JP4867932B2 - Embedded pipe damage monitoring method and buried pipe damage monitoring apparatus - Google Patents

Description

  The present invention relates to a buried pipe damage monitoring method and a buried pipe damage monitoring apparatus.

  The buried pipe buried in the ground may be damaged by a drilling machine in excavation work, and when the buried pipe is damaged, the buried pipe is corroded by contact with soil or the like. For this reason, it is necessary to quickly detect damage to the buried pipe, and various methods for monitoring the damage to the buried pipe have been studied.

  As a general method for monitoring the damage of the buried pipe, a monitoring AC signal is always applied from the transmitting section of the buried pipe, and this is always received by the receiving section away from the transmitting section, and its resistance value There is a method of issuing an alarm when the value falls below the reference value. However, the resistance value obtained at the receiver is greatly fluctuated due to anticorrosion equipment and AC induction noise, and even if the buried pipe is not damaged, the fluctuation of the resistance value due to the noise is lower than the reference value. In some cases, this causes a problem of false alarms.

As a method for preventing such misreporting, Patent Document 1 discloses a technique for separating a noise signal by synchronizing a commercial AC signal and a monitoring AC signal. Patent Document 2 discloses a technique for improving measurement accuracy by providing two monitoring AC signal receivers. Patent Document 3 discloses a technique for reducing noise by connecting a pass filter in parallel with a drain that is connected to a buried pipe. Patent Document 4 discloses a technique for detecting a change in received voltage by converting a received voltage into a digital quantity and performing a moving average process, and then comparing a current value with a past time point.
JP-A-7-128189 JP-A-7-128272 JP 7-55751 A Japanese Patent Laid-Open No. 9-33474

  However, according to the technique disclosed in Patent Document 1, by synchronizing the AC signal, the AC signal and the noise signal can be distinguished, but the measurement value is likely to fluctuate due to noise, and the measurement value is lower than the reference value. There is a risk of misreporting. Further, according to the technique disclosed in Patent Document 2, the reception accuracy is improved by using two AC signal reception points. However, since fluctuations due to noise may still occur, there is a possibility that the above-mentioned false alarm is issued. According to the technique disclosed in Patent Document 3, noise can be reduced by inserting a filter into the drain, but since the drain cannot increase the circuit resistance, a complete filter cannot be obtained. From the viewpoint of noise reduction, it is not sufficient. According to the technique disclosed in Patent Document 4, the influence of noise can be reduced by comparing the current value and the past value of the moving average of the received voltage, but when the damage of the buried pipe is short, Damage may be overlooked.

  The present invention has been made in view of such a situation, and prevents erroneous reports that may occur even when the buried pipe is not damaged due to the influence of noise, and the buried pipe is damaged in a short time. It is a main object to provide a buried pipe damage monitoring method and a buried pipe damage monitoring apparatus capable of accurately detecting damage.

  In the buried pipe damage monitoring method of the present invention for solving the above-mentioned problem, the monitoring AC signal to be constantly applied to the buried pipe in the monitoring transmitter is always received by the monitoring receiver, and the received monitoring AC signal is In the buried pipe damage monitoring method that compares the reference value when there is no damage to the buried pipe and monitors the damage of the buried pipe due to the fluctuation, the monitoring AC signal received by the monitoring receiver is damaged in the buried pipe. If there is a fluctuation from the reference value in the case where there is not, a confirmation DC signal is applied to the buried pipe from the confirmation transmitting section at a constant voltage, and the output current value or circuit resistance value obtained in the confirmation receiving section, and the buried pipe The presence or absence of damage to the buried pipe is determined by comparing the output current value or the circuit resistance value when there is no damage.

  Further, the confirmation DC signal applied from the confirmation transmission unit may be a DC voltage of 60 V or less.

  The buried pipe damage monitoring device of the present invention for solving the above-mentioned problem is a first transmission means for constantly applying a monitoring AC signal from a transmission point of the buried pipe, and a first transmission means for constantly receiving the monitoring AC signal. A receiving means, a first comparing means for comparing fluctuations between the received monitoring AC signal and a reference value when there is no damage, and a confirmation DC signal is applied according to the comparison result of the first comparing means. A second transmitting means, a second receiving means for receiving the confirmation DC signal, a second comparison means for comparing fluctuations between information obtained by the second receiving means and a reference value when the buried pipe is not damaged. And a second comparison means.

  Further, the buried pipe damage monitoring device is a switching means for switching between transmission of the monitoring AC signal and transmission of the confirmation DC signal, and reception of the monitoring AC signal and reception of the confirmation DC signal when the confirmation DC signal is applied. May be included.

  Further, the confirmation DC signal may be a DC voltage of 60V or less.

  According to the present invention, not only the conventional monitoring AC signal but also the confirmation DC signal is used, and even if it is determined that there is damage due to the reception of the monitoring AC signal, this is immediately performed. Since it is possible to confirm the authenticity of damage by transmitting and receiving a DC signal for confirmation rather than relying on it, it is possible to prevent false alarms that have conventionally occurred. In other words, the present invention is characterized in that a so-called double check is performed by a confirmation DC signal, and thereby it is possible to more accurately determine the presence or absence of damage.

  In addition, since the present invention uses a DC signal having a voltage higher than the cathodic protection DC voltage as the confirmation signal, the confirmation signal is not affected by noise and can be accurately determined. is there.

  In the present invention, the DC signal is only for “confirmation”, and the constant monitoring uses an AC signal, so that the buried pipe is not over-corroded.

  First, the buried pipe damage monitoring apparatus 100 of the present application will be specifically described with reference to the drawings.

  FIG. 1A conceptually shows a buried pipe damage monitoring apparatus 100 according to the present invention, in which a damage monitoring unit 20 is installed along the buried pipe 10, and a switching device is arranged at a location adjacent to the damage monitoring unit 20. A damage confirmation unit 23 is installed via 13.

  In the damage monitoring unit 20, a monitoring transmitter 21 and a monitoring receiver 22 are provided. The monitoring transmitter 21 transmits the energizing electrode 11 and a damage monitoring AC signal to the buried pipe 10. And. The monitoring receiver 22 is connected to the buried pipe 10 so as to receive the damage monitoring AC signal transmitted from the monitoring transmitter through the transmitting electrode 14 from the buried pipe 10, and the verification electrode 12 is received for monitoring. Connected to the unit 22. Information obtained by the monitoring receiver 22 is transmitted to the processing device 26. The processing device 26 transmits the information to the confirmation transmitter 24 based on the obtained information.

  In the damage confirmation unit 23, a confirmation transmission unit 24 and a confirmation reception unit 25 are provided. The confirmation transmission unit 24 transmits the conduction electrode 11 and a confirmation DC signal to the embedded pipe 10. An electrode 14 is provided via a switching device 13. Further, the receiving electrode 15 is connected to the buried tube 10 via the switching device 13 so that the confirmation receiving unit 25 receives the confirmation DC signal transmitted from the confirmation transmitting unit 24 through the transmitting electrode 14 from the buried tube 10, The verification electrode 12 is connected to the monitoring receiver 25 via the switching device 13. Information obtained by the confirmation receiving unit 25 is transmitted to the processing device 26.

  If the processing device 26 determines that the information obtained in the confirmation receiving unit 25 is determined to be damaged, the processing device 26 transmits the information to the alarm device 27, and the alarm device 27 generates an alarm. To do.

  In the present invention, when a monitoring AC signal is constantly applied from the monitoring transmitter 21 to the buried pipe 10 and the monitoring receiver 22 always receives the signal, the received monitoring AC signal and the buried pipe are damaged. When the received signal fluctuates from the reference value, a confirmation DC signal is applied to the buried pipe 10 from the confirmation transmission unit 24, and the output obtained by the confirmation reception unit 25 is compared. It is characterized in that the presence or absence of damage to the buried pipe 10 is determined by comparing the current value or the circuit resistance value with these values when the buried pipe is not damaged. Therefore, with regard to the function of constantly applying the monitoring AC signal to the buried pipe 10 and receiving it constantly, specifically, the monitoring AC signal is transmitted, the monitoring AC signal is received, and the monitoring AC signal is grounded. Used to calculate the resistance value, etc., compare the ground resistance and the like with the reference value when there is no damage to the buried pipe, measure the fluctuation from the reference value, and transmit the result to the confirmation transmitter 24 Various means and devices are not particularly limited, and conventionally known ones can be appropriately used.

  For example, the monitoring transmission unit 21 and the monitoring reception unit 22 may be installed in the damage monitoring unit 20 as illustrated, or the monitoring reception unit 22 is provided at a position appropriately separated from the monitoring transmission unit 21. Good. In general, these can be constituted by analog circuits or digital circuits. Further, a processing device 26 may be provided that calculates a ground resistance value or the like from the received signal, measures a change from a reference value, and makes a determination as illustrated. A computer or the like is generally used as such a processing apparatus. Furthermore, a transmission device (not shown) for transmitting the monitoring AC signal received by the monitoring receiver 22 to the processing device may be provided, and a transmission device for transmitting the determination result to the confirmation transmitter 24 is provided. It may be provided.

  As for the monitoring AC signal, a pseudo-random signal that selects a frequency of 10 Hz to 1000 Hz, is appropriately set in the range of 0.1 V to 5 V, and is constantly applied to the buried pipe is generally used.

  The installation locations of the confirmation transmitter 24 and the confirmation receiver 25 are not particularly limited. For example, the confirmation transmitter 24 and the confirmation receiver 25 are illustrated in the same manner as the damage monitoring unit 20 described above. May be provided in the damage confirmation unit 23, or the damage monitoring unit 20 and the damage confirmation unit 23 may be provided independently without using the switching device 13. The confirmation receiving unit 25 may be provided at a position away from the confirmation transmission unit 24.

  When the monitoring AC signal received by the monitoring receiver 22 fluctuates from a reference value, the confirmation transmitter 24 specifically includes the ground resistance value of the monitoring AC signal received by the confirmation receiver 22 and the like. Is calculated by the processing device 26, the reference value when the embedded pipe 10 is not damaged is compared with the received signal, and if the received signal fluctuates from the reference value, the processing device 26 confirms the result. The confirmation transmission unit 24 that has transmitted to the transmission unit 24 and received the result from the processing device 26 is provided to apply a confirmation DC signal to the embedded tube 10 according to the comparison result.

  In general, an AC signal is used as the monitoring signal so that it can be distinguished from noise such as stray current caused by leakage current of DC railway. Since the coating of the buried pipe is equivalent to a capacitor for AC components, the higher the frequency, the smaller the grounding resistance (AC impedance) of the buried pipe, and even if the coating is sound, it is measured with an alternating current. The ground resistance (AC impedance) is smaller than DC. Therefore, when the coating damage occurs, the change amount of the ground resistance is small compared to the direct current, and it is difficult to determine the fluctuation from the reference value due to the coating damage and the fluctuation from the reference value due to measurement noise.

  In consideration of such points, it is preferable to use a DC signal that does not have a frequency component and is insulated from the coating as the confirmation signal. By using a DC signal as a confirmation signal in this way, it is possible to easily compare the ground resistance or output current when sound and coating are damaged, compared to AC, so the ground resistance value obtained by the monitoring AC signal Even if the value fluctuates from the reference value, a confirmation DC signal value that is not affected by noise, more specifically, is output by applying a confirmation DC signal to the buried pipe 10 without generating an alarm immediately. Current values and circuit resistance values can be obtained.

  Here, when the DC voltage for generating the confirmation DC signal is small, it is difficult to separate from noise. Therefore, in order to clarify the separation from noise, the DC voltage is preferably a high voltage. More preferably, the direct current voltage is 60 V or less. If the DC voltage is less than 5V, it is difficult to separate from noise, and the maximum voltage of the cathodic protection device is determined to be 60V or less according to electrical equipment standards.

  In addition, when a high DC voltage is constantly applied to the buried pipe, the buried pipe is over-corroded and the buried pipe is easily corroded. Therefore, the DC voltage is preferably applied for a short time, preferably 1 minute to 5 minutes. It is more preferable that

  The confirmation receiving unit 25 receives a signal obtained when a constant DC voltage is applied to the buried pipe 10 from the confirmation transmitting unit 24, calculates an output current value and a circuit resistance value from the obtained signal, This value is used to determine damage by comparing the value of this value with the output current value or the circuit resistance value when the buried pipe 10 is not damaged. As long as the confirmation receiving unit 25 can achieve the above-described effects, the calculation method and determination method are not particularly limited, and a conventionally known technique can be appropriately selected and used.

  For example, the output current value and the circuit resistance value are calculated from the signal received by the confirmation receiving unit 25, and these values are compared with the output current value or the circuit resistance value when the embedded pipe 10 is not damaged. A processing device 26 for making the determination may be provided separately. Further, a transmission device for transmitting the information from the confirmation receiving unit 25 to the processing device 26 may be used.

  More specifically, when the monitoring transmission unit 21 and the confirmation transmission unit 24 are switched by the switching device 13 as shown in FIG. 1B, the energizing electrode 11 is switched between the switch 50 and the switch 51. The switch 51 is connected to the switch 58 and the transmitter electrode 14 is connected to the switch 59 by switching between the switch 52 and the switch 53. Switching to the transmission unit 22 is performed. In the switching between the monitoring receiver 22 and the confirmation receiver 25, the switch 60 is connected to the switch 55 by switching the switch 54 and the switch 55, and the verification electrode 12 is By switching between the switch 56 and the switch 57, the switch 61 is connected to the switch 57, thereby switching between the monitoring receiver 22 and the confirmation receiver 25. The energizing electrode 11 of the monitoring transmission unit 21 is connected to the switch 50 and the switch 58, and the transmitting electrode 14 is connected to the switch 52 and the switch 59. The receiving electrode 15 of the monitoring receiving unit 22 is connected to the switch 54 and the switch 60, and the verification electrode 12 is connected to the switch 56 and the switch 61. As described above, the transmission units and the reception units may be appropriately switched using the switching device 13 or may be configured independently without using the switching device.

  The DC current value or circuit resistance value is calculated from the DC voltage signal received by the receiving unit for confirmation, and compared with these when there is no damage to the buried pipe. Can be generated. When the alarm is generated, the processing device 26 compares the signal obtained by the receiving unit for confirmation with the reference value to determine the presence or absence of damage. When it is determined that there is damage, the processing device 26 issues an alarm device 27. It is good also as a structure which sends a signal to.

  An example of an operation for monitoring whether or not the buried pipe has been damaged by the damage monitoring apparatus 100 configured as described above will be described with reference to the flowchart of FIG.

  A monitoring AC signal is constantly applied from the monitoring transmitter 21 to the buried pipe 10 (S1), and the monitoring receiver 22 always receives the monitoring AC signal (S2). The monitoring receiver 13 transmits the obtained signal to the processing device 26, and the processing device 26 calculates a ground resistance value and the like from the signal (S3), and the buried pipe is damaged from the ground resistance and the reference value. These values are compared with those in the case where there is not, and it is determined whether or not there is a fluctuation from the reference value (S4). If it is determined that the grounding resistance has fluctuated from the reference value, the information is transmitted to the confirmation transmission unit 24, and the switching device 13 uses the monitoring transmission unit 21, the confirmation transmission unit 24, and the monitoring unit. Switching between the reception unit 22 and the confirmation reception unit 25 is performed (S5), and a confirmation DC signal is applied from the confirmation transmission unit 24 to the buried pipe (S6). The confirmation receiving unit 25 receives the confirmation DC signal (S7), transmits the obtained signal to the processing device 26, and the processing device 26 calculates an output current value and a circuit resistance value from the signal (S8). Then, the obtained output current value and circuit resistance value are compared with these values when the buried pipe 10 is not damaged, and the presence or absence of damage is determined (S9). When it is determined that the buried pipe 10 is damaged, the information is transmitted to the alarm device 27, and the alarm device 27 that receives the information generates an alarm (S10).

  Thus, even when the monitoring AC signal is applied, even if the ground resistance or the like fluctuates from the reference value, an alarm is not immediately generated, and there is no influence of noise obtained by applying the confirmation DC signal. This occurs when a monitoring AC signal is applied by comparing the output current value and circuit resistance value with these values when there is no damage to the buried pipe and generating an alarm only when it is determined that there is damage. It is possible to prevent the occurrence of a false alarm that occurs when the buried pipe is not damaged, and to accurately detect the damage of the buried pipe.

  The buried pipe monitoring method of the present invention will be described more specifically with reference to examples.

  FIG. 3A is a diagram showing a simulated damage monitoring test circuit in a water tank simulating a buried pipe. FIG. 3B is an enlarged view of the Y part in FIG.

  An anti-corrosion current that is -2000 V (saturated copper sulfate electrode reference) from the pseudo-random signal transmission / reception unit storage board 101 to the coated steel pipe 100 having a ground resistance of 10 Ω, a sine wave of AC signal 0.14 V, 20 Hz, code length 127 A pseudo-random signal for damage monitoring is applied to generate a noise current from the arbitrary waveform generator 102 and the constant current power supply device 103, and the electrode rod 111 having a ground resistance of 100Ω is applied to the covering defect portion 114 (# 01 to # 10). It was made to contact and the fall of grounding resistance was confirmed. Note that the coated steel pipe 100 includes a coated portion 113 and a coated missing portion 114 in which the coated portion is missing.

  Next, when DC voltage 12V is applied from the DC power supply device 104 to the coated steel pipe 100 having a ground resistance of 10Ω with the electrode rod 111 having a ground resistance of 100Ω being in contact with the covering defect portion 114 (# 01 to # 10). The DC tube ground potential and output current were measured. When a high voltage is applied, the pseudo-random signal receiver / receiver 101 is temporarily disconnected by operating the relay circuit 105 in order to circulate the pseudo-random signal and circulate DC current to the receiver 101 and protect the device.

  A noise signal was generated by the arbitrary waveform generator 102 based on the collected tube-to-ground potential fluctuation, and a constant current was applied between the electrodes in the water tank.

FIG. 4 shows a chart of output current and circuit resistance before and after application of a DC voltage with and without simulated damage contact. When there is no damaged contact, the circuit resistance value before high voltage application is X (i), the circuit resistance value after high voltage application is Y (i), and when there is damage contact, the circuit resistance value before high voltage application Is represented by X (ii), and the circuit resistance value after application of the high voltage is represented by Y (ii). As is clear from X (i), even when there is no damaged contact, before the DC voltage is applied, the output current fluctuates due to the influence of noise, so the circuit resistance fluctuates greatly. In some cases, the value drops below A. In addition, the circuit resistance decreases due to the simulated damage contact, but the decrease in the circuit resistance after the simulated damage contact falls within the range of the chart fluctuation width X (ii) when there is no simulated damage contact, so that the determination of damage cannot be made. On the other hand, the circuit resistance value after application of the DC voltage is not affected by noise, as is apparent from Y (i) and Y (ii). In the absence of the phenomenon, the phenomenon of lowering the reference value B (i) which is the reference value does not occur. Furthermore, comparing the circuit resistance value when there is no simulated damaged contact after high voltage application and the circuit resistance value when there is a simulated damaged contact, the circuit resistance value is the reference when there is damage compared to when there is no damage. It can be seen that the value is lower than the value B (i).

Also, the output current value (Y (iii)) when there is no simulated damage contact after high voltage application,
When compared with the output current value (Y (iv)) when there is a simulated damaged contact, the output current value is higher than the reference value B (ii) when there is damage compared to when there is no damage. Recognize.

  In this way, when there is damage by applying a high voltage, the circuit resistance value decreases and the output current value increases, so compare the circuit resistance value and output current value with those when there is no damage. You can monitor for damage.

  Next, when there is no simulated damage and when damaged contact is made on the coating defect portions 114, # 01, # 05, and # 10, the tube-to-ground potential (on potential) and DC voltage when a DC voltage is applied FIG. 5 shows the output current (ON current) at the time of application and the circuit resistance (tube-to-ground potential when DC voltage is applied / output current when DC voltage is applied). Damage contact was performed twice for each coating defect 114.

  As is clear from FIG. 5, the output current value and the circuit resistance value in the case of the simulated damaged contact show fluctuations of 1.06 to 1.1 times in the current value with respect to the case of no damage, and the circuit resistance The value shows a fluctuation of 0.925 to 0.9 times, and a remarkable fluctuation can be confirmed. By measuring the fluctuation of the DC current value or the circuit resistance value before and after the DC voltage application, the presence or absence of damage can be easily determined. can do.

(A) is the figure which showed the buried pipe damage monitoring apparatus notionally, (b) is the enlarged view of the X section in FIG. 1 (a). It is a flowchart which shows a buried pipe damage monitoring process. (A) is a figure which shows the simulation damage test circuit. FIG. 3B is an enlarged view of a Y portion in FIG. It is a chart of the output current and circuit resistance before and after the DC voltage application in the presence or absence of simulated damage contact. It is a figure which shows the tube ground potential at the time of DC voltage application, an output current, and circuit resistance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Embedded pipe 11 ... Current supply electrode 12 ... Collation electrode 13 ... Switching device 14 ... Transmitting electrode 15 ... Reception electrode 20 ... Damage monitoring unit 21 ... Monitoring transmission part 22 ... Monitoring receiving part 23 ... Damage confirmation unit 24 ... Confirmation Transmitter 25 ... Confirmation receiver 26 ... Processing device 27 ... Alarm device 100 ... Covering wire 101 with ground resistance of 10 Ω ... Pseudo random signal transmission / reception unit storage panel 102 ... Arbitrary waveform generator 103 ... Constant current power supply device 104 ... DC Power supply device 105 ... Relay circuit 111 ... Electrode rod 112 with ground resistance of 100Ω ... Noise conducting electrode 113 ... Coating part 114 ... Coating defect part

Claims (5)

A monitoring AC signal that is constantly applied to the buried pipe in the monitoring transmitter is constantly received by the monitoring receiver, and the received monitoring AC signal is compared with the reference value when the buried pipe is not damaged, and the fluctuation In the buried pipe damage monitoring method for monitoring the buried pipe damage by
When the monitoring AC signal received by the monitoring receiver varies from a reference value when the buried pipe is not damaged, a confirmation DC signal is applied to the buried pipe from the confirmation transmitter at a constant voltage, It is determined whether the buried pipe is damaged by comparing the output current value or circuit resistance value obtained in the receiving unit for confirmation with the output current value or circuit resistance value when the buried pipe is not damaged. Characterized buried pipe damage monitoring method.   2. The buried pipe damage monitoring method according to claim 1, wherein the confirmation DC signal applied from the confirmation transmission unit is a DC voltage of 60 V or less.   A first transmission means for constantly applying a monitoring AC signal from a transmission point of the buried pipe, a first receiving means for constantly receiving the monitoring AC signal, and a reference when the received monitoring AC signal is not damaged First comparison means for comparing fluctuations with the value, second transmission means for applying a confirmation DC signal according to the comparison result in the first comparison means, and second reception means for receiving the confirmation DC signal Embedded pipe damage monitoring, comprising: a receiving means; and a second comparing means for comparing information obtained by the second receiving means with a reference value when the buried pipe is not damaged. apparatus.   The buried pipe damage monitoring device includes switching means for switching between transmission of a monitoring AC signal and transmission of a confirmation DC signal, and reception of a monitoring AC signal and reception of a confirmation DC signal when the confirmation DC signal is applied. The buried pipe damage monitoring apparatus according to claim 3, comprising:   The buried pipe damage monitoring apparatus according to claim 3 or 4, wherein the confirmation DC signal is a DC voltage of 60V or less.

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