JP5470191B2 - Corrosion state monitoring method and monitoring system for cathode anticorrosion management probe - Google Patents

Description

  The present invention relates to a corrosion state monitoring method and a monitoring system for a cathodic protection control probe for an embedded structure.

  As an anti-corrosion measure for buried metal structures, a combination of high electrical resistance coating and cathodic protection is being implemented as an effective measure. Cathodic protection is a method in which a cathodic reaction (reduction reaction) is promoted on the surface of a buried metal structure by means of an anticorrosion current.

  The anticorrosion situation by cathodic protection can be evaluated by the potential with respect to the surrounding electrolyte of the embedded metal structure and the current density of the anticorrosion current flowing into the embedded metal structure. However, in a buried metal structure coated with a high electrical resistance, it is not possible to directly measure the potential with respect to the surrounding electrolyte of the buried metal structure or the current density of the anticorrosive current flowing into the buried metal structure. Corrosion protection of cathodic protection by burying a metal test piece called probe (or test coupon) in the vicinity of the buried metal structure and connecting it to the buried metal structure. Is evaluated.

  The probe described above is a columnar metal piece made of the same material as the buried metal structure to be protected against corrosion, and has a prescribed cross-sectional area for measuring the current density. This probe simulates a defective part of the coating applied to the buried metal structure and flows into the defective part assuming that a defective part occurs in the coating of the buried metal structure. The anticorrosion current to be detected is grasped by the current density flowing into the probe (probe inflow current density), and the anticorrosion situation is managed by this.

  FIG. 1 is an explanatory diagram showing a conventional technique described in Patent Document 1 below. This prior art is an external power source cathodic protection device for cathodic protection of a buried metal structure (buried metal pipeline P), which includes a probe 1 buried in the vicinity of the buried metal pipeline P and an external device. A power supply device 2 and an electrode (anode) 3 buried in the underground S are provided. The probe 1 is connected to the buried metal pipeline P via the probe current density measuring unit 2A, and the electrode 3 is connected to the buried metal pipeline P via the power control unit 2B. And the anticorrosion current output from the electrode 3 is controlled based on the measurement result of a probe inflow current density by controlling the electric power control part 2B according to the output of the probe current density measurement part 2A.

JP 2004-83996 A (see FIG. 1)

  A probe that is connected to a buried metal structure that is subject to corrosion protection and that is installed in the vicinity of the probe is always in a state where a corrosion protection current flows in if the cathodic protection of the buried metal structure is appropriate, and corrosion proceeds. There is nothing. However, if the cathodic protection situation becomes inadequate due to some external factor, the buried metal structure is exposed to the corrosion situation.

  In addition, the probe current density measured in the field may change due to various disturbances that change from moment to moment, such as the effects of rail leakage current and AC induction. The average value of the probe current density within the measurement period must be used. If it does so, even if the management of the corrosion protection status by the probe current density is appropriate, the buried metal structure may be temporarily exposed to the corrosion status.

  The influence of the buried metal structure being exposed to the corrosion state can be grasped by the corrosion state of the probe installed in the vicinity of the buried metal structure. However, until now, the only way to determine the corrosion status of the probe is to raise the probe buried underground to measure the amount of thinning, and to determine the corrosion status of the probe frequently and over time. There was a problem that could not be.

  This invention makes it an example of a subject to cope with such a problem. That is, by monitoring the corrosion state of the probe installed in the vicinity of the buried metal structure in the buried state, the influence caused by the buried metal structure being exposed to the corrosion state can be grasped frequently and over time. In other words, the object of the present invention is to improve the level of anticorrosion management of the buried metal structure by monitoring the corrosion state of the probe from the ground.

In order to achieve such an object, the corrosion state monitoring method and monitoring system for a cathodic protection control probe according to the present invention comprises at least the following configuration.
One is provided with a transmitting portion for transmitting a guide wave signal traveling along the longitudinal direction of the probe on one end side of the probe for cathodic protection control, and a guide transmitted from the transmitting portion on the other end side of the probe. A receiving unit for receiving a wave signal is provided, an AC signal is transmitted as a signal for generating a guide wave signal from the ground to the transmitting unit of the probe installed in the vicinity of the buried metal structure, and the signal received by the receiving unit is The corrosion state of the probe is monitored by the amount of thinning estimated with the sensitivity adjusted based on the attenuation ratio of the transmitted and received signals by changing the frequency of the AC signal detected on the ground, and embedded by the amount of thinning A method for monitoring a corrosion state of a probe for cathodic protection control, wherein the corrosion state of a metal structure is judged.

The method of monitoring the corrosion state of the cathode anticorrosion management probe is provided with a transmitting portion for transmitting a guide wave signal traveling along the longitudinal direction of the probe on one end side of the cathode anticorrosion management probe, and on the other end side of the probe. A receiving unit for receiving a guide wave signal transmitted from the transmitting unit is provided, and an AC signal is transmitted as a signal for generating a guide wave signal from the ground to the transmitting unit of the probe installed in the vicinity of an embedded metal structure, The signal received by the receiving unit is detected on the ground, and the corrosion state of the probe is monitored by the thinning amount estimated based on the attenuation ratio of the transmitted and received signals, and the corrosion status of the buried metal structure is measured by the thinning amount make decisions, also, you and controlling the protection current of buried metal structures by the thinning amount.

A system for monitoring the corrosion state of a probe for cathodic protection control, which is provided at one end of the probe and transmits a guide wave signal that travels along the longitudinal direction of the probe, and the other end of the probe AC signal as a signal for generating a guide wave signal from the ground to a receiving unit provided on the side for receiving a guide wave signal transmitted from the transmitting unit and the transmitting unit of the probe installed in the vicinity of an embedded metal structure A signal transmitting means for transmitting, and a signal detecting means for detecting the signal received by the receiving unit on the ground, and the frequency of the AC signal is changed, and the sensitivity is estimated based on the attenuation ratio of the transmitted / received signal. corrosion state of the probe is monitored by thinning amount that, cathodic protection management flops and performs corrosion situation determination buried metal structures by the thinning amount Over Breakfast corrosion condition monitoring system.

  The present invention having such a feature is affected by the exposure of the buried metal structure to the corroded state by monitoring the corrosion state of the probe installed in the vicinity of the buried metal structure in the buried state. Can be grasped frequently and over time. By monitoring the corrosion state of the probe from the ground, it is possible to improve the anticorrosion management level of the buried metal structure.

It is explanatory drawing of a prior art. It is explanatory drawing which showed the structural example of the corrosion state monitoring system of the cathodic protection management probe which concerns on embodiment of this invention. 1 shows a configuration example of a cathodic protection system using a corrosion monitoring system for a cathodic protection management probe according to an embodiment of the present invention. It is explanatory drawing which showed the more specific structural example of the corrosion state monitoring system of the cathodic protection management probe which concerns on embodiment of this invention. A graph in which the relationship between the attenuation ratio of the signal transmitted by the signal transmission means and the signal detected by the signal detection means and the thinning amount of the probe is measured for each signal frequency (the horizontal axis is the thinning amount (mm) and the vertical axis is the attenuation. Ratio (dB / m)).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, a buried metal pipeline will be described as an example of the buried metal structure. However, the embodiment of the present invention is not particularly limited to this. FIG. 2 is an explanatory diagram showing a configuration example of the corrosion state monitoring system for the cathodic protection control probe according to the embodiment of the present invention. The buried metal structure is, for example, a buried metal pipeline P, and this buried metal pipeline (hereinafter simply referred to as “pipeline”) P is laid in the underground S in a state of being covered with a high electrical resistance coating. For example, cathodic protection is performed by an external power supply system or the like.

  In the vicinity of the pipeline P, the probe 1 described above is installed. As described above, the probe 1 is a metal test piece that simulates a coating defect portion, is made of a metal material of the same material as the pipeline P, has a columnar shape with a prescribed cross-sectional area, and is as pipeline-as possible. It is installed in the underground S close to P.

  An electric wire L1 is connected to the probe 1. One end of the electric wire L1 is electrically connected to the end portion of the probe 1, and the other end of the electric wire L1 is pulled up to the ground via a predetermined lifting portion (for example, a terminal box TB). An electric wire L2 is connected to the pipeline P. One end of the electric wire L2 is electrically connected to the metal part of the pipeline P, and the other end of the electric wire L2 is pulled up to the ground via the pulling part (terminal box TB) described above. When measuring the probe current density, the probe current density measuring instrument 4 is connected between the ground terminals L1a and L2a of the electric wires L1 and L2.

  A cathodic protection monitoring system 100 for cathodic protection control according to an embodiment of the present invention includes a sensing unit 10 installed in a probe 1 buried underground and a monitoring unit 20 installed on the ground.

  The sensing unit 10 is provided at one end of the probe 1 and transmits a guide wave signal that travels along the longitudinal direction of the probe 1. The sensing unit 10 is provided at the other end of the probe 1 and is transmitted from the transmitting unit 11. And a receiving unit 12 that receives the guide wave signal. Signal lines L11 and L12 are connected to the transmitter 11 and the receiver 12, respectively. One end of the signal line L11 is connected to the transmitter 11 and the other end is drawn to the ground, and one end of the signal line L12 is connected to the receiver 12 and the other end is drawn to the ground. The signal lines L11 and L12 are preferably lifted to the ground along one or both of the electric wires L1 and L2. At this time, the other ends of the signal lines L11 and L12 are also pulled out via the pulling portion (terminal box TB). By protecting the electric wires L1 and L2 and the signal lines L11 and L12 and pulling them up, it becomes easy to protect the electric wires L1 and L2 and the signal lines L11 and L12 from being disconnected.

  The monitoring unit 20 detects the signal received by the receiving unit 12 via the signal transmission unit 21 that transmits a signal that causes the transmission unit 11 to generate a guide wave signal from the ground via the signal line L11 and the signal 12 L12 on the ground. And a monitoring means 23 for monitoring the corrosion state of the probe 1 based on the signal received by the receiving unit 12.

  A method for monitoring the corrosion state of the cathode anticorrosion management probe using such a system will be described. A transmitter 11 is provided at one end of the probe 1 and a receiver 12 is provided at the other end of the probe 1, and the probe 1 is installed in the vicinity of the pipeline P that is an embedded metal structure. Then, the signal transmitting means 21 is operated to transmit a signal for generating a guide wave signal from the ground to the transmitting unit 11 through the signal line L11, and the signal received by the receiving unit 12 through the signal line L12 is transmitted to the ground signal. Based on the signal detected by the detecting means 22 and received by the monitoring means 23, the corrosion state of the probe 1 is monitored.

  The signal transmission means 21 transmits a signal periodically or continuously for a desired period as necessary. The signal detection means 22 detects the received signal in accordance with the timing at which the signal transmission means 21 transmits the signal. The monitoring unit 23 estimates the corrosion state (thinning amount) of the probe 1 by comparing the signal transmitted by the signal transmission unit 21 with the signal detected by the signal detection unit 22.

  According to such a monitoring system and monitoring method, the corrosion state of the probe 1 can be monitored without lifting the probe 1 to the ground. In addition, since the corrosion state of the probe 1 can be monitored frequently or over time, the extent to which the buried metal structure (pipeline P) subject to corrosion protection is exposed to the corrosion state from the corrosion state of the probe 1. Can be easily grasped. Thereby, the improvement of the anticorrosion management level of the buried metal structure can be achieved.

  FIG. 3 shows an example of the structure of a cathodic protection system using the above-described cathodic protection management probe corrosion state monitoring system 100. Here, an example is shown in which the cathodic protection management system 100 for cathodic protection control is incorporated into an external power source cathodic protection system. Portions that overlap with the above description are given the same reference numerals and redundant description is omitted.

  An external power supply device 2 is connected to the pipeline P buried in the underground S, and an anticorrosion current is supplied to the pipeline P from an electrode (anode) 3 connected to the external power supply device 2. The probe 1 described above is embedded in the vicinity of the pipeline P in order to grasp the cathodic protection status due to the anticorrosion current.

  The output of the probe current density measuring device 4 is input to the remote control unit 5, and the output of the monitoring means 23 in the corrosion state monitoring system 100 for the cathodic protection control probe is input to the remote control unit 5. The remote control unit 5 controls the output of the external power supply device 2 according to these inputs. According to this, in addition to managing the cathodic protection status based on the probe current density, the cathodic protection status is managed based on how much the buried metal structure (pipeline P) is exposed to corrosion. Therefore, it becomes possible to control the appropriate anticorrosion current.

  FIG. 4 is an explanatory diagram showing a more specific configuration example of the corrosion protection monitoring system 100 for the cathode anticorrosion management probe. In this example, the transmission unit 11 and the reception unit 12 include coils 11A and 12A wound around the probe 1 and magnetic pole portions (magnets) 11B and 12B that form a magnetic field in the portion around which the coils 11A and 12A are wound. Yes. The signal lines L11 and L12 are connected to the coils 11A and 12A, and an AC signal is transmitted from the signal transmission unit 21 as a signal for generating a guide wave signal.

  As a function of the transmitter 11, when an AC signal is transmitted from the signal transmission means 21 to the coil 11A, the magnetic field in the longitudinal direction of the probe 1 changes, and a guide wave signal is generated in the longitudinal direction of the probe 1 by the magnetostriction effect. Propagate. As a function of the receiving unit 12, an AC signal generated by the guide wave signal is output, and the signal generated by the signal detection unit 22 is detected.

  The monitoring unit 23 compares the signal transmitted by the signal transmission unit 21 with the signal detected by the signal detection unit 22, and estimates the amount of thinning of the probe 1 based on the attenuation ratio. The thinning amount of the probe 1 is approximately proportional to the signal attenuation ratio, and it can be estimated that the larger the attenuation ratio (dB / m), the larger the thinning amount (mm) and the more the corrosion progresses. By changing the frequency of the signal to be transmitted, it is possible to adjust the sensitivity when converting the attenuation ratio into the thinning amount. When the frequency is relatively low (about 10 kHz), a wide range of thickness reduction can be measured with a high correlation with the attenuation ratio. Moreover, a slight thinning amount can be measured with high sensitivity by setting the frequency to a relatively high frequency (50 to 130 kHz). It is preferable to have a system configuration that allows measurement by changing the frequency according to the situation at the measurement site.

  FIG. 5 is a graph in which the relationship between the attenuation ratio of the signal transmitted by the signal transmission unit 21 and the signal detected by the signal detection unit 22 and the thinning amount of the probe 1 is measured for each signal frequency (the horizontal axis indicates the thinning amount ( mm) and the vertical axis represents the attenuation ratio (dB / m). Here, as is clear from the figure, when the signal frequency is 10 to 30 kHz, the thinning amount and the attenuation ratio have a linear correlation in a wide range. It can be seen that as the signal frequency increases, the linear range between the thinning amount and the attenuation ratio becomes narrow, but the thinning amount can be measured with high sensitivity by the attenuation ratio. The test condition here is that a steel probe 1 having a diameter of 10 mm is connected to an uncoated pipe having an outer diameter of 168 mm, a wall thickness of 7.1 mm, and a length of 3.139 m, and the distance between the transmitter 11 and the receiver 12. Was set to 30 mm.

  Further, the guide wave signal generated by the signal transmitted by the signal transmitting means 21 is repeatedly reflected on the end face of the probe 1, and the signal detecting means 22 detects the multiple reflected signal. The attenuation time of the multiple reflection signal and the amount of thinning of the probe 1 are in a substantially proportional relationship. Therefore, the monitoring unit 23 can also estimate the corrosion state of the probe 1 based on the degree of the decay time of the multiple reflection signal detected by the signal detection unit 22.

  Thus, according to the corrosion state monitoring method and monitoring system for the cathodic protection control probe according to the embodiment of the present invention, the corrosion state of the probe 1 installed in the vicinity of the buried metal structure is monitored in the buried state. Thus, it is possible to grasp the influence of the buried metal structure being exposed to the corrosion state frequently and over time. Further, by monitoring the corrosion state of the probe 1 from the ground, it is possible to improve the anticorrosion management level of the buried metal structure.

  As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to these embodiments, and the design can be changed without departing from the scope of the present invention. Is included in the present invention. The embodiments described in the above drawings can be combined with each other as long as there is no particular contradiction or problem in the purpose, configuration, or the like. Moreover, the description content of each figure can become independent embodiment, respectively, and embodiment of this invention is not limited to one embodiment which combined each figure.

1: probe, 2: external power supply, 3: electrode (anode),
4: Probe current density measuring instrument, 5: Remote control unit,
100: Corrosion state monitoring system for the probe for cathodic protection control,
10: sensing unit, 20: monitoring unit,
11: transmitter, 12: receiver, L11, L12: signal line,
21: Signal transmission means, 22: Signal detection means, 23: Monitoring means,
11A, 12A: Coil, 11B, 12B: Magnetic pole part (magnet),
P: Pipeline

Claims (3)

A transmitter for transmitting a guide wave signal traveling along the longitudinal direction of the probe is provided on one end of the probe for cathodic protection control, and a guide wave signal transmitted from the transmitter is received on the other end of the probe. Provided a receiving unit,
An AC signal is transmitted as a signal for generating a guide wave signal from the ground to the transmitter of the probe installed in the vicinity of the buried metal structure, and the signal received by the receiver is detected on the ground.
By changing the frequency of the AC signal, the corrosion state of the probe is monitored by the thinning amount estimated with the sensitivity adjusted based on the attenuation ratio of the transmitted and received signals, and the corrosion of the buried metal structure is monitored by the thinning amount. A method of monitoring a corrosion state of a probe for cathodic protection control, characterized by performing a situation judgment . A transmitter for transmitting a guide wave signal traveling along the longitudinal direction of the probe is provided on one end of the probe for cathodic protection control, and a guide wave signal transmitted from the transmitter is received on the other end of the probe. Provided a receiving unit,
An AC signal is transmitted as a signal for generating a guide wave signal from the ground to the transmitter of the probe installed in the vicinity of the buried metal structure, and the signal received by the receiver is detected on the ground.
A probe for cathodic protection control , wherein the corrosion state of the probe is monitored by a thinning amount estimated on the basis of an attenuation ratio of transmitted and received signals, and the anticorrosion current of the buried metal structure is controlled by the thinning amount. Corrosion state monitoring method. A system for monitoring the corrosion state of a probe for cathodic protection control,
A transmitter for transmitting a guide wave signal provided on one end side of the probe and traveling along the longitudinal direction of the probe;
A receiving unit that is provided on the other end side of the probe and receives a guide wave signal transmitted from the transmitting unit;
A signal transmission means for transmitting an alternating current signal as a signal for generating a guide wave signal from the ground to the transmitter of the probe installed in the vicinity of the buried metal structure;
Comprising signal detection means for detecting the signal received by the receiving unit on the ground;
By changing the frequency of the AC signal, the corrosion state of the probe is monitored by the thinning amount estimated with the sensitivity adjusted based on the attenuation ratio of the transmitted and received signals, and the corrosion of the buried metal structure is monitored by the thinning amount. Corrosion state monitoring system for cathodic protection control probe, characterized in that the situation is judged .

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