Pressure balance type expansion joint with monitoring and leakage handling functions

Abstract

The invention provides a pressure balance type expansion joint with monitoring and leakage disposal functions, which comprises an inlet pipe, an outlet pipe, a working corrugated pipe, a balance corrugated pipe, an inlet annular plate assembly, an outer pipe assembly, an outlet annular plate assembly, a first annular plate assembly, a second annular plate assembly and a third annular plate assembly, and is provided with a leakage emergency disposal device, the method is used for carrying out emergency treatment on medium leakage of the balance corrugated pipe, prolonging the service life of the expansion joint, monitoring the operation state of the expansion joint in real time, and realizing fatigue life analysis and abnormal state alarm of the expansion joint.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pressure pipelines, in particular to a pressure balance type expansion joint with monitoring and leakage handling functions. BACKGROUND

[0002] The pressure balance type expansion joint is a device specially designed to absorb the thermal expansion and contraction, vibration and other displacements of the pipeline system, while balancing the pressure fluctuations in the system. As shown in FIG. 1, it is usually composed of an inlet pipe, an outlet pipe, a working bellows, a balance bellows, an inlet ring plate assembly, an outer pipe assembly, an outlet ring plate assembly, a first ring plate assembly, a second ring plate assembly and a third ring plate assembly; the working bellows and the balance bellows are located between the inlet pipe, the outlet pipe, the inlet ring plate assembly, the outer pipe assembly and the outlet ring plate assembly; the two ends of the inlet ring plate assembly are connected with the inlet pipe and the outer pipe assembly respectively, and the outlet ring plate assembly is connected with the outer pipe assembly and the balance bellows; the two ends of the working bellows are connected with the first ring plate assembly and the second ring plate assembly respectively, and the two ends of the balance bellows are connected with the third ring plate assembly and the outlet ring plate assembly respectively. It is usually applied to high-temperature and high-pressure equipment connection, long-distance transportation pipelines and special pipeline systems. Figure 3

[0003] The bellows, as the core component of the expansion joint, its fatigue life is affected by many factors, such as displacement overload, over-temperature and overpressure, etc., which makes the evaluation of its working state complex and difficult. Due to the existence of these uncertain factors, the medium leakage problem is difficult to completely avoid, thereby further increasing the operation risk. Once the medium leakage occurs, how to carry out the rapid and effective emergency disposal becomes a big challenge. Therefore, the leakage problem of the bellows has become a technical difficulty that needs to be solved urgently, and at the same time highlights the importance of improving the monitoring means and optimizing the design (to deal with the leakage), which has a key significance for improving the overall reliability and safety of the expansion joint. At the same time, as the core element to realize the displacement compensation, the change of the displacement compensation amount of the bellows usually needs to be monitored in real time. The traditional manual periodic inspection method not only cannot achieve the purpose of instant monitoring, but also increases the maintenance labor cost. Therefore, the digital intelligentization of the expansion joint operation monitoring and emergency disposal has become an urgent demand of the industry development.

[0004] Chinese patent CN205842075U discloses a bypass straight pipe pressure type expansion joint with leakage monitoring function, which utilizes the structural characteristics of the outer pressure bypass straight pipe pressure balance type expansion joint, and through the detection of the non-pressure cavity, the real-time monitoring of the trace leakage can be realized, which is especially suitable for the expansion joint of high-risk medium such as toxic, harmful, flammable and explosive. However, the expansion joint does not have the functions of automatic disposal of medium leakage and compensation amount change monitoring.

[0005] ​Therefore, there is a need for a pressure balanced expansion joint with monitoring and leakage handling functions to meet the actual needs. SUMMARY

[0006] The present application aims to provide a pressure balanced expansion joint with monitoring and leakage handling functions, which can be used for emergency treatment of the leakage of the balanced bellows, prolong the service life of the expansion joint, and can monitor the operation state of the expansion joint in real time, analyze the fatigue life of the expansion joint, and alarm the abnormal state.

[0007] To achieve the above-mentioned purpose, the present application provides a pressure balanced expansion joint with monitoring and leakage handling functions. The technical scheme of the present application is as follows:

[0008] The pressure balanced expansion joint with monitoring and leakage handling functions comprises an inlet pipe, an outlet pipe, a working bellows, a balanced bellows, an inlet ring plate assembly, an outer pipe assembly, an outlet ring plate assembly, a first ring plate assembly, a second ring plate assembly, and a third ring plate assembly. The expansion joint is provided with a leakage emergency handling device for emergency treatment of the medium leakage of the balanced bellows. The leakage emergency handling device is arranged on the outer wall of the outlet pipe and connected with the outlet ring plate assembly. This arrangement can effectively prevent further leakage of the medium, thereby prolonging the service life of the expansion joint and reducing the loss caused by emergency shutdown.

[0009] Further, the leakage emergency handling device comprises a stuffing pump, a stuffing injection pipe, and a buffer cavity. The stuffing injection pipe is connected with the stuffing pump and the buffer cavity. When leakage occurs, the stuffing pump works to inject the stuffing into the buffer cavity through the stuffing injection pipe to block the medium leakage from the balanced bellows.

[0010] Further, a connecting pipe is arranged on the outlet ring plate assembly, and the leakage emergency handling device is connected with the outlet ring plate assembly through the connecting pipe. The connecting pipe provides physical structure support for the balanced bellows detection pipe and the leakage emergency handling device. When the balanced bellows leaks, the medium will overflow along the connecting pipe in the first non-pressure area, and at this time, the overflowing medium will be detected by the balanced bellows monitor.

[0011] Further, the buffer cavity is a closed cavity surrounded by the connecting pipe, a blocking piece, a sealing piece, and the outlet pipe. The baffle one and the baffle two are arranged on the connecting pipe. The baffle one is connected with the blocking piece, the baffle two is connected with the gland, and the sealing piece is located between the baffle two and the gland. The buffer cavity is used to accommodate the stuffing when leakage occurs, to achieve the sealing effect, and to prevent the medium from leaking.

[0012] Further, the third ring plate assembly, the inner side of the balance bellows, the outlet ring plate assembly, the leakage emergency treatment device and the outer side of the outlet pipe form a closed first non-pressure zone; the expansion joint is provided with a balance bellow detection pipe and a balance bellow monitor, the detection end of the balance bellow detection pipe is located in the first non-pressure zone, and the other end is connected with the balance bellow monitor; according to the monitoring result of the balance bellow monitor, the leakage emergency treatment device implements leakage treatment. The balance bellow monitor monitors the leakage of the balance bellow through the balance bellow detection pipe, records the monitoring data; when leakage occurs, an early warning is given and a leakage treatment instruction is sent to the leakage emergency treatment device 17.

[0013] Further, the expansion joint is provided with a displacement compensation monitoring device, which comprises a laser displacement sensor, a reflecting plate and a sensor mounting plate, the sensor mounting plate is located on the outer wall of the connecting pipe / outlet pipe, the reflecting plate is located on the outer pipe assembly, and the laser displacement sensor is located on the sensor mounting plate. Through the displacement compensation monitoring device, the displacement state of the expansion joint caused by starting, stopping, temperature fluctuation and the like can be displayed and recorded in real time, and real-time analysis of the fatigue life of the expansion joint can be realized; after setting a threshold value of displacement, an overrun alarm function can be provided.

[0014] Further, the first ring plate assembly, the inner side of the working bellow and the second ring plate assembly form a closed second non-pressure zone; the expansion joint is further provided with a working bellow detection pipe and a working bellow monitor, the detection end of the working bellow detection pipe is located in the second non-pressure zone, and the other end is connected with the working bellow monitor. When the working bellow leaks, the working bellow monitor detects the leakage medium signal in the second non-pressure zone through the working bellow detection pipe, reports to the upper computer, and realizes leakage alarm.

[0015] Further, the average diameter of the working bellow is greater than the average diameter of the balance bellow, so that the expansion joint has a self-adaptive pressure balance capability.

[0016] Further, the inlet ring plate assembly is an elliptical head structure. This setting can effectively disperse pressure, has high safety, can thin the thickness of the ring plate material, reduce the material cost, and is also beneficial to the flow of fluid in the pipe and reduces the residual dead angle of the medium.

[0017] Further, the outer pipe assembly is a tapered segment structure and adopts a butt weld, which can greatly reduce the stress level at the weld and improve the reliability of the pressure-bearing part.

[0018] Compared with the prior art, the pressure balance type expansion joint with monitoring and leakage treatment functions has the following advantages:

[0019] 1. The present application can realize emergency treatment when the balance bellow leaks, thereby prolonging the service life of the expansion joint.

[0020] 2. The application can monitor the operating state of the expansion joint in real time, including monitoring the leakage of the working bellows and the balance bellows and the change of displacement compensation, realizing fatigue life analysis and abnormal state alarm of the expansion joint.

[0021] 3. The application can realize self-adaptive pressure balance of the expansion joint according to the waveform parameter control. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Structure diagram of the pressure balance type expansion joint with monitoring and leakage treatment function according to embodiment 1 of the application;

[0023] Figure 2 Structure diagram of the leakage emergency treatment device according to embodiment 1 of the application;

[0024] Figure 3 Structure diagram of the existing pressure balance type expansion joint.

[0025] Explanation of reference signs:

[0026] 1, inlet pipe; 2, working bellow detection pipe; 3, working bellow monitor; 4, inlet ring plate assembly; 5, first ring plate assembly; 6, working bellow; 7, outer pipe assembly; 8, second ring plate assembly; 9, third ring plate assembly; 10, balance bellow; 11, outlet ring plate assembly; 12, balance bellow monitor; 13, balance bellow detection pipe; 14, filler injection pipe; 15, filler pump; 16, outlet pipe; 17, leakage emergency treatment device; 18, sensor mounting plate; 19, laser displacement sensor; 20, reflecting plate; 171, connecting pipe; 172, baffle one; 173, blocking piece; 174, buffer cavity; 175, sealing piece; 176, gland; 177, baffle two; 178, air guide pipe. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the described embodiments are part of the embodiments of the application, rather than all the embodiments. The specific embodiments described herein are only used to explain the application, and are not used to limit the application. It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other without conflict.

[0028] One of the embodiments of the application will be specifically described below in combination with the drawings.

[0029] Embodiment 1

[0030] A pressure balance type expansion joint with monitoring and leakage treatment function, referred to as expansion joint, like Figure 1As shown, the expansion joint comprises an inlet pipe 1, an outlet pipe 16, a working bellow 6, a balance bellow 10, an inlet ring plate assembly 4, an outer pipe assembly 7, an outlet ring plate assembly 11, a first ring plate assembly 5, a second ring plate assembly 8 and a third ring plate assembly 9. The expansion joint is provided with a leakage emergency treatment device 17 for emergency treatment of the medium leakage of the balance bellow 10.

[0031] In order to realize the monitoring and leakage emergency treatment functions of the balance bellow 10, a connecting pipe 171 is arranged on the outlet ring plate assembly 11, and a balance bellow detection pipe 13 and the leakage emergency treatment device 17 are installed on the connecting pipe 171.

[0032] The detection end of the balance bellow detection pipe 13 penetrates through the connecting pipe 171 and is located in the first non-pressure area, and the other end is connected with a balance bellow monitor 12. The balance bellow monitor 12 is installed at the end of the balance bellow detection pipe 13. The balance bellow monitor 12 monitors the leakage of the balance bellow 10 through the balance bellow detection pipe 13, records the monitoring data, and sends a leakage treatment instruction to the leakage emergency treatment device 17 when leakage occurs.

[0033] The connecting pipe 171 provides physical structural support for the balance bellow detection pipe 13 and the leakage emergency treatment device 17. When the balance bellow 10 leaks, the medium will overflow along the connecting pipe 171 in the first non-pressure area, and at this time, the overflowing medium will be detected by the balance bellow monitor 12.

[0034] The leakage emergency treatment device 17 is used for emergency treatment of the medium leakage of the balance bellow 10. The leakage emergency treatment device 17 is arranged on the outer wall of the outlet pipe 16 and is connected with the outlet ring plate assembly 11 through the connecting pipe 171. The third ring plate assembly 9, the inner side of the balance bellow 10, the outlet ring plate assembly 11, the leakage emergency treatment device 17 and the outer side of the outlet pipe 16 form a closed first non-pressure area. The leakage emergency treatment device 17 performs leakage treatment according to the instruction of the balance bellow monitor 12.

[0035] As shown in Figure 2 The leakage emergency treatment device 17 comprises a buffer cavity 174, a filler injection pipe 14, a gas guide pipe 178 and a filler pump 15. The filler injection pipe 14 connects the filler pump 15 and the buffer cavity 174. When leakage occurs, the filler pump 15 works to inject filler into the buffer cavity 174 through the filler injection pipe 14 to block the medium leakage from the balance bellow 10. The gas guide pipe 178 is connected to the top of the buffer cavity 174 and is in communication with the buffer cavity 174 and the atmosphere when filled. The gas guide pipe 178 can be replaced by other structure forms such as a hole.

[0036] The buffer cavity 174 is a closed cavity surrounded by the connecting pipe 171, the blocking piece 173, the sealing piece 175 and the outlet pipe 16, used to accommodate the filler when leakage occurs, achieve sealing effect and prevent medium leakage. The baffle one 172 and the baffle two 177 are both arranged on the connecting pipe 171, the baffle one 172 is connected with the blocking piece 173, the baffle two 177 is connected with the gland 176, and the sealing piece 175 is located between the baffle two 177 and the gland 176. The baffle one 172 is used to fix the blocking piece 173, and the baffle two 177 and the gland 176 are used to fix the sealing piece 175 together. The blocking piece 173 is installed on the side of the buffer cavity 174 of the baffle one 172, used to prevent the filler from entering the left cavity when emergency treatment of leakage occurs. The sealing piece 175 is tightly fixed by the baffle two 177 and the gland 176 to form the first level sealing of the first non-pressure area. The filler injection pipe 14 is a channel for injecting the filler into the buffer cavity 174. The filler pump 15 is used to provide power for injecting the filler. The filler is selected according to the specific characteristics of the medium, and is preferably mud-like oily graphite. When filling, the air in the buffer cavity 174 is guided out through the air guide pipe 178.

[0037] Preferably, the blocking piece 173 is a high-temperature rubber pad, the sealing piece 175 is a graphite packing with a wedge-shaped cross section, and the gland 176 is connected to the sealing piece 175 by bolts to tightly press the sealing piece 175 against the baffle two 177.

[0038] Preferably, the buffer cavity 174 is connected to the air guide pipe 178 in an inverted funnel shape, which helps to discharge the air in the cavity and makes the filler filling rapid and sufficient.

[0039] When no leakage occurs, the rainwater, dust and other environmental factors cannot enter the balance bellows 10 under the blocking effect of the sealing piece 175 and the blocking piece 173, which can reduce the risk of corrosion of the balance bellows 10 by the outside world. When leakage occurs, the balance bellows monitor 12 detects the leakage medium signal in the first non-pressure area and transmits the signal to the filler pump 15. The filler pump 15 starts to work upon receiving the instruction from the balance bellows monitor 12. The filler pump 15 controls the valves of the air guide pipe 178 and the filler injection pipe 14 to be opened, and the filler is injected into the buffer cavity 174 through the filler injection pipe 14, and the gas in the buffer cavity 174 is discharged through the air guide pipe 178. When the buffer cavity 174 is filled with the filler, the valves of the air guide pipe 178 and the filler injection pipe 14 are closed to form the second level sealing of the first non-pressure area. At this time, the first non-pressure area is sealed by the two levels of the filler and the sealing piece 175, forming a leakage isolation state, which can effectively prevent the medium from further leaking out of the expansion joint, thereby prolonging the service life of the expansion joint and reducing the loss caused by emergency shutdown.

[0040] In order to monitor the working bellows 6, the expansion joint is provided with a working bellows detection pipe 2 and a working bellows monitor 3. The working bellows monitor 3 monitors the working bellows 6 for leakage through the working bellows detection pipe 2. The detection end of the working bellows detection pipe 2 is located in the second non-pressure area, and the other end is connected with the working bellows monitor 3. When the working bellows 6 leaks, the working bellows monitor 3 detects the leakage medium signal in the second non-pressure area through the working bellows detection pipe 2, and reports to the upper computer to realize leakage alarm.

[0041] Preferably, the working bellows monitor 3 and the balance bellows monitor 12 adopt non-pressure type leakage monitoring, which can monitor specific gas or volatile organic compounds, and has high sensitivity.

[0042] In order to monitor the displacement compensation of the expansion joint, a displacement compensation monitoring device is arranged on the outer wall of the expansion joint, which comprises a laser displacement sensor 19, a reflecting plate 20 and a sensor mounting plate 18, as shown in Figure 1 The laser displacement sensor 19 is located on the sensor mounting plate 18, and the sensor mounting plate 18 is located on the outer wall of the connecting pipe 171 / outlet pipe 16, which is used to fix and install the laser displacement sensor 19. The reflecting plate 20 is located on the outer pipe assembly 7 of the expansion joint, and cooperates with the laser displacement sensor 19. During operation, the laser displacement sensor 19 emits laser, which is reflected back when encountering the reflecting plate 20 opposite to the position, and the laser displacement sensor 19 records the reflection data. Finally, the measurement result is obtained by calculation, and compared with the previous data to obtain the displacement change of the outer pipe wall of the expansion joint. Through the displacement compensation monitoring device, the displacement state of the expansion joint caused by start-up, shutdown, temperature fluctuation and the like can be recorded in real time, and real-time analysis of the fatigue life of the expansion joint can be realized; after setting the threshold of displacement, the over-limit alarm function can be realized.

[0043] Preferably, the sensor mounting plate 18 is located on the outer wall of the connecting pipe 171, and the reflecting plate 20 is located at the tail section of the tapered structure of the outer pipe assembly 7.

[0044] In order to make the expansion joint have self-adaptive pressure balance ability, the wave parameters are controlled, so that the average diameter of the working bellows 6 is greater than the average diameter of the balance bellows 10. The first ring plate assembly 5, the inner side of the working bellows 6 and the second ring plate assembly 8 form a second non-pressure area, which is a closed cavity. During the operation of the pipe system, according to the ideal gas state equation PV=nRT, it can be known that the internal pressure of the second non-pressure area becomes larger due to the influence of high temperature. The balance bellows 10 is in communication with the outside, and always bears atmospheric pressure. If the working bellows 6 and the balance bellows 10 have the same wave parameters, they will bear different pressures. In order to balance the stress of the expansion joint, the numerical relationship between the average diameters of the working bellows 6 and the balance bellows 10 should be designed. The formula derivation is as follows:

[0045] P is the pressure under working condition, T is the temperature under working condition, V is the volume of the second non-pressure area, is the internal pressure of the second non-pressure area under working condition. The value at normal temperature , the value at atmospheric pressure . According to the ideal gas state equation PV = nRT, we can get:

[0046] (1)

[0047] We can get:

[0048] (2)

[0049] Under the working condition, according to GB / T12777, the thrust provided by the working bellows 6 is:

[0050] (3)

[0051] Wherein: is the effective area of the working bellows 6; is the average diameter of the working bellows 6.

[0052] The thrust provided by the balance bellows 10 is:

[0053] (4)

[0054] Wherein: is the effective area of the balance bellows 10; is the average diameter of the balance bellows 10.

[0055] In order to balance the stress of the expansion joint, we need to make:

[0056] (5)

[0057] By substituting equation 3 and equation 4, we can get the relationship between the average diameter of the working bellows 6 and the average diameter of the balance bellows 10:

[0058] (6)

[0059] According to equation 6, the average diameters of the working bellows 6 and the balance bellows 10 of the expansion joint can be designed to meet the pressure balance requirement, that is, the average diameter of the working bellows 6 should be greater than the average diameter of the balance bellows 10.

[0060] The inlet ring plate assembly 4 is an elliptical head structure. This setting can effectively disperse pressure and has high safety; and can thin the material thickness of the ring plate, reduce the material cost; also can be beneficial to the flow of fluid in the pipe, reduce the medium residual dead angle.

[0061] The outer tube assembly 7 is a cone-section structure and adopts butt welding, which can greatly reduce the stress level at the weld and improve the reliability of the pressure-bearing parts. Figure 3 The fillet weld I in is replaced by Figure 1 The butt weld II in the expansion joint can greatly reduce the stress level and reduce the potential risk to the safe operation of the expansion joint.

[0062] It should be noted that all terms used in the present invention to indicate direction and position, such as: "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "inside", "outside", "top", "low", "tail end", "head end", "center", etc., are only used to explain the relative position relationship and connection status between the components in a certain state, and are only for the convenience of describing the present invention, rather than requiring the present invention to be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention. In addition, the descriptions of "first", "second", etc. in the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. In addition, the meaning of "and / or" appearing throughout the text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which both A and B are satisfied.

[0063] In the present invention, unless otherwise specified or limited, the terms "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can mean fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will be able to understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0064] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A pressure-balancing expansion joint with monitoring and leakage disposal functions, comprising an inlet pipe (1), an outlet pipe (16), a working bellows (6), a balancing bellows (10), an inlet ring plate assembly (4), an outer pipe assembly (7), an outlet ring plate assembly (11), a first ring plate assembly (5), a second ring plate assembly (8) and a third ring plate assembly (9), characterized in that: The expansion joint is provided with a leakage emergency treatment device (17) for emergency treatment of medium leakage from the balancing bellows (10); the leakage emergency treatment device (17) is provided on the outer wall of the outlet pipe (16) and is connected to the outlet ring plate assembly (11).

2. The expansion joint according to claim 1, characterized in that The leakage emergency disposal device (17) comprises a stuffing pump (15), a stuffing injection pipe (14) and a buffer chamber (174), wherein the stuffing injection pipe (14) connects the stuffing pump (15) and the buffer chamber (174); when a leakage occurs, the stuffing pump (13) operates to inject stuffing into the buffer chamber (154) through the stuffing injection pipe (12), thereby preventing the medium from leaking from the balancing bellows (10).

3. The expansion joint according to claim 2, characterized in that A connecting pipe (171) is provided on the outlet ring plate assembly (11), and the leakage emergency disposal device (17) is connected to the outlet ring plate assembly (11) via the connecting pipe (171).

4. The expansion joint according to claim 3, characterized in that The buffer chamber (174) is a closed chamber surrounded by a connecting pipe (171), a blocking member (173), a sealing member (175) and an outlet pipe (16); baffle plate 1 (172) and baffle plate 2 (177) are both arranged on the connecting pipe (171), baffle plate 1 (172) is connected to the blocking member (173), baffle plate 2 (177) is connected to the pressure cover (176), and the sealing member (175) is located between baffle plate 2 (177) and the pressure cover (176).

5. The expansion joint according to claim 1, characterized in that The third ring plate assembly (9), the inner side of the balancing bellows (10), the outlet ring plate assembly (11), the leakage emergency disposal device (17) and the outer side of the outlet pipe (16) form a closed first non-pressure zone; the expansion joint is provided with a balancing bellows detection tube (13) and a balancing bellows monitor (12); the detection end of the balancing bellows detection tube (13) is located in the first non-pressure zone, and the other end is connected to the balancing bellows monitor (12); according to the monitoring result of the balancing bellows monitor (12), the leakage emergency disposal device (17) implements leakage disposal.

6. The expansion joint according to claim 3, characterized in that The expansion joint is provided with a displacement compensation monitoring device, comprising a laser displacement sensor (19), a reflective plate (20) and a sensor mounting plate (18), wherein the sensor mounting plate (18) is located on the outer wall of the connecting pipe (171) / outlet pipe (16), the reflective plate (20) is located on the outer pipe assembly (7), and the laser displacement sensor (19) is located on the sensor mounting plate (18).

7. The expansion joint according to claim 1, characterized in that The first ring plate assembly (5), the inner side of the working bellows (6) and the second ring plate assembly (8) form a closed second non-pressure zone; the expansion joint is also provided with a working bellows detection tube (2) and a working bellows monitor (3); the detection end of the working bellows detection tube (2) is located in the second non-pressure zone, and the other end is connected to the working bellows monitor (3).

8. The expansion joint according to claim 1, characterized in that The average diameter of the working bellows (6) is greater than the average diameter of the balancing bellows (10).

9. The expansion joint according to claim 1, characterized in that The inlet ring plate assembly (4) is an elliptical head structure.

10. The expansion joint according to claim 1, characterized in that The outer tube assembly (7) is a cone-section structure and adopts butt welding.

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