JP4962379B2 - Buried pipe cathodic protection system - Google Patents

Description

  The present invention relates to a cathodic protection system for buried pipes.

  Usually, the surface of a buried pipe buried in the ground is coated to prevent corrosion due to moisture in the ground. However, it is also assumed that there is existing damage to the buried pipe coating, and the soil and buried pipe steel surface are in contact. In this case, a corrosion current flows from the buried pipe to the soil, and the buried pipe is Risk of corrosion.

  Therefore, at present, as a method of preventing the corrosion of the buried pipe due to the outflow of the corrosion current, an anticorrosion DC signal corresponding to the corrosion current flowing into the buried pipe is applied to the electrode buried in the ground from the external power source. The method of electrochemically preventing the corrosion of the buried pipe is carried out.

  On the other hand, coated pipes buried in the ground may be damaged by excavation machinery in excavation work, and if the buried pipe is damaged, the corrosion of the buried pipe proceeds due to contact with the soil, etc. End up. 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 method of monitoring the occurrence of such damage to the buried pipe, a monitoring AC signal is always applied from the transmitting section connected to the buried pipe, and this is always received by the receiving section provided on the buried pipe, A method of giving an alarm when the resistance value is lower than a reference value by observing the resistance value (for example, see Patent Document 1).

Thus, in the present situation, in order to prevent corrosion of the buried pipe and monitor damage to the buried pipe, the direct current signal for cathodic protection and the alternating current signal for damage monitoring are separately applied to the buried pipe.
Japanese Patent Laid-Open No. 7-55751

  However, the DC signal applied to prevent the buried pipe from being corroded is not a complete DC signal but often includes some AC signal. When an AC signal is included in the DC signal, interference between the AC signal and the AC signal for damage monitoring occurs, which may cause noise and reduce the accuracy of damage monitoring.

  In a buried pipe damage monitoring system, various noises often become a problem, and a method for suppressing this is currently being developed. For example, Patent Document 1 discloses a technique for reducing noise by connecting a filter in series and in parallel with a drain that is connected to a buried pipe.

  However, the method disclosed in Patent Document 1 is not originally a method for recognizing an AC signal included in a DC signal for preventing corrosion as noise and removing it.

  This invention is made | formed in view of such a condition, and provides the novel underground pipe | tube anticorrosion system which does not apply the alternating current signal which causes the noise in a damage monitoring system to a buried pipe. Is the main issue.

  The invention of the present application for solving the above-mentioned problems is an embedded pipe electric corrosion protection system that performs an electric protection of a buried pipe by applying a DC signal to the buried pipe, and the buried pipe electric corrosion protection system includes an external power source and an external A current-carrying electrode for anticorrosion connected to the positive terminal of the power source and installed in the ground, and a terminal for a buried pipe connected to the negative terminal of the external power source and connected to the buried pipe, The external power source and the electrically conductive electrode for anticorrosion, and the external power source and the buried pipe terminal are connected via an AC signal blocking filter capable of blocking an AC signal having a predetermined frequency.

  In the buried pipe cathodic protection system, the external power supply has a constant potential control circuit, and the AC signal cutoff filter may be provided in the constant potential control circuit.

  Furthermore, in the buried pipe cathodic protection system, the AC signal blocking filter is preferably a filter capable of blocking an AC signal of 50 Hz or more.

  According to the buried pipe cathodic protection system of the present invention, the DC signal applied to the buried pipe from the electrode for cathodic protection connected to the external power source and the terminal for the buried pipe is an AC signal that can always cut off an alternating current signal of a predetermined frequency. Since it is applied through the cutoff filter, even if an AC signal is included in the DC signal, the AC signal is blocked by the AC signal cutoff filter and is not applied to the buried pipe. Therefore, it is possible to reliably prevent generation of noise by interfering with the monitoring AC signal separately applied to the buried pipe, and as a result, the accuracy of the buried pipe damage monitoring system can be improved.

  In addition, when the external power supply has a constant potential control circuit, it is possible to further reliably prevent an AC signal from being applied to the buried pipe by providing an AC signal cutoff filter in the constant potential control circuit. .

  Furthermore, since the problem of noise becomes large when an AC signal having a frequency of 50 Hz or higher is applied to the buried pipe, it is effective to enable the AC signal cutoff filter to block an AC signal having the frequency or higher.

  Below, the underground pipe | tube anti-corrosion system of this invention is demonstrated concretely using drawing.

  FIG. 1 is a conceptual diagram of the buried pipe cathodic protection system of the present invention.

  As shown in the figure, the system of the present invention is connected to an external power source 10, a current-carrying electrode 11 connected to the positive terminal of the external power source 10 and installed in the ground, and a negative terminal of the external power source 10. And a buried pipe terminal 12 connected to the buried pipe P. Further, the external power supply 10 and the electrically conductive electrode 11 for anticorrosion, and the external power supply 10 and the buried pipe terminal 12 are connected via an AC signal blocking filter 13 capable of blocking an AC signal having a predetermined frequency. It has the characteristics.

  According to such a buried pipe anticorrosion system, since the potential of the buried pipe P is always negative, it is possible to prevent the buried pipe P from being corroded, and the DC signal applied from the external electrode 10 is Since it is always applied through the AC signal cutoff filter 13, even if an AC signal is included in the DC signal, the AC signal can be prevented from being applied to the buried pipe P.

  Here, the AC signal blocking filter 13 is not particularly limited as long as it is a filter capable of blocking the AC signal included in the DC signal applied from the external electrode, but has a frequency of 100 Hz or more. It is preferable to use a low-pass filter that can cut off an AC signal having a frequency higher than that frequency, and when further completeness is required, an AC signal having a frequency of 50 Hz or higher is preferable. It is particularly preferable to use a low-pass filter capable of blocking

  FIG. 2 is a schematic circuit diagram showing the configuration of a low-pass filter that can be used as the AC signal cutoff filter 13 in the system of the present invention.

  A low-pass filter having a circuit as shown in FIG. 2 can block an AC signal having a predetermined frequency.

  Here, in FIG. 1, the AC signal cutoff filter 13 is incorporated in the external electrode 10, but the present invention is not limited to this, and the AC signal cutoff filter is separately and independently provided outside the external electrode 10. May be provided.

  The external power source 10 in the buried pipe electric protection system of the present invention has a constant potential control circuit 14 as shown in FIG. 1, and the AC signal cutoff filter 13 is also provided in the constant potential control circuit. It may be done.

  As described above, by providing the AC signal cutoff filter 13 also in the constant potential control circuit 14, an AC signal that may be applied from the constant potential circuit 14 to the buried pipe P can be blocked.

  Here, the configuration of the constant potential control circuit 14 is not particularly limited, and a generally used constant potential circuit can be appropriately selected and used.

  For example, as shown in FIG. 1, an AC signal cutoff filter as shown in FIG. 2 is provided between the reference electrode 15 connected to the constant potential circuit 14 and the electrode 16 connected to the buried pipe P from the constant potential circuit 14. 13 may be provided.

  Further, the buried pipe P is provided with a damage monitoring system as shown in FIG. The damage monitoring system is not directly related to the buried pipe electro-corrosion protection system of the present invention, but the effect of the buried pipe electro-corrosion protection system of the present invention is noise reduction in the damage monitoring system. deep.

  In the damage monitoring system, for example, a transmission unit 21 for applying a monitoring AC signal to the buried pipe P and a receiving unit 22 for receiving the monitoring AC signal applied from the transmission unit 21 are integrated. A damage monitoring unit 20 is provided. The transmission unit 21 includes an energization electrode 23 and a transmission electrode 24 that is connected to the buried pipe P and applies a monitoring AC signal to the buried pipe P. On the other hand, the receiving unit 22 includes a receiving electrode 25 that is connected to the buried pipe P and receives a monitoring AC signal transmitted from the transmitting electrode 24 of the transmitting unit 21, and a verification electrode 26. Here, the frequency of the monitoring AC signal is not particularly limited, but is generally about 100 Hz to 1 kHz.

  FIG. 3 is a diagram illustrating a resistance value calculated from an AC signal received by the receiving unit 22 of the damage monitoring system illustrated in FIG.

  3 is a state (Comparative Example 1) in which the entire buried pipe electric protection system shown in FIG. 1 is turned off and only the damage monitoring system is turned on, and the Y part is buried pipe electrical protection. Although both the anticorrosion system and the damage monitoring system are turned on, the AC signal cutoff filter 13 in the buried pipe electrocorrosion protection system is turned off (Comparative Example 2: conventional technology), and the Z portion represents the buried pipe electrocorrosion protection. A state is shown in which both the system and the damage monitoring system are turned on, and the AC signal cutoff filter 13 is also turned on (an embodiment of the present invention).

  In addition, at the timing indicated by A in FIG. 3, a resistance of 100 Ω is intentionally added to the buried pipe P to create a state in which a small pseudo damage has occurred, and at the timing B shown in FIG. By intentionally adding a resistance of 5Ω, a state in which a large amount of pseudo damage occurred was created.

  The DC voltage applied from the external power supply 10 to the buried pipe was 2 V, and the frequency of the AC signal for damage monitoring was 200 Hz.

  The AC signal blocking filter 13 used is a low-pass filter that has the circuit shown in FIG. 2 and can block an AC signal of 50 Hz or higher.

  As is clear from FIG. 3, when only the damage monitoring system is turned on and the entire buried pipe electro-corrosion protection system is turned off (part X), the AC signal that becomes noise from the buried pipe electro-corrosion protection system is buried in the buried pipe P. The peak waveform obtained from the AC signal received by the receiving unit 22 of the damage monitoring system is sharp, and even when there is a small damage (A), the damage can be confirmed.

  However, when both the buried pipe electro-corrosion protection system and the damage monitoring system are turned on, but the AC signal blocking filter 13 in the buried pipe electro-corrosion protection system is turned off (Y portion), a DC signal is output from the buried pipe electro-corrosion protection system. Not only the AC signal is applied, but the AC signal and the AC signal for damage monitoring interfere with each other to generate noise, and the small damage (A) cannot be confirmed at all.

  Here, in the case of using the buried pipe cathodic protection system of the present invention, that is, when both the buried pipe cathodic protection system and the damage monitoring system are turned on, and the AC signal blocking filter 13 is also turned on (part Z), Even if an alternating current signal is included in the direct current signal applied by the buried pipe anticorrosion system, the alternating current signal is blocked by the alternating current signal cutoff filter 13 and is not applied to the buried pipe P. The peak waveform obtained from the AC signal is as sharp as when the buried pipe cathodic protection system is turned off (part X), so that even when there is a small damage (A), the damage can be confirmed. .

  That is, according to the present embodiment, according to the buried pipe cathodic protection system of the present invention, the influence of the buried pipe cathodic protection system in the damage monitoring system can be made almost zero, and the accuracy of damage monitoring can be improved. I understood.

It is a conceptual diagram of the underground pipe | tube anti-corrosion system of this invention. It is a schematic circuit diagram showing the composition of a low pass filter which can be used as an AC signal cutoff filter in the system of the present invention. It is a figure which shows the resistance value calculated from the alternating current signal received with the receiving part of the damage monitoring system shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... External power supply 11 ... Current-carrying electrode 12 for anticorrosion ... Terminal 13 for buried pipes ... AC signal cutoff filter 14 ... Constant potential control circuit 15 ... Reference electrode 16 ... Electrode 20 ... Damage monitoring unit 21 ... Transmitter 22 ... Receiver 23 ... Conductive electrode 24 ... Transmitting electrode 25 ... Receiving electrode 26 ... Verification electrode P ... Buried pipe

Claims (3)

A buried pipe electro-corrosion protection system that performs anti-corrosion of a buried pipe by applying a DC signal to the buried pipe,
The buried pipe electro-corrosion protection system is connected to the external power supply, the positive electrode of the external power supply that is connected to the positive terminal of the external power supply, and the negative terminal of the external power supply that is connected to the buried pipe. A buried pipe terminal,
Furthermore, the external power supply and the current-carrying electrode for anticorrosion, and the external power supply and the buried pipe terminal are connected via an AC signal blocking filter capable of blocking an AC signal having a predetermined frequency. Anticorrosion system. The external power source has a constant potential control circuit,
The buried pipe anticorrosion system according to claim 1, wherein the AC signal cutoff filter is also provided in the constant potential control circuit.   The buried pipe cathodic protection system according to claim 1 or 2, wherein the AC signal blocking filter is a filter capable of blocking an AC signal of 50 Hz or more.

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