A bending limiter with a special screw column plate

Abstract

The application provides a bend limiter with a special-shaped spiral column plate, which is composed of a plurality of bend limiter units, and each bend limiter unit comprises a bend limiter unit body, a special-shaped spiral column plate and a soft gasket; the bend limiter unit body is divided into a head part, a middle part and a tail part along the pipeline central axis direction, the soft gasket is embedded in the tail part and is provided with a first embedding groove corresponding to the head part; the special-shaped spiral column plate is spirally arranged along the outer wall of the bend limiter unit body, one end of the special-shaped spiral column plate starts from the outer edge close to the middle part in the tail part, the other end of the special-shaped spiral column plate ends at the outer edge away from the middle part in the tail part, and the cross section of the special-shaped spiral column plate perpendicular to the central axis is a special-shaped cross section, and the cross line corresponding to the side surface of the special-shaped spiral column plate is an arc line; by improving the cross section shape of the spiral column plate, the vortex-induced vibration response is further inhibited, the amplitude peak of the pipeline is reduced, the protection of the pipeline and the bend limiter is strengthened, and the service life of the pipeline is improved.

Description

Technical Field

[0001] This invention relates to the field of marine pipeline bend limiters, and more particularly to a marine pipeline bend limiter with irregularly shaped spiral plates. Background Technology

[0002] With increasing consumption of oil and natural gas, land-based resources are insufficient to meet demand, leading to a shift in focus towards the deep sea. Simultaneously, the booming renewable energy industry presents a significant development prospect for offshore wind power. Marine pipelines (such as flexible oil pipelines and cables) are crucial equipment in offshore oil development and offshore wind power transmission. Significantly affected by the dynamic marine environment, the boundary layer on both sides of the pipeline's cross-section separates under the influence of waves, currents, and other marine loads, generating alternating vortices. These vortices exert unsteady loads on the pipeline. When their frequency approaches a certain natural frequency of the pipeline, large-amplitude vibrations occur in a direction perpendicular to the current direction—this is known as vortex-induced vibration. Vortex-induced vibration not only exacerbates pipeline bending deformation and generates bending stress but also leads to fatigue failure due to long-term vibration, causing severe economic losses and ecological damage.

[0003] Bending limiters are commonly used to restrict excessive bending in marine pipelines. These limiters are nested cylindrical components around the pipeline. When the bending reaches a certain curvature, the limiters lock together and provide additional bending stiffness to protect the pipeline. However, traditional bending limiters only restrict the bending of the pipeline and cannot suppress vortex-induced vibration, one of the causes of bending. Therefore, in harsh marine environments, the connections between the bending limiter units often fail due to long-term vortex-induced vibration, resulting in the loss of their pipeline protection function. Thus, bending limiters need further improvement to reduce the large-scale vortex-induced vibration of both the pipeline and themselves.

[0004] In the prior art, early patents, such as those with publication numbers US6896447B1 and US6695540B1, which are related to marine pipelines, only disclosed the arrangement of helical plates or blades. Recent patents, such as CN116972257A, CN114482876A, and CN218762094U, all involve technical features related to helical plates or improving the suppression effect of vortex-induced vibration. However, none of them have found the influence of the cross-sectional shape of the helical plates on the suppression effect of vortex-induced vibration. By improving the cross-sectional shape of the helical plates, the degree of influence of vortex-induced vibration on marine pipelines can be changed. Thus, it can be found that there is still room for further improvement in the suppression of vortex-induced vibration. Furthermore, current patents related to bending limiters, such as CN116972257A, CN114482876A, and CN218762094U, do not involve technologies for suppressing the vortex-induced vibration of the limiter itself. In actual engineering, bending limiters often fail due to vortex-induced vibration in harsh marine environments. Based on this, a novel bending limiter is proposed that not only prevents excessive bending but also suppresses the vortex-induced vibration of the bending limiter itself, which has significant engineering application prospects. Summary of the Invention

[0005] Based on this, the present invention provides a bend suppressor with irregularly shaped spiral plates. Its purpose is to suppress the vortex-induced vibration effect of the bend suppressor itself by setting irregularly shaped spiral plates on the surface of the bend suppressor, thereby further reducing the bend of the pipeline caused by the vortex-induced vibration of the entire marine pipeline.

[0006] To achieve the above objectives, the embodiments in this specification provide the following technical solutions: This invention provides a bend limiter with a shaped spiral plate for suppressing vortex-induced oscillations and limiting bends in marine pipelines. The bend limiter is fitted onto the marine pipeline and consists of multiple bend limiter units. Each bend limiter unit includes a main body, a shaped spiral plate, and a soft washer. The main body of the bend limiter unit is divided into a head, a middle, and a tail section along the central axis of the pipeline. The soft washer is embedded in the tail section and has a first embedding groove corresponding to the head section. The shaped spiral plate is spirally arranged along the outer wall of the main body of the bend limiter unit. One end of the shaped spiral plate starts at the outer edge of the tail section near the middle section, and the other end terminates at the outer edge of the tail section away from the middle section. The cross-section of the shaped spiral plate perpendicular to the central axis is a shaped cross-section, and the cross-section corresponding to the side of the shaped spiral plate is an arc.

[0007] Furthermore, the diameter of the main body of the bending limiter unit is D, and the cross-section of the irregular spiral plate corresponds to two arcs with a radius of curvature of 0.16D on the side of the plate; the length of the irregular cross-section at one end of the outer wall of the main body of the bending limiter unit is 0.25D, and the length at the other end is 0.02D; the height of the irregular spiral plate is 0.17D, the pitch is 17.2D, and the helix angle is 12°.

[0008] Furthermore, the number of bending limiter units is at least 5, and the number of irregular spiral plates in a single bending limiter unit is at least 3 and they are evenly spaced.

[0009] Furthermore, the irregular spiral plates on adjacent bending limiter units are distributed in a continuous spiral pattern, and the interval angle of the irregular spiral plates on adjacent bending limiter units satisfies the following condition: interval angle = 360° / total number of bending limiter units.

[0010] Furthermore, the irregular spiral plates on adjacent bending limiter units are distributed in a continuous spiral pattern, and the interval angle of the irregular spiral plates on adjacent bending limiter units satisfies the following condition: interval angle = 360° / total number of irregular spiral plates.

[0011] Furthermore, the number of bending limiter units is 15, the number of irregular spiral plates in a single bending limiter unit is 3, and the spacing angle between irregular spiral plates on adjacent bending limiter units is 24°.

[0012] Furthermore, the head of the bending limiter unit body is a smooth arc-shaped convex structure, the inner edge of the soft washer is provided with a first embedding groove adapted to the arc-shaped convex structure, and the tail is provided with a second embedding groove adapted to the outer edge of the soft washer.

[0013] Furthermore, the soft washer is provided with a soft washer tenon extending into the tail, and the tail is provided with a tail mortise corresponding to the soft washer tenon to form a mortise and tenon connection structure; the head is provided with a head tenon extending into the soft washer, and the soft washer is provided with a soft washer mortise corresponding to the head tenon to form a mortise and tenon connection structure.

[0014] Preferably, the head, middle, and tail of the bending limiter unit body and the irregular spiral plate are an integrated structure.

[0015] Preferably, the bending limiter unit is divided into a left half and a right half with a plane coplanar with the central axis of the pipeline as the cross section, and the left half and the right half are connected and fastened by bolts.

[0016] Based on the above design, the beneficial effects of the present invention are: First, this invention improves upon traditional marine pipeline bending limiters by incorporating a spiral plate on the outer wall of the bending limiter. This modulates the vortex 3D structure to suppress vortex-induced vibration of the bending limiter itself, thereby reducing the vibration response of the marine pipeline and the bending limiter at its source.

[0017] Secondly, this invention improves upon conventional rectangular and trapezoidal cross-section spiral plates by adopting arc-shaped cross-section spiral plates. Compared with marine pipeline bending limiters with conventional spiral plates, the amplitude is reduced by about 15% under the same spiral plate height and pitch conditions.

[0018] Third, in this invention, the irregular spiral plate with arc-shaped cross-section and the main body of the bending limiter unit achieve a smooth transition, avoiding stress concentration at the connection between the conventional cross-section spiral plate and the bending limiter, and improving the life of the spiral plate.

[0019] Fourth, by setting a tenon and mortise connection structure on the head and soft washer of the limiter unit, the present invention achieves the fixation of the relative rotation angle between different bending limiter units within a combined structure, which can maintain the spiral distribution of the spiral plate and eliminates the need to measure the interval rotation angle on site, making it convenient for direct installation and alignment.

[0020] Fifth, the present invention reduces stress concentration at the connection between the previous and subsequent bending limiter units by combining the smooth arc surface of the bending limiter unit head with the soft washer. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a bending limiter with irregularly shaped spiral plates according to this application; Figure 2 These are schematic cross-sectional views of two bending limiter units in this application; Figure 3 This is a schematic cross-sectional view of a single bending limiter unit in this application; Figure 4 This is a schematic diagram of the structure of the soft washer in this application; Figure 5 This is a schematic diagram of the cross-section of the bending limiter unit in this application; Figure 6 This is a schematic cross-sectional view of the bending limiter unit with different spiral plates arranged in this application; Figure 7 The numerical simulation results of the transverse dimensionless vibration amplitude of the bending limiter with different spiral plates arranged in this application are shown. Figure 8 This is a schematic diagram of a preferred bending limiter in this application.

[0023] Explanation of reference numerals in the attached figures: 1. Bending limiter; 2. First bending limiter unit; 3. Second bending limiter unit; 4. Bolt; 5. Irregular spiral plate; 6. Washer; 7. Marine pipeline; 21. Head; 22. Middle; 23. Tail; 24. Tail recess; 25. Bolt mounting hole; 26. Pipeline groove; 27. Tail tenon; 28. Head tenon; 61. Washer tenon; 62. Washer recess; 63. Washer tenon. Detailed Implementation

[0024] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0025] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0027] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The illustrations only show the elements related to this application and are not drawn according to the number, shape and size of the elements in actual implementation. In actual implementation, the form, quantity and proportion of each element can be arbitrarily changed, and the layout of the elements may also be more complex.

[0028] Additionally, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that practice can be carried out without these specific details.

[0029] Based on this, this specification provides a bend limiter 1 with irregularly shaped spiral plates for suppressing vortex-induced oscillations and limiting bends in a marine pipeline 7. The bend limiter 1 is fitted onto the marine pipeline 7 and consists of multiple bend limiter units. Each bend limiter unit includes a bend limiter unit body, irregularly shaped spiral plates 5, and a soft washer 6. The bend limiter unit body is divided into a head 21, a middle section 22, and a tail section 23 along the pipeline's central axis. The soft washer 6 is embedded in the tail section 23 and has a first embedding groove corresponding to the head 21. The irregularly shaped spiral plates 5 are spirally arranged along the outer wall of the bend limiter unit body. One end of the irregularly shaped spiral plates 5 starts at the outer edge of the tail section 23 near the middle section 22, and the other end terminates at the outer edge of the tail section 23 away from the middle section 22. The cross-section of the irregularly shaped spiral plates 5 perpendicular to the pipeline's central axis is an irregularly shaped cross-section, and the cross-section corresponding to the side of the irregularly shaped spiral plates 5 is an arc. This basic embodiment emphasizes that the spiral plate outside the main body of the bending limiter unit in the bending limiter 1 has an irregular cross section. The irregular cross section is set to be arc-shaped on the side of the irregular spiral plate 5, thereby suppressing the vortex-induced vibration effect of the bending limiter itself.

[0030] To illustrate the specific implementation of the above solution in detail, this specification provides... Figure 1 The diagram shows a bending limiter with irregularly shaped spiral plates. The bending limiter 1 consists of five bending limiter units connected end-to-end. Each bending limiter unit is divided into a left half and a right half along a plane coplanar with the pipeline's central axis. The left and right halves are connected and secured by bolts 4, facilitating installation. It should be noted that the number of bending limiter units in this embodiment is not intended to limit the scope of the independent claim.

[0031] Based on the above embodiments, this specification provides a detailed explanation using two disassembled bending limiter units as an example. Figure 2 The diagram shows cross-sectional views of two bending limiter units, where the first bending limiter unit 2 and the second bending limiter unit 3 are connected end-to-end by a soft washer 6; as shown... Figure 2 As shown, the bending limiter unit includes a bending limiter unit body, an irregularly shaped spiral plate 5, and a soft washer 6. The bending limiter unit body includes a head 21, a middle part 22, and a tail part 23.

[0032] In addition, this manual also provides Figure 3 The diagram shows a cross-sectional view of a single bending limiter unit, with the head 21 and tail 23 located at both ends of the middle section 22. Figure 2 The soft washer 6 shown is embedded in the corresponding tail portion 23, and the tail portion 23 is provided with a tail insertion groove 24 corresponding to the soft washer 6, which facilitates the installation of the soft washer 6. In a preferred embodiment, the head 21, middle portion 22 and tail portion 23 are an integrated structure, which can be made of rigid polyurethane, resulting in low production cost, high production efficiency, good corrosion resistance, and suitability for seawater environments. In this embodiment, bolt mounting holes 25 are respectively provided on the head 21 and tail portion 23 to facilitate the installation and fixing of bolts 4, thereby achieving the wrapping and fastening of the bending limiter unit body onto the marine pipeline 7. In this example, pipeline grooves 26 are provided in the head 21 and middle portion 22 to facilitate assembly onto the marine pipeline 7.

[0033] Figure 3 The head 21 and tail 23 shown in the figure are also provided with tenons and mortises to form a mortise and tenon structure. For detailed explanation, this specification provides Figure 4 The schematic diagram of the soft washer shown illustrates that the soft washer 6 has a soft washer tenon 61 extending into the tail 23, and the tail 23 has a tail mortise 27 corresponding to the soft washer tenon 61 of the soft washer 6, forming a mortise and tenon connection structure. Figure 2 The schematic cross-sectional view of the two bending limiter units shown indicates that the tenon 61 of the soft washer 6 points vertically towards the wall of the tail 23. The soft washer 6 is locked within the bending limiter unit body via a mortise and tenon connection structure. In this embodiment, the head 21 of the bending limiter unit body is provided with a head tenon 28 extending into the soft washer 6. The soft washer 6 is provided with a soft washer mortise 63 corresponding to the head tenon 28 of the head 21, forming a mortise and tenon connection structure. Figure 2 Taking the structure shown as an example, the relative rotation angle between adjacent bending limiter units is fixed by the tenon and tenon connection between the head of the second bending limiter unit 3 and the soft washer of the first bending limiter unit 2. This can maintain the spiral distribution pattern of the spiral plate unchanged, and there is no need to measure the interval rotation angle on site. The head tenon 28 and the soft washer mortise 63 can be directly aligned and installed, which is convenient and quick.

[0034] In a preferred embodiment of the bending limiter, each bending limiter unit body in the same bending limiter unit has three irregularly shaped spiral plates 5 extending from its outer wall surface. These three irregularly shaped spiral plates are evenly arranged along the outer wall surface of the bending limiter unit body. The irregularly shaped spiral plates on adjacent bending limiter unit bodies are arranged along a continuous spiral line. The spacing angle between the irregularly shaped spiral plates on adjacent bending limiter unit bodies satisfies the following condition: Spacing angle = 360° / Total number of irregularly shaped spiral plates. Figure 5 The schematic diagram of the cross-section of the bending limiter unit shown illustrates that the irregularly shaped spiral plate 5 has an irregular cross-section. The diameter of the bending limiter unit body is D. The length of the irregularly shaped cross-section at one end of the outer wall of the bending limiter unit body is 0.25D, and the length at the other end is 0.02D. The two ends of the irregularly shaped cross-section are connected by an arc with a radius of curvature of 0.16D. In this embodiment, the height of the irregularly shaped spiral plate 5 is 0.17D, the pitch is 17.2D, and the helix angle is 12°. Simultaneously, the irregularly shaped spiral plate with its arc-shaped cross-section achieves a smooth transition with the bending limiter unit body, avoiding stress concentration at the connection between a conventional cross-section spiral plate and the bending limiter, thus improving the lifespan of the spiral plate.

[0035] To illustrate the suppression effect of the preferred embodiment on the vortex-induced oscillation effect of the bend limiter itself, this specification also provides comparative simulation results between this embodiment and existing bend limiters. This specification, for a common marine condition with an incoming flow velocity of 2 m / s, uses numerical simulation to calculate the transverse dimensionless vibration amplitude of bend limiters composed of five bend limiter units without helical plates, five bend limiter units with conventional helical plates (plate height 0.17D, pitch 17.2D, helix angle 12°), and five bend limiter units with the irregular helical plates of this embodiment (plate height 0.17D, pitch 17.2D, helix angle 12°). Cross-sectional views of the above three types of bend limiter units are shown below. Figure 6 As shown, (a) is a schematic cross-sectional view of a bending limiter unit without spiral plates, where there are no spiral plates outside the unit body; (b) is a schematic cross-sectional view of a bending limiter unit with conventional spiral plates, where the spiral plates outside the unit body have a trapezoidal cross-section; and (c) is a schematic cross-sectional view of a bending limiter unit with irregular spiral plates, where the spiral plates outside the unit body have an irregular cross-section. The numerical simulation results of the above three bending limiters are as follows: Figure 7 As shown in the figure, the dashed waveform and the dotted-line waveform are simulation results of a bend limiter with conventional spiral plates and a bend limiter with irregular spiral plates, respectively. The comparison shows that, compared with the marine pipeline bend limiter with conventional spiral plates, the bend limiter with irregular spiral plates in this embodiment reduces the peak amplitude of the pipeline by about 20% under the same spiral plate height and pitch conditions.

[0036] In the above embodiments, Figure 3 The head 21 of the main body of the bending limiter unit shown is a smooth semi-ellipse. Figure 4 The soft washer 6 shown has a soft washer insertion groove 62 corresponding to the head 21, which is combined with Figure 2 The illustrated structure shows that the head of the second bend limiter unit 3 is positioned within the soft washer 6 at the tail of the first bend limiter unit 2. The soft washer 6 wraps around the head 21, reducing stress concentration at the connection between the tail 23 of the first bend limiter unit 2 and the head 21 of the second bend limiter unit 3, thus reducing component damage. The elastic deformation of the soft washer 6 provides buffering for small-amplitude bending deformations of the marine pipeline 7, reducing bending fatigue damage. As the bending continues to increase, the engagement between the head and the corresponding tail increases the pipeline's bending strength.

[0037] This instruction manual also provides Figure 8 The schematic diagram of the preferred bend limiter shown indicates that when the marine pipeline 7 is installed at sea, the pipeline bend limiter unit is first arranged according to... Figure 2 The process involves connecting the marine pipeline 7 in the pipeline groove 26 of the connected marine pipeline bend limiter, then reversing the bend limiter and securing it with bolts. Finally, a matching clamp is installed at the end to fix the installed bend limiter to the pipeline and allow it to be lowered into the water along with the pipeline.

[0038] In summary, the bend limiter with irregularly shaped spiral plates disclosed in this invention not only restricts the bending of marine pipelines, but also suppresses vortex-induced vibration through the irregularly shaped spiral plates, thereby further reducing pipeline bending and fatigue damage. The soft gasket is tenon-and-mortise connected to the head, which can maintain the position of the spiral arrangement unchanged and allow for quick alignment and installation. At the same time, the soft gasket wraps around the smooth arc-shaped head, reducing stress concentration at the connection contact.

[0039] In this specification, the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the descriptions of the embodiments described later are relatively simple, and relevant parts can be referred to the descriptions of the foregoing embodiments.

[0040] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A bend limiter with irregularly shaped helical plates, used for vortex-induced oscillation suppression and bend limitation of marine pipelines, sleeved on the marine pipeline, characterized in that, The bending limiter is composed of multiple bending limiter units, each of which includes a bending limiter unit body, an irregularly shaped spiral plate, and a soft washer. The main body of the bending limiter unit is divided into a head, a middle and a tail along the central axis of the pipeline. The soft washer is embedded in the tail and is provided with a first embedding groove corresponding to the head. The irregularly shaped spiral plate is spirally arranged along the outer wall of the main body of the bending limiter unit. One end of the irregularly shaped spiral plate starts at the outer edge of the tail near the middle and the other end ends at the outer edge of the tail away from the middle. The cross section of the irregularly shaped spiral plate perpendicular to the central axis of the pipeline is an irregularly shaped cross section, and the cross section of the irregularly shaped cross section corresponding to the side of the irregularly shaped spiral plate is an arc. The head of the bending limiter unit body is a smooth arc-shaped convex structure, the inner edge of the soft washer is provided with a first embedding groove adapted to the arc-shaped convex structure, and the tail is provided with a second embedding groove adapted to the outer edge of the soft washer.

2. The bending limiter with irregularly shaped spiral plates according to claim 1, characterized in that, The diameter of the main body of the bending limiter unit is D, and the cross-section of the irregular spiral plate corresponds to the two arcs with a radius of curvature of 0.16D on the side of the plate. The length of the irregular cross section at one end of the outer wall of the bending limiter unit body is 0.25D, and the length at the other end is 0.02D; the height of the irregular spiral plate is 0.17D, the pitch is 17.2D, and the helix angle is 12°.

3. The bending limiter with irregularly shaped spiral plates according to claim 1, characterized in that, The number of bending limiter units is at least 5, and the number of irregular spiral plates in a single bending limiter unit is at least 3 and they are evenly spaced.

4. The bending limiter with irregularly shaped spiral plates according to claim 3, characterized in that, The irregular spiral plates on adjacent bending limiter units are distributed in a continuous spiral pattern, and the interval angle of the irregular spiral plates on adjacent bending limiter units satisfies the following condition: interval angle = 360° / total number of bending limiter units.

5. The bending limiter with irregularly shaped spiral plates according to claim 3, characterized in that, The irregular spiral plates on adjacent bending limiter units are distributed in a continuous spiral pattern, and the interval angle of the irregular spiral plates on adjacent bending limiter units satisfies the following condition: interval angle = 360° / total number of irregular spiral plates.

6. The bending limiter with irregularly shaped spiral plates according to claim 1, characterized in that, The number of bending limiter units is 15, the number of irregular spiral plates in a single bending limiter unit is 3, and the spacing angle of the irregular spiral plates on adjacent bending limiter units is 24°.

7. The bending limiter with irregularly shaped spiral plates according to claim 1, characterized in that, The soft washer is provided with a soft washer tenon extending to the tail, and the tail is provided with a tail mortise corresponding to the soft washer tenon to form a mortise and tenon connection structure. The head is provided with a head tenon extending into the soft washer, and the soft washer is provided with a soft washer mortise corresponding to the head tenon to form a mortise and tenon connection structure.

8. The bending limiter with irregularly shaped spiral plates according to claim 1, characterized in that, The head, middle, and tail of the bending limiter unit body and the irregular spiral plate are an integrated structure.

9. The bending limiter with irregularly shaped spiral plates according to claim 1, characterized in that, The bending limiter unit is divided into a left half and a right half with a plane coplanar with the central axis of the pipeline as the cross section, and the left half and the right half are connected and fastened by bolts.

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