JP2009139095A - Apparatus and method for monitoring coating damage on underground pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for monitoring coating damage by using frequencies in which presence or absence of coating damage and its location are easier to determine even on a long pipe and the number of measuring instruments for determining the damaged section can be reduced. <P>SOLUTION: A monitoring apparatus 100 for coating damage on an underground pipe comprises: a signal transmitter 20 for transmitting an asynchronous pseudo-random signal with a plurality of fundamental frequencies from at least one transmission location 12 on the underground pipe 10; a receiver 30 for receiving the asynchronous pseudo-random signal at the transmission location 12; a receiver 40 for receiving the asynchronous pseudo-random signal at a distant location on the underground pipe from the transmission location 12; and a computer 50 for monitoring the pipe-to-ground potential and energization current and monitoring coating damage occurrence and its section on the underground pipe based on changes in the ground resistance and the pipe-to-ground potential of the underground pipe due to changes in the correlation peak value of the asynchronous pseudo-random signal with the plurality of fundamental frequencies. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a coating damage monitoring apparatus and a coating damage monitoring method for underground pipes.

  In order to prevent corrosion of the steel itself, the coated steel pipe buried in the ground is coated with the outer surface to insulate it from the soil. If the coating of the coated steel pipe comes into contact with a drilling machine or the like, for example, during civil engineering work, the steel itself may come into contact with the soil and corrode. In order to prevent corrosion of the steel itself, it is necessary to constantly monitor the state of damage to the coating of the coated (coated) steel pipe embedded in the ground.

  As the coating damage monitoring apparatus and coating damage monitoring method for underground pipes, for example, the following patent documents 1 to 3 are reported.

  The underground coating damage monitoring method described in Patent Document 1 applies an AC signal between an application electrode embedded in a reference position of a coated steel pipe and a pipe body, and detects the pipe-to-ground detection for each measurement section. The presence or absence of damage to the coated steel pipe is determined from the change in ground resistance calculated from the potential, the pipe-to-tube potential, and the conductivity of the pipe body, and the measurement section where the damage has occurred is specified from the change in the pipe-to-tube potential. In-tube current calculated from the tube-to-tube potential of the detection point adjacent to both sides of the detection point on the reference position P side of the measurement section where the damage occurred, and the tube-to-tube of the detection point on the reference position side of the measurement section where the damage occurred This is a method of calculating the distance from the detection point on the reference position side of the measurement section where the damage has occurred to the position where the damage has occurred from the potential, the distance of the measurement section, and the conductivity of the tube.

The method for monitoring the coating damage of underground pipes described in Patent Document 2 is to measure two or more measurement points installed so as to cover the section to be monitored, with metal conduits buried in the ground as measurement targets It is a method of providing. That is, from the amplitude of the tube current and tube-to-ground voltage at each measurement point, and the phase difference between the tube current and tube-to-ground voltage and the standard signal generating means that generates the same phase at the same frequency of the AC power supply, between the measurement points Calculate the characteristic impedance and propagation constant, and estimate the damage position and damage level by comparing the amount of fluctuation of each calculated value of the monitored area on the complex plane with the amount of fluctuation caused by simulated damage that has been applied in the past. This is a method of complementing between simulated damages using the circuit formula.

  In the method for monitoring coating damage of underground pipes described in Patent Document 3, an M-sequence signal having a constant voltage is applied between an application electrode embedded in a reference position of a coated steel pipe and a pipe body, and is measured for each measurement section. A method to determine the presence or absence of damage to a coated steel pipe from the change in ground resistance calculated from the detected tube-to-ground potential, the tube-to-tube potential, and the conductivity of the tube body, and to identify the measurement section where the damage occurred from the change in the tube-to-tube potential It is. That is, the in-tube current calculated from the tube-to-tube potential of the detection point adjacent to both sides of the detection point on the reference position side of the measurement section where the damage occurred, and the tube pair of the detection point on the reference position side of the measurement section where the damage occurred. This is a method of calculating the distance from the detection point on the reference position side of the measurement section where the damage has occurred to the position where the damage has occurred, from the tube potential, the distance of the measurement section, and the conductivity of the tube body.

The coating damage coating damage monitoring device and the coating damage monitoring method described in Patent Documents 1 to 3 cause a contact accident of heavy machinery such as a civil engineering machine with respect to a metal conduit buried in the ground. It is reported that the position of damage and the degree of damage can be easily detected.
JP-A-9-189505 JP 2001-116714 A Japanese Patent Laid-Open No. 2003-232764

  However, in the coating damage coating damage monitoring methods described in Patent Documents 1 to 3, it is necessary to install a large number of measuring devices and measure the tube-to-ground potential and the tube current in order to obtain the damaged section. It is. Accordingly, a site for installing a large number of devices as well as the large number of devices is required, which may be difficult to install.

  The method for monitoring coating damage of underground pipes described in Patent Document 2 is to install at least two power sources and two measurement points with different frequencies for each section in order to monitor the coating damage position. is necessary. The characteristic impedance and the propagation constant are calculated by the devices related to the large number of power sources and measurement points, and the impedance obtained in advance by the simulated resistance is compared in the computer to obtain the position. The coating damage monitoring device disclosed in the document is a lock-in amplifier, and it is difficult to synchronize for a long period of time if the signal transmitter and the signal receiver are separated from each other, and phase adjustment The precision is improved by using the equipment for long-term detailed synchronization.

  In addition, the coating damage monitoring method for underground pipes described in Patent Document 3 is a measuring instrument and a pipe for measuring the pipe-to-ground potential and the pipe current for each section in order to detect the section of the occurrence of coating damage. It is also necessary to lay an electric wire and a communication line along the line.

  In addition, when monitoring the coating damage by frequency, if the pipe is long, it may be difficult to confirm the presence / absence of the coating damage and the location.

  The present invention has been made in view of solving the above-mentioned problems, etc., and coating damage monitoring by frequency makes it easier to check the presence or absence of coating damage and the location even if the tube is long, and Providing a coating damage monitoring device and coating damage monitoring method for underground pipes that require fewer measuring instruments to determine the damage zone and require less land to install the equipment. Main purpose.

  The present invention is a coating damage monitoring apparatus for underground pipes, a signal transmitter for transmitting an asynchronous pseudo-random signal having a plurality of fundamental frequencies from at least one transmission point of the buried pipe, and the transmission point A receiver that receives the asynchronous pseudo-random signal, and a change in ground resistance and tube-to-ground potential of the underground buried pipe due to a change in a correlation peak value of the asynchronous pseudo-random signal having the plurality of fundamental frequencies. And a monitoring device for monitoring the occurrence of coating damage and the occurrence of coating damage.

  The coating damage monitoring apparatus for the underground pipe, wherein the plurality of fundamental frequencies are different from a first frequency at which a current increases when coating damage occurs, and a coating frequency different from the first frequency. It is preferable to include a second frequency at which the tube-to-ground potential decreases depending on the location of the covering damage and the current increases or decreases.

  It is preferable that the device is a coating damage monitoring apparatus for the underground pipe, and further includes a second receiver that is separated from the transmission point in addition to the receiver.

  The present invention is a coating damage monitoring method for underground pipes, which transmits an asynchronous pseudo-random signal having a plurality of fundamental frequencies from at least one transmission point of the embedded pipe, and the asynchronous pseudo-random signal at the transmission point. Receiving the signal, the grounding resistance of the underground pipe due to the change of the correlation peak value of the asynchronous pseudo-random signal having the plurality of fundamental frequencies, and the change in the ground potential of the underground pipe, It is characterized by monitoring the occurrence of coating damage.

  The method for monitoring coating damage to underground pipes, wherein the plurality of fundamental frequencies are different from a first frequency at which a current increases when coating damage occurs, and the first frequency. It is preferable to include a second frequency at which the tube-to-ground potential decreases depending on the location of the covering damage and the current increases or decreases.

  It is preferable that the method for monitoring coating damage to the underground pipe further includes a second reception that is separated from the transmission point in addition to the reception.

  For coating damage monitoring by frequency, even if the pipe is long, it is easier to check the presence or absence of the coating damage and the location, and the number of measuring instruments to determine the damage section is reduced, and the equipment is installed together It is possible to provide a coating damage monitoring apparatus and a coating damage monitoring method for a buried underground pipe and a coating damage monitoring method.

  FIG. 1 is an explanatory diagram showing the configuration of a coating damage monitoring apparatus 100 for a coated (coated) steel pipe 10 according to the present invention. The coating damage monitoring apparatus 100 includes a signal transmitter 20 that transmits an asynchronous pseudo-random signal having a plurality of fundamental frequencies from a transmission point 12 to the coated steel pipe 10 embedded in the ground, and a transmission point 12. The signal receiver 30 that receives the asynchronous pseudo-random signal from the signal transmitter 20 and the asynchronous pseudo-random signal from the signal transmitter 20 are received at a point away from the transmission point 12 of the steel pipe 10 and the underground pipe. The signal receiver 40, and the underground burial by the change of the correlation peak value of the asynchronous pseudo-random signal having the plurality of fundamental frequencies, with respect to the information received from the signal receiver 40 and the signal receiver 30, 40. A computer 50 is configured as a monitoring device for monitoring the coating damage occurrence section and the coating damage occurrence of the buried pipe according to changes in the pipe ground resistance and the pipe ground potential.The computer 50 is connected to the signal transmitter 20 and the signal receivers 30 and 40 so that they can be controlled and operated.

  The signal transmitter 20 includes an energization electrode 21 and a transmission electrode 22 for transmitting an asynchronous pseudorandom signal from the transmission point 12 of the steel pipe 10. The energizing electrode 21 and the transmitting electrode 22 are connected to a current amplifier 23. The current amplifier 23 is connected to an adder 24 that adds a transmitter 25 that transmits a first frequency and a transmitter 26 that transmits a second frequency. With such a configuration, an asynchronous pseudorandom signal obtained by adding the first frequency and the second frequency can be transmitted from the transmission point 12 of the steel pipe 10 through the transmission electrode 22.

  From the transmitter 25, the first frequency (frequency 1) at which the current increases when coating damage occurs, is different from the first frequency from the transmitter 26, and when the coating damage occurs, its location The second frequency (frequency 2) at which the tube ground potential decreases and the current increases / decreases is transmitted, and the frequency 1 and the frequency 2 are added by the adder 24 to form an asynchronous pseudo-random signal.

The signal receiver 30 is configured such that the reception electrode 31 is connected to the steel pipe 10 so as to receive an asynchronous pseudorandom signal transmitted from the transmitter 20 from the transmission point 12 of the steel pipe 10 through the transmission electrode 22, and further, the reception electrode A receiver 35 that receives frequency 1 from 31, a receiver 36 that receives frequency 2 from the receiving electrode 31, and a matching electrode 34 connected to the receivers 35, 36.
It is comprised including. Information from the receivers 35 and 36 is transmitted to the computer 50. The receivers 35 and 36 may not be separate but may be a single unit.

The signal receiver 40 is configured such that the reception electrode 41 is connected to the steel pipe 10 so as to receive an asynchronous pseudorandom signal transmitted from the transmitter 20 from the transmission point 12 of the steel pipe 10 through the transmission electrode 22. Receiver 45 for receiving frequency 1 from receiver 41, receiver 46 for receiving frequency 2 from receiver electrode 41, and reference electrode 44 connected to receivers 45 and 46.
It is comprised including. Information from the receivers 45 and 46 is transmitted to the computer 50. The receivers 45 and 46 may not be separate but may be a single unit.

  The receiving electrodes 31 and 41 are connected to the coated steel pipe 10 so that the signal receiver 30 is at the transmitting point 12 and the signal receiver 40 is far from the transmitting point 12. As shown in FIG. 1, the transmission point 12 is defined as follows: the direction where the receiving electrode 31 of the coated steel pipe 10 is provided is the energizing side, the direction where the receiving electrode 41 is provided is the far side, and the interval is defined as the center side. Call it.

  In addition to the energization side signal receiver 30 and the far side signal receiver 40 as the signal receiver, a signal receiver may be provided on the center side to receive signals. There may be a single signal receiver, or even a plurality of signal receivers may be arranged on the same position side without being paired with the transmission point.

  Frequency 1 is a low frequency suitable for confirming the presence or absence of a flaw, and frequency 2 is a high frequency suitable for identifying the location of a flaw. The frequency 1 is preferably 40 Hz or less, and the frequency 2 is preferably 100 Hz or more and 1000 Hz or less, but is not limited to this, and can be appropriately selected and adopted. As for the frequency, an appropriate frequency may be appropriately selected and used in consideration of the ferrant effect (effect in which the potential farther from the transmission point 12 is higher than the energization side). Using the ferrant effect, an actual line test is performed in advance to reduce the ground resistance and the tube-to-ground potential due to the frequency, and by comparing this with the computer 50, the damaged place can be specified.

  If the coating damage monitoring of the coated steel pipe 10 is performed by the coating damage monitoring apparatus 100, it is possible to prevent the necessity of a site for installing a large number of apparatuses as well as a large number of apparatuses. It is not necessary to install at least two power sources and two measurement points with different frequencies for each section in order to monitor the coating damage position, and since it is not a lock-in amplifier, a signal transmitter and a signal receiver If the distance is long, it is difficult to achieve detailed synchronization for a long period of time, and a phase adjustment device is not required. In addition, in order to detect the occurrence of coating damage, it is not necessary to lay an electric wire and a communication line along a pipe and a measuring instrument for measuring the pipe-to-ground potential and pipe current for each section.

  In addition, when monitoring the coating damage by frequency, it may be difficult to confirm the presence or absence of the coating coating and the location if the pipe is long. Since the high frequency is suitable for identification, even if the pipe is long, it is possible to monitor the coating damage by the frequency with higher accuracy.

  As described above, monitoring of coating damage by frequency makes it easier to confirm the presence or absence of coating damage and the location even if the pipe is long, and the number of measuring instruments to determine the damaged section is reduced, and the device is also installed. It is possible to provide a coating damage monitoring method for underground pipes that requires less land for installation.

  FIG. 2 shows the result of monitoring the coating damage of the coated steel pipe 10 by the coating damage monitoring apparatus 100. In the embodiment, a receiver connected to the steel pipe 10 is further provided on the center side, and the first frequency and the second frequency are detected by the computer 50.

  Note that the first frequency is 20 Hz, and the second frequency is 200 Hz.

  When the energized side was damaged, both the ground resistance at frequency 1 and the ground resistance at frequency 2 were lowered, but the tube-to-ground potential at frequency 2 was hardly changed.

  When the center side was damaged, the ground resistance at frequency 1 and the tube-to-ground potential at frequency 2 both decreased, but the ground resistance at frequency 2 decreased only to a certain extent.

  When the far side was damaged, the ground resistance at frequency 1 and the tube-to-ground potential at frequency 2 both decreased, but the ground resistance at frequency 2 increased.

  Thus, it has been found that the ground resistance at frequency 1, the ground resistance at frequency 2, and the tube-to-ground potential at frequency 2 appear as characteristic behaviors on the energizing side, the center side, and the far side of the section. Therefore, it was found that the use of the difference in the behavior of the frequency 1 ground resistance, the frequency 2 ground resistance, and the frequency 2 tube-to-ground potential enables effective identification of the damaged portion in addition to the occurrence of damage. Therefore, by acquiring this behavior as data in advance, it is possible to know where the damage has occurred at the energized side, the center side, or the far side when this data is output.

It is a schematic diagram which shows the coating damage monitoring apparatus which concerns on this embodiment. It is a data figure which concerns on the generation | occurrence | production of damage based on a present Example, and specification of a damage location.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Coating damage monitoring apparatus 10 ... Coated steel pipe 20 ... Signal transmitter 30, 40 ... Signal receiver 50 ... Computer

Claims (6)

A coating damage monitoring device for underground pipes,
A signal transmitter for transmitting an asynchronous pseudorandom signal having a plurality of fundamental frequencies from at least one transmission point of the buried pipe;
A receiver for receiving the asynchronous pseudo-random signal at the transmission point;
Due to changes in ground resistance and pipe-to-ground potential of the underground pipe due to changes in correlation peak values of the asynchronous pseudo-random signals having the plurality of fundamental frequencies, the coating damage occurrence section and the coating damage occurrence of the buried pipe A monitoring device for monitoring the coating damage monitoring device for buried underground pipes. It is a coating damage monitoring device for underground buried pipes according to claim 1,
The plurality of fundamental frequencies are:
A first frequency at which the current increases when coating damage occurs;
Unlike the first frequency, when a coating damage occurs, the coating damage to the underground pipe including the second frequency at which the pipe-to-ground potential decreases and the current increases or decreases depending on the location. Monitoring device. A coating damage monitoring apparatus for underground pipes according to claim 1 or 2,
Furthermore, the coating damage monitoring apparatus containing the 2nd receiver away from the said transmission point in addition to the said receiver. A coating damage monitoring method for underground pipes,
Asynchronous pseudorandom signals with multiple fundamental frequencies are transmitted from at least one transmission point of the buried pipe,
Receiving the asynchronous pseudo-random signal at the origination point;
Due to changes in ground resistance and pipe-to-ground potential of the underground pipe due to changes in correlation peak values of the asynchronous pseudo-random signals having the plurality of fundamental frequencies, the coating damage occurrence section and the coating damage occurrence of the buried pipe A method for monitoring the coating damage of underground pipes. It is a coating damage monitoring method for underground buried pipes according to claim 4,
The plurality of fundamental frequencies are:
A first frequency at which the current increases when there is a coating damage;
Unlike the first frequency, when a coating damage occurs, the coating damage to the underground pipe including the second frequency at which the pipe-to-ground potential decreases and the current increases or decreases depending on the location. Monitoring method. It is a coating damage monitoring method for underground buried pipe according to claim 4 or 5,
Furthermore, in addition to the reception, the damage monitoring method includes a second reception farther away from the transmission point than the first reception.

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