JP2016188596A - Centrifugal multistage pump and maintenance method of centrifugal multistage pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently discharge fluid in a casing at the time of maintenance and restrain the fluid from scattering at the time of an overhaul.SOLUTION: A centrifugal multistage pump comprises: a rotor provided with a plurality of impellers along a main shaft; and a casing configured so as to be able to be disassembled into a plurality of impeller chambers. By opening a drain hole, fluid in the casing is led to the drain hole via bypass holes provided in partition walls separating the impeller chambers, and discharged to the outside.SELECTED DRAWING: Figure 4

Description

  The present disclosure relates to a centrifugal multistage pump having a rotor provided with a plurality of impellers along a main shaft, and a maintenance method for the centrifugal multistage pump.

  Nowadays, pump devices are used in various applications as one of fluid pumping means. As an example of this type of pump device, a centrifugal force is generated by rotating a rotor provided with an impeller (hereinafter referred to as “impeller” as appropriate) on a main shaft in a casing to generate a centrifugal force and pump a fluid. There is a pump. As the centrifugal pump, a so-called centrifugal multistage pump is known in which pump efficiency is improved by providing a plurality of impellers in series on a main shaft of a rotor.

  An example of this type of centrifugal multistage pump is, for example, Patent Document 1. Patent Document 1 exemplifies a pump that is operated in a gas mixture, and particularly describes that a plurality of impellers are provided in a multistage shape on the vertical axis.

Sho 60-28294

  In a pump device such as a centrifugal pump, when performing overhaul for maintenance management, it is necessary to discharge the fluid in the casing in advance. In particular, pumps used in nuclear power plants may handle fluids containing components that are harmful to the human body, and it takes a lot of time to discharge the fluids to prevent the fluids from being scattered during overhaul. ing. In particular, the centrifugal multi-stage pump has a complicated structure as compared with a single-stage pump, and there is a problem that fluid tends to remain inside during discharge.

  The fluid discharge operation in such a pump device is performed by opening a drain hole for discharge provided in the casing. In the centrifugal multistage pump, it is also effective to promote discharge by providing a drain hole for each impeller chamber in which each impeller is accommodated. However, such a method has a problem in that the number of joints increases in the casing as the drain hole increases, and the risk of leakage due to vibration effects during operation of the pump, aging deterioration of the material, and the like increases.

  At least one embodiment of the present invention has been made in view of the above-mentioned problems, and is a centrifugal multistage pump capable of efficiently discharging the fluid in the casing during maintenance and suppressing the scattering of fluid during disassembly and inspection, and An object of the present invention is to provide a maintenance method for the centrifugal multistage pump.

(1) In order to solve the above-described problem, a centrifugal multistage pump according to at least one embodiment of the present invention supports a rotor provided with a plurality of impellers along a main shaft, and rotatably supports the rotor. A casing configured to be disassembled into a plurality of impeller chambers each housing each impeller, and the casing is provided with a drain hole communicating with the outside along a direction intersecting the rotor, Each of the partition walls provided between the plurality of impeller chambers is formed so as to penetrate along the extending direction of the rotor on the drain hole side from the rotor as viewed from the extending direction of the rotor. A bypass hole is provided.

  According to the configuration of (1) above, when the drain hole provided in the casing is opened, the fluid in the plurality of impeller chambers is discharged from the drain hole via the bypass holes provided in the partition walls that partition the impeller chambers. It is discharged outside. Here, the bypass hole provided in each partition wall is provided on the drain hole side from the rotor as viewed from the extending direction of the rotor, so that the fluid in each impeller chamber is guided to the drain hole through the bypass hole. With such a configuration, since the fluid in the casing can be efficiently discharged to the outside, the risk of scattering due to the fluid remaining in the casing at the time of overhaul inspection can be effectively reduced.

(2) In some embodiments, in the configuration of the above (1), the rotor is disposed along the horizontal direction, and the drain hole is provided on the lower side in the gravity direction of the casing.

  According to the configuration of (2) above, when the centrifugal multistage pump is placed horizontally so that the rotor is along the horizontal direction, the fluid in the casing is discharged from the drain hole provided on the lower side in the gravity direction by gravity. Is efficiently discharged. For example, in a centrifugal multistage pump used in a nuclear power plant, the center of gravity can be lowered and the earthquake resistance can be improved by arranging the centrifugal multistage pump horizontally. In this configuration, the above-described effect can be effectively enjoyed particularly when the centrifugal multistage pump is employed for such applications.

(3) In some embodiments, in the configuration of (1) or (2), the bypass hole provided in each of the partition walls is provided at an equal distance from the rotor.

  According to the configuration of (3) above, since each bypass hole is provided at an equal distance from the rotor, the fluid in each impeller chamber can be smoothly guided to the drain hole via the bypass hole.

(4) In some embodiments, in any one of the configurations (1) to (3), the bypass hole is provided at a position away from the rotor from the tips of the plurality of impellers, Each of the bypass holes is configured such that a common plug extending along the rotor can be inserted therethrough.

  According to the configuration of (4) above, each of the bypass holes provided in each partition wall is configured such that a common plug can be inserted therethrough. If there is a bypass hole in the partition wall between the impeller chambers, there is a risk that the fluid will flow backward from the high-pressure side to the low-pressure side through the bypass hole, which may reduce the pump efficiency. Backflow in the bypass hole can be suppressed by inserting a plug common to the hole. Particularly in this configuration, since the bypass hole is provided at a position farther from the rotor than the tip of the impeller, the plug does not interfere with the impeller when the plug is inserted during pump operation.

(5) In some embodiments, in the configuration of (1) or (2), the bypass hole provided in each of the partition walls has a gradient so as to be separated from the rotor as the drain hole is approached. A flow path is provided.

  According to the configuration of (5) above, each bypass hole is provided such that a flow path having a gradient is formed so as to be separated from the rotor as it approaches the drain hole. Thereby, since a gradient is generated in the height of each bypass hole in the casing, the fluid is efficiently guided from each impeller chamber toward the drain hole.

(6) In some embodiments, in any one of the configurations (1) to (5), the casing includes an attachment portion to which a decompression device capable of decompressing the inside of the casing can be attached.

  According to the configuration of (6) above, the pressure reducing device can be attached to the casing, so that even if the fluid remains in the casing after the fluid is discharged, the pressure reducing device can be operated to operate the vacuum. Can be removed by drying. Thereby, the risk that the fluid scatters during the overhaul of the casing can be further reduced.

(7) In some embodiments, in any one of the above configurations (1) to (6), a containment vessel spray pump in a nuclear power plant facility having a pressurized water reactor, or fluid injection into a primary cooling system It is a pump.

  According to the configuration of (7) above, the centrifugal multi-stage pump employed for such applications handles fluids containing components that are harmful to the human body. It can be enjoyed particularly effectively.

(8) In order to solve the above problems, a maintenance method for a centrifugal multistage pump according to at least one embodiment of the present invention rotatably supports a rotor provided with a plurality of impellers along a main shaft, and A maintenance method for a centrifugal multi-stage pump including a casing configured to be disassembled into a plurality of impeller chambers each housing each of the impellers, wherein a partition provided between the plurality of impeller chambers has a drain hole side from the rotor. The fluid guided from the plurality of impeller chambers via bypass holes provided along the extending direction of the rotor is provided to communicate with the casing along the direction intersecting the rotor. A discharging step of discharging from the drain hole, a disassembling step of disassembling the casing from which the fluid has been discharged into the plurality of impeller chambers; Provided.

  According to the method of (8) above, when maintaining the centrifugal multistage pump having the above-described configuration, the fluid remaining in the casing in the disassembling step is efficiently discharged in the discharging step. Can be effectively prevented from scattering.

(9) In some embodiments, in the method of (8), a decompression device installation step of attaching a decompression device to the casing from which the fluid has been discharged and the decompression device are attached before the decomposition step. A pressure reducing step of sealing the casing and operating the pressure reducing device.

  According to the method (9), after discharging the fluid in the casing, the fluid remaining in the casing can be removed by vacuum drying by attaching the decompression device and sealing the casing and operating the decompression device. .

  According to at least one embodiment of the present invention, there is provided a centrifugal multistage pump capable of efficiently discharging a fluid in a casing during maintenance and suppressing fluid scattering during disassembly and inspection, and a maintenance method for the centrifugal multistage pump. Can be provided.

It is a schematic diagram which shows the whole structure of the nuclear power plant in which the centrifugal multistage pump which concerns on at least 1 embodiment of this invention is used. It is a schematic diagram which shows the water supply system of the core of the nuclear power plant of FIG. 1, and a containment vessel spray. It is an external view which shows the centrifugal multistage pump which concerns on at least 1 embodiment of this invention from a front and a side with a drive motor. It is the sectional view on the AA line of the centrifugal multistage pump of FIG. FIG. 5 is a schematic diagram schematically showing the casing extracted from FIG. 4. It is a schematic diagram which shows the example of attachment of the decompression device and the cover member to the casing of FIG. It is a schematic diagram which shows schematically the other structure of the casing of FIG. It is a schematic diagram which shows schematically the other structure of the casing of FIG. It is a flowchart which shows the maintenance method of the centrifugal multistage pump which concerns on at least 1 embodiment of this invention for every process.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. Absent.
For example, expressions expressing relative or absolute arrangements such as “in a certain direction”, “along a certain direction”, “parallel”, “orthogonal”, “center”, “concentric” or “coaxial” are strictly In addition to such an arrangement, it is also possible to represent a state of relative displacement with an angle or a distance such that tolerance or the same function can be obtained.
In addition, for example, expressions representing shapes such as quadrangular shapes and cylindrical shapes not only represent shapes such as quadrangular shapes and cylindrical shapes in a strict geometric sense, but also within the range where the same effect can be obtained. A shape including a chamfered portion or the like is also expressed.
On the other hand, the expressions “comprising”, “comprising”, “comprising”, “including”, or “having” one constituent element are not exclusive expressions for excluding the existence of the other constituent elements.

  First, an overall configuration of a nuclear power plant using a centrifugal multistage pump according to at least one embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing an overall configuration of a nuclear power plant in which a centrifugal multistage pump according to at least one embodiment of the present invention is used, and FIG. 2 is a schematic diagram showing a water supply system of a core and a containment spray of the nuclear power plant of FIG. FIG.

  The nuclear power plant AP is a light water reactor that uses light water as a core coolant and a neutron moderator. In the nuclear power plant AP, the primary cooling water heated by the thermal energy generated by the nuclear fission reaction in the nuclear reactor 1 generates the high-temperature and high-pressure steam of the secondary cooling water in the steam generator 5, and power is generated by the steam. . That is, the nuclear power plant AP is a nuclear power plant including a nuclear reactor 1 that is a pressurized water reactor (PWR). The nuclear power plant AP includes a nuclear reactor system CS1 including a primary cooling system through which primary cooling water circulates, and a turbine system CS2 including a secondary cooling system through which secondary cooling water circulates.

  The nuclear reactor 1 includes a reactor pressure vessel 7 that houses a core 2 that heats primary cooling water with thermal energy generated by a nuclear reaction, a pressurizer 4 that pressurizes primary cooling water, and primary and secondary cooling water. A steam generator 5 that generates high-temperature and high-pressure steam of secondary cooling water by exchanging heat between them, and a primary cooling water pump 6 that pumps primary cooling water are housed in the reactor containment vessel 3. . The core 2 includes a fuel assembly having a plurality of fuel rods in which a plurality of fuel pellets containing low enriched uranium are stacked in a cladding tube, and is supported by the reactor containment vessel 3 by a support structure (not shown). Yes.

  The primary cooling water in the nuclear reactor system CS1 is heated by the thermal energy generated by the nuclear reaction in the core 2 and is pressurized by the pressurizer 4 and then supplied to the steam generator 5 through the pipe 8. In the steam generator 5, the secondary cooling water is heated by the primary cooling water, and high-temperature high-pressure steam is generated. The primary cooling water deprived of heat by overheating the secondary cooling water in the steam generator 5 is returned to the core 4 by the primary cooling water pump 6 through the pipe 9.

  In the nuclear reactor system CS1, the primary cooling water is heated to about 320 ° C. by the core 2 and is pressurized to about 150 to 160 atm by the pressurizer 4, thereby suppressing boiling. In the steam generator 5, the secondary cooling water becomes high-temperature and high-pressure steam (saturated steam) of about 270 degrees and 60 atmospheres by the high-temperature and high-pressure primary cooling water.

  The secondary cooling water in the turbine system CS2 is heated by the primary cooling water in the steam generator 5 to become high-temperature and high-pressure steam. The secondary cooling water that has become steam is supplied to a steam turbine 12 via a pipe 11 provided with an isolation valve 10. The steam turbine 12 includes a high pressure turbine 12A and a low pressure turbine 12B, and each is driven by the steam of the secondary cooling water. The generator 13 is driven by the steam turbine 12 to generate power.

  The steam of the secondary cooling water that has finished work in the steam turbine 12 is returned to the liquid by the condenser 14. The condenser 14 uses seawater taken as cooling water through an intake pipe 15 provided with a circulation pump 15P, and the seawater after use is discharged via a drain pipe 16. The secondary cooling water liquefied by the condenser 14 passes through the pipe 17, the condensate pump 18, the ground condenser 19, the condensate demineralizer 20, the condensate booster pump 21, the low pressure feed water heater 22, and the deaeration. Is supplied to the vessel 23. A secondary cooling water pump 24 is provided on the downstream side of the deaerator 23, and the secondary cooling water is supplied to the steam generator 5 via a pipe 27 provided with a high-pressure feed water heater 25 and a water absorption control valve 26. Returned to

  As shown in FIG. 2, the reactor plant AP includes a containment vessel spray 30 for cooling the reactor containment vessel 7 when an abnormality occurs, and a core injection line 31A for injecting cooling water into the core 2. 31B and 31C are provided. The containment vessel spray 30 is supported on the inner upper side of the reactor pressure vessel 3 and sprays cooling water on the inner side of the lower reactor containment vessel 7 when an abnormality is detected. The sprayed cooling water is stored in a cavity 32 provided below the reactor pressure vessel 3.

  The condensate storage tank (CST) 34 and the fuel replacement water tank (RWST) 35 are supply water sources for the containment vessel spray 30 and the core injection lines 31A, 31B, and 31C. It is a storage tank. The condensate storage tank 34 is connected to a core injection line 31C via a line 37, and a filling / high pressure injection pump 36 is provided in the core injection line 31C. The condensate stored in the condensate storage tank 34 is boosted by the filling / high pressure injection pump 36 to a pressure slightly higher than that of the primary cooling system as an injection destination, and can be injected into the core 2.

The fuel replacement water tank 35 is connected to the core injection lines 31A and 31B, and containment vessel spray pumps 38A and 38B are provided in the core injection lines 31A and 31B. The fuel replacement water stored in the fuel replacement water tank 35 can be injected into the core 2 after being pressurized by the containment vessel spray pumps 38A and 38B so that the pressure is slightly higher than the primary cooling system as the water injection destination. It has become. The core injection lines 31A and 31B are connected to the storage container spray 30 via the branch lines 39 and 40, so that the fuel replacement water stored in the fuel replacement water tank 35 can be supplied to the storage container spray 30. It is configured.
The branch lines 39 and 40 are connected to the containment vessel spray 30, and are further configured to be able to supply fuel replacement water to the cavity 32 by further branching.

  Here, the storage container spray pumps 38A and 38B are provided with alternative CV spray pumps 41A and 41B for backup in the event of a malfunction. Alternative CV spray pumps 41A and 41B are provided on parallel lines 42A and 42B provided between line 37 and core injection lines 31A and 31B, respectively. By providing such a backup configuration, the storage container spray pumps 38A and 38B temporarily become inoperable for some reason, or there is an abnormality in the fuel replacement water tank 35 that is the water supply source of the storage container spray pumps 38A and 38B. Even when this occurs, by operating the alternative CV spray pumps 41A and 41B, water supply and core injection to the containment spray 30 can be secured using the condensate storage tank 34 as a water supply source.

  As described above, various types of pumps are used in the nuclear power plant AP, but the specifications of these pumps are selected according to the intended use. In this embodiment, in particular, centrifugal multistage pumps are employed as the filling / high pressure infusion pump 36 and the alternative CV spray pumps 41A and 41B (in the nature of the filling / high pressure infusion pump 36 and the alternative CV spray pumps 41A and 41B, This is because the degree of pressure increase during pumping is large). In such a filling / high pressure injection pump 36 and alternative CV spray pumps 41A and 41B, the condensate stored in the condensate storage tank (CST) 34 and the fuel replacement stored in the fuel replacement water tank (RWST) 35 Handles fluids that contain components that are harmful to the human body, such as water. Therefore, when disassembling and inspecting the casing during maintenance, it is necessary to prevent the fluid from scattering to workers during disassembly by discharging the fluid from the casing in advance. Such a subject is achieved by the configuration and maintenance method of the centrifugal multistage pump described below.

  Subsequently, a centrifugal multistage pump and a maintenance method thereof according to at least one embodiment of the present invention will be described. In the following description, the centrifugal multi-stage pump employed as the filling / high pressure infusion pump 36 and the alternative CV spray pumps 41A and 41B is indicated by reference numeral 50. Also, in the following description, these pumps have the same configuration as the centrifugal multistage pump 50 unless the filling / high pressure infusion pump 36 and the alternative CV spray pumps 41A and 41B are individually referred to.

  3 is an external view showing the centrifugal multistage pump 50 according to at least one embodiment of the present invention from the front and side along with the drive motor 54, and FIG. 4 is a cross-sectional view of the centrifugal multistage pump 50 of FIG. 5 is a schematic diagram schematically showing the casing 52 extracted from FIG. 4, and FIG. 6 is a schematic diagram showing an example of attaching the decompression device 70 and the lid member 72 to the casing 52 of FIG. 7 is a schematic diagram schematically showing another configuration of the casing 52 of FIG. 5, and FIG. 8 is a schematic diagram schematically showing still another configuration of the casing 52 of FIG.

As shown in FIG. 3, the centrifugal multistage pump 50 includes a rotor 51 and a casing 52 that accommodates the rotor 51 while rotatably supporting the rotor 51 therein. One end of the rotor 51 is connected to a drive motor 54 that is a power source, and the drive motor 54 is installed on a base 53 that is shared with the centrifugal multistage pump 50. The drive motor 54 is driven by power supplied from a power source (not shown) and supplies power to the centrifugal multistage pump 50.
The power source of the drive motor 54 may be a normal system power source, an emergency power source for backup of the system power source, or an external power source (for example, a mobile vehicle such as a power supply car). It may be an on-board mobile power supply.

As shown in FIG. 4, the rotor 51 is housed in the casing 52 while being rotatably supported on both sides by bearings 55 provided on the casing 52. The rotor 51 has a plurality of impellers 57 provided along the main shaft 56. Particularly in the present embodiment, the centrifugal multi-stage pump 50 employs a three-stage compression system, and the rotor 51 has three impellers 57A, 57B, and 57C correspondingly.
In the present embodiment, a single casing is illustrated as the casing 52, but a double casing may be used.

  The casing 52 includes a suction chamber 58 for sucking fluid, a compression chamber 59 for compressing the sucked fluid in multiple stages, and a discharge chamber 60 for discharging the compressed fluid. The suction chamber 58, the compression chamber 59, and the discharge chamber 60 that constitute the casing 52 are configured as separate members, and are assembled coaxially with the rotor 51 as the center. During maintenance, these components are moved along the rotor 51 so that they can be disassembled and inspected.

The suction chamber 58 and the discharge chamber 60 are provided with a suction port 80 and a discharge port 82 so that fluid is sucked and discharged from a direction intersecting the extending direction of the rotor 51 (a vertical direction of the rotor 51).
The suction chamber 58 and the discharge chamber 60 are connected to each other by a bolt 61, so that the mechanical strength of the casing 52 is reinforced.

The compression chamber 59 is configured such that it can be further disassembled into a plurality of impeller chambers 62 that respectively accommodate the plurality of impellers 57. In the present embodiment, three impeller chambers 62A, 62B, and 62C are provided so as to correspond to the three impellers 57A, 57B, and 57C. Partition walls 63A, 63B, and 63C are provided between the adjacent impeller chambers 62A, 62B, and 62C, respectively, and the impellers 57A, 57B, and 57C rotate between the impeller chambers 62A, 62B, and 62C. The fluid is configured to be compressed in multiple stages.
In the compression chamber (each of the impeller chambers 62A, 62B, and 62C), a diffuser 67 that is a pressure conversion unit is provided.

  The impeller chambers 62A, 62B, and 62C are also configured as separate members, similarly to the suction chamber 58 and the discharge chamber 60 described above, and are assembled coaxially with the rotor 51 as the center. During maintenance, these components are moved along the rotor 51 so that they can be disassembled and inspected.

  The casing 52 is provided with a drain hole 64 for discharging the fluid in the casing 52 to the outside by opening it during maintenance. The drain hole 64 is opened along the direction intersecting the extending direction of the rotor 51. Particularly in the present embodiment, when the centrifugal multistage pump 50 is installed horizontally on the pedestal 53 so that the rotor 51 is in the horizontal direction, the drain hole 64 is at least more gravitational than the rotor 51 as viewed from the extending direction of the rotor 51. The drain hole 64 is preferably provided in the lowermost part of the internal space of the casing 52 in the direction of gravity. Although the drain hole 64 is normally sealed (during non-maintenance), the fluid in the casing 52 is discharged to the outside through the drain hole 64 by gravity by being opened during maintenance.

  The partition walls 63A, 63B, and 63C are each provided with a bypass hole 66 that is opened along the extending direction of the rotor 51, and the adjacent impeller chambers 62 communicate with each other. Here, the bypass hole 66 provided in each partition wall is provided on the drain hole 64 side as viewed from the extending direction of the rotor 51 (that is, the lower side in the gravity direction when the centrifugal multistage pump 50 is installed on the pedestal 53). Yes. Therefore, the fluid in each impeller chamber 62 is guided to the drain hole 64 through the bypass hole 66 and then discharged from the drain hole 64 to the outside. Thus, since the fluid in the casing 52 is smoothly discharged to the outside, it is possible to effectively prevent the fluid remaining in the casing 52 from scattering when the casing 52 is overhauled.

  The bypass hole 66 is also provided in the partition between the suction chamber 58 and the discharge chamber 60 as well as the partitions 63A, 63B, and 63C. Thereby, in addition to the impeller chamber 57, the fluid in the suction chamber 58 and the discharge chamber 60 can be similarly guided to the drain hole 64 through the bypass hole 66 and discharged to the outside.

  Here, as shown in FIGS. 4 and 5, the bypass hole 66 provided in each of the partition walls 63 is provided at an equal distance from the rotor 51. Thereby, the fluid in each impeller chamber 62 is smoothly guided toward the drain hole 64 through each bypass hole 66.

The casing 52 has an attachment portion 71 to which a decompression device 70 capable of decompressing the inside of the casing 52 can be attached. FIG. 6 shows a state in which the decompression device 70 is attached to the attachment portion 71. When the decompression device 70 is used, the suction port 80 is sealed with the lid member 72 and the drain pipe 65 connected to the drain hole 64 is sealed with the plug member 68 as shown in FIG. The interior space of the casing 52 is isolated from the outside to ensure airtightness. The lid member 72 may be, for example, a flange structure that seals the suction port 80 via an O-ring, or may be a screw-in type cap that can be fitted to the suction port 80.
In FIG. 6, the rotor 51 housed in the casing 52 is indicated by a broken line for easy understanding, and the vicinity of the bearing 55 that supports the rotor 51 in the casing 52 is also airtight.

  In this embodiment, when the fluid is discharged from the casing 52 at the time of maintenance, the pressure reducing device 70 is operated, so that the fluid remaining in the casing 52 can be removed by vacuum drying. Thereby, when disassembling and inspecting the casing 52, it is possible to more reliably prevent the fluid remaining in the casing 52 from scattering.

In another embodiment, as shown in FIG. 7, the bypass holes 66 are provided at positions away from the rotor 51 from the tips of the respective impellers 57, and the bypass holes 66 extend along the rotor 51. The common plug 90 can be inserted. When the bypass hole 66 is provided in the partition wall 63, the fluid in the plurality of impeller chambers 62 may flow backward from the high pressure side toward the low pressure side, and thus pump efficiency may be reduced. In the present embodiment, for example, by inserting the plug 90 into the bypass hole 66 and sealing it when the pump is operating (during maintenance), it is possible to prevent such a backflow of fluid and prevent a decrease in pump efficiency. Further, since the bypass hole 66 is located farther from the rotor 51 than the tip of the impeller 57, it does not interfere with the impeller 57 even when the plug 90 is inserted. On the other hand, by removing the plug 90 from the bypass hole 66 at the time of maintenance, the fluid from each impeller chamber 62 is guided to the drain hole 64 through the bypass hole 66 as described above, and is discharged to the outside.
It should be noted that such an operation of detaching the plug 90 from the bypass hole 66 may be performed automatically or manually.

  In another embodiment, as shown in FIG. 8, the bypass hole 66 of each partition wall 63 is provided so that the flow path is formed so that the distance from the rotor 51 increases as the drain hole 64 is approached. Yes. As a result, a gradient is generated in the flow path provided with each bypass hole 66 in the casing 52, so that the fluid is efficiently guided from each impeller chamber 57 toward the drain hole 64.

  Next, a maintenance method for the centrifugal multistage pump 50 having the above configuration will be described. FIG. 9 is a flowchart showing a maintenance method of the centrifugal multistage pump 50 according to at least one embodiment of the present invention for each process.

  First, the operating centrifugal multistage pump 50 is stopped (step S1), and the drain hole 64 provided in the casing 52 is opened to discharge the fluid from the casing 52 to the outside (step S2: discharge process). When the drain hole 64 is opened, as described above, the fluid in each impeller chamber 62 is guided to the drain hole 64 via the bypass hole 66 provided in the partition wall 63 and then discharged to the outside. The centrifugal multistage pump 50 has a complicated structure as compared with a single-stage centrifugal pump, but with the above configuration, the fluid in the casing 52 can be discharged with a simple operation.

Subsequently, the decompression device 70 is attached to the casing 52 from which the fluid has been discharged (step S3: decompression device installation step). Specifically, as described above with reference to FIG. 6, the decompression device 70 is attached to the attachment portion 71, the suction port 80 is sealed with the lid member 72, and the drain pipe 65 connected to the drain hole 64 is plugged. By sealing with the member 68, the internal space of the casing 52 is isolated from the outside and airtightness is ensured, and then the pressure reducing device 70 is operated (step S4: pressure reducing step). As a result, the remaining fluid in the casing 52 is removed by vacuum drying.
After the fluid in the casing is removed in this manner, the casing 52 is disassembled into members, and an inspection for disassembly is performed (step S5: disassembly process).

  As described above, according to at least one embodiment of the present invention, since the fluid existing in the casing 52 can be efficiently discharged to the outside, it is effective that the fluid remaining in the casing is scattered during the overhaul. Can be prevented.

  The present disclosure can be used for a centrifugal multistage pump having a rotor provided with a plurality of impellers along a main shaft, and a maintenance method for the centrifugal multistage pump.

DESCRIPTION OF SYMBOLS 1 Reactor 2 Core 3 Reactor containment vessel 4 Pressurizer 5 Steam generator 6 Primary cooling water pump 7 Reactor pressure vessel 12 Steam turbine 12A High pressure turbine 12B Low pressure turbine 13 Generator 14 Condenser 15P Circulating water pump 18 Condensate Pump 19 Ground condenser 20 Condensate demineralizer 21 Condensate booster pump 22 Low pressure feed water heater 23 Deaerator 24 Secondary cooling water pump 25 High pressure feed water heater 26 Water absorption control valve 30 Containment vessel spray 31 Core injection line 32 Cavity 34 Condensate storage tank (CST)
35 Fuel replacement water tank (RWST)
36 Filling / High Pressure Injection Pump 38 Containment Vessel Spray Pump 41 Alternative CV Spray Pump 50 Centrifugal Multistage Pump 51 Rotor 52 Casing 53 Base 54 Drive Motor 56 Spindle 57 Impeller 58 Suction Chamber 59 Compression Chamber 60 Discharge Chamber 61 Bolt 62 Impeller Chamber 63 Partition 64 Drain hole 65 Discharge pipe 66 Bypass hole 68 Diffuser 70 Pressure reducing device 71 Mounting portion 72 Lid member 80 Suction port 82 Suction port 90 Plug

Claims (9)

A rotor provided with a plurality of impellers along the main axis;
A casing that rotatably supports the rotor, and is configured to be disassembled into a plurality of impeller chambers that respectively house the plurality of impellers;
With
The casing is provided with a drain hole communicating with the outside along a direction intersecting the rotor,
Each of the partition walls provided between the plurality of impeller chambers is formed so as to penetrate along the extending direction of the rotor on the drain hole side from the rotor as viewed from the extending direction of the rotor. A centrifugal multistage pump, characterized in that a bypass hole is provided. The rotor is disposed along a horizontal direction;
The centrifugal multistage pump according to claim 1, wherein the drain hole is provided on a lower side in the gravity direction of the casing.   The centrifugal multistage pump according to claim 1 or 2, wherein the bypass holes provided in each of the partition walls are provided at an equal distance from the rotor. The bypass hole is provided at a position away from the rotor from the tips of the plurality of impellers,
The centrifugal multistage pump according to any one of claims 1 to 3, wherein each of the bypass holes is configured to allow a common plug extending along the rotor to be inserted therethrough.   3. The bypass hole provided in each of the partition walls is provided so that a flow path having a gradient is formed so as to be separated from the rotor as the drain hole is approached. The centrifugal multistage pump described in 1.   The centrifugal multistage pump according to any one of claims 1 to 5, wherein the casing has an attachment portion to which a decompression device capable of decompressing the inside of the casing can be attached.   The centrifugal multistage pump according to any one of claims 1 to 6, wherein the centrifugal multistage pump is a containment vessel spray pump in a nuclear power plant having a pressurized water reactor or a pump for injecting fluid into a primary cooling system. A maintenance method for a centrifugal multi-stage pump including a casing configured to rotatably support a rotor provided with a plurality of impellers along a main shaft and to be disassembled into a plurality of impeller chambers each housing the plurality of impellers. Because
The fluid introduced from the plurality of impeller chambers to the partition wall provided between the plurality of impeller chambers via a bypass hole provided along the extending direction of the rotor on the drain hole side from the rotor. A discharge step of discharging from a drain hole provided in the casing so as to communicate with the outside along a direction intersecting the rotor;
A disassembling step of disassembling the casing from which the fluid has been discharged into the plurality of impeller chambers;
A maintenance method for a centrifugal multistage pump, comprising: Before the decomposition step,
A decompression device installation step of attaching a decompression device to the casing from which the fluid is discharged;
While sealing the casing to which the decompression device is attached, a decompression step of operating the decompression device;
The maintenance method of the centrifugal multistage pump according to claim 8, further comprising:

Images