A coal gas pipeline pressure plugging method

Abstract

This invention discloses a method for pressurized leak sealing of gas pipelines, belonging to the field of pipeline leak sealing technology. It includes three steps: pre-construction pretreatment, flexible sealing body implantation, and external permanent magnet clamping. Pre-construction pretreatment includes: using a portable gas detector to measure the gas concentration around the leak point to ensure the on-site gas concentration is below 5% of the explosion limit; using calipers to measure the maximum diameter of the leak point; selecting a flexible sealing body of appropriate material based on the sulfide content of the gas inside the pipeline; and pre-treating large-sized leak points with adhesive coating. In this invention, the flexible sealing body is implanted into the leak point cavity, and then continuously clamped by an external permanent magnet mechanism, forming a radially expanded embedded sealing structure within the leak point cavity. This differs from existing patents that only attach seals to the outer wall of the pipeline, effectively avoiding seal detachment and leakage problems caused by media erosion and pressure fluctuations, significantly reducing the number of subsequent shutdowns and repairs, and ensuring long-term continuous gas supply from the gas pipeline.

Description

Technical Field

[0001] This invention belongs to the field of pipeline leak sealing technology, and in particular relates to a method for sealing gas pipeline leaks under pressure. Background Technology

[0002] In the field of live gas pipeline leak sealing, chemical and metallurgical enterprises often experience point leaks due to long-term corrosion from sulfur-containing media. Gas is flammable and explosive and contains toxic carbon monoxide components. Leak repair is restricted by on-site hot work and gas shutdown controls. The industry generally adopts three conventional construction methods: welding repair, adhesive sealing, and external magnetic pressure sealing. These methods rely on sealant, rubber gaskets, and external clamping components to seal the leaks, thus completing the leak control work without interrupting the gas supply.

[0003] According to Chinese Patent No. CN101900238A, a method for sealing gas pipelines without interrupting gas supply or welding is disclosed: (1) Locate the leak point of the gas pipeline and clean it; (2) Select a sealing device that matches the diameter of the gas pipeline and install it around the leak point of the gas pipeline; select a soft sealing block and place it between the arc-shaped clamping block of the sealing device and the leak point of the gas pipeline; (3) By rotating the clamping screw of the sealing device, the clamping screw pushes the arc-shaped clamping block to move radially, and the arc-shaped clamping block pushes the soft sealing block to press on the leak point until the soft sealing block completely seals the leak point; (4) Tighten the fine-tuning anti-loosening screw on the sealing device, and the fine-tuning anti-loosening screw acts on the arc-shaped clamping block.

[0004] However, the above solution still has the following drawbacks: the seal only adheres and presses tightly to the outer wall and cannot extend into the leak point to fill and seal it. Impurities and fluctuations in medium pressure can easily cause the seal to fail, requiring repeated shutdowns and repairs to plug the leak. Summary of the Invention

[0005] The purpose of this invention is to provide a method for sealing leaks in gas pipelines under pressure, which addresses the problem that the sealing element only adheres tightly to the outer wall and cannot penetrate into the leak point to fill and seal it, and that impurities and pressure fluctuations in the medium can easily cause the seal to fail, requiring repeated shutdowns and repairs.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for sealing gas pipeline leaks under pressure, specifically including the following steps: S1. Pre-construction pretreatment: Use a portable gas detector to detect the gas concentration around the leak point to ensure that the gas concentration on site is less than 5% of the explosion limit. Use calipers to measure the maximum diameter of the leak point. Combine the content of sulfides in the gas inside the pipeline to select a flexible sealing body of the corresponding material. For large-sized leak points, complete the pretreatment of sealing body by applying glue in advance. S2. Flexible sealing body insertion: Use non-metallic plastic positioning tooling to hold the sealing body, accurately align the tip of the sealing body with the leak hole in the pipeline, and slowly press it into the leak hole with a constant pressure of 0.3MPa to 0.5MPa until the base of the sealing body is completely attached to the outer wall of the pipeline. Maintain the pressure for about 20 seconds, and rely on the pre-applied sealant to form a temporary seal, initially blocking the gas leakage. S3. Permanent Magnet External Compression Sealing: Select the corresponding grade of neodymium iron boron strong magnetic compression component according to the pipe wall thickness. Place the permanent magnet compression mechanism against the outer wall of the pipe and align it with the center position of the sealing body base. The permanent magnet achieves automatic positioning and adsorption by its own magnetic attraction. Manual assistance is required to press for about 10 seconds to improve the tightness of the permanent magnet and the pipe wall. The permanent magnet generates a continuous compression force, which forces the sealing body to compress axially and expand radially, adaptively filling the irregular corrosion cavity of the leak point. The triple sealing structure is formed by mechanical blocking, sealant bonding, and long-term magnetic compression to complete the pressurized sealing.

[0007] Preferably, the flexible sealing body is prepared according to the following mass fraction ratio: 61% rubber substrate, 28% carbon black reinforcing agent, 7% diphenylamine anti-aging agent, and 4% dioctyl adipate plasticizer; The vulcanization molding process involves high-temperature vulcanization at 165℃ and 18MPa. When the mass fraction of sulfides in the coal gas is >5%, modified fluororubber is selected as the base material; when the sulfide content is ≤5%, modified oil-resistant nitrile rubber is selected. After molding, the axial elastic deformation rate of the sealing body is ≥85%. After immersion in a gas environment at 20℃~80℃ for 3000h, the volume change rate is ≤3.5% and the hardness change is ≤7 Shore A.

[0008] Preferably, the flexible sealing body is an integrated structure of a pointed tip, a gradually thickening rod, and a circular fitted base. Under normal working conditions, the taper of the rod is 1:6, and the outer diameter of the sealing body base is 4.5 times the maximum diameter of the leakage point. Two annular glue storage grooves are opened on the lower surface of the base. The grooves are 1.8mm deep and 2.8mm wide. The glue storage grooves are used to retain sealant to form a buffer sealing layer.

[0009] Preferably, when the leak diameter is greater than 20mm or the pipeline operating pressure fluctuation is greater than ±0.08MPa, a 1.8mm thick silicone or polyurethane gas-resistant sealant is evenly applied to the outer wall of the sealing body tip, while the sealant is completely filled into the annular storage tank of the base to ensure that the sealant has no gaps and does not overflow.

[0010] Preferably, this method is for sealing leaks in negative pressure pipelines with internal pressures ranging from -0.05 MPa to -0.01 MPa: N48 or higher grade neodymium iron boron permanent magnets are selected to ensure that the magnetic attraction force in the central area of ​​the permanent magnet is ≥70N / cm². A 0.6mm thick modified oil-resistant rubber gasket is added between the sealing body base and the outer wall of the pipe to prevent outside air from being sucked in by the negative pressure of the pipe. After the sealing is completed, the concentration of leaking gas at the leak point is controlled below 8ppm.

[0011] Preferably, for sealing large-diameter leaks with orifice diameters of 30mm to 50mm, a main-multiple-auxiliary combined sealing structure is adopted: One main flexible sealing body is arranged at the center of the leak point, and three auxiliary sealing bodies with a pointed diameter of 12mm are evenly arranged on a 35mm circumference around the main leak point. All sealing parts are pre-coated with sealant. A disc-shaped permanent magnet clamping component with a base diameter twice that of the main sealing body base is selected. A single permanent magnet simultaneously covers the entire sealing body area of ​​both the main and auxiliary bodies, resulting in a leakage concentration of less than 5 ppm after sealing.

[0012] Preferably, for leak sealing of severely corroded pipelines where the pipe wall thinning exceeds 30% of the original pipe wall thickness: the taper of the sealing body rod is adjusted to 1:7 to reduce the compressive stress on the thin-walled pipe wall during the sealing body pressing process; a large-size disc structure is selected for the permanent magnet to increase the contact area between the permanent magnet and the outer wall of the pipe, disperse the unit area compression load, and avoid local high pressure causing damage to the corroded pipe wall.

[0013] Preferred grading standards for neodymium iron boron permanent magnets: N38 grade for pipe wall thickness ≤ 8mm, N48 grade for wall thickness 8mm~15mm, and N52 grade for wall thickness > 15mm. The permanent magnet finished product is entirely galvanized for corrosion protection, with a zinc coating thickness of 1.0mm; After permanent magnet adsorption, the magnetic attraction force in the central area is ≥65N / cm², and the magnetic attraction force in the edge area is ≥55N / cm². Under the conditions of pipeline amplitude ≤2.5mm and gas pressure fluctuation ±0.08MPa, the permanent magnet does not deviate or fall off. After sealing under normal positive pressure conditions, the leakage is <10ppm.

[0014] Compared with existing technologies, the gas pipeline pressurized leak sealing method using the above-mentioned technical solution has the following beneficial effects: 1. In this invention, a flexible sealing body is implanted into the hole of the leak point, and then continuously pressed by an external permanent magnet mechanism, so that the sealing body forms a radially expanded embedded sealing structure in the inner cavity of the leak point. This is different from the existing patent method of attaching the seal only to the outer wall of the pipeline. It effectively avoids the problem of seal detachment and leakage caused by medium erosion and pressure fluctuation, greatly reduces the number of repeated shutdowns and repairs in the later stage, and ensures long-term continuous gas supply of the gas pipeline.

[0015] 2. In this invention, the embedded sealing structure relies on an external permanent magnet to provide clamping force. The sealing and locking force does not depend on the gas pressure of the medium inside the pipeline. Under positive pressure conditions, the gas pressure inside the pipe can help to tighten the sealing body. Under negative pressure conditions, there will be no problem of the sealing element being sucked out by the negative pressure of the pipeline. It can be used in conventional positive pressure gas transmission pipelines and is also suitable for negative pressure gas recovery pipelines, solving the pain point that traditional sealing cannot be used in negative pressure pipelines.

[0016] 3. In this invention, a standardized three-step process of pretreatment, sealing implantation, and magnetic clamping is used, which does not require open flame or mechanical fastening with bolts. The construction operation of a single leak point is simple and quick. Compared with the traditional screw fastening and external wall adhesive sealing process, it greatly shortens the time spent on on-site repair and improves the efficiency of emergency repair of pipeline leaks. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process of the present invention; Figure 2 A schematic diagram of a pressurized leak sealing method for gas pipelines and a magnetic fastening device.

[0018] Legend: 1. Gas pipeline; 2. Flexible sealing body; 3. Strong magnetic clamping component. Detailed Implementation

[0019] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0020] Please see Figures 1-2 A method for sealing gas pipelines under pressure, specifically including the following steps: S1. Pre-construction pretreatment: Use a portable gas detector to detect the gas concentration around the leak point to ensure that the gas concentration on site is less than 5% of the explosion limit. Use calipers to measure the maximum diameter of the leak point. Combine the content of sulfides in the gas inside the pipeline to select a flexible sealing body of the corresponding material. For large-sized leak points, complete the pretreatment of sealing body by applying glue in advance. S2. Flexible sealing body insertion: Use non-metallic plastic positioning tooling to hold the sealing body, accurately align the tip of the sealing body with the leak hole in the pipeline, and slowly press it into the leak hole with a constant pressure of 0.3MPa to 0.5MPa until the base of the sealing body is completely attached to the outer wall of the pipeline. Maintain the pressure for about 20 seconds, and rely on the pre-applied sealant to form a temporary seal, initially blocking the gas leakage. S3. Permanent Magnet External Compression Sealing: Select the corresponding grade of neodymium iron boron strong magnetic compression component according to the pipe wall thickness. Place the permanent magnet compression mechanism against the outer wall of the pipe and align it with the center position of the sealing body base. The permanent magnet achieves automatic positioning and adsorption by its own magnetic attraction. Manual assistance is required to press for about 10 seconds to improve the tightness of the permanent magnet and the pipe wall. The permanent magnet generates a continuous compression force, which forces the sealing body to compress axially and expand radially, adaptively filling the irregular corrosion cavity of the leak point. The triple sealing structure is formed by mechanical blocking, sealant bonding, and long-term magnetic compression to complete the pressurized sealing.

[0021] The flexible sealing body is prepared according to the following mass fraction ratios: 61% rubber substrate, 28% carbon black reinforcing agent, 7% diphenylamine anti-aging agent, and 4% dioctyl adipate plasticizer; the vulcanization molding process is high-temperature vulcanization at 165℃ and 18MPa; when the mass fraction of sulfides in the coal gas is >5%, modified fluororubber is selected as the substrate, and when the sulfide content is ≤5%, modified oil-resistant nitrile rubber is selected; after molding, the axial elastic deformation rate of the sealing body is ≥85%, and after immersion in a coal gas environment at 20℃~80℃ for 3000h, the volume change rate is ≤3.5% and the hardness change is ≤7 Shore A; The flexible sealing body is an integrated structure of a pointed tip, a gradually thickening rod, and a circular fitting base. Under normal working conditions, the taper of the rod is 1:6, and the outer diameter of the sealing body base is 4.5 times the maximum diameter of the leakage point. Two annular glue storage grooves are opened on the lower surface of the base. The glue storage grooves are 1.8mm deep and 2.8mm wide. The glue storage grooves are used to retain sealant to form a buffer sealing layer. When the leak diameter is greater than 20mm or the pipeline operating pressure fluctuation is greater than ±0.08MPa, apply a 1.8mm thick silicone or polyurethane gas-resistant sealant evenly to the outer wall of the sealing body tip, and completely fill the annular storage tank of the base with the sealant to ensure that the sealant has no gaps and does not overflow. For leak sealing operations in negative pressure pipelines with internal pressure of -0.05MPa to -0.01MPa: N48 or higher grade neodymium iron boron permanent magnets are selected, with the magnetic attraction force in the center area of ​​the permanent magnet ≥70N / cm²; a modified oil-resistant rubber gasket with a thickness of 0.6mm is added between the sealing body base and the outer wall of the pipeline to prevent outside air from being sucked in by the negative pressure of the pipeline. After the sealing is completed, the concentration of leaking gas at the leak point is controlled below 8ppm.

[0022] For sealing large-diameter leaks with orifice diameters of 30mm to 50mm, a combined main and auxiliary sealing structure is adopted: one main flexible sealing body is arranged at the center of the leak, and three auxiliary sealing bodies with a pointed diameter of 12mm are evenly arranged on a 35mm circumference around the main leak. All sealing parts are pre-coated with sealant. A disc-type permanent magnet clamping part with a base diameter twice that of the main sealing body base is selected. A single permanent magnet covers the entire area of ​​the main and auxiliary sealing bodies at the same time, and the leakage concentration after sealing is less than 5ppm.

[0023] For severely corroded pipes where the thinning of the pipe wall exceeds 30% of the original pipe wall thickness, the following measures are taken: the taper of the sealing body rod is adjusted to 1:7 to reduce the compressive stress on the thin-walled pipe wall during the sealing body pressing process; a large-size disc structure is selected for the permanent magnet to increase the contact area between the permanent magnet and the outer wall of the pipe, disperse the unit area compression load, and avoid local high pressure causing damage to the corroded pipe wall.

[0024] The grading standards for NdFeB permanent magnets are as follows: N38 grade is used for pipe wall thickness ≤ 8mm, N48 grade is used for wall thickness 8mm~15mm, and N52 grade is used for wall thickness > 15mm; the finished permanent magnet is galvanized for corrosion protection with a zinc coating thickness of 1.0mm; after adsorption, the magnetic attraction force in the central area is ≥ 65N / cm², and the magnetic attraction force in the edge area is ≥ 55N / cm². Under the conditions of pipe amplitude ≤ 2.5mm and gas pressure fluctuation ± 0.08MPa, the permanent magnet does not shift or fall off, and the leakage is < 10ppm after sealing under normal positive pressure conditions.

[0025] Example 1: Sealing small leaks in conventional positive pressure systems; A carbon steel industrial coal gas pipeline with a wall thickness of 9mm was selected. The working pressure of the medium was 0.13MPa, the medium temperature range was 20~70℃, the coal gas sulfide content was 2.9%, the measured leak point diameter was 7mm, the pipeline amplitude was less than 2.5mm, and the pressure fluctuation was ±0.05MPa.

[0026] S1. Pretreatment: The portable gas detector detects that the gas concentration around the leak point is less than 5% of the explosion limit; based on the sulfide content ≤5%, a modified nitrile rubber integrated sealant is selected, and no sealant is required if the leak point diameter is less than 20mm; the 9mm thick wall is matched with N48 grade zinc-plated neodymium iron boron permanent magnet.

[0027] S2. Sealing and Implantation: Using a special plastic tool, the sealing tip is pressed into the leak hole at a uniform pressure of 0.4MPa. After the base is fully attached to the outer wall of the pipe, the pressure is stabilized for 20 seconds, and the leak is temporarily sealed by the deformation of the sealing body.

[0028] S3. Permanent Magnet Pressing: The permanent magnet aligns with the center of the sealing base and naturally attracts the seal. Light manual pressure for 10 seconds ensures a secure fit. Continuous pressure from the permanent magnet causes the seal to expand radially, filling the corrosion pores and forming a triple seal. Upon completion, the leakage concentration was measured at 9 ppm. After 36 months of continuous on-site use, no leaks or repairs were required.

[0029] Example 2: Leak plugging of negative pressure recovery pipeline; The gas negative pressure recovery pipeline has a pipe wall thickness of 6mm, an internal working negative pressure of -0.03MPa, a medium sulfide content of 6.3%, a leak point diameter of 15mm, and an ambient temperature of 30~65℃.

[0030] S1. Pretreatment: For sulfides > 5%, use modified fluororubber sealant; for leaks > 10mm, apply 1.8mm polyurethane sealant to the sealing tip and the annular rubber storage groove of the base; for walls 6mm thick, use N48 high-strength permanent magnets, and add 0.6mm modified oil-resistant rubber gaskets to the base.

[0031] S2. Sealing and Implantation: The plastic tooling controls the pressure of 0.35MPa to press the sealing component. After the base is attached to the pipe wall, the pressure is stabilized for 20 seconds to allow the sealant to initially cure.

[0032] S3, Permanent Magnet Compression: The gasket is placed between the base and the pipe wall, and the N48 permanent magnet adsorbs and compresses the entire structure. After sealing, the actual leakage concentration is 7ppm. After 38 months of continuous operation, there are no problems with air backflow or seal detachment.

[0033] Example 3: Sealing large-diameter leaks The factory's main gas pipe has a wall thickness of 12mm, an operating pressure of 0.09MPa, a measured leak diameter of 42mm, a medium sulfide content of 4.1%, and a pipeline pressure fluctuation of ±0.07MPa.

[0034] S1. Pretreatment: Nitrile rubber seals are selected, and a combination structure of 1 main seal body + 3 φ12mm auxiliary seal bodies is adopted. All seals are coated with sealant. N48 disc permanent magnets are selected, and the outer diameter of the permanent magnet is twice that of the main seal base.

[0035] S2. Sealing and Implantation: The main sealing body is pressed into the leak hole in the center, and three auxiliary sealing bodies are installed at equal intervals around the leak point with a 35mm circumference. Each body is stabilized for 20 seconds to complete the temporary seal.

[0036] S3, Permanent Magnet Compression: The large disc permanent magnet covers all sealing components and adsorbs and secures them. The sealing body expands radially under pressure to fill the gaps. The leakage was 4ppm after completion and the system operated stably for 37 months.

[0037] Example 4: Pipeline Leakage Repair under Severe Corrosion and Thinning The old coking gas pipeline was originally designed with a wall thickness of 14mm. The pipe wall has been thinned by 43% due to corrosion, leaving a remaining wall thickness of about 8mm. The positive pressure inside the pipe is 0.06MPa, the leak point diameter is 11mm, and the sulfide content is 3.5%.

[0038] S1. Pretreatment: Due to severe corrosion of the pipe wall, a custom-made sealing body with a taper of 1:7 is selected to reduce the pressure during pressing; N48 permanent magnets are selected for the 8mm wall thickness, and the permanent magnets adopt a disc structure to disperse the pressure.

[0039] S2. Sealing and Implantation: Slowly press the sealing body in at a low pressure of 0.3MPa, stabilize the pressure for 20 seconds, and avoid cracking and corroding the pipe wall.

[0040] S3. Permanent Magnet Compression: The disc permanent magnet steadily adsorbs and compresses, dispersing local loads. After sealing, the leakage concentration is 8ppm. After 36 months of use, there is no damage to the pipe wall and no secondary leakage.

[0041] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for sealing leaks in a gas pipeline under pressure, characterized in that, Specifically, the following steps are included: S1. Pre-construction pretreatment: Use a portable gas detector to detect the gas concentration around the leak point to ensure that the gas concentration on site is less than 5% of the explosion limit. Use calipers to measure the maximum diameter of the leak point. Combine the content of sulfides in the gas inside the pipeline to select a flexible sealing body of the corresponding material. For large-sized leak points, complete the pretreatment of sealing body by applying glue in advance. S2. Flexible sealing body insertion: Use non-metallic plastic positioning tooling to hold the sealing body, accurately align the tip of the sealing body with the leak hole in the pipeline, and slowly press it into the leak hole with a constant pressure of 0.3MPa to 0.5MPa until the base of the sealing body is completely attached to the outer wall of the pipeline. Maintain the pressure for about 20 seconds, and rely on the pre-applied sealant to form a temporary seal, initially blocking the gas leakage. S3. Permanent Magnet External Compression Sealing: Select the corresponding grade of neodymium iron boron strong magnetic compression component according to the pipe wall thickness. Place the permanent magnet compression mechanism against the outer wall of the pipe and align it with the center position of the sealing body base. The permanent magnet achieves automatic positioning and adsorption by its own magnetic attraction. Manual assistance is required to press for about 10 seconds to improve the tightness of the permanent magnet and the pipe wall. The permanent magnet generates a continuous compression force, which forces the sealing body to compress axially and expand radially, adaptively filling the irregular corrosion cavity of the leak point. The triple sealing structure is formed by mechanical blocking, sealant bonding, and long-term magnetic compression to complete the pressurized sealing.

2. The method for sealing gas pipelines under pressure according to claim 1, characterized in that, The flexible sealing body is prepared according to the following mass fraction ratio: 61% rubber substrate, 28% carbon black reinforcing agent, 7% diphenylamine anti-aging agent, and 4% dioctyl adipate plasticizer; The vulcanization molding process involves high-temperature vulcanization at 165℃ and 18MPa. When the mass fraction of sulfides in the coal gas is >5%, modified fluororubber is selected as the base material; when the sulfide content is ≤5%, modified oil-resistant nitrile rubber is selected. After molding, the axial elastic deformation rate of the sealing body is ≥85%. After immersion in a gas environment at 20℃~80℃ for 3000h, the volume change rate is ≤3.5% and the hardness change is ≤7 Shore A.

3. The method for sealing gas pipelines under pressure according to claim 1, characterized in that, The flexible sealing body is an integrated structure of a pointed tip, a gradually thickening rod, and a circular fitting base. Under normal working conditions, the taper of the rod is 1:6, and the outer diameter of the sealing body base is 4.5 times the maximum diameter of the leakage point. Two annular glue storage grooves are opened on the lower surface of the base. The grooves are 1.8mm deep and 2.8mm wide. The glue storage grooves are used to retain sealant to form a buffer sealing layer.

4. The method for sealing gas pipelines under pressure according to claim 1, characterized in that, When the leak diameter is greater than 20mm or the pipeline operating pressure fluctuation is greater than ±0.08MPa, apply a 1.8mm thick layer of silicone or polyurethane gas-resistant sealant evenly to the outer wall of the sealing body tip. At the same time, completely fill the annular storage tank of the base with sealant to ensure that there are no gaps or overflows.

5. A method for sealing gas pipelines under pressure according to claim 1, characterized in that, For leak sealing operations in negative pressure pipelines with internal pressure of -0.05MPa to -0.01MPa: N48 or higher grade neodymium iron boron permanent magnets are selected to ensure that the magnetic attraction force in the central area of ​​the permanent magnet is ≥70N / cm². A 0.6mm thick modified oil-resistant rubber gasket is added between the sealing body base and the outer wall of the pipe to prevent outside air from being sucked in by the negative pressure of the pipe. After the sealing is completed, the concentration of leaking gas at the leak point is controlled below 8ppm.

6. The method for sealing gas pipelines under pressure according to claim 1, characterized in that, For sealing large-diameter leaks with orifice diameters of 30mm to 50mm, a main-multiple-auxiliary combined sealing structure is adopted: One main flexible sealing body is arranged at the center of the leak point, and three auxiliary sealing bodies with a pointed diameter of 12mm are evenly arranged on a 35mm circumference around the main leak point. All sealing parts are pre-coated with sealant. A disc-shaped permanent magnet clamping component with a base diameter twice that of the main sealing body base is selected. A single permanent magnet simultaneously covers the entire sealing body area of ​​both the main and auxiliary bodies, resulting in a leakage concentration of less than 5 ppm after sealing.

7. A method for sealing gas pipelines under pressure according to claim 1, characterized in that, For severely corroded pipelines where the pipe wall thinning exceeds 30% of the original pipe wall thickness, the following measures are taken: the taper of the sealing body rod is adjusted to 1:7 to reduce the compressive stress on the thin-walled pipe wall during the sealing body pressing process; a large-size disc structure is selected for the permanent magnet to increase the contact area between the permanent magnet and the outer wall of the pipe, disperse the unit area compression load, and avoid local high pressure causing damage to the corroded pipe wall.

8. A method for sealing gas pipelines under pressure according to claim 1, characterized in that, NdFeB permanent magnet material selection and grading standards: N38 grade is selected for pipe wall thickness ≤ 8mm, N48 grade is selected for wall thickness 8mm~15mm, and N52 grade is selected for wall thickness > 15mm. The permanent magnet finished product is entirely galvanized for corrosion protection, with a zinc coating thickness of 1.0mm; After permanent magnet adsorption, the magnetic attraction force in the central area is ≥65N / cm², and the magnetic attraction force in the edge area is ≥55N / cm². Under the conditions of pipeline amplitude ≤2.5mm and gas pressure fluctuation ±0.08MPa, the permanent magnet does not deviate or fall off. After sealing under normal positive pressure conditions, the leakage is <10ppm.

Images