Pipeline cathode protection and lining repair composite protection method

Abstract

The invention relates to the technical field of buried pipeline repair and protection, in particular to a pipeline cathode protection and lining repair composite protection method. The method includes the steps of pipeline current situation multi-dimensional detection and transformation range pipe section determination; constructing and arranging a segmented operation pit; the non-excavation HDPE lining is repaired; the ends of the HDPE lining pipe are heated, softened and flanged to form lining flanged flanges, an elastic sealing gasket is arranged between the two lining flanged flanges in an attached mode, the two lining flanged flanges are connected in a fastening and pressing mode through a steel flange and a fastening bolt, a conductive lining ring is arranged between the lining flanged flanges and the steel flange, and the lining flanged flanges and the steel flange are in conductive connection through a conductive contact. The conductive contact passes through and is embedded in the two lining flanging flanges and the elastic sealing gasket; performing adaptive cathode protection installation; and acceptance and performance detection. The technical problems that cathode protection and lining repair cannot be effectively coordinated, cathode protection cannot be fully covered, and a protection blind area exists, so that diversion interruption and uneven current distribution are caused, and the protection efficiency is greatly reduced are solved.

Description

Technical Field

[0001] This application relates to the field of buried pipeline repair and protection technology, and in particular to a composite protection method for pipeline cathodic protection and lining repair. Background Technology

[0002] Because reclaimed water contains various corrosive ions, long-term transportation will cause scale to form on the inner wall of the pipeline. The oxygen-deficient area under the scale is highly susceptible to localized corrosion, leading to pitting corrosion and perforation, resulting in frequent leaks. Furthermore, long-term transportation also increases the risk of corrosion and aging on the outer wall of the pipeline. Therefore, to prevent the specific corrosion risks and pipeline aging problems during reclaimed water transportation, and to ensure water supply safety, extend pipeline life, meet production needs, and reduce maintenance costs, it is necessary to carry out anti-corrosion repair on buried reclaimed water replenishment pipelines.

[0003] Currently, the main technologies for corrosion prevention and repair of buried greywater replenishment pipelines include the following: First, there are internal lining repair technologies: One approach involves laying an internal lining material on the inner wall of the original pipe to isolate the water from the pipe's inner wall. For example, this can be done by manually applying cement mortar lining at pipe joints. However, this method results in uneven thickness and is prone to cracking at misaligned joints, leading to poor long-term stability. Another approach is to use HDPE (high-density polyethylene) linings installed in the original pipe via a "straight pipe insertion" method. However, this method is easily scratched by pipe welds and misaligned joints during insertion, and it cannot be adapted to elbows. Furthermore, it has poor fit at joints of mixed pipe materials (such as the connection between steel pipes and steel-concrete composite pipes), easily leading to increased local water erosion and limited restoration of water supply capacity. Elbows require stainless steel lining repairs, which involves a large amount of work and is costly. This internal lining repair technology also reduces the pipe's flow area, and the gap between the lining and the original pipe increases water flow resistance, limiting the actual water supply capacity. The actual water supply may not meet design requirements, making it difficult to satisfy the water demand during peak industrial production periods. Furthermore, this HDPE material is an insulating material, which will cut off the conductivity of the pipe. If cathodic protection technology is subsequently added, the current will not be able to be conducted across the flange, forming a protection blind zone, and will also cause the conductivity to be interrupted.

[0004] Secondly, cathodic protection technology: This technology uses sacrificial anodes along the pipeline to protect the outer wall of the steel pipeline from soil corrosion using electrochemical principles. The anodes and steel pipeline are connected by wires to form a circuit, and test stakes are used to monitor the protection potential. However, this technology only protects the outer wall of the steel pipeline and cannot solve the problem of under-deposit corrosion caused by corrosive ions in the water inside the pipeline. Moreover, due to the non-conductive nature of steel cylinder concrete pipe sections, the anode current cannot cover the pipe, especially at the joints where the seals are prone to aging due to long-term immersion, leading to the risk of leakage and pipe burst. If used in conjunction with lining repair technology, the insulation of the HDPE lining will prevent the current from being conducted across the flange, creating a protection blind spot, and will also cause uneven current distribution, with the current tending to concentrate in the non-lining section, resulting in insufficient protection in the lining section, a significant decrease in protection efficiency, and a failure to form effective synergistic protection.

[0005] Third, the traditional excavation and replacement pipe technology involves excavating the entire length of a severely corroded pipe section, removing the original pipe, replacing it with a new one, and then reapplying external anti-corrosion treatment. This technology requires the requisition of a large area of ​​surface space along the route, resulting in high coordination costs, long construction periods, and potential damage to the surrounding environment, such as farmland and roads, dust and noise pollution. Furthermore, coordinating with local authorities is extremely difficult. Summary of the Invention

[0006] The purpose of this application is to provide a composite protection method for pipeline cathodic protection and lining repair, in order to solve the technical problems of existing technologies where external cathodic protection and internal repair protection of pipelines cannot effectively coordinate protection, cathodic protection cannot provide full coverage, there are blind spots in protection, resulting in interruption of flow and uneven current distribution, and a significant decrease in protection efficiency.

[0007] Firstly, this application provides a composite protection method for pipeline cathodic protection and lining repair, comprising: Step S10: Multi-dimensional inspection of the current status of the pipeline and determination of the pipeline segment to be renovated; Step S20: The segmented operation pit construction layout and the coordinated inner lining interlacing path and cathodic protection current coverage path are synchronously set up in segments for operation pits. Step S30, trenchless HDPE lining repair, includes step S31, pipe pretreatment, and step S32, HDPE lining pipe preparation and repair layout. Step S40: Conductive sealing connection at the end interface. The ends of the two HDPE inner-lined pipes to be connected are heated and softened to form inner-lined flanges. Then, an elastic sealing gasket is attached between the two inner-lined flanges. The two inner-lined flanges are fastened and pressed together on both sides by steel flanges and fastening bolts. A conductive bushing is set between the inner-lined flange and the steel flange on one side. The two conductive bushings are electrically connected by conductive contacts. The conductive contacts pass through and are embedded in the two inner-lined flanges and the elastic sealing gasket located between the two conductive bushings. The two ends of the pipe are symmetrically arranged. Step S50: Adapt to cathodic protection installation, install sacrificial anode protection outside the pipeline, and fill with compatible packing material; Step S60, acceptance and performance testing.

[0008] Furthermore, in step S32, the process of preparing and repairing the HDPE inner lining pipe includes: Step S321, HDPE inner lining pipe preparation: PE100 grade HDPE inner lining pipe is selected, with nominal outer diameter matching pipe inner diameter, wall thickness 20mm, melt flow index ≤0.15g / 10min, and welded according to the segment length of the operation pit. Step S322: Fold the HDPE inner liner tube. The HDPE inner liner tube is pressed into a U-shape by a folding machine, reducing the diameter by 30~35%, and then wrapped with soft polyester tape to fix the shape. Step S323: HDPE inner lining pipe is inserted. The HDPE inner lining pipe is pulled from the operating pit by a traction machine. Anti-wear pads are provided at the pulling end, and guide rollers are provided on the top, left and right sides of the pipe opening. Step S324, HDPE inner lining pipe expansion in stages: First, pressurize with 0.15MPa compressed air for 5 minutes to release the air, then increase the pressure to 0.25MPa and pressurize for 10 minutes for initial bonding, then reduce the pressure to 0.2MPa and pressurize for 30 minutes for complete bonding, and ensure that the gap between the HDPE inner lining pipe and the inner wall of the pipe is ≤3mm.

[0009] Furthermore, in step S31, the pipeline pretreatment includes: A portable high-pressure water pump is used to clean the scale layer inside the pipe, and a traction-type pipe cleaning ball is used to remove wooden wedges and corrosion products to ensure that there are no sharp protrusions on the inner wall. For misaligned or stepped joints of steel cylinder concrete pipes, epoxy asphalt is used to fill and level them, and all aged rubber rings are replaced to ensure that the joint gap is ≤1mm.

[0010] Furthermore, in step S40, the conductive contact is made of copper alloy or stainless steel coated with an anti-corrosion coating; and / or The elastic sealing gasket is a modified sealing gasket made of embedded EPDM rubber or fluororubber, and the elastic sealing gasket is a double-lip elastic sealing gasket. Furthermore, step S40 also includes: continuity verification: checking whether the conductive resistance at both ends of the connector is less than 0.1Ω using a multimeter; and / or In step S40, the end of the HDPE liner is heated to 120~130℃ to soften and flange, and the outer edge of the flange extends at least 3mm beyond the sealing line of the steel flange. M20 bolts are used for fastening, and they are tightened symmetrically to a torque of 50~60N. m, and fixed by perforation.

[0011] Furthermore, step S10 includes: Step S11, Multi-dimensional inspection of pipeline status: Collect soil samples and greywater samples along the pipeline. The soil samples are tested for pH value, corrosive ion content and resistivity. The greywater samples are tested for pH value, conductivity and corrosive ion content. The degree of pipeline corrosion, interface condition and structural integrity are evaluated by thickness measurement and observation of inner wall morphology. Step S12, Determine the scope of the renovation: Exclude pipe sections that have been operating well recently, and focus on designating pipe sections with severe corrosion and frequent leaks that are laid with mixed pipe materials as the target pipe sections for renovation.

[0012] Furthermore, step S20 includes: Step S21, Segmented Operation Pit Construction Layout: Divide the pipeline into several segments and set up operation pits. The location selection of operation pits follows the principles of: one pit for every ≤1km of straight pipe section, one pit must be set at bends >15°, priority should be given to steel pipe sections, and the pits should be avoided in farmland; operation pits near rivers are supported by steel pipe piles or steel sheet piles, and water collection pits and water pumps are set up to ensure that the pits are dry. Protective fences and warning signs are set up around the operation pits. Step S22, Collaborative Planning and Setup: Combining the insertion path of the HDPE inner liner pipe and the current coverage requirements of cathodic protection, simultaneously determine the location of the operating pit, taking into account both the inner liner pulling and anode installation, with a spacing of ≤1km, and the sacrificial anode arrangement should be densified at 1.5 times the density of the non-inner liner section for the inner liner section, and the end connection position must be set.

[0013] Furthermore, step S50 includes: Step S51, Sacrificial Anode Selection and Arrangement: After the HDPE inner lining pipe is repaired, sacrificial anode protection is added to the steel pipe section. High-potential magnesium alloy anodes are selected, arranged in groups of 3 every 500m, and specifically designed for high Cl... - In soil areas, the anode spacing is shortened to 300m to ensure that the current coverage is free of blind spots; Step S52, Backfill material optimization: The anode is buried in a 3m deep well and filled with low-resistance backfill material, which consists of 75% gypsum, 20% bentonite and 5% sodium sulfate, so that the grounding resistance is ≤20Ω, ensuring that the current penetrates the soil to cover the outer wall of the inner lining section.

[0014] Furthermore, step S50 also includes: Step S53, Installation of jumper wires and test piles: With the HDPE inner liner pipe isolating the pipeline's conductivity, weld jumper wires to ensure the continuity of power supply to the steel structures on both sides of the flange, guaranteeing electrical connectivity; set up test piles every 500m to monitor the protection potential.

[0015] Furthermore, step S60 includes: Step S61, visual inspection: Observe with an endoscope to see if the plastic inner lining is wrinkle-free and hollow, the weld joints are free of defects, the sacrificial anode arrangement is standardized, the filler material is not lost, and the interface sealing structure is intact. Step S62, performance testing, includes: Conductivity detection: The test pile monitors whether the protection potential is uniform throughout the entire section and there are no blind spots; Sealing test: Hydrostatic test to check sealing performance; Insulation testing: Perform spark testing on the HDPE inner lining pipe to check for leaks at 3~5kV. Step S63, Functional Verification: After water is supplied, verify whether the water supply volume of the pipeline meets the standard, whether the pressure is stable, and whether there is any leakage or abnormal water flow noise.

[0016] Compared with existing technologies, the composite protection method of cathodic protection and lining repair provided in this application for the corrosion prevention and repair of buried reclaimed water supply pipelines not only provides synergistic protection for the inside and outside of the pipeline through trenchless HDPE lining repair and cathodic protection, but also completely blocks corrosion inside and outside the pipeline.

[0017] Furthermore, a conductive sealing connection is applied to the pipe end joints. Specifically, the ends of the two HDPE lined pipes to be connected are heated and softened to form lining flanges. An elastic sealing gasket is then fitted between the two lining flanges for sealing. Steel flanges and bolts are used to tighten and press the flanges together on both sides. A conductive bushing is placed between each lining flange and each steel flange, and these two bushings are electrically connected via conductive contacts. These conductive contacts pass through and are embedded in the two lining flanges and the elastic sealing gasket located between the two conductive bushings, achieving a conductive connection at the end joint while preventing corrosion from contact with water, eliminating blind spots in protection, and achieving full cathodic protection coverage at the end flange joints. This significantly improves protection efficiency. This conductive sealing connection method simultaneously solves the two major problems of conductive interruption and sealing leakage at the end joints. Furthermore, by optimizing the filling material, the problem of uneven current distribution is solved, further improving protection efficiency.

[0018] Furthermore, the use of trenchless lining repair segmented construction technology reduces the excavation area, lowers social impact and coordination costs, minimizes damage to the surrounding environment, and significantly shortens the construction period, ensuring smooth construction and improving efficiency. In addition, it significantly improves long-term economic efficiency, extends pipeline life, eliminates the need for frequent emergency repairs, and reduces operation and maintenance costs. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the conductive sealing structure at the pipe end interface provided in the embodiment of this application; Figure 2 This is a schematic diagram of the composite protection structure for pipelines provided in an embodiment of this application; Figure 3 This is a schematic flowchart illustrating the composite protection method for pipeline cathodic protection and lining repair provided in the embodiments of this application.

[0021] Figure label: 10 - Target pipe section to be modified; 11-Steel pipe section; 12- Concrete cylinder pipe section; 20-HDPE lined pipe; 21-Inner lining flange; 30 - End conductive seal; 31 - Elastic sealing gasket; 32-Conductive bushing; 33 - Conductive contact; 34-Steel flange; 35 - Fastening bolt; 40-Sacrificial anode; 50 - Filling material; 60-Patch wire; 70 - Test pile; 80-Guide sliding protection structure. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0024] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0025] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0026] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0027] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0028] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0029] like Figures 1 to 3 As shown in the embodiment of this application, a composite protection method for pipeline cathodic protection and lining repair is provided, including: Step S10: Multi-dimensional inspection of the current pipeline status and determination of the pipeline segment to be modified, including: Step S11, Multi-dimensional inspection of pipeline status: Collect soil and greywater samples along the pipeline. The soil samples are tested for pH value, corrosive ion content and resistivity. The greywater samples are tested for pH value, conductivity and corrosive ion content. The degree of pipeline corrosion, interface condition and structural integrity are evaluated by thickness measurement and observation of inner wall morphology.

[0030] Step S12, Determining the Pipeline Section to be Modified: Excluding pipe sections that have been operating well recently, the focus is on designating pipe sections with severe corrosion and frequent leaks (such as the connection section between steel pipe section 11 and steel cylinder concrete pipe section 12) as the target pipe section 10 for modification. Figure 1 As shown.

[0031] Step S20, the segmented operation pit construction layout and the coordinated lining interleaving path and cathodic protection current coverage path are synchronously set up in segments, including: Step S21, Segmented Operation Pit Construction and Layout: Divide the pipeline into several segments and set up operation pits. The location selection of operation pits follows the following principles: one pit is set for every ≤1km of straight pipe section, one pit must be set at bends >15°, steel pipe sections 11 are preferred, and farmland should be avoided. The operating pit near the river is supported by steel pipe piles or steel sheet piles. The steel pipe pile support uses Φ200mm steel pipes, spaced 1m apart. The operating pit is 6m×3m×3.5m in size and has a complete support structure, drainage plan and safety protection measures. It is necessary to ensure that the tension and speed during pipe laying are controllable to reduce construction difficulty and risk. A sump pit and water pump are set up and the pit is kept dry. Protective railings and warning signs are set up around the operating pit.

[0032] Step S22, Collaborative Planning and Setup: Combining the insertion path of the HDPE inner liner pipe 20 and the current coverage requirements of cathodic protection, the location of the operating pit is determined simultaneously, taking into account both the inner liner pulling and anode installation, with a spacing of ≤1km. The sacrificial anode 40 is arranged with a density 1.5 times that of the non-inner liner section, and the end connection position must be set.

[0033] Step S30, trenchless HDPE lining repair, includes: Step S31, perform pipeline pretreatment: use a 7.5kW portable high-pressure water pump with a pressure of 15MPa to clean the scale layer inside the pipe, and use a traction-type pig to remove wooden wedges and corrosion product residues, so that there are no sharp protrusions on the inner wall, and the pipe can be scratched without breaking when wearing nitrile gloves. A traction-type pig with a diameter of 1180mm made of polyurethane can be used. For misaligned or stepped joints in steel cylinder concrete pipes, epoxy asphalt is used for filling and leveling, and all aged rubber rings are replaced, ensuring that the joint gap is ≤1mm. The epoxy asphalt can be used in a 1:1 ratio.

[0034] Step S32 involves the preparation and repair of the HDPE inner liner pipe 20, including: Step S321, HDPE inner lining pipe 20 preparation, select PE100 grade HDPE inner lining pipe 20 (such as PE100-RC), nominal outer diameter matches pipe inner diameter (such as DN1200), wall thickness 20mm, melt flow index ≤0.15g / 10min, weld according to the segment length of the operation pit, hot melt temperature 210±10℃, heat absorption time 30s / mm wall thickness, weld flange height ≥1.5mm.

[0035] Step S322: Fold the HDPE inner liner 20. The HDPE inner liner 20 is pressed into a U-shape by a folding machine, reducing the diameter by 30~35%. This diameter reduction rate can be selected based on factors such as the difficulty of pipe insertion and pipe fit. The tube is then wrapped and shaped with soft polyester tape. The wrapping speed is preferably 5~8m / min to avoid damage to the pipe wall during the folding process.

[0036] In step S323, the HDPE inner liner pipe 20 is inserted and pulled from the operating pit using a traction machine. The traction force is ≤ 50% of the allowable tensile force of the HDPE pipe cross section, and the pulling speed is 5 ~ 8 m / min. At least 5 mm thick anti-wear pads can be provided at the pulling end, and a guide sliding protection structure 80 can be provided at the pipe opening. Specifically, guide sliding rollers can be provided on the upper, left, and right sides of the pipe opening to avoid scratching the weld joint.

[0037] Step S324, HDPE inner liner tube 20 expands in stages: First, pressurize with 0.15MPa compressed air for 5 minutes to release the air, then increase the pressure to 0.25MPa and pressurize for 10 minutes for initial bonding, then reduce the pressure to 0.2MPa and pressurize for 30 minutes for complete bonding, and ensure that the gap between HDPE inner liner tube 20 and the inner wall of the pipe is ≤3mm, which is monitored by endoscopy.

[0038] In the U-shaped pressing process (i.e., the process of pressing the inner liner into a U-shape), the hydraulic or mechanical pressure range of the equipment must be precisely calculated and adjusted; in the circular restoration process (i.e., the 20-stage expansion process of the HDPE inner liner), the specific values ​​of water or air pressure, the pressure holding time, and the steps and principles of staged pressurization are determined based on the material properties and pipe structure of the HDPE pipe.

[0039] Compared with existing technologies, the embodiments of this application use trenchless HDPE lining repair. The HDPE lining is installed by first compressing the U-shaped diameter, then pulling it to the target position, and then expanding the pipe. Compared with the existing direct straight pipe insertion, it can effectively prevent scratches from pipe welds and misaligned joints during insertion. It can also adapt well to elbows during the pipe expansion process, with high adaptability. At the same time, it has a high degree of fit with the inner wall of each pipe section, ensuring the flow area of ​​the pipe. It also effectively avoids the problem of intensified local water flow scouring and limited water supply capacity recovery, greatly improving the water supply capacity and meeting the water demand during peak industrial production periods.

[0040] Furthermore, the use of trenchless lining repair segmented construction organization technology reduces the excavation area, lowers social impact and coordination costs, reduces damage to the surrounding environment, and significantly shortens the construction cycle, ensuring smooth construction and improving construction efficiency. In addition, the long-term economic benefits are significantly improved, extending the pipeline life from 20 years in the existing technology to more than 50 years in this application, and reducing the average annual operation and maintenance cost to less than 10% of the existing technology, eliminating the need for frequent emergency repairs and reducing operation and maintenance costs.

[0041] Step S40, conductive sealing connection at the end interface, such as... Figure 2 As shown, it includes: Step S41, end flange: Heat the ends of the two HDPE inner lining pipes 20 to be connected to 120~130℃ respectively to soften and flange to form inner lining flange 21, and the outer edge of the flange of the inner lining flange 21 preferably extends at least 3mm beyond the sealing line of the steel flange 34.

[0042] Step S42: Conductive sealing connection of the end is performed using the end conductive seal 30: An elastic sealing gasket 31 is fitted between the two inner lining flanges 21 for sealing. The two inner lining flanges 21 are fastened and pressed together on both sides by steel flanges 34 and fastening bolts 35. Conductive bushings 32 are respectively set between the two inner lining flanges 21 and the steel flange 34 on one side. The two conductive bushings 32 are electrically connected by conductive contacts 33. The conductive contacts 33 pass through and are embedded in the two inner lining flanges 21 and the elastic sealing gasket 31 located between the two conductive bushings 32, and are symmetrically arranged on both sides of the pipe end.

[0043] Step S43, continuity verification: Use a multimeter to check whether the conductive resistance at both ends of the connector is less than 0.1Ω to ensure that the cathodic protection current is conducted without obstruction.

[0044] The conductive contact 33 can be made of copper alloy or stainless steel with an anti-corrosion coating, providing good conductivity. The fastening bolt 35 can be an M20 bolt, tightened symmetrically to a torque of 50-60 N·m, and fixed by piercing to prevent shrinkage leakage during operation.

[0045] The elastic sealing gasket 31 can be made of embedded EPDM rubber or a modified sealing gasket made of fluororubber, and the thickness of the elastic sealing gasket 31 can be 5mm.

[0046] Preferably, the elastic sealing gasket 31 can be a double-lip elastic sealing gasket 31. The double-lip sealing gasket usually has two or more protruding sealing lips. When compressed, these sealing lips will independently undergo elastic deformation to form two or more independent elastic sealing barriers on the sealing surface, thereby improving the sealing fit and sealing reliability.

[0047] Compared with the prior art, the embodiments of this application solve the two major problems of conductive interruption and sealing leakage at the end connection by sealing and conductive connection treatment at the pipe end connection, and avoid corrosion of conductive parts by contact with water; achieve cathodic protection coverage at the end flange connection, eliminate protection blind spots, and thus achieve full cathodic protection coverage, greatly improving protection efficiency.

[0048] Step S50, adapting to cathodic protection installation, includes: Step S51, Sacrificial Anode 40 Selection and Arrangement: After the HDPE inner liner 20 is repaired, sacrificial anodes 40 are added to the steel pipe section 11 for protection. High-potential magnesium alloy anodes or zinc alloy anodes are selected. Specifically, AZ63 material, cylindrical Φ200mm×1500mm, 45kg single high-potential magnesium alloy anodes can be selected, arranged in groups of 3 every 500m; and for high Cl - In soil areas, the anode spacing is shortened to 300m to ensure that the current coverage is free of blind spots.

[0049] Step S52, Backfill Material 50 Optimization: The anode is buried in a 3m deep well and filled with low-resistance backfill material. Specifically, a low-resistance backfill material composed of 75% gypsum, 20% bentonite, and 5% sodium sulfate can be selected to ensure that the grounding resistance is ≤20Ω, ensuring that the current penetrates the soil covering the outer wall of the inner lining section. This solves the problem of uneven current distribution and further improves protection efficiency.

[0050] Step S53, Installation of jumper wire 60 and test post 70: With the HDPE inner liner 20 isolating the pipeline's conductivity, the continuity of power supply to the steel structures on both sides of the flange is ensured by welding jumper wire 60. Specifically, jumper wire 60 can be VV-1×10mm. 2 Acid-resistant cables ensure electrical continuity; test piles are installed every 500m to monitor the protection potential (e.g., -1.1~-0.85V).

[0051] Step S60, acceptance and performance testing, includes: Step S61, visual inspection: Observe with an endoscope to see if the plastic inner lining is wrinkle-free and hollow, the weld joint is free of defects, the sacrificial anode 40 is arranged in a standardized manner, whether the filler material 50 has been lost, and whether the interface sealing structure is intact.

[0052] Step S62, performance testing, includes: Conductivity detection: Test pile 70 monitors whether the protection potential is uniform throughout the entire section and whether there are no blind spots; Sealing test: The water pressure test is used to check the sealing performance. The pressure is 1.5 times the design pressure, and the pressure drop is ≤1% after stabilizing the pressure for 30 minutes. Insulation testing: Perform an electric spark test on the HDPE inner liner pipe 20 to check for leaks at 3~5kV. Step S63, Functional Verification: After water is supplied, verify whether the water supply volume of the pipeline meets the standard, whether the pressure is stable, and whether there is any leakage or abnormal water flow noise.

[0053] Compared with existing technologies, the composite protection method of cathodic protection and lining repair provided in this application provides corrosion protection and repair for buried reclaimed water supply pipelines. It not only achieves dual synergistic protection of the pipeline's internal and external surfaces through trenchless HDPE lining repair and cathodic protection, completely blocking corrosion from both sides, but also solves the problems of conductive interruption and sealing leakage at end connections, eliminating blind spots in protection, achieving full coverage of cathodic protection, and greatly improving protection efficiency. Furthermore, the trenchless HDPE lining repair technology, which involves first compressing the U-shaped diameter, then pulling it to the target position, and finally expanding the pipe, effectively prevents scratches from pipe welds and misaligned joints during installation. It can adapt well to elbows, has high adaptability, and a high degree of fit with the inner wall of each pipe section. The large flow area of ​​the pipeline effectively ensures water supply capacity, meeting the water demand during peak industrial production periods. Furthermore, it reduces the excavation area, lowers social impact and coordination costs, reduces damage to the surrounding environment, and significantly shortens the construction cycle, ensuring smooth construction and improving construction efficiency. Moreover, it significantly improves long-term economic efficiency, extending pipeline life from 20 years in existing technologies to more than 50 years in this application, reducing the average annual operation and maintenance cost to less than 10% of existing technologies, eliminating the need for frequent emergency repairs, and reducing operation and maintenance costs.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A composite protection method for pipeline cathodic protection and lining repair, characterized in that, include: Step S10: Multi-dimensional inspection of the current status of the pipeline and determination of the pipeline segment to be renovated; Step S20: The segmented operation pit construction layout and the coordinated inner lining interlacing path and cathodic protection current coverage path are synchronously set up in segments for operation pits. Step S30, trenchless HDPE lining repair, includes step S31, pipe pretreatment, and step S32, HDPE lining pipe preparation and repair layout. Step S40: Conductive sealing connection at the end interface. The ends of the two HDPE inner-lined pipes to be connected are heated and softened to form inner-lined flanges. Then, an elastic sealing gasket is attached between the two inner-lined flanges. The two inner-lined flanges are fastened and pressed together on both sides by steel flanges and fastening bolts. A conductive bushing is set between the inner-lined flange and the steel flange on one side. The two conductive bushings are electrically connected by conductive contacts. The conductive contacts pass through and are embedded in the two inner-lined flanges and the elastic sealing gasket located between the two conductive bushings. The two ends of the pipe are symmetrically arranged. Step S50: Adapt to cathodic protection installation, install sacrificial anode protection outside the pipeline, and fill with compatible packing material; Step S60, acceptance and performance testing.

2. The composite protection method for pipeline cathodic protection and lining repair according to claim 1, characterized in that, In step S32, the process of preparing and repairing the HDPE inner lining pipe includes: Step S321, HDPE inner lining pipe preparation: PE100 grade HDPE inner lining pipe is selected, with nominal outer diameter matching pipe inner diameter, wall thickness 20mm, melt flow index ≤0.15g / 10min, and welded according to the segment length of the operation pit. Step S322: Fold the HDPE inner liner tube. The HDPE inner liner tube is pressed into a U-shape by a folding machine, reducing the diameter by 30~35%, and then wrapped with soft polyester tape to fix the shape. Step S323: HDPE inner lining pipe is inserted. The HDPE inner lining pipe is pulled from the operating pit by a traction machine. Anti-wear pads are provided at the pulling end, and guide rollers are provided on the top, left and right sides of the pipe opening. Step S324, HDPE inner lining pipe expansion in stages: First, pressurize with 0.15MPa compressed air for 5 minutes to release the air, then increase the pressure to 0.25MPa and pressurize for 10 minutes for initial bonding, then reduce the pressure to 0.2MPa and pressurize for 30 minutes for complete bonding, and ensure that the gap between the HDPE inner lining pipe and the inner wall of the pipe is ≤3mm.

3. The composite protection method for pipeline cathodic protection and lining repair according to claim 2, characterized in that, In step S31, the pipeline pretreatment includes: A portable high-pressure water pump is used to clean the scale layer inside the pipe, and a traction-type pipe cleaning ball is used to remove wooden wedges and corrosion products to ensure that there are no sharp protrusions on the inner wall. For misaligned or stepped joints of steel cylinder concrete pipes, epoxy asphalt is used to fill and level them, and all aged rubber rings are replaced to ensure that the joint gap is ≤1mm.

4. The composite protection method for pipeline cathodic protection and lining repair according to claim 1, characterized in that, In step S40, The conductive contacts are made of copper alloy or stainless steel coated with an anti-corrosion coating; and / or The elastic sealing gasket is a modified sealing gasket made of embedded EPDM rubber or fluororubber, and the elastic sealing gasket is a double-lip elastic sealing gasket.

5. The composite protection method for pipeline cathodic protection and lining repair according to claim 1 or 4, characterized in that, Step S40 further includes: continuity verification: checking whether the electrical resistance at both ends of the connector is less than 0.1Ω using a multimeter; and / or In step S40, the end of the HDPE liner is heated to 120~130℃ to soften and flange, and the outer edge of the flange extends at least 3mm beyond the sealing line of the steel flange. M20 bolts are used for fastening, and they are tightened symmetrically to a torque of 50~60N. m, and fixed by perforation.

6. The composite protection method for pipeline cathodic protection and lining repair according to claim 1, characterized in that, Step S10 includes: Step S11, Multi-dimensional inspection of pipeline status: Collect soil samples and greywater samples along the pipeline. The soil samples are tested for pH value, corrosive ion content and resistivity. The greywater samples are tested for pH value, conductivity and corrosive ion content. The degree of pipeline corrosion, interface condition and structural integrity are evaluated by thickness measurement and observation of inner wall morphology. Step S12, Determine the scope of the renovation: Exclude pipe sections that have been operating well recently, and focus on designating pipe sections with severe corrosion and frequent leaks that are laid with mixed pipe materials as the target pipe sections for renovation.

7. The composite protection method for pipeline cathodic protection and lining repair according to claim 1, characterized in that, Step S20 includes: Step S21, Segmented Operation Pit Construction Layout: Divide the pipeline into several segments and set up operation pits. The location selection of operation pits follows the principles of: one pit for every ≤1km of straight pipe section, one pit must be set at bends >15°, priority should be given to steel pipe sections, and the pits should be avoided in farmland; operation pits near rivers are supported by steel pipe piles or steel sheet piles, and water collection pits and water pumps are set up to ensure that the pits are dry. Protective fences and warning signs are set up around the operation pits. Step S22, Collaborative Planning and Setup: Combining the insertion path of the HDPE inner liner pipe and the current coverage requirements of cathodic protection, simultaneously determine the location of the operating pit, taking into account both the inner liner pulling and anode installation, with a spacing of ≤1km, and the sacrificial anode arrangement should be densified at 1.5 times the density of the non-inner liner section for the inner liner section, and the end connection position must be set.

8. The composite protection method for pipeline cathodic protection and lining repair according to claim 1, characterized in that, Step S50 includes: Step S51, Sacrificial Anode Selection and Arrangement: After the HDPE inner lining pipe is repaired, sacrificial anode protection is added to the steel pipe section. High-potential magnesium alloy anodes are selected, arranged in groups of 3 every 500m, and specifically designed for high Cl... - In soil areas, the anode spacing is shortened to 300m to ensure that the current coverage is free of blind spots; Step S52, Backfill material optimization: The anode is buried in a 3m deep well and filled with low-resistance backfill material, which consists of 75% gypsum, 20% bentonite and 5% sodium sulfate, so that the grounding resistance is ≤20Ω, ensuring that the current penetrates the soil to cover the outer wall of the inner lining section.

9. The composite protection method for pipeline cathodic protection and lining repair according to claim 8, characterized in that, Step S50 further includes: Step S53, Installation of jumper wires and test piles: With the HDPE inner liner pipe isolating the pipeline's conductivity, weld jumper wires to ensure the continuity of power supply to the steel structures on both sides of the flange, guaranteeing electrical connectivity; set up test piles every 500m to monitor the protection potential.

10. The composite protection method for pipeline cathodic protection and lining repair according to claim 9, characterized in that, Step S60 includes: Step S61, visual inspection: Observe with an endoscope to see if the plastic inner lining is wrinkle-free and hollow, the weld joints are free of defects, the sacrificial anode arrangement is standardized, the filler material is not lost, and the interface sealing structure is intact. Step S62, performance testing, including: Conductivity detection: The test pile monitors whether the protection potential is uniform throughout the entire section and there are no blind spots; Sealing test: Hydrostatic test to check sealing performance; Insulation testing: Perform spark testing on the HDPE inner lining pipe to check for leaks at 3~5kV. Step S63, Functional Verification: After water is supplied, verify whether the water supply volume of the pipeline meets the standard, whether the pressure is stable, and whether there is any leakage or abnormal water flow noise.

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