Backpressure-controlled high-performance full lift safety valve, backpressure control method thereof and pressure vessel system

Abstract

The invention relates to a backpressure-controlled high-performance full lift safety valve, a backpressure control method thereof and a pressure vessel system. The full lift safety valve comprises a valve body assembly and a load control assembly. The valve body assembly comprises a valve seat, a guide backpressure base and a valve cover which are coaxially assembled and are hermetically connected to form a backpressure chamber; the load control assembly comprises a valve clack assembly, a spring and an adjusting screw which are coaxially arranged; the guiding backpressure base integrates the guiding function, the limiting function and the backpressure control function of the valve clack assembly. The guiding function is achieved through clearance fit between the inner wall of the guiding backpressure base and the valve clack assembly. The limiting structure at the lower end limits the opening height of the valve clack assembly to achieve the limiting function. A groove hole formed in the center of the base is communicated with the valve seat flow channel and the backpressure cavity to achieve the backpressure control function; and the whole safety valve is not provided with any adjusting ring. And meanwhile, the long-standing problem of performance exclusion of pressure exceeding and seating pressure of a traditional safety valve is effectively solved, it is ensured that the discharging process is stable, and the frequency vibration phenomenon is avoided.

Description

Technical Field

[0001] The present invention relates to a safety pressure relief device in the field of mechanical engineering, and specifically to a high-performance full-lift safety valve with back pressure control, a back pressure control method thereof, and a pressure vessel system. In particular, the present invention relates to a safety valve that achieves a low opening and closing pressure difference through an innovatively designed guide back pressure base and a slotted hole structure, and does not require an adjusting ring, and a control method thereof. Background Art

[0002] Traditional full-lift safety valves face a core contradiction: According to the GB / T12243-2021 standard, the reseat pressure must be ≥ 85% of the set pressure, and the overpressure must be ≤ 110% of the set pressure. This results in a potential opening and closing pressure differential of approximately 25%. In practice, due to the mutual incompatibility between the overpressure and reseat pressure performance, the opening and closing pressure differential of conventional safety valves is generally close to 25%. This means that after discharge, the system pressure must drop by approximately 25% for the valve to reseat and close, resulting in a significant waste of precious fluid.

[0003] In order to solve the problem of high opening and closing pressure difference, the existing technology adopts a structure that adds 1-2 adjusting rings to the safety valve. Although the adjusting ring can adjust the return seat pressure, it has the following significant disadvantages: 1. Mutual exclusion of performance: when the return seat pressure is increased, the excess pressure will inevitably deteriorate; conversely, optimizing the excess pressure will lead to a decrease in the return seat pressure. It is difficult to achieve low excess pressure and high return seat pressure at the same time. 2. Complex structure and leakage risk: It is necessary to machine threaded holes in the valve body to install a pin to fix the adjusting ring, which adds additional parts and potential leakage points. 3. Increased cost: The debugging process is cumbersome and the position of the adjusting ring needs to be adjusted repeatedly, which significantly increases the production cost and time cost. 4. Frequency vibration problem: During debugging or operation, improper setting of the adjustment ring position or slight changes can easily cause the safety valve to vibrate violently in the discharge state, which not only damages the valve itself, but may also endanger the safe operation of the connected equipment.

[0004] Therefore, there is an urgent need for a full-opening safety valve and its back pressure control method and pressure vessel system that does not require an adjustment ring, can automatically achieve a low opening and closing pressure difference, and ensure a stable discharge process. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-performance full-lift safety valve with back pressure control, a back pressure control method thereof and a pressure vessel system. By adopting the principle of self-balancing of the pressure difference between the valve seat and the valve cover, the traditional regulating ring structure is replaced. Without any regulating ring, the opening and closing pressure difference is ≤ the value of the excess pressure minus the return pressure, that is, the opening and closing pressure difference is ≤ 5% of the set pressure. At the same time, it effectively solves the long-standing problem of mutual exclusion between the discharge pressure and the return pressure performance of the traditional safety valve, ensures the stability of the discharge process, and avoids the occurrence of frequency vibration.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: According to a first aspect of the present invention, a high-performance, full-lift safety valve with backpressure control is provided, comprising a valve body assembly and a load control assembly; the valve body assembly comprises a coaxially assembled valve seat, a guide backpressure base, and a valve cover, the three being sealed and connected to form a backpressure chamber; The load control assembly includes a coaxially arranged valve disc assembly, a spring and an adjusting screw; The guide back pressure base integrates the guiding function, limiting function and back pressure control function of the valve disc assembly: the guiding function is achieved by the clearance between its inner wall and the valve disc assembly; the limiting function is achieved by limiting the opening height of the valve disc assembly through the limiting structure at its lower end; and the back pressure control function is achieved by connecting the valve seat flow channel and the back pressure chamber through the slot opened in the center of the base. Furthermore, the safety valve as a whole is not provided with any adjustment ring.

[0007] Optionally, the guide back pressure base is provided with two symmetrically arranged slots; The total flow area of ​​the slots meets the following two conditions: it is less than one-sixth of the throat diameter area of ​​the safety valve, and less than one-sixtieth of the recoil disk area of ​​the valve disc assembly.

[0008] Optionally, the slot is located in an upper region of the recoil disc of the valve disc assembly; When the safety valve is in the fully open discharge state, the upper end surface of the valve flap assembly abuts against the lower end surface of the guide back pressure base, so that the medium needs to change its flow direction when flowing through the slot hole, forming a circuitous path, thereby delaying the pressure rise in the back pressure chamber.

[0009] Optionally, the recoil disc area of ​​the valve disc assembly is 9.2 times the throat diameter area of ​​the safety valve.

[0010] Optionally, the discharge outlet area of ​​the safety valve meets the following two conditions: greater than three times the throat diameter area of ​​the safety valve, and greater than thirty times the total area of ​​the two slots.

[0011] Optionally, the performance parameters of the safety valve meet the following requirements: the opening and closing pressure difference ≤ the value of the excess pressure minus the return pressure, that is, the opening and closing pressure difference ≤ 5% of the set pressure, the return pressure ≥ 96% of the set pressure, and the excess pressure ≤ 101% of the set pressure.

[0012] Optionally, the guide back pressure base limits the opening height of the valve flap assembly to be greater than or equal to one quarter of the throat diameter of the safety valve.

[0013] According to a second aspect of the present invention, there is provided a back pressure control method for the above-mentioned full lift safety valve, comprising: Discharge stage: When the disc assembly presses against the guide back pressure base, the medium flowing through the slot needs to change its flow direction to form a circuitous path, blocking the medium from flowing into the back pressure chamber and delaying the pressure rise in the back pressure chamber; Reseat stage: When the system pressure is lower than the set pressure, the medium gradually flows into the back pressure chamber through the slot, causing the pressure in the back pressure chamber to slowly rise and approach the system pressure; the rising back pressure cooperates with the spring preload to act on the upper end of the valve disc assembly, driving the valve disc assembly to achieve sealing when the system pressure is greater than or equal to 96% of the set pressure.

[0014] Optionally, during the reseating stage, when the pressure in the back pressure chamber rises close to the system pressure, the back pressure and the spring preload work together to enable the valve disc assembly to reseat and seal when the system pressure is greater than or equal to 96% of the set pressure.

[0015] According to a third aspect of the present invention, there is provided a pressure vessel system comprising the above-mentioned full-lift safety valve, which is used for overpressure protection of gas manufacturing, storage or transportation equipment.

[0016] The advantages of the present invention are: 1. Ultra-low opening and closing pressure difference: Through the unique guide back pressure base and slot hole design, the opening and closing pressure difference is ≤ the value of the excess pressure minus the return pressure, that is, the opening and closing pressure difference is ≤ 5% of the set pressure, which is much better than the opening and closing pressure difference of about 25% required by the GB / T12243-2021 standard, significantly reducing the discharge loss of precious media.

[0017] 2. Performance synergistic optimization: It overcomes the inherent contradictions of traditional safety valves with adjusting rings, while achieving low excess pressure and high return seat pressure.

[0018] 3. Simplified structure and high reliability: The adjustment ring, ejector pin and its mounting threaded hole are completely eliminated, eliminating the leakage points and potential failure points caused by them, reducing the number of parts and making the structure simpler and more reliable.

[0019] 4. Low cost and high efficiency: It eliminates the processing, installation and tedious debugging process of the adjustment ring, significantly reducing the manufacturing cost and debugging time cost.

[0020] 5. Discharge stability: In the fully open discharge state, the upper end face of the valve disc abuts against the lower end face of the guide back pressure base. The circuitous path formed by the slot effectively delays the pressure rise in the back pressure chamber, so that the valve disc is stably supported on the base, fundamentally avoiding the frequency vibration problem when the safety valve is discharged. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1This is a cross-sectional view of the overall structure of the full-lift safety valve according to an embodiment of the present invention; Figure 2 Schematic diagram of the process of the safety valve back pressure control method of the present invention; Figure 3 This is a structural schematic diagram of the guide back pressure base of the present invention.

[0023] In the figure: 1. Valve seat; 2. Valve disc assembly; 3. Guide back pressure base; 4. Valve cover; 5. Spring; 6. Adjusting screw; 7. Recoil disc; 8. Slot hole; 9. Back pressure chamber; 10. Valve housing; A. Throat diameter. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] Example 1

[0026] like Figure 1 and Figure 3 As shown, a high-performance full-lift safety valve with back pressure control includes a valve body assembly and a load control assembly; the valve body assembly includes a coaxially assembled valve seat 1, a guide back pressure base 3 and a valve cover 4, the three of which are sealed and connected to form a back pressure chamber 9; The load control assembly includes a coaxially arranged valve flap assembly 2, a spring 5 and an adjusting screw 6; The guide back pressure base 3 integrates the guiding function, limiting function and back pressure control function of the valve disc assembly 2: the guiding function is achieved by the clearance between its inner wall and the valve disc assembly 2; the limiting function is achieved by limiting the opening height of the valve disc assembly 2 through the limiting structure at its lower end; and the back pressure control function is achieved by connecting the flow channel of the valve seat 1 with the back pressure chamber 9 through the slot 8 opened in the center of the base. Furthermore, the safety valve as a whole is not provided with any adjustment ring.

[0027] Its advantages are: eliminating the adjustment ring, eliminating leakage points and debugging costs, and reducing the number of parts; a single component solves the problems of guidance, limit, and back pressure control, and the structure is compact; the back pressure chamber delays pressure transmission and avoids high-frequency vibration of traditional safety valves.

[0028] Backpressure control controls the flow rate and time delay of the medium entering the backpressure chamber by adjusting the total area of ​​slot 8 (≤ 1 / 6 of the throat diameter and ≤ 1 / 60 of the recoil disc 7 area) and designing a circuitous path. If the total area of ​​slot 8 is too large, the backpressure chamber pressure rises instantaneously, causing frequency oscillation. If the total area of ​​slot 8 is too small, the backpressure rises too slowly, preventing the valve from reseating.

[0029] By utilizing back pressure control, the precision of the recoil disc 7 does not need to be very high, and a smaller opening and closing pressure difference can be achieved more easily. The traditional safety valve is controlled by an adjusting ring, while the safety valve of the present invention is controlled by the value obtained through repeated full performance tests. The diameter and depth of the recoil disc 7 are modified according to the test data each time to determine the final data ratio parameters.

[0030] In the specific experimental test: First, the upper part must be fully sealed. After removing the valve cap or drilling a small hole in the valve cover 4, no back pressure will be generated on the upper part, so the test re-seating pressure is less than 85% of the set pressure. Conversely, if the upper part is fully sealed, the re-seating pressure is greater than or equal to 96% of the set pressure.

[0031] Secondly, backpressure control is achieved by adjusting the area of ​​the slot 8 in the guide backpressure base 3 and the circuitous route. Experimentation initially employed two 5mm diameter apertures, without a right-angle route, leading directly to the valve cover 4 chamber. However, due to the excessive size of the apertures, gas entered the valve cover 4 chamber too quickly, causing frequency oscillation. Conversely, testing determined an appropriate area for the slot 8 in the guide backpressure base 3, and provided a circuitous route for gas to enter the valve cover 4 chamber, eliminating frequency oscillation.

[0032] In this embodiment, the guide backpressure base 3 has two symmetrically arranged slots 8. The total flow area of ​​these two slots 8 meets the following two conditions: less than one-sixth of the throat diameter of the safety valve and less than one-sixtieth of the area of ​​the recoil disk 7 of the valve disc assembly 2. The small hole area limits the inflow rate of the medium, slowing the rise in pressure in the backpressure chamber. The dual-hole design prevents eccentric wear of the valve disc caused by unilateral flow impact.

[0033] In this embodiment, the slot 8 is located in the upper area of ​​the recoil disk 7 of the valve flap assembly 2; and when the safety valve is in the fully open discharge state, the upper end surface of the valve flap assembly 2 abuts against the lower end surface of the guide back pressure base 3, so that the medium needs to change its flow direction when flowing through the slot 8, forming a circuitous path, thereby delaying the pressure rise in the back pressure chamber 9.

[0034] The location of two slots 8 was determined. Testing revealed that one slot 8 was located near the safety valve outlet, while the other slot 8 was located at the deepest point within the valve housing 10, resulting in optimal return pressure, approaching 96% of the set pressure. When both slots 8 were located in the valve housing 10, the return pressure was approximately 90%-93% of the set pressure.

[0035] In this embodiment, the recoil disc 7 of the valve disc assembly 2 has an area 9.2 times the throat diameter of the safety valve. The opening force is increased by 3 times, with the excess pressure only reaching 101% of the set pressure. The sealing force per unit area during reseating is ≥15 MPa.

[0036] In this embodiment, the discharge outlet area of ​​the safety valve meets the following two conditions: greater than three times the throat diameter of the safety valve and greater than thirty times the total area of ​​the two slots 8. This reduces outlet flow resistance by 42%, improving discharge efficiency; the large outlet area prevents excessive pressure from being fed back into the backpressure chamber.

[0037] In this embodiment, the safety valve's performance parameters meet the following requirements: opening / closing differential pressure ≤ 5% of the set pressure, reseat pressure ≥ 96% of the set pressure, and excess pressure ≤ 101% of the set pressure. This saves 20% of precious fluid compared to a 25% opening / closing differential pressure, far exceeding the GB / T12243-2021 standard.

[0038] In this embodiment, the guide back pressure seat 3 limits the opening height of the valve flap assembly 2 to be greater than or equal to one-quarter of the throat diameter of the safety valve, ensuring that the discharge flow rate is ≥ 95% of the theoretical value and preventing the spring 5 from being unable to return to its seat due to insufficient force due to excessive height.

[0039] The position of the valve disc assembly 2 is primarily limited by the thickness of the guide back-pressure seat 3. The guide back-pressure seat 3 is fixed between the valve housing 10 and the valve cover 4, so it is a fixed component. When the valve disc assembly 2 is discharged, it will stick to the guide back-pressure seat 3, thus limiting the position. By controlling the thickness of the guide back-pressure seat 3, the opening height can be controlled to ≥ 1 / 4 of the valve body flow channel diameter. Generally, when defining a full-lift safety valve, the valve disc opening height must be ≥ 1 / 4 of the valve body flow channel diameter.

[0040] In this embodiment, the reason why there is no frequency vibration during the discharge stage is that in order to reduce the value of the excess pressure, the area of ​​the valve disc is increased and the depth of the recoil disk 7 is deepened. The corresponding excess pressure will be very close to the set pressure. When the system pressure is slightly higher than the set pressure, the valve disc assembly 2 will jump and be firmly dragged by the gas in the system pressure at the limit position of the valve disc assembly 2.

[0041] During the reseating phase, the set pressure is generally set within 1.1 times the system pressure. For the safety valve of the present invention, the set pressure can be set to 1.03 times the system pressure (or similar multiples), so that the reseating pressure can return to the system pressure. Furthermore, the entire opening and closing pressure differential can be adjusted in this way to achieve an opening and closing pressure differential of ≤10% by varying the outer diameter or depth of the recoil disc 7 on the lower disc. The opening and closing pressure differential of ≤5% of the set pressure mentioned in the current invention patent is the best data obtained in experiments. The smaller the opening and closing pressure differential, the more energy-efficient it is.

[0042] like Figure 2 As shown, the back pressure control method of the full-lift safety valve of this embodiment includes: Discharge stage: When the valve disc assembly 2 presses against the guide back pressure base 3, the medium flowing through the slot 8 needs to change its flow direction to form a circuitous path, blocking the medium from flowing into the back pressure chamber 9 and delaying the pressure rise in the back pressure chamber 9; Return to seat stage: When the system pressure is lower than the set pressure, the medium gradually flows into the back pressure chamber 9 through the slot 8, causing the pressure in the back pressure chamber 9 to slowly rise and approach the system pressure; the rising back pressure cooperates with the preload force of the spring 5 to act on the upper end of the valve flap assembly 2, driving the valve flap assembly 2 to achieve sealing when the system pressure is greater than or equal to 96% of the set pressure.

[0043] The specific principles or steps are as follows: Operation steps: When the valve disc assembly 2 is installed, there are two slots 8, so that one slot 8 is closest to the safety valve outlet.

[0044] Sealing stage: The medium pressure is within 90% of the safety valve's set pressure. By rotating the adjusting screw 6 and compressing the spring 5, a preload is generated between the disc assembly 2 and the valve body sealing surface. The medium enters the safety valve seat 1 through the Venturi effect, reducing the excess pressure as it approaches the narrowed flow section.

[0045] Pre-discharge stage: When the medium pressure begins to rise and approaches about 97%~100% of the safety valve set pressure, the safety valve begins to leak slightly. The medium passes through the valve seat 1 and the recoil disc 7 in the valve disc assembly 2, so that the medium is discharged downward. The valve disc assembly 2 is located at the center of the safety valve outlet. The area of ​​the two slots 8 should be less than 1 / 6 of the throat diameter area and less than 1 / 60 of the recoil disc 7 area after testing. The slots 8 are located at the upper end of the safety valve disc recoil disc 7, so that the medium discharged through the valve body is discharged from the safety valve outlet, and the pressure at the valve cover 4 of the safety valve does not rise.

[0046] Taking-off stage: When the medium pressure reaches the set pressure, the valve disc rises rapidly due to the increase in the area of ​​the recoil disc 7.

[0047] Discharge stage: When the medium pressure reaches 101% of the set pressure, the safety valve disc assembly 2 will instantly hit the guide back pressure seat 3. At this time, the upper end of the valve disc and the two slots 8 of the guide back pressure seat 3 form a circuitous route at right angles, so that the internal pressure at the valve cover 4 will not rise immediately, and the valve disc is stably supported on the guide back pressure seat 3. The guide back pressure seat 3 also limits the opening height of the safety valve, preventing the valve disc assembly 2 from opening too high, resulting in the safety valve being unable to return to its seat and close.

[0048] Reseat stage: When the medium pressure is lower than the set pressure of the safety valve, the medium slowly enters the valve cover 4 through the two slots 8. The pressure at the valve cover 4 begins to rise and approaches the medium pressure, thereby generating a back pressure on the valve cover 4. The area of ​​the two slots 8 is less than 1 / 60 of the area of ​​the recoil disc 7. The internal pressure cannot be released quickly, and acts on the valve disc assembly 2. In addition, the pre-tightening force of the spring 5 on the valve disc causes the valve disc and the valve body to seal quickly when the medium pressure reaches 96% of the set pressure.

[0049] Finally, the opening and closing pressure difference of the safety valve is within 5%.

[0050] In this embodiment, during the reseating stage, when the pressure in the back pressure chamber 9 rises to close to the system pressure, the back pressure and the preload force of the spring 5 work together to enable the valve disc assembly 2 to achieve reseating sealing when the system pressure is greater than or equal to 96% of the set pressure.

[0051] Example 2

[0052] A pressure vessel system, comprising the above-mentioned full-lift safety valve, is used for overpressure protection of gas manufacturing, storage or transportation equipment.

[0053] Taking the safety valve of a hydrogen storage bottle as an example, the design pressure of the hydrogen storage bottle is 70MPa, and the set pressure of the safety valve is 70MPa, which is used to store hydrogen.

[0054] The throat diameter = 20mm, so the throat area = π×(10)²=314mm²; the recoil disc area = 9.2 times the throat area = 9.2×314=2890mm²; the corresponding recoil disc diameter = 61mm; the slot hole is a semicircular hole, and the radius of each slot hole is 3.9mm; the total slot hole area = 2×π×3.9² / 2=47.8mm²; less than 1 / 6 of the throat diameter area, 314 / 6=52.3mm²>47.8mm²; less than 1 / 60 of the recoil disc area, 2890 / 60=48.2 mm²>47.8mm²; the discharge outlet area is greater than 3 times the throat diameter area (942mm²) and greater than 30 times the total slot hole area (1434mm²), and the designed discharge outlet diameter = 44mm; the opening height is ≥ 1 / 4 of the throat diameter, 20 / 4=5mm, and the design is 5.5mm.

[0055] Example 3, comparison of the application effects of hydrogen storage tanks: Natural gas tank truck with traditional safety valve, volume 25.1m 3 , gas pressure 20MPa, storage natural gas, safety valve set pressure 20MPa, over pressure ≤110% of the set pressure, 22MPa, return pressure ≥85% of the set pressure, 17MPa, opening and closing pressure difference = 25%, 5MPa. When the pressure rises to 22MPa, the safety valve will fully open and discharge, and it will return to the seat and close only after the pressure reaches 17MPa.3 Natural gas costs 1,000 yuan, and the single loss is about 6,000 yuan.

[0056] A hydrogen storage tank with a capacity of 25.1m2 using the fully open safety valve of this application 3 , design pressure 20MPa, opening and closing pressure difference ≤ 5% of the set pressure, calculated based on the maximum 5%, compared with the use of traditional safety valves, saving more than 80%.

[0057] Example 4: The safety valve is applied to a hydrogen refueling station: Hydrogen refueling stations, as the core infrastructure of hydrogen fuel cell vehicles, require safety valves for their high-pressure hydrogen storage tanks, hydrogen compressor outlet pipelines, and hydrogen refueling machine high-pressure hoses to prevent explosions from overpressure. Traditional safety valves suffer from a large opening and closing pressure differential of approximately 25%, leading to significant hydrogen waste during frequent opening and closing operations. Furthermore, frequency fluctuations caused by the regulating ring threaten pipeline sealing.

[0058] After three tests:

[0059] Excess pressure ≤ 101% of set pressure, reseat pressure ≥ 96% of set pressure, and opening and closing differential pressure ≤ 5% of set pressure. In low-pressure, large-volume systems, the absolute value of the opening and closing differential pressure is relatively small. The advantage of increased volume in terms of total volume of media can achieve more significant cost savings. For example, for a 20MPa natural gas tank truck, every kilogram of natural gas saved can save approximately 1,000 yuan.

[0060] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A high-performance full-lift safety valve with back pressure control, comprising a valve body assembly and a load control assembly; characterized in that: The valve body assembly includes a coaxially assembled valve seat, a guide back pressure base and a valve cover, the three of which are sealed and connected to form a back pressure chamber; The load control assembly includes a coaxially arranged valve disc assembly, a spring and an adjusting screw; The guide back pressure base integrates the guiding function, limiting function and back pressure control function of the valve disc assembly: the guiding function is achieved by the clearance between its inner wall and the valve disc assembly; the limiting function is achieved by limiting the opening height of the valve disc assembly through the limiting structure at its lower end; and the back pressure control function is achieved by connecting the valve seat flow channel and the back pressure chamber through the slot opened in the center of the base. Furthermore, the safety valve as a whole is not provided with any adjustment ring.

2. The full-lift safety valve according to claim 1, characterized in that: The guide back pressure base is provided with two symmetrically arranged slots; The total flow area of ​​the slots meets the following two conditions: it is less than one-sixth of the throat diameter area of ​​the safety valve, and less than one-sixtieth of the recoil disk area of ​​the valve disc assembly.

3. The full-lift safety valve according to claim 2, characterized in that: The slot is located in the upper area of ​​the recoil disc of the valve disc assembly; When the safety valve is in the fully open discharge state, the upper end surface of the valve flap assembly abuts against the lower end surface of the guide back pressure base, so that the medium needs to change its flow direction when flowing through the slot hole, forming a circuitous path, thereby delaying the pressure rise in the back pressure chamber.

4. The full-lift safety valve according to claim 1, characterized in that: The recoil disc area of ​​the valve disc assembly is 9.2 times the throat diameter area of ​​the safety valve.

5. The full-lift safety valve according to claim 2, characterized in that: The discharge outlet area of ​​the safety valve meets the following two conditions: it is greater than three times the throat diameter area of ​​the safety valve and greater than thirty times the total area of ​​the slot holes.

6. The full-lift safety valve according to claim 1, characterized in that: The performance parameters of the safety valve meet the following requirements: the opening and closing pressure difference ≤ the value of the excess pressure minus the return seat pressure, that is, the opening and closing pressure difference ≤ 5% of the set pressure, the return seat pressure ≥ 96% of the set pressure, and the discharge pressure ≤ 101% of the set pressure.

7. The full-lift safety valve according to claim 1, characterized in that: The guide back pressure base limits the opening height of the valve flap assembly to be greater than or equal to one quarter of the throat diameter of the safety valve.

8. A back pressure control method for a full lift safety valve according to any one of claims 1 to 7, characterized in that: include: Discharge stage: When the valve disc assembly presses against the guide back pressure base, the medium flows through the slot hole and changes the flow direction to form a circuitous path, blocking the medium from flowing into the back pressure chamber and delaying the pressure rise in the back pressure chamber; Reseating stage: When the system pressure is lower than the set pressure, the medium gradually flows into the back pressure chamber through the slot, causing the pressure in the back pressure chamber to slowly rise to the system pressure; the rising back pressure cooperates with the spring preload to act on the upper end of the valve disc assembly, driving the valve disc assembly to achieve sealing when the system pressure is greater than or equal to 96% of the set pressure.

9. The back pressure control method according to claim 8, characterized in that: In the reseating stage, when the pressure in the back pressure chamber rises to the system pressure, the back pressure and the spring preload force work together to make the valve disc assembly return to its seat and seal when the system pressure is greater than or equal to 96% of the set pressure.

10. A pressure vessel system, characterized in that: The fully-open safety valve according to any one of claims 1 to 7 is used for overpressure protection of gas manufacturing, storage or transportation equipment.

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