potential difference is determined by the distance between the electrodes (that is, the distance between the wheels). Therefore, it is more difficult to discriminate when two or more damaged portions of the coating film are located closer to each other than the distance between the electrodes. In consideration of reducing the electrode spacing, the resolution of the damaged position is improved, but the difference between the potentials detected by the two wheel electrodes is reduced. Therefore, if the distance between the electrodes is too small, the S / N ratio of the detection signal itself detected as the potential difference is deteriorated, and it becomes difficult to detect the presence or absence of a damaged portion of the coating film.
【００１１】もう１つの問題点は、実際に塗膜損傷の検
出する場合に生じる。塗膜損傷の検出は、探査機をアス
ファルト上に走らせて行う。そのため、接地抵抗が大き
く、車輪電極間の電位差として検出される検出信号は微
弱なものとならざるを得ない。一方、地中には迷走電流
が流れており、このため、土壌が固有電位を有してい
る。これが車輪電極間の電位差を検出するときにノイズ
として現れる。これらのノイズはフィルタ処理によりあ
る程度は除去されるものの、もともとの信号のＳ／Ｎ比
が低いため、ノイズを完全に除去することができない。
このため塗膜損傷を精度よく、確実に検知することは困
難である。Another problem arises when actually detecting coating damage. Detection of paint film damage is performed by running a spacecraft on asphalt. For this reason, the ground resistance is large, and the detection signal detected as the potential difference between the wheel electrodes must be weak. On the other hand, a stray current flows in the ground, so that the soil has a specific potential. This appears as noise when detecting the potential difference between the wheel electrodes. Although these noises are removed to some extent by the filter processing, the noise cannot be completely removed because the S / N ratio of the original signal is low.
For this reason, it is difficult to detect coating film damage accurately and reliably.
【００１２】本発明はこのような問題点を解決するため
になされたもので、２つ以上の塗膜損傷部の位置を確実
に検出する方法及びこの方法を実施するのに好適なシス
テムを提供することを目的とする。さらに、Ｓ／Ｎ比を
向上させ、塗膜損傷部の位置を精度よく検出する方法及
びシステムを提供することを目的とする。The present invention has been made in order to solve such a problem, and provides a method for reliably detecting the positions of two or more damaged coating films and a system suitable for carrying out the method. The purpose is to do. It is another object of the present invention to provide a method and a system for improving the S / N ratio and accurately detecting the position of the damaged portion of the coating film.
【００１３】[0013]
【課題を解決するための手段】本発明の請求項１に係る
埋設鋼管の塗膜損傷検出方法は、埋設鋼管と地面との間
に電圧を印加して、埋設鋼管に電流を流し、一方、地表
面上において、ある２点を埋設鋼管の管軸方向に一定距
離間隔で走査させて、２点間の電位差の分布を検出す
る。この際、２点の距離を異ならせた電位差の分布を２
つ以上検出する。埋設鋼管に施した塗膜に損傷がある場
合に、流した電流の漏れにより地表面の電位が変化する
ことを利用して、検出した電位差の分布に基づいて塗膜
損傷の有無及び位置を検出する。距離を異ならせた電位
差の分布を２つ以上検出することにより、全体の塗膜損
傷の有無及び各塗膜損傷の位置の双方を高精度で検出す
る。According to a first aspect of the present invention, there is provided a method for detecting paint film damage on a buried steel pipe, wherein a voltage is applied between the buried steel pipe and the ground to cause a current to flow through the buried steel pipe. On the ground surface, two points are scanned at a fixed distance in the pipe axis direction of the buried steel pipe, and the distribution of the potential difference between the two points is detected. At this time, the distribution of the potential difference where the distance between the two points is different is 2
Detect more than one. If there is damage to the coating applied to the buried steel pipe, the presence or absence and position of coating damage is detected based on the distribution of the detected potential difference, utilizing the fact that the potential of the ground surface changes due to leakage of the flowing current. I do. By detecting two or more distributions of the potential difference at different distances, both the presence or absence of the entire coating film damage and the position of each coating film damage are detected with high accuracy.
【００１４】また、本発明の請求項２に係る埋設鋼管の
塗膜損傷検出方法は、埋設鋼管と地面との間に印加する
電圧を、搬送波を位相変調させて生成した、周期内では
ランダム性を有する擬似ランダム信号に基づいた波形の
電圧とし、埋設鋼管にその波形の電流を流す。一方、地
表面上において、ある２点を前記埋設鋼管の管軸方向に
一定距離間隔で走査させて、前記２点間の電位差の分布
を検出する。この際、２点の距離を異ならせた電位差の
分布を２つ以上検出する。この電位差の分布は、擬似ラ
ンダム信号と同じランダムパターンを有する独立に生成
した参照信号と電位差との相関演算を行い、相関のピー
クの値が算出されたときの電位差に基づく値を代表値と
して算出し、代表値の分布を電位差の分布とする。埋設
鋼管に施した塗膜に損傷がある場合に、流した電流の漏
れにより地表面の電位が変化することを利用して、検出
した電位差の分布に基づいて塗膜損傷の有無及び位置を
特定する。距離を異ならせた電位差の分布を２つ以上検
出することにより、全体の塗膜損傷の有無及び各塗膜損
傷の位置の双方を高精度で検出する。また、相関演算を
行い、ノイズの影響を抑え、明確な電位差の分布を検出
する。According to a second aspect of the present invention, there is provided a method for detecting paint film damage on a buried steel pipe, wherein a voltage applied between the buried steel pipe and the ground is generated by phase-modulating a carrier wave. And a current having the waveform is applied to the buried steel pipe. On the other hand, two points on the ground surface are scanned at a fixed distance in the pipe axis direction of the buried steel pipe, and the distribution of the potential difference between the two points is detected. At this time, two or more potential difference distributions having different distances between the two points are detected. The distribution of the potential difference is calculated by performing a correlation operation between an independently generated reference signal having the same random pattern as the pseudo-random signal and the potential difference, and a value based on the potential difference when the peak value of the correlation is calculated as a representative value. Then, the distribution of the representative values is defined as the distribution of the potential difference. If there is damage to the coating applied to the buried steel pipe, use the fact that the potential of the ground surface changes due to the leakage of the flowing current, and identify the presence and location of coating damage based on the distribution of the detected potential difference I do. By detecting two or more distributions of the potential difference at different distances, both the presence or absence of the entire coating film damage and the position of each coating film damage are detected with high accuracy. Further, a correlation operation is performed to suppress the influence of noise and detect a distribution of a clear potential difference.
【００１５】また、本発明の請求項３に係る埋設鋼管の
塗膜損傷検出装置は、交流電圧発生器と、埋設鋼管と地
面との間に、前記交流電圧発生器の出力に比例した電圧
を印加する電圧増幅器と、埋設鋼管の管軸方向と平行に
隔離して配置され、地面との接触部位の電位を検出する
一対の車輪電極を、車輪電極の距離間隔を異ならせて２
組以上備え、地表面を埋設鋼管の管軸方向に沿って走行
する探査機と、一対の車輪電極のそれぞれの組に対し、
車輪電極間の電位差を測定する電圧測定器と、電圧測定
器が測定したそれぞれの組の車輪電極間の電位差の分布
に基づいて、埋設鋼管の塗膜損傷位置を検出する手段と
を備え、全体の塗膜損傷の有無及び各塗膜損傷の位置の
双方を高精度で検出する。According to a third aspect of the present invention, there is provided an apparatus for detecting paint film damage on a buried steel pipe, wherein a voltage proportional to an output of the AC voltage generator is applied between the AC voltage generator and the buried steel pipe and the ground. A voltage amplifier to be applied and a pair of wheel electrodes, which are arranged separately in parallel with the tube axis direction of the buried steel pipe and detect the potential of a contact portion with the ground, are arranged at different distances between the wheel electrodes.
With more than one set, for the spacecraft traveling along the pipe axis direction of the buried steel pipe on the ground surface, for each set of a pair of wheel electrodes,
A voltage measuring device for measuring a potential difference between the wheel electrodes, and means for detecting a coating film damaged position of the buried steel pipe based on a distribution of the potential difference between each pair of wheel electrodes measured by the voltage measuring device, Both the presence or absence of coating damage and the position of each coating damage are detected with high accuracy.
【００１６】また、本発明の請求項４に係る埋設鋼管の
塗膜損傷検出装置は、周期内ではランダム性を有する擬
似ランダム信号を搬送波を位相変調させて生成する第１
の信号発生器と、埋設鋼管と地面との間に、第１の信号
発生器の出力に比例した電圧を印加する電圧増幅器と、
埋設鋼管の管軸方向と平行に隔離して配置され、地面と
の接触部位の電位を検出する一対の車輪電極を、車輪電
極の距離間隔を異ならせて２組以上備え、地表面を埋設
鋼管の管軸方向に沿って走行する探査機と、一対の車輪
電極のそれぞれの組に対し、車輪電極間の電位差を測定
する電圧測定器と、第１の信号発生器が生成した擬似ラ
ンダム信号と同じパターンの波形を有する第２の信号発
生器によって生成された参照信号と電位差との相関演算
を行って相関のピークの値を算出し、ピーク値における
電位差に基づく値を代表値として、代表値の分布を検出
する相関処理装置と、相関処理装置が算出したそれぞれ
の組の代表値の分布に基づいて、埋設鋼管の塗膜損傷の
有無及び位置位置を検出する手段とを備え、ノイズの影
響を抑え、電位差に基づく代表値の分布を明確に検出
し、全体の塗膜損傷の有無及び各塗膜損傷の位置の双方
を高精度で検出する。Further, according to a fourth aspect of the present invention, there is provided a coating film damage detecting apparatus for a buried steel pipe, wherein a pseudorandom signal having randomness within a period is generated by phase-modulating a carrier.
A voltage generator for applying a voltage proportional to the output of the first signal generator between the buried steel pipe and the ground,
A buried steel pipe is provided with two or more pairs of wheel electrodes which are arranged in parallel with the pipe axis direction of the buried steel pipe and detect a potential of a contact portion with the ground at different distances between the wheel electrodes. A spacecraft traveling along the tube axis direction, a voltage measuring device for measuring a potential difference between the wheel electrodes for each pair of wheel electrodes, and a pseudo-random signal generated by the first signal generator. A correlation peak value is calculated by performing a correlation operation between the reference signal generated by the second signal generator having the same pattern waveform and the potential difference, and a value based on the potential difference at the peak value is set as a representative value. And a means for detecting the presence or absence and position of paint film damage on the buried steel pipe based on the distribution of the representative value of each set calculated by the correlation processing device, and the influence of noise. Suppress the potential difference Based clearly detect the distribution of the representative values, to detect both the position of the presence and the coating damage of the entire coating damage with high accuracy.
【００１７】[0017]
【発明の実施の形態】実施形態１．図１は本発明の第１
の実施の形態に係る埋設鋼管の塗膜損傷検出方法を実現
するための構成を表す図である。図において、１は埋設
鋼管、３は電力増幅器、４は接地電極、５は埋設鋼管１
の塗膜損傷部、６は探査機、６−１ａ及び６−１ｂは探
査機６の外側車輪電極（電極間隔が広い）、６−２ａ及
び６−２ｂは探査機６の内側車輪電極（電極間隔が狭
い）、１０は第１のＭ系列信号発生器、１１は第２のＭ
系列信号発生器、１２は相関処理部、１３はパーソナル
コンピュータ演算部、１４及び１６は正弦波発生器、１
５及び１７は掛算器である。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. FIG. 1 shows the first embodiment of the present invention.
It is a figure showing the structure for realizing the coating film damage detection method of a buried steel pipe which concerns on embodiment. In the figure, 1 is a buried steel pipe, 3 is a power amplifier, 4 is a ground electrode, and 5 is a buried steel pipe 1.
6 is a probe, 6-1a and 6-1b are outer wheel electrodes of the probe 6 (the electrode interval is wide), 6-2a and 6-2b are inner wheel electrodes of the probe 6 (electrode (The interval is small), 10 is the first M-sequence signal generator, 11 is the second M-sequence signal generator.
A sequence signal generator, 12 is a correlation processing unit, 13 is a personal computer operation unit, 14 and 16 are sine wave generators, 1
5 and 17 are multipliers.
【００１８】本実施の形態においては、埋設鋼管１に印
加する電圧（埋設鋼管１を流れる電流）として、Ｍ系列
による符号パターンを二位相変調した正弦波信号を用い
る。Ｍ系列による符号パターンは、長期的に見ると周期
を有し、ランダムな符号パターンとは言えない。しか
し、その周期内においては、ランダム性が保たれている
擬似的にランダムな符号パターンである。したがって、
相関値を算出すると、その値は同じ符号パターンの時に
最大となる。したがって、ノイズが正弦波信号と同じパ
ターンの電位を有さない限り、その最大の相関値には影
響をあたえない。そこで、最大の相関値が演算されたと
きの電位差を検出し、処理することで、地面の迷走電流
のノイズの影響等を受けずに精度の高い電位差分布を導
き出せ、ゼロクロス点が発見しやすい。また、Ｍ系列に
よる符号パターンの生成は、シフトレジスタと排他的論
理和回路で構成されるので、小型で簡単である。In the present embodiment, a sine wave signal obtained by two-phase modulation of an M-sequence code pattern is used as the voltage applied to the buried steel pipe 1 (current flowing through the buried steel pipe 1). A code pattern based on the M-sequence has a cycle in a long term, and cannot be said to be a random code pattern. However, within the period, the code pattern is a pseudo-random code pattern in which randomness is maintained. Therefore,
When a correlation value is calculated, the value becomes maximum when the same code pattern is used. Therefore, unless the noise has the same pattern of potentials as the sinusoidal signal, its maximum correlation value is not affected. Therefore, by detecting and processing the potential difference when the maximum correlation value is calculated, a highly accurate potential difference distribution can be derived without being affected by the noise of the stray current on the ground, and the zero-cross point can be easily found. Further, since the generation of the code pattern by the M-sequence is constituted by the shift register and the exclusive OR circuit, it is small and simple.
【００１９】また、正弦波の位相を変調する方法とし
て、公知のＰＳＫ（Phase Shift Keying）を用いる。Ｐ
ＳＫとは、搬送波の位相をずらせることによって情報を
伝送する方式の一つである。搬送波の位相を反転（位相
をπだけずらせること）により、二値の信号を送ること
ができる。ＰＳＫは正弦波であるので、理想的には波形
には直流成分が含まれない。また、実際にも直流成分は
少ない。したがって、直流成分の減衰が著しい地中の電
位伝搬特性でも、極度の電位伝搬減衰を抑えることがで
きる。As a method of modulating the phase of the sine wave, a known PSK (Phase Shift Keying) is used. P
SK is one of the systems for transmitting information by shifting the phase of a carrier wave. By inverting the phase of the carrier (shifting the phase by π), a binary signal can be sent. Since PSK is a sine wave, the waveform ideally does not include a DC component. Also, the DC component is actually small. Therefore, even in the potential propagation characteristics in the ground where the DC component is significantly attenuated, the extreme potential propagation attenuation can be suppressed.
【００２０】本実施の形態は、電極間隔が異なる外側車
輪電極６−１ａ及び６−１ｂ並びに内側車輪電極６−２
ａ及び６−２ｂを用いて、近接して２点以上の塗膜損傷
部が存在した場合でも、それぞれの塗膜損傷位置の検出
ができるように分解能を向上させようとするものであ
る。In this embodiment, the outer wheel electrodes 6-1a and 6-1b and the inner wheel electrode 6-2 having different electrode intervals are used.
Using a and 6-2b, it is intended to improve the resolution so that even when two or more paint film damaged portions exist in close proximity, the respective paint film damaged positions can be detected.
【００２１】次に図１のシステムの動作について説明す
る。正弦波発生器１４が発生する正弦波信号に同期させ
て、第１のＭ系列信号発生器１０はＭ系列信号を発生さ
せる。掛算器３はそれぞれの信号を掛け合わせる。掛け
合わせて作成されたＭ系列による符号パターンを二位相
変調した正弦波信号は、電力増幅器３で増幅され、埋設
鋼管１と接地電極４との間の電圧として印加される。こ
の電圧により、埋設鋼管１には、正弦波信号に基づいた
波形の電流が管軸方向に流れる。Next, the operation of the system shown in FIG. 1 will be described. The first M-sequence signal generator 10 generates an M-sequence signal in synchronization with the sine-wave signal generated by the sine-wave generator 14. The multiplier 3 multiplies each signal. The sine wave signal obtained by multi-phase modulating the M-sequence code pattern created by the multiplication is amplified by the power amplifier 3 and applied as a voltage between the embedded steel pipe 1 and the ground electrode 4. With this voltage, a current having a waveform based on the sine wave signal flows through the buried steel pipe 1 in the pipe axis direction.
【００２２】一方、探査機６は地表面上を埋設鋼管の管
軸方向に沿って移動する。その際、探査機６に設けられ
た２組の車輪電極（外側車輪電極６−１ａ及び６−１
ｂ、内側車輪電極６−２ａ、６−２ｂ）が、それぞれ、
接触している地面の電位を検出する。それぞれが検出し
た電位に対し、例えば、フィルタ、電位差検出器（図示
せず）により、外側車輪電極６−１ａ及び６−１ｂが検
出した電位の差を導き出す。また内側車輪電極６−２ａ
及び６−２ｂが検出した電位の差を導き出す。それぞれ
の電位差は、Ａ／Ｄ変換器（図示せず）でサンプリング
され、ディジタル値に変換される。変換されたディジタ
ル値は検出信号としてパーソナルコンピュータ演算部１
３の相関処理部１２に入力される。On the other hand, the probe 6 moves on the ground surface along the pipe axis direction of the buried steel pipe. At this time, two sets of wheel electrodes (outer wheel electrodes 6-1a and 6-1a) provided on the spacecraft 6 are used.
b, inner wheel electrodes 6-2a and 6-2b)
Detect the potential of the ground in contact. For each of the detected potentials, for example, a filter and a potential difference detector (not shown) derive a difference between the potentials detected by the outer wheel electrodes 6-1a and 6-1b. Also, the inner wheel electrode 6-2a
And 6-2b derive the difference between the detected potentials. Each potential difference is sampled by an A / D converter (not shown) and converted into a digital value. The converted digital value is used as a detection signal by the personal computer arithmetic unit 1
3 is input to the correlation processing unit 12.
【００２３】パーソナルコンピュータ演算部１３では、
第２のＭ系列信号発生器１１、正弦波発生器１４及び掛
算器１７により、埋設鋼管１と接地電極４との間の電圧
として印加された正弦波信号と同じＭ系列パターンの二
位相変調の正弦波信号が、参照用Ｍ系列信号として相関
処理部１２に入力される。相関処理部１２は、参照用Ｍ
系列信号と検出信号との相関演算を行う。ここで、例え
ば検出信号をｆ（ｔ）、参照用Ｍ系列信号をｇ（ｔ）と
すると、相関結果は次式（３）により演算される。Ｔは
繰り返し周期である。In the personal computer operation section 13,
The second M-sequence signal generator 11, the sine wave generator 14, and the multiplier 17 perform two-phase modulation of the same M-sequence pattern as the sine wave signal applied as a voltage between the buried steel pipe 1 and the ground electrode 4. The sine wave signal is input to the correlation processing unit 12 as a reference M-sequence signal. The correlation processing unit 12 uses the reference M
A correlation operation between the sequence signal and the detection signal is performed. Here, for example, assuming that the detection signal is f (t) and the reference M-sequence signal is g (t), the correlation result is calculated by the following equation (3). T is a repetition period.
【００２４】[0024]
【数１】 (Equation 1)
【００２５】検出信号ｆ（ｔ）にはＭ系列信号成分が含
まれ、参照用Ｍ系列信号ｇ（ｔ）はこれと同じパターン
のＭ系列符号パターンであるので、相互相関演算は時間
遅延をおこした自己相関演算と同じになる。したがっ
て、相関演算結果は周期的なピーク値を有する。例えば
符号長１２７の同じＭ系列符号パターンであれば、最大
１２７回の相互相関演算によってピーク値が得られる。
このピーク値を検出して検出信号の代表値とする。この
代表値が、外側車輪電極６−１ａ及び６−１ｂが検出し
た電位の差又は内側車輪電極６−２ａ及び６−２ｂが検
出した電位の差を最もよく表している値となる。相関処
理部１２は、算出した代表値に基づいて、電位差を処理
し、電位差分布として検出する。電位差分布に基づい
て、オペレータの目視やゼロクロスを検出する手段（図
示せず）等により、ゼロクロス点が検出され、塗膜損傷
位置として検出されることになる。The detection signal f (t) contains an M-sequence signal component, and the reference M-sequence signal g (t) has the same pattern as the M-sequence code pattern. Autocorrelation operation. Therefore, the correlation operation result has a periodic peak value. For example, in the case of the same M-sequence code pattern having a code length of 127, a peak value is obtained by a maximum of 127 cross-correlation calculations.
This peak value is detected and used as a representative value of the detection signal. This representative value is a value that best represents the difference between the potentials detected by the outer wheel electrodes 6-1a and 6-1b or the difference between the potentials detected by the inner wheel electrodes 6-2a and 6-2b. The correlation processing unit 12 processes the potential difference based on the calculated representative value and detects the potential difference as a potential difference distribution. Based on the potential difference distribution, a zero cross point is detected by means of an operator's visual observation or a means (not shown) for detecting a zero cross, and is detected as a paint film damage position.
【００２６】図２は近接して存在する２点の塗膜損傷部
が埋設鋼管に存在する場合を表す図である。対象とした
埋設鋼管１は、管径１００Ａ、管長１０ｍのＰＬＰ導管
であり、約１ｍの深さに埋設されたものである。塗膜損
傷箇所は２箇所で、各々の損傷のサイズは５ｍｍ×４ｍ
ｍである。両損傷箇所の間隔は１０ｃｍであった。ま
た、探査機６の車輪電極の間隔は、外側車輪電極６−１
ａ及び６−１ｂの間が１ｍ、内側車輪電極６−１ａ及び
６−１ｂの間が１０ｃｍである。埋設鋼管１への流入電
流は１ｍＡ（搬送波の周期は４４０Ｈｚ）である。FIG. 2 is a diagram showing a case where two adjacent paint film damaged portions exist in a buried steel pipe. The target embedded steel pipe 1 is a PLP pipe having a pipe diameter of 100 A and a pipe length of 10 m, and is buried at a depth of about 1 m. There are two places where the coating film is damaged, and the size of each damage is 5 mm x 4 m
m. The distance between the two damage points was 10 cm. Further, the interval between the wheel electrodes of the spacecraft 6 is set to the outer wheel electrode 6-1.
The distance between the inner wheel electrodes 6-1a and 6-1b is 10 cm, and the distance between the inner wheel electrodes 6-1a and 6-1b is 10 cm. The current flowing into the buried steel pipe 1 is 1 mA (the period of the carrier wave is 440 Hz).
【００２７】ここで、塗膜損傷部が１箇所しかなけれ
ば、一対の電極で塗膜損傷位置を十分検出できる。しか
し、２箇所の塗膜損傷部が近接して存在したときは、電
極間隔と損傷部間距離によって塗膜損傷部の分解能が決
まるので、電極間隔に対して損傷部間隔が十分小さいと
各々の損傷部の位置が弁別できない。そこで、電極間隔
の小さい電極系と組合せて、塗膜損傷位置の弁別能を向
上しようとするものである。Here, if there is only one damaged portion of the coating film, the damaged position of the coating film can be sufficiently detected by a pair of electrodes. However, when two damaged portions of the paint film exist close to each other, the resolution of the damaged portion of the paint film is determined by the distance between the electrodes and the distance between the damaged portions. The location of the damaged part cannot be identified. Therefore, an attempt is made to improve the discriminating ability of a coating film damaged position in combination with an electrode system having a small electrode interval.
【００２８】図２（ａ）は塗膜損傷に起因する地表面の
電位分布である。また、図２（ｂ）は外側車輪電極によ
る検出信号を処理したときの波形、図２（ｃ）は内側車
輪電極による検出信号を処理したときの波形を表してい
る。波形のＳ字型カーブが符号反転（零点横断）する地
点に基づいて、塗膜損傷部の位置を同定する本方法にお
いて、互いに近接した塗膜損傷部については、各々の塗
膜損傷部の真上の地表面では、外側車輪電極はゼロクロ
スしていないので、弁別することができないが（図２
（ｂ））、内側車輪電極では弁別できている（図２
（ｃ））。ここで、特定した位置ではなく、全体におけ
る塗膜損傷部の有無を検出するのは、外側車輪電極の方
が電位の差が大きくなる分だけ確実に検出できるので、
二対の車輪電極間隔の広狭の特徴を有効に活用し、精度
の高い塗膜損傷の検出が可能である。FIG. 2A shows the potential distribution on the ground surface caused by damage to the paint film. FIG. 2B shows a waveform when the detection signal from the outer wheel electrode is processed, and FIG. 2C shows a waveform when the detection signal from the inner wheel electrode is processed. In the method for identifying the position of a damaged film based on the point where the sign of the S-shaped curve of the waveform reverses (crosses the zero point), the true value of each damaged film is determined for the damaged film in proximity to each other. On the ground surface above, the outer wheel electrode is not zero-crossed and cannot be discriminated (Fig. 2
(B)), the inner wheel electrode can be discriminated (FIG. 2)
(C)). Here, instead of the specified position, the presence / absence of the coating film damaged portion in the whole is detected more reliably because the outer wheel electrode has a larger potential difference,
By effectively utilizing the wide and narrow characteristics of the distance between the two pairs of wheel electrodes, it is possible to detect coating film damage with high accuracy.
【００２９】以上のように第１の実施の形態によれば、
外側車輪電極６−１ａ及び６−１ｂが検出した電位差分
布又は内側車輪電極６−２ａ及び６−２ｂが検出した電
位の差分布に基づいて、車輪電極間隔の広狭による分解
能に応じた塗膜損傷の検出が可能となる。したがって、
車輪電極間隔が広い外側車輪電極６−１ａ及び６−１ｂ
により処理された電位差分布では、全体における塗膜損
傷部の有無がより正確に検出できる。また、車輪電極間
隔が狭い内側車輪電極６−２ａ及び６−２ｂにより処理
された電位差では、近接する２箇所以上の塗膜損傷の位
置が各々検出可能となる。また、埋設鋼管１に印加する
電圧として、擬似ランダムなＭ系列信号を搬送波の位相
を変調することによって生成した正弦波信号を用い、電
位差として検出した検出信号を正弦波信号と同じ符号パ
ターンで相関処理して算出した、相関の最大値である代
表値に基づいて、電位差分布を求めるようにしたので、
ノイズの影響が除去され、Ｓ／Ｎ比を改善することがで
き、埋設鋼管の塗膜損傷位置を高感度で精度よく、確実
に検出することができる。また、正弦波であるので、直
流成分の減衰が著しい地中の電位伝搬特性でも、電位伝
搬減衰を少なくすることができる。したがって、検出感
度がよくなり、印加電圧能力の低減、検査面への散水処
理の省略、車輪電極間距離の縮少化による探査機の小型
化が可能となり、システムを安価なものにすることがで
きる。As described above, according to the first embodiment,
Based on the potential difference distribution detected by the outer wheel electrodes 6-1a and 6-1b or the potential difference distribution detected by the inner wheel electrodes 6-2a and 6-2b, the coating film damage corresponding to the resolution due to the width of the wheel electrode interval. Can be detected. Therefore,
Outer wheel electrodes 6-1a and 6-1b with wide wheel electrode spacing
In the potential difference distribution treated by the above, the presence or absence of a coating film damaged portion can be more accurately detected in the whole. Further, the potential difference processed by the inner wheel electrodes 6-2a and 6-2b having a narrow wheel electrode interval makes it possible to detect the positions of two or more adjacent coating film damages. Further, as a voltage applied to the buried steel pipe 1, a sine wave signal generated by modulating the phase of a carrier wave of a pseudo-random M-sequence signal is used, and a detection signal detected as a potential difference is correlated with the same code pattern as the sine wave signal. Since the potential difference distribution is calculated based on the representative value that is the maximum value of the correlation calculated and processed,
The influence of noise can be eliminated, the S / N ratio can be improved, and the coating film damage position on the buried steel pipe can be detected with high sensitivity, accuracy, and reliability. Further, since the waveform is a sine wave, the potential propagation attenuation can be reduced even in the potential propagation characteristics in the ground where the DC component is significantly attenuated. Therefore, the detection sensitivity is improved, the applied voltage capacity can be reduced, the sprinkling treatment on the inspection surface can be omitted, and the spacecraft can be downsized by reducing the distance between the wheel electrodes, thereby making the system inexpensive. it can.
【００３０】実施形態２．上述の実施の形態では、Ｍ系
列による符号パターンを二位相変調した正弦波信号を印
加して塗膜損傷位置を検出するようにしたが、本発明で
はこれに限定されるものではなく、構造が単純な通常の
正弦波等による検出に適用することも可能である。Embodiment 2 In the above-described embodiment, a sine wave signal obtained by applying a two-phase modulation to the code pattern of the M sequence is applied to detect the damage position of the coating film. However, the present invention is not limited to this. It is also possible to apply to detection by a simple ordinary sine wave or the like.
【００３１】実施形態３．また、上述の実施の形態で
は、同じ符号パターンの正弦波信号と参照用Ｍ系列信号
とをそれぞれ独立に発生させるようにした。しかし、正
弦波信号と参照用Ｍ系列信号とは元々同じパターンを有
する二値の信号であるから、正弦波信号を参照用Ｍ系列
信号として相関処理させることも可能である。Embodiment 3 In the above-described embodiment, the sine wave signal and the reference M-sequence signal having the same code pattern are independently generated. However, since the sine wave signal and the reference M-sequence signal are originally binary signals having the same pattern, the sine wave signal can be correlated as the reference M-sequence signal.
【００３２】実施形態４．また第１の実施の形態では、
一対の車輪電極を、電極間隔を異ならせて管軸方向に沿
って内外に２組配したが、本発明ではこれに限定される
ものではなく、２組以上の電極を用いてもよい。また、
電極の配列も並列であれば内外に限ったものではない。
さらに、一対の車輪電極を２組ではなく、距離間隔の異
なる車輪電極を２組（つまり、例えば最も後ろにある車
輪電極と他の２つの車輪電極との間の電位差をそれぞれ
算出する組）で電位差の分布を検出するようにしてもよ
い。Embodiment 4 FIG. In the first embodiment,
Although two pairs of wheel electrodes are arranged inside and outside along the tube axis direction with different electrode intervals, the present invention is not limited to this, and two or more pairs of electrodes may be used. Also,
The arrangement of the electrodes is not limited to the inside and outside as long as the arrangement is parallel.
Further, instead of two pairs of wheel electrodes, two pairs of wheel electrodes having different distance intervals are used (that is, a pair for calculating the potential difference between the rearmost wheel electrode and the other two wheel electrodes, for example). The distribution of the potential difference may be detected.
【００３３】[0033]
【発明の効果】以上のように本発明によれば、２点間の
電位差の分布を検出する際に、２点の距離間隔を異なら
せた電位差の分布を２つ以上検出するようにしたので、
距離間隔の広狭による分解能に応じた塗膜損傷の検出が
可能となる。したがって、距離間隔が広い電位差の分布
では、全体における塗膜損傷の有無がより正確に検出で
きる。また、距離間隔が狭い電位差の分布では、近接す
る２箇所以上の塗膜損傷の位置が各々検出可能となる。As described above, according to the present invention, when detecting the potential difference distribution between two points, two or more potential difference distributions having different distance intervals between the two points are detected. ,
The coating film damage can be detected in accordance with the resolution due to the width of the distance. Therefore, in the distribution of the potential difference with a large distance interval, the presence or absence of coating film damage can be more accurately detected as a whole. Further, in the distribution of the potential difference with a small distance interval, the positions of two or more adjacent coating film damages can be detected.
【００３４】また、本発明によれば、参照信号を信号発
生器からのランダム信号又は擬似ランダム信号に基づい
て生成するようにしたので、あらためて別の手段を設け
なくても、同じランダムパターンの参照信号を生成する
ことができる。According to the present invention, since the reference signal is generated based on the random signal or the pseudo random signal from the signal generator, the reference of the same random pattern can be performed without providing another means. A signal can be generated.
【図１】本発明の第１の実施の形態に係る埋設鋼管の塗
膜損傷検出方法を実現するための構成を表す図である。FIG. 1 is a diagram illustrating a configuration for realizing a method for detecting a coating film damage on a buried steel pipe according to a first embodiment of the present invention.
【図２】近接して存在する２点の塗膜損傷部が埋設鋼管
に存在する場合を表す図である。FIG. 2 is a diagram illustrating a case where two paint film damaged portions existing close to each other are present in a buried steel pipe.
【図３】電位差法を実現するためのシステム構成を表す
図である。FIG. 3 is a diagram illustrating a system configuration for realizing a potential difference method.
【図４】塗膜損傷部を検出したときの電位分布と距離及
び車輪電極６ａ及び６ｂにより測定された電位の電位差
と距離との関係を表す図である。FIG. 4 is a diagram showing a relationship between a potential distribution and a distance when a damaged coating film is detected and a potential difference between a potential measured by the wheel electrodes 6a and 6b and a distance.
１ 埋設鋼管 ３ 電力増幅器 ４ 接地電極 ５ 塗膜損傷部 ６ 探査機 ６−１ａ、６−１ｂ 外側車輪電極 ６−２ａ、６−２ｂ 内側車輪電極 １０ 第１のＭ系列信号発生器 １１ 第２のＭ系列信号発生器 １２ 相関処理部 １３ パーソナルコンピュータ演算部 １４、１６ 正弦波発生器 １５、１７ 掛算器 REFERENCE SIGNS LIST 1 buried steel pipe 3 power amplifier 4 ground electrode 5 damaged coating film 6 probe 6-1a, 6-1b outer wheel electrode 6-2a, 6-2b inner wheel electrode 10 first M-sequence signal generator 11 second M-sequence signal generator 12 Correlation processing unit 13 Personal computer operation unit 14, 16 Sine wave generator 15, 17 Multiplier
───────────────────────────────────────────────────── フロントページの続き Ｆターム(参考） 2F063 AA02 BC02 BC09 BC10 BD07 DA01 DB04 FA16 LA06 LA18 LA23 2G053 AA12 AB21 BA12 BA19 BA26 BC02 CA18 DB05 DB25 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F063 AA02 BC02 BC09 BC10 BD07 DA01 DB04 FA16 LA06 LA18 LA23 2G053 AA12 AB21 BA12 BA19 BA26 BC02 CA18 DB05 DB25
Claims (4)
て、前記埋設鋼管に電流を流し、一方、地表面上におい
て、ある２点を前記埋設鋼管の管軸方向に一定距離間隔
で走査させて、前記２点間の電位差の分布を検出し、前
記埋設鋼管に施した塗膜に損傷がある場合に、前記流し
た電流の漏れにより地表面の電位が変化することを利用
して、前記検出した電位差の分布に基づいて塗膜損傷の
有無及び位置を検出する埋設鋼管の塗膜損傷位置検出方
法において、 前記２点の距離間隔を異ならせた電位差の分布を２つ以
上検出することを特徴とする埋設鋼管の塗膜損傷位置検
出方法。1. A voltage is applied between a buried steel pipe and the ground to cause a current to flow through the buried steel pipe, while two points on the ground surface are spaced at a fixed distance in the pipe axis direction of the buried steel pipe. By scanning, the distribution of the potential difference between the two points is detected, and when the coating applied to the buried steel pipe is damaged, utilizing the fact that the potential of the ground surface changes due to the leakage of the flowing current. A method for detecting the presence or absence and position of a coating damage based on the distribution of the detected potential difference, wherein the two or more potential difference distributions having different distance intervals between the two points are detected. A method for detecting a paint film damage position on a buried steel pipe.
圧は、正弦波である搬送波を位相変調させて生成した、
周期内ではランダム性を有する擬似ランダム信号に基づ
いた波形の電圧とし、 また、前記電位差の分布は、前記擬似ランダム信号と同
じランダムパターンを有する独立に生成した参照信号と
前記電位差との相関演算を行い、相関のピークの値が算
出されたときの前記電位差に基づく値を代表値として算
出し、前記代表値の分布を前記電位差の分布として検出
することを特徴とする請求項１記載の埋設鋼管の塗膜損
傷位置検出方法。2. A voltage applied between the buried steel pipe and the ground is generated by phase-modulating a carrier wave that is a sine wave.
Within the cycle, a voltage having a waveform based on a pseudo-random signal having randomness, and the distribution of the potential difference is obtained by performing a correlation operation between an independently generated reference signal having the same random pattern as the pseudo-random signal and the potential difference. The buried steel pipe according to claim 1, wherein a value based on the potential difference when the peak value of the correlation is calculated is calculated as a representative value, and the distribution of the representative value is detected as the distribution of the potential difference. Method for detecting paint film damage position.
比例した電圧を印加する電圧増幅器と、 前記埋設鋼管の管軸方向と平行に隔離して配置され、地
面との接触部位の電位を検出する一対の車輪電極を、該
車輪電極の距離間隔を異ならせて２組以上備え、地表面
を前記埋設鋼管の管軸方向に沿って走行する探査機と、 前記一対の車輪電極のそれぞれの組に対し、車輪電極間
の電位差を測定する電圧測定器と、 該電圧測定器が測定したそれぞれの組の車輪電極間の電
位差の分布に基づいて、前記埋設鋼管の塗膜損傷有無及
び位置を検出する手段とを備えたことを特徴とする埋設
鋼管の塗膜損傷位置検出装置。3. An AC voltage generator, a voltage amplifier for applying a voltage proportional to an output of the AC voltage generator between a buried steel pipe and the ground, and a voltage amplifier isolated in parallel with a pipe axis direction of the buried steel pipe. And two or more pairs of wheel electrodes for detecting a potential of a contact portion with the ground are provided at different distance intervals between the wheel electrodes, and the ground surface runs along the tube axis direction of the buried steel pipe. A spacecraft, a voltage measuring device for measuring a potential difference between the wheel electrodes for each set of the pair of wheel electrodes, and a distribution of the potential difference between the wheel electrodes of each set measured by the voltage measuring device. Means for detecting the presence or absence and position of paint film damage on the buried steel pipe.
ダム信号を搬送波を位相変調させて生成する第１の信号
発生器と、 埋設鋼管と地面との間に、前記第１の信号発生器の出力
に比例した電圧を印加する電圧増幅器と、 前記埋設鋼管の管軸方向と平行に隔離して配置され、地
面との接触部位の電位を検出する一対の車輪電極を、該
車輪電極の距離間隔を異ならせて２組以上備え、地表面
を前記埋設鋼管の管軸方向に沿って走行する探査機と、 前記一対の車輪電極のそれぞれの組に対し、車輪電極間
の電位差を測定する電圧測定器と、 前記第１の信号発生器が生成した前記擬似ランダム信号
と同じパターンの波形を有する第２の信号発生器によっ
て生成された参照信号と前記電位差との相関演算を行っ
て相関のピークの値を算出し、該ピーク値における前記
電位差に基づく値を代表値として、該代表値の分布を検
出する相関処理装置と、 該相関処理装置が算出したそれぞれの組の代表値の分布
に基づいて、前記埋設鋼管の塗膜損傷の有無及び位置を
検出する手段とを備えたことを特徴とする埋設鋼管の塗
膜損傷位置検出装置。4. A first signal generator for generating a pseudo-random signal having randomness within a period by phase-modulating a carrier wave, and an output of the first signal generator between a buried steel pipe and the ground. A voltage amplifier that applies a voltage proportional to a pair of wheel electrodes that are arranged separately in parallel with the pipe axis direction of the buried steel pipe and that detects the potential of a contact portion with the ground, and that the distance between the wheel electrodes is An explorer provided with two or more sets different from each other, running on the ground surface along the pipe axis direction of the buried steel pipe; and a voltage measuring instrument for measuring a potential difference between the wheel electrodes for each set of the pair of wheel electrodes. And performing a correlation operation between a reference signal generated by a second signal generator having a waveform of the same pattern as the pseudo-random signal generated by the first signal generator and the potential difference, and a peak value of the correlation. Is calculated. A correlation processing device that detects a distribution of the representative value, using a value based on the potential difference in the value as a representative value, and a coating film of the embedded steel pipe based on the distribution of the representative value of each set calculated by the correlation processing device. Means for detecting the presence or absence and position of damage to a coating film on a buried steel pipe.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10183841A JP2000019159A (en) | 1998-06-30 | 1998-06-30 | Method and device for detecting paint film damaged position of buried steel pipe |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10183841A JP2000019159A (en) | 1998-06-30 | 1998-06-30 | Method and device for detecting paint film damaged position of buried steel pipe |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2000019159A true JP2000019159A (en) | 2000-01-21 |
Family
ID=16142785
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10183841A Pending JP2000019159A (en) | 1998-06-30 | 1998-06-30 | Method and device for detecting paint film damaged position of buried steel pipe |
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| Country | Link |
|---|---|
| JP (1) | JP2000019159A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7034539B2 (en) | 2003-07-16 | 2006-04-25 | Canon Kabushiki Kaisha | Underground exploration apparatus, system and method |
-
1998
- 1998-06-30 JP JP10183841A patent/JP2000019159A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7034539B2 (en) | 2003-07-16 | 2006-04-25 | Canon Kabushiki Kaisha | Underground exploration apparatus, system and method |
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