Check function valve group and heat supply reactor

Abstract

The application provides a cut-off check function valve group and a heat supply reactor, the cut-off check function valve group comprising a first valve and a second valve, the first valve comprising a first valve body, a first valve core and a first valve rod, one end of the first valve rod being connected with the first valve core, the first valve body comprising an upper chamber and a lower chamber, the first valve core being located in the upper chamber, one end of the first valve rod being connected with the first valve core and the other end extending to the lower chamber, the lower chamber being communicated with a first branch and a second branch; the second valve comprising a second valve body, a second valve core and a second valve rod, the second valve body comprising a first communication chamber and a second communication chamber, the second valve core being located in the first communication chamber, one end of the second valve rod being connected with the second valve core and extending to the second communication chamber, the first communication chamber being communicated with a third branch and a fourth branch, one end of the third branch extending to the top side of the upper chamber, and one end of the fourth branch extending to a control valve group. The cut-off check function valve group is self-driven by medium, and is multi-functional and integrated.

Description

Technical Field

[0001] This invention relates to the field of nuclear power technology, specifically to a shut-off check valve assembly and a heating reactor. Background Technology

[0002] Currently, high-temperature and high-pressure valves used in the nuclear power, oil, and natural gas industries typically include gate valves, check valves, globe valves, and ball valves. Except for check valves, which are self-actuating, all other valves require an external actuator to open and close.

[0003] External drive devices limit the ambient temperature range in which these types of valves can operate. Components such as cables, motors, coils, and seals are particularly unsuitable for high-temperature environments. While self-driven check valves can be used in high-temperature environments, their unidirectional flow presents process constraints, and they generally require additional valves to meet process functional requirements. Traditional gate valves, globe valves, and ball valves are large and heavy, making on-site installation difficult. Furthermore, their limited functionality necessitates combining multiple traditional valves to achieve more functions, leading to increased costs and maintenance expenses.

[0004] Based on this, the inventors of this application propose a shut-off check valve assembly and a heating stack to solve the aforementioned technical problems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing valves, which have a single function and are difficult to arrange on site, and to provide a valve group with shut-off and check valve functions and a heating stack.

[0006] The present invention solves the above-mentioned technical problems through the following technical solution:

[0007] This invention provides a shut-off check valve assembly, characterized in that it includes:

[0008] The first valve includes a first valve body, a first valve core, and a first valve stem. One end of the first valve stem is connected to the first valve core. The first valve body includes an upper chamber and a lower chamber. The first valve core is located in the upper chamber. One end of the first valve stem is connected to the first valve core, and the other end extends to the lower chamber. The lower chamber is connected to a first branch and a second branch.

[0009] The second valve includes a second valve body, a second valve core, and a second valve stem. The second valve body includes a first communicating chamber and a second communicating chamber. The second valve core is located within the first communicating chamber. One end of the second valve stem is connected to the second valve core and extends into the second communicating chamber. The first communicating chamber is connected to a third branch and a fourth branch. One end of the third branch extends to the top side of the upper chamber, and one end of the fourth branch extends to a control valve assembly.

[0010] The first branch is connected to the bottom of the second connecting chamber, so that when the pressure of the first branch increases, the first branch and the second branch are disconnected, and the third branch and the fourth branch are disconnected; when the pressure of the first branch decreases, the first branch and the second branch are connected, and the third branch and the fourth branch are connected.

[0011] According to one embodiment of the present invention, a first return spring is provided inside the first valve core. When the control valve group is filling the top of the upper chamber of the first valve core with medium through the fourth branch and the third branch, the first valve stem descends and closes the second branch, and the first return spring is compressed; when the pressure in the first branch drops to a preset value, the first return spring resets, and the first branch and the second branch are connected.

[0012] The second valve core is equipped with a second return spring. When the pressure in the first branch increases, the second return spring is compressed; when the pressure in the first branch decreases to a preset value, the second return spring is reset, and the third branch and the fourth branch are connected.

[0013] According to one embodiment of the present invention, the first branch and the second branch are arranged perpendicularly, and the axial extension direction of the first valve stem corresponds to the inlet end of the second branch.

[0014] According to one embodiment of the present invention, a first partition is provided between the upper chamber and the lower chamber, and the peripheral wall of the first partition abuts against the inner wall of the upper chamber to separate the upper chamber and the lower chamber;

[0015] A second partition is provided between the first connecting chamber and the second connecting chamber, and the peripheral wall of the second partition abuts against the inner wall of the first connecting chamber to separate the first connecting chamber and the second connecting chamber.

[0016] According to one embodiment of the present invention, a spring limiting plate is provided on the top of the first valve core, and the first reset spring is disposed between the first partition plate and the spring limiting plate;

[0017] The third branch is connected to the upper chamber in the space above the spring limiting plate.

[0018] According to one embodiment of the present invention, the top of the second valve core is provided with a sealing portion, which is used to press against the fourth branch to disconnect the third branch and the fourth branch.

[0019] According to one embodiment of the present invention, the fourth branch is opened above the first communicating chamber and communicates with the first communicating chamber. When the third branch is disconnected from the fourth branch, the sealing part presses against the fourth branch to disconnect the third branch and the fourth branch.

[0020] According to one embodiment of the present invention, a first valve cover is provided on the top of the first valve body, and the first valve cover is connected to the first valve body by a threaded connector;

[0021] The second valve body is provided with a second valve cover on its top, and the second valve cover is connected to the second valve body by a threaded connector.

[0022] According to one embodiment of the present invention, the control valve group includes a reset solenoid valve and a drain solenoid valve, wherein the reset solenoid valve and the drain solenoid valve are connected in parallel and communicate with the fourth branch.

[0023] The present invention also provides a heating stack, characterized in that it includes a shut-off check valve assembly as described above.

[0024] The positive and progressive effects of this invention are as follows:

[0025] The present invention provides a shut-off check valve assembly in which the first and second valves can be used together to meet functions such as isolation and check, reducing the number of valve devices, lowering the failure points of valve devices, saving maintenance or repair time during material change and overhaul, simplifying the control system, simplifying the control logic, and increasing the redundancy design of the pipeline to prevent misoperation.

[0026] The shut-off and check valve assembly is self-driven by the medium, which reduces power consumption, frees up the power resources required by traditional designs, and greatly reduces the weight and size of the valve, making the pipeline and support layout simpler and more reliable. Attached Figure Description

[0027] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein:

[0028] Figure 1 This is a schematic diagram of the structure of the check valve assembly of the present invention.

[0029] 1. First valve; 11. First valve body; 12. First valve core; 13. First valve stem; 14. Upper chamber; 15. Lower chamber; 151. First partition plate; 152. Spring limiting plate; 16. First branch; 17. Second branch; 18. First return spring; 19. First valve cover;

[0030] 2. Second valve; 21. Second valve body; 22. Second valve core; 221. Sealing part; 23. Second valve stem; 24. First communicating chamber; 25. Second communicating chamber; 251. Second partition; 26. Third branch; 27. Fourth branch; 28. Second return spring; 29. ​​Second valve cover;

[0031] 3. Control valve assembly; 31. Reset solenoid valve; 32. Drain solenoid valve. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0034] Please refer to Figure 1 This invention proposes a shut-off check valve assembly, which includes a first valve 1 and a second valve 2. The first valve 1 includes a first valve body 11, a first valve core 12, and a first valve stem 13. One end of the first valve stem 13 is connected to the first valve core 12. The first valve body 11 includes an upper chamber 14 and a lower chamber 15. The first valve core 12 is located in the upper chamber 14. One end of the first valve stem 13 is connected to the first valve core 12, and the other end extends to the lower chamber 15. The lower chamber 15 is connected to a first branch 16 and a second branch 17.

[0035] The second valve 2 includes a second valve body 21, a second valve core 22, and a second valve stem 23. The second valve body 21 includes a first connecting chamber 24 and a second connecting chamber 25. The second valve core 22 is located in the first connecting chamber 24. One end of the second valve stem 23 is connected to the second valve core 22 and extends to the second connecting chamber 25. The first connecting chamber 24 is connected to a third branch 26 and a fourth branch 27. One end of the third branch 26 extends to the top side of the upper chamber 14, and one end of the fourth branch 27 extends to the control valve assembly 3. The first branch 16 is connected to the bottom of the second connecting chamber 25, so that when the pressure of the first branch 16 rises, the first branch 16 and the second branch 17 are disconnected, and the third branch 26 and the fourth branch 27 are disconnected; when the pressure of the first branch 16 drops, the first branch 16 and the second branch 17 are connected, and the third branch and the fourth branch 27 are connected.

[0036] It should be noted that if traditional valves are to achieve multiple valve functions, multiple traditional valves need to be combined, which increases costs and maintenance expenses, and the structure is relatively complex.

[0037] The valve assembly provided by the present invention includes a first valve 1 and a second valve 2. The first valve 1 and the second valve 2 are integrated into one unit, which has the characteristics of being integrated, multifunctional, and small in size, and also has functions such as isolation and check flow.

[0038] The first valve 1 and the second valve 2 are made of steel and flexible graphite, which have advantages such as high temperature resistance, high pressure resistance, radiation resistance and corrosion resistance.

[0039] The shut-off check valve assembly consists of a first valve 1 and a second valve 2, achieving miniaturization and integration to meet the usage requirements of small heating stacks. When a valve assembly closing command is received, for example, the control valve assembly 3 controls the injection of medium into the top of the first valve core 12 via the fourth branch 27 and the third branch 26, causing the first valve stem 13 to move downwards, thereby closing the second branch 17. At this time, the first branch 16 and the second branch 17 are disconnected, and the first valve 1 is closed.

[0040] When an opening command is received, the high-pressure medium at the top of the first valve core 12 is discharged, the first branch 16 and the second branch 17 are connected, and the valve group is opened. The second valve 2 is provided to prevent the first valve 1 from being opened accidentally, to ensure that the first valve 1 is in a normal closed state, and to maintain the integrity of the heating stack pressure boundary.

[0041] In one embodiment, a first return spring 18 is provided inside the first valve core 12. When the control valve assembly 3 is filled with medium into the top of the upper chamber 14 of the first valve core 12 via the fourth branch 27 and the third branch 26, the first valve stem 13 descends and closes the second branch 17, and the first return spring 18 is compressed. When the pressure in the first branch 16 drops to a preset value, the first return spring 18 resets, and the first branch 16 and the second branch 17 are connected. A second return spring 28 is provided inside the second valve core 22. When the pressure in the first branch 16 rises, the second return spring 28 is compressed. When the pressure in the first branch 16 drops to a preset value, the second return spring 28 resets, and the third branch 26 and the fourth branch 27 are connected.

[0042] That is, the first branch 16 and the second branch 17 are the main pipelines of the valve group, and the third branch 26 and the fourth branch 27 are the control pipelines of the valve group, used to introduce or release high-pressure media. The fourth branch 27 is connected to the reset solenoid valve 31 and the vent solenoid valve 32 respectively. The reset solenoid valve 31 is connected to the high-pressure media source, and the vent solenoid valve 32 is connected to the vent end. The vent end can be set according to the actual scenario.

[0043] In one embodiment, the first branch 16 and the second branch 17 are arranged perpendicularly, and the axial extension direction of the first valve stem 13 corresponds to the inlet end of the second branch 17.

[0044] That is, the upward and downward movement of the first valve stem 13 can close or open the second branch 17. When the first valve stem 13 moves upward, the first branch 16 is connected to the second branch 17; while when the second valve stem 23 moves downward and blocks the second branch 17, the first branch 16 and the second branch 17 are disconnected.

[0045] Furthermore, a first partition 151 is provided between the upper chamber 14 and the lower chamber 15, and the peripheral wall of the first partition 151 abuts against the inner wall of the upper chamber 14 to separate the upper chamber 14 and the lower chamber 15; a second partition 251 is provided between the first connecting chamber 24 and the second connecting chamber 25, and the peripheral wall of the second partition 251 abuts against the inner wall of the first connecting chamber 24 to separate the first connecting chamber 24 and the second connecting chamber 25.

[0046] That is, the first partition 151 is used to separate the upper chamber 14 and the lower chamber 15, and the second partition 251 is used to separate the first connecting chamber 24 and the second connecting chamber 25, thereby separating the upper chamber 14 and the lower chamber 15 as well as the first connecting chamber 24 and the second connecting chamber 25.

[0047] Furthermore, a spring limiting plate 152 is provided on the top of the first valve core 12, and a first reset spring 18 is provided between the first partition 151 and the spring limiting plate 152; the third branch 26 is connected to the upper chamber 14 in the space at the top of the spring limiting plate 152.

[0048] The pressure source medium introduced by the third branch 26 through the fourth branch 27 is injected into the top of the first valve core 12. When the pressure of the pressure source medium rises above the set point a, the power source medium pushes the spring limit plate 152 to move down, the first reset spring 18 is compressed and drives the first valve stem 13 to move down, and the first branch 16 and the second branch 17 are disconnected to achieve the cut-off and check-back of the medium. At the same time, the higher the pressure of the first branch 16, the better the cut-off and check-back performance of the first valve 1.

[0049] The third branch 26 releases the high-pressure medium at the top of the first valve 1 through the fourth branch 27. As the pressure at the top of the first valve core 12 decreases and falls below point b, the first reset spring 18 resets, pushing the spring limit plate 152 upward. The first branch 16 and the second branch 17 are connected, thus enabling the first valve 1 to be turned on.

[0050] In one embodiment, the top of the second valve core 22 is provided with a sealing part 221, which is used to press against the fourth branch 27 to disconnect the third branch 26 and the fourth branch 27.

[0051] The sealing part 221 is used to isolate the third branch 26 and the fourth branch 27. The shape of the sealing part 221 can correspond to the pipe diameter of the fourth branch 27, and the specific shape is not limited here.

[0052] Furthermore, the fourth branch 27 is located above the first connecting chamber 24 and communicates with the first connecting chamber 24. When the third branch 26 and the fourth branch 27 are disconnected, the sealing part 221 presses against the fourth branch 27 to disconnect the third branch 26 and the fourth branch 27.

[0053] The up-and-down movement of the second valve core 22 can open or close the connection between the third branch 26 and the fourth branch 27.

[0054] In one embodiment, a first valve cover 19 is provided on the top of the first valve body 11, and the first valve cover 19 is connected to the first valve body 11 by a threaded connector; a second valve cover 29 is provided on the top of the second valve body 21, and the second valve cover 29 is connected to the second valve body 21 by a threaded connector.

[0055] The first valve cover 19 and the first valve body 11, as well as the second valve cover 29 and the second valve body 21, are detachably connected by threaded connectors, allowing for the inspection and replacement of the first valve core 12 and the second valve core 22.

[0056] Because the second connecting chamber 25 of the second valve body 21 is connected to the first branch 16, when the medium pressure of the first branch 16 rises, the pressure at the bottom of the second connecting chamber 25 rises to the set point c or above, the medium of the first branch will push the second valve core 22 to move upward and cause the sealing part 221 to seal the fourth branch 27. At this time, the second valve 2 is closed and the second return spring 28 is compressed to store energy. The third branch 26 and the fourth branch 27 are isolated, realizing the cut-off or isolation of the control pipeline corresponding to the control valve group 3.

[0057] As the medium pressure in the first branch 16 decreases and reaches d or below, the second return spring 28 resets, causing the second valve core 22 to move downward, connecting the third branch 26 and the fourth branch 27, opening the second valve 2, and connecting the control pipeline corresponding to the control valve group 3.

[0058] The pressure setpoints a, b, c, and d mentioned above can be set according to actual application scenarios and requirements, and are not limited here.

[0059] The present invention also proposes a heating stack, including the aforementioned shut-off check valve assembly.

[0060] When the reset solenoid valve 31 receives the stack start command, it opens. High-pressure medium is injected above the valve core of the first valve 1 through the third branch 26 and the fourth branch 27. The valve stem of the first valve 1 moves down, and the first branch 16 and the second branch 17 are disconnected. At this time, the first reset spring 18 is in a compressed and stored state. The pressure inside the pressure vessel gradually rises, causing the pressure in the first branch 16 to gradually rise. At this time, the second branch 17 is closed. The high pressure in the first branch 16 drives the valve core of the second valve 2 to move up and close the fourth branch 27. At this time, the third branch 26 and the fourth branch 27 are disconnected, and the control pipeline corresponding to the control valve group 3 is cut off or isolated. This state is the normal working state of the corresponding shut-off check valve group.

[0061] The above describes the operation flow of the shut-off check valve group during normal reactor startup. During startup, abnormal pressure conditions may occur within the pressure vessel, such as cryogenic overpressure. When the pressure vessel pressure rises, the shut-off check valve group receives a cryogenic overpressure signal. In this case, the venting solenoid valve 32 opens, releasing the pressure medium at the top of the valve core of the first valve 1. The first return spring 18 resets, and the first branch 16 and the second branch 17 are connected, depressurizing the pressure vessel and thus achieving cryogenic overpressure protection.

[0062] During normal operation, if the pressure in the pressure vessel drops abnormally, causing a decrease in pressure in the first branch 16, the second return spring 28 of the second valve 2 will reset, at which point the third branch 26 and the fourth branch 27 will be connected. If the abnormal pressure drop in the pressure vessel is resolved and the pressure returns to normal, the second valve 2 will close again, causing the second return spring 28 to compress again, and the third branch 26 and the fourth branch 27 will be disconnected or isolated. However, if the abnormal pressure drop in the pressure vessel is not resolved and the pressure continues to drop, i.e., the pressure in the first branch 16 continues to drop, the main control system will detect the signal and determine that an accident is in place, such as a drop in the pressure vessel water level or a rise in the containment water level. At this time, an accident signal will be issued, and the venting solenoid valve 32 will receive the signal and open. The third branch 26 and the fourth branch 27 will release the high-pressure medium at the top of the valve core of the first valve 1, realizing functions such as pressure vessel depressurization (medium flow direction from the first branch 16 to the second branch 17) or core cooling injection of coolant (medium flow direction from the second branch 17 to the first branch 16).

[0063] Once the accident situation has eased and it is confirmed that the reactor can continue to be started, only a reactor start command needs to be given. The reset solenoid valve 31 will open, and the high-pressure medium will be injected into the top of the first valve core 12 through the fourth branch 27 and the third branch 26 to disconnect the first branch 16 and the second branch 17, so that the pressure vessel can be pressurized and enter the normal working state.

[0064] Under normal operating conditions, since the second valve 2 is in the closed state, the third branch 26 and the fourth branch 27 of the control pipeline of the shut-off check valve group are in the cut-off state. If the venting solenoid valve 32 is mistakenly opened, even if the venting solenoid valve 32 completes the opening action, the pressure in the upper chamber of the first valve 1 will continue to be maintained, keeping the first branch 16 and the second branch 17 in the cut-off state, ensuring the cut-off or isolation state of the main pipeline of the shut-off check valve group, and avoiding the accidental opening of the shut-off check valve group.

[0065] In summary, the check valve assembly of the present invention allows the first valve 1 and the second valve 2 to be used in conjunction to satisfy functions such as isolation and check valve, reducing the number of valve devices, lowering the failure points of valve devices, saving maintenance or repair time for material replacement and major overhauls, simplifying the control system, simplifying the control logic, and increasing the redundancy design of the pipeline to prevent misoperation.

[0066] The shut-off and check valve assembly is self-driven by the medium, which reduces power consumption, frees up the power resources required by traditional designs, and greatly reduces the weight and size of the valve, making the pipeline and support layout simpler and more reliable.

[0067] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation", "connection", "joining", and "fixing" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can also refer to mechanical connections. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0068] This application uses specific terms to describe embodiments of the application. Terms such as "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of the application. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0069] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. A shut-off check valve assembly, characterized in that, include: The first valve includes a first valve body, a first valve core, and a first valve stem. One end of the first valve stem is connected to the first valve core. The first valve body includes an upper chamber and a lower chamber. The first valve core is located in the upper chamber. One end of the first valve stem is connected to the first valve core, and the other end extends to the lower chamber. The lower chamber is connected to a first branch and a second branch. The second valve includes a second valve body, a second valve core, and a second valve stem. The second valve body includes a first communicating chamber and a second communicating chamber. The second valve core is located within the first communicating chamber. One end of the second valve stem is connected to the second valve core and extends into the second communicating chamber. The first communicating chamber is connected to a third branch and a fourth branch. One end of the third branch extends to the top side of the upper chamber, and one end of the fourth branch extends to a control valve assembly. The first branch is connected to the bottom of the second connecting chamber, so that when the pressure of the first branch increases, the first branch and the second branch are disconnected, and the third branch and the fourth branch are disconnected; when the pressure of the first branch decreases, the first branch and the second branch are connected, and the third branch and the fourth branch are connected.

2. The shut-off check valve assembly according to claim 1, characterized in that, The first valve core is provided with a first return spring. When the control valve group fills the top of the upper chamber of the first valve core with medium through the fourth branch and the third branch, the first valve stem descends and closes the second branch, and the first return spring is compressed. When the pressure in the first branch drops to a preset value, the first return spring resets, and the first branch and the second branch are connected. The second valve core is equipped with a second return spring. When the pressure in the first branch increases, the second return spring is compressed; when the pressure in the first branch decreases to a preset value, the second return spring is reset, and the third branch and the fourth branch are connected.

3. The shut-off check valve assembly according to claim 2, characterized in that, The first branch and the second branch are arranged perpendicularly, and the axial extension direction of the first valve stem corresponds to the inlet end of the second branch.

4. The shut-off check valve assembly according to claim 2, characterized in that, A first partition is provided between the upper chamber and the lower chamber, and the peripheral wall of the first partition abuts against the inner wall of the upper chamber to separate the upper chamber and the lower chamber; A second partition is provided between the first connecting chamber and the second connecting chamber, and the peripheral wall of the second partition abuts against the inner wall of the first connecting chamber to separate the first connecting chamber and the second connecting chamber.

5. The shut-off check valve assembly according to claim 4, characterized in that, The first valve core is provided with a spring limiting plate at its top, and the first reset spring is located between the first partition plate and the spring limiting plate; The third branch is connected to the upper chamber in the space above the spring limiting plate.

6. The shut-off check valve assembly according to claim 2, characterized in that, The second valve core has a sealing part at the top, which is used to press against the fourth branch to disconnect the third branch and the fourth branch.

7. The shut-off check valve assembly according to claim 6, characterized in that, The fourth branch is located above the first connecting chamber and communicates with the first connecting chamber. When the third branch is disconnected from the fourth branch, the sealing part presses against the fourth branch to disconnect the third branch from the fourth branch.

8. The shut-off check valve assembly according to claim 1, characterized in that, The first valve body is provided with a first valve cover on its top, and the first valve cover is connected to the first valve body by a threaded connector; The second valve body is provided with a second valve cover on its top, and the second valve cover is connected to the second valve body by a threaded connector.

9. The shut-off check valve assembly according to claim 1, characterized in that, The control valve group includes a reset solenoid valve and a drain solenoid valve, which are connected in parallel and connected to the fourth branch.

10. A heating stack, characterized in that, Includes the shut-off check valve assembly as described in any one of claims 1-9.

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