External pressure straight tube pressure balance expansion joint

Abstract

The utility model relates to the technical field of expansion joint, specifically disclose a kind of outer pressure straight pipe pressure balance type expansion joint, including connecting pipe and the pipe joint being arranged in the one side of connecting pipe, pipe joint one end is sleeved in the outside of connecting pipe, and the other end of pipe joint is equipped with isolated bellows, working bellows A is equipped between connecting pipe and pipe joint, and working bellows A is sleeved in the outside of connecting pipe;Balance valve is equipped outside shell, and balance valve is communicated with balance bellows inner chamber, isolated bellows one end is fixedly connected with pipe joint, and isolated bellows other end is fixedly connected with the port of working bellows B. Whole inner layer bellows directly contacted with atmosphere is placed in a closed cavity isolated from outside corrosive environment, since the humid air rich in chloride ions is isolated, even if working bellows and balance bellows adopt conventional austenitic stainless steel material, electrochemical corrosion does not occur, to ensure that the long-term, safe, reliable operation of the entire expansion joint in harsh environment.

Description

Technical Field

[0001] This utility model relates to the field of expansion joint technology, and in particular to an external pressure straight pipe pressure balance expansion joint. Background Technology

[0002] External pressure straight-pipe pressure-balanced expansion joints are important compensating elements in piping systems, used to absorb axial displacement and balance the thrust generated by the pressure of the medium inside the pipeline. Their classic structure includes a working bellows, a balancing bellows, an inner bellows, and an outer shell. A key design feature of fully external pressure straight-pipe pressure-balanced expansion joints is that the inner cavity of its inner bellows (including the working and balancing bellows sides) is directly connected to the atmosphere. This design aims to ensure that the expansion joint's own pressure remains balanced under any operating condition, unaffected by the pressure of the medium inside the pipeline.

[0003] However, this design reveals a serious flaw when applied to projects near the sea, such as chemical, oil, LNG, and nuclear power plants. The high humidity and salinity (containing chloride ions) of marine climates make them highly corrosive. While the austenitic stainless steel commonly used to manufacture the inner bellows has good overall performance, it is highly susceptible to pitting corrosion, crevice corrosion, and even stress corrosion cracking after long-term service in this humid, chloride-rich environment. This leads to premature failure of the inner bellows, consequently affecting the safety and service life of the entire expansion joint. To address this corrosion problem, the current industry standard is to upgrade the material of the inner bellows, which is in direct contact with the atmosphere, to a more corrosion-resistant special alloy. However, these special alloys are expensive and not suitable for large-scale production. Therefore, a new technological solution is urgently needed that can effectively prevent the inner bellows from corroding in marine climates while significantly reducing manufacturing costs. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes an external pressure straight pipe pressure-balanced expansion joint to overcome the shortcomings of existing systems.

[0005] To achieve the purpose of this utility model, the utility model is achieved through the following technical solution: an external pressure straight pipe pressure balance expansion joint, including a connecting pipe and a pipe joint provided on one side of the connecting pipe, one end of the pipe joint is sleeved on the outside of the connecting pipe, the other end of the pipe joint is provided with an isolation bellows, and a working bellows A is provided between the connecting pipe and the pipe joint, with the working bellows A sleeved on the outside of the connecting pipe. The outer casing is fitted around the pipe connector and pipe fitting. The working bellows B and the balance bellows are fitted around the outer casing. The working bellows B and the balance bellows are placed inside the outer casing. The balance bellows is fixedly connected to the inner wall of the outer casing. A balance valve is provided on the outside of the outer casing. The balance valve is connected to the inner cavity of the balance bellows. One end of the isolation bellows is fixedly connected to the pipe joint, and the other end of the isolation bellows is fixedly connected to the port of the working bellows B.

[0006] A further improvement is that the balance valve includes a valve body, which is fixedly installed on the outside of the outer shell. The valve body is provided with a first interface and a second interface. The first interface is located inside the outer shell, and the second interface is located outside the outer shell. A valve core is provided inside the valve body, which is positioned between the first interface and the second interface. An adjusting bolt is installed at the end of the valve body away from the outer shell. One end of the adjusting bolt is screwed into the valve body and fixedly connected to the valve core.

[0007] A further improvement is that the inner cavity of the balanced bellows is filled with inert gas.

[0008] A further improvement is that the outer shell is stepped, and the outer shell includes a first stepped surface and a second stepped surface. The balance bellows is placed in the first stepped surface, and the working bellows B is placed in the second stepped surface.

[0009] A further improvement is that a first reinforcing part is provided between the connecting pipe and the outer shell, a second reinforcing part is provided between the balanced bellows and the pipe joint, and a third reinforcing part is provided between the first stepped surface and the second stepped surface.

[0010] A further improvement is that the first reinforcing part includes a plurality of first ribs, which are disposed at the angle between the outer wall of the nozzle and the outer wall of the housing. Each first rib is evenly arranged in the circumferential direction of the nozzle axis, and the first ribs are fixedly connected to the nozzle and the housing.

[0011] A further improvement is that the second reinforcing part includes multiple second ribs, which are disposed at the angle between the outer wall of the balance bellows and the outer wall of the pipe joint. Each second rib is evenly arranged in the circumferential direction of the pipe joint axis, and the second ribs are fixedly connected to the pipe joint and the balance bellows.

[0012] A further improvement is that the third reinforcing part includes multiple third ribs, which are disposed at the angle between the first step surface and the second step surface on the outer side wall of the outer shell. Each third rib is evenly arranged in the circumferential direction of the outer shell axis, and the third ribs are fixedly connected to the outer shell.

[0013] Compared with the prior art, the beneficial effects of this utility model are: The entire inner bellows, which is in direct contact with the atmosphere, is placed in a sealed cavity that isolates it from the corrosive environment. Because it is isolated from the humid air rich in chloride ions, even if the working bellows and the balance bellows are made of conventional austenitic stainless steel, electrochemical corrosion will not occur, thus ensuring the long-term, safe and reliable operation of the entire expansion joint in harsh environments. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a structural diagram of the pipe in this utility model.

[0016] Figure 2 This is a structural diagram of the outer shell in this utility model.

[0017] Figure 3 This is a structural diagram of the valve body in this utility model.

[0018] The components are: 1. Connecting pipe; 2. Pipe fitting; 3. Working bellows A; 4. Working bellows B; 5. Isolation bellows; 6. Balancing bellows; 7. Outer shell; 9. Balancing valve; 91. Valve body; 92. First interface; 93. Second interface; 94. Valve core; 95. Adjusting bolt; 10. First rib; 11. Second rib; 12. Third rib. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] according to Figure 1 , 2 As shown in Figure 3, this embodiment proposes an external pressure straight pipe pressure balance type expansion joint, including a pipe 1 and a pipe joint 2 provided on one side of the pipe 1. One end of the pipe joint 2 is sleeved on the outside of the pipe 1, and the other end of the pipe joint 2 is provided with an isolation bellows 5. A working bellows A3 is provided between the pipe 1 and the pipe joint 2, and the working bellows A3 is sleeved on the outside of the pipe 1. The outer casing 7 is fitted around the outside of the pipe connector 1 and the pipe fitting 2. The working bellows B4 and the balance bellows 6 are fitted around the outside of the pipe fitting 2. The working bellows B4 and the balance bellows 6 are placed inside the outer casing 7. The balance bellows 6 is fixedly connected to the inner wall of the outer casing 7. A balance valve 9 is provided on the outside of the outer casing 7. The balance valve 9 is connected to the inner cavity of the balance bellows 6. One end of the isolation bellows 5 is fixedly connected to the pipe joint 2, and the other end of the isolation bellows 5 is fixedly connected to the port of the working bellows B4.

[0021] A balancing valve 9 is installed on the channel connecting the inner cavity of the balancing bellows 6 to the atmosphere. The balancing valve 9 isolates or connects the inner cavity of the inner bellows on the balancing wave side to the outside atmosphere, thereby balancing the air pressure inside and outside the balancing bellows 6.

[0022] During installation, transportation, or initial setup of the expansion joint, the balancing valve 9 remains open, with the internal air pressure matching the external atmospheric pressure. After the equipment is put into operation, the balancing valve 9 is normally closed, forming a sealed cavity between the inner bellows cavity on the balancing wave side and the inner bellows cavity on the working wave side, which is connected via an internal channel. The gas within this sealed cavity is completely isolated from the corrosive external atmosphere.

[0023] At the end of the working bellows B4, where the inner bellows originally connected to the atmosphere, a thin-walled insulating bellows 5 is added. One end of the insulating bellows 5 is sealed to the port of the working bellows B4, and the other end is sealed to the external flange or connecting pipe of the pipe joint 2. The insulating bellows 5 completely isolates the inner cavity of the working bellows from the outside atmosphere. When a pressurized medium is introduced into the pipeline, the pressure acts on the outer surfaces of the working bellows A3, working bellows B4, and balancing bellows 6. Because the insulating bellows 5 has an extremely thin wall and very low stiffness, it has virtually no impact on the axial displacement compensation function of the working bellows B4.

[0024] Through the synergistic effect of the two core components, the entire inner bellows, including the working and balancing bellows sides, which were previously in direct contact with the atmosphere, are now placed within a sealed cavity isolated from the external corrosive environment. Because of the isolation from humid air rich in chloride ions, even though the working bellows A3, B4, and 6 are made of conventional austenitic stainless steel, electrochemical corrosion will not occur, thus ensuring the long-term, safe, and reliable operation of the entire expansion joint in harsh environments.

[0025] Since the inner bellows can continue to use inexpensive austenitic stainless steel instead of expensive special alloys like 625, and the added cost of the insulating bellows 5 and balancing valve 9 is far lower than the cost of material upgrades, the economic benefits of this solution are significant. Furthermore, the added insulating bellows 5 and balancing valve 9 are mature standard parts or easy-to-manufacture components, requiring minimal modification to the existing expansion joint structure, and the processes are mature, making them easy to produce and implement.

[0026] It should be noted that the sockets referred to in this solution all use a fixed connection method to connect the two mating parts.

[0027] In a preferred embodiment, the balancing valve 9 includes a valve body 91, which is fixedly disposed on the outside of the housing 7. The valve body 91 is provided with a first interface 92 and a second interface 93. The first interface 92 is disposed on the inside of the housing 7, and the second interface 93 is disposed on the outside of the housing 7. A valve core 94 is disposed on the inside of the valve body 91, which is located between the first interface 92 and the second interface 93. An adjusting bolt 95 is fitted to the end of the valve body 91 away from the housing 7. One end of the adjusting bolt 95 is screwed into the valve body 91 and fixedly connected to the valve core 94.

[0028] Rotate the adjusting bolt 95 to screw it into the valve body 91. The adjusting bolt 95 pushes the valve core 94 to lock between the first port 92 and the second port 93, sealing the first port 92 and the second port 93. Rotate the adjusting bolt 95 in the opposite direction to screw it out of the valve body 91, so that the first port 92 and the second port 93 are opened, and the inside and outside air can flow through the valve body 91.

[0029] In the preferred embodiment, the inner cavity of the balance bellows 6 is filled with inert gas.

[0030] During installation and commissioning, the balance valve 9 can be opened to connect the entire sealed cavity surrounded by the inner cavity of the balance bellows 6 and the working bellows B4 to the atmosphere, thereby balancing the internal and external pressures. When the expansion joint is officially put into operation, the balance valve 9 should be closed. At this time, the sealed cavity is completely sealed, and the dry, clean air or inert gas inside can be filled in before leaving the factory to completely isolate the inner bellows from the humid, saline marine atmosphere outside.

[0031] It is worth explaining in detail that the outer shell 7 is stepped, and the outer shell 7 includes a first stepped surface and a second stepped surface. The balance bellows 6 is placed in the first stepped surface, and the working bellows B4 is placed in the second stepped surface.

[0032] A first reinforcing part is provided between the connecting pipe 1 and the outer shell 7, a second reinforcing part is provided between the balanced bellows 6 and the pipe joint 2, and a third reinforcing part is provided between the first stepped surface and the second stepped surface.

[0033] More specifically, the first reinforcing part includes a plurality of first ribs 10, which are disposed at the angle between the outer wall of the nozzle 1 and the outer wall of the housing 7. The first ribs 10 are evenly distributed in the circumferential direction along the axis of the nozzle 1, and are fixedly connected to the nozzle 1 and the housing 7. This enhances the structural strength at the connection between the nozzle 1 and the housing 7 without changing the wall thickness of the nozzle 1 and the housing 7.

[0034] More specifically, the second reinforcing part includes multiple second ribs 11, which are disposed at the angle between the outer wall of the balancing bellows 6 and the outer wall of the pipe joint 2. The second ribs 11 are evenly distributed circumferentially along the axis of the pipe joint 2, and are fixedly connected to the pipe joint 2 and the balancing bellows 6. This enhances the structural strength of the connection between the pipe joint 2 and the balancing bellows 6 without changing their wall thickness.

[0035] More specifically, the third reinforcing part includes multiple third ribs 12, which are disposed at the angle between the first and second step surfaces on the outer wall of the outer shell 7. The third ribs 12 are evenly distributed circumferentially along the axis of the outer shell 7 and are fixedly connected to the outer shell 7. This enhances the structural strength of the outer shell 7 itself and the area between the step surfaces without changing the wall thickness of the outer shell 7.

[0036] How this application works: During installation, transportation, or initial setup of the expansion joint, the balancing valve 9 remains open, with its internal air pressure matching the external atmospheric pressure. After the equipment is put into operation, the balancing valve 9 is normally closed, forming a sealed cavity between the inner bellows cavity on the balancing side and the inner bellows cavity on the working side, which is connected via an internal channel. This sealed cavity completely isolates the gas from the corrosive external atmosphere. At the end of the working bellows B4, where the inner bellows previously connected to the atmosphere, a thin-walled isolation bellows 5 is added. One end of the isolation bellows 5 is sealed to the port of the working bellows B4, and the other end is sealed to the external flange or connecting pipe of the pipe joint 2, completely isolating the inner bellows cavity on the working side from the external atmosphere. When pressurized media are introduced into the pipeline, the pressure acts on the outer surfaces of the working bellows A3, working bellows B4, and balancing bellows 6. Because the wall thickness of the insulating bellows 5 is extremely thin and its stiffness is extremely low, it has virtually no impact on the axial displacement compensation function of the working bellows B4.

[0037] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0038] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An external pressure straight pipe pressure-balanced expansion joint, comprising a connecting pipe (1) and a pipe fitting (2) disposed on one side of the connecting pipe (1), wherein one end of the pipe fitting (2) is sleeved on the outside of the connecting pipe (1), characterized in that, The other end of the pipe joint (2) is provided with an insulating corrugated pipe (5), and a working corrugated pipe A (3) is provided between the pipe joint (1) and the pipe joint (2). The working corrugated pipe A (3) is sleeved on the outside of the pipe joint (1). The outer side of the pipe connector (1) and the pipe joint (2) is fitted with a shell (7), and the outer side of the pipe joint (2) is fitted with a working bellows B (4) and a balance bellows (6). The working bellows B (4) and the balance bellows (6) are placed inside the shell (7), and the balance bellows (6) is fixedly connected to the inner wall of the shell (7). The outer shell (7) is provided with a balance valve (9), which is connected to the inner cavity of the balance bellows (6). One end of the isolation bellows (5) is fixedly connected to the pipe joint (2), and the other end of the isolation bellows (5) is fixedly connected to the port of the working bellows B (4).

2. The external pressure straight pipe pressure-balanced expansion joint according to claim 1, characterized in that: The balancing valve (9) includes a valve body (91), which is fixedly disposed on the outside of the housing (7). The valve body (91) is provided with a first interface (92) and a second interface (93). The first interface (92) is disposed on the inside of the housing (7), and the second interface (93) is disposed on the outside of the housing (7). The valve body (91) is provided with a valve core (94) on the inside. The valve core (94) is placed between the first interface (92) and the second interface (93). An adjusting bolt (95) is fitted at one end of the valve body (91) away from the housing (7). One end of the adjusting bolt (95) is screwed into the valve body (91) and fixedly connected to the valve core (94).

3. The external pressure straight pipe pressure-balanced expansion joint according to claim 1, characterized in that: The inner cavity of the balanced bellows (6) is filled with inert gas.

4. The external pressure straight pipe pressure-balanced expansion joint according to claim 1, characterized in that: The outer shell (7) is stepped, and the outer shell (7) includes a first stepped surface and a second stepped surface. The balance bellows (6) is placed in the first stepped surface, and the working bellows B (4) is placed in the second stepped surface.

5. The external pressure straight pipe pressure-balanced expansion joint according to claim 4, characterized in that: A first reinforcing part is provided between the connecting pipe (1) and the outer shell (7), a second reinforcing part is provided between the balanced corrugated pipe (6) and the pipe joint (2), and a third reinforcing part is provided between the first stepped surface and the second stepped surface.

6. The external pressure straight pipe pressure-balanced expansion joint according to claim 5, characterized in that: The first reinforcing part includes a plurality of first ribs (10), the first ribs (10) are disposed at the angle between the outer wall of the pipe (1) and the outer wall of the outer shell (7), each of the first ribs (10) is evenly arranged in the circumferential direction of the axis of the pipe (1), and the first ribs (10) are fixedly connected to the pipe (1) and the outer shell (7).

7. The external pressure straight pipe pressure-balanced expansion joint according to claim 5, characterized in that: The second reinforcing part includes a plurality of second ribs (11). The second ribs (11) are disposed at the angle between the outer wall of the balance corrugated pipe (6) and the outer wall of the pipe joint (2). Each of the second ribs (11) is evenly arranged in the circumferential direction of the axis of the pipe joint (2). The second ribs (11) are fixedly connected to the pipe joint (2) and the balance corrugated pipe (6).

8. The external pressure straight pipe pressure-balanced expansion joint according to claim 5, characterized in that: The third reinforcing part includes a plurality of third ribs (12), which are disposed at the angle between the first step surface and the second step surface on the outer side wall of the outer shell (7). Each of the third ribs (12) is evenly arranged in the circumferential direction of the axis of the outer shell (7), and the third ribs (12) are fixedly connected to the outer shell (7).

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