JPH09281069A - Reduction method of erroneous judgment in the damage degree monitoring method of coated steel pipe - Google Patents

Abstract

(57) [Abstract] [Purpose] In the damage level monitoring method for coated steel pipes, it is possible to prevent erroneous determination due to current noise flowing in from an anticorrosion facility or electric railway. A pipe ground potential and / or an output of an anticorrosion facility is measured in addition to the measurement of damage resistance, and when the timings of changes in these measured values and changes in damage resistance match, or within a fixed time. If it is within the range, it is judged as current noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing erroneous judgment in a method for quantitatively evaluating the degree of coating damage of a coated steel pipe buried in soil.

[0002]

2. Description of the Related Art The steel surface of a coated steel pipe buried in soil is
The coating is insulated from the soil and prevents the progress of corrosion. However, the steel surface of the coated steel pipe will come into contact with the soil if it is damaged by contact with other buried objects, workpieces, stones in the soil, etc., or if the coating is damaged due to natural deterioration, etc. there is a possibility. Therefore, it is important for security to constantly monitor the coating damage location of the coated steel pipe and its extent.

As a technique for evaluating a coating damage portion of a coated steel pipe buried in soil and its degree, a. Coating resistance measurement method, b. Coating film damage area search method, c. In-tube current measurement method, d. The direct method pipe locator can be used.

However, in the above-mentioned coating film measuring method, when the length of the coated steel pipe buried in the soil to be measured is short, the ground resistance can be converted into the coating film resistance, and deterioration of the coating, etc. Effective for evaluation. However, if the coated steel pipe to be measured has a long electrical continuity, the applied current does not reach the far-off point in the above method. Since it is not the value of the total extension of the steel pipe but the apparent ground resistance of the unidentified portion of the coated steel pipe, it cannot be converted into the coating film resistance, and the deterioration of the coating or the like cannot be accurately evaluated.

Next, in the above-mentioned method for detecting a damaged portion of the coating film, there are a needle electrode method, a Pearson method, a coating film defect detecting device and the like. These methods detect the position and size of a coating film defect from the potential difference on the ground surface. However, they cannot be used for constant monitoring because of the nature of exploration on the road.

Next, in the above-mentioned pipe current measuring method, a damaged portion is detected from the distribution of the pipe current of the coated steel pipe. However, when the coated steel pipe is provided with a corrosion preventive facility such as a drainage device and a galvanic anode, it is necessary to evaluate while eliminating changes in these resistances. Further, it is not accurate to evaluate the degree of damage only from the current value.

Next, in the method using the direct method pipe locator, a pipe locator for exploring the position of the buried pipe is used to detect the contact position between the covered steel pipe and another buried object. In addition to being difficult, it cannot be used for constant monitoring because of the nature of exploration on the road.

Further, in any of the above-mentioned conventional methods, in order to detect the coating damage portion of the coated steel pipe, there is no choice but to search from the ground surface directly above the coated steel pipe or to evaluate from the in-pipe current. However, the method of evaluating from the current in the tube is
It requires skillful techniques and is low in accuracy. In addition, it is necessary to conduct a field survey at the location where the coated steel pipe is buried, and it is difficult to perform simultaneous measurement at multiple locations, as well as constant monitoring.

Therefore, the present inventor has proposed a method of monitoring the degree of damage of the coated steel pipe by the following two methods. One point of the covered steel pipe to be monitored is used as a reference point, a constant signal current is applied to the coated steel pipe from this reference point, and the current value and the potential value measured at two points of the covered steel pipe at appropriate intervals are 2 A method of observing the degree of damage of a coated steel pipe that determines damage resistance between locations and determines that there is no damage if this damage resistance value is greater than a specified value, and determines that there is damage if it is less than the specified value (special (Japanese Patent Application No. 5-274286) and the covered steel pipe to be monitored are divided into appropriate ranges, and one point within each divided range is used as a reference point. From these reference points, from other divided range reference points Signal currents that can be distinguished from the signal currents of (1) and (2) are applied to the covered steel pipes to be monitored, respectively, and the corresponding division range is set as the monitoring range, and the current value and potential value measured in this monitoring range Find the damage resistance and have this damage resistance value Is greater than meta value is determined to no damage in the interval, there damage in the interval is smaller and determines coated steel pipe damage degree monitoring method (Japanese Patent Application No. 6-289911).

[0010]

[Patent Document 1] Japanese Patent Application No. 5-274
According to the inventions of Japanese Patent Application No. 286 and Japanese Patent Application No. 6-289911, a. Accurate determination of damage degree, b. Since it can be applied even for long distances, it is extremely effective for constantly monitoring the degree of coating damage on the main line of gas, oil, etc. c. Since it is possible to immediately judge the degree of damage using a computer, it has the feature that it does not require experience or skill in the judgment work, but on the other hand, there is a railway track etc. near the pipeline, and the pipe itself There is a case such as the cathodic protection equipment, and noise (current) flowing in from now on may erroneously determine the occurrence of damage. It is an object of the present invention to propose a method for monitoring the degree of damage to a coated steel pipe that does not make an erroneous determination due to noise.

[0011]

The erroneous determination mitigating method in the damage degree monitoring method for a coated steel pipe proposed in the present invention is as follows.

1. One point of the covered steel pipe to be monitored is used as a reference point, a constant signal current is applied to the coated steel pipe from this reference point, and the current value and the potential value measured at two points of the covered steel pipe at appropriate intervals are 2 In the method of monitoring the degree of damage of the coated steel pipe, it is determined that there is no damage when the damage resistance value between the points is larger than a predetermined value and the damage resistance value is smaller than the specified value. At the time of this judgment, the changes in the pipe ground potential and the output of the anticorrosion equipment are measured, and when the timing of these two changes and the change of the damage resistance coincide or are within a fixed time, it is judged as noise and the degree of damage of the coated steel pipe. Mitigation judgment mitigation method in monitoring method.

2. One point of the covered steel pipe to be monitored is used as a reference point, a constant signal current is applied to the coated steel pipe from this reference point, and the current value and the potential value measured at two points of the covered steel pipe at appropriate intervals are 2 In the method of monitoring the degree of damage of the coated steel pipe, it is determined that there is no damage when the damage resistance value between the points is larger than a predetermined value and the damage resistance value is smaller than the specified value. When this judgment is made, the pipe-to-ground potential is measured, and when the change in the measured value and the change in the damage resistance coincide or are within a certain period of time, it is judged as noise. Method.

3. One point of the covered steel pipe to be monitored is used as a reference point, a constant signal current is applied to the coated steel pipe from this reference point, and the current value and the potential value measured at two points of the covered steel pipe at appropriate intervals are 2 In the method of monitoring the degree of damage of the coated steel pipe, it is determined that there is no damage when the damage resistance value between the points is larger than a predetermined value and the damage resistance value is smaller than the specified value. Measure the output change of the anticorrosion equipment at the time of this judgment, and if the timing of this change and the change of the damage resistance match or it is within a certain time, it is judged as noise Reduction of erroneous judgment in the damage degree monitoring method of coated steel pipe Method.

4. The covered steel pipe to be monitored is divided into appropriate ranges, one point within each divided range is used as a reference point, and a signal current that can be distinguished from the signal current from the reference points in other divided ranges from these reference points To the coated steel pipes to be monitored,
The corresponding division range is set as the monitoring target range, the damage resistance in each section is calculated from the current value and the potential value measured in this monitoring target range, and if this damage resistance value is larger than a specified value, In the method of monitoring the degree of damage of a coated steel pipe, it is determined that there is no damage in the section, and if it is small, there is damage in the section. During this determination, changes in the pipe ground potential and the output of the anticorrosion equipment are measured, and the two An erroneous determination mitigating method in a method for monitoring the degree of damage to a coated steel pipe, wherein when the change and the change in the damage resistance coincide with each other or fall within a certain time, it is judged as noise.

5. The covered steel pipe to be monitored is divided into appropriate ranges, one point within each divided range is used as a reference point, and a signal current that can be distinguished from the signal current from the reference points in other divided ranges from these reference points To the coated steel pipes to be monitored,
The corresponding division range is set as the monitoring target range, the damage resistance in each section is calculated from the current value and the potential value measured in this monitoring target range, and if this damage resistance value is larger than a specified value, It is determined that there is no damage in the section, and if it is small, it is determined that there is damage in the section In the damage degree monitoring method of the coated steel pipe, the pipe ground potential is measured during this determination,
An erroneous determination mitigating method in a method for monitoring the degree of damage to a coated steel pipe, wherein when the change of the measured value and the change of the damage resistance coincide or fall within a certain time, it is judged as noise.

6. The covered steel pipe to be monitored is divided into appropriate ranges, one point within each divided range is used as a reference point, and a signal current that can be distinguished from the signal current from the reference points in other divided ranges from these reference points To the coated steel pipes to be monitored,
The corresponding division range is set as the monitoring target range, the damage resistance in each section is calculated from the current value and the potential value measured in this monitoring target range, and if this damage resistance value is larger than a specified value, It is determined that there is no damage in the section, and if it is small, it is determined that there is damage in the section In the damage degree monitoring method of the coated steel pipe, the change in the output of the anticorrosion equipment is measured during this determination, and this change and the damage resistance A method for reducing erroneous determination in a method for monitoring the degree of damage to a coated steel pipe, which judges that noise occurs when the timing of change coincides or falls within a fixed time.

[0018]

In the case of reducing the erroneous judgment by the above method,
In addition to monitoring the degree of damage, measure the output from the pipe ground potential / corrosion protection equipment. At this time, if there is a specific point where the potential measuring device is not installed and the potential (direct current) has a large correlation with the damage resistance, the potential (direct current) is also measured at that point.

The potentials and outputs measured in this way are compared individually or in combination with the changes in the damage resistance, and if the timings match or if they fall within a certain period of time, it is caused by current noise. Judge as behavior and ignore the change in damage resistance. On the other hand, when the timing is shifted and it is outside a certain time, or when only the damage resistance is changed, it is evaluated that the damage actually occurs.

The output from the tube-to-ground potential / corrosion protection equipment has the highest accuracy when two values are measured and compared at the same time, but any one of them has no problem in practical use.

[Embodiment 1] This embodiment is an embodiment corresponding to the present invention described in claims 1 to 3, and will be described with reference to FIG. This FIG. 1 shows the above-mentioned Japanese Patent Application No. 5-274.
It is explanatory drawing at the time of implementing this invention in the damage detection method and apparatus of invention which concerns on 286. In FIG. 1, point 0 and other points (for example, point x and point x +
Equipment is shown in 1). Passing electrode 2 at point 0
Is installed and attached to the coated steel pipe 1 for energizing lead wire 3
And the lead wire 4 of the energizing electrode 2 is set up on the surface A of the ground. An electric potential measuring electrode 5 is installed at each point,
The potential measuring lead wire 6 attached to the coated steel pipe 1 and the lead wire 7 of the potential measuring electrode 5 are set up on the surface A of the ground. In addition, the coated steel pipe 1 is provided with a certain interval (a distance that does not reach the neighboring site) at each point of the coated steel pipe 1.
The in-tube current measuring lead wires 8 and 9 attached to the respective two positions are set up on the surface A of the ground surface.

The energization lead wire 3 and the lead wire 4 of the energization electrode 2 are used for the energization power source 10, and the potential measurement lead wire 6 and the lead wire 7 of the potential measurement electrode 5 are used for the potential measurement device 1.
First, the in-tube current measuring leads 8 and 9 are connected to the in-tube current measuring device 12, respectively. The potential measuring device 11 and the in-pipe current measuring device 12 are connected to the transmitting device 13, and the potential data and the in-pipe current data are transmitted to the computer 15 via the transmitting device 13 and the receiving device 14. In addition,
Here, in-tube current measurement uses the voltage drop method,
Alternatively, a method of measuring a current flowing through a lead wire connecting both sides of the insulating joint or a method using a clip-on ammeter can be used.

Reference numeral 16 denotes a potential (direct current) measuring device inserted between the potential measuring lead wire 6 and the lead wire 7 of the potential measuring electrode 5. The potential (direct current) measured by this device 16 is a communication line 16a. Via the communication device 13/14 to the computer 15.

At the time of measuring the damage resistance, the computer 15 measures the potential with a potential (DC) measuring device 16 and simultaneously or independently measures the output of the anticorrosion equipment 17, which will be described later,
Compare the timings of changes in this potential (DC) and / or output and changes in damage resistance, and if these timings match, or if they are within a certain time, there is an effect of noise current. Even if there is a change in damage resistance, it is ignored.

Reference numeral 17 denotes an anticorrosion facility such as an external power source. This facility 17 comprises an anticorrosion electrode 18, a conducting wire 19, an anticorrosion electrode lead wire 20, an anticorrosion current / voltage source 21, and a communication device 22 for communication. The device 22 is connected to the communication device 14 via a communication cable 23.

[Embodiment 2] This embodiment includes claims 4 to 6.
The present invention corresponds to the present invention described in 1. and this embodiment will be described with reference to FIG. This FIG. 2 shows equipments installed at a point 0, a point y, an appropriate intermediate point (point x + 1), and a point next to the intermediate point (point x and point x + 2) in the figure. . Electrodes 51 for energization are installed at the point 0 and the point y, respectively.
Energizing lead wire 52 and energizing electrode 5 attached to 0
The first lead wire 53 is set up on the ground surface A. The potential measuring electrode 54 is installed at each of the point x, the point x + 1, and the point x + 2, and the potential measuring lead wire 55 attached to the coated steel pipe 50 and the lead wire 56 of the potential measuring electrode 54 are placed on the ground surface A. Stand up. In addition, at each point of the coated steel tube 50, in-tube current measurement lead wires 57 and 58 attached to two points of the coated steel tube 50 at certain intervals (distances that do not reach adjacent points) are set up. .

At point 0, the energization lead wire 52 and the lead wire 53 of the energization electrode 51 are connected to the energization power supply 59.
At the point y, the conducting lead wire 52 and the conducting electrode 5
The first lead wire 53 is connected to the power supply 62 for energization. At the point x, the potential measuring lead wire 55 and the lead wire 56 of the potential measuring electrode 54 are connected to the potential value measuring device 60, and the tube current measuring lead wires 57 and 58 are connected to the tube current value measuring device 61, respectively. . From point 1 to point x + 1, x +
The same applies to item 2.

At the point x + 1, the potential measuring lead wire 55 and the lead wire 56 of the potential measuring electrode 54 are connected to the potential value measuring device 60 by the tube current measuring lead wires 57 and 58.
Are connected to the in-pipe current value measuring device 61, respectively.

At the point x + 2, the potential measuring lead wire 55 and the lead wire 56 of the potential measuring electrode 54 are connected to the potential value measuring device 60 by the in-tube current value measuring lead wires 57 and 58.
Are connected to the in-pipe current value measuring device 61, respectively. The same applies when there is a point y + 1 from a point x + 3.

A potential value measuring device 60 installed at each point
The in-pipe current value measuring device 61 is connected to the transmitting device 65, and the potential data and the in-pipe current data are transmitted to the transmitting device 6.
5, transmitted to the computer 67 via the receiving device 66. The potential value measuring device 60 and the in-pipe current value measuring device 61 installed at each point are connected to the transmitting device 65, and the potential data and the in-pipe current data are transmitted to the computer 67 via the transmitting device 65 and the receiving device 66. It

At a point sufficiently close to the computer 67, the transmitter 65 and the receiver 66 are unnecessary,
The data may be directly fetched into the computer 67. In addition, although the voltage drop method is used here for measuring the in-tube current, a method of measuring the current flowing through the lead wire connecting both sides of the insulated joint, or a method using a clip-on ammeter can also be used.

Reference numeral 68 denotes a potential (DC) measuring device inserted between the potential measuring lead wire 55 and the lead wire 56 of the potential measuring electrode 54. The potential (DC) measured by this device 68 is a communication line 69. Also, it is connected to the computer 67 via the communication devices 65 and 66.

At the time of measuring the damage resistance, the computer 67 measures the potential with a potential (DC) measuring device 68, and simultaneously or independently measures the output of the anticorrosion equipment 70 described later.
This potential (DC) is compared with the output and the timing of changes in the damage resistance. If these timings match, or if they are within a certain time, it is judged that there is an influence of noise current. Ignore any changes in damage resistance.

Reference numeral 70 denotes an anticorrosion equipment such as an external power source. This equipment 70 comprises an anticorrosion electrode 71, a lead wire 72 for energization, an anticorrosion electrode lead wire 73, an anticorrosion current / voltage source 74, and a communication device 75. The device 75 is connected to the communication device 66 via a communication cable 76.

Next, a method of monitoring damage to the coating will be described with reference to FIG. The damage to the coating occurs between the point X and the point X + 1, and is the case where an alternating current signal is used as the energizing current. The ground resistance between the point x and the point x + 1 is measured by measuring the AC potentials E (x) and E (x + 1) of the coated steel pipe 1 and the coated steel pipe 1 at the points x and x + 1 at both ends of the range. AC current i (x), i (x
The measurement is performed by applying an AC signal or the like from the through electrode 2 to the coated steel pipe 1 at the point 0 using the power supply 10 for energization while measuring +1). The ground resistance R (x to x + 1) of the coated steel pipe 1 between the point x and the point x + 1 is

It is obtained as shown in the equation (1).

[0036]

[Equation 1]

Here, between the point x and the point + 1, when contact of another grounding resistance Rd (x to x + 1) with another buried object or a machine tool or a corresponding coating defect is generated, Rd ( x to x + 1) and R (x to x + 1) and the ground resistance RO (x to x in the steady state between the point x and the point +1)
x + 1),

There is a relationship of the expression (2) of [Expression 2]. Hereinafter, Rd (x to x
Let +1) be the damage resistance between point x and point x + 1.

[0038]

[Equation 2]

Solving the equation (2) for Rd (x to x + 1),

Expression (3) of [Equation 3] is obtained.

(Equation 3)

Therefore, the AC potential and the AC current in the tube at each point are continuously measured and transmitted to the host computer 15 by the transmitter / receivers 13 and 14, and the data are synchronized between the points by the above formula while synchronizing the data. Seeking Rd,
By constantly monitoring this, it is possible to detect, in real time, the contact with another embedded object or the work piece, or the generation of a coating covering defect corresponding to this, and the degree thereof.

[Experimental Example] An experimental example will be described with reference to FIG. In FIG. 3, (a) shows a change in damage resistance, and (b) shows a change in tube-to-ground potential. For this example,
Simulated damage is given three times for 0.5 minutes, 2.5 minutes, and 4.5 minutes. Along with this, the value of the damage resistance clearly decreases, indicating that damage detection is possible. But,
In 0.5 minutes to 0.8 minutes and 3.7 minutes, although the simulated damage was not given, there was a change in damage resistance such that the damage was erroneously determined to have occurred. .

(B) shows the change in the tube-to-ground potential at this time. The time (timing) at which the damage resistance decreased, which was seen in (a), even though the simulated damage was not given, coincides with the time at which the tube-ground potential greatly shifts to the negative side. Therefore, by comparing this time (timing), it can be seen that the change is due to current noise. The above-mentioned (b) change in the tube-to-ground potential also appears in the case of the output of the anticorrosion equipment. It should be noted that some deviation in timing can be regarded as coincidence.

[0043]

As described above, according to the present invention, erroneous determination caused by current noise can be prevented by monitoring the tube ground potential and / or the output of the anticorrosion facility when measuring the damage resistance.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of Examples 1 to 3 in which the present invention is applied to a method for monitoring the degree of damage of a coated steel pipe according to Japanese Patent Application No. 5-274286.

FIG. 2 is an explanatory view of Examples 4 to 6 in which the present invention is applied to the method for monitoring the degree of damage to a coated steel pipe according to Japanese Patent Application No. 6-289911.

FIG. 3 is an explanatory diagram of an experimental example.

[Explanation of symbols]

 1 coated steel pipe 2 energizing electrode 3 energizing lead wire 4 lead wire 5 potential measuring electrode 6 potential measuring lead wire 7 lead wire 8.9 in-tube current measuring lead wire 10 energizing power supply 11 potential measuring device 12 in-tube current measurement Device 13 Transmitter 14 Receiver 15 Computer 16 Potential (DC) measuring device 16a Communication line 17 Anticorrosion equipment 18 Anticorrosion electrode 19 Conductive lead wire 20 Anticorrosion electrode lead wire 21 Anticorrosion current / voltage source 22 Communication device 23 Communication table

Claims (6)

[Claims] 1. A current value measured at two points of the coated steel pipe at appropriate intervals by setting one point of the coated steel pipe to be monitored as a reference point, applying a constant signal current to the coated steel pipe from this reference point. Also, the damage resistance between two locations is calculated from the potential value, and if this damage resistance value is larger than a specified value, it is judged as no damage, and if it is smaller, it is judged as damaged. In the monitoring method, changes in the tube ground potential and the output of the anticorrosion equipment are measured at the time of this determination, and if the timing of these two changes and the timing of the change in the damage resistance match or are within a certain time, it is determined to be noise. A method for reducing erroneous judgments in the method of monitoring the damage of coated steel pipes. 2. A current value measured at two points of the coated steel pipe with an appropriate interval, in which one point of the coated steel pipe to be monitored is set as a reference point, a constant signal current is applied to the coated steel pipe from this reference point. Also, the damage resistance between two locations is calculated from the potential value, and if this damage resistance value is larger than a specified value, it is judged as no damage, and if it is smaller, it is judged as damaged. In the monitoring method, the pipe-to-ground potential is measured during this determination, and when the change in the measured value and the change in the damage resistance match or are within a certain time, it is judged as noise. Method of reducing false positives in method. 3. A coated steel pipe to be monitored is set as a reference point, a constant signal current is applied to the coated steel pipe from this reference point, and the current value is measured at two points with an appropriate interval between the coated steel pipes. Also, the damage resistance between two locations is calculated from the potential value, and if this damage resistance value is larger than a specified value, it is judged as no damage, and if it is smaller, it is judged as damaged. In the method of monitoring, the change in the output of the anticorrosion equipment is measured at the time of this determination, and if the timing of this change and the change in the damage resistance match or are within a certain time, it is judged as noise Monitoring the degree of damage to the coated steel pipe Method of reducing false positives in method. 4. The covered steel pipe to be monitored is divided into appropriate ranges, and one point within each divided range is used as a reference point. From these reference points, the signal current from the reference points of other divided ranges is defined. A distinguishable signal current is applied to each of the steel pipes to be monitored, and the corresponding division range is set as the monitoring range, and the damage resistance in each section is calculated from the current value and potential value measured in this monitoring range. If the damage resistance value is larger than a specified value, it is judged that there is no damage in the section, and if it is smaller, it is judged that there is damage in the section. An error in the damage level monitoring method of the coated steel pipe, which measures changes in the ground potential and the output of the anticorrosion equipment, and judges that these two changes and the change in the damage resistance coincide with each other or that they fall within a certain period of time as noise. Judgment Reduction method. 5. A steel pipe to be monitored is divided into appropriate ranges, and one point within each divided range is used as a reference point. From these reference points, the signal currents from the reference points of other divided ranges are defined. A distinguishable signal current is applied to each of the steel pipes to be monitored, and the corresponding division range is set as the monitoring range, and the damage resistance in each section is calculated from the current value and potential value measured in this monitoring range. If the damage resistance value is larger than a specified value, it is judged that there is no damage in the section, and if it is smaller, it is judged that there is damage in the section. An erroneous determination mitigating method in a damage level monitoring method for a coated steel pipe, which measures a ground potential, and judges that it is a noise when the change of the measured value and the change of the damage resistance coincide with each other or fall within a certain time. 6. The covered steel pipe to be monitored is divided into appropriate ranges, and one point within each divided range is used as a reference point. From these reference points, the signal current from the reference points of other divided ranges is defined. A distinguishable signal current is applied to each of the steel pipes to be monitored, and the corresponding division range is set as the monitoring range, and the damage resistance in each section is calculated from the current value and potential value measured in this monitoring range. If the damage resistance value is larger than a specified value, it is judged that there is no damage in the section, and if it is smaller, it is judged that there is damage in the section. An erroneous determination mitigating method in a damage level monitoring method of a coated steel pipe, which measures a change in output of equipment, and judges that the change is a noise when the timing of the change and the change of the damage resistance coincide or are within a certain time.