Device non-stop steam pipeline under-pressure welding maintenance method

Abstract

The invention relates to the field of chemical equipment and pipeline maintenance operation, in particular to a steam pipeline under-pressure welding maintenance method without stopping a device, solves the problem that in the prior art, steam leakage is likely to be intensified through direct welding, accidents are caused, and can safely and efficiently repair leakage of a steam pipeline under pressure and determine a leakage point of the steam pipeline under the condition without stopping the device. A cover pipe is selected, the valve is opened firstly, then the welding end of the cover pipe and the peripheral area of the leakage point of the steam pipeline are assembled to form an assembly gap, and steam leaked from the leakage point is discharged through the valve; welding the assembly gap to form a welding seam, and checking the sealing performance of the welding seam.

Description

Technical Field

[0001] This invention relates to the field of chemical equipment and pipeline maintenance, specifically to a method for live welding maintenance of steam pipelines without shutting down the equipment. Background Technology

[0002] In chemical production, steam pressure pipelines are crucial equipment for transporting high-temperature, high-pressure steam. After prolonged operation, they are prone to corrosion, cracks, and other defects, leading to steam leaks. Traditional maintenance methods typically require shutdown and depressurization before welding repairs. Furthermore, the restart process necessitates slow reheating of the pipeline, which is time-consuming. Shutdowns can cause production interruptions and substantial economic losses. In existing technologies, attempts are made to directly weld leaks in steam pipelines under pressure. However, due to the high steam pressure (e.g., above 1 MPa), the molten iron is easily blown away by the steam during welding, preventing the formation of an effective weld. Furthermore, direct welding can lead to overheating of the weld, exacerbating steam leakage and even causing safety accidents. Another method is to temporarily seal the leak using clamps or sealant, but this method does not fundamentally solve the problem and has poor durability, making it prone to re-leakage.

[0003] Therefore, there is an urgent need for a method that can safely and efficiently repair leaks in pressurized steam pipelines without stopping the machine, and to solve problems such as molten iron being blown away, weld overheating, and increased steam leakage during direct welding. Summary of the Invention This invention provides a method for repairing pressurized steam pipelines by welding without stopping the equipment, which solves the problem that direct welding in the prior art can easily aggravate steam leakage and cause accidents. It can safely and efficiently repair leaks in pressurized steam pipelines without stopping the equipment.

[0004] This invention is achieved through the following technical solution: A method for live welding repair of a steam pipeline without shutting down an equipment includes the following steps: S01. Identify the leak in the steam pipe; S02, Select the cover tube; A metal tube is selected as the cover tube, with one end of the cover tube sealed and the other end open for welding. A valve is installed on the cover tube. S03. First, open the valve, then assemble the welded end of the cover pipe with the area around the leak point of the steam pipe to form an assembly gap, so that the steam leaking from the leak point can be discharged through the valve. S04. Weld the gap between the assembly pieces to form a weld and check the sealing performance of the weld. S05. Close the valve.

[0005] Furthermore, in step S02, when the cross-section of the leak point is circular and the diameter of the leak point is d, the inner diameter D of the cover tube is 5d, and D≥32mm; When the cross-section of the leak point is irregularly shaped, with the long side dimension being a and the short side dimension being b, then the inner diameter D of the cover tube is D = 3a + 2b.

[0006] Furthermore, when selecting the cover pipe, the material of the cover pipe should be the same as that of the steam pipe with leakage points, and the valve should be a high-temperature and high-pressure resistant valve.

[0007] Furthermore, step S03 includes the following steps: S0301. Use an angle grinder to grind the area around the leak until a metallic luster is visible, and process the end face of the welded end of the cover pipe into an arc surface that matches the curvature of the outer wall of the steam pipe. S0302. Grind the bevel at the end face of the welded end of the cover tube; S0303. First, open the valve and use a chain clamp to temporarily fix the cover pipe to the steam pipe, so that the welded end of the cover pipe and the area around the leak point of the steam pipe are aligned to form an alignment gap. Use a copper hammer to tap the outer surface of the cover pipe evenly and moderately from the position with the largest alignment gap to both sides. While tapping, observe the gap between the edge of the welded end of the cover pipe and the surface of the steam pipe, so that the maximum gap does not exceed 1mm, and the welded end of the cover pipe is tightly fitted to the area around the leak point.

[0008] Furthermore, step S04 includes the following steps: S0401. Select two points at the 0° and 180° positions of the assembly gap for spot welding; S0402. Starting from spot welding, welding is carried out in both directions using segmented back welding and skip welding methods, with intermittent welding using low current. The root pass is welded with a low current. After the root pass is completed, wait for the weld to cool to the range of process parameters, then weld with a low current to speed up the welding process. Repeat this process three times to ensure the weld reinforcement height.

[0009] Furthermore, it also includes: S0403. After welding, inspect the appearance of the weld surface and perform penetrant or magnetic particle testing according to the actual temperature of the pipeline to ensure that there are no defects visible to the naked eye on the weld surface.

[0010] Furthermore, in step S01, the leak point in the steam pipe is determined; Includes the following steps: S0101. Obtain the upstream pressure through the upstream pressure gauge of the steam pipe, and obtain the downstream pressure through the downstream pressure gauge of the steam pipe, and obtain the pressure drop ΔP. 实 The formula for calculating the relative deviation γ is: γ = (ΔP) 实 -ΔP 基 ) / ΔP 基 *100% Wherein, ΔP基 This is the normal value for steam pipeline pressure drop; S0102. When the relative deviation γ is within the range of 15%-30%, check the valve status, whether the drainage system is working properly, whether the insulation layer is intact, and whether the flow rate is matched. When the relative deviation γ is greater than 30%, leakage is the primary suspect and a detailed investigation must be conducted immediately, following step S0103; S0103. Use an infrared thermal imager to detect abnormal temperature rises on the surface of the insulation layer of steam pipes and identify leaks in the operating steam pipes.

[0011] The beneficial effects achieved by this invention compared with the prior art are as follows: 1. This invention provides a method for repairing pressurized steam pipelines without stopping the device by welding the welding end of the cover pipe with the area around the leak point of the steam pipeline to form a gap, allowing the steam leaking from the leak point to be discharged through a valve; the gap is then welded to form a weld, solving the problem that direct welding in the prior art easily aggravates steam leakage and causes accidents, and enabling safe and efficient repair of pressurized steam pipeline leaks without stopping the device. This invention eliminates the need for additional materials to seal leaks before welding. It employs a corresponding welding method without depressurizing the pipeline, and only requires closing the valve after welding is completed. 2. Regardless of the diameter of the steam pipe, only the specifications and shape of the leak point are used to make a cover pipe of the corresponding specifications. The cover pipe isolates the high-pressure steam, ensuring that the molten iron is not blown away and improving the welding quality. 3. During the welding process, low-current intermittent welding and valve control effectively prevent overheating of the weld and aggravation of steam leakage; 4. The non-stop steam pipeline welding maintenance method of the present invention is simple to operate, highly safe, and suitable for efficient maintenance of chemical plants. Attached Figure Description

[0012] Figure 1 A schematic diagram showing a leak in a steam pipeline; Figure 2 This is a schematic diagram of the cover tube and the leakage point described in this invention; In the diagram: 1. Steam pipe, 2. Leak point, 3. Cover pipe, 4. Valve. Detailed Implementation

[0013] 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. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0014] In the description of the invention, it should be understood that the terms "front," "rear," "upper," "lower," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention 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. Therefore, they should not be construed as limiting the invention. The invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] Example 1 Taking the repair of a leak in a DN200 steam pipeline (pressure 1.27 MPa) at a coal chemical plant as an example, this embodiment discloses a method for live welding repair of a steam pipeline without shutting down the plant, including the following steps: S01. Determine the leak point 2 in steam pipe 1; S0101. Obtain the upstream pressure through the upstream pressure gauge of steam pipe 1, and obtain the downstream pressure through the downstream pressure gauge of steam pipe 1, and obtain the pressure drop ΔP. 实 The formula for calculating the relative deviation γ is as follows: γ=ΔP 实 -ΔP 基 / ΔP 基 *100% Wherein, ΔP 基 This is the normal value for steam pipeline pressure drop; S0102. When the relative deviation γ is in the range of 15%-30%, this is a threshold that deserves high attention and should be investigated. It is necessary to start troubleshooting and check the status of valve 4, whether the drainage system is working properly, whether the insulation layer is intact, and whether the flow rate is matched. When the relative deviation γ is greater than 30%, there is a very high probability of a serious problem. A leak in the steam pipeline is the primary suspect and must be investigated immediately. Proceed with step S0103. S0103, such as Figure 1 As shown, an infrared thermal imager was used to detect the point where the temperature of the insulation layer of steam pipe 1 rose abnormally (steam leakage at the leak point would cause local high temperature), thereby finding the leak point 2 in the operating steam pipe 1.

[0016] S02, Select cover tube 3; A metal pipe is selected as the cover pipe 3. One end of the cover pipe 3 is sealed and the other end is open for welding. A valve 4 is installed on the cover pipe 3. When selecting the cover pipe 3, the material of the cover pipe 3 is the same as that of the steam pipe 1 with leakage point 2 to ensure that the materials are consistent and thus facilitate subsequent welding. The valve 4 is a high temperature and high pressure resistant valve. The inner diameter of the cover tube 3 is directly related to the shape and size of the leak point 2. When the cross-section of the leak point 2 is circular, the diameter of the leak point 2 is d, then the inner diameter D of the cover tube 3 is 5d, and D≥32mm. When the cross-section of leak point 2 is irregular, the long side dimension of leak point 2 is a, the short side dimension is b, then the inner diameter D of cover tube 3 is 3a + 2b. In this embodiment, the inner diameter of the cover tube is 250mm; S03, such as Figure 2 As shown, first open valve 4, then assemble the welded end of the cover pipe 3 with the area surrounding the leak point 2 of the steam pipe 1 to form an assembly gap, allowing the steam leaking from the leak point 2 to be discharged through valve 4. The specific steps include: S0301. Use an angle grinder to grind the area around the leak point 2 until a metallic luster is visible, and process the end face of the welded end of the cover pipe 3 into an arc surface that matches the curvature of the outer wall of the steam pipe 1. S0302. Grind the bevel at the end face of the welding end of the cover tube 3. The bevel is generally 30°. After completion, perform a penetration test on the entire cover tube 3 to ensure that the body of the cover tube 3 is free of defects. S0303. First, open valve 4 and use chain clamps to temporarily fix the cover pipe 3 to the steam pipe 1, so that the welded end of the cover pipe 3 and the surrounding area of ​​the leak point 2 of the steam pipe 1 are aligned to form an alignment gap. Use a copper hammer to evenly and moderately tap the outer surface of the cover pipe 3 from the position with the largest alignment gap to both sides. While tapping, observe the gap between the edge of the welded end of the cover pipe 3 and the surface of the steam pipe 1. Focus on tapping the area with the larger gap, so that the maximum gap does not exceed 1mm, and make the welded end of the cover pipe 3 and the surrounding area of ​​the leak point 2 fit tightly together. The cover completely covers the leak, isolating the welding area from the high-pressure steam and preventing the molten iron from being blown away by the steam. S04. Weld the assembly gaps to form a weld, and check the weld's sealing performance; specifically including the following steps: S0401. Select two points at the 0° and 180° positions of the assembly gap for spot welding; S0402. Starting from spot welding, welding is carried out in sections and skip welding towards both sides, using a small current of 80A for intermittent welding. The small current intermittent welding method is used to avoid overheating of the weld and to prevent the steam leakage from aggravating. The root pass is welded with a low current. After the root pass is completed, wait for the weld to cool to the range of process parameters, then weld with a low current to speed up the welding. Repeat this process three times to ensure the weld height. This design can prevent overheating during welding and avoid burning through the main pipeline or causing the leak to expand. S0403. After welding, inspect the appearance of the weld surface and perform penetrant or magnetic particle testing according to the actual temperature of the pipeline to ensure that there are no defects visible to the naked eye on the weld surface.

[0017] S05. Close valve 4 to complete the entire welding repair process.

[0018] The above solution involves assembling the welded end of the cover pipe with the area surrounding the leak point in the steam pipeline to form a gap, allowing the leaking steam to be discharged through the valve. The gap is then welded to form a weld, solving the problem that direct welding in existing technologies can easily exacerbate steam leakage and cause accidents. This solution enables safe and efficient repair of pressurized steam pipeline leaks without shutting down the pipeline. No additional materials are needed for sealing the leak before welding; the appropriate welding method is adopted without depressurizing the pipeline. After welding, only the valve needs to be closed.

[0019] Example 2 Taking the repair of a leak in a DN150 steam pipeline (pressure 1.0 MPa) as an example, this embodiment discloses a method for live welding repair of a steam pipeline without shutting down the equipment, including the following steps: S01. Determine the leak point 2 in steam pipe 1; S0101. Obtain the upstream pressure through the upstream pressure gauge of steam pipe 1, and obtain the downstream pressure through the downstream pressure gauge of steam pipe 1, and obtain the pressure drop ΔP. 实 The formula for calculating the relative deviation γ is as follows: γ=ΔP 实 -ΔP 基 / ΔP 基 *100% Wherein, ΔP 基 This is the normal value for steam pipeline pressure drop; S0102. When the relative deviation γ is in the range of 15%-30%, this is a threshold that deserves high attention and should be investigated. It is necessary to start troubleshooting and check the status of valve 4, whether the drainage system is working properly, whether the insulation layer is intact, and whether the flow rate is matched. When the relative deviation γ is greater than 30%, there is a very high probability of a serious problem. A leak in the steam pipeline is the primary suspect and must be investigated immediately. Proceed with step S0103. S0103. Using an infrared thermal imager, detect the point where the surface temperature of the insulation layer of steam pipe 1 rises abnormally (steam leakage at the leak point will cause local high temperature), thereby finding the leak point 2 in the operating steam pipe 1.

[0020] S02, Select cover tube 3; A metal pipe is selected as the cover pipe 3. One end of the cover pipe 3 is sealed and the other end is open for welding. A valve 4 is installed on the cover pipe 3. When selecting the cover pipe 3, the material of the cover pipe 3 is the same as that of the steam pipe 1 with the leakage point 2 to ensure that the materials are consistent and facilitate subsequent welding. In this embodiment, the steam pipe is made of carbon steel, so the cover pipe must also be made of carbon steel. The valve 4 is a high temperature and high pressure resistant valve. The inner diameter of the cover tube 3 is directly related to the shape and size of the leak point 2. When the cross-section of the leak point 2 is circular, the diameter of the leak point 2 is d, then the inner diameter D of the cover tube 3 is 5d, and D≥32mm. When the cross-section of leak point 2 is irregular, the long side dimension of leak point 2 is a, the short side dimension is b, then the inner diameter D of cover tube 3 is 3a + 2b. In this embodiment, the inner diameter of the cover tube is 200mm; S03. First, open valve 4, then assemble the welded end of the cover pipe 3 with the area surrounding the leak point 2 of the steam pipe 1 to form an assembly gap, allowing the steam leaking from the leak point 2 to be discharged through valve 4. This specifically includes the following steps: S0301. Use an angle grinder to grind the area around the leak point 2 until a metallic luster is visible, and process the end face of the welded end of the cover pipe 3 into an arc surface that matches the curvature of the outer wall of the steam pipe 1. S0302. Grind the bevel at the end face of the welding end of the cover tube 3. The bevel is generally 30°. After completion, perform a penetration test on the entire cover tube 3 to ensure that the body of the cover tube 3 is free of defects. S0303. First, open valve 4 and use chain clamps to temporarily fix the cover pipe 3 to the steam pipe 1, so that the welded end of the cover pipe 3 and the surrounding area of ​​the leak point 2 of the steam pipe 1 are aligned to form an alignment gap. Use a copper hammer to evenly and moderately tap the outer surface of the cover pipe 3 from the position with the largest alignment gap to both sides. While tapping, observe the gap between the edge of the welded end of the cover pipe 3 and the surface of the steam pipe 1. Focus on tapping the area with the larger gap, so that the maximum gap does not exceed 1mm, and make the welded end of the cover pipe 3 and the surrounding area of ​​the leak point 2 fit tightly together. The cover completely covers the leak, isolating the welding area from the high-pressure steam and preventing the molten iron from being blown away by the steam. S04. Weld the assembly gaps to form a weld, and check the weld's sealing performance; specifically including the following steps: S0401. Select two points at the 0° and 180° positions of the assembly gap for spot welding; S0402. Starting from spot welding, welding is carried out in sections and skip welding towards both sides, using a small current of 70A for intermittent welding. The small current intermittent welding method is used to avoid overheating of the weld and to prevent the steam leakage from aggravating. The root pass is welded with a low current. After the root pass is completed, wait for the weld to cool to the range of process parameters, then weld with a low current to speed up the welding. Repeat this process three times to ensure the weld height. This design can prevent overheating during welding and avoid burning through the main pipeline or causing the leak to expand. S0403. After welding, inspect the appearance of the weld surface and perform penetrant or magnetic particle testing according to the actual temperature of the pipeline to ensure that there are no defects visible to the naked eye on the weld surface.

[0021] S05. Close valve 4 to complete the entire welding repair process.

[0022] Comparative Example A leak was found in the steam pipe of a compound fertilizer plant. An attempt was made to weld the leak point directly onto the DN200 steam pipe (without a cover or valve). During the welding process, the molten metal was blown away by the steam, preventing the formation of a viable weld. Overheating of the weld exacerbated the leak, forcing a shutdown for repairs.

Claims

1. A method for live welding repair of a steam pipeline without shutting down the device, characterized in that, Includes the following steps: S01. Determine the leak point (2) of the steam pipe (1); S02, Select the cover tube (3); Select a metal tube as the cover tube (3). One end of the cover tube (3) is sealed and the other end is open for welding. A valve (4) is installed on the cover tube (3). S03. First, open the valve (4), then assemble the welded end of the cover pipe (3) with the area around the leak point (2) of the steam pipe (1) to form an assembly gap, so that the steam leaking from the leak point (2) can be discharged through the valve (4). S04. Weld the gap between the assembly pieces to form a weld and check the sealing performance of the weld. S05, Close the valve (4).

2. The method for non-stop steam pipeline welding maintenance according to claim 1, characterized in that, In step S02, when the cross-section of the leak point (2) is circular, the diameter of the leak point (2) is d, and the inner diameter D of the cover tube (3) is 5d, and D≥32mm; When the cross-section of the leak point (2) is irregular, the long side dimension of the leak point (2) is a, and the short side dimension is b. Then the inner diameter D of the cover tube (3) is 3a+2b.

3. The method for non-stop steam pipeline welding repair according to claim 2, characterized in that, When selecting the cover pipe (3), the material of the cover pipe (3) is the same as that of the steam pipe (1) with the leak point (2), and the valve (4) is a high temperature and high pressure resistant valve.

4. The method for non-stop steam pipeline welding repair according to claim 1, characterized in that, Step S03 includes the following steps: S0301. Use an angle grinder to grind the area around the leak point (2) until a metallic luster is visible, and process the end face of the welded end of the cover pipe (3) into an arc surface that matches the curvature of the outer wall of the steam pipe (1). S0302, grind the bevel on the end face of the welding end of the cover tube (3); S0303. First, open the valve (4) and use the chain clamp to temporarily fix the cover pipe (3) on the steam pipe (1) so that the welded end of the cover pipe (3) and the surrounding area of ​​the leak point (2) of the steam pipe (1) form a pairing gap. Use a copper hammer to evenly and moderately tap the outer surface of the cover pipe (3) from the position with the largest pairing gap to both sides. While tapping, observe the gap between the edge of the welded end of the cover pipe (3) and the surface of the steam pipe (1) so that the maximum gap does not exceed 1mm and the welded end of the cover pipe (3) is tightly attached to the surrounding area of ​​the leak point (2).

5. The method for non-stop steam pipeline welding repair according to claim 1, characterized in that, Step S04 includes the following steps: S0401. Select two points at the 0° and 180° positions of the assembly gap for spot welding; S0402. Starting from spot welding, welding is carried out in both directions using segmented back welding and skip welding methods, with intermittent welding using low current. The root pass is welded with a low current. After the root pass is completed, wait for the weld to cool to the range of process parameters, then weld with a low current to speed up the welding process. Repeat this process three times to ensure the weld reinforcement height.

6. The method for non-stop steam pipeline welding repair according to claim 5, characterized in that, Also includes: S0403. After welding, inspect the appearance of the weld surface and perform penetrant or magnetic particle testing according to the actual temperature of the pipeline to ensure that there are no defects visible to the naked eye on the weld surface.

7. The method for non-stop steam pipeline welding maintenance according to any one of claims 1-6, characterized in that, In step S01, the leak point (2) of the steam pipe (1) is determined; Includes the following steps: S0101. Obtain the upstream pressure through the upstream pressure gauge of the steam pipe (1), and obtain the downstream pressure through the downstream pressure gauge of the steam pipe, and obtain the pressure drop ΔP. 实 The formula for calculating the relative deviation γ is: γ=(ΔP 实 -ΔP 基 ) / ΔP 基 *100%, Wherein, ΔP 基 This is the normal value for steam pipeline pressure drop; S0102. When the relative deviation γ is within the range of 15%-30%, check the status of valve (4), whether the drainage system is working properly, whether the insulation layer is intact, and whether the flow rate is matched. When the relative deviation γ is greater than 30%, leakage is the primary suspect and a detailed investigation must be conducted immediately, following step S0103; S0103. Using an infrared thermal imager, detect the abnormal temperature rise point on the outer surface of the insulation layer of the steam pipe (1) and find the leak point (2) in the operating steam pipe (1).

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