JPH03282072A - Shaft sealing device for pump - Google Patents

Abstract

PURPOSE:To sharply improve reliability on structural strength by providing a shaft seal water cooling device to cool shaft seal water in the vicinity of the upper part of a casing cover and a shaft seal heating device to heat shaft seal water in the vicinity of the lower part of the casing cover. CONSTITUTION:A shaft seal cooling device 21 to cool shaft seal water in a seal chamber 3 is mounted to the side of a shaft sleeve 20a and a shaft seal water heating device 22 to heat shaft seal water is located to the under surface of a casing cover 14. A pump action by a centrifugal force is created by means of a plurality of longitudinal grooves 39 formed in a part of a pump shaft 2. Hot pump water is discharged through pores formed in a rotary cylinder 20c of the shaft seal water heating device 22 in a manner to cover the longitudinal grooves 39 therewith, and by mixture of pump water (hot water) with shaft seal water (cold water), the temperature increase effect of the shaft seal water is produced. Hot water discharged from an underwater bearing 15 is caused to flow through a heating cylinder 37 located to the lower part of the casing cover 14.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention alleviates thermal stress on the pump shaft of a nuclear reactor recirculation pump that efficiently circulates the primary cooling water of a light water nuclear reactor, for example. This invention relates to a shaft sealing device for a pump.

(Conventional technology) Reactor recirculation pumps used in light water reactors are large-capacity pumps that handle high-temperature, high-pressure pure water. It is a winding pump.

Hereinafter, a nuclear reactor recirculation pump incorporating a conventional pump shaft sealing device will be described with reference to FIG. In FIG. 10, reference numeral 1 indicates an upper casing, and a seal chamber 3 formed of a shaft sealing cover for sealing the pump shaft 2 is provided in the upper casing 1. A mechanical seal 4 is provided in the seal chamber 3 so as to surround the side surface of the pump shaft 2. A shaft-sealing water injection pipe 5 is provided in the upper part of the seal chamber 3, and a heat exchanger 6 is provided around the outer periphery of the seal chamber 3. The upper end of the pump shaft 2 is connected to a motor shaft 8 via a flexible joint 7. A labyrinth portion 9 is formed on the lower side surface of the pump shaft 2, and an impeller 10 is attached below the labyrinth portion 9, which has a plurality of annular grooves stacked one on top of the other in the axial direction. Impeller 10
is disposed in a lower goose sink 11 serving as a pump chamber, and the lower casing 11 is connected to a base 12 connected to the lower end of the upper casing 1 by tightening bolts 13. A casing cover 14 is interposed between the base 12 and the lower casing 11. An underwater bearing 15 is attached to the lower end surface of the casing cover 14, and the underwater bearing 15 pivotally supports the details of the impeller IO.

The lower casing 11 has a suction port 16 through which reactor primary cooling water, that is, pump water (hot water) flows in, and a discharge port 17 through which the primary cooling water sucked in by the impeller IO from the suction port 16 is discharged downward. It is formed. Further, a circulation vane 18 is attached to the pump shaft 2, and this circulation vane 18 circulates the shaft sealing water in the seal chamber 3.

In the figure, 19 is a flange of the upper casing 1. In this way, the conventional pump shaft 2 is surrounded by the mechanical seal 4 and the inner surface of the casing cover 14, and has an impeller 10 that functions as a pump to suck in and discharge pump water, and a pump that rotates the impeller 10. A shaft 2, an underwater bearing 15 that pivotally supports a part of the impeller IO attached to the pump shaft 2, and a casing cover that attaches the underwater bearing 15 and separates the upper casing 1 and the lower casing 11. It consists of 14. In addition, the shaft sealing water, that is, the cold water part in the seal chamber 3 containing the mechanical seal 4, and the hot water part filled with pump water such as the one impeller IO and the submersible bearing are attached to the pump shaft 2. Circulation vane 18 and labyrinth part 9
It is divided into The heat exchanger 6 is used to cool the shaft sealing water in order to prevent the mechanical seal 4 from being damaged due to lifting in case the injection of the shaft sealing water is stopped. The shaft seal is for sealing the mechanical seal 4 to prevent pump water from flowing into it.

(Problem to be Solved by the Invention) In the conventional shaft sealing device for a nuclear reactor recirculation pump shown in FIG. It forms a narrow flow path. For example, in the case of a boiling water reactor, the temperature of the reactor recirculated water, that is, the pump water, is hot water at a fairly high temperature, and the inside of the seal chamber 3 is cold water that circulates through the shaft sealing water.
There is a fairly large temperature difference between the seal chamber 3 and the pump chamber. In order to maintain the temperature of the seal chamber 3 in a cold water state, shaft sealing water (also referred to as purge water) is injected from the outside through a shaft sealing water flow pipe 5.

However, in such a pump shaft sealing device, there is a large temperature difference between the hot water in the lower pump chamber and the cold water in the upper seal chamber 3, that is, a large density difference, so the cold/thermal interface is unstable due to gravity. Pump water (hot water) with low density rises from the pump chamber in the lower casing 11 to the labyrinth section 9, and shaft sealing water (cold water) injected from the upper seal chamber 3 descends through the labyrinth section 9. . As a result, the cold/thermal interface becomes undulating, and the temperature of the pump shaft 2 and the labyrinth part of the casing cover 14 undergoes large temperature fluctuations with the maximum amplitude being the temperature difference between hot water and cold water, which generates thermal stress on the pump shaft. There are 11 problems that cause heat fatigue.

Furthermore, when the flow rate of shaft sealing water changes, the cold/thermal interface also moves up and down (in the axial direction). For this reason, the pump shaft 2 and the casing cover 14 in the labyrinth part 9, which is the cold/heat boundary part,
large thermal stress is likely to occur in the metal parts of the If thermal stress is repeated many times over many years, cracks may occur in the labyrinth portion 9 due to thermal fatigue.

Therefore, there is a need for a shaft sealing device for a pump shaft that does not cause large temperature fluctuations even if the flow rate of shaft sealing water and the rotational speed of the pump change somewhat.

The present invention has been made to solve the above problems, and is a pump shaft that can alleviate temperature fluctuations at the cold/hot boundary, prevent thermal fatigue, and significantly improve reliability in terms of structural strength. The purpose of the present invention is to provide a sealing device.

[Structure of the invention]

(Means for Solving the Problems) The present invention includes a pump shaft disposed in an upper casing, a mechanical seal provided in a seal chamber for sealing the pump shaft, and a shaft sealing water circulating in the seal chamber. a circulation mechanism that separates the upper casing and a lower casing connected to the lower end, a labyrinth inlet formed in the pump shaft located at a portion separating the upper casing and a lower casing connected to the lower end, and a casing cover provided between the upper casing and the lower casing. , a shaft sealing device for a pump having an impeller attached to the pump shaft in the lower casing, a shaft sealing water cooling device for cooling shaft sealing water near the upper part of the casing cover; A shaft sealing water heating device for heating shaft sealing water is provided near the lower part.

(Function) The shaft sealing water cooling device eliminates the conventional heat exchanger to make the shaft sealing structure more compact, and the shaft sealing water heating device reduces the temperature difference between cold and hot water flowing into the labyrinth entrance. Keep the temperature amplitude of temperature fluctuations below the thermal fatigue generation limit. By forming the shaft-sealed water heating device into a multi-cylindrical body, the temperature of the shaft-sealed water gradually increases as it goes upward, and the density is higher at the bottom and lower at the top, stabilizing the flow of cold and hot water against gravity. It can be done. Further, by providing a vertical groove in the upward flow portion of the shaft sealing water, the cold/thermal interface can be stabilized by centrifugal force.

(Embodiment) A first embodiment of a shaft sealing device for a pump according to the present invention will be described with reference to FIGS. 1 to 5.

In addition, in the figure, the same parts as in FIG. 10 are given the same reference numerals and explained.

In FIG. 1, a seal chamber 3 formed by a shaft seal cover for sealing a pump shaft 2 is provided in an upper casing 1. As shown in FIG. A mechanical seal 4 is provided in the seal chamber 3 so as to surround the side surface of the pump shaft 2. Seal chamber 3
A shaft sealing water injection pipe 5 is provided at the upper part of the mechanical seal 4 for injecting shaft sealing water to cool the mechanical seal 4. The upper end of the pump shaft 2 is connected to a motor shaft 8 via a flexible joint 7, and an impeller 10 is attached to the lower part.By driving a motor (not shown), the pump shaft 2 rotates, and the impeller 10 also rotates. . The impeller 10 is disposed within a lower casing 11, that is, in a pump chamber, and the lower casing 11 is connected to a base 12 connected to the lower end of the upper casing 1 by bolts 1.
3 is tightened and connected. A casing cover 14 is interposed between the base 12 and the lower casing 11. An underwater bearing 15 is attached to the lower end surface of the casing cover 14, and this underwater bearing 15 supports the impeller 1.
0 shaft is supported. The lower casing 11 has a nuclear reactor
Suction port 16 into which the next cooling water, ie pump water (hot water) flows in
A discharge port 17 is formed to discharge the primary cooling water sucked in by the impeller 10 from the suction port 1-6. Also,
A circulation vane 18 is attached to the pump shaft 2, and the circulation vane 18 circulates shaft sealing water in the seal chamber 3. Note that 19 in the figure is a flange of the upper casing 1, which is connected to a motor chamber (not shown). The pump shaft 2 is equipped with a mechanical seal 4 and cylindrical shaft sleeves 20 (20a) at the top and bottom to prevent humidity fluctuations from being transmitted to the pump shaft 2.

20b) is provided. This upper shaft sleeve 2
A shaft sealing water cooling device 21 for cooling the shaft sealing water in the seal chamber 3 and a shaft sealing water heating device 22 located on the lower surface of the casing cover 14 for heating the shaft sealing water are provided on the side surface of 0a. It is provided.

As shown in an enlarged view in FIG. 2, the shaft seal water cooling device 21 is a cooling water inlet provided within the wall of the shaft seal cover 24 that forms the seal chamber 3 fixed to the casing cover 14 with bolts 23. It consists of a passage 25 and an outflow passage 26 communicating with the inflow passage 25. The lower portions of these channels 25 and 26 are formed in a U-shape. A rotary cylinder 27 is provided whose lower part is inserted into the U-shape and whose upper part protrudes into the seal chamber 3, and this rotary cylinder 27 is fixed to the lower shaft sleeve 20b by tightening bolts 28. .

In addition, the reference numeral 29 in the figure is a presser flange constituting the upper part of the seal chamber 3, and a holding member 30, 31 of the mechanical seal 4.
is held and fixed to the shaft seal cover 24 with bolts 32. The upper shaft sleeve 20a located in the seal chamber 3 that seals the pump shaft 2 is fixed to an upper flange 33 for attaching the sleeve with bolts 34.

The shaft seal water suspension w22 is located below the lower shaft sleeve 20b, as shown enlarged in FIGS. 3 and 4, and is provided near the underwater bearing 15. That is, the shaft sealing water heating device 22 has a hot water inflow hole 3 for primary cooling water in the underwater bearing 15.
5, and a flow path 36 that communicates with the hot water inflow hole 35 and through which hot water flows so as to heat the side surface of the lower shaft sleeve 20b.
A heating cylinder 37 having a diameter is provided on the lower surface of the casing cover 14. Further, the lower part of the lower shaft sleeve 20b is cut into a thin wall to form a rotating cylinder 20c, and a large number of small holes 38 are provided in this rotating cylinder 20c. As described above, the shaft sealing water heating device 22 is composed of the hot water flow path 36 provided in the casing cover 14 and the rotating cylinder 20c attached to the lower shaft sleeve 20b.

Note that, as shown in FIG. 5(a), a plurality of vertical grooves 39 are provided in a part of the pump shaft 2. A plurality of small holes 38 in the rotating cylinder 20c provided to cover the vertical groove 39 are pumped by the centrifugal force generated as the vertical groove 39 rotates.
Hot water is blown out and mixed with the shaft sealing water.

As described above, in this embodiment, the lower casing 11 that constitutes the pressure-resistant section, the impeller 10 that is the pump section, the pump shaft 2 that rotates the impeller IO, and the casing that supports the underwater bearing 15 and constitutes the pressure-resistant section are used. A cover 14, a mechanical seal 4 that seals the pressure-resistant part of the pump shaft 2, a cylindrical shaft sleeve 20 that covers the pump shaft 2 to prevent temperature fluctuations from being transmitted to the pump shaft 2, and a mechanical seal 4 that prevents hot pump water from being transmitted to the pump shaft 2. Shaft seal water is injected into the seal chamber 3 from the outside to prevent it from flowing into the seal chamber 3, and a shaft seal water cooling device 21 installed in case the supply of shaft seal water stops, and the heat inside the casing cover 14 are It consists of a shaft-sealed water heating device 22 consisting of a water flow path 36 and a heating cylinder 37.

Therefore, according to this embodiment, as shown in FIG. 5(a), a plurality of vertical grooves 39 provided in a part of the pump shaft 2 generate a pumping action due to centrifugal force, and the vertical grooves 39 are covered. In this way, hot pump water is blown out from the small hole 38 provided in the rotating cylinder 20c, and the pump water (
By mixing hot water (hot water) with shaft sealing water (cold water), the effect of increasing the temperature of shaft sealing water is produced.

In addition, a heating cylinder 3 provided at the bottom of the casing cover 14
Hot water blown out from the submersible bearing 15 is made to flow through the inside of the submersible bearing 7 .

FIG. 5(b) shows the height distribution of the labyrinth portion in the axial direction of the pump shaft 2, and it can be seen that the temperature becomes higher as it goes downward from the upper end of the vertical groove 39.

This indicates that the temperature becomes lower in the upper part of the labyrinth part.

Therefore, the labyrinth part 9 where the shaft sealing water (cold water) descends
The shaft sealing water is heated or mixed with hot water to increase the humidity, and the difference in humidity between the pump water (hot water) in the lower casing 11, that is, the pump chamber, is reduced, and the temperature amplitude of temperature fluctuations is kept below the thermal fatigue generation limit. Can be made smaller.

FIG. 6(a) shows only the main parts of the second embodiment of the present invention, and the same parts as in FIG. 4 are designated by the same reference numerals, and the explanation of other parts is omitted.

That is, the lower shaft sleeve 20b surrounding the pump shaft 2
A rotating cylinder 20c is provided in the rotating cylinder 20c, and a large number of small holes 38 are provided in this rotating cylinder 20c. This rotating cylinder 20
C has a large-diameter cylindrical body 20d connected at the bottom to form a double cylindrical body shaped like a cylindrical container.

A shaft sealing water heating cylinder 40 suspended from the lower part of the casing cover 14 is inserted into the double cylindrical bodies 20e and 20d. Inside this heating cylinder 40, a partition cylinder 41 is arranged to form a flow path 4.
2 to form a triple heating cylinder. Therefore, a triple cylinder including the double cylinder and the triple cylinder is provided within the pump shaft 2 and the casing cover 14.

According to this second embodiment, a triple heating cylinder is nested into a double rotating cylinder connected to the shaft sleeve 20b to form a multi-cylinder structure, and an upward flow section 43 of shaft sealing water is provided. .

According to this second embodiment, due to the heat input q, as shown in FIG.
As shown in Figure 2, the temperature of the shaft sealing water gradually increases as it goes upward, so the density is high at the bottom and low at the top, making it possible to stabilize the flow of cold and hot water against gravity.

FIG. 7 shows a third embodiment of the present invention, and like FIG. 6, only the essential parts are shown. In other words, this third
In this embodiment, a large-diameter rotating cylindrical body 20e is connected directly to the lower sleeve 20b provided on the pump shaft 2 at the bottom, and a partition cylinder 44 suspended from the casing cover 14 is inserted into the cylindrical body 20e to form a flow path 45. This is because we have established Note that a vertical groove 46 is formed on the inner surface of the rotating cylindrical body 20e.

According to this third embodiment, as shown in FIGS. 7(b) and 7(c), the temperature distribution in the height direction of the shaft sealing water rising flow section 43 becomes higher as it goes upward; The temperature distribution in the radial direction of the sealing water rising flow section 43 becomes lower along the outer direction.

Therefore, by providing the vertical groove 46 in the shaft sealing water upward flow section 43, the interface between cold and hot water can be stabilized by centrifugal force.

FIG. 8 shows a fourth embodiment of the present invention. Like FIG. 7, only the main parts are shown, and the same parts as in FIG. Omitted.

In this fourth embodiment, the shaft sleeve 20b is not used, and a plurality of link-shaped labyrinths 47 are formed on the inner surface of the inner cylinder 37a of the double shaft sealing water heating cylinder 37 suspended on the lower surface of the casing cover 14. be.

According to this fourth embodiment, the shaft seal water can be heated only by the shaft seal water heating cylinder 37, and the labyrinth 47 can prevent rotation in the direction of the cold/hot water interface.

FIG. 9 shows a fifth embodiment of the present invention, and like FIG. 8, only the essential parts are shown and overlapping parts are omitted.

In this fifth embodiment, the inner cylinder 3 in the fourth embodiment is
7a is provided with a large number of small holes 47 that are inclined downward, and the hot water flow path 36 at the lower end of the heating cylinder 37 is closed.

According to this fifth embodiment, the hot water inflow hole 3 of the underwater bearing 15
The hot water flowing in from 5 is blown out from a large number of inclined small holes 48 through the hot water flow path 36, and mixed with the cold water flowing out from between the pump shaft 2 and the casing cover 14, thereby reducing the temperature difference between the hot water and the hot water. Furthermore, rotation of the cold/hot water interface in the axial direction can be prevented.

The following is a summary of the embodiments of the pump shaft sealing device according to the present invention.

■ Used in the shaft sealing device for the pump shaft of the primary cooling water recirculation bomb of light water nuclear reactors.The pump shaft is sealed with a mechanical seal, and the mechanical seal is held in the seal chamber.
Shaft sealing water circulates in this sealing chamber, and a shaft sealing water cooling device that cools the shaft sealing water and a shaft sealing water heating device that heats the shaft sealing water are provided above and below the casing cover as a boundary.

■ The shaft seal water cooling device consists of a cooling water circulation passage provided within the wall of the shaft seal cover that forms the inside of the seal chamber, and a rotating cylinder attached to the upper shaft sleeve.

■ The shaft sealed water heating device shall consist of a hot water flow path provided within the casing cover and a rotating cylinder attached to the lower shaft sleeve.

@) In the shaft-sealed water heating device, a plurality of vertical grooves are provided in a part of the pump shaft, and a plurality of small holes are provided in the rotating cylinder covering the vertical grooves.

■ A shaft sealing water heating cylinder is attached to the bottom of the casing cover.

0 The shaft-sealed water heating cylinder shall have a flow path through which hot water blown out from the submersible bearing will flow.

■ The shaft sealing water heating cylinder has a multi-cylindrical structure and is provided with an upward flow section for the shaft sealing water.

(8) A vertical groove is provided in the upward flow section of the shaft sealing water to stabilize the interface between cold and hot water using centrifugal force.

〔Effect of the invention〕

According to the present invention, temperature fluctuations in the cold/heat mixing section in the shaft sealing section of the pump shaft can be alleviated, and thermal fatigue can be prevented. Therefore, cracks do not occur in the shaft sealing portion, and reliability in terms of structural strength can be greatly improved.

This leads to further improvements in the reliability and safety of nuclear power plants, and is extremely useful industrially.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing a nuclear reactor recirculation pump incorporating a shaft sealing device for a pump according to the present invention, and FIG. 2 is an enlarged view of the vicinity of the seal chamber and shaft seal water cooler in FIG. 1. Longitudinal sectional view, 3rd
FIG. 4 is an enlarged longitudinal sectional view showing the vicinity of the shaft-sealed water heating device in FIG. 1, and FIG. 4 is an enlarged longitudinal sectional view showing the main part in FIG. 3. FIG. 5(a) is a perspective view for explaining the effect of FIG. 1;
FIG. 5(b) is a characteristic diagram showing the temperature distribution in the height direction of the labyrinth part corresponding to FIG. 5(a), and FIG. 6(a) is a characteristic diagram of the shaft sealing water heating part in the second embodiment of the present invention. FIG. 6(b) is a longitudinal cross-sectional view showing an enlarged view of the vicinity of , FIG. 6(b) is a characteristic diagram showing the temperature distribution of the purge water rising part corresponding to FIG.
7 is a vertical sectional view of main parts in the third embodiment of the present invention.
Figure (b) is a characteristic diagram showing the temperature distribution in the height direction of the rising part of the purge water in Figure 7 (a), and Figure 7 (C) is a characteristic diagram showing the temperature distribution in the height direction of the purge water rising part in Figure 7 (a).
) is a characteristic diagram showing the radial temperature distribution of the purge water rising part. FIGS. 8 and 9 are longitudinal sectional views showing essential parts of other embodiments of the present invention, and FIG. 10 is a longitudinal sectional view showing a nuclear reactor recirculation pump incorporating a conventional pump shaft sealing device. It is. DESCRIPTION OF SYMBOLS 1... Upper casing, 3... Seal chamber, 5... Shaft seal water injection pipe, 7... Flexible joint, 9... Labyrinth part, 2... Pump shaft, 4... Mechanical Seal, 6... Heat exchanger, 8... Motor shaft. IO... impeller, 11... lower casing, 12... base, 13
...Bolt, 14...Casing cover 15...Underwater bearing, 16...Suction port, 17
...Discharge port, 18...Circulation vane. 19... Upper flange, 20... Shaft sleeve,
21... Shaft seal water cooling device, 22... Shaft seal water heating device, 23... Bolt, 24... Shaft seal cover 25... Inflow channel, 26... Outflow channel,
27... Rotating cylinder, 28... Bolt, 29
... Presser flange, 3o/31... Holding member,
32... Bolt, 33... Upper flange, 34... Bolt, 35... Hot water inlet, 36... Hot water flow path, 37... Heating cylinder,
38...Small hole, 39...Vertical groove, 40...
・・Heating cylinder, 41・44・・Partition cylinder,
42, 45...flow path, 43...rising flow section,
44... Partition tube, 46... Vertical groove, 47... Ring-shaped labyrinth, 48... Inclined small hole.

Claims (1)

[Claims] A pump shaft disposed in the upper casing, a mechanical seal provided in a seal chamber for sealing the pump shaft, a circulation mechanism that circulates shaft sealing water in the seal chamber, and connected to the lower end of the upper casing. A labyrinth portion formed on the pump shaft located at a portion separating the inside of the lower casing, a casing cover provided between the upper casing and the lower casing, and a labyrinth portion attached to the pump shaft inside the lower casing. In the shaft sealing device for a pump, the shaft sealing device has a shaft sealing water cooling device that cools the shaft sealing water near the top of the casing cover, and a shaft sealing device that heats the shaft sealing water near the bottom of the casing cover. A shaft sealing device for a pump, characterized in that it is equipped with a water heating device.