A double ball valve type PCV valve for power station

Abstract

This invention proposes a double ball valve type PCV valve for power plants, relating to valve technology. Specifically, it discloses a central valve body with a valve passage within it. The valve passage contains a first valve ball and a second assembly groove. The second assembly groove houses a second valve ball and a self-sealing valve seat. A second valve seat is located at the inlet of the central valve body. The second valve seat and the self-sealing valve seat clamp the second valve ball within the second assembly groove for opening and closing the valve passage. A valve seat sealing ring is fitted onto the outer wall of the self-sealing valve seat, with a portion of the outer wall of the sealing ring fitting against the inner wall of the second assembly groove. When the second valve ball is closed, the medium pressure pushes the second valve ball to compress the self-sealing valve seat, causing the valve seat sealing ring to elastically deform and expand towards the inner wall of the second assembly groove. The sealing effect increases with increasing medium pressure, making it suitable for high and low pressure conditions in power plant systems.

Description

Technical Field

[0001] This invention relates to the field of valve technology, and more specifically, to a double ball valve type PCV valve for power plants. Background Technology

[0002] As a core control component in power plant systems, PCV valves are mainly used for opening and closing of media transportation, pressure regulation, and sealing protection. They are widely used in key scenarios such as power plant boilers and pipeline transportation. Their sealing reliability, structural stability, and ease of operation and maintenance directly affect the safe and stable operation of power plant systems.

[0003] Currently, most PCV valves used in power plants employ a single-ball valve structure. This design, with only a single valve ball and its associated sealing components, suffers from insufficient sealing reliability. When the valve ball or seals wear or age, media leakage is likely to occur, potentially affecting the normal operation of the power plant system and even posing safety hazards. Furthermore, existing PCV valves often use a fixed sealing structure, failing to adapt to changes in media pressure. This results in significant fluctuations in sealing performance during high- and low-pressure switching in the power plant system, making it difficult to meet the requirements for long-term stable sealing. Summary of the Invention

[0004] The purpose of this invention is to provide a double ball valve type PCV valve for power plants, which addresses the shortcomings of existing technologies and solves the problems mentioned in the background.

[0005] The technical solution of this invention is implemented as follows: This invention provides a double ball valve type PCV valve for power plants, including a middle valve body, an outlet valve body is provided on one side of the middle valve body, and an inlet valve body is provided on the other side of the middle valve body; a valve passage is provided inside the middle valve body; A first assembly groove is provided on the side of the valve body near the outlet end of the valve passage. A first valve ball is installed in the first assembly groove. A first valve seat is provided in the first assembly groove. The valve body at the outlet end and the first valve seat clamp the first valve ball in the first assembly groove for opening and closing the valve passage. A second assembly groove is provided on the side of the valve body near the inlet end of the valve passage. A second valve ball is installed in the second assembly groove. A self-sealing valve seat is provided in the second assembly groove. A second valve seat is provided in the valve body at the inlet end. The second valve seat and the self-sealing valve seat clamp the second valve ball in the second assembly groove for opening and closing the valve passage. An installation chamber is provided between the self-sealing valve seat and the second assembly groove. A valve seat sealing ring is fitted on the outer wall of the self-sealing valve seat, and a portion of the outer wall of the valve seat sealing ring abuts against the inner wall of the second assembly groove. When the second valve ball is closed, the medium in the valve passage will push the second valve ball to squeeze the self-sealing valve seat, forcing the valve seat sealing ring to deform and move towards the inner wall of the second assembly groove and fit against it.

[0006] In some technical solutions of the present invention, a first straight section and a first outer conical section are sequentially provided on the outer side wall of the self-sealing valve seat, the small diameter end of the first outer conical section is integrally formed with the first straight section; the outer side wall of the first straight section abuts against the inner wall of the valve passage; the outer arc surface of the first outer conical section abuts against the second assembly groove; an inner conical section is provided on the inner side wall of the valve seat sealing ring, and a sealing arc surface is provided on the inner conical surface of the inner conical section that abuts against the outer side wall of the first outer conical section.

[0007] In some technical solutions of the present invention, a second straight section and a second outer conical section are sequentially provided on the outer side of the valve seat sealing ring, wherein the second straight section abuts against the inner wall of the second assembly groove; the second straight section abuts against the bottom of the second assembly groove; and a clearance space is provided between the second outer conical section and the inner wall of the second assembly groove.

[0008] In some technical solutions of the present invention, an arc-shaped structure is provided on the end face of the second straight section facing the bottom of the second assembly groove, and the arc-shaped structure abuts against the bottom of the second assembly groove.

[0009] In some technical solutions of the present invention, a plurality of inlets and outlets are provided around the outer side wall of the second outer cone section, a liquid supply channel is provided inside the valve seat sealing ring, the liquid supply channel is arranged along the circumference of the valve seat sealing ring, the plurality of inlets and outlets are connected to the liquid supply channel, an installation groove is provided on the inner cone surface of the inner cone section, a spiral sealing strip is provided in the installation groove, any two adjacent spiral segments in the sealing strip are in contact with each other, and the sealing strip is floating in the installation groove, the two free ends of the sealing strip are elastically connected to the inner wall of the installation groove, the installation groove is connected to the liquid supply channel, an movable gap is provided at the connection between the installation groove and the liquid supply channel, and a piston connected to the sealing strip is slidably provided in the liquid supply channel.

[0010] In some technical solutions of the present invention, an annular groove communicating with the inlet and outlet is provided on the end face of the second straight section, a sealing ring is installed in the annular groove, and a plurality of blocking rings are installed on the side wall of the sealing ring that fits against the second assembly groove.

[0011] In some technical solutions of the present invention, a valve seat support ring is also included, which is assembled between the bottom of the first valve seat and the second assembly groove. The outer wall of the first straight section is provided with external threads, and the inner wall of the valve seat support ring is provided with internal threads that mesh with the external threads.

[0012] In some technical solutions of the present invention, a first elastic telescopic structure is installed between the valve seat support ring and the first valve seat; A second elastic telescopic structure is installed between the bottom of the second assembly slot and the second valve seat. The first elastic telescopic structure is a butterfly spring or a flat-top wave spring structure; The second elastic telescopic structure is a butterfly spring or a flat-top wave spring structure.

[0013] In some technical solutions of the present invention, two sets of valve stem controllers are provided on the outer wall of the middle valve body, which are respectively connected to the first valve ball and the second valve ball in a driving connection.

[0014] In some technical solutions of the present invention, an outlet valve body embedding section is provided on the side of the outlet valve body near the middle valve body; An inlet valve body embedment section is provided on the side of the inlet valve body near the middle valve body; Both the outer wall of the valve body embedded section at the outlet end and the outer wall of the valve body embedded section at the inlet end are fitted with valve body main sealing rings that abut against the middle valve body. A secondary valve body sealing ring is provided on the side wall opposite to the middle valve body at the inlet or outlet end of the valve body, and the secondary valve body sealing ring abuts against the middle valve body.

[0015] Compared with the prior art, the present invention has at least the following advantages or beneficial effects: It adopts a double ball valve structure, using two independent valve stem controllers to convert external control force into valve ball rotation torque, driving the first and second valve balls to rotate respectively, achieving independent or linked opening and closing of the valve passage. The double-opening and closing structure significantly reduces the leakage risk caused by a single valve ball failure, improving the overall reliability of the valve. An installation chamber is provided between the self-sealing valve seat and the second assembly groove. The valve seat sealing ring is fitted onto the outside of the self-sealing valve seat, utilizing the pressure of the medium itself as the sealing force. When the second valve ball is closed, the medium pressure pushes the second valve ball to squeeze the self-sealing valve seat, causing the valve seat sealing ring to become elastic. The deformation extends and expands to fit the inner wall of the second assembly groove, and the sealing effect improves with the increase of medium pressure, making it suitable for high and low pressure conditions in power plant systems. The elastic relief structure formed by the second straight section and the second outer conical section on the outer side of the valve seat sealing ring can automatically compensate for valve seat wear and thermal deformation, maintaining long-term sealing performance. A spiral sealing strip is floating on the inner conical surface of the valve seat sealing ring. The sealing strip is used to fill the space enclosed by the valve seat sealing ring, the self-sealing valve seat, and the middle valve body. At the same time, it also actively adjusts the tension of the spiral sealing strip by utilizing the medium pressure in this area to change with the medium pressure in the valve passage, thereby filling the micro gap between the valve seat sealing ring and the self-sealing valve seat and improving sealing stability. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall installation structure of the double ball valve type PCV valve in this invention.

[0017] Figure 2 for Figure 1 A magnified schematic diagram of the structure at point A in the middle.

[0018] Figure 3 This is a schematic diagram of the valve seat support ring in this invention.

[0019] Figure 4 This is a schematic diagram of the valve seat sealing ring in this invention.

[0020] Figure 5 This is a schematic diagram of the self-sealing valve seat in this invention.

[0021] Figure 6 This is a three-dimensional structural diagram of the valve seat sealing ring and sealing strip in this invention.

[0022] Figure 7 This is a schematic diagram of the installation structure of the sealing strip in this invention.

[0023] Figure 8 This is a schematic diagram of the assembly structure of the self-sealing valve seat of the sealing strip in this invention.

[0024] Figure 9 for Figure 8 A magnified schematic diagram of the structure at point B in the middle.

[0025] Figure 10 for Figure 7 A magnified schematic diagram of the side view of the structure in the CC direction.

[0026] Reference numerals: 1. Middle valve body; 101. Valve passage; 102. Second assembly groove; 103. First assembly groove; 104. Mounting chamber; 105. Recess space; 2. First valve ball; 3. Second valve ball; 4. Self-sealing valve seat; 401. First straight section; 402. First external conical section; 403. External thread; 5. Second valve seat; 6. Valve seat sealing ring; 601. Internal conical section; 602. Sealing arc surface; 603. Second straight section; 604. Second external conical section; 605. Arc surface structure; 606. Inlet and outlet; 6 7. Mounting groove; 608. Sealing strip; 609. Ring groove; 610. Sealing ring; 611. Retaining ring; 612. Liquid supply channel; 613. Piston; 7. Outlet valve body; 701. Outlet valve body embedded section; 8. Inlet valve body; 801. Inlet valve body embedded section; 9. First valve seat; 10. Valve seat support ring; 1001. Internal thread; 11. First elastic telescopic structure; 12. Second elastic telescopic structure; 13. Valve stem controller; 14. Valve body main sealing ring; 15. Valve body secondary sealing ring. Detailed Implementation

[0027] 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.

[0028] 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.

[0029] Example This invention provides a double ball valve type PCV valve for power plants, such as... Figures 1-10 As shown, the valve includes a central valve body 1, an outlet valve body 7, and an inlet valve body 8, which together constitute the main valve structure. Internally, it is equipped with a double ball valve and a matching sealing structure. The specific structure is as follows: The middle valve body 1 is the core load-bearing component of the overall structure. It has a through valve channel 101 for media flow. One side of the middle valve body 1 is detachably connected to an outlet valve body 7 via a threaded connection, and the other side is also detachably connected to an inlet valve body 8. The outlet valve body 7 and inlet valve body 8 correspond to the two ends of the valve channel 101, respectively, enabling media entry and exit. To improve the sealing performance of the valve body mating surfaces, the outlet valve body 7 has an outlet valve body embedding section 701 on the side near the middle valve body 1, and the inlet valve body 8 has an inlet valve body embedding section 801 on the side near the middle valve body 1. A valve body main sealing ring 14 is fitted onto the outer wall of both the outlet valve body embedding section 701 and the inlet valve body embedding section 801. The valve body main sealing ring 14 tightly abuts against the inner wall of the middle valve body 1, forming a radial main seal. Meanwhile, a secondary sealing ring 15 is provided on the side wall opposite to the middle valve body 1 of the inlet valve body 8 or the outlet valve body 7. The secondary sealing ring 15 fits against the end face of the middle valve body 1 to form an auxiliary end face seal. Through the main and secondary double sealing rings, the leakage of medium at the joint surface between the middle valve body 1 and the inlet valve body 8 or the outlet valve body 7 is prevented.

[0030] A first assembly groove 103 is provided on the side of the valve body 7 near the outlet end of the valve passage 101. A first valve ball 2 is installed in the first assembly groove 103, and a first valve seat 9 is also provided within the first assembly groove 103. The outlet end valve body 7 cooperates with the first valve seat 9 to clamp the first valve ball 2 within the first assembly groove 103. The rotation of the first valve ball 2, forced by the valve stem controller 13, controls the opening and closing of the valve passage 101 near the outlet end. A second assembly groove 102 is provided on the side of the valve body 8 near the inlet end of the valve passage 101. A second valve ball 3 is installed in the second assembly groove 102, and a self-sealing valve seat 4 is also provided within the second assembly groove 102. A second valve seat 5 is provided within the inlet end valve body 8. The second valve seat 5 cooperates with the self-sealing valve seat 4 to clamp the second valve ball 3 within the second assembly groove 102. The rotation of the second valve ball 3 controls the opening and closing of the valve passage 101 near the inlet end, forming a double-start / close structure for a double ball valve.

[0031] To enhance self-sealing after the second valve ball 3 is closed, an installation chamber 104 is provided between the self-sealing valve seat 4 and the second assembly groove 102. A valve seat sealing ring 6 is fitted onto the outer wall of the self-sealing valve seat 4, and a portion of the outer wall of the valve seat sealing ring 6 is in contact with the inner wall of the second assembly groove 102. When the second valve ball 3 is closed, the medium pressure in the valve passage 101 will push the second valve ball 3 to squeeze the self-sealing valve seat 4, forcing the valve seat sealing ring 6 to deform and move towards the inner wall of the second assembly groove 102, forming a surface-to-surface contact with it. This creates a self-sealing structure driven by medium pressure, thereby achieving a seal between the valve seat sealing ring 6 and the valve passage 101 and preventing medium leakage.

[0032] To further optimize the self-sealing performance, a first straight section 401 and a first outer conical section 402 are sequentially provided on the outer wall of the self-sealing valve seat 4. The small-diameter end of the first outer conical section 402 is integrally formed with the first straight section 401. The outer wall of the first straight section 401 abuts against and is clearance-fitted with the inner wall of the valve passage 101 to achieve radial positioning of the self-sealing valve seat 4. The outer arc surface of the first outer conical section 402 abuts against and is clearance-fitted with the second assembly groove 102 to achieve circumferential positioning. Correspondingly, an inner conical section 601 is provided on the inner wall of the valve seat sealing ring 6. The inner conical section 601 fits against the outer wall of the conical section of the self-sealing valve seat 4, and a sealing arc surface 602 is provided on the inner conical surface. By the cooperation between the outer conical surface of the first outer conical section 402 and the sealing arc surface 602, the sealing contact area and fit are improved, resulting in a better sealing effect.

[0033] The outer side of the valve seat sealing ring 6 is provided with a second straight section 603 and a second outer conical section 604 in sequence. The second straight section 603 abuts against the inner wall of the second assembly groove 102 and fits against the bottom of the second assembly groove 102, realizing the basic positioning of the valve seat sealing ring 6. A clearance space 105 is provided between the second outer conical section 604 and the inner wall of the second assembly groove 102 to provide compensation space for the valve seat sealing ring 6 under pressure deformation and prevent the sealing ring from getting stuck. At the same time, an arc surface structure 605 is formed on the end face of the second straight section 603 facing the bottom of the second assembly groove 102. The arc surface structure 605 fits against the bottom of the second assembly groove 102 and can adaptively adjust the contact position to compensate for machining or assembly errors and improve the end face sealing stability.

[0034] Furthermore, when the second valve ball 3 inside the valve body 1 is in the closed state, the medium pressure acts on the second valve ball 3, causing it to press the self-sealing valve seat 4 to the left. The self-sealing valve seat 4, under the pressure to the left, presses the valve seat sealing ring 6, and the valve seat sealing ring 6, under the pressure to the left, presses the valve body 1. As the medium pressure gradually increases, the medium enters the relief space 105 between the inner wall of the second outer cone section 604 and the second assembly groove 102. As the compressive force on the self-sealing valve seat 4 gradually increases, the self-sealing valve seat 4 undergoes axial micro-movement, and the self-sealing valve seat 4 compresses the valve seat sealing ring 6, causing deformation. The sealing specific pressure in the relief space 105 increases with the increase of the medium pressure. The medium entering the relief space 105 will push the valve seat sealing ring 6 towards the self-sealing valve seat 4 in the opposite direction, keeping the contact surfaces of the two in contact and preventing medium leakage. Thus, the higher the medium pressure, the greater the force of the second valve ball 3 pressing against the self-sealing valve seat 4, the force of the self-sealing valve seat 4 pressing against the valve seat sealing ring 6, and the force of the valve seat sealing ring 6 pressing against the valve body 1. The better the sealing effect of the sealing structure formed by the two, the more reliably the medium is blocked on the side of the self-sealing valve seat 4 facing the inlet end valve body 8.

[0035] To further improve sealing reliability, an active sealing structure is provided on the valve seat sealing ring 6. Specifically, several inlets and outlets 606 are provided around the outer wall of the second outer cone section 604. The valve seat sealing ring 6 is provided with a liquid supply channel 612 that communicates with the several inlets and outlets 606 respectively. The liquid supply channels 612 are arranged around the circumference of the valve seat sealing ring 6 and are interconnected. The inner cone surface of the inner cone section 601 is provided with a mounting groove 607. The mounting groove 607 is provided with a spiral sealing strip 608. The outer diameter of one end of the spiral sealing strip 608 is larger than the outer diameter of the other end, and its cross-section is frustoconical. The small-diameter end of the sealing strip 608 is integrally molded with the inner wall of the mounting groove 607 using elastic, high-temperature resistant, wear-resistant, and somewhat elastic rubber. The gap between the sealing strip 608 and the outer wall of the mounting groove 607 is tightly fitted by the tension of the spiral sealing strip 608 itself to prevent media leakage. Any two adjacent spiral segments within the sealing strip 608 fit together through their own elasticity to seal the gaps they create. The sealing strip 608 is floating within the mounting groove 607, which is connected to the liquid supply channel 612. The piston 613 is detachably connected to the large-diameter end of the sealing strip 608 via a rubber block. Furthermore, the connection between the mounting groove 607 and the liquid supply channel 612 is provided with an movable gap for the piston 613 to move circumferentially along the valve seat sealing ring 6. The piston 613 is slidably disposed in the liquid supply channel 612, and the movable gap is blocked by a rubber block. When the medium enters the liquid supply channel 612 from the inlet / outlet 606, the piston 613 located in the liquid supply channel 612 is pushed due to the increase in medium pressure, thereby pulling the spiral sealing strip 608 to one side to tighten and press against the self-sealing valve seat 4, thus achieving micro-gap sealing.

[0036] Preferably, a rubber sealing layer can be sleeved around the sealing strip 608, and the cross-section of the spiral segment of the sealing strip 608 is rectangular, which can increase the contact area between any two adjacent spiral segments inside the sealing strip 608, and with the cooperation of the rubber sleeve sealing layer, the gap between any two adjacent spiral segments is blocked. The spiral sealing strip 608 tightly wraps around the outer wall of the first outer cone segment 402 by its own characteristics.

[0037] Furthermore, in order to guide the movement of the sealing strip 608, an inner groove matching the spiral sealing strip 608 can be provided on the inner wall of the mounting groove 607. At this time, a portion of the sealing strip 608 is embedded in the inner groove. Thus, when the piston 613 moves circumferentially along the valve seat sealing ring 6, it can pull the large-diameter end of the sealing strip 608 to move, that is, pull the sealing strip 608 to perform a tightening movement on the first outer cone section 402, thereby improving the sealing performance between the self-sealing valve seat 4 and the valve seat sealing ring 6.

[0038] As the medium pressure gradually increases, the medium enters the clearance space 105 between the inner wall of the second outer cone section 604 and the second assembly groove 102. As the compressive force on the self-sealing valve seat 4 gradually increases, the self-sealing valve seat 4 undergoes axial micro-movement, causing deformation of the valve seat sealing ring 6. The medium pressure within the clearance space 105 gradually increases, and the medium entering the clearance space 105 enters the liquid supply channel 612, pushing the piston 613 to move. This forces the sealing strip 608 to contract circumferentially along the valve seat sealing ring 6 under the traction of the piston 613, causing the inner cone surface of the inner cone section 601 to contact the outer cone surface of the second outer cone section 604. An active sealing structure is formed between the mating surfaces, creating an active sealing layer in addition to the original sealing surfaces. This ensures that there is no gap between the self-sealing valve seat 4 and the valve seat sealing ring 6, preventing media leakage. As a result, the higher the medium pressure, the greater the force exerted by the second valve ball 3 on the self-sealing valve seat 4, the self-sealing valve seat 4 on the valve seat sealing ring 6, and the valve seat sealing ring 6 on the valve body 1. The traction force applied to the sealing strip 608 will also gradually increase, causing the sealing strip 608 to press tightly against the self-sealing valve seat 4. This results in a good sealing effect of the sealing structure, and the medium is reliably blocked on the side of the self-sealing valve seat 4 facing the inlet valve body 8.

[0039] An annular groove 609 communicating with the liquid supply channel 612 is provided on the end face of the second straight section 603. A sealing ring 610 is installed in the annular groove 609. When the medium entering the relief space 105 enters the liquid supply channel 612, it forces the sealing ring 610 to move axially. In this way, the sealing ring 610 will press against the bottom of the second assembly groove 102 to form an active seal. Several blocking rings 611 are installed on the side wall where the sealing ring 610 abuts against the second assembly groove 102. The sealing ring 610 and the blocking rings 611 cooperate. After the pressure is released, the blocking rings 611 return to their initial state, forming a multi-stage end face seal, further blocking the medium leakage path.

[0040] To improve the stability and assembly accuracy of the valve seat structure, the PCV valve also includes a valve seat support ring 10, which is assembled between the first valve seat 9 and the bottom of the second assembly groove 102. An external thread 403 is provided on the outer wall of the first straight section 401, and an internal thread 1001 is provided on the inner wall of the valve seat support ring 10 to mate with the external thread 403. This threaded connection allows for detachable assembly, facilitating debugging and maintenance. Simultaneously, a first elastic telescopic structure 11 is installed between the valve seat support ring 10 and the first valve seat 9, and a second elastic telescopic structure 12 is installed between the bottom of the second assembly groove 102 and the second valve seat 5. Both the first elastic telescopic structure 11 and the second elastic telescopic structure 12 employ a flat-topped wave spring structure, or alternatively, a butterfly spring, providing axial elastic preload to compensate for valve seat wear and thermal deformation.

[0041] To achieve independent control of the double ball valve, two sets of valve stem controllers 13 are provided on the outer wall of the middle valve body 1, which are respectively connected to the first valve ball 2 and the second valve ball 3. By operating the valve stem controllers 13, the first valve ball 2 and the second valve ball 3 can be driven to rotate respectively, so as to realize the independent opening and closing or linkage opening and closing of the valve passage 101, which can adapt to different working conditions.

[0042] Specifically, two valve stem holes are provided within a vertical 180° range of the middle valve body 1. The valve stem is installed from the inside to the outside through the valve chambers on the left and right sides of the middle valve body 1, and bearings, valve stem packing and packing gland are installed in sequence. The packing gland is fixed to the middle valve body 1 by studs, hexagonal nuts and disc springs, and the valve stem packing is pressed by the preload of the hexagonal nuts.

[0043] The manual actuator drives the valve stem to rotate, and the valve stem drives the second valve ball 3 to rotate, thereby realizing the opening and closing operation of the second valve ball 3 in the middle valve body 1; The automatic control actuator drives the valve stem to rotate, and the valve stem drives the first valve ball 2 to rotate, thereby realizing the opening and closing operation of the first valve ball 2 in the valve body 1.

[0044] The operation of the double ball valve type PCV valve used in this power plant is based on the synergistic effect of the independent control of the double ball valve and its self-sealing structure, as detailed below: Medium flow and basic opening and closing: The medium enters from the inlet valve body 8, flows through the valve passage 101 inside the middle valve body 1 to the outlet valve body 7; by controlling the two sets of valve stem controllers 13 on the outside of the middle valve body 1, the first valve ball 2 and the second valve ball 3 are driven to rotate respectively. When both the first valve ball 2 and the second valve ball 3 are in the open state, the medium can be smoothly transported through the valve passage 101; when it is necessary to close the valve, the first valve ball 2 and the second valve ball 3 can be driven to rotate to the closed position by the valve stem controller 13, realizing the double closure of the valve passage 101 and improving the closure reliability.

[0045] Self-sealing reinforcement process: When the second valve ball 3 is closed, the medium pressure in the valve passage 101 acts on the second valve ball 3, pushing the second valve ball 3 to squeeze towards the self-sealing valve seat 4; the self-sealing valve seat 4 undergoes a slight displacement under pressure, causing the valve seat sealing ring 6 on its outer side to be simultaneously stressed. The second outer cone section 604 of the valve seat sealing ring 6 undergoes elastic deformation towards the relief space 105. At the same time, the first outer cone section 402 of the self-sealing valve seat 4 guides the inner cone section 601 of the valve seat sealing ring 6 to expand evenly through the cone surface fit, so that the outer wall of the valve seat sealing ring 6 and the inner wall of the second assembly groove 102 fit together surface to surface, forming a self-sealing structure. The greater the medium pressure, the tighter the seal fit.

[0046] Auxiliary sealing process: Under pressure, the medium enters the liquid supply channel 612 through the inlet and outlet 606 of the second outer cone section 604, pushing the piston 613 to move circumferentially along the valve seat sealing ring 6, thereby pulling the spiral sealing strip 608 to tighten. Since the sealing strip 608 is floating and adjacent spiral sections are in contact, the sealing strip 608 tightens inward under the pulling force applied by the piston 613, filling the gap between the valve seat sealing ring 6 and the self-sealing valve seat 4, realizing micro-gap sealing; if the medium pressure in this space increases, the medium continues to push the piston 613 to slide, and the piston 613 moves circumferentially along the valve seat sealing ring 6 again, thereby pulling the spiral sealing strip 608 to tighten; at the same time, the sealing ring 610 and the blocking ring 611 cooperate to form a multi-stage end face sealing structure, blocking the leakage path of the medium along the end face gap.

[0047] Structural compensation and maintenance: The first elastic telescopic structure 11 and the second elastic telescopic structure 12 provide axial preload when the valve ball is closed, ensuring the valve ball and valve seat are in close contact; when the valve seat is worn or deformed by heat, the elastic telescopic structure can perform axial compensation to maintain sealing performance; the valve seat support ring 10 is connected to the self-sealing valve seat 4 by threads, and the detachable design facilitates the maintenance and replacement of sealing components, valve ball and other parts in the later stage; the valve body main sealing ring 14 and the valve body secondary sealing ring 15 work together to always ensure the sealing of the valve body mating surface and prevent external leakage.

[0048] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A double ball valve type PCV valve for power plants, characterized in that, Includes a middle valve body, with an outlet valve body on one side and an inlet valve body on the other side; a valve passage is provided inside the middle valve body; A first assembly groove is provided on the side of the valve passage near the outlet valve body. A first valve ball is installed in the first assembly groove. A first valve seat is provided in the first assembly groove. The outlet valve body and the first valve seat clamp the first valve ball in the first assembly groove for opening and closing the valve passage. The valve passage has a second assembly groove on the side of the valve body near the inlet end. A second valve ball is installed in the second assembly groove. A self-sealing valve seat is provided in the second assembly groove. A second valve seat is provided in the valve body at the inlet end. The second valve seat and the self-sealing valve seat clamp the second valve ball in the second assembly groove for opening and closing the valve passage. An installation chamber is provided between the self-sealing valve seat and the second assembly groove. A valve seat sealing ring is fitted on the outer wall of the self-sealing valve seat, and a portion of the outer wall of the valve seat sealing ring abuts against the inner wall of the second assembly groove. When the second valve ball is closed, the medium in the valve passage will push the second valve ball to squeeze the self-sealing valve seat, causing the valve seat sealing ring to deform and move towards the inner wall of the second assembly groove and fit against it. The self-sealing valve seat has a first straight section and a first outer conical section sequentially arranged on its outer side wall. The small diameter end of the first outer conical section is integrally formed with the first straight section. The outer side wall of the first straight section abuts against the inner wall of the valve passage. The outer side wall of the first outer conical section abuts against the second assembly groove. The valve seat sealing ring has an inner conical section on its inner side wall. A sealing arc surface is provided on the inner conical surface of the inner conical section that abuts against the outer side wall of the first outer conical section. The valve seat sealing ring has a second straight section and a second outer conical section on its outer side, wherein the second straight section abuts against the inner wall of the second assembly groove; the second straight section abuts against the bottom of the second assembly groove; and a clearance space is provided between the second outer conical section and the inner wall of the second assembly groove. The outer wall of the second outer cone section has several inlets and outlets. A liquid supply channel is provided around the valve seat sealing ring along the circumference of the valve seat sealing ring. Several inlets and outlets are connected to the liquid supply channel. An installation groove is provided on the inner cone surface of the inner cone section. A spiral sealing strip is provided in the installation groove. Any two adjacent spiral segments in the sealing strip abut against each other. The sealing strip is floating in the installation groove. The two free ends of the sealing strip are elastically connected to the inner wall of the installation groove. The installation groove is connected to the liquid supply channel. There is a movable gap at the connection between the installation groove and the liquid supply channel. A piston connected to the sealing strip is slidably provided in the liquid supply channel. The end face of the second straight section is provided with an annular groove that communicates with the inlet and outlet. A sealing ring is installed in the annular groove, and several blocking rings are installed on the side wall of the sealing ring that abuts against the second assembly groove.

2. A double ball valve type PCV valve for power plants according to claim 1, characterized in that, The second straight section has an arc-shaped structure on its end face facing the bottom of the second assembly groove, and the arc-shaped structure abuts against the bottom of the second assembly groove.

3. A double ball valve type PCV valve for power plants according to claim 1, characterized in that, It also includes a valve seat support ring, which is assembled between the bottom of the first valve seat and the second assembly groove; The outer wall of the first straight section is provided with an external thread, and the inner wall of the valve seat support ring is provided with an internal thread that meshes with the external thread.

4. A double ball valve type PCV valve for power plants according to claim 3, characterized in that, A first elastic telescopic structure is installed between the valve seat support ring and the first valve seat; A second elastic telescopic structure is installed between the bottom of the second assembly groove and the second valve seat; The first elastic telescopic structure is a butterfly spring or a flat-top wave spring structure; The second elastic telescopic structure is a butterfly spring or a flat-top wave spring structure.

5. A double ball valve type PCV valve for power plants according to claim 1, characterized in that, The outer wall of the valve body is provided with two sets of valve stem controllers that are respectively connected to the first valve ball and the second valve ball.

6. A double ball valve type PCV valve for power plants according to claim 1, characterized in that, The outlet valve body is provided with an outlet valve body embedding section on the side near the middle valve body; The inlet valve body is provided with an inlet valve body embedding section on the side near the middle valve body; The outer wall of the valve body embedding section at the outlet end and the outer wall of the valve body embedding section at the inlet end are both fitted with valve body main sealing rings that abut against the middle valve body. The inlet valve body and outlet valve body are each provided with a secondary valve body sealing ring on the side wall opposite to the middle valve body, and the secondary valve body sealing ring abuts against the middle valve body.

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