High back pressure pilot operated safety valve and opening and closing method thereof

Abstract

This invention discloses a high back pressure pilot-operated safety valve and its opening and closing method, relating to the field of safety valve technology. The safety valve includes a pilot valve, a main valve, and connecting pipelines; the main valve includes a valve body, a valve seat, a main valve core sleeve, and a combined valve core; the upper and lower sealing rings of the combined valve core form a sealed space with the inner wall of the main valve core sleeve, and after the valve seat is installed, this space forms a vacuum cavity, whose negative pressure completely replaces the return spring to make the valve core fit against the valve seat; the upper sealing ring has a diameter S. 上阀芯 Larger than the diameter S of the lower sealing ring 下阀芯 And S 下阀芯 Equal to valve seat sealing diameter S 阀座 This invention replaces the spring with vacuum negative pressure, eliminating the risk of spring failure, reducing the volume of the upper chamber of the main valve, and controlling the opening and closing pressure difference to 5%; simultaneously, due to S 下阀芯 =S 阀座 The upward and downward thrust generated by the outlet back pressure cancel each other out, so even with extremely high back pressure, it will not open accidentally, thus achieving reliable operation under high back pressure conditions.

Description

Technical Field

[0001] This invention relates to the field of safety valve technology, and more specifically to a high back pressure pilot-operated safety valve and its opening and closing method. Background Technology

[0002] Pilot-operated safety valves are overpressure protection devices widely used in industries such as petroleum, chemical, and power. Their basic structure consists of two parts: a main valve and a pilot valve. The pilot valve senses the system pressure; when the pressure reaches a set value, the pilot valve actuates, controlling the main valve to open and release pressure. When the pressure drops to the reseating pressure, the pilot valve resets, and the main valve closes. Because the opening and closing of the main valve in a pilot-operated safety valve is controlled by the pilot valve, which rapidly senses the system pressure using a signal pipeline and amplifies and transmits the control signal to the main valve, causing it to actuate, pilot-operated safety valves have advantages such as good sealing performance and small pressure differential between opening and closing, making them widely used in high-pressure and high-flow-rate applications.

[0003] In the main valve design of conventional pilot-operated safety valves, a self-tightening sealing structure is typically used to ensure reliable sealing when the valve is closed. For example... Figure 4 As shown, the sealing diameter of the main valve core in a conventional design (denoted as S) 阀芯 The diameter of the valve seat seal is greater than the sealing diameter at the valve seat seal (denoted as S). 阀座 The main valve utilizes the pressure of the imported medium to generate a downward sealing force on the area difference, achieving a self-tightening sealing effect where "the higher the pressure, the tighter the seal." Simultaneously, a return spring is typically installed inside the main valve to provide initial preload when the valve is closed, ensuring a tight fit between the valve core and the valve seat.

[0004] However, the above conventional structure has the following problems in practical applications: (1) Prone to accidental opening under high back pressure conditions. When there is high back pressure at the outlet of the safety valve (e.g., high resistance in the discharge pipeline, high pressure in downstream equipment), the back pressure will act on some exposed surfaces of the main valve core. Due to the conventional design, S 阀芯 >S 阀座 Back pressure acting on the valve core generates an overall upward force. When the back pressure is large enough, this upward force overcomes the preload of the return spring and the sealing force formed by the inlet medium, causing the main valve to open unexpectedly. This results in the safety valve discharging the medium before reaching the set pressure, causing system failure or energy waste. Therefore, conventional pilot-operated safety valves typically only allow a very small amount of back pressure, severely limiting their application in high-pressure, high-back-pressure applications.

[0005] (2) Limitations of the return spring. The presence of the return spring not only increases the number of valve parts and assembly complexity, but also, under certain special working conditions (such as high temperature, corrosive media, etc.), the spring material is prone to performance degradation and corrosion, affecting the service life and reliability of the valve. In addition, due to the presence of the physical spring, a larger air intake channel needs to be designed, resulting in a larger volume of the upper cavity of the valve core, which is not conducive to the rapid opening and closing of the main valve, making it difficult to control the opening and closing pressure difference within a small range.

[0006] Therefore, how to design a pilot-operated safety valve that can be used under high back pressure conditions, does not require a return spring, and can achieve reliable self-tightening sealing is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] In order to overcome the defects in the prior art, the present invention discloses a high back pressure pilot-operated safety valve and its opening and closing method. The safety valve of the present invention can work reliably under the condition of high back pressure at the outlet end, avoiding the main valve from being opened unexpectedly due to excessive back pressure. At the same time, the physical return spring in the main valve is completely eliminated, improving the opening and closing response speed and the adaptability to working conditions.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a high back pressure pilot-operated safety valve, including a main valve, a pilot valve and a connecting pipeline connecting the main valve and the pilot valve, wherein the main valve includes a valve body, a valve seat, a main valve core sleeve, a top cover and a combined valve core disposed in the main valve core sleeve; 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. When the valve seat is installed, it pushes the combined valve core upward, causing the combined valve core to move upward in the sealed space to form a vacuum cavity. The negative pressure generated by the vacuum cavity replaces the return spring, making the combined valve core and the valve seat fit tightly together. 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 .

[0009] 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.

[0010] Preferably, an annular step is provided in the middle of the inner side of the main valve core sleeve. When the lower end face of the upper combined valve core is assembled, it is tightly attached to the upper end face of the annular step. 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.

[0011] Preferably, the bottom of the lower combined valve core is provided with a sealing gasket and a sleeve gasket, and the sealing gasket is in sealing fit with the sealing surface of the valve seat.

[0012] Preferably, the valve body is provided with a main valve inlet and a main valve outlet. The main valve inlet is provided with a pilot valve inlet, which is connected to the pilot valve through the connecting pipe. The valve seat is fixed in the valve body. The upper cover is installed on the upper part of the valve body and is provided with a gas passage. The gas passage is connected to the pilot valve through the connecting pipe. The main valve core sleeve is disposed in the valve body, and the main valve core sleeve, the upper cover, and the upper combined valve core form the upper chamber of the main valve, which is connected to the gas passage.

[0013] Preferably, the pilot valve is a pilot valve with a set pressure regulation function, 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 upper chamber of the main valve.

[0014] Secondly, the present invention provides a method for opening and closing a high back pressure pilot-operated safety valve, comprising the following steps: Initial closing procedure: When the valve seat is installed, push the combined valve core upwards, causing the combined valve core to move upwards within the sealed space, forming a vacuum chamber. The negative pressure generated by the vacuum chamber presses the combined valve core downwards onto the valve seat, so that the main valve is in the closed state when no medium is flowing through it. Self-tightening sealing procedure: After the medium is introduced, the medium pressure enters the upper chamber of the main valve through the pilot valve, acting downwards on the upper combined valve core; simultaneously, the medium pressure acts upwards on the bottom of the lower combined valve core, but due to S... 上阀芯 >S 下阀芯 =S 阀座 The total force generated by the medium is downward, and the greater the medium pressure, the greater the sealing force, thus achieving a self-tightening seal; Opening procedure: When the inlet pressure reaches the set pressure and then drops from the set pressure to the discharge pressure, the pilot valve opens to release pressure, the medium in the upper chamber of the main valve is discharged through the pilot valve, the pressure in the upper chamber of the main valve drops, the total force of the medium on the combined valve core is upward and overcomes the vacuum negative pressure, the combined valve core moves upward, and the main valve opens quickly. Reseating and closing procedure: When the inlet pressure drops to the reseating pressure, the pilot valve closes, and the medium enters the upper chamber of the main valve through the pilot valve. The pressure in the upper chamber of the main valve rises rapidly due to S 上阀芯 >S 下阀芯 =S 阀座 The total force of the medium is downward and superimposed with the vacuum negative pressure, causing the combined valve core to move downward, thus quickly closing the main valve.

[0015] Preferably, in the opening step, since there is no return spring in the main valve, the cross-sectional area of ​​the air intake channel is small, and the volume of the upper chamber of the main valve is small, the opening and closing pressure difference can be controlled to 5%.

[0016] Preferably, in the self-tightening sealing step and the reseating closing step, due to S 下阀芯 =S 阀座 The back pressure at the outlet of the safety valve acts on the lower combined valve core with an upward thrust and a downward thrust that are equal in magnitude and opposite in direction. The net back pressure force is zero, thus preventing the high back pressure from opening the main valve in the reverse direction.

[0017] Preferably, in the reseating and closing step, the negative pressure of the vacuum chamber and the total force of the medium work together to make the combined valve core quickly reseated and achieve leak-free closure; By adjusting the volume of the vacuum chamber, the vacuum level can be changed to match different equivalent reset spring forces, thereby adjusting the opening and closing characteristics of the main valve.

[0018] The beneficial effects of this invention are: 1. 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.

[0019] 2. The diameter "S" is sealed by the O-ring seal of 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 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 inlet channel is needed, thus reducing the volume of the air inlet cavity and facilitating the rapid opening and closing of the main valve. In safety valve tests with a diameter of DN100 and below, the opening and closing pressure difference can be controlled to 5%, demonstrating significant effectiveness; second, because there is no physical return spring, it is more practical for applications requiring specific spring materials.

[0020] 3. The diameter "S" is sealed by the lower combined valve core O-ring seal. 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 closing downwards, thus closing downwards faster and the main valve sealing is more reliable."

[0021] 4. 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. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the high back pressure pilot-operated safety valve of the present invention; Figure 2 This is a schematic diagram of the main valve of the high back pressure pilot-operated safety valve of the present invention; Figure 3 This is a schematic diagram of the main valve assembly valve core of the present invention; Figure 4 A schematic diagram of a safety valve design that conventionally incorporates a physical return spring in existing technology; Figure label: 1. Main valve; 101. Valve body; 102. Valve seat; 103. Main valve core sleeve; 104. Top cover; 105. Upper combined valve core; 106. Lower combined valve core; 107. Connecting shaft; 108. Upper sealing ring; 109. Lower sealing ring; 110. Vacuum chamber; 111. Annular step; 112. Sealing gasket; 113. Gasket; 114. Main valve inlet; 115. Main valve outlet; 116. Pilot valve inlet; 117. Gas passage; 118. Upper chamber of main valve; 2. Pilot valve; 3. Connecting pipeline; 31. Inlet pipe; 32. Discharge pipe; 33. Control pipe. Detailed Implementation

[0023] 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.

[0024] Example 1 A high back pressure pilot-operated safety valve, such as Figures 1-3 As shown, it includes a main valve 1, a pilot valve 2 and a connecting pipeline 3 connecting the main valve 1 and the pilot valve 2. The main valve 1 includes a valve body 101, a valve seat 102, a main valve core sleeve 103, an upper cover 104 and a combined valve core disposed in the main valve core sleeve 103.

[0025] The combined valve core includes an upper combined valve core 105, a lower combined valve core 106, and a connecting shaft 107 connecting the two. The upper combined valve core 105 is provided with an upper sealing ring 108 on its outer periphery, and the lower combined valve core 106 is provided with a lower sealing ring 109 on its outer periphery. The upper sealing ring 108 and the lower sealing ring 109 form a sealed space with the inner wall of the main valve core sleeve 103.

[0026] When the valve seat 102 is installed, it pushes the combined valve core upward, causing the combined valve core to move upward in the sealed space to form a vacuum chamber 110. The negative pressure generated by the vacuum chamber 110 replaces the return spring, making the combined valve core and the valve seat 102 fit tightly together.

[0027] The sealing diameter of the upper sealing ring 108 is denoted as S. 上阀芯 The sealing diameter of the lower sealing ring 109 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 .

[0028] In this embodiment, the high back pressure pilot-operated safety valve consists of three main parts: a main valve 1, a pilot valve 2, and a connecting pipeline 3. The main valve 1 is used to control the opening and closing of the main flow channel of the medium, the pilot valve 2 is used to sense the inlet pressure and control the opening and closing of the main valve 1, and the connecting pipeline 3 connects the air passages of the main valve 1 and the pilot valve 2. The pilot valve 2 can be a pilot valve 2 known in the art, such as a spring-preloaded pilot valve, including a valve body, valve core, set spring, adjusting screw, etc., and the set pressure is set by adjusting the spring compression.

[0029] The main valve 1 has the following structure: the valve body 101 is a pressure-bearing shell with a medium flow channel inside; the valve seat 102 is fixedly installed inside the valve body 101, and its upper end face is a sealing surface; the main valve core sleeve 103 is cylindrical and installed inside the valve body 101, and its inner wall is a smooth cylindrical surface; the upper cover 104 is fixed to the upper part of the valve body 101 by bolts and is used to seal the upper end of the main valve 1; the combined valve core is installed inside the main valve core sleeve 103 and can move up and down along the axial direction.

[0030] The combined valve core consists of an upper combined valve core 105, a lower combined valve core 106, and a connecting shaft 107. The upper combined valve core 105 is inverted T-shaped or similar, with a sealing groove machined on its outer circumference, into which an upper sealing ring 108 is installed. The lower combined valve core 106 is also similarly shaped, with a sealing groove machined on its outer circumference, into which a lower sealing ring 109 is installed. The upper combined valve core 105 and the lower combined valve core 106 are coaxially and fixedly connected via the connecting shaft 107, forming an integral combined valve core. Both the upper sealing ring 108 and the lower sealing ring 109 slide and seal against the inner wall of the main valve core sleeve 103.

[0031] The upper sealing ring 108, the lower sealing ring 109, and the inner wall of the main valve core sleeve 103 together form a sealed space. When the valve seat 102 is installed in place, during assembly or initial state, the combined valve core will move slightly upward relative to the main valve core sleeve 103. At this time, the gas volume in the sealed space increases and the pressure decreases, forming a vacuum chamber 110. The negative pressure in this vacuum chamber 110 generates a downward force on the combined valve core. This force completely replaces the function of the return spring in a traditional pilot-operated safety valve, pressing the combined valve core downward against the valve seat 102 to achieve a closed seal.

[0032] The three key sealing diameters are defined as: S 上阀芯 S is the sealing diameter (i.e., the average diameter of the effective sealing surface) of the upper sealing ring 108 in contact with the inner wall of the main valve core sleeve 103; 下阀芯 S is the sealing diameter where the lower sealing ring 109 contacts the inner wall of the main valve core sleeve 103; 阀座 This refers to the average diameter of the annular sealing surface where the sealing surface of the valve seat 102 contacts the bottom sealing gasket 112 of the lower combined valve core 106. This invention specifies that these three diameters satisfy two relationships: S 上阀芯 >S 下阀芯 , and S 下阀芯 = S 阀座 S 上阀芯 >S 下阀芯 = S 阀座 Its function is to ensure that after the medium is introduced, the medium pressure acts on the combined valve core to generate a net downward force, achieving a self-tightening seal; S 下阀芯 = S 阀座 Its function is to make the upward and downward thrusts of the outlet back pressure acting on the lower combined valve core 106 cancel each other out, so that the net back pressure is zero, and to prevent the valve from being opened accidentally under high back pressure.

[0033] In this embodiment, both the upper sealing ring 108 and the lower sealing ring 109 are O-rings. The sealing rings are made of wear-resistant and low-friction materials to reduce the risk of friction and leakage when the valve core moves, and to ensure that the vacuum level does not decrease after long-term use.

[0034] like Figures 1-3 As shown, there is no physical return spring in the main valve 1. The negative pressure generated by the vacuum chamber 110 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.

[0035] This embodiment further specifies that no physical return spring (such as a helical spring, disc spring, etc.) is installed in the main valve 1. When no medium is introduced (i.e., no medium pressure is applied), the main force that keeps the combined valve core pressed tightly against the valve seat 102 is the negative pressure generated by the vacuum chamber 110. In traditional designs, when no medium is introduced, the preload of the spring is required to ensure the initial seal between the valve core and the valve seat; this invention completely replaces the preload with vacuum negative pressure, thereby eliminating all the drawbacks of the spring, such as high-temperature creep and corrosion fatigue. At the same time, since there is no spring, the volume of the upper chamber 118 of the main valve can be designed to be smaller, which is beneficial for rapid opening and closing.

[0036] like Figure 3 As shown, an annular step 111 is provided in the middle of the inner side of the main valve core sleeve 103. When the lower end face of the upper combined valve core 105 is assembled, it is tightly attached to the upper end face of the annular step 111. After being tightened by the connecting shaft 107, the upper sealing ring 108, the lower sealing ring 109 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 cavity 110.

[0037] This embodiment specifically describes the formation of the sealed space and the generation of the vacuum cavity. An annular step 111 is machined into the middle of the inner side of the main valve core sleeve 103, and this step has an upward-facing annular plane. During assembly, the upper combined valve core 105 is first inserted downwards from the upper end of the main valve core sleeve 103 until the lower end face of the upper combined valve core 105 contacts and presses against the upper end face of the annular step 111; then, the lower combined valve core 106 is inserted upwards from the lower end of the main valve core sleeve 103 and tightened to the upper combined valve core 105 via the connecting shaft 107. Thus, the upper sealing ring 108 is located above the annular step 111, and the lower sealing ring 109 is located below the annular step 111. The upper sealing ring 108, the lower sealing ring 109, and the inner wall of the main valve core sleeve 103 form a closed annular space, i.e., the sealed space. Then, valve seat 102 is installed. When valve seat 102 pushes the lower combined valve core 106 upward, the combined valve core as a whole undergoes a slight upward displacement relative to the main valve core sleeve 103, resulting in an increase in the volume of the sealed space and a thinner internal gas, forming a vacuum cavity 110.

[0038] like Figure 3 As shown, the bottom of the lower combined valve core 106 is provided with a sealing gasket 112 and a sleeve gasket 113, and the sealing gasket 112 is sealed and fitted with the sealing surface of the valve seat 102.

[0039] This embodiment further defines the bottom structure of the lower combined valve core 106. The sealing gasket 112, made of an elastic or soft sealing material (such as rubber, polytetrafluoroethylene, etc.), is installed in a groove at the bottom of the lower combined valve core 106. When a vacuum negative pressure or media pressure presses the combined valve core downwards, the sealing gasket 112 comes into close contact with the sealing surface at the upper end of the valve seat 102, forming a reliable main sealing pair. The sealing gasket 112 is replaceable for easy maintenance.

[0040] like Figures 1-3 As shown, the valve body 101 is provided with a main valve inlet 114 and a main valve outlet 115. The main valve inlet 114 is provided with a pilot valve inlet 116, which is connected to the pilot valve 2 through a connecting pipe 3. The valve seat 102 is fixed inside the valve body 101. The upper cover 104 is installed on the upper part of the valve body 101, and a gas passage 117 is provided on the upper cover 104. The gas passage 117 is connected to the pilot valve 2 through a connecting pipe 3. The main valve core sleeve 103 is provided inside the valve body 101. The main valve core sleeve 103, the upper cover 104 and the upper combined valve core 105 form the main valve upper chamber 118, which is connected to the gas passage 117.

[0041] This embodiment describes in detail the fluid passage and gas path control structure of the main valve 1. The valve body 101 has a main valve inlet 114 (medium inlet) and a main valve outlet 115 (medium outlet). The medium enters through the main valve inlet 114, passes through the gap between the valve seat 102 and the combined valve core, and exits through the main valve outlet 115. A pilot valve inlet 116 is provided on the passage wall of the main valve inlet 114. This pilot valve inlet 116 is connected to the inlet of the pilot valve 2 via the inlet pipe 31 in the connecting pipe 3, and is used to introduce the inlet medium pressure into the pilot valve 2. A gas passage 117 is machined on the upper cover 104. One end of the gas passage 117 is connected to the upper chamber 118 of the main valve, and the other end is connected to the control port of the pilot valve 2 via the control pipe 33 in the connecting pipe 3. The upper chamber 118 of the main valve is a closed chamber formed by the inner wall of the main valve core sleeve 103, the lower end face of the upper cover 104, and the upper end face of the upper combined valve core 105. Pilot valve 2 controls the opening and closing of main valve 1 by controlling the pressure in the chamber.

[0042] like Figure 1 As shown, pilot valve 2 is a pilot valve with a set pressure regulation function. The connecting pipeline 3 includes an inlet pipe 31 for introducing the inlet medium into pilot valve 2, a discharge pipe 32 for leading out the outlet medium of pilot valve 2, and a control pipe 33 for transmitting the control pressure of pilot valve 2 to the upper chamber 118 of the main valve.

[0043] 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 set pressure regulation function known in the art, such as a spring-loaded pilot valve, where the set pressure can be set by adjusting the compression of the spring. The connecting pipeline 3 consists of three independent pipes: the inlet pipe 31 connects the pilot valve inlet 116 at the main valve inlet 114 and the inlet end of the pilot valve 2, and is used to provide an inlet pressure signal to the pilot valve 2; the discharge pipe 32 connects to the discharge port of the pilot valve 2, and is used to discharge the overpressure medium to the atmosphere or the recovery system; the control pipe 33 connects the control output port of the pilot valve 2 and the gas passage 117 on the top cover 104, and is used to transmit the control pressure of the pilot valve 2 to the upper chamber 118 of the main valve. When the pilot valve 2 is closed, the inlet pressure enters the upper chamber 118 of the main valve through the internal passage of the pilot valve 2; when the pilot valve 2 is open, the pressure in the upper chamber 118 of the main valve is released through the discharge port of the pilot valve 2.

[0044] In this embodiment, the pilot-operated safety valve consists of a pilot valve, a main valve, and connecting pipelines. The pilot valve can adopt a conventional pilot valve structure in the art, only needing to achieve the basic functions of the pilot valve. The main valve, such as... Figure 2 and Figure 3 The main valve consists of an upper cover, a main valve core sleeve, a valve body, 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 and the combined valve core 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 design includes a sealing diameter "S" for the O-ring of 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.

[0045] Example 2 A method for opening and closing a high back pressure pilot-operated safety valve includes the following steps: Initial closing procedure: When the valve seat 102 is installed, push the combined valve core upward to move the combined valve core upward in the sealed space, so that the sealed space forms a vacuum chamber 110. The negative pressure generated by the vacuum chamber 110 presses the combined valve core downward onto the valve seat 102, so that the main valve 1 is in the closed state when no medium is flowing through it. Self-tightening sealing step: After the medium is introduced, the medium pressure enters the upper chamber 118 of the main valve through the pilot valve 2, acting downward on the upper combined valve core 105; at the same time, the medium pressure acts upward on the bottom of the lower combined valve core 106, but due to S 上阀芯 >S 下阀芯 =S 阀座 The total force generated by the medium is downward, and the greater the medium pressure, the greater the sealing force, thus achieving a self-tightening seal; Opening procedure: When the inlet pressure reaches the set pressure and then drops from the set pressure to the discharge pressure, the pilot valve 2 opens to release pressure. The medium in the upper chamber 118 of the main valve is discharged through the pilot valve 2. The pressure in the upper chamber 118 of the main valve drops. The total force of the medium on the combined valve core moves upward and overcomes the vacuum negative pressure. The combined valve core moves upward, causing the main valve 1 to open quickly. Reseating and closing procedure: When the inlet pressure drops to the reseating pressure, pilot valve 2 closes, and the medium enters the upper chamber 118 of the main valve through pilot valve 2. The pressure in the upper chamber 118 of the main valve rises rapidly due to S 上阀芯 >S 下阀芯 =S 阀座 The total force of the medium is downward and superimposed with the vacuum negative pressure, causing the combined valve core to move downward, making the main valve 1 close quickly.

[0046] This embodiment provides a method for pressure control using the aforementioned high back pressure pilot-operated safety valve, comprising four consecutive steps: In the initial closing step, the safety valve is not yet operational. After the valve seat 102 is installed, it forces the combined valve core to move slightly upward, forming a vacuum chamber 110. The negative pressure within this vacuum chamber 110 (depending on the chamber volume and sealing performance) acts alone to press the combined valve core downward onto the valve seat 102, achieving an initial seal. No spring force is required in this step.

[0047] In the self-tightening sealing step, the system begins to be circulated with the medium. The medium pressure enters the upper chamber 118 of the main valve through the pilot valve 2 and the connecting pipe 3, acting downwards on the upper surface of the upper combined valve core 105 (area S). 上阀芯 (corresponding area); on the other hand, the medium pressure acts directly from the main valve inlet 114 on the bottom of the lower combined valve core 106 (area S). 阀座 (corresponding area). Because S 上阀芯 >S 下阀芯 = S 阀座 Therefore, the downward force area is greater than the upward force area, resulting in a net downward force that further presses the valve core against the valve seat 102. The higher the medium pressure, the greater this net downward force, leading to a more reliable seal and achieving a self-tightening seal.

[0048] During the opening process, when the inlet pressure rises to the set pressure of pilot valve 2 and then rises to the discharge pressure, the valve core of pilot valve 2 leaves the valve seat, and pilot valve 2 opens. The pressure in the upper chamber 118 of the main valve is rapidly released through the discharge pipe 32 of pilot valve 2, and the pressure in the upper chamber 118 of the main valve drops sharply. At this time, the pressure distribution of the medium acting on the combined valve core changes: the bottom of the lower combined valve core 106 still bears the inlet pressure (upward), while the pressure on the upper surface of the upper combined valve core 105 (i.e., the pressure in the upper chamber 118 of the main valve) is close to zero. Therefore, the direction of the total force of the medium on the combined valve core becomes upward (because the upward area S...). 阀座 The corresponding force is greater than the downward force (the upward force overcomes the downward negative pressure generated by the vacuum chamber 110, pushes the combined valve core upward, away from the valve seat 102, and the main valve 1 quickly opens to release pressure.

[0049] During the reseating and closing step, when the inlet pressure drops to the reseating pressure of pilot valve 2, pilot valve 2 closes. At this time, the inlet medium re-enters the upper chamber 118 of the main valve through the internal channel of pilot valve 2, causing the pressure in the upper chamber 118 of the main valve to quickly recover to near the inlet pressure. Therefore, the force of the medium on the combined valve core becomes downward again (because S...). 上阀芯 >S 下阀芯 = S 阀座 Simultaneously, the vacuum negative pressure also moves downwards. The combined effect of these two forces pushes the combined valve core downwards rapidly, pressing it back onto the valve seat 102, thus closing the main valve 1. Due to the presence of the vacuum negative pressure, the closing process is rapid and the seal is reliable.

[0050] As a preferred embodiment of this example, in the opening step, since there is no return spring in the main valve 1, the cross-sectional area of ​​the air intake channel is small, and the volume of the upper chamber 118 of the main valve is small, the opening and closing pressure difference can be controlled to 5%.

[0051] This embodiment further defines the superior performance of the opening step. Traditional pilot-operated safety valves have a return spring inside the main valve. To provide installation space and actuation stroke for the spring, the volume of the upper chamber 118 of the main valve is typically large, and the cross-sectional area of ​​the air intake channel (the channel from the pilot valve to the upper chamber of the main valve) is also large. This results in a relatively slow pressure release rate in the upper chamber 118 of the main valve during opening; and a slow pressure build-up rate in the upper chamber 118 of the main valve during closing, leading to a large opening-closing pressure difference (i.e., the percentage of the difference between the set pressure and the reseating pressure to the set pressure). In this invention, because the return spring is eliminated, the upper chamber 118 of the main valve can be designed very compactly, with a significantly reduced volume; at the same time, the air intake channel only requires a small cross-sectional area to meet the control requirements. Thus, during the opening step, the pressure in the upper chamber 118 of the main valve can be quickly released, and the combined valve core moves upward rapidly; during the closing step, the upper chamber 118 of the main valve can be quickly pressurized, and the combined valve core quickly reseated. Experiments show that, on safety valves with a diameter of DN100 and below, the opening and closing pressure difference of the present invention can be controlled to 5%, which is far superior to the prior art.

[0052] In a preferred embodiment of this invention, during the self-tightening sealing step and the reseating closing step, due to S 下阀芯 =S 阀座 The back pressure at the outlet of the safety valve acts on the lower combined valve core 106. The upward thrust and the downward thrust are equal in magnitude and opposite in direction. The net back pressure force is zero, thus preventing the high back pressure from opening the main valve 1 in the reverse direction.

[0053] This embodiment focuses on illustrating the mechanism by which the present invention resists high back pressure. At the outlet end of the safety valve (i.e., at the main valve outlet 115), a high back pressure p may sometimes exist due to factors such as discharge pipeline resistance and back pressure from downstream equipment. 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 106 to the bottom of the lower combined valve core 106, generating an upward thrust F. 上 Second, back pressure enters the upper space of the lower combined valve core 106 through the gap between the main valve core sleeve 103 and the lower combined valve core 106, 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 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 reverse (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 during the self-tightening sealing step (valve closed state) and the reseating closing step (valve re-closed).

[0054] In a preferred embodiment of this invention, during the reseating and closing step, the negative pressure of the vacuum chamber 110 and the total force of the medium work together to make the combined valve core quickly reseated and achieve leak-free closing. By adjusting the volume of the vacuum chamber 110, the vacuum level is changed to match different equivalent reset spring forces, thereby adjusting the opening and closing characteristics of the main valve 1.

[0055] This embodiment further illustrates two important characteristics of the vacuum chamber 110. First, during the reseating and closing step, the negative pressure in the vacuum chamber 110 is always present and directed downwards. When the pilot valve 2 closes and the pressure in the upper chamber 118 of the main valve recovers, the total force of the medium (downwards) and the negative vacuum pressure (downwards) are superimposed, causing the combined valve core to experience a greater downward resultant force than a traditional spring return. Therefore, the reseating speed is faster, the closing impact is smaller, and a leak-free tight seal can be achieved. Second, the volume of the vacuum chamber 110 can be designed. Specifically, by changing the inner diameter of the main valve core sleeve 103, the initial volume of the sealed space can be adjusted. The larger the initial volume, the greater the vacuum degree and the greater the negative pressure when the combined valve core moves upwards to form a vacuum. This is equivalent to designing a stiffness-adjustable "virtual spring". For different operating conditions (such as requiring different closing pressure or reseating pressure characteristics), the volume of the vacuum chamber 110 can be adjusted to match the requirements without replacing the physical spring, greatly improving the design flexibility and adaptability.

[0056] In this embodiment, 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 via 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, and then enters the upper chamber of the main valve through the pilot valve. 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 "They are equal. Therefore, under the effect of the area difference, the total force of the medium is downward. The greater the medium pressure, the greater the sealing force under the effect of the area difference, achieving a self-tightening and reliable seal. When the set pressure is reached and the pressure drops from the set pressure to the discharge pressure, the pilot valve opens, the medium gas in the upper chamber of the main valve is discharged through the pilot valve, the pressure in the upper chamber drops, the total force of the medium in the combined valve core is upward, and it overcomes the spring-like force of the vacuum negative pressure, causing the main valve to open quickly. When it approaches the reseating pressure, the pilot valve closes. The medium gas enters the upper chamber of the main valve through the pilot valve, the pressure in the upper chamber rises rapidly, and under the effect of the area difference, the total force of the medium in the combined valve core is downward, and it is superimposed with the spring-like force of the vacuum negative pressure, causing the main valve to close quickly."

[0057] In this embodiment, see Figure 3 The 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 4 It is a conventional 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. However, the 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."

[0058] 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, characterized in that, It includes a main valve (1), a pilot valve (2) and a connecting pipeline (3) connecting the main valve (1) and the pilot valve (2). The main valve (1) includes a valve body (101), a valve seat (102), a main valve core sleeve (103), a top cover (104) and a combined valve core disposed in the main valve core sleeve (103). The combined valve core includes an upper combined valve core (105), a lower combined valve core (106), and a connecting shaft (107) connecting the two. The upper combined valve core (105) is provided with an upper sealing ring (108) on its outer periphery, and the lower combined valve core (106) is provided with a lower sealing ring (109) on its outer periphery. The upper sealing ring (108) and the lower sealing ring (109) form a sealed space with the inner wall of the main valve core sleeve (103). When the valve seat (102) is installed, it pushes the combined valve core upward, causing the combined valve core to move upward in the sealed space to form a vacuum cavity (110). The negative pressure generated by the vacuum cavity (110) replaces the return spring, making the combined valve core and the valve seat (102) fit tightly together. The sealing diameter of the upper sealing ring (108) is denoted as S. 上阀芯 The sealing diameter of the lower sealing ring (109) 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 .

2. The high back pressure pilot-operated safety valve according to claim 1, characterized in that, The main valve (1) has no physical return spring. The negative pressure generated by the vacuum chamber (110) 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.

3. A high back pressure pilot-operated safety valve according to claim 1, characterized in that, An annular step (111) is provided in the middle of the inner side of the main valve core sleeve (103). When the lower end face of the upper combined valve core (105) is assembled, it is closely attached to the upper end face of the annular step (111). After being tightened by the connecting shaft (107), the upper sealing ring (108), the lower sealing ring (109) 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 (110).

4. A high back pressure pilot-operated safety valve according to claim 1, characterized in that, The bottom of the lower combined valve core (106) is provided with a sealing gasket (112) and a sleeve gasket (113), and the sealing gasket (112) is sealed to the sealing surface of the valve seat (102).

5. A high back pressure pilot-operated safety valve according to claim 1, characterized in that, The valve body (101) is provided with a main valve inlet (114) and a main valve outlet (115). The main valve inlet (114) is provided with a pilot valve inlet (116), which is connected to the pilot valve (2) through the connecting pipe (3). The valve seat (102) is fixed inside the valve body (101). The upper cover (104) is installed on the upper part of the valve body (101), and a gas channel (117) is provided on the upper cover (104). The gas channel (117) is connected to the pilot valve (2) through the connecting pipe (3). The main valve core sleeve (103) is provided inside the valve body (101). The main valve core sleeve (103), the upper cover (104), and the upper combined valve core (105) form a main valve upper chamber (118), which is connected to the gas channel (117).

6. A high back pressure pilot-operated safety valve according to claim 5, characterized in that, The pilot valve (2) is a pilot valve with a set pressure regulation function. 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 upper chamber (118) of the main valve.

7. A method for opening and closing a high back pressure pilot-operated safety valve based on any one of claims 1 to 6, characterized in that, Includes the following steps: Initial closing step: When the valve seat (102) is installed, it pushes the combined valve core upward, causing the combined valve core to move upward in the sealed space, so that the sealed space forms a vacuum chamber (110). The negative pressure generated by the vacuum chamber (110) presses the combined valve core downward onto the valve seat (102), so that the main valve (1) is in the closed state when no medium is flowing through it. Self-tightening sealing step: After the medium is introduced, the medium pressure enters the upper chamber (118) of the main valve through the pilot valve (2) and acts downward on the upper combined valve core (105); at the same time, the medium pressure acts upward on the bottom of the lower combined valve core (106), but due to S 上阀芯 >S 下阀芯 =S 阀座 The total force generated by the medium is downward, and the greater the medium pressure, the greater the sealing force, thus achieving a self-tightening seal; Opening steps: When the inlet pressure reaches the set pressure and changes from the set pressure to the discharge pressure, the pilot valve (2) opens to release pressure, the medium in the upper chamber (118) of the main valve is discharged through the pilot valve (2), the pressure in the upper chamber (118) of the main valve drops, the total force of the medium on the combined valve core is upward and overcomes the vacuum negative pressure, the combined valve core moves upward, and the main valve (1) opens quickly. Reseating and closing procedure: When the inlet pressure drops to the reseating pressure, the pilot valve (2) closes, and the medium enters the upper chamber (118) of the main valve through the pilot valve (2). The pressure in the upper chamber (118) of the main valve rises rapidly due to S 上阀芯 >S 下阀芯 =S 阀座 The total force of the medium is downward and superimposed with the vacuum negative pressure, causing the combined valve core to move downward, making the main valve (1) close quickly.

8. The opening and closing method of a high back pressure pilot-operated safety valve according to claim 7, characterized in that, In the opening step, since there is no return spring in the main valve (1), the cross-sectional area of ​​the air intake channel is small, and the volume of the upper chamber (118) of the main valve is small, the opening and closing pressure difference can be controlled to 5%.

9. The opening and closing method of a high back pressure pilot-operated safety valve according to claim 7, characterized in that, In the self-tightening sealing step and the reseating closing step, due to S 下阀芯 =S 阀座 The back pressure at the outlet of the safety valve acts on the lower combined valve core (106) with an upward thrust and a downward thrust of equal magnitude and opposite direction. The net back pressure force is zero, thereby preventing the high back pressure from opening the main valve (1) in the reverse direction.

10. The opening and closing method of a high back pressure pilot-operated safety valve according to claim 7, characterized in that, In the reseating and closing step, the negative pressure of the vacuum chamber (110) and the total force of the medium work together to make the combined valve core quickly reseated and achieve leak-free closure; By adjusting the volume of the vacuum chamber (110), the vacuum level is changed to match different equivalent reset spring forces, thereby adjusting the opening and closing characteristics of the main valve (1).

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