Method for testing sacrificial anode protection performance of low-pressure steel gas pipeline

Abstract

The invention relates to a method for testing cathode protection performance of a buried pipeline, in particular to a method for testing sacrificial anode protection performance of a low-pressure steel gas pipeline, which comprises the following steps of: firstly, determining the position and the burial depth of the low-pressure steel gas pipeline and the position and the burial depth of a sacrificial anode; a shunt and a current interrupter are connected in series between a sacrificial anode and a low-voltage steel gas pipeline, a plurality of reference electrodes are arranged, and a polarization test piece and a reference pipe are embedded in the position of a test point of the low-voltage steel gas pipeline. Determining the cathode protection effect of the low-voltage steel gas pipeline at the sacrificial anode embedding point according to the power-off potential and the soil resistivity of the polarization test piece, testing whether the sacrificial anode is effective according to the open-circuit potential and the output current of the sacrificial anode, and switching on the sacrificial anode according to different positions of the pipeline. And the influence range of the sacrificial anode is tested according to the difference value of the pipeline potential during disconnection. According to the method, the corrosion risk of the low-pressure steel gas pipeline can be known under the condition that the pipeline is not excavated.

Description

Technical Field

[0001] The invention relates to a method for testing the cathodic protection performance of a buried pipeline, in particular to a method for testing the sacrificial anode protection performance of a low-pressure steel gas pipeline. Background Art

[0002] In recent years, with the increase in the service time of buried steel gas pipelines and the increasing complexity of the urban underground service environment, corrosion and leakage of steel gas pipeline networks have occurred frequently, seriously affecting safe operation. In order to slow down the corrosion rate of steel gas pipeline networks, some protective measures are usually taken for steel pipeline networks. Among them, cathodic protection, as an important corrosion protection measure for buried steel pipelines, has been widely used worldwide; low-pressure steel gas pipeline networks mainly adopt sacrificial anode cathodic protection technology. After the existing low-pressure steel gas pipeline networks adopt cathodic protection measures, there is currently no unified and clear test method that can test the protection effect of the sacrificial anode and the specific protection range of the sacrificial anode. It is impossible to grasp the effect of the implementation of the cathodic protection measures of the low-pressure steel gas pipeline network in actual operation and the influence range of the sacrificial anode, resulting in the possibility that there may still be locations in the low-pressure steel gas pipeline network where the sacrificial anode protection is insufficient, and there is a risk of corrosion leakage. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a testing method for the sacrificial anode protection performance of a low-pressure steel gas pipeline, which can understand the corrosion risk of the low-pressure steel gas pipeline without excavating the pipeline.

[0004] In order to solve the above technical problems, this application provides the following technical solutions:

[0005] The present invention provides a method for testing the sacrificial anode protection performance of a low-pressure steel gas pipeline.

[0006] The steps include:

[0007] S1. Determine the position and burial depth of the low-pressure steel gas pipeline and the position and burial depth of the sacrificial anode, connect a current divider and a current interrupter in series between the sacrificial anode and the low-pressure steel gas pipeline, set a plurality of reference electrodes, bury a polarization test piece at the test point of the low-pressure steel gas pipeline, and connect the polarization test piece to the low-pressure steel gas pipeline.

[0008] S2. Test the cathodic protection effect of the low-pressure steel gas pipeline at the sacrificial anode buried point:

[0009] Testing the soil resistivity at the location where the low-pressure steel gas pipeline is buried,

[0010] After the polarization test piece is fully polarized, the power-off potential of the polarization test piece is tested. When the soil resistivity is less than 100Ω·m, the power-off potential of the polarization test piece is negative -0.85V. When the soil resistivity is between 100Ω·m and 1000Ω·m, the power-off potential of the polarization test piece is negative -0.75V. When the soil resistivity is greater than 1000Ω·m, the power-off potential of the polarization test piece is negative -0.65V. When the power-off potential of the polarization test piece meets the above standards, it is judged that the cathodic protection effect of the low-pressure steel gas pipeline at the sacrificial anode buried point is good.

[0011] Test whether the sacrificial anode is effective:

[0012] In the disconnected state of the current interrupter, the open circuit potential and the output current of the sacrificial anode are tested using a multimeter and the reference electrode. If the open circuit potential of the sacrificial anode is close to the theoretical open circuit potential, the forward offset is less than 200 mV, and the output current of the sacrificial anode is greater than 10 mA, then the open circuit potential and the output current of the sacrificial anode are both normal, and the sacrificial anode (12) is judged to be effective;

[0013] The influence range of the sacrificial anode was tested:

[0014] When the sacrificial anode is connected and disconnected, the pipeline potential at different positions of the low-pressure steel gas pipeline is tested respectively. At a certain position of the low-pressure steel gas pipeline, if the difference between the pipeline potential when the sacrificial anode is connected and the pipeline potential when the sacrificial anode is disconnected is greater than 100mV, it is judged that the protection effect of the low-pressure steel gas pipeline at this position is good; if the difference between the pipeline potential when the sacrificial anode is connected and the pipeline potential when the sacrificial anode is disconnected is between 20mV and 100mV, it is judged that the protection effect of the low-pressure steel gas pipeline at this position is general; if the difference between the pipeline potential when the sacrificial anode is connected and the pipeline potential when the sacrificial anode is disconnected is less than 20mV, it is judged that the low-pressure steel gas pipeline has no obvious protection effect at this position; the pipeline length where the difference between the pipeline potential when the sacrificial anode is connected and the pipeline potential when the sacrificial anode is disconnected is greater than 20mV is calculated, that is, the protection range of each group of sacrificial anodes.

[0015] Furthermore, the area of ​​the polarization test piece is selected according to the material of the anti-corrosion coating on the outer surface of the low-pressure steel gas pipeline. When the anti-corrosion coating is 3PE, the area of ​​the polarization test piece is selected to be 6.5 cm 2 When the anti-corrosion coating is petroleum asphalt, the area of ​​the polarization test piece is selected as 50cm 2 .

[0016] Furthermore, the burial depth of the polarization test piece is the same as that of the low-pressure steel gas pipeline, and the distance between the polarization test piece and the low-pressure steel gas pipeline is between 100 mm and 300 mm.

[0017] Furthermore, it also includes a reference tube, which is located directly above the polarization test strip. After the polarization test strip is effectively polarized, a reference electrode is placed in the reference tube. When the polarization test strip is disconnected, the multimeter and the reference electrode are used to test the power-off potential of the polarization test strip.

[0018] Furthermore, when testing whether the sacrificial anode is effective, when the current interrupter is in the off-circuit state, the open-circuit potential of the sacrificial anode is tested using a multimeter and the reference electrode, the voltage difference V1 across the shunt is tested using the multimeter, and the output current I1 of the sacrificial anode is calculated based on the resistance value of the shunt.

[0019] Furthermore, the resistance value of the shunt is R1, 0.01Ω≤R1≤0.1Ω.

[0020] Furthermore, the reference electrode is located directly above the low-pressure steel gas pipeline, and the distance between two adjacent reference electrodes should be 3.46 times the burial depth of the low-pressure steel gas pipeline.

[0021] Furthermore, the reference electrode is a copper sulfate reference electrode.

[0022] Compared with the prior art, the test method for the sacrificial anode protection performance of low-pressure steel gas pipelines of the present invention has at least the following advantages:

[0023] Beneficial effects:

[0024] The present invention discloses a method for testing the sacrificial anode protection performance of a low-pressure steel gas pipeline. Since the method can test the cathodic protection effect of the low-pressure steel gas pipeline at the sacrificial anode burying point, test whether the sacrificial anode is effective, and test the influence range of the sacrificial anode, the corrosion risk of the low-pressure steel gas pipeline can be understood without excavating the pipeline, thereby providing technical support for the technical transformation of the low-pressure steel gas pipeline and the determination of an overhaul plan.

[0025] The test method for the sacrificial anode protection performance of the low-pressure steel gas pipeline of the present invention is further described below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the installation of the polarization test piece and the reference tube in the test method of the sacrificial anode protection performance of the low-pressure steel gas pipeline of the present invention;

[0027] Figure 2It is a schematic diagram of the placement of the diverter, interrupter wiring and reference electrode in the test method of the sacrificial anode protection performance of the low-pressure steel gas pipeline of the present invention. DETAILED DESCRIPTION

[0028] like Figure 1 , Figure 2 As shown, a method for testing the sacrificial anode protection performance of a low-pressure steel gas pipeline of the present invention comprises the following steps:

[0029] S1. Determine the position and burial depth of the low-pressure steel gas pipeline 11 and the position and burial depth of the sacrificial anode 12, connect a current divider 13 and a current interrupter 14 in series between the sacrificial anode 12 and the low-pressure steel gas pipeline 11, set a plurality of reference electrodes 15, bury a polarization test piece 16 and a reference tube 17 at the test point of the low-pressure steel gas pipeline 11, and connect the polarization test piece 16 to the low-pressure steel gas pipeline 11. Specifically, verify the basic information, pipeline position and pipeline burial depth of the low-pressure steel gas pipeline on site according to the design, construction data and measurement drawings of the low-pressure gas pipeline, or use a buried pipeline testing instrument to test and locate the pipeline position and burial depth. In this embodiment, the buried depth of the pipe top of a certain community pipeline is about 1m, the pipeline adopts 20# steel, the pipeline specification is DN200, the wall thickness is 6mm, the pipeline adopts 3PE anti-corrosion layer, the sacrificial anode 12 is buried at the same depth as the pipeline, each group of sacrificial anodes 12 contains 2 14kg magnesium anodes, and is electrically connected to the low-pressure steel gas pipeline 11 through the test pile 21. The test pile 21 is provided with a terminal board 22, and the terminal board 22 is provided with a plurality of terminal posts 23. The polarization test piece 16 is connected to one terminal post 23.

[0030] S2. Test the cathodic protection effect of the low-pressure steel gas pipeline 11 at the buried point of the sacrificial anode 12:

[0031] Testing the soil resistivity at the location where the low-pressure steel gas pipeline 11 is buried,

[0032] After the polarization test piece 16 is fully polarized, the off-power potential of the polarization test piece 16 is tested. When the soil resistivity is less than 100Ω·m, the off-power potential of the polarization test piece 16 is negative to -0.85V. When the soil resistivity is between 100Ω·m and 1000Ω·m, the off-power potential of the polarization test piece 16 is negative to -0.75V. When the soil resistivity is greater than 1000Ω·m, the off-power potential of the polarization test piece 16 is negative to -0.65V. When the off-power potential of the polarization test piece 16 meets the above standards, it is judged that the cathodic protection effect of the low-pressure steel gas pipeline 11 at the buried point of the sacrificial anode 12 is good.

[0033] In this embodiment, the Wenner quadrupole method is used to test the average soil resistivity of the buried depth of the pipeline to be 28.27Ω·m. The reference tube 17 is located directly above the polarization test piece 16. After the polarization test piece 16 is effectively polarized, the reference electrode is placed in the reference tube 17. When the polarization test piece 16 is disconnected, the multimeter 18 and the reference electrode 15 are used to test the power-off potential of the polarization test piece 16. The power-off potential of the polarization test piece 16 is measured to be -1.032V, which meets the criterion of the potential being negative to -0.85V. It is judged that the cathodic protection effect of the pipeline at the location of the sacrificial anode buried point is good.

[0034] Test whether the sacrificial anode 12 is effective:

[0035] When the current interrupter 14 is in the off-circuit state, the open circuit potential and output current of the sacrificial anode 12 are tested by using a multimeter 18 and a reference electrode 15. If the open circuit potential of the sacrificial anode 12 is close to the theoretical open circuit potential, the forward offset is less than 200mV, and the output current of the sacrificial anode 12 is greater than 10mA, then the output current and the open circuit potential are both normal, and it is judged that the sacrificial anode 12 is effective. In this embodiment, the resistance of the shunt 13 is selected as 0.01Ω. When the current interrupter 14 is in the off-circuit state, the open circuit potential of the sacrificial anode 12 is tested by using a multimeter 18 and a reference electrode 15. The open circuit potential of the sacrificial anode 12 is -1.573V. The voltage difference across the shunt 13 tested by the multimeter 18 is 0.52mV. It is calculated that the output current of the sacrificial anode 12 is 52mA. The output current and the open circuit potential are both normal, indicating that the sacrificial anode 12 is normal and effective.

[0036] The influence range of the test sacrificial anode 12 is:

[0037] When the sacrificial anode 12 is connected and disconnected, the pipeline potential at different positions of the low-pressure steel gas pipeline 11 is tested respectively. At a certain position of the low-pressure steel gas pipeline 11, if the difference between the pipeline potential when the sacrificial anode 12 is connected and the pipeline potential when the sacrificial anode 12 is disconnected is greater than 100mV, it is judged that the protection effect of the low-pressure steel gas pipeline 11 at this position is good; if the difference between the pipeline potential when the sacrificial anode 12 is connected and the pipeline potential when the sacrificial anode 12 is disconnected is between 20mV and 100mV, it is judged that the protection effect of the low-pressure steel gas pipeline 11 at this position is general; if the difference between the pipeline potential when the sacrificial anode 12 is connected and the pipeline potential when the sacrificial anode 12 is disconnected is less than 20mV, it is judged that the low-pressure steel gas pipeline 11 has no obvious protection effect at this position. The pipeline length where the difference between the pipeline potential when the sacrificial anode 12 is connected and the pipeline potential when the sacrificial anode 12 is disconnected is greater than 20mV is calculated, that is, the protection range of each group of sacrificial anodes 12.

[0038] In this embodiment, the distance between the reference electrode 15 and the sacrificial anode 12, and the distance between two adjacent reference electrodes 15 are all set to be less than 4m. Figure 2As shown, when the current interrupter 14 is turned on and off, the pipeline potential at different positions of the low-pressure steel gas pipeline 11 is tested when the sacrificial anode 12 is turned on and off. The test results are shown in the following table:

[0039]

[0040] If the difference is greater than 100mV, it indicates that the protection effect is good, if the difference is between 20mV and 100mV, the protection effect is general, and if the difference is less than 20mV, it indicates that there is no obvious protection effect. The length of the pipeline with a difference greater than 20mV is calculated to determine the protection range of each group of sacrificial anodes. In this embodiment, the pipeline range with a difference greater than 100mV is 4m, and the pipeline range with a difference between 20mV and 100mV is 4m to 11m. The sacrificial anode 12 has a good protection effect on the 8m long pipeline of the low-pressure steel gas pipeline 11, and a general protection effect on the 14m long pipeline. A total of 22m of pipelines are protected, and the protection effect of pipelines beyond 22m is not obvious.

[0041] The present invention provides a method for testing the sacrificial anode protection performance of a low-pressure steel gas pipeline. Since it is capable of testing the cathodic protection effect of the low-pressure steel gas pipeline 11 at the buried point of the sacrificial anode 12, testing whether the sacrificial anode 12 is effective, and testing the influence range of the sacrificial anode 12, it is possible to understand the corrosion risk of the low-pressure steel gas pipeline 11 without excavating the pipeline, thereby providing technical support for the technical transformation of the low-pressure steel gas pipeline and determining the overhaul plan.

[0042] Optionally, the area of ​​the polarization test piece 16 is selected according to the material of the anti-corrosion coating on the outer surface of the low-pressure steel gas pipeline 11. When the anti-corrosion coating is 3PE, the area of ​​the polarization test piece 16 is selected to be 6.5 cm 2 When the anticorrosion coating is petroleum asphalt, the area of ​​the polarization test piece 16 is selected to be 50 cm 2 .

[0043] Optionally, the burial depth of the polarization test piece 16 is the same as that of the low-pressure steel gas pipeline 11, and the distance between the polarization test piece 16 and the low-pressure steel gas pipeline 11 is between 100 mm and 300 mm.

[0044] Optionally, the reference tube 17 is placed directly above the polarization test strip 16, and the polarization test strip 16 is connected to the pipeline and polarized for 2 hours before the test strip potential is tested.

[0045] Optionally, when testing whether the sacrificial anode 12 is effective, when the current interrupter 14 is in the open-circuit state, the open-circuit potential of the sacrificial anode 12 is tested using a multimeter 18 and a reference electrode 15, and the voltage difference V1 across the shunt 13 is tested using the multimeter 18. The output current I1 of the sacrificial anode 12 is calculated based on the resistance value of the shunt 13.

[0046] Optionally, the resistance value of the shunt 13 is R1, 0.01Ω≤R1≤0.1Ω.

[0047] Optionally, the reference electrode 15 is located directly above the low-pressure steel gas pipeline 11 , and the distance between two adjacent reference electrodes 15 should be 3.46 times the buried depth of the low-pressure steel gas pipeline 11 .

[0048] Optionally, the reference electrode 15 is a copper sulfate reference electrode.

[0049] The embodiments described above are merely descriptions of preferred implementation modes of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for testing the sacrificial anode protection performance of a low-pressure steel gas pipeline, characterized in that: The steps include: S1. Determine the position and burial depth of the low-pressure steel gas pipeline (11) and the position and burial depth of the sacrificial anode (12), connect a current divider (13) and a current interrupter (14) in series between the sacrificial anode (12) and the low-pressure steel gas pipeline (11), set a plurality of reference electrodes (15), bury a polarization test piece (16) at the test point position of the low-pressure steel gas pipeline (11), and connect the polarization test piece (16) to the low-pressure steel gas pipeline (11). S2. Testing the cathodic protection effect of the low-pressure steel gas pipeline (11) at the buried point of the sacrificial anode (12): Testing the soil resistivity at the location where the low-pressure steel gas pipeline (11) is buried, After the polarization test piece (16) is fully polarized, the off-power potential of the polarization test piece (16) is tested. When the soil resistivity is less than 100Ω·m, the off-power potential of the polarization test piece (16) is negative to -0.85V. When the soil resistivity is between 100Ω·m and 1000Ω·m, the off-power potential of the polarization test piece (16) is negative to -0.75V. When the soil resistivity is greater than 1000Ω·m, the off-power potential of the polarization test piece (16) is negative to -0.65V. When the off-power potential of the polarization test piece (16) meets the above standards, it is judged that the cathodic protection effect of the low-pressure steel gas pipeline (11) at the buried point of the sacrificial anode (12) is good. Test whether the sacrificial anode (12) is effective: In the disconnected state of the current interrupter (14), the open circuit potential and the output current of the sacrificial anode (12) are tested using a multimeter and the reference electrode (15); if the open circuit potential of the sacrificial anode (12) is close to the theoretical open circuit potential, the forward offset is less than 200 mV, and the output current of the sacrificial anode (12) is greater than 10 mA, then the open circuit potential and the output current of the sacrificial anode (12) are both normal, and the sacrificial anode (12) is judged to be effective; The influence range of the sacrificial anode (12) is tested: When the sacrificial anode (12) is connected and disconnected, the pipeline potential at different positions of the low-pressure steel gas pipeline (11) is tested respectively. At a certain position of the low-pressure steel gas pipeline (11), if the difference between the pipeline potential when the sacrificial anode (12) is connected and the pipeline potential when the sacrificial anode (12) is disconnected is greater than 100mV, it is judged that the protection effect of the low-pressure steel gas pipeline (11) at this position is good; if the difference between the pipeline potential when the sacrificial anode (12) is connected and the pipeline potential when the sacrificial anode (12) is disconnected is between 2 If the difference between the pipeline potential when the sacrificial anode (12) is connected and the pipeline potential when the sacrificial anode (12) is disconnected is less than 20 mV, it is judged that the low-pressure steel gas pipeline (11) has no obvious protection effect at this position. The length of the pipeline where the difference between the pipeline potential when the sacrificial anode (12) is connected and the pipeline potential when the sacrificial anode (12) is disconnected is greater than 20 mV, that is, the protection range of each group of sacrificial anodes (12).

2. The method for testing the sacrificial anode protection performance of a low-pressure steel gas pipeline according to claim 1, characterized in that: The area of ​​the polarization test piece (16) is selected according to the material of the anti-corrosion coating on the outside of the low-pressure steel gas pipeline (11). When the anti-corrosion coating is 3PE, the area of ​​the polarization test piece (16) is selected to be 6.5 cm 2 When the anti-corrosion coating is petroleum asphalt, the area of ​​the polarization test piece (16) is selected to be 50 cm 2 .

3. The method for testing the sacrificial anode protection performance of a low-pressure steel gas pipeline according to claim 2, characterized in that: The buried depth of the polarization test piece (16) is the same as that of the low-pressure steel gas pipeline (11), and the distance between the polarization test piece (16) and the low-pressure steel gas pipeline (11) is between 100 mm and 300 mm.

4. The method for testing the sacrificial anode protection performance of a low-pressure steel gas pipeline according to claim 3 is characterized in that: It also includes a reference tube (17), which is located directly above the polarization test strip (16). After the polarization test strip (16) is effectively polarized, the reference electrode (15) is placed in the reference tube (17). When the polarization test strip (16) is disconnected, the multimeter (18) and the reference electrode (15) are used to test the power-off potential of the polarization test strip (16).

5. The method for testing the sacrificial anode protection performance of a low-pressure steel gas pipeline according to claim 1, characterized in that: When testing whether the sacrificial anode (12) is effective, the current interrupter (14) is in an open circuit state, and the open circuit potential of the sacrificial anode (12) is tested using a multimeter (18) and the reference electrode (15). The voltage difference V1 across the shunt (13) is tested using the multimeter (18), and the output current I1 of the sacrificial anode (12) is calculated based on the resistance value of the shunt (13).

6. The method for testing the sacrificial anode protection performance of a low-pressure steel gas pipeline according to claim 5, characterized in that: The resistance value of the shunt (13) is R1, 0.01Ω≤R1≤0.1Ω.

7. The method for testing the sacrificial anode protection performance of a low-pressure steel gas pipeline according to claim 1, characterized in that: The reference electrode (15) is located directly above the low-pressure steel gas pipeline (11), and the distance between two adjacent reference electrodes (15) should be 3.46 times the buried depth of the low-pressure steel gas pipeline (11).

8. The method for testing the sacrificial anode protection performance of a low-pressure steel gas pipeline according to claim 7, characterized in that: The reference electrode (15) is a copper sulfate reference electrode.

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