A nuclear main pump mechanical seal test device with leakage phase monitoring and method thereof

Abstract

The present invention relates to a nuclear main pump mechanical seal test device with leakage phase monitoring and a method thereof, comprising a phase state peepscope probe, a back pressure regulating device and an image processing module: the phase state peepscope probe is used to collect the phase state image of the leakage side of the tertiary seal; the back pressure regulating device is used to adjust the pressure on the leakage side of the tertiary seal; the image processing module is connected to the phase state peepscope probe for edge processing of the received phase state image. The present invention adopts a miniature phase state peepscope probe to obtain the phase state image of the tertiary low-pressure leakage flow, and obtains the mean square error of the image after edge detection through the Sobel edge detection algorithm, thereby realizing the online monitoring of the phase state of the main pump shaft seal low-pressure leakage flow based on the endoscopic image. The leakage back pressure is adjusted to improve the lubrication state of the floating seal, and a multi-level back pressure test is carried out to obtain the relationship between the pressure on the leakage side of the tertiary seal and the clarity of the phase state image, which can be used to troubleshoot during the main pump mechanical performance test stage.

Description

Technical Field

[0001] The invention relates to a device for monitoring the working state and performance of a nuclear power plant main pump mechanical seal, and in particular to a nuclear main pump mechanical seal test device with leakage phase monitoring and a method thereof. Background Art

[0002] The shaft seals of the reactor coolant pump (RCP) of nuclear power plants are mainly divided into two categories: hydrostatic shaft seals and hydrodynamic shaft seals. Both types of shaft seals are composed of three-stage seals arranged in series. The three-stage structure of the hydrodynamic shaft seal is the same. Each stage has a continuous micro-waveform groove processed on one of the sealing surfaces. During operation, the hydrodynamic pressure effect is generated by fluid shear to maintain a gap of several microns and control leakage.

[0003] The RCP of a 1080MWe nuclear power unit in China uses a fluid dynamic pressure shaft seal. At the end of the operation cycle, it was observed that the three-stage low-pressure leakage increased, and the pressure of the three-stage seal chamber dropped from 5.3MPa to 4.5MPa. After dismantling the shaft seals of the three main pumps, it was observed that the outer surfaces of the three-stage seal static ring guide sleeve and the three-stage shaft sleeve were yellow and blue, and the static ring assembly O-rings all had traces of serpentine bending. Therefore, it was initially suspected that the performance degradation of the mechanical seal was caused by the increase in the friction of the floating O-ring. The leakage pressure on the third-stage leakage side of the main pump mechanical seal is atmospheric pressure, and the temperature of the shaft sleeve boundary layer is relatively high. Through simulation, the temperature in this area will reach about 123°C. When the medium leaks here, due to the decrease in pressure and the increase in temperature, it is easy to cause the three-stage seal guide ring and the static ring seat to get stuck, causing the main pump mechanical seal to lose pressure, increase leakage and other faults.

[0004] The third-stage low-pressure leakage of the main pump mechanical seal does not have sufficient back pressure, the minimum gap between the rotating parts and the stationary parts is only 2mm, and the fluid shearing effect is strong. The temperature of the main pump chamber is as high as 320℃. The main pump shaft is solid stainless steel, which is a good heat conductor. Therefore, there is a high temperature of 123℃ in the low-pressure leakage area of ​​the third-stage seal of the main pump shaft seal, which makes the low-pressure leakage water more likely to be vaporized and condensed into liquid after rising to the upper part of the leakage channel. The third-stage leakage medium is oxygen-rich. Since the medium is a boric acid solution, the ions in the water are charged under the shearing effect. For the above reasons, the low-pressure leakage side of the third-stage seal has been working for a long time under the combined effects of high temperature, oxygen enrichment, fluid shearing, electrochemistry, and gas-liquid two phases, which makes the floating O-ring stuck, and finally reduces the sealing performance, threatening the normal operation of the reactor. Summary of the invention

[0005] In view of the deficiencies in the prior art, one of the purposes of the present invention is to provide a nuclear main pump mechanical seal test device with leakage phase monitoring, which has the advantage of being able to be used to troubleshoot during the main pump mechanical performance test stage.

[0006] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0007] A nuclear main pump mechanical seal test device with leakage phase monitoring includes a phase state scope probe, a back pressure regulating device and an image processing module: the phase state scope probe is used to collect the phase state image of the leakage side of the tertiary seal; the back pressure regulating device is used to adjust the pressure on the leakage side of the tertiary seal; the image processing module is connected to the phase state scope probe for edge processing of the received phase state image.

[0008] By adopting the above technical solution, a micro phase endoscope probe is used to obtain the phase image of the three-stage low-pressure leakage flow, and the Sobel edge detection algorithm is used to obtain the mean square error after the image is edged, so as to realize the online monitoring of the phase state of the main pump shaft seal low-pressure leakage flow based on the endoscope image. The lubrication state of the floating seal is improved by adjusting the leakage back pressure, and a multi-level back pressure test is carried out to obtain the relationship between the pressure on the leakage side of the three-stage seal and the clarity of the phase image. It is convenient to better observe the color of the contact surface between the three-stage sleeve and the static ring seat, so as to obtain whether there is a jam between the guide sleeve and the static ring seat of the three-stage seal, which can be used to troubleshoot during the mechanical performance test stage of the main pump.

[0009] In a preferred example, the present invention can be further configured as follows: the back pressure regulating device includes a back pressure high-level water tank and a regulating component for regulating the water level in the back pressure high-level water tank, and the back pressure high-level water tank is connected to the leakage side of the third-level seal.

[0010] By adopting the above technical solution, the regulating component adjusts the height of the water level in the back pressure high-level water tank, thereby increasing the back pressure on the leakage side of the tertiary seal, increasing the lubrication of the tertiary seal O-ring, reducing the oxidation of the tertiary sleeve surface, and improving the sealing performance of the nuclear main pump machinery.

[0011] In a preferred example, the present invention can be further configured as follows: the adjustment component includes a plurality of pressure relief holes opened on the back pressure high-level water tank, the plurality of pressure relief holes are arranged along the height direction of the back pressure high-level water tank, and the pressure relief holes are detachably connected with hole covers.

[0012] By adopting the above technical solution, the water level in the back pressure high-level water tank can be changed by opening the pressure relief holes at different heights, and the structure is simple.

[0013] In a preferred example, the present invention can be further configured as follows: comprising two splash probes, the two splash probes are respectively located at different radii at the top of the tertiary seal, and one splash probe points to the contact surface between the tertiary sleeve and the tertiary stationary ring seat.

[0014] By adopting the above technical solution, two splash probes monitor the splash of the medium, and the medium is in a gas-liquid two-phase state at the third-level seal; one splash probe monitors the splash image between the shaft and the third-level static ring seat, and the other splash probe monitors the image of the medium ejected.

[0015] In a preferred example, the present invention can be further configured as follows: including through holes opened in the tertiary static ring seat and the tertiary guide ring, and the through holes are used for the cables of the phase scope probe to pass through.

[0016] By adopting the above technical solution, through holes are opened on the third-stage static ring seat and the third-stage guide ring to facilitate the installation of the cable of the phase mirror probe, and the cable will not affect the operation of the nuclear main pump machinery.

[0017] In a preferred example, the present invention can be further configured as follows: a semi-rigid tube is provided in the through hole, and the cable of the phase scope probe is located in the semi-rigid tube.

[0018] By adopting the above technical solution, the semi-rigid tube can protect the cable of the phase scope probe and reduce the wear of the cable.

[0019] The second object of the present invention is achieved through the following technical solutions:

[0020] A nuclear main pump mechanical seal test method with leakage phase monitoring includes the above test device and the following steps:

[0021] S1. Simulate the operation of the nuclear main pump mechanical seal through the test bench driving components;

[0022] S2, adjust the back pressure at the low pressure leakage of the third-stage shaft seal;

[0023] S3, using a micro endoscope device to obtain online phase images of the three-level low-pressure leakage flow under different back pressures;

[0024] S4. Edge processing is performed on each phase image according to the Sobel edge detection algorithm to quantify the relationship between the pressure on the leakage side of the tertiary seal and the degree of internal flow turbulence.

[0025] By adopting the above technical solution, a micro phase endoscope probe is used to obtain the phase image of the three-stage low-pressure leakage flow, and the Sobel edge detection algorithm is used to obtain the mean square error after the image is edged, so as to realize the online monitoring of the phase state of the main pump shaft seal low-pressure leakage flow based on the endoscope image. The lubrication state of the floating seal is improved by adjusting the leakage back pressure, and a multi-level back pressure test is carried out to obtain the relationship between the pressure on the leakage side of the three-stage seal and the clarity of the phase image. It is convenient to better observe the color of the contact surface between the three-stage sleeve and the static ring seat, so as to obtain whether there is a jam between the navigation and the static ring seat of the three-stage seal, which can be used to troubleshoot during the mechanical performance test stage of the main pump.

[0026] In a preferred example, the present invention can be further configured as follows: the Sobel edge detection algorithm is defined as:

[0027] , ;

[0028] The acquired endoscope image adopts 320×240 pixels, and the pixel value of the image is preset as a function , the first-order derivative of each pixel along the X direction is , the first-order derivative along the Y direction is ,but:

[0029] , ;

[0030] Then the grayscale value of each pixel in the horizontal and vertical directions on the image can be obtained as shown in the following formula:

[0031] .

[0032] By adopting the above technical solution, two Sobel edge detection result matrices processed with different comparison thresholds are used to obtain the image matrix difference as the final leakage flow pattern image clarity judgment value, so that the optimal pressure on the leakage side of the third-level seal can be obtained.

[0033] In a preferred example, the present invention can be further configured as follows: in step S2, the third-level sealing leakage side is externally connected to a back-pressure high-level water tank, and the back pressure on the third-level low-pressure leakage side is adjusted by the water level of the back-pressure high-level water tank.

[0034] By adopting the above technical solution, the height of the water level in the back pressure high-level water tank is adjusted to achieve the purpose of regulating the pressure on the leakage side of the third-level seal, and the adjustment is convenient.

[0035] In a preferred example, the present invention can be further configured as follows: the highest water level of the back pressure high-level water tank is determined according to the inherent factors of the dynamic pressure shaft seal, wherein the inherent factors include the height of the elliptical hole of the parking seal limit switch rod.

[0036] By adopting the above technical solution, the leaking medium will not overflow from the holes of the parking seal, so that the back pressure high-level water tank can better provide pressure support for the leakage side of the tertiary seal.

[0037] In summary, the present invention includes at least one of the following beneficial technical effects:

[0038] 1. A miniature phase endoscope probe is used to obtain the phase image of the tertiary low-pressure leakage flow. The Sobel edge detection algorithm is used to obtain the mean square error after the image is edged, and the online monitoring of the phase state of the main pump shaft seal low-pressure leakage flow based on the endoscope image is realized. The lubrication state of the floating seal is improved by adjusting the leakage back pressure, and a multi-level back pressure test is carried out to obtain the relationship between the pressure on the leakage side of the tertiary seal and the clarity of the phase image. It is convenient to better observe the color of the contact surface between the tertiary shaft sleeve and the static ring seat, so as to determine whether there is a jam between the guide sleeve and the static ring seat of the tertiary seal, which can be used to troubleshoot during the main pump mechanical performance test stage;

[0039] 2. By opening the pressure relief holes at different heights, the water level in the back high pressure water tank can be changed to achieve the purpose of regulating the pressure on the leakage side of the tertiary seal. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a partial structural schematic diagram of an embodiment of the present invention;

[0041] Figure 2 Schematic diagram of the structure of the back pressure regulating device in an embodiment of the present invention.

[0042] In the figure, 1. phase endoscope probe; 21. back pressure high position water tank; 22. pressure relief hole; 23. hole cover; 3. splash probe; 4. through hole; 5. semi-rigid tube; 6. third-level guide ring; 7. third-level static ring seat. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0044] A nuclear main pump mechanical seal test device with leakage phase monitoring, referring to Figure 1 and Figure 2, including a phase-state endoscope probe 1, a back pressure regulating device and an image processing module: the phase-state endoscope probe 1 is used to collect the phase image of the leakage side of the third-level seal; the back pressure regulating device is used to adjust the pressure on the leakage side of the third-level seal; the image processing module is connected to the phase-state endoscope probe 1 for edge processing of the received phase image. The phase-state endoscope probe 1 in the present invention adopts a Bosch industrial endoscope with a diameter of 2.5 mm, and the phase-state endoscope probe 1 is deflected about 5 degrees toward the axis.

[0045] A miniature phase endoscope probe 1 is used to obtain the phase state image of the tertiary low-pressure leakage flow. The Sobel edge detection algorithm is used to obtain the mean square error after the image is edged, and the online monitoring of the phase state of the main pump shaft seal low-pressure leakage flow based on the endoscope image is realized. The lubrication state of the floating seal is improved by adjusting the leakage back pressure, and a multi-level back pressure test is carried out to obtain the relationship between the pressure on the leakage side of the tertiary seal and the clarity of the phase state image. It is convenient to better observe the color of the contact surface between the tertiary shaft sleeve and the tertiary static ring seat 7, so as to obtain whether there is a jam between the guide sleeve and the static ring seat of the tertiary seal, which can be used to troubleshoot during the mechanical performance test stage of the main pump.

[0046] The back pressure regulating device includes a back pressure high position water tank 21 and a regulating component for regulating the water level in the back pressure high position water tank 21. The back pressure high position water tank 21 is connected to the leakage side of the third-level seal, wherein the back pressure high position water tank 21 is connected to the highest position of the third-level seal low pressure leakage port by a hose; the regulating component regulates the height of the water level in the back pressure high position water tank 21 to achieve the purpose of regulating the pressure on the leakage side of the third-level seal, and the regulation is convenient. The regulating component includes a plurality of pressure relief holes 22 opened on the back pressure high position water tank 21, and the plurality of pressure relief holes 22 are arranged along the height direction of the back pressure high position water tank 21. The pressure relief holes 22 are detachably connected with a hole cover 23; opening the pressure relief holes 22 of different heights can change the water level in the back pressure high position water tank 21, and the structure is simple. The regulating component of the present invention can also be realized by adjusting the height of the back pressure high position water tank 21, such as installing a lifting platform below the back pressure high position water tank 21, and the lifting platform is one of a hydraulic lifting platform and an electric lifting platform in the prior art.

[0047] It includes two splash probes 3, which are respectively located at different radii at the top of the third-level seal, and one splash probe 3 points to the contact surface between the third-level shaft sleeve and the third-level static ring seat 7; the two splash probes 3 monitor the splash of the medium, and the medium is in a gas-liquid two-phase state at the third-level seal; one splash probe 3 monitors the splash image between the shaft and the third-level static ring seat 7, and the other splash probe 3 monitors the image of the medium ejected. It includes a through hole 4 opened on the third-level static ring seat 7 and the third-level guide ring 6, and the through hole 4 is for the cable of the phase state mirror probe 1 to pass through, wherein the third-level static ring seat 7 reaches the inner diameter side of the third-level seal end face; the through hole 4 is opened on the third-level static ring seat 7 and the third-level guide ring 6, which is convenient for the cable installation of the phase state mirror probe 1, and the cable will not affect the operation of the nuclear main pump machinery. A semi-rigid tube 5 is installed in the through hole 4, and the cable of the phase state mirror probe 1 is located in the semi-rigid tube 5; the semi-rigid tube 5 can protect the cable of the phase state mirror probe 1 and reduce the wear of the cable. The spatter probe 3 in the present invention adopts an ADM-5 industrial endoscope with a diameter of 5.3 mm.

[0048] The structural diagram of the fluid dynamic pressure type main pump shaft seal is as follows Figure 1 As shown. The dynamic ring is a graphite ring, which is inlaid with inner and outer metal rings. The static ring is a carbide ring with a metal ring inlaid on the outside and a continuous sinusoidal waveform groove is processed on the end face of the carbide ring. The auxiliary seal is used to seal the gap between the static ring seat, the dynamic ring seat and the sleeve. Among them, the auxiliary seal of the static ring assembly is a dynamic seal, which is in a floating state during operation and has a certain axial and radial displacement tracking function. Through examples, the present invention can be observed that on the side of the three-level low-pressure leakage, the smaller the gap, the more obvious the yellowing. No obvious yellowing phenomenon was observed in the relatively static small gap area. The causes of this phenomenon should be considered from multiple angles, such as: fluid shearing, leakage medium phase change, excessive sleeve metal temperature, medium oxygen enrichment, etc. First of all, the temperature distribution of the main pump shaft system should be analyzed.

[0049] A nuclear main pump mechanical seal test method with leakage phase monitoring includes the above test device and the following steps:

[0050] S1. Simulate the operation of the nuclear main pump mechanical seal through the test bench driving components;

[0051] S2, adjust the back pressure at the low pressure leakage of the third-stage shaft seal;

[0052] S3, using a micro endoscope device to obtain online phase images of the three-level low-pressure leakage flow under different back pressures;

[0053] S4. Edge processing is performed on each phase image according to the Sobel edge detection algorithm to quantify the relationship between the pressure on the leakage side of the tertiary seal and the degree of internal flow turbulence.

[0054] The Sobel edge detection algorithm is defined as:

[0055] , ;

[0056] The acquired endoscope image adopts 320×240 pixels, and the pixel value of the image is preset as a function , the first-order derivative of each pixel along the X direction is , the first-order derivative along the Y direction is ,but:

[0057] , ;

[0058] Then the grayscale value of each pixel in the horizontal and vertical directions on the image can be obtained as shown in the following formula:

[0059] .

[0060] The Sobel edge detection result matrix processed by two different comparison thresholds is used to obtain the image matrix difference as the final leakage flow state image clarity discrimination value, so that the optimal pressure on the leakage side of the third-level seal can be obtained. In step S2, the leakage side of the third-level seal is externally connected to a back pressure high-level water tank 21, and the size of the back pressure is adjusted by the water level of the back pressure high-level water tank 21; the height of the water level in the back pressure high-level water tank 21 is adjusted to achieve the purpose of regulating the pressure on the leakage side of the third-level seal. The highest water level of the back pressure high-level water tank 21 is determined according to the inherent factors of the dynamic pressure shaft seal, and the inherent factors include the height of the elliptical hole of the parking seal limit switch rod; the leakage medium will not overflow from the hole of the parking seal, so that the back pressure high-level water tank 21 can better provide pressure support for the leakage side of the third-level seal.

[0061] In the example of the method of the present invention, it is observed through the Sobel edge image of the endoscope that raising the level of the three-level low-pressure leakage water level can eliminate the fluid cavitation inside the annular gap on the low-pressure leakage side to a certain extent. The effect is best at a height of 1.8m, and a good effect is achieved at a height of 1.55m. Due to the limitation of the dynamic pressure shaft seal parking seal medium drainage function, the maximum water level of the back pressure high-level water tank 21 cannot exceed the height of the elliptical hole of the parking seal limit switch rod. According to the data analysis of the experiment, the maximum design water level of the back pressure high-level water tank 21 is 1.55m, which is 25cm higher than the original low-pressure leakage water level. At this time, the clarity of the phase state image is improved by 27%.

[0062] Taking the online monitoring data of the RCP shaft seal of a 1080MWe unit as the boundary condition, the FEA heat transfer model was established, and the temperature distribution of the pump shaft system under normal working conditions was calculated and simulated. The results show that the pump shaft temperature in the shaft seal section is between 89℃ and 100℃, and the highest temperature of the shaft metal wall is 129℃ in the third-stage shaft seal section. A flow state monitoring method for the three-stage leakage flow field of the shaft seal based on peephole image processing. The image edge detection algorithm with the Sobel operator as the core is used in the developed Prometheus important rotating equipment health status online monitoring system. The experiment adjusts the back pressure of the low-pressure leakage flow by adding a back pressure high-level water tank 21 to the three-stage low-pressure leakage pipeline. It can be found from the mean square error value of the edge image that this method can distinguish the state of the three-stage low-pressure leakage flow field. The experimental results show that by adding a back pressure high-level water tank 21 to raise the drainage level, it does play a role in reducing the degree of cavitation in the three-stage low-pressure leakage flow.

[0063] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A nuclear main pump mechanical seal test method with leakage phase monitoring, characterized in that: The test method is based on a nuclear main pump mechanical seal test device with leakage phase monitoring, the test device comprising a phase state peepscope probe (1), a back pressure regulating device and an image processing module; the nuclear main pump mechanical seal is a dynamic pressure shaft seal, the dynamic pressure shaft seal is composed of three-stage seals arranged in series, the phase state peepscope probe (1) is used to collect the phase state image of the leakage side of the three-stage seal; the back pressure regulating device is used to regulate the pressure on the leakage side of the three-stage seal; the image processing module is connected to the phase state peepscope probe (1) for edge processing of the received phase state image; the test method steps are as follows: S1. Simulate the operation of the nuclear main pump mechanical seal through the test bench driving components; S2, adjust the back pressure at the leakage point of the third-level seal; S3, using a phase scope probe (1) to obtain online phase images of the leakage fluid of the third-level seal under different back pressures; S4. Edge processing is performed on each phase image according to the Sobel edge detection algorithm to quantify the relationship between the pressure on the leakage side of the tertiary seal and the degree of internal flow turbulence.

2. A nuclear main pump mechanical seal test method with leakage phase monitoring according to claim 1, characterized in that: The back pressure regulating device comprises a back pressure high level water tank (21) and a regulating assembly for regulating the water level in the back pressure high level water tank (21); the back pressure high level water tank (21) is connected to the leakage side of the third-level seal.

3. A nuclear main pump mechanical seal test method with leakage phase monitoring according to claim 2, characterized in that: The regulating component comprises a plurality of pressure relief holes (22) opened on the back pressure high-position water tank (21); the plurality of pressure relief holes (22) are arranged along the height direction of the back pressure high-position water tank (21); and a hole cover (23) is detachably connected to the pressure relief holes (22).

4. A nuclear main pump mechanical seal test method with leakage phase monitoring according to claim 1, characterized in that: The test device also includes two splash probes (3), which are respectively located at different radii at the top of the third-level seal, and one of the splash probes (3) points to the contact surface between the third-level shaft sleeve and the third-level stationary ring seat (7).

5. A nuclear main pump mechanical seal test method with leakage phase monitoring according to claim 1, characterized in that: The test device also includes a through hole (4) opened on the third-level static ring seat (7) and the third-level guide ring (6), and the through hole (4) is used for the cable of the phase-state endoscope probe (1) to pass through.

6. A nuclear main pump mechanical seal test method with leakage phase monitoring according to claim 5, characterized in that: A semi-rigid tube (5) is arranged in the through hole (4), and the cable of the phase scope probe (1) is located in the semi-rigid tube (5).

7. A nuclear main pump mechanical seal test method with leakage phase monitoring according to claim 1, characterized in that: The Sobel edge detection algorithm is defined as: The acquired endoscope image uses 320×240 pixels. The pixel value of the image is preset as a function f(x, y). The first-order derivative of each pixel point along the X direction is G x (x, y), the first-order derivative along the Y direction is G y (x, y), then: G x (x,y)=T x ×f(x,y),G y (x,y)=T y ×f(x,y); Then the grayscale value of each pixel in the horizontal and vertical directions on the image can be obtained as shown in the following formula: 。 8. A nuclear main pump mechanical seal test method with leakage phase monitoring according to claim 1, characterized in that: In step S2, the third-level sealing leakage side is externally connected to a back-pressure high-level water tank (21), and the back pressure on the third-level low-pressure leakage side is adjusted by the water level of the back-pressure high-level water tank (21).

9. A nuclear main pump mechanical seal test method with leakage phase monitoring according to claim 8, characterized in that: The highest water level of the back pressure high level water tank (21) is determined according to the inherent factors of the dynamic pressure shaft seal, wherein the inherent factors include the height of the elliptical hole of the parking seal limit switch rod.

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