Corrosion-proof coating damaged position detection method and corrosion-proof coating damaged position detection device

Abstract

To provide a corrosion-proof coating damaged position detection method and a corrosion-proof coating damaged position detection device which facilitate detection of even a small damage.SOLUTION: A corrosion-proof coating damaged position detection method for detecting a position of a coating damaged part Bs in an underground buried object B whose outer surface is subjected to corrosion-proof coating using a reception device 10 having a wheel electrode 11 includes a detection step of moving the reception device 10 along the underground buried object B on a ground surface immediately above the underground buried object B, and detecting a potential difference on the ground surface by the wheel electrode 11, an integration step of integrating sines or cosines of the potential difference detected in the detection step, and a display step of displaying an integral waveform of potential distribution integrated in the integration step on a display device 15, wherein the integration step sets a reference value to the amplitude of the potential difference, and integrates the sines or the cosines of a ratio of the amplitude of the potential difference based on the reference value.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method and an apparatus for detecting the location of damage in a corrosion-protective coating. [Background technology]

[0002] There are techniques for detecting, from above ground, the location of a damaged portion of an underground object with an anticorrosive coating on its outer surface. For example, Patent Document 1 discloses a technique in which a receiving device is provided with an integrator that integrates the sine or cosine of the earth surface potential difference, the earth surface potential distribution obtained by the integration is displayed on a display device, and the location of the damage to the anticorrosive coating is detected from the peak point of the waveform. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4106202 Summary of the Invention [Problem to be solved by the invention]

[0004] When an integrated waveform of a specified range is displayed on a display device, if there is large damage within the graph, and the integrated waveform is displayed on a scale that can display the peak points of the large damage, the peak points of the integrated waveform of small damage will be displayed relatively small, and experience is required to find the damage.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a method and device for detecting the location of damage in a corrosion-protective coating, which can easily detect even small damage. [Means for solving the problem]

[0006] <1> A corrosion-protection coating damage location detection method according to aspect 1 of the present invention is a corrosion-protection coating damage location detection method for detecting the location of a coating damage portion in an underground buried object having a corrosion-protection coating on its outer surface using a receiving device having a wheel electrode, and includes a detection step of moving the receiving device along the underground buried object at the ground surface directly above the underground buried object and detecting a potential difference on the ground surface using the wheel electrode, an integration step of integrating the sine or cosine of the potential difference detected in the detection step, and a display step of displaying an integrated waveform of the potential distribution obtained by integration in the integration step on a display device, wherein in the integration step, a reference value for the amplitude of the potential difference is set, and the sine or cosine of a ratio of the amplitude of the potential difference based on the reference value is integrated.

[0007] According to this invention, in the integration step of integrating the sine or cosine of the potential difference detected in the detection step, a reference value for the amplitude of the potential difference is set, and the sine or cosine of the ratio of the amplitude of the potential difference based on the reference value is integrated. The integrated waveform of the potential distribution obtained by integration in the integration step is displayed on the display device in the display step. By appropriately setting the reference value, the magnitude of the integrated value can be appropriately changed, and for example, a relatively small waveform can be amplified and displayed as a large waveform on the display device. Therefore, the integrated waveform of a small damage can be displayed relatively large on the display device. Therefore, the peak point of the integrated waveform is easily visible, and even a small damage can be easily found.

[0008] <2> A corrosion-protective coating damage location detection method according to a second aspect of the present invention is the corrosion-protective coating damage location detection method according to the first aspect, in which, when the amount of change in the integrated waveform is continuously below a predetermined set value while the receiving device moves a certain distance along the underground buried object, the integrated waveform is reset so that the integrated value becomes zero.

[0009] When measuring the potential of an underground buried object, continuing to accumulate error potentials not subject to measurement, which are caused by the insulation resistance value of the coating material arising from areas other than the damaged coating portion, can cause the accumulated waveform to go outside the display range of the display device. According to this invention, when the amount of change in the integrated waveform is continuously equal to or less than a set value while the receiving device advances a certain distance along the buried object, the integrated waveform is reset to zero so that the integrated value becomes zero. This makes it possible to prevent the integrated waveform from going out of the display range of the display device, for example, when the receiving device continues to detect only an error potential that is not the measurement target. In addition, by removing the waveform due to the error potential from the integrated waveform displayed on the display device, the peak points of the integrated waveform can be made easier to see.

[0010] <3> A corrosion-protective coating damage location detection method according to a third aspect of the present invention is the corrosion-protective coating damage location detection method according to the first or second aspect, wherein in the integration step, a gain is set for the integrated waveform, thereby enlarging or reducing the size of the integrated waveform.

[0011] According to this invention, in the integration step, the size of the integrated waveform is enlarged or reduced by setting a gain to the integrated waveform. As a result, for example, on a display device, a relatively small waveform can be enlarged and displayed as a large waveform. Furthermore, a relatively large waveform can be reduced and displayed as a small waveform. Therefore, the integrated waveform can be freely adjusted to a size that is easier to see.

[0012] <4> A corrosion-protective coating damage location detection method according to a fourth aspect of the present invention is the corrosion-protective coating damage location detection method according to any one of the first to third aspects, wherein in the integration step, an offset is added to a calculation formula for the integration to correct a slope of the integrated waveform.

[0013] According to this invention, in the integration step, the integration device adds an offset to the integration formula to correct the slope of the integrated waveform, thereby making the integrated waveform easier to see.

[0014] <5> A corrosion-protective coating damage location detection method according to a fifth aspect of the present invention is the corrosion-protective coating damage location detection method according to any one of the first to fourth aspects, wherein the reference value is a range corresponding to a display range of the display device.

[0015] According to this invention, the reference value is a range corresponding to the display range of the display device. Thus, by appropriately setting the range, for example, a relatively small waveform can be amplified and displayed as a large waveform on the display device. Therefore, the integrated waveform of a small damage can be displayed relatively large on the display device. Therefore, the peak point of the integrated waveform is easily visible, and even a small damage can be easily found.

[0016] <6> A corrosion-protective coating damage location detection method according to a sixth aspect of the present invention is the corrosion-protective coating damage location detection method according to any one of the first to fifth aspects, in which the reference value can be changed manually or automatically.

[0017] According to this invention, when the reference value can be manually changed, the amplitude waveform and the integrated waveform can be expanded or contracted according to the operator's sense. When the reference value can be automatically changed, the operator does not need to change the reference value, and the efficiency of the work can be improved.

[0018] <7> A corrosion-protective coating damage location detection method according to aspect 7 of the present invention is a corrosion-protective coating damage location detection method according to any one of aspects 1 to 6, in which the integrated waveforms before and after the setting of the reference value is changed are simultaneously displayed on the display device.

[0019] According to the present invention, for example, a relatively small enlarged waveform and a relatively large reduced waveform can be simultaneously viewed on a display device, so that, for example, the position of a coating damage part in an underground buried object can be easily grasped regardless of the size of the coating damage part.

[0020] <8> A corrosion-protective coating damage location detection method according to an eighth aspect of the present invention is a corrosion-protective coating damage location detection method according to any one of the first to seventh aspects, in which, in response to a change in the reference value, the integrated waveform from the point in time when the reference value is changed is changed to a display mode corresponding to the magnitude of the reference value after the reference value is changed.

[0021] According to this invention, on the display device, an enlarged, relatively small waveform and a reduced, relatively large waveform can be simultaneously viewed.

[0022] <9> A corrosion-resistant coating damage location detection device according to a ninth aspect of the present invention is a corrosion-resistant coating damage location detection device that detects the location of a damaged portion of a coating in an underground buried object having a corrosion-resistant coating on its outer surface, and includes a receiving device having a wheel electrode that detects a potential difference on the ground surface directly above the underground buried object by moving along the underground buried object, an integrating device that integrates the sine or cosine of the potential difference detected by the wheel electrode, and a display device that displays an integrated waveform of the potential distribution obtained by integration by the integrating device, and the integrating device integrates the sine or cosine of a ratio of the amplitude of the potential difference based on a reference value set for the amplitude of the potential difference.

[0023] According to this invention, an integrating device that integrates the sine or cosine of the potential difference detected by the receiving device integrates the sine or cosine of a ratio of the amplitude of the potential difference detected by the receiving device based on a reference value set for the amplitude of the potential difference. The integrated waveform of the potential distribution obtained by the integration device is displayed on a display device. As a result, by appropriately setting the reference value, for example, it is possible to amplify a relatively small waveform on the display device and display it as a large waveform. Therefore, it is possible to display the integrated waveform of a small damage relatively large on the display device. Therefore, the peak point of the integrated waveform is easy to see, and even a small damage can be easily found. Effect of the Invention

[0024] According to the present invention, it is possible to provide a method and an apparatus for detecting the location of damage in a corrosion-protective coating, which can easily detect even small damage. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram of a corrosion protection coating damage location detection device. [Diagram 2] 2 is a schematic diagram of a receiving device of the corrosion-protective coating damage position detection device shown in FIG. 1. [Diagram 3] 2 is an example of a waveform output by a lock-in amplifier. [Figure 4] 4 is an example of a waveform displayed on a display device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, a corrosion-protective coating damage location detection device 100 and a corrosion-protective coating damage location detection method according to an embodiment of the present invention will be described with reference to the drawings. The corrosion-protective coating damage location detection device 100 according to this embodiment detects the location of a coating damage portion Bs in, for example, an underground buried object B having an outer surface coated with a corrosion-protective coating. The underground buried object B is, for example, a buried pipe. The underground buried object B may also be, for example, a metal pipe such as a steel pipe. As shown in FIGS. 1 and 2, the corrosion-protection coating damage location detection device 100 includes a receiving device 10 and a measurement signal transmitter 20.

[0027] The receiving device 10 detects the potential difference on the ground surface and includes a wheel electrode 11, a lock-in amplifier 12, a reference signal generator 13, an integrator 14, a display device 15, an offset setting device 16, and a range switch 17. The wheel electrode 11 continuously detects the potential difference on the ground surface while moving along the underground buried object B on the ground surface directly above the underground buried object B. For example, a conductive sponge rubber wheel is suitably used as the wheel electrode 11. As shown in Figs. 1 and 2, two wheel electrodes 11 are provided in the receiving device 10. In this way, the potential difference between the potential detected by one wheel electrode 11 and the potential detected by the other wheel electrode 11 is detected.

[0028] The wheel electrode 11 is connected to the input of a lock-in amplifier 12, and the output of the reference signal generator 13 is connected to the reference signal input of the lock-in amplifier 12. The output signal of the lock-in amplifier 12 is connected to a display device 15 via an integrator 14.

[0029] In the above-mentioned corrosion-protection coating damage position detection device 100, an AC signal current is passed between the underground buried object B and a counter electrode 22 (described later) using a measurement signal generator 20, and the two wheel electrodes 11 moving along the underground buried object B detect a potential difference between two points on the ground surface generated by the measurement signal generator 20, and the detection signal is input to a detection signal input section of a lock-in amplifier 12. Note that the wheels of the wheel electrodes 11 are provided with a rotation signal generator such as an encoder (not shown) to convert the amount of wheel rotation into a travel distance and display it on a display device 15.

[0030] On the other hand, the reference signal transmitted from the reference signal generator 13 is a signal of the same frequency in which the degree of relative phase change with respect to the AC signal current output from the measurement signal generator 20 is at least less than 180 degrees / hour, and this reference signal is input to the reference signal input section of the lock-in amplifier 12.

[0031] In the lock-in amplifier 12, as shown in FIG. Waveform W1 of amplitude A calculated from the input detection signal [Figure 3(A)] Waveform of Acosφ W2 [Figure 3(b)] ·Waveform W3 of Asinφ [Figure 3(c)] Phase φ waveform W4 [Figure 3(d)] will be output. In FIG. 3, the horizontal axis indicates the distance from the damaged coating part Bs, and the vertical axis in FIGS. 3(a), (b) and (c) indicates the potential difference, and the vertical axis in FIG. 3(d) indicates the magnitude of the phase φ.

[0032] A range switch 17 is provided to set a range for the amplitude A of the potential difference. The range is the maximum amplitude of the amplitude A (mV or V) of the potential difference that the display device 15 can display, that is, the display range (full scale). In order to accurately display values ​​from small to large, it is desirable to select a range in which the amplitude of the potential difference to be measured is as close as possible to the display range of the display device 15. As shown in FIG. 2, among the waveforms output from the lock-in amplifier 12 shown in FIG. 3, the output signal of the waveform W1 of the amplitude A is converted into information on the percentage amplitude %A based on the range set by the range switch 17 and then input to the integrating device 14, and at the same time, the output signal of the waveform W4 of the phase φ is also input to the integrating device 14, where %A in φ is calculated from %A and φ, and %A in φ is further integrated (details will be described later). Furthermore, the result of the integrating device 14 is input to the display device 15, which displays the waveform W5 shown in FIG.

[0033] Of the waveforms, in Fig. 3(a) showing the waveform W1 of amplitude A, the minimum position of the potential is the position of the damaged coating part Bs, in Fig. 3(b) showing the waveform W2 of Acosφ and Fig. 3(c) showing the waveform W3 of Asinφ, the positive / negative change position of the potential is the position of the damaged coating part Bs, and in Fig. 3(d) showing the waveform W4 of phase φ, the inversion position of phase φ is the position of the damaged coating part Bs. Furthermore, the shape of the waveform W5 obtained by integrating %Asinφ has a peak point that indicates the position of the damaged coating part Bs, as shown in Fig. 3(e). In this embodiment, the peak point refers to the maximum value of the waveform. When calculating the earth surface potential distribution, a similar waveform can be obtained by integrating the cosine %Acosφ instead of the sine %A sinφ.

[0034] The integrating device 14 integrates the sine or cosine of the potential difference. This allows the potential difference detected by the receiving device 10 to be displayed as a waveform on the display device 15. Specifically, the integrating device 14 integrates, for example, the sine or cosine of a percentage of the amplitude of the potential difference based on a range set for the amplitude of the potential difference (details will be described later). The display device 15 displays an integrated waveform of the potential distribution obtained by the integration device 14. For example, a known display is used for the display device 15. That is, the display device 15 includes a display device 15 such as a CRT (Cathode Ray Tube) display, a liquid crystal display, or an organic EL (Electro-Luminescence) display. The display device 15 may be, for example, a known display of a PC. In this case, the functions of the above-mentioned integration device 14 and the like may be ensured by the PC by executing a program using a processor such as a CPU (Central Processing Unit) and a memory and the like included in the PC. The display device 15 may be, for example, a pen recorder such as a known balance recorder.

[0035] (Method for detecting damage position of anti-corrosion coating) Next, a description will be given of a corrosion-protective coating damage location detection method using the above-mentioned corrosion-protective coating damage location detection device 100. The corrosion-protective coating damage location detection method according to this embodiment is a method for detecting the location of a coating damage part Bs in an underground buried object B having an anticorrosive coating on its outer surface, by using a receiving device 10 having a wheel electrode 11. The corrosion-protective coating damage position detection method according to the present embodiment includes a detection step, an integration step, and a display step.

[0036] The detection step is a step of moving the receiving device 10 along the underground buried object B on the ground surface above the underground buried object B, and detecting the potential difference on the ground surface by the wheel electrode 11. As shown in Figs. 1 and 2, a measurement signal transmitter 20 is provided on the underground buried object B. The measurement signal transmitter 20 is connected to the underground buried object B and a counter electrode 22 arranged in the ground (inside the soil). The measurement signal transmitter 20 applies an AC voltage between the underground buried object B and the counter electrode 22 to pass an AC current. At this time, if the underground buried object B has a damaged coating portion Bs, a current I flows into the underground buried object B via the damaged coating portion Bs. This causes a potential difference to occur around the damaged coating portion Bs. In the detection process, the potential difference thus generated on the ground surface is detected by the receiving device 10.

[0037] The integration step is a step of integrating the sine or cosine of the ratio of the amplitude of the potential difference based on a reference value set for the amplitude of the potential difference. In this embodiment, the reference value is a range, and the ratio is a percentage. In this embodiment, for example, the sine (%A in φ) of the percentage %A of the amplitude A of the potential difference based on the range set for the amplitude of the potential difference is integrated. The integration of the sine of the percentage of the amplitude of the potential difference based on the range set for the amplitude of the potential difference is performed every time the receiving device 10 moves along the underground buried object B. The integrated result is appropriately plotted on the display device 15. This makes it possible to display the sine of the percentage of the amplitude of the potential difference based on the range set for the amplitude of the potential difference received by the receiving device 10 on the display device 15 as an integrated waveform.

[0038] In this embodiment, in the integrating step, the integrating device 14 integrates the sine or cosine of the percentage of the amplitude of the potential difference based on the range set for the amplitude of the potential difference. The percentage is calculated by the range switcher 17. The range can be changed to a range of, for example, 50 mV to 10 V. That is, for example, when the range is set to 50 mV, the display device 15 displays the amplitude with the maximum amplitude of the potential difference being 50 mV. When the range is set to 100 mV, the display device 15 displays the amplitude with the maximum amplitude of the potential difference being 100 mV.

[0039] In this embodiment, the percentage of the amplitude A of the potential difference based on the range set for the amplitude of the potential difference is defined as the percentage amplitude % A. That is, the percentage amplitude % A is calculated based on the amplitude A of the potential difference detected by the receiving device 10 by the following formula. %A = A ÷ range × 100 For example, if amplitude A is 200mV and range is 500mV, percent amplitude %A is: %A = 200 ÷ 500 × 100 = 40 (%) In other words, when the range of the display device 15 is set to 500 mV and the receiving device 10 detects an amplitude A of 200 mV, the range selector 17 calculates the percentage amplitude %A as "40% of the maximum value of the display range," the integrating device 14 integrates the sine of this, and the result is plotted on the display device 15 as an integrated waveform. The integration is calculated, for example, using equation (1). Σ%Asinφ …(1) The accumulation may be performed by multiplying formula (1) by the interval (travel distance) over which the accumulation is performed. Σ(%Asinφ×D) …(2) Here, D is the interval (m) at which the integration is performed. The integration is performed, for example, from the start of the movement of the wheel electrode 11, and the integration is performed at intervals of, for example, 0.01 m.

[0040] Here, the amplitude A of the potential difference caused by the damaged coating part Bs detected on the ground surface depends on the area of ​​the damaged coating part Bs, the potential of the buried object B, the buried depth, the soil resistivity, etc. The magnitude of the potential difference detected by the receiving device 10, that is, the magnitude of the integrated waveform output by the integrating device 14, may vary greatly depending on, for example, the area of ​​the damaged coating part Bs. For this reason, for example, if the range of the display device 15 is set large, it may be difficult to visually check the amplitude waveform of a small potential difference. If the range of the display device 15 is set small, the amplitude waveform of a large potential difference may not be displayed within the display range of the display device 15. To address this issue, in this embodiment, the range can be switched manually or automatically. That is, for example, the range can be switched by an operator operating the operation panel of range switch 17. Alternatively, the range can be automatically switched based on the result of the determination by range switch 17 as to whether or not switching is necessary.

[0041] Here, when measuring the potential of the buried object B, the accumulated waveform may go out of the display range of the display device 15 by continuing to accumulate error potentials not to be measured, which are caused by the insulation resistance value of the coating material generated from other than the damaged coating portion Bs. In this embodiment, in order to suppress this, when the amount of change in the accumulated waveform is continuously equal to or less than a set value while the receiving device 10 advances a certain distance along the buried object B, the accumulated waveform is reset to zero so that the accumulated value becomes zero. In this way, it is preferable to suppress the accumulated waveform from going out of the display range of the display device 15 when the receiving device 10 continues to detect only error potentials not to be measured. It is also preferable to make the peak point of the accumulated waveform easier to see by removing the waveform due to the error potential from the accumulated waveform displayed on the display device 15. The set value may be set to a predetermined value before the start of detection, or may be changed during detection. The set value may be set (input) by an operator in advance to an arbitrary value, for example, or may be automatically set to an arbitrary value. The set value may be, for example, 5% of the maximum value of the display range of the display device 15.

[0042] In addition, in the integration process, a gain may be set for the integrated waveform, and the size of the integrated waveform may be enlarged or reduced, so that the integrated waveform displayed on display device 15 can be freely adjusted to a size that is easier to see. In the integration step, an offset may be added to the integration formula in integration device 14 to correct the slope of the integrated waveform and make the integrated waveform displayed on display device 15 easier to see. When a gain is set, the integration is calculated, for example, using equation (3). Σ(G×%Asinφ) …(3) where G is the gain. When an offset is set, the integration is calculated, for example, using equation (4). Σ(%Asinφ+K) …(4) where K is the offset.

[0043] The display step is a step of displaying the integrated waveform of the potential distribution obtained by the integration step on the display device 15. The display step is performed, for example, by transmitting information on the integrated waveform output by the integration device 14 to the display device 15. In this embodiment, the integrated waveforms before and after the range is switched are simultaneously displayed on the display device 15. Specifically, in conjunction with switching the range size, the integrated waveform after the point at which the range is switched is changed to a display mode corresponding to the range size after the range is switched. The integrated waveform before the point at which the range is switched is displayed in a display mode corresponding to the range size before the range is switched. On one screen of the display device, the integrated waveform after the range is switched is displayed consecutively to the integrated waveform before the range is switched. The integrated waveform displayed in this manner is shown in FIG. 4.

[0044] Fig. 4(a) shows the percentage amplitude %A and phase φ according to an example of the measurement results, and Fig. 4(b) shows ΣAsinφ, which is the integrated waveform of Asinφ, and Σ%Asinφ, which is the integrated waveform of %Asinφ. That is, the waveform of ΣAsinφ is the waveform in a state where amplitude A is integrated without percentage calculation by range switcher 17, and the waveform of Σ%Asinφ is the waveform in a state where amplitude A is integrated without percentage calculation by range switcher 17, i.e., percentage amplitude %A, is integrated. In Fig. 4(a), the vertical axis indicates amplitude (%) and phase (deg) or range (mV), and the horizontal axis indicates distance (m). In Fig. 4(b), the vertical axis indicates integrated potential or range (mV), and the horizontal axis indicates distance (m). In Fig. 4, the line marked with the symbol R indicates the point where the range was switched and the set range value. That is, in Fig. 4, the range is switched from the point of distance 0 to 50mV, 500mV, 100mV, 500mV, 20mV, and 200mV.

[0045] In the example of Fig. 4(b), a total of five coating damaged parts Bs are located at the positions indicated by the arrows. That is, the positions of the coating damaged parts Bs are determined by the peak points of the integrated waveform.

[0046] As shown in Fig. 4(b), the waveform of ΣA sin φ before the percentage accumulation according to this embodiment has, for example, a portion where the waveform at the peak point is small, and a portion where the peak point exceeds the display range of the display device 15. In contrast, the waveform of Σ%A sin φ after the percentage accumulation according to this embodiment has a peak point that is easier to identify than the waveform of ΣA sin φ. Also, it becomes easier to prevent the peak point from exceeding the display range of the display device 15. In this way, it can be seen that the percentage integration according to this embodiment makes it easier for the operator to view the integrated waveform.

[0047] As described above, according to the corrosion protection coating damage position detection method of this embodiment, in the integration step of integrating the sine or cosine of the potential difference detected in the detection step, a reference value for the amplitude A of the potential difference is set, and the sine %A inφ or cosine %A cosφ of the ratio %A of the amplitude A of the potential difference based on the reference value is integrated. The integrated waveform Σ%A inφ or Σ%A cosφ of the potential distribution obtained by integration in the integration step is displayed on the display device 15 in the display step. As a result, by appropriately setting the reference value, the magnitude of the integrated value can be appropriately changed, and for example, a relatively small waveform can be amplified and displayed as a large waveform on the display device 15. Therefore, the integrated waveform Σ%A inφ or Σ%A cosφ of small damage can be displayed relatively large on the display device 15. Therefore, the peak point of the integrated waveform Σ%A inφ or Σ%A cosφ is easily visible, and even small damage can be easily found.

[0048] Here, when measuring the potential of the underground buried object B, by continuing to accumulate error potentials not subject to measurement, which are caused by the insulation resistance value of the coating material arising from areas other than the damaged coating portion Bs, the accumulated waveform may go outside the display range of the display device 15. To address the above, if the amount of change in the integrated waveform is continuously equal to or less than a set value while the receiving device 10 advances a certain distance along the underground buried object B, the integrated waveform is reset to zero so that the integrated value becomes zero. This makes it possible to prevent the integrated waveform from going out of the display range of the display device 15, for example, when the receiving device 10 continues to detect only an error potential that is not the measurement target. In addition, by removing the waveform due to the error potential from the integrated waveform displayed on the display device 15, the peak points of the integrated waveform can be made easier to see.

[0049] In addition, in the integration process, the size of the integrated waveform is enlarged or reduced by setting a gain on the integrated waveform. This allows, for example, a relatively small waveform to be enlarged and displayed as a large waveform on the display device 15. Furthermore, a relatively large waveform can be reduced and displayed as a small waveform. Therefore, the integrated waveform can be freely adjusted to a size that is easier to see.

[0050] Furthermore, in the integration step, the slope of the integrated waveform is corrected by adding an offset to the integration formula in the integration device 14. This makes it possible to make the integrated waveform even easier to see.

[0051] Moreover, the reference value is a range corresponding to the display range of the display device 15. As a result, by appropriately setting the range, for example, a relatively small waveform can be amplified and displayed as a large waveform on the display device 15. Therefore, the integrated waveform of small damage can be displayed relatively large on the display device 15. Therefore, the peak point of the integrated waveform is easily visible, and even small damage can be easily found.

[0052] In addition, the range can be switched (the setting can be changed) manually or automatically. When the range can be switched manually, the amplitude waveform and the integrated waveform can be expanded or reduced to suit the operator's sense. When the range can be switched automatically, the operator does not need to switch the range, and the efficiency of the work can be improved.

[0053] Furthermore, the integrated waveforms before and after the range switching are simultaneously displayed on the display device 15. Therefore, for example, a relatively small enlarged waveform and a relatively large reduced waveform can be simultaneously viewed on the display device 15. Therefore, for example, the position of the coating damaged part Bs in the underground buried object B can be easily grasped regardless of the size of the coating damaged part Bs.

[0054] In addition, in conjunction with the switching of the range size, the integrated waveform after the point in time when the range was switched is changed to a display mode corresponding to the range size after the range was switched. This allows the user to simultaneously view an enlarged relatively small waveform and a reduced relatively large waveform on the display device 15.

[0055] Moreover, according to the corrosion-protection coating damage position detection device 100 of this embodiment, the integrating device 14, which integrates the sine or cosine of the potential difference detected by the receiving device 10, integrates the sine or cosine of the ratio of the amplitude A of the potential difference detected by the receiving device 10 based on a reference value set for the amplitude of the potential difference. The integrated waveform Σ% Asinφ or Σ% Acosφ of the potential distribution obtained by integration by the integrating device 14 is displayed on the display device 15. As a result, by appropriately setting the reference value, for example, it is possible to amplify a relatively small waveform on the display device 15 and display it as a large waveform. Therefore, the integrated waveform Σ% Asinφ or Σ% Acosφ of small damage can be displayed relatively large on the display device 15. Therefore, the peak point of the integrated waveform Σ% Asinφ or Σ% Acosφ is easy to see, and even small damage can be easily found.

[0056] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment, the explanation is given on the assumption that the range is switched during the detection operation by the corrosion-protective coating damage location detection device 100, but this is not limiting. That is, the method according to the present embodiment may be used, for example, when storing data on the potential difference detected by the corrosion-protective coating damage location detection device 100 and verifying the integrated waveform by switching the range after the detection operation. For example, instead of the range described in the embodiment, an arbitrary reference value may be set. Also, instead of the percentage described in the embodiment, a ratio to an arbitrary reference value may be used. That is, for example, as described in the embodiment, when the amplitude A is 200 mV and the range is 500 mV, the percentage amplitude %A is %A = 200 ÷ 500 × 100 = 40 (%) It becomes. If you define this as an "arbitrary reference value" and the reference value is, for example, range x 1.2, then the reference value = 500mV x 1.2 = 600mV. Percentage = 200 / 600 = 0.333 It can be said that: By integrating the sine of this "ratio," an integrated waveform having the same shape as the integrated waveform of the sine of "%A" can be obtained. In the above example, the reference value is defined based on the range, but the present invention is not limited to this. That is, the reference value may be, for example, twice the average of the amplitude A over 5 m, or three times the amplitude A for every 10 m. In this way, for example, the reference value may be set based on the average value of the amplitude A for a predetermined moving distance of the wheel electrode 11, or based on the value of the amplitude A for every predetermined moving distance. Alternatively, any other reference value may be set.

[0057] In addition, within the scope of the invention, the components in the above-described embodiments may be replaced with well-known components, and the above-described modified examples may be combined as appropriate. [Explanation of symbols]

[0058] 10 Receiving device 11 Wheel electrode 12 Lock-in amplifier 13 Reference signal generator 14. Accumulator 15 Display device 16 Offset setting device 17 Range switch 20 Measurement signal generator 22 Opposite 100 Corrosion protection coating damage location detection device A Amplitude B Underground objects Bs Damaged part of coating φ Phase

Claims

1. A method for detecting a location of damage to a corrosion-resistant coating in an underground buried object having an outer surface coated with a corrosion-resistant coating, the method comprising the steps of: a detection step of moving the receiving device along the underground buried object on the ground surface directly above the underground buried object and detecting a potential difference on the ground surface by the wheel electrodes; an integrating step of integrating a sine or cosine of the potential difference obtained by detection in the detecting step; and a displaying step of displaying an integrated waveform of the potential distribution obtained by integration in the integrating step on a display device, The corrosion-protective coating damage location detection method, in which the integrating step sets a reference value for the amplitude of the potential difference, and integrates the sine or cosine of a ratio of the amplitude of the potential difference based on the reference value.

2. resetting the integrated waveform so that the integrated value becomes zero when the amount of change in the integrated waveform is continuously equal to or smaller than a predetermined set value while the receiving device moves a certain distance along the underground buried object; The method for detecting a location of damage to a corrosion-resistant coating according to claim 1.

3. In the integration step, a gain is set to the integrated waveform to enlarge or reduce the size of the integrated waveform. The method for detecting a location of damage to a corrosion-resistant coating according to claim 1.

4. In the integration step, an offset is added to a calculation formula for the integration to correct a slope of the integrated waveform. The method for detecting a location of damage to a corrosion-resistant coating according to claim 2.

5. The reference value is a range corresponding to a display range of the display device. The method for detecting a location of damage to a corrosion-resistant coating according to claim 1.

6. The reference value can be changed manually or automatically. The method for detecting a location of damage to a corrosion-resistant coating according to any one of claims 1 to 5.

7. the integrated waveforms before and after the setting change of the reference value are simultaneously displayed on the display device. The method for detecting a location of damage to a corrosion-resistant coating according to claim 6.

8. The corrosion-protection coating damage location detection method according to claim 7, wherein, in conjunction with the change of the reference value, the integrated waveform from the point in time when the reference value is changed is changed to a display mode corresponding to the magnitude of the reference value after the reference value is changed.

9. A corrosion protection coating damage location detection device for detecting a location of a coating damage portion in an underground buried object having a corrosion protection coating applied to an outer surface thereof, comprising: a receiving device having wheel electrodes that move along the buried object on the ground surface directly above the buried object to detect a potential difference on the ground surface; A corrosion protection coating damage location detection device comprising: an integrating device that integrates the sine or cosine of the potential difference obtained by detection at the wheel electrode; and a display device that displays an integrated waveform of the potential distribution obtained by the integration device, wherein the integrating device integrates the sine or cosine of a ratio of the amplitude of the potential difference based on a reference value set for the amplitude of the potential difference.

Images