A sealing structure for a reheat butterfly valve in a nuclear power turbine.

Abstract

This invention discloses a sealing structure for a reheat butterfly valve in a nuclear power turbine, comprising a non-contact labyrinth seal ring for sealing the gap between the valve cover and the valve shaft, a butterfly plate-side sealing assembly, and a bearing-side sealing assembly; a balancing pipeline for discharging steam and water is installed on the valve cover corresponding to the gap between the butterfly plate-side sealing assembly and the bearing-side sealing assembly; a steam recovery pipeline connected to the shaft seal steam supply header is provided on the upper side of the valve cover, and a steam-water mixing pipeline connected to the shaft seal return steam header is provided on the lower side of the valve cover; the steam-water mixing pipeline is located on the butterfly plate side of the butterfly plate-side sealing assembly and close to it, and the steam recovery pipeline is located between the steam-water mixing pipeline and the valve body. This invention can prevent high-temperature steam and condensate from entering the bearing and diluting the lubricating grease, damaging the bearing lubrication effect and causing valve jamming; it can also prevent bearing lubricating grease from entering the internal steam system of the valve and contaminating the nuclear island equipment.

Description

Technical Field

[0001] This invention belongs to the field of valves, and specifically relates to a sealing structure for a reheat butterfly valve of a nuclear power turbine. Background Technology

[0002] Existing butterfly valves typically have a sealing structure at the connection between the valve shaft and the valve body to prevent leakage of the medium through the valve shaft during operation. Butterfly valves are also used in nuclear power turbines. During normal operation of a nuclear power turbine, reheated steam enters the intermediate-pressure or low-pressure cylinder through a reheat butterfly valve. The reheat butterfly valve controls the steam flow rate into the intermediate-pressure or low-pressure cylinder by adjusting the valve opening.

[0003] Reheat butterfly valves are installed on the steam pipeline between the steam-water separator reheater (MSR) and the intermediate-pressure or low-pressure cylinder to shut off or control the steam entering the intermediate-pressure or low-pressure cylinder. Each unit typically has four or six sets of reheat butterfly valves, each set consisting of a main steam valve and a regulating valve connected in series. The main steam valve is a two-position valve, providing an on / off function, while the regulating valve is a continuously position valve, providing a regulating function. Each main steam valve and regulating valve has two sets of sealing structures at both ends of the valve shaft, primarily to prevent steam leakage from the shaft ends during unit operation or air leakage during unit startup.

[0004] Due to frequent valve opening and closing, after a period of use, the sealing structure / sealing packing between the valve body and valve shaft often wears or loosens due to aging. This allows steam in the reheat butterfly valve to leak from the shaft ends of the butterfly plate, or air and bearing lubricating grease to enter the steam system. Specifically, during reheat butterfly valve operation, high-temperature, high-pressure steam leaks outward through the gap between the valve shaft and valve body at both ends of the butterfly plate. After passing through the gap between the valve shaft and valve body, the steam leaks in two directions towards the shaft end: one is on the valve shaft side, where steam leaks through the gap between the valve shaft and the sealing structure; the other is on the valve cover side, where steam leaks through the gap between the valve cover and the sealing structure towards the shaft end. The leaked high-temperature steam and condensate can corrode the bearings, causing valve jamming and potentially leading to serious accidents. Furthermore, if the bearing lubricating grease enters the steam system, it can contaminate nuclear island equipment. In actual use, valve jamming and other risks may also occur. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a sealing structure for a reheat butterfly valve in a nuclear power turbine that is simple in structure, highly reliable, avoids damage to the butterfly valve caused by high-temperature steam, condensate, and lubricating grease, and reduces the risk of valve jamming.

[0006] The technical objective of this invention is achieved through the following technical solution:

[0007] A sealing structure for a reheat butterfly valve in a nuclear power turbine includes a non-contact labyrinth seal ring for sealing the gap between the valve cover and the valve shaft, a butterfly plate side sealing assembly, and a bearing side sealing assembly. The butterfly plate side sealing assembly and the bearing side sealing assembly are spaced apart. The butterfly plate side sealing assembly abuts against the non-contact labyrinth seal ring on the side facing the valve body, which is used to close the gap on the butterfly plate side. The bearing side sealing assembly is used to close the gap on the bearing side. The valve cover has through holes on its upper and lower sides corresponding to the gap between the butterfly plate side sealing assembly and the bearing side sealing assembly, and a balance pipe for discharging steam and water is installed at the through holes. The upper side of the valve cover is also provided with a steam recovery pipe connected to the shaft seal steam supply header, and the lower side is provided with a steam-water mixing pipe connected to the shaft seal return steam header. The steam-water mixing pipe is located on the butterfly plate side of the butterfly plate side sealing assembly and close to it. The steam recovery pipe is located between the steam-water mixing pipe and the valve body.

[0008] The butterfly plate side sealing assembly includes a butterfly plate side sealing part, a butterfly plate side retaining ring, and a butterfly plate side sealing ring. The butterfly plate side sealing part is used to seal the gap between the valve cover and the valve shaft on the side of the non-contact labyrinth seal ring. The upper part of the butterfly plate side retaining ring is connected to the inside of the valve cover by fixing screws, and its lower part is fixedly connected to the bearing side of the butterfly plate side sealing part by screws. The upper end of the butterfly plate side sealing part and the lower end of the butterfly plate side retaining ring are respectively provided with grooves, and the butterfly plate side sealing ring is installed in the grooves.

[0009] The bearing-side sealing assembly includes a bearing-side sealing part, a bearing-side retaining ring, and a bearing-side sealing ring; the bearing-side sealing assembly is used to seal the gap between the valve cover and the valve shaft on one side of the bearing; the bearing-side retaining ring abuts against the butterfly plate side of the bearing and is connected to the bearing-side sealing part by screws; the upper end of the bearing-side sealing part and the lower end of the bearing-side retaining ring are respectively provided with grooves, and the bearing-side sealing ring is installed in the grooves.

[0010] The non-contact labyrinth seal is composed of at least three seals with the same structure connected in series.

[0011] The non-contact labyrinth seal ring consists of a first-stage seal ring, a second-stage seal ring, and a third-stage seal ring arranged sequentially from the butterfly plate side towards the bearing side; the first-stage seal ring, the second-stage seal ring, and the third-stage seal ring abut against each other; a steam recovery pipeline is provided on the upper side of the valve cover between the second-stage seal ring and the third-stage seal ring; and a steam-water mixing pipeline is provided on the lower side of the valve cover between the third-stage seal ring and the butterfly plate side sealing assembly.

[0012] The sealing ring includes a sealing ring body and two spaced protrusions on the sealing ring body; the upper end of the protrusions is in clearance fit with the inner wall of the valve cover.

[0013] The balancing pipeline includes an upper balancing pipeline located on the upper side of the valve cover and a lower balancing pipeline located on the lower side of the valve cover; the upper balancing pipeline is used to discharge the gas in the gas-water mixture that enters from the butterfly plate side sealing assembly; the lower balancing pipeline is used to discharge the liquid in the gas-water mixture.

[0014] The balancing pipeline is equipped with a valve switch, which is normally open.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] 1. The main shaft seal of the reheat butterfly valve of this invention adopts a non-contact labyrinth seal ring. This technology reduces the valve's rotational torque and lowers the risk of valve jamming. The butterfly plate-side sealing assembly and the bearing-side sealing assembly prevent lubricating grease from entering the steam system and contaminating nuclear island equipment. A steam recovery pipeline connected to the shaft seal supply header is located on the upper side of the valve cover, and a steam-water mixing pipeline connected to the shaft seal return header is located on the lower side. This technology utilizes the shaft seal system to recover sealing steam and condensate, preventing steam leakage from both ends of the shaft during unit operation or air leakage during unit startup. A balancing pipeline is provided at the butterfly plate-side sealing assembly and the bearing-side seal. This balancing pipeline is used to remove leaked steam and condensate after seal ring failure or functional degradation, reducing the corrosion of rolling bearings by high-temperature steam and condensate and improving valve reliability. The nuclear power turbine reheat butterfly valve with the above-mentioned sealing structure effectively prevents steam leakage from both ends of the butterfly plate shaft or air leakage, as well as lubricating grease from the bearing side from entering the steam system. This technical measure can reduce the valve's rotation torque, prevent valve jamming, and improve safety and reliability.

[0017] 2. The butterfly plate side sealing assembly of the present invention includes a butterfly plate side sealing portion, a butterfly plate side retaining ring, and a butterfly plate side sealing ring. Axial limiting of the non-contact labyrinth seal ring is achieved by the valve cover and the butterfly plate side sealing portion of the butterfly plate side sealing assembly. Simultaneously, a secondary seal is formed by the butterfly plate side sealing assembly with the butterfly plate side sealing ring. This technical measure further improves the sealing effect and reduces steam leakage.

[0018] 3. The bearing-side sealing assembly of the present invention includes a bearing-side sealing part, a bearing-side retaining ring, and a bearing-side sealing ring. By providing a bearing-side sealing ring, the sealing effect can be improved, and the entry of lubricating grease into the steam system can be reduced / prevented.

[0019] 4. The valve cover of the present invention has through holes extending through both the upper and lower sides of the gap between the butterfly plate side sealing assembly and the bearing side sealing assembly, and a balancing pipeline for discharging steam and water is installed at the through holes. The balancing pipeline includes an upper balancing pipeline located on the upper side of the valve cover and a lower balancing pipeline located on the lower side of the valve cover; the upper balancing pipeline is used to discharge the gas in the steam-water mixture entering from the butterfly plate side sealing assembly; the lower balancing pipeline is used to discharge the liquid in the steam-water mixture. In actual use, the balancing pipeline is equipped with a valve switch, which is normally open. The balancing pipeline between the butterfly plate side sealing assembly and the bearing side sealing assembly discharges steam and liquid, preventing steam or water in the reheat butterfly valve from entering the bearing and avoiding steam or water entering the bearing's lubricating grease, thus preventing damage to the lubrication effect; at the same time, it also prevents the lubricating grease in the bearing from seeping into the steam. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the present invention;

[0021] Figure 2 yes Figure 1 Enlarged view of section A in the middle;

[0022] Figure 3 yes Figure 1 Enlarged view of section B in the middle;

[0023] Reference numerals: 1—valve body; 2—butterfly plate; 3—valve cover; 4—valve shaft; 5—bearing;

[0024] 6—Non-contact labyrinth seal; 61—First-stage seal; 62—Second-stage seal; 63—Third-stage seal; 601—Seal body; 602—Protrusion;

[0025] 7—Butterfly plate side sealing assembly; 71—Butterfly plate side sealing part; 72—Butterfly plate side retaining ring; 73—Butterfly plate side sealing ring;

[0026] 8—Bearing side sealing assembly; 81—Bearing side sealing part; 82—Bearing side retaining ring; 83—Bearing side sealing ring;

[0027] 9—Steam recovery pipeline;

[0028] 10—Steam-water mixing pipeline;

[0029] 11—Balancing pipeline; 111—Upper balancing pipeline; 112—Lower balancing pipeline; 113—Valve switch. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0031] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0032] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0033] like Figure 1 — Figure 2As shown, a sealing structure for a reheat butterfly valve in a nuclear power turbine includes a non-contact labyrinth seal ring 6 for sealing the gap between the valve cover 3 and the valve shaft 4, a butterfly plate side sealing assembly 7, and a bearing side sealing assembly 8; the butterfly plate side sealing assembly 7 and the bearing side sealing assembly 8 are spaced apart; the butterfly plate side sealing assembly 7 abuts against the non-contact labyrinth seal ring 6 on the side facing the valve body 1, which is used to close the gap on the butterfly plate side and axially limit it; the bearing side sealing assembly 8 is used to close the gap on the bearing side; the valve cover 3... The gap between the butterfly plate side sealing assembly 7 and the bearing side sealing assembly 8 is provided with through holes running through both the upper and lower sides, and a balance pipe 11 for discharging steam and water is installed at the through holes; a steam recovery pipe 9 connected to the shaft seal steam supply header is also provided on the upper side of the valve cover 3, and a steam-water mixing pipe 10 connected to the shaft seal return steam header is provided on its lower side; the steam-water mixing pipe 10 is located on the butterfly plate side of the butterfly plate side sealing assembly 7 and close to it, and the steam recovery pipe 9 is located between the steam-water mixing pipe 10 and the valve body 1. In actual use, the main seal at the shaft end of the reheat butterfly valve adopts a non-contact labyrinth seal ring 6. With this technical measure, the valve's rotation torque is small, reducing the risk of valve jamming. Through the butterfly plate side sealing assembly 7 and the bearing side sealing assembly 8, the lubricating grease of the bearing 5 is prevented from entering the steam system and contaminating the nuclear island equipment. A steam recovery pipeline 9, connected to the shaft seal steam supply header, is located on the upper side of the valve cover 3, and a steam-water mixing pipeline 10, connected to the shaft seal return steam header, is located on the lower side of the cover 3. This technical measure utilizes the shaft seal system to recover sealing steam and condensate, preventing steam leakage from both ends of the shaft during unit operation or air leakage during unit startup. A balancing pipeline 11 is provided at the butterfly plate side sealing assembly 7 and the bearing side seal. The balancing pipeline 11 is used to drain leaked steam and condensate after seal ring failure or functional degradation, reducing the corrosion of bearing 5 by high-temperature steam and condensate, and improving valve reliability. The nuclear power turbine reheat butterfly valve with the above-mentioned sealing structure effectively prevents steam in the reheat butterfly valve from leaking from both ends of the butterfly plate 2, preventing air leakage, and preventing lubricating grease from the bearing side from entering the steam system. This technical measure reduces the valve's turning torque, prevents valve jamming, and improves safety and reliability. This invention can prevent high-temperature steam and condensate from entering the bearing 5 and diluting the lubricating grease, thus damaging the lubrication effect of the bearing 5 and causing valve jamming; it can also prevent the lubricating grease of the bearing 5 from entering the steam system inside the valve and contaminating the nuclear island equipment; at the same time, this invention uses a non-contact labyrinth seal ring 6, which can reduce the rotational torque of the valve plate, thereby reducing the risk of valve jamming.

[0034] like Figure 1 , Figure 2As shown, the left end of the valve shaft 4 is connected to the butterfly plate 2, and the left end of the valve cover 3 is connected to the valve body 1. There is an active clearance between the valve cover 3 and the valve shaft 4. A non-contact labyrinth seal ring 6, a butterfly plate side seal assembly 7, and a bearing side seal assembly 8 for sealing the clearance are provided in the clearance between the valve cover 3 and the valve shaft 4. In actual use, the non-contact labyrinth seal ring 6 is composed of at least three seal rings with the same structure connected in series. The cross-section of the seal ring is in the shape of a grass head. The seal ring includes a seal ring body 601 and two spaced protrusions 602 provided on the seal ring body 601; the upper end of the protrusion 602 is in clearance fit with the inner wall of the valve cover 3. After the seal ring is installed in the clearance between the valve shaft 4 and the valve cover 3, a chamber is formed between the protrusion 602, the seal ring body 601, and the valve cover 3. By adopting this technical measure, a multi-stage seal ring is formed. When high-temperature and high-pressure steam moves from the butterfly plate side to the bearing side (from the left end of the valve shaft 4 to the right end of the valve shaft 4), after passing through two steam seal rings, the temperature and pressure will be greatly reduced. A steam recovery pipeline 9 connected to the shaft seal steam supply header pipe is provided on the upper side of the valve cover 3, and a steam-water mixing pipeline 10 connected to the shaft seal return steam header pipe is provided on the lower side thereof. The steam recovery pipeline 9 and the steam-water mixing pipeline 10 are arranged staggeredly, and the steam-water mixing pipeline 10 is arranged on the butterfly plate side of the butterfly plate side seal assembly 7 and is close to it; the steam recovery pipeline 9 is arranged between the steam-water mixing pipeline 10 and the valve body 1. Specifically, a through hole penetrating the upper side of the valve cover 3 is provided between the valve body 1 and the butterfly plate side seal assembly 7, and a steam recovery pipeline 9 connected to the shaft seal steam supply header pipe is provided at the through hole. A through hole penetrating the lower side of the valve cover 3 is provided between the steam recovery pipeline 9 and the butterfly plate side seal assembly 7, and a steam-water mixing pipeline 10 connected to the shaft seal return steam header pipe is provided at the through hole. Among them, when the seal ring adopts a multi-stage structure, the non-contact labyrinth seal ring 6 is composed of a first-stage seal ring 61, a second-stage seal ring 62, and a third-stage seal ring 63 arranged in sequence from the butterfly plate side to the bearing side; the first-stage seal ring 61, the second-stage seal ring 62, and the third-stage seal ring 63 are in contact with each other. A steam recovery pipeline 9 is provided on the upper side of the valve cover 3 between the second-stage seal ring 62 and the third-stage seal ring 63, and a steam-water mixing pipeline 10 is provided on the lower side of the valve cover between the third-stage seal ring 63 and the butterfly plate side seal assembly 7. Specifically, the steam on the shaft side of the valve shaft 4 flows through the clearance between the two seal rings to the chamber on the valve cover 3 side. By providing a steam recovery pipeline 9 connected to the shaft seal steam supply header pipe on the upper side of the valve cover 3, the mixed steam with greatly reduced temperature and pressure is introduced into the shaft seal system steam supply header pipe through a pipeline to reduce the steam supply demand of the shaft seal system. When the steam continues to leak to the right end of the valve shaft 4, after passing through a stage of seal ring again, when the steam reaches the left side (butterfly plate side) of the butterfly plate side seal assembly 7, the temperature and pressure are further reduced. The steam parameters here have been reduced to be equivalent to the shaft seal system return steam. A steam-water mixing pipeline 10 connected to the shaft seal return steam header pipe is provided on the lower side of the valve cover 3, and the mixed steam and condensate water here are introduced into the shaft seal system return steam header pipe or the steam seal heater through a pipeline.This technical measure utilizes the shaft sealing system to recover steam and condensate from the sealing structure, preventing steam from leaking outward from the shafts at both ends during unit operation or air from leaking inward during unit startup.

[0035] like Figure 1 , Figure 2 As shown, the butterfly plate side sealing assembly 7 abuts against the non-contact labyrinth seal ring 6 on the side facing the valve body 1, which is used to close the gap on the butterfly plate side and limit axial movement. Specifically, the butterfly plate side sealing assembly 7 includes a butterfly plate side sealing part 71, a butterfly plate side retaining ring 72, and a butterfly plate side sealing ring 73; the butterfly plate side sealing part 71 is used to seal the gap between the valve cover 3 and the valve shaft 4 on the side of the non-contact labyrinth seal ring 6; the upper part of the butterfly plate side retaining ring 72 is connected to the inside of the valve cover 3 by fixing screws, and its lower part is fixedly connected to the bearing side of the butterfly plate side sealing part 71 by screws; the upper end of the butterfly plate side sealing part 71 and the lower end of the butterfly plate side retaining ring 72 are respectively provided with grooves, and the butterfly plate side sealing ring 73 is installed in the grooves. The butterfly plate side sealing part 71, the butterfly plate side retaining ring 72, and the butterfly plate side sealing ring 73 of the butterfly plate side sealing assembly 7 are detachably connected, which facilitates replacement and maintenance. The axial limiting of the non-contact labyrinth seal ring 6 is achieved by the valve cover 3 and the butterfly plate side sealing part 71 of the butterfly plate side sealing assembly 7. At the same time, the butterfly plate side sealing assembly 7, which is equipped with a butterfly plate side sealing ring 73, forms a secondary seal. By adopting this technical measure, the sealing effect can be further improved and steam leakage can be reduced.

[0036] like Figure 1 , Figure 2 As shown, the bearing-side sealing assembly 8 includes a bearing-side sealing part 81, a bearing-side retaining ring 82, and a bearing-side sealing ring 83. The bearing-side sealing assembly 8 is used to seal the gap between the valve cover 3 and the valve shaft 4 on one side of the bearing 5. The bearing-side retaining ring 82 abuts against the butterfly plate side of the bearing 5 and is connected to the bearing-side sealing part 81 by screws. The upper end of the bearing-side sealing part 81 and the lower end of the bearing-side retaining ring 82 are respectively provided with grooves, and the bearing-side sealing ring 83 is installed in the grooves.

[0037] The bearing-side sealing part 81, the bearing-side retaining ring 82, and the bearing-side sealing ring 83 are detachably connected. By providing the bearing-side sealing ring 83, the sealing effect can be improved, reducing / preventing lubricating grease from entering the steam system.

[0038] like Figure 1 , Figure 2As shown, the valve cover 3 has through holes on both its upper and lower sides corresponding to the gap between the butterfly plate side sealing assembly 7 and the bearing side sealing assembly 8, and a balancing pipe 11 for discharging steam and water is installed at the through holes. Specifically, the balancing pipe 11 includes an upper balancing pipe 111 located on the upper side of the valve cover 3 and a lower balancing pipe 112 located on the lower side of the valve cover 3; the upper balancing pipe 111 is used to discharge the gas in the steam-water mixture entering from the butterfly plate side sealing assembly 7; the lower balancing pipe 112 is used to discharge the liquid in the steam-water mixture. In actual use, the balancing pipe 11 is equipped with a valve switch 113, which is normally open. The balancing pipe 11 is set between the butterfly plate side sealing assembly 7 and the bearing side sealing assembly 8 to discharge steam and liquid, so that steam or water in the reheat butterfly valve will not enter the bearing 5, avoiding steam or water from entering the lubricating grease in the bearing 5 and damaging the lubrication effect; at the same time, it also prevents the lubricating grease in the bearing 5 from seeping into the steam.

[0039] In actual use, when the shaft seal fan is running normally, the shaft seal return steam pipeline is under negative pressure, and the steam pressure between the butterfly plate side sealing assembly 7 and the third-stage sealing ring 63 is less than atmospheric pressure. At this time, air enters the space between the third-stage sealing ring 63 and the butterfly plate side sealing assembly 7 through the balance pipeline 11, mixes with the steam after the third-stage sealing ring 63, and then enters the shaft seal return steam pipeline, thus avoiding excessive extraction of steam from the reheat butterfly valve.

[0040] When the steam pressure between the third-stage sealing ring 63 and the butterfly plate side sealing assembly 7 is greater than atmospheric pressure, the steam between the third-stage sealing ring 63 and the butterfly plate side sealing assembly 7 passes through the butterfly plate side sealing ring 73 and forms a steam-water mixture. The water in the mixture is discharged through the lower balance pipe 112, and the gas in the steam-water mixture is discharged through the upper balance pipe 111.

[0041] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of the present invention. The descriptions of the embodiments above are only for helping to understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A sealing structure for a reheat butterfly valve in a nuclear power turbine, characterized in that, This includes a non-contact labyrinth seal ring for sealing the gap between the valve cover and valve shaft of a butterfly valve, a butterfly plate side sealing assembly, and a bearing side sealing assembly; The butterfly plate side sealing assembly and the bearing side sealing assembly are spaced apart; The butterfly plate side sealing assembly abuts against the non-contact labyrinth seal ring on the side facing the valve body, which is used to close the gap on the butterfly plate side and limit axial movement. The bearing-side sealing assembly is used to seal the gap on the bearing side; The valve cover is provided with a through hole that runs through both the upper and lower sides of the gap between the butterfly plate side sealing assembly and the bearing side sealing assembly, and a balance pipe for discharging steam and water is installed at the through hole. The valve cover is also provided with a steam recovery pipeline connected to the shaft seal steam supply header on the upper side, and a steam-water mixing pipeline connected to the shaft seal return steam header on the lower side. The steam-water mixing pipeline is located on the butterfly plate side of the butterfly plate side sealing assembly and is close to it. The steam recovery pipeline is located between the steam-water mixing pipeline and the valve body.

2. The sealing structure for a reheat butterfly valve in a nuclear power turbine according to claim 1, characterized in that, The butterfly plate side sealing assembly includes a butterfly plate side sealing part, a butterfly plate side retaining ring, and a butterfly plate side sealing ring. The butterfly plate side sealing part is used to seal the gap between the valve cover and the valve shaft on the side of the non-contact labyrinth seal ring. The upper part of the butterfly plate side retaining ring is connected to the inside of the valve cover by fixing screws, and its lower part is fixedly connected to the bearing side of the butterfly plate side sealing part by screws. The upper end of the butterfly plate side sealing part and the lower end of the butterfly plate side retaining ring are respectively provided with grooves, and the butterfly plate side sealing ring is installed in the grooves.

3. The sealing structure for a reheat butterfly valve in a nuclear power turbine according to claim 1, characterized in that, The bearing-side sealing assembly includes a bearing-side sealing part, a bearing-side retaining ring, and a bearing-side sealing ring; the bearing-side sealing assembly is used to seal the gap between the valve cover and the valve shaft on one side of the bearing; the bearing-side retaining ring abuts against the butterfly plate side of the bearing and is connected to the bearing-side sealing part by screws; the upper end of the bearing-side sealing part and the lower end of the bearing-side retaining ring are respectively provided with grooves, and the bearing-side sealing ring is installed in the grooves.

4. The sealing structure for a reheat butterfly valve in a nuclear power turbine according to claim 1, characterized in that, The non-contact labyrinth seal is composed of at least three seals with the same structure connected in series.

5. The sealing structure for a reheat butterfly valve in a nuclear power turbine according to claim 4, characterized in that, The non-contact labyrinth seal ring consists of a first-stage seal ring, a second-stage seal ring, and a third-stage seal ring arranged sequentially from the butterfly plate side towards the bearing side; the first-stage seal ring, the second-stage seal ring, and the third-stage seal ring abut against each other; a steam recovery pipeline is provided on the upper side of the valve cover between the second-stage seal ring and the third-stage seal ring; and a steam-water mixing pipeline is provided on the lower side of the valve cover between the third-stage seal ring and the butterfly plate side sealing assembly.

6. The sealing structure for a reheat butterfly valve in a nuclear power turbine according to claim 4, characterized in that, The sealing ring includes a sealing ring body and two spaced protrusions on the sealing ring body; the upper end of the protrusions is in clearance fit with the inner wall of the valve cover.

7. The sealing structure for a reheat butterfly valve in a nuclear power turbine according to claim 1, characterized in that, The balancing pipeline includes an upper balancing pipeline located on the upper side of the valve cover and a lower balancing pipeline located on the lower side of the valve cover; the upper balancing pipeline is used to discharge the gas in the gas-water mixture that enters from the butterfly plate side sealing assembly; the lower balancing pipeline is used to discharge the liquid in the gas-water mixture.

8. The sealing structure for a reheat butterfly valve in a nuclear power turbine according to claim 1 or 7, characterized in that, The balancing pipeline is equipped with a valve switch, which is normally open.

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