An insulation joint failure simulation experiment system and a testing method

Abstract

The present invention provides an insulation joint failure simulation experimental system and a testing method. The system includes a soil box, an experimental pipe section, a working condition simulation system, an applied magnetic field system, and an insulation performance testing system. The experimental pipe section is arranged in the soil box and includes a protected side pipe section, an insulation joint, and an unprotected side pipe section that are connected in sequence. The working condition simulation system includes a cathodic protection module and a medium circulation and transportation module that can protect the protected side pipe section. The applied magnetic field system can simulate the residual magnetism generated by magnetic flux leakage detection and measure the magnetic induction intensity. The insulation performance testing system can measure the pipe-to-earth potential. The method uses the above system for testing. The beneficial effects of the present invention may include: providing a testing method for an experimental system for the leakage failure phenomenon and problems of insulation joints caused by the magnetic flux leakage detection process of pipelines; and being used to analyze the insulation failure behavior and key influencing factors under different service environments.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas transportation, and more specifically, to the technical field of insulating joints for oil and gas pipelines. Background Art

[0002] An insulating joint is an important component that plays an electrical isolation role in a cathodic protection pipeline system. Its function is to electrically isolate the protected pipe section from the non-protected pipe section and equipment, prevent the leakage of cathodic protection current, and improve the cathodic protection efficiency. When there is stray current interference, the insulating joint can be used for segmenting the pipe section in the interference area or separating the pipe section in the interference area from the non-interference area pipe section to reduce the degree and scope of the influence of stray current interference on the pipeline.

[0003] During the service process of insulating joints for natural gas and oil pipelines, affected by factors such as the installation location and the transported medium, the phenomenon of reduced insulation performance and leakage may occur. In recent years, during the on-site investigation and testing of natural gas and oil pipelines, it has been found that on pipelines with a long service life, due to long-term medium erosion and the wear of the pig detector, the inner coating of the insulating joint gradually loses adhesion and falls off or wears out and fails, the insulation performance of the insulating joint decreases, and the phenomenon of leakage failure of the insulating joint is widespread. The leakage failure of the insulating joint seriously affects the operation of the pipeline cathodic protection system, causing problems such as the loss of cathodic protection current, the increase in the output current of the potentiostat, the low polarization potential of the pipeline at the far end of the cathodic protection station, the reduction of the protection effect, and the shrinkage of the effective protection range of the cathodic protection system. At the same time, the leakage of the insulating joint also brings uncertainty to the effectiveness of the key pipe section segmentation and isolation measures in the protection against stray current interference.

[0004] Currently, the existing detection techniques and methods for the insulation performance of in-service insulating joints include the potential method, the leakage resistance method, the leakage rate measurement method, and the grounding resistance measurement method, etc. For example, the leakage rate measurement method is adopted in the Chinese invention patent with the publication number CN110609221A. Summary of the Invention

[0005] The purpose of the present invention is to solve at least one of the above-mentioned deficiencies existing in the prior art. For example, there is no test means for the leakage failure phenomenon and problems of the insulating joint caused by the process of pipeline magnetic flux leakage detection.

[0006] The inventor has found through research that under the action of internal corrosive media, corrosion products exist in varying degrees inside steel pipelines. The main component of such corrosion products is Fe3O4, and Fe3O4 is a ferromagnetic and electrically conductive iron oxide. The magnetic flux leakage detection regularly performed on the pipeline causes residual magnetism on the pipe wall, and the residual magnetism on the pipe wall causes the conductive corrosion products to adsorb and deposit on the surface of the insulating part (insulating gasket) in the middle of the insulating joint. The conductive corrosion product layer acts as an electronic conductor to bridge the pipe sections on both sides of the insulating gasket, resulting in the short-circuiting of the pipe sections on both sides of the insulating gasket and the leakage failure of the insulating joint.

[0007] Therefore, one of the objectives of the present invention is to provide a simulation experiment system and a test method for problems such as leakage failure of an insulating joint caused by residual magnetism during a magnetic flux leakage detection process for natural gas or oil pipelines with magnetic and electrically conductive corrosion products.

[0008] To achieve the above objective, one aspect of the present invention provides a simulation experiment system for insulating joint failure. The system includes a soil box, an experimental pipe section, a working condition simulation subsystem, an external magnetic field subsystem, and an insulation performance test subsystem. The experimental pipe section is arranged in the soil box and includes a protected side pipe section, an insulating joint, and an unprotected side pipe section connected in sequence. The working condition simulation subsystem includes a cathodic protection module and a medium circulation and transportation module. The cathodic protection module can protect the protected side pipe section. The medium circulation and transportation module includes a circulating medium and can make the circulating medium flow in the experimental pipe section. The external magnetic field subsystem includes an external magnetizing member or an internal magnetizing member and also includes a Tesla meter. The external magnetic field subsystem is configured to be able to simulate the residual magnetism generated by magnetic flux leakage detection and measure the magnetic induction intensity. The insulation performance test subsystem can measure the insulation conditions of the protected side pipe section and the unprotected side pipe section.

[0009] Furthermore, another aspect of the present invention provides a simulation test method for insulating joint failure. The method uses the above system for testing and simulates the influence of the density of adsorbed corrosion products on the leakage rate under different magnetic forces by changing the magnetic field intensity.

[0010] Compared with the prior art, the beneficial effects of the present invention may include: being able to be used to analyze the insulation failure behavior and its key influencing factors under different service environments, and thus optimizing the size and structure of the insulating joint; being able to determine the influence of corrosion products on the insulation performance of the insulating joint; being able to be used for the performance evaluation and type screening of the inner coating of the insulating joint. Description of the Drawings

[0011] Figure 1 Shows a schematic structural diagram of a simulation experiment system for insulating joint failure in an exemplary embodiment of the present invention.

[0012] Markings in the figure:

[0013] 1 - Soil box, 2 - Soil, 3 - Experimental pipe section, 31 - Protected side pipe section, 32 - Insulating joint, 33 - Unprotected side pipe section, 4 - Inner coating, 41 - First inner coating break point, 42 - Second inner coating break point, 5 - Outer coating, 51 - First outer coating break point, 52 - Second outer coating break point, 6 - Potentiostat, 7 - Auxiliary electrode, 8 - Medium circulation and transportation module, 81 - Circulating medium, 82 - Medium storage device, 83 - Circulation power device, 84 - Medium circulation pipe, 9 - External magnet, 10 - Tesla meter, 11 - Digital multimeter, 12 - Reference electrode, 13 - Measuring point of the pipe - to - soil potential of the protected side pipe section, 14 - Measuring point of the pipe - to - soil potential of the unprotected side pipe section. Detailed implementation manners

[0014] After research, the inventor found that in the case of the existence of corrosion products in a steel pipe, both the adsorption or deposition of corrosion products on the surface of the insulating parts inside the insulating joint and the leakage failure of the insulating joint are closely related to the magnetic flux leakage detection process of the pipe. However, there is currently no test method and evaluation method for the leakage failure phenomenon and problems of the insulating joint caused by the magnetic flux leakage detection process of the pipe.

[0015] In the following, the insulating joint failure simulation experimental system and test method of the present invention will be described in detail in conjunction with exemplary embodiments.

[0016] In the present invention, detailed illustrative embodiments are disclosed. However, for the purpose of describing the exemplary embodiments, the specific structural and functional details disclosed in the present invention are merely representative. However, the present invention can be implemented in many alternative forms and should not be construed as being limited only to the embodiments stated in the present invention. Therefore, although the exemplary embodiments can be in various modified and alternative forms, these embodiments are shown by way of example in the drawings and are described in detail herein. However, it should be understood that the exemplary embodiments should not be limited to the specific forms disclosed. On the contrary, the exemplary embodiments cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure.

[0017] In the description of the present application, it should be understood that the terms "first", "second", etc. are only for convenience of description and easy distinction, and cannot be construed as indicating or implying relative importance or having a strict sequentiality.

[0018] In the description of the present application, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", "connected to", "combined" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0019] Example 1

[0020] Figure 1 Fig. shows a schematic diagram of the insulation joint failure simulation experimental system in an exemplary embodiment of the present invention. The experimental system includes a soil box 1, an experimental pipe section 3, a working condition simulation subsystem, an applied magnetic field subsystem, and an insulation performance test subsystem.

[0021] Among them, the experimental pipe section 3 is arranged in the soil box 1. At the same time, soil 2 is also arranged in the soil box 1, and the amount of soil 2 is set according to experimental needs. For example, the soil 2 is set to completely cover the experimental pipe section 3 so that the environment where the experimental pipe section 3 is located is closer to the environment of a real pipeline.

[0022] The experimental pipe section 3 includes a protected side pipe section 31, an insulation joint 32, and an unprotected side pipe section 33 connected in sequence. The experimental pipe section 3 can be a steel pipe. Further, the inner wall of the experimental pipe section 3 (including the inner wall of the protected side pipe section 31, the inner wall of the insulation joint 32, and the inner wall of the unprotected side pipe section 33) may have an inner coating 4 or may not have an inner coating 4. When the inner wall of the experimental pipe section 3 has an inner coating 4, the inner coating 4 can be a complete inner coating or a damaged inner coating, and the damaged inner coating can simulate the failure scenario after coating friction and erosion. For example Figure 1 As shown in, the inner wall of the experimental pipe section 3 has an inner coating 4, and the inner coating 4 is a damaged inner coating. The damaged part may include a first inner coating damage point 41 and a second inner coating damage point 42. The first inner coating damage point 41 is located on the protected side pipe section 31, and the second inner coating damage point is located on the unprotected side pipe section 33. The positions and sizes of the first inner coating damage point 41 and the second inner coating damage point 42 can be determined according to test requirements to facilitate the experiment for evaluating the performance of the inner coating of the insulation joint or screening the type.

[0023] The outer wall of the experimental pipe section 3 (including the outer wall of the protected side pipe section 31, the outer wall of the insulation joint 32, and the outer wall of the unprotected side pipe section 33) may have an outer coating 5 or may not have an outer coating 5. When the outer wall of the experimental pipe section 3 has an outer coating 5, the outer coating 5 is a damaged outer coating, and the damaged part may include a first outer coating damage point 51 and a second outer coating damage point 52. The first outer coating damage point 51 is located on the protected side pipe section 31, and the second outer coating damage point 52 is located on the unprotected side pipe section 33 to ensure that the cathodic protection current can be applied smoothly. Further, bare metal simulation grounding grids can be added to the protected side pipe section 31 and the unprotected side pipe section 33 respectively to increase the loop output current for facilitating on-site testing. The positions and sizes of the first outer coating damage point 51 and the second outer coating damage point 52 can be determined according to test requirements.

[0024] The working condition simulation subsystem includes a cathodic protection module and a medium circulation and transportation module. The cathodic protection module can protect the pipe section on the protected side. The cathodic protection module applies cathodic protection to the pipe section 31 on the protected side by means of external impressed current to simulate the cathodic protection of a real pipeline. The cathodic protection module can separately sacrifice an anode and be directly connected to the pipe section on the protected side. Further, as Figure 1 shown, the cathodic protection module may include a potentiostat 6 and an auxiliary electrode 7. One end of the potentiostat 6 is connected to the end of the pipe section 31 on the protected side away from the insulating joint 32, and the other end of the potentiostat 6 is connected to the auxiliary electrode 7.

[0025] The medium circulation and transportation module 8 includes a circulating medium 81 and can make the circulating medium 81 flow in the experimental pipe section 3 to simulate the transportation of refined oil. Further, the circulating medium 81 includes a liquid medium or a gaseous medium and also includes corrosion products to simulate the corrosion products generated by a real pipeline under the action of internal corrosive media. Further, the medium circulation and transportation module 8 also includes a medium storage device 82, a circulation power device 83, and a medium circulation pipe 84. The medium storage device 82 is used to store the medium, and the circulation power device 83 is used to provide pressure so that the circulating medium 81 can flow, thereby realizing the circulating transportation of the circulating medium 81 in the medium storage device 82, the medium circulation pipe 84, and the experimental pipe section 3.

[0026] The external magnetic field subsystem includes an external magnetizing member or an internal magnetizing member and also includes a Tesla meter, which can simulate the residual magnetism generated by magnetic flux leakage detection and measure the magnetic induction intensity. The external magnetizing member can be an external magnet or an external electromagnetic coil and other tools that can magnetize steel pipelines, used to simulate the residual magnetism generated by magnetic flux leakage detection. The internal magnetizing member can be an internal magnet and other tools that can magnetize steel pipelines, which can simulate the residual magnetism generated by magnetic flux leakage detection. The Tesla meter, for example, a millitesla meter can be used to measure the magnetic induction intensity.

[0027] The external magnetizing member is arranged on the outer wall of the experimental pipe section and is configured to be able to magnetize the experimental pipe section and can move along the axial direction of the experimental pipe section. The internal magnetizing member is arranged on the inner wall of the experimental pipe section and is configured to be able to magnetize the experimental pipe section and can move along the axial direction of the experimental pipe section. For example Figure 1 shown, the external magnetizing member is an external magnet 9, and the Tesla meter 10 is used to measure the magnetic induction intensity. The external magnet 9 is closely attached to the outer wall of the experimental pipe section and moves along the axial direction of the experimental pipe section to simulate the residual magnetism generated by magnetic flux leakage detection. When using the internal magnetizing member, the internal magnetizing member is closely attached to the inner wall of the experimental pipe section and moves along the axial direction of the experimental pipe section to simulate the residual magnetism generated by magnetic flux leakage detection.

[0028] The insulation performance test subsystem can measure the insulation conditions of the pipe section 31 on the protected side and the pipe section 33 on the non-protected side. For example, the insulation conditions of the pipe section 31 on the protected side and the pipe section 33 on the non-protected side are measured by measuring the pipe-to-earth potential at both ends of the pipe section on the protected side and the pipe section on the non-protected side. For exampleFigure 1 As shown, the insulation performance test subsystem may include a digital multimeter 11 and a long-term reference electrode 12 (e.g., a copper sulfate reference electrode) connected in sequence. The digital multimeter 11 can measure the pipe-to-soil potential of the protected side pipe section 31 and the non-protected side pipe section 33 to analyze and evaluate the leakage and insulation failure behaviors of the insulation joint 32, thereby providing support for the optimization of the structural design of the insulation joint 32. The pipe-to-soil potential measurement point 13 of the protected side pipe section and the pipe-to-soil potential measurement point 14 of the non-protected side pipe section are respectively located on both sides of the insulation joint. The digital multimeter can be connected to the pipe-to-soil potential measurement point 13 of the protected side pipe section or the pipe-to-soil potential measurement point 14 of the non-protected side pipe section for measurement. Further, the insulation conditions of the protected side pipe section and the non-protected side pipe section can also be measured by methods such as the leakage rate method, the current loop method, and the voltage drop method, as well as related equipment and facilities.

[0029] Embodiment 2

[0030] In an exemplary embodiment of the present invention, the insulation joint failure simulation test method uses the insulation joint failure simulation experimental system described in Embodiment 1.

[0031] The insulation joint failure simulation test method may include the following steps:

[0032] Connect the protected side pipeline potential test line, the non-protected side pipe section potential test line, and the auxiliary electrode test line;

[0033] After paving a thin layer of soil at the bottom of the soil box, bury the auxiliary electrode;

[0034] After connecting the insulation joint to be inspected with the protected side pipeline and the non-protected side pipe section, place it in the soil box;

[0035] Adsorb an external magnetizing member on the outer edge of the insulation joint to simulate residual magnetism;

[0036] Bury the long-term reference electrode and bury the soil. This experiment only tests the influence of conductive internal corrosion products on the performance of the insulation joint, and the soil height only needs to meet the requirements of the cathodic protection circuit;

[0037] Connect the cathodic protection module. For example, turn on the potentiostat switch to apply cathodic protection to the protected side pipe section;

[0038] Connect the oil pipeline, turn on the medium circulation and transportation module, and make the circulating medium circulate in the medium storage module, the medium circulation pipe, and the experimental pipe section;

[0039] Measure the pipe-to-soil potential of the protected side and the non-protected side pipe sections. Here, the voltage drop or the change in the current inside the pipe of the protected side and the non-protected side pipe sections can also be directly measured;

[0040] Dynamically adjust the test cycle according to the test results;

[0041] When the insulating joint is intact, the initial value of the pipe-to-soil potential of the protected side pipe section should be the cathodic protection potential, and the pipe-to-soil potential of the non-protected side pipe section should be the corrosion potential;

[0042] With the medium circulation, under the magnetic force, Fe3O4 deposits on the inner wall of the insulating joint, gradually causing the cross-connection of the protected side pipe section and the non-protected side pipe section and shunting part of the cathodic protection current, and resulting in changes in the pipe-to-soil potential on both sides;

[0043] The influence of the internal corrosion products on the insulation performance under the residual magnetic force can be analyzed through the change trend of the pipe-to-soil potential of the pipe sections on both sides of the insulating joint.

[0044] Furthermore, the influence of the density of the adsorbed corrosion products on the leakage rate under different magnetic forces can be simulated by changing the magnetic field intensity.

[0045] In summary, the beneficial effects of the present invention may include:

[0046] (1) It is possible to provide an experimental system and a test method for the leakage failure phenomenon and problems of insulating joints caused by the magnetic flux leakage detection process of pipelines that do not exist at present;

[0047] (2) It can be used to analyze the insulation failure behavior and key influencing factors in different service environments;

[0048] (3) It can be used for the performance evaluation and type screening of insulating joints and their inner coatings, and to test whether the width of the insulating gasket can avoid the leakage phenomenon caused by the adsorption of corrosion products by residual magnetism.

[0049] Although the present invention has been described above in conjunction with the exemplary embodiments and the drawings, those of ordinary skill in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. An insulation joint failure simulation experiment system, characterized in that, It includes a soil box, an experimental pipe section, a working condition simulation subsystem, an external magnetic field subsystem, and an insulation performance test subsystem. Among them, The experimental pipe section is arranged in the soil box and includes a protected side pipe section, an insulating joint, and an unprotected side pipe section that are connected in sequence; The working condition simulation subsystem includes a cathodic protection module and a medium circulation and transportation module. The cathodic protection module can protect the protected side pipe section. The medium circulation and transportation module includes a circulating medium and can make the circulating medium flow in the experimental pipe section; the circulating medium includes a liquid medium or a gaseous medium and also includes corrosion products; The external magnetic field subsystem includes an external magnetizing member or an internal magnetizing member and also includes a teslameter. The external magnetic field subsystem is configured to be able to simulate the residual magnetism generated by magnetic flux leakage detection and measure the magnetic induction intensity; The insulation performance test subsystem can measure the insulation condition between the protected side pipe section and the unprotected side pipe section; The coating condition of the inner wall of the experimental pipe section is a complete inner coating, a damaged inner coating, or no inner coating; the coating condition of the outer wall of the experimental pipe section is a damaged outer coating or no outer coating.

2. The insulation joint failure simulation experiment system according to claim 1, characterized in that, The external magnetizing member is arranged on the outer wall of the experimental pipe section and is configured to be able to magnetize the experimental pipe section and can move along the axial direction of the experimental pipe section; the internal magnetizing member is arranged on the inner wall of the experimental pipe section and is configured to be able to magnetize the experimental pipe section and can move along the axial direction of the experimental pipe section.

3. The insulation joint failure simulation experiment system according to claim 1, characterized in that, The medium circulation and transportation module also includes a medium circulation sub-module and a medium circulation pipe. The medium circulation sub-module includes a medium storage device and a circulation power device. One end of the medium circulation sub-module is connected to the protected side pipe section, and the other end is connected to the unprotected side pipe section through the medium circulation pipe. The circulating medium can realize the circulating transportation in the medium storage device, the medium circulation pipe, and the experimental pipe section under the action of the circulation power device.

4. An insulation joint failure simulation test method, characterized in that, The method uses the insulation joint failure simulation experimental system described in any one of claims 1 to 3, and analyzes the influence of the inner corrosion products on the insulation performance under the action of the residual magnetism through the change trends of the pipe-to-soil potential, voltage drop, or in-pipe current on both sides of the insulation joint.

5. The insulation joint failure simulation test method according to claim 4, characterized in that, By changing the magnetic field intensity, the influence of the density of the adsorbed corrosion products on the leakage rate under different magnetic forces is simulated.

6. The insulation joint failure simulation test method according to claim 4, characterized in that, The leakage current of the insulation joint is quantitatively measured using a current loop or a in-pipe current detector.

7. The insulation joint failure simulation test method according to claim 4, characterized in that, The insulation condition between the protected side pipe section and the unprotected side pipe section is measured by the potential method, the leakage rate method, the current loop method, or the voltage drop method.

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