Expansion joint

Abstract

The invention provides an expansion joint which comprises a corrugated sleeve, the corrugated sleeve comprises an inner-layer corrugated pipe and an outer-layer corrugated pipe arranged on the periphery of the inner-layer corrugated pipe in a sleeving mode, the inner-layer corrugated pipe is used for forming a medium main channel, one end of the corrugated sleeve is provided with a flange assembly, and the flange assembly comprises a first end ring flange and a second end ring flange; the first end ring flange is connected with the inner-layer corrugated pipe, the second end ring flange is connected with the outer-layer corrugated pipe, a gap exists between the first end ring flange and the second end ring flange, and the first end ring flange and the second end ring flange can move relatively to enable a closed first cavity to be formed between the inner-layer corrugated pipe and the outer-layer corrugated pipe. And then the first cavity is communicated with the medium main channel. The flange assembly is controlled to move through the clamp, the inner-layer corrugated pipe bears pressure independently at low pressure, and the damping effect is excellent; in high pressure, the inner-layer corrugated pipe relieves pressure, the outer-layer corrugated pipe bears pressure, and the low-pressure vibration reduction and high-pressure bearing functions are achieved at the same time.

Description

Technical Field

[0001] This invention relates to the field of expansion joints, and more specifically, to an expansion joint. Background Technology

[0002] Corrugated expansion joints are core components in pipeline systems, enabling displacement compensation, stress relief, and vibration buffering. They are widely used in petrochemical, shipbuilding, and hydropower industries, and their operating environments often involve complex pressure variations. During low-pressure operation, equipment vibration and fluid pulsation in the pipeline system can easily be transmitted through the pipes, creating resonance. Therefore, expansion joints need excellent vibration damping performance to buffer vibration impacts and ensure pipeline connection stability. Under high-pressure conditions, expansion joints must withstand the high-pressure loads of the medium, meeting both the axial and radial displacement compensation requirements of the pipeline and possessing sufficient high-pressure bearing capacity to prevent structural deformation or damage due to pressure overload. Therefore, the dual performance of low-pressure vibration damping and high-pressure bearing is the core requirement for corrugated expansion joints to adapt to complex industrial pipeline conditions and ensure the safe and stable operation of the system.

[0003] Patent application number 201620804180.3 discloses a straight-pipe pressure-balanced expansion joint based on a combination of internal and external pressure conditions. The medium enters the balancing bellows through a pressure communication hole or the second working bellows through a gap, allowing the balancing bellows and the second working bellows to bear internal pressure, while the first working bellows bears external pressure. However, this structure cannot achieve low-pressure vibration damping. Patent application number 202511811215.6 discloses an integrated pressure-protected double-layer bellows vibration damping pipe and its usage method. A safety valve and a check valve are installed in the sandwich cavity, allowing the medium under high pressure to flow into the sandwich cavity formed by the inner and outer bellows. However, the flanges at both ends of the bellows are fixed, resulting in unsatisfactory vibration damping.

[0004] Therefore, there is an urgent need for an expansion joint that combines low-pressure vibration reduction and high-pressure load-bearing functions. Summary of the Invention

[0005] In view of this, the present invention aims to propose an expansion joint that combines low-pressure vibration reduction and high-pressure load bearing functions to solve the problems in the prior art.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] This invention provides an expansion joint, including a corrugated sleeve. The corrugated sleeve includes an inner corrugated pipe and an outer corrugated pipe sleeved around its periphery. The inner corrugated pipe forms a main medium channel. A flange assembly is provided at one end of the corrugated sleeve. The flange assembly includes a first end ring flange and a second end ring flange. The first end ring flange is connected to the inner corrugated pipe, and the second end ring flange is connected to the outer corrugated pipe. There is a gap between the first end ring flange and the second end ring flange. The first end ring flange and the second end ring flange can move relative to each other to form a closed first chamber between the inner corrugated pipe and the outer corrugated pipe. Then, the first chamber communicates with the main medium channel.

[0008] This invention forms a closed first chamber by controlling the relative movement of the first and second end ring flanges. The first chamber is then connected to the main medium channel, so that the pressure difference between the inside and outside of the inner bellows is zero under high pressure conditions and it no longer bears pressure. The outer bellows bears the high pressure alone, thus having both low-pressure vibration reduction and high-pressure bearing functions.

[0009] Furthermore, it also includes a valve and a control system electrically connected to the valve. The two ends of the valve are respectively connected to the main medium channel and the first chamber. The control system controls the opening and closing of the valve to realize the connection between the main medium channel and the first chamber.

[0010] This invention incorporates a valve and control system to enable controllable connection and disconnection between the main medium channel and the first chamber. The valve can be opened and closed according to a preset pressure, ensuring that the pressure in the first chamber and the main channel quickly becomes consistent under high pressure conditions. This ensures timely pressure relief for the inner bellows and allows the outer bellows to withstand high pressure, preventing pressure surges from impacting the bellows.

[0011] Furthermore, it also includes a pressure relief valve and a control system electrically connected to the pressure relief valve. One end of the pressure relief valve is connected to the first chamber, and the control system controls the opening and closing of the pressure relief valve to balance the pressure in the first chamber.

[0012] The present invention is equipped with a pressure relief valve and a control system, which can balance the pressure in the first chamber to near atmospheric pressure, ensuring that the flange can be smoothly separated after the clamp is released, the outer bellows can stop working, and the inner bellows can be restored to a low-pressure state where it works alone.

[0013] Furthermore, it also includes a third end ring flange, which is disposed on the side of the bellows away from the flange assembly.

[0014] The present invention provides a third end ring flange to provide fixed and sealed support for the end of the bellows sleeve away from the flange assembly, thereby achieving a reliable connection between the far ends of the inner and outer bellows layers and ensuring the integrity and stability of the double-layer bellows structure.

[0015] Furthermore, the flange assembly is provided with a clamp for clamping or releasing the first end ring flange and the second end ring flange. When the clamp is clamped, it drives the first end ring flange and the second end ring flange to move closer to the seal. When it is released, it drives the first end ring flange and the second end ring flange to separate.

[0016] When clamped, the first and second end ring flanges seal to form a closed first chamber, ensuring that the medium will not leak from the flange gap under high pressure conditions and ensuring that the inner bellows can be depressurized smoothly; when loosened, the first and second end ring flanges separate, restoring the outer bellows to its non-working state under low pressure conditions, so that the expansion joint maintains low stiffness.

[0017] Furthermore, when the clamp is in the relaxed state, there are gaps between the first end ring flange and the second end ring flange, and between the flange assembly and the clamp, and the amount of the gaps is not less than the axial compensation amount of the expansion joint.

[0018] In this invention, the gap between the first and second end ring flanges serves two purposes. First, it provides space for the elastic reset of the outer bellows. When switching from high-pressure to low-pressure operation, the outer bellows can use its own elastic force to push the two flanges apart without the need for an additional drive structure, simplifying the control logic and reducing equipment energy consumption. Second, this gap is not less than the axial compensation of the expansion joint, preventing the displacement compensation of the inner bellows from being affected by the limited flange spacing under low-pressure conditions. The gap between the flange assembly and the clamp matches the axial compensation, effectively preventing structural interference between the displacement compensation action of the inner bellows and the flange and clamp under low-pressure vibration reduction conditions. This ensures that the inner bellows can freely complete deformation compensation, fully leveraging its design advantages of low stiffness and large compensation.

[0019] Furthermore, the clamps are multiple and spaced apart along the circumferential direction of the flange assembly.

[0020] This invention arranges multiple clamps circumferentially on the flange to avoid additional bending stress on the bellows due to flange off-center loading, thus extending the service life of the inner and outer bellows. At the same time, the uniform distribution of clamping force by the clamps improves the sealing capability of the first and second end ring flanges.

[0021] Furthermore, there are multiple corrugated sleeves, with adjacent inner corrugated sleeves connected by an inner intermediate tube, and adjacent outer corrugated sleeves connected by an outer intermediate tube.

[0022] This invention connects multiple corrugated sleeves in series through inner and outer intermediate pipes, which greatly improves the overall displacement compensation capability of the expansion joint, meets the large axial and lateral displacement compensation requirements of high-pressure long pipelines, and solves the problem of insufficient compensation by a single set of corrugated sleeves.

[0023] Furthermore, the inner corrugated pipe has a low stiffness structure and adopts an unreinforced U-shaped or multi-layer thin-walled reinforced U-shaped structure; the outer corrugated pipe has a high stiffness structure and adopts a reinforced U-shaped or Ω-shaped structure.

[0024] In this invention, the inner bellows adopts a low-stiffness structure with an unreinforced U-shape or multi-layer thin-walled reinforced U-shape, effectively reducing the overall stiffness of the expansion joint under low-pressure conditions, avoiding acoustic short circuits, and significantly improving vibration reduction capability. The outer bellows adopts a high-stiffness structure with a reinforced U-shape or Ω-shape, which can effectively improve load-bearing capacity, resist the pressure impact of high-pressure media, and prevent column instability, ensuring the pressure-bearing safety of high-pressure pipelines. This targeted design of high and low stiffness of the inner and outer bellows satisfies both the low-stiffness vibration reduction requirements under low-pressure conditions and the high-stiffness and high-pressure load-bearing requirements under high-pressure conditions, resolving the technical contradiction between high-pressure load-bearing and low-pressure vibration reduction from a structural design perspective.

[0025] Furthermore, it also includes a pressure sensor and a control system electrically connected to the pressure sensor, the control system being electrically connected to the clamp; the pressure sensor is used to detect the pressure of the main medium channel of the inner bellows, the pressure of the first chamber, and the clamping force of the clamp acting on the first end ring flange and the second end ring flange; the control system controls the clamp to clamp or loosen according to the pressure signal detected by the pressure sensor.

[0026] This invention utilizes pressure sensors to detect pressure and clamping force within the pipeline. The control system achieves fully automatic intelligent switching between high and low pressure conditions based on the pressure signal data, eliminating the need for manual intervention and improving the automation level of the equipment.

[0027] Compared with the prior art, the expansion joint described in this invention has the following advantages:

[0028] (1) Under high pressure conditions, the present invention drives the first end ring flange and the second end ring flange to fit together to form a closed first chamber and connects the chamber to the main medium channel, so that the pressure difference between the inside and outside of the inner bellows is 0 and no longer bears pressure, and the outer bellows bears the high pressure alone, which can effectively resist the impact of high pressure medium and prevent column instability; under low pressure conditions, the clamp drives the two flanges to separate, and the inner bellows bears the pressure alone, which can effectively avoid acoustic short circuit phenomenon, achieve excellent vibration reduction effect, and enable the expansion joint to meet the dual use requirements of low pressure vibration reduction and high pressure bearing at the same time.

[0029] (2) The present invention is equipped with a control system, a pressure sensor, an electric valve, a pressure relief valve and a clamp. The pressure sensor detects the pipeline medium pressure and the clamping force of the clamp in real time. The control system automatically completes the linkage operation of valve opening and closing, clamp loosening and clamping, and pressure relief valve opening and closing based on the detection data, realizing fully automatic intelligent switching between high and low pressure conditions. No manual intervention is required throughout the process, improving operating efficiency and convenience.

[0030] The present invention reserves gaps not less than the axial compensation amount of the expansion joint between the flange assembly and the clamp, and between the first end ring flange and the second end ring flange. This effectively avoids structural interference in the displacement compensation of the inner bellows under low-pressure vibration reduction conditions, and fully meets the actual needs of high-pressure pipelines for large axial and lateral displacement compensation, ensuring the smoothness of displacement compensation under all working conditions. Attached Figure Description

[0031] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0032] Figure 1 This is a schematic diagram of the expansion joint structure of the present invention with the clamp in a relaxed state and a gap between the first end ring flange and the second end ring flange;

[0033] Figure 2 This is a schematic diagram of the expansion joint structure of the present invention, in which the clamping fixture is in a clamped state and the first end ring flange and the second end ring flange are fitted and sealed together.

[0034] Figure 3 This is a schematic diagram of the expansion joint structure of the present invention, which consists of two sets of corrugated sleeves connected in series.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1. Control system; 2. End pipe; 3. Valve; 4. Bolt; 5. First end ring flange; 6. Second end ring flange; 7. Seal; 8. Clamp; 9. Outer bellows; 10. Inner bellows; 11. Third end ring flange; 12. Pressure relief valve; 13. Intermediate pipe; 14. Outer intermediate pipe; 15. Inner intermediate pipe. Detailed Implementation

[0037] The present invention will be further described below with reference to specific embodiments. First, it should be noted that the data in the following embodiments were obtained by the inventors through verification. Due to space limitations, only a portion of these data is shown in the specification, and those skilled in the art can understand and implement the present invention based on this data. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various modifications or alterations to the invention, and these modifications or alterations also fall within the scope of protection of this application.

[0038] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0039] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0040] This invention provides an expansion joint, including a corrugated sleeve. The corrugated sleeve includes an inner corrugated pipe 10 and an outer corrugated pipe 9 sleeved around it. The inner corrugated pipe 10 forms a main medium channel. A flange assembly is provided at one end of the corrugated sleeve. The flange assembly includes a first end ring flange 5 and a second end ring flange 6. The first end ring flange 5 is connected to the inner corrugated pipe 10, and the second end ring flange 6 is connected to the outer corrugated pipe 9. There is a gap between the first end ring flange 5 and the second end ring flange 6. The first end ring flange 5 and the second end ring flange 6 can move relative to each other to form a closed first chamber between the inner corrugated pipe 10 and the outer corrugated pipe 9. Then, the first chamber communicates with the main medium channel.

[0041] It should be noted that the medium can be either liquid or gas, and this invention does not limit this. When the pipeline pressure (the pressure inside the inner bellows 10) gradually increases to a set value, the first end ring flange 5 and the second end ring flange 6 approach each other, forming a closed first chamber between the inner bellows 10 and the outer bellows 9. Then, the first chamber is connected to the main medium channel, and eventually the medium pressure in the first chamber will be consistent with the pressure inside the inner bellows 10. Under high pressure, the pressure difference between the inner and outer surfaces of the inner bellows 10 is 0, and it no longer bears pressure. The pressure of the pipeline medium is borne by the outer bellows 9.

[0042] In a preferred embodiment of this invention, the expansion joint further includes an end pipe 2, one end of which is connected to the first chamber and the other end of which is connected to the main medium channel.

[0043] In this embodiment, the system also includes a valve 3 and a control system 1 electrically connected to the valve 3. The two ends of the valve 3 are respectively connected to the main medium channel and the first chamber. The control system 1 controls the opening and closing of the valve 3 to realize the connection between the main medium channel and the first chamber.

[0044] In this embodiment, a pressure relief valve 12 and a control system 1 electrically connected to the pressure relief valve 12 are also included. One end of the pressure relief valve 12 is connected to the first chamber, and the control system 1 controls the opening and closing of the pressure relief valve 12 to balance the pressure in the first chamber.

[0045] In a preferred embodiment, the other end of the pressure relief valve 12 is connected to another pipeline that is connected to the expansion joint.

[0046] In this embodiment, a third end ring flange 11 is also included, which is disposed on the side of the bellows away from the flange assembly.

[0047] In this embodiment, the flange assembly is provided with a clamp 8 for clamping or releasing the first end ring flange 5 and the second end ring flange 6. When the clamp 8 clamps, it drives the first end ring flange 5 and the second end ring flange 6 to move closer to the seal. When it releases, it drives the first end ring flange 5 and the second end ring flange 6 to separate.

[0048] like Figure 1 As shown, in a preferred embodiment, the expansion joint further includes an end pipe 2, a valve 3, a pressure relief valve 12, a clamp 8, and a control system 1, wherein the valve 3, the pressure relief valve 12, and the clamp 8 are all electrically connected to the control system 1; one end of the end pipe 2 is connected to the main medium channel, and a through hole on the circumferential surface of the other end is connected to a first chamber formed between the first end ring flange 5 and the second end ring flange 6; the valve 3 is disposed between the end pipe 2 and the first chamber, and the valve 3 is fixedly connected to the first end ring flange 5 on the side away from the end pipe 2; the clamp 8 is disposed on the outside of the first end ring flange 5 and the second end ring flange 6, and is used to drive the second end ring flange 6 to fit and seal with the first end ring flange 5 to form the first chamber; The corrugated sleeve has a third end ring flange 11 on the side away from the flange assembly. The third end ring flange 11 has a through hole. The pressure relief valve 12 is located on the side of the third end ring flange 11 with the through hole, so that the medium can flow from the first chamber to other pipelines connected to the expansion joint. The expansion joint also includes a pressure sensor, and the control system 1 is also electrically connected to the pressure sensor. The pressure sensor is used to detect the pressure of the main medium channel of the inner corrugated pipe 10, the pressure of the first chamber, and the clamping force of the clamp 8 on the first end ring flange 5 and the second end ring flange 6. The control system 1 controls the clamp 8 to clamp or loosen, and the valve 3 and the pressure relief valve 12 to open and close according to the pressure signal detected by the pressure sensor.

[0049] It should be noted that, as Figure 1 As shown, when the pipeline pressure P < P1 (P1 is the preset low pressure upper limit of control system 1), the pipeline is in a low pressure condition: valve 3 and pressure relief valve 12 are both closed, and the medium in the pipeline cannot pass through the through hole on the circumferential surface of end pipe 2, valve 3, first end ring flange 5, and second end ring flange 6 to enter the cavity formed by the outer side of the inner bellows 10 and the inner side of the outer bellows 9; clamp 8 is in a loose state, the second end ring flange 6 and the first end ring flange 5 do not contact each other, and the gap between them is not less than the axial compensation of the expansion joint, and the gap between clamp 8 and the side of the second end ring flange 6 is not less than the axial compensation of the expansion joint; at this time, the outer bellows 9 does not participate in the work, only the inner bellows 10 bears the pressure and works, the overall stiffness of the expansion joint is small, and it has excellent pipeline vibration reduction capability.

[0050] like Figure 2As shown, when the pipeline pressure P gradually increases to P1, the pressure relief valve 12 remains closed: the pressure sensor identifies the pipeline pressure (pressure inside the inner bellows 10) and transmits the signal to the control system 1. The control system 1 sends a signal to drive the clamp 8 to clamp. At this time, the second end ring flange 6 moves closer to the first end ring flange 5 until the preset clamping force is reached and maintained, thus achieving a sealing fit between the end faces of the first end ring flange 5 and the second end ring flange 6. After the clamp 8 reaches the preset clamping force, the control system 1 sends a signal to drive the valve 3 to open. The medium inside the pipeline (inside the inner bellows 10) enters the first chamber formed by the outer side of the inner bellows 10 and the outer bellows 9 through the through hole on the circumferential surface of the end pipe 2, the valve 3, the first end ring flange 5, and the second end ring flange 6. Finally, the medium pressure in this space is consistent with the pressure inside the pipeline, and the valve 3 remains open. Under high pressure conditions, the pressure difference between the inner and outer surfaces of the inner bellows 10 is 0, and it no longer bears pressure. The outer bellows 9 alone bears the pipeline medium pressure.

[0051] When the pipeline pressure P > P1, the expansion joint maintains the working state when P = P1: the clamp 8 is in the locked state, the mating surfaces of the first end ring flange 5 and the second end ring flange 6 remain sealed, the valve 3 remains open, the pressure relief valve 12 remains closed, and the outer bellows 9 still bears the pipeline medium pressure.

[0052] When the pipeline pressure drops to P < P1, the pressure sensor identifies the pressure inside the pipeline and transmits the signal to the control system 1. The control system 1 first sends a closing signal to valve 3, driving valve 3 to change from open to closed. After valve 3 is completely closed, the control system 1 sends an opening signal to pressure relief valve 12, driving pressure relief valve 12 to change from closed to open. The medium in the first chamber flows through pressure relief valve 12 to other pipelines in the pipeline system, and then connects with the main channel of the medium. When the pressure sensor identifies that the medium pressure in this space is close to atmospheric pressure, the control system 1 sends a closing signal to pressure relief valve 12, driving pressure relief valve 12 to close.

[0053] After the pressure relief valve 12 is completely closed, the control system 1 sends a release signal to the clamp 8, driving the clamp 8 to perform the release action. Under the elastic force of the outer bellows 9, the second end ring flange 6 is disengaged from the first end ring flange 5. The residual medium in the space formed by the outer side of the inner bellows 10 and the inner side of the outer bellows 9 flows into the collection container set between the outer side of the inner bellows 10 and the inner side of the outer bellows 9 under its own weight. At this time, the expansion joint resumes to bear the pipeline medium pressure alone by the inner bellows 10.

[0054] The expansion joint provided in this embodiment can achieve low stiffness design under low pressure conditions while ensuring load-bearing capacity under high pressure conditions, thereby meeting the vibration reduction requirements under low pressure conditions, effectively solving the technical contradiction between high pressure load-bearing and low pressure vibration reduction, and has a compact structure, small space occupation, and stronger applicability.

[0055] In a preferred embodiment, the first end ring flange 5 and / or the second end ring flange 6 have grooves on their opposite flat end faces near the second end ring flange 6. A sealing element 7 is provided in the grooves. A gap is left between the second end ring flange 6 and the first end ring flange 5. The gap is not less than the axial compensation amount of the expansion joint. When the clamp 8 is clamped, the sealing element 7 achieves a sealing fit between the first end ring flange 5 and the second end ring flange 6.

[0056] In a preferred embodiment, one end of the clamp 8 is fixed to the flat end face or circumferential side of the first end ring flange 5 near the end pipe 2 by bolts 4 or welding, and the other end is placed outside the flat end face of the second end ring flange 6 near the outer bellows 9, with a gap between the clamp 8 and the second end ring flange 6, the gap being not less than the axial compensation of the expansion joint; or, one end of the clamp 8 is fixed to the flat end face or circumferential side of the second end ring flange 6 near the bellows sleeve by bolts 4 or welding, and the other end is placed outside the flat end face of the first end ring flange 5 near the end pipe 2, with a gap between the clamp 8 and the first end ring flange 5, the gap being not less than the axial compensation of the expansion joint.

[0057] In a preferred embodiment, the clamp 8 is hydraulically or electrically driven.

[0058] In this embodiment, when the clamp 8 is in the relaxed state, there are gaps between the first end ring flange 5 and the second end ring flange 6, and between the flange assembly and the clamp 8. The amount of these gaps is not less than the axial compensation amount of the expansion joint.

[0059] In this embodiment, there are multiple clamps 8 arranged at intervals along the circumferential direction of the flange assembly.

[0060] like Figure 3 As shown, in this embodiment, there are multiple corrugated sleeves, and adjacent corrugated sleeves are connected by an intermediate tube 13. Specifically, the intermediate tube 13 includes an inner intermediate tube 15 and an outer intermediate tube 14 sleeved around it. Adjacent inner corrugated tubes 10 are connected by the inner intermediate tube 15, and adjacent outer corrugated tubes 9 are connected by the outer intermediate tube 14.

[0061] In this embodiment, the inner corrugated pipe 10 is a low-stiffness structure, adopting an unreinforced U-shaped or multi-layer thin-walled reinforced U-shaped structure; the outer corrugated pipe 9 is a high-stiffness structure, adopting a reinforced U-shaped or Ω-shaped structure.

[0062] It should be explained that under low-pressure conditions, the inner corrugated pipe bears the main load and meets the pressure and displacement compensation requirements under low-pressure conditions. Its stiffness is relatively low, and it usually adopts an unreinforced U-shaped or multi-layer thin-walled reinforced U-shaped structure. Under high-pressure conditions, the outer corrugated pipe bears the main load and meets the pressure and displacement compensation requirements under high-pressure conditions. Its stiffness is relatively high and it is not easy for column instability to occur. It usually selects a reinforced U-shaped or Ω-shaped structure.

[0063] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. An expansion joint, characterized in that, The system includes a corrugated sleeve, which includes an inner corrugated pipe (10) and an outer corrugated pipe (9) sleeved around it. The inner corrugated pipe (10) is used to form the main medium channel. A flange assembly is provided at one end of the corrugated sleeve. The flange assembly includes a first end ring flange (5) and a second end ring flange (6). The second end ring flange (6) is connected to the outer corrugated pipe (9). The first end ring flange (5) is connected to the inner corrugated pipe (10). There is a gap between the first end ring flange (5) and the second end ring flange (6). The first end ring flange (5) and the second end ring flange (6) can move relative to each other to form a closed first chamber between the inner corrugated pipe (10) and the outer corrugated pipe (9). Then the first chamber is connected to the main medium channel.

2. The expansion joint according to claim 1, characterized in that, It also includes a valve (3) and a control system (1) electrically connected to the valve (3). The two ends of the valve (3) are respectively connected to the main medium channel and the first chamber. The control system (1) controls the opening and closing of the valve (3) to realize the connection between the main medium channel and the first chamber.

3. The expansion joint according to claim 1, characterized in that, It also includes a pressure relief valve (12) and a control system (1) electrically connected to the pressure relief valve (12). One end of the pressure relief valve (12) is connected to the first chamber. The control system (1) controls the opening and closing of the pressure relief valve (12) to balance the pressure in the first chamber.

4. The expansion joint according to claim 1, characterized in that, It also includes a third end ring flange (11), which is disposed on the side of the bellows away from the flange assembly.

5. The expansion joint according to claim 1, characterized in that, The flange assembly is provided with a clamp (8) for clamping or releasing the first end ring flange (5) and the second end ring flange (6). When the clamp (8) clamps, it drives the first end ring flange (5) and the second end ring flange (6) to approach the seal. When it releases, it drives the first end ring flange (5) and the second end ring flange (6) to separate.

6. The expansion joint according to claim 5, characterized in that, When the clamp (8) is in the relaxed state, there are gaps between the first end ring flange (5) and the second end ring flange (6), and between the flange assembly and the clamp (8), and the gap amount is not less than the axial compensation amount of the expansion joint.

7. The expansion joint according to claim 5, characterized in that, The clamps (8) are multiple and are spaced apart along the circumferential direction of the flange assembly.

8. The expansion joint according to claim 1, characterized in that, The corrugated sleeve has multiple layers. Adjacent inner corrugated sleeves (10) are connected by an inner intermediate tube (15), and adjacent outer corrugated sleeves (9) are connected by an outer intermediate tube (14).

9. The expansion joint according to claim 1, characterized in that, The inner corrugated pipe (10) is a low-rigidity structure, using an unreinforced U-shaped or multi-layer thin-walled reinforced U-shaped structure; the outer corrugated pipe (9) is a high-rigidity structure, using a reinforced U-shaped or Ω-shaped structure.

10. The expansion joint according to claim 5, characterized in that, It also includes a pressure sensor and a control system (1) electrically connected to the pressure sensor. The control system (1) is also electrically connected to the clamp (8). The pressure sensor is used to detect the pressure of the main medium channel of the inner bellows (10), the pressure of the first chamber, and the clamping force of the clamp (8) on the first end ring flange (5) and the second end ring flange (6). The control system (1) controls the clamp (8) to clamp or loosen according to the pressure signal detected by the pressure sensor.

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