Nuclear power station evaporator blowdown system and cooling water flow regulating valve assembly thereof

Abstract

The utility model discloses a cooling water flow regulating valve assembly which comprises a valve body and a valve rod inserted into the valve body in the vertical direction, the top end of the valve rod extends out of the top of the valve body from bottom to top, and a driving mechanism is arranged above the valve body in an aligned mode. The driving mechanism is in linkage connection with the top end of the valve rod to drive the valve rod to reciprocate in the vertical direction; the valve rod is sleeved with a limiting check ring and a locking nut, the limiting check ring and the locking nut are sequentially arranged between the valve body and the driving mechanism from bottom to top in the axial direction of the valve rod, the limiting check ring and the locking nut are in threaded fit with the valve rod, and the top end of the limiting check ring abuts against the bottom end of the locking nut in the vertical direction. According to the cooling water flow regulating valve assembly, the water hammer phenomenon can be avoided, violent vibration, caused by strong water flow impact, of the cooling water pipeline is avoided, and therefore damage to related equipment is avoided. The utility model further discloses a nuclear power station evaporator blowdown system using the cooling water flow regulating valve assembly.

Description

Technical Field

[0001] The utility model relates to the technical field of supporting equipment for a nuclear power plant evaporator sewage discharge system, and in particular to a cooling water flow regulating valve assembly. The utility model also relates to a nuclear power plant evaporator sewage discharge system using the cooling water flow regulating valve assembly. Background Art

[0002] In the current layout structure of supporting equipment for the evaporator blowdown system of a nuclear power plant, a cooling water flow regulating valve is usually arranged for the heat exchanger of the evaporator blowdown system to control the cooling water flow at the heat exchanger, so as to match the cooling water flow control requirements of the heat exchanger and its related matching devices under different operating conditions.

[0003] Generally, depending on the operating status of the supporting equipment of the nuclear power plant, the opening and closing of the cooling water flow regulating valve used in the evaporator sewage system of the nuclear power plant will also be adjusted accordingly.

[0004] Specifically, during the operation of the evaporator blowdown system of a nuclear power plant, the cooling water flow regulating valve associated with its heat exchanger is also opened from the fully closed position. During this process, water hammer will occur at the cooling water flow regulating valve, that is, the cooling water flow regulating valve that is suddenly opened from the fully closed state will cause a large structural impact on the valve body and related cooling water pipes due to the suddenly increased liquid flow, thereby causing the corresponding cooling water pipes to vibrate violently, which will not only have an adverse effect on the liquid flow state inside the pipeline, but also cause damage to other related functional equipment in the evaporator blowdown system, resulting in a decrease in the reliability of the system operation, which will have an adverse effect on the smooth operation of the evaporator blowdown system and even the overall reliable operation of the nuclear power plant.

[0005] In view of this, how to avoid water hammer phenomenon at the cooling water flow regulating valve and avoid severe vibration of the cooling water pipeline caused by strong water flow impact, thereby avoiding damage to related equipment is an important technical problem that technical personnel in this field currently need to solve. Utility Model Content

[0006] The purpose of the utility model is to provide a cooling water flow regulating valve assembly, which can avoid the occurrence of water hammer phenomenon and avoid the violent vibration of cooling water pipelines caused by strong water flow impact, thereby avoiding damage to related equipment. Another purpose of the utility model is to provide a nuclear power plant evaporator sewage system using the above cooling water flow regulating valve assembly.

[0007] In order to solve the above technical problems, the utility model provides a cooling water flow regulating valve assembly, comprising a valve body and a valve stem inserted into the valve body in a vertical direction, the top end of the valve stem extends from the bottom to the top of the valve body, and a driving mechanism is arranged above the valve body, and the driving mechanism is linked to the top end of the valve stem to drive the valve stem to reciprocate in the vertical direction;

[0008] A limit ring and a locking nut are sleeved on the valve stem, and the limit ring and the locking nut are arranged in sequence from bottom to top along the axial direction of the valve stem between the valve body and the driving mechanism, and the limit ring and the locking nut are respectively matched with the valve stem thread, and the top end of the limit ring and the bottom end of the locking nut are abutted against each other in the vertical direction.

[0009] Preferably, a packing bolt is provided on the valve body, the top end of the packing bolt protrudes from the top end of the valve body in the vertical direction, and the top end of the packing bolt can abut against the bottom end of the limit retaining ring in the vertical direction.

[0010] Preferably, there are two packing bolts, and the two packing bolts are symmetrically arranged on both sides of the valve stem along the horizontal direction.

[0011] Preferably, the packing bolt and the valve stem are clearance-fitted in the horizontal direction.

[0012] Preferably, a buffer boss is provided at the bottom of the limit retaining ring, protruding downward in the vertical direction.

[0013] Preferably, the buffer boss is an annular boss extending along the circumference of the limit retaining ring and connected end to end.

[0014] Preferably, the buffer boss is located at the bottom of the limit retaining ring close to the outer edge.

[0015] Preferably, the axial thickness of the limit retaining ring increases linearly from the hole wall of its central threaded hole to the inner end edge of the bottom surface of the buffer boss to form a buffer cone surface between the buffer boss and the central threaded hole of the limit retaining ring.

[0016] Preferably, a coupling is provided at the bottom of the driving mechanism, and the driving mechanism and the valve stem are linked to each other through the coupling.

[0017] The utility model also provides a nuclear power plant evaporator sewage discharge system, including cooling water pipelines and cooling water flow regulating valves that are interconnected and coordinated, and the cooling water flow regulating valve assembly is a cooling water flow regulating valve assembly as described in any of the above items.

[0018] Compared with the above-mentioned background technology, the cooling water flow regulating valve assembly provided by the utility model, during its assembly and operation, the limit retaining ring is mounted on the valve stem, and then the valve flow of the cooling water flow regulating valve is manually adjusted online, and the valve operation is stopped after the minimum flow required by the working condition is reached; then, relying on the threaded cooperation between the threaded hole in the center of the limit retaining ring and the external thread on the valve stem, the limit retaining ring is screwed to make it move downward along the axial direction of the valve stem until the limit retaining ring is against the top of the valve body; then the locking nut is also mounted on the valve stem, and the locking nut is located above the limit retaining ring, relying on the threaded cooperation between the internal thread of the locking nut and the external thread of the valve stem, the locking nut is screwed to make it move downward along the axial direction of the valve stem until the bottom end of the locking nut is against the top end of the limit retaining ring, so that the locking nut and the limit retaining ring are back-tightened; after the above operation is completed, a full-close signal is sent to the cooling water flow regulating valve through the controller, or the cooling water flow regulating valve is manually operated by the staff to tend to the full-closed state, and it is confirmed that the minimum flow of the valve has not changed, and the entire operation is completed. Due to the abutment structure formed by the limit retaining ring and the top of the valve body, when the valve stem moves down with the driving mechanism to close the valve of the cooling water flow regulating valve, when the locking nut moves down with the valve stem to abut against the valve body, it forms a downward blockage for the valve stem, thereby preventing the valve stem from continuing to move downward, thereby ensuring that the valve of the cooling water flow regulating valve always has a certain small opening that meets the working conditions, so that the cooling water flow regulating valve maintains a certain small flow state to avoid water hammer caused by sudden flow of liquid when the valve is opened next time due to the complete closure of the valve, thereby greatly reducing the water flow impact when the valve of the cooling water flow regulating valve is opened, avoiding severe vibration of the cooling water pipeline due to strong water flow impact, thereby effectively avoiding damage to related equipment.

[0019] In another preferred embodiment of the utility model, a packing bolt is provided on the valve body, and the top end of the packing bolt protrudes from the top end of the valve body in the vertical direction, and the top end of the packing bolt can abut against the bottom end of the limit retaining ring in the vertical direction. When the limit retaining ring moves downward with the valve stem, the bottom end of the limit retaining ring abuts against the top end of the packing bolt and then stops moving downward, thereby using the packing bolt as a limiting fitting of the limit retaining ring to avoid the limit retaining ring directly abutting against the top of the valve body and causing structural impact and damage to the main structure of the valve body, further improving the durability of the main functional components of the cooling water flow control valve; in addition, by adjusting the height of the top end of the packing bolt extending upward in the vertical direction, the height of the lower limit position of the limit retaining ring when it moves downward synchronously with the valve stem can be adjusted accordingly, thereby adjusting the minimum opening of the valve, and thereby realizing the corresponding adjustment of the minimum flow of the cooling water flow control valve to match the equipment operation requirements under different working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic diagram of the arrangement structure of a cooling water flow regulating valve assembly and related matching parts provided in a specific implementation manner of the utility model;

[0022] Figure 2 for Figure 1 Side view of the center limit ring.

[0023] in:

[0024] 10- coupling;

[0025] 11-valve body; 111-valve stem; 112-packing bolt;

[0026] 12-limiting retaining ring; 121-buffering boss; 122-buffering cone surface;

[0027] 13-Lock nut. DETAILED DESCRIPTION

[0028] The core of the utility model is to provide a cooling water flow regulating valve assembly, which can avoid the occurrence of water hammer phenomenon and avoid severe vibration of cooling water pipelines caused by strong water flow impact, thereby avoiding damage to related equipment; in addition, a nuclear power plant evaporator sewage discharge system using the above cooling water flow regulating valve assembly is also provided.

[0029] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0030] It should be noted in advance that, in the present invention, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", "fix" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] In addition, in the present invention, unless otherwise clearly stipulated and limited, a first feature “on” or “under” a second feature may include the first and second features being in direct contact, or the first and second features not being in direct contact but being in contact through another feature therebetween.

[0032] In addition, the first feature being "above", "above" and "above" the second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature includes the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature. The terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0033] Please refer to Figure 1 and Figure 2 , Figure 1 A schematic diagram of the arrangement structure of a cooling water flow regulating valve assembly and related matching parts provided in a specific implementation manner of the utility model; Figure 2 for Figure 1 Side view of the center limit ring.

[0034] In a specific embodiment, the cooling water flow regulating valve assembly provided by the utility model includes a valve body 11 and a valve stem 111 inserted into the valve body 11 along the vertical direction. The top end of the valve stem 111 extends from the bottom to the top of the valve body 11. A driving mechanism is arranged above the valve body 11. The driving mechanism is linked to the top end of the valve stem 111 to drive the valve stem 111 to move back and forth in the vertical direction.

[0035] A limit ring 12 and a locking nut 13 are sleeved on the valve stem 111. The limit ring 12 and the locking nut 13 are arranged in sequence from bottom to top along the axial direction of the valve stem 111 between the valve body 11 and the driving mechanism. The limit ring 12 and the locking nut 13 are respectively threadedly matched with the valve stem 111, and the top end of the limit ring 12 and the bottom end of the locking nut 13 are abutted against each other in the vertical direction.

[0036] During assembly and operation, the limit retaining ring 12 is mounted on the valve stem 111, and then the valve flow of the cooling water flow regulating valve is manually adjusted online, and the valve operation is stopped after the minimum flow required by the working condition is reached.

[0037] Afterwards, by means of the threaded cooperation between the threaded hole in the center of the limit retaining ring 12 and the external thread on the valve stem 111 , the limit retaining ring 12 is screwed to move downward along the axial direction of the valve stem 111 until the limit retaining ring 12 abuts against the top of the valve body 11 .

[0038] Then, the locking nut 13 is also put onto the valve stem 111, and the locking nut 13 is located above the limit retaining ring 12. Relying on the threaded cooperation between the internal thread of the locking nut 13 and the external thread of the valve stem 111, the locking nut 13 is screwed to move downward along the axial direction of the valve stem 111 until the bottom end of the locking nut 13 abuts against the top end of the limit retaining ring 12, so that the locking nut 13 and the limit retaining ring 12 are back-tightened.

[0039] After the above operation is completed, the controller sends a full-close signal to the cooling water flow regulating valve, or the staff manually operates the cooling water flow regulating valve to a fully closed state, confirming that the minimum flow of the valve has not changed, and the entire operation is completed.

[0040] Due to the abutment structure formed by the limit retaining ring 12 and the top of the valve body 11, when the valve stem 111 moves down with the driving mechanism to close the valve of the cooling water flow regulating valve, when the locking nut 13 moves down with the valve stem 111 to abut against the valve body 11, it forms a downward blockage for the valve stem 111, thereby preventing the valve stem 111 from continuing to move downward, thereby ensuring that the valve of the cooling water flow regulating valve always has a certain small opening that meets the working conditions, so that the cooling water flow regulating valve maintains a certain small flow state to avoid water hammer caused by sudden flow of liquid when the valve is opened next time due to the complete closure of the valve, thereby greatly reducing the water flow impact when the valve of the cooling water flow regulating valve is opened, avoiding severe vibration of the cooling water pipeline due to strong water flow impact, thereby effectively avoiding damage to related equipment.

[0041] On this basis, the locking nut 13 is used to form a back-tight fit with the limit ring 12, thereby forming a reliable structural limit on the top of the limit ring 12 to prevent the limit ring 12 from moving upward relative to the valve stem 111 due to the bottom and the lower mating part abutting against each other during the synchronous movement of the limit ring 12 with the valve stem 111, thereby further ensuring that the relative mating position between the limit ring 12 and the valve stem 111 is constant, thereby ensuring stable control of the minimum valve opening of the cooling water flow regulating valve and precise control of the minimum flow of the regulating valve.

[0042] Generally, a coupling 10 is provided at the bottom of the driving mechanism, and the driving mechanism and the valve stem 111 are linked and connected via the coupling 10. In actual operation, the coupling 10 and the valve stem 111 need to be separated first, and then the limit ring 12 and the locking nut 13 can be sequentially mounted on the valve stem 111 from the top of the valve stem 111. After the corresponding assembly is completed, the coupling 10 and the top of the valve stem 111 can be reconnected.

[0043] It is not difficult to understand that the driving mechanism can be a cylinder or electric cylinder that can drive the valve stem 111 to move axially back and forth, or it can be other action mechanisms that can realize the linkage control of the valve stem 111. In actual application, it can be flexibly selected and adjusted according to specific working conditions and application requirements. In principle, as long as it can meet the actual application requirements of the cooling water flow control valve, it can be used.

[0044] Specifically, the valve body 11 is provided with a packing bolt 112, the top of which protrudes from the top of the valve body 11 in the vertical direction, and the top of the packing bolt 112 can abut against the bottom of the limit ring 12 in the vertical direction. When the limit ring 12 moves downward along with the valve stem 111, the bottom of the limit ring 12 abuts against the top of the packing bolt 112 and then stops moving downward, thereby using the packing bolt 112 as a limiting fitting for the limit ring 12, preventing the limit ring 12 from directly abutting against the top of the valve body 11 and causing structural impact and damage to the main structure of the valve body 11, thereby further improving the durability of the main functional components of the cooling water flow control valve.

[0045] In addition, by means of the threaded cooperation between the packing bolt 112 and the corresponding nut on the valve body 11, the height of the top end of the packing bolt 112 extending upward in the vertical direction can be adjusted by screwing, and the height of the lower limit position when the limit ring 12 moves downward synchronously with the valve stem 111 can be adjusted accordingly, so as to achieve the adjustment of the minimum opening of the valve, and thereby realize the corresponding adjustment of the minimum flow of the cooling water flow regulating valve to match the equipment operation requirements under different working conditions.

[0046] More specifically, there are two packing bolts 112, and the two packing bolts 112 are symmetrically arranged on both sides of the valve stem 111 in the horizontal direction. The two packing bolts 112 disposed on both sides of the valve stem 111 can abut and adapt with the limit retaining ring 12 at the same time, thereby ensuring that the abutting and adapting structure on both sides of the limit retaining ring 12 is more balanced and stable, avoiding local stress concentration on the limit retaining ring 12 to form a local structural impact and structural imbalance, and avoiding the limit retaining ring 12 and the valve stem 111 from corresponding structural damage.

[0047] Normally, the packing bolt 112 and the valve stem 111 are fitted with clearance in the horizontal direction. Maintaining a certain clearance between the two helps to avoid the packing bolt 112 and its contact structure with the limit retainer 12 from causing structural interference or retardation to the reciprocating motion of the valve stem 111, thereby ensuring smoother axial reciprocating motion of the valve stem 111, thereby ensuring efficient adjustment and precise control of the valve opening of the cooling water flow control valve.

[0048] On the other hand, the bottom of the limit ring 12 is provided with a buffer boss 121 protruding downward in the vertical direction. When the limit ring 12 moves downward synchronously with the valve stem 111, the buffer boss 121 can be used as a direct contact part to directly contact and abut against the top of the valve body 11 or the top of the packing bolt 112, thereby effectively alleviating the structural impact of the abutment structure on the main structure of the limit ring 12, avoiding structural imbalance or even loosening and dislocation of the matching part of the limit ring 12 and the valve stem 111 due to structural impact, thereby further improving the assembly structure reliability between the limit ring 12 and the valve stem 111, and optimizing the alignment and adaptation effect between the limit ring 12 and the relevant abutment matching parts.

[0049] On this basis, the buffer boss 121 is an annular boss that extends along the circumference of the limit retaining ring 12 and is connected end to end. The annular boss structure helps to further optimize the stress distribution when the buffer boss 121 is against the valve body 11 or the packing bolt 112, avoiding local stress concentration at the bottom of the limit retaining ring 12, thereby further avoiding structural imbalance and damage of the limit retaining ring 12 due to excessive impact on the local structure at the bottom, and ensuring the main structural strength of the limit retaining ring 12 and the reliability of the assembly structure between the limit retaining ring 12 and related adapters such as the valve stem 111.

[0050] Furthermore, the buffer boss 121 is located at the bottom of the limit retaining ring 12, close to the outer edge of the limit retaining ring 12. The buffer boss 121 is arranged closer to the outer edge of the limit retaining ring 12, which can effectively reduce the structural interference and structural impact of the buffer boss 121 and the abutment and matching structure with the valve body 11 or the packing bolt 112 below on the threaded hole at the center of the limit retaining ring 12, thereby effectively avoiding the threaded adapter structure between the limit retaining ring 12 and the valve stem 111 from being loosened, dislocated or structurally unbalanced due to structural impact, thereby further ensuring the connection strength and overall assembly reliability between the limit retaining ring 12 and the valve stem 111, and ensuring the linkage matching efficiency of the limit retaining ring 12 and the valve stem 111.

[0051] Generally, the bottom surface of the buffer boss 121 is a plane to increase the contact area between the buffer boss 121 and the valve body 11 or the packing bolt 112 to avoid local stress concentration during abutment and adaptation, thereby avoiding damage to the main structure of the valve body 11 and other major functional components.

[0052] Furthermore, the axial thickness of the limit ring 12 increases linearly from the hole wall of its central threaded hole to the inner end edge of the bottom surface of the buffer boss 121 to form a buffer cone surface 122 located between the buffer boss 121 and the central threaded hole of the limit ring 12 .

[0053] The buffer cone surface 122 can form a smooth transition structure between the buffer boss 121 and the threaded hole at the center of the limit retaining ring 12, thereby further optimizing the stress distribution between the buffer boss 121 and the threaded hole at the center of the limit retaining ring 12, avoiding the limit retaining ring 12 from being unbalanced due to local stress concentration or large structural impact at the bottom of the limit retaining ring 12, and further avoiding the limit retaining ring 12 from being loosened or misplaced from the valve stem 111, thereby further ensuring the assembly structure reliability of the limit retaining ring 12 and the valve stem 111, making the operation of the cooling water flow regulating valve more stable and controllable.

[0054] In a specific implementation, the nuclear power plant evaporator sewage system provided by the utility model includes a cooling water pipeline and a cooling water flow regulating valve that are interconnected and coordinated, and the cooling water flow regulating valve assembly is the cooling water flow regulating valve assembly as described above. The cooling water flow regulating valve assembly of the nuclear power plant evaporator sewage system can avoid the occurrence of water hammer phenomenon and avoid the cooling water pipeline from vigorous vibration caused by strong water flow impact, thereby avoiding damage to related equipment.

[0055] In summary, the cooling water flow regulating valve assembly provided in the utility model comprises a valve body and a valve stem inserted into the inside of the valve body in a vertical direction, the top end of the valve stem extends from the bottom to the top of the valve body, and a driving mechanism is arranged above the valve body, and the driving mechanism is linked to the top end of the valve stem to drive the valve stem to reciprocate in the vertical direction;

[0056] A limit ring and a locking nut are sleeved on the valve stem, and the limit ring and the locking nut are arranged in sequence from bottom to top along the axial direction of the valve stem between the valve body and the driving mechanism, and the limit ring and the locking nut are respectively matched with the valve stem thread, and the top end of the limit ring and the bottom end of the locking nut are abutted against each other in the vertical direction.

[0057] During its assembly and operation, the limit retaining ring is put on the valve stem, and then the valve flow of the cooling water flow regulating valve is manually adjusted online, and the valve operation is stopped after the minimum flow required by the working condition is reached; then, relying on the threaded cooperation between the threaded hole in the center of the limit retaining ring and the external thread on the valve stem, the limit retaining ring is screwed to make it move downward along the axial direction of the valve stem until the limit retaining ring is abutted against the top of the valve body; then the locking nut is also put on the valve stem, and the locking nut is located above the limit retaining ring, relying on the threaded cooperation between the internal thread of the locking nut and the external thread of the valve stem, the locking nut is screwed to make it move downward along the axial direction of the valve stem until the bottom end of the locking nut is abutted against the top end of the limit retaining ring, so that the locking nut and the limit retaining ring are back-tightened; after the above operations are completed, a full-close signal is sent to the cooling water flow regulating valve through the controller, or the cooling water flow regulating valve is manually operated by the staff to tend to the full-closed state, and it is confirmed that the minimum flow of the valve has not changed, and the entire operation is completed. Due to the abutment structure formed by the limit retaining ring and the top of the valve body, when the valve stem moves down with the driving mechanism to close the valve of the cooling water flow regulating valve, when the locking nut moves down with the valve stem to abut against the valve body, it forms a downward blockage for the valve stem, thereby preventing the valve stem from continuing to move downward, thereby ensuring that the valve of the cooling water flow regulating valve always has a certain small opening that meets the working conditions, so that the cooling water flow regulating valve maintains a certain small flow state to avoid water hammer caused by sudden flow of liquid when the valve is opened next time due to the complete closure of the valve, thereby greatly reducing the water flow impact when the valve of the cooling water flow regulating valve is opened, avoiding severe vibration of the cooling water pipeline due to strong water flow impact, thereby effectively avoiding damage to related equipment.

[0058] The utility model also provides a nuclear power plant evaporator sewage discharge system, whose cooling water flow regulating valve assembly can avoid the occurrence of water hammer phenomenon and avoid severe vibration of cooling water pipelines caused by strong water flow impact, thereby avoiding damage to related equipment.

[0059] The cooling water flow regulating valve assembly provided by the utility model and the evaporator sewage discharge system of a nuclear power plant using the cooling water flow regulating valve assembly are introduced in detail above. The principle and implementation method of the utility model are explained in this article using specific examples. The description of the above embodiments is only used to help understand the method of the utility model and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the utility model, the utility model can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the utility model.

Claims

1. A cooling water flow regulating valve assembly, characterized in that: It comprises a valve body and a valve stem vertically inserted into the valve body, the top end of the valve stem extends from the bottom to the top of the valve body, a driving mechanism is arranged above the valve body, and the driving mechanism is linked with the top end of the valve stem to drive the valve stem to reciprocate in the vertical direction; A limit ring and a locking nut are sleeved on the valve stem, and the limit ring and the locking nut are arranged in sequence from bottom to top along the axial direction of the valve stem between the valve body and the driving mechanism, and the limit ring and the locking nut are respectively matched with the valve stem thread, and the top end of the limit ring and the bottom end of the locking nut are abutted against each other in the vertical direction.

2. The cooling water flow regulating valve assembly according to claim 1, characterized in that: The valve body is provided with a packing bolt, the top end of which protrudes from the top end of the valve body in the vertical direction, and the top end of the packing bolt can abut against the bottom end of the limit retaining ring in the vertical direction.

3. The cooling water flow regulating valve assembly according to claim 2, characterized in that: There are two packing bolts, and the two packing bolts are symmetrically arranged on both sides of the valve stem along the horizontal direction.

4. The cooling water flow regulating valve assembly according to claim 3, characterized in that: The packing bolt and the valve stem are clearance-matched along the horizontal direction.

5. The cooling water flow regulating valve assembly according to claim 1, characterized in that: The bottom of the limit retaining ring protrudes downward in the vertical direction and is provided with a buffer boss.

6. The cooling water flow regulating valve assembly according to claim 5, characterized in that: The buffer boss is an annular boss extending along the circumference of the limit retaining ring and connected end to end.

7. The cooling water flow regulating valve assembly according to claim 6, characterized in that: The buffer boss is located at the bottom of the limit retaining ring close to the outer edge.

8. The cooling water flow regulating valve assembly according to claim 7, characterized in that: The axial thickness of the limit retaining ring increases linearly from the hole wall of its central threaded hole to the inner end edge of the bottom surface of the buffer boss to form a buffer cone surface located between the buffer boss and the central threaded hole of the limit retaining ring.

9. The cooling water flow regulating valve assembly according to claim 1, characterized in that: A coupling is provided at the bottom of the driving mechanism, and the driving mechanism and the valve stem are linked and connected via the coupling.

10. A nuclear power plant evaporator sewage system, comprising a cooling water pipeline and a cooling water flow regulating valve interconnected and coordinated with each other, characterized in that: The cooling water flow regulating valve assembly is the cooling water flow regulating valve assembly according to any one of claims 1 to 9.

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