JP2008096398A - Cathode corrosion preventing system and cathode corrosion preventing method by galvanic anode system, pipeline soundness evaluating system and soundness evaluating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To clearly set a corrosion preventing range, accurately evaluate the pipeline soundness including a detection of defects generated in a coating and a prediction of a lifetime of a galvanic anode as a cathode corrosion preventing situation is evaluated over the entire range, and quantitatively design a system based on the clear corrosion preventing range in a cathode corrosion prevention of a high-resistivity coated pipeline by a galvanic anode system. <P>SOLUTION: The system is provided with: probes 2A, 2B for setting a zone as a target for the cathode corrosion prevention in the pipeline 1, connected to the pipeline 1 at both ends of the zone, and simulating the defects having the same area in the coating; and the galvanic anode 3 connected to the pipeline 1 in the middle of the zone. A current generated from the galvanic anode 3 is set so as to make a probe OFF potential measured by the probe 2A, 2B be less than a corrosion preventing potential. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cathodic protection system using a galvanic anode method for a corrosion-resistant pipeline with a high resistivity coating, a cathodic protection method using this system, and a pipeline soundness evaluation based on this system The present invention relates to a system and a soundness evaluation method.

  In order to prevent the corrosion of the metal body present in the electrolyte such as soil, in addition to isolating the surface of the metal body and the electrolyte such as the soil, an electric current (corrosion protection current) is allowed to flow into the metal body surface to cause the anode reaction. It is known that a cathodic protection method that prevents the occurrence of cathodic oxidation (causing a cathodic reaction on the entire metal) is the most effective method.

  At present, the cathodic protection methods used for soil buried pipelines include the galvanic anode method and the external power supply method. In the external power supply method, a DC power supply is connected between the electrode (anode) installed in the soil and the anticorrosion target pipeline (cathode) to apply voltage, and direct current flows from the electrode through the soil into the pipeline. This is a method for preventing corrosion. In this external power supply method, the section to be protected is usually partitioned by an insulating joint, and one or more DC power supply devices having outputs corresponding to the section are installed for each section, and the desired output is adjusted by adjusting the output. Cathodic protection status is obtained.

  On the other hand, in the galvanic anode method, a metal having a corrosion potential lower than that of the anticorrosion target pipeline is connected as an anode (fluidic anode) with a pipeline and an electric wire, and a pipe is formed by the dissimilar metal battery action between the galvanic anode and the pipeline This is a method of preventing corrosion by flowing a corrosion-proof current into the line. For steel soil buried pipelines, Mg anodes are often used as galvanic anodes.

  According to the cathodic protection method using the galvanic anode method, when the cathodic protection target is a high resistivity coated pipeline such as a polyethylene-coated steel pipe, there is no defect in the coating and the metal part of the pipeline In a healthy state where there is no contact with the electrolyte, the pipeline does not cathodically polarize, so no anticorrosion current will flow when attempting to cathodic protect it. Only when a defect occurs in the coating, the anticorrosive current flowing out from the galvanic anode flows into the coating defective part, and the cathodic protection is performed.

  Therefore, when cathodic protection is applied to the high resistivity coated pipeline by the galvanic anode method, it is not possible to grasp the anticorrosion status at the time of installation or immediately after the installation, and then connect the wire between the pipeline and the galvanic anode. By monitoring the flowing current, it becomes possible to grasp the anticorrosion situation or the soundness of the pipeline.

  FIG. 1 is an explanatory diagram of the prior art disclosed in Patent Document 1 below. According to this prior art, the current flowing from the Mg anode J1 serving as the galvanic anode toward the pipeline L (the galvanic anode generation current) is monitored by the monitoring circuit J2, and the maximum when the change occurs is 2 It is determined that the coating defect portion P is generated in the second section, and the distance to the coating defect point is calculated from the ratio of the magnitude of the current value between the two points. The defect location is specified. The monitoring circuit J2 is disposed in the terminal box J3, and is connected to the pipeline L and the Mg anode J1 by electric wires J4 and J5.

  In addition, in the galvanic anode method, when the galvanic anode is consumed and the generated current becomes zero in a situation where a coating defect has occurred, the pipeline becomes non-corrosive and allows the progress of corrosion. . In addition, when the pipeline is under the influence of alternating current induction, the galvanic anode also serves as a ground electrode that reduces the alternating current induced voltage of the pipeline. AC corrosion progression will be allowed. Therefore, monitoring of the galvanic anode generation current is essential to determine the life of the galvanic anode.

  In the prior art described in Patent Document 2 below, the current flowing from the Mg anode serving as the galvanic anode to the embedded pipeline is monitored periodically, and simultaneously the alternating current generated from the Mg anode is monitored using an analog measuring circuit. By smoothing, the degree of consumption of the electric capacity of the Mg anode is calculated including the disappearance of the alternating current, and the lifetime of the Mg anode is numerically predicted based on this value.

JP 7-294478 A Japanese Patent No. 3214778

  When trying to prevent cathodic protection of a high resistivity coated pipeline by the galvanic anode method, as described above, if the coating does not contact the electrolyte due to a coating defect, etc., the corrosion preventing current does not flow. Therefore, even in a system equipped with the monitoring means described above, the cathodic protection situation cannot be evaluated in a state where the coating is maintained at a high quality. In such a case, a probe simulating a coating defect (a test piece of a predetermined area made of the same material as the pipeline material) is always electrically connected to the pipeline, and the probe off potential (conducted probe) By measuring the potential difference with respect to the reference electrode of the probe immediately after electrically disconnecting the pipe and the true pipe-to-ground potential not including IR, which is the product of the anticorrosion current I and the electrolyte resistance R), the pipeline A method for evaluating the cathodic protection situation is generally known (for example, ISO 15589-1: 2003 (E) INTERNATIONAL STANDARD Petroleum and natural gas industries-Cathodic protection of pipeline transportation systems-Part 1: On-land pipeline).

  However, even in the evaluation by the ISO described above, it is only possible to grasp the cathodic protection situation in the vicinity of the place where the probe is installed, and it is not possible to quantitatively grasp the quality of the cathodic protection situation in the entire predetermined section of the pipeline. There's a problem. The ISO describes that the installation interval of the probe should not exceed 1 km in cities and industrial areas, but if the probe is installed in an overcrowded state, the galvanic anode generation current increases and the cathodic protection efficiency decreases. In addition, the life of the galvanic anode is reduced, and the high resistance coating without defects does not allow accurate evaluation of the cathodic protection situation because current flows in and out between the probes. Must be set at some interval.

  Also, when cathodic protection is applied to the high resistivity coating coated pipeline using the galvanic anode method, it is not possible to quantitatively grasp the corrosion protection status at the installation stage where it is impossible to predict where coating defects will occur. . Therefore, the cathodic protection system using the galvanic anode method, including those equipped with the monitoring means described above, cannot be used for quantitative system design. The relationship with the installation position was left to empirical design. According to this, anti-corrosion management where coating defects occur at a location away from the current-carrying anode and the anti-corrosion current does not reach sufficiently, or coating defects occur near the current-carrying anode and become over-corrosion. There was a problem that all the above problems had to be dealt with empirically.

  Further, according to the prior art shown in FIG. 1 (Patent Document 1), when one coating defect occurs between the two galvanic anodes A and B, the coating is applied as described in the literature. Although it is possible to grasp the position of the covering defect, for example, when a coating defect portion P ′ having a grounding resistance lower than P occurs in the immediate vicinity of the B's galvanic anode, the flow of B Since an inflow current from the current anode to P ′ is generated, and this current is larger than a current flowing into P from the current anode of B, the current generated at the position A and the current at the position B is It becomes impossible to specify the position of the coating defect portion P from the electric anode generation current. In other words, if multiple coating defects occur at the same time, simple monitoring of the galvanic anode current will not be able to properly grasp the defect location, etc. There is a problem that sex cannot be evaluated.

  Furthermore, according to the prior art of Patent Document 2 described above, since the AC induction generation detection is not performed by obtaining the DC component and the AC component of the galvanic anode generation current, the consumption due to the AC corrosion from the galvanic anode is specified. There is a problem that it is not quantified and accurate life prediction cannot be performed.

  The present invention has been proposed to cope with such problems, and in the cathodic protection of a high resistivity coated pipeline by the galvanic anode method, a clear anticorrosion range is set and the range is set. While evaluating the cathodic protection situation in the entire area, more accurately assessing the soundness of the pipeline, including detection of coating defect occurrence and prediction of the galvanic anode life, a quantitative system based on a clear anticorrosion range The purpose is to enable the design.

  In order to achieve the above-mentioned object, the present invention has the following features.

  One is a system or method for cathodic protection by a galvanic anode method using a pipeline with a high resistivity coating as an anticorrosion target, and sets a section for the cathodic protection target of the pipeline. Connect the probe simulating the coating defect part of the same area to the pipeline at both ends of this section, connect the galvanic anode to the pipeline at the center position of this section, It is characterized in that the current generated from the galvanic anode is set so that the probe off potential measured by the probes connected to both ends is equal to or lower than the anticorrosion potential.

  In addition to the above-described features, the direct current generated from the current-carrying anode may be a direct current generated from one current-carrying anode or a total current generated from a plurality of current-carrying anodes. It is characterized in that it is set to be equal to or higher than the required anticorrosive current obtained from the electric potential, the probe ground potential before energizing the anticorrosive current, the ground resistance of the probe, and the electrical resistivity of the electrolyte in contact with the probe.

Further, in addition to the above-mentioned characteristics, the length of the section is 1 km, the coating defect area is 10 cm ² , and the required anticorrosion current I _p is obtained by the following formula (a). .

In addition to the above-described features, the current-carrying anode is n Mg anodes, and the total generated current DC current I (DC) represented by the following formula (b) is equal to or greater than the required anticorrosion current I _p. A total ground resistance R _{Mg (n)} of n Mg anodes is set.

In addition to the above-described features, the total ground resistance R _{Mg (n)} of the _n Mg anodes is set by the number of Mg anodes n determined by the following formula (c).

  The characteristics of a system or method for evaluating the soundness of a pipeline while performing cathodic protection with a galvanic anode method are targeted for anticorrosion of pipelines with high resistivity coating. Connecting a probe that simulates a coating defect portion of the same area to the pipeline at both ends of this section, connecting an galvanic anode to the pipeline at the center position of this section, pipe The precondition is that current monitoring means is installed between the wires connecting the line and the current-carrying anode, and the current generated from the current-carrying anode is monitored by this current monitoring means.

  When the current monitoring means monitors the direct current generated from the current-carrying anode so that the probe off potential measured by the probes connected to both ends of the section is equal to or lower than the anticorrosion potential. One feature is to detect an increase in the series data value and detect the occurrence of a coating defect in this section.

  In addition to the above-mentioned premise characteristics, the direct current generated from the current-carrying anode is set so that the probe-off potential measured by the probes connected to both ends of the section is equal to or lower than the anticorrosion potential. The time difference between the time indicating the maximum value and the time indicating the minimum value from the time series data value of the unit measurement time including the maximum value among the data monitored by the current monitoring means is one of one cycle of the commercial frequency. / 2 and detects that the difference between the maximum value and the average value of the time-series data values is equal to the difference between the average value and the minimum value, and detects AC induction acting on the section. It is characterized by that.

  In addition to the above-described characteristics, when an AC induction acting on the section is detected, the lifetime LS of the galvanic anode is calculated from the time series data value monitored by the current monitoring unit according to the following formula (d). It is characterized by predicting.

  In addition to the above-described features, the probe current density of the probe is measured, and the cathodic protection standard using the probe current density as an index and the result of the measurement are checked.

  According to such a feature, the following actions can be obtained.

[Cathode protection target section setting and galvanic anode connection position in the section]
If the high resistivity coated pipeline is to be protected against corrosion by simply connecting the flowing current anode to the pipeline at a predetermined interval, as in the conventional cathodic protection system using the galvanic anode method, the anticorrosion is performed when the system is installed. Current does not flow. Therefore, it was not possible to clearly identify the range of the pipeline covered by one galvanic anode, and the system design could not be quantitatively performed.

  On the other hand, in the present invention, the probe between the pair of probes connected to the pipeline is set as a cathodic protection target section, and the current flowing anode is connected to the pipeline in the section, so that the probe from the current flowing anode is used. The system design can be quantitatively performed by regarding the current flowing into the terminal as the anticorrosion current supplied to the end of the set cathodic protection target section.

  At this time, the area of the coating defect portion simulated by the probe is the same in the left and right areas, and the connection position of the galvanic anode is the central position of the set cathodic protection target section. The cathodic protection efficiency can be increased by making it as long as possible, and the anticorrosion current to the two end points of the section can be made uniform.

[Quantitative system design by setting the galvanic anode generation current]
Since the system configuration is such that a uniform anticorrosion current flows to the end of the anticorrosion target section due to the galvanic anode generation current from the time of system operation (corrosion protection current energization), a quantitative system configuration based on the galvanic anode generation current It becomes possible. The basic idea is that when the system is installed, the probe AC current density is measured by the probe on the premise that it has passed the cathodic protection standard (that is, it has no or no influence of AC induction). By setting the direct current component of the galvanic anode generation current so that the probe off potential is equal to or lower than the anticorrosion potential, it is possible to realize a favorable cathodic anticorrosion situation in which all the parts in the section are equal to or lower than the anticorrosion potential.

Specifically, a direct current generated from one galvanic anode or a total generated current generated from a plurality of galvanic anodes is equal to or greater than the required anticorrosion current obtained by the above formula (a). What is necessary is just to set an electric current generated by the galvanic anode, and when the galvanic anode is n Mg anodes according to the set section length (for example, 1 km), the total grounding of the n Mg anodes The number of resistors R _{Mg (n)} or Mg anodes can be determined.

[Evaluation of pipeline integrity by monitoring the galvanic anode current]
(Coating defect detection)
In the system configuration of the present invention, if the coating of the high resistivity coating pipeline is sound, the galvanic anode generated current measured in the section shows a constant value. When one or a plurality of coating defects occur in the section, the current flowing into the coating defect portion generated with respect to the current flowing into the probe is added. Will increase and the increased state will continue. Therefore, by detecting an increase in time-series data values monitored by one current monitoring means installed in a section defined by a pair of probes connected to the pipeline, it is not related to the situation in the adjacent section. In addition, it is possible to reliably detect that a coating defect has occurred in the section.

(AC induction occurrence detection)
In addition, by monitoring the galvanic anode generation current and detecting the AC component, it is possible to reliably detect the occurrence of AC induction in the section defined by the pair of probes connected to the pipeline. . As described above, the system of the present invention is based on the premise that the probe alternating current density passes the cathodic protection standard (that is, the influence of alternating current induction is not present or eliminated) when the system is installed. Therefore, the AC induction is newly generated in the section when the AC component is detected by monitoring the galvanic anode generation current.

(Life prediction of galvanic anode)
In addition, by monitoring the current generated by the galvanic anode and predicting the life from this monitoring value, if the occurrence of AC induction is detected, the consumption due to AC corrosion of the galvanic anode is quantitatively added. , More accurate life prediction becomes possible.

[Cathode protection maintenance by probe current density]
Measure the probe current density of the probe connected to the pipeline at the end of the set cathodic protection target section, check the cathodic protection standard using the probe current density as an index, and the measurement result. By confirming that it has passed, it is possible to confirm that the cathodic protection is soundly performed in the set section after the system is operating.

  The present invention has such a feature, and in the cathodic protection of the high resistivity coated pipeline by the galvanic anode method, a clear anticorrosion range is set, and the cathodic protection situation in the entire range is set. While evaluating, it is possible to more accurately evaluate the soundness of the pipeline including the detection of occurrence of coating defects, the detection of alternating current induction, and the prediction of the galvanic anode life. Further, it is possible to design a quantitative cathodic protection system or cathodic protection method based on a clear anticorrosion range.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is an explanatory diagram showing a cathodic protection system and a pipeline soundness evaluation system according to an embodiment of the present invention.

[Cathode Protection System / Cathode Protection Method Configuration and Design Technical Thought]
A cathodic protection system according to an embodiment of the present invention is a system that performs cathodic protection by a galvanic anode method using a pipeline 1 with a high resistivity coating as a corrosion protection target. A section for cathodic protection (cathodic protection target section) is set along the pipeline 1 with a predetermined length (for example, 1 km), and probes 2A and 2B are connected to the pipeline 1 at both ends of the section. That is, a section defined by a pair of probes 2A and 2B connected to the pipeline 1 is set as a cathodic protection target section.

The probes 2A and 2B simulate a coating defect portion having the same area (for example, 10 cm ² ) (coating defect portion simulating the black end), and the metal of the pipeline 1 as shown in the figure. It is connected to the surface via an electric wire 20. Since the probes 2A and 2B simulate the formation of a coating defect at the end of the above-described cathodic protection target section, the tip positions of the probes 2A and 2B and the metal surfaces of the electric wire 20 and the pipeline 1 are used. Are connected so that both are connected to the end of the cathodic protection target section.

  A seal 21 is provided at a connection portion between the electric wire 20 and the metal surface of the pipeline 1. The electric wire 20 is provided with a switch 22 for cutting and connecting the continuity, and an ammeter (not shown) for measuring the probe current density of the probes 2A and 2B is connected as necessary. Further, the electric wire 20 is also connected to a reference electrode (for example, a saturated copper sulfate electrode) 24, and a potential difference therebetween is measured by a voltmeter 23 to probe-to-ground potential (probe-off potential or probe-to-ground potential before energization of anticorrosion current described later). To be able to ask.

  Then, the galvanic anode 3 is connected to the pipeline 1 at the center position of the cathodic protection target section set by the pair of probes 2A and 2B. As the galvanic anode 3, a Mg anode can be used for the steel pipeline 1. The galvanic anode 3 is connected to the metal surface of the pipeline 1 through the electric wire 30, and the connection position and the burying position of the galvanic anode 3 are both set to the center position of the cathodic protection target section. .

  According to such a cathodic protection system, it is possible to construct a system in which an anticorrosion current flows from immediately after energization of the galvanic anode 3 and conduction of the probes 2A and 2B to the end of the cathodic protection target section.

FIG. 3 is an explanatory diagram showing the anticorrosion status of the cathodic protection system according to the embodiment of the present invention in which the coating defect portion is simulated by installing the probes 2A and 2B. According to this system, the coating defect portion Ph of the same area (for example, 10 cm ² ) is in a situation equivalent to that generated at the left and right ends of the cathodic protection target section. It will flow into the coating defect part Ph of the same area on the left and right.

Here, since the coating defect part Ph having the same area is set and the galvanic anode 3 is installed at the center position of the cathodic protection target section, the anticorrosion current flowing into the left and right coating defect parts Ph is equal. The (Probe / S) _pro (probe off potential) immediately after energization in the pipeline 1 is the lowest at the center position of the cathodic protection target section (the shift amount on the minus side is large), and is the highest at the end position of the section. (Probe / S) _cor in the figure is the probe ground potential before applying the anticorrosion current, and usually shows a constant value if the surrounding environment is uniform) . The probe off potential (Probe / S) _pro is a potential difference with respect to the reference electrode 24 of the probes 2A and 2B immediately after the conducted probes 2A and 2B and the pipeline 1 are electrically cut off by the switch 22, and the anticorrosion current. A true tube-to-ground potential that does not include IR, which is the product of I and electrolyte resistance R.

In this way, by setting the state where the coating defect part of the same area is formed at the end of the set cathodic protection target section and the electroplating anode is installed at the center position of the cathodic protection, the cathodic protection status is set at the time of system installation. will be able to grasp from the section center is a point of installation galvanic anode 3 does not become excessive corrosion probe off potential at the section ends (probe / S) so _{that the pro} is below anticorrosion potential E _p If the system configuration is designed, it is possible to perform a quantitative system design for the cathodic protection system using the galvanic anode method.

In the case of the pipeline 1 to which the high resistivity coating is applied, the pipe-to-ground potential cannot be measured because the metal of the pipeline 1 is not in contact with the electrolyte. Therefore, cathodic protection target interval ends two locations in the installed probe 2A, a probe-off potentials measured by 2B is (pass the cathodic protection criteria) to be less corrosion potential E _p performing cathodic protection designed. Here, the probes 2A and 2B simulate the coating defect portion of the same area, and the corrosion protection current flowing from the galvanic anode 3 toward the end 2 points of the cathodic protection target section is uniform. This is to make the distance of the cathodic protection target section as long as possible.

  Here, when installing the system, the probe AC current density must pass the cathodic protection standard (the influence of AC induction does not reach the pipeline 1 or the AC induction reduction measures have already been taken). On the premise. This premise is that if there is an influence of AC induction at the time of system installation, naturally the system will be installed after taking measures to reduce AC induction, and the installation of the galvanic anode itself will function as an earth electrode to reduce AC induction. In consideration of the fact that AC induction can be effectively reduced by distributed installation of galvanic anodes at intervals of about 1 km, this is an appropriate premise for system design.

  The system design parameters are the length of the cathodic protection target section and the magnitude of the current generated by the galvanic anode 3. These will be described below.

[Setting of cathodic protection target section]
To avoid over-corrosion at the center position of the section, it is obvious that the section length should be as short as possible (the longer the section, the smaller the shift to the minus side at the end). Therefore, if the terminal probe-off potential is set to be equal to or lower than the anticorrosion potential, the shift amount at the center position becomes too large). However, when the section is shortened and the probes are installed overly densely, the galvanic anode generation current increases and the cathodic protection efficiency decreases.In addition, in the high resistivity coating without coating defects, the current between the probes is reduced. The probe installation interval should be determined with a certain interval since the inflow and outflow will occur and the cathodic protection situation cannot be accurately evaluated.

  Thus, a. Reduction of over-corrosion risk at the site where the galvanic anode is installed, b. Probe installation interval, c. Uniformizing the anticorrosion current, d. Dispersive installation of galvanic anodes as earth electrodes for reduced AC induction, and e. Considering the realistic number of galvanic anodes installed at each location, it is appropriate to set the cathodic protection target section to about 1 km.

  Moreover, it is important not to install a probe other than the two end points in the cathodic protection target section. If the probe is installed in a section other than the two end points, the galvanic anode generation current flows into the probe in the section, and the end of the section tends to have insufficient anticorrosion current, so that the basic idea of the system design of the present invention is established. Disappear.

When the cathodic protection area is 1 km, the probe installation interval is the same as ISO 15589-1: 2003 (E) described above. Regarding the probe area, 1 cm ² to 10 cm ² is generally recommended (EN 13636: Cathodic protection of buried metallic tanks and related piping, 2004). When the electrolyte in contact with the probe is soil, it is necessary to improve the contact between the metal surface simulating the coating defect of the probe and the soil in order to allow the anticorrosion current to flow into the coating defect. . For that purpose, it is necessary to make the metal surface of the probe as large as possible. Therefore, in the embodiment of the present invention, the probe area is set to 10 cm ² .

[Design of cathodic protection system / cathodic protection method based on galvanic anode current]
In the system configuration of the present invention, the probes 2A and 2B are always connected to the pipeline 1 during operation, and the current generated from the current-carrying anode 3 (current-carrying anode generated current) is always used as an anticorrosion current when energized. It flows into the probes 2A and 2B. At this time, based on the basic concept of the system design described above, the galvanic anode generation current (when there are a plurality of galvanic anodes so that the probe off potential measured by the probes 2A and 2B is equal to or lower than the anticorrosion potential In order to set the total generated current), the galvanic anode generated current is set to be equal to or higher than the required anticorrosive current I _p shown below.

(Derivation of required anticorrosion current)
Defining the required anticorrosion current I _p as the current required to shift the probe ground potential (Probe / S) _cor before the anticorrosion current energization to the probe off potential (Probe / S) _pro after the anticorrosion current energization, It can be represented by (a1).

In the formula (a1), the probe ground potential (Probe / S) _cor before energization of the anticorrosion current can be measured by the voltmeter 23 with the switch 22 closed before the _galvanic anode 3 is connected. The probe off potential (Probe / S) _pro can be obtained as a voltage value that can be measured by the voltmeter 23 immediately after the switch 22 is opened after the galvanic anode 3 is connected. The ground resistance R _pipe of the pipeline 1 can be expressed as the following formula (a2).

  Coating resistance, also called coating resistance, is the sum of the electrical resistance of the coating component and the ground resistance of the pipeline metal surface that is in contact with the surrounding soil or other electrolyte at the defective coating. It is. However, in the system configuration that is the subject of the present invention, the coating material in question is a high resistivity coating material such as polyethylene, so the electrical resistance of the coating component material is significantly higher than the ground resistance. Value. Therefore, it can be considered that the coating resistance is determined by the ground resistance of the coating defect portion.

In the system configuration according to the embodiment of the present invention, the surface area Sm ² of the pipeline 1 is represented by the following formula (a3) when the outer diameter Dm and the distance of the cathodic protection target section are 1 km (1000 m).

  By substituting equation (a3) into equation (a2), the following equation (a4) is obtained.

On the other hand, ω can be expressed as the following formula (a5) using the grounding resistance R _c Ω of the coating defect portion and the coating defect portion existence rate n / m ² .

Here, R _c is expressed by the following equation (a6) assuming that the coating defect is circular (WVBaeckman, W. Schwenk: Handbuch des kathodischen Korrosionsschutzes).
, WILEY-VCH Verlag GmbH, 1999).

The grounding resistance R _c of the coating defect portion having an area of 10 cm ² is obtained by substituting 10 ⁻³ for S _c in the formula (a6) to obtain the following formula (a7).

This R _c is equal to the ground resistance of one probe. The coating defect portion existing rate n / m ² is expressed by the following formula (a8).

  Here, it is assumed that the n coating defect portions have the same area and the electrical resistivity of the electrolyte in contact with the coating defect portion. By substituting equation (a7) and equation (a8) into equation (a5), the following equation (a9) is obtained.

  Substituting into the equations (a9) and (a4), the following equation (a10) is obtained.

By substituting equation (a10) into equation (a1), the following equation (a11) is obtained. The probe 2A, a probe-off potential to be measured by setting the following corrosion potential E _p in 2B, the following formula (a) is obtained.

  That is, the cathodic protection system of the present invention may be designed so that the galvanic anode generation current is equal to or higher than the required anticorrosion current satisfying the formula (a). Note that the current generated by the galvanic anode at this time must be set to the minimum necessary value in order to extend the life of the galvanic anode as much as possible and not to interfere with other embedded metal structures.

(Design of total grounding resistance or total number of installed anodes)
Here, assuming that the galvanic anode is n Mg anodes, the total ground resistance and the total number of installed anodes are obtained. That is, the direct current I (DC) of the total generated current of n Mg anodes (n ≧ 1) may be equal to or greater than the required anticorrosion current I _p . Therefore, the following formula (b1) is obtained, and the following formula (b2) is obtained by substituting the above formula (a). Note that I (DC) is a measurement time average value of values sampled at intervals of 0.1 msec by a current monitoring unit described later.

That is, the total ground resistance R _{Mg (n)} Ω of _n Mg anodes is adjusted so as to satisfy the above (b2). At this time, since the grounding resistance R _Mg of one Mg anode and the correction coefficient K for the number of Mg anodes installed per location are known, the total number n of Mg anodes is obtained as in the following formula (c). be able to.

[Pipeline health evaluation system (method) and its function]
(Overall structure of pipeline soundness evaluation system (method))
The pipeline soundness evaluation system or the soundness evaluation method according to the embodiment of the present invention uses a pipeline with a high resistivity coating as a corrosion protection target, while performing cathodic protection with the above-described cathodic protection system. It evaluates the soundness of the line.

  The overall configuration of the system will be described with reference to FIG. 2. As described in the above-described cathodic protection system, a section to be cathodic protected in the pipeline 1 is set, and the pipeline 1 is coated with the same area at both ends of the section. Probes 2A and 2B simulating a covering defect portion are connected, and a galvanic anode 3 is connected to the pipeline 1 at the center position of this section, and a soundness evaluation device 6 is connected to this cathodic protection system By doing so, the soundness of the pipeline during the cathodic protection system operation is evaluated.

  The soundness evaluation device 6 is installed between the electric wire 30 connecting the pipeline 1 and the current-carrying anode 3, current monitoring means 4 for monitoring the current generated in the current-carrying anode 3, and the monitoring value of the current monitoring means 4 And arithmetic processing means 5 for arithmetic processing.

  The arithmetic processing means 5 includes, for example, a CPU that acquires monitoring value data and performs arithmetic processing, a memory that stores monitoring value data and arithmetic processing results, a display that displays the arithmetic processing results, and the like. Calculation processing for obtaining the average, maximum, and minimum values of data, or calculation processing for predicting remaining life, etc., and displaying the calculation processing results on a display by graph display or the like and storing them in a memory .

  This arithmetic processing means 5 includes coating defect detecting means 5A, alternating current induction detecting means 5B, and galvanic anode life predicting means 5C as arithmetic processing functions. Each function only needs to be provided by selecting one or more of them, but by providing all three functions, a system that can grasp all the signs of the phenomenon that greatly threatens the health of the pipeline 1 is constructed. be able to.

(Current monitoring means (process))
In the above-described cathodic protection system according to the embodiment of the present invention, the anticorrosion current flows after the start of energization of the system, and the galvanic anode generated current can be monitored. In addition, since the cathodic protection target section divided by the installation of the probes 2A and 2B can be formed, the galvanic anode generated current of the galvanic anode 3 installed at one place in the section is the galvanic anode of another adjacent section. Will not be affected. Therefore, by monitoring the galvanic anode generation current of the galvanic anode 3 installed at one location in the section, the cathodic protection status in the entire section can be grasped regardless of the other sections.

  The current monitoring means 4 outputs the measurement value of the ammeter interposed in the electric wire 30 that connects the pipeline 1 and the galvanic anode 3 as time series data. The sampling interval of the time series data is, for example, 0.1 msec interval. By setting the sampling interval to 0.1 msec, a. The direct current component and the alternating current component of the galvanic anode generation current can be obtained with high accuracy (when the pipeline 1 is subjected to alternating current induction, it can be evaluated whether or not it matches the commercial frequency), b . The maximum and minimum values and the time of occurrence can be accurately grasped; c. There is an advantage that it is possible to catch the influence phenomenon due to the passage of the high-speed AC electric railway such as the Shinkansen without missing it.

  Further, as an example of the current monitoring unit 4, monitoring is performed once a day for 15 minutes starting from a set time. The measured data is output as time series data corresponding to the time. The monitoring start time can be set as appropriate. For example, when the installation position of the current-carrying anode 3 is a parallel part or crossing part of the high-voltage AC overhead power transmission line, the setting time is 14:00 when the transmission current becomes maximum, When the installation position of the galvanic anode 3 is in the vicinity of the electric railway transportation route, the set time is set to the morning and evening rush hour of the electric railway (for example, 18:00).

  FIG. 4 is an explanatory diagram illustrating an example of a monitoring process by the current monitoring unit 4. Here, a basic measurement time of 15 minutes once a day is set, a unit measurement time of 20 msec is set in the basic measurement time, and data sampling is performed at a sampling interval of 0.1 msec in each unit measurement time. Done.

Unit measurement time, but which is one period for performing measurement evaluation data 200 sampled data _{I (t 1) ~I (t} 200) is saved primary corresponds to a time t ₁ ~t ₂₀₀ The Then, the average value I of the unit measurement time per the 200 pieces of data I of the unit measurement time _{(t a) (DC) m} (m = 1~45000) is obtained. That is, in the basic measurement time of 15 minutes, 45,000 pieces of data I (DC) _{1 to} I (DC) ₄₅₀₀₀ are obtained.

Then, an average value I (DC) ^ave at the basic measurement time is obtained by the following equation (e). In this embodiment, the basic measurement time is set to 15 minutes, but this basic measurement time can be arbitrarily set. Then, assuming that I (DC) ^ave obtained in the same manner at an arbitrarily set basic measurement time is an average value for one day, soundness evaluation to be described later is performed. Here, the basic measurement time is arbitrarily determined according to the environment of the evaluation target pipeline, for example, the operation frequency of an electric railway operated in the vicinity. For example, if the influence of electric railways in urban areas is taken into account, the safety factor for soundness evaluation is expected in a short basic measurement time by measuring only during rush hours where the operation frequency is high. Become.

Further, the maximum value I ^max and the minimum value I ^min are obtained for each unit measurement time, and the values and the times indicating the values are stored. By comparing the maximum value I ^max and the minimum value I ^min of each unit measurement time, the maximum value I seek ^max and a minimum value I ^min, time unit measurement time there are a maximum value I ^max of the basic measurement time ( In FIG. 4, the third unit measurement time) is extracted, and the waveform of the unit measurement time (sampling data I (t ₁ ) to I (t ₂₀₀ )) is stored (the waveform is referred to as a storage waveform). When the average value I (DC) ^ave , the maximum value I ^max , the minimum value I ^min, and the saved waveform are obtained in the basic measurement time, these are stored in the memory, and 200 × 45000 pieces of data in the basic measurement time Erase at that time.

(Coating defect detection means (process))
The coating defect detection unit 5A detects an increase in the time series data value monitored by the current monitoring unit 4 and detects that a coating defect has occurred in the cathodic protection target section.

Specifically, the average value I (DC) ^ave at the basic measurement time described above is considered as the average value of the galvanic anode generated current of the day, and changes in the average value I (DC) ^ave are observed on a daily basis. DC) From the increase in ^ave , it is detected that one or a plurality of coating defects have occurred in the cathodic protection target section defined by the probes 2A and 2B. Here, since the data acquired from the current monitoring means 4 in the cathodic protection target section can be considered as a value that is not affected by other sections, a coating defect in the section due to an increase in I (DC) ^ave. It is possible to reliably detect the occurrence of.

FIG. 5 is an explanatory view showing a specific detection technique of the coating defect detection means 5A. Here, when a coating defect occurs, attention is paid to the fact that the galvanic anode generation current increases and the increased state is maintained, and the average value I (DC) ^{ave of} a certain day is If the occurrence of coating defects is detected at the stage when the average value I (DC) ^ave of the previous day is increased by 15% or more, and this level is maintained for three consecutive days, the occurrence of coating defects will occur. Judging that the possibility is extremely high, an alarm is generated and a detailed evaluation of coating defects is performed.

High resistivity coated pipelines naturally have higher AC induced voltage than bituminous coated pipelines with high moisture content, so in the coating defects of high resistivity coated pipelines In particular, it is necessary to consider the influence of AC corrosion. From the research results so far, it has been clarified that the AC corrosion rate becomes maximum when the area of the high resistivity coating defect is 1 cm ² . Therefore, for the maintenance of the pipeline, it is required to detect the occurrence of a high resistivity coating defect with an area of 1 cm ² . In the embodiment of the present invention (cathode protection target section 1 km, probe area 10 cm ² each), it will be verified below whether or not it is possible to detect the occurrence of a high resistivity coating defect having an area of 1 cm ^2. .

In the embodiment of the present invention, a coating defect portion having an area of 10 cm ² is simulated at two points at the end of the cathodic protection target section 1 km, and in this section, a coating defect exceeding a total area of 20 cm ² is generated. The system is not acceptable. Here, whether or not an increase in the galvanic anode generation current can be detected when a coating defect area 1 cm ^{2 at} which the AC corrosion rate is maximized is generated from a state where there is a coating defect area of 20 cm ^2. I will verify that.

Ground resistance R ^{1 cm @ 2} of coating-covering defect area 1cm ² (10 ^-4 m ²⁾ is the equation (a6), the R ^1cm2 = 44.3ρ (Ω). Further, assuming that n ground resistances with an area of 1 cm ^{2 in} the coating defect portion are equal to two ground resistances with an area of 10 cm ^{2 in} the coating defect portion, 44.3ρ / n = 7.0ρ, and therefore n = 6.33 (pieces).

Assuming that the number of the coating defect area of 6.33 having an area of 1 cm ² is increased by one, the ground resistance in this case is 44.3ρ / (6.33 + 1) = 6.04ρ (Ω).

When one more coating defect portion having an area of 1 cm ² occurs, the ground resistance is 6.04 ρΩ. Therefore, when the required anticorrosion current at this time is I _p ′, the following equation (f) is obtained.

When this equation (f) is compared with the equation (a), the galvanic anode generation current is increased by 16%. (Probe / S) _cor to -500 mV _CSE, if the 15Ωm -1400mV _CSE, the ρ a _{(Probe / S) pro, I} p ' becomes 9.96mA from the equation (f). Therefore, the increase is 1.38 mA. This is an incremental current value that can be sufficiently detected by the minimum resolution of 0.01 mA of a general-purpose ammeter.

(AC induction occurrence detection means (process))
As described above, the design of the cathodic protection system according to the embodiment of the present invention is such that the probe AC current density passes the cathodic protection standard (the pipeline 1 is not affected by the AC induction when the system is installed or the influence is eliminated). It is assumed that However, the pipeline 1 may be affected by AC induction due to subsequent changes in the surrounding environment, and the AC induction generation detecting means 5B detects the AC induction generation accompanying such changes in the surrounding environment and the like. It is detected by monitoring.

When pipeline 1 is subjected to AC induction due to the influence of high-voltage AC overhead power transmission line, etc. at a certain point in the cathodic protection target section, a stored waveform (sampling of unit measurement time 20 msec indicating maximum value I ^max within basic measurement time) Data) is the same frequency as the commercial frequency. Therefore, it is determined that the frequency of the stored waveform is the same as the commercial frequency, and it is detected that AC induction has occurred in the pipeline 1.

  The determination that the stored waveform is the same as the commercial frequency is a value in the time-series data stored in units of 20 msec, and the time difference between the time indicating the maximum value and the time indicating the minimum value is one cycle of the commercial frequency. It is assumed that the difference is between 1/2 and the difference between the maximum value and the average value and the difference between the average value and the minimum value are equal. For example, when AC induction is detected for three consecutive days, an alarm is generated.

FIG. 6 is an explanatory diagram showing a specific detection method of the AC induction occurrence detection means 5B. Here, when the occurrence of AC induction is detected, an AC current value I (AC) ^save (when the mth unit measurement period is a saved waveform) represented by the following equation (g) is obtained, To monitor. When the occurrence of alternating current induction is detected for three consecutive days, the probe current density is measured, and when the probe alternating current density does not pass the cathodic protection standard, countermeasures are taken.

(Electrical anode life prediction means (process))
The galvanic anode life prediction means 5C is for predicting the life of the galvanic anode 3 based on the monitoring data of the galvanic anode generated current by the current monitoring means 4, and performs the life prediction calculation by the following equation (d). It is means to do.

  According to the embodiment of the present invention, when alternating current induction acting on the cathodic protection target section is detected by the alternating current induction detection means 5B, the life prediction is performed by taking into account the consumption due to alternating current corrosion. Here, the “effective electric capacity” is an electric capacity obtained by subtracting a self-corrosion component (generally referred to as 50%, also referred to as current efficiency) from the theoretical electric capacity of the galvanic anode. Since this “effective electric capacity” is consumed as a direct current and an alternating current of the galvanic anode generation current, which is the anticorrosion current, the life of the galvanic anode is determined by the consumption rate of the effective electric capacity. . In the embodiment of the present invention, since the prediction is based on the actual consumption rate of the effective electric capacity, an accurate value is obtained.

Specifically, in the formula (d), the conversion coefficient a is obtained by converting 1 day (24 hours) into a year (Y) unit since one year is 8760 hours (24 hours × 365 days). Yes, 24/8760 = 0.00274. In the embodiment of the current monitoring means, monitoring is performed once a day for 15 minutes starting from the set time. According to the formula (d), it is assumed that the average value I (DC) ^ave of the DC current of the daily flowing anode generation current continues this value until the set time of the next day, The AC corrosion electric quantity T is obtained on the assumption that the AC corrosion electric quantity obtained from the stored waveform continues for one day.

FIG. 7 is an explanatory diagram showing a method for deriving the amount of AC corrosion electricity of the Mg anode. In the stored waveform, the area of the hatched portion shown in the figure is obtained by Tm (mA · msec / m ² ) = 2 × (2 / π) × I _AC ^max × 10. Here, I _AC ^max = I ^max −I (DC) ^ave (I ^max : maximum value in saved waveform (unit measurement time), I (DC) ^ave : average value in saved waveform). Then, the AC corrosion electricity quantity ΣT is obtained as the above Tm continues only during the period (the day when the AC induction is continuously generated). Note that equation (d) is obtained from an arbitrarily set basic measurement time and does not depend on the measurement time of one day. In addition, because the life of the anode is predicted from the daily measurement results, the life prediction is performed by appropriately evaluating the cathodic protection situation without deriving the optimistic result by skipping rainy days with low rail leakage resistance. be able to.

[Pipeline soundness evaluation method]
8 to 10 are flowcharts for explaining a pipeline soundness evaluation method using the pipeline soundness evaluation system according to the embodiment of the present invention.

  First, in the cathodic protection system design (S1), as described above, a section for cathodic protection of the pipeline 1 (cathodic protection target section) is set, and a coating defect portion having the same area at both ends of the section. Are connected to the pipeline 1, and when connecting the galvanic anode 3 to the pipeline 1 at the center of the section, the probe off potential measured by the probes 2A and 2B is equal to or lower than the anticorrosion potential. The generated current from the galvanic anode 3 is set so that

  Thereafter, after the designed system is installed, the system is operated and an anticorrosion current is passed through the cathodic protection target section (S2). At the same time, the current monitoring means 4 monitors the galvanic anode generation current (S3).

  Then, a coating defect detection step by the coating defect detection means 5A while causing the current generated from the galvanic anode 3 to flow as the anticorrosion current so that the probe off potential measured by the probes 2A and 2B is equal to or lower than the anticorrosion potential. The soundness of the pipeline 1 is evaluated by (S4).

  In the coating defect detection step (S4), based on the monitoring of the galvanic anode generation current by the current monitoring means 4, does the galvanic anode generation current appear to exceed 15% of the previous (previous day) value? It is detected (S5), and when it appears, it is detected (YES), and the process proceeds to the flow (A) shown in FIG.

  When the above-described value of more than 15% does not appear in the coating defect detection step (S4) (S5: NO) or when the coating defect detection step (S4) is not performed, the AC induction occurrence detection means 5B The soundness of the pipeline 1 is evaluated by the AC induction generation detection step (S6).

  In the AC induction generation detection step (S6), based on the monitoring of the galvanic anode generation current by the current monitoring means 4, it is detected whether or not a sine wave that matches the cycle of the commercial frequency appears in the stored waveform (S7). When it appears, it is detected (YES), and the flow proceeds to (B) shown in FIG.

  When the above-described sine wave does not appear in the AC induction generation detection step (S6) (S7: NO) or when the AC induction generation detection step (S6) is not performed, the flow proceeds to the galvanic anode life prediction step (S8).

  In the galvanic anode life prediction step (S8) in this case, since the occurrence of AC induction is not detected, the life prediction calculation process described above is performed in consideration of only the DC corrosion consumption. Monitoring is continued (S3).

  Then, when there is a detection (S5: YES) in the coating defect detection step (S4), the countermeasure flow shown in FIG. 9 is executed. That is, it is determined whether the monitoring result of the galvanic anode generation current maintains the same level for three consecutive days (S10). If maintained (S10: YES), it is determined that a coating defect has occurred in the cathodic protection target section, and a coating defect inspection (ACVG or the like) is performed on this section (S11). ), The position of a specific defective portion is specified, and necessary countermeasures are taken (S12). In the embodiment of the present invention, since the inspection range is specified in the set section of about 1 km, the coating defect position inspection and countermeasures can be easily performed.

Further, when the same level value is not maintained for three consecutive days in S10 (S10: NO), it is determined whether I (DC) ^ave has returned to the level before S5 (S13), and has returned. In the case (S13: YES), the monitoring of the galvanic anode generation current is continued (S3). If I (DC) ^ave has not returned to the level before S5 in S13 (S13: NO), coating defect inspection (ACVG, etc.) is performed (S14), and necessary countermeasures are taken (S12). After the countermeasure (S12) is implemented, it is confirmed that I (DC) ^ave has returned to the level before S5 (S15), and monitoring of the galvanic anode generation current is continued (S3). .

  Further, in the case where there is detection (S7: YES) in the AC induction generation detection step (S6), the countermeasure flow shown in FIG. 10 is executed. That is, from the monitoring result of the galvanic anode generated current, it is determined whether or not the stored waveform is a sine wave that matches the cycle of the commercial frequency for three consecutive days (S20). : YES), the probe current density (probe DC current density and probe AC current density) is measured by the probes 2A and 2B (S21). Then, the cathodic protection standard using the probe current density as an index and the measurement result are checked to determine whether or not the cathodic protection standard is passed (S22). If it has passed (S22: YES), it is determined that no countermeasure is required in the determination ○ (S23), and the process proceeds to the galvanic anode life prediction step (S24). In the galvanic anode life prediction step (S24) in this case, life prediction calculation processing is performed taking into account consumption due to AC corrosion only during the period in which AC induction is detected, and monitoring of the galvanic anode generation current is continued again. (S3).

  If the cathodic protection standard is not passed in S22 (S22: NO), measure measures such as the addition of an galvanic anode are executed (S26), and then the probe current density measurement is repeated (S21). Countermeasures will continue until the current density measurement results pass the cathodic protection standards.

If no AC induction is detected for 3 consecutive days in S20 (S20: NO), it is determined whether I (AC) ^ave has returned to the level before S7 (S25), and the process returns. If it is present (S25: YES), monitoring of the galvanic anode generation current is continued (S3). If I (AC) ^ave has not returned to the level before S7 in S25 (S25: NO), the flow proceeds to the probe current density measurement flow (S21) described above.

It is explanatory drawing of a prior art. It is explanatory drawing which shows the cathodic protection system and pipeline soundness evaluation system which concern on embodiment of this invention. It is explanatory drawing which shows the anti-corrosion condition of the cathodic anti-corrosion system which concerns on embodiment of this invention. It is explanatory drawing which shows an example of the monitoring process by the current monitoring means in embodiment of this invention. It is explanatory drawing which showed the specific detection method of the coating defect detection means in embodiment of this invention. It is explanatory drawing which showed the specific detection method of the alternating current induction generation | occurrence | production detection means in embodiment of this invention. It is explanatory drawing which showed the derivation | leading-out method of the alternating current corrosive electricity quantity of a galvanic anode. It is a flow explaining the pipeline soundness evaluation method using the pipeline soundness evaluation system which concerns on embodiment of this invention. It is a flow explaining the pipeline soundness evaluation method using the pipeline soundness evaluation system which concerns on embodiment of this invention. It is a flow explaining the pipeline soundness evaluation method using the pipeline soundness evaluation system which concerns on embodiment of this invention.

Explanation of symbols

1 Pipeline 2A, 2B Probe (Coating defect with simulated black tip)
DESCRIPTION OF SYMBOLS 20 Electric wire 21 Seal 23 Voltmeter 24 Reference electrode 3 Current-flow anode 30 Electric wire 4 Current monitoring means 5 Arithmetic processing means 5A Coated defect detection means 5B AC induction generation detection means 5C Current-current anode life prediction means 6 Soundness evaluation apparatus

Claims (16)

A system that performs cathodic protection by the galvanic anode method, targeting a pipeline with a high resistivity coating,
Set the section for cathodic protection of the pipeline,
A probe that is connected to the pipeline at both ends of the section and that simulates a coating defect portion of the same area, and a galvanic anode that is connected to the pipeline at the center position of the section,
A cathodic protection system using a galvanic anode method, wherein a current generated from the galvanic anode is set so that a probe off potential measured by the probe is equal to or lower than a corrosion protection potential.   The direct current generated from the flowing current anode is the direct current generated from one flowing current anode or the total generated current generated from a plurality of flowing current anodes. 2. The cathodic protection by the galvanic anode method according to claim 1, wherein the cathodic protection is set to be equal to or higher than a required anticorrosion current obtained from an electric potential, a ground resistance of the probe, and an electric resistivity of an electrolyte in contact with the probe. system. 3. The galvanic anode according to claim 2, wherein the length of the section is 1 km, the coating defect area is 10 cm ² , and the required anticorrosion current I _p is obtained by the following formula (a). Cathodic protection system based on this method.

The current-carrying anode is n Mg anodes, and the total ground resistance of n Mg anodes is such that the direct current I (DC) of the total generated current represented by the following formula (b) is equal to or greater than the required anticorrosion current I _p. 4. The cathodic protection system according to the galvanic anode method according to claim 3, wherein R _{Mg (n)} is set.

5. The cathodic protection system according to the galvanic anode method according to claim 4, wherein the total ground resistance R _{Mg (n)} of the _n Mg anodes is set to the number n of Mg anodes obtained by the following formula (c).

It is a method of cathodic protection by a galvanic anode method for a corrosion-resistant pipeline covered with a high resistivity coating,
Setting a section to be cathodic protection target of the pipeline;
Connecting a probe simulating a coating defect portion of the same area at both ends of the section to the pipeline;
Connecting an galvanic anode to the pipeline at a central position of the section;
A cathodic protection method using a galvanic anode method, wherein a current generated from the galvanic anode is set so that a probe off potential measured by the probe is equal to or lower than a corrosion protection potential.   The direct current generated from the flowing current anode is the direct current generated from one flowing current anode or the total generated current generated from a plurality of flowing current anodes. 7. The cathodic protection by the galvanic anode method according to claim 6, wherein the cathodic protection method is set to be equal to or higher than a required anticorrosion current obtained from a potential, a ground resistance of the probe, and an electric resistivity of an electrolyte in contact with the probe. Method. The galvanic anode according to claim 7, wherein the length of the section is 1 km, the coating defect area is 10 cm ² , and the required anticorrosion current I _p is obtained by the following formula (a). Cathodic protection method by the system.

A system that evaluates the soundness of a pipeline while performing cathodic protection with a galvanic anode method, targeting a pipeline with a high resistivity coating,
Set the section for cathodic protection of the pipeline,
A probe that is connected to the pipeline at both ends of the section and simulates a coating defect of the same area;
A galvanic anode connected to the pipeline at a central position of the section;
A current monitoring means for monitoring a current generated from the current-carrying anode installed between wires connecting the pipeline and the current-carrying anode;
A coating defect detecting means for detecting an increase in the time series data value monitored by the current monitoring means and detecting that a coating defect has occurred in the section;
Evaluation of the soundness of the pipeline by the coating defect detection means in a state where the direct current generated from the galvanic anode is set so that the probe off potential measured by the probe is equal to or lower than the anticorrosion potential. Pipeline soundness evaluation system characterized by A system that evaluates the soundness of a pipeline while performing cathodic protection with a galvanic anode method, targeting a pipeline with a high resistivity coating,
Set the section for cathodic protection of the pipeline,
A probe that is connected to the pipeline at both ends of the section and simulates a coating defect of the same area;
A galvanic anode connected to the pipeline at a central position of the section;
A current monitoring means for monitoring a current generated from the current-carrying anode installed between wires connecting the pipeline and the current-carrying anode;
The time difference between the time indicating the maximum value and the time indicating the minimum value from the time series data value of the unit measurement time including the maximum value among the data monitored by the current monitoring means is 1 of one cycle of the commercial frequency. / 2 and detects that the difference between the maximum value and the average value of the time-series data values is equal to the difference between the average value and the minimum value, and detects AC induction acting on the section. AC induction occurrence detection means,
The state of the pipeline is evaluated by the AC induction generation detection means in a state where the direct current generated from the galvanic anode is set so that the probe off potential measured by the probe is equal to or lower than the anticorrosion potential. Pipeline soundness evaluation system. When the AC induction acting on the section is detected by the AC induction generation detecting means, the lifetime LS of the galvanic anode is obtained from the time series data value monitored by the current monitoring means by the following formula (d). The pipeline soundness evaluation system according to claim 10, further comprising a life prediction means.

  The cathode anticorrosion maintenance management means for measuring the probe current density of the probe and checking the cathodic protection standard using the probe current density as an index and the result of the measurement is further provided. The pipeline health assessment system described in 1. A method for evaluating the soundness of a pipeline coated with a high resistivity coating while subjecting it to cathodic protection by the galvanic anode method,
Setting a section to be cathodic protection target of the pipeline;
Connecting a probe simulating a coating defect portion of the same area at both ends of the section to the pipeline;
Connecting an galvanic anode to the pipeline at a central position of the section;
Installing a current monitoring means between wires connecting the pipeline and the current-carrying anode, and monitoring the current generated from the current-carrying anode by the current monitoring means;
A coating defect detection step for detecting an increase in time series data value monitored by the current monitoring means and detecting that a coating defect has occurred in the section;
Evaluation of the soundness of the pipeline by the coating defect detection step in a state in which the direct current generated from the galvanic anode is set so that the probe off potential measured by the probe is equal to or lower than the anticorrosion potential. Pipeline soundness evaluation method characterized by A method for evaluating the soundness of a pipeline coated with a high resistivity coating while subjecting it to cathodic protection by the galvanic anode method,
Setting a section to be cathodic protection target of the pipeline;
Connecting a probe simulating a coating defect portion of the same area at both ends of the section to the pipeline;
Connecting an galvanic anode to the pipeline at a central position of the section;
Installing a current monitoring means between wires connecting the pipeline and the current-carrying anode, and monitoring the current generated from the current-carrying anode by the current monitoring means;
The time difference between the time indicating the maximum value and the time indicating the minimum value from the time series data value of the unit measurement time including the maximum value among the data monitored by the current monitoring means is 1 of one cycle of the commercial frequency. / 2 and detects that the difference between the maximum value and the average value of the time-series data values is equal to the difference between the average value and the minimum value, and detects AC induction acting on the section. AC induction generation detection step,
The state of the pipeline is evaluated by the AC induction generation detection step in a state where the direct current generated from the galvanic anode is set so that the probe off potential measured by the probe is equal to or lower than the anticorrosion potential. Pipeline soundness evaluation method characterized by this. When an AC induction acting on the section is detected in the AC induction generation detection step, the lifetime LS of the galvanic anode is obtained from the time series data value monitored by the current monitoring means by the following formula (d). The pipeline soundness evaluation method according to claim 14, further comprising a life prediction step.

  The cathode anticorrosion maintenance management step of measuring the probe current density of the probe and checking the cathodic protection standard using the probe current density as an index and the result of the measurement is further provided. Pipeline soundness evaluation method described in 1.

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