System and method for detecting parking sealing position of main pump and sensor used by system and method

Abstract

The invention discloses a detection system and method for a parking sealing position of a main pump and a sensor used by the detection system and method, and relates to the field of detection of the parking sealing position of the main pump, the detection system comprises two eddy current sensors fixedly connected with a piston and a controller; the two eddy current sensors are both located between the pump coupler and a sealing chamber of the parking seal, one of the two eddy current sensors serves as a magnetic sensor, a probe of the magnetic sensor faces the lower surface of the pump coupler, and the distance between the probe and the lower surface can be obtained in a non-contact mode; one of the two eddy current sensors serves as a non-magnetic sensor, a probe installed on the non-magnetic sensor faces the upper surface of the sealed chamber, and the distance between the probe and the upper surface can be obtained in a non-contact mode; and the two eddy current sensors are connected with the input end of the controller. By means of the eddy current sensor, the position information of the parking seal can be continuously obtained in real time, the opening / closing state of the parking seal is accurately expressed, and prerequisite condition information is provided for starting and stopping of the main pump.

Description

Technical Field

[0001] This invention relates to the field of main pump shutdown seal position detection, and in particular to a main pump shutdown seal position detection system, method, and sensor used therein. Background Technology

[0002] The main pump is used to drive the circulation of coolant in the reactor to remove the heat generated by the fission reaction. The main pump is typically vertical, consisting of a motor, shaft seal, and hydraulic unit from top to bottom. The shaft seal is a combined sealing component that isolates the hydraulic unit and motor, secured to a heat-shielded flange by bolts and nuts. It includes a three-stage dynamic pressure seal and a shutdown seal. The shutdown seal is an emergency seal used to ensure no leakage in the main pump under accident conditions where all three stages of the shaft seal system fail. It is activated by injecting nitrogen when the main pump stops, causing the piston of the shutdown seal to move along the main shaft to the pump coupling sleeve, thus activating the shutdown seal. At this time, the shutdown seal is in the closed position. After the emergency is resolved, the shutdown seal needs to be returned to its inactive state, i.e., it needs to be in the open position. This is achieved by releasing the nitrogen to depressurize, causing the piston to move along the main shaft to the shutdown seal housing.

[0003] Throughout this entire process, it is necessary to obtain the position of the shutdown seal. Currently, a proximity switch is typically installed at the closed or open position to determine whether the shutdown seal has reached the closed or open position. For example, the reactor coolant pump shutdown seal device disclosed in Chinese Patent No. CN103267030B uses a control rod that functions as a proximity switch. Similarly, a 300MW reactor coolant pump measurement system disclosed in Chinese Patent No. CN103306967A describes a position sensor that also functions as a proximity switch. However, using proximity switches presents an inherent technical problem in this industry: the proximity switch can only be triggered after the shutdown seal is in position and cannot determine whether the shutdown seal has moved towards the closed or open position. In other words, if the shutdown seal cannot move due to a malfunction, the operator will not receive a signal from the proximity switch, potentially delaying emergency response time due to waiting for a signal.

[0004] Therefore, the industry needs a new detection system that can acquire the parking seal position in real time and continuously. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems by providing a detection system, method, and sensor for the main pump shutdown seal position. Utilizing an eddy current sensor, the system can acquire the shutdown seal position information in real time and continuously, accurately indicating the open / closed state of the shutdown seal, and providing prerequisite information for the main pump start-up and shutdown.

[0006] The technical solution adopted in this invention is as follows: A detection system for the main pump shutdown seal position includes two eddy current sensors fixedly connected to the piston and a controller; both eddy current sensors are located between the pump coupling and the sealing chamber of the shutdown seal; one of the two eddy current sensors is a magnetic sensor, with its probe facing the lower surface of the pump coupling, enabling non-contact acquisition of the distance between the probe and the lower surface; another of the two eddy current sensors is a non-magnetic sensor, with its probe facing the upper surface of the sealing chamber, enabling non-contact acquisition of the distance between the probe and the upper surface; both eddy current sensors are connected to the input terminal of the controller.

[0007] Furthermore, the probes of the two eddy current sensors are mounted on the bracket assembly, which is fixedly connected to the upper surface of the piston via a connector passing through the upper surface of the sealing chamber; the connector is fixedly connected to the bracket assembly.

[0008] Furthermore, the connector is a screw, and the connector is threadedly connected to the bracket assembly; a bracket pad is provided between the bracket assembly and the upper surface, and the screw passes through the bracket assembly, the bracket pad, and the upper surface before connecting to the piston.

[0009] Furthermore, the support pad is an elastic pad.

[0010] Furthermore, the bracket assembly includes a bracket base and a mounting base slidably connected to the bracket base; the probe is mounted on the top of the mounting base; the bracket base is connected to a support rod; an adjusting nut is rotatably connected to the bottom of the mounting base, the adjusting nut is threadedly connected to the bracket base, and the axis of the adjusting nut is parallel to the direction of the sliding stroke of the mounting base on the bracket base.

[0011] A method for detecting the main pump shutdown seal position, using the aforementioned main pump shutdown seal position detection system, includes the following steps: The piston moves synchronously with the two installed eddy current sensors. The distance from the probe of the magnetic sensor to the lower surface and the distance from the probe of the non-magnetic sensor to the upper surface changes continuously. The two eddy current sensors continuously generate changing electrical signals. The controller acquires the electrical signals and uses them to determine the distance from the probe to the lower surface and the distance from the probe of the non-magnetic sensor to the upper surface in real time, thereby determining the open / closed state of the parking seal. If the distance from the magnetic sensor probe to the lower surface is within the set range, then the parking seal is determined to be in the closed position. If the distance from the non-magnetic sensor probe to the upper surface is within the set range, then the parking seal is determined to be in the open position.

[0012] Furthermore, the installation of the two eddy current sensors includes the following steps S1-S2, which have no specific order requirement; S1: Install the magnetic sensor; including steps S11-S13; S11: Nitrogen gas is introduced into the sealing chamber. Under the pressure of nitrogen gas, the piston moves the main shaft to the position of the pump coupling sleeve until the stop seal reaches the closed position. S12: Install the magnetic sensor on the bracket assembly and, with the appropriate bracket pad, connect the bracket assembly to the piston so that the distance between the probe and the lower surface is less than the adjustment range of the adjusting nut; S13: Rotate the adjusting nut. The adjusting nut moves the mounting base and thus the probe, adjusting the distance between the probe and the lower surface to be within the set range; thus completing the installation of the magnetic sensor. S2: Install the non-magnetic sensor; including steps S21-S23; S11: Release the nitrogen gas in the sealing chamber, and the piston moves with the main shaft to the position of the sealing chamber until the stop seal reaches the open position; S22: Install the magnetic sensor on the bracket assembly and connect the bracket assembly to the piston with a suitable bracket pad so that the distance between the probe and the upper surface is less than the adjustment range of the adjusting nut. S23: Rotate the adjusting nut. The adjusting nut moves the mounting base and thus the probe, adjusting the distance between the probe and the upper surface to be within the set range; thus completing the installation of the non-magnetic sensor.

[0013] A sensor for obtaining the main pump shutdown sealing position, applied to a detection system for the main pump shutdown sealing position, includes a probe, a preamplifier for connection to a controller, and a cable connecting the probe and the preamplifier; the probe has a protective cover made of nickel-chromium-iron alloy, and from the bottom to the opening of the protective cover, a first insulating layer, a measuring coil, a second insulating layer, a metal partition, a third insulating layer, a compensation coil, a fourth insulating layer, a metal pressure plate, and a threaded connection for mounting to a bracket assembly are arranged sequentially; wherein: The connecting threaded part is fixedly connected to the protective cover to close the cover opening, and pressure is applied to the metal pressure plate to make the adjacent parts between the cover bottom and the cover opening fit together; the measuring coil and the compensation coil are both wound on the insulating column, and the measuring coil and the compensation coil are both led out from the connecting threaded part as cables after passing through the column wall of the insulating column. The metal pressure plate and the cover bottom, the fourth insulating layer and the first insulating layer, and the third insulating layer and the second insulating layer have the same thickness.

[0014] Furthermore, the cables connected to the same coil in the cable are twisted in pairs; cables connecting different coils are isolated by a shielding layer; all cables are wrapped with an external insulation layer; and the cable is covered with a stainless steel corrugated tube.

[0015] Furthermore, the preamplifier includes a protective housing, which encapsulates a power supply unit, a sensing and measurement unit, a signal processing unit, and a current output unit; wherein: The power supply unit is used for external power supply, and its output terminal is connected to the sensing and measurement unit, the signal processing unit, and the current output unit. The sensing and measurement unit is connected to the measuring coil and the compensation coil via cables, and is also connected to the input terminal of the signal processing unit; The output of the signal processing unit is connected to the current output unit.

[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: This invention uses two eddy current sensors fixedly connected to a piston. The piston's movement causes the two eddy current sensors to move synchronously, allowing for real-time acquisition of the distances between the eddy current sensors and the lower surface of the pump coupling and the upper surface of the sealing chamber. This provides a direct and accurate understanding of the specific position of the parking seal, offering operators precise control instructions and preventing accidental wear on the parking seal system. Furthermore, changes in the acquired distance information can determine whether the parking seal is in a normal state. Attached Figure Description

[0017] The present invention will be described by way of example and with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the installation position of the eddy current sensor disclosed in this invention; Figure 2 A schematic diagram illustrating the detection of the parking seal being in the closed position; Figure 3 A schematic diagram for detecting when the parking seal is in the open position; Figure 4 This is a schematic diagram of the probe's structure; Figure 5 This is a structural schematic diagram of the support assembly; Figure 6 This is a schematic diagram of the connecting cable structure; Figure 7 This is a schematic diagram of the extension cable structure; Figure 8 This is a schematic diagram of the structure of an eddy current sensor and a schematic diagram of its connection with a controller. The diagram shows the following markings: 10-Probe; 101-Protective cover; 102-First insulation layer; 103-Measuring coil; 104-Second insulation layer; 105-Metal partition; 106-Third insulation layer; 107-Compensation coil; 108-Fourth insulation layer; 109-Metal pressure plate; 110-Insulating column; 111-Connecting threaded part; 11-Magnetic sensor; 12-Non-magnetic sensor; 13-Connecting cable; 14-Stainless steel corrugated pipe; 15-Male and female connectors; 16-Extension cable; 17-Preamplifier; 171-Power supply unit; 172-Sensing and measuring unit; 173-Signal processing unit; 174-Current output unit; 2-Pump coupling; 21-Lower surface; 3-Sealing chamber; 31-Upper surface; 4-Piston; 5-Bracket assembly; 51-Bracket base; 52-Mounting base; 53-Adjusting nut; 54-Connector; 55-Bracket pad; 6-Controller. Detailed Implementation

[0018] In the description of this specification, it should be noted that if terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," or "outer" appear to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use, they are only for the convenience of describing this specification and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this specification.

[0019] Furthermore, the use of terms such as "horizontal" or "vertical" in this specification does not imply that the component must be absolutely horizontal or suspended, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0020] In the description of this specification, it should also be noted that, unless otherwise expressly specified and limited, the terms “set up,” “install,” “connect,” and “link” should be interpreted broadly. For example, a link can be a fixed link, a detachable link, or an integral link; it can be a mechanical link or an electrical link; it can be a direct link or an indirect link through an intermediate medium; it can be a connection within two components.

[0021] Example 1 like Figures 1-8As shown, a detection system for the main pump shutdown seal position includes two eddy current sensors fixedly connected to the piston 4 and a controller 6. Both eddy current sensors are located between the pump coupling 2 and the shutdown seal chamber 3. One of the two eddy current sensors is a magnetic sensor 11, with its probe 10 facing the lower surface 21 of the pump coupling 2, enabling non-contact acquisition of the distance between the probe 10 and the lower surface 21. Another eddy current sensor is a non-magnetic sensor 12, with its probe 10 facing the upper surface 31 of the seal chamber 3, also enabling non-contact acquisition of the distance between the probe 10 and the upper surface 31. Both eddy current sensors are connected to the input terminal of the controller 6.

[0022] In this embodiment, although the lower surface 21 of the pump coupling 2 is made of carbon steel, which is a magnetic material, and the upper surface 31 of the sealing chamber 3 is made of stainless steel, which is a non-magnetic material, both surfaces are metal. Therefore, the eddy current sensors can obtain the distances from the probe 10 to the lower surface 21 and from the probe 10 to the upper surface 31 through the eddy current effect. Furthermore, since both eddy current sensors are fixedly connected to the piston 4, in the industry context where the upper surface 31 and the lower surface 21 are stationary surfaces, the movement of the piston 4 causes the eddy current sensors to move synchronously, thereby obtaining the distances from the eddy current sensors to the lower surface 21 of the pump coupling 2 and the upper surface 31 of the sealing chamber 3 in real time. The distance between the piston and the gas chamber 3 is used to determine the direction of piston 4's movement and its real-time position. This allows for a direct and accurate understanding of the specific position of the gas chamber 3, providing operators with precise control instructions. With the assistance of the real-time position of the gas chamber 3, operators can precisely control the position of the gas chamber 3 by controlling the amount of nitrogen injected and released, thus preventing accidental wear of the gas chamber 3. Furthermore, the change in the distance information can be used to determine whether the gas chamber 3 is in a normal state. If the distance information does not change, it means that the position of the gas chamber 3 has not changed, that is, piston 4 is not being pushed by nitrogen pressure, which indicates that there is a high probability of nitrogen leakage in the sealing chamber 3.

[0023] It should be noted that, in reality, installing an eddy current sensor to obtain the distance between the sensor and one of the upper surface 31 or the lower surface 21 could also reflect the position information of the piston 4. However, this invention did not choose the cheaper method of "installing only one eddy current sensor" because of the redundant design. That is, the distance from the probe 10 to the lower surface 21 obtained by the magnetic sensor 11 and the distance from the probe 10 to the upper surface 31 obtained by the non-magnetic sensor 12 are mutually verified to reflect the position information of the piston 4, ensuring the accuracy of the position information of the piston 4. It can also overcome the situation where one sensor has no detection signal because the distance between the probe 10 and the target surface (the magnetic sensor 11 corresponds to the lower surface 21 of the pump coupling 2, and the non-magnetic sensor 12 corresponds to the upper surface 31 of the sealing chamber 3) is too large. That is, it can be determined whether the parking seal has reached the closed position by the position information obtained by the magnetic sensor 11, and it can be determined whether the parking seal has reached the open position by the position information obtained by the non-magnetic sensor 12.

[0024] Example 2 Based on Example 1, further feasible implementation methods are proposed.

[0025] Based on the sealing surface detection method of the mechanical seal of the nuclear main pump disclosed in Chinese Patent No. CN117606538A, those skilled in the art are aware that eddy current sensors can acquire position data in real time and continuously. However, the disclosed document is used to detect the oil film thickness in the three-stage seal, and it is based on a test bench environment. At the same time, the axial dimension of the probe 10 of commercially available eddy current sensors usually exceeds 30mm, which is much larger than the axial dimension of the installation chamber. The installation chamber cannot provide space for the installation of eddy current sensors. Therefore, the industry has not directly used eddy current sensors to solve the technical problem of obtaining the position of the parking seal. That is, although the industry is aware of the characteristics and performance of eddy current sensors, due to the limitations of the application environment, eddy current sensors cannot be effectively used. Therefore, the present invention provides a feasible implementation method, as follows.

[0026] Since both eddy current sensors are located between the pump coupling 2 and the sealing chamber 3 of the parking seal, the probes 10 of the two eddy current sensors are mounted on the bracket assembly 5. The bracket assembly 5 is fixedly connected to the upper surface 31 of the piston 4 through the connector 54 passing through the upper surface 31 of the sealing chamber 3. Normally, the nitrogen injection port is located below the piston 4. Therefore, this arrangement can effectively overcome the problem of the installation space limitation of the sealing chamber 3, and at the same time, it will not damage the sealing chamber 3's ability to seal nitrogen. The connector 54 is fixedly connected to the bracket assembly 5, ensuring that when the connector 54 moves synchronously with the piston 4, the bracket assembly 5 can move synchronously with the connector 54, thereby realizing that the probe 10 moves synchronously with the piston 4.

[0027] Furthermore, the connector 54 is a screw, and a support pad 55 is provided between the support assembly 5 and the upper surface 31. The screw passes through the support assembly 5, the support pad 55, and the upper surface 31 and is threadedly connected to the piston 4. If the connector 54 is a screw, the connector 54 is threadedly connected to the support assembly 5. The distance between the probe 10 and the target surface is initially adjusted by the support pad 55, which can also improve the stability of the connection between the support assembly 5 and the piston 4.

[0028] It should be noted that since the connector 54 passes through the upper surface 31 of the sealing chamber 3, the connector 54 can move relative to the upper surface 31 of the sealing chamber 3, that is, there will be no motion interference.

[0029] Furthermore, the support pad 55 is an elastic pad, which can be made of elastic steel. When compressed, it will undergo slight deformation, thus possessing elastic potential energy. After the support assembly 5 is connected to the piston 4, the support pad 55 generates elastic potential energy under compression. This elastic potential energy will be directly converted into the preload force connecting the connector 54 and the piston 4, thereby improving connection stability and reducing the occurrence of connection loosening. At the same time, as an elastic pad, the support pad 55 can effectively buffer the vibration of the main pump during the operation of the entire main pump device because it has the ability to undergo elastic deformation, further improving connection stability and reducing the occurrence of connection loosening.

[0030] It should be noted that, as mentioned above, the connector 54 will actually move relative to the sealing chamber 3, that is, the bracket assembly 5 will also move relative to the sealing chamber 3. As a result, the distance between the bracket assembly 5 and the sealing chamber 3 will change. The bracket pad 55 is an elastic pad that can generate elastic deformation, thereby compensating for the change in the distance between the bracket assembly 5 and the sealing chamber 3 and improving stability.

[0031] Of course, an elastic element, such as a spring, can also be fitted onto the connector 54. The spring can be fitted either outside or inside the sealing chamber 3. That is, the spring can be fitted onto the connector 54 between the bracket assembly 5 and the sealing chamber 3, or onto the connector 54 between the sealing chamber 3 and the piston 4. The effect is the same as that of the bracket pad 55 being an elastic pad. In this case, the bracket pad 55 serves as a limiting element.

[0032] It should be noted that the connection between connector 54 and bracket assembly 5 is actually a fixed connection with bracket base 51. When bracket pad 55 is an elastic pad, connector 54 can be threaded to bracket base 51 to achieve fixation. When using spring components, connector 54 can be used as a locking component, which, together with the screw cap, locks the screw to bracket base 51, thus achieving a fixed connection between connector 54 and bracket base 51.

[0033] In one feasible implementation, the bracket assembly 5 includes a bracket base 51 and a mounting base 52 slidably connected to the bracket base 51; the probe 10 is mounted on the top of the mounting base 52; the bracket base 51 is connected to a support rod; the bottom of the mounting base 52 is rotatably connected to an adjusting nut 53 via a bearing, ensuring that the mounting base 52 does not rotate when the adjusting nut 53 is rotated for adjustment; the adjusting nut 53 is threadedly connected to the bracket base 51, and the axis of the adjusting nut 53 is parallel to the direction of the sliding stroke of the mounting base 52 on the bracket base 51; the position of the probe 10 is finely adjusted by rotating the adjusting nut 53, and the final adjustment position and adjustment method of the probe 10 are detailed in the description of Embodiment 3.

[0034] It should be noted that, for the installation of the magnetic sensor 11, the probe 10 is installed with the lower surface 21 of the pump coupling 2 facing towards it. After installation, the bracket pad 55 is actually located between the bottom of the bracket base 51 and the upper surface 31 of the sealing chamber 3. For the installation of the non-magnetic sensor 12, the probe 10 is installed with the upper surface 31 of the sealing chamber 3 facing towards it. After installation, the bracket pad 55 is actually located between the top of the bracket base 51 and the upper surface 31 of the sealing chamber 3.

[0035] Example 3 A method for detecting the main pump shutdown sealing position, using the main pump shutdown sealing position detection system described in Examples 1-2, includes the following steps: Piston 4 moves synchronously with the two installed eddy current sensors. The distance from probe 10 of magnetic sensor 11 to the lower surface 21 and from probe 10 of non-magnetic sensor 12 to the upper surface 31 changes continuously. The two eddy current sensors continuously generate changing electrical signals. Controller 6 acquires the electrical signals and, based on the electrical signals, acquires the distance from probe 10 to the lower surface 21 and from probe 10 of non-magnetic sensor 12 to the upper surface 31 in real time, thereby acquiring the position of the parking seal and determining the open / closed state of the parking seal. If the distance from the probe 10 of the magnetic sensor 11 to the lower surface 21 is within the set range, then it is determined that the parking seal has reached the closed position; If the distance from the probe 10 of the non-magnetic sensor 12 to the upper surface 31 is within the set range, then the parking seal is determined to be in the open position.

[0036] Furthermore, the installation of the two eddy current sensors includes the following steps S1-S2, which have no specific order requirement; S1: Install magnetic sensor 11; including steps S11-S13; S11: Nitrogen gas is introduced into the sealing chamber 3. Under the pressure of nitrogen gas, the piston 4 moves the main shaft to the position of the pump coupling 2 sleeve until the stop seal reaches the closed position. S12: Install the magnetic sensor 11 on the bracket assembly 5, and with the appropriate bracket pad 55, connect the bracket assembly 5 to the piston 4, so that the distance between the probe 10 and the lower surface 21 is less than the adjustment range of the adjusting nut 53; if the adjustment range of the adjusting nut 53 is 5mm, then select the bracket pad 55 so that after the bracket assembly 5 is connected to the piston 4, the distance between the probe 10 and the lower surface 21 is less than 5mm, such as 3.5mm; S13: Rotate the adjusting nut 53. The adjusting nut 53 moves the mounting base 52 and then the probe 10. Adjust the distance between the probe 10 and the lower surface 21 to be within the set range. The set range is usually 0.5mm-0.7mm. That is, the adjusting nut 53 only needs to be adjusted by 3mm-2.8mm. The installation of the magnetic sensor 11 is completed. S2: Install the non-magnetic sensor 12; including steps S21-S23; S11: Release the nitrogen gas in the sealing chamber 3. The piston 4 moves along the main shaft to the position of the sealing chamber 3 until the stop seal reaches the open position. S22: Install the magnetic sensor 11 on the bracket assembly 5 and, with the appropriate bracket pad 55, connect the bracket assembly 5 to the piston 4 so that the distance between the probe 10 and the upper surface 31 is less than the adjustment range of the adjusting nut 53. S23: Rotate the adjusting nut 53. The adjusting nut 53 moves the mounting base 52 and then the probe 10, adjusting the distance between the probe 10 and the upper surface 31 to be within the set range; thus completing the installation of the non-magnetic sensor 12.

[0037] Of course, the installation of the non-magnetic sensor 12 in step S2 and the adjustment of the installation position of the probe 10 are the same as those in step S1 for installing the magnetic sensor 11, and will not be explained further here.

[0038] Example 4 A sensor for obtaining the main pump shutdown sealing position, applied to the main pump shutdown sealing position detection system described in Examples 1-2, as the eddy current sensor, includes a probe 10, a preamplifier 17 for connection to a controller 6, and a cable connecting the probe 10 and the preamplifier 17; the probe 10 has a protective cover 101 made of nickel-chromium-iron alloy, and from the bottom to the opening of the protective cover 101, a first insulating layer 102, a measuring coil 103, a second insulating layer 104, a metal partition 105, a third insulating layer 106, a compensation coil 107, a fourth insulating layer 108, a metal pressure plate 109, and a connecting threaded part 111 for installation with the bracket assembly 5; wherein: The connecting threaded part 111 is fixedly connected to the protective cover 101 to close the cover opening, and pressure is applied to the metal pressure plate 109 to make the adjacent parts between the cover bottom and the cover opening fit together; the measuring coil 103 and the compensation coil 107 are both wound on the insulating post 110, and the measuring coil 103 and the compensation coil 107 are both led out from the connecting threaded part 111 as cables after passing through the post wall of the insulating post 110; The metal pressure plate 109 and the cover bottom, the fourth insulating layer 108 and the first insulating layer 102, and the third insulating layer 106 and the second insulating layer 104 have the same thickness, thus achieving a symmetrical design. This ensures that the impact of temperature changes on the electrical parameters of the measuring coil 103 and the compensation coil 107 is basically consistent. Furthermore, since the two coils are opposite arms in the sensing and measurement unit 172, the sensor output is less affected by temperature and has strong resistance to temperature interference.

[0039] In this embodiment, the protective cover 101 is made of nickel-chromium-iron alloy. Nickel-chromium-iron alloy can withstand temperatures from -195°C to 649°C and is corrosion-resistant, making it suitable for use in corrosive gas and liquid environments. It also has good corrosion resistance. Making the protective cover 101 of nickel-chromium-iron alloy allows the sensor to adapt to the main pump environment and has a long service life.

[0040] In this embodiment, the threaded connector 54 is used to mount the probe 10 on the mounting base 52. It is feasible that the mounting base 52 is fixed with a threaded sleeve with internal threads, and the threaded connector 54 is connected to the threaded sleeve to enable the probe 10 to be mounted on the mounting base 52.

[0041] In this embodiment, the metal partition 105 is a pure iron partition, which can effectively isolate the mutual interference between the measuring coil 103 and the compensation coil 107. The second insulating layer 104 between the metal partition 105 and the measuring coil 103, and the third insulating layer 106 between the metal partition 105 and the compensation coil 107, both isolate the coil from the metal partition 105 to prevent power loss.

[0042] In this embodiment, a first insulating layer 102 is provided to increase the actual distance between the measuring coil 103 and the target surface, so that the probe 10 can measure the target surface of both non-magnetic materials and magnetic materials. Increasing the actual distance effectively reduces signal noise caused by magnetization interference.

[0043] In this embodiment, high-temperature epoxy resin can also be potted between the metal pressure plate 109 and the connecting thread 111 to ensure a sealing effect; similarly, high-temperature epoxy resin (not shown in the figure) can also be potted inside the insulating column 110 to stabilize the cable, so that the cable is subjected to force at the high-temperature epoxy resin during the pulling process, thus preventing the cable from breaking off from the coil during the pulling process.

[0044] Furthermore, the cables connected to the same coil in the cable are twisted together to improve anti-interference capability; the cables connecting different coils are isolated by a shielding layer, which can be a mesh structure woven from tinned copper wire, effectively reducing signal interference between the measuring coil 103 and the compensation coil 107; all cables are wrapped with an external insulation layer; the cable is covered with a stainless steel corrugated tube 14, and both the corrugated tube and the insulation layer serve a protective function.

[0045] In a feasible implementation, the cable consists of two parts: a connecting cable 13 and an extension cable 16. One end of the connecting cable 13 is connected to the probe 10 via a male-female connector 15, and the other end of the connecting cable 13 is connected to one end of the extension cable 16 via a male-female connector 15. The other end of the extension cable 16 is connected to the preamplifier 17 via a male-female connector 15.

[0046] Furthermore, the preamplifier 17 includes a protective housing with corresponding sockets, such as holes for connecting the power supply unit 171 to a power source; the protective housing encapsulates the power supply unit 171, the sensing and measurement unit 172, the signal processing unit 173, and the current output unit 174; wherein: The power supply unit 171 is used for external power supply, and its output is connected to the sensing and measurement unit 172, the signal processing unit 173, and the current output unit 174. Specifically, the power supply unit 171 uses Zener diodes to obtain the required 5V, 5.6V, 12V, and 12.4V operating voltages for other functional circuits. To improve product stability and reliability, the power supply unit 171 uses transient suppression transistors, common-mode inductors, Schottky reverse protection diodes, capacitor protection filters, and other components in its front-end to provide protection against lightning strikes, reverse power connection, and EMC electromagnetic interference for the hardware circuit modules.

[0047] The sensing and measurement unit 172 is connected to both the measuring coil 103 and the compensation coil 107 via cables, and is also connected to the input terminal of the signal processing unit 173. The sensing and measurement unit 172 is mainly divided into a signal generation circuit, a differential bridge, and a signal conditioning circuit. The signal generation circuit generates a square wave signal of the required frequency. The measuring coil 103, the compensation coil 107, and two pairs of resistors and capacitors connected in series form a differential bridge. The signal output from the bridge is converted from AC to DC by a circuit composed of filters and transistors before being output to the signal processing circuit. When the high-frequency signal loaded on the measuring coil 103 generates an electromagnetic field, it acts on the metal being measured through the metal sealing layer, generating eddy currents on the metal surface. The electromagnetic field generated by the eddy currents, in turn, changes the electrical parameters of the measuring coil 103. The degree of this change is related to the distance between the measuring coil 103 and the surface of the metal being measured, thereby breaking the balance of the bridge and outputting an electrical signal related to the distance. Because a bridge output is used, the compensation coil 107 and the measuring coil 103 are in the same environment and are designed to be completely symmetrical. Temperature changes have a similar effect on the electrical parameters of the measuring coil 103 and the compensation coil 107. Since they are in opposite arms of the bridge, the sensor output is not affected by temperature to a certain extent and has strong resistance to temperature interference.

[0048] The output of signal processing unit 173 is connected to current output unit 174. Signal processing unit 173 consists of an instrumentation amplifier and a non-inverting amplifier composed of two low-power dual operational amplifiers LM158A, which perform differential amplification and gain adjustment on the two DC signals after bridge processing, respectively. The current output circuit converts the voltage signal into a current signal and outputs it to controller 6. It mainly consists of one low-power dual operational amplifier LM158A and one transistor.

[0049] This invention is applicable to nuclear power irradiation environments. The complete product can operate for at least 10 years under nuclear irradiation at a dose rate of up to 0.5 Gy / h, and has undergone LOCA testing verification, ensuring the structural and functional integrity during and after LOCA accident conditions.

[0050] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A detection system for the sealing position of a main pump during shutdown, characterized in that: The system includes two eddy current sensors fixedly connected to the piston (4) and a controller (6); both eddy current sensors are located between the pump coupling (2) and the sealing chamber (3) of the parking seal. One of the two eddy current sensors is a magnetic sensor (11), with the probe (10) of the magnetic sensor (11) facing the lower surface (21) of the pump coupling (2), and can obtain the distance between the probe (10) and the lower surface (21) without contact; one of the two eddy current sensors is a non-magnetic sensor (12), with the probe (10) of the non-magnetic sensor (12) facing the upper surface (31) of the sealing chamber (3), and can obtain the distance between the probe (10) and the upper surface (31) without contact; both eddy current sensors are connected to the input end of the controller (6).

2. The detection system according to claim 1, characterized in that: The probes (10) of the two eddy current sensors are mounted on the bracket assembly (5), and the bracket assembly (5) is fixedly connected to the upper surface (31) of the piston (4) through the upper surface (31) of the sealing chamber (3) via the connector (54); the connector (54) is fixedly connected to the bracket assembly (5).

3. The detection system according to claim 2, characterized in that: The connector (54) is a screw. A bracket pad (55) is provided between the bracket assembly (5) and the upper surface (31). The screw passes through the bracket assembly (5), the bracket pad (55), and the upper surface (31) and then connects to the piston (4).

4. The detection system according to claim 3, characterized in that: The support pad (55) is an elastic pad.

5. The detection system according to any one of claims 2-4, characterized in that: The bracket assembly (5) includes a bracket base (51) and a mounting base (52) slidably connected to the bracket base (51); the probe (10) is mounted on the top of the mounting base (52); the bracket base (51) is connected to the support rod; an adjusting nut (53) is rotatably connected to the bottom of the mounting base (52), the adjusting nut (53) is threadedly connected to the bracket base (51), and the axis of the adjusting nut (53) is parallel to the direction of the sliding stroke of the mounting base (52) on the bracket base (51).

6. A method for detecting the sealing position of a main pump during shutdown, characterized in that: The application of the detection system according to any one of claims 1-5 includes the following steps: The piston (4) moves synchronously with the two installed eddy current sensors. The distance from the probe (10) of the magnetic sensor (11) to the lower surface (21) and the probe (10) of the non-magnetic sensor (12) to the upper surface (31) changes continuously. The two eddy current sensors continuously generate changing electrical signals. The controller (6) acquires the electrical signals and, based on the electrical signals, acquires the distance from the probe (10) to the lower surface (21) and the probe (10) of the non-magnetic sensor (12) to the upper surface (31) in real time, thereby determining the open / closed state of the parking seal. If the distance from the probe (10) of the magnetic sensor (11) to the lower surface (21) is within the set range, then the parking seal is determined to be in the closed position. If the distance from the probe (10) of the non-magnetic sensor (12) to the upper surface (31) is within the set range, then the parking seal is determined to be in the open position.

7. The detection method according to claim 6, characterized in that: The installation of the two eddy current sensors includes the following steps S1-S2, which have no specific order requirement; S1: Install the magnetic sensor (11); including steps S11-S13; S11: Nitrogen gas is introduced into the sealing chamber (3). Under the pressure of nitrogen gas, the piston (4) moves the main shaft to the position of the pump coupling (2) sleeve until the stop seal reaches the closed position. S12: Install the magnetic sensor (11) on the bracket assembly (5) and connect the bracket assembly (5) to the piston (4) with a suitable bracket pad (55) so that the distance between the probe (10) and the lower surface (21) is less than the adjustment range of the adjusting nut (53); S13: Rotate the adjusting nut (53), the adjusting nut (53) moves by moving the mounting base (52) and thus the probe (10), adjust the distance between the probe (10) and the lower surface (21) to be within the set range; complete the installation of the magnetic sensor (11); S2: Install the non-magnetic sensor (12); including steps S21-S23; S11: Release the nitrogen gas in the sealing chamber (3), and the piston (4) moves along the main shaft to the position of the sealing chamber (3) until the stop seal reaches the open position; S22: Install the magnetic sensor (11) on the bracket assembly (5) and connect the bracket assembly (5) to the piston (4) with a suitable bracket pad (55) so that the distance between the probe (10) and the upper surface (31) is less than the adjustment range of the adjusting nut (53); S23: Rotate the adjusting nut (53), and the adjusting nut (53) moves by moving the mounting base (52) and then the probe (10), adjusting the distance between the probe (10) and the upper surface (31) to be within the set range; complete the installation of the non-magnetic sensor (12).

8. A sensor for obtaining the sealing position of a main pump during shutdown, applied to the detection system according to any one of claims 1-5, characterized in that: Includes a probe (10), a preamplifier (17) for connection to a controller (6), and a cable connecting the probe (10) and the preamplifier (17); the probe (10) has a protective cover (101), from the bottom of the protective cover (101) to the opening, arranged in sequence a first insulating layer (102), a measuring coil (103), a second insulating layer (104), a metal partition (105), a third insulating layer (106), a compensation coil (107), a fourth insulating layer (108), a metal pressure plate (109), and a connecting thread (111) for mounting to the bracket assembly (5); wherein: The connecting threaded part (111) is fixedly connected to the protective cover (101) to close the cover opening, and pressure is applied to the metal pressure plate (109) to make the adjacent parts between the bottom of the cover and the cover opening fit together; the measuring coil (103) and the compensation coil (107) are both wound on the insulating post (110), and the measuring coil (103) and the compensation coil (107) are both led out from the connecting threaded part (111) as cables after passing through the post wall of the insulating post (110); The metal pressure plate (109) and the cover bottom, the fourth insulating layer (108) and the first insulating layer (102), and the third insulating layer (106) and the second insulating layer (104) have the same thickness.

9. The sensor according to claim 8, characterized in that: The cables connected to the same coil in the cable are twisted in pairs; the cables connecting different coils are isolated by a shielding layer; all cables are wrapped with an external insulation layer; and the cable is covered with a stainless steel corrugated tube (14).

10. The sensor according to claim 8, characterized in that: The preamplifier (17) includes a protective enclosure, which encapsulates a power supply unit (171), a sensing and measurement unit (172), a signal processing unit (173), and a current output unit (174); wherein: The power supply unit (171) is used for external power supply, and its output terminal is connected to the sensing and measurement unit (172), the signal processing unit (173) and the current output unit (174); The sensing and measurement unit (172) is connected to the measuring coil (103) and the compensation coil (107) via cables, and is also connected to the input terminal of the signal processing unit (173); The output of the signal processing unit (173) is connected to the current output unit (174).

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