High back pressure pilot operated safety valve suitable for large pass diameter

Abstract

This invention discloses a pilot-operated safety valve suitable for large-diameter, high-back-pressure applications, relating to the field of pilot-operated safety valve technology. It includes a main valve, a pilot valve, and connecting pipelines. The combined valve core in the main valve is located within the main valve core sleeve, forming a sealed space with it. When the valve seat is installed, the combined valve core moves upward, creating a vacuum chamber within the sealed space. This generates a downward negative pressure force, replacing the return spring and causing the combined valve core to fit against the valve seat. A floating sleeve in the main valve is located within the main valve core sleeve and slidably positioned above the combined valve core. The floating sleeve has a damping orifice. The floating sleeve, the upper cover, the main valve core sleeve, and the combined valve core form a hysteresis chamber and the upper chamber of the main valve. The damping orifice connects the hysteresis chamber and the upper chamber of the main valve. This invention achieves rapid closure and reliable sealing and stable operation of a large-diameter safety valve under high back-pressure conditions through a comprehensive design that utilizes vacuum negative pressure to replace the spring, the coordinated hysteresis pressure build-up of the floating sleeve and damping orifice, and equal sealing diameters to achieve back-pressure balance.

Description

Technical Field

[0001] This invention relates to the field of pilot-operated safety valve technology, and more specifically to a high back pressure pilot-operated safety valve suitable for large-diameter valves. Background Technology

[0002] Pilot-operated safety valves are widely used in high-pressure, large-diameter pipeline systems in industries such as petroleum, chemical, and power due to their advantages such as stable operation, reliable sealing, and wide adjustable pressure range. A typical pilot-operated safety valve consists of a main valve and a pilot valve. The pilot valve controls the opening and closing of the main valve, while the main valve is responsible for the discharge and shut-off of the medium.

[0003] Existing pilot-operated safety valves still have the following technical problems under large-diameter, high-back-pressure conditions: 1. To ensure the flow rate and discharge volume, the main valve has a long stroke and a large upper chamber volume, while the pilot valve has a small inlet flow rate. This results in a long pressure build-up time during the closing process and a large opening-closing pressure difference (usually reaching 10%-15%, or the stroke is limited to meet national standards). It is difficult to meet the requirements of rapid closing and low opening-closing pressure difference.

[0004] 2. Generally, physical return springs are relied upon. Springs not only occupy space and increase the volume of the upper cavity, but are also subject to material limitations under special working conditions. Furthermore, back pressure can affect the sealing performance through the spring preload.

[0005] 3. Under high back pressure conditions, the existing structure is difficult to completely balance the back pressure force, which can easily cause the safety valve to open abnormally or fail to reseat.

[0006] Therefore, how to achieve rapid closure, low opening and closing pressure differential, and high back pressure adaptability of pilot-operated safety valves under large-diameter conditions is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To overcome the shortcomings of the existing technology, this invention discloses a pilot-operated safety valve suitable for large-diameter valves with high back pressure. The purpose of this invention is to solve the problems of slow closing and excessive opening-closing pressure difference (usually reaching 10%-15%, or using stroke limitation to meet national standards) caused by the large volume of the main valve upper chamber and the small air flow of the pilot valve in the existing technology. At the same time, it overcomes the defects of traditional return spring structure in material limitations under special working conditions and the easy abnormal opening or reseating failure of safety valve under back pressure. This invention achieves rapid closing of large-diameter safety valves (opening-closing pressure difference controllable to 5%) and reliable sealing and stable operation under high back pressure conditions through comprehensive design such as vacuum negative pressure replacing spring, floating sleeve and damping orifice working together to delay pressure build-up, and equal sealing diameter to achieve back pressure balance.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A high back pressure pilot-operated safety valve suitable for large diameter includes a main valve, a pilot valve, and a connecting pipeline. The main valve includes a valve body, a valve seat, a main valve core sleeve, a top cover, a combined valve core, and a floating sleeve. The combined valve core is located inside the main valve core sleeve and forms a sealed space with the main valve core sleeve. When the valve seat is installed, the combined valve core moves upward to make the sealed space a vacuum cavity, thereby generating a downward negative pressure force to replace the return spring and make the combined valve core fit with the valve seat. The floating sleeve is located inside the main valve core sleeve and is slidably disposed above the combined valve core. The floating sleeve has a damping hole. The floating sleeve, the upper cover, the main valve core sleeve and the combined valve core form a hysteresis cavity and a main valve upper cavity. The damping hole connects the hysteresis cavity and the main valve upper cavity.

[0009] Preferably, the combined valve core includes an upper combined valve core, a lower combined valve core, and a connecting shaft connecting the two. The upper combined valve core is provided with an upper sealing ring on its outer periphery, and the lower combined valve core is provided with a lower sealing ring on its outer periphery. The upper sealing ring and the lower sealing ring form a sealed space with the inner wall of the main valve core sleeve.

[0010] Preferably, the inner side of the main valve core sleeve is provided with an annular step, and the lower end face of the upper combined valve core is tightly attached to the upper end face of the annular step during assembly. After being tightened by the connecting shaft, the upper sealing ring, the lower sealing ring and the inner wall of the main valve core sleeve together form the sealed space. When the valve seat is installed, it pushes the combined valve core upward, so that the combined valve core moves upward in the sealed space to form a vacuum cavity. The negative pressure generated by the vacuum cavity replaces the return spring to make the combined valve core and the valve seat fit tightly together.

[0011] Preferably, the sealing diameter of the upper sealing ring is denoted as S. 上阀芯 The sealing diameter of the lower sealing ring is denoted as S. 下阀芯 The sealing diameter at the valve seat seal is denoted as S. 阀座 Satisfying: S 上阀芯 >S 下阀芯 And S 下阀芯 =S 阀座 .

[0012] Preferably, the upper cover is provided with a boss shaft, and the floating sleeve can slide up and down along the boss shaft; the lower end of the floating sleeve forms a hysteresis cavity with the combined valve core, the main valve core sleeve, and the boss shaft, and the upper end of the floating sleeve forms a main valve upper cavity with the main valve core sleeve and the upper cover.

[0013] Preferably, an outer sealing ring is provided between the outer periphery of the floating sleeve and the main valve core sleeve, and an inner sealing ring is provided between the inner periphery of the floating sleeve and the boss shaft; the hysteresis cavity is formed by the outer sealing ring, the floating sleeve below the inner sealing ring, the main valve core sleeve, the boss shaft and the combined valve core; the upper cavity of the main valve is formed by the floating sleeve above the outer sealing ring and the inner sealing ring, the main valve core sleeve, the upper cover and the boss shaft.

[0014] Preferably, the valve body is provided with a main valve inlet, a main valve outlet and an axially extending mounting cavity, the mounting cavity being connected to the main valve inlet and the main valve outlet, and the main valve inlet being provided with a pilot valve air inlet for connecting a pilot valve; the upper cover is sealed and fixed to the top of the mounting cavity and is provided with an upper cover channel communicating with the hysteresis cavity; The main valve core sleeve is vertically disposed in the mounting cavity, the valve seat is fixed to the bottom of the mounting cavity and is sealed to the lower end of the combined valve core, and the combined valve core is axially slidably inserted into the main valve core sleeve; The bottom of the combined valve core is provided with a sleeve and a sealing gasket in sequence, and the sealing gasket is in sealing fit with the sealing surface of the valve seat.

[0015] Preferably, the pilot valve is a pilot valve with a pressure regulating mechanism, and the connecting pipeline includes an inlet pipe for introducing the inlet medium into the pilot valve, a discharge pipe for leading out the outlet medium of the pilot valve, and a control pipe for transmitting the control pressure of the pilot valve to the hysteresis chamber.

[0016] Preferably, the main valve does not contain a physical return spring. The negative pressure generated by the vacuum chamber replaces the return spring and serves as the main downward pressure source for keeping the combined valve core and the valve seat in contact when no medium is flowing through them. By adjusting the volume of the vacuum chamber, the vacuum level is changed to match different equivalent return spring forces, thereby adjusting the opening and closing characteristics of the main valve.

[0017] Preferably, the diameter of the damping orifice is a preset value, which is determined based on the required floating sleeve downward movement speed and the main valve opening and closing pressure difference.

[0018] The beneficial effects of this invention are: 1. The function of a pilot-operated valve is simply to provide a small pressure signal, so its structural design typically results in a very small flow channel diameter, only a few millimeters, meaning the flow rate it provides is very small. In contrast, the main valve of a large-diameter safety valve must meet the discharge capacity requirements, resulting in a large stroke and valve seat flow channel diameter. Therefore, the volume of the upper chamber of the main valve is very large, far exceeding the flow rate that the pilot valve can provide during the reseating and closing time. Currently, the main valve structure of a conventional pilot-operated safety valve, due to the presence of a physical spring and the need to meet stroke and diameter requirements, also has a large volume. This means that the medium gas needs a considerable amount of time to build up sufficient pressure to close the main valve after passing through the pilot valve into the upper chamber. Therefore, the opening and closing pressure difference can easily reach 15%, or even exceed national standards. To achieve rapid closure of large-diameter pilot-operated safety valves, this invention innovatively adopts a structure combining a floating sleeve with a damping orifice, and then combines it with a valve core. By utilizing the time difference created by the delayed movement of the floating sleeve and the damping orifice, it substantially achieves the rapid establishment of pressure in a small volume, and when the volume increases, the airflow already matches the pressure build-up requirements, enabling the large-diameter safety valve to close quickly, and the opening and closing pressure difference can be controlled to 5%.

[0019] 2. A floating sleeve must be combined with a damping orifice to achieve rapid closure of a large-diameter safety valve. If the floating sleeve has no damping orifice and only a large through hole, the medium gas will enter the upper chamber of the main valve without delay due to the lack of pressure difference. This would cause the floating sleeve to descend synchronously with the combined valve core, resulting in a rapid increase in the volume of the upper chamber of the main valve. The air intake of the pilot valve would be insufficient to support the rapid closure of the main valve. Similarly, if the floating sleeve has no opening at all, due to the sealing effect of the sealing ring, the floating sleeve will not move downwards with the combined valve core, and the volume of the hysteresis chamber of the main valve would increase rapidly. The air intake of the pilot valve would also be insufficient to support the rapid closure of the main valve. Furthermore, by matching damping orifices of different sizes, the rate of descent of the floating sleeve can be adjusted, thereby adjusting the opening and closing pressure difference of the main valve (adjustable according to on-site conditions). Therefore, the design of adding a damping orifice to the floating sleeve is one of the innovative designs of this invention.

[0020] 3. The innovative vacuum negative pressure design retains the requirement for the main valve to be self-tight and sealed, while also achieving a balance of back pressure. Even with high back pressure, the safety valve will not open, thus realizing the function of a high back pressure pilot-operated safety valve.

[0021] 4. The diameter "S" is sealed by the upper combined valve core sealing ring. 上阀芯 "S" is greater than the sealing diameter of the lower combined valve core sealing ring. 下阀芯 The design, which forms a vacuum cavity with the valve core sleeve, innovatively replaces the function of the return spring with vacuum negative pressure. This has two advantages: first, because there is no physical return spring, only a very small air intake channel is needed, thus reducing the volume of the air intake cavity and making it more conducive to the rapid closing of large-diameter safety valves; second, because there is no physical return spring, it is more practical for applications requiring specific spring materials.

[0022] 5. The diameter "S" is sealed by the lower combined valve core sealing ring. 下阀芯 "Sealing diameter at the valve seat seal" S 阀座 "Equal back pressure balance is achieved, so the main valve does not have to bear the excess back pressure of the previous main valve when it closes downward, which is also conducive to the rapid closing of large-diameter safety valves."

[0023] 6. By combining the valve core and valve core sleeve in a reasonable design, the size of the vacuum chamber can be varied. The larger the vacuum chamber, the greater the vacuum degree and the greater the negative pressure. This means that the spring force of the return spring can also be designed and adjusted, which is also conducive to the rapid closing of large-diameter safety valves. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the present invention applicable to large-diameter high-back-pressure pilot-operated safety valves; Figure 2 This is a schematic cross-sectional view of the main valve structure of the pilot-operated safety valve of the present invention; Figure 3 This is a schematic diagram of the main valve in the closed state of the present invention; Figure 4 This is a schematic diagram of the main valve in the open state of the present invention; Figure 5 This is a structural diagram of the main valve of a conventional pilot-operated safety valve in existing technology. Figure label: 1. Main valve; 101. Valve body; 102. Valve seat; 103. Main valve core sleeve; 104. Top cover; 105. Floating sleeve; 106. Vacuum chamber; 107. Damping orifice; 108. Hysteresis chamber; 109. Upper chamber of main valve; 110. Upper combined valve core; 111. Lower combined valve core; 112. Connecting shaft; 113. Upper sealing ring; 114. Lower sealing ring; 115. Annular step; 116. Boss shaft; 117. Outer sealing ring; 118. Inner sealing ring; 119. Main valve inlet; 120. Main valve outlet; 121. Mounting chamber; 122. Pilot valve inlet; 123. Top cover channel; 124. Gasket; 125. Sealing gasket; 2. Pilot valve; 3. Connecting pipeline; 31. Inlet pipe; 32. Discharge pipe; 33. Control pipe. Detailed Implementation

[0025] The following will provide a clear and complete description of the concept, specific structure, and technical effects of the present invention in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention.

[0026] A type of pilot-operated safety valve suitable for large-diameter applications with high back pressure, such as Figures 1-4As shown, it includes a main valve 1, a pilot valve 2, and a connecting pipeline 3. The main valve 1 includes a valve body 101, a valve seat 102, a main valve core sleeve 103, an upper cover 104, a combined valve core, and a floating sleeve 105.

[0027] The combined valve core is located inside the main valve core sleeve 103 and forms a sealed space with the main valve core sleeve 103. When the valve seat 102 is installed, the combined valve core moves upward to make the sealed space a vacuum chamber 106, thereby generating a downward negative pressure force to replace the return spring and make the combined valve core fit with the valve seat 102.

[0028] The floating sleeve 105 is located inside the main valve core sleeve 103 and is slidably disposed above the combined valve core. The floating sleeve 105 is provided with a damping hole 107. The floating sleeve 105, the upper cover 104, the main valve core sleeve 103 and the combined valve core form a hysteresis chamber 108 and a main valve upper chamber 109. The damping hole 107 connects the hysteresis chamber 108 and the main valve upper chamber 109.

[0029] In this embodiment, the main valve 1, pilot valve 2, and connecting pipeline 3 together constitute the main body of the pilot-operated safety valve. A valve seat 102 is installed inside the valve body 101 of the main valve 1, and a main valve core sleeve 103 is fixed inside the valve body 101. The combined valve core is axially slidably disposed inside the main valve core sleeve 103. After the valve seat 102 is installed, the sealed space formed between the combined valve core and the main valve core sleeve 103 increases in volume due to the upward push of the combined valve core, forming a vacuum chamber 106. This vacuum chamber 106 generates a downward negative pressure force, which completely replaces the physical return spring in a traditional pilot-operated safety valve, allowing the combined valve core and valve seat 102 to maintain a tight fit even when no medium is flowing through them. A floating sleeve 105 is disposed above the combined valve core and can slide axially up and down. A damping hole 107 is machined on the floating sleeve 105, which connects the hysteresis chamber 108 to the upper chamber 109 of the main valve. During the closing process of the safety valve, the medium gas enters the hysteresis chamber 108 and the upper chamber of the main valve 109 in sequence through the pilot valve 2. Due to the throttling effect of the damping orifice 107, the pressure building process of the upper chamber of the main valve 109 is delayed, which is conducive to the rapid closing of the large-diameter safety valve.

[0030] like Figures 2-4 As shown, the combined valve core includes an upper combined valve core 110, a lower combined valve core 111, and a connecting shaft 112 connecting the two. The upper combined valve core 110 is provided with an upper sealing ring 113 on its outer periphery, and the lower combined valve core 111 is provided with a lower sealing ring 114 on its outer periphery. The upper sealing ring 113 and the lower sealing ring 114 form a sealed space with the inner wall of the main valve core sleeve 103.

[0031] This embodiment further defines the specific structure of the combined valve core. The combined valve core adopts a split structure, consisting of an upper combined valve core 110, a lower combined valve core 111, and a connecting shaft 112. An upper sealing ring 113 is installed on the outer periphery of the upper combined valve core 110, and a lower sealing ring 114 is installed on the outer periphery of the lower combined valve core 111. When the upper combined valve core 110 and the lower combined valve core 111 are connected by the connecting shaft 112, the upper sealing ring 113, the lower sealing ring 114, and the inner wall of the main valve core sleeve 103 together form a sealed space. This sealed space is stretched to form a vacuum cavity 106 during the subsequent installation of the valve seat 102, thereby generating a negative pressure force.

[0032] like Figures 2-4 As shown, an annular step 115 is provided on the inner side of the main valve core sleeve 103. The lower end face of the upper combined valve core 110 is tightly attached to the upper end face of the annular step 115 during assembly. After being tightened by the connecting shaft 112, the upper sealing ring 113, the lower sealing ring 114 and the inner wall of the main valve core sleeve 103 together form a sealed space. When the valve seat 102 is installed, it pushes the combined valve core upward, so that the combined valve core moves upward in the sealed space to form a vacuum chamber 106. The negative pressure generated by the vacuum chamber 106 replaces the return spring to make the combined valve core and the valve seat 102 fit tightly together.

[0033] This embodiment further defines the assembly relationship between the main valve core sleeve 103 and the combined valve core, as well as the formation method of the vacuum chamber 106. The inner side of the main valve core sleeve 103 is machined with an annular step 115. During assembly, the upper combined valve core 110 is first inserted from above the main valve core sleeve 103, so that the lower end face of the upper combined valve core 110 is tightly against the upper end face of the annular step 115. Then, the upper combined valve core 110 and the lower combined valve core 111 are connected and tightened through the connecting shaft 112. At this time, the upper sealing ring 113, the lower sealing ring 114, and the inner wall of the main valve core sleeve 103 together form a closed, sealed space. When the valve seat 102 is installed from below, the valve seat 102 pushes the combined valve core upwards, causing the combined valve core to move upwards relative to the main valve core sleeve 103. The volume of the sealed space increases accordingly, thereby forming the vacuum chamber 106. The negative pressure generated by the vacuum chamber 106 keeps the combined valve core and valve seat 102 in close contact, completely replacing the function of the traditional return spring.

[0034] like Figure 3 As shown, the sealing diameter of the upper sealing ring 113 is denoted as S. 上阀芯 The sealing diameter of the lower sealing ring 114 is denoted as S. 下阀芯 The sealing diameter at the valve seat 102 is denoted as S. 阀座 Satisfying: S 上阀芯 >S 下阀芯 And S 下阀芯 =S 阀座 .

[0035] This embodiment defines the dimensional relationships of each key sealing diameter. The sealing diameter of the upper sealing ring 113 (which is also the sealing diameter of the outer end of the floating sleeve 105) is denoted as S. 上阀芯 The sealing diameter of the lower sealing ring 114 is denoted as S. 下阀芯 The sealing diameter at the sealing surface of valve seat 102 is denoted as S. 阀座 The three diameters mentioned above satisfy two relationships: First, S 上阀芯 Greater than S 下阀芯 S 下阀芯 equals S 阀座 In this way, under the pressure of the medium, the combined valve core will be subjected to a net downward force, achieving a self-tightening seal. The higher the pressure, the more reliable the seal. The specific principle is as follows: After the medium gas is introduced, it acts upward on the lower combined valve core 111 at valve seat 102. Simultaneously, the medium gas enters pilot valve 2 through a pipeline, then enters hysteresis chamber 108 through pilot valve 2, and then enters the upper chamber 109 of the main valve through damping orifice 107. The medium gas generates a downward force on the upper combined valve core 110 in hysteresis chamber 108 and the upper chamber 109 of the main valve, due to S... 上阀芯 Greater than S 下阀芯 S 下阀芯 equals S 阀座 Therefore, the area of ​​the downward force is greater than the area of ​​the upward force, so the combined valve core will be subjected to a net downward force, achieving a self-tightening seal.

[0036] Second, S 下阀芯 equals S 阀座 ,like Figure 3 As shown, this causes the upward and downward thrusts of the back pressure at the outlet of the safety valve acting on the lower combined valve core 111 to cancel each other out, resulting in a net back pressure of zero, thus preventing the valve from opening accidentally under high back pressure. The specific principle is as follows: At the outlet of the safety valve (i.e., at the main valve outlet 120), there may sometimes be a high back pressure p due to factors such as discharge pipeline resistance and downstream equipment back pressure. 背 The lower combined valve core has a convex structure, and its lower sealing ring is located above the convex shoulder. For example... Figure 3 As shown, the back pressure acts on the combined valve core through two paths: First, the back pressure pushes upward from the space between the valve seat 102 and the lower combined valve core 111, pressing against the bottom of the lower combined valve core 111 and generating an upward thrust F. 上 Second, back pressure enters the upper space of the lower combined valve core 111 through the gap between the main valve core sleeve 103 and the lower combined valve core 111, generating a downward thrust F on the shoulder of the convex lower combined valve. 下 Because the present invention sets S 下阀芯 = S 阀座 Therefore F 上 and F下 The effective areas are equal, therefore F 上 = F 下 The net force generated by back pressure is zero. Regardless of the back pressure p 背 No matter the height, it will not affect the axial balance of the combined valve core, thus preventing the main valve from opening in the reverse direction (i.e., preventing the valve from accidentally opening from the closed state). This characteristic ensures the reliability of the valve under high back pressure environments.

[0037] like Figures 2-4 As shown, a boss shaft 116 is provided on the upper cover 104, and the floating sleeve 105 can slide up and down along the boss shaft 116; the lower end of the floating sleeve 105 forms a hysteresis chamber 108 between the combined valve core, the main valve core sleeve 103, and the boss shaft 116, and the upper end of the floating sleeve 105 forms a main valve upper chamber 109 between the main valve core sleeve 103 and the upper cover 104.

[0038] This embodiment further defines the installation and cavity formation method of the floating sleeve 105. A downwardly extending boss shaft 116 is provided below the upper cover 104. The floating sleeve 105 is fitted onto this boss shaft 116 and can slide freely up and down along the axial direction of the boss shaft 116. The lower end of the floating sleeve 105, together with the upper end face of the combined valve core, the inner wall of the main valve core sleeve 103, and the outer wall of the boss shaft 116, forms a closed cavity, namely the hysteresis cavity 108. The upper end of the floating sleeve 105, together with the inner wall of the main valve core sleeve 103, the lower end face of the upper cover 104, and the outer wall of the boss shaft 116, forms another closed cavity, namely the main valve upper cavity 109. The hysteresis cavity 108 and the main valve upper cavity 109 are interconnected through a damping hole 107 on the floating sleeve 105.

[0039] like Figures 2-4 As shown, an outer sealing ring 117 is provided between the outer periphery of the floating sleeve 105 and the main valve core sleeve 103, and an inner sealing ring 118 is provided between the inner periphery of the floating sleeve 105 and the boss shaft 116; the hysteresis chamber 108 is formed by the floating sleeve 105 below the outer sealing ring 117 and the inner sealing ring 118, the main valve core sleeve 103, the boss shaft 116 and the combined valve core; the upper chamber 109 of the main valve is formed by the floating sleeve 105 above the outer sealing ring 117 and the inner sealing ring 118, the main valve core sleeve 103, the upper cover 104 and the boss shaft 116.

[0040] This embodiment further refines the specific sealing structure of the hysteresis chamber 108 and the upper chamber 109 of the main valve. An outer sealing ring 117 is installed between the outer peripheral surface of the floating sleeve 105 and the inner wall of the main valve core sleeve 103, and an inner sealing ring 118 is installed between the inner peripheral surface of the floating sleeve 105 and the outer wall of the boss shaft 116. These two sealing rings divide the gap between the floating sleeve 105 and the main valve core sleeve 103 and the boss shaft 116 into two isolated regions. The region located below the outer sealing ring 117 and the inner sealing ring 118 (i.e., the space enclosed by the lower end of the floating sleeve 105, the inner wall of the main valve core sleeve 103, the outer wall of the boss shaft 116, and the upper end of the combined valve core) is the hysteresis chamber 108. The area above the outer sealing ring 117 and the inner sealing ring 118 (i.e., the space enclosed by the upper end of the floating sleeve 105, the inner wall of the main valve core sleeve 103, the lower end face of the upper cover 104, and the outer wall of the boss shaft 116) is the upper chamber 109 of the main valve. The two chambers are connected only through the damping hole 107, thereby achieving a hysteresis effect in pressure transmission.

[0041] In this embodiment, the upper sealing ring 113, the lower sealing ring 114, the outer sealing ring 117, and the inner sealing ring 118 can all be O-rings.

[0042] like Figures 2-4 As shown, the valve body 101 is provided with a main valve inlet 119, a main valve outlet 120 and an axially extending mounting cavity 121. The mounting cavity 121 is connected to the main valve inlet 119 and the main valve outlet 120. The main valve inlet 119 is provided with a pilot valve inlet 122 for connecting the pilot valve 2. The upper cover 104 is sealed and fixed to the top of the mounting cavity 121 and is provided with an upper cover channel 123 that communicates with the hysteresis cavity 108.

[0043] The main valve core sleeve 103 is vertically disposed in the mounting cavity 121, and the valve seat 102 is fixed to the bottom of the mounting cavity 121 and is sealed to the lower end of the combined valve core. The combined valve core can slide axially through the main valve core sleeve 103.

[0044] The bottom of the combined valve core is provided with a sleeve 124 and a sealing gasket 125 in sequence, and the sealing gasket 125 is sealed and fitted with the sealing surface of the valve seat 102.

[0045] This embodiment describes in detail the specific structure and assembly relationship of the valve body 101 and its internal components. The valve body 101 has a main valve inlet 119 (medium inlet), a main valve outlet 120 (medium discharge port), and an axially extending mounting cavity 121, which communicates with both the main valve inlet 119 and the main valve outlet 120. A pilot valve inlet 122 is also provided at the main valve inlet 119 for connecting the pilot valve 2 to introduce a medium pressure signal. The top cover 104 is sealed and fixed to the top of the mounting cavity 121 by bolts or other fasteners. The top cover 104 has a cover channel 123 machined inside, which communicates with the hysteresis chamber 108 to introduce the control pressure of the pilot valve 2 into the hysteresis chamber 108. The main valve core sleeve 103 is vertically installed inside the mounting cavity 121, and the valve seat 102 is fixed to the bottom of the mounting cavity 121, with the upper end face of the valve seat 102 serving as the sealing surface. The combined valve core (composed of an upper combined valve core 110 and a lower combined valve core 111) is axially slidably inserted inside the main valve core sleeve 103. A sleeve gasket 124 and a sealing gasket 125 are sequentially installed at the bottom of the combined valve core. The sealing gasket 125 mates with the sealing surface of the valve seat 102. When the safety valve is closed, the sealing gasket 125 is pressed tightly against the valve seat 102 to achieve a reliable seal.

[0046] like Figure 1 As shown, the pilot valve 2 is a pilot valve with a pressure regulating mechanism. The connecting pipeline 3 includes an inlet pipe 31 for introducing the inlet medium into the pilot valve 2, a discharge pipe 32 for leading out the outlet medium of the pilot valve 2, and a control pipe 33 for transmitting the control pressure of the pilot valve 2 to the hysteresis chamber 108.

[0047] This embodiment defines the specific configuration of the pilot valve 2 and the connecting pipeline 3. The pilot valve 2 is a pilot valve with a pressure regulating mechanism, and its set pressure can be adjusted as needed. The connecting pipeline 3 consists of three pipes: one end of the inlet pipe 31 is connected to the pilot valve inlet port 122 at the main valve inlet 119, and the other end is connected to the inlet of the pilot valve 2, for introducing the medium pressure into the pilot valve 2; the discharge pipe 32 is connected to the outlet of the pilot valve 2, for guiding the medium discharged by the pilot valve 2 to a safe area; one end of the control pipe 33 is connected to the control port of the pilot valve 2, and the other end is connected to the upper cover channel 123 on the upper cover 104, for transmitting the control pressure output by the pilot valve 2 to the hysteresis chamber 108. Through the above pipeline connection, the pilot valve 2 can sense the pressure at the main valve inlet 119 and control the opening and closing of the main valve 1 when the set pressure is reached.

[0048] In a preferred embodiment of this invention, the main valve 1 does not contain a physical return spring. The negative pressure generated by the vacuum chamber 106 replaces the return spring and serves as the main source of downward pressure to keep the combined valve core and valve seat 102 in contact when no medium is flowing through them. By adjusting the volume of the vacuum chamber 106, the vacuum level is changed to match different equivalent return spring forces, thereby adjusting the opening and closing characteristics of the main valve 1.

[0049] This embodiment further emphasizes one of the key features that distinguishes the present invention from the prior art: the complete elimination of the physical return spring. Traditional pilot-operated safety valves require a return spring inside the main valve to provide closing force, while the main valve 1 of this invention does not have any physical return spring inside. When no medium is introduced, the contact pressure between the combined valve core and the valve seat 102 is entirely provided by the negative pressure generated by the vacuum chamber 106. This negative pressure is the main source of downward pressure that keeps them in contact (in addition to minor forces such as the weight of the combined valve core). By adjusting the volume of the vacuum chamber 106 (for example, by selecting combined valve cores of different sizes), the vacuum level of the vacuum chamber 106 can be changed, thereby obtaining different equivalent return spring forces, and thus adjusting the opening and closing pressure difference and operating characteristics of the main valve 1. This design not only eliminates the material limitations of springs under special operating conditions (such as corrosion and high temperatures), but also reduces the volume of the upper chamber 109 of the main valve, which is beneficial for the rapid closing of large-diameter safety valves.

[0050] In a preferred embodiment of this invention, the diameter of the damping orifice 107 is a preset value, which is determined based on the required downward movement speed of the floating sleeve 105 and the opening and closing pressure difference of the main valve 1.

[0051] This embodiment defines the principle for determining the diameter of the damping orifice 107. The diameter of the damping orifice 107 directly affects the flow rate and velocity of the medium gas flowing from the hysteresis chamber 108 into the upper chamber 109 of the main valve, thereby affecting the downward movement speed of the floating sleeve 105 during the closing process and the pressure build-up speed of the upper chamber 109 of the main valve. Based on specific engineering requirements (e.g., the required opening and closing pressure difference), a suitable diameter value for the damping orifice 107 can be preset. This preset value ensures that the downward movement speed of the floating sleeve 105 matches the inlet flow rate provided by the pilot valve 2, thereby achieving rapid closure of the main valve 1 and controlling the opening and closing pressure difference within an ideal range (e.g., reaching 5%). In practical applications, the optimal orifice diameter under different operating conditions can be determined through experimentation or calculation, and adjustment can be achieved by replacing the damping orifice 107 with different diameters. In addition, the diameter of the damping orifice has a minimum threshold. When the orifice is small enough to reach the minimum threshold, the floating sleeve will move down very slowly. In extreme cases, if the floating sleeve has no opening at all, the volume of the hysteresis chamber will increase rapidly, which will cause insufficient air supply to the pilot valve and thus affect the rapid closing of the main valve. Therefore, the diameter of the damping orifice should be greater than or equal to the minimum threshold.

[0052] In summary, the main inventive points of this invention are as follows: like Figure 1 This pilot-operated safety valve consists of a pilot valve, a main valve, and connecting pipelines. The pilot valve is not the focus of our invention; we only need to implement its function. The main valve is as follows: Figure 2 and Figure 3The main valve consists of an upper cover, a main valve core sleeve, a valve body, a floating sleeve, a combined valve core, and a valve seat. The combined valve core further comprises an upper combined valve core, a lower combined valve core, a connecting shaft, a gasket, and a sealing gasket. The structure and assembly method of the main valve are as follows: the lower combined valve core has a sealing gasket and a gasket underneath, which connects to the upper combined valve core via the connecting shaft. When the upper combined valve core passes down from the main valve core sleeve and connects to the lower combined valve core, the lower end face of the upper combined valve core must be tightly against the step of the main valve core sleeve before being tightened via the connecting shaft. After the combined valve core and valve core sleeve are assembled, the O-rings of the upper and lower combined valve cores form a sealed space with the valve core sleeve. After the valve seat is installed, the combined valve core moves upward to form a vacuum cavity, thereby generating a downward negative pressure force, replacing the function of the return spring to return downward, ensuring that the combined valve core and valve seat are tightly fitted together. The floating sleeve is located on top of the combined valve core. The upper cover has a boss shaft with a through hole, allowing the floating sleeve to slide up and down along the boss shaft. The floating sleeve also has small holes with damping holes. The floating sleeve has an O-ring seal, and its lower end forms a hysteresis chamber with the upper combined valve core, valve core sleeve, and the boss shaft of the upper cover via the O-ring seal. The upper end of the floating sleeve forms the upper chamber of the main valve with the valve core sleeve and the upper cover via the O-ring seal. The upper chamber of the main valve communicates with the hysteresis chamber through the damping hole. The design includes a sealing diameter "S" for the O-ring seal on the upper combined valve core. 上阀芯 "S" is greater than the sealing diameter of the O-ring seal of the lower combined valve core. 下阀芯 “S” 下阀芯 "Sealing diameter at the valve seat seal" S 阀座 "equal.

[0053] To better understand this invention, the working principle of this invention will be described in full below: 1. See Figure 1 , Figure 2 , Figure 3 When the upper combined valve core passes down from the main valve core sleeve and connects to the lower combined valve core, the lower end face of the upper combined valve core must be tightly against the step of the main valve core sleeve before being tightened by the connecting shaft. After the combined valve core and valve core sleeve are assembled, a sealed space is formed between the O-ring seals of the upper and lower combined valve cores and the valve core sleeve. After the valve seat is installed, the combined valve core moves upward to form a vacuum cavity, thereby generating a downward negative pressure force, replacing the function of the return spring to return downward, making the combined valve core and valve seat fit tightly together. When no medium gas is supplied, the main valve is in the closed state under the action of vacuum negative pressure. After the medium gas is supplied, the medium gas enters the pilot valve through the pipeline, then enters the hysteresis cavity through the pilot valve, and then enters the upper cavity of the main valve through the damping orifice. Because the sealing diameter of the O-ring seal of the upper combined valve core is "S 上阀芯 "S" is greater than the sealing diameter of the O-ring seal of the lower combined valve core. 下阀芯 “S” 下阀芯 "Sealing diameter at the valve seat seal" S阀座 "Equal. Therefore, under the action of the area difference, the total force of the medium is downward. The greater the medium pressure, the greater the sealing force under the action of the area difference, achieving a self-tightening reliable seal. When the set pressure is reached and the pressure drops from the set pressure to the discharge pressure, the pilot valve opens, and the medium gas in the upper chamber of the main valve passes through the damping hole to the hysteresis chamber, to the upper cover channel, and is discharged from the pilot valve. The pressure in the upper chamber drops, and the total force of the medium in the combined valve core is upward, overcoming the spring-like force of the vacuum negative pressure. The main valve opens smoothly, and the combined valve core drives the floating sleeve to move upward until it is fully opened to the limit. When it approaches the reseating pressure, the pilot valve closes. The medium gas enters the hysteresis chamber through the pilot valve into the upper cover channel of the main valve, and then enters the upper chamber of the main valve through the damping hole. Because the volume of the hysteresis chamber is very small, the pressure in the hysteresis chamber rises rapidly. Because the sealing diameter of the O-ring seal of the upper combined valve core is "S" 上阀芯 "S" is greater than the sealing diameter of the O-ring seal of the lower combined valve core. 下阀芯 “S” 下阀芯 "Sealing diameter at the valve seat seal" S 阀座 "Equal. Therefore, under the action of the area difference, the total force of the medium is downward, and superimposed with the vacuum negative pressure similar to the return spring force, the combined valve core moves downward rapidly; initially, the floating sleeve and the upper cover are almost tightly pressed together, and the pressure difference formed when the medium gas enters through the damping hole is small. Under the action of its own weight, the floating sleeve completely follows the combined valve core downward; see..." Figure 4 As the combined valve core and floating sleeve continue to move downwards, the volume of the upper chamber of the main valve formed by the floating sleeve and the upper cover increases. Due to the presence of the damping orifice, the entry of the medium gas into the upper chamber of the main valve is delayed. The resulting pressure difference slows down the downward movement of the floating sleeve, creating a gap between the lower end of the floating sleeve and the upper combined valve core. The volume of the hysteresis chamber gradually increases. However, because medium gas continuously enters the hysteresis chamber from the pilot valve, and due to the hysteresis effect of the damping orifice, this gradually increasing time difference is sufficient to allow the pressure in the hysteresis chamber to continuously increase (in contrast, the upper chamber volume of a conventional safety valve does not have this gradual increase process; it is directly at its maximum volume, and the pressure build-up time is longer). Therefore, under the continuous increase in pressure in the hysteresis chamber, the combined valve core moves downwards more rapidly under the combined action of the medium pressure, the vacuum negative pressure spring, and its own weight, until the combined valve core contacts the valve seat and completely closes the main valve. At this point, the distance between the floating sleeve and the combined valve core is at its maximum. Then, as the combined valve core contacts the valve seat and stops moving, the pressure difference under the floating sleeve continuously decreases as the medium gas continues to enter the upper chamber of the main valve through the damping orifice. Under the action of gravity, it eventually moves down to be close to the upper combined valve core. This completes the entire main valve closing process.

[0054] 2. See Figure 3 Our design includes a combined valve core O-ring with a sealing diameter of "S". 下阀芯 "Sealing diameter at the valve seat seal" S 阀座"Equal. Thus, when there is a high back pressure at the outlet of the safety valve, because the two areas are equal, the force exerted by the back pressure on the combined valve core is balanced. Therefore, even with a very high back pressure, it is balanced and cannot open the safety valve in the reverse direction, forming a function similar to a check valve. See..." Figure 5 This is our standard safety valve design with a physical return spring. Because it needs to meet the design requirements of a self-tightening seal, it has an "S"... 阀芯 "Greater than" S 阀座 "When back pressure acts on the valve core, it creates an overall upward force. When the back pressure is large enough, it overcomes the force of the return spring and the sealing force formed by the inlet medium, opening the main valve and causing the safety valve to fail and discharge. Therefore, previous pilot-operated safety valves only allowed a very small amount of back pressure. Our high back pressure safety valve, due to its innovative vacuum negative pressure design, achieves back pressure balance. Even with very high back pressure, it will not open the safety valve, thus realizing the function of a high back pressure pilot-operated safety valve. At the same time, the back pressure balance means that no work is done to overcome back pressure during reseating and closing, resulting in a faster downward closing speed. This is particularly effective in improving the accuracy of the opening and closing pressure difference of large-diameter pilot-operated safety valves."

[0055] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalents or substitutions are all included within the scope defined by the claims of the present invention.

Claims

1. A high back pressure pilot-operated safety valve suitable for large diameter applications, characterized in that, It includes a main valve (1), a pilot valve (2) and a connecting pipeline (3). The main valve (1) includes a valve body (101), a valve seat (102), a main valve core sleeve (103), a top cover (104), a combined valve core and a floating sleeve (105). The combined valve core is located inside the main valve core sleeve (103) and forms a sealed space with the main valve core sleeve (103). When the valve seat (102) is installed, the combined valve core moves upward to make the sealed space a vacuum chamber (106), thereby generating a downward negative pressure force to replace the return spring and make the combined valve core fit with the valve seat (102). The floating sleeve (105) is located inside the main valve core sleeve (103) and is slidably disposed above the combined valve core. The floating sleeve (105) has a damping hole (107). The floating sleeve (105) forms a hysteresis cavity (108) and a main valve upper cavity (109) between the upper cover (104), the main valve core sleeve (103) and the combined valve core. The damping hole (107) connects the hysteresis cavity (108) and the main valve upper cavity (109).

2. A high back pressure pilot-operated safety valve suitable for large diameter vessels as described in claim 1, characterized in that, The combined valve core includes an upper combined valve core (110), a lower combined valve core (111), and a connecting shaft (112) connecting the two. The upper combined valve core (110) is provided with an upper sealing ring (113) on its outer periphery, and the lower combined valve core (111) is provided with a lower sealing ring (114) on its outer periphery. The upper sealing ring (113) and the lower sealing ring (114) form a sealed space with the inner wall of the main valve core sleeve (103).

3. A high back pressure pilot-operated safety valve suitable for large diameter vessels as described in claim 2, characterized in that, The inner side of the main valve core sleeve (103) is provided with an annular step (115). When the lower end face of the upper combined valve core (110) is assembled, it is closely attached to the upper end face of the annular step (115). After being tightened by the connecting shaft (112), the upper sealing ring (113), the lower sealing ring (114) and the inner wall of the main valve core sleeve (103) together form the sealed space. When the valve seat (102) is installed, it pushes the combined valve core upward, so that the combined valve core moves upward in the sealed space to form a vacuum cavity (106). The negative pressure generated by the vacuum cavity (106) replaces the return spring to make the combined valve core and the valve seat (102) fit tightly together.

4. A high back pressure pilot-operated safety valve suitable for large diameter vessels as described in claim 2, characterized in that, The sealing diameter of the upper sealing ring (113) is denoted as S. 上阀芯 The sealing diameter of the lower sealing ring (114) is denoted as S. 下阀芯 The sealing diameter at the valve seat (102) is denoted as S. 阀座 Satisfying: S 上阀芯 >S 下阀芯 And S 下阀芯 =S 阀座 .

5. A high back pressure pilot-operated safety valve suitable for large diameter vessels as described in claim 1, characterized in that, The upper cover (104) is provided with a boss shaft (116), and the floating sleeve (105) can slide up and down along the boss shaft (116); the lower end of the floating sleeve (105) forms a hysteresis cavity (108) with the combined valve core, the main valve core sleeve (103) and the boss shaft (116), and the upper end of the floating sleeve (105) forms a main valve upper cavity (109) with the main valve core sleeve (103) and the upper cover (104).

6. A high back pressure pilot-operated safety valve suitable for large diameter vessels as described in claim 5, characterized in that, An outer sealing ring (117) is provided between the outer periphery of the floating sleeve (105) and the main valve core sleeve (103), and an inner sealing ring (118) is provided between the inner periphery of the floating sleeve (105) and the boss shaft (116); the hysteresis cavity (108) is formed by the floating sleeve (105) below the outer sealing ring (117), the main valve core sleeve (103), the boss shaft (116) and the combined valve core below; the upper cavity of the main valve (109) is formed by the floating sleeve (105) above the outer sealing ring (117), the main valve core sleeve (103), the upper cover (104) and the boss shaft (116).

7. A high back pressure pilot-operated safety valve suitable for large diameter vessels as described in claim 1, characterized in that, The valve body (101) is provided with a main valve inlet (119), a main valve outlet (120) and an axially extending mounting cavity (121). The mounting cavity (121) is connected to the main valve inlet (119) and the main valve outlet (120). The main valve inlet (119) is provided with a pilot valve air inlet (122) for connecting the pilot valve (2). The upper cover (104) is sealed and fixed to the top of the mounting cavity (121) and is provided with an upper cover channel (123) communicating with the hysteresis cavity (108). The main valve core sleeve (103) is vertically disposed in the mounting cavity (121), the valve seat (102) is fixed to the bottom of the mounting cavity (121) and is sealed to the lower end of the combined valve core, and the combined valve core is axially slidably inserted into the main valve core sleeve (103); The bottom of the combined valve core is provided with a sleeve (124) and a sealing gasket (125) in sequence, and the sealing gasket (125) is sealed to the sealing surface of the valve seat (102).

8. A high back pressure pilot-operated safety valve suitable for large diameter vessels as described in claim 1, characterized in that, The pilot valve (2) is a pilot valve with a pressure regulating mechanism. The connecting pipeline (3) includes an inlet pipe (31) for introducing the inlet medium into the pilot valve (2), a discharge pipe (32) for leading out the outlet medium of the pilot valve (2), and a control pipe (33) for transmitting the control pressure of the pilot valve (2) to the hysteresis chamber (108).

9. A high back pressure pilot-operated safety valve suitable for large diameter vessels as described in claim 1, characterized in that, There is no physical return spring in the main valve (1). The negative pressure generated by the vacuum chamber (106) replaces the return spring and serves as the main source of downward pressure to keep the combined valve core and the valve seat (102) in contact when no medium is flowing through. By adjusting the volume of the vacuum chamber (106), the vacuum degree is changed to match different equivalent return spring forces, thereby adjusting the opening and closing characteristics of the main valve (1).

10. A high back pressure pilot-operated safety valve suitable for large diameter vessels as described in claim 1, characterized in that, The diameter of the damping orifice (107) is a preset value, which is determined based on the required downward movement speed of the floating sleeve (105) and the opening and closing pressure difference of the main valve (1).

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