A method and device for simulating soil corrosion of buried pipelines

Abstract

The present invention relates to a method and apparatus for simulating soil corrosion experiments on buried pipelines. The method comprises a test chamber, a soil temperature control device, a soil moisture control device, a soil temperature and humidity monitoring probe, a corrosion-resistant container, a graphite sheet, and a computer system. The corrosion-resistant container is disposed within the test chamber, and the test chamber is provided with the soil moisture control device and the soil temperature control device. Sample soil is placed in the corrosion-resistant container, and the test sheet is inserted into the sample soil. Two graphite sheets are placed parallel to the sample, and the graphite sheets are grounded via wires. The soil temperature and humidity monitoring probe is inserted into the sample soil, and the soil temperature and humidity monitoring probe is connected to the computer system. The soil temperature and humidity control device and the soil moisture control device are also connected to the computer system. The present invention can simulate the corrosion process of buried pipelines caused by real-world service soil and stray current, thereby enhancing simulation accuracy. Furthermore, it provides a method for evaluating the degree of soil corrosion and the impact of stray current on soil corrosion, providing strong support for related research.

Description

Technical Field

[0001] The present invention relates to the technical field of material property testing, and in particular to a method and device for simulating soil corrosion of buried pipelines, specifically to corrosion resistance testing of steel materials under soil and current-loaded environments. Background Art

[0002] With the rapid development of the Chinese economy and the continuous increase in national income, the demand for oil and natural gas has increased year by year, and the construction and corrosion protection of oil and gas transportation pipelines have received increasing attention. Judging from the coverage area of ​​oil and gas pipelines, my country has established a relatively complete oil and gas pipeline transportation system. Oil and gas pipelines are mostly laid in densely populated areas. Once an oil and gas leak occurs, it not only pollutes the environment, but in serious cases, it can cause huge property losses and threaten the lives and safety of residents along the pipeline. Numerous safety issues caused by pipeline failures have occurred both domestically and internationally, and numerous experts and scholars have conducted extensive research on pipeline failures. Studies have found that buried pipelines often serve in soil environments, and soil corrosion poses a serious challenge to pipeline safety. In addition to the large amount of corrosive ions and soil microorganisms in the soil, stray currents in the soil are also one of the main causes of buried pipeline corrosion. The traction current of the urban rail transit system escapes the track and leaks into the earth and the surrounding environment, which is called stray current. After the stray current escapes into the soil, it will greatly accelerate the corrosion of buried metal equipment. Soil conditions such as soil moisture content, permeability, temperature, pH value, dissolved ion types and concentrations, redox potential, resistivity, organic matter content, and microorganisms, as well as various complex external environments, will affect the corrosion of buried metal equipment, especially metal pipes in the soil, caused by stray current.

[0003] Experimental methods for testing the soil corrosion resistance of buried pipelines are mainly divided into outdoor field burial and indoor accelerated corrosion testing. Outdoor field burial involves burying a large number of test specimens in typical soil, then excavating them according to a certain burial period to measure the sample weight loss rate and corrosion rate. This method is simple and easy to implement, and the observed sample surface morphology and measured data can intuitively and realistically reflect the quality of the material's corrosion resistance. Therefore, it has been widely used in early soil corrosion research both domestically and internationally. However, due to its long experimental period, it cannot accurately and timely obtain detailed information on the corrosion behavior of the material in soil and information on corrosion dynamics, thus failing to meet the needs of in-depth research on soil corrosion of materials. Indoor accelerated corrosion testing is an experimental method that artificially controls experimental conditions to simulate accelerated corrosion, striving to determine the tendency of a material to undergo certain corrosion in various soils in a relatively short period of time. However, for the special service environment of charged soil, current experimental equipment does not meet research requirements. Based on these considerations, the present invention provides a method for simulating soil corrosion of buried pipelines and a corresponding experimental equipment.

[0004] The Chinese patent application "A Soil Corrosion Test Method and Test Production Line for Hot-Rolled H-Beams" (Publication No.: CN117388157 A) discloses a soil corrosion test method and test production line for hot-rolled H-beams. The method uses soil from the area where the product is used to conduct corrosion tests and simulates the environmental conditions of the area where the product is used. The corrosion level is calculated based on the weight of the hot-rolled H-beams before and after the test, thereby enabling the evaluation of the accelerated corrosion level of the hot-rolled H-beams in soils from different regions. However, the experimental equipment used does not take into account the influence of stray currents and cannot accurately simulate the actual service environment. Furthermore, the corrosion level evaluation does not involve stray currents, which is a limitation.

[0005] The Chinese patent application, "A Method for Predicting the Remaining Life of Buried Pipelines Affected by Subway Stray Current Corrosion" (Publication No.: CN 113609640 A), discloses a method for predicting the remaining life of buried pipelines affected by subway stray current corrosion, suitable for subway maintenance. The method includes a stray current interference distribution calculation module, a coordinate transformation module, a defect limit size calculation module, and a cumulative corrosion depth experiment and distribution calculation module. By fully simulating the changing characteristics of stray current corrosion and combining electrochemical experimental results, the method can predict the remaining life of the pipeline in the current corrosive environment by calculating the depth of corrosion defects at different locations along the longitudinal direction of the pipeline. However, this method only incorporates natural corrosion data of buried pipelines into the model calculation and does not consider the interaction between soil and current, resulting in insufficient prediction accuracy. Summary of the Invention

[0006] In order to overcome the shortcomings of the existing technology and meet the experimental needs, the present invention designs a method and device for simulating soil corrosion of buried pipelines. This method uses real soil from the service environment combined with a circuit system to simulate a real charged soil environment, and adjusts the temperature and humidity according to real-time soil parameters to improve the simulation accuracy.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for simulating soil corrosion of buried pipelines includes the following steps:

[0009] Experimental preparation: Soil sampling is carried out in the actual service environment of the sample, and soil parameters and corrosion environment parameters are tested, and test conditions are set accordingly; the sample to be tested is cut, polished step by step with sandpaper, and its surface is degreased. After drying, it is weighed M0; a wire with an insulating sleeve is welded to the edge of the sample, and the welded part is sealed with resin; according to the requirements of the soil corrosion test, the soil is dried, crushed, and sieved to obtain the test soil, and the soil and sample are placed in a container. When placing the sample in the soil, a wire is led out from the side of the test box and connected to the positive pole of the power supply device. Two graphite plates are placed parallel to the sample and grounded. A soil temperature and humidity monitoring probe is inserted into the soil. If there is no stray current in the service environment soil, the power supply device is not used;

[0010] Equipment parameter setting: adjust the soil parameters and environmental parameters according to the set accelerated corrosion test conditions to meet the test requirements, then turn on the power supply to allow a certain amount of current to pass through the sample to meet the needs of simulating stray current;

[0011] Experimental operation: During the test, soil parameters and environmental parameters as well as the current size parameters passing through the sample are monitored and kept stable according to the test requirements; the total test time is three to six months, during which samples are taken and soil iron ion analysis is performed according to the set period, and the corrosion degree of the samples at different periods is observed; Corrosion level evaluation: After the test, the power supply is turned off, the sample container is removed, and the corrosion products on the surface of the sample are cleaned. After drying, the sample is weighed as M1. If the test process does not simulate stray current, the sample is weighed as M2. The corrosion level of the sample in the service soil is evaluated as follows:

[0012] Charged soil: When ≤1%, the soil corrosion degree is mild; 1%< When ≤2%, the soil corrosion level is moderate; When it is greater than 2%, the degree of soil corrosion is severe;

[0013] Normal soil: When ≤0.5%, the soil corrosion degree is mild; 0.5%< When ≤1.5%, the soil corrosion level is moderate; When it is greater than 1.5%, the degree of soil corrosion is severe;

[0014] Evaluation of the impact of stray current on soil corrosion: When ≤0.5%, the influence of stray current on soil corrosion is slight; 0.5%< When ≤1%, the influence of stray current on soil corrosion is moderate; When the stray current is greater than 1%, the degree of soil corrosion caused by the stray current is severe. The cutting size of the sample is (35-50) mm × (35-50) mm × (3-5) mm.

[0015] The outside of the wire is provided with an insulating sleeve, and the welding position is sealed with resin.

[0016] A device used in a method for simulating soil corrosion of buried pipelines comprises a test chamber, a soil temperature control device, a soil moisture control device, a soil temperature and humidity monitoring probe, a corrosion-resistant container, a graphite sheet, and a computer system. The corrosion-resistant container is disposed within the test chamber, and the test chamber is provided with the soil moisture control device and the soil temperature control device. Sample soil is placed in the corrosion-resistant container, and the test sheet is inserted into the sample soil. Two graphite sheets are placed parallel to the sample, and the graphite sheets are grounded via wires. The soil temperature and humidity monitoring probe is inserted into the sample soil, and the soil temperature and humidity monitoring probe is connected to the computer system. The soil temperature and humidity control device and the soil moisture control device are also connected to the computer system.

[0017] It also includes a power supply device, and the test piece is connected to the power supply device through a wire.

[0018] An ultraviolet lamp is also provided in the test box.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The soil corrosion experimental device designed in this invention can simulate the corrosion process of buried pipelines caused by real service soil and stray current, thereby enhancing the accuracy of soil corrosion simulation of buried pipelines. Using this soil corrosion experimental device, a research method for soil corrosion experiments on buried pipelines was designed, and an evaluation method for the soil corrosion degree of the sample and the degree of influence of stray current on soil corrosion was designed, providing strong support for related research.

[0021] 2. The test chamber is equipped with a current device to meet the frequency characteristics of stray currents in different soils. It can test the impact of stray currents on soil corrosion and has stronger functionality than general soil corrosion test chambers.

[0022] 3. A method for evaluating the corrosion level of samples in soil was developed. The corrosion level of samples in charged and uncharged soil can be evaluated separately. In particular, the difference between the two can be used to specifically evaluate the effect of stray current on soil corrosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the buried pipeline soil corrosion experimental device of the present invention

[0024] In the figure: 1-test chamber, 2-soil moisture control device, 3-vent, 4-ultraviolet lamp, 5-soil temperature control device, 6-soil temperature and humidity monitoring probe, 7-corrosion-resistant container, 8-test piece, 9-graphite sheet, 10-sample soil, 11-grounding device, 12-power supply device, 13-computer system. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the specific implementation methods of the present invention are further described below in conjunction with examples. The following examples are used to specifically illustrate the contents of the present invention. These examples are only general descriptions of the contents of the present invention and do not limit the contents of the present invention.

[0026] A method for simulating soil corrosion of buried pipelines includes the following steps:

[0027] Experimental preparation: Soil sampling is carried out in the actual service environment of the sample, and soil parameters and corrosion environment parameters are tested, and test conditions are set accordingly; the sample to be tested is cut, polished step by step with sandpaper, and its surface is degreased. After drying, it is weighed M0; a wire with an insulating sleeve is welded to the edge of the sample, and the welded part is sealed with resin; according to the requirements of the soil corrosion test, the soil is dried, crushed, and sieved to obtain the test soil, and the soil and sample are placed in a container. When placing the sample in the soil, a wire is led out from the side of the test box and connected to the positive pole of the power supply device. Two graphite plates are placed parallel to the sample and grounded. A soil temperature and humidity monitoring probe is inserted into the soil. If there is no stray current in the service environment soil, the power supply device is not used;

[0028] Equipment parameter setting: adjust the soil parameters and environmental parameters according to the set accelerated corrosion test conditions to meet the test requirements, then turn on the power supply to allow a certain amount of current to pass through the sample to meet the needs of simulating stray current;

[0029] Experimental operation: During the test, soil parameters and environmental parameters as well as the current size parameters passing through the sample are monitored and kept stable according to the test requirements; the total test time is three to six months, during which samples are taken and soil iron ion analysis is performed according to the set period, and the corrosion degree of the samples at different periods is observed; Corrosion level evaluation: After the test, the power supply is turned off, the sample container is removed, and the corrosion products on the surface of the sample are cleaned. After drying, the sample is weighed as M1. If the test process does not simulate stray current, the sample is weighed as M2. The corrosion level of the sample in the service soil is evaluated as follows:

[0030] Charged soil: When ≤1%, the soil corrosion degree is mild; 1%< When ≤2%, the soil corrosion level is moderate; When it is greater than 2%, the degree of soil corrosion is severe;

[0031] Normal soil: When ≤0.5%, the soil corrosion degree is mild; 0.5%< When ≤1.5%, the soil corrosion level is moderate; When it is greater than 1.5%, the degree of soil corrosion is severe;

[0032] Evaluation of the impact of stray current on soil corrosion: When ≤0.5%, the influence of stray current on soil corrosion is slight; 0.5%< When ≤1%, the influence of stray current on soil corrosion is moderate; When the stray current is greater than 1%, the degree of soil corrosion caused by the stray current is severe. The cutting size of the sample is (35-50) mm × (35-50) mm × (3-5) mm.

[0033] The outside of the wire is provided with an insulating sleeve, and the welding position is sealed with resin.

[0034] like Figure 1 As shown, a device used in a method for simulating soil corrosion of buried pipelines includes a test box 1, a soil temperature control device 5, a soil moisture control device 2, a soil temperature and humidity monitoring probe 6, a corrosion-resistant container 7, a graphite sheet 9, and a computer system 13. The corrosion-resistant container 7 is arranged in the test box 1, and the test box 1 is provided with the soil moisture control device 2 and the soil temperature control device 5. A sample soil 10 is placed in the corrosion-resistant container 7, and a test sheet 8 is inserted into the sample soil 10. Two graphite sheets 9 are placed parallel to the sample 8, and the graphite sheets 9 are grounded through a wire. The soil temperature and humidity monitoring probe 6 is inserted into the sample soil 10, and the soil temperature and humidity monitoring probe 6 is connected to the computer system. The soil temperature control device 5 and the soil moisture control device 2 are also connected to the computer system.

[0035] It also includes a power supply device 12, and the test strip 8 is connected to the power supply device 13 via a wire.

[0036] An ultraviolet lamp 4 is also provided in the test box 1 .

[0037] Example 1:

[0038] This embodiment provides a buried pipeline soil corrosion test device, which includes a test box 1, a soil temperature and humidity monitoring probe 6 and a soil temperature control device 5, a soil moisture control device 2, a computer system 13, a power supply device 12 and a grounding device 11.

[0039] Soil temperature and humidity monitoring probe 6 is buried in the sample soil 10 and is connected to the computer system 13 for monitoring soil temperature and humidity.

[0040] The soil moisture control device 2 is installed above the test box, and the soil temperature control device 5 is installed at the bottom of the test box. Both are connected to the computer system 13 and can adjust the soil humidity and temperature in real time according to the soil parameters fed back by the soil parameter (temperature and humidity) monitoring system.

[0041] A corrosion-resistant container 7 capable of holding the sample soil 10 and the specimen 8 is placed in the test box.

[0042] A plurality of ventilation holes 3 are provided above the periphery of the test box 1 and above the position of the corrosion-resistant container 7 containing the sample soil 10 and the specimen 8 for ventilation.

[0043] In the corrosion-resistant container 7, two graphite plates 9 are placed parallel to the sample 8, and the graphite plates 9 are connected to the laboratory grounding point through a wire.

[0044] The power supply 12 has AC and DC functions to meet the requirements of different soil stray current frequency characteristics, including power frequency and other frequencies. The AC power supply current and voltage are adjustable.

[0045] A wire outlet is provided on the side of the test box 1 , through which the wire connected to the sample 8 is led out and connected to the positive pole of the power supply device 12 ; the negative pole of the power supply device 12 is connected to the grounding device 11 of the laboratory.

[0046] This embodiment provides a method for simulating soil corrosion of buried pipelines, which includes the steps of experimental preparation, equipment parameter setting, experimental operation, and corrosion level evaluation.

[0047] Experimental preparation: The sample soil 10 used in the example was taken from Yibin City, Sichuan Province. The soil there is reddish-brown clay with a soil moisture content of about 17.5%, a soil resistivity of 27.7 Ω·m, and a pH value of about 6.5. The corrosion environment parameters of the site are a temperature of 30°C and a normal atmospheric environment, and the test conditions are set accordingly; the test piece 8 is X80 pipeline steel, cut to a size of 50mm×50mm×5mm, polished step by step with sandpaper, and its surface is degreased, and weighed M0 after drying; a wire with an insulating sheath is welded to the edge of the sample, and the weld is sealed with resin; in accordance with the requirements of the soil corrosion test, the soil is dried, crushed, and sieved to obtain the test soil, and the sample soil 10 and the test piece 8 are placed in the corrosion-resistant container 7, with the test pieces 8 spaced not less than 50mm apart. When placing the test piece 8 in the sample soil 10, the wire is led out from the side of the test box 1 and connected to the positive pole of the power supply device 12, two graphite plates 6 are placed parallel to the test piece 8, the graphite plates 6 are grounded, and a soil temperature and humidity monitoring probe 6 is inserted into the sample soil 10.

[0048] Equipment parameter setting: According to the monitored soil parameters and environmental parameters, each control system is adjusted so that the soil environmental parameters and the box environmental parameters meet the test requirements. Then, the power supply device 12 is turned on to pass AC power through the test piece 8, and the current density is 15mA / cm 2 , to meet the needs of simulating stray current.

[0049] Experimental operation: During the test, soil parameters and environmental parameters as well as the current size parameters passing through the sample are monitored and kept stable according to the test requirements; the total test time is 90 days, during which samples can be taken and soil iron ion analysis can be performed according to the set period to observe the corrosion degree of samples in different periods. Corrosion level evaluation: After the test, turn off the power supply device 13, take out the test piece 8, clean the corrosion products on the surface of the test piece 8, and weigh the sample after drying M1. The corrosion rate is calculated and evaluated by the weight loss method. The corrosion level evaluation of X80 pipeline steel in service soil is as follows: After calculation,

[0050] 1%< =1.537%≤2%, the corrosion degree of X80 pipeline steel in Yibin soil is moderate.

[0051] Example 2:

[0052] The device used in Example 2 is the same as that in Example 1.

[0053] This embodiment provides a method for simulating soil corrosion of buried pipelines, which includes the steps of experimental preparation, equipment parameter setting, experimental operation, and corrosion level evaluation.

[0054] Experimental Preparation: The sample soil 10 used in this example was collected from Yibin City, Sichuan Province. The soil there is reddish-brown clay with a moisture content of approximately 17.5%, a resistivity of 27.7 Ω·m, and a pH of approximately 6.5. The test conditions were set based on the local corrosion environment parameters of 30°C and normal atmospheric conditions. The test sample was X80 pipeline steel, cut to 50 mm × 50 mm × 5 mm dimensions, sanded and degreased, and weighed after drying (M0). Following the soil corrosion test requirements, the soil was dried, crushed, and sieved to obtain the sample soil 10. Sample soil 10 and test pieces 8 were placed in a container, with the test pieces 8 separated by at least 50 mm. A soil temperature and humidity monitoring probe 6 was inserted into the soil.

[0055] Equipment parameter setting: Adjust each control system according to the monitored soil parameters and environmental parameters so that the soil environmental parameters and box environmental parameters meet the test requirements and no stray current is input.

[0056] Experimental operation: During the test, soil parameters and environmental parameters were monitored and kept stable according to the test requirements. The total test duration was 90 days, during which samples were taken and soil iron ion analysis was performed according to the set period to observe the corrosion degree of the samples at different periods. Corrosion level evaluation: After the test, the test piece 8 was removed, the corrosion products on the surface of the test piece 8 were cleaned, and the sample was weighed M2 after drying. The corrosion rate was calculated and evaluated by the weight loss method. The corrosion level evaluation of X80 pipeline steel in the service soil is as follows: After calculation,

[0057] 0.5%< =0.887%≤1,5%, the corrosion degree of X80 pipeline steel in Yibin soil is moderate;

[0058] Combined with Example 1, the evaluation of the effect of stray current on soil corrosion can be obtained: 0.5% < =0.65%≤1%, the influence of stray current on the corrosion of X80 pipeline steel in Yibin soil is moderate.

[0059] It can be seen from Examples 1 and 2 that stray current has a strong promoting effect on soil corrosion of buried pipelines and cannot be ignored. The device and test method of the present invention can more accurately simulate the actual environment of soil corrosion and have good applicability.

Claims

1. A method for simulating soil corrosion of buried pipelines, characterized in that: The following steps are involved: Experimental preparation: Soil sampling is carried out in the actual service environment of the sample. Soil parameters and corrosion environment parameters are tested and test conditions are set accordingly. The test sample is cut, polished, degreased, and weighed after drying. A wire is welded to the edge of the sample. According to the requirements of the soil corrosion test, the soil is dried, crushed, and sieved to obtain test soil. The soil and sample are placed in a container. When the sample is placed in the soil, a wire is led out and connected to the positive pole of the power supply device. Two graphite plates are placed parallel to the sample and grounded. A soil temperature and humidity monitoring probe is inserted into the soil. If there is no stray current in the service environment soil, the power supply device is not used. Equipment parameter setting: adjust the soil parameters and environmental parameters according to the set accelerated corrosion test conditions, then turn on the power supply to allow a certain amount of current to pass through the sample to meet the needs of simulating stray current; Experimental operation: During the test, soil and environmental parameters as well as the current through the sample are monitored and maintained stable according to the test requirements. The total test duration is three to six months. During this period, samples are taken and soil iron ion analysis is performed at set intervals to observe the degree of corrosion of the samples at different intervals. Corrosion level evaluation: After the test, turn off the power supply, remove the sample from the container, clean the corrosion products on the surface of the sample, and weigh the sample after drying as M1. If the test process does not simulate stray current, the sample is weighed as M2. The corrosion level evaluation method of the sample in the service soil is as follows: Charged soil: When ≤1%, the degree of soil corrosion is mild; 1%< When ≤2%, the soil corrosion level is moderate; When it is greater than 2%, the degree of soil corrosion is severe; Normal soil: When ≤0.5%, the degree of soil corrosion is mild; 0.5%< When ≤1.5%, the soil corrosion level is moderate; When it is greater than 1.5%, the degree of soil corrosion is severe; Evaluation of the impact of stray current on soil corrosion: When ≤0.5%, the influence of stray current on soil corrosion is mild; 0.5%< When ≤1%, the influence of stray current on soil corrosion is moderate; When it is greater than 1%, the influence of stray current on soil corrosion is severe.

2. A method for simulating soil corrosion of buried pipelines according to claim 1, characterized in that: The cutting size of the sample is (35-50) mm×(35-50) mm×(3-5) mm.

3. The method for simulating soil corrosion of buried pipelines according to claim 1, characterized in that: The outside of the wire is provided with an insulating sleeve, and the welding position is sealed with resin.

4. A device for simulating soil corrosion of buried pipelines according to any one of claims 1 to 3, characterized in that: The invention comprises a test box, a soil temperature control device, a soil moisture control device, a soil temperature and humidity monitoring probe, a corrosion-resistant container, a graphite plate, and a computer system. The corrosion-resistant container is arranged in the test box, the test box is provided with a soil moisture control device and a soil temperature control device, a sample soil is placed in the corrosion-resistant container, the sample is inserted into the sample soil, two graphite plates are placed parallel to the sample, the graphite plates are grounded through a wire, the soil temperature and humidity monitoring probe is inserted into the sample soil, the soil temperature and humidity monitoring probe is connected to the computer system, and the soil temperature control device and the soil moisture control device are also connected to the computer system.

5. The device used in the experimental method for simulating soil corrosion of buried pipelines according to claim 4 is characterized in that: A power supply device is also included, and the sample is connected to the power supply device via a wire.

6. The device used in the experimental method for simulating soil corrosion of buried pipelines according to claim 4 is characterized in that: An ultraviolet lamp is also provided in the test box.

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