A nuclear power pressure reducing valve for gas

Abstract

The present invention relates to a nuclear power pressure reducing valve for gas, wherein a two-stage pressure reducing valve unit is provided on the valve body, namely a first-stage pressure reducing valve unit and a second-stage pressure reducing valve unit. An inlet chamber is provided on one side of the valve body, and an outlet chamber is provided on the other side. The inlet chamber is connected to the first-stage pressure reducing valve unit, and the outlet chamber is connected to the second-stage pressure reducing valve unit. The first and second-stage pressure reducing valves are connected via a d flow channel. The first-stage pressure reducing unit adopts a high-rigidity spring to quickly coarsely adjust the high pressure to an intermediate pressure value. The second-stage pressure reducing unit adopts a high-precision low-rigidity spring to stabilize the outlet pressure at a set value. The two-stage pressure reducing device is designed as a unit and can be assembled offline as a whole, making replacement and maintenance convenient. Due to the horizontal left and right arrangement, vertical installation space is saved and working conditions are met. The pressure reducing valve adopts a flow-opening structural design to prevent the pressure reducing valve from being completely closed in a failed state.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure reducing valves, in particular to a nuclear power pressure reducing valve for gas. Background Art

[0002] Pressure reducing valves are widely used today and are essential pressure regulating devices in various fluid piping systems. During system operation, pressure reducing valves typically reduce the upstream high pressure to the low pressure set point required by the downstream process. The valves also automatically maintain a stable outlet pressure through the energy of the fluid itself.

[0003] In the high-pressure gas pipeline of a nuclear power plant of a national project, the operating conditions are as follows:

[0004] Pressure requirements: The inlet pressure range is 27.58~1.38MPa@26.7℃, the outlet pressure requirement is 0.83MPa@26.7℃, and the accuracy requirement is ±5%.

[0005] Earthquake resistance requirements: Earthquake resistance level I, three-direction acceleration 6.6g

[0006] Frequency: Natural frequency greater than 33Hz

[0007] Space and weight requirements: limited upper and lower space, no more than 41Kg

[0008] Structural requirements: Flow-open type, to ensure that the pressure reducing valve will not be completely closed in the failure state.

[0009] Analyzing the pressure reducing valve with the above requirements, the maximum inlet pressure is 27.58MPa, the outlet stable pressure is 0.83MPa, the inlet pressure variation range is 27.58~1.38MPa, the span difference is about 20 times, and the maximum outlet pressure reduction ratio reaches about 33 times.

[0010] This operating condition far exceeds the requirements of the current GB standard. According to GB / T12244 "General Requirements for Pressure Reducing Valves", the pressure change at the inlet of the pressure reducing valve is generally controlled at 80%-105% of the inlet pressure, and the outlet pressure is required to remain stable. Exceeding this range will affect the performance of the pressure reducing valve. The pressure after the pressure reducing valve is generally controlled at about 0.5 times the pressure before the valve. Excessive or low pressure after the valve will cause premature damage to the compression spring or cavitation damage to the valve seat, thereby shortening the life of the pressure reducing valve and worsening the operating conditions of the pipeline (such as vibration and noise). At present, there are no domestic manufacturers that manufacture such valves in the field of nuclear power engineering applications. They have always relied on imports, which are expensive and inconvenient to maintain.

[0011] Therefore, it is urgent for domestic manufacturers to develop pressure reducing valve products with independent intellectual property rights that meet the given working conditions, so as to meet the strategic needs of localizing key equipment for national key projects. Summary of the Invention

[0012] The purpose of the present invention is to provide a nuclear power pressure reducing valve for gas, which meets the requirements of earthquake-resistant nuclear power pressure reducing valves for gas by setting a two-stage pressure reducing valve and improves safety performance.

[0013] In order to achieve the above-mentioned purpose, the technical solution of the present invention is: a nuclear power pressure reducing valve for gas, including a valve body, characterized in that: a two-stage pressure reducing valve is provided on the valve body, namely a first-stage pressure reducing valve unit and a second-stage pressure reducing valve unit, an inlet cavity is provided on one side of the valve body, and an outlet cavity is provided on the other side, the inlet cavity is communicated with the first-stage pressure reducing valve unit, the outlet cavity is communicated with the second-stage pressure reducing valve unit, the first and second-stage pressure reducing valves are connected through a d flow channel, the first-stage pressure reducing valve includes a first valve cover and a first piston cylinder, a first piston and a first valve stem matched with the first piston are provided in the first valve cover, and a first piston cavity f, a first first valve stem matched with the first piston are provided in the first-stage pressure reducing valve from top to bottom. The piston cylinder cavity b and the first valve stem cavity c, the first piston cylinder cavity b is connected to the inlet cavity, the first piston cavity f is connected to the d flow channel through the e flow channel, and the bottom of the first valve stem cavity c is connected to the d flow channel; the second-stage pressure reducing valve includes a second valve cover and a second piston cylinder, a second piston and a second valve stem cooperating with the second piston are provided in the second valve cover valve, and the second-stage pressure reducing valve is provided with a second piston cavity k, a second piston cylinder cavity g and a second valve stem cavity h from top to bottom, the second valve stem cavity h is connected to the outlet cavity through the i flow channel, the second piston cylinder cavity g is connected to the d flow channel, and the second piston cavity k is connected to the i flow channel and the outlet cavity through the j flow channel.

[0014] Preferably, a first intersection angle is formed between the e flow channel and the d flow channel, and the angle is 95-135 degrees; a second intersection angle is formed between the j flow channel and the i flow channel, and the angle is 65-89 degrees.

[0015] Furthermore, a first adjusting screw matching it is provided on the top of the first valve cover, a first nut is sleeved on the first adjusting screw, a first protective cover is provided on the outer cover of the first valve cover, a first spring seat is provided inside the first valve cover, the top surface of the first spring seat is in conflict with the bottom of the first adjusting screw, and a first main spring is provided between the first spring seat and the first piston.

[0016] Furthermore, a second adjusting screw matching it is provided on the top of the second valve cover, a second nut is sleeved on the second adjusting screw, a second protective cover is provided on the outer cover of the second valve cover, a second spring seat is provided inside the second valve cover, the top surface of the second spring seat is in conflict with the bottom of the second adjusting screw, and a second main spring is provided between the second spring seat and the second piston.

[0017] Compared with the prior art, the technical solution of the present invention not only improves the overall technical solution, but also includes many improvements in details. Specifically, it has the following beneficial effects:

[0018] 1. The improved solution of the present invention has a two-stage pressure reducing valve on the valve body, which comprises two independent first-stage pressure reducing valve units and second-stage pressure reducing valve units. The first and second-stage pressure reducing valves are connected via flow channel d. Due to the use of an integral valve body structure, the leakage points of the valve are reduced and safety is increased.

[0019] 2. In the technical solution of the present invention, a first intersection angle is formed between the e and d flow channels, which is 95-135 degrees; a second intersection angle is formed between the j and i flow channels, which is 65-89 degrees. This large-angle oblique flow channel hole utilizes the space of the larger formed hole on the plane of the valve body to machine the oblique long flow channel hole in the valve body, thereby avoiding weakening the strength of the valve body.

[0020] 3. The first and second stage pressure reducing valve units of the present invention are respectively made into an integral structure, which is assembled into the unit offline and then installed into the valve body online. The replacement and maintenance are convenient, safe and reliable, and the installation precision is high, which can fully ensure the integrity and reliability of the pressure reducing valve unit.

[0021] 4. The present invention utilizes a flow-to-open design to prevent the pressure reducing valve from completely closing in the event of a failure. This flow-to-open design ensures that the inlet pressure always pushes the valve disc toward the open position. When the pressure reducing valve spring fails, the pressure drops but the disc does not completely close. Under the influence of inlet pressure, the disc maintains a certain opening, maintaining a constant downstream pressure flow rate. The downstream pressure in the failure condition is designed to be less than or equal to 2.07 MPa.

[0022] 5. The present invention adopts an integral structure, with two-stage pressure reducing units arranged horizontally on the left and right sides, which is convenient for pipeline replacement and maintenance, while reducing the upper and lower installation space of the valve. The operating mechanism is arranged vertically upward, with good visibility, which is more suitable for the pressure regulation operation of the pressure reducing unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the present invention.

[0024] Figure 2 4 is a cross-sectional view of the second valve seat of the present invention.

[0025] Figure 3 It is a structural schematic diagram of the valve body of the present invention.

[0026] Figure 4 It is a structural schematic diagram of the valve cover of the present invention.

[0027] Figure 5 It is a structural schematic diagram of the piston of the present invention.

[0028] Figure 6 It is a structural schematic diagram of the piston cylinder of the present invention.

[0029] Reference numerals:

[0030] 1 valve body, 2 first auxiliary spring, 3 first valve stem, 4 first piston cylinder, 5 first O-ring, 11 first piston, 12 first hexagonal thin nut, 13 first main spring, 14 first spring seat, 15 first valve cover, 16 protective sleeve, 17 first adjusting screw, 18 first nut;

[0031] 19 second adjusting screw, 20 second nut, 21 second valve cover, 22 second spring seat, 23 second main spring, 24 second hexagonal thin nut, 25 second O-ring, 26 second piston, 31 second piston cylinder, 33 second valve seat, 34 second valve stem, 35 second auxiliary spring, 36 compression sleeve;

[0032] 111 step hole, 112 spring positioning groove, 113 mounting hole;

[0033] 331 C-type rubber, 332 connecting thread, 333 process hole. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] The present invention provides a nuclear power pressure reducing valve for gas, see Figure 1 , including a valve body, which differs from the prior art in that: a two-stage pressure reducing valve is provided on the valve body 1, namely a first-stage pressure reducing valve unit and a second-stage pressure reducing valve unit, an inlet cavity is provided on one side of the valve body, and an outlet cavity is provided on the other side, the inlet cavity is communicated with the first-stage pressure reducing valve unit, the outlet cavity is communicated with the second-stage pressure reducing valve unit, the first and second-stage pressure reducing valves are connected through a flow channel d, the first-stage pressure reducing valve includes a first valve cover and a first piston cylinder 4, a first piston 11 and a first valve stem 3 matched with the first piston are provided in the first valve cover 15, and a first piston cavity f, a first piston cylinder cavity b and a first valve stem cavity are provided in the first-stage pressure reducing valve from top to bottom. Body c, the first piston cylinder cavity b is connected to the inlet cavity, the first piston cavity f is connected to the d flow channel through the e flow channel, and the bottom of the first valve stem cavity c is connected to the d flow channel; the second-stage pressure reducing valve includes a second valve cover 21 and a second piston cylinder 31, a second piston 26 and a second valve stem 34 cooperating with the second piston are provided in the second valve cover valve, and the second-stage pressure reducing valve is provided with a second piston cavity k, a second piston cylinder cavity g and a second valve stem cavity h from top to bottom, the second valve stem cavity h is connected to the outlet cavity through the i flow channel, the second piston cylinder cavity g is connected to the d flow channel, and the second piston cavity k is connected to the i flow channel and the outlet cavity through the j flow channel.

[0036] Specifically, the first and second pistons are provided with three cavities from top to bottom, namely the piston cavity, the piston rod cavity and the valve stem cavity. The medium is first introduced into the piston rod cavity, and the outlet pressure at the bottom of the valve stem cavity is fed back to the upper piston cavity, and then fed back to the piston. The piston will drive the valve stem to move up and down to adjust the size change of the medium flow channel, thereby stabilizing the outlet pressure set by the first and second pressure reducing valve units.

[0037] The pressure regulating units of the present invention are arranged on the left and right sides, and the high and low pressure combined regulating mechanism is centrally located on the upper part of the pipeline, which is convenient for operation. At the same time, it also saves space above and below the pipeline, meeting the space requirements of on-site working conditions.

[0038] The integrated valve body structure also reduces valve leakage points and increases safety. Specific features are as follows: 1) Conventional pressure reducing valves with a bottom cover are installed below the valve stem, spring, and other components from the bottom, requiring a packing seal between the bottom cover and the valve body. This pressure reducing valve, through optimized design, eliminates the bottom cover and allows valve components to be installed uniformly from the top, reducing leakage from the lower valve cover of conventional pressure reducing valves. 2) The large-angle inclined flow holes are machined through three-dimensional modeling, process optimization, and specialized tooling positioning. The large, pre-existing formed holes on the upper surface of the valve body are then used for CNC precision drilling to create the long, inclined flow holes. This avoids leaving process holes on the side of the valve body that could increase leakage points and prevents the process holes from weakening the valve body.

[0039] Integrated pressure reducing components: The primary and secondary pressure reducing units are designed as a single unit, assembled offline, and then installed into the valve body online. This facilitates replacement and maintenance, ensuring safety and reliability. Offline assembly and testing provide ample space, excellent visibility, and high installation precision, fully ensuring the integrity and reliability of the pressure reducing valve unit. Furthermore, the integrated structure facilitates pipeline replacement and maintenance. In this case, the limited installation space and poor visibility make the integrated pressure reducing components particularly suitable for operation.

[0040] Optimized pairing of high and low pressures: The high-pressure end utilizes a high-rigidity spring and a hard-sealed valve seat, which offers high pressure bearing capacity, resistance to wear, and the ability to quickly coarsely adjust the high pressure to an intermediate pressure value. The low-pressure end utilizes a high-precision, low-rigidity spring, which offers high pressure regulation accuracy. While sensitive to feedback pressure, it can quickly respond to pressure changes, provide prompt feedback, and stabilize the pressure setting. A soft seal is used on the low-pressure end to minimize leakage. Specifically, the first-stage pressure reducing unit utilizes a high-rigidity spring and a hard-sealed valve seat, allowing for rapid coarse adjustments of the high pressure to an intermediate pressure value. The second-stage pressure reducing unit utilizes a high-precision, low-rigidity spring and a soft-sealed valve seat, allowing for rapid responses to pressure changes and feedback to stabilize the outlet pressure at the set value.

[0041] The flow-to-open design (i.e., fluid flow points toward the open position) prevents the pressure reducing valve from completely closing in the event of a failure, meeting the requirements of specific operating conditions. This mechanism ensures that in the event of a first- or second-stage failure, the remaining operable first stage will limit the outlet pressure to below 2.07 MPa. Case analysis: If the first-stage spring fails (e.g., due to fatigue fracture), the spring transitions from a compressed state to a free state, weakening the elastic force and disrupting the force balance. Under medium pressure, the valve disc opening decreases, and the pressure drops to below the original regulated pressure.

[0042] In one embodiment, a first-stage pressure reducing valve unit and a second-stage pressure reducing valve unit are provided on the valve body, an inlet cavity is provided on one side of the valve body, and an outlet cavity is provided on the other side. The inlet cavity is connected to the first-stage pressure reducing valve unit, and the outlet cavity is connected to the second-stage pressure reducing valve unit. The first and second-stage pressure reducing valves are connected through a d flow channel.

[0043] Furthermore, a first intersection angle is formed between flow channel e and flow channel d, which is 95-135 degrees, preferably 105-120 degrees; a second intersection angle is formed between flow channel j and flow channel i, which is 65-89 degrees, preferably 70-85 degrees. The diameters of flow channel d are 6 cm, flow channel e are 6 cm, flow channel i are 12.5 cm, and flow channel j are 6 cm.

[0044] Specifically, a first adjusting screw is mounted on the top of the first valve cover, which is sleeved with a first nut. A first protective sleeve is provided on the exterior of the first valve cover. A first spring seat is mounted on the interior of the first valve cover, the top surface of which contacts the bottom of the first adjusting screw. A first main spring is mounted between the first spring seat and the first piston. A second adjusting screw is mounted on the top of the second valve cover, which is sleeved with a second nut. A second protective sleeve is provided on the exterior of the second valve cover. A second spring seat is mounted on the interior of the second valve cover, the top surface of which contacts the bottom of the second adjusting screw. A second main spring is mounted between the second spring seat and the second piston.

[0045] Specifically, the first and second valve covers here have the same structure. A first valve cover thread is provided on the top of the valve cover for connecting the protective sleeve, a second valve cover thread is provided on the bottom of the valve cover for connecting the valve body, and a hexagonal chamfered surface is provided on the valve cover for tightening the valve cover thread.

[0046] The first piston is connected to a first valve stem, the end of which is disposed within the first valve stem cavity c. A first valve seat is located at the bottom of the first piston cylinder. The bottom of the first valve seat is shaped to match the first valve stem. The gap between the first valve stem and the first valve seat represents the first-stage medium flow passage. Up and down movement of the first valve stem adjusts the size of the first-stage medium flow passage. The second piston is connected to a second valve stem, the end of which is disposed within the second valve stem cavity l. A second valve seat is located at the bottom of the second piston cylinder. The bottom of the second valve seat is shaped to match the second valve stem. The gap between the second valve stem and the second valve seat represents the second-stage medium flow passage. Up and down movement of the second valve stem adjusts the size of the second-stage medium flow passage.

[0047] Specifically, the second valve seat is vulcanized as a whole by the valve seat body and rubber. A through hole is provided at the center of the valve seat body for the valve stem to pass through the valve seat body. C-type rubber is attached to the side wall of the through hole. The angle between the bottom of the C-type rubber and the valve seat body is 60 degrees. Process holes are provided on both sides of the through hole, and a connecting thread is provided on the outside of the top of the valve seat body.

[0048] The first piston is provided with an annular opening, one end of which communicates with flow channel e and the other with the first piston cavity f. This allows the outlet gas pressure of the first valve stem cavity c to be fed back to the first piston through the first piston cavity f. The first piston comprises a cylindrical portion and a plug portion located at the top of the cylindrical portion. The cylindrical portion is a hollow structure with two stepped holes 111 for securing the first valve stem. The plug portion has a spring positioning groove 112 at the top and two mounting holes 113 symmetrically arranged along the cylindrical portion. The second piston is provided with an annular opening, one end of which communicates with flow channel i and the other end with the second piston cavity k. This allows the outlet gas pressure of the second valve stem cavity l to be fed back to the second piston through the second piston cavity k. The second piston comprises a cylindrical portion and a plug portion located at the top of the cylindrical portion. The cylindrical portion is a hollow structure with two stepped holes for securing the second valve stem. The plug portion has a spring positioning groove at the top and two mounting holes symmetrically arranged along the cylindrical portion.

[0049] In another specific embodiment, the pressure reducing valve is divided into two-stage pressure reducing units, see Figure 1. For the first-stage pressure reducing valve unit, rotate the first adjusting screw 17, the first spring seat 14 moves downward, compresses the first main spring 13, and pushes the first piston 11 downward. The first piston 11 drives the first valve stem 3 to open the medium flow channel port in contact with the lower part of the first piston cylinder 4. The medium gas enters the first piston cylinder cavity b from the inlet cavity a through the annular channel at the lower part of the first piston cylinder 4, and enters the first valve stem cavity c from the medium flow channel port. The gas in the first valve stem cavity c enters the first piston cavity f through the internal flow channels d and e, and feeds back the first-stage outlet pressure to the first piston 11. When the first-stage outlet pressure fluctuates, its fluctuation value drives the first piston together with the first valve stem 3 to move up and down, and then the medium flow channel port of the first stage either reduces or increases in area, thereby stabilizing the outlet pressure set by the first-stage pressure reducing valve unit.

[0050] The outlet fluid of the first stage enters the second piston cylinder cavity g of the second piston cylinder 31 through the d flow channel. Rotating the second adjusting screw 19 presses down the second spring seat, compressing the second main spring, pushing the second piston 26 downward, driving the second piston rod 24 downward, and opening the flow channel of the second-stage pressure reducing unit. The medium enters the second valve stem cavity h from the second piston cylinder cavity g, enters the L outlet cavity and the j flow channel through the i flow channel, and the gas in the j flow channel enters the second piston cavity k through the annular port of the second piston 31, and the outlet pressure of the second stage is fed back to the second piston. When the outlet pressure of the second stage fluctuates, its fluctuation value drives the second piston 26 together with the second valve stem 34 to move up and down, and then the medium flow channel of the second stage either reduces or increases in area, thereby stabilizing the outlet pressure set by the second-stage pressure reducing valve unit.

[0051] A computational simulation experiment is performed on this embodiment:

[0052] A. Strength Analysis

[0053] The calculation software used is ANSYS, employing a three-dimensional elastic finite element analysis method. Through finite element simulation analysis, the valve body strength under operating conditions is guaranteed, redundant materials are removed, the valve body dimensions are optimized, and the valve body weight is reduced to meet the size and weight requirements of special nuclear-grade operating conditions.

[0054] B. Natural frequency analysis

[0055] According to the modal analysis, the first ten frequencies are shown in Table 1. As can be seen from Table 1, the first-order frequency is 203.57 Hz, which is much larger than 33 Hz, so it meets the requirements.

[0056] Table 1 The first ten frequencies

[0057]

[0058]

[0059] Valve stress analysis and assessment

[0060] According to modal analysis, the first-order frequency is 203.57 Hz, which is much larger than the 33 Hz required by the case, and therefore meets the regulatory requirements.

[0061] c. Seismic analysis:

[0062] Pressure loads were applied to the valve body and valve cover of the model, and seismic loads (6.6g acceleration in three directions) and deadweight were applied to the model.

[0063] The valve body stress assessment is as follows:

[0064] Valve body stress assessment

[0065] stress Calculated value (MPa) Limit (MPa) Assessment results Primary film stress strength 88.68 138 qualified Primary film + bending stress strength 129.24 207 qualified

[0066] (1) The bonnet stress assessment is as follows:

[0067] Bonnet stress assessment

[0068] stress Calculated value (MPa) Limit (MPa) Assessment results Primary film stress strength 15.20 138 qualified Primary film + bending stress strength 17.91 207 qualified

[0069] According to the results of valve stress analysis, under the combined action of internal pressure, deadweight, earthquake and other loads, the calculated stress values ​​of each weak part of the valve are all less than the allowable stress values ​​specified in the corresponding design criteria, thus proving that the structural integrity of the valve can be guaranteed under various load combinations and meets the requirements of ASME Code Section III D3500.

[0070] The final performance test data is as follows:

[0071] Requirements: The inlet pressure range is 27.58~1.38MPa, the outlet pressure requirement is 0.83MPa, and the accuracy requirement is ±5%.

[0072]

[0073]

[0074] The measured results show that when the inlet pressure varies within the range of 27.58 to 1.38 MPa, the outlet pressure is stable within the range of 0.83 MPa ± 5%, meeting the working conditions.

[0075] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be considered that the specific implementation of the present invention is limited to the above description. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A nuclear power pressure reducing valve for gas, comprising a valve body, characterized in that: A two-stage pressure reducing valve is provided on the valve body, namely a first-stage pressure reducing valve unit and a second-stage pressure reducing valve unit. An inlet cavity is provided on one side of the valve body, and an outlet cavity is provided on the other side. The inlet cavity is communicated with the first-stage pressure reducing valve unit, and the outlet cavity is communicated with the second-stage pressure reducing valve unit. The first and second-stage pressure reducing valves are communicated through the d flow channel. The first-stage pressure reducing valve includes a first valve cover and a first piston cylinder. A first piston and a first valve stem cooperating with the first piston are provided in the first valve cover. A first piston cavity f, a first piston cylinder cavity b and a first valve stem cavity c are provided in the first-stage pressure reducing valve from top to bottom. The first piston cylinder cavity b is communicated with the inlet cavity, the first piston cavity f is communicated with the d flow channel through the e flow channel, and the bottom of the first valve stem cavity c is communicated with the d flow channel. The medium gas enters the first piston cylinder cavity b from the inlet cavity, and enters the first valve stem cavity c from the medium flow channel. The gas in the first valve stem cavity c enters the first piston cavity f through the internal flow channels d and e, feeding back the first stage outlet pressure to the first piston. When the first stage outlet pressure fluctuates, the fluctuation value drives the first piston and the first valve stem to move up and down, thereby reducing or increasing the area of ​​the first stage medium flow channel, so that the outlet pressure set by the first stage pressure reducing valve unit remains stable. The second-stage pressure reducing valve includes a second valve cover and a second piston cylinder. A second piston and a second valve stem cooperating with the second piston are provided in the second valve cover. The second-stage pressure reducing valve is provided with a second piston cavity k, a second piston cylinder cavity g, and a second valve stem cavity h from top to bottom. The second valve stem cavity h is connected to the outlet cavity through the i flow channel, the second piston cylinder cavity g is connected to the d flow channel, and the second piston cavity k is connected to the i flow channel and the outlet cavity through the j flow channel. The outlet fluid of the first stage enters the second piston cylinder cavity g of the second piston cylinder 31 through the d flow channel. The medium gas enters the second valve stem cavity h from the second piston cylinder cavity g, and enters the L outlet cavity and the j flow channel through the i flow channel. The gas in the j flow channel enters the second piston cavity k through the annular opening of the second piston 31, so that the outlet pressure of the second stage is fed back to the second piston. When the outlet pressure of the second stage fluctuates, the fluctuation value drives the second piston 26 and the second valve stem 34 to move up and down, thereby reducing or increasing the area of ​​the medium flow channel opening of the second stage, so that the outlet pressure set by the second-stage pressure reducing valve unit remains stable. The first-stage pressure reducing unit adopts high-rigidity springs and hard-sealed valve seats to quickly adjust the high pressure to the intermediate pressure value; the second-stage pressure reducing unit adopts high-precision low-rigidity springs and soft-sealed valve seats to quickly respond to pressure changes, provide feedback, and stabilize the outlet pressure at the set value; The flow-open structure design is adopted, so that when the first-stage spring or the second-stage spring fails, the remaining operable first-stage spring will limit the outlet pressure to below 2.07MPa; A first intersection angle is formed between the e flow channel and the d flow channel, and the angle is 105-120 degrees; a second intersection angle is formed between the j flow channel and the i flow channel, and the angle is 70-85 degrees.

2. A nuclear power pressure reducing valve for gas according to claim 1, characterized in that: The diameter of the d flow channel is 6 cm, the diameter of the e flow channel is 6 cm, the diameter of the i flow channel is 12.5 cm, and the diameter of the j flow channel is 6 cm.

3. A nuclear power pressure reducing valve for gas according to claim 1, characterized in that: A first adjusting screw matching with it is provided on the top of the first valve cover, a first nut is sleeved on the first adjusting screw, a first protective cover is provided on the outer cover of the first valve cover, a first spring seat is provided inside the first valve cover, the top surface of the first spring seat is in conflict with the bottom of the first adjusting screw, and a first main spring is provided between the first spring seat and the first piston.

4. A nuclear power pressure reducing valve for gas according to claim 1, characterized in that: A second adjusting screw matching it is provided on the top of the second valve cover, a second nut is sleeved on the second adjusting screw, a second protective cover is provided on the outer cover of the second valve cover, a second spring seat is provided inside the second valve cover, the top surface of the second spring seat is in conflict with the bottom of the second adjusting screw, and a second main spring is provided between the second spring seat and the second piston.

5. A nuclear power pressure reducing valve for gas according to claim 1, characterized in that: The first piston is connected to a first valve stem, the end of the first valve stem is arranged in a first valve stem cavity c, a first valve seat is provided at the lower part of the first piston cylinder, the bottom of the first valve seat is provided with a shape matching the first valve stem, the gap between the first valve stem and the first valve seat is a first-level medium flow channel opening, and the up and down movement of the first valve stem can adjust the size of the first-level medium flow channel opening.

6. A nuclear power pressure reducing valve for gas according to claim 1, characterized in that: The second piston is connected to a second valve stem, the end of which is arranged in the second valve stem cavity 1. A second valve seat is provided at the lower part of the second piston cylinder, and the bottom of the second valve seat is provided with a shape that matches the second valve stem. The gap between the second valve stem and the second valve seat is the second-stage medium flow channel opening, and the up and down movement of the second valve stem can adjust the size of the second-stage medium flow channel opening.

7. The nuclear power pressure reducing valve for gas according to claim 1, characterized in that: The first piston is provided with an annular opening, one end of the annular opening is connected to the e flow channel, and the other end is connected to the first piston cavity f, so that the outlet gas pressure of the first valve stem cavity c is fed back to the first piston through the first piston cavity f. The first piston includes a columnar part and a plug body part provided at the top of the columnar part. The columnar part is a hollow structure, and two step holes are provided in the hollow structure for fixing the first valve stem. A spring positioning groove is provided on the top of the plug body part, and the plug body part is provided with two mounting holes symmetrically arranged along the columnar part.

8. The nuclear power pressure reducing valve for gas according to claim 1, characterized in that: The second piston is provided with an annular opening, one end of the annular opening is connected to the i flow channel, and the other end is connected to the second piston cavity k, so that the outlet gas pressure of the second valve stem cavity l is fed back to the second piston through the second piston cavity k. The second piston includes a columnar part and a plug body part provided at the top of the columnar part. The columnar part is a hollow structure, and two step holes are provided in the hollow structure for fixing the second valve stem. A spring positioning groove is provided on the top of the plug body part, and the plug body part is provided with two mounting holes symmetrically arranged along the columnar part.

Images