Heat preservation gate valve capable of keeping liquid state in low-temperature environment

Abstract

The invention relates to a heat preservation gate valve capable of keeping liquid in a low-temperature environment. In order to solve the problems that an existing low-temperature gate valve is insufficient in pressure relief control, structural stability, sealing performance and the like and cannot meet the requirements of the low-temperature environment for safety and reliability of the gate valve, a three-stage pressure relief device close to the upstream side of a valve plate is arranged at the bottom of a valve body of the heat preservation gate valve, and an outlet of the three-stage pressure relief device is connected to a pipeline on the upstream side of the valve body through a stainless steel corrugated pipe. The device comprises a cylindrical body and different valve cores, and different pressure relief channels are sequentially formed through a central through hole, an annular cavity and a specific through hole. The pressure relief pressure of the valve elements is increased progressively, and precise staged pressure relief is achieved. And meanwhile, the structural design is optimized, the stability and sealing performance at low temperature are guaranteed, the action of the valve element and the medium flow and flow velocity are accurately controlled, the safety and reliability of the gate valve in the low-temperature environment are greatly improved, and the gate valve has important application value.

Description

Technical Field

[0001] The present invention relates to the field of gate valves, and specifically to a heat-insulating gate valve that maintains a liquid state in a low-temperature environment. Background Art

[0002] In a low-temperature environment, such as in the storage, transportation, and related processing of liquefied natural gas (LNG), a large number of gate valves are required to control the flow of fluids. However, existing low-temperature gate valves have many problems in practical applications, seriously affecting the safety and stability of the system.

[0003] First of all, the low-temperature environment causes changes in the physical properties of the medium, such as volume contraction, increased viscosity, etc., which makes the pressure change situation in the middle cavity of the valve body complex. When the pressure is too high, if there is no effective pressure relief measure, it may cause damage to the gate valve, such as gate plate deformation, valve seat seal failure, etc., and then lead to medium leakage, causing serious safety accidents and economic losses. Traditional low-temperature gate valves often adopt a single pressure relief device and cannot accurately relieve pressure according to different stages of pressure. When the pressure is relatively low, it may not be able to relieve pressure in time due to the too high opening pressure of the pressure relief device; when the pressure is too high, it may not be able to quickly reduce the pressure due to insufficient pressure relief capacity, resulting in the gate valve bearing excessive pressure.

[0004] Secondly, existing low-temperature gate valves also have deficiencies in structural stability and sealing performance. Under the dual action of low temperature and pressure changes, the components of the gate valve are prone to loosening, deformation, etc., affecting the normal operation of the gate valve. For example, the connection part between the pressure relief device and the valve body may leak due to poor sealing, affecting the pressure relief effect; components such as the valve core inside the gate valve may have sealing failure or movement obstruction in a low-temperature environment, unable to open and close normally, and thus affecting the overall performance of the gate valve.

[0005] In addition, in a low-temperature environment, the control and position limit of the valve core movement of the gate valve also face challenges. Since low temperature will change the performance of materials, traditional valve core driving and limiting methods may not meet the requirements, resulting in inaccurate valve core movement and affecting the timeliness and accuracy of pressure relief. At the same time, after the pressure relief is completed, the reset problem of the valve core also needs to be properly solved, otherwise it will affect the next normal operation of the gate valve.

[0006] In addition, the control of the medium flow rate and velocity in different pressure relief stages is also a key issue. If the medium flow rate and velocity are not properly controlled during the pressure relief process, it may cause an impact on the gate valve and the entire system, accelerate the damage of the equipment, and reduce the service life of the system. Traditional low-temperature gate valves often do not fully consider this point in their design, resulting in an unstable and unreasonable pressure relief process.

[0007] In summary, the existing cryogenic gate valves have many deficiencies in aspects such as pressure relief control, structural stability, sealing performance, spool movement control, and medium flow rate control, and cannot meet the strict requirements for the safety and reliability of gate valves in cryogenic environments. Therefore, it is of great practical significance and application value to develop a heat preservation gate valve that can effectively solve the above problems and maintain the liquid state in a cryogenic environment. Summary of the Invention

[0008] Based on this, it is necessary to provide a heat preservation gate valve that maintains the liquid state in a cryogenic environment to address the problems of the existing technology.

[0009] To solve the problems of the existing technology, the technical solution adopted by the present invention is as follows: A heat preservation gate valve that maintains the liquid state in a cryogenic environment, comprising a valve body, a gate plate disposed in the middle cavity of the valve body, a screw lifting drive mechanism disposed above the gate plate, and valve seats closely attached to both sides of the gate plate. A three-stage pressure relief device is provided at the bottom of the valve body, which communicates with the middle cavity of the valve body and is arranged near the upstream side of the valve plate. The outlet end of the three-stage pressure relief device is connected to the upstream side pipeline of the valve body through a stainless steel bellows. The three-stage pressure relief device includes a cylindrical body, a first-stage spool, a second-stage spool, and a third-stage spool. A central through hole is provided axially through the center of the cylindrical body. The cylindrical body is also provided with a first annular cavity and a second annular cavity that are concentric with the central through hole and are distributed from the inside to the outside. The second-stage spool is movably sealed in the central through hole, and the first-stage spool is disposed at the center of the second-stage spool. Second-stage upper through holes and second-stage lower through holes for allowing the medium to pass through are provided between the central through hole and the first annular cavity. When the second-stage spool is in the closed state, it closes the second-stage upper through holes, and the second-stage lower through holes are located below the second-stage spool. Third-stage upper through holes and third-stage lower through holes for allowing the medium to pass through are provided between the first annular cavity and the second annular cavity. A final flow hole for allowing the medium flowing out of the third-stage lower through holes to enter the central through hole is provided at the lower end of the first annular cavity. The third-stage spool is movably sealed between the first annular cavity and the second annular cavity. The second-stage lower through holes are located above the third-stage lower through holes. The third-stage spool simultaneously opens or closes the third-stage upper through holes and the third-stage lower through holes by displacement in the axial direction of the cylindrical body. The pressure relief pressures of the first-stage spool, the second-stage spool, and the third-stage spool gradually increase; The first-stage spool to the central through hole constitutes a first-stage pressure relief channel; The second-stage upper through holes, the first annular cavity, the second-stage lower through holes, and the central through hole sequentially constitute a second-stage pressure relief channel; The second-stage upper through holes, the first annular cavity, the third-stage upper through holes, the second annular cavity, the third-stage lower through holes, the second-stage lower through holes, the final flow hole, and the central through hole sequentially constitute a third-stage pressure relief channel.

[0010] Further, the cylindrical body is composed of a central tube, a middle layer tube, and an outer layer tube. A first annular cavity is formed between the central tube and the middle layer tube, and a second annular space is formed between the middle layer tube and the outer layer tube. The secondary upper through hole, the secondary lower through hole, and the final flow hole are all arranged on the tube wall of the central tube. The tertiary upper through hole and the tertiary lower through hole are both arranged on the tube wall of the middle layer tube. The central through hole is the inner hole of the central tube. The upper ends of the central tube, the middle layer tube, and the outer layer tube are fixedly embedded and connected with an upper end cover. An upper thread seat for threaded connection with the valve body is formed on the top of the upper end cover. On the bottom surface of the upper end cover, a first fitting ring and a second fitting ring are formed in a concentric state. The first fitting ring is downwardly fitted into the top of the first annular cavity, and the second fitting ring is downwardly fitted into the top of the second annular cavity.

[0011] Further, on the inner wall of the middle layer tube, a secondary annular upper flange and a secondary annular lower flange are formed. The secondary annular upper flange is closely arranged along the lower edge of the tertiary upper through hole, and the secondary annular lower flange is closely arranged along the lower edge of the tertiary lower through hole. The inner edges of the secondary annular upper flange and the secondary annular lower flange are in dynamic sealing fit with the outer wall of the central tube. Downwardly inclined bevel structures are arranged at the inner edges of the secondary annular upper flange and the secondary annular lower flange. The lower end of the bevel structure of the secondary annular upper flange extends to the lower edge of the secondary lower through hole, and the lower end of the bevel structure of the secondary annular lower flange extends to the lower edge of the final flow hole. An annular flange is formed on the inner wall at the lower end of the outer layer tube. The upper end of the annular flange is flush with the lower edge of the tertiary lower through hole. The tertiary valve core is movably arranged in a dynamic sealing state between the annular flange and the middle layer tube.

[0012] Further, the tertiary valve core is in a circular tubular shape, and a cross-shaped grid is formed at the opening of its bottom. First through holes and second through holes are formed on the cylindrical wall of the tertiary valve core. When the cross-shaped grid abuts upward against the bottom wall of the middle layer tube, the first through hole and the second through hole respectively close the tertiary upper through hole and the tertiary lower through hole in a misaligned state. A limiting column extending upward to the inside of the central tube is formed at the center of the cross-shaped grid. An upward sunken groove is formed at the bottom of the secondary valve core for avoiding and accommodating the limiting column. When the lower end of the secondary valve core is flush with the upper edge of the secondary lower through hole, at this time, the top end of the limiting column contacts the top wall of the sunken groove. A tertiary spring is arranged below the cross-shaped grid, and a secondary spring is arranged above the cross-shaped grid. The upper end of the secondary spring abuts against the top wall of the sunken groove.

[0013] Further, a section of threaded wall is formed at the lower end of the outer layer pipe, and a lower end cover is screwed onto the threaded wall. A lower threaded seat for connecting the corrugated pipe is formed at the bottom of the lower end cover. A limiting ring is fixedly arranged inside the lower end of the threaded wall, and the bottom wall of the limiting ring is attached to the inner wall of the lower end cover. When the lower end of the three-stage valve core abuts against the upper end of the limiting ring, the first through hole and the second through hole are respectively at the same horizontal height as the three-stage upper through hole and the three-stage lower through hole to keep the three-stage pressure relief channel open. A positioning flange extending upward for positioning the lower end of the three-stage spring is formed at the center of the lower end cover. An annular positioning groove for positioning the upper end of the three-stage spring is reserved between the cross-shaped grille and the inner wall of the lower end of the three-stage valve core.

[0014] Further, the first-stage valve core is a check valve, and an installation insert ring for abutting against the upper and lower ends of the check valve is clamped at both the upper and lower ends of the central hole of the second-stage valve core.

[0015] Further, the diameter of the second-stage valve core is smaller than the inner diameter of the central pipe. A plurality of polytetrafluoroethylene sealing rings are embedded on the outer wall of the second-stage valve core and are distributed at intervals up and down. The polytetrafluoroethylene slides and fits against the inner wall of the central pipe. The three-stage valve core is made of polytetrafluoroethylene.

[0016] Further, the apertures of the second-stage upper through hole and the second-stage lower through hole are the same, and the apertures of the three-stage upper through hole and the three-stage lower through hole are the same. The apertures of the second-stage upper through hole, the three-stage upper through hole, and the final flow hole increase in sequence.

[0017] Further, a limiting retaining ring extending downward and fitting into the upper edge of the inner wall of the central pipe is formed at the center of the upper end cover. When the second-stage valve core fits against the limiting retaining ring, the second-stage upper through hole is closed.

[0018] The beneficial effects of the present invention compared with the prior art are as follows: First, precise pressure relief, safe and reliable: Most existing cryogenic gate valves adopt a single pressure relief device and it is difficult to accurately respond to different pressure stages. The three-stage pressure relief device of this solution realizes staged and precise pressure relief by the first-stage, second-stage, and third-stage valve cores opening the pressure relief in sequence from small to large pressure. When the pressure is relatively low, the first-stage valve core can open in time for preliminary pressure relief; when the pressure rises, the second-stage and third-stage valve cores respond in sequence to ensure effective pressure relief at different pressures and avoid damage to the gate valve and the system caused by excessive pressure, greatly improving the safety and reliability of the gate valve; Second, it has a stable structure and good sealing: Under the action of low temperature and pressure changes, the components of traditional low-temperature gate valves are prone to loosening and deformation, the connection parts are prone to leakage, and the sealing and movement of the valve core are also easily affected. In this solution, the cylindrical body is composed of a central pipe, a middle layer pipe, and an outer layer pipe, and is fixedly installed and connected through the upper end cover, with a stable structure. The polytetrafluoroethylene sealing ring on the outer wall of the secondary valve core and the tertiary valve core are made of polytetrafluoroethylene, ensuring the sealing performance and smooth movement at low temperatures, and effectively solving the problems of structural stability and sealing; Third, the valve core control is precise and the flow rate can be controlled: Existing gate valves have difficulties in controlling the movement and position limit of the valve core at low temperatures, and problems such as reset after pressure relief often occur, and the control of the medium flow rate is insufficient. In this solution, the position of the secondary valve core and the tertiary valve core is limited by the cooperation of the limit columns and the sinking grooves, and the secondary spring and the tertiary spring ensure the reset of the valve core. At the same time, through holes with different apertures are set according to different pressure relief stages to reasonably control the medium flow rate and velocity, making the pressure relief process stable and reasonable, and ensuring the normal operation of the gate valve and the service life of the system. Description of the Drawings

[0019] Figure 1 is a three-dimensional structure schematic diagram of the present invention; Figure 2 is a plane cross-sectional view of the present invention; Figure 3 is a plane cross-sectional view of the three-stage pressure relief device of the present invention in the state of the first-stage pressure relief hole; Figure 4 is a plane cross-sectional view of the three-stage pressure relief device of the present invention in the state of the second-stage pressure relief hole; Figure 5 is a plane cross-sectional view of the three-stage pressure relief device of the present invention in the state of the third-stage pressure relief hole; Figure 6 is a three-dimensional cross-sectional view of the three-stage pressure relief device of the present invention; Figure 7 is a three-dimensional exploded schematic diagram of the three-stage pressure relief device of the present invention; Figure 8 is a three-dimensional exploded schematic diagram of the secondary valve core and the primary valve core of the present invention; The reference numerals in the figure are: 1 - valve body; 2 - gate plate; 3 - screw lifting drive mechanism; 4 - valve seat; 5 - three - stage pressure relief device; 6 - central through - hole; 7 - first annular cavity; 8 - second annular cavity; 9 - second - stage upper through - hole; 10 - second - stage lower through - hole; 11 - third - stage upper through - hole; 12 - third - stage lower through - hole; 13 - final flow hole; 14 - central tube; 15 - middle - layer tube; 16 - outer - layer tube; 17 - upper end - cover; 18 - upper thread seat; 19 - first fitting ring; 20 - second fitting ring; 21 - second - stage annular upper flange; 22 - second - stage annular lower flange; 23 - bevel structure; 24 - annular flange; 25 - cross grid; 26 - first through - hole; 27 - second through - hole; 28 - sinking groove; 29 - limit upright post; 30 - third - stage spring; 31 - second - stage spring; 32 - threaded wall; 33 - lower end - cover; 34 - lower thread seat; 35 - limit ring; 36 - positioning flange; 37 - annular positioning groove; 38 - check valve; 39 - installation fitting ring; 40 - polytetrafluoroethylene sealing ring; 41 - limit retaining ring; 42 - first - stage valve core; 43 - second - stage valve core; 44 - third - stage valve core. Specific embodiments

[0020] To further understand the features, technical means, specific purposes, and functions achieved by the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0021] Refer to Figures 1 to 8As shown in the figure, a heat-insulating gate valve that remains liquid in a low-temperature environment includes a valve body 1, a gate plate 2 disposed in the middle cavity of the valve body 1, a screw lifting drive mechanism 3 disposed above the gate plate 2, and valve seats 4 fitted on both sides of the gate plate 2. A three-stage pressure relief device 5 that communicates with the middle cavity of the valve body 1 and is arranged near the upstream side of the valve plate is provided at the bottom of the valve body 1. The outlet end of the three-stage pressure relief device 5 is connected to the upstream side pipeline of the valve body 1 through a stainless steel bellows. The three-stage pressure relief device 5 includes a cylindrical body, a first-stage valve core, a second-stage valve core, and a third-stage valve core. A central through hole 6 that penetrates axially is provided at the center of the cylindrical body. The cylindrical body is also provided with a first annular cavity 7 and a second annular cavity 8 that are concentric with the central through hole 6 and are distributed from the inside to the outside. The second-stage valve core is movably sealed in the central through hole 6. The first-stage valve core is disposed at the center of the second-stage valve core. A second-stage upper through hole 9 and a second-stage lower through hole 10 for allowing the medium to pass through are provided between the central through hole 6 and the first annular cavity 7. When the second-stage valve core is in the closed state, the second-stage upper through hole 9 is closed and the second-stage lower through hole 10 is located below the second-stage valve core. A third-stage upper through hole 11 and a third-stage lower through hole 12 for allowing the medium to pass through are provided between the first annular cavity 7 and the second annular cavity 8. A final flow hole 13 for allowing the medium flowing out of the third-stage lower through hole 12 to enter the central through hole 6 is provided at the lower end of the first annular cavity 7. The third-stage valve core is movably sealed between the first annular cavity 7 and the second annular cavity 8. The second-stage lower through hole 10 is located above the third-stage lower through hole 12. The third-stage valve core simultaneously opens or closes the third-stage upper through hole 11 and the third-stage lower through hole 12 by displacement in the axial direction of the cylindrical body. The pressure relief pressures of the first-stage valve core, the second-stage valve core, and the third-stage valve core gradually increase; The first-stage valve core to the central through hole 6 constitutes a first-stage pressure relief channel; The second-stage upper through hole 9, the first annular cavity 7, the second-stage lower through hole 10, and the central through hole 6 sequentially constitute a second-stage pressure relief channel; The second-stage upper through hole 9, the first annular cavity 7, the third-stage upper through hole 11, the second annular cavity 8, the third-stage lower through hole 12, the second-stage lower through hole 10, the final flow hole 13, and the central through hole 6 sequentially constitute a third-stage pressure relief channel.

[0022] Working principle: When the pressure in the middle cavity of the valve body 1 increases, first it reaches the pressure relief pressure of the first-stage valve core, and the first-stage valve core opens. The medium enters the central through-hole 6 through the first-stage pressure relief channel (from the first-stage valve core to the central through-hole 6), achieving preliminary pressure relief. If the pressure continues to rise and reaches the pressure relief pressure of the second-stage valve core, the second-stage valve core opens, and the medium is further pressure-relieved through the second-stage pressure relief channel (formed by the second upper through-hole 9, the first annular cavity 7, the second lower through-hole 10, and the central through-hole 6 in sequence). When the pressure continues to increase and reaches the pressure relief pressure of the third-stage valve core, the third-stage valve core opens, and the medium is largely pressure-relieved through the third-stage pressure relief channel (formed by the second upper through-hole 9, the first annular cavity 7, the third upper through-hole 11, the second annular cavity 8, the third lower through-hole 12, the second lower through-hole 10, the final flow hole 13, and the central through-hole 6 in sequence), and finally is discharged into the pipeline on the upstream side of the valve body 1 through the stainless steel bellows.

[0023] Problem solved: It solves the problem of excessive pressure in the middle cavity of the heat preservation gate valve in a low-temperature environment, avoids damage to the gate valve or medium leakage caused by excessive pressure, and ensures the safe and stable operation of the gate valve in a low-temperature environment.

[0024] Effect achieved: By setting the three-stage pressure relief device 5 and the pressure relief pressures of each stage of valve core gradually increasing, it realizes accurate pressure relief in stages according to the pressure magnitude, effectively reduces the impact of instantaneous pressure changes on the gate valve and the system, and improves the reliability and safety of the gate valve.

[0025] The cylindrical body is composed of a central tube 14, a middle layer tube 15, and an outer layer tube 16. The first annular cavity 7 is formed between the central tube 14 and the middle layer tube 15, and the second annular space is formed between the middle layer tube 15 and the outer layer tube 16. The second upper through-hole 9, the second lower through-hole 10, and the final flow hole 13 are all arranged on the pipe wall of the central tube 14. The third upper through-hole 11 and the third lower through-hole 12 are all arranged on the pipe wall of the middle layer tube 15. The central through-hole 6 is the inner hole of the central tube 14. The upper ends of the central tube 14, the middle layer tube 15, and the outer layer tube 16 are fixedly embedded and connected with an upper end cover 17. The top of the upper end cover 17 is formed with an upper thread seat 18 for threaded connection with the valve body 1. The bottom surface of the upper end cover 17 is formed with a first fitting ring 19 and a second fitting ring 20 distributed concentrically. The first fitting ring 19 is downwardly fitted into the top of the first annular cavity 7, and the second fitting ring 20 is downwardly fitted into the top of the second annular cavity 8.

[0026] Working principle: The cylindrical body is composed of a central tube 14, a middle layer tube 15, and an outer layer tube 16. This structure forms a first annular cavity 7 and a second annular cavity 8, providing space for the flow of the medium at different pressure relief stages. The upper end cover 17 is fixedly and embeddedly connected to the central tube 14, the middle layer tube 15, and the outer layer tube 16, which not only ensures the sealing of the cylindrical body but also facilitates the connection with the valve body 1 through the upper threaded seat 18, ensuring that the entire three-stage pressure relief device 5 can be stably installed at the bottom of the valve body 1.

[0027] Problems solved: Solved the problems of the structural stability and sealing of the three-stage pressure relief device 5, ensuring that under low-temperature environments and pressure changes, the pressure relief device will not loosen or leak, affecting the pressure relief effect.

[0028] Achieved effects: Ensured the reliable operation of the pressure relief device. The tight connection and reasonable layout between components enable the medium to flow orderly in different pressure relief channels, improving the service life and working efficiency of the pressure relief device.

[0029] A secondary annular upper flange 21 and a secondary annular lower flange 22 are formed on the inner wall of the middle layer tube 15. The secondary annular upper flange 21 is closely arranged along the lower edge of the third-stage upper through hole 11, and the secondary annular lower flange 22 is closely arranged along the lower edge of the third-stage lower through hole 12. The inner edges of the secondary annular upper flange 21 and the secondary annular lower flange 22 are in dynamic sealing fit with the outer wall of the central tube 14. An inclined angle structure 23 is provided at the inner edges of the secondary annular upper flange 21 and the secondary annular lower flange 22. The lower end of the inclined angle structure 23 of the secondary annular upper flange 21 extends to the lower edge of the secondary lower through hole 10, and the lower end of the inclined angle structure 23 of the secondary annular lower flange 22 extends to the lower edge of the final flow hole 13. A ring flange 24 is formed on the inner wall at the lower end of the outer layer tube 16, and the upper end of the ring flange 24 is flush with the lower edge of the third-stage lower through hole 12. The third-stage valve core is movably arranged in a dynamic sealing state between the ring flange 24 and the middle layer tube 15.

[0030] Working principle: The secondary annular upper flange 21 and the secondary annular lower flange 22 on the inner wall of the middle layer tube 15, and the ring flange 24 on the inner wall at the lower end of the outer layer tube 16 cooperate with the third-stage valve core to control the flow of the medium during three-stage pressure relief. When the third-stage valve core moves between the ring flange 24 and the middle layer tube 15, the opening and closing control of the third-stage upper through hole 11 and the third-stage lower through hole 12 is achieved through the change in the relative position with these flanges. The inclined angle structure 23 at the inner edges of the secondary annular upper flange 21 and the secondary annular lower flange 22 helps to guide the flow of the medium, enabling the medium to smoothly pass through the secondary lower through hole 10 and the final flow hole 13.

[0031] Problems solved: Solved the problems of controlling and guiding the flow of the medium during three-stage pressure relief, avoiding the occurrence of turbulent flow or reverse flow of the medium during the flow process, which affects the pressure relief effect.

[0032] Achieved effects: Ensured the smooth progress of the three - stage pressure relief, improved the efficiency and stability of pressure relief, reduced the impact of the medium on the inner wall of the pressure relief device, and extended the service life of the device.

[0033] The three - stage valve core is in a round - tube shape, and a cross - shaped grid 25 is formed at the bottom opening thereof. First through - holes 26 and second through - holes 27 are formed on the cylindrical wall of the three - stage valve core. When the cross - shaped grid 25 abuts upward against the bottom wall of the middle - layer tube 15, the first through - holes 26 and the second through - holes 27 are in a misaligned state to close the upper three - stage through - hole 11 and the lower three - stage through - hole 12 respectively. A limiting upright column 29 extending upward to the inside of the central tube 14 is formed at the center of the cross - shaped grid 25. An upward sunken groove 28 is formed at the bottom of the second - stage valve core for avoiding and accommodating the limiting upright column 29. When the lower end of the second - stage valve core is flush with the upper edge of the second - stage lower through - hole 10, the top end of the limiting upright column 29 contacts the top wall of the sunken groove 28 at this time. A three - stage spring 30 is arranged below the cross - shaped grid 25, and a second - stage spring 31 is arranged above the cross - shaped grid 25. The upper end of the second - stage spring 31 abuts against the top wall of the sunken groove 28.

[0034] Working principle: The three - stage valve core is in a round - tube shape. The cross - shaped grid 25 at the bottom, the first through - holes 26 and the second through - holes 27 on the cylindrical wall cooperate with the upper three - stage through - hole 11 and the lower three - stage through - hole 12 on the middle - layer tube 15 to realize the opening and closing of the three - stage pressure - relief channel. When the pressure does not reach the three - stage pressure - relief pressure, the cross - shaped grid 25 abuts upward against the bottom wall of the middle - layer tube 15 to close the upper three - stage through - hole 11 and the lower three - stage through - hole 12. When the pressure reaches the three - stage pressure - relief pressure, the three - stage valve core moves downward under the action of the pressure, so that the first through - holes 26 and the second through - holes 27 are respectively aligned with the upper three - stage through - hole 11 and the lower three - stage through - hole 12, opening the three - stage pressure - relief channel. The cooperation of the limiting upright column 29 and the sunken groove 28 plays a role in limiting the positions of the second - stage valve core and the three - stage valve core, ensuring that the actions of the valve cores are accurate in different pressure - relief stages. The second - stage spring 31 and the three - stage spring 30 provide the elastic force for the valve core to reset, ensuring that after the pressure relief is completed, the valve core can return to the initial position in time to close the pressure - relief channel.

[0035] Problems solved: Solved the problems of the action control and position limitation of the three - stage valve core, and the reset problem of the valve core after the pressure relief is completed, ensuring that the pressure - relief device can reliably perform multiple pressure - relief operations.

[0036] Achieved effects: Improved the automation degree and reliability of the pressure - relief device, made the three - stage pressure - relief process more accurate and stable, and reduced the manual intervention and maintenance cost.

[0037] A threaded wall 32 is formed at the lower end of the outer layer pipe 16. A lower end cover 33 is screwed onto the threaded wall 32. A lower threaded seat 34 for connecting the corrugated pipe is formed at the bottom of the lower end cover 33. A limiting ring 35 is fixedly arranged on the inner side of the lower end of the threaded wall 32. The bottom wall of the limiting ring 35 abuts against the inner wall of the lower end cover 33. When the lower end of the three-stage valve core abuts against the upper end of the limiting ring 35, the first through hole 26 and the second through hole 27 are respectively at the same horizontal height as the three-stage upper through hole 11 and the three-stage lower through hole 12 to keep the three-stage pressure relief channel open. A positioning flange 36 extending upward for positioning the lower end of the three-stage spring 30 is formed at the center of the lower end cover 33. An annular positioning groove 37 for positioning the upper end of the three-stage spring 30 is reserved between the cross-shaped grille 25 and the inner wall of the lower end of the three-stage valve core.

[0038] Working principle: The threaded wall 32 at the lower end of the outer layer pipe 16 is screwed onto the lower end cover 33, which is convenient for installation and disassembly. The lower threaded seat 34 on the lower end cover 33 is used to connect the corrugated pipe to ensure that the pressure relief medium can be discharged smoothly. The limiting ring 35 limits the position of the lower end of the three-stage valve core. When the lower end of the three-stage valve core abuts against the limiting ring 35, the first through hole 26 and the second through hole 27 are at the same horizontal height as the three-stage upper through hole 11 and the three-stage lower through hole 12 to keep the three-stage pressure relief channel open. The positioning flange 36 and the annular positioning groove 37 respectively position the lower end and the upper end of the three-stage spring 30 to ensure the stability of the spring during operation, so that the three-stage valve core can accurately reset under the action of the spring.

[0039] Problems solved: It solves the connection problem between the three-stage pressure relief device 5 and the corrugated pipe, as well as the positioning of the three-stage spring 30 and the position control of the three-stage valve core, ensuring the coordinated operation of each component during the pressure relief process.

[0040] Effects achieved: It ensures the smooth discharge of the pressure relief medium and the stable operation of the three-stage pressure relief device 5, improving the reliability of the entire gate valve system.

[0041] The first-stage valve core is a one-way valve 38. Installation rings 39 for abutting against the upper and lower ends of the one-way valve 38 are respectively clamped at the upper and lower ends of the central hole of the second-stage valve core.

[0042] Working principle: The first-stage valve core is a one-way valve 38 to ensure that the medium can only flow from the middle cavity of the valve body 1 to the central through hole 6, preventing the reverse flow of the medium. The installation rings 39 at the upper and lower ends of the central hole of the second-stage valve core are used to fix the one-way valve 38 to ensure its stability during operation.

[0043] Problems solved: It solves the problem of reverse flow of the medium during the first-stage pressure relief process, ensures the normal progress of the first-stage pressure relief, and improves the reliability of the first-stage pressure relief.

[0044] Achieved effect: Ensured the unidirectional flow of the primary pressure relief channel, making the pressure relief process safer and more reliable, and reducing the damage to the gate valve and the system caused by the reverse flow of the medium.

[0045] The diameter of the secondary valve core is smaller than the inner diameter of the central pipe 14. A number of polytetrafluoroethylene sealing rings 40 are embedded on the outer wall of the secondary valve core, and are spaced up and down. The polytetrafluoroethylene slides and fits against the inner wall of the central pipe 14, and the tertiary valve core is made of polytetrafluoroethylene.

[0046] Working principle: The diameter of the secondary valve core is smaller than the inner diameter of the central pipe 14, and the outer wall is embedded with polytetrafluoroethylene sealing rings 40, ensuring the dynamic sealing performance of the secondary valve core in the central pipe 14. At the same time, the polytetrafluoroethylene sealing rings 40 slide and fit against the inner wall of the central pipe 14, enabling the secondary valve core to move up and down smoothly in the central pipe 14. The tertiary valve core is made of polytetrafluoroethylene, which has good low-temperature resistance and self-lubricity, ensuring the normal operation of the tertiary valve core in a low-temperature environment and reducing the friction between the valve core and other components.

[0047] Problem solved: Solved the sealing and movement problems of the secondary valve core and the tertiary valve core in a low-temperature environment, ensuring that the valve core of the pressure relief device can operate normally in a low-temperature environment and will not affect the pressure relief effect due to seal failure or movement obstruction.

[0048] Achieved effect: Improved the adaptability and reliability of the pressure relief device in a low-temperature environment, ensuring the stable operation of the gate valve under low-temperature working conditions.

[0049] The diameters of the secondary upper through-hole 9 and the secondary lower through-hole 10 are the same, the diameters of the tertiary upper through-hole 11 and the tertiary lower through-hole 12 are the same, and the diameters of the secondary upper through-hole 9, the tertiary upper through-hole 11, and the final flow hole 13 increase in sequence.

[0050] Working principle: The diameters of the secondary upper through-hole 9 and the secondary lower through-hole 10 are the same, the diameters of the tertiary upper through-hole 11 and the tertiary lower through-hole 12 are the same, and the diameters of the secondary upper through-hole 9, the tertiary upper through-hole 11, and the final flow hole 13 increase in sequence. This aperture setting enables the reasonable control of the flow rate and flow volume of the medium according to the pressure magnitude and the medium flow demand at different pressure relief stages. At the initial stage of primary pressure relief and secondary pressure relief, the through-holes with smaller diameters can achieve small-flow pressure relief, avoiding too rapid a sudden drop in pressure; as the pressure rises and enters the tertiary pressure relief stage, the through-holes with larger diameters can meet the demand for rapid discharge of a large amount of medium.

[0051] Problem solved: Solved the problem of controlling the flow volume and flow rate of the medium at different pressure relief stages, making the pressure relief process smoother and more reasonable, and avoiding the impact on the gate valve and the system due to improper flow volume and flow rate.

[0052] Achieved effects: Ensure the stability and controllability of the pressure relief process, improve the safety and reliability of the gate valve, and also contribute to extending the service life of the gate valve and related equipment.

[0053] A limiting retaining ring 41 extending downward is formed at the center of the upper end cap 17 and is fitted to the upper edge of the inner wall of the central pipe 14. When the secondary valve core abuts against the limiting retaining ring 41, the secondary upper through hole 9 is closed.

[0054] Working principle: The limiting retaining ring 41 extending downward at the center of the upper end cap 17. When the secondary valve core abuts against the limiting retaining ring 41, the secondary upper through hole 9 is closed. This structure limits the position of the secondary valve core to ensure that after the secondary pressure relief is completed, the secondary valve core can accurately return to the initial position to close the secondary upper through hole 9 and prevent medium leakage.

[0055] Problems solved: Solve the problems of position control and sealing of the secondary valve core, ensure the sealing performance of the secondary pressure relief channel in the non-pressure relief state, and improve the reliability of the pressure relief device.

[0056] Achieved effects: Ensure the normal operation of the secondary pressure relief channel, avoid medium leakage caused by inaccurate position or poor sealing of the secondary valve core, and improve the safety and stability of the gate valve.

[0057] The above embodiments only represent one or several implementation manners of the present invention, and the description is relatively specific and detailed, but it should not be construed as a limitation to the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A thermal insulation gate valve for maintaining liquid in a low temperature environment, comprising a valve body (1), a gate plate (2) arranged in a central cavity of the valve body (1), a screw lifting drive mechanism (3) arranged above the gate plate (2), and valve seats (4) arranged in close contact with both sides of the gate plate (2), characterized in that: The bottom of the valve body (1) is provided with a three-stage pressure relief device (5) which is connected to the central cavity of the valve body (1) and arranged near the upstream side of the valve plate. The outlet end of the three-stage pressure relief device (5) is connected to the upstream side pipeline of the valve body (1) through a stainless steel bellows. The three-stage pressure relief device (5) comprises a cylindrical body, a primary valve core, a secondary valve core and a third-stage valve core. A central through hole (6) is provided at the center of the cylindrical body along the axial direction. The cylindrical body is also provided with a first annular cavity (7) and a second annular cavity (8) which are concentric with the central through hole (6) and are distributed from the inside to the outside. The secondary valve core is dynamically sealed and arranged in the central through hole (6). The primary valve core is arranged at the center of the secondary valve core. A secondary upper through hole (9) and a secondary lower through hole (10) for medium to pass through are provided between the central through hole (6) and the first annular cavity (7). 0), the secondary valve core closes the secondary upper through hole (9) in the closed state and the secondary lower through hole (10) is located below the secondary valve core, a tertiary upper through hole (11) and a tertiary lower through hole (12) for medium to pass through are arranged between the first annular cavity (7) and the second annular cavity (8), a final flow hole (13) for medium flowing out of the tertiary lower through hole (12) to enter the central through hole (6) is arranged at the lower end of the first annular cavity (7), the tertiary valve core is dynamically sealed and arranged between the first annular cavity (7) and the second annular cavity (8), the secondary lower through hole (10) is located above the tertiary lower through hole (12), the tertiary valve core simultaneously opens or closes the tertiary upper through hole (11) and the tertiary lower through hole (12) by displacement in the axial direction of the cylindrical body, and the pressure relief pressure of the primary valve core, the secondary valve core and the tertiary valve core gradually increases; The first-stage valve core to the central through hole (6) forms a first-stage pressure relief channel; The secondary upper through hole (9), the first annular cavity (7), the secondary lower through hole (10) and the central through hole (6) sequentially constitute a secondary pressure relief channel; The secondary upper through hole (9), the first annular cavity (7), the tertiary upper through hole (11), the second annular cavity (8), the tertiary lower through hole (12), the secondary lower through hole (10), the final flow hole (13) and the central through hole (6) sequentially form a three-stage pressure relief channel.

2. The thermal insulation gate valve capable of maintaining liquid state in a low temperature environment according to claim 1, characterized in that: The cylindrical body is composed of a central tube (14), a middle tube (15) and an outer tube (16); the first annular cavity (7) is formed between the central tube (14) and the middle tube (15); the second annular space is formed between the middle tube (15) and the outer tube (16); the secondary upper through hole (9), the secondary lower through hole (10) and the final flow hole (13) are all arranged on the wall of the central tube (14); the tertiary upper through hole (11) and the tertiary lower through hole (12) are all arranged on the wall of the middle tube (15); the central through hole (6) is a central through hole; An upper end cover (17) is fixedly embedded in the inner hole of the core tube (14), the upper ends of the center tube (14), the middle tube (15) and the outer tube (16), and the top of the upper end cover (17) is formed with an upper threaded seat (18) for threaded connection to the valve body (1), and the bottom surface of the upper end cover (17) is formed with a first embedding ring (19) and a second embedding ring (20) distributed in a concentric state, the first embedding ring (19) is embedded downwardly in the top of the first annular cavity (7), and the second embedding ring (20) is embedded downwardly in the top of the second annular cavity (8).

3. The thermal insulation gate valve capable of maintaining liquid state in a low temperature environment according to claim 2, characterized in that: A secondary annular upper flange (21) and a secondary annular lower flange (22) are formed on the inner wall of the middle tube (15); the secondary annular upper flange (21) is arranged adjacent to the lower edge of the tertiary upper through hole (11); the secondary annular lower flange (22) is arranged adjacent to the lower edge of the tertiary lower through hole (12); the inner edges of the secondary annular upper flange (21) and the secondary annular lower flange (22) are both dynamically sealed against the outer wall of the central tube (14); and the inner edges of the secondary annular upper flange (21) and the secondary annular lower flange (22) are both provided with downwardly inclined The second-stage annular upper flange (21) has an oblique angle structure (23), the lower end of the oblique angle structure (23) of the second-stage annular lower flange (21) extends to the lower edge of the second-stage lower through hole (10), the lower end of the oblique angle structure (23) of the second-stage annular lower flange (22) extends to the lower edge of the final flow hole (13), an annular flange (24) is formed on the inner wall of the lower end of the outer tube (16), the upper end of the annular flange (24) is flush with the lower edge of the third-stage lower through hole (12), and the third-stage valve core is movably arranged between the annular flange (24) and the middle tube (15) in a dynamic sealing state.

4. The thermal insulation gate valve capable of maintaining liquid state in a low temperature environment according to claim 3, characterized in that: The three-stage valve core is in the shape of a circular tube, and a cross grid (25) is formed at the bottom opening thereof. A first through hole (26) and a second through hole (27) are formed on the cylindrical wall of the three-stage valve core. When the cross grid (25) contacts the bottom wall of the middle tube (15) upward, the first through hole (26) and the second through hole (27) are in a dislocated state to close the three-stage upper through hole (11) and the three-stage lower through hole (12). A cross grid (25) is formed at the center thereof and extends upward to the inner side of the center tube (14). The bottom of the secondary valve core is formed with an upward recess (28) for accommodating the limiting column (29). When the lower end of the secondary valve core is flush with the upper edge of the secondary lower through hole (10), the top end of the limiting column (29) contacts the top wall of the recess (28). A third-stage spring (30) is arranged below the cross grid (25), and a second-stage spring (31) is arranged above the cross grid (25). The upper end of the second-stage spring (31) contacts the top wall of the recess (28).

5. The thermal insulation gate valve capable of maintaining liquid state in a low temperature environment according to claim 4, characterized in that: The lower end of the outer tube (16) is formed with a threaded wall (32), a lower end cover (33) is screwed onto the threaded wall (32), the bottom of the lower end cover (33) is formed with a lower threaded seat (34) for connecting to the corrugated tube, a limiting ring (35) is fixedly provided on the inner side of the lower end of the threaded wall (32), the bottom wall of the limiting ring (35) is fitted to the inner wall of the lower end cover (33), and when the lower end of the three-stage valve core contacts the upper end of the limiting ring (35), the valve core is The first through hole (26) and the second through hole (27) are respectively located at the same level as the third-stage upper through hole (11) and the third-stage lower through hole (12) to keep the third-stage pressure relief channel open; a positioning flange (36) extending upward for positioning the lower end of the third-stage spring (30) is formed at the center of the lower end cover (33); an annular positioning groove (37) for positioning the upper end of the third-stage spring (30) is reserved between the cross grid (25) and the inner wall of the lower end of the third-stage valve core.

6. The thermal insulation gate valve capable of maintaining liquid state in a low temperature environment according to claim 1, characterized in that: The primary valve core is a one-way valve (38), and the upper and lower ends of the central hole of the secondary valve core are both clamped with a mounting ring (39) for abutting against the upper and lower ends of the one-way valve (38).

7. The thermal insulation gate valve capable of maintaining liquid state in a low temperature environment according to claim 2, characterized in that: The diameter of the secondary valve core is smaller than the inner diameter of the central tube (14); a plurality of polytetrafluoroethylene sealing rings (40) are embedded on the outer wall of the secondary valve core and are spaced apart from each other; the polytetrafluoroethylene is slidably fitted to the inner wall of the central tube (14); and the tertiary valve core is made of polytetrafluoroethylene.

8. The thermal insulation gate valve capable of maintaining liquid state in a low temperature environment according to claim 1, characterized in that: The apertures of the secondary upper through hole (9) and the secondary lower through hole (10) are the same, the apertures of the tertiary upper through hole (11) and the tertiary lower through hole (12) are the same, and the apertures of the secondary upper through hole (9), the tertiary upper through hole (11) and the final flow hole (13) increase in sequence.

9. The thermal insulation gate valve capable of maintaining liquid state in a low temperature environment according to claim 2, characterized in that: A limit retaining ring (41) extending downward and engaging with the upper edge of the inner wall of the center tube (14) is formed at the center of the upper end cover (17). When the secondary valve core is attached to the limit retaining ring (41), the secondary upper through hole (9) is closed.

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