CN113916768A - Experimental device and method for researching interference influence of grounding electrode discharge on buried pipeline - Google Patents
Experimental device and method for researching interference influence of grounding electrode discharge on buried pipeline Download PDFInfo
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Abstract
The invention provides an experimental device and method for researching interference influence of grounding electrode discharge on a buried pipeline. The experimental device comprises a pipeline test piece, a grounding electrode direct current interference simulation system, a cathode protection system and an interference test system. The pipeline test piece is provided with a cathode region coating defect and an anode region coating defect, and the grounding electrode interference simulation system can simulate the discharging current of the grounding electrode so as to simulate a cathode corrosion region and an anode corrosion region under the protection of the cathode. The cathodic protection system can provide cathodic protection for the pipeline. The interference test system enables anode zone electrochemical testing. The experimental method was carried out using the experimental set-up described above. The beneficial effects of the invention can include: the cathode and anode reactions of the pipelines at the current inflow and outflow points in the indoor grounding electrode discharge environment can be simulated simultaneously, and reference is provided for the evaluation and prevention and control of the interference influence of the grounding electrode discharge of the high-voltage transmission line on the buried steel oil-gas pipeline.
Description
Technical Field
The invention relates to the technical field of corrosion simulation experiments and measurement, in particular to an electrochemical experimental device and an experimental method for researching the interference influence of high-voltage direct-current grounding electrode discharge on a buried pipeline.
Background
China is wide in territory, energy is mainly distributed in western regions, population and industry are mainly concentrated in eastern regions, so that long-distance, high-capacity, high-efficiency and low-cost energy transmission strategies are developed at the same time, and high-voltage power grids and long-distance oil and gas transmission pipe network projects are also in peak construction. By the end of 2020, China has become the world with the largest number of direct current transmission projects, the highest voltage level and the largest transmission capacity. The direct current transmission project and the long-distance oil and gas transmission pipe network have very similar site selection requirements, the direct current transmission project and the long-distance oil and gas transmission pipe network can be crossed or overlapped on a transmission path, the direct current grounding electrode is not adjacent to a buried oil and gas pipeline frequently, and the buried steel pipeline cannot be prevented from being influenced by the interference of the direct current grounding electrode grounding current.
When the system normally operates, the unbalanced current passing through the grounding electrode is only 1% of the rated direct current of the system, and the interference to the surrounding buried pipelines is small. When a power transmission system is debugged or has a fault, the power transmission system is converted into monopolar operation, the earth is added into the power transmission system as a conducting wire, current flows through the earth from a receiving end grounding electrode and returns to a transmitting end grounding electrode, the earth-entering current is rated direct current of the system, the numerical value can reach thousands of amperes, the coating of the buried pipeline can be punctured by large current in the moment, the cathode protection equipment nearby can be burnt, and personal injury is caused to operators. The current flows into the pipeline, the cathode reaction occurs at the metal/electrolyte interface, the potential of the pipeline is caused to shift towards the negative direction, and the excessive cathode current or oxygen deficiency can cause the water to be decomposed to generate OH-And H, OH-The pH value of the surface of the pipeline is increased, and the coating can be peeled off due to serious hydrogen evolution reaction; atomic hydrogen dissolved in a metal pipeline can cause hydrogen damage to a steel pipe; the current flows out of the pipeline, and the metal/electrolyte interface undergoes anodic reaction, so that the anode is dissolved and corroded; at the same time, the interference may cause cathodic under-protection, increasing the risk of corrosion of the pipe.
At present, the direct-current grounding electrode has not been studied for the influence of the interference and corrosion of the metal pipeline, and the existing research results generally adopt field tests, indoor simulation calculations and the like to detect the influence of the discharge of the direct-current grounding electrode on the pipeline interference. On-site testing generally carries out a cathodic protection effectiveness test of an interference pipeline, a test piece method carries out corrosion rate detection, electric potential remote monitoring and the like; and the other method is to perform indoor pipeline material polarization curve test, anode reflection simulation, interference simulation calculation and the like. The pipeline service field environment is complex, the discharge polarity may be cathode or anode when the grounding electrode is operated in a single pole mode in practice, the detection results of single cathode protection effectiveness or test piece corrosion rate and the like are not matched with the indoor simulation test, and the two tests often have great errors, so that the experimental data can not truly reflect the interference influence of the grounding electrode on the buried pipeline.
The interference influence degree generated by the discharge of the high-voltage direct-current grounding electrode is far greater than that of a conventional stray current interference source, and under the condition of large-amplitude high-voltage direct-current interference, the electrochemical polarization rule and corrosion behavior of a metal/soil interface at the defect of a pipeline coating, the electromigration of soil water and ions in an electric field, the electric effect and the thermal effect of soil and other phenomena and problems are not clear; in addition, the polarity of the grounding electrode and the single-pole operation time are uncertain, the high-voltage direct-current interference also has the characteristics of high interference intensity, large influence range, short interference time and the like, the time and the labor are consumed in field detection and research, and the quantitative research is difficult.
Therefore, it is necessary to develop a set of experimental device and method, which can simultaneously simulate the cathode reaction of the pipeline at the discharge current inflow point of the grounding electrode and the anode reaction of the pipeline at the current outflow point indoors, quantitatively research and evaluate the corrosion behavior and the hydrogen damage characteristics and rules of the pipeline material under different interference levels, and realize the indoor simulation experimental research aiming at the interference influence of the discharge of the grounding electrode of the high voltage direct current transmission line on the buried steel pipeline.
Disclosure of Invention
The present invention aims to address at least one of the above-mentioned deficiencies of the prior art. For example, the anode reaction of indoor simulation is asynchronous with field detection, and the reference value of the result is reduced due to the fact that the ground electrode is interfered with the buried pipeline really. As another example, the room disturbance influencing parameter simulation test simulates only the anode reaction.
In order to achieve the above object, an aspect of the present invention provides an experimental apparatus for studying an influence of ground electrode discharge on a buried pipeline, wherein the ground electrode is a ground electrode of a high voltage direct current transmission line, and the apparatus includes a pipeline test block, a ground electrode direct current interference simulation system, a cathode protection system, and a ground electrode interference test system. The surface of the pipeline test piece is coated with a coating which is a polyethylene anticorrosive coating, an epoxy powder anticorrosive coating or a petroleum asphalt anticorrosive coating with a three-layer structure, and the coating has the coating defects of a cathode area and the coating defects of an anode area. The grounding electrode direct current interference simulation system comprises a direct current power supply control unit, a cathode area electrolytic cell and an anode area electrolytic cell. The direct current power supply is used for simulating the discharge current of the grounding electrode and can control the current intensity, the positive electrode of the direct current power supply is connected with the electrolytic cell in the cathode area, and the negative electrode of the direct current power supply is connected with the electrolytic cell in the anode area. The cathode area electrolytic cell is filled with corrosive medium, the corrosive medium is in defect contact with the cathode area coating, and the cathode area electrolytic cell can simulate a corrosive cathode area caused by the fact that discharge current of a grounding electrode flows into a pipeline under cathode protection. The anode area electrolytic cell is filled with a corrosion medium, the corrosion medium is in defect contact with the anode area coating, and the anode area electrolytic cell can simulate a corrosion anode area caused by a discharge current flowing out of a pipeline of a grounding electrode under the protection of a cathode. The cathodic protection system is capable of providing cathodic protection to the pipe. The interference test system comprises a reference electrode, a test counter electrode, an electrochemical workstation and a computer. The electrochemical workstation is capable of testing electrochemical parameters. The computer is connected to the electrochemical workstation and is capable of recording the electrochemical parameters. Three electrodes of the electrochemical workstation are respectively connected with a test wiring point, a reference electrode and a test counter electrode through lines to form a three-electrode system. The test wiring point is located on the pipeline and is located between the cathode electrolytic cell and the anode area electrolytic cell, the test wiring point is closer to the anode area electrolytic cell and is closer to the anode area electrolytic cell, one end, which is not connected with the electrochemical workstation, of the reference electrode is arranged in a corrosion medium of the anode area electrolytic cell, the test counter electrode is arranged in the corrosion medium of the anode area electrolytic cell, and the electrochemical parameters comprise an open circuit potential of coating defects of the anode area.
In an exemplary embodiment of the invention, the direct current source is connected to the cathode area cell via a first pair of electrodes arranged in the aggressive medium of the cathode area cell, the direct current source is connected to the anode area cell via a fourth pair of electrodes arranged in the aggressive medium of the anode area cell.
In an exemplary embodiment of the invention, the experimental set-up further comprises a pH meter capable of monitoring the pH value of the corrosive medium in the cathode compartment electrolytic cell.
In one exemplary embodiment of the invention, the experimental set-up further comprises an oxygen removal device capable of removing oxygen from the cathode area cell.
In an exemplary embodiment of the invention, the corrosive medium is soil or a soil solution.
In an exemplary embodiment of the invention, the area of the coating defect of the cathode region is 7-10 cm2The area of the coating defect of the anode region is 7-10 cm2。
In one exemplary embodiment of the invention, the area of the cathode region coating defect is 6.5cm2The area of the coating defect of the anode region is 6.5cm2。
In one exemplary embodiment of the invention, the cathode region coating defect area is equal to the anode region coating defect area.
The invention also provides an experimental method for researching the interference influence of the grounding electrode discharge on the buried pipeline. The method uses the experimental device for researching the interference influence of the grounding electrode discharge on the buried pipeline, and comprises the following steps: and (3) deoxidizing: removing oxygen in the electrolytic cell in the cathode area; and (3) cathodic protection: starting a cathode protection system to provide cathode protection for the coating defects of the cathode region and the coating defects of the anode region; simulating discharge: starting a direct current power supply, setting a current value, and providing simulated earth electrode discharge current for the cathode region coating defects and the anode region coating defects; and (3) testing: starting a computer, setting measurement parameters of an electrochemical workstation, and measuring the electrochemical parameters; sampling and observing: and disconnecting all power supplies, taking down the cathode area electrolytic cell and the anode area electrolytic cell, sampling the coating defects of the cathode area and the anode area, and testing the interference data of the earth electrode discharge on the buried pipeline. The data of the interference of the discharge of the grounding electrode on the buried pipeline comprises any one or more of the electrochemical parameters, the corrosion appearance of the coating defects of the cathode region and the coating defects of the anode region of the pipeline coating, corrosion weight loss, current density curve integral, yield strength, tensile strength and elongation rate.
In an exemplary embodiment of the invention, the method further comprises: the experiment was repeated: and (3) changing any one of the direct current intensity, the coating type, the coating thickness, the corrosion medium type, the cathode region coating defect area and the anode region coating defect area according to the sampling observation result, and then repeating the steps of simulating discharge, testing and sampling observation on the cathode region coating defect and the anode region coating defect until enough data of the interference of the ground electrode discharge on the buried pipeline is obtained.
Compared with the prior art, the beneficial effects of the invention can include: (1) the cathode and anode reactions of the current inflow and outflow points on the pipeline can be simulated indoors in the discharge environment of the grounding electrode at the same time; (2) the corrosion and hydrogen damage rules of the pipeline under different interference levels can be quantitatively researched and evaluated; (3) the method can be used for acquiring comprehensive and reliable data for simulating the interference of the discharge of the grounding electrode of the high-voltage transmission line on the buried pipeline indoors; (4) the corrosion simulation experiment of the anode region and the cathode region of the pipeline under the combined action of electrical interference and cathode protection can be synchronously carried out, and the influence rule of the interference current intensity on the pH value of the cathode reaction interface of the pipeline, the hydrogen evolution degree, the interference current intensity, the duration, the interference period, the cathode protection level and the like on the corrosion of the pipeline in the anode region is synchronously evaluated; (5) the method can provide reference for evaluation and prevention and control of the interference influence of the discharge of the grounding electrode of the high-voltage transmission line on the oil-gas pipeline.
Drawings
FIG. 1 shows a schematic structural diagram of an experimental apparatus for studying the interference effect of earth electrode discharge on a buried steel pipeline in an exemplary embodiment of the invention;
FIG. 2 shows an applied Anodic DC interference curve in an exemplary embodiment of the invention, with Time on the abscissa representing Time(s) and Potential on the ordinate representing Potential (vs. SCE/V), and the Anodic interference representing Anodic interference;
FIG. 3 illustrates an applied cathodic current disturbance curve in an exemplary embodiment of the present invention, with Time on the abscissa representing Time(s) and Potential on the ordinate representing Potential (vs. SCE/V);
FIG. 4 shows a corrosion behavior curve of a HVDC voltage disturbance specimen of pipeline steel in acid soil with Time on the abscissa representing Time(s) and iDC on the ordinate representing current density (A.m) in an exemplary embodiment of the invention-2)。
The labels in the figure are:
1-pipeline test piece, 2-coating, 3-cathode region coating defect, 4-anode region coating defect, 5-cathode region electrolytic cell, 6-anode region electrolytic cell, 71-first pair of electrodes, 72-second pair of electrodes, 73-third pair of electrodes, 74-fourth pair of electrodes, 75-test pair of electrodes, 81-oxygen-removing air inlet pipe, 82-oxygen-removing air outlet pipe, 9-pH meter, 10-potentiostat, 11-direct current power supply, 12-ammeter, 13-reference electrode, 14-electrochemical workstation, 15-computer and 16-test wiring point.
Detailed Description
Hereinafter, the experimental apparatus and method for studying the interference effect of the earth electrode discharge on the buried pipeline according to the present invention will be described in detail with reference to exemplary embodiments. Herein, "first," "second," "third," "fourth," and the like are for convenience of description and for ease of distinction only and are not to be construed as indicating or implying relative importance or a strict order of magnitude.
Detailed illustrative embodiments are disclosed in the present invention. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. This invention may, however, be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein.
Accordingly, while example embodiments are capable of various modifications and alternative forms, these embodiments are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments to the particular forms disclosed. Rather, the example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure. Like reference numerals refer to like elements throughout the description of the figures.
In the description of the present application, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present application and simplifying the description, but do not indicate or imply that the referred device or element must have a particular orientation, be constructed in a particular orientation, and be operated, and thus should not be construed as limiting the present application.
In a first exemplary embodiment of the present invention, as shown in fig. 1, the experimental apparatus for studying the interference effect of the earth electrode discharge on the buried pipeline may include a pipeline test block 1, an earth electrode direct current interference simulation system, a cathode protection system, and an interference test system. Here, the buried pipeline is a buried steel pipeline. Here, fig. 1 shows a schematic structural diagram of an experimental apparatus for studying the influence of ground electrode discharge on the interference of a buried pipeline in this embodiment.
Wherein, the surface of the pipeline test piece 1 is coated with a coating 2, the pipeline test piece 1 adopts the same material of a research pipeline, can be X65, X70 or X80 and the like, and the coating 2 has a cathode region coating defect 3 and an anode region coating defect 4. Here, the coating layer 2 may be a polyethylene anticorrosive coating layer, an epoxy powder anticorrosive coating layer, or a petroleum asphalt anticorrosive coating layer of a three-layer structure.
The area of the cathode region coating defect 3 may be 6.5cm2The area of the coating defect 4 of the anode region can be 6.5cm2。
The area of the coating defect 3 of the cathode region can be 7-10 cm2E.g. 7.5cm2、8cm2、8.5cm2、9cm2Or 9.5cm2The area of the coating defect 4 in the anode region can be 7-10 cm2E.g. 7.5cm2、8cm2、8.5cm2、9cm2Or 9.5cm2。
The cathode region coating defects 3 and the anode region coating defects 4 may have the same area or different areas. For example, the cathode region coating defect 3 and the anode region coating defect 4 are both 7.5cm2To be as close as possible to the maximum defect area of the pipe coating. The same corrosion reaction parameters can be created due to the consistent defect areas of the coating, and the reference comparison data of the test for changing the defect area parameters of the coating are also facilitated.
The grounding electrode direct current interference simulation system comprises a direct current power supply 11, a cathode area electrolytic cell 5 and an anode area electrolytic cell 6. The direct current power supply 11 is used for simulating the discharge current of the grounding electrode of the high-voltage direct current transmission line, and can control the current intensity, so as to simulate the corrosion cathode region and the corrosion anode region on the pipeline test piece 1 under cathodic protection. The anode of the direct current power supply 11 is connected with the cathode area electrolytic cell 5, and the cathode is connected with the anode area electrolytic cell 6.
In an exemplary embodiment of the present invention, for example, as shown in fig. 1, the ground dc interference simulation system may further include an ammeter 12 for testing the current magnitude of the dc power supply 11.
And a corrosive medium is arranged in the cathode area electrolytic cell 5 and can be in contact with the cathode area coating defect 3, and the cathode area electrolytic cell 5 can simulate a corrosion cathode area caused by the fact that discharge current of a grounding electrode flows into the pipeline test piece 1 under cathode protection. Also be equipped with in the positive pole district electrolysis trough 6 and corrode the medium, and corrode the medium with the contact of positive pole district coating defect 4, positive pole district electrolysis trough 6 can simulate under the cathodic protection and extremely discharge current and flow out the corruption positive pole district that pipeline test block 1 caused. Here, the corrosion medium may be soil or a soil solution according to the test requirements, and the type of the soil or the soil solution may also be selected according to the test requirements.
In an exemplary embodiment of the present invention, for example, as shown in fig. 1, the cathode-area electrolytic cell 5 may be provided with a cathode-area electrolytic cell cover plate, and the anode-area electrolytic cell 6 may be provided with an anode-area electrolytic cell cover plate to avoid external interference.
For example, the dc power source 11 may be connected to the cathode section 5 through a first pair of electrodes 71, and the first pair of electrodes 71 is disposed in the corrosive medium of the cathode section 5, the dc power source 11 is connected to the anode section 6 through a fourth pair of electrodes 74, and the fourth pair of electrodes 74 is disposed in the corrosive medium of the anode section 6 for providing dc current to the cathode section coating defects 3 and the anode section coating defects 4 of the coating 2 to simulate a ground discharge. Here, each of the first counter electrode 71 and the fourth counter electrode 74 may be a cathode electrode material such as a platinum-plated titanium mesh, a platinum sheet, or a stainless steel sheet.
The cathodic protection system can provide cathodic protection for the pipeline test piece 1, and further provide cathodic protection potential for the coating defect 3 of the cathode region and the coating defect 4 of the anode region on the pipeline test piece 1, so as to simulate the actual pipeline cathodic protection.
The cathodic protection system can comprise a potentiostat 10, a second counter electrode 72 and a third counter electrode 73, wherein the positive electrode of the potentiostat 10 is connected with the second counter electrode 72 and the third counter electrode 73, the second counter electrode 72 is arranged in a corrosive medium of an electrolytic cell 5 in a cathode area, the third counter electrode 73 is arranged in a corrosive medium of an electrolytic cell in an anode area, the negative electrode of the potentiostat 10 is connected with a pipeline test piece 1, and a cathodic protection potential is provided for a coating defect 3 in the cathode area and a coating defect 4 in the anode area on the pipeline test piece 1 to simulate the actual pipeline cathodic protection.
Here, the second counter electrode 72 and the third counter electrode 73 may be made of a cathode electrode material such as a platinum-plated titanium mesh, a platinum sheet, or a stainless steel sheet. Here, the cathodic protection current of the cathodic protection system is controlled by a potentiostat 10, for example, the cathodic protection current of the cathodic protection subsystem of the cathodic area is-1.05VCSE. Platinum-plated titanium mesh can be selected.
The interference test system includes a reference electrode 13, a test counter electrode 75, an electrochemical workstation 14, and a computer 15. Wherein the electrochemical workstation 14 is capable of testing electrochemical parameters. The computer 15 is connected to the electrochemical workstation 14 and is capable of recording said electrochemical parameters. And three electrodes of the electrochemical workstation 14 are respectively connected with the test wiring point 16, the reference electrode 13 and the test counter electrode 75 through lines to form a three-electrode system. One end of the reference electrode 13 is arranged in the corrosive medium of the anode area electrolytic cell 6, and the other end is connected with the electrochemical workstation 14 through a circuit. The test connection point 16 is located on the pipe coupon 1 between the cathode zone cell 5 and the anode zone cell 6 and closer to the anode zone coating defect. The test counter electrode 75 is arranged in the corrosive medium of the anode field cell 6.
Here, the electrochemical parameters include an open circuit potential of the coating defect 4 of the anode region. The reference electrode 13 can be vertically inserted into the anode region electrolytic cell 6, and one end of the reference electrode 13 extends to the lower part of the anode region electrolytic cell 6. Further, when the anode area electrolytic cell 6 is sealed by the anode area electrolytic cell 6 cover plate, the reference electrode 13 can be vertically inserted on the anode area electrolytic cell 6 cover plate. The test counter electrode 75 may be a platinum-plated titanium mesh.
In an exemplary embodiment of the invention, the experimental set-up further comprises a pH meter 9. The pH meter 9 is used for monitoring the pH value (pH value) of a corrosive medium in the electrolytic cell 5 in the cathode region and assisting in evaluating the influence of the interference current intensity on the pH value of the reaction interface of the cathode of the pipeline. For example, as shown in FIG. 1, the lower end of the pH meter 9 extends to the lower portion inside the cathode field cell 5 to measure the pH value of the corrosive medium of the cathode field cell 5.
In an exemplary embodiment of the invention, the experimental set-up further comprises an oxygen removal device capable of removing oxygen from the cathode compartment cell 5 to maintain a true pH in the cell during the reaction. The oxygen removing device can comprise an oxygen removing air inlet pipe 81 and an oxygen removing air outlet pipe 82, for example, as shown in fig. 1, the oxygen removing air inlet pipe 81 and the oxygen removing air outlet pipe 82 are vertically inserted on the cover plate of the cathode region electrolytic cell 5, and inert gases with chemical properties such as nitrogen and the like are introduced into the cathode region corrosive medium through the oxygen removing air inlet pipe 81 so as to exhaust oxygen in the corrosive medium of the cathode region electrolytic cell 5, for example, oxygen in soil and oxygen dissolved in soil solution.
In an exemplary embodiment of the present invention, the experimental method for studying the influence of the earth electrode discharge on the interference of the buried pipeline uses the experimental apparatus for studying the influence of the earth electrode discharge on the interference of the buried pipeline described in exemplary embodiment 1, and the method includes the following steps: and (3) deoxidizing: removing oxygen from the cathode area electrolytic cell 5; and (3) cathodic protection: starting a cathode protection system to provide cathode protection for the cathode region coating defect 3 and the anode region coating defect 4; simulating discharge: starting a direct current power supply 11, setting a current value, and providing simulated earth electrode discharge current for the cathode region coating defect 3 and the anode region coating defect 4; and (3) testing: starting the computer 15, setting the measurement parameters of the electrochemical workstation 14, and measuring the electrochemical parameters; sampling and observing: disconnecting all power supplies, taking down a cathode area electrolytic cell 5 and an anode area electrolytic cell 6, sampling the cathode area coating defect 3 and the anode area coating defect 4, and testing the data of the interference of the grounding electrode discharge on the buried pipeline, wherein the data of the interference of the grounding electrode discharge on the buried pipeline comprises any one or more of the electrochemical parameters, the corrosion appearance of the pipeline coating at the cathode area coating defect 3 and the anode area coating defect 4, the corrosion weight loss, the current density curve integral, the yield strength, the tensile strength and the elongation rate. Here, the ground electrode is a ground electrode of a high voltage direct current transmission line.
Here, the oxygen removing step: oxygen is removed from the cathode area electrolytic cell 5. Here, nitrogen gas can be fed into the cathode region electrolytic cell 5 through the oxygen-removing gas feed pipe 81 to remove oxygen gas from the corrosive medium of the cathode region electrolytic cell 5.
The cathodic protection step comprises: and starting a cathode protection system to provide cathode protection for the cathode region coating defect 3 and the anode region coating defect 4. Here, the cathodic protection potential value can be set by opening the switch of the potentiostat 10 (for example, the cathodic protection point potential is set to-1.05VCSE) A cathodic protection potential is provided for the cathodic coating defect 3 and the anodic coating defect 4.
The testing step comprises the following steps: the computer 15 is turned on and the measurement parameters of the electrochemical workstation 14 are set, and the electrochemical parameters are measured. The electrochemical parameters include the anode region coating defect 4 open circuit potential. Further, the testing step can simultaneously obtain the pH value of the corrosive medium of the cathode area electrolytic cell 5 monitored by the pH meter 9 in real time.
The sampling observation step comprises: and (3) disconnecting all power supplies, taking down the cathode area electrolytic cell 5 and the anode area electrolytic cell 6, sampling the cathode area coating defect 3 and the anode area coating defect 4, and testing the interference data of the earth electrode discharge on the buried pipeline. The data of the interference of the earth electrode discharge on the buried pipeline comprise the electrochemical parameters, the cathode region coating defects 3 and the corrosion appearance, corrosion weight loss, current density curve integral, yield strength, tensile strength, elongation and the like of the cathode region coating defects 3.
In an exemplary embodiment of the invention, the experimental method for studying the influence of the earth electrode discharge on the interference of the buried pipeline further comprises repeating the experimental steps. The repeated experimental steps are as follows: and (3) carrying out a direct current gradient test on the coating defect 3 of the cathode region and the coating defect 4 of the anode region according to the result of sampling observation, changing any one of the type of the coating 2, the thickness of the coating 2, the type of the corrosion medium, the area of the coating defect 3 of the cathode region and the area of the coating defect 4 of the anode region, and repeating the steps of simulating discharge, testing and sampling observation until enough data of the interference of the discharge of the grounding electrode on the buried pipeline are obtained. The interference data of enough grounding electrode discharges on the buried pipeline can be judged according to field feedback information and experience.
In order that the above-described exemplary embodiments of the invention may be better understood, further description thereof with reference to specific examples is provided below.
Example 1
The experimental device is installed as shown in figure 1, corrosive media are respectively filled in the cathode area electrolytic cell 5 and the anode area electrolytic cell 6, and the experiment of the interference influence of the discharge of the grounding electrode of the high-voltage direct-current transmission line on the buried pipeline is carried out according to the following steps:
s1, deoxidizing the electrolytic cell 5 in the cathode region by adopting nitrogen;
s2, opening the switch of the constant potential rectifier 10, setting the cathodic protection potential value to-1.05VCSEProviding cathodic protection potentials for cathodic coating defects 3 and anodic coating defects 4;
s3, turning on a switch of the direct current power supply 11, setting a current value, and providing simulated earth electrode discharge current for the cathode region coating defect 3 and the anode region coating defect 4;
s4, opening the computer 15, setting the measurement parameters of the electrochemical workstation 14, and carrying out electrochemical parameter tests such as anode region coating defect 4 open circuit potential and the like;
s5, monitoring and recording the pH value of the corrosive medium in the electrolytic cell 5 in the cathode region in real time by using a pH meter 9;
s6, disconnecting the power supply of all the equipment, and taking down two electrolytic cells: a cathode area electrolytic cell 5 and an anode area electrolytic cell 6 are sampled at two coating defects (a cathode area coating defect 3 and an anode area coating defect 4) to carry out tests such as appearance observation, corrosion weight loss and the like;
s7, if a direct current gradient experiment needs to be carried out according to the field feedback information, or the defect area of the coating needs to be changed according to the field feedback information, or the type and the thickness of the coating needs to be changed according to the field feedback information, or if the soil and solution type needs to be changed according to the field feedback information, and other multi-parameter influence experiments, the steps S3-S6 are repeated.
S8, evaluating the corrosion rate of the pipeline material under different interference levels according to parameters such as corrosion appearance, corrosion weight loss, current density curve integral (electric quantity) value and the like of the pipeline coating defect; and evaluating the hydrogen damage degree of the pipeline material according to the mechanical performance index parameters of the yield strength, the tensile strength, the elongation and the like of the sample before and after the experiment.
By the device and the method, indoor simulation experiments are carried out, and the following rules are obtained by respectively carrying out corrosion tests on the pipeline steel under the direct current interference of the cathode and the anode with different current densities:
1) and (3) interfering with the polarization law of the pipeline coating defect: as shown in fig. 2, an anodic DC disturbance is applied and the steel potential shifts in the positive direction; as shown in fig. 3, with the application of cathodic current perturbation, the steel potential shifts negatively, with the amount of shift increasing with the perturbation current density. In FIG. 2, the abscissa Time represents Time(s), the ordinate Potential represents Potential (vs. SCE/V), and the Anodic interference represents Anodic interference. In fig. 3, the abscissa Time represents Time(s) and the ordinate Potential represents Potential (vs.
2) As shown in fig. 4, the steady state polarization potentials of the anode region (a) and the cathode region (b) of the pipeline steel under the direct current interference in the acid soil, the potentials become more positive as the current density increases in the anode region; the cathode region is more negative in potential at higher current densities. In FIG. 4, the abscissa DC current density represents the direct current interference current density (mA · cm)-2) The ordinate Potential represents the Potential (vs. SCE/V).
The result shows that the method can synchronously simulate the cathodic corrosion reaction of the pipeline at the point of the inflow of the discharge current of the grounding electrode under cathodic protection and the anodic corrosion reaction of the pipeline at the point of the outflow of the discharge current indoors, and realize the indoor simulation experiment research on the interference influence of the discharge of the grounding electrode of the high-voltage direct-current transmission line on the pipeline.
In summary, the beneficial effects of the invention can include:
(1) the device can generate direct current interference current, can simulate cathode protection, and can perform multi-factor influence experiments of different direct current densities, different pipeline materials, different coatings, different coating defect areas, different corrosion media and the like;
(2) the method can synchronously simulate the cathodic corrosion reaction of the pipeline at the point of the discharge current of the grounding electrode under cathodic protection and the anodic corrosion reaction of the pipeline at the point of the discharge current, and realize the indoor simulation experiment research on the interference influence of the discharge of the grounding electrode of the high-voltage direct-current transmission line on the pipeline;
(3) the influence rule of the interference current intensity on the pH value of the cathode reaction interface of the pipeline, the hydrogen evolution degree, the interference current intensity, the duration, the interference period, the cathode protection level and the like on the corrosion of the pipeline in the anode area can be synchronously evaluated, and reference is provided for the evaluation and prevention and control of the interference influence of the discharge of the grounding electrode of the high-voltage transmission line on the oil-gas pipeline;
(4) the corrosion and hydrogen damage rules of the pipeline under different interference levels can be quantitatively researched and evaluated, and reference is provided for evaluation, prevention and control of interference influence of discharge of the grounding electrode of the high-voltage transmission line on the oil-gas pipeline.
Although the present invention has been described above in connection with the exemplary embodiments and the accompanying drawings, it will be apparent to those of ordinary skill in the art that various modifications may be made to the above-described embodiments without departing from the spirit and scope of the claims.
Claims (10)
1. An experimental device for researching the interference influence of grounding electrode discharge on a buried pipeline is characterized in that the grounding electrode is the grounding electrode of a high-voltage direct-current transmission line, the device comprises a pipeline test piece, a grounding electrode interference simulation system, a cathode protection system and an interference test system, wherein,
the surface of the pipeline test piece is coated with a coating, the coating is a polyethylene anticorrosive coating, an epoxy powder anticorrosive coating or a petroleum asphalt anticorrosive coating with a three-layer structure, and the coating has coating defects of a cathode region and coating defects of an anode region;
the grounding electrode interference simulation system comprises a direct-current power supply control unit, a cathode area electrolytic cell and an anode area electrolytic cell,
the direct current power supply is used for simulating the discharge current of the grounding electrode and can control the current intensity, the anode of the direct current power supply is connected with the electrolytic cell in the cathode region, the cathode of the direct current power supply is connected with the electrolytic cell in the anode region,
the cathode area electrolytic cell is filled with corrosive medium, the corrosive medium is in contact with the defects of the cathode area coating, the cathode area electrolytic cell can simulate a corrosive cathode area caused by the fact that discharge current of a grounding electrode flows into a pipeline under cathode protection, the anode area electrolytic cell is filled with corrosive medium, the corrosive medium is in contact with the defects of the anode area coating, and the anode area electrolytic cell can simulate a corrosive anode area caused by the fact that discharge current of the grounding electrode flows out of the pipeline under cathode protection;
the cathodic protection system can provide cathodic protection for the pipeline test piece, the cathodic protection system comprises a potentiostat, a second pair of electrodes and a third pair of electrodes, the cathode of the potentiostat is connected with the pipeline test piece and provides cathodic protection for the pipeline test piece, and the anode of the potentiostat is respectively connected with the second pair of electrodes and the third pair of electrodes. The second pair of electrodes is arranged in the corrosive medium of the electrolytic cell in the cathode area, and the third pair of electrodes is arranged in the corrosive medium of the electrolytic cell in the anode area;
the interference test system comprises a reference electrode, a counter electrode, an electrochemical workstation and a computer, wherein the electrochemical workstation can test electrochemical parameters, the computer is connected with the electrochemical workstation and can record the electrochemical parameters, three electrodes of the electrochemical workstation are respectively connected with a test wiring point, the reference electrode and the counter electrode through lines to form a three-electrode system, the test wiring point is positioned on a pipeline and is positioned between a cathode electrolytic cell and an anode area electrolytic cell and is closer to the anode area electrolytic cell, one end of the reference electrode, which is not connected with the electrochemical workstation, is arranged in a corrosion medium of the anode area electrolytic cell, the test counter electrode is arranged in the corrosion medium of the anode area electrolytic cell, and the electrochemical parameters comprise open-circuit potential of coating defects of the anode area.
2. The experimental device for researching the interference influence of the discharge of the grounding electrode on the buried pipeline is characterized in that the direct current power supply is connected with the electrolytic cell in the cathode area through a first pair of electrodes, the first pair of electrodes are arranged in the corrosive medium of the electrolytic cell in the cathode area, the direct current power supply is connected with the electrolytic cell in the anode area through a fourth pair of electrodes, and the fourth pair of electrodes are arranged in the corrosive medium of the electrolytic cell in the anode area.
3. The experimental device for researching the interference influence of the discharge of the grounding electrode on the buried pipeline is characterized by further comprising a pH meter, wherein the pH meter can monitor the pH value of a corrosive medium in an electrolytic cell in a cathode area.
4. The experimental device for researching the interference influence of the grounding electrode discharge on the buried pipeline is characterized by further comprising an oxygen removing device, wherein the oxygen removing device can remove oxygen in the electrolytic cell in the cathode region.
5. The experimental device for researching the interference influence of the discharge of the grounding electrode on the buried pipeline is characterized in that the corrosive medium is soil or a soil solution.
6. The experimental device for researching the interference influence of the discharge of the grounding electrode on the buried pipeline is characterized in that the area of the coating defect of the cathode region is 7-10 cm2The area of the coating defect of the anode region is 7-10 cm2。
7. The experimental facility for studying the interference influence of the discharge of the grounding electrode on the buried pipeline as claimed in claim 6, wherein the area of the coating defect of the cathode region is equal to the area of the coating defect of the anode region.
8. The experimental facility for researching interference influence of discharge of the grounding electrode on a buried pipeline according to claim 1, wherein the area of the coating defect of the cathode region is 6.5cm2The area of the coating defect of the anode region is 6.5cm2。
9. An experimental method for researching the interference influence of grounding electrode discharge on a buried pipeline is characterized in that the grounding electrode is the grounding electrode of a high-voltage direct-current transmission line, the experimental device for researching the interference influence of the grounding electrode discharge on the buried pipeline is used in the method according to any one of claims 1 to 8, and the method comprises the following steps:
and (3) deoxidizing: removing oxygen in the electrolytic cell in the cathode area;
and (3) cathodic protection: starting a cathode protection system to provide cathode protection for the coating defects of the cathode region and the coating defects of the anode region;
simulating discharge: starting a direct current power supply, setting a current value, and providing simulated earth electrode discharge current for the cathode region coating defects and the anode region coating defects;
and (3) testing: starting a computer, setting measurement parameters of an electrochemical workstation, and measuring the electrochemical parameters;
sampling and observing: and disconnecting all power supplies, taking down the cathode area electrolytic cell and the anode area electrolytic cell, sampling the cathode area coating defects and the anode area coating defects, and testing the data of the interference of the grounding electrode discharge on the buried pipeline, wherein the data of the interference of the grounding electrode discharge on the buried pipeline comprises any one or more of the electrochemical parameters, the cathode area coating defects and the corrosion appearance, the corrosion weight loss, the current density curve integral, the yield strength, the tensile strength and the elongation of the pipeline test piece at the anode area coating defects.
10. The experimental method for studying the interference influence of earth electrode discharge on a buried pipeline according to claim 9, characterized in that the method further comprises:
the experiment was repeated: and (3) changing any one of the direct current intensity, the coating type, the coating thickness, the corrosion medium type, the cathode area coating defect area and the anode area coating defect area according to the sampling observation result, then repeating the steps of simulating discharge, testing and sampling observation until enough data of the interference of the ground electrode discharge on the buried pipeline is obtained.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114492141A (en) * | 2022-02-18 | 2022-05-13 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Method and device for evaluating pipeline interference of power grid system |
| CN114638510A (en) * | 2022-03-22 | 2022-06-17 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | High-voltage direct-current interference analysis method, device, equipment, system and storage medium |
| CN115014955A (en) * | 2022-05-31 | 2022-09-06 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Test method for simulating hydrogen embrittlement of buried pipeline under interference current and cathode protection |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114492141A (en) * | 2022-02-18 | 2022-05-13 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Method and device for evaluating pipeline interference of power grid system |
| CN114492141B (en) * | 2022-02-18 | 2024-06-18 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Pipeline interference assessment method and device for power grid system |
| CN114638510A (en) * | 2022-03-22 | 2022-06-17 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | High-voltage direct-current interference analysis method, device, equipment, system and storage medium |
| CN114638510B (en) * | 2022-03-22 | 2024-05-28 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | High-voltage direct-current interference analysis method, device, equipment, system and storage medium |
| CN115014955A (en) * | 2022-05-31 | 2022-09-06 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Test method for simulating hydrogen embrittlement of buried pipeline under interference current and cathode protection |
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