CN110702736A - Buried pipeline anticorrosive coating damage detection method based on induced voltage distribution - Google Patents
Buried pipeline anticorrosive coating damage detection method based on induced voltage distribution Download PDFInfo
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- CN110702736A CN110702736A CN201911130314.2A CN201911130314A CN110702736A CN 110702736 A CN110702736 A CN 110702736A CN 201911130314 A CN201911130314 A CN 201911130314A CN 110702736 A CN110702736 A CN 110702736A
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- induced voltage
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- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
Abstract
The application provides a buried pipeline anticorrosive coating damage detection method based on induced voltage distribution, which comprises the following steps: s1: constructing a target pipeline potential testing system; s2: measuring and recording the induced voltage of each section of the target pipeline; s3: fitting an induced voltage distribution curve I of each section of a target pipeline according to the measured value of the induced voltage, and determining the coordinate of the lowest point of the distribution curve I; s4: acquiring an induced voltage distribution curve II of the target pipeline in an undamaged state, and determining the coordinate of the lowest point of the distribution curve II; s5: judging whether the coordinate of the lowest point of the distribution curve I is overlapped with the coordinate of the lowest point of the distribution curve II, if so, judging that the target pipeline is not damaged; and if not, the position corresponding to the abscissa of the lowest point of the distribution curve I is a damaged point. The detection method can be used for realizing anticorrosive coating damage detection and damaged point positioning regardless of the influence of environmental electromagnetic interference and under the condition of no excavation.
Description
Technical Field
The invention relates to the field of industrial nondestructive testing, in particular to a buried pipeline anticorrosive coating damage detection method based on induced voltage distribution.
Background
Pipeline transportation is a transportation mode for long-distance transportation of liquid and gas materials by using pipelines as transportation tools, is a transportation mode for specially transporting petroleum, natural gas and chemical products to markets from production places, and is a special component part for trunk transportation in a uniform transportation network. In the operation of buried pipelines, a pipeline anticorrosive coating is the most important barrier for preventing corrosion, and accidents such as cracking and perforation of a pipe body caused by the damage of the pipeline anticorrosive coating not only affect the normal production and operation of the pipeline, but also cause huge energy waste and economic loss, and simultaneously cause environmental pollution and loss of lives and properties, so that the detection work of the damage of the pipeline anticorrosive coating is the key work for ensuring the safe operation of the pipeline, and is also a technical difficulty, the existing pipeline anticorrosive coating damage nondestructive detection and evaluation method usually has high requirements on the environment, for example, an external corrosion direct evaluation technology (ECDA) is a set of commonly used and mature method for detecting and evaluating the corrosion of the pipeline anticorrosive coating, as is well known, the ECDA technology has high requirements on the cleanness of an electromagnetic environment, but due to the limitations of conditions such as population density, land resources, geographical environment and the like, buried oil and gas transmission metal pipelines are often built in public energy corridors with high-voltage transmission lines. In a public energy corridor, the high-voltage transmission line inevitably generates electromagnetic interference on adjacent metal pipelines. Alternating current flowing in the power transmission line excites a magnetic field in air and soil, and the buried pipeline can generate induced electromotive force along the axis of the pipeline when being in the magnetic field. From the perspective of a circuit, the metal pipeline can be regarded as a pi-type distributed circuit similar to a transmission line, and according to a transmission line equation, when the pipeline generates longitudinal induced electromotive force excitation, current along the axis of the pipeline and earth leakage current are generated certainly, both of the current and the earth leakage current influence an electrical detection method in ECDA (electronic dynamic random access memory), error evaluation or leakage evaluation is caused, and the detection work of the corrosion state of an anticorrosive coating of the buried pipeline is difficult.
Therefore, a method for accurately judging whether the pipeline anticorrosive coating is damaged and positioning the damaged point regardless of the influence of environmental electromagnetic interference is needed.
Disclosure of Invention
In view of this, the invention provides a method for detecting damage of an anticorrosive coating of a buried pipeline based on induced voltage distribution, which can accurately judge whether the anticorrosive coating of the pipeline is damaged and locate a damaged point regardless of the influence of electromagnetic interference of the environment.
The invention provides a buried pipeline anticorrosive coating damage detection method based on induced voltage distribution, which is characterized by comprising the following steps of: the method comprises the following steps:
s1: constructing a target pipeline potential testing system;
s2: measuring and recording the induced voltage of each section of the target pipeline;
s3: fitting an induced voltage distribution curve I of each segment of a target pipeline according to the coordinate value of the induced voltage, and determining the coordinate of the lowest point of the distribution curve I;
s4: acquiring an induced voltage distribution curve II of the target pipeline in an undamaged state, and determining the coordinate of the lowest point of the distribution curve II;
s5: judging whether the coordinate of the lowest point of the distribution curve I is overlapped with the coordinate of the lowest point of the distribution curve II, if so, judging that the target pipeline is not damaged; and if not, the position corresponding to the abscissa of the lowest point of the distribution curve I is a damaged point.
And furthermore, the potential testing system comprises a potential testing pile, a reference electrode and a digital voltmeter, wherein the potential testing pile is buried underground at the position of the target pipeline, the reference electrode is placed on the ground 1m away from the potential testing pile during measurement, the reference electrode is connected with the grounding end of the digital voltmeter through a cable, and the red wiring end of the potential testing pile and the voltage wiring end of the digital voltmeter are connected through another cable.
Further, the potential testing systems are distributed along the length direction of the target pipeline at equal intervals.
Further, the step S1 further includes setting a reference point of the target pipeline, and setting a pipeline length of the reference point to 0 meter.
Further, the step S2 is to electrically connect two ends of the digital voltmeter with the potential testing pile cable and the reference electrode respectivelyConnecting with cable, reading the value of digital voltmeter, recording the distance between the current potential test pile and the reference point, and forming coordinate value A of distance and induced voltagei(X, V), where X denotes a distance from the reference point of the ith potential testing pile, V denotes an induced voltage of the ith potential testing pile, i is 1,2,3 … n, and n denotes the number of potential testing piles.
Further, the distribution curve takes the distance from the potential testing pile to a reference point as an abscissa and takes the induced voltage of the potential testing pile as an ordinate.
Further, the step S4 includes the steps of:
s401: determining the induced voltage of each section of the target pipeline in an undamaged state: calculating the induction voltage of each segment by the formula (1);
wherein, U represents the induced voltage, gamma represents the transmission coefficient of the equivalent circuit of the buried pipeline, and E represents the induced electromotive force; l represents the total length of the buried pipeline and x represents the distance from a reference point;
s402: the calculated values of induced voltage were curve fitted using a curve fitting tool in Matlab.
The invention has the beneficial technical effects that: the application provides a buried pipeline anticorrosive coating damage detection method based on induced voltage distribution is used for the parallel buried pipeline that has come into use and the transmission line is neighbouring, and it can be regardless of environmental electromagnetic interference influence, can realize anticorrosive coating damage detection and damaged point location simultaneously under the condition of not digging.
Drawings
The invention is further described below with reference to the following figures and examples:
fig. 1 is a flowchart of the breakage detection of the present application.
FIG. 2 is a schematic diagram of the potential testing system of the present application.
Fig. 3 is a schematic diagram of the distribution curve ii of the non-broken case and the distribution curve i of the actual case of the present application.
Detailed Description
The invention is further described with reference to the accompanying drawings in which:
the invention provides a buried pipeline anticorrosive coating damage detection method based on induction voltage distribution, which is characterized by comprising the following steps: the method comprises the following steps: as shown in figure 1 of the drawings, in which,
s1: constructing a target pipeline potential testing system;
s2: measuring and recording the induced voltage of each section of the target pipeline;
s3: fitting an induced voltage distribution curve I of each section of a target pipeline according to the measured value of the induced voltage, and determining the coordinate of the lowest point of the distribution curve I;
s4: acquiring an induced voltage distribution curve II of the target pipeline in an undamaged state, and determining the coordinate of the lowest point of the distribution curve II;
s5: judging whether the coordinate of the lowest point of the distribution curve I is overlapped with the coordinate of the lowest point of the distribution curve II, if so, judging that the target pipeline is not damaged; and if not, the position corresponding to the abscissa of the lowest point of the distribution curve I is a damaged point. The coincidence means that the coordinate of the lowest point of the distribution curve I is completely equal to the coordinate value of the lowest point of the distribution curve II, or the deviation of the two is within a preset range, wherein the preset range is +5 percent, namely the two are
The value of the difference of-divided by the coordinate of the lowest point of the distribution curve ii is within 5%.
The method is suitable for the pipeline buried in the public energy corridor and meets the following two conditions: the first is that: the target buried pipeline is parallel or approximately parallel to the adjacent high-voltage transmission line, wherein the approximately parallel refers to the parallel which is laid according to the parallel standard of the buried pipeline and the high-voltage transmission line and has deviation in the actual engineering; secondly, the following steps: buried pipelines with parallel lengths greater than 10 km.
The traditional method for actively injecting a detection signal to obtain a response signal is not adopted for judging the state of the anticorrosive coating, because the method is necessarily influenced in the environment with electromagnetic interference. Because the induced electromotive force generated by the adjacent high-voltage transmission line on the parallel buried pipeline can be considered to be equal everywhere, the induced voltage formed under the excitation is regularly and symmetrically distributed according to the transmission line equation, and the damage of the symmetry can judge that the pipeline anticorrosive coating is damaged and position the damaged position. The invention can be directly applied to the parallel buried pipelines which are used and are adjacent to the transmission line, does not need to reinstall equipment on the pipeline engineering or the potential measurement system, is simple and easy to operate, and can realize accurate anticorrosive coating damage detection without digging the ground.
In this embodiment, as shown in fig. 2, the electric potential testing system includes an electric potential testing pile, a reference electrode and a digital voltmeter, the electric potential testing pile is buried underground at the position of the target pipeline, the reference electrode is placed on the ground 1m away from the electric potential testing pile during measurement, the reference electrode and a grounding terminal of the digital voltmeter are connected by a cable, and a red terminal of the electric potential testing pile and a voltage terminal of the digital voltmeter are connected by another cable. And respectively carrying out temporary grounding treatment on the head end and the tail end of the target pipeline through a grounding rod. All cables are led to the wiring terminals through the bottoms of the steel pipes of the test piles; after the test pile is buried underground, concrete is poured, the test pile is perpendicular to the ground, firm and reliable, the electric connection with the pipeline is effective, and the door of the test pile is locked. During testing, only the testing pile door needs to be opened, the digital voltmeter is adjusted to a proper range gear, then the two ends of the digital voltmeter are respectively connected with the corresponding wiring terminals, and data are read and recorded.
In this embodiment, the electric potential testing systems are distributed along the length direction of the target pipeline at equal intervals. The equal spacing can be set to 1-3 kilometers, and in the embodiment, 1 kilometer is selected as the equal spacing. The step S1 further includes setting a reference point of the target pipe, and setting a pipe length of the reference point to 0 meter. The distance of the potential testing pile is convenient to count. By the technical scheme, a smooth curve can be fitted according to the coordinate values of the induction voltages, and suspicious points of pipeline anticorrosive coating damage can be found visually and accurately from the potential curve.
In this embodiment, the step S2 is to respectively connect two ends of the digital voltmeterConnecting with potential test pile cable and reference electrode cable, reading value of digital voltmeter, recording distance between current potential test pile and reference point, and forming coordinate value A of distance and induced voltagei(X, V), where X denotes a distance from the reference point of the ith potential testing pile, V denotes an induced voltage of the ith potential testing pile, i is 1,2,3 … n, and n denotes the number of potential testing piles. And sequentially measuring until all the potential testing piles are tested.
The distribution curve takes the distance from a reference point of the electric potential testing pile as an abscissa, the distribution curve comprises a distribution curve I and a distribution curve II, and the induced voltage of the electric potential testing pile is taken as an ordinate. The distance and the coordinate value A of the induced voltage are measurediInputting the voltage into Matlab software, and fitting by a curve fitting tool of the Matlab software to form a voltage V with a horizontal coordinate of the unit of the distance of the potential testing pile and a vertical coordinate of the unit of kilometer km of the induced voltage of the potential testing pile;
in this embodiment, the step S4 includes the following steps:
s501: determining the induced voltage of each section of the target pipeline in an undamaged state: calculating the induction voltage of each segment by the formula (1);
wherein, U represents the induced voltage, gamma represents the transmission coefficient of the equivalent circuit of the buried pipeline, and E represents the induced electromotive force; l represents the total length of the buried pipeline and x represents the distance from a reference point; obtaining the coordinate value A of the distance and the induction voltagej(X, V), where X denotes a distance from the reference point of the jth potential testing pile, V denotes an induced voltage of the jth potential testing pile, j is 1,2,3 … n, and n denotes the number of potential testing piles. And sequentially measuring until all the potential testing piles are tested. In order to facilitate the comparison of the subsequent fitting curve I and the fitting curve II, the position of the potential testing pile and the reference point of the target pipeline under the undamaged condition are consistent with the position of the potential testing pile and the reference point of the target pipeline in actual measurement.
S502: the calculated values of induced voltage were curve fitted using a curve fitting tool in Matlab. The distance obtained by the equation (1) and the coordinate value A of the induced voltagejInputting the voltage into Matlab software, and fitting by a curve fitting tool of the Matlab software to form a voltage V with the abscissa of the unit of the distance of the potential testing pile and the kilometer km and the ordinate of the induced voltage of the potential testing pile.
As shown in fig. 3, a comparison graph of the fitting curve ii in the non-damaged state and the fitting curve i in the actual measurement state shows that the electromagnetic interference on the buried pipeline can generate induced electromotive force distributed along the pipeline axis, and the magnitude of the induced electromotive force mainly depends on the geometric distance between the pipeline and the power transmission line, the magnitude and frequency of the current flowing through the power transmission line, and the soil resistivity. When the high-voltage transmission line is in steady operation, the magnitude of the induced electromotive force on the equally spaced segments can be considered to be constant for a buried pipeline laid parallel to the high-voltage transmission line. According to the solution of the transmission line equation, the distribution curve of the pipeline to the ground potential is a V-shaped highly symmetrical curve, and the symmetrical center, namely the lowest point of the potential, is just at the midpoint of the pipeline. The transmission line equation of the buried pipeline is as follows:
wherein z is unit impedance (omega/m) of the pipeline unit, y is unit admittance (S/m) of the pipeline unit, E is induced electromotive force (V) generated by inductive coupling of the pipeline unit, I is current (A) flowing through the pipeline unit, U is induced voltage (V) of the pipeline unit, and x is length (m) from a reference starting point. This property can be used to detect and locate pipe corrosion protection failures.
Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.
Claims (7)
1. A buried pipeline anticorrosive coating damage detection method based on induced voltage distribution is characterized in that: the method comprises the following steps:
s1: constructing a target pipeline potential testing system;
s2: measuring and recording the induced voltage of each section of the target pipeline;
s3: fitting an induced voltage distribution curve I of each segment of a target pipeline according to the coordinate value of the induced voltage, and determining the coordinate of the lowest point of the distribution curve I;
s4: acquiring an induced voltage distribution curve II of the target pipeline in an undamaged state, and determining the coordinate of the lowest point of the distribution curve II;
s5: judging whether the coordinate of the lowest point of the distribution curve I is overlapped with the coordinate of the lowest point of the distribution curve II, if so, judging that the target pipeline is not damaged; and if not, the position corresponding to the abscissa of the lowest point of the distribution curve I is a damaged point.
2. The buried pipeline anticorrosive coating damage detection method based on induced voltage distribution is characterized in that: the potential testing system comprises a potential testing pile, a reference electrode and a digital voltmeter, wherein the potential testing pile is buried underground at the position of a target pipeline, the reference electrode is placed on the ground 1m away from the potential testing pile during measurement, the reference electrode is connected with the grounding end of the digital voltmeter through a cable, and the red wiring end of the potential testing pile and the voltage wiring end of the digital voltmeter are connected through another cable.
3. The buried pipeline anticorrosive coating damage detection method based on induced voltage distribution is characterized in that: the potential testing systems are distributed at equal intervals along the length direction of the target pipeline.
4. The buried pipeline anticorrosive coating damage detection method based on induced voltage distribution is characterized in that: the step S1 further includes setting a reference point of the target pipe, and setting a pipe length of the reference point to 0 meter.
5. The buried pipeline anticorrosive coating damage detection method based on induced voltage distribution is characterized in that: step S2 is to connect two ends of the digital voltmeter with the electric potential testing pile cable and the reference electrode cable respectively, read the value of the digital voltmeter, and record the distance between the current electric potential testing pile and the reference point, to form the coordinate value a of the distance and the induced voltagei(X, V), where X denotes a distance from the reference point of the ith potential testing pile, V denotes an induced voltage of the ith potential testing pile, i is 1,2,3 … n, and n denotes the number of potential testing piles.
6. The buried pipeline anticorrosive coating damage detection method based on induced voltage distribution is characterized in that: the distribution curve takes the distance from the potential testing pile to a reference point as an abscissa and takes the induced voltage of the potential testing pile as an ordinate.
7. The buried pipeline anticorrosive coating damage detection method based on induced voltage distribution is characterized in that: the step S4 includes the steps of:
s401: determining the induced voltage of each section of the target pipeline in an undamaged state: calculating the induction voltage of each segment by the formula (1);
wherein, U represents the induced voltage, gamma represents the transmission coefficient of the equivalent circuit of the buried pipeline, and E represents the induced electromotive force; l represents the total length of the buried pipeline and x represents the distance from a reference point;
s402: the calculated values of induced voltage were curve fitted using a curve fitting tool in Matlab.
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