Series sleeve structure for repairing circumferential weld defect of large-thickness-wall-difference pipeline and repairing method

Abstract

The invention discloses a series sleeve structure for repairing circumferential weld defects of large-thickness-wall-difference pipelines, which comprises a first pipeline, one end of the first pipeline is connected with a second pipeline, the outer diameter of the second pipeline is larger than that of the first pipeline, the first pipeline is partially sleeved with a B-type sleeve, and one end, close to the second pipeline, of the B-type sleeve is connected with a first reducing pipe; the small end of the first reducing pipe is connected with the B-type sleeve, and the large end of the first reducing pipe is arranged on the outer side of the second pipeline; the B-type sleeve and the first reducing pipe are divided into two parts along the axis; the B-type sleeve can be replaced by a second reducing pipe, and the first reducing pipe can be replaced by a third reducing pipe; the invention further provides a method for repairing the circumferential weld defect of the large-thickness-wall-difference pipeline through the series sleeve structure. According to the series sleeve structure for repairing the circumferential weld defect of the large-thickness-wall-difference pipeline, the problems that in the prior art, a machining method is adopted, so that a hot working flow line of a metal product is damaged, and the alignment tolerance of the pipeline repaired by a manufactured sleeve is limited are solved.

Description

Technical Field

[0001] This invention belongs to the field of repair technology for in-service oil and gas transmission pipelines, specifically relating to a series sleeve structure for repairing circumferential weld defects in pipelines with large wall thickness differences, and also relating to a method for repairing circumferential weld defects in pipelines with large wall thickness differences using the aforementioned series sleeve structure. Background Technology

[0002] Inspection results from multiple long-distance pipelines in China indicate that repairing weld joint defects is a key aspect of improving the quality of in-service pipelines. Among these defects, excessive wall thickness deviation between joints accounts for a high proportion of problematic circumferential welds, and on-site welding personnel are eager to improve this situation.

[0003] Currently, among the more than twenty existing methods for repairing pipeline defects, pipe replacement and B-type sleeve repair are two permanent repair methods frequently used. B-type sleeve repair, in particular, allows for defect repair without interrupting pipeline operation, offering advantages such as low cost, high effectiveness, and high reliability. Traditional B-type sleeves typically consist of two symmetrical semi-cylindrical arc plates. During installation, these plates are first placed over the upper and lower sides of the steel pipe to be repaired, covering the defect. Then, two longitudinal welds are used to weld the two semi-cylinders into a single complete cylinder. Finally, two circumferential fillet welds at the ends of the cylinder are used to weld the sleeve to the steel pipe to be repaired. This method is only suitable for repairing concentric steel pipe components with identical external contours on both sides of the defect. Currently, pipeline circumferential weld defects often exist in welded joints with unequal wall thicknesses, especially in circumferential welds where there is a significant difference in wall thickness between the tee main pipe and the trunk steel pipe, or between the induction heating bend and the trunk steel pipe. Field measurements showed that the maximum misalignment of the welded joint in a tee main pipe was 31mm, making traditional B-type sleeves unsuitable for installation.

[0004] Existing technologies include in-service welding, which is an environmentally friendly, economical, and efficient oil and gas pipeline repair technology that ensures the continuous and safe operation of pipelines. Type B sleeve repair technology, as a permanent repair method for oil and gas pipeline defects, requires no shutdown, only appropriate pressure reduction and flow restriction, and the repair cost is only 10% of the cost of pipe replacement. Therefore, it is widely used in the management of hidden dangers in in-service pipelines.

[0005] Currently, the repair of defects in thick-walled differential ring welds often uses reducing sleeves. The main manufacturing approach is to select thick-walled steel pipes and use machining methods such as cutting to produce sleeves with shapes that meet the requirements of field applications. However, there are two problems: first, the machining method destroys the heat treatment flow lines of the metal products, reducing the overall mechanical properties of the products; second, the sleeves manufactured by this method have limited capacity to repair pipe misalignment, which cannot meet the repair needs of pipes with even larger thick-walled differential welds. Summary of the Invention

[0006] The purpose of this invention is to provide a tandem sleeve structure for repairing defects in circumferential welds of thick-walled pipes, which solves the problems of existing technologies where machining methods destroy the heat treatment flow lines of metal products and the limited amount of pipe misalignment repaired by the sleeves.

[0007] Another object of the present invention is to provide a method for repairing defects in circumferential welds of thick-walled pipelines using a series sleeve structure.

[0008] The technical solution adopted in this invention is: a tandem sleeve structure for repairing defects in circumferential welds of thick-walled pipelines, comprising a first pipeline, one end of which is connected to a second pipeline via a butt circumferential weld. The outer diameter of the second pipeline is 6-20 mm larger than that of the first pipeline. A type B sleeve is fitted onto the first pipeline. A first reducer is connected to the end of the type B sleeve near the second pipeline. The first reducer is frustum-shaped. The small end of the first reducer is connected to the type B sleeve via a butt weld, and the large end of the first reducer is located outside the second pipeline. The type B sleeve and the first reducer are divided into two parts along the central axis, and the ends of the type B sleeve and the first reducer connected to each other are respectively provided with welding bevels.

[0009] The invention is further characterized by:

[0010] The inner diameter of the type B sleeve shall not be less than the outer diameter of the first pipe, and the difference between the two shall be 0 to 6 mm. The difference between the outer diameter of the type B sleeve and the outer diameter of the small end of the first reducer shall be within ±2 mm. The length of the type B sleeve shall not be less than 200 mm.

[0011] The length of the first reducer shall not be less than 200 mm, the inner diameter of the larger end of the first reducer shall not be less than the outer diameter of the second pipe, and the difference between the two shall be 0 to 6 mm; the inner diameter of the smaller end of the first reducer shall not be less than the outer diameter of the first pipe, and the difference between the two shall be 0 to 6 mm.

[0012] The end face of the type B sleeve away from the first reducer and the contact part with the first pipe, as well as the end face of the large end of the first reducer and the contact part with the second pipe, are all welded using a circumferential lap fillet weld. The type B sleeve and the first reducer are connected by a butt weld or a lap fillet weld. The two symmetrical semi-cylindrical arc plates of the type B sleeve and the two symmetrical semi-cylindrical arc plates of the first reducer are all connected by butt welds.

[0013] The second technical solution adopted in this invention is: a tandem sleeve structure for repairing defects in circumferential welds of thick-walled pipelines, comprising a first pipeline, one end of which is connected to a second pipeline via a butt circumferential weld, the outer diameter of the second pipeline being more than 20mm larger than the outer diameter of the first pipeline, a second reducer fitted over the first pipeline, the second reducer being frustoconical, a third reducer connected to the larger end of the second reducer via a butt weld, the third reducer being frustoconical, the smaller end of the third reducer being connected to the second reducer, and the larger end of the third reducer being located outside the second pipeline; the second reducer and the third reducer are divided into two along a central axis, and the ends of the second reducer and the third reducer connected to each other are respectively provided with welding bevels.

[0014] The invention is further characterized by:

[0015] The inner diameter of the smaller end of the second reducer shall not be less than the outer diameter of the first pipe, and the difference between the two shall be 0 to 6 mm. The length of the second reducer shall not be less than 200 mm.

[0016] The length of the third reducer shall not be less than 200 mm, and the inner diameter of the large end of the third reducer shall not be less than the outer diameter of the second pipe, with a difference of 0 to 6 mm. The outer diameter of the small end of the third reducer shall be consistent with the outer diameter of the large end of the second reducer, with an error within ±2 mm.

[0017] The second reducer and the third reducer are connected by butt welds. The two symmetrical semi-cylindrical arc plates of the second reducer and the two symmetrical semi-cylindrical arc plates of the third reducer are connected by butt welds. The contact area between the small end face of the second reducer and the first pipe and the contact area between the large end face of the third reducer and the second pipe are all welded by circumferential fillet welds.

[0018] The third technical solution adopted in this invention is: a method for repairing defects in circumferential welds of thick-walled pipelines using a tandem sleeve structure, the specific steps of which are as follows:

[0019] Step 1: Measure the difference in outer diameter between the first pipe and the second pipe. If the difference is 6-20mm, select the first reducer and type B sleeve based on the outer diameter of the first pipe and the second pipe.

[0020] Step 2: Divide the first reducer and the B-type sleeve horizontally in two along the axis, and process welding bevels on the end faces where the first reducer and the B-type sleeve are connected.

[0021] Step 3: Cover the first and second pipes to be repaired with the two symmetrical semi-cylindrical arc plates of the first reducer and the B-type sleeve arc plate, respectively. Then weld the components together. The B-type sleeve is connected to the first reducer by lap fillet weld. The two symmetrical semi-cylindrical arc plates of the B-type sleeve and the two symmetrical semi-cylindrical arc plates of the first reducer are connected by butt weld. The end face of the B-type sleeve away from the first reducer and the contact part with the first pipe, and the end face of the large end of the first reducer and the contact part with the second pipe are all welded by circumferential fillet weld. This completes the repair of the circumferential weld defect of the thick wall differential.

[0022] The fourth technical solution adopted in this invention is: a method for repairing defects in circumferential welds of thick-walled pipelines using a tandem sleeve structure, the specific steps of which are as follows:

[0023] Step 1: Measure the difference in outer diameter between the first pipe and the second pipe. If the difference is greater than 20mm, select the second reducer and the third reducer based on the outer diameter of the first pipe and the second pipe.

[0024] Step 2: Divide the second reducer and the third reducer in half along the axis, and process welding bevels on the end faces where the second reducer and the third reducer are connected.

[0025] Step 3: Cover the first and second pipes to be repaired with the two symmetrical semi-cylindrical arc plates of the second and third reducers respectively. Then weld the components together. The second and third reducers are connected by lap fillet welds. The two symmetrical semi-cylindrical arc plates of the second reducer and the two symmetrical semi-cylindrical arc plates of the third reducer are connected by butt welds. The contact area between the small end face of the second reducer and the first pipe, and the contact area between the large end face of the third reducer and the second pipe, are all welded with circumferential fillet welds. This completes the repair of the defect of the thick-walled differential circumferential weld.

[0026] The beneficial effects of this invention are:

[0027] This invention provides a series sleeve structure and a graded repair method for repairing defects in circumferential welds of pipes with large wall thickness differences. For circumferential weld defects with large wall thickness differences and different external misalignment, the method uses reducers and B-type sleeves or large reducers and small reducer standard parts in series combination. This provides a larger repair cavity, solving the problem of covering defects in welded joints with unequal wall thicknesses. It also allows for the selection of appropriate standard parts for combined repair according to the size of the circumferential weld misalignment, thereby reducing repair costs. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a conventional Type B sleeve for repairing pipe defects;

[0029] Figure 2 This is a schematic diagram of a tandem sleeve structure for repairing defects in pipe circumferential welds with external faults ranging from 6 to 20 mm.

[0030] Figure 3 This is a schematic diagram of a series sleeve structure for repairing defects in pipe circumferential welds with an external error variable greater than 20mm.

[0031] In the diagram, 1. First pipe, 2. Second pipe, 3. Type B sleeve, 4. First reducer, 5. Second reducer, 6. Third reducer. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0033] A tandem sleeve structure for repairing defects in circumferential welds of thick-walled pipelines with large differential thicknesses, such as... Figure 2 As shown, it includes a first pipe 1, one end of which is connected to a second pipe 2 via a butt weld. The outer diameter of the second pipe 2 is 6-20 mm larger than that of the first pipe 1. A type B sleeve 3 is fitted onto the first pipe 1. A first reducer 4 is connected to the end of the type B sleeve 3 near the second pipe 2. The first reducer 4 is frustoconical. The small end of the first reducer 4 is connected to the type B sleeve 3 via a butt weld, and the large end of the first reducer 4 is located outside the second pipe 2. The type B sleeve 3 and the first reducer 4 are divided into two parts along the central axis, and the ends of the type B sleeve 3 and the first reducer 4 that are connected to each other are respectively provided with welding bevels.

[0034] Among them, the inner diameter of the B-type sleeve 3 is not less than the outer diameter of the first pipe 1, and the difference between the two is 0 to 6 mm. The difference between the outer diameter of the B-type sleeve 3 and the outer diameter of the small end of the first reducer 4 is within ±2 mm. The length of the B-type sleeve 3 is not less than 200 mm.

[0035] The length of the first reducer 4 shall not be less than 200 mm, the inner diameter of the large end of the first reducer 4 shall not be less than the outer diameter of the second pipe 2, and the difference between the two shall be 0 to 6 mm; the inner diameter of the small end of the first reducer 4 shall not be less than the outer diameter of the first pipe 1, and the difference between the two shall be 0 to 6 mm.

[0036] The end face of the B-type sleeve 3 away from the first reducer 4 and the contact part with the first pipe 1, and the end face of the large end of the first reducer 4 and the contact part with the second pipe 2 are all welded by circumferential lap fillet welds. The B-type sleeve 3 and the first reducer 4 are connected by butt welds or lap fillet welds. The two symmetrical semi-cylindrical arc plates of the B-type sleeve 3 and the two symmetrical semi-cylindrical arc plates of the first reducer 4 are connected by butt welds.

[0037] Use such as Figure 2The method for repairing defects in circumferential welds of thick-walled pipelines using the tandem sleeve structure shown is as follows:

[0038] Step 1: Measure the difference in outer diameter between the first pipe 1 and the second pipe 2. If the difference is 6 to 20 mm, select the first reducer 4 and the type B sleeve 3 according to the outer diameter of the first pipe 1 and the second pipe 2.

[0039] Step 2: Divide the first reducer 4 and the type B sleeve 3 horizontally in two along the axis, and process welding bevels on the end faces where the first reducer 4 and the type B sleeve 3 are connected.

[0040] Step 3: Cover the first pipe 1 and the second pipe 2 with the two symmetrical semi-cylindrical arc plates of the first reducer 4 and the B-type sleeve 3 respectively. Then weld the components together. The B-type sleeve 3 is connected to the first reducer 4 by lap fillet weld. The two symmetrical semi-cylindrical arc plates of the B-type sleeve 3 and the two symmetrical semi-cylindrical arc plates of the first reducer 4 are connected by butt weld. The part of the B-type sleeve 3 away from the first reducer 4 that contacts the first pipe 1 and the part of the large end of the first reducer 4 that contacts the second pipe 2 are all welded by circumferential fillet weld. The repair of the circumferential weld defect of the thick wall differential is completed.

[0041] A tandem sleeve structure for repairing defects in circumferential welds of thick-walled pipelines with large differential thicknesses, such as... Figure 3 As shown, it includes a first pipe 1, one end of which is connected to a second pipe 2 via a butt weld. The outer diameter of the second pipe 2 is more than 20 mm larger than the outer diameter of the first pipe 1. The first pipe 1 is fitted with a second reducer 5, which is frustoconical in shape. The large end of the second reducer 5 is connected to a third reducer 6 via a butt weld. The third reducer 6 is also frustoconical in shape. The small end of the third reducer 6 is connected to the second reducer 5, and the large end of the third reducer 6 is located outside the second pipe 2. The second reducer 5 and the third reducer 6 are divided into two parts along the central axis, and the ends of the second reducer 5 and the third reducer 6 that are connected to each other are respectively provided with welding bevels.

[0042] The inner diameter of the small end of the second reducer 5 is not less than the outer diameter of the first pipe 1, and the difference between the two is 0 to 6 mm. The length of the second reducer 5 is not less than 200 mm.

[0043] The length of the third reducer 6 shall not be less than 200 mm, and the inner diameter of the large end of the third reducer 6 shall not be less than the outer diameter of the second pipe 2, with a difference of 0 to 6 mm; the outer diameter of the small end of the third reducer 6 shall be consistent with the outer diameter of the large end of the second reducer 5, with an error within ±2 mm.

[0044] The second reducer 5 and the third reducer 6 are connected by butt welds. The two symmetrical semi-cylindrical arc plates of the second reducer 5 and the two symmetrical semi-cylindrical arc plates of the third reducer 6 are connected by butt welds. The contact area between the small end face of the second reducer 5 and the first pipe 1, and the contact area between the large end face of the third reducer 6 and the second pipe 2 are all welded by circumferential fillet welds.

[0045] Use as Figure 3 The method for repairing defects in circumferential welds of thick-walled pipelines using the tandem sleeve structure shown is as follows:

[0046] Step 1: Measure the difference in outer diameter between the first pipe 1 and the second pipe 2. If the difference is greater than 20mm, select the second reducer 5 and the third reducer 6 based on the outer diameter of the first pipe 1 and the second pipe 2.

[0047] Step 2: Divide the second reducer 5 and the third reducer 6 into two parts along the axis, and process welding bevels on the end faces where the second reducer 5 and the third reducer 6 are connected.

[0048] Step 3: Cover the first pipe 1 and the second pipe 2 with the two symmetrical semi-cylindrical arc plates of the second reducer 5 and the third reducer 6 respectively. Then weld the components together. The second reducer 5 and the third reducer 6 are connected by lap fillet welds. The two symmetrical semi-cylindrical arc plates of the second reducer 5 and the two symmetrical semi-cylindrical arc plates of the third reducer 6 are connected by butt welds. The contact area between the small end face of the second reducer 5 and the first pipe 1, and the contact area between the large end face of the third reducer 6 and the second pipe 2 are all welded by circumferential fillet welds. This completes the repair of the defect of the large thick-walled differential circumferential weld.

[0049] Because all components are of standard size, they are easy to produce and procure. Furthermore, the alignment accuracy between components is high, making installation and welding relatively easy. The selection of reducers aims to completely cover the defects of the pipe circumferential weld.

[0050] The defect in the circumferential weld of the pipeline to be repaired has a large amount of misalignment. Using a reducer as the main structure can well meet the repair space requirements. Using a reducer or a type B sleeve can complete the connection between the reducer and the pipeline, and achieve the installation and sealing requirements of the encapsulation structure.

[0051] When selecting sleeve accessories, the dimensional requirements of the misalignment of the thick-walled differential ring weld were considered. Specific dimensional requirements for reducers and type B sleeves were proposed, and selection requirements for accessories were formulated to ensure the quality of installation, welding, and repair.

[0052] This application can use two components in series or multiple components in series.

[0053] Example 1

[0054] A tandem sleeve structure for repairing defects in circumferential welds of thick-walled pipelines with large differential thicknesses, such as... Figure 2 As shown, it includes a first pipe 1, one end of which is connected to a second pipe 2 via a butt weld. The outer diameter of the second pipe 2 is 8mm larger than that of the first pipe 1. A B-type sleeve 3 is fitted onto the first pipe 1. A first reducer 4 is connected to the end of the B-type sleeve 3 near the second pipe 2. The first reducer 4 is frustum-shaped. The small end of the first reducer 4 is connected to the B-type sleeve 3 via a butt weld, and the large end of the first reducer 4 is located outside the second pipe 2. The B-type sleeve 3 and the first reducer 4 are divided into two parts along the central axis, and the ends of the B-type sleeve 3 and the first reducer 4 that are connected to each other are respectively provided with welding bevels.

[0055] Among them, the inner diameter of the B-type sleeve 3 is 4mm larger than the outer diameter of the first pipe 1, the outer diameter of the B-type sleeve 3 has an error of 1mm with the small end outer diameter of the first reducer 4, and the length of the B-type sleeve 3 is 300mm.

[0056] The first reducer 4 has a length of 230mm. The inner diameter of the large end of the first reducer 4 is 3mm larger than the outer diameter of the second pipe 2. The inner diameter of the small end of the first reducer 4 is 3mm larger than the outer diameter of the first pipe 1.

[0057] The end face of the B-type sleeve 3 away from the first reducer 4 and the contact area with the first pipe 1, and the end face of the large end of the first reducer 4 and the contact area with the second pipe 2 are all welded by circumferential lap fillet welds. The B-type sleeve 3 and the first reducer 4 are connected by lap fillet welds. The two symmetrical semi-cylindrical arc plates of the B-type sleeve 3 and the two symmetrical semi-cylindrical arc plates of the first reducer 4 are connected by butt welding.

[0058] Use such as Figure 2 The method for repairing defects in circumferential welds of thick-walled pipelines using the tandem sleeve structure shown is as follows:

[0059] Step 1: Select the first reducer 4 and the type B sleeve 3 according to the outer diameter of the first pipe 1 and the second pipe 2;

[0060] Step 2: Divide the first reducer 4 and the type B sleeve 3 horizontally in two along the axis, and process welding bevels on the end faces where the first reducer 4 and the type B sleeve 3 are connected.

[0061] Step 3: Cover the first pipe 1 and the second pipe 2 with the two symmetrical semi-cylindrical arc plates of the first reducer 4 and the B-type sleeve 3 respectively. Then weld the components together. The B-type sleeve 3 is connected to the first reducer 4 by lap fillet weld. The two symmetrical semi-cylindrical arc plates of the B-type sleeve 3 and the two symmetrical semi-cylindrical arc plates of the first reducer 4 are connected by butt weld. The part of the B-type sleeve 3 away from the first reducer 4 that contacts the first pipe 1 and the part of the large end of the first reducer 4 that contacts the second pipe 2 are all welded by circumferential fillet weld. The repair of the circumferential weld defect of the thick wall differential is completed.

[0062] Example 2

[0063] A series sleeve structure for repairing defects in circumferential welds of thick-walled pipelines, such as... Figure 3 As shown, it includes a first pipe 1, one end of which is connected to a second pipe 2 via a butt weld. The outer diameter of the second pipe 2 is 25mm larger than that of the first pipe 1. The first pipe 1 is fitted with a second reducer 5, which is frustoconical in shape. The larger end of the second reducer 5 is connected to a third reducer 6 via a butt weld. The third reducer 6 is also frustoconical in shape. The smaller end of the third reducer 6 is connected to the second reducer 5, and the larger end of the third reducer 6 is located outside the second pipe 2. The second reducer 5 and the third reducer 6 are divided into two parts along the central axis, and the ends of the second reducer 5 and the third reducer 6 that are connected to each other are respectively provided with welding bevels.

[0064] The inner diameter of the small end of the second reducer 5 is not less than the outer diameter of the first pipe 1, and the difference between the two is 6mm. The length of the second reducer 5 is not less than 260mm.

[0065] The length of the third reducer 6 shall not be less than 250 mm. The inner diameter of the large end of the third reducer 6 shall be 5 mm larger than the outer diameter of the second pipe 2. The outer diameter of the small end of the third reducer 6 shall be the same as the outer diameter of the large end of the second reducer 5.

[0066] The second reducer 5 and the third reducer 6 are connected by butt welds. The two symmetrical semi-cylindrical arc plates of the second reducer 5 and the two symmetrical semi-cylindrical arc plates of the third reducer 6 are connected by butt welds. The contact area between the small end face of the second reducer 5 and the first pipe 1, and the contact area between the large end face of the third reducer 6 and the second pipe 2 are all welded by circumferential fillet welds.

[0067] Use as Figure 3 The method for repairing defects in circumferential welds of thick-walled pipelines using the tandem sleeve structure shown is as follows:

[0068] Step 1: Select the second reducer 5 and the third reducer 6 based on the outer diameter of the first pipe 1 and the second pipe 2;

[0069] Step 2: Divide the second reducer 5 and the third reducer 6 into two parts along the axis, and process welding bevels on the end faces where the second reducer 5 and the third reducer 6 are connected.

[0070] Step 3: Cover the first pipe 1 and the second pipe 2 with the two symmetrical semi-cylindrical arc plates of the second reducer 5 and the third reducer 6 respectively. Then weld the components together. The second reducer 5 and the third reducer 6 are connected by lap fillet welds. The two symmetrical semi-cylindrical arc plates of the second reducer 5 and the two symmetrical semi-cylindrical arc plates of the third reducer 6 are connected by butt welds. The contact area between the small end face of the second reducer 5 and the first pipe 1, and the contact area between the large end face of the third reducer 6 and the second pipe 2 are all welded by circumferential fillet welds. This completes the repair of the defect of the large thick-walled differential circumferential weld.

[0071] Example 3

[0072] A tandem sleeve structure for repairing defects in circumferential welds of thick-walled pipelines with large differential thicknesses, such as... Figure 2 As shown, it includes a first pipe 1, one end of which is connected to a second pipe 2 via a butt weld. The outer diameter of the second pipe 2 is 10mm larger than that of the first pipe 1. A B-type sleeve 3 is fitted onto the first pipe 1. A first reducer 4 is connected to the end of the B-type sleeve 3 near the second pipe 2. The first reducer 4 is frustoconical. The small end of the first reducer 4 is connected to the B-type sleeve 3 via a butt weld, and the large end of the first reducer 4 is located outside the second pipe 2. The B-type sleeve 3 and the first reducer 4 are divided into two parts along the axis, and the ends of the B-type sleeve 3 and the first reducer 4 that are connected to each other are respectively provided with welding bevels.

[0073] Among them, the inner diameter of the B-type sleeve 3 is 2mm larger than the outer diameter of the first pipe 1, the outer diameter of the B-type sleeve 3 is the same as the outer diameter of the small end of the first reducer 4, and the length of the B-type sleeve 3 is 200mm.

[0074] The first reducer 4 has a length of 220mm. The inner diameter of the larger end of the first reducer 4 is 1mm larger than the outer diameter of the second pipe 2. The inner diameter of the smaller end of the first reducer 4 is 2mm larger than the outer diameter of the first pipe 1.

[0075] The end face of the B-type sleeve 3 away from the first reducer 4 and the contact area with the first pipe 1, and the end face of the large end of the first reducer 4 and the contact area with the second pipe 2 are all welded by circumferential lap fillet welds. The B-type sleeve 3 and the first reducer 4 are connected by lap fillet welds. The two symmetrical semi-cylindrical arc plates of the B-type sleeve 3 and the two symmetrical semi-cylindrical arc plates of the first reducer 4 are connected by butt welding.

[0076] Use as Figure 2 The method for repairing defects in circumferential welds of thick-walled pipelines using the tandem sleeve structure shown is as follows:

[0077] Step 1: Select the first reducer 4 and the type B sleeve 3 according to the outer diameter of the first pipe 1 and the second pipe 2;

[0078] Step 2: Divide the first reducer 4 and the type B sleeve 3 horizontally in two along the axis and process the welding bevel;

[0079] Step 3: Cover the first pipe 1 and the second pipe 2 with the two symmetrical semi-cylindrical arc plates of the first reducer 4 and the B-type sleeve 3 respectively. Then weld the components together. The B-type sleeve 3 is connected to the first reducer 4 by lap fillet weld. The two symmetrical semi-cylindrical arc plates of the B-type sleeve 3 and the two symmetrical semi-cylindrical arc plates of the first reducer 4 are connected by butt weld. The part of the B-type sleeve 3 away from the first reducer 4 that contacts the first pipe 1 and the part of the large end of the first reducer 4 that contacts the second pipe 2 are all welded by circumferential fillet weld. This completes the repair of the circumferential weld defect of the thick wall differential.

Claims

1. A tandem sleeve structure for repairing defects in circumferential welds of thick-walled pipelines, characterized in that, The system includes a first pipe (1), one end of which is connected to a second pipe (2) via a butt weld. The outer diameter of the second pipe (2) is 6-20 mm larger than that of the first pipe (1). A type B sleeve (3) is fitted onto the first pipe (1). A first reducer (4) is connected to the end of the type B sleeve (3) near the second pipe (2). The first reducer (4) is frustum-shaped. The small end of the first reducer (4) is connected to the type B sleeve (3) via a butt weld. The large end of the first reducer (4) is located outside the second pipe (2). The type B sleeve (3) and the first reducer (4) are divided into two parts along the central axis, and the ends of the type B sleeve (3) and the first reducer (4) connected to each other are respectively provided with welding bevels.

2. The tandem sleeve structure for repairing defects in circumferential welds of thick-walled pipelines according to claim 1, characterized in that, The inner diameter of the B-type sleeve (3) is not less than the outer diameter of the first pipe (1), and the difference between the two is 0 to 6 mm. The difference between the outer diameter of the B-type sleeve (3) and the outer diameter of the small end of the first reducer (4) is within ±2 mm. The length of the B-type sleeve (3) is not less than 200 mm.

3. The tandem sleeve structure for repairing defects in circumferential welds of thick-walled pipelines according to claim 2, characterized in that, The first reducer (4) has a length of not less than 200 mm, and the inner diameter of the large end of the first reducer (4) is not less than the outer diameter of the second pipe (2), with a difference of 0 to 6 mm; the inner diameter of the small end of the first reducer (4) is not less than the outer diameter of the first pipe (1), with a difference of 0 to 6 mm.

4. The tandem sleeve structure for repairing defects in circumferential welds of thick-walled pipelines according to claim 3, characterized in that, The end face of the B-type sleeve (3) away from the first reducer (4) and the contact part with the first pipe (1), and the end face of the large end of the first reducer (4) and the contact part with the second pipe (2) are all welded by circumferential lap fillet welds. The B-type sleeve (3) and the first reducer (4) are connected by butt welds or lap fillet welds. The two semi-cylindrical arc plates of the B-type sleeve (3) and the two semi-cylindrical arc plates of the first reducer (4) are connected by butt welds.

5. A tandem sleeve structure for repairing defects in circumferential welds of thick-walled pipelines, characterized in that, The system includes a first pipe (1), one end of which is connected to a second pipe (2) via a butt weld. The outer diameter of the second pipe (2) is more than 20 mm larger than that of the first pipe (1). The first pipe (1) is fitted with a second reducer (5), which is frustum-shaped. The large end of the second reducer (5) is connected to a third reducer (6) via a butt weld. The third reducer (6) is frustum-shaped. The small end of the third reducer (6) is connected to the second reducer (5), and the large end of the third reducer (6) is located outside the second pipe (2). The second reducer (5) and the third reducer (6) are divided into two parts along the central axis, and the ends of the second reducer (5) and the third reducer (6) connected to each other are respectively provided with welding bevels.

6. The tandem sleeve structure for repairing defects in circumferential welds of thick-walled pipelines according to claim 5, characterized in that, The inner diameter of the small end of the second reducer (5) is not less than the outer diameter of the first pipe (1), and the difference between the two is 0 to 6 mm. The length of the second reducer (5) is not less than 200 mm.

7. The tandem sleeve structure for repairing defects in circumferential welds of thick-walled pipelines according to claim 6, characterized in that, The length of the third reducer (6) is not less than 200 mm, and the inner diameter of the large end of the third reducer (6) is not less than the outer diameter of the second pipe (2), with a difference of 0 to 6 mm; the outer diameter of the small end of the third reducer (6) is consistent with the outer diameter of the large end of the second reducer (5), with an error within ±2 mm.

8. The tandem sleeve structure for repairing defects in circumferential welds of thick-walled pipelines according to claim 7, characterized in that, The second reducer (5) and the third reducer (6) are connected by butt welds. The two semi-cylindrical arc plates of the second reducer (5) and the two semi-cylindrical arc plates of the third reducer (6) are connected by butt welds. The small end face of the second reducer (5) and the contact part with the first pipe (1) and the large end face of the third reducer (6) and the contact part with the second pipe (2) are all welded by circumferential fillet welds.

9. A method for repairing circumferential weld defects in thick-walled pipelines using the tandem sleeve structure as described in any one of claims 1 to 4, characterized in that, The specific steps are as follows: Step 1: Measure the difference in outer diameter between the first pipe (1) and the second pipe (2). If the difference is 6 to 20 mm, select the first reducer (4) and the type B sleeve (3) according to the outer diameter of the first pipe (1) and the second pipe (2). Step 2: Divide the first reducer (4) and the B-type sleeve (3) horizontally into two parts along the axis, and process welding bevels on the end faces where the first reducer (4) and the B-type sleeve (3) are connected. Step 3: Cover the first pipe (1) and the second pipe (2) with the two symmetrical semi-cylindrical arc plates of the first reducer (4) and the B-type sleeve (3) respectively. Then weld the components together. The B-type sleeve (3) and the first reducer (4) are connected by lap fillet welds. The two symmetrical semi-cylindrical arc plates of the B-type sleeve (3) and the two symmetrical semi-cylindrical arc plates of the first reducer (4) are connected by butt welds. The end face of the B-type sleeve (3) away from the first reducer (4) and the contact part with the first pipe (1) and the end face of the large end of the first reducer (4) and the contact part with the second pipe (2) are all welded by circumferential fillet welds. The repair of the defect of the thick wall differential circumferential weld can be completed.

10. A method for repairing circumferential weld defects in thick-walled pipelines using the tandem sleeve structure as described in any one of claims 5 to 8, characterized in that, The specific steps are as follows: Step 1: Measure the difference in outer diameter between the first pipe (1) and the second pipe (2). If the difference is greater than 20mm, select the second reducer (5) and the third reducer (6) based on the outer diameter of the first pipe (1) and the second pipe (2). Step 2: Divide the second reducer (5) and the third reducer (6) into two parts along the axis, and process welding bevels on the end faces where the second reducer (5) and the third reducer (6) are connected. Step 3: Cover the first pipe (1) and the second pipe (2) with the two symmetrical semi-cylindrical arc plates of the second reducer (5) and the third reducer (6) respectively. Then weld the components together. The second reducer (5) and the third reducer (6) are connected by lap fillet welds. The two symmetrical semi-cylindrical arc plates of the second reducer (5) and the two symmetrical semi-cylindrical arc plates of the third reducer (6) are connected by butt welds. The contact parts between the small end face of the second reducer (5) and the first pipe (1) and the contact parts between the large end face of the third reducer (6) and the second pipe (2) are all welded by circumferential fillet welds. The repair of the defect of the large thick wall differential circumferential weld can be completed.

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