Method, system and device for determining ac stray current interference corrosion of buried pipeline

Abstract

The present application belongs to the technical field of oil and natural gas buried pipelines, and particularly relates to a buried pipeline alternating current stray current interference corrosion determination method, system and device, and aims to solve the problem that the prior art cannot effectively determine the corrosion degree and corrosion rate of a buried pipeline under alternating current interference. The present application provides a buried pipeline alternating current stray current interference corrosion determination method, which obtains the change of the pipeline potential with time under the combined action of the buried pipeline alternating current stray current and the buried pipeline cathode protection direct current, calculates the change of the current causing the corrosion of the buried pipeline with time, obtains the unit time corrosion rate of the buried pipeline according to the change of the current causing the corrosion of the buried pipeline with time, and predicts the annual corrosion rate of the buried pipeline. The present application can determine the corrosion rate under the interference of the buried pipeline alternating current stray current, and further predict the service life of the buried pipeline, thereby facilitating the management and maintenance of the buried pipeline.

Description

Technical Field

[0001] This invention belongs to the field of buried oil and natural gas pipeline technology, specifically relating to a method, system, and equipment for determining AC stray current interference corrosion in buried pipelines. Background Technology

[0002] With the development of the national economy, the demand for energy and transportation is increasing day by day. The mileage of AC transmission lines, AC electrified railways, and pipelines is increasing daily, and the interference of AC interference sources on buried pipelines is becoming increasingly prominent. Under long-term interference from AC transmission lines, AC electrified railways, and other AC interference sources, pipelines are prone to AC corrosion, threatening the operational safety of pipelines.

[0003] Currently, relevant domestic and international standards for AC interference, such as the "Technical Standard for DC Interference Protection of Buried Steel Pipelines" (GB50991-2014), "Evaluation of accorrosion likelihood of buried pipelines applicable to cathodically protected pipelines" (EN 15280-2013), and "Corrosion of metals and alloys - Determination of AC corrosion - Protection criteria" (ISO18086-2019), use the AC current density method. However, there is currently a lack of calculation methods for predicting AC corrosion rates both domestically and internationally. This can lead to the following consequences: when designing AC interference protection measures for pipelines, there may be an overemphasis or underemphasis on mitigation measures; although routine testing of interference voltage and current is conducted during pipeline operation, it cannot directly reflect the degree and rate of corrosion under AC interference, thus failing to predict pipeline lifespan and hindering pipeline management and maintenance.

[0004] This invention considers the potential change of the pipeline under the combined action of external AC stray current and pipeline cathodic protection DC current, so as to calculate the actual current causing pipeline corrosion, i.e. corrosion current, and then solve the corrosion rate of the pipeline under the combined action of external AC stray current and pipeline cathodic protection DC current. Summary of the Invention

[0005] In order to solve the above-mentioned problems in the prior art, namely, the problem that the prior art cannot effectively determine the degree and rate of corrosion of buried pipelines under AC interference, the first aspect of the present invention proposes a method for determining the AC stray current interference corrosion of buried pipelines.

[0006] The method includes the following steps:

[0007] Step S100: Obtain the change value of the buried pipeline potential over time under the combined action of AC stray current and DC current of cathodic protection of the buried pipeline, and construct the buried pipeline potential change curve.

[0008] Step S200: Based on the change value on the potential change curve of the buried pipeline, calculate the change value of the corrosion current that causes corrosion of the buried pipeline over time and construct the corrosion current curve of the buried pipeline.

[0009] Step S300: Obtain the current density of the corrosion current based on the change value on the corrosion current curve of the buried pipeline, and calculate the corrosion rate of the buried pipeline per unit time based on the current density of the corrosion current and the corrosion depth of the buried pipeline per unit time.

[0010] Step S400: Predict the annual corrosion rate of the buried pipeline based on the unit time corrosion rate of the buried pipeline.

[0011] In some preferred embodiments, the specific method for obtaining the "change value of pipeline potential over time under the combined action of AC stray current and cathodic protection DC current" in step S100 is as follows:

[0012] Step A110: Obtain the AC potential caused by stray AC current in the buried pipeline based on the preset first calculation method;

[0013] Step A120: Obtain the superimposed potential of the AC potential caused by the stray AC current of the buried pipeline and the DC potential of the cathodic protection of the buried pipeline. That is, obtain the value of the pipeline potential change over time under the combined action of the AC stray current of the buried pipeline and the DC current of the cathodic protection of the buried pipeline.

[0014] In some preferred embodiments, the first calculation method is a peak value calculation method for AC potential or an effective value calculation method for AC potential.

[0015] In some preferred embodiments, the specific method for step S200, "calculating the change in current causing corrosion of the buried pipeline over time based on the change in potential on the buried pipeline potential change curve," is as follows:

[0016] Step A210: Based on the equivalent diameter of the leak point in the buried pipeline coating, calculate the resistance of the exposed steel surface at the leak point relative to the distant ground and the surface area of ​​the exposed steel surface at the leak point.

[0017] Step A220: Based on the resistance of the exposed steel surface at the coating leak point relative to the distant ground and the surface area of ​​the exposed steel surface at the coating leak point, obtain the current density of the current that causes corrosion caused by the positive potential shift of the buried pipeline flowing from the exposed steel surface at the coating leak point to the soil.

[0018] In some preferred embodiments, the specific method for step S300, "calculating the corrosion rate of the buried pipeline per unit time based on the current density of the corrosion current and the corrosion depth of the buried pipeline per unit time," is as follows:

[0019] Step A310: Calculate the corrosion depth of the buried pipeline per unit time, that is, the corrosion depth of the buried pipeline within 1 second under the combined action of AC stray current and cathodic protection DC current.

[0020] Step A320: Based on the corrosion depth of the buried pipeline per unit time and the current density, calculate the corrosion depth caused by the positive shift of the potential of the buried pipeline during one cycle of the AC sine wave, which causes the current to flow from the exposed steel surface at the leak point to the soil and cause corrosion.

[0021] Step A330: Calculate the corrosion rate of the buried pipeline per unit time based on the corrosion depth caused by the current flowing from the exposed steel surface at the leak point to the soil due to the positive potential shift of the buried pipeline.

[0022] In some preferred embodiments, the specific method for step S300, "calculating the corrosion rate of the buried pipeline per unit time based on the current density of the corrosion current and the corrosion depth of the buried pipeline per unit time," is as follows:

[0023]

[0024]

[0025] Among them, v corr(1s) t1 is the cumulative corrosion rate of the buried pipeline potential shifting positively within 1 second and f cycles; f is the actual frequency of the alternating current; t1 is the start time of the buried pipeline potential shifting positively within 1 cycle, and t2 is the end time of the buried pipeline potential shifting positively within 1 cycle. V represents the corrosion depth during the time period t1 to t2 when the potential of the buried pipeline experiences a positive shift. shift(t) The positive shift of the buried pipeline potential during the time interval T' from t1 to t1; ρ soil t represents the soil resistivity near the exposed steel surface at the leak point; corr(1s) Within a time interval of 1 second, 1A / m 2 The corrosion depth of the pipe when a constant current flows out of the coating leak point; corr(t) The current density is the current density of the corrosion caused by the positive potential shift of the buried pipeline, which flows from the exposed steel surface at the leak point to the soil; M is the atomic weight of the steel; n is the number of electrons transferred; F is the Faraday constant; ρ FeLet be the density of the steel, and d be the equivalent diameter of the coating leak point. It is understood that f is preferably 50, meaning 50 cycles per second is determined based on an AC frequency of 50Hz. When the AC frequency is other values, such as 16.67Hz, 25Hz, or 60Hz, the frequency 50 in the formula should be replaced with the actual AC frequency.

[0026] In some preferred embodiments, the specific method for step S400, "calculating the annual corrosion rate of the pipeline based on the corrosion rate per unit time of the pipeline," is as follows:

[0027] v corr(1year) =365·24·60·60·v corr(1s)

[0028] Where: v corr(1year) denoted as , where is the annual corrosion rate of the buried pipeline's potential shifting in the positive direction; f is the actual frequency of the alternating current.

[0029] In some preferred embodiments, in step A210, the method for calculating the resistance of the exposed steel surface at the leak point relative to the distant ground, based on the equivalent diameter of the leak point in the buried pipeline coating, is as follows:

[0030]

[0031] Where R remote ρ is the resistance of the exposed steel surface at the leak point relative to the distant ground; ρ is the soil resistivity of the soil near the exposed steel surface at the leak point; d is the equivalent diameter of the leak point.

[0032] In a second aspect, the present invention provides a buried pipeline life detection system, which includes a detection device and a computing device. The detection device is used to detect the AC stray current of the buried pipeline, the DC current of the cathodic protection of the buried pipeline, the soil resistivity of the soil near the exposed steel surface at the leakage point of the buried pipeline coating, and the equivalent diameter of the leakage point of the buried pipeline coating.

[0033] The computing device is configured to: acquire the change value of the buried pipeline potential over time under the combined action of AC stray current and DC cathodic protection current of the buried pipeline, and construct a potential change curve of the buried pipeline; and, based on the change value on the potential change curve of the buried pipeline, calculate the change value of the corrosion current causing corrosion of the buried pipeline over time and construct a corrosion current curve of the buried pipeline; acquire the current density of the corrosion current according to the change value on the corrosion current curve of the buried pipeline, calculate the corrosion rate per unit time of the buried pipeline based on the current density of the corrosion current and the corrosion depth of the buried pipeline per unit time; predict the annual corrosion rate of the buried pipeline based on the corrosion rate per unit time of the buried pipeline, and predict the life of the buried pipeline based on the annual corrosion rate of the buried pipeline.

[0034] A third aspect of the present invention provides an electronic device comprising: at least one processor; and a memory communicatively connected to at least one of the processors; wherein the memory stores instructions executable by the processor for implementing the above-described method for determining AC stray current interference corrosion in buried pipelines.

[0035] In a fourth aspect, the present invention provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores computer instructions, which are executed by the computer to implement the above-described method for determining the corrosion caused by AC stray current interference in buried pipelines.

[0036] The beneficial effects of this invention are:

[0037] The method for determining the corrosion rate of buried pipelines due to AC stray current interference of the present invention can be applied to pipelines with cathodic protection under AC interference conditions such as interference from AC power transmission lines and AC electrified railways. It can determine the corrosion rate of buried pipelines under the interference of AC stray current, thereby predicting the lifespan of buried pipelines and facilitating the management and maintenance of buried pipelines. Attached Figure Description

[0038] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0039] Figure 1 This is a flowchart of a calculation method for AC stray current interference corrosion of buried pipelines according to an embodiment of the present invention;

[0040] Figure 2 This is a time-varying potential diagram of a typical buried pipeline under the combined action of AC and DC in one embodiment of the present invention;

[0041] Figure 3 This is a time-varying diagram of current density during a typical period of corrosion in a buried pipeline under the combined action of AC and DC, according to an embodiment of the present invention.

[0042] Figure 4 This is a time-varying potential diagram of a buried pipeline under the combined action of AC and DC in one embodiment of the present invention;

[0043] Figure 5 This is a typical time-varying potential diagram of a certain point in a pipeline caused by the dynamic AC interference of an AC electrified railway to the pipeline, according to an embodiment of the present invention.

[0044] Figure 6 This is a time-varying potential diagram of a certain point in a pipeline during a certain time period, illustrating the dynamic AC interference of an AC electrified railway on a pipeline according to an embodiment of the present invention.

[0045] Figure 7 This is a time-varying potential diagram of a certain point in a pipeline during the first 1-second time period and one cycle within a certain time period, which is an embodiment of the present invention, showing the dynamic AC interference of an AC electrified railway on a pipeline.

[0046] Figure 8 This is a time-varying potential diagram of a certain point in a pipeline during the second 1-second time period and one cycle within a certain time period, representing an embodiment of the present invention, of the dynamic AC interference of an AC electrified railway on a pipeline.

[0047] Figure 9 This is a time-varying potential diagram of a certain point in a pipeline during the third 1-second time period and one cycle within a certain time period, which is an embodiment of the present invention, showing the dynamic AC interference of an AC electrified railway on a pipeline.

[0048] Figure 10 This is a time-varying potential diagram of a certain point in a pipeline during the fourth 1-second time period and one cycle within a certain time period, representing an embodiment of the present invention, of the dynamic AC interference of an AC electrified railway on a pipeline.

[0049] Figure 11 This is a schematic diagram of the structure of a computer system suitable for implementing an electronic device according to an embodiment of the present invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0051] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0052] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0053] The present invention provides a method for determining corrosion caused by stray AC current interference in buried pipelines, such as... Figure 1 As shown, it includes the following steps:

[0054] Step S100: Obtain the change value of the buried pipeline potential over time under the combined action of AC stray current and DC current of cathodic protection of the buried pipeline, and construct the buried pipeline potential change curve.

[0055] Step S200: Based on the change value on the potential change curve of the buried pipeline, calculate the change value of the corrosion current that causes corrosion of the buried pipeline over time and construct the corrosion current curve of the buried pipeline.

[0056] Step S300: Obtain the current density of the corrosion current based on the change value on the corrosion current curve of the buried pipeline, and calculate the corrosion rate of the buried pipeline per unit time based on the current density of the corrosion current and the corrosion depth of the buried pipeline per unit time.

[0057] Step S400: Predict the annual corrosion rate of the buried pipeline based on the unit time corrosion rate of the buried pipeline.

[0058] To more clearly illustrate the method for determining AC stray current interference corrosion of buried pipelines according to the present invention, the steps in the embodiments of the method of the present invention will be described in detail below with reference to the accompanying drawings.

[0059] Figure 2 This invention provides a typical time-varying potential diagram of a buried pipeline under the combined action of AC and DC currents, applicable to the interference of AC transmission lines on pipelines. Specifically, it shows the change in potential at a point on the pipeline over time, with the horizontal axis representing time (t) and the vertical axis representing potential (V). m T represents the peak voltage of the AC current; T represents the period of the AC current; curve a under T / 2 represents the positive half-cycle of the AC current; curve a represents the sinusoidal curve of the AC current potential induced by the buried pipeline; curve b represents the cathodic protection potential curve of the buried pipeline; curve c represents the superposition potential of the AC current induced by the buried pipeline and the DC potential of the cathodic protection (i.e., the sum of the induced AC potential and the DC potential of the cathodic protection); T' represents the positive offset period of the potential after the superposition of the AC current induced by the buried pipeline and the DC potential of the cathodic protection, from time t1 to t2; curve c under T' represents the positive offset curve of the potential after the superposition of the AC current induced by the buried pipeline and the DC potential of the cathodic protection.

[0060] Alternatively, the peak value of the AC potential caused by the stray AC current in the pipeline can be used for calculation. The peak value of the AC potential can be obtained by methods such as a stray current meter (SCM) or oscilloscope that can record AC current curves and peak values.

[0061] Corrosion of buried pipelines occurs due to oxidation on the pipeline's metal surface. The pipeline's electrical potential becomes positive relative to the surrounding soil, causing current to flow from the pipeline surface into the soil, leading to corrosion. Because buried pipelines typically have a high-insulation-strength organic anti-corrosion layer, such as a three-layer polyethylene anti-corrosion layer or an epoxy powder anti-corrosion layer, corrosion usually occurs at leaks in the coating—where the anti-corrosion layer is damaged, allowing direct contact between the soil and the pipeline metal. At these points, the resistance to ground is very low. In areas where the anti-corrosion coating is intact, the high insulation resistance of the coating results in a very high resistance to ground, making it almost completely insulated. Therefore, current flows more easily from the pipeline metal into the soil at these damaged points, causing corrosion.

[0062] The method for determining AC stray current interference corrosion of buried pipelines provided in this application specifically includes the following steps:

[0063] Step S100: Obtain the change value of the buried pipeline potential over time under the combined action of AC stray current and DC current of cathodic protection of the buried pipeline, and construct the buried pipeline potential change curve.

[0064] Step S200: Based on the change value on the potential change curve of the buried pipeline, calculate the change value of the corrosion current that causes corrosion of the buried pipeline over time and construct the corrosion current curve of the buried pipeline.

[0065] Step S300: Obtain the current density of the corrosion current based on the change value on the corrosion current curve of the buried pipeline, and calculate the corrosion rate of the buried pipeline per unit time based on the current density of the corrosion current and the corrosion depth of the buried pipeline per unit time.

[0066] Step S400: Predict the annual corrosion rate of the buried pipeline based on the unit time corrosion rate of the buried pipeline.

[0067] The specific method for obtaining the "change value of pipeline potential over time under the combined action of AC stray current and cathodic protection DC current" in step S100 is as follows:

[0068] Step A110: Obtain the AC potential caused by stray AC current in the buried pipeline based on the preset first calculation method;

[0069] Step A120: Obtain the superimposed potential of the AC potential caused by the stray AC current of the buried pipeline and the DC potential of the cathodic protection of the buried pipeline.

[0070] In some preferred embodiments, the first calculation method is a peak value calculation method for AC potential or an effective value calculation method for AC potential.

[0071] The change in pipeline potential over time under the combined action of AC stray current and cathodic protection DC current is as follows:

[0072] Curve a represents the change in AC potential over time caused by stray AC current in the pipeline. According to the peak AC potential method, its mathematical expression is:

[0073]

[0074] Among them, V ac(t) AC potential caused by stray AC current in the pipeline, in volts (V). m t represents the peak value of the AC potential, in V; f represents the frequency of the AC potential, in Hz; t represents time, in s. The initial phase angle of the alternating current.

[0075] Curve b represents the cathodic protection potential of the pipeline, defined as V. cp , unit V.

[0076] See appendix Figure 2 Curve c represents the superposition potential of the induced AC current and the cathodic protection DC potential in the buried pipeline, that is, the sum of the induced AC potential and the cathodic protection DC potential:

[0077] V (t) =V ac(t) +V cp (2)

[0078] Among them, V (t) The superposition potential of the alternating current induced in the buried pipeline and the direct current potential of the cathodic protection, in V; V ac(t) AC potential caused by stray AC current in the pipeline, in volts (V). cp This represents the cathodic protection potential of the pipeline, expressed in volts (V).

[0079] The specific method for step S200, "calculating the change in current causing corrosion of the buried pipeline over time based on the change in potential curve of the buried pipeline," is as follows:

[0080] Step A210: Based on the equivalent diameter of the leak point in the buried pipeline coating, calculate the resistance of the exposed steel surface at the leak point relative to the distant ground and the surface area of ​​the exposed steel surface at the leak point.

[0081] Step A220: Based on the resistance of the exposed steel surface at the coating leak point relative to the distant ground and the surface area of ​​the exposed steel surface at the coating leak point, obtain the current density of the current that causes corrosion caused by the positive potential shift of the buried pipeline flowing from the exposed steel surface at the coating leak point to the soil.

[0082] In step A210, the method for calculating the resistance of the exposed steel surface at the leak point relative to the distant ground, based on the equivalent diameter of the leak point in the buried pipeline coating, is as follows:

[0083]

[0084] Among them, R remote ρ is the resistance of the exposed steel surface at the leak point relative to the distant ground, in Ω; ρ is the soil resistivity of the soil near the exposed steel surface at the leak point, in Ω·m; d is the equivalent diameter of the leak point, in m.

[0085] Furthermore, the exposed steel surface at the coating leak point is calculated as follows:

[0086]

[0087] Among them, A holiday The surface area of ​​the exposed steel surface at the coating leak point, in meters. 2 d is the equivalent diameter of the coating leak point, in meters.

[0088] The current density of the current causing corrosion due to the positive potential shift of the buried pipeline flowing from the exposed steel surface at the leak point into the soil is calculated as follows:

[0089]

[0090] Among them, i corr(t) This is the current density, measured in A / m, representing the current that causes corrosion due to the current flowing from the exposed steel surface at the leak point into the soil caused by a positive potential shift in buried pipelines. 2 V shift(t) V represents the positive shift in the potential of the buried pipeline during the time interval T' from t1 to t2. shift(t) =V t =V ac(t) +V cp Units: V; ρ soil d represents the soil resistivity near the exposed steel surface at the leak point, in Ω·m; d represents the equivalent diameter of the leak point in the coating, in m.

[0091] Figure 3 This invention provides a time-varying diagram of current density during the corrosion period of a typical buried pipeline under the combined action of AC and DC. T' represents the change of current density over time within the positive offset period of the potential after the superposition of the AC current induced in the buried pipeline and the DC potential of cathodic protection, from time t1 to t2.

[0092] The specific method for step S300, "calculating the corrosion rate of the buried pipeline per unit time based on the current density of the corrosion current and the corrosion depth of the buried pipeline per unit time," is as follows:

[0093] Step A310: Calculate the corrosion depth of the buried pipeline per unit time, that is, the corrosion depth of the buried pipeline within 1 second under the combined action of AC stray current and cathodic protection DC current.

[0094] Step A320: Based on the corrosion depth of the buried pipeline per unit time and the current density, calculate the corrosion depth caused by the positive shift of the potential of the buried pipeline during one cycle of the AC sine wave, which causes the current to flow from the exposed steel surface at the leak point to the soil and cause corrosion.

[0095] Step A330: Calculate the corrosion rate of the buried pipeline per unit time based on the corrosion depth caused by the current flowing from the exposed steel surface at the leak point to the soil due to the positive potential shift of the buried pipeline.

[0096] Specifically, calculate 1A / m per unit time, that is, within 1 second. 2 The corrosion depth of the pipeline when a constant current flows out of the coating leak point.

[0097]

[0098] Where: t corr(1s) Within a time interval of 1 second, 1A / m 2 The corrosion depth of the pipe when a constant current flows out of the coating leak point, in cm; M is the atomic weight of steel, 55.85 g; n is the number of electrons transferred, 2; F is the Faraday constant, 96500 C; ρ Fe The density of steel is 7.87 × g / cm³. 3 .

[0099] The result of formula (6) is:

[0100]

[0101] Next, calculate the corrosion depth caused by the current flowing from the exposed steel surface at the leak point to the soil during the positive potential shift of the buried pipeline within one cycle (i.e., from time t1 to t2):

[0102]

[0103] in: The corrosion depth of the buried pipeline during the time period t1 to t2, representing the positive potential shift during which the potential of the buried pipeline changes, is expressed in cm; M is the atomic weight of the steel, 55.85 g; n is the number of electrons transferred, 2; F is the Faraday constant, 96500 C; V shift(t) The positive shift of the buried pipeline potential during the time interval T' from t1 to t1, in V; ρ Fe The density of steel is 7.87 × g / cm³. 3 ;ρ soild represents the soil resistivity near the exposed steel surface at the leak point, in Ω·m; d is the equivalent diameter of the leak point in the coating, in cm. According to relevant research results and standards, 1 cm is considered a diameter of 1 cm. 2 The AC corrosion rate is highest at the coating leak point; therefore, the exposed metal surface area of ​​the coating leak point is set to 1 cm². 2 This is equivalent to d being 1.13cm.

[0104] This can be understood as follows: the corrosion depth of the buried pipeline during the positive shift of the pipeline potential from time t1 to t2 is equal to the integral of the pipeline potential over time during the time period from t1 to t2 multiplied by a specific coefficient.

[0105] Since alternating current is a sinusoidal curve with a frequency of 50Hz, equivalent to 50 cycles per second, the superposition of the alternating current with the cathodic protection DC potential is only equivalent to a certain displacement of the alternating current sinusoidal curve in the negative vertical direction, while the frequency remains 50Hz, equivalent to 50 cycles per second. Therefore, the corrosion depth caused by the positive potential shift of the buried pipeline per unit time, i.e., within 1 second, is equivalent to 50 times the corrosion depth during the time interval t1 to t2 of the positive potential shift of the buried pipeline within one cycle. According to formula (7), the corrosion rate of the buried pipeline per unit time under the combined action of alternating current and direct current is calculated as follows:

[0106] Where: v corr(1s) The cumulative corrosion rate of the buried pipeline potential shifting in the positive direction within 1 second (f cycles) is expressed in cm / s; f is the actual frequency of the alternating current, typically 50 Hz in China.

[0107]

[0108] Where: v corr(1s) V represents the cumulative corrosion rate of a buried pipeline's potential shift to the positive direction within 50 cycles per second, expressed in cm / s. shift(t) The positive shift of the buried pipeline potential during the time interval T' from t1 to t1, in V; ρ soil t1 represents the soil resistivity near the exposed steel surface at the leak point, in Ω·m; t2 represents the start time of the positive potential shift of the buried pipeline within one cycle, and t1 represents the end time of the positive potential shift of the buried pipeline within one cycle, in seconds. It is understood that 50 cycles per second is based on an AC frequency of 50Hz. When the AC frequency is other values, such as 16.67Hz, 25Hz, or 60Hz, the frequency 50 in the formula should be replaced with the actual AC frequency. Unless otherwise specified, the AC frequency f is taken as 50Hz.

[0109] The specific method for step S400, "calculating the annual corrosion rate of the pipeline based on the corrosion rate per unit time of the pipeline," is as follows:

[0110] Specifically, the annual corrosion rate of the pipeline is calculated using the following steps:

[0111]

[0112] Where: v corr(1year) The annual corrosion rate of buried pipelines due to positive potential shift, in cm / yr; v corr(1s) The cumulative corrosion rate of a buried pipeline's potential shift to the positive direction within 50 cycles per second, expressed in cm / s.

[0113] Optionally, for the AC potential in step S100, in actual testing, if a multimeter or similar device is used to test the AC interference potential, the effective value of the AC current is tested. In this case, the superposition potential of the AC current induced by the buried pipeline and the DC potential of the cathodic protection needs to be calculated first based on the tested effective value to determine the peak value of the AC potential.

[0114] Then, the calculated peak value of the AC potential is used to perform steps S100 to S400. The method for calculating the peak value of the AC potential based on the effective value of the AC potential is as follows:

[0115]

[0116] Among them, V m The peak value of the AC potential caused by stray AC current in the pipeline, in volts (V). RMS This is the effective value of the AC potential caused by stray AC current in the pipeline, expressed in V.

[0117] Furthermore, for step S400, the annual corrosion rate of the pipeline is calculated based on the effective value of the AC potential caused by the stray AC current in the pipeline, as follows:

[0118]

[0119] Example of the first application scenario:

[0120] Figure 4 This invention provides a time-varying potential diagram of a buried pipeline under the combined action of AC and DC. The horizontal axis represents time (t), and the vertical axis represents potential. Curve a represents the induced AC potential of the buried pipeline, a sinusoidal curve within one cycle (0.02s). Curve b represents the cathodic protection potential curve of the buried pipeline. Curve c represents the superimposed potential of the induced AC and cathodic protection DC potentials (i.e., the sum of the induced AC potential and the cathodic protection DC potential). The peak voltage V of the AC potential is... mThe voltage is 3.0V; T represents the period of the alternating current, which is 0.02s; the positive offset period of the potential after the superposition of the induced alternating current in the buried pipeline and the DC potential of the cathodic protection is from time t1 to t2, where t1 = 1.22 × 10 - 3 s,t2=8.78×10 -3 s; the soil resistivity ρ is 20Ω·m.

[0121] Alternatively, if the obtained data is the peak value of the alternating current potential, the annual corrosion rate calculated according to formula (9) is:

[0122]

[0123] Alternatively, if the effective value of the AC potential is obtained, for example, if the effective value of the AC potential is 1.9V, then the peak potential of the AC potential is 2.69V. Then, the annual corrosion rate calculated according to formula (11) is:

[0124]

[0125] Figure 5 This is a typical time-varying potential diagram of a pipeline point, illustrating the dynamic AC interference of an AC electrified railway on a pipeline, provided for the second application scenario of this invention. The horizontal axis represents time, and the vertical axis represents potential. The characteristics of AC interference from an AC electrified railway on a pipeline are as follows:

[0126] AC interference to nearby buried pipelines only occurs when railway locomotives are running on the rails, i.e., when there is current in the railway traction system (overhead contact network, electric locomotives, traction substations). Moreover, the magnitude of the interference potential is "dynamic" because different locomotives pass by on the railway, and the speed, load, acceleration, and deceleration of the locomotives all affect the magnitude of the interference potential. External conditions, such as soil resistivity, also affect the magnitude of the interference potential.

[0127] The testing of dynamic AC interference in pipelines of AC electrified railways generally uses instruments that can continuously record data, such as stray current testers and oscilloscopes. The test result is usually the peak value of the AC potential.

[0128] The testing of dynamic AC interference in pipelines of AC electrified railways generally uses instruments that can continuously record data or waveforms, such as stray current meters (SCMs) and oscilloscopes. These instruments all have a certain sampling frequency, which is usually different from the frequency of AC power. Commonly used sampling frequencies are 0.6-64Hz, 1KHz, 10KHz, etc. Generally, one data point is taken per second, which is the peak potential of AC power.

[0129] Includes the following steps:

[0130] Step S100: Obtain the change value of the buried pipeline potential over time under the combined action of AC stray current and DC current of cathodic protection of the buried pipeline, and construct the buried pipeline potential change curve.

[0131] Step S200: Based on the change value on the potential change curve of the buried pipeline, calculate the change value of the corrosion current that causes corrosion of the buried pipeline over time and construct the corrosion current curve of the buried pipeline.

[0132] Step S300: Calculate the corrosion rate of the pipeline per unit time based on the change of the current causing pipeline corrosion over time.

[0133] Step S400: Predict the annual corrosion rate of the buried pipeline based on the unit time corrosion rate of the buried pipeline.

[0134] The calculation steps are as follows:

[0135] Step S100: Obtain the change value of the buried pipeline potential over time under the combined action of AC stray current and DC current of cathodic protection, and construct the buried pipeline potential change curve. The steps are as follows:

[0136] First, based on the peak AC potential of the electrified railway interfering with the pipeline measured within 1 second at a certain moment, the change of the AC potential of the pipeline interference with time within this 1 second is calculated, and its mathematical expression is:

[0137]

[0138] Where λt represents a certain time; The value of AC potential change over time (V) caused by stray AC current in the pipeline within 1 second at a certain moment; V m The peak AC potential of the electrified railway interfering with the pipeline, measured within 1 second at a certain moment, is expressed in V; f is the frequency of the AC current, expressed in Hz; t is the time, expressed in s. The initial phase angle of the alternating current.

[0139] The sum of the superimposed potentials of the AC potential induced by the buried pipeline and the DC potential of the cathodic protection is calculated as follows:

[0140]

[0141] in, The superimposed potential of the AC potential induced in the buried pipeline and the DC potential of the cathodic protection within 1 second at a certain moment changes over time, in units of V; The value of AC potential change over time (V) caused by stray AC current in the pipeline within 1 second at a certain moment; V cp This represents the cathodic protection potential of the pipeline, expressed in volts (V).

[0142] Step S200: Based on the change value on the potential change curve of the buried pipeline, calculate the change value of the corrosion current causing corrosion of the buried pipeline over time and construct the corrosion current curve of the buried pipeline. The steps are as follows:

[0143]

[0144] in, The current density, expressed in A / m, is the current density caused by the positive shift in the pipeline's potential due to interference from an AC electrified railway at a certain moment. This current flows from the exposed steel surface at the leak point into the soil, causing corrosion. 2 ; The positive shift of the buried pipeline potential is the result of the superposition of the AC induced potential sinusoidal wave and the cathodic protection DC potential within one cycle at a certain moment. Units V; ρ soil d represents the soil resistivity near the exposed steel surface at the leak point, in Ω·m; d represents the equivalent diameter of the leak point in the coating, in m.

[0145] Step S300: Calculate the corrosion rate per unit time of the pipeline based on the change in current causing pipeline corrosion over time. The calculation steps are as follows:

[0146] Calculate the period of positive potential shift of the buried pipeline within one AC sinusoidal wave cycle (defined as λ) at a certain moment. t1 To λ t2 The corrosion depth that causes current to flow from the exposed steel surface at the leak point into the soil and result in corrosion is:

[0147]

[0148] in: Within one second of an alternating current sinusoidal wave at a certain moment, the potential of the buried pipeline shifts positively, from λ... t1 To λ t2 Corrosion depth at any given time, in cm; M is the atomic weight of steel, 55.85 g; n is the number of electrons transferred, 2; F is the Faraday constant, 96500 C. For λ t1 To λ t2 The buried pipeline's potential shifts positively over a given time period, measured in V; ρ Fe The density of steel is 7.87 × g / cm³. 3 ;ρ soil d represents the soil resistivity near the exposed steel surface at the leak point, in Ω·m; d is the equivalent diameter of the leak point in the coating, in cm. According to relevant research results and standards, 1 cm is considered a diameter of 1 cm. 2 The AC corrosion rate is highest at the coating leak point; therefore, the exposed metal surface area of ​​the coating leak point is set to 1 cm².2 This is equivalent to d being 1.13cm.

[0149] This can be understood as follows: within one cycle of an alternating current sinusoidal wave (1 second) at a certain moment, the potential of the buried pipeline undergoes a positive shift λ. t1 To λ t2 The corrosion depth over a given time period is equal to λ. t1 To λ t2 The pipeline potential is generated over a time period by integrating the potential over time and multiplying it by a specific coefficient.

[0150] Since alternating current is a sinusoidal curve with a frequency of 50Hz, equivalent to 50 cycles per second, the superposition of alternating current with the cathodic protection DC potential is only equivalent to a certain displacement of the alternating current sinusoidal curve in the negative vertical direction, while the frequency remains 50Hz, equivalent to 50 cycles per second. Therefore, the corrosion depth caused by the positive potential shift of the buried pipeline per unit time, i.e., within 1 second, is equivalent to 50 times the corrosion depth during the time interval t1 to t2 of the buried pipeline potential shift within one cycle. According to formula (15), the typical actual frequency of alternating current is 50Hz. Therefore, the corrosion rate per unit time of the buried pipeline under the combined action of alternating current and DC is calculated as follows:

[0151]

[0152] in: The cumulative corrosion rate of positive potential shift of buried pipeline within 50 cycles per second at a certain moment, expressed in cm / s; For a certain moment, within one sine wave period, from λ t1 To λ t2 Positive shift of buried pipeline potential over time, in V; ρ soil λ represents the soil resistivity near the exposed steel surface at the leak point, in Ω·m. t1 Let λ be the start time of a positive potential shift in the buried pipeline within one cycle at a certain moment. t2 The time in seconds (s) is the end time of a positive potential shift in the potential of a buried pipeline within one cycle at a certain moment.

[0153] Step S400: Calculate the annual corrosion rate of the pipeline. The calculation steps are as follows:

[0154]

[0155] Where: v corr(1year) λ is the annual corrosion rate of buried pipelines caused by positive potential shift due to AC electrified railways, expressed in cm / yr. t1 Let λ be the start time of a positive potential shift in the buried pipeline within one cycle at a certain moment. t2λ represents the end time (in seconds) of a positive potential shift in a buried pipeline within one cycle at a given moment. t For a certain moment; λ t+1 Add 1 second to a certain moment; λ ranges from 0 to i, representing the moments within one year when all AC electrified railways cause a positive potential shift in the potential of buried pipelines. The cumulative corrosion rate of positive potential shift of buried pipeline within 50 cycles per second at a certain moment, expressed in cm / s; For a certain moment, within one sine wave period, from λ t1 To λ t2 The positive shift of the potential of the buried pipeline within a given time period, in units of V.

[0156] Example of the second application scenario:

[0157] Figure 6 This invention provides a time-varying potential diagram of a point on an AC electrified railway pipeline during a specific time period, recording the AC interference potential from 0 to 3 seconds, corresponding to the AC interference potential data measured at four times: second 0, second 1, second 2, and second 3. In the diagram, the horizontal axis represents time t; the vertical axis represents potential; the symbol ■ represents the peak voltage Vm of the AC potential measured per second; the symbol ▲ represents the measured cathodic protection potential; and the symbol △ represents the sum of the AC interference potential and the cathodic protection potential. The peak AC interference potential measured at second 0 is 1.18V; the peak AC interference potential measured at second 1 is 2.7V; the peak AC interference potential measured at second 2 is 3.6V; and the peak AC interference potential measured at second 3 is 4.4V.

[0158] Figure 7 This invention provides a time-varying potential diagram of a point on a pipeline during the first 1-second period (one cycle) of a certain time interval, representing the dynamic AC interference of an AC electrified railway. The positive shift period of the potential after superimposing the AC induced in the buried pipeline and the DC potential of cathodic protection is shown: In the first second, from t... 11 To t 12 At time t 11 =4.3×10 -3 s,t 12 =4.6×10 -3 s.

[0159] Figure 8 This invention provides a time-varying potential diagram of a point on a pipeline during the second 1-second time period (one cycle) of a certain time interval, representing the dynamic AC interference of an AC electrified railway. The positive shift period of the potential resulting from the superposition of the induced AC potential and the cathodic protection DC potential in the buried pipeline is: Second second, from t... 21 To t 22 At time t 21=1.4×10 -3 s,t 22 =8.6×10 -3 s.

[0160] Figure 9 This invention provides a time-varying potential diagram of a point on a pipeline during the third 1-second time period (one cycle) of a certain time interval, representing the dynamic AC interference of an AC electrified railway. The positive shift period of the potential resulting from the superposition of the AC potential induced in the buried pipeline and the DC potential of cathodic protection is: In the 3rd second, from t... 31 To t 32 At time t 31 =1.1×10 -3 s,t 32 =8.9×10 -3 s.

[0161] Figure 10 This invention provides a time-varying potential diagram of a point on a pipeline during the fourth 1-second time period (one cycle) of a certain time interval, representing the dynamic AC interference of an AC electrified railway. The positive shift period of the potential resulting from the superposition of the induced AC potential and the cathodic protection DC potential in the buried pipeline is: In the 4th second, from t... 41 To t 42 At time t 41 =0.89×10 -3 s,t 42 =9.1×10 -3 The soil resistivity ρ is 20 Ω·m.

[0162] According to formula (16), the corrosion rate per unit time under the combined action of the AC current induced in the buried pipeline and the DC potential of cathodic protection in each 1-second time interval is calculated:

[0163] The corrosion rate per unit time under the combined effect of the induced alternating current and the cathodic protection DC potential of the buried pipeline during the first second time interval is calculated as follows:

[0164]

[0165] The corrosion rate per unit time under the combined effect of the induced AC potential and the cathodic protection DC potential of the buried pipeline during the 2-second time interval is calculated as follows:

[0166]

[0167] The corrosion rate per unit time under the combined effect of the induced AC potential and the cathodic protection DC potential of the buried pipeline during the 3-second time interval is calculated as follows:

[0168]

[0169] The corrosion rate per unit time under the combined effect of the induced AC potential and the cathodic protection DC potential of the buried pipeline during the 4-second time interval is calculated as follows:

[0170]

[0171] The calculation steps given above are merely illustrative, intended to explain the calculation method and steps. Since the total annual amount is 3.15 × 10⁻⁶... 7 s, which cannot all be shown in this invention.

[0172] Furthermore, it can be based on obtaining something similar to Figure 5 By using the AC interference diagram of the electrified railway to the pipeline throughout the year, and following the calculation steps and methods described above, the corrosion rate of the buried pipeline caused by the AC interference of the electrified railway to the pipeline throughout the year can be calculated.

[0173] In some preferred embodiments, if the AC electrified railway locomotives have a certain operating pattern, such as passenger dedicated lines, where the locomotive operating pattern is basically similar every day, only 24-hour AC interference data needs to be tested. The pipeline corrosion rate can be calculated for one day using the above calculation method and steps. Then, the result is multiplied by the number of days in a year, usually 365 days, to calculate the annual corrosion rate of buried pipelines caused by AC interference from electrified railways. The result obtained in this way will have a certain error because: although the AC electrified railway locomotives have the same operating pattern every day, the locomotive speed, load, and soil resistivity will be different every day, causing the current of the AC electrified railway traction system to change. Therefore, the degree of interference at the same time each day will be different.

[0174] Preferably, several typical time periods can be selected throughout the year for multiple tests, such as testing once in each of the four seasons of spring, summer, autumn and winter, because the soil resistivity often varies greatly in different seasons throughout the year, which can reduce the error caused by soil resistivity; alternatively, the number of tests can be increased in different seasons, and the average value of multiple test results in the same season can be used for calculation.

[0175] A second embodiment of the present invention proposes a method for maintaining buried pipelines, the method comprising the following steps:

[0176] Step B100: Obtain the change of pipeline potential over time under the combined action of AC stray current and DC current of cathodic protection for buried pipeline.

[0177] Step B200: Based on the change of pipeline potential over time under the combined action of AC stray current and cathodic protection DC current, calculate the change of current over time that causes corrosion of buried pipelines.

[0178] Step B300: Calculate the corrosion rate per unit time of the buried pipeline based on the change of the current causing corrosion over time.

[0179] Step B400: Predict the annual corrosion rate of the buried pipeline based on the unit time corrosion rate of the buried pipeline.

[0180] Step B500: Determine the lifespan of the buried pipeline based on its annual corrosion rate and perform maintenance on the buried pipeline.

[0181] It is understood that the above steps B100-B400 are the same as the determination method of S100-S400 in the aforementioned method for determining AC stray current interference corrosion of buried pipelines, and will not be repeated here. Step B500, which involves maintaining the buried pipeline, can be carried out using known techniques.

[0182] In some preferred embodiments, the above calculation method can be selected as a computer programming method to turn the calculation process into an executable program, and can automatically import the test data of the testing instrument.

[0183] The third embodiment of the present invention proposes a buried pipeline life detection system. The system includes a detection device and a calculation device. The detection device is used to detect the AC stray current of the buried pipeline, the DC current of the cathodic protection of the buried pipeline, the soil resistivity of the soil near the exposed steel surface at the leakage point of the buried pipeline coating, and the equivalent diameter of the leakage point of the buried pipeline coating.

[0184] The computing device is configured to: acquire the change value of the buried pipeline potential over time under the combined action of AC stray current and DC cathodic protection current of the buried pipeline, and construct a potential change curve of the buried pipeline; based on the change value on the potential change curve of the buried pipeline, calculate the change value of the corrosion current causing corrosion of the buried pipeline over time, and construct a corrosion current curve of the buried pipeline; acquire the current density of the corrosion current based on the change value on the corrosion current curve of the buried pipeline, calculate the corrosion rate per unit time of the buried pipeline based on the current density of the corrosion current and the corrosion depth of the buried pipeline per unit time; predict the annual corrosion rate of the buried pipeline based on the corrosion rate per unit time of the buried pipeline, and obtain the life of the buried pipeline based on the annual corrosion rate of the buried pipeline.

[0185] It is understood that the detection device in this embodiment can employ known technologies, such as detecting AC stray current in buried pipelines using a stray current tester, etc., which will not be listed here. The computing device in this embodiment can be a processor with computing capabilities, such as a CPU or GPU, which internally stores the method for determining AC stray current interference corrosion in buried pipelines as described in the first embodiment above. The specific process can be referred to the foregoing embodiments, and will not be repeated here.

[0186] A fourth embodiment of the present invention provides an electronic device comprising: at least one processor; and a memory communicatively connected to at least one of the processors; wherein the memory stores instructions executable by the processor, the instructions being executed by the processor to implement the above-described method for determining AC stray current interference corrosion in buried pipelines.

[0187] The fifth embodiment of the present invention proposes a computer-readable storage medium, characterized in that the computer-readable storage medium stores computer instructions, which are executed by the computer to implement the above-described method for determining the corrosion caused by AC stray current interference in buried pipelines.

[0188] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process and related descriptions of the storage device and processing device described above can be found in the corresponding process in the aforementioned method examples, and will not be repeated here.

[0189] The following is for reference. Figure 11 It shows a schematic diagram of the structure of a computer system suitable for implementing the methods, systems, and devices of this application. Figure 11 The server shown is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments of this application.

[0190] like Figure 11 As shown, the computer system includes a Central Processing Unit (CPU) 601, which can perform various appropriate actions and processes based on programs stored in Read Only Memory (ROM) 602 or programs loaded from storage section 608 into Random Access Memory (RAM) 603. RAM 603 also stores various programs and data required for system operation. The CPU 601, ROM 602, and RAM 603 are interconnected via bus 604. Input / output (I / O) interface 605 is also connected to bus 604.

[0191] The following components are connected to I / O interface 605: an input section 606 including a keyboard, mouse, etc.; an output section 607 including a cathode ray tube (CRT), liquid crystal display (LCD), and speakers, etc.; a storage section 608 including a hard disk, etc.; and a communication section 609 including a network interface card such as a LAN (Local Area Network) card and a modem, etc. Communication section 609 performs communication processing via a network such as the Internet. Drive 610 is also connected to I / O interface 605 as needed. Removable media 611, such as a disk, optical disk, magneto-optical disk, semiconductor memory, etc., are installed on drive 610 as needed so that computer programs read from them can be installed into storage section 608 as needed.

[0192] In particular, according to embodiments of this disclosure, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of this disclosure include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via communication section 609, and / or installed from removable medium 611. When the computer program is executed by the central processing unit (CPU 601), it performs the functions defined in the method of this application. It should be noted that the computer-readable medium mentioned above in this application can be a computer-readable signal medium or a computer-readable storage medium, or any combination of the two. A computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination of the above. In this application... In this context, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in connection with an instruction execution system, apparatus, or device. In this application, a computer-readable signal medium can include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium can also be any computer-readable medium other than a computer-readable storage medium, capable of transmitting, propagating, or transmitting a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wireless, wireline, optical fiber, RF, etc., or any suitable combination thereof.

[0193] Computer program code for performing the operations of this application can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0194] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0195] The terms “first”, “second”, etc., are used to distinguish similar objects, not to describe or indicate a specific order or sequence.

[0196] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent in such process, method, article, or apparatus / device.

[0197] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for determining corrosion caused by stray AC current interference in buried pipelines, characterized in that, The method includes the following steps: Step S100: Obtain the change value of the buried pipeline potential over time under the combined action of AC stray current and DC current of cathodic protection of the buried pipeline, and construct the buried pipeline potential change curve. Step S200: Based on the change value on the potential change curve of the buried pipeline, calculate the change value of the corrosion current that causes corrosion of the buried pipeline over time and construct the corrosion current curve of the buried pipeline. Step S300: Based on the change value on the corrosion current curve of the buried pipeline, obtain the current density of the corrosion current, and calculate the corrosion rate of the buried pipeline per unit time based on the current density of the corrosion current and the corrosion depth of the buried pipeline per unit time. ； in, t1 is the cumulative corrosion rate of the buried pipeline potential shifting positively within 1 second and f cycles, where f is the actual frequency of the alternating current; t2 is the start time of the buried pipeline potential shifting positively within 1 cycle and t1 is the end time of the buried pipeline potential shifting positively within 1 cycle. The corrosion depth during the time period t1 to t2 during which the potential of the buried pipeline shifts positively. Within a time interval of 1 second, 1A / m 2 The corrosion depth of the pipe when a constant current flows out of the coating leak point; This refers to the atomic weight of steel. The number of electrons transferred; It is Faraday's constant; The density of steel; ; The current density is the current density of the corrosion caused by the positive potential shift of buried pipelines flowing from the exposed steel surface at the leak point into the soil. The calculation method is as follows: ； The positive shift of the buried pipeline potential during the time interval T' from t1 to t2; This refers to the resistance of the exposed steel surface at the point of coating leakage relative to the distant ground. , The soil resistivity is the soil near the exposed steel surface at the leak point. The equivalent diameter of the coating leak point; This refers to the surface area of ​​the exposed steel surface at the point of coating leakage. ; Step S400: Predict the annual corrosion rate of the buried pipeline based on the unit time corrosion rate of the buried pipeline.

2. The method for determining AC stray current interference corrosion of buried pipelines according to claim 1, characterized in that, The specific method for obtaining the "change value of pipeline potential over time under the combined action of AC stray current and cathodic protection DC current" in step S100 is as follows: Step A110: Obtain the AC potential caused by stray AC current in the buried pipeline based on the preset first calculation method; Step A120: Obtain the superimposed potential of the AC potential caused by the stray AC current of the buried pipeline and the DC potential of the cathodic protection of the buried pipeline.

3. The method for determining AC stray current interference corrosion of buried pipelines according to claim 2, characterized in that, The specific method for step S200, "calculating the change in current causing corrosion of the buried pipeline over time based on the change in potential curve of the buried pipeline," is as follows: Step A210: Based on the equivalent diameter of the leak point in the buried pipeline coating, calculate the resistance of the exposed steel surface at the leak point relative to the distant ground and the surface area of ​​the exposed steel surface at the leak point. Step A220: Based on the resistance of the exposed steel surface at the coating leak point relative to the distant ground and the surface area of ​​the exposed steel surface at the coating leak point, obtain the current density of the corrosion current that causes the current to flow from the exposed steel surface at the coating leak point to the soil due to the positive potential shift of the buried pipeline, resulting in corrosion.

4. The method for determining AC stray current interference corrosion of buried pipelines according to claim 3, characterized in that, The specific method for step S400, "calculating the annual corrosion rate of the pipeline based on the unit time corrosion rate of the pipeline," is as follows: ； in: The annual corrosion rate at which the potential of a buried pipeline shifts positively.

5. The method for determining AC stray current interference corrosion of buried pipelines according to claim 2, characterized in that, The first calculation method is either a peak value calculation method for AC potential or an effective value calculation method for AC potential.

6. A buried pipeline life testing system, based on the method for determining AC stray current interference corrosion of buried pipelines as described in any one of claims 1-5, characterized in that, The system includes a detection device and a computing device. The detection device is used to detect the AC stray current of the buried pipeline, the DC current of the cathodic protection of the buried pipeline, the soil resistivity of the soil near the exposed steel surface at the leakage point of the buried pipeline coating, and the equivalent diameter of the leakage point of the buried pipeline coating. The computing device is configured to: acquire the change value of the buried pipeline potential over time under the combined action of AC stray current and DC current of cathodic protection of the buried pipeline, and construct a potential change curve of the buried pipeline; and, based on the change value on the potential change curve of the buried pipeline, calculate the change value of the corrosion current causing corrosion of the buried pipeline over time and construct a corrosion current curve of the buried pipeline; acquire the current density of the corrosion current according to the change value on the corrosion current curve of the buried pipeline, calculate the corrosion rate per unit time of the buried pipeline based on the current density of the corrosion current and the corrosion depth of the buried pipeline per unit time; predict the annual corrosion rate of the buried pipeline based on the corrosion rate per unit time of the buried pipeline, and predict the life of the buried pipeline based on the annual corrosion rate of the buried pipeline.

7. An electronic device, characterized in that, include: At least one processor; as well as A memory communicatively connected to at least one of the processors; wherein, The memory stores instructions that are executed by the processor to implement the steps of the method for determining AC stray current interference corrosion of buried pipelines as described in any one of claims 1-5.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that are executed by the computer to implement the steps of the method for determining AC stray current interference corrosion of buried pipelines according to any one of claims 1-5.

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