Method of repairing dual oil tubes

Abstract

The present disclosure provides a double oil pipe repairing method, belonging to the technical field of mechanical processing. The repairing method comprises the following steps: cutting off the inner threaded joint and the outer threaded joint from both ends of the outer steel pipe, so that both ends of the inner oil pipe protrude outside the outer steel pipe; providing a new inner threaded joint; coaxially assembling the new inner threaded joint at one end of the outer steel pipe, so that the inner thread of the inner wall of the new inner threaded joint is coaxially arranged with the outer steel pipe; inserting a concentricity device into the new inner threaded joint, and welding the new inner threaded joint and the outer steel pipe together; coaxially welding a threadless joint and the outer steel pipe together; machining outer threads on the outer wall of the threadless joint coaxially with the inner oil pipe, to obtain an outer threaded joint connected with the outer steel pipe. The present disclosure can simplify the repairing process of the double oil pipe and reduce the repairing cost.

Description

Technical Field

[0001] This disclosure belongs to the field of machining technology, and specifically relates to a method for repairing dual oil pipes. Background Technology

[0002] In controllable pitch propeller (CPP) systems, dual oil lines are often used to transmit high-pressure hydraulic oil and prevent leakage, ensuring safe and reliable system operation. The dual oil lines consist of an outer oil line, an inner oil line, and connecting screws. The inner oil line is coaxially located inside the outer oil line. The inner and outer oil lines are connected together by connecting screws. The outer oil line includes an internally threaded connector, an externally threaded connector, and an outer steel tube. The internally and externally threaded connectors are welded to both ends of the outer steel tube. To ensure that the internal thread of the internally threaded connector and the external thread of the externally threaded connector are concentric with the inner oil line, the internal and external threads are machined into the internally and externally threaded connectors after the outer oil line is assembled and welded.

[0003] In related technologies, when the inner holes of the internal and external threaded connectors at both ends of a dual oil pipe are damaged or deformed, or the threads of the internal or external threaded connector are damaged, the internal or external threaded connectors will become unusable. In this case, the internal and external threaded connectors in the external oil pipe should be replaced promptly. Because the internal oil pipe obstructs the internal threaded connector, it is not possible to replace the internal threaded connector by first assembling an unmachined connector in the end of the external steel pipe and then machining the internal thread. The only solution is to first remove the connecting screws to separate the internal and external oil pipes, then re-weld the external oil pipe, and finally reassemble the welded external oil pipe onto the outside of the internal oil pipe.

[0004] However, such repairs and rework are very troublesome and waste labor and material costs. Summary of the Invention

[0005] This disclosure provides a method for repairing dual oil pipes, which simplifies the repair process and reduces repair costs. The technical solution is as follows: This disclosure provides a method for repairing a dual oil pipe, the dual oil pipe including an inner oil pipe and an outer oil pipe sleeved outside the inner oil pipe, the outer oil pipe including an internal threaded joint, an external threaded joint and an outer steel pipe, the internal threaded joint and the external threaded joint being respectively welded to both ends of the outer steel pipe, the outer steel pipe being connected to the inner oil pipe; The repair method includes: cutting off both the internal threaded connector and the external threaded connector from both ends of the outer steel pipe, so that both ends of the inner oil pipe protrude outside the outer steel pipe; providing a new internal threaded connector, the inner wall of which has an internal thread; coaxially assembling the new internal threaded connector at one end of the outer steel pipe, such that the internal thread of the inner wall of the new internal threaded connector is coaxially arranged with the outer steel pipe; inserting a concentricity device into the new internal threaded connector, the outer circle of which has an external thread that matches the internal thread of the inner wall of the new internal threaded connector, the concentricity device having an inner hole that is coaxial with the inner oil pipe; welding the new internal threaded connector to the outer steel pipe; coaxially welding a threadless connector to the outer steel pipe; and machining an external thread coaxial with the inner oil pipe on the outer wall of the threadless connector to obtain an external threaded connector connected to the outer steel pipe.

[0006] In another implementation of this disclosure, the concentricity device includes a connector and a connecting sleeve. One end of the connector is connected to one end of the connecting sleeve, and the other end of the connector is away from the outer steel pipe. The other end of the connecting sleeve is threadedly connected to the new internal threaded connector. The connecting sleeve is fitted over the inner oil pipe and has a clearance fit with the inner oil pipe.

[0007] In another implementation of this disclosure, the outer wall of the new internal threaded connector has a welding bevel in the middle; the coaxial assembly of the new internal threaded connector with one end of the outer steel pipe includes: inserting one end of the new internal threaded connector into one end of the outer steel pipe; adjusting the position of the new internal threaded connector in the outer steel pipe such that there is a gap between the welding bevel and the end face of the outer steel pipe, and the end of the new internal threaded connector away from the outer steel pipe protrudes outside the inner oil pipe to allow for welding shrinkage.

[0008] In another implementation of this disclosure, when the width of the gap is not greater than 6 mm and not less than 4 mm, the welding shrinkage is 1 mm; or, when the width of the gap is not greater than 8 mm and greater than 6 mm, the welding shrinkage is 1.5 mm.

[0009] In another implementation of this disclosure, the step of cutting off both the internal threaded joint and the external threaded joint from both ends of the outer steel pipe includes: machining the outer steel pipe along the weld seam between the outer steel pipe and the external threaded joint; and machining the outer steel pipe along the weld seam between the outer steel pipe and the internal threaded joint.

[0010] In another implementation of this disclosure, welding the new internal threaded joint to the outer steel pipe includes: dividing the new internal threaded joint into multiple arc segments along its circumference, the multiple arc segments being divided into multiple arc segment pairs, and the two arc segments in each arc segment pair being centrally symmetrical about the center of the new internal threaded joint; welding each arc segment sequentially in units of the arc segment pairs until the entire circumference of the new internal threaded joint is welded, with at least one arc segment spaced between two adjacent welding operations.

[0011] In another implementation of this disclosure, the repair method further includes: grinding the weld between the new internal threaded joint and the outer steel pipe, and the weld between the unthreaded joint and the outer steel pipe.

[0012] In another implementation of this disclosure, the repair method further includes vibrating the welded outer steel pipe and the inner oil pipe.

[0013] In another implementation of this disclosure, the repair method further includes: performing combined flaw detection on the welded outer steel pipe and the inner oil pipe.

[0014] In another implementation of this disclosure, the repair method further includes: performing a bluing treatment on the repaired dual oil pipes, and spraying an anti-rust coating on the inner and outer surfaces of the dual oil pipes.

[0015] The beneficial effects of the technical solutions provided in this disclosure are: When repairing a bent double oil pipe using the repair method provided in this embodiment, the method involves first cutting off the internal and external threaded joints at both ends of the outer steel pipe. Then, a new internal threaded joint with pre-existing internal threads is directly installed at one end of the outer steel pipe. This new internal threaded joint is then coaxially mounted at one end of the outer steel pipe. A concentricity device is then inserted into the internal threaded joint to ensure that it remains coaxial with the outer steel pipe after welding. Next, a threadless joint is sequentially installed at the other end of the outer steel pipe and welded to it. Finally, external threads are machined into the threadless joint, thus completing the repair of the double oil pipe.

[0016] The above repair method, by pre-machining the new internal threaded connector before welding, ensures both the dimensions of the dual oil pipe assembly and the quality of the weld. This repair method allows for the repair of the dual oil pipe assembly without removing the screws, making it both quick and convenient. Attached Figure Description

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

[0018] Figure 1 This is a schematic diagram of the structure of the dual oil pipe provided in an embodiment of this disclosure; Figure 2 For along Figure 1 A cross-sectional view along the BB direction in the middle; Figure 3 For along Figure 1 A cross-sectional view along the AA direction; Figure 4 A flowchart illustrating a method for repairing dual oil pipes provided in this embodiment of the disclosure; Figure 5 A flowchart illustrating another method for repairing dual oil pipes provided in this embodiment of the disclosure; Figure 6 for Figure 1 A schematic diagram showing the process after cutting off the internal threaded joint and the external threaded joint; Figure 7 In order to be in Figure 6 A schematic diagram of the structure after assembling the internal threaded connector based on the above. Figure 8 In order to be in Figure 7 A schematic diagram of the structure after inserting the concentricity device on the basis of the above. Figure 9 for Figure 8 Enlarged view of the middle left end; Figure 10 for Figure 8 A schematic diagram of the segmentation during welding of an internal threaded joint; Figure 11 This is a schematic diagram of the repaired dual oil pipe structure.

[0019] The symbols in the diagram represent the following meanings: 100. External oil pipe; 101. Internal threaded connector; 102. External threaded connector; 103. External steel pipe; 104. Support component; 1041. Tile; 200. Inner oil pipe; 201. Inner oil pipe fitting; 202. Inner steel pipe; 300. Connecting screws; 400. Concentricity device; 401. Connector; 402. Connecting sleeve. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this disclosure clearer, the embodiments of this disclosure will be described in further detail below with reference to the accompanying drawings.

[0021] Figure 1 This is a schematic diagram of the structure of the dual oil pipe provided in the embodiments of this disclosure, combined with... Figure 1 The dual oil pipes include an outer oil pipe 100, an inner oil pipe 200, and multiple connecting screws 300.

[0022] The outer oil pipe 100 includes an internally threaded connector 101, an externally threaded connector 102, and an outer steel pipe 103. The internally threaded connector 101 and the externally threaded connector 102 are partially inserted into both ends of the outer steel pipe 103 and are both welded to the outer steel pipe 103. The internally threaded connector 101 has internal threads on its inner wall. The externally threaded connector 102 has external threads on its outer wall.

[0023] The inner oil pipe 200 is coaxially located inside the outer oil pipe 100. The inner oil pipe 200 includes an inner oil pipe joint 201 and an inner steel pipe 202. One end of the inner oil pipe joint 201 is inserted into the inner steel pipe 202 and welded together with the inner steel pipe 202.

[0024] To further increase the rigidity of the outer oil pipe 100, the outer oil pipe 100 also has a plurality of support members 104. The plurality of support members 104 are distributed at intervals along the axial direction of the outer oil pipe 100. Each support member 104 is fitted over the outer steel pipe 103 and welded to the outer steel pipe 103.

[0025] Figure 2 For along Figure 1 The sectional view along the BB direction in the middle, combined with Figure 2 Furthermore, to facilitate the assembly of the support member 104, the support member 104 includes two arc-shaped tiles 1041, which are arranged symmetrically on opposite sides of the outer steel pipe 103 with the axis of the outer steel pipe 103 as the axis. Each tile 1041 is attached to the outer wall of the outer steel pipe 103. Welding is performed around the perimeter of the tile 1041 to weld each tile 1041 to the outer steel pipe 103. In this embodiment, the central angle α corresponding to the arc shape of the tile 1041 is 120 degrees.

[0026] Figure 3 For along Figure 1 The sectional view along the AA direction, combined with Figure 3 The multiple connecting screws 300 are arranged in multiple groups at intervals along the axial direction of the inner oil pipe 200. Each group of connecting screws 300 contains multiple connecting screws 300. The multiple connecting screws 300 in the same group are arranged at intervals along the circumference of the inner oil pipe 200. One end of each connecting screw 300 abuts against the outer wall of the inner steel pipe 202, and the other end is inserted into the outer steel pipe 103.

[0027] After the connecting screw 300 is assembled, welding can be performed at the connection between the connecting screw 300 and the outer steel pipe 103 to further increase the firmness.

[0028] In practical applications, when assembling dual oil pipes, the outer and inner oil pipes are typically fabricated separately first, ensuring that the joints in both pipes are machined according to the construction drawings. The inner oil pipe is then inserted into the outer oil pipe, ensuring concentricity. Once concentric, the connecting screw is installed in the outer oil pipe, abutting against the outer wall of the inner pipe. Finally, welding is performed at the connection point between the connecting screw and the outer oil pipe to further secure the screw and seal any gaps between them.

[0029] When the dual oil pipes bend and the external and internal threaded connectors in the outer oil pipe need to be replaced promptly, the conventional approach is simply to remove the external and internal threaded connectors, weld new ones, and then re-machine the corresponding internal or external threads after welding. However, because the internal oil pipe obstructs the internal threaded connector, it's impossible to directly machine the internal thread within it. The only solution is to remove the weld on the connecting screws, disassemble the inner and outer oil pipes, re-weld a new outer oil pipe, and then reassemble it with the inner pipe. This rework is extremely cumbersome and wastes both labor and material costs.

[0030] Furthermore, the pre-machined internal threaded joints or external threaded joints will not be assembled and welded to both ends of the outer steel pipe at the same time, because the welding process will cause thermal deformation. If the pre-machined internal threaded joints and external threaded joints are directly welded to both ends of the outer steel pipe, the axis of the threads may not coincide with the axis of the outer oil pipe after welding, thus affecting the sealing or connection reliability.

[0031] To address the aforementioned issues, this disclosure provides a method for repairing dual oil pipes, ensuring that the internal threaded joint can be pre-machined before welding, thus guaranteeing both the dimensions of the dual oil pipe assembly and the welding quality. This repair method allows for the repair of dual oil pipes without disassembling the connecting screws, making it both quick and convenient.

[0032] Figure 4 A flowchart illustrating a method for repairing dual oil pipes provided in this disclosure embodiment, in conjunction with... Figure 4 Repair methods for dual oil pipes include: S401: Both the internal threaded connector and the external threaded connector are cut off from both ends of the outer steel pipe, so that both ends of the inner oil pipe protrude outside the outer steel pipe.

[0033] S402: Provides a new internal threaded fitting.

[0034] The new internal threaded connector has internal threads on its inner wall.

[0035] S403: The new internal threaded connector is coaxially assembled on one end of the outer steel pipe, so that the internal thread of the inner wall of the new internal threaded connector is arranged coaxially with the outer steel pipe.

[0036] S404: Insert a concentricity device into the new internal threaded fitting.

[0037] The outer circle of the concentricity device has an external thread that matches the internal thread of the internal threaded connector. The concentricity device has an inner hole that is coaxial with the inner oil pipe and has a clearance fit. S405: Weld the new internal threaded connector to the outer steel pipe.

[0038] S406: Provide a threadless fitting and weld the threadless fitting coaxially to the outer steel pipe.

[0039] S407: An external thread coaxial with the inner oil pipe is machined on the outer wall of the unthreaded joint to obtain an external threaded joint that connects to the outer steel pipe.

[0040] When repairing a bent double oil pipe using the repair method provided in this embodiment, the method involves first cutting off the internal and external threaded connectors at both ends of the outer steel pipe. Then, a new internal threaded connector with pre-existing internal threads is directly installed at one end of the outer steel pipe. This new internal threaded connector is then coaxially mounted at one end of the outer steel pipe. A concentricity device is then inserted into the internal threaded connector to ensure that it remains coaxial with the outer steel pipe after welding. Next, a threadless connector is sequentially installed at the other end of the outer steel pipe and welded to it. Finally, external threads are machined into the threadless connector, thus completing the repair of the double oil pipe.

[0041] The above repair method, by pre-machining the new internal threaded connector before welding, ensures both the dimensions of the dual oil pipe assembly and the quality of the weld. This repair method allows for the repair of the dual oil pipe assembly without removing the screws, making it both quick and convenient.

[0042] On the other hand, embodiments of this disclosure also provide another method for repairing dual oil pipes, such as... Figure 5 As shown, the repair method includes: S501: Both the internal threaded joint and the external threaded joint shall be cut off from both ends of the outer steel pipe.

[0043] Optionally, step S501 can be implemented in the following way: 5011: The outer steel pipe is machined along the weld seam between the outer steel pipe and the external threaded joint.

[0044] 5012: The outer steel pipe is machined along the weld seam between the outer steel pipe and the internal threaded joint.

[0045] In other words, the two ends of the outer steel pipe are machined directly on a lathe, so that the internal threaded joint and the external threaded joint are separated from the outer steel pipe.

[0046] Figure 6 for Figure 1 A schematic diagram showing the process after cutting off the internal and external threaded joints, combined with... Figure 6 In this embodiment of the present disclosure, when the two ends of the outer steel pipe are removed by a lathe, the turning position can be determined according to the theoretical distance between the weld seam between the inner threaded joint and the outer threaded joint and the outer oil pipe and the end faces of the two ends of the inner oil pipe.

[0047] For example, the theoretical distance from the weld between the internal threaded joint and the outer steel pipe to the end face of one end of the inner steel pipe is L1. The cutting position should be a distance greater than L1 from the end face of one end of the inner steel pipe (e.g., L1 + 2-3 mm). This way, the weld can be completely removed. In other words, it is acceptable as long as the weld can be completely removed without excessively cutting the length of the outer steel pipe.

[0048] Similarly, the theoretical distance between the weld between the external threaded joint and the outer steel pipe and the end face of the other end of the inner oil pipe is L2. The cutting position is based on a distance greater than L2 from the end face of the other end of the outer steel pipe (e.g., L2+2-3mm).

[0049] This allows for the complete removal of the weld. In other words, the goal is to completely remove the weld without excessively cutting the length of the outer steel pipe.

[0050] S502: Provides a new internal threaded fitting.

[0051] The new internal threaded connector has internal threads on its inner wall.

[0052] In this embodiment of the disclosure, the inner wall of the new internal threaded connector has been pre-machined with an internal thread arranged coaxially with the outer circle of the internal threaded connector.

[0053] Meanwhile, to facilitate subsequent welding, a welding bevel A is pre-machined on the outer wall of the new internal threaded joint.

[0054] In other words, the new internal threaded connector is manufactured according to the theoretical requirements of the drawings, with all necessary structural features already machined, eliminating the need for further machining.

[0055] S503: The new internal threaded connector is coaxially assembled on one end of the outer steel pipe, so that the internal thread of the inner wall of the new internal threaded connector is arranged coaxially with the outer steel pipe.

[0056] In this embodiment, when the internal threaded connector is assembled at one end of the outer steel pipe, deformation occurs during welding. Before welding, a concentricity device is inserted into the internal threaded connector to reduce radial deformation; however, axial deformation is difficult to control. Therefore, axial expansion and contraction occur during welding. To ensure that the end face of the internal threaded connector is flush with the end face of the inner oil pipe after welding, the end of the internal threaded connector furthest from the outer steel pipe must protrude beyond the inner oil pipe during assembly to allow for welding shrinkage.

[0057] Alternatively, S503 can be implemented through a fitter's operation. For example, it can be performed as follows: First, insert one end of the new internal threaded connector into one end of the outer steel pipe.

[0058] Next, the position of the new internal threaded connector in the outer steel pipe is adjusted so that there is a gap between the welding bevel and the end face of the outer steel pipe, and the end of the new internal threaded connector away from the outer steel pipe protrudes outside the inner oil pipe to allow for welding shrinkage.

[0059] Next, check the width of the gap and the distance by which the new internal threaded connector protrudes outside the inner oil pipe.

[0060] Finally, based on the gap and distance, determine whether the new internal threaded connector has been assembled successfully.

[0061] Figure 7 In order to be in Figure 6 Based on the structural diagram of the assembled internal threaded connector, combined with Figure 7 When assembling the internal threaded connector onto one end of the cut external oil pipe, first insert one end of the new internal threaded connector into the external steel pipe, and then adjust the position of the internal threaded connector according to the gap between the welding bevel A and the end face of the external steel pipe. Figure 7 L4 in the middle) and welding shrinkage ( Figure 7 The size of L3 in the figure is used to ensure that the internal threaded connector is installed correctly.

[0062] In this embodiment of the disclosure, if the width of the gap L4 is not greater than 6mm and not less than 4mm, the welding shrinkage L3 is 1mm.

[0063] Alternatively, if the gap width is no greater than 8mm and greater than 6mm, and the welding shrinkage is 1.5mm, then the new internal threaded joint assembly is complete.

[0064] By assembling as described above, the deformation of the internal threaded joint during subsequent welding can be controlled, so that the end face of the welded internal threaded joint can be basically flush with the end face of the internal oil pipe, and the distance between the end face of the internal threaded joint and the end face of the internal oil pipe is within 0.5mm.

[0065] S504: Insert a concentricity device into the new internal threaded fitting.

[0066] Figure 8 In order to be in Figure 7 Based on the structural diagram after inserting the concentricity device, combined with Figure 8 For example, the outer circle of the concentricity device 400 has an external thread that matches the internal thread of the internal threaded connector, and the concentricity device 400 has an inner hole that is coaxial with the inner oil pipe and has a clearance fit.

[0067] By inserting the concentricity device 400 between the internal threaded connector and the internal oil pipe, radial deformation of the internal threaded connector can be prevented during subsequent welding, ensuring that the internal thread of the internal threaded connector remains coaxial with the internal oil pipe after welding.

[0068] Figure 9 for Figure 8 Enlarged view of the middle left end, combined with Figure 9 Optionally, the concentricity device 400 includes a connector 401 and a connecting sleeve 402. One end of the connector 401 is connected to one end of the connecting sleeve 402, the other end of the connector 401 is away from the outer steel pipe 103, and the other end of the connecting sleeve 402 is threadedly connected to a new internal thread connector.

[0069] The connecting sleeve 402 is fitted outside the inner oil pipe joint 201 of the inner oil pipe 200 and is clearance-fitted with the inner oil pipe joint 201 of the inner oil pipe 200.

[0070] In the above implementation, the outer wall of the connecting sleeve 402 is provided with an external thread, which is used to connect with the internal thread of the internal threaded joint, thereby connecting the connecting sleeve 402 to the internal threaded joint. At the same time, the inner hole of the connecting sleeve 402 is used to have a clearance fit with the inner oil pipe 200, so as to provide radial support for the connecting sleeve 402 through the inner oil pipe 200, thereby preventing the internal thread and the inner oil pipe from being misaligned after the internal threaded joint is welded.

[0071] The connector 401 protrudes beyond the internal thread connector 101 and the internal oil pipe 200 to facilitate connection with tools for fixing or control, enabling it to connect with the internal thread connector.

[0072] In this embodiment, the connector 401 is a frustum structure. The end of the connector 401 with the larger outer diameter is connected to the connecting sleeve 402. This design facilitates the engagement of the connector 401 with a tool via the step on its outer circumference, thereby making it easier for the connector 401 to connect with an internally threaded connector.

[0073] In other examples, the concentricity device can also be other structures, such as a cylindrical body, as long as it can be threaded to the internal threaded connector and simultaneously achieve a clearance fit with the internal oil pipe.

[0074] In this embodiment of the disclosure, after the concentricity device 400 is assembled, the assembly gap between the concentricity device 400 and the inner oil pipe in the circumferential direction can be detected to further verify whether the internal threaded joint 101 is coaxial with the inner oil pipe 200.

[0075] In addition, to facilitate subsequent welding, the internal threaded joint is pre-fixed by spot welding with a fitter, and the assembly clearance of the internal threaded joint is checked.

[0076] S505: Weld the new internal threaded connector to the outer steel pipe.

[0077] In this embodiment, before welding, acetone or similar substances are used to clean the welding wire, the bevel of the internal threaded joint, and the oil, water, and other contaminants within a 20mm radius around the bevel until the cleaned areas are exposed to a metallic luster.

[0078] Optionally, step S505 can be implemented in the following ways: First, the new internal threaded connector is divided into multiple arc segments along its circumference. These multiple arc segments are further divided into multiple arc segment pairs, and the two arc segments in each arc segment pair are arranged in a centrally symmetrical manner about the center of the new internal threaded connector.

[0079] Secondly, weld each arc segment in sequence, using arc segments as units, until the entire circumference of the new internal thread joint is welded. There should be at least one arc segment between the arc segments during two adjacent welding operations.

[0080] The above-mentioned welding of each arc segment in sequence by arc segment pair means that each welding operation is performed on a pair of arc segments.

[0081] In this embodiment of the disclosure, manual argon arc welding is used during welding, with DC positive polarity, TIG-50 welding wire, Φ2.0, welding current of 160~200A, welding voltage of 18~22V, and welding speed of 8~12cm / min.

[0082] Figure 10 for Figure 8 The diagram shows the segmentation during welding of the internal threaded joint, combined with... Figure 10 Welding each arc segment sequentially, in pairs, means that each welding operation involves welding a pair of arc segments at a time. For example, Figure 10 The weld of the internal threaded joint can be divided into 8 arc segments, which are welded according to the following steps: Figure 10 The welding is performed in the sequence of 1-2, 3-4, 5-6, and 7-8 as shown in the figure.

[0083] In other examples, the number of arc segments can also be different, such as 6 or 10. The number of arc segments can be flexibly set according to the perimeter of the weld of the internal threaded joint.

[0084] In addition, when welding, place a damp cloth on both sides of the weld. During the welding process, pay attention to carefully cleaning the interlayer oxides and control the interlayer temperature to ≤60℃. If defects that affect the quality, such as cracks, undercut, lack of fusion, slag inclusions, and porosity, are found, the defects must be removed before welding can continue.

[0085] The above welding process can control the axial shrinkage of the internal threaded joint, so that the welding shrinkage allowance reserved when clamping the internal threaded joint can meet the actual axial shrinkage of the internal threaded joint, and ensure that the size of the external oil pipe after welding deviates from the drawing requirements within 0.5mm.

[0086] S506: Provide a threadless fitting and weld the threadless fitting coaxially to the outer steel pipe.

[0087] In this embodiment, the outer wall of the threadless connector is smooth and has no external threads.

[0088] S507: Grind the weld between the new internal threaded joint and the outer steel pipe, as well as the weld between the unthreaded joint and the outer steel pipe.

[0089] After welding is completed, the weld seam usually needs to be ground and polished to improve the weld quality, appearance, or meet the requirements of subsequent processes.

[0090] S508: Vibrate the welded outer steel pipe and inner oil pipe.

[0091] Vibration treatment after welding is performed mainly to eliminate or reduce residual welding stress, improve structural stability, and prevent subsequent deformation or cracking.

[0092] S509: Perform combined flaw detection on the welded outer steel pipe and inner oil pipe.

[0093] Twenty-four hours after welding, ultrasonic testing (UT) and penetrant testing (PT) are performed on the weld between the internal threaded joint and the outer steel pipe, as well as the weld between the unthreaded joint and the outer steel pipe. If the flaw detection meets the requirements of 100%UT (Level II) + 100%PT (Level I) in the welding inspection standard NB / T47013-2015, it is considered qualified.

[0094] S510: Remove the concentricity device.

[0095] Remove the concentricity device and check whether it can rotate freely.

[0096] At the same time, check the concentricity device and internal threaded joints for any scratches or burns.

[0097] S511: The unthreaded connector is machined so that the outer wall of the unthreaded connector has an external thread that is coaxial with the inner oil pipe.

[0098] Figure 11 This is a schematic diagram of the repaired dual oil pipe structure, combined with... Figure 11 The threadless connector is machined according to the drawings to ensure that its outer contour and external thread meet the final dimensions of the drawings.

[0099] S512: After repair, the double oil pipes are bluing and the inner and outer surfaces of the double oil pipes are sprayed with an anti-rust coating.

[0100] After the double oil pipes turn blue, immediately apply a special anti-rust coating (such as anti-rust oil) evenly to the inner and outer surfaces of the double oil pipes for protection.

[0101] The above method can be used to repair the double oil pipe without disassembly. All dimensions of the double oil pipe and weld flaw detection can meet the technical requirements of the drawings, which greatly shortens the repair cycle and reduces labor costs.

[0102] The above description is merely an optional embodiment of this disclosure and is not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A method for repairing dual oil pipes, characterized in that, The dual oil pipe includes an inner oil pipe and an outer oil pipe sleeved outside the inner oil pipe. The outer oil pipe includes an internal threaded joint, an external threaded joint, and an outer steel pipe. The internal threaded joint and the external threaded joint are respectively welded to both ends of the outer steel pipe, and the outer steel pipe is connected to the inner oil pipe. The repair method includes: Both the internal threaded connector and the external threaded connector are cut off from both ends of the outer steel pipe, so that both ends of the inner oil pipe protrude outside the outer steel pipe; A new internal threaded connector is provided, wherein the inner wall of the new internal threaded connector has an internal thread; The new internal threaded connector is coaxially assembled at one end of the outer steel pipe, such that the internal thread of the inner wall of the new internal threaded connector is arranged coaxially with the outer steel pipe. A concentricity device is inserted into the new internal threaded connector. The outer circle of the concentricity device has an external thread that matches the internal thread of the inner wall of the new internal threaded connector. The concentricity device has an inner hole that is coaxial with the inner oil pipe. The new internal threaded connector is welded to the outer steel pipe; The threadless connector is coaxially welded to the outer steel pipe; An external thread coaxial with the inner oil pipe is machined on the outer wall of the threadless joint to obtain an externally threaded joint that connects to the outer steel pipe.

2. The repair method according to claim 1, characterized in that, The concentricity device includes a connector (401) and a connecting sleeve (402). One end of the connector (401) is connected to one end of the connecting sleeve (402), the other end of the connector (401) is away from the outer steel pipe (203), and the other end of the connecting sleeve (402) is threadedly connected to the new internal thread connector. The connecting sleeve (402) is fitted over the inner oil pipe (100) and is clearance-fitted with the inner oil pipe (200).

3. The repair method according to claim 1, characterized in that, The new internal threaded connector has a welding bevel in the middle of its outer wall. The coaxial assembly of the new internal threaded connector to one end of the outer steel pipe includes: One end of the new internal threaded connector is inserted into one end of the outer steel pipe; The position of the new internal threaded connector in the outer steel pipe is adjusted so that there is a gap between the welding bevel and the end face of the outer steel pipe, and the end of the new internal threaded connector away from the outer steel pipe protrudes outside the inner oil pipe to allow for welding shrinkage.

4. The repair method according to claim 3, characterized in that, When the width of the gap is not greater than 6mm and not less than 4mm, the welding shrinkage is 1mm; Alternatively, when the width of the gap is no greater than 8 mm and greater than 6 mm, the welding shrinkage is 1.5 mm.

5. The repair method according to any one of claims 1-4, characterized in that, The step of cutting off both the internal threaded joint and the external threaded joint from both ends of the outer steel pipe includes: The outer steel pipe is machined along the weld seam between the outer steel pipe and the external threaded joint; The outer steel pipe is machined along the weld seam between the outer steel pipe and the internal threaded joint.

6. The repair method according to any one of claims 1-4, characterized in that, The step of welding the new internal threaded connector to the outer steel pipe includes: The new internal threaded connector is divided into multiple arc segments along its circumference. These multiple arc segments are further divided into multiple arc segment pairs, and the two arc segments in each arc segment pair are arranged in a centrally symmetrical manner about the center of the new internal threaded connector. Welding is performed sequentially on each arc segment as a unit until the entire circumference of the new internal threaded joint is welded. At least one arc segment is spaced between the arc segments during two adjacent welding operations.

7. The repair method according to any one of claims 1-4, characterized in that, The repair method also includes: The weld between the new internal threaded joint and the outer steel pipe, as well as the weld between the unthreaded joint and the outer steel pipe, are ground down.

8. The repair method according to any one of claims 1-4, characterized in that, The repair method also includes: The welded outer steel pipe and the inner oil pipe are vibrated.

9. The repair method according to any one of claims 1-4, characterized in that, The repair method also includes: The welded outer steel pipe and the inner oil pipe are subjected to combined flaw detection.

10. The repair method according to any one of claims 1-4, characterized in that, The repair method also includes: The repaired double oil pipes are bluing and the inner and outer surfaces of the double oil pipes are sprayed with an anti-rust coating.

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