JP2008151696A - Method and system for controlling prevention of cathodic corrosion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To immediately improve a prevention state of cathodic corrosion that is deteriorated against an object to be prevented from cathodic corrosion in which cathodic corrosion is prevented by a sacrificial anode method, without large construction such as resolution construction of metal touch. <P>SOLUTION: The configuration for the method and the system for controlling the prevention of cathodic corrosion, comprises, a DC power supply system 3 that specifies a sacrificial anode 2 installed, as an anode, and an object 1 to be prevented from cathodic corrosion, as a cathode; a measuring means 4 for measuring a potential between the object and an electrolyte under in a state that a voltage from the DC power supply system 3 is applied and measuring the current of the sacrificial anode; and an operation processing means 5 for operating measurement data provided by the measuring unit 4. A potential P/S between a pipe and the earth is measured by connecting a wire W3 of which the top end is connected to a connecting section 1B, via a DC voltmeter 4A to a reference electrode (a saturated copper sulfate electrode) 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cathodic protection management method and a cathodic protection management system, and more particularly, to a cathodic protection management method for improving a corrosion protection situation deteriorated in a galvanic anode method and a cathodic protection management system for executing the same. .

  In order to prevent 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, an electric current (anticorrosive current) is caused to flow into the metal body surface to cause an anode reaction. It is known that the cathodic protection method that prevents the cathodic reaction (causing a cathodic reaction on the entire metal surface) is the most effective method.

  Currently, 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 voltage is applied by connecting a direct current power supply device between the electrode (anode) and the anticorrosion target (cathode) installed in the soil, and a direct current flows from the electrode through the soil to the anticorrosion target. This is a method for preventing corrosion, and is particularly effective for cathodic protection of pipelines whose surfaces are covered with a high resistivity coating.

  On the other hand, in the galvanic anode method, a metal having a negative corrosion potential as compared to the anticorrosion object is used as an anode (galvanic anode), and this is connected to the anticorrosion object with an electric wire. In this method, the current generated from the galvanic anode (the galvanic anode generated current) is caused to flow into the anticorrosion target as an anticorrosive current to prevent corrosion. This galvanic anode method is often used for cathodic protection of pipelines with bituminous coating (such as asphalt coating) where the surface of the pipeline and the electrolyte are in contact with each other over time. It has been adopted. In general, Mg anodes are often used as galvanic anodes for steel bitumen-coated pipelines embedded in soil.

In this cathodic protection method using the galvanic anode method, a potential difference (tube-to-ground potential) measured by a reference electrode in contact with the metal surface of the pipeline and the electrolyte is measured, and this is used as a corrosion protection potential (for example, a saturated copper sulfate electrode (CSE). ) The galvanic anode generation current I ₀ is set to be −1200 mV _CSE ) or less. The effective electric capacity M (mA · year) of the galvanic anode determined by the material and mass is set as M = I ₀ × Y by the set galvanic anode generation current I ₀ and the service life Y. .

  The installed current-carrying anode will end its life when the generated current ceases to be generated, so it must be replaced.However, after the current-carrying anode is installed, the current generated by the current-carrying anode is monitored and this monitoring value is set in advance. The remaining capacity is obtained by calculating the degree of wear of the flowing current anode from the effective electric capacity of the flowing current anode, and the remaining function days or time of the flowing current anode can be calculated from this remaining capacity (see Patent Document 1 below). ).

JP 7-294479 A

  When another metal body is in electrical contact with the corrosion protection target in the electrolyte that is cathodic protected by the galvanic anode method (this is called metal touch), most of the current generated from the galvanic anode is low grounded When flowing into the metal body, there may occur a situation in which the anti-electrolytic potential of the anticorrosion target becomes a value greater than the anticorrosion potential. When the object of cathodic protection that is cathodic protected by the galvanic anode method is a soil-buried pipeline, the galvanic anode is generated when the pipeline touches another buried metal structure due to subsidence due to secular change after laying the pipeline. Since the current flows into the buried metal structure in addition to the low ground, the corrosion prevention situation that does not satisfy the required corrosion prevention current of the pipeline to be protected against corrosion may occur.

  In particular, bitumen-coated pipelines buried in urban areas where buried metal structures are congested are water that has penetrated the coating due to the characteristics of the pipeline itself that is originally long in the horizontal direction. Therefore, even if the contact is through the coating, it is electrically connected, so it can be said that there is a high risk of insufficient corrosion protection current due to metal touch. In addition, the galvanic anode method cathodic protects the anticorrosion target using the potential difference between the galvanic anode and the anticorrosion target as the driving force. Once the current generated by the galvanic anode does not satisfy the required anticorrosion current, the anticorrosion Subject is forced to continue corrosive.

  On the other hand, even if it is confirmed that the anti-electrolytic potential of the anti-corrosion target is more positive than the anti-corrosion potential during periodic inspections such as once a year, even if it is confirmed that the anti-corrosion situation deteriorates, it is a direct cause such as metal touch Often cannot be resolved immediately. In particular, when soil buried pipelines are subject to anticorrosion, the cancellation of metal touch involves discussion with metal touch structure owners and with road managers, metal touch cancellation work after road excavation, etc. Immediate response is extremely difficult or impossible, and it must be planned response. Therefore, there is a need for an anticorrosion management method that can improve the deteriorated anticorrosion situation without immediately performing the metal touch elimination work.

  As a measure to improve the anticorrosion situation of the anticorrosion target cathodic protected by the galvanic anode method, install a load power source between the galvanic anode and the anticorrosion target, and increase the galvanic anode generation current by applying the DC power supply voltage Can be considered.

  However, not only can the voltage applied to the dark clouds be used to determine the minimum applied voltage required to improve the anticorrosion situation, but also the remaining current of the anode There is a problem of not knowing how short it will be. Furthermore, in the case of a galvanic anode that has already a short remaining life, the required anticorrosion current may not be obtained no matter how much voltage is applied, and simply by comparing the predicted life calculated with the prior art with the buried years. There is a problem that it is not known whether or not the current galvanic anode has an improvement capability. In addition, in soil buried pipelines, it is common to check the anticorrosion status through periodic inspections, but in periodic inspections that simply check the anticorrosion status, deterioration of the anticorrosion status has been confirmed at the site of periodic inspections. Even in such a case, there is a problem that subsequent management measures cannot be promptly planned in the field response.

  An object of the present invention is to cope with such a situation, and the cathodic protection situation deteriorated with respect to the anticorrosion target cathodic protected by the galvanic anode method is a large-scale construction such as a metal touch elimination work. It is possible to quickly improve without performing any construction work, to determine the optimum setting conditions quickly, and to quickly grasp the remaining life of the galvanic anode after the determined conditions. The ability to promptly determine whether or not the galvanic anode has the ability to improve the anticorrosion status, the ability to promptly plan subsequent management measures at the site during periodic inspections of the soil buried pipeline, etc. It is an object of the present invention.

  The present invention for achieving such an object has the following features.

  For one, in the cathodic protection management method for improving the anticorrosion situation that has deteriorated against the anticorrosion target cathodically protected by the galvanic anode method, the installed galvanic anode is the anode and the anticorrosion target is the cathode. A connecting step of connecting a DC power supply device with variable applied voltage, and measuring the negative shift state of the anti-electrolytic potential of the anticorrosion target while increasing the applied voltage of the DC power supply device, From the measurement process for measuring the shift state, and the measurement data in the measurement process, the negative shift relational expression of the anti-electrolytic potential of the anticorrosion target with respect to the increase in the applied voltage, and the positive shift relation of the galvanic anode generation current with respect to the increase in the applied voltage The set applied voltage at which the anti-electrolytic potential of the anticorrosion target is on the negative side of the anticorrosion potential according to the negative shift relational expression. A calculation step of obtaining a flowing current generated by the set applied voltage according to the positive shift relational expression, and a remaining current of the flowing current after loading the set applied voltage according to the current generated by the flowing anode obtained in the calculation step And a remaining life prediction step for predicting the life.

  In addition, in the cathodic protection management system for improving the anti-corrosion situation that has been cathodic protected by the galvanic anode method, the application is made with the galvanic anode installed as the anode and the anticorrosion target as the cathode. A DC power supply device with variable voltage, a measurement means for measuring the anti-electrolytic potential of the anticorrosion target in the voltage application state of the DC power supply device, and a measurement current measured by the measurement means, and a measurement process by the measurement means And an arithmetic processing means that performs a negative shift relational expression on the anti-electrolytic potential of the anticorrosion target with respect to an increase in the applied voltage by the DC power supply and a positive current of the galvanic anode generated with respect to the increase in the applied voltage. The relational expression setting means for obtaining the shift relational expression, and the negative shift relational expression makes the anti-electrolytic potential of the anticorrosion target more A set applied voltage calculating means for obtaining a set applied voltage on the negative side, a flowing anode generating current calculating means for obtaining a flowing anode generating current generated by the set applied voltage by the plus shift relational expression, and the flowing anode generation And a remaining life prediction means for predicting a remaining life of the anode of the flowing current after the set applied voltage is loaded, based on a current generated by the current of the anode obtained by the current calculation means.

Further, in the cathode anticorrosion management method or system, the remaining galvanic anode life L _R (year) after the set applied voltage load is predicted by the following equation (1).

  Further, in the cathode anticorrosion management method or system, from the measurement data in the measurement step or the measurement means, a negative shift gradient of the anti-electrolytic potential of the anticorrosion target with respect to an increase in applied voltage and generation of a galvanic anode with respect to an increase in applied voltage The present invention is characterized in that a positive shift gradient of current is obtained, and the anti-corrosion situation improving ability of the installed electroplating anode is determined based on the negative shift gradient and the positive shift gradient.

  According to the cathodic protection management method or system of the present invention having such characteristics, the cathodic protection situation deteriorated against the anticorrosive object cathodic protected by the galvanic anode method can be used for large-scale construction such as metal touch elimination work. It can be improved quickly without doing. Further, in the improvement, it is possible to quickly determine the optimum setting condition and to quickly grasp the remaining life of the galvanic anode after the determined condition. Then, it is possible to quickly grasp whether or not the currently installed galvanic anode has the ability to improve the anticorrosion situation. Furthermore, it is possible to quickly plan subsequent management measures at the site during periodic inspections of the soil burial pipeline.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the bituminous coating pipeline that is embedded in the soil as an anticorrosion target will be described as an example, but the anticorrosion target in the embodiment of the present invention is not limited to this, This includes all anticorrosion objects that are installed in all electrolytes such as soil and ocean and are cathodically protected by the galvanic anode method. However, considering the difficulty of the metal touch elimination work as described above, it is needless to say that the invention is very effective when the soil buried pipeline is an anticorrosion target.

FIG. 1 is an explanatory diagram (system configuration diagram) for explaining a cathodic protection management method and a cathodic protection management system according to an embodiment of the present invention. The pipeline 1 that is the object of corrosion prevention is provided with a bitumen coating 1A such as asphalt on the surface, and a connection portion 1B is provided on the surface of the pipeline 1. The situation in which the pipeline 1 is cathodic protected by the galvanic anode method is that the electric wire W ₁ whose tip is connected to the connecting portion 1B and the galvanic anode (for example, Mg flow) installed around the pipeline 1 conductive anode) wire W ₂ whose tip is connected to the 2 have been drawn in the terminal box T _B, by connecting the electric wire W ₁ and the wire W _2, pairs electrolyte potential pipeline 1 and galvanic The current generated from the galvanic anode 2 (current generated by the galvanic anode) is caused by causing the anode reaction of the galvanic anode 2 using the potential difference from the potential of the anode 2 (the surface is covered with the backfill 2A) as a driving force. ) Where I is the anticorrosion current I _C of the pipeline 1.

In this way, the cathodic protection system provided for improving the anticorrosion situation which has been deteriorated against the anticorrosion target cathodically protected by the galvanic anode method is a pipe which is an anticorrosion target using the installed galvanic anode 2 as an anode. DC power supply 3 with variable applied voltage using cathode as line 1 and the voltage applied to DC power supply 3 to measure the electrolyte potential (tube-to-ground potential) of pipeline 1 and the current flowing to anode. Measuring means 4 for performing measurement, and arithmetic processing means 5 for performing arithmetic processing on measurement data obtained by the measuring means 4. Pipe ground potential P / S is measured by connecting the wires W ₃ whose tip is connected to the connecting portion 1B via the DC voltmeter 4A to reference electrode (saturated copper sulfate electrode) 6.

The arithmetic processing means 5 obtains a negative shift relational expression of the anti-electrolytic potential of the corrosion protection target with respect to the increase of the applied voltage E by the DC power supply device 3 and a positive shift relational expression of the galvanic anode generation current I with respect to the increase of the applied voltage E. a relational expression setting means 5A, the set application voltage calculating means 5B for determining the set application voltage E _S versus electrolyte potential corrosion subject by negative shift relational expression (tube ground potential P / S) becomes minus side from corrosion potential, plus galvanic anode generator generated by setting the applied voltage E _S by shifting relationship current I and a galvanic anode generating current calculation unit 5C for determining an _S, galvanic anode generating current calculation unit galvanic anodes generated current obtained by the 5C I _S by, and a galvanic anode remaining life prediction means 5D for predicting the galvanic anode remaining lifetime L _R after setting the voltage applied load.

  Moreover, the arithmetic processing means 5 is a negative shift gradient of the anti-electrolytic potential (tube-to-ground potential P / S) of the anticorrosion object with respect to the increase in the applied voltage E by the DC power supply device 3 and the increase in the applied voltage E as necessary. The anti-corrosion situation improvement which calculates | requires the plus shift gradient of the galvanic anode generation | occurrence | production current I, and determines whether the installed galvanic anode 2 has the anti-corrosion situation improvement capability by the minus shift gradient Δm and the plus shift gradient Δp A capability determination means 5E is provided.

Direct-current power supply 3, a DC battery 3A and the variable resistor 3B or AC power source and the rectifier, there can be used those composed of a transformer or the like, the negative of the DC power source to an end portion of the wire W ₁ drawn into the terminal box T _B side, connect the positive side of the DC power source to an end portion of the wire W _2, in which the voltage applied between the pipeline 1 and the galvanic anode 2 can be variably adjusted. The applied voltage E may be variably adjusted by a control output signal from the arithmetic processing means 5.

Measuring means 4 is provided in the terminal box T _B, reference electrode (e.g., saturated copper sulfate electrode) DC voltmeter 4A installed in 6 and the wire W ₃ which is connected to the connecting portion 1B of the pipeline 1, the flow A DC ammeter 4 </ _b > B is connected between electric wires W ₂ connecting the electric anode 2 and the DC power supply device 3. The measurement data of the DC voltmeter 4A and the DC ammeter 4B can be taken into the arithmetic processing means 5.

  The arithmetic processing means 5 can be constituted by an arithmetic processing device such as a personal computer (PC), and as its arithmetic processing function (arithmetic processing program), a relational expression setting means 5A, a set applied voltage calculation means 5B, a galvanic anode The generated current calculation means 5C and the galvanic anode remaining life prediction means 5D are incorporated.

  The cathode anticorrosion management method executed by such a system configuration will be described together with details of each function in the arithmetic processing means described above. FIG. 2 is an explanatory diagram showing a schematic flow of the cathodic protection management method according to the embodiment of the present invention. In the cathodic protection management method according to the embodiment of the present invention, it is confirmed that the pipe ground potential P / S does not pass the cathodic protection standard at the regular inspection for the pipeline 1 to be protected, and the pipe ground potential This is executed when P / S is a value greater than the anticorrosion potential.

First, the DC power supply device 3 is connected to the electric wires W ₁ and W ₂ (S1: connection process). Then, the pipe-to-ground potential P / S of the pipeline 1 is measured by the DC voltmeter 4A while the applied voltage E of the DC power supply device 3 is sequentially increased, and the galvanic anode generated current I is measured by the DC ammeter 4B (S2). : Measurement process). At this time, as the applied voltage E increases, the tube-to-ground potential P / S shifts to the minus side, and the galvanic anode generation current I shifts to the plus side. Therefore, the applied voltages E _n1 , E _n2 , _{En 3} that are sequentially adjusted are shifted. ,... Are measured according to the tube-to-ground potentials P / S _n1 , P / S _n2 , P / S _n3 ,... And the galvanic anode generation currents II _n1 , I _n2 , I _n3 ,. The negative shift state of P / S and the positive shift state of the galvanic anode generation current I are measured.

Measurement data (P / S _n1 , P / S _n2 , P / S _n3 ,...), (I _n1 , I _n2 , I _n3 ,...) _Are sent to the arithmetic processing means 5, and the adjusted applied voltage _{En 1} , E _n2, E _n3, ... arithmetic processing is carried out with (S3: processing step).

Here, first, a regression line: {P / S} = a ₁ · from (E _n1 , E _n2 , E _n3 ,...) And (P / S _n1 , P / S _n2 , P / S _n3 ,...) {E} + b ₁ is obtained (a ₁ is a regression coefficient, b ₁ is a constant term), and this is a negative shift relational expression of the tube-to-ground potential P / S with respect to an increase in the applied voltage E. _{Additionally, (E n1, E n2,} E n3, ...) and _{(I n1, I n2, I} n3, ...) because the regression _{line: {I} = a 2 ·} {E} + b 2 a determined (a ₂ is The regression coefficient, b ₂ is a constant term), and this is a positive shift relational expression of the galvanic anode generation current I with respect to the increase of the applied voltage E. Since the relationship between the applied voltage E and the tube-to-ground potential P / S and the relationship between the applied voltage E and the galvanic anode generation current I are theoretically linear, a regression line with a high correlation coefficient can be obtained.

Then, α · P / S _C (P / S _C : anticorrosion potential, α: safety factor) is substituted into the negative shift relational expression {P / S} = a ₁ · {E} + b ₁ of the pipe-to-ground potential P / S Then, the set voltage E _S is obtained by E _S = (α · P / S _C −b ₁ ) / a ₁ . Further, the obtained set voltage E _S is substituted into the positive shift relational expression {I} = a ₂ · {E} + b ₂ of the galvanic anode generation current I with respect to the increase in the applied voltage E, and the set applied voltage E _S The galvanic anode generation current I _S is obtained by I _S = a ₂ · E _S + b ₂ .

At this time, measurement data (P / S _n1 , P / S _n2 , P / S _n3 ,...), (I) are obtained before obtaining the set application voltage E _S and the galvanic anode generation current I _S with respect to the set application voltage E _{S. n1} , _In2 , _In3 , ...), it is possible to determine whether or not the installed galvanic anode 2 has an anticorrosion condition improving ability (S5: anticorrosion condition improving ability determining step).

Regression straight line obtained from measurement data (P / _Sn1 , P / _Sn2 , P / _Sn3 ,...), ( _In1 , _In2 , _In3 ,...): {P / S} = a _1. {E } + B ₁ and {I} = a ₂ · {E} + b ₂ , the regression coefficients a ₁ and a ₂ are respectively the negative shift gradient Δm of the tube-to-ground potential P / S with respect to the increase of the applied voltage E and the applied voltage. The positive shift gradient Δp of the galvanic anode generation current I with respect to the increase of E is obtained. Depending on whether or not the minus shift gradient Δm and the plus shift gradient Δp are larger than the minimum reference values Δm _min and Δp _min, whether or not the installed galvanic anode 2 has the ability to improve the anticorrosion situation, that is, the applied voltage E It is possible to determine whether or not the tube-to-ground potential P / S can be made lower than the anticorrosion potential and the galvanic anode generation current I can be made higher than the required anticorrosion current.

Here, the minimum reference values Δm _min and Δp _min are the tube-to-ground potential P / S ₁ before the applied voltage E load, the average galvanic anode generation current I ₁ before the applied voltage E load, the anticorrosion potential P / S _C , the applied It can be set by the voltage adjustable range F or the like.

Finally, the sacrificial anode generator current I _S obtained by the calculation step S3, predicted galvanic anode remaining lifetime L _R after setting the applied voltage load (year) (S4: galvanic anode remaining life prediction step). This galvanic anode remaining life L _R is according to the following formula (1).

Galvanic anode remaining lifetime L _R is predictable reasons later by equation (1) Load settings applied voltage E _S is the surface of the pipeline 1 is chemically stable, the cathode after the load of setting the applied voltage E _S This is because polarization does not progress greatly. The bitumen-coated pipeline 1 is in a state in which oxidation-reduction reaction hardly occurs due to the influence of the oxide layer including the rust layer, and the pipe-to-ground potential P / S does not greatly decrease after the applied voltage is applied. . Accordingly, it believed to galvanic anode generator current I _S continues at a substantially constant value, it is possible to obtain a galvanic anode remaining lifetime L _R simply by Equation (1).

According to such a cathodic protection system and a cathodic protection management method, when it is confirmed that the cathodic protection status of the pipeline 1 that is the anticorrosion has deteriorated at a site such as periodic inspection, the connecting step S1. executes measurement step S2, by executing the calculation process S3, based on the obtained measurement data, it is possible to obtain the set application voltage E _S can improve the corrosion situation that easily and quickly deteriorate. Accordingly, the deteriorated anticorrosion situation can be reliably improved without immediately performing a large-scale construction such as a metal touch elimination construction.

Moreover, by loading the set application voltage E _S, but the life of galvanic anode 2 installed by increased galvanic anode current generated is shorter than originally expected life, galvanic anode remaining lifetime L _R at that time Can be promptly determined by the remaining current predicting life step S4, so that it is possible to quickly plan the subsequent response according to the life of the current flowing anode 2.

  Furthermore, in the case of the galvanic anode 2 whose life is already close from the initially predicted life of the galvanic anode and the number of years of burial, the required anticorrosion current cannot be obtained no matter how much the applied voltage E is increased, and the tube ground potential P / In some cases, S cannot be shifted to a negative value from the anticorrosion potential, and simply comparing the predicted life of the prior art with the buried years may not reveal whether the current galvanic anode has an improvement capability. However, by executing the anticorrosion situation improving ability determination step S5, it is possible to quantitatively know whether or not there is an improving ability, and it is possible to effectively use the installed electroplating anode 2 without waste. In addition, if it is determined that there is no improvement capability, measures such as replacement can be planned quickly. At this time, when it is determined that there is no improvement capability, the ground resistance of the galvanic anode 2 is separately measured. If, for example, 1 kΩ or more, it is determined that the galvanic anode cannot exhibit its function.

  The determination of the improvement ability by the minus shift gradient Δm of the tube-to-ground potential P / S with respect to the increase of the applied voltage E and the plus shift gradient Δp of the galvanic anode generation current I with respect to the increase of the applied voltage E is determined by the existing galvanic anode 2. Since it is possible to quantitatively grasp that it can fully function, it is possible to quantitatively compare the abilities of the galvanic anodes 2 at different installation locations, and the galvanic anodes at different installation locations. It is possible to prioritize countermeasures for 2.

  Examples of the present invention will be described below. FIG. 3 is an explanatory diagram of the embodiment, and the above-described negative shift relational expression of the tube-to-ground potential P / S with respect to the increase of the applied voltage E and the positive shift relational expression of the galvanic anode generation current I with respect to the increase of the applied voltage E. It is the graph which showed the specific example of.

Pipeline that has been cathodic-protected by the galvanic anode method, the tube-to-ground potential at the time of 24 years of burial is the anti-corrosion potential (here, -1200 mV _CSE . In addition, the potential is shown on the basis of saturated copper sulfate electrode (CSE) ) It is no longer below, and shows the case where the cathodic protection standards are not met. In addition, it has been confirmed separately that this pipeline has no DC interference risk and AC corrosion risk.

[Example conditions]
Pipe diameter: 300mm
Coating: Asphalt jute Years of burial: 24 years Current anode: One Mg anode with an effective electrical capacity of 2760 mA · year

[Measurement results after 24 years of burial]
Tube-to-ground potential: -650 mV _CSE
Mg anode generation current: 30 mA
Mg anode to ground potential: -1500 mV _CSE
Corrosion protection pipeline resistance: 0.8Ω
Ground resistance of Mg anode: 20.0Ω

In buried 24 years elapse, tube ground potential 550mV cathodic polarization amount -1200MV _CSE is -650 mV _CSE and corrosion potential was insufficient. Therefore, the applied voltage E is increased by the above-described DC power supply device, and the measurement process and the calculation process are executed, and the negative shift relational expression of the tube-to-ground potential P / S with respect to the increase of the applied voltage E and the flow with respect to the increase of the applied voltage E A positive shift relational expression of the electric anode generation current I was determined as shown in FIG.

As shown in the figure, the relationship between the applied voltage E and the tube-to-ground potential P / S has a high negative correlation with a correlation coefficient of −0.999, and the relationship between the applied voltage E and the Mg anode generation current I is A result supporting the theory was obtained with a relational number of 1.000. The set applied voltage E _S at which the tube-to-ground potential P / S becomes −1200 mV _CSE , which is the anticorrosion potential P / S _C , is 5.8V. Mg anode current generated at the time of setting the applied voltage E _S load becomes 238MA.

From this result, when the galvanic anode remaining life _LR is predicted by the equation (1), the following equation is obtained.

  Therefore, it was found that the remaining life of the Mg anode was about 8 years. Detailed investigations such as metal touch will be conducted within 8 years, and improvement measures will be taken. Until the improvement measures are taken, the Mg anode generation current is increased by the DC power supply device so as to maintain a state of passing the cathodic protection standard. Here, it is assumed that the Mg anode satisfies the required anticorrosion current by the DC power supply device, and that the galvanic anode has a certain remaining life in this state. Consider a design in which the internal battery of the DC power supply is replaced at a periodic inspection cycle (for example, once / year).

  FIG. 4 is a specific flowchart for executing the cathodic protection management method of the present invention from the periodic inspection of the pipeline.

  First, the pipe ground potential P / S is measured during periodic inspection (S10), and it is determined whether or not this pipe ground potential P / S passes the cathodic protection standard (S11). If this passes the cathodic protection standard, no countermeasure is required, and the periodic inspection is continued (S11A).

  If the above-mentioned determination does not pass the cathodic protection standard, it is determined whether or not the profile of the pipe-to-ground potential P / S of the pipeline route has a shift from plus (S12). If there is no shift in this determination, a detailed survey is conducted to find out the reason for not passing the cathodic protection standard, and improvement work is performed based on the survey result (S12A).

  If there is a shift in determining whether there is a shift from the plus in the profile of the tube-to-ground potential, the connection step S1, the measurement step S2, and the calculation step S3 are executed, and the increase in the applied voltage E described above is performed. A negative shift relational expression of the tube-to-ground potential P / S and a positive shift relational expression of the galvanic anode generation current I with respect to the increase of the applied voltage E are obtained (S13).

Then, it is confirmed whether the tube-to-ground potential P / S has achieved the anticorrosion potential by the applied voltage E load or whether the Mg anode generation current I has reached the required anticorrosion current (S14). It considers that there is no improvement capability anode, and perform other improvements construction (S14A), if these have been achieved together with determining a set applied voltage E _S, to predict the Mg anode remaining life ( S15). After that, the tube-to-ground potential is continuously measured during periodic inspections and checked against the cathodic protection standards.

It is explanatory drawing (system block diagram) for demonstrating the cathodic protection management method and cathodic protection management system which concern on embodiment of this invention. It is explanatory drawing (schematic process flow) for demonstrating the cathode anticorrosion management method which concerns on embodiment of this invention. FIG. 2 is an explanatory diagram of an embodiment of the present invention, in which a negative shift relational expression of the tube-to-ground potential P / S with respect to the increase of the applied voltage E and a positive shift relational expression of the galvanic anode generation current I with respect to the increase of the applied voltage E. It is the graph which showed the specific example of. It is a specific coping flow chart for performing the cathodic protection management method of the present invention from the periodic inspection of the pipeline.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pipeline 1A Bituminous coating 2 Current-flow anode 2A Backfill 3 DC power supply 3A DC battery 3B Variable resistance 4 Measuring means 4A DC voltmeter 4B DC ammeter 5 Arithmetic processing means 5A Relational expression setting means 5B Setting applied voltage Calculation means 5C Current-flow anode generation current calculation means 5D Current-flow anode remaining life prediction means 5E Corrosion protection condition improvement ability determination means 6 Reference electrode (saturated copper sulfate electrode)
W _1, W _2, W ₃ wire I galvanic anode generator current I _C protection current T _B terminal box

Claims (8)

In the cathodic protection management method for improving the anti-corrosion situation which deteriorated against the anti-corrosion target cathodic protected by the galvanic anode method,
A connecting step of connecting a direct current power supply device having a variable applied voltage with an anode of an installed galvanic anode and a cathode of an anticorrosion target;
While increasing the applied voltage of the DC power supply, while measuring the negative shift state of the anti-electrolytic potential of the anticorrosion target, and measuring the positive shift state of the galvanic anode generation current,
From the measurement data in the measurement step, a negative shift relational expression of the anti-electrolytic potential of the anticorrosion target with respect to the increase in the applied voltage and a positive shift relational expression of the galvanic anode generation current with respect to the increase in the applied voltage are obtained, A calculation step for obtaining a set applied voltage at which the anti-electrolytic potential of the corrosion protection target is negative from the corrosion prevention potential by an equation, and obtaining a galvanic anode generation current generated by the set application voltage by the plus shift relational expression;
A remaining life prediction step of predicting a remaining life of the anode of the flowing current after the set applied voltage load, according to the current generated by the flowing current of the anode obtained in the calculation step,
A cathodic protection management method comprising: 2. The cathodic protection management method according to claim 1, wherein, in the remaining life prediction step, the remaining life of the galvanic anode L _R (year) after the set applied voltage load is predicted by the following formula (1).
L _R = (Ma−I ₁ · Y _E ) / I _S (1)
Here, Ma: effective electric capacity of the galvanic anode (mA · year)
I ₁ : Average galvanic anode generation current (mA) before applied voltage load
Y _E : Number of years of galvanic anode installation (year)
I _S : galvanic anode generation current (mA) generated by the set applied voltage   From the measurement data in the measurement step, a negative shift gradient of the anti-electrolytic potential of the anticorrosion target with respect to the increase of the applied voltage, and a positive shift gradient of the galvanic anode generated current with respect to the increase of the applied voltage, the negative shift gradient and the above The cathodic protection management method according to claim 1 or 2, wherein a determination step of determining the anticorrosion condition improving ability of the installed electroplating anode is performed based on the plus shift gradient.   The cathodic protection management method according to any one of claims 1 to 3, wherein the anticorrosion target is a bituminous coating pipeline embedded in soil. In the cathodic protection management method for improving the anti-corrosion situation which deteriorated against the anti-corrosion target cathodic protected by the galvanic anode method,
A connecting step of connecting a direct current power supply device having a variable applied voltage with an anode of an installed galvanic anode and a cathode of an anticorrosion target;
While increasing the applied voltage of the DC power supply, while measuring the negative shift state of the anti-electrolytic potential of the anticorrosion target, and measuring the positive shift state of the galvanic anode generation current,
From the measurement data in the measurement step, a negative shift gradient of the anti-electrolytic potential of the anticorrosion target with respect to the increase of the applied voltage, and a positive shift gradient of the galvanic anode generation current with respect to the increase of the applied voltage, the negative shift gradient and the above Judgment process for judging the anti-corrosion situation improving ability of the installed galvanic anode by the plus shift gradient,
A cathodic protection management method comprising: In the cathodic protection management system to improve the anti-corrosion situation, which is cathodic protected by the galvanic anode method,
An applied voltage variable DC power supply device in which the installed galvanic anode is the anode and the anticorrosion target is the cathode; and
In the voltage application state of the DC power supply device, while measuring the anti-electrolytic potential of the anticorrosion target, measuring means for measuring the galvanic anode generated current,
An arithmetic processing means for arithmetically processing the measurement data by the measuring means,
The arithmetic processing means includes:
Relational expression setting means for obtaining a negative shift relational expression of the anti-electrolytic potential of the anticorrosion target with respect to an increase in the applied voltage by the DC power supply apparatus and a positive shift relational expression of the galvanic anode generated current with respect to the increase in the applied voltage;
A set applied voltage calculation means for obtaining a set applied voltage at which the anti-electrolytic potential of the anticorrosion target is on the minus side of the anticorrosion potential by the negative shift relational expression;
A galvanic anode generation current calculating means for obtaining a galvanic anode generation current generated by the set applied voltage according to the plus shift relational expression;
Cathodic anticorrosion management, comprising: a remaining life predicting means for predicting a remaining life of the flowing current anode after the set applied voltage load based on a flowing current generated by the flowing current anode generated by the flowing current anode generation current calculation means system. 7. The cathodic protection management system according to claim 6, wherein the remaining life predicting means predicts a galvanic anode remaining life L _R (year) after the set applied voltage load by the following formula (1).
L _R = (Ma−I ₁ · Y _E ) / I _S (1)
Here, Ma: effective electric capacity of the galvanic anode (mA · year)
I ₁ : Average galvanic anode generation current (mA) before applied voltage load
Y _E : Number of years of galvanic anode installation (year)
I _S : galvanic anode generation current (mA) generated by the set applied voltage The arithmetic processing means includes:
The negative shift gradient of the anti-electrolytic potential of the anticorrosion target with respect to the increase in the applied voltage by the DC power supply device, and the positive shift gradient of the galvanic anode generated current with respect to the increase in the applied voltage are obtained, and the negative shift gradient and the positive shift gradient The cathode anticorrosion management system according to claim 6, further comprising: a determination unit that determines an anticorrosion situation improvement ability of the installed electroplating anode.

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