A marine low-speed engine EGR stainless steel gas pipeline welding tool and a using method thereof

Abstract

The application provides a marine low-speed engine EGR stainless steel gas pipeline welding tool and a use method, and comprises a tool workbench, a guide rail, a first elbow positioning frame, a second elbow positioning frame, a straight pipe positioning frame and a base pressing limiting part; the guide rail is fixedly arranged on the tool workbench, and the elbow positioning frame and the straight pipe positioning frame are arranged on the guide rail; the first elbow positioning frame is arranged at one end of the straight pipe positioning frame, the second elbow positioning frame is arranged at the other end of the straight pipe positioning frame, the first elbow positioning frame and the second elbow positioning frame are composed of support plates with different heights, the straight pipe positioning frame is composed of support plates with the same height, the upper end of the support plate is provided with an arc-shaped opening, and the lower end is fixed on the tool workbench through a fixed plate. Through the multiple limiting structures, welding defects caused by unstable tooling are reduced, the error of pipeline installation is effectively reduced, and the problem of low welding qualification rate of pipeline manufacturing is solved.

Description

Technical Field

[0001] This invention belongs to the field of welding clamping fixture technology, specifically relating to a welding fixture for stainless steel EGR gas pipelines of marine low-speed engines and its usage method. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] In marine low-speed engine EGR (exhaust gas recirculation) systems, stainless steel gas pipelines are a critical component, and their welding quality plays a decisive role in the performance and reliability of the entire system. With the increasingly widespread application of EGR systems, higher standards are being set for the installation accuracy and welding quality of gas pipelines.

[0004] Traditional gas pipeline welding methods struggle to ensure precise pipeline positioning before welding, leading to significant installation errors and poor weld accuracy and consistency. The lack of tooling versatility and flexibility makes them unsuitable for welding gas pipelines of varying sizes, shapes, and layouts. When dealing with complex pipeline structures and different types of flange connections, precise positioning is often difficult to achieve, resulting in low welding efficiency and inconsistent weld quality. Furthermore, the absence of effective fixing and limiting measures during welding allows pipelines to easily move or rotate, causing discontinuities in the weld and large dimensional deviations, increasing rework costs and time, and failing to meet the shipbuilding industry's requirements for efficient and high-quality production. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a welding fixture and method for EGR stainless steel gas pipelines in marine low-speed engines. Through a multi-limiting structure, it reduces welding defects caused by fixture instability, effectively minimizing pipeline installation errors. This solves the problem of low welding pass rates in spatially sized pipeline fabrication, improves weld precision and consistency, and enhances welding efficiency and quality.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] In a first aspect, the present invention provides a welding fixture for stainless steel gas pipelines of marine low-speed engines (EGR), comprising: a fixture worktable, a guide rail, an elbow positioning frame, a straight pipe positioning frame, and a base for clamping and limiting; the guide rail is fixedly mounted on the fixture worktable, and the elbow positioning frame and the straight pipe positioning frame are both mounted on the guide rail.

[0008] The elbow positioning frame includes a first elbow positioning frame and a second elbow positioning frame; the first elbow positioning frame is disposed at one end of the straight pipe positioning frame, and the second elbow positioning frame is disposed at the other end of the straight pipe positioning frame. Both the first elbow positioning frame and the second elbow positioning frame are composed of support plates of different heights, and the straight pipe positioning frame is composed of support plates of the same height. The upper end of the support plate is provided with an arc-shaped opening, and the lower end is provided with a fixing plate. The fixing plate is pressed and limited to the tooling worktable by the base.

[0009] As a further implementation, it also includes: upper and lower clamping limits, which are set on one side of the tooling workbench; the upper and lower clamping limits are composed of a vertical support rod, a horizontal support rod and a clamping rod, the lower end of the vertical support rod is fixedly set on the tooling workbench, one end of the horizontal support rod is fixedly set on the top of the vertical support rod, and the other end of the horizontal support rod is threadedly connected to the clamping rod, so that the clamping rod can move vertically to achieve the clamping of the pipeline.

[0010] As a further implementation, the guide rail includes a first guide rail, a second guide rail, and a third guide rail; the second guide rail is disposed at one end of the first guide rail, and the third guide rail is disposed at the other end of the first guide rail; the straight pipe positioning frame is slidably disposed on the first guide rail, the first elbow positioning frame is slidably disposed on the second guide rail, and the second elbow positioning frame is slidably disposed on the first guide rail.

[0011] As a further implementation, a first flange positioning device is slidably disposed on the second guide rail, and a second flange positioning device is slidably disposed on the third guide rail.

[0012] As a further implementation, the first flange positioning device consists of a first ring, a first fixing frame, and a mounting plate. The lower end of the mounting plate is slidably disposed on the fixing plate and positioned by the base pressing and limiting. The upper end of the mounting plate is fixedly connected to the first fixing frame. The first ring is disposed on the first fixing frame, and there is a set angle between the first fixing frame and the mounting plate.

[0013] The second flange positioning device consists of a second ring and a second fixing frame. The lower end of the second fixing frame is mounted on the fixing plate, and the upper end is mounted on the second ring.

[0014] As a further implementation, the multiple support plates of the first elbow positioning frame are parallel to each other, and an auxiliary plate is arranged perpendicular to the multiple support plates. The multiple support plates are perpendicular to the auxiliary plate and form a cross-shaped structure to improve the stability of the positioning frame at the elbow of the gas pipeline.

[0015] As a further implementation, the second elbow positioning frame also includes two mutually perpendicular auxiliary plates, and the two support plates are arranged perpendicularly to each other, forming a grid structure.

[0016] As a further implementation, the bottom of the auxiliary plate is fixedly mounted on the fixed plate, and the top of the auxiliary plate is also provided with an arc-shaped opening.

[0017] As a further implementation, the base clamping limiter includes an L-shaped bending plate and a clamping block. Both planes of the L-shaped bending plate are provided with waist holes. One waist hole is installed on the tooling workbench through a connector, and the other waist hole is installed with the clamping block through a connector. The clamping block is used to press the fixing block on the tooling workbench.

[0018] Secondly, the present invention also provides a method for using a welding fixture for EGR stainless steel gas pipelines in marine low-speed engines, comprising the following steps:

[0019] S1. Place the tooling workbench in the designated position and adjust the tooling workbench to the designated welding height;

[0020] S2. According to the pipeline drawing requirements, install the first flange positioning device and the second flange positioning device on the second guide rail and the third guide rail respectively, adjust them to the precise position, and use the base to press and limit the positioning.

[0021] S3. Install the first elbow positioning frame, the second elbow positioning frame, and the straight pipe positioning frame on the first guide rail and the second guide rail respectively, and press and position them sequentially by pressing and limiting them with the base.

[0022] S4. Install the gas pipeline onto the fixture in the order of flange-straight pipe-elbow-slanted pipe. The flange is positioned with three holes between it and the first or second fixed bracket, and then tightened with bolts and nuts. Adjust all pipelines and weld gaps to keep the welding position horizontal. Use upper and lower clamping limit devices for positioning to prevent the pipeline from rotating during the welding process.

[0023] S5. After the above work is completed, the welding work can be carried out.

[0024] Compared with the prior art, the advantages and positive effects of this invention are:

[0025] The tooling workbench, guide rail, positioning frame, and flange positioning device of this invention work together to form a precise positioning system. The guide rail provides a precise sliding track and positioning reference for the positioning frame and flange positioning device, enabling them to be accurately installed and adjusted on the tooling. The elbow positioning frame and straight pipe positioning frame can fit tightly with the pipeline through the arc-shaped opening of the support plate, positioning the pipeline from multiple directions. The flange positioning device uses a ring and a fixing frame to limit the flange circumferentially and axially, ensuring the accurate connection position between the flange and the pipeline. The synergistic effect of these structures allows the gas pipeline to be precisely positioned on the tooling before welding, effectively reducing pipeline installation errors, improving the accuracy and consistency of the weld joint, and the multiple stabilizing structures reduce welding defects caused by tooling instability, lowering the rework rate and improving welding efficiency and quality.

[0026] This invention securely fixes the positioning frame and flange positioning device by cooperating with the upper and lower clamping limits and the base clamping limit. The upper and lower clamping limits, connected by threaded clamping rods, can flexibly clamp the pipeline, preventing the pipeline from moving or rotating during welding. The base clamping limit utilizes an L-shaped bending plate and clamping blocks to stabilize the positioning frame and flange positioning device on the tooling worktable. Meanwhile, the cross-shaped or grid-shaped structure and auxiliary plates of the elbow positioning frame enhance stability at elbows.

[0027] The guide rail design of this invention allows for the movable installation of the positioning frame and flange positioning device. Combined with the clamping and limiting mounting hole array on the tooling workbench base, the tooling can flexibly adjust the positions of the positioning frame and flange positioning device to adapt to the welding of gas pipelines of different sizes, shapes, and layouts. The flange positioning device is adjustable in angle and position to meet the connection requirements of various flanges and pipelines; the liftable support legs can adapt to different work sites and operator habits. This high degree of versatility and flexibility reduces equipment investment costs for enterprises, improves equipment utilization, and is suitable for welding various specifications of stainless steel gas pipelines in marine low-speed engine EGR systems. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0029] Figure 1 This is an overall structural diagram of the gas pipeline welding fixture of the present invention;

[0030] Figure 2 This is a diagram of the base clamping and limiting structure of the present invention;

[0031] Figure 3 This is a structural diagram of the straight pipe positioning frame of the present invention;

[0032] Figure 4 This is a structural diagram of the first elbow positioning frame of the present invention;

[0033] Figure 5 This is a structural diagram of the second elbow positioning frame of the present invention.

[0034] In the diagram: 1. Tooling workbench; 2. First flange positioning device; 3. Second flange positioning device; 4. First elbow positioning frame; 5. Second elbow positioning frame; 6. Straight pipe positioning frame; 7. Horizontal support rod; 8. Base clamping limiter; 9. First guide rail; 10. Vertical support rod; 11. Clamping rod; 12. Support leg; 13. L-shaped bending plate; 14. Clamping block; 15. Fixing plate; 16. Support plate; 17. Auxiliary plate. Detailed Implementation

[0035] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0037] Example 1

[0038] This embodiment provides a welding fixture for stainless steel gas pipelines used in marine low-speed engines, such as... Figures 1-5 As shown, the fixture includes: a worktable 1, guide rails, an elbow positioning frame, a straight pipe positioning frame 6, a flange positioning device, and a base clamping and limiting device 8. The guide rails are fixedly mounted on the worktable 1, and the elbow positioning frame and straight pipe positioning frame 6 are both mounted on the guide rails. The worktable 1, guide rails, positioning frames, and flange positioning device cooperate with each other to form a precise positioning system. The guide rails provide precise sliding tracks and positioning references for the positioning frames and flange positioning devices, enabling them to be accurately installed and adjusted in position on the fixture.

[0039] The elbow positioning frame includes a first elbow positioning frame 4 and a second elbow positioning frame 5. The first elbow positioning frame 4 is located at one end of the straight pipe positioning frame 6, and the second elbow positioning frame 5 is located at the other end of the straight pipe positioning frame 6. Both the first elbow positioning frame 4 and the second elbow positioning frame 5 are composed of support plates 16 of different heights. The straight pipe positioning frame 6 is composed of support plates 16 of the same height. The upper end of the support plate 16 is provided with an arc-shaped opening, and the lower end is provided with a fixing plate 15. The fixing plate 15 is fixed on the tooling workbench 1 by the base pressing and limiting 8, and is used to press the height of the support plate 16. The elbow positioning frame and the straight pipe positioning frame 6 can fit tightly with the pipeline through the arc-shaped opening of the support plate 16, and position the pipeline from multiple directions. The flange positioning device limits the flange circumferentially and axially through the ring and the fixing frame, ensuring that the connection position between the flange and the pipeline is accurate. The synergistic effect of these structures allows the gas pipeline to be precisely positioned on the tooling before welding, effectively reducing pipeline installation errors, improving the accuracy and consistency of welded joints, and thus ensuring the installation quality and performance of the gas pipeline.

[0040] As a further implementation, it also includes: upper and lower clamping limits, which are set on one side of the tooling workbench 1; the upper and lower clamping limits are composed of a vertical support rod 10, a horizontal support rod 7, and a clamping rod 11. The lower end of the vertical support rod 10 is fixedly set on the tooling workbench 1, one end of the horizontal support rod 7 is fixedly set on the top of the vertical support rod 10, and the other end of the horizontal support rod 7 is threadedly connected to the clamping rod 11, so that the clamping rod 11 can move vertically to clamp the pipeline and prevent the pipeline from moving or rotating during the welding process. The upper and lower clamping limits, together with the base clamping limit 8, firmly fix the positioning frame and flange positioning device on the tooling workbench 1 to prevent them from shifting during the welding process, thereby ensuring the welding accuracy of the pipeline.

[0041] As a further implementation, the guide rail includes a first guide rail 9, a second guide rail, and a third guide rail; the second guide rail is disposed at one end of the first guide rail 9, and the third guide rail is disposed at the other end of the first guide rail 9; the straight pipe positioning bracket 6 is slidably disposed on the first guide rail 9, the first elbow positioning bracket 4 is slidably disposed on the second guide rail, and the second elbow positioning bracket 5 is slidably disposed on the first guide rail 9; the flange positioning device includes a first flange positioning device 2 and a second flange positioning device 3, with the first flange positioning device 2 slidably disposed on the second guide rail and the second flange positioning device 3 slidably disposed on the third guide rail. The positioning bracket and the flange positioning device are movably mounted on the guide rail, and in conjunction with the base clamping limit 8 mounting hole array design on the tooling workbench 1, the welding tooling has strong versatility and flexibility; by adjusting the position of the base clamping limit 8 and the position of the positioning bracket on the guide rail, it can adapt to the welding requirements of gas pipelines of different sizes, shapes, and layouts. The adjustable angle and position of the flange positioning device can meet the connection requirements of different types of flanges and pipelines.

[0042] As a further implementation, the first flange positioning device 2 consists of a first ring, a first fixing frame, and a mounting plate. The lower end of the mounting plate is slidably mounted on the fixing plate 15 and positioned by the base clamping limit 8. The upper end of the mounting plate is fixedly connected to the first fixing frame. The first ring is mounted on the first fixing frame, and there is a set angle between the first fixing frame and the mounting plate. This angle is designed according to the connection angle between the flange and the pipeline and the installation requirements, so that the first ring can accurately position the flange. The inner diameter of the first ring is adapted to the outer diameter of the flange, and it can fit on the flange to limit the flange circumferentially. At the same time, the first fixing frame is also provided with positioning holes, which correspond to the bolt holes on the flange. The flange is positioned by three holes through bolt and nut connection, ensuring that the flange is accurately positioned during the welding process.

[0043] The second flange positioning device 3 consists of a second ring and a second fixing frame. The lower end of the second fixing frame is mounted on the fixing plate 15, and the upper end is mounted on the second ring. Specifically, the lower end of the second fixing frame is mounted on the fixing plate 15 and is fixed by the base pressing and limiting 8. The upper end is mounted on the second ring. The structure and function of the second ring are similar to those of the first ring. Its inner diameter matches the outer diameter of the flange, which can circumferentially position the flange.

[0044] As a further implementation, the multiple support plates 16 of the first elbow positioning frame 4 are parallel to each other, and an auxiliary plate 17 is arranged perpendicular to the multiple support plates 16. The multiple support plates 16 and the auxiliary plate 17 are all perpendicular to each other in a cross shape to improve the stability of the positioning frame at the elbow of the gas pipeline. The auxiliary plate 17 not only increases the structural strength of the positioning frame at the elbow, but also limits the elbow in the horizontal and vertical directions to prevent the elbow from shifting during welding. The upper end of the support plate 16 is provided with an arc-shaped opening, the curvature of which matches the curvature of the outer surface of the elbow, so as to better fit the elbow and improve the positioning accuracy.

[0045] As a further implementation, the second elbow positioning frame 5 also includes two mutually perpendicular auxiliary plates 17, and the two support plates 16 are arranged perpendicularly to each other, forming a grid structure. This structure further enhances the positioning frame's support and limiting capabilities for the elbow, making it particularly suitable for positioning elbows with complex angles and shapes. The bottom of the auxiliary plate 17 is fixedly mounted on the fixed plate 15, and the top is also provided with an arc-shaped opening, which works together with the arc-shaped opening of the support plate 16 to position and fix the elbow from multiple directions, effectively improving the reliability of elbow positioning.

[0046] As a further implementation, the bottom of the auxiliary plate 17 is fixedly mounted on the fixed plate 15, and the top of the auxiliary plate 17 is also provided with an arc-shaped opening, the curvature of which is consistent with the curvature of the outer surface of the straight tube, which can tightly wrap the straight tube and provide stable support and positioning.

[0047] As a further implementation, the base clamping limiter 8 includes an L-shaped bending plate 13 and a clamping block 14. Both planes of the L-shaped bending plate 13 are provided with waist holes. One waist hole is installed on the tooling workbench 1 through a connector, and the other waist hole is installed with the clamping block 14 through a connector. The clamping block 14 is used to press the fixing block on the tooling workbench 1.

[0048] The tooling workbench 1 is provided with an array of mounting holes for the base clamping limit 8, which are used to adjust the position of the base clamping limit 8, so as to facilitate the installation and positioning of the positioning frame applicable to pipes of different sizes; the lower part of the tooling workbench 1 is provided with multiple support legs 12, which are liftable support legs, so as to adjust the tooling workbench 1 to the indicated welding height.

[0049] Example 2

[0050] This embodiment provides a method for using a welding fixture for EGR stainless steel gas pipelines in marine low-speed engines, including the following steps:

[0051] S1. Place the tooling workbench 1 in the designated position and adjust the tooling workbench 1 to the designated welding height; check whether the tooling workbench 1 is level by observing the level on the tooling workbench 1 or using tools such as a spirit level; if the tooling workbench 1 is found to be not level, the height of each support leg 12 can be finely adjusted according to the adjustment method of the support leg 12, such as rotating the threaded adjustment assembly or operating the hydraulic adjustment device;

[0052] S2. According to the pipeline drawing requirements, the first flange positioning device 2 and the second flange positioning device 3 are installed on the second guide rail and the third guide rail respectively and adjusted to the precise position, and are clamped and positioned by the base clamping limit 8; the mounting plate and the fixing bracket are firmly fixed on the guide rail by the L-shaped bending plate 13 and the clamping block 14 of the base clamping limit 8.

[0053] S3. Install the first elbow positioning frame 4, the second elbow positioning frame 5, and the straight pipe positioning frame 6 on the first guide rail 9 and the second guide rail respectively, and clamp and position them sequentially through the base clamping limit 8; slide the first elbow positioning frame 4 and the second elbow positioning frame 5 along the guide rail to a suitable position, ensuring that the arc-shaped opening of the support plate 16 can fit tightly with the outer surface of the elbow; install the straight pipe positioning frame 6 on the first guide rail 9, and adjust it according to the length and position requirements of the straight pipe; during the installation of the positioning frame, ensure that the installation of the positioning frame conforms to the requirements of the pipeline drawing; after adjusting the position of the positioning frame, firmly fix the fixing plate 15 of the positioning frame on the tooling workbench 1 through the base clamping limit 8, tighten the connecting parts, and make the clamping block 14 press the fixing plate 15 to prevent the positioning frame from moving during the welding process;

[0054] S4. Install the gas pipeline onto the fixture in the order of flange-straight pipe-elbow-slanted pipe. The flange is positioned with three holes between it and the first or second fixed bracket, and then tightened with bolts and nuts. Adjust all pipelines and weld gaps to keep the welding position horizontal. Use upper and lower clamping limit devices for positioning to prevent the pipeline from rotating during the welding process.

[0055] S5. After the above work is completed, the welding work can be carried out.

[0056] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A welding fixture for stainless steel gas pipelines used in marine low-speed engines' EGR systems, characterized in that, include: The tooling workbench, guide rail, elbow positioning frame, straight pipe positioning frame, and base clamping and limiting device are provided; the guide rail is fixedly mounted on the tooling workbench, and the elbow positioning frame and straight pipe positioning frame are both mounted on the guide rail; The elbow positioning frame includes a first elbow positioning frame and a second elbow positioning frame; the first elbow positioning frame is disposed at one end of the straight pipe positioning frame, and the second elbow positioning frame is disposed at the other end of the straight pipe positioning frame. Both the first elbow positioning frame and the second elbow positioning frame are composed of support plates of different heights, and the straight pipe positioning frame is composed of support plates of the same height. The upper end of the support plate is provided with an arc-shaped opening, and the lower end is provided with a fixing plate. The fixing plate is fixed to the tooling workbench by the base pressing and limiting device. It also includes: an upper and lower clamping limit device, which is disposed on one side of the tooling workbench; the upper and lower clamping limit device consists of a vertical support rod, a horizontal support rod and a clamping rod, the lower end of the vertical support rod is fixedly disposed on the tooling workbench, one end of the horizontal support rod is fixedly disposed on the top of the vertical support rod, and the other end of the horizontal support rod is threadedly connected to the clamping rod, so that the clamping rod can move vertically to achieve the clamping of the pipeline; The guide rail includes a first guide rail, a second guide rail, and a third guide rail; the second guide rail is disposed at one end of the first guide rail, and the third guide rail is disposed at the other end of the first guide rail; the straight pipe positioning frame is slidably disposed on the first guide rail, the first elbow positioning frame is slidably disposed on the second guide rail, and the second elbow positioning frame is slidably disposed on the first guide rail; The multiple support plates of the first elbow positioning frame are parallel to each other, and an auxiliary plate is arranged perpendicular to the multiple support plates. The multiple support plates are perpendicular to the auxiliary plate and form a cross-shaped structure to improve the stability of the positioning frame at the elbow of the gas pipeline. The second elbow positioning frame also includes two mutually perpendicular auxiliary plates, and the two support plates are arranged perpendicularly to each other, forming a grid structure with the two auxiliary plates and the support plates. The bottom of the auxiliary plate is fixedly mounted on the fixed plate, and the top of the auxiliary plate is also provided with an arc-shaped opening; The base clamping and limiting device includes an L-shaped bending plate and a clamping block. The L-shaped bending plate has waist holes on both planes. One waist hole is installed on the tooling workbench through a connector, and the other waist hole is installed with the clamping block through a connector. The clamping block is used to press the fixing block on the tooling workbench.

2. The welding fixture for a marine low-speed engine EGR stainless steel gas pipeline as described in claim 1, characterized in that, A first flange positioning device is slidably mounted on the second guide rail, and a second flange positioning device is slidably mounted on the third guide rail.

3. The welding fixture for a marine low-speed engine EGR stainless steel gas pipeline as described in claim 2, characterized in that, The first flange positioning device consists of a first ring, a first fixing frame, and a mounting plate. The lower end of the mounting plate is slidably mounted on the fixing plate and positioned by the base pressing and limiting device. The upper end of the mounting plate is fixedly connected to the first fixing frame. The first ring is mounted on the first fixing frame, and there is a set angle between the first fixing frame and the mounting plate. The second flange positioning device consists of a second ring and a second fixing frame. The lower end of the second fixing frame is mounted on the fixing plate, and the upper end is mounted on the second ring.

4. The method of using the welding fixture for EGR stainless steel gas pipelines of marine low-speed engines as described in any one of claims 2-3, characterized in that, Includes the following steps: S1. Place the tooling workbench in the designated position and adjust the tooling workbench to the designated welding height; S2. According to the pipeline drawing requirements, install the first flange positioning device and the second flange positioning device on the second guide rail and the third guide rail respectively, adjust them to the precise position, and use the base pressing and limiting device to press and position them. S3. Install the first elbow positioning frame, the second elbow positioning frame, and the straight pipe positioning frame on the first guide rail and the second guide rail respectively, and then press and position them sequentially through the base pressing and limiting device; S4. Install the gas pipeline onto the fixture in sequence according to the steps of flange-straight pipe-elbow-angled pipe. The flange is positioned with three holes between it and the first flange positioning device or the second flange positioning device, and then tightened with bolts and nuts. Adjust all pipelines and weld gaps to keep the height of the welding position horizontal. Use upper and lower clamping limit devices for positioning to prevent the pipeline from rotating during the welding process. S5. After the above work is completed, the welding work can be carried out.

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