JP5014247B2 - Potential measuring electrode and potential measuring method - Google Patents

Description

  The present invention relates to an electric potential measuring electrode and an electric potential measuring method for measuring an anticorrosion potential made of steel which is subjected to electric corrosion protection and embedded.

  Structures such as steel pipelines buried in the ground are often not only provided with anti-corrosion coating but also with anti-corrosion so that the structure is not corroded. For example, when a pipeline is buried in the ground, the pipeline potential is shifted from the outside to the negative side (base side) so as to be an inert region where the steel material does not corrode through direct current from the outside with the pipeline as a cathode. To. This method is referred to as “electrocorrosion protection”, and the potential at which the steel material does not corrode or when corrosion is virtually negligible is referred to as “corrosion protection potential”.

  It is important to monitor the ground potential of the pipeline in the maintenance management of such a steel pipeline buried underground, which is subjected to such anticorrosion. That is, when the ground potential does not reach the anti-corrosion potential, the pipeline may be corroded. Therefore, the pipeline is maintained and managed by measuring the ground potential.

  More specifically, using a potential measurement terminal cable provided at a predetermined interval in a steel pipeline, in the soil where the terminal cable is embedded, for example, a saturated copper sulfate electrode Install “reference electrode”. And the operation | work which measures the electric potential of the pipeline with respect to the soil on the basis of this collation electrode, and confirms that a measurement electric potential is a negative side (base side) from an anticorrosion electric potential is performed. At this time, a member called the “probe (simulated rod)” made of the same material (for example, steel) as the pipeline is electrically connected to the pipeline and brought into contact with the soil, and the probe is generated in the pipeline. In many cases, a method of managing the anticorrosion current flowing into the damage and the potential of the steel surface is taken. According to this method, the electric potential in the vicinity of the probe is measured with a reference electrode as a criterion for determining the anticorrosion state of an embedded steel structure (for example, steel material buried in the ground), and the contact surface of the probe reaches the complete anticorrosion region. It can be confirmed whether or not. The effectiveness of this method has been confirmed, and as shown in Patent Document 1 or Patent Document 2, a method of managing not only with direct current but also with alternating current has been proposed.

  Here, it is effective to measure the degree of polarization of the surface of the object to be protected (for example, steel), for example, to confirm whether or not the electric protection is sufficiently applied. (Also referred to as “on potential”), ground probe potential when the anticorrosion current is cut off (hereinafter also referred to as “off potential”), and current density flowing into the probe (hereinafter referred to as “probe current”, It is also referred to as “probe current density”) and is used as an evaluation index of the polarization state.

JP-A-10-332622 JP 2004-80842 A

  On the other hand, for example, in the construction of steel pipelines that cross rivers and roads, it is difficult to consider the impact on safety and socio-economic activities, and to attach or open the pipeline to bridges. For the reason, the double pipe method using the propulsion method is often adopted. From one of the shafts on both sides of the river or road, a “casing (sheath tube)” (for example, a steel pipe, a fume tube, etc.) with a diameter larger than the main pipe was penetrated to the other shaft by the propulsion method. After that, the main pipe (pipeline) is drawn into it, and the gap between the casing and the main pipe is filled with, for example, sand or mortar. And also in this casing, construction is often performed so that cathodic protection acts on the main pipe.

  In the pipeline part in the casing thus constructed, maintenance becomes almost impossible after completion. Therefore, in order to monitor the anticorrosion potential, the above-described method is often employed. That is, as a maintenance method, collation electrodes and probes are arranged alone or in combination in the gap between the casing and the main pipe. In general, these are used at the time of service, and an on-potential, an off-potential, a probe current, a current density, and the like are measured to monitor the anticorrosion effect.

However, the anticorrosion current and potential distribution of the propulsion unit are considered to be very different from the general buried part that has been cut open and buried because the interference between the casing and the gap between the casing and the main pipe are extremely narrow. . In general, a collation electrode (collation electrode 5) and a probe (probe 3) are arranged close to each other in a gap between the casing (casing 22) and the main pipe (pipeline 12) (FIG. 7). However, since it is physically limited, it is considered that accurate information is difficult to obtain especially for the tube-to-ground on potential. Therefore, pairs of verification electrodes and probes are arranged along the pipeline at a plurality of locations including the center of the work area, and the potential at each position is measured. However, it is often unclear whether the anticorrosion potential can actually be measured.

  Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to make steel that has been subjected to anticorrosion, including a corrosion protection target having a double-pipe structure, etc. This is to measure the anticorrosion potential of the anticorrosion target more accurately.

  In order to solve the above-described problem, according to one aspect of the present invention, there is provided a potential measuring electrode for measuring a potential of a steel anticorrosion target that has been subjected to electrocorrosion protection, and is formed using a conductive material. An embedded environment in which the anticorrosion target is embedded, and a hole formed in the center portion and one or more terminals electrically connected to at least one of the anticorrosion target and the voltmeter A probe that contacts, and a reference electrode that is insulated from the probe and is arranged to face the embedded environment through a hole in the probe, and has a terminal that is electrically connected to the voltmeter, An electric potential measuring electrode is provided, wherein the electric potential between the probe and the reference electrode can be measured via the embedded environment by the voltmeter.

  In addition, the probe may be in contact with the embedded environment at a ring-shaped probe surface in which the hole is formed, and the reference electrode may be embedded in the probe surface.

  The central axis of the verification electrode may coincide with the central axis of the hole of the probe.

  Moreover, the said collation electrode may have a shape where the site | part on the center axis | shaft of the hole of the said probe protruded in the direction which faced the said embedded environment rather than another site | part.

  The probe is formed in a circular or regular polygonal ring shape, and the reference electrode has an interval between an outer periphery of a part of the reference electrode facing the embedded environment and an inner surface of the ring on the probe surface of the probe. You may have a shape which becomes fixed.

  Further, in order to solve the above-mentioned problem, according to another aspect of the present invention, there is provided a potential measuring method for measuring a potential of a steel anticorrosive object that has been subjected to anticorrosion and is embedded in a conductive material. Embedded in which the anticorrosion target is embedded and has a hole formed in the center and one or more terminals electrically connected to at least one of the anticorrosion target and the voltmeter A probe in contact with the environment, and a reference electrode that is insulated from the probe and is arranged to face the embedded environment through the hole of the probe, and has a terminal that is electrically connected to the voltmeter A potential measurement electrode, wherein a potential measurement electrode is embedded in the embedded environment in the vicinity of the measurement object, and the potential between the probe and the reference electrode through the embedded environment is measured by the voltmeter. A method is provided.

  Further, at least a part of the anticorrosion object is covered with a conductive casing, and a filling material through which an anticorrosion current flows is filled between the anticorrosion object and the casing, and the potential measuring electrode is , You may arrange | position in the said filler between the said anti-corrosion object and the said casing.

  In addition, the potential measuring electrode is placed at a position where it enters between the anticorrosion object and the casing at least a distance corresponding to the interval between the anticorrosion object and the casing from the end of the casing covering the anticorrosion object. You may arrange.

  Moreover, when the space | interval between the said anticorrosion object and the said casing is set to D, D / tan 30 degrees or more from the edge part of the said casing surrounding the said anticorrosion object, The position which entered between the said anticorrosion object and the said casing In addition, the potential measuring electrode may be disposed.

  The potential measuring electrode may be disposed at each end of the casing.

  As described above, according to the present invention, it is possible to more accurately measure the anticorrosion potential of an anticorrosion object that has been subjected to anticorrosion, including an anticorrosion object having a double tube structure or the like.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  Prior to describing the potential measuring electrodes and the like according to the embodiments of the present invention, problems and the like that have been clarified as a result of intensive studies on electrocorrosion by the inventors of the present invention will be described before the present invention is completed. In the following, for convenience of explanation, a case will be described in which the object (that is, the anticorrosion object) whose potential measurement electrode according to each embodiment of the present invention measures the potential is a steel pipeline. However, the anticorrosion target that can measure this potential is not limited to the pipeline, and the potential measurement electrode and the like according to each embodiment of the present invention can be various anticorrosion as long as the anticorrosion target is subjected to the anticorrosion. Applicable to the subject.

  The investigation of the polarization state at the time of normal pipeline operation is an investigation in the situation where the anticorrosion power supply is operated, and the measured potential is only the on potential. However, in order to confirm the anticorrosion state reliably, it is effective to confirm the off potential in a state where the anticorrosion current is cut off. Therefore, in order to confirm the anticorrosion state, an operation for periodically measuring the potential at the time of on / off of the anticorrosion current is performed as a maintenance item of the pipeline.

  Usually, the buried environment of the buried pipeline is filled with uniform soil without any large conductive foreign matter in the vicinity. Therefore, as shown in FIG. 6, the error (this is also referred to as “IR drop”) due to the voltage drop due to the electrical resistance of the soil between the reference electrode and the probe depends on the magnitude of the soil resistance. However, if the probe and the verification electrode are brought close to each other, the level is not problematic (see FIG. 6). That is, the equipotential surface due to the anticorrosion current is formed in a substantially spherical shape with the damaged portion d (or probe) stopped. Therefore, by arranging the probe and the verification electrode in the vicinity of the pipeline 12 and bringing them close to each other, it is possible to measure an on-potential that is not much different from an off-potential with almost no IR drop. In such a case, the anticorrosion state can be confirmed by measuring only the ON potential.

  On the other hand, as shown in FIG. 7, in the double tube structure, the probe 3 and the verification electrode 5 are placed in a special situation where they are laid in a narrow space surrounded by the conductive casing 22 and the pipeline 12. . That is, the bare casing 22 with nothing coated on the inner and outer surfaces is a good conductor, and the pipeline 12 covered with the coating (corrosion-proof coating 12A) is arranged inside thereof. Here, according to the knowledge of the inventor of the present invention, as shown in FIG. The conduction path in the double pipe portion of the anticorrosion current generated in step 1 flows preferentially through the casing 22 which is a good conductor, flows out from the inner wall of the casing 22 near the damaged portion d to the mortar 21 on the inner surface of the casing 22, It will flow into the coating damage part d. For this reason, the anticorrosive current distribution in the casing 22 is characterized in that the anticorrosive current density is very high only in the mortar 21 near the damaged portion d of the anticorrosive coating 12A of the pipeline 12, as shown in FIG.

  Therefore, the inventor of the present invention measured the anticorrosive current density flowing into the damaged portion d, and found that the anticorrosive current density was almost within an angle of about 60 degrees with respect to the normal of the surface of the damaged portion d, that is, within π steradians. It was discovered that the current was concentrated and the inflow of current from other areas was negligible. This is considered to be caused by the fact that the anticorrosion current once flows into the casing 22 and flows into the damaged portion d so that the path from the casing 22 becomes short. Moreover, it is clear from the research of the inventors of the present invention that the flow path of the anticorrosion current is the same regardless of whether the current-carrying anode used for the anticorrosion is inside or outside the casing 22. It was. Such anticorrosion current density is the same in the case of the simulated soot by the probe 3, and as shown in FIG. 7, when the probe 3 is provided in the longitudinal direction of the pipeline 12, the conduction path of the anticorrosion current greatly deviates. Become. Therefore, when the probe 3 or the like is disposed in the double-pipe structure, the density of the anticorrosion current flowing through the mortar 21 becomes very high and the influence of the resistance of the mortar 21 is large compared to the probe operation method in normal land burying. Therefore, the potential drop, that is, the IR drop becomes large, which becomes a large error factor in the on-potential measurement. As a result, as shown in FIG. 7, the gradient of the potential distribution in the longitudinal direction of the pipeline near the probe 3 is large, which causes a problem in the potential measurement in the double tube structure.

  In order to reduce the IR drop, it is conceivable to reduce the distance between the probe 3 and the verification electrode 5 or to arrange the verification electrode 5 in the conduction path of the anticorrosion current. Will be disturbed. Therefore, unlike the general buried portion in the double tube, the pair structure in which the reference electrode 5 and the probe 3 are simply brought close to each other has a large IR drop, and an accurate on-potential cannot be measured.

  Furthermore, since the double pipe is low-grounded, it tends to be a path for DC and AC stray currents. Therefore, the probe potential is often affected by this stray current. Therefore, the anticorrosion state of the pipeline 12 in the double pipe must be evaluated based on the potential when the stray current flows, but the off-potential measurement that completely eliminates the IR drop interrupts the current. Therefore, it is impossible to grasp the potential fluctuation when the stray current is affected. Therefore, it is difficult to determine whether the pipeline 12 is in the anticorrosion state in the off-potential measurement. Further, in order to measure the influence of such stray current, IR drop, etc., potential measurement may be performed at a plurality of measurement points along the pipeline 12, but in this case, measured values at each measurement point are measured. In many cases, it is doubtful whether or not the anticorrosion potential can be measured.

  Since voltage measurement is difficult in this way, anticorrosion standard management based on probe current has been performed recently. However, as shown in FIG. 7, the probe 3 in the double tube collects a lot of anticorrosion currents and stray currents in the casing 22, so that more current is more likely to flow into the general soil burying site. Therefore, there must be a probe current density management standard corresponding to the double tube, but since the probe current density management standard in general soil is applied so far, an accurate evaluation cannot be performed.

  In addition, when the measurement lead wires from the probe 3 and the verification electrode 5 become long, when the stray current flowing through the casing 22 is alternating current, it is greatly affected by electromagnetic induction and has a large error with respect to the measured potential value and the measured current value. Will be added, making correct measurement impossible.

  When constructing a double pipe structure, the collation electrode 5 and the probe 3 are preliminarily fixed in close proximity to the pipeline 12 before being pulled in, and the positional relationship between the collation electrode 5 and the probe 3 is maintained. It is difficult and troublesome to pull the pipeline 12 into the casing 22 while extending the cable drawn from the verification electrode 5 and the probe 3.

  Furthermore, as mentioned above, the double pipe construction method is often applied to river crossings, etc. Once the pipeline is laid, it is impossible to maintain the pipeline and add a potential measurement method, or Since enormous construction costs are incurred, probes and reference electrodes are installed in advance at a plurality of locations. However, this increases the material cost associated with the number of installations, and the handling of the cables drawn from the respective verification electrodes 5 and probes 3 becomes complicated as the number of attachment points increases, which increases the time and labor of the construction and thus increases the construction cost. It was supposed to be.

  The inventor of the present invention has devised the above problems and the like as a result of earnest research on anticorrosion potential measurement. Further, the inventors have conducted further research and development, and in the double tube structure constituted by the pipeline 12 and the casing 22, the IR drop represented by the probe potential measurement represented by the probe potential in a narrow space surrounded by a good conductor. Reduces measurement error, accurately measures pipeline potential when affected by stray current in on-potential measurement, and eliminates the effects of construction complexity and noise superposition on multiple points The present invention has been completed. Hereinafter, an embodiment of the present invention will be described in detail.

<Configuration of Potential Measurement Electrode According to One Embodiment>
1A and 1B are explanatory diagrams for explaining the configuration of the potential measurement electrode 23 according to an embodiment of the present invention. 1B is a cross-sectional view taken along line AA in FIG. 1A.

  As shown in FIGS. 1A and 1B, the potential measuring electrode 23 is a probe-integrated verification electrode in which the probe 3 and the verification electrode 5 are integrally formed. The potential measurement electrode 23 mainly includes the probe 3 and the verification electrode 5. As will be described later, the potential measuring electrode 23 is disposed in the vicinity of the corrosion protection target in an embedded environment in which the corrosion protection target (for example, the steel pipeline 12) is embedded. Therefore, the potential measuring electrode 23 is also embedded in the embedded environment. As used herein, “embedded environment” means the environment around the anticorrosion target when the anticorrosion target is embedded, and more specifically, the mortar in which the anticorrosion target is embedded and contacts the anticorrosion target. Means buried object such as soil.

  The probe 3 is formed in a ring shape having a through hole at the center. Although FIG. 1A shows the case where the probe 3 is formed in a circular ring shape, the probe 3 may be formed in a polygonal ring shape, for example. The ring-shaped surface of the probe 3 is also referred to herein as a “probe surface”. As shown in FIG. 1A, the reference electrode 5 is arranged at the center of the probe surface. The probe 3 is equidistant to the reference electrode 5 at an equal interval and within the probe surface (xy plane). It is preferable to have. This is because when the anticorrosive current flows into the probe 3 isotropically in the probe plane, the anticorrosive potential and the like between the reference electrode 5 can be measured more accurately. Therefore, it is desirable that the probe 3 has a circular ring shape as shown in FIG. 1A or a regular polygonal ring shape.

  When the potential measurement electrode 23 is embedded in the embedded environment, the probe 3 comes into contact with the embedded environment in which the corrosion protection target (for example, the pipeline 12) is embedded on one probe surface. At this time, it is desirable that the probe surface of the probe 3 is in surface contact with the embedded environment so that there is no gap. Here, the direction of one probe surface (the through direction of the through hole, the positive z-axis direction) is referred to as the “measurement direction”. The probe 3 has a terminal 4A and a terminal 4B, and a cable that can be electrically connected to the anticorrosion target and the voltmeter is connected to the terminal 4A and the terminal 4B. Here, a case where the terminal 4A is a terminal electrically connected to the anticorrosion target and the terminal 4B is a terminal electrically connected to the voltmeter will be described. However, of course, it is also possible to connect the terminal 4A to the anticorrosion object and connect the terminal 4B to the voltmeter. Moreover, the probe 3 has only one terminal, and it is also possible to connect an anticorrosion object and a voltmeter to the terminal, and the probe 3 can also have three or more terminals.

  Ideally, the material of the probe 3 should be the same as that of the object to be protected, but it is also possible to use a conductive material that can be regarded as having substantially the same natural potential as the material of the object to be protected. It is. Since each material has a natural potential with a unique value, by using such a material, the probe 3 can have the same natural potential as that of the anticorrosion target that is originally an anticorrosion management target, and true damage is caused. An environment equal to the portion d can be formed, and can act more effectively as a simulated ridge of the anticorrosion coating applied to the anticorrosion target.

  When the potential measurement electrode 23 is embedded in the embedded environment, the verification electrode 5 is disposed at a position (may contact) through the through hole of the probe 3 so as to face the embedded environment. That is, the verification electrode 5 faces the embedded environment in the measurement direction through the through hole. At this time, the central axis of the verification electrode 5 is preferably coincident with the central axis of the through hole of the probe 3. By arranging the verification electrode 5 so as not to change the center of the through hole of the probe 3, the measurement accuracy of the potential measurement electrode 23 can be increased. Here, the central axis of the through hole of the probe 3 means the central axis of the through hole in the penetrating direction. In other words, the normal direction (z (Axis direction, measurement direction).

  Further, the shape of the verification electrode 5 on the probe 3 side is set so that the distance from the inner surface of the ring of the probe 3 is constant. That is, as shown to FIG. 1A, the space | interval of the outer periphery of the site | part which faced the embedding environment of the collation electrode 5 and the ring inner surface in a probe surface becomes fixed. In other words, when the collation electrode 5 and the probe 3 are projected in the z-axis direction (the direction in which the through hole is drilled), the outer periphery of the region of the collation electrode 5 facing the embedded environment and the inner periphery of the ring of the probe 3 The interval between them is constant. More specifically, the shape of the verification electrode 5 will be described. In the case of FIG. 1A, since a circular through hole is formed in the probe 3, the verification electrode 5 has a circular cross section with a diameter slightly smaller than the through hole. Since the potential between the verification electrode 5 and the probe 3 is measured, the potential between the verification electrode 5 and the probe 3 is measured by making the gap between the verification electrode 5 and the probe 3 constant in this way. Accuracy can be improved.

  Similarly, in order to improve accuracy, as shown in FIG. 1B, the reference electrode 5 has a shape in which the portion on the central axis of the ring-shaped probe 3 protrudes in the measurement direction from the other portions (for example, a right cone). It is desirable to have That is, the verification electrode 5 has, for example, a shape with a sharp measurement direction. Since the collation electrode 5 has such a shape, the equipotential surface due to the anticorrosion current that has flowed into the probe 3 has an angle with respect to the outer surface of the probe 3 that is nearly vertical, and the potential measurement between the collation electrode 5 and the probe 3 is performed. The accuracy can be further improved. As the shape of the probe 3, for example, a right conical shape, a cylindrical shape, a polygonal pyramid shape or a hemispherical shape is desirable, and FIG. 1B shows a case where the shape is a right conical shape. The reason for the right conical shape is to increase the electrode surface area as much as possible.

  Moreover, the collation electrode 5 is arrange | positioned in the position embedded rather than the probe surface where the probe 3 contacts an embedding environment. That is, when the probe surface is viewed, the verification electrode 5 is disposed at a position deeper from the probe surface, and a step is formed between the probe surface and the end of the verification electrode 5 in the measurement direction. In other words, a recess is formed by the probe surface and the end portion of the verification electrode 5 in the measurement direction. When the potential measuring electrode 23 is buried in the buried environment, the buried environment enters and fills the recess. On the other hand, this concave portion may be prefilled with a filler (for example, a backfill material made of the same material as the embedding environment). The verification electrode 5 contacts the embedded environment when the embedded environment enters the recess, and faces the embedded environment when the recess is filled with the filler. In any case, the collation electrode 5 faces the embedded environment and comes into contact with the embedded environment directly or indirectly through a filler. At this time, it is desirable that the concave portion is filled with an object to be embedded or a filler without a gap.

  As described later, as shown in FIG. 2A, the potential measuring electrode 23 is fixed in the vicinity of the anticorrosion target such as the pipeline 12 and disposed in the double pipe structure, and then between the pipeline 12 and the casing 22. Is filled with a filler such as mortar 21. Accordingly, the collation electrode 5 can be prevented from being damaged when the collation electrode 5 is laid by denting the collation electrode 5. Moreover, even if the collation electrode 5 is brought close to the probe 3 by arranging the collation electrode 5 so as to be recessed, the collation electrode 5 does not interfere with the anticorrosion current.

  The verification electrode 5 is formed insulated from the probe 3. On the other hand, the verification electrode 5 has at least one terminal 4C, and a cable that can be electrically connected to the voltmeter is connected to the terminal 4C.

  Examples of the material of the reference electrode 5 include lead and manganese dioxide as the reference electrode in the mortar 21, and it is desirable to use a material that can be used for a long time. However, the material of the verification electrode 5 is not limited to these examples. For example, an optimal verification electrode may be applied for each environment where the verification electrode 5 is installed. In addition, for example, when the filler in the gap between the double tubes is soil such as sand, it is possible to use a permanent saturated copper sulfate electrode as the reference electrode 5.

  The probe 3 and the verification electrode 5 are disposed in a groove formed on the surface of the housing 1 in the measurement direction, and are fixed to the housing 1 by a fixing means such as a bolt and nut. The housing 1 is formed of an insulating material, and an insulating material 6 is filled between the groove of the housing 1 and the probe 3. As a result, the probe 3 and the verification electrode 5 are integrally formed while maintaining an insulated state. The probe 3 is exposed to the embedded environment (including the filler, for example, mortar 21) and directly contacts the probe surface in the measurement direction (z-axis positive direction), and the verification electrode 5 is also directly in the measurement direction. Or indirectly contact the buried environment.

  A housing back cover 2 is formed on the back surface of the housing 1, and the probe 3 and the verification electrode 5 are connected to the plurality of cables in the measurement cable 7 via the terminals 4A to 4C. Connected to. More specifically, at least three cables (the probe potential measurement cable 9, the verification electrode potential measurement cable 10, and the probe corrosion protection target connection cable 11) are arranged in the measurement cable 7. The probe potential measurement cable 9 is connected to the terminal 4B of the probe 3, the probe anticorrosion target connection cable 11 is connected to the terminal 4A of the probe 3, and the verification electrode potential measurement cable 10 is connected to the terminal 4C of the verification electrode 5. . It is desirable to use a multi-core cable as such a measurement cable 7 from the viewpoint of reducing labor and cost of wiring work. The measurement cable 7 is fixed to the housing 1 via the cable connector 8 and wired from the position where the potential measurement electrode 23 is disposed to a potentiometer or the like disposed on the ground.

  In addition, as described later, it is desirable that the potential measurement electrode 23 is disposed so that the back surface thereof is in contact with the measurement target. In this case, the back surface of the potential measurement electrode 23 has a shape along the surface of the measurement target that is in contact with the potential measurement electrode 23. It is desirable to be formed by.

The potential measuring electrode 23 according to one embodiment of the present invention has been described above.
Next, a state where the potential measuring electrode 23 is arranged will be described.

<Arrangement of Potential Measurement Electrode According to One Embodiment>
2A and 2B are explanatory diagrams for explaining the arrangement of potential measurement electrodes according to an embodiment of the present invention. FIG. 2B shows a cross-sectional view taken along line BB in FIG. 2A. FIG. 3 is an explanatory diagram for explaining a schematic circuit when the potential measurement electrode according to the present embodiment is arranged.

  Here, a case will be described in which the anticorrosion object whose potential is measured by the potential measuring electrode 23 according to the present embodiment is, for example, the pipeline 12 having a double pipe structure is made of steel.

  The steel pipeline 12 is subjected to cathodic protection. That is, the energizing anode 14 is embedded in the ground. The external power supply 13 has a negative (base) ground potential in the pipeline 12 via the positive trunk cable 15 connected to the energizing anode 14 and the negative trunk cable 16 connected to the pipeline 12. A DC voltage is applied to the pipeline 12 so that Accordingly, during operation of the external power supply device 13, the anticorrosion current 20 is supplied from the energizing anode 14 to the pipeline 12.

  On the other hand, the pipeline 12 is embedded in a casing 22 constructed by a propulsion method such as a steel pipe or a fume pipe. The casing 22 is an example of a conductor that surrounds a corrosion protection target, and is formed of a conductive material such as a steel material, for example. A filler is filled between the casing 22 and the pipeline 12. That is, the entire double-pipe structure is buried in the ground, but when the pipeline 12 that is the object of anticorrosion is viewed, the pipeline 12 is buried in this filler. Therefore, in this case, it can be said that the embedded environment of the pipeline 12 is a filler. Examples of the filler include mortar 21 and sand shown in FIGS. 2A and 2B. Below, the case where the mortar 21 is used as a filler is demonstrated.

  The potential measuring electrode 23 is disposed in the mortar 21. At this time, the potential measurement electrode 23 is arranged so that the z-axis positive direction shown in FIG. 1B, that is, the measurement direction faces the inner surface of the casing 22. The potential measurement electrode 23 is disposed in the vicinity of the pipeline 12, but is preferably disposed in contact with the pipeline 12.

  The measurement cable 7 connected to the probe 3 and the verification electrode 5 of the potential measurement electrode 23 is wired to the ground.

  Among the plurality of cables in the measurement cable 7, the probe potential measurement cable 9 connected to the probe 3 is connected to the verification electrode potential measurement cable 10 connected to the verification electrode 5 via the potentiometer 17. Therefore, the potentiometer 17 indicates a potential with respect to the verification electrode 5 of the probe 3, and this potential indicates a potential against the mortar because the verification electrode 5 is disposed in the mortar 21.

  On the other hand, among the plurality of cables in the measurement cable 7, another probe anticorrosion target connection cable 11 connected to the probe 3 is connected to the pipeline start-up cable 24 connected to the pipeline 12 that is the anticorrosion target, to the switch 19 and It is connected via an ammeter 18. Therefore, when the switch 19 is turned on, at least a part of the anticorrosion current 20 flows into the casing 22 through the ground, and flows from the casing 22 into the probe 3 (simulated rod) of the potential measuring electrode 23. The anticorrosion current 20 that has flowed into the probe 3 flows into the pipeline 12 via the ammeter 18 or the like, and then returns to the power source 13. Therefore, the ammeter 18 indicates the amount of current that flows into the pipeline 12 through the probe 3 that is a simulated soot, and this current indicates a part of the anticorrosion current 20 that flows into the probe 3.

  Therefore, according to the potential measurement electrode 23, when the switch 19 is turned on, the anticorrosion current 20 flows into the probe 3, and the on-potential can be measured by the potentiometer 17. Further, the off potential can be measured by the potentiometer 17 at the moment when the switch 19 is turned off. Furthermore, when the switch 19 is on, the probe current can be measured by the ammeter 18.

<Potential distribution by potential measuring electrode according to one embodiment>
Here, with reference to FIG. 4, the installation situation and potential distribution in the double tube by the potential measuring electrode 23 arranged in this way will be described. FIG. 4 is an explanatory diagram for explaining a potential distribution by the potential measurement electrode according to an embodiment of the present invention.

In FIG. 4, SM (Structure Marine) material is used as the material of the pipeline 12, the same SM material is used for the probe 3, and a steel pipe is used for the casing 22. Then, lead is used as the reference electrode 5, vinyl chloride is used as the housing 1, and an epoxy resin is used as the insulating material 6. The outer shape of the verification electrode 5 was 20 mm, the inner diameter of the through hole of the probe 3 was 30 mm, the outer diameter was 50 mm, and the area of the probe surface in contact with the mortar 21 in which the pipeline 12 was embedded was 12.6 cm ² . The potential measurement electrode 23 was arranged so that the probe surface was positioned 40 mm from the surface of the pipeline 12. Further, the interval D between the casing 22 and the pipeline 12 is set to 150 mm, and the anticorrosion coating 12A is thin, and is omitted in FIG.

  In this way, the potential measurement electrode 23 is arranged in the casing 22, and a DC voltage is applied by the external power supply device 13 so that the potential difference between the casing 22 and the probe 3 is 1.0V. As a result, the potential distribution around the potential measuring electrode 23 (IR drop distribution) is shown in FIG.

  As a result, in the case of the double pipe structure, the inventors of the present invention have a mortar 21 in which the pipeline 12 is a filler via the probe 3 (simulated rod) connected to the pipeline 12 inside the casing 22. It was clarified that the inflow path of the anticorrosive current that flows in contact with the battery is greatly different from that without the casing 22.

  That is, the anticorrosion current 20 supplied from the energizing anode 14 of the external power supply device 13 for anticorrosion spreads over the soil. Here, when the pipeline 12 reaches a river crossing portion or the like and has a double pipe structure, the casing 22 is often applied with a bare material without a cover, but the casing 22 is very much in comparison with soil. Good conductor with low electrical resistance. Accordingly, the anticorrosion current is preferentially conducted through the steel casing 22. When the probe 3 is connected to the pipeline 12 (main pipe) inside the steel casing 22, as shown in FIG. 4, the anticorrosion current 20 flows from the portion closest to the probe 3 on the inner wall of the casing 22 to the mortar 21. It flows out and flows into the probe 3 through the mortar 21.

  Here, since the gap distance D between the casing 22 and the pipeline 12 is as small as 150 mm, the flow area of the anticorrosion current 20 from the casing 22 through the mortar 21 to the probe 3 is also very narrow. According to the experiment and analysis of the inventor of the present invention, as shown in FIG. 4 or FIG. 8, the anticorrosion current is a normal line raised on the probe surface of the probe 3 (if it is a damaged part d, a method set on the damaged part d It was found that the current input from other regions is at a negligible level, and is concentrated within an angle of about 60 degrees with respect to the line), that is, within π steradians. As a result, the inventors of the present invention believe that the current inflow path is the central part of the double pipe construction part in the cathodic protection in a structure where a narrow space surrounded by good conductors such as a double pipe structure is connected endlessly. It has been clarified that the range of π steradians from the center of the damaged part d should be taken into consideration, whether it is the end part or not. That is, the current distribution of the distance within D / tan 30 ° (D is the gap distance between the casing 22 and the pipeline 12) in the longitudinal direction on both sides starting from the damaged part d is most of the current flowing into the probe 3. Therefore, if the anticorrosion current flowing from within the range of π steradians and the ground potential within the range can be measured with high accuracy, the anticorrosion state of the pipeline 12 can be monitored.

  Therefore, the inventor of the present invention, based on the above knowledge, in the anticorrosion monitoring inside the double tube structure, the anticorrosion current 20 and the ground potential flowing into the probe 3 are within D / tan 30 ° from the center of the probe 3. As a result of intensive studies, the above-described potential measuring electrode 23 and the like were invented.

  As shown in FIG. 4, in the potential measurement electrode 23 according to the present embodiment, it can be seen that the potential of the verification electrode 5 includes only a slight IR drop from the potential of the probe 3. On the other hand, when the reference electrode is arranged in the longitudinal direction of the pipeline 12, it can be seen that the IR drop has a very large value even if the reference electrode is brought close to the probe 3. This means that the potential measuring electrode 23 can accurately measure the mortar potential of the pipeline 12.

  In order to perform accurate potential measurement in this way, it is desirable that the potential measurement electrode 23 is laid at a position that enters the inside of the double pipe by D / tan 30 ° or more from the start end of the double pipe construction range. Further, if such a potential measuring electrode 23 is arranged at one place, it can measure the potential representing the entire pipeline 12 with sufficient accuracy, but more preferably, one potential measuring electrode 23 is provided near the end of the casing 22. It is desirable to arrange them one by one. That is, for example, when the casing 22 is a sheath tube such as a steel tube or a fume tube, one potential measuring electrode 23 is desirably disposed at each end of the sheath tube.

<Example of Effect by Potential Measuring Electrode According to One Embodiment>
The potential measuring electrode 23 according to one embodiment of the present invention has been described above.
On the other hand, when drawing a measurement cable (corresponding to the measurement cable 7 etc.) from the center of the double pipe construction range as is conventionally done, not only the workability is poor, but also the routing Inductive current is likely to occur in long cables, and accurate anticorrosion potential could not be measured. However, according to the potential measurement electrode 23 according to an embodiment of the present invention, the probe potential is simply laid at a position that enters the double pipe by D / tan 30 ° or more from the start end of the double pipe construction range. Can represent the anticorrosion state representative of the entire double pipe construction section.

  Therefore, according to the potential measurement electrode 23 according to an embodiment of the present invention, the IR drop is minimized in an environment where an error such as a conventional large error has not been able to be measured, particularly a probe potential inside the double tube structure. Can be measured. Therefore, it becomes possible to grasp the anticorrosion state of the pipeline in a state where there is a stray current, and it is possible to more reliably perform the anticorrosion management of the double pipe portion, which has been almost impossible to maintain. Further, conventionally, the verification electrode is arranged in the entire area of the propulsion construction part. However, according to the potential measurement electrode 23 according to one embodiment of the present invention, the stationary part in which the potential measurement electrode 23 is arranged at both construction end points is specified. The distance to be calculated can be calculated. Therefore, the number of verification electrodes can be reduced, the construction cost can be reduced, and since the cable is not routed long, the cost of the cable is reduced and the induction noise to the cable is reduced. It is possible.

  Further, according to the flow path of the anticorrosion current revealed by the present inventor, the anticorrosion current is concentrated in the vicinity of the probe, and the potential gradient becomes intense. Therefore, when formed separately from each other like the conventional probe and the reference electrode, if the reference electrode is separated from the probe and deviates from the path where the anticorrosive current concentrates, the filling between the probe and the reference electrode will occur. A large potential difference due to a large voltage drop (that is, IR drop) is generated by the resistivity and the anticorrosive current density of the mortar 21. Such a large potential difference causes a large difference from the true probe potential that can be measured by the reference electrode, and decreases the measurement accuracy. However, according to the potential measurement electrode 23 according to an embodiment of the present invention, the position and shape of the verification electrode 5 are the center of the path where the anticorrosion current 20 is concentrated, and the path of the anticorrosion current 20 is affected. Set to not. Therefore, according to the electrode structure of the potential measuring electrode 23, it is possible to suppress the IR drop as much as possible by bringing the probe 3 and the verification electrode 5 close to each other. That is, in the electrode structure of the potential measuring electrode 23 shown in FIG. 1A, the reference electrode 5 is incorporated in the ring hole of the ring-shaped probe 3, and the ring-shaped probe 3 and the reference electrode 5 are concentrically arranged. By arranging, the surface of the probe 3 and the collation electrode 5 can be arranged point-symmetrically, and as a result, the separation imbalance caused by the shape of the surface of the probe 3 and the collation electrode 5 can be suppressed as much as possible.

  Further, according to the potential measuring electrode 23 according to the embodiment of the present invention, the verification electrode 5 is embedded in the inner cylindrical space of the ring-shaped probe 3 with the tip having a right cone shape. Then, a space formed by the verification electrode 5 and the ring-shaped probe 3 is filled with an anticorrosive current medium such as an embedded environment or a filler. Therefore, according to the potential measuring electrode 23, the surface of the verification electrode 5 and the embedded environment (mortar 21) can be brought into close contact with each other, and the surface shape of the verification electrode 5 can be reduced by the anticorrosion current 20 gathered on the probe 3. It is possible to follow the generated potential surface distribution shape, and as a result, the potential measurement accuracy can be further improved.

  Further, according to the potential measuring electrode 23 according to the embodiment of the present invention, it can be arranged at the end portion of the double pipe construction section, and therefore, even in the worst case, the minimum to the electrode installation portion by excavation is possible. It becomes possible to repair and repair by excavating.

<Example with potential measurement electrode according to one embodiment>
Next, examples of the potential measurement electrode 23 according to an embodiment of the present invention will be described.
In this example, the potential measuring electrode 23 having the configuration and arrangement described in the above <potential distribution by the potential measuring electrode according to one embodiment> was prepared. Then, another minute collation electrode is arranged in the immediate vicinity of the probe 3, the external power supply device 13 is set so that the potential V0 of the probe 3 with respect to this minute collation electrode becomes a constant potential of −1.0 V, and time t = At about 3 seconds, the switch 19 was turned on, and the current I flowing into the probe 3 of the potential measurement electrode 23 (a part of the anticorrosion current 20) was measured by the ammeter 18. Further, the potential V1 (ON potential) of the pipeline 12 (that is, the probe 3) with respect to the verification electrode 5 was measured by the potentiometer 17 while the switch 19 was kept on. Furthermore, at the time t = about 23 seconds, the switch 19 was turned off, and the potential V1 (off potential) of the pipeline 12 (that is, the probe 3) with respect to the verification electrode 5 at that moment was also measured.

  For comparison with the conventional potential measurement, another verification electrode was arranged at a position 10 mm away from the probe 3 in the longitudinal direction of the pipeline 12, and the potential V2 of the probe 3 with respect to this verification electrode was also measured. The measurement results are shown in FIG.

  As shown in FIG. 5, when the switch 19 is turned on, the current I flows into the probe 3, and the potential V1 (example) of the probe 3 with respect to the verification electrode 5 is a natural potential (a part of the anticorrosive current 20 flows into the probe). (Probe potential when not) −0.75V gradually shifts to the negative side and approaches the set potential V0. At the same time, the current I flowing into the probe 3 gradually decreases.

  Finally, V1 becomes substantially the same potential as V0, and the current I flowing into the probe 3 becomes a substantially constant current (also referred to as “sustain current”). When V1 and I become constant values, it can be determined that the probe 3, that is, the pipeline 12 is in a stable anticorrosion state (in FIG. 5, before the probe is in a stable anticorrosion state, the probe 3 The current I flowing into the is turned off.)

  On the other hand, the probe potential V2 (comparative example) by the conventional reference electrode showed a potential of -1.2 V at the same time as the switch 19 was turned on. Thereafter, the current I flowing into the probe decreased and V2 also decreased. However, V2 always includes a large IR drop, and from the potential at the moment when the switch 19 is turned off, an IR drop of 100 mV or more is present in V2. It can be confirmed that there is.

  On the other hand, the potential V1 of the probe 3 with respect to the verification electrode 5 can be confirmed from the potential at the moment when the switch 19 is turned off to have a very small IR drop in V1. Therefore, if the probe potential is measured by the potential measuring electrode 23, the IR drop is very small, and a potential approximate to the true probe potential (potential without IR drop) can be measured.

  Thus, as a comparative example, the potential V2 (conventional potential measurement method) of the probe 3 measured by arranging the reference electrode at a position slightly separated from the probe end by 10 mm includes a large IR drop. Therefore, in the electrode as in the comparative example, “a state in which the anticorrosion state goes to stability” such as “originally the probe potential gradually approaches the set potential V0” like the probe potential V1 with respect to the verification electrode 5 according to the present embodiment. I could not figure out. However, since the potential measurement electrode 23 according to the present embodiment can measure the probe potential V1 with respect to the verification electrode 5 and the current I flowing into the probe, it is clearly confirmed whether or not the anticorrosion has reached a stable state. be able to.

  As described above, the potential measuring electrode 23 can accurately measure the off-potential and the probe current in addition to the accurate on-potential, and further, the state of the anticorrosion that has not been confirmed so far (referred to as “negative polarization”). )). It can also be seen that the potential measuring electrode 23 is a more compact and economical tool than the conventional combination of the verification electrode and the probe.

  As mentioned above, although preferred embodiment of this invention was described in detail, referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, in the above-described embodiment, the steel pipeline 12 laid by the double pipe method is described as an example of the anticorrosion target for measuring the anticorrosion potential, but the present invention is not limited to this example. Absent. Of course, the present invention can measure the anticorrosion potential of the general buried pipeline 12, and the anticorrosion target is not limited to the pipeline 12. The present invention is particularly effective and accurate for steel anticorrosion objects that are subjected to anticorrosion, are laid and surrounded by a conductor (for example, the casing 22), and a corrosion-proof current flows from the conductor. Can be measured. In addition, the steel here includes various steels such as synthetic steel such as ordinary steel, stainless steel and high-tensile steel, nickel chrome steel, nickel chrome molybdenum steel, chrome steel, chrome molybdenum steel and manganese steel. It is.

  Moreover, although the said embodiment demonstrated the case where the probe 3 was formed in the ring shape which has a through-hole in center part, this invention is not limited to this example. For example, a hole may be formed in the center portion of the probe, and the hole does not need to be a through hole. In this case, the verification electrode 5 is disposed in the drilled hole. Further, the surface of the probe in which the hole is formed becomes a ring shape by forming the hole. Therefore, in this case, the surface in which the hole is formed corresponds to the ring surface, and the direction in which the hole is formed corresponds to the above-described penetration direction (measurement direction, z-axis).

It is explanatory drawing for demonstrating the structure of the electric potential measurement electrode which concerns on one Embodiment of this invention. It is explanatory drawing for demonstrating the structure of the electric potential measurement electrode which concerns on the same embodiment. It is explanatory drawing for demonstrating arrangement | positioning of the electric potential measurement electrode which concerns on the same embodiment. It is explanatory drawing for demonstrating arrangement | positioning of the electric potential measurement electrode which concerns on the same embodiment. It is explanatory drawing for demonstrating the schematic circuit when the electric potential measurement electrode which concerns on the embodiment is arrange | positioned. It is explanatory drawing for demonstrating the electric potential distribution by the electric potential measurement electrode which concerns on the same embodiment. It is explanatory drawing for demonstrating the Example of the electric potential measurement electrode which concerns on the same embodiment. It is explanatory drawing for demonstrating electric potential distribution when damage arises in the anticorrosion coating | coated applied to the pipeline of a single pipe | tube structure. It is explanatory drawing for demonstrating the probe and collation electrode which are arrange | positioned at the pipeline of a double pipe structure. It is explanatory drawing for demonstrating electric potential distribution when damage arises in the anticorrosion coating applied to the pipeline of a double pipe structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Housing back cover 3 Probe 4A, 4B, 4C Terminal 5 Reference electrode 6 Insulation material 7 Measurement cable 8 Cable connector 9 Probe potential measurement cable 10 Reference electrode potential measurement cable 11 Probe anticorrosion object connection cable 12 Pipeline 12A Anticorrosion coating 13 External power supply 14 Current-carrying anode 15 Positive trunk cable 16 Negative trunk cable 17 Potentiometer 18 Ammeter 19 Switch 20 Corrosion protection current 21 Mortar 22 Casing 23 Potential measurement electrode 24 Pipeline startup cable I Part of the corrosion protection current V0 Setting probe Potential V1 Probe potential according to example V2 Probe potential according to comparative example d Damaged part

Claims (10)

Potential measurement for measuring the potential of an anticorrosion target made of steel that has been subjected to electrocorrosion protection and is at least partially covered by a conductive casing and in which an anticorrosion current flows between the casing and the casing. An electrode,
A hole formed in a central portion using a conductive material, and one or more terminals electrically connected to at least one of the anticorrosion object and the voltmeter, and the anticorrosion object A probe in contact with the embedded environment where
A reference electrode that is insulated from the probe and is arranged to face the embedded environment through a hole in the probe, and has a terminal that is electrically connected to the voltmeter;
Have
By the voltmeter, Ri measurable der the potential between the reference electrode and the probe via the embedded environment,
The potential measuring electrode, wherein the potential measuring electrode is disposed in the vicinity of an end of the casing . The probe is in contact with the embedded environment at a ring-shaped probe surface in which the hole is formed,
The potential measurement electrode according to claim 1, wherein the reference electrode is disposed so as to be embedded in the probe surface.   The potential measuring electrode according to claim 1 or 2, wherein a central axis of the reference electrode coincides with a central axis of a hole of the probe.   The reference electrode has a shape in which a portion on a central axis of the hole of the probe protrudes in a direction facing the embedded environment as compared with other portions. The potential measuring electrode according to 1. The probe is formed in a circular or regular polygonal ring shape,
The reference electrode has a shape such that an interval between an outer periphery of a part of the reference electrode facing the embedded environment and a ring inner surface of the probe surface of the probe is constant. 5. The potential measuring electrode according to any one of 4 above. Potential measurement for measuring the potential of an anticorrosion target made of steel that has been subjected to electrocorrosion protection and is at least partially covered by a conductive casing and in which an anticorrosion current flows between the casing and the casing. A method,
A hole formed in a central portion using a conductive material, and one or more terminals electrically connected to at least one of the anticorrosion object and the voltmeter, and the anticorrosion object A probe in contact with an embedded environment, and a reference electrode that is insulated from the probe and is arranged to face the embedded environment through a hole in the probe, and has a terminal electrically connected to the voltmeter Embedded in the embedded environment in the vicinity of the measurement object, and disposed in the vicinity of the end of the casing,
A potential measuring method, comprising: measuring a potential between the probe and the verification electrode through the embedded environment by the voltmeter. Between the front Symbol anticorrosion subject and the casing, fillers protection current flows is filled,
The potential measuring method according to claim 6, wherein the potential measuring electrode is disposed in the filler between the anticorrosion object and the casing.   The electric potential measuring electrode is disposed at a position where it enters between the anticorrosion object and the casing by a distance corresponding to or more than the distance between the anticorrosion object and the casing from the end of the casing covering the anticorrosion object. The potential measuring method according to claim 7, wherein:   When the distance between the anticorrosion object and the casing is D, D / tan 30 ° or more from the end of the casing that surrounds the anticorrosion object, at a position that enters between the anticorrosion object and the casing, The potential measuring method according to claim 8, wherein the potential measuring electrode is arranged. 10. The potential measuring method according to claim 8, wherein the potential measuring electrodes are arranged in the vicinity of both end portions of the casing. 11.