A manufacturing and installation method for a circular docking large flange

Abstract

The present application provides a method for manufacturing and installing a large circular butt-jointed flange, comprising: dividing a first large flange and a second large flange into a plurality of first flange petals and a second flange petal, and cutting and shaping the petals; assembling and welding two adjacent first flange petals and two adjacent second flange petals; installing each group of first flange petals on the outer circumferential wall of a first pipe and spot welding a plurality of first triangular ribs; installing the second flange petals on the first large flange; welding the first large flange and the first pipe; installing the removed second flange petals on the second large flange; sequentially removing the other second flange petals and welding and assembling them using the same method; spot welding a plurality of second triangular ribs at intervals along the circumference on the outer circumferential wall of the second large flange and the second pipe, welding the second large flange and the second pipe; and closing the first large flange, the first pipe, and the second large flange. This method can improve construction efficiency and save costs.

Description

Technical Field

[0001] The present application relates to the field of wind tunnels, and in particular to a method for manufacturing and installing a large annular butt-jointed flange. Background Art

[0002] A wind tunnel is a pipe-like device used to generate artificial airflow. It consists of a pressure-bearing shell on the outside and a pipe-like airflow channel on the inside. The pipes are connected by circular flanges, which are welded to the flanges. With the rapid development of my country's national defense modernization and aerospace industry, wind tunnels are becoming more high-performance and larger, and the size of the circular flanges connecting the internal pipes has also increased accordingly.

[0003] The traditional method for manufacturing and installing circular butt flanges involves first assembling and welding them as a whole, then installing them on the pipe and welding them again. The surface and flange holes are then outsourced for machining, and finally, they are installed together with the pipe in the wind tunnel's pressure shell. However, the internal pipe sizes of wind tunnels are generally over 10 meters. Outsourcing the machining of large flanges presents challenges with transportation and equipment limitations. Using portable machining equipment on-site significantly increases construction costs. The low efficiency of portable machining equipment also lengthens the construction cycle, indirectly increasing construction costs. Summary of the Invention

[0004] The present application provides a method for manufacturing and installing a large circular butt flange, aiming to solve the problem of low manufacturing efficiency of existing circular butt flanges.

[0005] The technical solution of this application is:

[0006] A method for manufacturing and installing a large annular butt flange comprises the following steps:

[0007] S1, sequentially dividing the first large flange into an even number of at least eight first flange petals, and sequentially dividing the second large flange into an even number of at least eight second flange petals, and blanking the first flange petals and the second flange petals;

[0008] S2: Draw a first pattern of the first flange petal on the steel platform, compare the first pattern with the first flange petal, and correct any deformation of the first flange petal; draw a second pattern of the second flange petal on the steel platform, compare the second pattern with the second flange petal, and correct any deformation of the second flange petal;

[0009] S3, spot-welding the inner arc edges and outer arc edges of each group of two adjacent first flange petals to the steel platform, and installing two first arched plates on the welds. Then, assembling and welding the two adjacent first flange petals in the first large flange on the steel platform. Spot-welding the inner arc edges and outer arc edges of each group of two adjacent second flange petals to the steel platform, and installing two second arched plates on the welds. Then, assembling and welding the two adjacent second flange petals in the second large flange.

[0010] S4, subjecting each set of welded first flange petals to water and fire straightening, and after passing the straightening, drilling first flange holes on the first flange petals; subjecting each set of welded second flange petals to water and fire straightening, and after passing the straightening, drilling second flange holes on the second flange petals;

[0011] S5, placing the first pipe vertically, installing each set of the first flange petals on the outer peripheral wall of the first pipe, and then spot-welding a plurality of first triangular ribs at intervals along the circumference between the lower surface of each set of the first flange petals and the upper edge of the outer peripheral wall of the first pipe;

[0012] S6, performing a bottom weld on the butt welds between each set of flange petals using gas tungsten arc welding, and installing each set of second flange petals on the assembled first large flange using multiple bolts;

[0013] S7, welding the first large flange to the first pipe using gas tungsten arc welding, and then welding the small groove of the butt weld between each group of first flange petals; after the weld has cooled, removing a group of second flange petals, and welding the large groove of the butt weld between a group of first flange petals corresponding to the removed second flange petals using gas tungsten arc welding; installing the removed second flange petals on the second large flange and fastening them with bolts; sequentially removing other second flange petals and welding and assembling them using the same method until the butt welds between each group of first flange petals are completed;

[0014] S8, hoisting the second pipeline into position, then hoisting the first pipeline, the first large flange, and the second large flange into position in sequence, and adjusting the amount of misalignment and the gap between the second large flange and the second pipeline until they are qualified;

[0015] S9, spot welding a plurality of second triangular ribs at intervals along the circumferential direction on the outer circumferential walls of the second large flange and the second pipeline, and welding the second large flange and the second pipeline by gas tungsten arc welding;

[0016] S10: Remove multiple bolts connecting the first large flange and the second large flange, and connect the first large flange and the second large flange using studs; then remove the remaining bolts, grind off the spot weld between the first large flange and the second large flange, and slide the first large flange and the first pipe together 40 to 50 mm in a direction away from the second large flange;

[0017] S11, welding the butt welds between the petals of each set of the second flanges using gas tungsten arc welding, welding the small groove first and then the large groove;

[0018] S12: Install a sealing ring between the first large flange and the second large flange, with the sealing ring close to the inner arc side of the first large flange and the second large flange; close the first large flange, the first pipe, and the second large flange and tighten them with bolts; finally, apply low-temperature glue at the position where there is a gap on the inner arc side of the first large flange and the second large flange.

[0019] As a technical solution of the present application, in step S1, the first large flange and the second large flange are the same.

[0020] As a technical solution of the present application, in step S3, the groove form of the two ends of the first flange petal is an asymmetric X-shaped groove, and the small groove of each group of the first flange petals is facing the steel platform when assembled, and the large groove on the first flange petal is welded first, and then the first bow plate on the weld is removed, and the spot weld between each group of the first flange petals and the steel platform is ground and removed, and then each group of the first flange petals is flipped 180° and placed on the steel platform, and the inner arc edge and outer arc edge of each group of the first flange petals are spot welded to the steel platform respectively, and after the weld is cleaned, the two first bow plates are installed, and finally the small groove on the first flange petal is welded.

[0021] As a technical solution of the present application, in step S3, the groove form of the two ends of the second flange petals is an asymmetric X-shaped groove, and the small groove of each group of the second flange petals is facing the steel platform when assembled, and the large groove on the second flange petals is welded first, and then the second bow plate on the weld is removed, and the spot weld between each group of the second flange petals and the steel platform is ground off, and then each group of the second flange petals is flipped 180° and placed on the steel platform, and the inner arc edge and outer arc edge of each group of the second flange petals are spot welded to the steel platform respectively, and after the weld is cleaned, two second bow plates are installed, and finally the small groove on the second flange petals is welded.

[0022] As a technical solution of the present application, in step S5, the first triangular rib is provided with a first through-welding hole at a right-angle position, and the radius of the first through-welding hole is greater than 40 mm.

[0023] As a technical solution of the present application, in step S5, when the first large flange is installed on the first pipe, the small groove of the butt weld between each group of the first flange petals faces downward.

[0024] As a technical solution of the present application, in step S7, the butt welds between each group of the first flange petals and the butt welds between each corresponding group of the second flange petals are staggered by 100 to 200 mm.

[0025] As a technical solution of the present application, in step S7, when the second large flange is installed on the first large flange, the small groove of the butt weld between each group of the second flange petals faces upward.

[0026] As a technical solution of the present application, in step S8, before the first pipeline, the first large flange, and the second large flange are hoisted together, the outer peripheral walls of the first large flange and the second large flange are fixed by spot welding at intervals along the circumferential direction.

[0027] As a technical solution of the present application, in step S9, the second triangular rib is provided with a second welding hole at a right angle position, and the radius of the second welding hole is greater than 40 mm.

[0028] Beneficial effects of this application:

[0029] The present application provides a method for manufacturing and installing a large circular butt-jointed flange, which adopts a process of dividing the large flange into multiple flange petals and manufacturing them in sections until they are qualified, and then installing them in sections. This solves the problem of limited transportation and limited equipment processing capacity when the large flange is manufactured and installed as a whole and outsourced for machining in the traditional method. At the same time, it installs the butt-jointed large flange as a whole on the ground, and then connects it to the internal pipeline after hoisting it into position, and adopts effective welding anti-deformation measures to effectively ensure the flatness of the butt-jointed large flange, avoids the use of portable machining equipment for processing, greatly reduces construction costs, and improves construction efficiency. In addition, it solves the problem of local cross-flow of the large flange when the airflow passes through the internal pipeline by setting a sealing ring after the large flange is installed and filling the inside with low-temperature glue, thereby ensuring the process quality of the internal pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate the following technical solutions of the present application.

[0031] Certain embodiments of the application should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 Schematic diagram of the installation of the first large flange and the second large flange provided in the embodiment of the present application;

[0033] Figure 2 for Figure 1 A is an enlarged schematic diagram;

[0034] Figure 3 A schematic diagram of a first state of manufacturing a first flange petal provided in an embodiment of the present application;

[0035] Figure 4 A schematic diagram of a second state of the first flange splitting process provided in an embodiment of the present application;

[0036] Figure 5 A schematic diagram of a first large flange installed in a first state according to an embodiment of the present application;

[0037] Figure 6 for Figure 5 A is an enlarged schematic diagram;

[0038] Figure 7 A schematic diagram of the second large flange in the first installation state provided in an embodiment of the present application;

[0039] Figure 8 for Figure 7 A is an enlarged schematic diagram;

[0040] Figure 9 A schematic diagram of a first state where the first pipe and the second pipe are closed, provided in an embodiment of the present application;

[0041] Figure 10 for Figure 9 A is an enlarged schematic diagram.

[0042] Icon: 1-first pipeline; 2-second pipeline; 3-first large flange; 4-second large flange; 5-steel platform; 6-first flange petal; 7-first bow plate; 8-first triangular rib plate. DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0044] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without making any creative efforts shall fall within the scope of protection of the present application.

[0045] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0046] In the description of this application, it should be noted that the terms "upper" and "lower" etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships in which the invented product is usually placed when in use. These are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on this application.

[0047] In addition, in this application, unless otherwise expressly specified or limited, the phrase "a first feature is above or below a second feature" may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, the phrases "above, above, and above the second feature" may include the first feature being directly above and obliquely above the second feature, or simply indicate that the first feature is higher in level than the second feature. The phrases "below, below, and below the second feature" may include the first feature being directly below and obliquely below the second feature, or simply indicate that the first feature is lower in level than the second feature.

[0048] Furthermore, terms such as "horizontal" and "vertical" do not necessarily mean that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.

[0049] It should also be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0050] Example:

[0051] Please refer to Figure 1 , with reference Figures 2 to 10 In this embodiment, a method for manufacturing and installing a circular large butt flange is provided, wherein the first large flange 3 and the second large flange 4 are a pair of identical large butt flanges, both of which have an inner diameter of 10500 mm, a width of 150 mm, a thickness of 30 mm, and are made of S30403.

[0052] The first large flange 3 is sequentially divided into eight identical first flange petals 6, and each of the first flange petals 6 is cut using a laser cutting machine. A ground pattern of the first flange petals 6 is drawn on the steel platform 5 and compared with the first flange petals 6. Any deformed first flange petals 6 are corrected. The second large flange 4 is sequentially divided into eight identical second flange petals, and each of the second flange petals is cut using a laser cutting machine. A ground pattern of the second flange petals is drawn on the steel platform 5 and compared with the second flange petals. Any deformed second flange petals are corrected.

[0053] The groove form of the two ends of the first flange petal 6 is an asymmetric X-shaped groove. The first flange petals 6 of the first large flange 3 are assembled in groups of two on the steel platform 5. During assembly, the small groove faces the steel platform 5, and the inner arc edge and outer arc edge of each group of first flange petals 6 are spot welded to the steel platform 5, and two first bow plates 7 are installed on the weld to prevent deformation; first weld the large groove, then remove the first bow plate 7, grind and remove the spot welds between each group of first flange petals 6 and the steel platform 5, and then turn each group of first flange petals 6 180° and place it on the steel platform 5, spot weld the inner arc edge and outer arc edge of each group of first flange petals 6 to the steel platform 5, install two first bow plates 7 to prevent deformation after the weld root is cleaned, and finally weld the small groove; each group of welded first flange petals 6 is subjected to water and fire correction, and after the correction is qualified, a plurality of spaced first flange holes are drilled in sequence on each group of first flange petals 6.

[0054] The groove form of the two ends of the second flange petal is an asymmetric X-shaped groove. The second flange petals of the second large flange 4 are assembled in groups of two on the steel platform 5. During assembly, the small groove faces the steel platform 5, and the inner arc edge and outer arc edge of each group of second flange petals are spot welded to the steel platform 5, and two second bow plates are installed on the weld to prevent deformation; first weld the large groove, then remove the second bow plate, grind and remove the spot weld between each group of second flange petals and the steel platform 5, and then turn each group of second flange petals 180° and place them on the steel platform 5, spot weld the inner arc edge and outer arc edge of each group of second flange petals to the steel platform 5, and install two second bow plates to prevent deformation after the weld root is cleaned, and finally weld the small groove; each group of welded second flange petals is subjected to water and fire correction, and after the correction is qualified, a plurality of spaced second flange holes are drilled in sequence on each group of second flange petals.

[0055] Place the first pipeline 1 vertically and install each set of first flange petals 6 of the first large flange 3 on the first pipeline 1, with the small groove of the butt weld between each set of first flange petals 6 facing downward. Then, spot weld first triangular ribs 8 at intervals along the circumference of the lower surface of the first large flange 3 and the outer wall of the first pipeline 1. The first triangular ribs 8 are provided with first through-weld holes at right angles, with a radius of 45 mm. Perform a bottom weld on the butt weld between each set of first flange petals 6 of the first large flange 3 using gas tungsten arc welding.

[0056] Install each set of second flange petals of the second large flange 4 on the first large flange 3, with the small groove of the butt weld between each set of second flange petals facing upward. Stagger the butt welds between each set of first flange petals 6 of the first large flange 3 and the butt welds between each set of second flange petals of the second large flange 4 by 160 mm, and fasten them with bolts. Weld the first large flange 3 to the first pipeline 1 using tungsten inert gas welding, and then weld the small groove of the butt welds between each set of first flange petals 6 of the first large flange 3. After the weld cools to room temperature, one of the groups of second flange petals on the second large flange 4 is taken out, and the large groove of the butt weld between a group of first flange petals 6 corresponding to the taken out group of second flange petals is completed by tungsten inert gas welding, and the taken out second flange petals are installed on the first large flange 3 and fastened with bolts; the other second flange petals are taken out in turn and welded and assembled using the same method as above until the butt weld between each group of first flange petals 6 on the first large flange 3 is completed; finally, the outer peripheral walls of the first large flange 3 and the second large flange 4 are fixed by spot welding at intervals along the circumferential direction.

[0057] Hoist the second pipeline 2 into position, then hoist the first pipeline 1, first large flange 3, and second large flange 4 into position together. Adjust the offset and clearance between the second large flange 4 and the second pipeline 2 until they meet the requirements. Spot weld first triangular ribs 8 at intervals along the circumference of the outer walls of the second large flange 4 and the second pipeline 2. Use tungsten inert gas welding to weld the second large flange 4 to the second pipeline 2.

[0058] Longer studs were used to replace a small number of bolts between the first large flange 3 and the second large flange 4, and the remaining bolts were removed. The spot weld between the first large flange 3 and the second large flange 4 was then ground away. The first large flange 3 and the first pipe 1 were then slid 45 mm away from the second large flange 4. The butt welds between each set of second flange petals on the second large flange 4 were welded using gas tungsten arc welding, with the small groove welded first, followed by the large groove. Two second bow plates were installed on the welds before welding to prevent deformation.

[0059] Install a SONKIT sealing ring with a specification of 30×5mm between the first large flange 3 and the second large flange 4, with the sealing ring close to the inner arc side of the large flange; close the first large flange 3, the first pipe 1 and the second large flange 4, install the bolts and tighten them, and finally apply Henkel MS930 low-temperature glue at the gap on the inner arc side of the first large flange 3 and the second large flange 4.

[0060] In summary, the present application provides a method for manufacturing and installing a large circular butt-jointed flange, which adopts a process of dividing the large flange into multiple flange petals and manufacturing them in sections until they are qualified, and then installing them in sections. This solves the problem of limited transportation and limited equipment processing capacity when the overall manufacturing and installation of the large flange is outsourced for machining in the traditional method. At the same time, it installs the large butt-jointed flange as a whole on the ground, and then connects it to the internal pipeline after hoisting it into position, and adopts effective welding anti-deformation measures to effectively ensure the flatness of the large butt-jointed flange, avoids the use of portable machining equipment for processing, greatly reduces construction costs, and improves construction efficiency. In addition, it solves the problem of local cross-flow of the large flange when the airflow passes through the internal pipeline by setting a sealing ring after the large flange is installed and filling the inside with low-temperature glue, thereby ensuring the process quality of the internal pipeline.

[0061] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for manufacturing and installing a large annular butt flange, characterized in that: The following steps are involved: S1, sequentially dividing the first large flange into an even number of at least eight first flange petals, and sequentially dividing the second large flange into an even number of at least eight second flange petals, and blanking the first flange petals and the second flange petals; S2: Draw a first pattern of the first flange petal on the steel platform, compare the first pattern with the first flange petal, and correct any deformation of the first flange petal; draw a second pattern of the second flange petal on the steel platform, compare the second pattern with the second flange petal, and correct any deformation of the second flange petal; S3, spot-welding the inner arc edges and outer arc edges of each group of two adjacent first flange petals to the steel platform, and installing two first arched plates on the welds. Then, assembling and welding the two adjacent first flange petals in the first large flange on the steel platform. Spot-welding the inner arc edges and outer arc edges of each group of two adjacent second flange petals to the steel platform, and installing two second arched plates on the welds. Then, assembling and welding the two adjacent second flange petals in the second large flange. S4, subjecting each set of welded first flange petals to water and fire straightening, and after passing the straightening, drilling first flange holes on the first flange petals; subjecting each set of welded second flange petals to water and fire straightening, and after passing the straightening, drilling second flange holes on the second flange petals; S5, placing the first pipe vertically, installing each set of the first flange petals on the outer peripheral wall of the first pipe, and then spot-welding a plurality of first triangular ribs at intervals along the circumference between the lower surface of each set of the first flange petals and the upper edge of the outer peripheral wall of the first pipe; S6, performing a bottom weld on the butt welds between each set of the first flange petals using gas tungsten arc welding, and installing each set of the second flange petals on the assembled first large flange using multiple bolts; S7, welding the first large flange to the first pipe by gas tungsten arc welding, and then welding the small groove of the butt weld between each group of first flange petals; after the weld has cooled, removing a group of second flange petals, and welding the large groove of the butt weld between a group of first flange petals corresponding to the removed second flange petals by gas tungsten arc welding; installing the removed second flange petals on the first large flange and fastening them with bolts; sequentially removing other second flange petals and welding and assembling them by the same method until the butt welds between each group of first flange petals are completed; S8, hoisting the second pipeline into position, then hoisting the first pipeline, the first large flange, and the second large flange into position in sequence, and adjusting the amount of misalignment and the gap between the second large flange and the second pipeline until they are qualified; S9, spot welding a plurality of second triangular ribs at intervals along the circumferential direction on the outer circumferential walls of the second large flange and the second pipeline, and welding the second large flange and the second pipeline by gas tungsten arc welding; S10: Remove multiple bolts connecting the first large flange and the second large flange, and connect the first large flange and the second large flange using studs; then remove the remaining bolts, grind off the spot weld between the first large flange and the second large flange, and slide the first large flange and the first pipe together 40 to 50 mm in a direction away from the second large flange; S11, welding the butt welds between the petals of each set of the second flanges by gas tungsten arc welding, welding the small groove first and then the large groove; S12: Install a sealing ring between the first large flange and the second large flange, with the sealing ring close to the inner arc side of the first large flange and the second large flange; close the first large flange, the first pipe, and the second large flange and tighten them with bolts; finally, apply low-temperature glue at the position where there is a gap on the inner arc side of the first large flange and the second large flange.

2. The method for manufacturing and installing a large annular butt flange according to claim 1, characterized in that: In step S1 , the first large flange and the second large flange are identical.

3. The method for manufacturing and installing a large annular butt flange according to claim 1, characterized in that: In step S3, the grooves at both ends of the first flange flap are in the form of asymmetric X-shaped grooves, and the small grooves of each group of the first flange flaps are facing the steel platform when assembled, and the large grooves on the first flange flaps are welded first, and then the first bow plate on the weld is removed, and the spot welds between each group of the first flange flaps and the steel platform are ground off, and then each group of the first flange flaps is flipped 180° and placed on the steel platform, and the inner arc edge and outer arc edge of each group of the first flange flaps are spot welded to the steel platform respectively, and after the welds are cleaned, the two first bow plates are installed, and finally the small grooves on the first flange flaps are welded.

4. The method for manufacturing and installing a large annular butt flange according to claim 1, characterized in that: In step S3, the grooves at both ends of the second flange flaps are in the form of asymmetric X-shaped grooves, and the small grooves of each group of the second flange flaps are facing the steel platform when assembled, and the large grooves on the second flange flaps are welded first, and then the second bow plates on the welds are removed, and the spot welds between each group of the second flange flaps and the steel platform are ground off, and then each group of the second flange flaps is flipped 180° and placed on the steel platform, and the inner arc edge and outer arc edge of each group of the second flange flaps are spot welded to the steel platform respectively, and after the welds are cleaned, two second bow plates are installed, and finally the small grooves on the second flange flaps are welded.

5. The method for manufacturing and installing a large annular butt flange according to claim 1, characterized in that: In step S5, a first through-welding hole is provided at a right-angle position on the first triangular rib plate, and a radius of the first through-welding hole is greater than 40 mm.

6. The method for manufacturing and installing a large annular butt flange according to claim 1, characterized in that: In step S5, when the first large flange is installed on the first pipeline, the small groove of the butt weld between each group of the first flange petals faces downward.

7. The method for manufacturing and installing a large annular butt flange according to claim 1, characterized in that: In step S7, the butt welds between each group of the first flange petals are staggered by 100-200 mm from the butt welds between each corresponding group of the second flange petals.

8. The method for manufacturing and installing a large annular butt flange according to claim 1, characterized in that: In step S7, when the second large flange is mounted on the first large flange, the small groove of the butt weld between each set of the second flange petals faces upward.

9. The method for manufacturing and installing a large annular butt flange according to claim 1, characterized in that: In step S8, before the first pipeline, the first large flange, and the second large flange are hoisted together, the outer peripheral walls of the first large flange and the second large flange are fixed by spot welding at intervals along the circumferential direction.

10. The method for manufacturing and installing a large annular butt flange according to claim 1, characterized in that: In step S9, a second through-welding hole is provided at a right angle on the second triangular rib plate, and the radius of the second through-welding hole is greater than 40 mm.

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