Safety valve with electrostatic field auxiliary function and control method

Abstract

This invention discloses a safety valve with electrostatic field assistance, belonging to the field of safety valve technology. The safety valve includes a valve body, valve seat, valve disc, valve stem, main spring, recoil disc, valve cap, multi-electrode plate electrostatic field auxiliary setting mechanism, and a control module. The electrostatic field auxiliary setting mechanism includes a first electrode plate located axially above the intermediate electrode plate, a second electrode plate insulated from and connected to the valve stem and moving with the valve stem, and a third electrode plate located axially below the second electrode plate. The control module receives detection signals from a pressure sensor, a temperature sensor, and a valve stem displacement sensor, and controls the high-voltage power supply, high-voltage switching circuit, and active discharge branch based on cold-state calibration parameters, hot-state compensation parameters, preset setting pressure, and preset reseating pressure. The control module uses the preset setting pressure and preset reseating pressure as closed-loop control thresholds to achieve forced assisted opening and forced assisted reseating or closing, thereby improving the control accuracy of the safety valve's opening pressure and reseating pressure.

Description

Technical Field

[0001] This invention relates to the field of safety valve technology, and in particular to a safety valve and control method with electrostatic field auxiliary function, which is applicable to overpressure protection and set pressure auxiliary control of boilers, pressure vessels, steam pipelines and various pressure systems. Background Technology

[0002] A safety valve is an automatic valve that is normally closed under external force. When the pressure of the medium in the equipment or pipeline rises above a specified value, it discharges the medium to the outside of the system to prevent the pressure of the medium in the pipeline or equipment from exceeding the allowable range. Spring-loaded safety valves are widely used in boilers, pressure vessels, storage tanks, and process pipelines due to their mature structure and reliable operation.

[0003] Traditional spring-loaded safety valves typically set the set pressure by adjusting the preload of the main spring, relying on the preload provided by the main spring to ensure the sealing pressure between the valve disc and the valve seat. In practical applications, to adapt to changes in set pressure, reseating pressure, or sealing requirements under different operating conditions, it is often necessary to disassemble the valve cap or adjust the compression nut to change the main spring preload. This operation is cumbersome, and the adjustment accuracy is greatly affected by site conditions and personnel experience.

[0004] For steam safety valves, there is a significant setting deviation between cold-state testing and hot-state operation. The opening pressure and reseating pressure obtained by the safety valve on a normal temperature or low-temperature calibration bench may deviate due to changes in medium temperature, valve body thermal expansion, stiffness changes of the main spring after heating, valve stem thermal elongation, friction state of the sealing pair, and back pressure conditions during hot-state operation. This type of deviation can lead to the opening pressure being higher or lower than the design requirements during field hot-state operation, or unstable reseating pressure and reseating sealing condition.

[0005] Currently, engineering practices typically address hot-cold state deviations through cold-state test correction coefficients, empirical compensation, or repeated on-site verification. However, these methods rely heavily on mechanical preload adjustments and empirical judgment, making it difficult to perform real-time corrections based on medium temperature, actual pressure, and valve displacement during operation. For steam systems requiring frequent changes in operating conditions or high consistency in set pressure, these methods still suffer from long commissioning cycles, insufficient repeatability, and high maintenance costs.

[0006] In existing technologies, some solutions attempt to apply additional axial force to the valve stem using electromagnets or permanent magnets to improve the sealing and opening characteristics of safety valves. However, electromagnetic solutions typically rely on coils, iron cores, and magnetic circuit structures, resulting in large mechanisms, significant heat generation, and potential performance degradation of ferromagnetic materials at high temperatures. Furthermore, continuous energization of the coil leads to power consumption and temperature rise issues, which are detrimental to long-term stable operation.

[0007] During the initial opening of a safety valve, the valve stem and valve disc experience significant acceleration and displacement. If the auxiliary mechanism directly transmits force through rigid contact, it is prone to impact, wear, and fatigue damage during rapid stem movement. Therefore, there is an urgent need for a safety valve structure capable of applying an adjustable additional axial force to the valve stem in a non-contact manner, and capable of actively compensating for opening pressure, reseating pressure, and hot / cold state deviations by combining pressure, temperature, and valve stem displacement signals. Simultaneously, a precise control scheme is needed that uses preset set pressure and preset reseating pressure as control targets, actively applying an additional electric field force when the corresponding pressure threshold is reached, thereby forcibly assisting opening and forcibly assisting reseating or closing. Summary of the Invention

[0008] The technical problem solved by this invention overcomes the shortcomings of the prior art and provides a safety valve and control method with electrostatic field assistance function, so as to achieve precise control of the opening pressure and the reseating pressure.

[0009] The technical solution adopted in this invention is as follows: This invention discloses a safety valve with electrostatic field assistance function, comprising a valve body, valve seat, valve disc, recoil plate, valve stem, main spring, valve cap, electrostatic field assistance setting mechanism, and control module; wherein, The valve seat is connected to the valve body, forming a cavity structure for the medium flow channel; The valve disc mates with the valve seat, and the valve seat, valve disc, recoil disc, and valve stem are sequentially connected axially along the cavity structure. The main spring is mounted on the outside of the valve stem; the valve cap is located at the end of the valve body away from the valve seat; The valve disc opens or closes relative to the valve seat under the combined action of the main spring and the medium pressure. An electrostatic field-assisted setting mechanism includes a first electrode plate, a second electrode plate, a third electrode plate, a high-voltage power supply, and a high-voltage switching circuit; the second electrode plate is insulated from the end of the valve stem, the first electrode plate is electrically insulated from the valve cap, and the third electrode plate is electrically insulated from the valve body; the high-voltage power supply provides power to or de-energizes the first and third electrode plates through the high-voltage switching circuit; The control module, when the valve disc is in a closed, sealed state or in a reseating and falling state, controls the high-pressure switching circuit to supply power to the third electrode plate, forming an electrostatic field between the third electrode plate and the second electrode plate to apply an additional electrostatic attraction to the valve stem towards the valve seat; when the medium pressure reaches a preset set pressure, the control module controls the high-pressure switching circuit to de-energize the third electrode plate and controls the high-pressure switching circuit to supply power to the first electrode plate, establishing an electrostatic field between the first electrode plate and the second electrode plate, and the second electrode plate experiences an electrostatic attraction pointing towards the first electrode plate; when the medium pressure drops to or below the preset reseating pressure, the electrostatic field between the first electrode plate and the second electrode plate is shut off, and the electrostatic field is switched to be formed between the third electrode plate and the second electrode plate to assist the valve disc in reseating.

[0010] Furthermore, in the aforementioned safety valve, the first electrode plate, the second electrode plate, and the third electrode plate are all annular electrode plates, arranged coaxially around the axis of the valve stem; the first electrode plate is connected to the valve cap via an electrode plate position adjusting screw, and its axial position is adjustable; the third electrode plate is connected to the valve body via an insulating support, and its axial position is also adjustable.

[0011] Furthermore, in the aforementioned safety valve, a contact pair with a spherical and conical surface mating is formed between the valve stem and the recoil disc.

[0012] Furthermore, in the aforementioned safety valve, the control module includes a logic control unit, a pressure sensor P1, a temperature sensor T1, a valve stem displacement sensor S1, a cold-state calibration parameter storage unit, and a hot-state compensation calculation unit, wherein... The pressure sensor P1 is used to acquire the cold-state opening pressure and cold-state reseating pressure of the valve stem; The valve stem displacement sensor S1 is disposed in the cavity of the valve cap and is used to detect the axial displacement of the valve stem, the second electrode plate and the valve disc; The temperature sensor T1 is used to detect the temperature of the medium; The thermal compensation calculation unit is used to calculate the target voltage of the first electrode plate and the third electrode plate based on the cold start pressure, the cold reseating pressure, the medium temperature detected by the temperature sensor T1, the preset thermal setting pressure, and the preset thermal reseating pressure, and then send the result to the logic control unit. The cold-state verification parameter storage unit is used to store the cold-state start-up pressure, the cold-state reseating pressure, and the corresponding target voltage. The logic control unit is configured to, when the real-time medium pressure reaches a preset set pressure and the valve stem displacement detected by the valve stem displacement sensor S1 does not reach a preset opening displacement, increase or maintain the target voltage of the first electrode plate to establish an electrostatic field between the first electrode plate and the second electrode plate and form a forced assisted opening; and when the real-time medium pressure decreases to a preset reseating pressure or below and the valve stem displacement does not return to a preset closing displacement, increase or maintain the target voltage of the third electrode plate to establish an electrostatic field between the third electrode plate and the second electrode plate and form a forced assisted reseating or closing.

[0013] Furthermore, in the aforementioned safety valve, the calculation of the target voltages of the first electrode plate and the third electrode plate specifically involves:

[0014]

[0015] Where U is the target voltage, Fc is the required axial compensation force, d is the electrode gap, ΔP is the pressure deviation to be compensated, Av is the effective pressure-bearing area, A is the effective electrode area, and ε is the dielectric constant.

[0016] Furthermore, in the aforementioned safety valve, the high-pressure switching circuit includes an upper electrode switch K1, a lower electrode switch K2, a first high-resistance discharge resistor R1, a second high-resistance discharge resistor R2, a third high-resistance discharge resistor R3, and a control module; wherein, The upper electrode switch K1 is connected between the high voltage output terminal of the high voltage power supply and the first electrode plate; The lower electrode switch K2 is connected between the high voltage output terminal of the high voltage power supply and the third electrode plate; The control module is used to control the lower electrode switch K2 to close and the upper electrode switch K1 to open when the valve disc is in a closed and sealed state or in a repositioned and fallen state, so that an electrostatic attraction is formed between the third electrode plate and the second electrode plate in the direction of the valve disc; when the medium pressure reaches the preset set pressure, it controls the upper electrode switch K1 to close and the lower electrode switch K2 to open, so that an electrostatic attraction is formed between the first electrode plate and the second electrode plate in the direction of the valve cap; the first electrode plate, the second electrode plate and the third electrode plate are respectively connected to the reference terminal or the ground terminal of the high voltage power supply through the first high resistance discharge resistor R1, the second high resistance discharge resistor R2 and the third high resistance discharge resistor R3.

[0017] Furthermore, in the aforementioned safety valve, the high-voltage switching circuit further includes a first active discharge branch Q1 and a second active discharge branch Q2. Both the first active discharge branch Q1 and the second active discharge branch Q2 include a fast discharge switch and a discharge resistor connected in series. The first active discharge branch Q1 is connected in parallel with the first high-resistance discharge resistor R1 to quickly release the residual charge on the first electrode plate when it exits the working state. The second active discharge branch Q2 is connected in parallel with the second high-resistance discharge resistor R3 to quickly release the residual charge on the third electrode plate when it exits the working state.

[0018] Furthermore, in the aforementioned safety valve, the first electrode plate and the second electrode plate are set according to the maximum stroke of the valve stem and the safety margin, so that the electrode plates will not collide during the valve stem's start-up and opening process, and the gap between the third electrode plate and the second electrode plate is smaller than the gap between the first electrode plate and the second electrode plate.

[0019] Furthermore, in the aforementioned safety valve, the initial gap between the first electrode plate and the second electrode plate at the closed position is set to 10~15 mm, with a mechanical safety margin of not less than 2 mm; the initial gap between the third electrode plate and the second electrode plate at the closed position is set to 1~3 mm.

[0020] This invention discloses a control method for a safety valve, characterized by comprising: In the cold-state verification mode, the medium is kept at room temperature, and the cold-state start-up pressure and cold-state reseating pressure without electric field are recorded, as well as the corresponding cold-state start-up pressure and cold-state reseating pressure under different electric field compensation voltages. Establish the correspondence between the electric field compensation voltage and the changes in starting pressure and reseating pressure, form cold-state verification parameters and store them; In hot operation mode, the medium is kept at the working temperature, the medium pressure is detected by pressure sensor P1, and the medium temperature is detected by temperature sensor T1. Based on the cold-state verification parameters, medium temperature, preset hot-state setting pressure, and preset hot-state reseating pressure, calculate the target voltages of the first and third electrode plates used to assist in opening and reseating. In hot operation mode, when the real-time medium pressure is lower than the preset set pressure and the valve stem displacement is 0, it is determined that the valve disc is in a closed and sealed state. The lower electrode switch K2 is closed, so that an electrostatic field is established between the third electrode plate and the second electrode plate, and an additional electrostatic attraction is applied to the valve stem in the direction of the valve disc to increase the sealing specific pressure in the closed and sealed state.

[0021] Furthermore, the above method also includes: In hot operation mode, when the real-time medium pressure reaches the preset set pressure and the valve stem displacement does not reach the preset opening displacement, it is determined to enter the auxiliary opening state, cut off the high-pressure output of the third electrode plate and connect the second active discharge branch Q2 to release the residual charge on the third electrode plate. At the same time or subsequently, the upper electrode switch K1 is controlled to close, so that an electrostatic field is established between the first electrode plate and the second electrode plate, and an additional electrostatic attraction is applied to the valve stem in the direction of the first electrode plate to force auxiliary jumping.

[0022] Furthermore, the above method also includes: In hot operation mode, when the real-time medium pressure drops to or below the preset reseating pressure and the valve stem displacement does not return to the preset closing displacement, it is determined that the valve has entered the reseating and falling state. The high-pressure output of the first electrode plate is cut off and the first active discharge branch Q1 is connected to release the residual charge on the first electrode plate. At the same time or subsequently, the lower electrode switch K2 is closed to establish an electrostatic field between the third electrode plate and the second electrode plate to force the auxiliary valve disc to reseated.

[0023] Furthermore, the above method also includes: In hot operation mode, when the valve stem displacement returns to the preset closing displacement, it is determined that the valve disc has entered the closed sealing state. The control module reduces or maintains the target voltage of the third electrode plate, so that the electrostatic attraction between the third electrode plate and the second electrode plate is maintained in the direction of the valve disc or the auxiliary reseating output is withdrawn.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention utilizes an electrostatic field to apply a non-contact additional axial force to the valve stem, thereby avoiding the impact that the traditional rigid additional mechanism would bear when the valve stem jumps up rapidly; (2) By selectively establishing the field between the upper and lower electrode plates and the middle electrode plate, the present invention can provide a downward auxiliary sealing force in the closed and sealed state, an upward auxiliary jumping force in the auxiliary opening state, and a downward auxiliary recoil force in the recoil and falling state. (3) The present invention uses pressure, temperature and valve stem displacement signals to participate in control, which can compensate for the deviation of set pressure and reseating pressure between cold test and hot operation of steam safety valve; (4) The gap between the upper and lower electrode plates of the present invention can be designed according to the needs of sealing assistance and jumping assistance, which is beneficial to take into account the magnitude of electrostatic force, mechanical safety clearance and power consumption. (5) The present invention uses the spherical and conical surfaces of the backflush disc and the valve stem to make active contact, which improves the valve disc centering and is conducive to further improving the sealing performance and reseating reliability.

[0025] (6) The control module of the present invention can form a closed-loop control based on the pressure threshold and valve stem displacement feedback. When the preset set pressure is reached, the target voltage of the first electrode plate is used to force the opening. When the preset reseating pressure is reached, the target voltage of the third electrode plate is used to force the reseating or closing, thereby improving the control accuracy of the safety valve opening pressure and reseating pressure.

[0026] (7) This invention overcomes the problems of inconvenient fine-tuning of the set pressure, difficulty in online compensation of deviations in hot and cold tests of steam safety valves, the limitation of sealing performance by the characteristics of the main spring, and the complex structure of the electromagnetic auxiliary mechanism in the prior art, and provides a safety valve with electrostatic field auxiliary function. The safety valve adopts a multi-electrode plate electrostatic field auxiliary setting mechanism composed of upper, middle and lower electrode plates, and combines the detection signals such as pressure, temperature and valve stem displacement to realize the controllable adjustment of the direction and magnitude of the additional axial force of the valve stem. Through this structure, the control module can no longer rely solely on the passive response of the main spring, but actively generate an upward electric field force using the target voltage of the first electrode plate when the detected pressure reaches the preset set pressure, and actively generate a downward electric field force using the target voltage of the third electrode plate when the detected pressure drops to the preset reseating pressure, thereby realizing precise control of the opening pressure and reseating pressure. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of the overall structure of a safety valve with electrostatic field assistance function according to the present invention; Figure 2 This is a schematic diagram illustrating the working principle of the multi-electrode plate electrostatic field auxiliary adjustment mechanism of the present invention. Figure 3 This is a schematic diagram showing the connection relationship between the control module, high-voltage switch circuit, sensor assembly, and high-impedance discharge resistor of the present invention.

[0028] In the diagram, 1. Electrode plate position adjusting screw; 2. First electrode plate; 3. Second electrode plate; 4. Third electrode plate; 5. Valve stem; 6. Valve cap; 7. Main spring; 8. Valve body; 9. Backflush disc; 10. Valve disc; 11. Valve seat. Figure 3 In the diagram, P1 is a pressure sensor, T1 is a temperature sensor, S1 is a valve stem displacement sensor, K1 is an upper electrode switch, K2 is a lower electrode switch, R1, R2, and R3 are high-resistance discharge resistors, and Q1 and Q2 are active discharge branches. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments described are for illustrative purposes only and are not intended to limit the scope of protection of the present invention; various equivalent modifications, substitutions, or combinations made by those skilled in the art based on the present invention without departing from its spirit should fall within the scope of protection of the present invention.

[0030] like Figure 1 As shown, this embodiment provides a safety valve with electrostatic field assistance. The safety valve includes a valve body 8, a valve seat 11 mounted on the valve body 8, a valve disc 10 cooperating with the valve seat 11, a back pressure plate 9 positioned above the valve disc 10, a valve stem 5 movably connected to the back pressure plate 9, a main spring 7 fitted around the valve stem 5 and applying preload to the valve stem 5, and a valve cap 6 covering the main spring 7. A medium flow channel is formed inside the valve body 8, and the valve disc 10 opens or closes relative to the valve seat 11 under the combined action of the main spring 7 and the medium pressure.

[0031] The lower end of the valve stem 5 is movably connected to the backflush plate 9. Preferably, the lower end of the valve stem 5 is provided with a spherical contact portion, and the backflush plate 9 is provided with a conical receiving portion that mates with the spherical contact portion; or the lower end of the valve stem 5 is provided with a conical contact portion, and the backflush plate 9 is provided with a spherical receiving portion that mates with it. Through the cooperation of the spherical and conical surfaces, the backflush plate 9 can generate a slight oscillation or self-aligning movement relative to the valve stem 5 during the valve opening and closing process, thereby improving the alignment between the valve disc 10 and the valve seat 11 and avoiding localized unbalanced loading of the sealing surface due to valve stem misalignment, machining errors, or assembly errors.

[0032] An electrostatic field-assisted setting mechanism is arranged in the upper region of the valve stem 5, including a first electrode plate 2, a second electrode plate 3, and a third electrode plate 4. The first electrode plate 2 is the upper electrode plate, located axially above the second electrode plate 3, and electrically insulated and fixed to the valve cap 6 through an insulating support. The second electrode plate 3 is the middle electrode plate, fixedly connected to the valve stem 5 through an insulating sleeve or an insulating connector, and can move up and down synchronously with the valve stem 5. The third electrode plate 4 is the lower electrode plate, located axially below the second electrode plate 3, and electrically insulated and fixed to the valve body 8 or the valve cap 6 through an insulating support. The second electrode plate is insulated from the valve stem and moves with the valve stem.

[0033] The first electrode plate 2, the second electrode plate 3, and the third electrode plate 4 are preferably annular electrode plates and are arranged coaxially around the valve stem 5. When using annular electrode plates, the valve stem 5 can pass through the central area of ​​the electrode plates, and the electrode plates will not hinder the axial movement of the valve stem 5, while also forming a relatively uniform electrostatic field around the valve stem 5. Depending on the structural space and stress requirements, the first electrode plate 2, the second electrode plate 3, and the third electrode plate 4 can also be disc-shaped, segmented annular, or other electrode structures capable of forming axial electrostatic attraction.

[0034] The first electrode plate 2 can be axially adjusted relative to the valve cap 6 via the electrode plate position adjusting screw 1 to change the initial gap between the first electrode plate 2 and the second electrode plate 3. The third electrode plate 4 can also be axially adjusted via an insulating gasket, threaded parts, or a sliding locking part to change the initial gap between the third electrode plate 4 and the second electrode plate 3. By adjusting the gaps between the upper and lower electrodes respectively, the auxiliary jumping force and the auxiliary sealing force can be optimized respectively.

[0035] The control module includes sensor components, a logic control unit, a cold-state calibration parameter storage unit, and a hot-state compensation calculation unit. The sensor components include at least a pressure sensor, and preferably also a temperature sensor and a valve stem displacement sensor. The pressure sensor can be located on the safety valve inlet side, at the valve body pressure testing port upstream of the valve seat inlet, on the protected pressure vessel, or on the inlet pipeline, and is used to detect the medium pressure reflecting the valve opening conditions. The temperature sensor can be located on the safety valve inlet side, in the valve body steam chamber, at the medium temperature measuring point of the protected system, or in the vicinity of the valve cap, and is used to reflect the temperature difference between cold-state calibration and hot-state operation. The valve stem displacement sensor can be located on the upper end of the valve cap or in the vicinity of the valve stem, and is used to detect the axial displacement of the valve stem, the second electrode plate, or the valve disc.

[0036] The high-voltage switching circuit includes an upper electrode switch for controlling the connection of the first electrode plate to the high-voltage output and a lower electrode switch for controlling the connection of the third electrode plate to the high-voltage output. The second electrode plate is connected to the reference terminal of the high-voltage power supply through a high-resistance bleeder resistor or a controlled reference branch to maintain a stable reference potential during operation. The first, second, and third electrode plates can also be connected to the reference terminal or ground terminal of the high-voltage power supply through high-resistance bleeder resistors to achieve residual charge discharge and potential stabilization.

[0037] like Figure 2 As shown, when the valve disc is in the closed and sealed state, the control module controls the lower electrode switch to close and the upper electrode switch to open, so that the high-voltage power supply uses the target voltage of the third electrode plate to establish an electrostatic field between the third electrode plate 4 and the second electrode plate 3. The second electrode plate 3 is subjected to an electrostatic attraction pointing towards the third electrode plate 4. Since the second electrode plate 3 is connected to the valve stem 5, this electrostatic attraction is transmitted to the valve seat 11 through the valve stem 5, the backflush plate 9 and the valve disc 10, which further compresses the valve disc 10, thereby increasing the sealing specific pressure and improving the sealing performance of the safety valve in the low-pressure critical condition and the closed and sealed state.

[0038] When the medium pressure reaches the preset set pressure, the control module controls the third electrode plate 4 to exit the working state and controls the first electrode plate 2 to connect to the high-voltage output, so that an electrostatic field is established between the first electrode plate 2 and the second electrode plate 3. At this time, the second electrode plate 3 is subjected to an electrostatic attraction pointing towards the first electrode plate 2. This electrostatic attraction applies an upward additional load to the valve disc 10 through the valve stem 5, which helps to overcome part of the main spring force, the sealing surface adhesion force and frictional resistance, so that the valve disc 10 can jump more quickly and smoothly.

[0039] When the medium pressure reaches the preset set pressure, the control module controls the lower electrode switch to open and releases the residual charge on the third electrode plate through the second active discharge branch. Simultaneously, it controls the upper electrode switch to close, allowing the high-voltage power supply to establish an electrostatic field between the first and second electrode plates using the target voltage of the first electrode plate. Since the first electrode plate is located above the second electrode plate, the second electrode plate experiences an electrostatic attraction pointing towards the first electrode plate. This attraction, through the valve stem, applies an upward additional load to the valve disc, offsetting part of the main spring force, sealing surface adhesion force, and movement resistance. This improves the safety valve's opening sensitivity, shortens the response time, and enhances repeatability. If the pressure has reached the preset set pressure but the valve stem displacement has not yet reached the preset opening displacement, the control module can maintain or increase the target voltage of the first electrode plate, allowing the upward electrostatic attraction to continue acting until the valve completes its opening. This reduces opening pressure drift caused by friction, thermal deformation, or spring deviation.

[0040] like Figure 3As shown, the high-voltage output terminal of the high-voltage power supply is electrically connected to the first electrode plate 2 and the third electrode plate 4 via the upper electrode switch K1 and the lower electrode switch K2, respectively. The second electrode plate 3 is connected to the reference terminal or ground terminal of the high-voltage power supply via a high-resistance bleeder resistor R2. The first electrode plate 2 and the third electrode plate 4 can also be connected to the reference terminal or ground terminal of the high-voltage power supply via high-resistance bleeder resistors R1 and R3, respectively. The high-resistance bleeder resistors R1, R2, and R3 are used to ensure that each electrode plate has a clear potential fallback path after power failure or switching, preventing the electrode plates from being suspended and improving electrical safety during equipment maintenance and use.

[0041] When the medium pressure drops to or below the preset reseating pressure, the control module opens the upper electrode switch and releases the residual charge on the first electrode plate through the first active discharge branch. Simultaneously, it closes the lower electrode switch, allowing the high-voltage power supply to restore the electrostatic field between the third and second electrode plates using the target voltage of the third electrode plate. At this point, the downward electrostatic attraction and the main spring force together cause the valve disc to reseat and fall, entering a closed sealing state after the valve stem displacement returns to the preset closing displacement. If the pressure has dropped to or below the preset reseating pressure but the valve disc has not yet reseaten, the control module can maintain or increase the target voltage of the third electrode plate, allowing the downward electrostatic attraction to continue acting until the valve stem or valve disc displacement returns to the preset closing position, thereby improving the reseating pressure control accuracy and closing reliability.

[0042] This invention can also be configured with a cold-state verification mode and a hot-state operation mode. In the cold-state verification mode, the control module records the cold-state start-up pressure and cold-state reseating pressure under no electric field, as well as the corresponding cold-state start-up pressure and cold-state reseating pressure under different electric field compensation voltages. It establishes the correspondence between the electric field compensation voltage and the changes in start-up pressure and reseating pressure, forming and storing the cold-state verification parameters. In the hot-state operation mode, the control module calculates the target voltages for the first and third electrode plates used to assist in opening and reseating based on the cold-state verification parameters, the medium temperature, the preset hot-state setting pressure, and the preset hot-state reseating pressure. This causes the safety valve to be assisted in opening by an upward electrostatic attraction near the target hot-state setting pressure and to be assisted in reseating by a downward electrostatic attraction near the target hot-state reseating pressure.

[0043] Through the above method, the present invention can compensate for the set pressure deviation between cold-state testing and hot-state operation using a controllable electric field force. If the actual valve opening pressure is too high under hot conditions, the control module can apply an upward additional load to assist opening by connecting the target voltage of the first electrode plate when the preset hot-state set pressure is reached; if the reseating pressure deviates from the target range, the control module can apply a downward additional load to assist reseating and sealing by connecting the target voltage of the third electrode plate when the preset hot-state reseating pressure is reached. This control process does not require repeated disassembly of the valve cap or mechanical adjustment of the main spring preload. Furthermore, the control module can adjust the target voltage of the first or third electrode plate in stages or continuously according to the magnitude of the pressure deviation, so that the additional electrostatic force matches the pressure deviation, rather than simply performing on / off compensation.

[0044] To ensure rapid response, the high-voltage switching circuit can be equipped with an active discharge branch in addition to the high-resistance discharge resistor. The high-resistance discharge resistor is mainly used for stabilizing the electrode plate potential and for safe discharge after power failure, while the active discharge branch is used to quickly release the residual charge on the electrode plate that has exited the working state during the valve disc opening or reseating switching process, avoiding response delay caused by relying solely on high-resistance discharge.

[0045] The lower end of the valve stem is movably connected to the backflush disc, forming a contact pair with a spherical and conical surface. This structure allows the backflush disc to produce a slight adaptive oscillation relative to the valve stem during valve disc compression, opening, and reseating, thereby compensating for minor valve stem misalignment and machining / assembly errors, improving the alignment of the valve disc and valve seat, reducing off-center wear, and enhancing sealing reliability.

[0046] Figure 3 In this circuit, the control module is electrically connected to the high-voltage power supply and high-voltage switching circuit, and also connected to pressure sensor P1, temperature sensor T1, and valve stem displacement sensor S1. Pressure sensor P1 can be installed on the safety valve inlet side, upstream of the valve body pressure measuring port of valve seat 11, on the protected pressure vessel, or on the inlet pipeline to detect the medium pressure. Temperature sensor T1 can be installed on the safety valve inlet side, in the valve body steam chamber, at the medium temperature measuring point of the protected system, or in the vicinity of valve cap 6 to detect the medium temperature or reflect the thermal state of the valve body. Valve stem displacement sensor S1 can be installed on the upper end of valve cap 6, in the vicinity of valve stem 5, or in the vicinity of the second electrode plate 3 to detect the axial displacement of valve stem 5, second electrode plate 3, or valve disc 10. Inductive, magnetostrictive, Hall effect, photoelectric, capacitive displacement sensors or limit switches can be used.

[0047] The valve stem displacement sensor S1 can be installed through the mounting hole on the upper end of the valve cap, an insulating bracket, or a sealing sleeve, so that its detection end is positioned opposite the valve stem, the second electrode plate, or the valve disc connector, thereby obtaining the axial displacement signal of the valve stem. The sensor can output detection signals to the control module via analog, digital, or digital communication methods.

[0048] The valve stem displacement sensor S1 can be an inductive displacement sensor, a magnetostrictive displacement sensor, a Hall effect displacement sensor, a photoelectric displacement sensor, a capacitive displacement sensor, or a limit switch. The control module determines whether the safety valve has opened, reached the preset opening height, and completed reseating based on the valve stem displacement signal. It also determines the timing of high-pressure connection, holding, reduction, or disconnection of the first electrode plate 2 and the third electrode plate 4 by combining the pressure and temperature detection signals. When the real-time pressure has reached the preset set pressure but the valve stem displacement has not yet reached the preset opening displacement, the control module determines that forced auxiliary opening is required. When the real-time pressure has decreased to or below the preset reseating pressure but the valve stem displacement has not yet returned to the preset closing displacement, the control module determines that forced auxiliary reseating or closing is required.

[0049] It should be noted that the high-impedance discharge resistors R1, R2, and R3 primarily serve the functions of potential stabilization and safe discharge, and are not the sole channel for rapid switching. For safety valve opening and closing processes requiring millisecond or tens of millisecond response times, the high-voltage switching circuit can also be configured with active discharge branches Q1 and Q2. When a certain electrode plate exits the working state, the control module can first disconnect the corresponding high-voltage switch, then connect the corresponding active discharge branch, allowing the residual charge on that electrode plate to be quickly released through the discharge resistor, and then connect the high-voltage channel of the other electrode plate.

[0050] The control module can have a cold-state calibration mode. In cold-state calibration mode, the safety valve is installed on a cold-state calibration bench or in a normal-temperature test system. The control module records the cold-state tripping pressure and cold-state reseating pressure under no electric field, as well as the corresponding cold-state tripping pressure and cold-state reseating pressure under different electric field compensation voltages. It establishes a correspondence between the electric field compensation voltage and the changes in tripping pressure and reseating pressure, forming and storing cold-state calibration parameters. This correspondence is used in hot-state operation mode to determine the target voltage based on the required pressure deviation to be compensated.

[0051] The control module can also have a hot-state operation mode. In hot-state operation mode, the control module calls the cold-state calibration parameters and the pre-set hot-state compensation rules based on the medium temperature or valve body temperature detected by the temperature sensor T1, and calculates the target voltages of the first electrode plate 2 and the third electrode plate 4 for assisting opening and assisting reseating based on the preset hot-state set pressure and preset hot-state reseating pressure. Thus, when the steam safety valve is operating in hot state, the control module can use upward electrostatic attraction to make the valve open near the preset hot-state set pressure, and use downward electrostatic attraction to make the valve reseating near the preset hot-state reseating pressure.

[0052] The target voltage can be determined using cold calibration tables, interpolation algorithms, empirical functions, or closed-loop control algorithms, or it can be determined using theoretical estimation methods.

[0053] One approach is the calibration mapping method: During cold-state calibration, the cold-state tripping pressure and cold-state reseating pressure under different electric field compensation voltages are recorded to establish a correspondence between the electric field compensation voltage and the changes in tripping pressure and reseating pressure. During hot-state operation, the target voltage is obtained by looking up a table or interpolating based on the pressure deviation to be compensated.

[0054] Another method is theoretical estimation: Calculate the required axial compensation force Fc based on the pressure deviation ΔP and effective pressure-bearing area Av to be compensated; then calculate the target voltage U based on the electrode plate gap d, effective electrode area A, and dielectric constant ε.

[0055]

[0056] Where Fe is the electrostatic additional force, Fc is the required axial compensation force, ε is the dielectric constant, A is the effective electrode area, U is the inter-electrode voltage, d is the electrode gap, ΔP is the pressure deviation to be compensated, and Av is the effective pressure-bearing area. If the pressure deviation to be compensated is ΔP, then the required axial compensation force Fc is:

[0057] Then, the target voltage U is calculated as follows:

[0058] When operating normally and the real-time medium pressure is lower than the preset set pressure and the valve stem displacement is close to 0, the logic control unit determines that the valve disc 10 is in a closed and sealed state, and controls the lower electrode switch K2 to close and the upper electrode switch K1 to open, so that the third electrode plate 4 is connected to the high-pressure output, and an electrostatic field is formed between the third electrode plate 4 and the second electrode plate 3. The second electrode plate 3 is subjected to a downward electrostatic attraction, which further increases the sealing pressure between the valve disc 10 and the valve seat 11 on the basis of the preload of the main spring 7.

[0059] When the real-time medium pressure reaches the preset set pressure and the valve stem displacement does not reach the preset opening displacement, the logic control unit determines that it has entered the auxiliary opening state, controls the lower electrode switch K2 to open, and connects the second active discharge branch Q2 as needed to quickly release the residual charge on the third electrode plate 4; subsequently or simultaneously controls the upper electrode switch K1 to close, so that the first electrode plate 2 is connected to the high-voltage output. After an electrostatic field is formed between the first electrode plate 2 and the second electrode plate 3, the second electrode plate 3 is subjected to an upward electrostatic attraction, thereby making it easier for the valve stem 5 and the valve disc 10 to open. During the forced auxiliary opening process, the logic control unit can maintain or increase the target voltage of the first electrode plate 2, and reduce or cut off the high-voltage output when the preset opening displacement is reached, the pressure drops to a safe range, or the duration reaches the preset upper limit.

[0060] When the real-time medium pressure drops to or below the preset reseating pressure and the valve stem displacement does not return to the preset closing displacement, the logic control unit determines that it has entered the reseating and falling state, controls the upper electrode switch K1 to open, and connects the first active discharge branch Q1 as needed to quickly release the residual charge on the first electrode plate 2; then, or simultaneously controls the lower electrode switch K2 to close, so that the downward electrostatic attraction between the third electrode plate 4 and the second electrode plate 3 is restored, forcing the auxiliary valve disc 10 to reseated. When the valve stem displacement returns to the preset closing displacement, the logic control unit determines that the valve disc 10 has entered the closed sealing state, and the control module reduces or maintains the target voltage of the third electrode plate 4, so that the downward electrostatic attraction between the third electrode plate 4 and the second electrode plate 3 is maintained or the auxiliary reseating output is withdrawn.

[0061] In this embodiment, the gap between the first electrode plate 2 and the second electrode plate 3 can be set according to the maximum stroke and safety margin of the valve stem 5, so that the electrode plates will not collide during valve opening and closing. The gap between the third electrode plate 4 and the second electrode plate 3 can be designed to be relatively small to obtain sufficient downward sealing assistance force at lower voltages. Thus, the upper electrode gap and the lower electrode gap can be optimized for auxiliary opening and auxiliary sealing, respectively, avoiding design contradictions when a single electrode gap simultaneously considers multiple operating conditions.

[0062] As an optional implementation, the initial gap between the first electrode plate 2 and the second electrode plate 3 in the closed position can be set to 10 mm to 15 mm, with a mechanical safety margin of not less than 2 mm; the initial gap between the third electrode plate 4 and the second electrode plate 3 in the closed position can be set to 1 mm to 3 mm. The output voltage of the high-voltage power supply can be determined according to the electrode plate area, the electrode plate gap, and the required electrostatic force; for example, an adjustable DC high-voltage output in the range of 5 kV to 35 kV can be used.

[0063] As an example, in a spring-loaded steam safety valve with a nominal diameter of DN20 and a set pressure of approximately 0.10 MPa, if the preload of the main spring 7 is approximately 150 N and the effective area of ​​the electrode plate is 80 cm² to 150 cm², by reasonably designing the gap between the third electrode plate 4 and the second electrode plate 3 and the output voltage of the high-voltage power supply, a downward electrostatic attraction of several Newtons to more than ten Newtons can be obtained to improve the sealing pressure between the valve disc 10 and the valve seat 11. During the opening phase, by establishing an electrostatic field between the first electrode plate 2 and the second electrode plate 3, an upward additional load can be applied to the valve stem 5, reducing the total downward force that the valve stem 5 actually needs to overcome.

[0064] For steam safety valves exhibiting cold / hot test deviations, if the opening pressure obtained from cold-state calibration deviates from the preset hot-state setting pressure, the control module can correct the actual opening pressure by increasing or decreasing the target voltage of the first electrode plate 2. Similarly, if the cold-state reseating pressure deviates from the preset hot-state reseating pressure, the control module can correct the actual reseating pressure by adjusting the target voltage of the third electrode plate 4. This reduces the number of times the main spring preload needs repeated mechanical adjustment on-site, improving the consistency of the conversion from cold-state calibration results to hot-state operation results. For applications requiring higher pressure control accuracy, the control module can also set the preset setting pressure and preset reseating pressure as closed-loop control targets, and use pressure and displacement signals to jointly verify the valve's operating status, ensuring that the safety valve opens promptly upon reaching the set pressure and closes promptly upon reaching the reseating pressure, reducing operating errors caused by cold / hot state deviations, friction changes, or spring performance drift.

[0065] This invention is not limited to the specific embodiments described above. The shape, size, material, insulation support method, and installation position of the first electrode plate 2, the second electrode plate 3, and the third electrode plate 4 can all be adjusted according to the structural dimensions, working pressure, medium temperature, and actuation stroke of the safety valve; the high-voltage power supply can be a single-channel adjustable DC high-voltage power supply or a multi-channel isolated high-voltage power supply; the control module can simultaneously receive pressure, temperature, valve stem displacement, valve opening, outlet back pressure, or medium flow signals to achieve more precise action control. As long as the upper and lower fixed electrode plates and the intermediate electrode plate that moves with the valve stem are used to selectively establish a field, and the additional electrostatic force is adjusted in conjunction with the control module to achieve closing sealing, assisted start-up, assisted reseating, or cold and hot pressure deviation compensation, all fall within the protection scope of this invention.

Claims

1. A safety valve with electrostatic field assistance function, characterized in that, It includes a valve body (8), a valve seat (11), a valve disc (10), a backflush plate (9), a valve stem (5), a main spring (7), a valve cap (6), an electrostatic field auxiliary setting mechanism, and a control module; among which, The valve seat (11) is connected to the valve body (8) to form a medium flow channel with a cavity structure; The valve disc (10) and the valve seat (11) are matched, and the valve seat (11), valve disc (10), backflush disc (9) and valve stem (5) are connected in sequence along the axial direction of the cavity structure; The main spring (7) is fitted on the outside of the valve stem (5); the valve cap (6) is placed on the end of the valve body (8) away from the valve seat (11); The valve disc (10) opens or closes relative to the valve seat (11) under the combined action of the main spring (7) and the medium pressure; The electrostatic field-assisted setting mechanism includes a first electrode plate (2), a second electrode plate (3), a third electrode plate (4), a high-voltage power supply, and a high-voltage switching circuit; the second electrode plate (3) is insulated from the end of the valve stem (5), the first electrode plate (2) is electrically insulated from the valve cap (6), and the third electrode plate (4) is electrically insulated from the valve body (8); the high-voltage power supply provides power to the first electrode plate (2) and the third electrode plate (4) or cuts off power through the high-voltage switching circuit; When the valve disc (10) is in a closed and sealed state or in a reseating and falling state, the control module controls the high-pressure switch circuit to supply power to the third electrode plate (4), and an electrostatic field is formed between the third electrode plate (4) and the second electrode plate (3) to apply an additional electrostatic attraction to the valve stem (5) in the direction of the valve seat (11); when the medium pressure reaches the preset set pressure, the control module controls the high-pressure switch circuit to de-energize the third electrode plate (4) and controls the high-pressure switch circuit to supply power to the first electrode plate (2), and an electrostatic field is established between the first electrode plate (2) and the second electrode plate (3), and the second electrode plate (3) is subjected to an electrostatic attraction pointing towards the first electrode plate (2); when the medium pressure drops to the preset reseating pressure or below, the electrostatic field between the first electrode plate (2) and the second electrode plate (3) is closed, and the electrostatic field is switched to be formed between the third electrode plate (4) and the second electrode plate (3) to assist the valve disc (10) in reseating.

2. The safety valve according to claim 1, characterized in that, The first electrode plate (2), the second electrode plate (3) and the third electrode plate (4) are all annular electrode plates, arranged coaxially around the axis of the valve stem (5); the first electrode plate (2) is connected to the valve cap (6) through the electrode plate position adjustment screw (1), and its axial position is adjustable; the third electrode plate (4) is connected to the valve body (8) through an insulating support, and its axial position is adjusted.

3. The safety valve according to claim 1, characterized in that, The valve stem (5) and the backflush disc (9) form a contact pair with a spherical and a conical surface.

4. The safety valve according to claim 1, characterized in that, The control module includes a logic control unit, a pressure sensor P1, a temperature sensor T1, a valve stem displacement sensor S1, a cold-state calibration parameter storage unit, and a hot-state compensation calculation unit, wherein... The pressure sensor P1 is used to obtain the cold start pressure and cold reseating pressure of the valve stem (5); The valve stem displacement sensor S1 is installed in the cavity of the valve cap (6) and is used to detect the axial displacement of the valve stem (5), the second electrode plate (3) and the valve disc (10). The temperature sensor T1 is used to detect the temperature of the medium; The thermal compensation calculation unit is used to calculate the target voltage of the first electrode plate (2) and the third electrode plate (4) based on the cold start pressure, the cold reseating pressure, the medium temperature detected by the temperature sensor T1, the preset thermal setting pressure and the preset thermal reseating pressure, and send it to the logic control unit. The cold-state verification parameter storage unit is used to store the cold-state start-up pressure, the cold-state reseating pressure, and the corresponding target voltage. The logic control unit is used to increase or maintain the target voltage of the first electrode plate (2) when the real-time medium pressure reaches the preset set pressure and the valve stem displacement detected by the valve stem displacement sensor S1 does not reach the preset opening displacement, so as to establish an electrostatic field between the first electrode plate (2) and the second electrode plate (3) and form a forced assisted opening; when the real-time medium pressure drops to the preset reseating pressure and the valve stem displacement does not return to the preset closing displacement, it increases or maintains the target voltage of the third electrode plate (4) so ​​as to establish an electrostatic field between the third electrode plate (4) and the second electrode plate (3) and form a forced assisted reseating or closing.

5. The safety valve according to claim 4, characterized in that, The calculation of the target voltage of the first electrode plate (2) and the third electrode plate (4) is specifically as follows: Where U is the target voltage, Fc is the required axial compensation force, d is the electrode gap, ΔP is the pressure deviation to be compensated, Av is the effective pressure-bearing area, A is the effective electrode area, and ε is the dielectric constant.

6. The safety valve according to any one of claims 1, characterized in that, The high-voltage switching circuit includes an upper electrode switch K1, a lower electrode switch K2, a first high-resistance discharge resistor R1, a second high-resistance discharge resistor R2, a third high-resistance discharge resistor R3, and a control module; wherein, The upper electrode switch K1 is connected between the high voltage output terminal of the high voltage power supply and the first electrode plate (2); The lower electrode switch K2 is connected between the high voltage output terminal of the high voltage power supply and the third electrode plate (4); The control module is used to control the lower electrode switch K2 to close and the upper electrode switch K1 to open when the valve disc (10) is in a closed and sealed state or in a seated and fallen state, so that an electrostatic attraction is formed between the third electrode plate (4) and the second electrode plate (3) in the direction of the valve disc (10); when the medium pressure reaches the preset set pressure, the upper electrode switch K1 to close and the lower electrode switch K2 to open, so that an electrostatic attraction is formed between the first electrode plate (2) and the second electrode plate (3) in the direction of the valve cap (6); the first electrode plate (2), the second electrode plate (3) and the third electrode plate (4) are respectively connected to the reference terminal or ground terminal of the high voltage power supply through the first high resistance discharge resistor R1, the second high resistance discharge resistor R2 and the third high resistance discharge resistor R3.

7. The safety valve according to claim 6, characterized in that, The high-voltage switching circuit further includes a first active discharge branch Q1 and a second active discharge branch Q2. Both the first active discharge branch Q1 and the second active discharge branch Q2 include a fast discharge switch and a discharge resistor connected in series. The first active discharge branch Q1 is connected in parallel with the first high-resistance discharge resistor R1 to quickly release the residual charge on the first electrode plate (2) when it exits the working state. The second active discharge branch Q2 is connected in parallel with the second high-resistance discharge resistor R3 to quickly release the residual charge on the third electrode plate (4) when it exits the working state.

8. The safety valve according to claim 1, characterized in that, The first electrode plate (2) and the second electrode plate (3) are set according to the maximum stroke and safety margin of the valve stem (5) so that the electrode plates will not collide during the valve stem (5) jump and open. The gap between the third electrode plate (4) and the second electrode plate (3) is smaller than the gap between the first electrode plate (2) and the second electrode plate (3).

9. The safety valve according to claim 8, characterized in that, The initial gap between the first electrode plate (2) and the second electrode plate (3) at the closed position is set to 10~15 mm, with a mechanical safety margin of not less than 2 mm; the initial gap between the third electrode plate (4) and the second electrode plate (3) at the closed position is set to 1~3 mm.

10. A control method for the safety valve according to any one of claims 1 to 9, characterized in that, include: In the cold-state verification mode, the medium is kept at room temperature, and the cold-state start-up pressure and cold-state reseating pressure without electric field are recorded, as well as the corresponding cold-state start-up pressure and cold-state reseating pressure under different electric field compensation voltages. Establish the correspondence between the electric field compensation voltage and the changes in starting pressure and reseating pressure, form cold-state verification parameters and store them; In hot operation mode, the medium is kept at the working temperature, the medium pressure is detected by pressure sensor P1, and the medium temperature is detected by temperature sensor T1. Based on the cold-state verification parameters, medium temperature, preset hot-state setting pressure and preset hot-state reseating pressure, calculate the target voltages of the first electrode plate (2) and the third electrode plate (4) used for assisting opening and assisting reseating; In the hot operation mode, when the real-time medium pressure is lower than the preset set pressure and the valve stem displacement is 0, it is determined that the valve disc (10) is in the closed sealing state. The lower electrode switch K2 is controlled to close, so that an electrostatic field is established between the third electrode plate (4) and the second electrode plate (3), and an additional electrostatic attraction is applied to the valve stem (5) in the direction of the valve disc (10) to increase the sealing pressure in the closed sealing state.

11. The method according to claim 10, characterized in that, Also includes: In the hot operation mode, when the real-time medium pressure reaches the preset set pressure and the valve stem (5) displacement does not reach the preset opening displacement, it is determined to enter the auxiliary opening state, cut off the high pressure output of the third electrode plate (4) and connect the second active discharge branch Q2 to release the residual charge on the third electrode plate (4), and at the same time or subsequently control the upper electrode switch K1 to close, so that an electrostatic field is established between the first electrode plate (2) and the second electrode plate (3), and an additional electrostatic attraction force is applied to the valve stem (5) in the direction of the first electrode plate (2) to force auxiliary jumping.

12. The method according to claim 10, characterized in that, Also includes: In the hot operation mode, when the real-time medium pressure drops to the preset reseating pressure and below and the valve stem (5) displacement does not return to the preset closing displacement, it is determined to enter the reseating and falling state, cut off the high-pressure output of the first electrode plate (2) and connect the first active discharge branch Q1 to release the residual charge on the first electrode plate (2), and at the same time or subsequently control the lower electrode switch K2 to close, so that an electrostatic field is established between the third electrode plate (4) and the second electrode plate (3) to force the auxiliary valve disc (10) to reseated.

13. The method according to claim 10, characterized in that, Also includes: In the hot operation mode, when the valve stem (5) returns to the preset closing position, it is determined that the valve disc (10) has entered the closed sealing state. The control module reduces or maintains the target voltage of the third electrode plate (4) so ​​that the third electrode plate (4) and the second electrode plate (3) maintain electrostatic attraction towards the valve disc (10) or exit the auxiliary reseating output.

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