WO2012128164A1

WO2012128164A1 - Abrasion monitoring device for mechanical seal

Info

Publication number: WO2012128164A1
Application number: PCT/JP2012/056639
Authority: WO
Inventors: 杉山　憲一; 紀久雄西山; 高東　智佳子; 加藤　弘之
Original assignee: 株式会社荏原製作所
Priority date: 2011-03-23
Filing date: 2012-03-15
Publication date: 2012-09-27
Also published as: JP5718695B2; JP2012197907A

Abstract

Provided is an abrasion monitoring device for a mechanical seal, capable of monitoring abrasion of a seal ring used in a mechanical seal and forecasting the service life of the seal ring. A multi-stage mechanical seal (8) has a control bleed-off mechanism (30) for adjusting a pressure difference between stages, and a seal leak passage (35) for discharging fluid that passes between surfaces where sliding occurs between rotating seal rings and stationary seal rings of the stages. The abrasion monitoring device for the multi-stage mechanical seal (8) comprises a concentration measuring instrument (41) for continuously measuring the concentration of abrasive particles in the liquid that is discharged from the control bleed-off mechanism (30), and a processing device (70) for estimating the amount of abrasion of the multi-stage mechanical seal (8) from the concentration of abrasive particles measured by the concentration measuring instrument (41).

Description

Mechanical seal wear monitoring device

The present invention relates to a mechanical seal wear monitoring device, and more particularly to a device for monitoring the wear of a multistage mechanical seal used in a pump and predicting the remaining life of the mechanical seal.

A pump for transferring liquid is generally provided with a shaft seal mechanism for preventing leakage of liquid pressurized by rotation of an impeller. A mechanical seal, which is a representative example of the shaft seal mechanism, minimizes liquid leakage by bringing a rotary seal ring arranged on the rotation side and a stationary seal ring arranged on the stationary side in close contact with each other.

As the impeller rotates, the rotary seal ring and the stationary seal ring are brought into sliding contact with each other, so that these seal rings gradually wear. When the seal ring is greatly worn, the sealing function of the mechanical seal is lowered, and the liquid exceeding the allowable amount leaks. Therefore, it is necessary to monitor the wear of the seal ring to predict its life and replace the seal ring before the seal function is degraded.

によって Some types of pumps are required to strictly limit liquid leakage to the outside of the pump. For example, in a cooling water circulation system of a nuclear power plant, a circulation pump for primary cooling water for cooling a nuclear reactor is used. Since leakage of the primary cooling water has a serious impact on the reactor and the surrounding environment, leakage of the primary cooling water from the cooling water circulation system must be avoided. Therefore, extremely high reliability is required for the mechanical seal used in the circulation pump.

JP-A-4-128648

The present invention has been made in view of the above-mentioned circumstances, and provides a mechanical seal wear monitoring device capable of monitoring the wear of a seal ring used for a mechanical seal and predicting the life of the seal ring. Objective.

In order to achieve the above-described object, one aspect of the present invention provides a control bleed-off mechanism for adjusting a pressure difference between stages of a multistage mechanical seal, and a sliding contact between a rotary seal ring and a stationary seal ring at each stage. A wear monitoring device for a multistage mechanical seal having a seal leakage passage for discharging liquid that has passed through the surface, and a concentration for continuously measuring the concentration of wear powder in the liquid discharged from the control bleed-off mechanism It is characterized by comprising a measuring device and a processing device for estimating the wear amount of the multistage mechanical seal from the concentration of the abrasion powder measured by the concentration measuring device.

In a preferred aspect of the present invention, the concentration measuring instrument comprises: a flow cell through which the liquid passes; a light source that irradiates light to the liquid flowing through the flow cell; And a concentration analyzer for determining the concentration of the wear powder in the liquid from the intensity of light detected by the light receiving element.
In a preferred aspect of the present invention, the processing apparatus determines the amount of wear of the sliding contact surface by integrating the concentration of the wear powder with respect to time.
In a preferred aspect of the present invention, the processing apparatus estimates the remaining life of the rotary seal ring and the stationary seal ring by comparing the determined wear amount with a preset allowable wear amount. It is characterized by.
In a preferred aspect of the present invention, the apparatus further comprises a particle size distribution measuring instrument connected to the control bleed-off flow path and the seal leakage path.

Another aspect of the present invention is a control bleed-off mechanism for adjusting the pressure difference between the stages of the multistage mechanical seal, and for discharging the liquid that has passed through the sliding contact surfaces of the rotary seal ring and stationary seal ring of each stage. A multi-stage mechanical seal wear monitoring apparatus having a plurality of seal leakage passages, comprising the control bleed-off passage and a particle size distribution measuring instrument connected to the seal leakage passage.

In a preferred aspect of the present invention, the particle size distribution measuring device detects a sample cell for storing the liquid, a light source for irradiating the liquid in the sample cell with light, and an intensity distribution of the light that has passed through the liquid. And a particle size distribution analyzer for analyzing the intensity distribution of the light and measuring the particle size distribution of the wear powder in the liquid.
In a preferred aspect of the present invention, the apparatus further comprises a processing device for determining a wear ratio between the stationary seal ring and the rotary seal ring from the particle size distribution.

In a preferred aspect of the present invention, the particle size distribution analyzer further has a function of measuring a volume of wear powder in a liquid, the processing device calculates a cumulative value of the volume of the wear powder, and further the wear. The wear amount of the stationary seal ring and the wear amount of the rotary seal ring are determined from the ratio and the cumulative value of the volume of the wear powder.
In a preferred aspect of the present invention, the processing apparatus estimates a remaining life of the rotary seal ring by comparing a wear amount of the rotary seal ring with a preset allowable wear amount, and the stationary seal ring The remaining life of the stationary seal ring is estimated by comparing the amount of wear with a preset allowable wear amount.

According to the present invention, the wear amount of the seal ring can be accurately estimated based on the concentration of the wear powder contained in the liquid that has passed through the mechanical seal or the volume of the wear powder. Furthermore, the life of the seal ring can be predicted from the estimated wear amount.

It is sectional drawing which shows schematic structure of the pump which has a shaft seal mechanism. It is sectional drawing which shows a two-stage tandem mechanical seal. It is a figure which shows the liquid leak path | route of the multistage mechanical seal shown in FIG. It is a figure which shows one Embodiment of the wear monitoring apparatus which monitors wear of the mechanical seal shown in FIG. It is a graph which shows the particle size distribution of the iron clad fine particle contained in the primary cooling water of a nuclear reactor. It is a figure which shows the example which combined the particle size distribution measuring device and the automatic sampler. Wear monitoring comprising a continuous analysis system connected to the control bleed-off flow path, a first batch analysis system connected to the seal leakage passage, and a second batch analysis system connected to the continuous analysis system It is a figure which shows the example of an apparatus. It is a graph which shows transition of the abrasion of the sliding contact surface of a 1st step seal assembly. It is a figure explaining a mode that a rotation seal ring and a stationary seal ring wear. It is a graph which shows the relationship between the cumulative value of the density | concentration of a wear powder, and the amount of wear. It is a graph which shows the relationship between wear amount [mm], the cumulative value [g] of wear powder concentration, and operation time [hour]. FIG. 12A is a diagram showing a result of wear measurement of a first-stage seal assembly of a two-stage mechanical seal. FIG. 12B is a diagram showing a result of wear measurement of the first-stage seal assembly of the two-stage mechanical seal. FIG. 13A is a graph showing the particle size distribution of wear powder at the initial wear stage shown in FIG. FIG. 13B is a graph showing the particle size distribution of wear powder at the stable wear stage shown in FIG. 8. FIG. 13C is a graph showing the particle size distribution of the wear powder in the final wear stage shown in FIG. FIG. 14A is a diagram illustrating an operation cycle of a nuclear power plant. FIG. 14B is a graph showing the relationship between the operation time of the nuclear power plant and the estimated wear amount of the mechanical seal.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view showing a schematic configuration of a pump having a shaft seal mechanism. As shown in FIG. 1, the pump includes a shaft 1 connected to a drive source such as a motor, an impeller 2 fixed to the shaft 1, a casing 3 that houses the impeller 2, and an opening of the casing 3. A casing cover 5 for covering and a shaft sealing mechanism 8 for preventing leakage of the liquid pressurized by the impeller 2 are provided. As the impeller 2 rotates, the liquid is sucked from the suction port 3a of the casing 3, and the pressurized liquid is discharged from the discharge port 3b.

As an example of the pump shown in FIG. 1, there is a pump used for circulation of primary cooling water of a nuclear power plant. Such a pump is required to limit the amount of liquid leaking outside the pump as little as possible due to the high internal pressure and the nature of the liquid. Therefore, in the pump shown in FIG. 1, a multistage mechanical seal is used as the shaft seal mechanism 8. The multistage mechanical seal includes at least two seals, and is configured such that even if one seal fails, the other seals can maintain the shaft seal function.

The shaft seal mechanism 8 is a two-stage tandem mechanical seal provided with a first-stage seal assembly 10 and a second-stage seal assembly 20. The first stage seal assembly 10 is disposed upstream of the second stage seal assembly 20, and the first stage seal assembly 10 and the second stage seal assembly 20 are disposed in series along the shaft 1. . The first stage seal assembly 10 and the second stage seal assembly 20 are accommodated in the seal cartridge 9.

Mechanical seal 8 shown in FIG. 1, the load pressure P _U applied to the second-stage seal assembly 20, is designed to be about one-half of the load pressure P _L applied to the first stage seal assembly 10 (That is, P _U ≈0.5P _L ). In the event that either the first stage seal assembly 10 or the second stage seal assembly 20 fails, the first stage seal assembly 10 and the second stage seal assembly 20 are maintained so that the sealing function is maintained. any of is configured to seal the full load pressure P _L. In the pump shown in FIG. 1, a two-stage mechanical seal is used, but a three-stage or more mechanical seal may be used. In the case of a three-stage mechanical seal, the design is such that one third of the total load pressure is applied to each stage, but the assignment of the load pressure to each stage is not limited to this.

FIG. 2 is a cross-sectional view showing a two-stage tandem mechanical seal. The mechanical seal 8 includes a first stage seal assembly 10, a second stage seal assembly 20 disposed downstream of the first stage seal assembly 10, the first stage seal assembly 10 and the second stage seal assembly 10. And a seal cartridge 9 for accommodating the step seal assembly 20. The first-stage seal assembly 10 and the second-stage seal assembly 20 are mounted on the seal cartridge 9, and the first-stage seal assembly 10, the second-stage seal assembly 20, and the seal cartridge 9 are one unit as a whole. The body cartridge structure is constituted. The first stage seal assembly 10 and the second stage seal assembly 20 are respectively disposed in a first seal chamber 15 and a second seal chamber 25 formed in the seal cartridge 9.

The first stage seal assembly 10 is disposed adjacent to the first rotary seal ring 11 that rotates with the shaft 1, the first stationary seal ring 12 that contacts the first rotary seal ring 11, and the first stationary seal ring 12. The first backup ring 13 and the first spring 14 that presses the first stationary seal ring 12 against the first rotary seal ring 11 through the first backup ring 13 are provided. Similarly, the second stage seal assembly 20 is adjacent to the second rotary seal ring 21 that rotates with the shaft 1, the second stationary seal ring 22 that contacts the second rotary seal ring 21, and the second stationary seal ring 22. And a second spring 24 that presses the second stationary seal ring 22 against the second rotary seal ring 21 via the second backup ring 23.

The rotary seal rings 11 and 21 are made of a hard material such as ceramic, and the stationary seal rings 12 and 22 are made of a soft material such as carbon graphite. The backup rings 13 and 23 are provided to press the stationary seal rings 12 and 22 made of a soft material uniformly against the rotary seal rings 11 and 21 with the

springs

14 and 24. Depending on the type of seal, a soft material may be used for the rotary seal ring, and a hard material may be used for the stationary seal ring.

FIG. 3 is a diagram showing a liquid leakage path of the multistage mechanical seal shown in FIG. As shown in FIG. 3, the multistage mechanical seal has two liquid leakage paths. The right side of FIG. 3 shows the first liquid leakage path. The first liquid leakage path is a path through a control bleed-off mechanism that intentionally flows part of the pressurized liquid out of the pump. This control bleed-off mechanism is provided to adjust the pressure difference between the stages of the mechanical seal 8. In the two-stage mechanical seal 8, the relationship between the load pressure P _L applied to the first-stage seal assembly 10 and the load pressure P _U applied to the second-stage seal assembly 20 is P _U ≈0.5 P _L. The pressure difference between the stages is adjusted.

As shown in FIG. 2, the control bleed-off mechanism includes a control bleed-off flow path 30 that communicates with the outside of the pump 1, a first-stage decompression cell 31 that communicates the first seal chamber 15 and the second seal chamber 25. The second-stage depressurization cell 32 communicates with the second seal chamber 25 and the control bleed-off flow path 30.

A part of the liquid (total pressure P _L ) in the first seal chamber 15 flows into the second seal chamber 25 through the first-stage decompression cell 31, and further the liquid (pressure P _U ) in the second seal chamber 25. Almost the entire amount flows through the second-stage decompression cell 32 and flows out of the pump 1 through the control bleed-off flow path 30. Hereinafter, the flow rate Qb of the liquid leaking through the control bleed-off flow path 30 is referred to as a control bleed-off flow rate. The control bleed-off flow rate Qb is a flow rate necessary for maintaining the lubrication of the second stage seal assembly 20 and removing heat generated in the second stage seal assembly 20. For example, if the main circulation pump for a boiling water reactor, the full-load pressure _{P L} is approximately 7 MPa, it controls the bleed-off flow rate Qb is about 3L / min.

The left side of FIG. 3 shows the second liquid leakage path. The second liquid leakage path includes the sliding contact surface of the first stage seal assembly 10 (that is, the contact surface between the first rotary seal ring 11 and the first stationary seal ring 12), and the second stage seal assembly 20. This is a leakage path through the sliding contact surface (that is, the contact surface between the second rotary seal ring 21 and the second stationary seal ring 22). The liquid slightly leaks through the sliding contact surface of the first stage seal assembly 10 and the sliding contact surface of the second stage seal assembly 20, and is discharged to the outside of the pump 1 through the seal leakage passage 35. Hereinafter, the flow rate of the liquid flowing through the seal leakage passage 35 is referred to as a seal leakage flow rate Qs. This seal leakage flow rate Qs varies within the range of 0 to 1.5 L / min depending on the operation state of the pump 1. During steady operation of the pump, the seal leakage flow rate Qs is as small as several cc / min.

As can be seen from FIG. 3, the liquid leaked from the sliding contact surface of the first stage seal assembly 10 into the second seal chamber 25 flows into the second seal chamber 25 through the first stage decompression cell 31 (control bleed-off). Flow). Further, a part of the liquid in the second seal chamber 25 is discharged to the outside of the pump 1 through the sliding contact surface of the second stage seal assembly 20 and the seal leakage passage 35, and the remainder is stored in the second stage decompression cell 32 and It is discharged out of the pump 1 through the control bleed-off flow path 30.

Therefore, the liquid discharged to the outside from the seal leakage passage 35 includes wear powder generated on both the sliding contact surface of the first stage seal assembly 10 and the sliding contact surface of the second stage seal assembly 20. On the other hand, the liquid discharged from the control bleed-off flow path 30 mainly includes wear powder generated on the sliding contact surface of the first stage seal assembly 10. Therefore, by analyzing the properties of the liquid discharged from the seal leakage passage 35 and the liquid discharged from the control bleed-off flow path 30, the sliding contact surface of the first stage seal assembly 10 and the second stage seal assembly are analyzed. The wear state of the 20 sliding contact surfaces can be estimated.

Next, a wear monitoring device that monitors the wear of the sliding surface of the mechanical seal based on the properties of the liquid discharged from the mechanical seal will be described. FIG. 4 is a diagram showing an embodiment of a wear monitoring device for monitoring the wear of the mechanical seal shown in FIG. The wear monitoring device is obtained from the continuous analysis system 40 connected to the control bleed-off flow path 30, the batch analysis system 60 connected to the seal leakage passage 35, and the continuous analysis system 40 and the batch analysis system 60. And a processing device 70 for determining the wear amount of the mechanical seal from the measurement result.

The continuous analysis system 40 is a concentration measurement system that measures the concentration of wear powder mixed in the liquid continuously discharged from the control bleed-off flow path 30. On the other hand, the batch type analysis system 60 is a particle size distribution measuring system that collects the liquid discharged intermittently from the seal leakage passage 35 and measures the particle size distribution of the wear powder mixed in the liquid.

As shown in FIG. 4, the continuous analysis system 40 includes a concentration measuring device 41 connected to the control bleed-off flow path 30 via the introduction line 37. This concentration measuring device 41 is detected by a flow cell 42 in which a liquid flows, a light source 43 that irradiates light to the liquid flowing in the flow cell 42, a light receiving element 44 that detects the intensity of light that has passed through the liquid, And a concentration analyzer 45 that determines the concentration of the abrasion powder in the liquid based on the intensity of light. As such an optical concentration measuring device 41, a measuring device using ultraviolet / visible light absorption, a measuring device using infrared light absorption, a measuring device using fluorescent light emission, a measuring device using Rayleigh scattering, Raman scattering light, A measuring instrument that uses a refractive index can be used.

A filter 50 is disposed on the upstream side of the concentration measuring device 41, and the liquid discharged from the control bleed-off flow path 30 is introduced into the flow cell 42 through the filter 50. The filter 50 is provided to remove particles originally contained in the liquid. For example, the primary cooling water of the nuclear reactor includes iron clad fine particles having a particle diameter of 2 μm to 12 μm, as shown in FIG. Therefore, in this case, the filter 50 preferably has a function of capturing particles having a particle diameter of 2 μm or more. The filter 50 may incorporate a magnet filter for capturing particles containing iron.

The liquid discharged from the control bleed-off flow path 30 flows in the flow cell 42. The flow cell 42 is provided with a transparent window 46, and the light beam from the light source 43 is applied to the liquid through the transparent window 46. The intensity of light that has passed through the liquid is detected by the light receiving element 44. The intensity of light varies depending on the concentration of wear powder mixed in the liquid. That is, when light is applied to the wear powder in the liquid, part of the light is absorbed, light is emitted from the wear powder, or the light is scattered or refracted. As a result, the light intensity varies depending on the concentration of the wear powder. Therefore, the concentration of the wear powder in the liquid can be estimated from the intensity of light that has passed through the liquid.

The concentration analyzer 45 is connected to the light receiving element 44, and a light intensity detection signal is sent from the light receiving element 44 to the concentration analyzer 45. The concentration analyzer 45 stores in advance a table or a relational expression indicating the relationship between the content of wear powder in the liquid and the intensity of light that has passed through the liquid. Therefore, the concentration analyzer 45 can continuously determine the content of wear powder contained in the liquid from the detected value of the intensity of the light transmitted from the light receiving element 44. More specifically, the concentration analyzer 45 calculates the concentration of wear powder per unit time (for example, per hour) based on the intensity of light. For example, the concentration of the wear powder is defined as the mass [g / h] of the wear powder contained in the liquid discharged every hour.

The flow rate of liquid required for measuring the wear powder concentration varies depending on the type of concentration measuring instrument. Therefore, in order to adjust the flow rate of the liquid flowing through the flow cell 42, a bypass line 51 that bypasses the concentration measuring device 41 is provided. The bypass line 51 branches off from the introduction line 37 so that a part of the liquid bypasses the concentration measuring device 41 through the bypass line 51. A bypass valve 52 is provided in the bypass line 51, and the flow rate of the liquid that bypasses the concentration measuring device 41 is adjusted by the bypass valve 52. Therefore, the flow rate of the liquid flowing through the flow cell 42 can be adjusted by the opening degree of the bypass valve 52.

The batch analysis system 60 includes a particle size distribution measuring device 61 that measures the volume and particle size distribution of wear powder mixed in the liquid discharged intermittently from the seal leakage passage 35. The particle size distribution measuring device 61 includes a sample cell 62 for storing a liquid, a light source 63 for irradiating the liquid in the sample cell 62 with light, a light receiving element 64 for detecting an intensity distribution of the light that has passed through the liquid, A particle size distribution analyzer 65 that analyzes the intensity distribution of light detected by the light receiving element 64 to determine the volume and particle size distribution of the wear powder in the liquid is provided.

The liquid discharged from the seal leakage passage 35 is guided to the sample cell 62 through the switching valve 68. The sample cell 62 is movable, and the sample cell 62 in which the liquid is stored is carried to a measurement position between the light source 63 and the light receiving element 64. When the sample cell 62 is in the measurement position, the liquid discharged from the seal leakage passage 35 is transferred to the storage portion 72 through the switching valve 68.

The particle size distribution measuring device 61 measures the particle size distribution of the wear powder in the liquid by irradiating the liquid with light and analyzing the light passing through the liquid. Since the particle size distribution measuring device 61 performs batch analysis by liquid sampling, it is possible to measure the volume of wear powder contained in the liquid and the particle size distribution thereof. As such an optical particle size distribution measuring device 61, a measuring device using a laser light scattering diffraction method or a measuring device using dynamic light scattering can be used.

The liquid discharged from the seal leakage passage 35 contains wear powder generated in both the first stage seal assembly 10 and the second stage seal assembly 20. For this reason, from the measurement result obtained by the batch analysis system 60, it cannot be specified which of the first stage seal assembly 10 or the second stage seal assembly 20 is more worn. Therefore, not only the liquid discharged from the seal leakage passage 35 but also the liquid discharged from the control bleed-off flow path 30 is analyzed by the batch type analysis system 60.

The particle size distribution measuring device 61 of the batch analysis system 60 is also connected to the control bleed-off channel 30 via the continuous analysis system 40. Specifically, as shown in FIG. 4, the liquid from the control bleed-off flow path 30 is introduced into the batch analysis system 60 by operating the switching valve 55 after passing through the concentration measuring device 41. ing. The switching valve 55 is a valve for selectively guiding the liquid to either the storage unit 57 or the batch analysis system 60.

The batch type analysis system 60 is provided with a sample cell 67, and the liquid from the continuous analysis system 40 (that is, the liquid discharged from the control bleed-off flow path 30) is stored in the sample cell 67. The sample cell 67 is conveyed to the particle size distribution measuring device 61, where the particle size distribution of the wear powder in the liquid is measured. While the sample cell 67 is at the measurement position of the particle size distribution measuring device 61, the liquid is guided to the storage portion 57 through the switching valve 55.

FIG. 6 is a diagram showing an example in which the particle size distribution measuring device 61 and the automatic sampler 75 are combined. In this example, both the liquid discharged from the control bleed-off flow path 30 and the liquid discharged from the seal leakage passage 35 are introduced into the automatic sampler 75. The automatic sampler 75 includes a container 76 that stores liquid, a circulation pump 77 that stirs the liquid in the container 76 and circulates the liquid between the container 76 and the sample cell 62 of the particle size distribution measuring device 61, and the container The liquid level sensor 78 which detects the liquid level position of the liquid in 76 is provided. Since the flow rate of the liquid discharged from the seal leakage passage 35 is small, the liquid level sensor 78 detects that the liquid has accumulated in the container 76.

The liquid discharged from the seal leakage passage 35 is guided to the container 76 through the switching valve 68. On the other hand, the liquid discharged from the control bleed-off flow path 30 passes through the concentration measuring device 41 and is further guided to the container 76 through the switching valve 55. The sample cell 62 and the container 76 of the particle size distribution measuring device 61 are connected by a transfer line 81 and a return line 82. The liquid in the container 76 is transferred to the sample cell 62 through the transfer line 81, and the liquid in the sample cell 62 is returned to the container 76 through the return line 82. The container 76 is provided with a drain 79 for discharging the liquid in the container 76.

By alternately operating the two switching

valves

55 and 68, either the liquid discharged from the control bleed-off flow path 30 or the liquid discharged from the seal leakage passage 35 is guided to the container 76 of the automatic sampler 75. . Therefore, both the liquid from the control bleed-off flow path 30 and the liquid from the seal leakage passage 35 can be alternately analyzed by the particle size distribution measuring device 61.

FIG. 7 shows a continuous analysis system 40 connected to the control bleed-off flow path 30, a first batch analysis system 60 A connected to the seal leakage passage 35, and a second batch connected to the continuous analysis system 40. It is a figure which shows the example of the wear monitoring apparatus provided with the type | formula analysis system 60B. The configuration and arrangement of the continuous analysis system 40 are the same as in the above example. The basic configuration of the first batch analysis system 60A and the second batch analysis system 60B is the same as that of the batch analysis system 60 shown in FIG.

In this example, elements corresponding to the switching

valves

55 and 68 and the

reservoirs

57 and 72 shown in FIG. 6 are not provided. The volume and particle size distribution of the wear powder in the liquid discharged from the seal leakage passage 35 are measured by the first batch analysis system 60A, and the volume of the wear powder in the liquid discharged from the control bleed-off flow path 30 and The particle size distribution is measured by the second batch analysis system 60B.

Next, a method for determining the seal life using the wear monitoring device for the mechanical seal 8 described above will be described. FIG. 8 is a graph showing the transition of wear on the sliding contact surface of the first stage seal assembly 10. The vertical axis of the graph shown in FIG. 8 represents the wear powder concentration C [g / h] in the liquid, and the horizontal axis represents the operation time [hour] of the mechanical seal (or pump). As can be seen from FIG. 8, mechanical seal wear is divided into an initial wear stage in which wear is relatively large, a stable wear stage in which wear is low, and an end wear stage in which wear gradually increases.

Most of the abrasion powder generated on the sliding contact surface of the first stage seal assembly 10 is discharged together with the liquid from the control bleed-off flow path 30, while the abrasion powder generated on the sliding contact surface of the second stage seal assembly 20. Is not discharged from the control bleed-off flow path 30. Therefore, by analyzing the liquid from the control bleed-off flow path 30 by the continuous analysis system 40, the wear amount of the first stage seal assembly 10 can be estimated.

FIG. 9 is a diagram for explaining how the rotary seal ring 11 and the stationary seal ring 12 are worn. As shown in FIG. 9, the wear amount W of the sliding contact surface is defined as the thickness [mm] of the stationary seal ring 12 and the rotary seal ring 11 that has been worn away. The wear amount W of the first-stage seal assembly 10 is obtained by integrating the wear powder concentration C [g / h] with respect to time to obtain a cumulative value Ct [g] of the concentration C, and a cumulative value Ct [g prepared in advance. ] And the amount of wear [mm].

FIG. 10 is a graph showing the relationship between the cumulative value of wear powder concentration and the amount of wear. In FIG. 10, the vertical axis represents the wear amount [mm] of the sliding surface of the seal ring, and the horizontal axis represents the cumulative value [g] of the concentration of wear powder. As shown in FIG. 10, the amount of wear on the sliding surface of the seal ring is proportional to the cumulative value of the concentration of wear powder. The correspondence between the wear amount and the accumulated value of the wear powder concentration can be obtained in advance by actual measurement. A table or a relational expression indicating the relationship between the wear amount of the sliding contact surface of the seal ring and the accumulated value of the concentration of wear powder is stored in the processing device 70 in advance. Therefore, the processing device 70 integrates the wear powder concentration [g / h] per unit time measured by the continuous analysis system 40 with respect to time to obtain a cumulative value Ct of the wear powder concentration, and the obtained cumulative value Ct. From this, the amount of wear on the sliding contact surface of the first stage seal assembly 10 can be estimated.

FIG. 11 is a graph showing the relationship between the wear amount [mm], the cumulative value Ct [g] of the wear powder concentration, and the operation time t [hour]. In the graph of FIG. 11, the left vertical axis represents the amount of wear on the sliding surface of the seal ring, the right vertical axis represents the cumulative value of wear powder concentration, and the horizontal axis represents the operating time of the mechanical seal (or pump). To express. As can be seen from FIG. 11, the cumulative value of the wear powder concentration and the wear amount increase with the operation time. Therefore, it is possible to determine the life of the rotary seal ring and / or the stationary seal ring from the obtained amount of wear. That is, the processing device 70 can determine that the rotating seal ring and / or the stationary seal ring has reached the end of its life when the wear amount reaches a predetermined threshold (allowable wear amount). Furthermore, it is possible to estimate the remaining life of the rotary seal ring and / or the stationary seal ring from a comparison between the current wear amount and a threshold value (allowable wear amount).

12A and 12B are diagrams showing the results of wear measurement of the first-stage seal assembly 10 of the two-stage mechanical seal 8. This two-stage mechanical seal was installed in a pump used for circulation of the primary cooling water of the nuclear reactor, and the operation time of the pump was about 9000 hours. The stationary seal ring was made of carbon and the rotary seal ring was made of ceramic.

As shown in FIG. 12B, the arithmetic average roughness Ra of the stationary seal ring was about 2 μm, and the maximum height Ry was about 12 μm. On the other hand, the arithmetic average roughness Ra of the rotary seal ring was about 0.03 μm, and the maximum height Ry was about 0.4 μm. From this measurement result, it can be seen that the wear amount of the rotary seal ring is considerably smaller than the wear amount of the stationary seal ring. Further, since the particle size of the wear powder is assumed to be an arithmetic average roughness Ra or less, the particle size of the wear powder generated from the stationary seal ring is 2 μm or less from the measurement result, and the wear powder particles generated from the rotating seal ring It can be seen that the diameter is 0.03 μm or less.

As shown in FIG. 4, since the filter 50 is installed on the upstream side of the concentration measuring device 41, particles having a particle size of 2 μm or more are removed from the liquid by the filter 50. Therefore, the particles measured by the concentration measuring device 41 are not originally contained in the reactor water, but are abrasion powder generated in the first stage seal assembly 10. In the embodiment described above, the concentration of all components of the wear powder is measured, but the concentration of a specific component of the wear powder may be measured. In that case, the concentration of the wear powder of the rotary seal ring 11 and the concentration of the wear powder of the stationary seal ring 12 can be measured separately.

13A is a graph showing the particle size distribution of the wear powder in the initial wear stage shown in FIG. 8, and FIG. 13B is a graph showing the particle size distribution of the wear powder in the stable wear stage shown in FIG. These are the graphs which show the particle size distribution of the abrasion powder in the last stage abrasion stage shown in FIG. The graphs shown in FIGS. 13A to 13C are graphs showing the results of measuring the particle size distribution of the wear powder in the liquid discharged from the control bleed-off flow path 30, and the vertical axis represents the relative amount (volume) of the particles in the liquid. %), And the horizontal axis represents the particle size.

As described above, the particle size of the wear powder generated from the stationary seal ring is assumed to be 2 μm or less, and the particle size of the wear powder generated from the rotating seal ring is assumed to be 0.03 μm or less. That is, the particle size of the wear powder generated from the stationary seal ring is about 70 times the particle size of the wear powder generated from the rotating seal ring, and there is a large difference between the particle sizes of the two. Therefore, each peak particle size clearly appears on the particle size distribution as shown in FIGS. 13A to 13C.

The sign v1 in FIG. 13B indicates the volume% at the peak particle diameter d1 of the wear powder generated from the stationary seal ring, and the sign v2 indicates the volume% at the peak particle diameter d2 of the wear powder generated from the rotating seal ring. Show. The volume% v1 and v2 are measured by the particle size distribution measuring device 61. As can be seen from FIGS. 13A to 13C, in each of the initial wear stage, the stable wear stage, and the final wear stage, the ratio between the volume% at the peak particle diameter d1 and the volume% at the peak particle diameter d2 is It is approximately v1: v2. Therefore, the processing device 70 can obtain the wear ratio v1: v2 between the stationary seal ring and the rotating seal ring at the time of sampling the sample liquid from the measured volume% v1, v2.

As described above, the batch analysis system 60 measures not only the particle size distribution but also the volume of the wear powder contained in the liquid. The volume of the wear powder in the liquid is approximately proportional to the amount of wear on the sliding contact surfaces of the rotary seal ring and the stationary seal ring. Therefore, it is also possible to estimate the amount of wear on the sliding contact surface of the seal ring from the volume of wear powder measured by the batch analysis system 60.

The particle size distribution measuring device 61 measures the volume of wear powder in the liquid in units of sample cells. Therefore, the amount of wear on the sliding contact surfaces of the stationary seal ring and the rotary seal ring can be determined from the cumulative value of the volume of wear powder. The processing device 70 stores in advance a table or a relational expression indicating the relationship between the volume of wear powder and the amount of wear on the sliding surface. The processing device 70 integrates the volume of the wear powder measured by the particle size distribution measuring device 61 to obtain a cumulative value of the volume of the wear powder, and further, from the obtained cumulative value, the static seal ring and the rotary seal ring. The wear amount “mm” of the sliding contact surface is determined.

The liquid collected from the seal leakage passage 35 contains wear powder generated on the sliding contact surfaces of both the first stage seal assembly 10 and the second stage seal assembly 20. On the other hand, the liquid collected from the control bleed-off flow path 30 contains only wear powder generated on the sliding contact surface of the first stage seal assembly 10. Therefore, the amount of wear of the first stage seal assembly 10 can be estimated from the cumulative value of the volume of wear powder contained in the liquid discharged from the control bleed-off flow path 30.

Further, the wear amount of each seal ring can be calculated from the wear amount of the first stage seal assembly 10 and the wear ratio v1: v2 between the stationary seal ring 12 and the rotary seal ring 11. Specifically, the processing device 70 determines the wear amount of the stationary seal ring 12 and the wear amount of the rotary seal ring 11 of the first stage seal assembly 10 as follows.
Abrasion amount of stationary seal ring = Abrasion amount of first stage seal assembly × v1 / (v1 + v2)
Abrasion amount of rotating seal ring = Abrasion amount of first stage seal assembly × v2 / (v1 + v2)

The processing device 70 further estimates the remaining life of the rotary seal ring 11 by comparing the obtained wear amount of the rotary seal ring 11 with a predetermined threshold (that is, the allowable wear amount). ing. Similarly, the processing device 70 estimates the remaining life of the stationary seal ring 12 by comparing the obtained wear amount of the static seal ring 12 with a predetermined threshold (that is, the allowable wear amount). It has become.

The amount of wear of the second stage seal assembly 20 is obtained by subtracting the amount of wear of the first stage seal assembly 10 from the total amount of wear of the first stage seal assembly 10 and the second stage seal assembly 20. That is, the batch analysis system 60 measures the volume of wear powder contained in the liquid discharged from the seal leakage passage 35, and the processing device 70 calculates the cumulative value of the volume of wear powder and calculates the total wear amount. Then, the wear amount of the second stage seal assembly 20 is obtained by subtracting the wear amount of the first stage seal assembly 10 from the total wear amount.

Also in the second stage seal assembly 20, the ratio of the volume% at the peak particle diameter d1 to the volume% at the peak particle diameter d2 is generally assumed to be v1: v2. Therefore, the processing device 70 calculates the rotational seal of the second stage seal assembly 20 from the calculated wear amount of the second stage seal assembly 20 and the wear ratio v1: v2 between the stationary seal ring 22 and the rotary seal ring 21. The wear amount of the ring 21 and the wear amount of the stationary seal ring 22 can be calculated.

In this way, the processing device 70 obtains the wear amount of the first stage seal assembly 10 in real time from the measurement data from the continuous analysis system 40 and uses the measurement data from the batch analysis system 60 to obtain the first stage seal assembly. The wear amount of the stationary seal ring and the wear amount of the rotary seal ring of the 10 and second stage seal assemblies 20 can be determined in batches. Since the wear powder contained in the liquid is submicron-sized particles, in the measurement of the particle size distribution by the batch analysis system 60, an additive that prevents aggregation of nanoparticles such as polyethylene glycol is added to the liquid. Also good.

Next, a method for setting the seal ring replacement time using the above-described wear monitoring device will be described. FIG. 14A is a diagram illustrating an operation cycle of a nuclear power plant. From the viewpoint of fuel life, one operation cycle is set to about one year. Therefore, the mechanical seal used for the circulation pump is designed so that it can be continuously operated for at least one year.

In the pump operation, the pressure P _L in the first seal chamber 15 and the pressure P _U (see FIG. 2) in the second seal chamber 25 and the flow rate Qs of the liquid discharged from the seal leakage passage 35 are mainly monitored. . Conventionally, when at least one of these P _L , P _U , and Qs reaches a preset value, the operation of the pump is stopped, and the mechanical seal is disassembled, inspected, and replaced with a new seal ring. The The wear amount and sliding contact surface of the seal ring cannot be evaluated until the mechanical seal is disassembled. For this reason, even if the state of the seal ring is good, the seal ring is replaced every cycle.

Since the wear monitoring apparatus according to the present embodiment can reasonably estimate the wear amount of the seal ring, as shown in FIG. 14B, if the estimated wear amount is sufficiently small relative to the allowable wear amount, the seal ring is removed. Multi-cycle operation is possible without replacement. That is, the seal ring may be replaced only when the remaining life Tr of the seal ring at the end of a certain operation cycle is equal to or shorter than the operation time Tc of the next operation cycle. By such operation management, it is possible to obtain various advantageous effects such as reduction of seal ring replacement cost, reduction of waste during replacement of the seal ring, and reduction of exposure dose during replacement of the seal ring.

The above-described embodiments are described for the purpose of enabling the person having ordinary knowledge in the technical field to which the present invention belongs to implement the present invention. Various modifications of the above embodiment can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Accordingly, the present invention is not limited to the described embodiments, but is to be construed in the widest scope according to the technical idea defined by the claims.

The present invention can be applied to a mechanical seal wear monitoring device, and in particular to a device that monitors the wear of a multistage mechanical seal used in a pump and predicts the remaining life of the mechanical seal.

1 shaft 2 impeller 3 casing 8 shaft sealing mechanism (mechanical seal)
9 Seal cartridge 10 First stage seal assembly 20 Second stage seal assembly 30 Control bleed-off flow path 35 Seal leakage path 40 Continuous analysis system 41 Concentration measuring device 42 Flow cell 43 Light source 44 Light receiving element 45 Concentration analyzer 60 Batch type analysis System 61 Particle size distribution measuring device 62 Sample cell 63 Light source 64 Light receiving element 65 Particle size distribution analyzer 70 Processing device

Claims

A control bleed-off mechanism for adjusting the pressure difference between the stages of the multistage mechanical seal, and a seal leakage passage for discharging the liquid that has passed through the sliding contact surface between the rotary seal ring and the stationary seal ring of each stage A multistage mechanical seal wear monitoring device,
A concentration measuring device for continuously measuring the concentration of wear powder in the liquid discharged from the control bleed-off mechanism;
A wear monitoring device comprising: a processing device that estimates a wear amount of the multistage mechanical seal from a wear powder concentration measured by the concentration measuring device.
The concentration measuring device is detected by the flow cell through which the liquid passes, a light source that irradiates light to the liquid flowing through the flow cell, a light receiving element that detects the intensity of light that has passed through the liquid, and the light receiving element. The wear monitoring apparatus according to claim 1, further comprising a concentration analyzer that determines a concentration of the wear powder in the liquid from light intensity.
The wear monitoring apparatus according to claim 1 or 2, wherein the processing device determines the wear amount of the sliding contact surface by integrating the concentration of the wear powder with respect to time.
The said processing apparatus estimates the remaining lifetime of the said rotation seal ring and the said stationary seal ring by comparing the determined said wear amount with the preset allowable wear amount. The wear monitoring device described in 1.
The wear monitoring apparatus according to any one of claims 1 to 4, further comprising a particle size distribution measuring instrument connected to the control bleed-off flow path and the seal leakage passage.
A multistage having a control bleed-off mechanism for adjusting the pressure difference between the stages of the multistage mechanical seal, and a seal leakage passage for discharging the liquid that has passed through the sliding contact surface of each stage of the rotary seal ring and the stationary seal ring A mechanical seal wear monitoring device,
A wear monitoring apparatus comprising a particle size distribution measuring instrument connected to the control bleed-off flow path and the seal leakage passage.
The particle size distribution measuring device includes a sample cell for storing a liquid, a light source that irradiates light to the liquid in the sample cell, a light receiving element that detects an intensity distribution of light that has passed through the liquid, and the light. The wear monitoring apparatus according to claim 6, further comprising: a particle size distribution analyzer that analyzes a strength distribution of the wear powder to measure a particle size distribution of the wear powder in the liquid.
The wear monitoring device according to claim 7, further comprising a processing device for determining a wear rate between the stationary seal ring and the rotary seal ring from the particle size distribution.
The particle size distribution analyzer further has a function of measuring the volume of the wear powder in the liquid, and the processing device calculates a cumulative value of the volume of the wear powder, and further calculates the wear ratio and the volume of the wear powder. The wear monitoring apparatus according to claim 8, wherein the wear amount of the stationary seal ring and the wear amount of the rotary seal ring are determined from the accumulated value of the above.
The processor is
By comparing the wear amount of the rotary seal ring and a preset allowable wear amount, the remaining life of the rotary seal ring is estimated,
The wear monitoring apparatus according to claim 9, wherein the remaining life of the stationary seal ring is estimated by comparing a wear amount of the stationary seal ring with a preset allowable wear amount.