JP4885258B2 - Sealing capacity determination method and apparatus - Google Patents

Description

  The present invention relates to a sealing capacity determination method and apparatus, and more particularly, to a sealing capacity determination method and apparatus for determining sealing capacity in a pump in which mechanical seals are divided in multiple stages.

As a pump having mechanical seals divided into multiple stages, for example, recirculation for forcibly circulating cooling water in a reactor containment vessel of a boiling water reactor (BWR) used for nuclear power generation There is a (Primary Loop Reciprocation: PLR) pump (see, for example, Patent Document 1).
Therefore, a PLR pump will be described below as an example of a pump having mechanical seals divided into multiple stages.

The PLR pump is disposed in the middle of each of the two recirculation paths installed in the reactor pressure vessel, and is driven by a driving motor (motor) to operate. In order to prevent cooling water in the nuclear reactor flowing through the recirculation path from flowing through the rotating shaft connecting the PLR pump and the motor to the motor side between the PLR pump and the motor. A shaft seal portion having a two-stage structure including a step shaft seal portion and a second step shaft seal portion is provided.
The first stage shaft seal part and the second stage shaft seal part, and the second stage shaft seal part and the outside of the shaft seal part slide on the stationary ring (sheet ring) fixedly installed on the shaft seal part structure and the stationary ring. While being in contact with each other, it is isolated by a mechanical seal constituted by a rotating ring that rotates integrally with the rotating shaft.

  Like the PLR pump, when the shaft seal part has a two-stage structure with two mechanical seals, the seal moves from the first stage side to the second stage side when the first stage sealing capacity is reduced. The amount of water increases and the pressure and temperature on the second stage increase. Further, when the sealing ability of the second stage is reduced, it is detected as an increase in the amount of seal water flowing out.

JP-A-9-281274

  However, conventionally, a decrease in the sealing ability can be detected as an increase in the amount of outflow water of the seal water or a change in the pressure or temperature of the shaft seal. Since it was after the situation where the sealing ability was being lost, in the detection by these indexes, there was little time margin from the detection until the equipment or the nuclear power plant was stopped.

For this reason, it has been desired to improve the detection so that a sufficient margin can be obtained from the detection until the equipment or the nuclear power plant is stopped without immediately leading to repair and replacement.
In addition, in the detection based on the conventional index, it is impossible to evaluate the soundness of the sealing ability indicating that each seal has the original sealing ability, and thus it is impossible to determine the service life of each seal. .

In other words, the soundness of the sealing ability at the shaft seal can be evaluated, and further, the deterioration of the sealing ability can be detected at an early stage, which is closely related to the efficient operation and maintenance of a pump having a multi-stage mechanical seal. It is an important issue that leads to
An object of the present invention is to provide a sealing ability determination method and apparatus capable of evaluating the soundness of sealing ability in a pump in which mechanical seals are divided into multiple stages and detecting a decrease in sealing ability at an early stage. It is to be.

In order to achieve the above object, the seal capacity determination method according to the present invention relates to a mechanical seal installed in a shaft seal portion of a pump in which mechanical seals are divided in multiple stages. The fluctuation component is evaluated using Auto Power Spectral Density (APSD), and the APSD level of the pressure of the shaft seal portion is higher than the value of the normal device of the redundant configuration based on the evaluation result. Based on that, it is recognized that the APSD has increased , and is determined as a sign of a decrease in sealing ability.

In order to achieve the above object, the seal capacity determination device according to the present invention is based on a seal pressure signal indicating a seal pressure of a mechanical seal installed in a shaft seal portion of a pump in which the mechanical seal is divided into multiple stages. power spectral density (Auto power spectral density: APSD) and APSD calculating means for calculating a, the APSD calculated by the APSD operation means, and APSD comparing means for comparing the APSD reference value, the comparison result of the APSD comparison means The seal for determining that the sealing ability of the shaft seal portion having the detected seal pressure has decreased based on the fact that the APSD level of the pressure of the shaft seal portion is higher than the value of the normal-side device in the redundant configuration. Ability judging means.

According to this invention, regarding the mechanical seal installed in the shaft seal portion of the pump in which the mechanical seal is divided into multiple stages, the minute fluctuation component included in the seal pressure signal of the shaft seal portion is evaluated using the APSD. Based on the evaluation result, the APSD level of the shaft seal pressure is increased compared to the value of the normal device in the redundant configuration, and it is determined that the APSD has increased , and is determined as a sign of a decrease in sealing ability. Thereby, while being able to evaluate the soundness of the sealing capability in a shaft seal part, the fall of a sealing capability can be detected at an early stage.
In addition, the sealing ability determination device according to the present invention can realize the sealing ability determination method.

It is a block diagram which shows the structure of the sealing capability determination apparatus which concerns on one embodiment of this invention. It is explanatory drawing which shows typically the structure of the nuclear reactor containment vessel of FIG. It is explanatory drawing which shows the structure of a PLR pump schematically. It is explanatory drawing which carried out the partial cross section which shows typically the internal structure of the 1st shaft seal part of FIG. It is explanatory drawing which shows the time series data which represented the change of the seal pressure signal in each shaft seal part in time series with a graph. It is explanatory drawing which shows the APSD level data which represented the change of the seal pressure signal in each shaft seal part by APSD with a graph.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a sealing ability determination device according to an embodiment of the present invention. As shown in FIG. 1, the seal capability determination device 10 includes an APSD calculation unit (APSD calculation unit) 11, an APSD comparison unit (APSD comparison unit) 12, and a seal capability determination unit (seal capability determination unit) 13. Yes.

This sealing capacity determination device 10 determines whether or not there is an indication that the sealing capacity of a pump with mechanical seals divided into multiple stages is reduced. Hereinafter, a pump with such mechanical seals divided into multiple stages. As a typical example, two PLR pumps (first pump 15a, second pump 15b, see FIG. 1) provided in the BWR reactor containment vessel 14 used for nuclear power generation will be described as an example. .
The mechanical seal is provided in each shaft sealing portion (first shaft sealing portion 16a, second shaft sealing portion 16b) of the two pumps (first pump 15a, second pump 15b).

  The first pump 15a is provided with a first pump first-stage seal pressure detector (seal pressure detector) 17a and a first pump second-stage seal pressure detector (seal pressure detector) 17b. A second pump first-stage seal pressure detector (seal pressure detector) 17c and a second pump second-stage seal pressure detector (seal pressure detector) 17d are installed on the pump 15b. Each seal pressure detection part 17a-17d detects the seal pressure of the mechanical seal provided in each shaft seal part (the 1st shaft seal part 16a, the 2nd shaft seal part 16b), and outputs the seal pressure signal which is a detection result. And output to the APSD calculation unit 11 (see FIG. 1).

  FIG. 2 is an explanatory view schematically showing the structure of the reactor containment vessel. As shown in FIG. 2, the reactor pressure vessel 18 provided inside the reactor containment vessel 14 is formed in a capsule shape containing a coolant (for example, water) C, and is created by nuclear fission. It has a discharge path 19a for discharging steam, a supply path 19b for supplying the coolant C, and two recirculation paths 20a and 20b.

  Pumps (first pump 15a and second pump 15b) are arranged in the middle of the two recirculation paths (20a and 20b), and the reactor pressure vessel is operated by the operation of each pump (15a and 15b). The coolant C in 18 is taken out to each recirculation path (20a, 20b), and is again sent into the reactor pressure vessel 18 through each recirculation path (20a, 20b). That is, the coolant C in the reactor pressure vessel 18 is recirculated via the two recirculation paths (20a, 20b).

In the reactor containment vessel 14, located below the pumps 15 a and 15 b, for example, seal water Ws, which will be described later, flows out from each shaft sealing portion (first shaft sealing portion 16 a and second shaft sealing portion 16 b). Tanks 21a and 21b for receiving the effluent are installed.
FIG. 3 is an explanatory diagram schematically showing the configuration of the PLR pump.
The shaft seal portion is provided in each of the two pumps (15a, 15b), but both shaft seal portions (the first shaft seal portion 16a and the second shaft seal portion 16b) have the same configuration and operation. In the following description, only one (the first shaft seal portion 16a of the first pump 15a) will be described, and the other (the second shaft seal portion 16b of the second pump 15b) will not be described.

  As shown in FIG. 3, the first pump 15 a is mounted on a rotary shaft 24 that transmits the rotational driving force of the motor 23 together with a pump main body 22 and a driving electric motor (motor) 23 that drives the pump main body 22. A single shaft sealing portion 16a is provided. One end of the rotary shaft 24 is connected to the output shaft of the motor 23, and the other end is located in the coolant channel 22a in the pump body 22, and an impeller 22b is attached to the other end. . The coolant channel 22a communicates with the recirculation path 20a via the coolant inlet and the coolant outlet, and constitutes a part of the recirculation path 20a through which the coolant C circulates.

When the rotational driving force of the motor 23 is transmitted to the rotary shaft 24 and the impeller 22b rotates, the coolant C flowing through the recirculation path 20a is drawn into the coolant channel 22a from the coolant inlet and from the coolant outlet. It is sent out to the recirculation path 20a.
The first shaft sealing portion 16a is sealed so that the coolant C flowing through the coolant channel 22a does not flow out to the motor 23 side through the rotating shaft 24 to which the impeller 22b is attached. Yes.

FIG. 4 is a partially sectional explanatory view schematically showing the internal structure of the first shaft seal portion of FIG. As shown in FIG. 4, the first-stage shaft sealing portion 25 a and the second-stage shaft sealing portion 25 b of the first shaft sealing portion 16 a have a two-stage configuration that is arranged so as to overlap along the direction of the rotation axis 24. ing. The first-stage shaft sealing portion 25a, the second-stage shaft sealing portion 25b, and the rotary shaft 24 are sealed by mechanical seals 26, respectively. The first-stage shaft sealing portion 25a and the second-stage shaft sealing portion 25b are mechanically sealed. It is defined by a seal 26.
The mechanical seal 26 includes a stationary ring (sheet ring) 26a fixedly installed on the shaft seal structure 27, and a rotating ring 26b that slidably contacts the stationary ring 26a and rotates integrally with the rotating shaft 24. Has been.

  The first stage shaft seal 25a includes an intake port 28 for taking in the seal water Ws, a first pressure detection port 29 for detecting the internal pressure of the first stage shaft seal 25a, and a second stage shaft seal 25b. The second stage shaft sealing portion 25b includes a second pressure detection port 31 for detecting the internal pressure of the second stage shaft sealing portion 25b, and the second stage shaft sealing portion 25b. An orifice 32 communicating with the outside is provided. The first pressure detection port 29 is connected to the first pump first-stage seal pressure detection unit 17a (see FIG. 1) of the seal capability determination device 10, and the second pressure detection port 31 is connected to the first pump second-stage seal pressure detection unit. 17b (see FIG. 1) communicate with each other.

  The seal water Ws is held at a pressure higher than the internal pressure of the reactor pressure vessel 18 (seal water pressure> water pressure in the pressure vessel), and the coolant C in the reactor comes out of the reactor from the first shaft seal portion 16a. It has a function of sealing so as not to stutter. The sealing water Ws taken into the first stage shaft sealing portion 25a from the intake port 28 is sent out to the second stage shaft sealing portion 25b through the orifice 30, and from the second stage shaft sealing portion 25b through the orifice 32, to the second stage shaft sealing portion 25b. It flows out to the outside of the single shaft sealing portion 16a and is stored in a tank 21a installed outside the first shaft sealing portion 16a.

A part of the sealing water Ws taken into the first stage shaft sealing portion 25 a passes through the gap between the first stage shaft sealing portion 25 a and the rotary shaft 24 where the mechanical seal 26 is not attached, and then the first shaft sealing portion 25 a. It flows out of the portion 16a and is stored in a tank 21a installed outside the first shaft seal portion 16a.
In this way, by mounting the first shaft sealing portion 16a on the rotating shaft 24, the coolant C in the nuclear reactor flows through the rotating shaft 24 to the motor 23 side by the first shaft sealing portion 16a, and the atoms. It is sealed so that it does not leak out of the furnace.

  By the way, the cause of the decrease in the sealing ability of the mechanical seal 26 installed in the first shaft seal portion 16a may be due to the inclusion of foreign matter on the seal surface or wear due to aging of the seal surface. In such a situation, it can be estimated that the fluctuation component of the seal pressure signal is somewhat larger than normal. This can be applied not only to the first shaft seal portion 16a but also to the second shaft seal portion 16b. However, in the following description, only the first shaft seal portion 16a will be described. The description of the second shaft sealing portion 16b is omitted.

Therefore, by monitoring the fluctuation component of the seal pressure signal, it is considered that a reduction in the seal capability due to the deterioration of the seal surface can be detected at an early stage.
In general, the pressure in the second stage shaft seal 25b during normal plant operation is very stable and shows a substantially constant value with almost no fluctuation component. Therefore, attention is paid to the fact that even if the fluctuation component of the fluctuation component of the seal pressure signal is very slight, it may be observed as noise on the seal pressure signal of the second stage shaft seal portion 25b.

However, since the noise on the seal pressure signal is very small, it is predicted that observation is difficult as time series data (Time Series Data) and statistics.
FIG. 5 is an explanatory diagram showing, in a graph, time-series data representing changes in the seal pressure signal at each shaft seal portion in time series. As shown in FIG. 5, the seal pressure signal at each shaft seal portion (first shaft seal portion 16a, second shaft seal portion 16b), that is, the first pump first stage seal pressure signal a, the first pump second stage. For the seal pressure signal b, the second pump first stage seal pressure signal c, and the second pump second stage seal pressure signal d, signs of seal surface deterioration are detected on time-series data representing changes with respect to elapsed time. It is difficult.

  That is, on the time series data, the first pump first-stage seal pressure signal a and the second pump first-stage seal pressure signal c indicating substantially the same value, and the first pump second-stage seal pressure signal indicating a nearby value. In both of b and the second pump second stage seal pressure signal d, it shows a substantially constant value and no change with respect to the elapsed time.

  Therefore, in order to evaluate a minute fluctuation component included in the seal pressure signal, APSD is used. Further, the APSDs of redundant devices (in this example, two first pumps 15a and second pumps 15b) are compared with each other as a reference value (reference) for the normal operation state of the plant. In comparison, if the sealing surfaces are normal and the APSD of the pressure of the first-stage shaft seal 25a is the same level for both devices in a redundant relationship, the APSD of the pressure of the second-stage shaft seal 25b Also show the same level. "

As a result, at the stage where the seal surface of either the first stage shaft seal 25a or the second stage shaft seal 25b deteriorates and the fluctuation component of the seal pressure signal increases, the APSD of the pressure of the second stage shaft seal 25b increases. Based on the fact that the level rises compared to the normal device, it becomes possible to detect at the stage where signs of deterioration appear on the seal surface.
That is, in the mechanical seal 26 installed in the shaft seal portions (first shaft seal portion 16a, second shaft seal portion 16b) of the pumps (first pump 15a, second pump 15b) provided in the reactor pressure vessel 18. Regarding the fluctuation component of the generated seal pressure signal, the minute fluctuation component included in the seal pressure signal of the shaft seal portion is evaluated by using APSD. Is detected.

The detection at the stage where the sign of deterioration appears on the sealing surface can be performed by the sealing ability determination device 10 according to the present invention.
The first pump first-stage seal pressure detection unit 17a that detects the seal pressure of the first pump 15a shown in FIG. 1 includes, for example, a pressure sensor. By this pressure sensor, the first-stage shaft sealing unit 25a The internal (seal) pressure of the first stage shaft sealing portion 25a is detected through the first pressure detection port 29. The first pump second-stage seal pressure detector 17b includes, for example, a pressure sensor, and the second-stage shaft seal portion is provided by the pressure sensor via the second pressure detection port 31 of the second-stage shaft seal section 25b. The internal (seal) pressure of 25b is detected.

  Similarly, the second pump first-stage seal pressure detection unit 17c that detects the seal pressure of the second pump 15b includes, for example, a pressure sensor, and the first pressure of the first-stage shaft seal portion is detected by this pressure sensor. The internal (seal) pressure of the first stage shaft seal is detected via the detection port 29, and the second pump second stage seal pressure detector 17d includes, for example, a pressure sensor. The internal (seal) pressure of the second stage shaft seal is detected via the second pressure detection port 31 of the second stage shaft seal.

That is, the first pump first stage seal pressure detector 17a, the first pump second stage seal pressure detector 17b, the second pump first stage seal pressure detector 17c, and the second pump second stage seal pressure detector 17d are The seal pressure of the pumps (first pump 15a, second pump 15b) provided in the reactor pressure vessel 18 is detected.
The APSD calculation unit 11 uses a fast Fourier transform (FFT) algorithm because the index APSD is defined as the Fourier transform of the autocovariance function as the intensity of the frequency component f in the fluctuation signal. An autocovariance function is calculated, and APSD is calculated from the calculation result.

  That is, the APSD calculation unit 11 includes a first pump first stage seal pressure detection unit 17a, a first pump second stage seal pressure detection unit 17b, a second pump first stage seal pressure detection unit 17c, and a second pump second stage. APSD is calculated based on the seal pressure detected by the seal pressure detector 17d.

The APSD comparison unit 12 compares the APSDs of the first pump 15a and the second pump 15b based on the APSD calculated by the APSD calculation unit 11, that is, the APSD of the first pump 15a becomes the reference value in the redundant configuration. Compare with APSD. Based on the comparison result in the APSD comparison unit 12, the seal capability determination unit 13 is provided with each stage shaft seal (25a, 16a, 16b) having the seal pressure detected by each seal pressure detection unit (17a-17d). 25b, not shown), that is, a decrease in the sealing ability is determined.
The determination of the presence or absence of a sign of seal surface deterioration that causes a decrease in the sealing ability is performed as follows.

First, the average value / standard deviation of the APSD obtained from a plurality of data collected during normal operation of the plant is obtained.
Next, using the obtained average value and standard deviation of APSD, the value obtained by the following equation is set as the upper limit threshold value.
Upper threshold = average value + standard deviation × coefficient (α)
Here, the coefficient (α) varies depending on the reliability. For example, when α = 2.58, it means about 99% reliability in the normal distribution.

Subsequently, when the APSD level obtained from arbitrary data exceeds the obtained upper limit threshold value, it is determined that there is a possibility of seal surface deterioration in the mechanical seal 26, that is, a sign of seal surface deterioration is recognized.
FIG. 6 is an explanatory diagram showing APSD level data in which the change in the seal pressure signal at each shaft seal is expressed in APSD. As shown in FIG. 6, the seal pressure signal at each shaft seal portion (first shaft seal portion 16a, second shaft seal portion 16b), that is, the first pump first stage seal pressure signal a, the first pump second stage. Regarding the seal pressure signal b, the second pump first stage seal pressure signal c, and the second pump second stage seal pressure signal d, on the APSD level data representing the change with respect to the frequency, an indication of the seal surface deterioration as an increase in the APSD level. Can be detected.

  That is, when the seal pressure signals b and d at the respective second stage shaft seals are compared between the first pump 15a and the second pump 15b, they are compared with the APSD level of the seal pressure signal d on the second pump 15b side. The APSD level of the seal pressure signal b on the first pump 15a side is higher (see the white arrow in the figure). Therefore, as the seal surface deteriorates and the fluctuation component of the seal pressure signal increases, the APSD level rises compared to the value of the normal device (reference), and there is an indication of a decrease in seal capability due to the deterioration of the seal surface. Can be detected at a certain stage.

  Here, the comparison of the APSD level is performed on the values of the normal-side devices in the redundant configuration (the two first pumps 15a and the second pump 15b). Alternatively, it may be performed on a reference value (reference) set based on the accumulated data.

  As described above, the sealing capacity determination device 10 is provided with each shaft sealing portion (first shaft sealing portion 16a, first shaft 15a) provided in each of the PLR pumps (first pump 15a, second pump 15b) in the reactor containment vessel 14. A decrease in the sealing ability of the mechanical seal 26 installed in the biaxial sealing portion 16b) can be detected at an early stage, that is, at a stage where signs of deterioration appear on the sealing surface, and in addition, the sealing of the mechanical seal 26 It is possible to evaluate the soundness of capabilities. For this reason, it is possible to contribute to more efficient operation of the plant equipment, such as preparation for seal repair when the seal capacity is reduced, selection of the operation stop timing, and use of the mechanical seal 26 for multiple years.

Data relating to the respective seal pressure signals a to d for detecting signs of this seal surface deterioration can be collected during plant operation.
As described above, the sealing capacity determination method and the sealing capacity determination device 10 according to the present invention are the shaft seals (16a) of the pumps (first pump 15a and second pump 15b) provided in the reactor pressure vessel 18. 16b), the sealing ability of the mechanical seal 26 is determined. However, the target of the sealing ability determination is not limited to the seal member in the reactor pressure vessel 18, and the mechanical seal is multistage. The present invention can also be applied to the case where the sealing ability of a sealing member in a separate pump is determined.

According to this invention, regarding the mechanical seal installed in the shaft seal portion of the pump in which the mechanical seal is divided into multiple stages, the minute fluctuation component included in the seal pressure signal of the shaft seal portion is evaluated using APSD, from the evaluation results, APSD level pressure shaft seal is, on the basis of the rise compared to the value of the normal side equipment redundancy, admitted APSD rises, by determining the signs of the sealing ability decreases, shaft seal As a method and an apparatus for determining the sealing ability of a seal member in a pump in which a mechanical seal is divided into multiple stages, it is possible to evaluate the soundness of the sealing ability in the section and to detect a decrease in the sealing ability at an early stage. Is optimal.

DESCRIPTION OF SYMBOLS 10 Sealing capacity determination apparatus 11 APSD calculating part 12 APSD comparison part 13 Sealing capacity determination part 14 Reactor containment vessel 15a 1st pump 15b 2nd pump 16a 1st shaft sealing part 16b 2nd shaft sealing part 17a 1st pump 1st stage Seal pressure detector 17b First pump second-stage seal pressure detector 17c Second pump first-stage seal pressure detector 17d Second pump second-stage seal pressure detector 18 Reactor pressure vessel 19a Discharge path 19b Supply path 20a, 20b Circulation path 21a, 21b Tank 22 Pump body 22a Coolant flow path 22b Impeller 23 Motor 24 Rotating shaft 25a First stage shaft sealing part 25b Second stage shaft sealing part 26 Mechanical seal 26a Stationary ring 26b Rotating ring 27 Shaft sealing part Structure 28 Intake port 29 First pressure detection port 30, 32 Orifice 31 Second pressure detection Mouth C coolant W water Ws seal water a first pump the first stage seal pressure signal b first pump second stage seal pressure signal c second pump first stage seal pressure signal d second pump second stage seal pressure signal

Claims (3)

For mechanical seals installed in shaft seals of pumps with mechanical seals divided into multiple stages, the auto power spectral density (APSD) is applied to minute fluctuation components contained in the seal pressure signal of the shaft seals. Evaluate using
From the evaluation results , the seal ability is judged as an indication that the APSD has risen based on the fact that the APSD level of the pressure at the shaft seal portion is higher than the value of the normal device in the redundant configuration, and is determined as a sign of a reduction in the seal ability. Judgment method. An APSD computing means for calculating an auto power spectral density (APSD) based on a seal pressure signal indicating a seal pressure of a mechanical seal installed in a shaft seal portion of a pump in which the mechanical seal is divided into multiple stages;
APSD comparing means for comparing the APSD calculated by the APSD calculating means with an APSD of a reference value;
Based on the comparison result in the APSD comparison means, the seal for the shaft seal portion having the detected seal pressure is based on the fact that the APSD level of the pressure of the shaft seal portion is higher than the value of the normal side device in the redundant configuration. A sealing ability judging device comprising: a sealing ability judging means for judging that the ability has declined. The seal capacity determination device according to claim 2 , wherein the seal pressure signal is an output signal from a seal pressure detection unit that detects a seal pressure of the mechanical seal provided in the pump.

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