Expansion joint structure used for controlling communicating pipe to expand due to temperature and pressure changes and not prone to damage

Abstract

The invention discloses an expansion joint structure used for controlling a communicating pipe to expand due to temperature and pressure changes and not prone to damage, and relates to the technical field of thermal displacement compensation and damping devices of pipeline systems. The problems that an existing reinforcing plate expansion joint structure is low in anti-fatigue reliability, inaccurate in control and limited in universality due to stress concentration, insufficient multidirectional displacement control collaboration and poor working condition adaptability are solved. Straight pipe sections (1) are connected to the two ends of a corrugated pipe expansion joint (2), and a first connecting plate (3A) and a second connecting plate (3B) are installed in the axial direction of the corrugated pipe expansion joint (2). The third connecting plate (3C) is mounted in the transverse direction of the corrugated pipe expansion joint (2); the two ends of the first connecting plate (3A), the two ends of the second connecting plate (3B) and the two ends of the third connecting plate (3C) stretch across the corrugated pipe expansion joint (2) and are fixedly welded to the straight pipe section (1) respectively. The invention is used for compensating and protecting the communicating pipe.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of pipeline connection and compensation, and relates to an expansion joint structure for controlling expansion of a communication pipe due to temperature and pressure changes and not prone to damage, which is suitable for connecting a high-temperature and high-pressure steam pipeline between a steam inlet valve and a steam cylinder of a steam turbine. BACKGROUND

[0002] During operation of a steam turbine, the communication pipe, such as a pipeline connecting the steam inlet valve and the high-pressure cylinder or the high-low pressure cylinder, will expand and contract due to changes in the temperature and pressure of the steam being transported, resulting in displacement and deformation of the pipeline. In order to compensate for this displacement and protect the pipeline system from excessive stress damage, a bellows expansion joint is usually installed on the communication pipe. As a thin-walled flexible element, the bellows joint can produce elastic deformation in the axial, lateral and angular directions, effectively absorbing the displacement of the pipeline. However, the bellows joint itself is flexible in structure, and when subjected to varying degrees of expansion and contraction displacement, it is prone to fatigue damage and leakage due to alternating stress. At the same time, due to its low stiffness, it is easy to induce harmful vibration of the communication pipe under the action of high-speed steam flow and system vibration, affecting the safety and stability of the unit operation.

[0003] To solve the above problems of vibration and displacement control, the prior art proposes a scheme of adding a reinforcing structure to the bellows expansion joint. For example, in Chinese invention patent CN119435869A, a "communication pipe expansion joint structure with reinforcing plate" is disclosed. In this scheme, a connecting plate is welded inside the straight pipe at both ends of the bellows pipe section, and the rigidity of the connecting plate is used to constrain the excessive deformation of the bellows pipe, thereby inhibiting the vibration of the pipeline and controlling the range of thermal displacement to a certain extent.

[0004] However, the closest prior art scheme still has the following shortcomings:

[0005] Firstly, the connecting plate and the straight pipe are rigidly connected through four circumferential welds, and the connecting plate is usually of equal cross-section structure. Under high temperature and high pressure and cyclic loading, stress concentration is easily formed at the weld area and the transition of the plate body, which may lead to fatigue cracking during long-term operation, and the problem of structural damage caused by excessive stress cannot be fundamentally solved.

[0006] Secondly, this scheme relies on a single connecting plate to achieve overall displacement constraint, and for the complex displacement that may occur simultaneously in the axial, lateral and angular directions in actual working conditions, there is a lack of fine and collaborative control mechanism, which may cause local over-constraint or insufficient compensation.

[0007] Finally, the structural parameters of the connecting plate are fixed, and it is difficult to adapt to changes in working conditions under different steam parameter temperatures, pressures and expansion amounts, and the universality and adaptability are limited.

[0008] In summary, the existing reinforcing plate expansion joint structure has the problems of stress concentration, poor multi-directional displacement control coordination and poor working condition adaptability, resulting in low fatigue resistance reliability, inaccurate control and limited universality. SUMMARY

[0009] The purpose of the present application is to solve the problems of stress concentration, poor multi-directional displacement control coordination and poor working condition adaptability of the existing reinforcing plate expansion joint structure, resulting in low fatigue resistance reliability, inaccurate control and limited universality. Furthermore, an expansion joint structure for controlling the expansion of a communication pipe due to temperature and pressure changes and not easily damaged is provided.

[0010] The technical solution of the present application is:

[0011] An expansion joint structure for controlling the expansion of a communication pipe due to temperature and pressure changes and not easily damaged, comprising a bellows expansion joint, both ends of the bellows expansion joint being connected with a straight pipe section, further comprising: a first connecting plate, a second connecting plate and a third connecting plate; the first connecting plate and the second connecting plate are installed along the axial direction of the bellows expansion joint; the third connecting plate is installed along the transverse direction of the bellows expansion joint; both ends of the first connecting plate, the second connecting plate and the third connecting plate span the bellows expansion joint and are respectively welded and fixed to the straight pipe section.

[0012] Further, the first connecting plate and the second connecting plate are symmetrically arranged about the axis of the bellows expansion joint, and the plate body trend of the third connecting plate is orthogonal to the plate body trend of the first connecting plate and the second connecting plate, both ends of the first connecting plate, the second connecting plate and the third connecting plate are welded on the straight pipe section, forming a spatially crossed layout.

[0013] Further, the plate body trend of the first connecting plate and the second connecting plate is parallel to the axis of the bellows expansion joint, and the plate body trend of the third connecting plate is perpendicular to the axis of the bellows expansion joint.

[0014] Preferably, the welding fixed part is located on the inner side wall of the straight pipe section.

[0015] Further, the outer side surface of the plate body of the first connecting plate, the second connecting plate and the third connecting plate is a circular arc surface that fits the inner wall of the straight pipe section.

[0016] Further, the first connecting plate, the second connecting plate and the third connecting plate each include two plate bodies and a connecting rod, the two plate bodies being connected by the connecting rod.

[0017] Further, the bottom of the first connecting plate, the second connecting plate and the third connecting plate is a horizontal plane, and the horizontal plane has a height difference b between the lowest point of the welding part at both ends.

[0018] Preferably, the thickness of the connecting rod in the first connecting plate, the second connecting plate and the third connecting plate is two-thirds of the width of the connecting rod.

[0019] Compared with the prior art, the present application has the following effects:

[0020] 1. The present application realizes the collaborative and fine control of complex thermal displacement, avoiding single-point over-constraint. The prior art such as CN119435869A uses a single connecting plate to rigidly constrain the corrugated pipe as a whole, which is difficult to cope with the simultaneous multi-directional displacement of the pipeline in actual operation, such as axial, lateral and other complex displacement, and is prone to cause local stress overload. The present application designs the structure of the connecting plate as a specific shape extending in the axial and lateral directions of the corrugated pipe, so that the single component can provide constraint force in multiple directions at the same time. Specifically, the part of the connecting plate extending in the axial direction mainly absorbs and limits the axial thermal expansion and contraction displacement, while the part extending in the lateral direction mainly constrains the lateral displacement. The collaborative and fine control of the complex thermal displacement of the pipeline system is realized, effectively avoiding the problem of local over-constraint and stress concentration caused by single constraint direction or excessive global rigidity.

[0021] 2. The present application optimizes the stress distribution at the connection, significantly improving the fatigue resistance and reliability of the structure. In view of the defect that the existing reinforcing plate and the pipeline welding place are prone to stress concentration, the present application optimizes the detailed structure of the connecting plate. First of all, it is clearly required that the connecting plate be welded to the inner side wall of the straight pipe section, and this embedded installation method can provide better support and force flow transmission. Secondly, the outer side surface of the connecting plate body is limited to a circular arc surface that matches the inner wall of the straight pipe, ensuring good matching of the welding surface and reducing additional stress caused by geometric mismatch. Finally, by setting the thickness of the connecting plate to be two-thirds of its width and setting the height difference b between the bottom horizontal surface and the welding point, the connecting plate is given a reasonable rigidity and flexibility distribution and installation gap. These combined technical means enable the load caused by thermal displacement to be transmitted more smoothly through the connecting plate to the pipeline, greatly relieving the stress peak in the weld area, thereby significantly reducing the risk of fatigue crack initiation and prolonging the overall service life of the expansion joint. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a schematic diagram of the overall structure of the present application; Figure 2 is a partial enlarged view of the first connecting plate 3A; Figure 3 is Figure 2 is a sectional view along A-A; Figure 4 is Figure 3 is a K view of Figure 5 is a top view of the first connecting plate 3A; Figure 6 is Figure 5 is a longitudinal sectional view along the length direction thereof; Figure 7 isFigure 5 A view along the longitudinal direction of the width thereof after being cut open.

[0023] Wherein: 1, straight pipe section; 2, bellows expansion joint; 3A, first connecting plate; 3B, second connecting plate; 3C, third connecting plate;

[0024] a- The width of the connecting plate is calculated according to the expansion amount of the steam parameters, and the value of a is obtained. The thickness of the connecting plate is 2 / 3 of the width.

[0025] b- The bottom of the connecting plate is a horizontal plane, and the difference between the lowest point of the welding part at both ends.

[0026] c- is the inner wall radius of the communication pipe. DETAILED DESCRIPTION

[0027] Specific implementation one: combined Figures 1 to 7 In this embodiment, the bellows expansion joint 2 is connected at both ends with the straight pipe section 1, and further includes: a first connecting plate 3A, a second connecting plate 3B and a third connecting plate 3C; the first connecting plate 3A and the second connecting plate 3B are installed along the axial direction of the bellows expansion joint 2; the third connecting plate 3C is installed along the transverse direction of the bellows expansion joint 2; both ends of the first connecting plate 3A, the second connecting plate 3B and the third connecting plate 3C span the bellows expansion joint 2 and are respectively welded and fixed to the straight pipe section 1.

[0028] The present application is aimed at the communication pipe between the inlet valve and the high-pressure cylinder, controls the displacement load caused by the excessive displacement of the bellows joint due to thermal expansion and cold contraction during the expansion process of the communication pipe bellows joint, and aims to control the displacement load range of the bellows pipe caused by the expansion of the communication pipe due to temperature and pressure changes and ensure the stability of the pipeline system. Improve the service life of the pipeline.

[0029] The present application is used for connecting the communication pipe between the high and intermediate pressure or the inlet valve and the high-pressure cylinder. When the steam is introduced into the communication pipe, due to the temperature and pressure difference at both ends of the communication pipe, the pipe will expand or contract. If the expansion or contraction amount is too large, it will cause flange leakage, excessive vibration of the communication pipe, or rupture and leakage of the bellows joint. The expansion joint with the connecting plate can well control the damage caused by excessive vibration or stress in all directions due to expansion or contraction of the communication pipe. Fatigue damage caused by thermal expansion and cold contraction is effectively inhibited, and the system is ensured to operate stably under long-term alternating load. The connecting plate matches the material linear expansion coefficient and structural rigidity, so that the displacement load is uniformly distributed in the entire pipeline system, avoiding local stress concentration. Further improve the sealing reliability and structural integrity.

[0030] Specific implementation two: combined Figure 1In this embodiment, the first connecting plate 3A and the second connecting plate 3B are symmetrically arranged about the axis of the bellows expansion joint 2, and the plate body of the third connecting plate 3C is orthogonal to the plate bodies of the first connecting plate 3A and the second connecting plate 3B. The two ends of the first connecting plate 3A, the second connecting plate 3B, and the third connecting plate 3C are welded on the straight pipe section 1 to form a spatially intersecting layout. This effectively enhances the constraint stiffness of the overall structure and suppresses thermal displacement deformation in multiple directions. This spatially intersecting layout can effectively limit excessive displacement in the axial, lateral, and torsional directions when the bellows expansion joint is in operation, significantly reducing the dynamic stress amplitude and preventing fatigue failure caused by alternating loads. Through the synergistic effect of the three-directional connecting plates, thermal expansion deformation is guided within the design allowable range, improving system operation stability and safety, and is particularly suitable for long-term stable operation under high-temperature and high-pressure steam pipeline working conditions.

[0031] In addition, as a preferred mode of this embodiment, the plate body of the third connecting plate 3C is not completely orthogonal to the plate bodies of the first connecting plate 3A and the second connecting plate 3B, but allows an installation angle deviation of ±5° to adapt to actual assembly requirements and welding process errors on site. This design improves construction convenience while ensuring structural function, and through finite element analysis verification, within this angle deviation range, the displacement constraint effect of the connecting plate on the bellows expansion joint does not significantly decrease, and the three-directional thermal displacement can still be effectively controlled and the load can be uniformly transmitted, ensuring that the system stability and sealing performance are not affected.

[0032] Specific implementation method three: combination Figure 1 In this embodiment, the plate body of the first connecting plate 3A and the second connecting plate 3B is parallel to the axis of the bellows expansion joint 2, and the plate body of the third connecting plate 3C is perpendicular to the axis of the bellows expansion joint 2. The two ends of the three are welded on the straight pipe section 1 to form a planar orthogonal support structure. When the expansion joint expands and contracts, the first connecting plate 3A and the second connecting plate 3B mainly bear the axial displacement constraint, and the third connecting plate 3C effectively suppresses lateral deviation and angular torsion, cooperatively reducing the vibration amplitude. Through the reasonable arrangement of the plate body, the stiffness of the connecting plate system is matched with the deformation characteristics of the bellows segment, avoiding stress concentration caused by excessive local stiffness, while ensuring the smooth release of thermal displacement along the designed path. This structure is particularly suitable for steam communication pipe systems with high requirements for sealing performance and structural fatigue life under large temperature difference conditions.

[0033] In addition, in the preferred mode of the embodiment, the "vertical" direction of the plate body of the third connecting plate 3C is not completely vertical, but allows an installation angle deviation of ±5° to adapt to the field assembly conditions and the influence of welding deformation. This slight angle adjustment significantly improves the installation fault tolerance capability while ensuring that the third connecting plate effectively suppresses lateral displacement and torsion. Simulation verification shows that within this tolerance range, the structural stiffness distribution is uniform, the load transmission path is stable, and there is no abnormal stress concentration or constraint failure phenomenon, and the expansion joint can still maintain its coordinated deformation capability under multi-dimensional displacement, ensuring the long-term operation reliability of the system.

[0034] Specific implementation mode four: combination Figure 3 In this embodiment, the welding fixed part is located on the inner side wall of the straight pipe section 1.

[0035] In this embodiment, the connecting plate is welded on the inner side wall of the straight pipe section, so that the restraint force is directly applied to the core area of the pipe wall thickness, avoiding eccentric load and additional bending moment caused by external installation, and significantly improving the force transmission efficiency and stability. At the same time, this structure is completely contained in the internal profile of the pipeline, without occupying additional external space, so that the layout of the entire device is more compact, facilitating installation in the space-limited cabin, and providing convenience for subsequent pipeline insulation layer construction. In addition, the connecting plate is protected by the pipe wall, which can effectively reduce the damage caused by external environmental corrosion and accidental mechanical impact, thereby improving the reliability of the structure during long-term service.

[0036] Specific implementation mode five: combination Figure 3 and Figure 7 In this embodiment, the outer side surface of the plate body of the first connecting plate 3A, the second connecting plate 3B and the third connecting plate 3C is a circular arc surface that is attached to the inner wall of the straight pipe section 1.

[0037] This design facilitates the realization of surface contact between the plate body and the inner wall of the pipeline during welding, avoiding gaps or only partial point contact due to shape mismatch, thereby improving the load uniformity and connection reliability of the weld. The circular arc surface design allows the load to be smoothly transmitted to the pipe wall through a larger contact area, effectively dispersing local stress and preventing premature cracking of the weld due to stress concentration, while also facilitating the implementation of the welding process and ensuring the welding quality.

[0038] Specific implementation mode six: combination Figure 5 In this embodiment, the first connecting plate 3A, the second connecting plate 3B and the third connecting plate 3C each include two plate bodies and a connecting rod, and the two plate bodies are connected by the connecting rod.

[0039] The two plate bodies are connected by the intermediate connecting rod, which can ensure reliable welding and fixation of the two ends with the pipeline, and provide flexibility to adapt to and buffer the slight deformation of the bellows segment. This design can constrain the overall displacement of the pipeline while not hindering the normal working deformation of the bellows or generating excessive additional stress due to excessive rigidity of the connecting plate, thereby achieving a balance between "effective constraint" and "avoiding interference", and improving the coordination and durability of the expansion joint as a whole.

[0040] Specific embodiment seven: combination Figure 7 In this embodiment, the bottom of the first connecting plate 3A, the second connecting plate 3B and the third connecting plate 3C is a horizontal plane, which has a height difference b with the lowest point of the welding position at both ends.

[0041] In this embodiment, the horizontal plane is provided at the bottom of the connecting plate and has a height difference b with the lowest point of the welding position. The main function is to provide a deformation space in the vertical direction when the connecting plate expands due to heat. This height difference forms a gap that can accommodate a small amount of vertical displacement. When the temperature of the pipeline system rises and causes the connecting plate to expand due to heat, it can avoid rigid contact and top dead center between the bottom of the connecting plate and the lower pipeline or support structure, thereby preventing the generation of a large secondary thermal stress due to blocked thermal expansion, and protecting the safety of the weld and the connecting structure.

[0042] Specific embodiment eight: combination Figure 5 In this embodiment, the thickness of the connecting rod in the first connecting plate 3A, the second connecting plate 3B and the third connecting plate 3C is two-thirds of the width of the connecting rod.

[0043] In this embodiment, the thickness of the connecting rod is set to two-thirds of its width, which can ensure sufficient bending and torsional stiffness of the connecting plate while avoiding unnecessary rigidity due to excessive thickness. The specific thickness-to-width ratio allows the connecting rod to provide effective constraint force while having appropriate flexibility to buffer local stress when bearing the load transmitted by the pipeline displacement, thereby achieving a balance between structural strength and adaptability, and preventing stress concentration due to excessive rigidity or instability due to excessive weakness.

[0044] The above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions described in the foregoing embodiments can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An expansion joint structure for controlling expansion of a communication pipe due to temperature and pressure changes without being easily damaged, comprising a bellows expansion joint (2) having straight pipe sections (1) connected to both ends of the bellows expansion joint (2), characterized in that: Also included are: a first connecting plate (3A), a second connecting plate (3B), and a third connecting plate (3C); the first connecting plate (3A) and the second connecting plate (3B) are installed along the axial direction of the bellows expansion joint (2); the third connecting plate (3C) is installed along the transverse direction of the bellows expansion joint (2); the two ends of the first connecting plate (3A), the second connecting plate (3B), and the third connecting plate (3C) span the bellows expansion joint (2) and are respectively welded and fixed to the straight pipe section (1).

2. The expansion joint structure for controlling the expansion of a communication pipe due to temperature and pressure changes without being easily damaged according to claim 1, wherein: The first connecting plate (3A) and the second connecting plate (3B) are symmetrically arranged about the axis of the bellows expansion joint (2), and the plate body trend of the third connecting plate (3C) is orthogonal to the plate body trend of the first connecting plate (3A) and the second connecting plate (3B). The two ends of the first connecting plate (3A), the second connecting plate (3B), and the third connecting plate (3C) are commonly welded on the straight pipe section (1), forming a spatially crossed layout.

3. The expansion joint structure according to claim 2, wherein: The plate body trend of the first connecting plate (3A) and the second connecting plate (3B) is parallel to the axis of the bellows expansion joint (2), and the plate body trend of the third connecting plate (3C) is perpendicular to the axis of the bellows expansion joint (2).

4. The expansion joint structure according to claim 3, wherein: The welded and fixed part is located on the inner side wall of the straight pipe section (1).

5. The expansion joint structure for controlling the expansion of communication pipes due to temperature and pressure changes without being easily damaged according to claim 4, wherein: The outer side surface of the plate body of the first connecting plate (3A), the second connecting plate (3B), and the third connecting plate (3C) is a circular arc surface that is attached to the inner wall of the straight pipe section (1).

6. The expansion joint structure for controlling the communication pipe expansion due to temperature and pressure changes without being easily damaged according to claim 5, wherein: The first connecting plate (3A), the second connecting plate (3B), and the third connecting plate (3C) each include two plate bodies and a connecting rod, and the two plate bodies are connected by the connecting rod.

7. The expansion joint structure for controlling the communication pipe expansion due to temperature and pressure changes and not easily damaged according to claim 6, wherein: The bottom of the first connecting plate (3A), the second connecting plate (3B), and the third connecting plate (3C) is a horizontal plane, and there is a height difference b between the horizontal plane and the lowest point of the two end welding parts.

8. The expansion joint structure for controlling the communication pipe expansion due to temperature and pressure changes without being easily damaged according to claim 7, wherein: The thickness of the connecting rod in the first connecting plate (3A), the second connecting plate (3B), and the third connecting plate (3C) is two-thirds of the width of the connecting rod.

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