JP2000019158A - Method and device for detecting paint film damage position of buried steel pipe - Google Patents
Method and device for detecting paint film damage position of buried steel pipeInfo
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- JP2000019158A JP2000019158A JP10183840A JP18384098A JP2000019158A JP 2000019158 A JP2000019158 A JP 2000019158A JP 10183840 A JP10183840 A JP 10183840A JP 18384098 A JP18384098 A JP 18384098A JP 2000019158 A JP2000019158 A JP 2000019158A
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- Prior art keywords
- steel pipe
- buried steel
- potential difference
- axis direction
- 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
傷検出位置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 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つ目の
問題点は、管軸方向に沿って配置された一対の車輪電極
が検出した電位の差を電位差としてその分布を検出して
いるので、埋設鋼管の管軸方向では電位差の分布に基づ
いて塗膜損傷位置の検出ができるものの、周方向の位置
（０〜１２時）に関しては、塗膜損傷位置の検出ができ
ないことである。特に大径鋼管の場合においては、損傷
部の補修をする際に、損傷部が鋼管の上下（０時か６時
の方向）左右（３時か９時の方向）のどの位置にあるか
を検出することは、検出精度等との関係で非常に重要と
なる。However, the above-mentioned potential difference method has the following problems. The first problem is that the distribution of the potential difference is detected in the tube axis direction of the buried steel pipe because the potential difference is detected as the potential difference between the pair of wheel electrodes arranged along the tube axis direction. Although the damage position of the paint film can be detected based on the position, the damage position of the paint film cannot be detected at the circumferential position (0 to 12:00). In particular, in the case of large diameter steel pipes, when repairing damaged parts, it is necessary to determine the position of the damaged part at the top and bottom (0 o'clock or 6 o'clock) and left and right (3 o'clock or 9 o'clock) of the steel pipe. Detection is very important in relation to detection accuracy and the like.
【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、周方向についても、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。SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is an object of the present invention to provide a method for reliably detecting the position of a damaged portion in the circumferential direction and a system suitable for implementing the method. The purpose is to provide. Furthermore, S
It is an object of the present invention to provide a method and a system for improving the / N ratio and accurately detecting the position of a damaged portion of a 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点の管軸方向への走査を、複数の前記管
軸方向に平行な直線上に沿って行い、２点間の電位差の
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。塗膜損傷の位
置からの距離が短いほど、検出する電位差の分布の振幅
が大きいことを利用し、２つ以上の電位差の分布に基づ
いて、管軸方向だけでなく、周方向における塗膜損傷位
置も検出する。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, scanning in the tube axis direction at two points is performed along a plurality of straight lines parallel to the tube axis direction, and two or more potential difference distributions between the two points are detected. 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. Utilizing the fact that the shorter the distance from the position of the coating film damage, the greater the amplitude of the distribution of the detected potential difference, based on the distribution of two or more potential differences, the coating film damage in the circumferential direction as well as the tube axis direction. The position is also detected.
【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、複数の前記管軸方向に平行な直線
上に沿って走査して検出した電位差の分布を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 distributions of potential differences detected by scanning along a plurality of straight lines parallel to the tube axis direction 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, the presence / absence of the entire coating film damage and the position of each coating film damage can be 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、管軸方向に平行な複数の直線上の電
位を検出するように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、管軸方向だけでなく、周
方向における塗膜損傷位置も検出する。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 supplied 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 pipe axis direction of the buried steel pipe and detect the potential of a contact portion with the ground, apply a plurality of potentials on a plurality of straight lines parallel to the pipe axis direction. A probe equipped with at least two sets to detect the ground surface and running along the pipe axis direction of the buried steel pipe, and a voltage measuring device for measuring a potential difference between the wheel electrodes for each pair of the wheel electrodes. Means for detecting the coating damage position of the buried steel pipe based on the distribution of the potential difference between each pair of wheel electrodes measured by the voltmeter, and coating damage not only in the pipe axis direction but also in the circumferential direction. The position is also detected.
【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、管軸方
向に平行な複数の直線上の電位を検出するように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、管軸方向だけでなく、周方向
における塗膜損傷位置も検出する。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,
Two pairs of wheel electrodes, which are arranged in parallel with the tube axis direction of the buried steel pipe and detect the potential of the contact portion with the ground, and detect two pairs of potentials on a plurality of straight lines parallel to the tube axis direction. A probe for traveling along the pipe axis direction of the buried steel pipe on the ground surface, a voltage measuring device for measuring a potential difference between the wheel electrodes for each pair of the wheel electrodes, and a first signal generator A correlation peak value is calculated by 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 detector and a potential difference, and the value of the correlation is calculated based on the potential difference at the peak value. A correlation processing device that detects the distribution of the representative value using the value as a representative value, and detects the presence or absence and position of the coating film damage of the buried steel pipe based on the distribution of the representative value of each set calculated by the correlation processing device. Means and provisions of noise Suppressing the sound, the distribution of the representative values based on a potential difference clearly detected, not only the tube axial direction, also detects coating damage position in the circumferential direction.
【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の中央車輪電極、６−２ａ及び６−２ｂは探査機
６の右側車輪電極、６−３ａ及び６−３ｂは探査機６の
左側車輪電極、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、１５及び１７は掛算器である。ここで、中央車輪
電極６−１ａ、右側車輪電極６−２ａ及び左側車輪電極
６−３ａは、管軸方向（移動方向）と垂直に配置されて
いる。また、中央車輪電極６−１ａ、右側車輪電極６−
２ａ及び左側車輪電極６−３ａも同様に、管軸方向（移
動方向）と垂直に配置されている。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 center wheel electrodes of the probe 6, 6-2a and 6-2b are right wheel electrodes of the probe 6, 6-3a and 6-3b. Is a left wheel electrode of the spacecraft 6, 10 is a first M-sequence signal generator, 11 is a second M-sequence signal generator, 12 is a correlation processing unit, 13 is a personal computer operation unit, and 14 and 16 are sine waves. Generators 15 and 17 are multipliers. Here, the center wheel electrode 6-1a, the right wheel electrode 6-2a, and the left wheel electrode 6-3a are arranged perpendicular to the tube axis direction (moving direction). The center wheel electrode 6-1a and the right wheel electrode 6-
Similarly, the 2a and the left wheel electrode 6-3a are also arranged perpendicular to the tube axis direction (moving direction).
【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、中央車輪電極６−１ａ及
び６−１ｂ、右側車輪電極６−２ａ及び６−２ｂ並びに
左側車輪電極６−３ａ及び６−３ｂを用いて、塗膜損傷
の位置からそれぞれの電極までの距離の差に基づいて、
周方向についても、塗膜損傷位置の検出を可能とするも
のである。This embodiment uses the center wheel electrodes 6-1a and 6-1b, the right wheel electrodes 6-2a and 6-2b, and the left wheel electrodes 6-3a and 6-3b to determine the position of the coating film damage. Based on the difference in distance from
Also in the circumferential direction, it is possible to detect the damaged position of the coating film.
【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３組の車輪電極（中央車輪電極６−１ａ及び６−１
ｂ、右側車輪電極６−２ａ及び６−２ｂ並びに左側車輪
電極６−３ａ及び６−３ｂ）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、中央車輪電極６−１ａ及び６−１ｂが検出した電位
の差を導き出す。また右側車輪電極６−２ａ及び６−２
ｂ並びに右側車輪電極６−２ａ及び６−２ｂに関して
も、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１３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 that time, three sets of wheel electrodes (central wheel electrodes 6-1a and 6-1a) provided on the spacecraft 6 were used.
b, the right wheel electrodes 6-2a and 6-2b and the left wheel electrodes 6-3a and 6-3b) detect the potential of the ground contacting, respectively. 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 center wheel electrodes 6-1a and 6-1b. Also, right wheel electrodes 6-2a and 6-2
b and the right wheel electrodes 6-2a and 6-2b, a difference between the detected potentials is derived. Each potential difference is sampled by an A / D converter (not shown) and converted into a digital value. The converted digital value is input to the correlation processing unit 12 of the personal computer calculation unit 13 as a detection signal.
【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、中央車輪電極６−１ａ及び６−１ｂ、右側車
輪電極６−２ａ及び６−２ｂ又は左側車輪電極６−３ａ
及び６−３ｂ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. The representative values are the center wheel electrodes 6-1a and 6-1b, the right wheel electrodes 6-2a and 6-2b, or the left wheel electrodes 6-3a.
And 6-3b are the values that best represent the difference between the detected potentials. 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は塗膜損傷部５と各電極との距離関係
及び電位差との関係を表す図である。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１箇所で、埋設鋼管１に流れる電流の方向に対し、
３時方向に存在する。損傷のサイズは５ｍｍ×４ｍｍで
ある。また、探査機６の中央車輪電極６−１ａ、右側車
輪電極６−２ａ及び左側車輪電極６−３ａを管軸方向
（移動方向）に垂直に配置している。右側車輪電極６−
２ａ及び左側車輪電極６−３ａは、それぞれ中央車輪電
極６−１ａに対して３０ｃｍ離している。そして、中央
車輪電極６−１ｂ、右側車輪電極６−２ｂ及び左側車輪
電極６−３ｂはそれぞれ、中央車輪電極６−１ａ、右側
車輪電極６−２ａ及び左側車輪電極６−３ａから１ｍ離
して、管軸方向（移動方向）に垂直に配置している。埋
設鋼管１への流入電流は１ｍＡ（搬送波の周期は４４０
Ｈｚ）である。FIG. 2 is a diagram showing the relationship between the distance between the damaged portion 5 of the coating film and each electrode and the potential difference. 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. The coating film is damaged in one place, and the direction of the current flowing through the buried steel pipe 1 is
Present at 3 o'clock. The size of the lesion is 5 mm x 4 mm. In addition, the center wheel electrode 6-1a, the right wheel electrode 6-2a, and the left wheel electrode 6-3a of the probe 6 are arranged perpendicular to the tube axis direction (moving direction). Right wheel electrode 6
2a and the left wheel electrode 6-3a are respectively separated by 30 cm from the center wheel electrode 6-1a. Then, the center wheel electrode 6-1b, the right wheel electrode 6-2b, and the left wheel electrode 6-3b are separated from the center wheel electrode 6-1a, the right wheel electrode 6-2a, and the left wheel electrode 6-3a by 1 m, respectively. It is arranged perpendicular to the tube axis direction (moving direction). 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、管軸方向の塗膜損傷部の位置だけ
を検出するのであれば、一対の電極で塗膜損傷位置を十
分検出できる。しかし、周方向に関する位置までは検出
できない。そこで、（２）式から導き出せるように、塗
膜損傷部の位置と電極との距離が短いほど、電位差の振
幅が大きいことを利用し、２組以上の電極を、管軸方向
と平行にのびている異なる直線に沿って移動させ、その
電位差の分布に基づいて周方向における塗膜損傷位置を
検出しようとするものである。Here, if only the position of the damaged coating film in the tube axis direction is detected, the damaged coating film position can be sufficiently detected by a pair of electrodes. However, the position cannot be detected up to the position in the circumferential direction. Therefore, as can be derived from equation (2), utilizing the fact that the shorter the distance between the position of the damaged portion of the coating film and the electrode, the greater the amplitude of the potential difference, the two or more pairs of electrodes are connected in parallel to the tube axis direction. The position of the coating film in the circumferential direction is detected based on the distribution of the potential difference.
【００２８】図２（ａ）は塗膜損傷の位置を表してい
る。また、図２（ｂ）は検出された電位差分布の波形を
表している。どの波形においても、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、管軸方向
における塗膜損傷位置は検出できる。右側車輪電極６−
２ａ及び６−２ｂにより検出された電位差の波形が、中
央車輪電極６−１ａ及び６−１ｂ並びに左側車輪電極６
−３ａ及び６−３ｂにより検出された電位差の波形に比
べ、振幅が大きい。これは、塗膜損傷位置と右側車輪電
極６−２ａ及び６−２ｂとの距離が最も短いことを表し
ている。したがって、電位差の振幅の大きさに基づい
て、周方向における塗膜損傷部の位置を検出する本方法
において、塗膜損傷位置は右側（埋設鋼管１に流れる電
流の方向に対し、３時方向）に存在するものと判断でき
る。FIG. 2A shows the position of the coating film damage. FIG. 2B shows a waveform of the detected potential difference distribution. In any waveform, the coating film damage position in the tube axis direction can be detected based on the point where the S-shaped curve of the waveform reverses the sign (crosses the zero point). Right wheel electrode 6
The waveforms of the potential differences detected by the center wheel electrodes 6-1a and 6-1b and the left wheel electrode 6
The amplitude is larger than the waveform of the potential difference detected by -3a and 6-3b. This indicates that the distance between the paint film damaged position and the right wheel electrodes 6-2a and 6-2b is the shortest. Therefore, in the present method for detecting the position of the damaged portion of the coating film in the circumferential direction based on the magnitude of the amplitude of the potential difference, the damaged coating film position is on the right side (3 o'clock direction with respect to the direction of the current flowing through the buried steel pipe 1). Can be determined to exist.
【００２９】以上のように第１の実施の形態によれば、
管軸方向に垂直な方向に、探査機６の中央車輪電極６−
１ａ、右側車輪電極６−２ａ及び左側車輪電極６−３ａ
を配置し、また中央車輪電極６−１ｂ、右側車輪電極６
−２ｂ及び左側車輪電極６−３ｂを配置して、探査機６
を管軸方向に移動させ、塗膜損傷位置と電極との距離が
短いほど振幅が大きいことを利用し、中央車輪電極６−
１ａ及び６−１ｂ、右側車輪電極６−２ａ及び６−２ｂ
並びに左側車輪電極６−３ａ及び６−３ｂがそれぞれ検
出した電位差の分布に基づいて、管軸方向だけでなく、
周方向についても塗膜損傷位置が検出できるようにした
ので、確実に塗膜損傷位置を検出できる。これは、特に
径の大きい埋設鋼管には有効である。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,
In the direction perpendicular to the pipe axis direction, the center wheel electrode 6 of the spacecraft 6
1a, right wheel electrode 6-2a and left wheel electrode 6-3a
And the center wheel electrode 6-1b and the right wheel electrode 6
-2b and the left wheel electrode 6-3b,
Is moved in the axial direction of the tube, and the smaller the distance between the coating damage position and the electrode, the greater the amplitude.
1a and 6-1b, right wheel electrode 6-2a and 6-2b
In addition, based on the distribution of the potential difference detected by the left wheel electrodes 6-3a and 6-3b, not only in the tube axis direction,
Since the paint film damage position can be detected also in the circumferential direction, the paint film damage position can be reliably detected. This is particularly effective for buried steel pipes having a large diameter. In addition, buried steel pipe 1
As a voltage to be applied to a sine wave signal generated by modulating the phase of a carrier wave of a pseudo-random M-sequence signal, a detection signal detected as a potential difference was calculated by performing correlation processing with the same code pattern as the sine wave signal. Since the potential difference distribution is obtained based on the representative value which is the maximum value of the correlation, the influence of noise can be eliminated, the S / N ratio can be improved, and the coating damage position of the buried steel pipe can be detected with high sensitivity. And can be detected accurately and reliably. 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３組、管軸方向に平行して配置した
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
れば等間隔、等電極間隔に限ったものではない。Embodiment 4 FIG. In the first embodiment,
Although three pairs of wheel electrodes are arranged in parallel in the tube axis direction, the present invention is not limited to this, and two or more pairs of electrodes may be used. In addition, the arrangement of the electrodes is not limited to equal intervals, as long as the electrodes are arranged in parallel.
【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点の管軸方向への走査
を、複数の前記管軸方向に平行な直線上に沿って行い、
２点間の電位差の分布を２つ以上検出するようにしたの
で、塗膜損傷の位置からの距離が短いほど、検出する電
位差の分布の振幅が大きいことを利用し、２つ以上の電
位差の分布の振幅に基づいて、管軸方向だけでなく、周
方向における塗膜損傷位置も検出することができ、精度
との高い位置検出が行える。これは、特に径の大きい埋
設鋼管には有効である。As described above, according to the present invention, when detecting the distribution of the potential difference between two points, the scanning of the two points in the tube axis direction is performed on a plurality of straight lines parallel to the tube axis direction. Do along
Since two or more distributions of the potential difference between the two points are detected, the smaller the distance from the position of the coating film damage, the greater the amplitude of the distribution of the potential difference to be detected. Based on the amplitude of the distribution, not only the tube axis direction but also the coating film damage position in the circumferential direction can be detected, and highly accurate position detection can be performed. This is particularly effective for buried steel pipes having a large diameter.
【００３４】また、本発明によれば、埋設鋼管と地面と
の間に印加する電圧を擬似ランダム信号に基づいた波形
の電圧とし、また、２点間の電位差の分布を検出する際
に、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、
算出した代表値の分布を電位差の分布として検出するよ
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、電位差が小さくても、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、搬送波は正弦波であるので、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。According to the present invention, the voltage applied between the buried steel pipe and the ground is a voltage having a waveform based on a pseudo-random signal, and when detecting the potential difference distribution between two points, Perform a correlation operation between the independently generated reference signal and the potential difference having the same random pattern as the random signal,
Since the distribution of the calculated representative value is detected as the distribution of the potential difference, the influence of noise is removed, the S / N ratio can be improved, and even if the potential difference is small, the paint film damage position on the buried steel pipe can be determined. High sensitivity, high accuracy and reliable detection. Further, since the carrier wave 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.
【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】塗膜損傷部５と各電極との距離関係及び電位差
との関係を表す図である。FIG. 2 is a diagram illustrating a relationship between a distance between a coating damaged portion 5 and each electrode and a relationship between potential differences.
【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 中央車輪電極 ６−２ａ、６−２ｂ 右側車輪電極 ６−３ａ、６−３ｂ 左側車輪電極 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 center wheel electrode 6-2a, 6-2b right wheel electrode 6-3a, 6-3b left 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 BA30 BB02 BC02 BD07 CA08 DA01 DD05 EB25 FA08 KA10 LA06 LA11 LA18 LA30 2G053 AA11 AB21 BA12 BA19 BA26 BC02 CA02 CA18 CB14 CB16 CB24 DB02 DB20 DB25 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F063 AA02 BA30 BB02 BC02 BD07 CA08 DA01 DD05 EB25 FA08 KA10 LA06 LA11 LA18 LA30 2G053 AA11 AB21 BA12 BA19 BA26 BC02 CA02 CA18 CB14 CB16 CB24 DB02 DB20 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点の前記管軸方向への走査を、複数の前記管軸方
向に平行な直線上に沿って行い、前記２点間の電位差の
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. In the method for detecting a paint film damage position of a buried steel pipe based on the distribution of the detected potential difference, the method comprising: detecting the presence or absence and position of a paint film damage in a buried steel pipe; A method of detecting a damage position of a coating film on a buried steel pipe, wherein the method is performed along a straight line parallel to the above, and two or more potential difference distributions between the two points are detected.
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、前
記管軸方向に平行な複数の直線上における電位を検出す
るように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 an isolator parallel to 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 so as to detect potentials on a plurality of straight lines parallel to the pipe axis direction, and a ground surface of the buried steel pipe is provided. 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 the pair of wheel electrodes, and a wheel electrode 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 based on the distribution of the potential difference between the buried steel pipes.
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、前
記管軸方向に平行な複数の直線上の電位を検出するよう
に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 the, and a pair of wheel electrodes that are arranged separately in parallel with the tube axis direction of the buried steel pipe and that detect the potential of a contact portion with the ground, are parallel to the tube axis direction. A probe that is provided with at least two sets to detect a plurality of potentials on a straight line, and that travels on the ground surface along the pipe axis direction of the buried steel pipe; and for each set of the pair of wheel electrodes, A voltage measuring device for measuring a potential difference between the reference signal and 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 a correlation operation between the potential difference and the reference signal The correlation peak And a correlation processing device that detects the distribution of the representative value, using a value based on the potential difference at the peak value as a representative value, 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 the paint film on the buried steel pipe.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10183840A JP2000019158A (en) | 1998-06-30 | 1998-06-30 | Method and device for detecting paint film damage position of buried steel pipe |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10183840A JP2000019158A (en) | 1998-06-30 | 1998-06-30 | Method and device for detecting paint film damage position of buried steel pipe |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2000019158A true JP2000019158A (en) | 2000-01-21 |
Family
ID=16142768
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10183840A Pending JP2000019158A (en) | 1998-06-30 | 1998-06-30 | Method and device for detecting paint film damage position of buried steel pipe |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2000019158A (en) |
Cited By (3)
| 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 |
| CN102175759A (en) * | 2011-03-03 | 2011-09-07 | 南昌航空大学 | Method for detecting ferromagnetism blockage of pipeline by utilizing magnetic method |
| CN103196991A (en) * | 2013-04-05 | 2013-07-10 | 保定驰骋千里科技有限公司 | Complete-coverage transient electromagnetic detection method for continuously diagnosing corrosion and defects of pipe body metal |
-
1998
- 1998-06-30 JP JP10183840A patent/JP2000019158A/en active Pending
Cited By (3)
| 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 |
| CN102175759A (en) * | 2011-03-03 | 2011-09-07 | 南昌航空大学 | Method for detecting ferromagnetism blockage of pipeline by utilizing magnetic method |
| CN103196991A (en) * | 2013-04-05 | 2013-07-10 | 保定驰骋千里科技有限公司 | Complete-coverage transient electromagnetic detection method for continuously diagnosing corrosion and defects of pipe body metal |
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