Medium self-driven main steam quick-closing isolation valve for nuclear power plant

Abstract

The present application belongs to the field of nuclear power plant valve engineering design, and particularly relates to a medium self-driven main steam quick-closing isolation valve for nuclear power plant. The valve body, piston cylinder, valve rod and valve cover are connected, the piston cylinder is sleeved in the valve body and fixed on the valve cover, the valve rod is sleeved in the piston cylinder, the upper end of the valve rod penetrates the middle of the valve cover and is connected with the shaft coupling, the upper guide sleeve is installed on the valve cover, the upper part of the shaft coupling is connected with the limiter assembly, the shaft coupling and the limiter assembly are covered in the bracket cover, and the bracket cover is connected on the top of the valve cover. The present application has the advantages of faster valve closing speed, compact structure design, small size, uniform mass distribution, no external driving pipeline, good overall rigidity and high anti-seismic performance.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power plant valve engineering design, specifically relating to a medium-driven main steam quick-closing isolation valve for nuclear power plants. Background Technology

[0002] In the main steam piping system of a pressurized water reactor nuclear power plant, the main steam isolation valve is installed on the secondary main steam piping outside the containment. One main steam isolation valve is installed on each main steam pipeline, which is classified as a Class 2 nuclear equipment. Under normal steady-state operating conditions, the main steam isolation valve remains fully open to allow steam flow. In abnormal or accident conditions (such as a main steam pipeline rupture), upon receiving an isolation signal, the main steam isolation valve can quickly close, achieving rapid isolation between the steam generator and the main steam pipeline.

[0003] In the development of main steam isolation valves, various types of main steam isolation valves have emerged, including Y-type gate valves with electric drive, Y-type gate valves with pneumatic drive and spring energy storage, gate valves with pneumatic-hydraulic linkage mechanisms, self-medium driven valves, and check valve-like valves. Currently, most main steam isolation valves in nuclear power plants operating or under construction worldwide are gate valves with pneumatic-hydraulic linkage mechanisms, and the main valve type is a double-gate valve structure.

[0004] Practical engineering experience shows that gate valves with pneumatic-hydraulic linkage mechanisms have the following main drawbacks:

[0005] (1) The drive mechanism is large in size, heavy in weight, and uneven in mass distribution. It also has a large number of external drive pipelines, and the overall layout and seismic support are complex and occupy a lot of space.

[0006] (2) The drive mechanism uses hydraulic oil to store energy by compressing the nitrogen chamber through the piston, and relies on the energy stored in the nitrogen chamber to complete the drive; the oil circuit for pressurizing and maintaining the pressure of nitrogen is always under high pressure, and internal leakage of the control solenoid valve and leakage defects of each joint occur frequently; when the solenoid valve leaks internally, it will cause the oil pump to pressurize frequently; the oil quality needs to be carefully maintained, and there have been cases of solenoid valve jamming due to oil deterioration.

[0007] (3) The maintenance process is complex, difficult and time-consuming. It mostly relies on the return of spare parts to the factory for maintenance, which results in high maintenance costs and is not conducive to optimizing the refueling and overhaul period of the unit.

[0008] (4) The drive mechanism has a complex structure, many parts, many failure points, and low overall reliability; its control part contains a large number of hydraulic components such as solenoid valves, check valves, and pressure transmitters, which have poor reliability.

[0009] (5) The cylinder pressure of the drive mechanism is significantly affected by the ambient temperature. When the temperature changes, it will cause oil pressure fluctuations, resulting in a high failure alarm rate.

[0010] (6) The drive mechanism involves independent drive pumps, filters, etc., which are prone to leakage and blockage, affecting the safe operation of the valve;

[0011] (7) The drive requires a large amount of hydraulic oil. The leakage of hydraulic oil onto the hot surface of the main steam pipe poses a significant fire hazard to the plant. Similar fire incidents have occurred in nuclear power plants.

[0012] (8) The structure of the gate valve determines that when the valve is in the fully open position, space needs to be reserved in the upper cavity of the valve body for the position of the valve plate. This structure will form a local flow field of swirling flow and eddy current. Flow-induced vibration is a common feature of large-diameter gate valves used in the main steam system of nuclear power plants. Vibration will cause wear between the valve plate and the valve seat or between the valve plate and the anti-rotation pin, and wear between the valve plate bracket and the guide rail. The maintenance workload is large, and these defects will affect the tightness of the valve when it is closed. The gate valve plate and the bracket are connected by threads. Under long-term vibration, the threaded connection has failed and the valve plate has fallen off.

[0013] (10) The valve stem is sealed with packing, which poses a risk of leakage.

[0014] Therefore, developing a new type of main steam quick-closing isolation valve that can meet the requirements of the main steam system of nuclear power plants of 1,000 kilowatts and above, and effectively solve the shortcomings of gas-liquid linkage gate valves such as poor seismic performance, complex drive mechanism design, improved operational reliability, reduced maintenance workload and risks, and simplified system design is of great significance to improving nuclear safety and industrial safety. Summary of the Invention

[0015] The purpose of this invention is to provide a self-driven main steam quick-closing isolation valve for nuclear power plants, which uses the energy of the main steam medium without requiring a dedicated actuation drive mechanism or external energy source; the pilot-operated control has high actuation accuracy, good anti-vibration performance, and simplifies system design. It can effectively solve the problems of poor anti-vibration performance and complex drive mechanism design of gas-liquid linkage gate valves, and can effectively improve its operational reliability and reduce maintenance workload and risks.

[0016] The technical solution of the present invention is as follows: A medium-driven main steam quick-closing isolation valve for nuclear power plants includes a valve body, a piston cylinder, a valve stem, and a valve cover. The valve cover is connected to the valve body. The piston cylinder is fitted inside the valve body and fixed on the valve cover. The valve stem is fitted inside the piston cylinder. The upper end of the valve stem passes through the middle of the valve cover and is connected to a coupling. An upper guide sleeve is installed on the valve cover. A limiter assembly is connected to the upper part of the coupling. The coupling and the limiter assembly are covered inside a support cover. The support cover is connected to the top of the valve cover.

[0017] The valve stem is a rod-shaped structure with a protrusion in the middle. The piston cylinder sleeve is outside the valve stem and provides guidance for the movement of the protrusion in the middle of the valve stem. The lower guide sleeve is fitted on the rod-shaped part of the valve stem and provides guidance for the movement of the valve stem. The piston ring is installed on the piston cylinder. The lower guide sleeve is installed on the piston cylinder by a second screw and fixed with a second stop washer. The valve core and the valve stem are connected by a T-shaped structure and fixed with an anti-rotation connecting plate.

[0018] The valve position indicator is installed on the top of the valve stem; a limiter assembly is installed on the top of the valve stem to limit the axial movement of the valve stem; and the valve cover is provided with an oblique flow channel connecting the upper part of the valve stem and the cavity formed between the valve cover and the valve stem.

[0019] The edge of the valve cover is connected to the top of the valve body by a first fastener, which includes a first bolt, a first washer, and a first nut.

[0020] A second pin is fixed between the edge of the valve cover and the top of the valve body, and a first sealing gasket is used to achieve a seal.

[0021] The piston cylinder is fitted into the valve body and fixed to the valve cover by a second fastener, which includes a third bolt, a third washer and a third nut, and is positioned by a first pin, the two ends of which are inserted into the valve cover and the piston cylinder, respectively.

[0022] The upper guide sleeve is mounted on the valve cover by a first screw and fixed with a first stop washer.

[0023] The bracket cover is connected to the top of the valve cover by a third fastener, which includes a second bolt, a second washer, and a second nut, and is sealed with a second sealing gasket.

[0024] The piston ring is one or more, used to achieve a seal between the piston cylinder and the valve body;

[0025] The lower guide sleeve is mounted on the piston cylinder by a second screw and fixed with a second stop washer.

[0026] The beneficial effects of this invention are as follows:

[0027] 1) The valve closes faster, has a compact structure and small size, uniform mass distribution, no external drive pipeline, good overall rigidity and high seismic performance;

[0028] 2) The main valve and pilot valve have a simple structure, few parts, are easy and convenient to maintain, and have high reliability;

[0029] 3) The main valve is driven by the system medium and uses redundant drive. It does not require an independent air source or hydraulic oil drive, has no external pipelines or pipe joints, has a low risk of leakage, and greatly improves overall reliability.

[0030] 4) The valve stem is contained within the pressure boundary, so there is no valve stem leakage problem. The valve stem and valve core are connected by threads and special connecting components, so there is no risk of valve core falling off.

[0031] 5) A mechanical coupling is installed to reliably keep the valve stem and valve core in the fully open position, preventing the valve from closing accidentally.

[0032] 6) The shut-off function of the main steam isolation valve can be verified through the controllability test of the pilot valve (without the actual operation of the main steam isolation valve), which reduces the risk of unit operation and has advantages in manufacturing cost and automation. Attached Figure Description

[0033] Figure 1 This invention provides a structural diagram of a self-driven main steam quick-closing isolation valve for nuclear power plants.

[0034] Figure 2 This is a top view of a self-driven main steam quick-closing isolation valve for nuclear power plants provided by the present invention;

[0035] Figure 3 A schematic diagram of a self-driven main steam quick-closing isolation valve for nuclear power plants that remains open, provided by the present invention.

[0036] Figure 4 This is a first schematic diagram of the closed state of a self-driven main steam quick-closing isolation valve for nuclear power plants provided by the present invention.

[0037] Figure 5 This is a second schematic diagram of the closed state of a self-driven main steam quick-closing isolation valve for nuclear power plants provided by the present invention.

[0038] Figure 6 This is a schematic diagram of the open state of a self-driven main steam quick-closing isolation valve for nuclear power plants provided by the present invention.

[0039] In the diagram: 1 Valve body, 2 Piston cylinder, 3 Valve stem, 4 First pin, 5 Valve cover, 6 First sealing gasket, 7 Second pin, 8 First bolt, 9 First washer, 10 First nut, 40 Coupling, 11 Limiter assembly, 12 Bracket cover, 13 Second bolt, 14 Second washer, 15 Second nut, 16 Second sealing gasket, 17 Upper guide sleeve, 18 First screw, 19 First stop washer, 20 Third bolt, 21 Third washer, 22 Third nut, 23 Piston ring, 24 Lower guide sleeve, 25 Second screw, 26 Second stop washer, 27 Anti-rotation connecting disc, 28 Valve core, 29 Single electromagnetic pilot valve, 30 First double electromagnetic pilot valve, 31 Second double electromagnetic pilot valve, 32 First channel connecting sealing device, 33 Electric shut-off valve, 34 Second channel connecting sealing assembly, 35 Flange. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] A self-driven main steam quick-closing isolation valve for nuclear power plants, such as Figure 3 As shown, it is equipped with three electromagnetic pilot valves and one electric shut-off valve, with the three-way shut-off valve serving as the main isolation valve.

[0042] The pilot solenoid valves are divided into: a first dual solenoid pilot valve and a second dual solenoid pilot valve that perform the "quick shut-off" safety function, and a single solenoid pilot valve 29 that performs the opening function.

[0043] The main steam isolation valve is made of forged steel; it is a three-way shut-off valve with a piston-driven mechanism for opening and closing. An electromagnetic pilot valve controls the steam inside to operate the main valve. The pilot valve is directly mounted on the main valve body. Finite element analysis is used to study the matching design between the electromagnetic pilot valve and the main valve, determining the basic parameter requirements of the electromagnetic pilot valve. The erosion-resistant channel structure of the electromagnetic pilot valve is also a key focus of the research. During normal operation, the valve is held in the open position by a mechanical retaining device, without relying on system pressure. Regardless of whether a pipeline rupture occurs upstream or downstream of the valve, steam can be connected to the valve's inlet or outlet side through a selectively controlled check valve assembly, ensuring the stability of the steam source in the piston chamber. The sliding surface of the main valve undergoes surface hardening treatment, and related processes are studied to ensure the valve's sealing and operational life. All control pipelines are integrated inside the valve body of the main steam isolation valve or its pilot valve.

[0044] like Figure 1 As shown, a self-driven main steam quick-closing isolation valve for nuclear power plants includes a valve body 1, a piston cylinder 2, a valve stem 3, and a valve cover 5. The edge of the valve cover 5 is connected to the top of the valve body 1 by a first fastener, which includes a first bolt 8, a first washer 9, and a first nut 10. A second pin 7 is fixed between the edge of the valve cover 5 and the top of the valve body 1, and a first sealing gasket 6 is used to achieve sealing.

[0045] Piston cylinder 2 is fitted inside valve body 1 and fixed to valve cover 5 by a second fastener, which includes a third bolt 20, a third washer 21, and a third nut 22, and is positioned by a first pin 4, the two ends of which are inserted into valve cover 5 and piston cylinder 2 respectively; valve stem 3 is fitted inside piston cylinder 2, the upper end of valve stem 3 passes through the middle of valve cover 5 and is connected to coupling 40, upper guide sleeve 17 is installed on valve cover 5 by a first screw 18 and fixed by a first stop washer 19; limiter assembly 11 is connected to the upper part of coupling 10, coupling 40 and limiter assembly 11 are covered inside bracket cover 12, which can keep the valve in the fully open state, bracket cover 12 is connected to the top of valve cover 5 by a third fastener, which includes a second bolt 13, a second washer 14 and a second nut 15, and is sealed by a second sealing gasket 16.

[0046] The valve stem 3 is a rod-shaped structure with a protrusion in the middle. The piston cylinder 2 is sleeved on the outside of the valve stem 3 and provides guidance for the movement of the protrusion in the middle of the valve stem 3. The lower guide sleeve 24 is sleeved on the rod-shaped part of the valve stem 3 and provides guidance for the movement of the valve stem 3. The piston ring 23 is installed on the piston cylinder 2. There can be one or more piston rings 23, which are used to achieve the seal between the piston cylinder 2 and the valve body 1. The lower guide sleeve 24 is installed on the piston cylinder 2 by the second screw 25 and fixed by the second stop washer 26. The valve core 28 is connected to the valve stem 3 by a T-shaped structure and fixed by the anti-rotation connecting plate 27.

[0047] The valve stem 3 is installed inside the valve body 1. The valve stem 3 has a rod-shaped part, a middle protrusion and a head. The valve stem 3 has a flow channel to realize the discharge and sealing of the medium. A valve position indicator can be installed on the top of the valve stem 3. The limiter assembly 11 is installed on the top of the valve stem 3 to limit the axial movement position of the valve stem 3. The valve cover 5 is provided with an oblique flow channel connecting the upper part of the valve stem 3 and the chamber formed between the valve cover 5 and the valve stem 3. It is connected to the single electromagnetic pilot valve 29 to realize the charging and releasing of air pressure.

[0048] like Figure 2 As shown, a single electromagnetic pilot valve 29 is mounted on the valve body 1, a first double electromagnetic pilot valve 30 and a second double electromagnetic pilot valve 31 are mounted on the valve body 1, a first channel connection sealing device 32 is provided between the first double electromagnetic pilot valve 30, the second double electromagnetic pilot valve 31 and the valve body 1, an electric shut-off valve 33 is mounted on the valve body 1, a flange 35 is mounted on the valve body 1, and a second channel connection sealing assembly 34 is provided between the flange 35 and the valve body 1.

[0049] The operation control process of this invention is as follows:

[0050] like Figure 3 As shown, the main steam isolation valve remains open.

[0051] During normal operation, coupling 40 ensures that the main steam isolation valve remains in the open position. The two dual-solenoid pilot valves, first dual-solenoid pilot valve 30 and second dual-solenoid pilot valve 31, which control rapid closure, are closed; the single-solenoid pilot valve 29, which controls opening, is closed; and the electrically operated shut-off valve 33 is open. All internal cavities of the valves withstand system pressure and temperature through the steam inlet and clearance.

[0052] like Figure 4 As shown, the main steam isolation valve is closed – the upstream pipeline has ruptured.

[0053] If the upstream main steam pipeline ruptures, the upper chamber of the piston remains filled with steam by selectively opening the check valve assembly connected to the outlet side of the main valve. The connection between the upper chamber of the piston and the inlet side is then severed by the check valve assembly connected to the outlet side of the main valve. Opening the two dual-solenoid pilot valves, the first dual-solenoid pilot valve 30 and the second dual-solenoid pilot valve 31, reduces the pressure in the lower chamber of the piston. Due to the pressure difference between the upper and lower parts of the piston, the main steam isolation valve closes.

[0054] like Figure 5 The main steam isolation valve shown is closed – downstream pipeline rupture.

[0055] When the upstream main steam pipeline ruptures, the piston upper chamber remains filled with steam by selectively opening the check valve assembly connected to the inlet side of the main valve.

[0056] like Figure 6 As shown, the main steam isolation valve is open.

[0057] The main steam isolation valve can open when the pressure between its inlet and outlet is approximately balanced. The opening of the main steam isolation valve is controlled by a single solenoid pilot valve 29, which simultaneously closes the electrically operated shut-off valve 33 to stop steam supply to the upper chamber of the piston. The pressure difference between the upper and lower chambers of the piston causes the valve to open, and the valve stem 3 enters the mechanical coupling 10 to hold the main steam isolation valve in the open position. After the main steam isolation valve opens, the single solenoid pilot valve 29 closes, and the electrically operated isolation valve reopens.

Claims

1. A medium-driven main steam quick-closing isolation valve for nuclear power plants, characterized in that: The valve includes a valve body, a piston cylinder, a valve stem, and a valve cover. The valve cover is connected to the valve body. The piston cylinder is fitted inside the valve body and fixed to the valve cover. The valve stem is fitted inside the piston cylinder. The upper end of the valve stem passes through the middle of the valve cover and is connected to a coupling. An upper guide sleeve is installed on the valve cover. A limiter assembly is connected to the upper part of the coupling. The coupling and the limiter assembly are covered inside a bracket cover. The bracket cover is connected to the top of the valve cover. The valve stem is a rod-shaped structure with a protrusion in the middle. The piston cylinder sleeve is outside the valve stem and provides guidance for the movement of the protrusion in the middle of the valve stem. The lower guide sleeve is fitted on the rod-shaped part of the valve stem and provides guidance for the movement of the valve stem. The piston ring is installed on the piston cylinder. The lower guide sleeve is installed on the piston cylinder by a second screw and fixed with a second stop washer. The valve core and the valve stem are connected by a T-shaped structure and fixed with an anti-rotation connecting plate. The valve position indicator is installed on the top of the valve stem; a limiter assembly is installed on the top of the valve stem to limit the axial movement of the valve stem; and the valve cover is provided with an oblique flow channel connecting the upper part of the valve stem and the cavity formed between the valve cover and the valve stem.

2. The self-driven main steam quick-closing isolation valve for nuclear power plants as described in claim 1, characterized in that: The edge of the valve cover is connected to the top of the valve body by a first fastener, which includes a first bolt, a first washer, and a first nut.

3. The self-driven main steam quick-closing isolation valve for nuclear power plants as described in claim 1, characterized in that: A second pin is fixed between the edge of the valve cover and the top of the valve body, and a first sealing gasket is used to achieve a seal.

4. The self-driven main steam quick-closing isolation valve for nuclear power plants as described in claim 1, characterized in that: The piston cylinder is fitted into the valve body and fixed to the valve cover by a second fastener, which includes a third bolt, a third washer and a third nut, and is positioned by a first pin, the two ends of which are inserted into the valve cover and the piston cylinder, respectively.

5. A self-driven main steam quick-closing isolation valve for nuclear power plants as described in claim 1, characterized in that: The upper guide sleeve is mounted on the valve cover by a first screw and fixed with a first stop washer.

6. The self-driven main steam quick-closing isolation valve for nuclear power plants as described in claim 1, characterized in that: The bracket cover is connected to the top of the valve cover by a third fastener, which includes a second bolt, a second washer, and a second nut, and is sealed with a second sealing gasket.

7. A self-driven main steam quick-closing isolation valve for nuclear power plants as described in claim 1, characterized in that: The piston ring is one or more, used to achieve a seal between the piston cylinder and the valve body.

8. A self-driven main steam quick-closing isolation valve for nuclear power plants as described in claim 1, characterized in that: The lower guide sleeve is mounted on the piston cylinder by a second screw and fixed with a second stop washer.

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