Construction method of pipeline external anti-corrosion damage protection system

Abstract

The invention relates to a construction method of a pipeline external anti-corrosion damage protection system, and relates to the technical field of construction engineering non-excavation, and the construction method mainly comprises the following steps: excavating a deep well, arranging anode bodies at intervals on the outer wall of an exhaust pipe before the exhaust pipe is lowered into the deep well, connecting the anode bodies in series through a cable and binding the anode bodies on the outer wall of the exhaust pipe, the anode body and the exhaust pipe are lowered to the bottom of the deep well together, and after the anode body and the exhaust pipe are completely lowered, the anode body and the exhaust pipe are installed; installing a power-on point and a reference electrode at the pre-protection pipeline; cable connection and laying are carried out; according to the method, debugging and testing are carried out, installation of the pipeline external anti-corrosion damage protection system is completed, the mode that no sleeve is arranged is adopted, the anode bodies arranged in series are bound to the exhaust pipe and put down together with the exhaust pipe, the pipeline protection effect is guaranteed on the basis that well wall disturbance is reduced, and well wall collapse is avoided, and the construction efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of trenchless construction technology, and specifically relates to a construction method for a pipeline external corrosion protection system. Background Technology

[0002] In horizontal directional drilling (WD) operations, WD often encounters complex geological formations such as rock, gravel, karst caves, and isolated boulders. The uneven geological structure can easily lead to serpentine boreholes or protrusions. In rocky sections, variations in lithology and weathering, along with the presence of fissures and fracture zones, can result in irregular borehole formations. Furthermore, hole cleaning can be ineffective, as hard fragments may remain inside the borehole. Long-distance crossings through sand and gravel layers create significant friction on the pipeline. In areas where casing sections are added, the casing ends may have depressions or sharp edges. These issues can cause pipe jamming, scuffing, and damage to the anti-corrosion coating or steel pipe during pullback. Once the anti-corrosion coating of the pipeline is damaged, it is almost impossible to repair, posing potential risks and safety hazards to future pipeline operation and management. Protecting pipelines crossing such geological formations has become a major challenge in WD operations.

[0003] Currently, cathodic protection is used to protect pipelines. However, when lowering the anode, a casing is used to prevent well wall collapse. But the casing separates the anode and the surrounding carbonaceous backfill (petroleum coke) from the original soil, so that the current can only flow out from the bottom of the casing or a pre-drilled hole. This greatly limits the current outflow area, increases the ground resistance, and affects the protection effect. Moreover, setting up a casing will increase the number of procedures and reduce construction efficiency.

[0004] Therefore, it is necessary to design the construction method of the pipeline external corrosion protection system. Ensuring the protection effect of the pipeline while minimizing disturbance to the well wall and avoiding well wall collapse, and improving construction efficiency are key technical issues that urgently need to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a construction method for a pipeline external corrosion protection system, which ensures pipeline protection while minimizing disturbance to the well wall and preventing well wall collapse, thereby improving construction efficiency.

[0006] To achieve the above objectives, the present invention provides the following solution: A construction method for a pipeline external corrosion protection system mainly includes the following steps: A deep well is excavated, and anode bodies are installed at intervals on the outer wall of the exhaust pipe before the deep well is lowered. The anode bodies are connected in series by cables and tied to the outer wall of the exhaust pipe. The anode bodies and the exhaust pipe are lowered together to the bottom of the deep well. After the well is completely lowered, the anode bodies and the exhaust pipe are installed. Install the energizing point and reference electrode at the pre-protected pipeline; To connect and lay cables; Debugging and testing were carried out to complete the installation of the pipeline external corrosion protection system.

[0007] Preferably, the anode body is tied to the exhaust pipe every 0.2 meters to 0.6 meters.

[0008] Preferably, the energizing point includes the point where the cathode output cable of the potentiostat is connected to the pipe and the potential feedback point.

[0009] Preferably, the step of installing the reference electrode is as follows: The assembled reference electrode is placed in a pre-dug burial pit, close to the pre-protected pipe, and then soil is filled into the burial pit while an appropriate amount of fresh water is poured in. The reference electrode cable, the zero-position female cable, and the cathode cable are laid in the same trench and connected to the potentiostat in the cathodic protection room.

[0010] Preferably, the assembly process of the reference electrode is as follows: copper sulfate crystals are dissolved in distilled water or clean fresh water, and then the Cu / CuSO4 electrode is immersed in the copper sulfate crystal mixture solution for 24 hours. An appropriate amount of fresh water is poured into the reference electrode filler to make it into a uniform slurry, and the reference electrode is placed in the center of the filler.

[0011] Preferably, the cable includes an anode cable, a cathode cable, a zero-position cathode cable, a reference cable, and a housing grounding cable. The anode cable is used to connect multiple anodes in series and is connected to the cathode cable of the pre-protected pipeline through a potentiostat. One end of the zero-position cathode cable is connected to the potentiostat, and the other end is connected to the reference cable. One end of the reference cable is connected to the reference electrode, and the other end is connected to the potentiostat. One end of the housing grounding cable is connected to the housing of the potentiostat, and the other end is grounded.

[0012] Preferably, the cable connection and laying steps include: Excavation of cable trenches; Cables are laid in the cable trench. The cable was covered with sand and bricks; Connect the cable connection points.

[0013] Preferably, the cable is laid at a depth of not less than 1000 mm.

[0014] Preferably, the connection point between the cable and the pre-protected pipe is welded, and the weld point is protected against corrosion and insulated.

[0015] Preferably, the corrosion-resistant and insulating method is to use viscoelastic paste, viscoelastic tape, or cold-applied tape for corrosion protection.

[0016] The present invention achieves the following technical effects compared to the prior art: By employing a method without casing and binding the series-connected anodes to the exhaust pipe and lowering them together, the backfill material can directly and fully contact the original soil around the well wall. This allows the conductive material formed by the carbonaceous backfill material to be directly connected to the ground, and the current can be released unimpeded from the entire backfill material column surface to the surrounding soil. This greatly reduces the grounding resistance of the anode bed, thereby improving the protection effect. By binding the series-connected anodes to the exhaust pipe and lowering them together, collisions and disturbances to the well wall can be reduced. Even without casing, there will be no well wall collapse. This avoids the well wall collapse problem caused by the impact of the exhaust pipe and anodes during the lowering process when the exhaust pipe and anodes are lowered separately, or the problem of entanglement when the exhaust pipe and anodes are lowered at the same time, which would increase the disturbance to the well wall. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Appendix Figure 1 This is a flowchart of the construction method for the pipeline external corrosion protection system disclosed in the embodiments of the present invention; Appendix Figure 2 This is a schematic diagram of the cable connection relationship in the construction method of the pipeline external corrosion protection system disclosed in the embodiments of the present invention; Appendix Figure 3 This is a schematic diagram showing the connection relationship of the power supply points in the construction method of the pipeline external corrosion protection system disclosed in the embodiments of the present invention. Appendix Figure 4 This is a schematic diagram of cable laying in the construction method of the pipeline external corrosion protection system disclosed in the embodiments of the present invention; Among them, 1. Potentiostat; 2. Electrolyte; 3. Reference electrode; 4. Pre-protected pipeline; 5. Deep well; 6. Anode body; 7. Power-on point; 8. Reference cable; 9. Cathode cable; 10. Zero-position grounding cable; 11. Anode cable; 12. Casing grounding cable; 13. Anti-corrosion layer; 14. Fine sand; 15. Square brick; 16. Original soil. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The purpose of this invention is to provide a construction method for an external corrosion protection system for pipelines, which ensures the protection of the pipeline while minimizing disturbance to the well wall and preventing well wall collapse, and improves construction efficiency.

[0021] refer to Figures 1-4 This invention discloses a construction method for a pipeline external corrosion protection system, which includes at least the following steps: Deep well 5 is excavated. Before lowering deep well 5, anode bodies 6 are spaced apart on the outer wall of the exhaust pipe. The anode bodies 6 are connected in series by cables and tied to the outer wall of the exhaust pipe. The anode bodies 6 and the exhaust pipe are lowered together to the bottom of deep well 5. After complete lowering, the anode bodies 6 and the exhaust pipe are installed. The energizing point 7 and the reference electrode 3 are installed at the pre-protected pipeline 4. Cables are connected and laid. Debugging and testing are conducted to complete the installation of the external corrosion protection system for the pre-protected pipeline 4. By using a method without casing, and by tying the series-connected anode bodies 6 to the exhaust pipe and lowering them together with the exhaust pipe, the backfill material can directly and fully integrate with the original soil around the well wall. The contact allows the conductive material formed by the carbonaceous backfill to be directly connected to the ground, enabling current to be released unimpeded from the entire backfill column surface to the surrounding soil. This significantly reduces the grounding resistance of the anode bed, thereby improving the protection effect. By binding the series-connected anode body 6 to the exhaust pipe and lowering it together with the exhaust pipe, collisions and disturbances to the well wall can be reduced. Even without the casing, there will be no problem of well wall collapse. This avoids the problem of well wall collapse caused by the impact of the exhaust pipe and anode body 6 on the well wall during the lowering process, or the problem of entanglement caused by the exhaust pipe and anode body 6 being lowered at the same time, which would increase the disturbance to the well wall.

[0022] It should be noted that after the anode body 6 is tied to the exhaust pipe, a clamp is installed on the exhaust pipe to hold it in place. Two or more steel wire ropes are then connected around the clamp and connected to the hoisting equipment. The exhaust pipe and anode body 6 are then lowered to ensure that they are lowered vertically and stably, thus preventing the well wall from collapsing due to violent shaking.

[0023] When excavating deep well 5, a test pit with a width and length of 1.5 meters and a depth of 2 meters shall be excavated at the selected location of deep well 5 to ensure that there are no cables, pipes or other facilities below to ensure the safety of well drilling. If other facilities are found during the excavation process, the excavation site shall be changed. Install the derrick and other drilling equipment at position 5 of the deep well, and drill the well using a drill bit; When drilling reaches the predetermined depth, stop drilling, remove the drill bit, and check the connection between the conductor and the anode before installing the anode body 6. Protect the conductor insulation layer to prevent wear and damage from sharp objects. The minimum bending radius should be consistent with the manufacturer's requirements. Before installation, visually inspect the conductor insulation layer for defects or damage. Position the crane vehicle at the lifting location, connect the pre-packaged anode body 6 with the anode cap at the bottom with a steel wire rope, lift the pre-packaged anode body 6, slowly move it to the wellhead, release the steel wire rope, and slowly lower the anode body 6 into the well. When all the pre-packaged anode bodies 6 reach the bottom of the well, fill it with petroleum coke. Install the exhaust pipes in sequence until the wire rope releases the anode body 6 to the bottom of the well. When the precast ferrosilicon anode body 6 reaches the bottom of the well, backfill fine soil to the wellhead, install the exhaust pipe and cable pipe elbow, and build the anode well frame according to the design drawings. The installation of the anode body 6 in the deep well 5 is completed.

[0024] Install an auxiliary anode junction box. The junction box should be explosion-proof and have 10 terminals in 2 rows. Connect the cables of the three anode bodies 6 to the anode wires inside the junction box. Insulate and seal the wire entry points of the junction box and the anode wire bundles.

[0025] After the deep well anode ground bed construction is completed, the grounding resistance of the anode ground bed is measured.

[0026] refer to Figure 1 As one implementation method, the exploration and design are carried out before excavating the deep well 5, which mainly includes the following steps: 1. Collect technical data related to the project, such as the four parameters of the pre-protected pipeline (length, diameter, wall thickness, pipe type and grade, anti-corrosion layer type and grade), the transport medium, the design pressure, the geological and geomorphological parameters and soil characteristics of the crossing section, the underground pipeline situation in the proposed protection area and nearby areas, etc.; conduct on-site surveys to investigate the distribution of existing pipelines, structures, and available power facilities and equipment in the proposed protection area. 2. Calculate the grounding resistance of anode 5 in deep well 5. Based on the measured soil resistivity and other parameters on site, the grounding resistance of anode 5 in deep well 5 is calculated according to the following formula.

[0027] Where: Rv——Deep-buried auxiliary anode grounding resistance, in ohms (Ω); ρ—soil resistivity, in ohm (Ω·m); La—Length of auxiliary anode (including packing), in meters (m); Da—Auxiliary anode diameter (including packing), in meters (m); t—Auxiliary anode burial depth (the distance from the top of the packing to the ground surface), in meters (m).

[0028] refer to Figure 1 As one implementation method, the anode body 6 is tied to the exhaust pipe every 0.2 to 0.6 meters, preferably 0.4 meters, to ensure that the anode body 6 and the exhaust pipe always remain parallel and completely eliminate the risk of entanglement. If the site conditions limit it, it can be fixed in sections and lowered into the well in sections.

[0029] refer to Figure 2 In one implementation, the energizing point 7 is the connection point between the potentiostat 1, the cathode cable 9, and the pre-protected pipeline 4, as well as the potential feedback point. The cathode cable 9 and the zero-position cathode cable 10 are connected from the potentiostat 1 to the protected object. The reference cable 8 is connected from the potentiostat 1 to the reference electrode 3, and the reference electrode 3 is set near the connection point of the pre-protected pipeline 4. A marker post is set directly above the energizing point 7. The energizing point 7 is installed outside the insulating joint on the outer wall of the pre-protected pipeline 4. The specific location is determined according to the on-site positioning of the pre-protected pipeline 4.

[0030] refer to Figure 1 and Figure 2 As one implementation method, the steps for installing the reference electrode 3 are as follows: place the reference electrode 3 into the electrolyte 2, that is, dissolve copper sulfate crystals in distilled water or clean fresh water, and then immerse the Cu / CuSO4 electrode in the solution for 24 hours. Open the special cloth bag for reference electrode 3, pour an appropriate amount of fresh water into the filler of reference electrode 3, mix it into a uniform thin mud, place reference electrode 3 in the center of the filler, the filler should be compacted and tightly bonded to the electrode, and there should be no gaps. Place the assembled reference electrode 3 into the pre-dug burial pit, as close as possible to the pre-protected pipe 4 to be tested, then fill the burial pit with soil and pour in an appropriate amount of fresh water to ensure good electrical connection between the electrode and the soil; the backfill soil should not contain stones, bricks, plastic bags or other debris. After the reference electrode 3 is installed, the reference electrode 3 cable is laid in the same trench as the zero-position female cable 10 and the cathode cable 9, and connected to the potentiostat 1 in the cathodic protection room. The installation of reference electrode 3 is complete.

[0031] refer to Figure 2In this embodiment, the cable includes an anode cable 11, a cathode cable 9, a zero-position cathode cable 10, a reference cable 8, and a housing grounding cable 12. The cable laying depth is not less than 1000mm, and it is ensured to be buried below the frost line. Sufficient slack should be left both above and below ground to prevent the cable from being broken by soil sinking. Sand is buried above the cable and bricks are laid. When the cable needs to cross the wall, road, pipeline, ditch, or other cables, a protective sleeve is added. The two ends of the protective sleeve should be at least 200mm longer than the two ends of the crossing section. The anode cable 11 is used to connect multiple anode bodies 6 in series and is connected to the cathode cable 9 of the pre-protected pipeline 4 through the potentiostat 1. One end of the zero-position cathode cable 10 is connected to the potentiostat 1, and the other end is connected to the reference cable 8. One end of the reference cable 8 is connected to the reference electrode 3, and the other end is connected to the potentiostat 1. One end of the housing grounding cable 12 is connected to the housing of the potentiostat 1, and the other end is grounded.

[0032] refer to Figures 1-4 As one implementation method, the cable connection and laying steps are as follows: I. Earthwork Excavation 1. Operating conditions: a. Before excavation, all underground and above-ground obstacles in the construction area must be cleared and dealt with. b. Determine the excavation location as marked by the layout lines; c. Arrange the excavation sequence reasonably and prevent incorrect or over-excavation; d. All excavation within 5 meters of pipelines and optical cables shall be carried out manually to ensure pipeline safety.

[0033] 2. Earthwork excavation sequence and route The sequence and method of earthwork excavation are consistent with the design conditions and follow the principles of "trenching and supporting, supporting before excavation, excavating in layers, and strictly prohibiting over-excavation". The excavation of the pit is carried out in layers. During the construction process, the soil piled on the side of the ditch shall not exceed the design load. During excavation, the supporting structure and dewatering facilities shall not be collided with or damaged. During the construction of pits and earthwork, the support structure and surrounding environment should be observed and monitored. If any abnormalities occur, they should be dealt with in a timely manner, and construction should continue after the situation is restored to normal. After the pit is excavated to the design elevation, the bottom of the pit is protected. Once the pit passes inspection, the foundation layer is constructed. For extra-large foundation pits, excavation is carried out in sections to the design elevation, and the foundation layer is poured in a timely manner for each section. If necessary, the foundation layer is reinforced.

[0034] II. Cable Laying 1. Cable trench line measurement and layout; 2. When laying cables in cable trenches, some slack should be left during laying to avoid the cables breaking due to stress caused by ground settlement, etc. 3. After the cable laying is completed, cover it with sand and bricks.

[0035] III. Earthwork Backfill 1. When backfilling the cable trench, backfill the perimeter with 100mm of fine sand 14 (or fine soil), and lay square bricks 15 on top. If there is no fine sand 14 (fine soil) that meets the backfilling requirements on site, use sieved backfill soil or purchase sand and soil for backfilling. 2. After the fine soil backfill is completed, the trench is backfilled and compacted in layers with the original soil 16. The compaction must be continuous and there should be no omissions. The thickness of each backfill layer should not exceed 200mm when compacted manually, and should not exceed 300mm when compacted mechanically.

[0036] IV. Cable Connection Point Connection The cable is connected to the pre-protected pipe 4 by aluminothermic welding. The welding must be conductive and not incomplete. After welding, the weld point is strictly protected against corrosion and insulated. The weld between the cable and the pre-protected pipe 4 is protected against corrosion by viscoelastic paste, viscoelastic tape and cold wrapping tape. The cables are connected by copper pipe crimping. After the connection is completed, the electrical connection of each joint is checked one by one with a multimeter. 1. Cable welding and corrosion protection a. The connection between the cable and the pre-protected conduit 4 is made by aluminothermic welding, which is convenient to construct and simple to operate, giving aluminothermic welding an almost irreplaceable advantage in cathodic protection construction. b. Peel off the anti-corrosion layer 13 of the pre-protected pipe 4 to expose a round hole with sufficient welding area, and use a tool to remove the oxide layer on the surface of the pipe wall to expose the metallic luster. c. The cable core wires should extend 50mm out and be clean, dry, and free of grease.

[0037] d. Carefully clean the welding slag from the inner surface of the graphite mold before use to prevent it from affecting the welding result. Place the cleaned mold on the weld joint, ensuring there are no obvious gaps; otherwise, the molten iron may easily leak out during welding. e. The weld point should be more than 150mm away from the pre-protected pipe weld joint, the distance between the weld points of the two test lines should be 100mm, there should be no false welds, good conductivity must be ensured, and strict anti-corrosion and insulation should be performed after welding; f. Test leads are connected to each other using copper tubing clamps; g. After the test line is connected, leave sufficient slack (10% expansion allowance) on both the ground and underground to prevent the test line from breaking when the soil settles. 2. Precautions for aluminothermic welding construction A good weld has a full, bright surface, free of porosity and slag inclusions. When cut open, the cross-section appears as a single, seamless surface without any pores or imperfections. The main factor affecting welding results is moisture or water vapor. Since the mold, welding powder, and the surface of the pipe being welded can all absorb moisture, preventing and removing moisture is a crucial step, similar to other welding methods. Another factor affecting welding results is the cleanliness of the mold and the steel pipe being welded. If the surface of the pipe is not properly cleaned, and there is dust, oxides, or other deposits, these must be removed until it is clean and bright before welding can proceed. Otherwise, the electrical and mechanical properties of the weld will be affected. If residue remains in the mold, the weld surface will be rough and dull.

[0038] 3. Weld joint corrosion protection When performing anti-corrosion construction on the weld points of the pre-protected pipeline 4, please note: First, clean the surface around the weld point, and roughen the anti-corrosion layer 13 within the overlap width range. Use viscoelastic paste, viscoelastic tape, and cold-applied tape for anti-corrosion of the welded joint.

[0039] 4. Viscoelastic corrosion protection and cold-applied tape protection a. When applying viscoelastic adhesive for corrosion protection, maintain gentle tension and roll / press the adhesive while applying it to keep the tape flat and ensure a good seal with the tube surface; b. The overlap width between the viscoelastic anti-corrosion tape and the anti-corrosion layer 13 of the pre-protected pipe 4 shall not be less than 10mm. If the temperature is low during construction, the viscoelastic anti-corrosion tape can be heated with a small flame. c. After the viscoelastic anti-corrosion tape layer passes the inspection, cold-apply tape is applied to the outer layer of the viscoelastic anti-corrosion tape and the outer layer of the steel pipe. The cold-apply tape is heated with a small flame to shrink and seal the anti-corrosion treatment. d. After the corrosion protection is completed, use a 15KV electric spark test to check for leaks. Only if there are no leaks can the next step be carried out.

[0040] refer to Figure 1 In one embodiment, the system debugging and testing steps are as follows: After the system is built, joint commissioning of multiple stations will be carried out. The set value of potentiostat 1 will be determined by the polarization potential at the junction point. System protection potential standard for pre-protected pipeline 4; 1. Under energized conditions, the measured polarization potential of the pre-protected pipe 4 is -850mV (relative to Cu / CuSO4, the same below) or more negative, and the measurement method complies with the specifications. 2. The cathode specific potential difference measured between the surface of the pre-protected pipe 4 and the reference electrode 3 in contact with the soil shall not be less than 100mV. This criterion can be used in the polarization establishment process or the attenuation process. 3. When the soil or water contains sulfate-reducing bacteria and the sulfate content is greater than 0.5%, the power protection potential should reach -950mV or more negative. 4. The maximum polarization potential should be -1.20V. 5. Detect the protection potential after the cathodic protection polarization stabilizes at both the soil entry point and the soil exit point. The polarization time should not be less than 24 hours. Compare the test data with the data before construction to determine the operational effect.

[0041] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A construction method for a pipeline external corrosion protection system, characterized in that, The main steps include: A deep well is excavated, and anode bodies are installed at intervals on the outer wall of the exhaust pipe before the deep well is lowered. The anode bodies are connected in series by cables and tied to the outer wall of the exhaust pipe. The anode bodies and the exhaust pipe are lowered together to the bottom of the deep well. After the well is completely lowered, the anode bodies and the exhaust pipe are installed. Install the energizing point and reference electrode at the pre-protected pipeline; To connect and lay cables; Debugging and testing were carried out to complete the installation of the pipeline external corrosion protection system.

2. The construction method of the pipeline external corrosion protection system according to claim 1, characterized in that, The anode body is tied to the exhaust pipe every 0.2 to 0.6 meters.

3. The construction method of the pipeline external corrosion protection system according to claim 1, characterized in that, The energized points include the point where the cathode output cable of the potentiostat connects to the pipeline and the potential feedback point.

4. The construction method of the pipeline external corrosion protection system according to claim 1, characterized in that, The steps for installing the reference electrode are as follows: The assembled reference electrode is placed in a pre-dug burial pit, close to the pre-protected pipe, and then soil is filled into the burial pit while an appropriate amount of fresh water is poured in. The reference electrode cable, the zero-position female cable, and the cathode cable are laid in the same trench and connected to the potentiostat in the cathodic protection room.

5. The construction method of the pipeline external corrosion protection system according to claim 4, characterized in that, The assembly process of the reference electrode is as follows: copper sulfate crystals are dissolved in distilled water or clean fresh water, and then the Cu / CuSO4 electrode is immersed in the copper sulfate crystal mixture solution for 24 hours. An appropriate amount of fresh water is poured into the reference electrode filler to make it into a uniform slurry, and the reference electrode is placed in the center of the filler.

6. The construction method of the pipeline external corrosion protection system according to claim 1, characterized in that, The cable includes an anode cable, a cathode cable, a zero-position cathode cable, a reference cable, and a housing grounding cable. The anode cable is used to connect multiple anodes in series and is connected to the cathode cable of the pre-protected pipeline through a potentiostat. One end of the zero-position cathode cable is connected to the potentiostat, and the other end is connected to the reference cable. One end of the reference cable is connected to the reference electrode, and the other end is connected to the potentiostat. One end of the housing grounding cable is connected to the housing of the potentiostat, and the other end is grounded.

7. The construction method of the pipeline external corrosion protection system according to claim 1, characterized in that, The cable connection and laying steps include: Excavation of cable trenches; Cables are laid in the cable trench. The cable was covered with sand and bricks; Connect the cable connection points.

8. The construction method of the pipeline external corrosion protection system according to claim 6, characterized in that, The cable is laid at a depth of not less than 1000mm.

9. The construction method of the pipeline external corrosion protection system according to claim 6, characterized in that, The connection point between the cable and the pre-protected pipeline is welded, and the weld point is protected against corrosion and insulated.

10. The construction method of the pipeline external corrosion protection system according to claim 9, characterized in that, The method of corrosion protection and insulation is to use viscoelastic paste, viscoelastic tape or cold-applied tape for corrosion protection.

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