JP6420594B2 - pump - Google Patents

Description

  The present invention relates to a pump for draining water stored in a suction water tank.

  The vertical shaft pump includes a rotating shaft that is connected to an impeller inside a casing that extends in the vertical direction. The rotating shaft is rotatably supported by a bearing on the downstream side of the impeller in the direction of drainage. The bearing includes a radial bearing that supports the rotating shaft inside the casing, and a thrust bearing that supports the end of the rotating shaft outside the casing. When the pump is operated, the pressure (back pressure) on the downstream side of the impeller in the direction of drainage increases due to drainage. Therefore, a large thrust load is applied to the thrust bearing, causing damage and vibration.

  Patent Document 1 proposes a thrust reduction device for a pump that reduces the axial thrust load applied to the thrust bearing so that breakage and vibration can be suppressed. In this pump, a balance hole (drainage channel) through which a part of drainage can be led out is formed in a radial bearing that supports the impeller. One end side of the balance pipe communicates with the balance hole. The other end of the balance tube is connected to a suction bell mouth, which is upstream of the impeller, and communicates with the inside of the casing. Thereby, the waste water on the downstream side of the impeller is discharged to the upstream side of the impeller. As a result, since the pressure difference between the upstream pressure and the downstream pressure of the impeller can be reduced, the thrust load applied to the thrust bearing can be reduced.

  However, the pump of Patent Document 1 has a low degree of freedom for reducing the axial thrust load, and an improvement is desired. In addition, no measures are taken for radial thrust loads.

JP 07-332281 A

  An object of the present invention is to effectively reduce the axial thrust load applied to the pump. Another object is to effectively reduce the radial thrust load.

In order to solve the above-mentioned problem, the pump of the present invention is provided with a casing in which a suction port for sucking water in a suction water tank is formed on one end side and a discharge pipe is connected on the other end side, and disposed in the casing. A rotating shaft coupled with an impeller for sucking water from the suction port, a bearing for rotatably supporting the rotating shaft, and fixed to the rotating shaft so as to be located downstream of the impeller in the draining direction. A bearing plate is disposed in the casing so as to be adjacent to the downstream side in the drain direction of the impeller, and the balance plate is disposed on the impeller side of the bearing casing , A portion of the bearing casing facing the balance plate is provided with a back pressure chamber, and a connection pipe laid between the bearing casing and the casing is provided in the back pressure chamber. And, draining unit for draining water in said back pressure chamber to the outside of the casing is in communication with.

In this pump, since the balance plate is fixed to the rotating shaft, the pressure (back pressure) on the downstream side of the balance plate can be reduced. Therefore, the axial thrust load along the axial direction of the rotating shaft can be effectively reduced. Moreover, since the diameter of the balance plate can be arbitrarily set regardless of the diameter of the impeller, the degree of freedom in design is large. As a result, damage and vibration of the thrust bearing that rotatably supports the end of the rotating shaft can be effectively suppressed. Moreover, since the drainage part which drains internal water to the exterior of a casing is connected to the back pressure chamber of the downstream of a balance board, it can maintain in the state which reduced the back pressure of the balance board. Further, a shaft thrust in the direction opposite to the impeller shaft thrust can be applied to the rotation shaft. Therefore, damage and vibration of the radial bearing can be suppressed.

  The balance plate is disposed on the upstream side in the drain direction of a radial bearing that rotatably supports the impeller. In this way, since the pressure at the radial bearing is reduced, the radial thrust load can be reduced, and damage and vibration of the radial bearing can be suppressed.

Further, the casing, the a through portion causes outwardly projecting part of the rotary shaft, and a shaft seal device disposed in the through portion, the impeller side of the shaft sealing device, and the balance plate A different second balance plate is provided. In this way, since the pressure on the shaft seal device side is reduced, damage to the shaft seal device can be suppressed, and leakage of water from the shaft seal device can be reliably prevented.

The drainage unit, it is preferable to provide an adjustable throttling the amount of waste water. In this way, since the axial thrust load can be adjusted, damage and vibration of the thrust bearing and the like can be effectively suppressed.

  The pump according to the present invention further includes an intake pipe having one end opened on the upstream side of the impeller in the casing and the other end opened to a predicted water vortex generation predicted water level set in the suction water tank. In this way, the air in the suction water tank sucked from the intake pipe is crushed into a large number of bubbles (microbubbles) having a diameter of several millimeters or less by the impeller in the casing and discharged to the downstream side together with the pumped water. . Since the micro bubbles serve as cushions, the radial thrust load of the radial bearing can be effectively reduced. Therefore, vibration and noise of the pump can be suppressed, and damage to the radial bearing and the like can be suppressed.

  The opening area on the casing side of the intake pipe is 5% or less of the smallest opening area of the casing located on the upstream side of the impeller. In this way, the amount of air supplied into the casing can be set to a flow rate that does not hinder operation. A known pump (for example, Japanese Patent No. 4690134) is one in which one end of the air pipe is opened in the installation floor and the other end of the air pipe is opened in the casing so as to be located on the upstream side of the impeller. However, this conventional pump is for inhaling a large amount of air to perform an air lock operation. The pipe has a large diameter and is designed so that drainage stops when the air is sucked. The present invention is not intended to stop the drainage but to reduce the fluid force caused by the underwater vortex, so the opening area of the intake pipe is set as described above. As a result, a very small amount of air that does not significantly lower the head is sucked in, so that an amount of air that can continue drainage can be secured.

  In the pump of the present invention, since the balance plate is provided on the downstream side of the impeller of the rotating shaft in the drain direction, the axial thrust load can be effectively reduced. Further, since the intake pipe opened at the predicted level of underwater vortex generation in the suction water tank is connected to the upstream side of the impeller, the radial thrust load can be effectively reduced. Therefore, damage and vibration of the bearing and the like can be suppressed.

Sectional drawing which shows the vertical shaft pump of 1st Embodiment of this invention. The partially expanded sectional view of FIG. Sectional drawing which shows the vertical shaft pump of 2nd Embodiment. The partial expanded sectional view of FIG. The partial expanded sectional view of the vertical shaft pump of 3rd Embodiment. Sectional drawing which shows the vertical shaft pump of 4th Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows a vertical shaft pump 10 according to a first embodiment of the present invention. The vertical shaft pump 10 includes a casing 11 that is arranged in the suction water tank 3 through the arrangement hole 2 of the installation floor 1. The casing 11 is formed with a suction port 12 for sucking water in the suction water tank 3 on the lower end side, and a discharge pipe 13 piped to a downstream discharge water tank (not shown) is connected to the upper end side. The vertical shaft pump 10 of the present invention effectively reduces the axial thrust load and the radial thrust load by disposing the balance plate 26 on the rotating shaft 18 and disposing the intake pipe 33 on the casing 11.

  Specifically, the casing 11 includes a straight tubular pumping pipe 14 extending in the vertical direction. An elliptical vane case 15 bulging outward in the radial direction is connected to the lower end of the pumping pipe 14. The lower end of the vane case 15 is connected to a suction bell mouth 16 having a conical cylindrical shape whose diameter gradually increases downward. A suction port 12 is formed at the lower end of the suction bell mouth 16. The suction port 12 faces the bottom wall 4 of the suction water tank 3 with a predetermined interval. In addition, a discharge bend 17 curved by 90 degrees is connected to the upper end of the pumping pipe 14. A discharge pipe 13 is connected to the discharge bend 17.

  A rotating shaft 18 is disposed in the casing 11 along the axial direction of the pumped-up pipe 14. The upper end of the rotating shaft 18 passes through the discharge bend 17 of the casing 11 and protrudes outward. A motor (not shown), which is a driving means for rotationally driving the rotary shaft 18, is connected to the upper end of the protruding rotary shaft 18. The lower end of the rotating shaft 18 is located in the vane case 15. An impeller 19 for sucking water into the casing 11 from the suction port 12 is connected to the lower end of the rotating shaft 18.

  The upper end of the rotating shaft 18 is rotatably supported by a bearing 20 that is a thrust bearing. The lower end side of the rotating shaft 18 to which the impeller 19 is connected is rotatably supported by underwater bearings 21A and 21B that are radial bearings. An intermediate portion of the rotating shaft 18 is rotatably supported by an underwater bearing 22 that is a radial bearing.

  As shown in FIG. 2, the underwater bearings 21 </ b> A and 21 </ b> B that support the lower end side of the rotating shaft 18 are disposed in a bearing casing 23 disposed in the vane case 15. This bearing casing 23 is located in the upper part (downstream in the direction of drainage) of the impeller 19 and is fixed in the vane case 15 via the guide vanes 24 that extend radially. An insertion portion 25 through which the rotary shaft 18 is rotatably inserted is formed at the shaft center of the bearing casing 23. An underwater bearing 21 </ b> A is disposed at the lower end of the insertion portion 25, and an underwater bearing 21 </ b> B is disposed at the upper end of the insertion portion 25.

  A balance plate 26 having a circular shape in plan view is fixed to the rotary shaft 18 so as to be positioned at the lower end of the bearing casing 23. The balance plate 26 is located on the downstream side of the impeller 19 in the direction of drainage and on the upstream side of the submersible bearings 21A and 21B in the direction of drainage. The diameter of the balance plate 26 is set in proportion to the discharge capacity of the vertical pump 10 corresponding to the axial thrust load by the impeller 19.

  The bearing casing 23 is provided with a back pressure chamber 27 having a predetermined volume of space so as to be located downstream of the balance plate 26 in the direction of drainage. The back pressure chamber 27 communicates with a drainage section 28 that discharges the water flowing into the suction water tank 3 outside the casing 11 due to a pressure difference. The drainage portion 28 includes a communication passage 29 formed in the bearing casing 23, a discharge passage 30 formed in the casing 11, and a connection pipe 31 that communicates these passages 29, 30. The communication passage 29 is formed to extend radially outward from the back pressure chamber 27. The discharge passage 30 is formed so as to be positioned on the radially outer side of the communication passage 29, and the outer end side is opened in the suction water tank 3. The connection pipe 31 extends between the bearing casing 23 and the vane case 15 in the radial direction. An orifice 32 is arranged at the outlet of the discharge passage 30 as a throttle for adjusting the amount of drainage.

  As shown in FIG. 1, the casing 11 is provided with an intake pipe 33 for introducing the air in the suction water tank 3 into the casing 11. In the present embodiment, a plurality of (four in the present embodiment) intake pipes 33 are provided at equal intervals so that air can be uniformly supplied into the casing 11. One end 33 a side of the intake pipe 33 is connected to the suction bell mouth 16, which is the upstream side of the impeller 19, and is opened in the casing 11. Specifically, the one end 33 a side of the intake pipe 33 is connected to the throttle portion 16 a having the smallest opening area of the suction bell mouth 16 located on the upstream side of the impeller 19. The other end 33 b side of the intake pipe 33 extends upward in the suction water tank 3 and is opened at an underwater vortex generation predicted water level H set in the suction water tank 3.

  Here, the underwater vortex is a vortex extending from the bottom wall 4 toward the suction port 12, and is generated when the amount of water in the suction water tank 3 decreases and the water flow sucked from the suction port 12 becomes faster. The water level H at which the underwater vortex is predicted to occur is approximately located at the top of the impeller 19, specifically the height of the upper end of the vane case 15 that houses the impeller 19 from the bottom wall 4. Therefore, in the present embodiment, the other end 33 b of the intake pipe 33 is opened at the upper end of the vane case 15. The opening of the other end 33 b is set so as to face the bottom wall 4 by providing the curved portion 34.

  The opening area (diameter) on the one end 33a side of the intake pipe 33 is set to 2% or more and 5% or less of the opening area of the throttle portion 16a of the suction bell mouth 16. The opening area of the other end 33b of the intake pipe 33 is set to 5% or more and 10% or less of the opening area of the throttle portion 16a. When the one end 33a side of the intake pipe 33 is made larger than 5% or the other end 33b side of the intake pipe 33 is made larger than 10%, the air suction amount into the casing 11 increases. As a result, there is a problem that the drainage operation is affected and the drainage is stopped in the worst case. In the present embodiment, by setting as described above, it is possible to supply a minute amount of air that does not significantly lower the head, so that the operation is not hindered.

  Next, the draining operation of the vertical shaft pump 10 of this embodiment will be described.

  When water accumulates in the suction water tank 3 to the set water level, the rotating shaft 18 is rotated and the operation is started. Then, the water in the suction water tank 3 is pumped by the impeller 19 and discharged through the discharge pipe 13 to the discharge water tank on the downstream side. At this time, the pressure (back pressure) on the downstream side of the impeller 19 is increased by the drainage, and the axial thrust along the axis acts on the rotary shaft 18 to which the impeller 19 is connected.

  In the vertical shaft pump 10 of the present embodiment, the balance plate 26 is disposed on the rotary shaft 18, so that the pressure (back pressure) on the downstream side of the balance plate 26 can be reduced. Further, since the discharge portion is provided in the back pressure chamber 27 provided on the downstream side of the balance plate 26, the back pressure of the balance plate 26 can be maintained in a reduced state. Therefore, the thrust load along the axial direction of the rotating shaft 18 can be effectively reduced. Specifically, the axial thrust load on the bearing 20 can be reduced, and the radial thrust load of the underwater bearings 21A and 21B on the back of the balance plate 26 can be reduced.

Specifically, when the outlet (downstream) side pressure of the impeller 19 is P ₁ , the pressure in the back pressure chamber 27 is P ₂ , and the outlet side pressure P ₃ of the discharge portion, the pressure P ₁ is the highest and the pressure P ₃ is the highest. (P ₁ > P ₂ > P ₃ ). Therefore, in order to effect axial thrust T _u along the drainage direction with the balance plate 26, the axial thrust T _a drainage direction opposite that shown in FIG. 1 is increased. As a result, it is possible to reduce the axial thrust _{T b} applied to the bearing 20.

More specifically, when the axial thrust when the balance plate 26 is not a T _a, the axial thrust T _b applied to the bearing 20 can be calculated by the following equation (1).

T_ａ:バランス板が無いときの軸スラスト T_ｂ:スラスト軸受に加わる軸スラスト
T_ｕ:軸受ケーシング上部の軸スラスト
D_d:バランス板の直径 D_s:シャフト直径
P_１:インペラ出口圧力 P_２:背圧室の圧力

T _a : Shaft thrust when there is no balance plate T _b : Shaft thrust applied to the thrust bearing
_Tu : Shaft thrust at the top of the bearing casing
D _d : Balance plate diameter D _s : Shaft diameter
P ₁ : Impeller outlet pressure P ₂ : Back pressure chamber pressure

Although loss leakage and increasing the diameter of the water discharge section 28 is increased, since the outlet side pressure P ₁ and the back pressure P ₂ of the impeller 19 is increased, it is possible to reduce the axial thrust load T _b. And since the orifice 32 which can adjust the amount of drainage is provided in the exit of the drainage part 28, an axial thrust load can be adjusted easily.

Further, it is possible by reducing the gap between the balance plate 26 and the back pressure chamber 27, also to reduce the axial thrust load with leakage loss T _b. And since the diameter of the balance plate 26 can be arbitrarily set irrespective of the diameter of the impeller 19, the freedom degree of design is large.

  Moreover, since the vertical shaft pump 10 of this embodiment is arrange | positioned in the upstream of the underwater bearing 21A, 21B which supports the impeller 19, the pressure in the underwater bearing 21A, 21B is reduced. Therefore, damage and vibration of the radial bearing can be effectively suppressed.

  In addition, when drainage advances by drainage operation and the water in the suction tank 3 falls to the underwater vortex generation predicted water level H, an underwater vortex is generated in the suction tank 3. The vortex core of the underwater vortex heading toward the suction port 12 has a high rotational angular velocity, and a vortex is formed by cavitation. When this vortex passes through the impeller 19, a hydrodynamic force (radial axis thrust) 7 to 8 times that in the case where no underwater vortex is generated acts on the underwater bearings 21 </ b> A and 21 </ b> B.

  However, the vertical shaft pump 10 of the present embodiment is provided with the intake pipe 33 that introduces the air in the suction water tank 3 into the casing 11 when the water level drops to the predicted level H of the underwater vortex generation. Therefore, cavitation can be relaxed, the radial thrust load can be reduced, and vibration can be prevented. Specifically, the air sucked from the intake pipe 33 is pulverized into a large number of bubbles (microbubbles) having a diameter of several millimeters or less by the impeller 19 in the casing 11 and discharged to the downstream side together with the pumped water. Since the micro bubbles serve as cushions, the radial thrust load of the underwater bearings 21A and 21B can be effectively reduced. Further, since the amount of air introduced into the casing 11 is set to a flow rate at which the head does not greatly decrease, the drainage operation is not hindered.

  As described above, the vertical shaft pump 10 of the present invention is provided with the balance plate 26 on the rotary shaft 18, so that the axial thrust load can be effectively reduced. Moreover, since the intake pipe 33 for introducing the air in the suction water tank 3 is provided, the radial thrust load can be effectively reduced. Therefore, damage and vibration of the bearing 20 that is a thrust bearing and the underwater bearings 21A and 21B that are radial bearings can be effectively suppressed.

(Second Embodiment)
3 and 4 show the vertical shaft pump 10 of the second embodiment. In the second embodiment, the balance plate 38 for reducing the back pressure, the back pressure chamber 39 for maintaining the back pressure in a reduced state, and the drainage part 40 are also provided on the bearing 20 side. It is different from the embodiment.

  As shown in FIG. 4, the discharge bend 17 of the casing 11 is formed with an accommodating portion 35 that protrudes outward at a portion that penetrates the rotation shaft 18 and protrudes outward. A penetrating part 36 is provided at the upper end of the accommodating part 35. A gap between the penetrating portion 36 and the rotary shaft 18 is sealed by a shaft seal device 37.

  A balance plate 38 is fixed to the rotary shaft 18 so as to be positioned at an intermediate portion of the overall height of the accommodating portion 35. The balance plate 38 is located on the upstream side of the shaft seal device 37. By providing the balance plate 38, a back pressure chamber 39 is defined in the accommodating portion 35 on the downstream side of the balance plate 38. The back pressure chamber 39 communicates with a drainage section 40 that discharges water flowing into the suction water tank 3 outside the casing 11 due to a pressure difference. Referring to FIG. 3, the drainage part 40 is a pipe having one end connected to the accommodating part 35 so as to communicate with the back pressure chamber 39 and the other end arranged in the suction water tank 3 through the arrangement hole 2.

Vertical shaft pump 10 of the second embodiment can be the pressure P ₂ in the back pressure chamber 39 side is disposed a shaft sealing device 37 by the balance plate 38 lower than the pressure P ₁ on the upstream side. And the state which reduced the back pressure of the balance board 38 by the waste_water | drain part 40 can be maintained. Therefore, the axial thrust load applied to the bearing 20 can be further effectively reduced. Moreover, breakage of the shaft seal device 37 can be suppressed and leakage of water from the shaft seal device 37 can be reliably prevented.

(Third embodiment)
FIG. 5 shows the vertical shaft pump 10 of the third embodiment. In the third embodiment, a concave groove 41 that is recessed inward in the radial direction is provided in the central outer peripheral portion along the axis of the balance plate 38, and the drainage portion 42 is positioned so as to be radially outward of the concave groove 41. Is different from the second embodiment in that it is piped. Similarly to the drainage part 40, the drainage part 42 is a pipe having one end side connected to the accommodation part 35 so as to communicate with the back pressure chamber 39 and the other end side arranged in the suction water tank 3 through the arrangement hole 2.

In the vertical shaft pump 10 of the third embodiment, the water in the portion of the concave groove 41 can be discharged by the drainage part 42. Further, the water in the back pressure chamber 39 on the upstream side of the shaft seal device 37 can be discharged by the drainage part 40. Therefore, the pressure difference ΔP between the upstream pressure P ₁ and the downstream pressure P ₂ of the balance plate 38 can be increased. As a result, the pressure applied to the shaft seal device 37 can be further reduced, and the shaft thrust load can be further effectively reduced. Further, the air in the suction water tank 3 can be sucked into the back pressure chamber 39 from the drainage part 40 and the drainage part 41 when the vacuum inside the pump is stopped when the pump is stopped. Therefore, since the shaft seal device 37 is not evacuated and is maintained at atmospheric pressure, reliability can be improved.

(Fourth embodiment)
FIG. 6 shows a vertical shaft pump 10 according to the fourth embodiment. In the fourth embodiment, an intake pipe 43 is piped from the suction bell mouth 16 located in the suction water tank 3 to the motor chamber on the installation floor 1, and a variable throttle capable of adjusting an opening area that can flow into the intake pipe 43. The difference from the first embodiment is that 49 is interposed.

  The intake pipe 43 includes an annular portion 44 having a circular shape in a plan view and positioned at a predetermined interval on the outer peripheral portion of the throttle portion 16 a of the suction bell mouth 16. The annular portion 44 is provided with a plurality (four in the present embodiment) of connecting portions 45 protruding radially inward at equal intervals in the circumferential direction. The connecting portion 45 is connected to the throttle portion 16 a of the suction bell mouth 16 and is opened in the casing 11. The annular portion 44 is provided with an ascending portion 46 that extends through the arrangement hole 2 to above the installation floor 1. A curved portion 47 that turns 180 degrees downward is provided at the upper end of the upper portion. The curved portion 47 is provided with a descending portion 48 that extends again into the suction water tank 3 through the arrangement hole 2. The lower end of the descending portion 48 is disposed at the set underwater vortex generation predicted water level H in the suction water tank 3.

  The variable throttle 49 adjusts the amount of air introduced into the casing 11 by adjusting the flowable opening area. The variable throttle 49 is interposed in a descending portion 48 located on the installation floor 1.

  In the fourth embodiment, the same operations and effects as in the first embodiment can be obtained. In addition, since the variable throttle 49 is disposed in the intake pipe 43, the degree of freedom of pipes that can be used as the intake pipe 43 can be increased. Moreover, since the intake pipe 43 is extended to the installation floor 1 and the variable throttle 49 is disposed at that portion, the operator can easily operate (adjust). Further, by using the variable throttle 49 that can change the opening area electrically, the intake pipe 43 can also be used as the air pipe of the preceding standby pump.

  In addition, the pump of this invention is not limited to the structure of the said embodiment, A various change is possible.

  For example, in the first embodiment, the balance plate 26 is disposed on the upstream side of the underwater bearings 21A and 21B that support the impeller 19, and in the second embodiment, on the upstream side of the underwater bearings 21A and 21B and the shaft seal device 37. Although the balance plates 26 and 38 are disposed, the balance plate 38 may be disposed only on the shaft seal device 37 side. Moreover, in each embodiment, although the drainage parts 28 and 40 were provided in order to keep the back pressure of the balance plates 26 and 38 reduced, the drainage parts 28 and 40 may not be provided. Further, the intake pipe 43 of the fourth embodiment may be applied to the vertical shaft pump 10 of the first to third embodiments.

  In the above-described embodiment, the balance plates 26 and 38 and the intake pipe 33 of the present invention are applied to the vertical shaft pump 10. However, the present invention can also be applied to a horizontal shaft pump that has a rotating shaft extending laterally with respect to the casing. Thus, similar actions and effects can be obtained. Further, the balance plates 26 and 38 and the intake pipe 33 may be provided in a pump using a so-called double trumpet pipe in which a bell mouth having a small diameter is arranged inside the suction bell mouth 16.

DESCRIPTION OF SYMBOLS 1 ... Installation floor 3 ... Suction water tank 10 ... Vertical shaft pump 11 ... Casing 12 ... Suction port 13 ... Discharge pipe 18 ... Rotating shaft 19 ... Impeller 20 ... Bearing (thrust bearing)
21A, 21B ... Underwater bearings (radial bearings)
23 ... Bearing casing 26 ... Balance plate 27 ... Back pressure chamber 28 ... Drainage part 32 ... Orifice (throttle)
33 ... Intake pipe 33a ... One end 33b ... The other end 36 ... Penetration part 37 ... Shaft seal device 38 ... Balance plate 39 ... Back pressure chamber 40 ... Drainage part

Claims (6)

A suction port for sucking water in the suction water tank is formed on one end side, and a casing having a discharge pipe connected to the other end side,
A rotary shaft disposed in the casing and connected to an impeller for sucking water from the suction port;
A bearing that rotatably supports the rotating shaft;
A balance plate fixed to the rotating shaft so as to be located downstream of the impeller in the direction of drainage,
In the casing, a bearing casing is disposed so as to be adjacent to the downstream side in the drain direction of the impeller ,
The balance plate is disposed on the impeller side of the bearing casing ;
A back pressure chamber is provided in a portion of the bearing casing facing the balance plate,
The back pressure chamber has a connection pipe erected between the bearing casing and the casing, and a drainage portion for draining water in the back pressure chamber to the outside of the casing is communicated. pump.   The pump according to claim 1, wherein the balance plate is disposed upstream of a radial bearing that supports the impeller rotatably. The casing includes a penetrating part that projects a part of the rotating shaft outward, and a shaft seal device disposed in the penetrating part,
The pump according to claim 1, wherein a second balance plate different from the balance plate is disposed on the impeller side of the shaft seal device. The pump according to any one of claims 1 to 3, wherein the drainage part is provided with a throttle capable of adjusting a drainage amount. Is upstream in the one end opening of the impeller in the casing, according to claim 1 to claim 4 is the other end, characterized in that it comprises an intake pipe which is open to the set water vortex generator prediction water level in the suction water tank The pump according to any one of the above. 6. The pump according to claim 5 , wherein an opening area of the intake pipe on the casing side is 5% or less of a portion having the smallest opening area of the casing located on the upstream side of the impeller.

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