JPS6029838B2 - Multistage centrifugal pump for liquefied gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Tafumien 0 pump that pumps liquefied gas such as liquefied natural gas or liquefied petroleum gas.

In the prior art, the liquefied gas that has balanced the thrust and flowed through the gap in the mechanism is guided to a ball bearing that supports the main shaft for cooling and lubrication. This gap changes during operation due to thrust balancing, so that it cannot be guaranteed that the ball bearings are reliably supplied with the required amount of liquefied gas. As a result, the kinematic viscosity is extremely low, about 4.0 mm, and the ball bearings tend to be lubricated insufficiently by the liquefied gas. Prior art for reliably achieving ball bearing lubrication includes, for example, Utility Model Publication No. 43-1459.
As shown in Fig. 1, a part of the pump output pressure is guided to ball bearings arranged on both sides of the motor that drives the impeller in the axial direction.

In this prior art, the liquefied gas that has passed through one of the bearings is discharged to the outside from the other ball bearing through a rotor chamber that houses the rotor of the motor. Therefore, the pressure loss of the liquefied gas for lubrication increases, and there is a possibility that lubrication may not be achieved reliably. An object of the present invention is to provide a multi-stage centrifugal pump for liquefied gas that can reliably cool and lubricate ball bearings with liquefied gas.

In conventional water pumps, even if air is trapped in the pump chamber that houses the impeller at the beginning of operation, the amount of air is generally small and does not cause any major problems; at room temperature, gas does not enter the pump chamber. It never accumulates in large quantities. However, when attempting to pump liquefied natural gas using such a pump, the liquefied natural gas vaporizes and fills the pump chamber, making operation impossible.
Another object of the present invention is to provide a multistage centrifugal pump for liquefied gas whose operation is not affected by vaporized liquefied gas. Single-suction centrifugal pumps that pump water in a pot also have the problem that thrust force from the impeller acts on the rotationally driven shaft, shortening the life of the bearing that supports the shaft. Still another object of the present invention is to provide a multistage centrifugal pump for liquefied gas in which an unnecessarily large thrust force is not applied.

It is also desired that such a pump for pumping liquefied gas be easy to maintain and maintain safe operation.

Another object of the invention is to provide an improved multi-stage centrifugal pump for liquefied gases that is easy to maintain.

In the present invention, an upward flow section 2, a downward flow section 3, and a motor casing 29 are arranged in order from the bottom to the top in a space 42 of a bottomed cylindrical barrel casing 1 that is open downward into which liquefied gas is introduced.
The motor 4 housed in the pump chamber 39 of An impeller 15 is provided, these impellers 11 and 15 are fixed to a single main shaft 20, and this main shaft 20 is driven by a motor 4. The outlet 23 of the countercurrent section 2 is connected to the conduit 24
is connected to the inlet 25 of the downward flow section 3, and the inlet 25
The upper wall surface 40 is formed to be inclined upward along the radial direction outward of the main shaft 20, and the valve body 43 of the gas vent valve 41 is fixed near the inlet 25 of the downward flow section 3. The lower part of the formed valve chamber 46 that extends vertically is passed through the inlet 25 of the downward flow section 3 at the upper wall surface 40, and the seating surface 50' formed in the lower part of the valve chamber 46 extends vertically within the valve chamber 46. The lower end surface 5 of the valve body 45 which is displaceable and has a roughly right circular column shape.
8 is seated, and a recess 51 extending from the seating surface 50 along the axis of the valve body 43 and facing the valve seat 46 is formed.
5 is constructed by forming large and light parts and small diameter parts alternately in the axial direction, and a valve seat 49 facing downward and a space 42 in the barrel casing are provided at the upper part of the valve chamber 46 of the valve body 43. A continuous gas vent hole 48 is formed, and one end of each of the motor 4 side of the pair of ball bearings 21 and 53 located on both sides of the motor 4 in the track line direction faces the motor chamber 39 in the motor casing 29. A portion of the liquefied gas from the first-stage diffuser chamber 33 of the upward flow section 2 is transferred from the conduit 34 to the motor 4 of each ball bearing 21, 53.
The pump chamber 39 is passed through the space 42 of the barrel casing 1, and the liquefied gas supplied to the chambers 59, 6 is supplied to the chambers 59, 6 facing the other end facing away from the pump chamber 39. through the space 42 of the barrel casing 1
There is a gas vent port 5 at the top of the barrel casing.
6 and fixed to the main shaft 20', the balance body 36 has a cylindrical shape, protrudes radially outward from the main shaft 20, and has both ends 36a and 36b connected to the inlet 25 of the downward flow section 3.
and a space 37 that fits into the room 59 for the ball bearing 21 on the downward flow section 3 side, respectively, and the balance body 36 has a room 59 and a space 37 for the ball bearing 21 on the downward flow section 3 side.
The force due to the liquefied gas at the inlet 25 of the downward flow section 3 acts larger than the force due to the liquefied gas within the upward flow section 2.
A plurality of volute casings 12 surrounding each impeller 11 and forming a diffuser chamber 33 are connected between the suction cover and the stage casing 10 by fixing bolts 13, and the stage casing 10 and the connecting member are connected to each other in the downward flow section 3. 14, a plurality of volute casings 16 surrounding each impeller 15 to form a diffuser chamber are connected by fixing bolts 17, and a motor casing 29 is connected to the connecting member 14 by bolts. A motor casing cover is connected to the motor casing cover by bolts, and a barrel cover 31 is connected to the motor casing cover by bolts.
1 is connected to the upper end of the barrel casing by a bolt to close the upper end of the barrel casing 1, and the stage casing 10 is formed with an outlet 23 of the upward flow section 2 and an outlet 26 of the downward flow section 3. is formed, and the connecting member 14
The inlet 25 of the downward flow section 3 is formed, and the space 37 is formed to accommodate the chamber 59 for the ball bearing 21 on the side of the downward flow section 3, and the outlet 26 of the downward flow section 3 is also formed. A flow section 28 is formed in which the pipe line 27 connected to the connecting member 14 passes through, and a flow section 30 is formed in the motor casing 29 to pass through the flow section 28 of the connecting member 14. A flow part communicating with the flow part 30' formed in the motor casing 29 is formed, and a discharge port 6 is formed in the barrel cover 31 to fit into the flow part formed in the motor casing cover 1. A gas vent port 56 is formed to fit into the space 42 inside the barrel casing, and a gas vent port 56 is formed in the lower part of the motor casing 29, and a gas vent port 56 is formed in the lower part of the motor casing 29 and is connected to a chamber 59 facing the other end of the ball bearing on the side of the downward flow section 3. A flow section 3 connected to a conduit 34 that leads the liquefied gas from the chamber 33
5 is formed, and another one is inside the motor casing cover.
A pipe line 5 branched from a pipe line 34 that passes through the chamber 60 facing the pond end of the upper ball bearing 53 and guides the liquefied gas.
This multi-stage centrifugal pump for liquefied gas is characterized in that a flow section 55 connected to the pump 4 is formed.

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention. This embodiment can be advantageously used for pumping liquefied natural gas in boiling state. In this submerged pump, basically, an upper same flow section 2, a lower flow section 3, and a motor 4 are arranged in order from bottom to top inside a bottomed cylindrical barrel casing that is open upward. . The liquefied gas introduced from the suction port 5 of the barrel casing 1 flows into an upward flow section 2 and a downward flow section 3.
The pressure is increased at the pump and discharged from the discharge port 6. moyu 4
Electric power is supplied to the lead wire 8 in the lead wire connection tube 7. In the upward flow section 2, the suction cover 9 and the stay
For example, five stages of impellers 11 are provided between the two casings 10 .

This impeller 11 is connected to a ring-shaped volute casing 12 surrounding it with fixing bolts 13 . In the downward flow section 3, five stages of impellers 15 are similarly provided within the stage casing 10.

A ring-shaped porlute casing 16 is connected to the impeller 15 with fixing bolts 17 surrounding it. In the upward flow section 2 and the downward flow section 3, guide vanes 18, 19 are provided at the exits of each impeller 11, 15. As a result, impeller 1
The flow at the outlets 1 and 15 is decelerated to convert velocity energy into pressure energy. The impellers 11 and 15 are connected to a single main shaft 2
01 is fixed. The main shaft 2 is connected to the output shaft 52 of the motor 4 by a joint 32 . This output shaft 52
is supported by ball bearings 21 and 53. impeller 11,
15 are arranged in the opposite direction to the koji direction (vertical direction in FIG. 1) of the main shaft 20. Upward flow section 2 in suction cover 9
The liquefied gas sucked in from the inlet 22 facing downward is pressurized in the upper flow section 2, and passes from the outlet 23 of the upward flow section 2 in the stage casing 10 through the pipe line 24 to the downward flow section 3 in the connecting member 14. is led to the entrance 25 of Entrance 2
The liquefied gas from the stage casing 5 is pressurized as it passes through the impeller 15 in the downward direction in FIG.
Outlet 26 of the downward flow section 3 in the stage casing 10
The liquefied gas from the pipe 27 passes through the flow section 2 of the connecting member
8, and through the flow section 30 in the motor casing 29,
It is discharged from the discharge port 6 formed in the barrel cover 31. Impellers 11, 1 in the upward flow section 2 and the downward flow section 3
5 are equal to 5, and are provided on the main shaft 20 in opposite directions to the direction of the arrow, so that the downward thrust force acting on the main shaft 20' in the upward flow section 2 and the downward thrust force in the downward flow section 3 are reduced. The upward thrust force acting on the main shaft 20 is balanced and canceled out.

In order to cool and lubricate the ball bearing 21, a relatively low pressure is supplied from the first stage diffuser chamber 33 of the upward flow section 2 to the chamber 59 from the flow section 35 formed in the motor casing 29 via the pipe line 34. of liquefied natural gas will be supplied.

By supplying relatively low-pressure liquid to the ball bearing 21 in this manner, the power loss of the pump is reduced. Similarly, the ball bearing 53 is connected to the conduit 54 branched from the conduit 34 through a flow path 55 in the motor casing cover that closes the upper end of the motor casing 29, and is formed by a downward recess in the motor casing cover. Liquefied natural gas is supplied to the room 60. The end of the ball bearing 21 on the side away from the motor 4 (lower side in FIG. 1) faces the room 59. Further, the end of the ball bearing 53 on the side away from the motor 4 (upper part in FIG. 1) faces the room 60. Ball bearing 21,5
The liquefied gas that cooled and lubricated the motor casing 29
The motor enters the motor chamber 39 and cools the motor 4. The motor chamber 39 is connected to the barrel casing space 42 via a vent valve 57a from the passage 58. A gas vent port 56 formed in the barrel cover 31 is delivered to the space 42 . In the motor chamber 39, the liquefied natural gas is vaporized by the heat of the motor 4, the motor 4 is cooled, and the vaporized gas flows into the space 42 of the barrel casing 1 via the aforementioned gas vent valve 57a.

The mode chamber 39 includes the first stage diffuser chamber 3 as mentioned above.
3 is supplied with liquefied natural gas, so that the pressure in this motor chamber 39 is higher than the pressure in the barrel casing space. Therefore, the liquefied natural gas and vaporized gas in the motor chamber 39 reach the inside of the barrel casing via the gas vent valve 57a as described above. The vaporized gas is exhausted from the gas vent port 56. A balance body 36 is fixed to the two main shafts.

One end 36a of this balance body 36 faces the inlet 25 of the downward flow section 3. The other end portion 36b of the balance body 36 faces a space 37 in the motor casing 29 that fits into a chamber 59 for the ball bearing 21 on the downward flow section 3 side. The balance body 36 has a pressure receiving surface at one end 36 a facing the inlet 25 of the downward flow section 3 and a pressure receiving surface at the other end 36 b facing the space 37 . Part of the liquefied natural gas is supplied to the chamber 59 from the flow section 35, and the pressure is maintained in the chamber 59 and the space 37, so that the liquefied natural gas is prevented from vaporizing. This allows stable cooling and lubrication of the ball bearing 21. The balance body 36 contacts a bush 38 provided on the motor casing 29. The space 37 is connected to the motor chamber 39 via the ball bearing 21. balance body 36
When one end portion 36a receives a large upward force from the liquefied gas at the inlet 25 of the downward flow section 3, an upward force acts on the main shaft 20', and this causes the rotor of the motor 4, the main shaft 20, and the impeller to 11 and 15 is supported, and the thrust force acting on the ball bearing 21 is reduced. The upper wall surface 40 of the inlet 25 of the downward flow section 3 is formed to be inclined upward along the radial direction outward of the main shaft 20 .

Near this inlet 25, a gas vent valve 41 is provided along the upper wall surface 40. FIG. 2 is a longitudinal sectional view of the gas vent valve 41, and FIG. 3 is a sectional view taken along the section line mm in FIG.

A valve body 43 of the gas vent valve 41 is connected to the pipe line 2 by a screw 44 near the inlet 25 of the downward flow section 3 . A valve chamber 46 extending vertically is formed within the valve body 43, and a valve body 45 is accommodated within the valve chamber 46. The upper end 47 of the valve body 45 is raised upward, and this upper end 47 is connected to the valve body 4.
It is guided to a gas vent hole 48 formed in the upper part of the valve chamber 46 of No. 3. This gas vent hole 48 communicates with the space 42 inside the barrel casing 1 and the valve chamber 46 . A valve seat 49 facing downward is also formed above the valve chamber 46 of the valve body 43. The upper end portion 47 of the valve body 45 is tapered upward. When the pressure of the liquefied gas near the inlet 25 of the downward flow section 3 is higher than the pressure of the liquefied gas in the space 42 of the barrel casing, the valve body 45 is displaced upward and the upper end surface 57 of the valve body 45 is brought into contact with the valve seat. 49 and the valve is closed.

A seating surface 50 is formed in the lower part of the valve chamber 46 . The lower end surface 58 of the valve body 45 is seated on this seating surface 50'. The valve body 45 is vertically displaceable within the valve chamber 46 and is formed roughly in the shape of a right cylinder. The valve body 45 is configured such that large strain portions and small strain portions are alternately formed in the axial direction. A recess 51 is formed in the valve body 43 and extends from the seating surface 50 in the axial direction of the valve body 43 and faces the valve chamber 46 . The gas that is vaporized from the liquefied gas near the inlet 25 of the downward flow section 3 passes through the recess 51 from the gas vent hole 48 to the barrel casing with the lower end surface 58 of the valve body 45 seated on the seating surface 5. Escape into the space 42 is allowed.

The vent valve 41 has the function of closing only when the pressure in the inlet 25 is higher than the space 42 in the barrel casing 1 and opening when the pressure in the inlet 25 is equal to or lower than the pressure in the space 42.

The function of the gas vent valve 41 can also be considered as follows. When the vicinity of the inlet 25 is filled with liquefied gas, this liquefied gas collides with the lower end surface 58 of the valve body 45. Although the valve body 45 is not pushed upward even when the gas collides with the lower end surface 58, the liquefied gas has a much higher specific gravity than the gas, so the liquefied gas collides with the lower end surface 58 of the valve body 45. The valve body 45 is pushed up. In this way, the liquefied gas at the inlet 25 brings the valve into a closed state. The valve body 45 has a generally right cylindrical shape, and is composed of large-diameter portions and small-diameter portions alternately formed in the axial direction (vertical direction in FIG. 2). Therefore, dirt and the like are likely to enter the gap between the inner circumferential surface of the valve chamber 46 and the small diameter portion of the valve body 45. This prevents dust from getting caught between the large portion of the valve body 45 and the inner peripheral surface of the valve chamber 46, thereby preventing the valve body 45 from moving. Therefore, the valve body 4
The vertical movement of 5 is performed smoothly. Further, the function of the small recessed portion of the valve body 45 allows the radially inward force of the valve body 45 to be applied almost uniformly over the entire circumference.
This is because the gap between the outer circumferential surface of the large concave portion of the valve body 45 and the inner circumferential surface of the valve chamber 46 is formed to be 4 mm in order to guide the valve body 45 coaxially with the valve chamber 46 . If the valve body 45 is in the shape of a right cylinder, and the gap between its outer peripheral surface and the inner peripheral surface of the valve chamber 46 is extremely small and uneven on the outer peripheral surface of the valve body 45,
The force exerted by the gas or liquefied gas flowing into the recess 51 differs in all directions around the valve body 45. Therefore, the valve body 4
5 is pressed against a portion of the inner circumferential surface of the valve chamber 46, which makes it difficult for the valve body 45 to move up and down smoothly. In the present invention, since the small diameter portion is formed, the force of the gas or liquefied gas acting on the valve body 45 is substantially uniform in the circumferential direction. Therefore, the valve body 45 can be smoothly moved up and down. During the initial operation of the present pump, liquefied gas in a boiling liquid state is introduced from the suction port 5 to fill the space 42, and the motor 4 rotates the main shaft 20 and hence the impellers 11 and 15.

The liquefied gas in the space 42 is sucked into the upward flow section 2 through the inlet 22 and reaches the downward flow section 3 through the pipe 24 . At this time, the gas filled in advance in the downward flow section 3 and the liquefied gas are vaporized along the inner wall surface 4 of the inlet 25.
It's within. When gas is present near the inlet 25, the valve body 45 of the gas vent valve 41 is seated on the seating surface 50' due to its own weight. The inlet 25 of the high-pressure section 3 therefore communicates with the space 42 via the vent valve 41 . Therefore, the gas in the high pressure section 3 is discharged from the gas vent port 56 via the gas vent valve 41 and the space 42 . In this way, cavitation is prevented, and the ball bearings 21 and 53 are prevented from being damaged or having a shortened lifespan due to the large thrust force generated by the impeller 11 of the upflow section 2. As described above, according to the present invention, a portion of the liquefied gas from the diffuser chamber 33 is transferred to the pair of ball bearings 21 and 53 disposed on both sides of the motor 4 in the inguinal direction. ,6
0 and then into a pump chamber 39, which fits into the space 42 of the barrel casing 1.

Therefore, the liquefied gas for lubricating the ball bearings 21 and 53 can be smoothly supplied without causing a large pressure loss, thereby reliably achieving lubrication of the ball bearings and also cooling them. be able to. Furthermore, in the present invention, the number of the plurality of impellers 11 provided in the upflow section 2 and the downflow section 3 is equal, so that the downward thrust force acting on the main shaft 2 in the upflow section 2 and the downward thrust force In the countercurrent section 3, the upward thrust forces acting on the two main shafts are balanced and canceled out.

Both ends 36a, 36 of the balance body fixed to the two main shafts
b faces the inlet 25 and the space 37 of the downward flow section 3, and the space 37 communicates with a room 59 for the ball bearing 21 on the downward flow section 3 side.

This room 59 includes the first stage diffuser room 3 of the upward flow section 2.
A portion of the liquefied gas from 3 is supplied at relatively low pressure. The balance body 36 and therefore the main shaft 20 are therefore subjected to a large upward force at the inlet 25. Therefore, the weight of the rotor, main shaft 20, impellers 11, 15, etc. of the motor 4 is supported, and the thrust force acting on the ball bearings 21, 53 is reduced. The gas vent valve 41 is formed at the inlet 25 of the downward flow section 3.

The upper wall surface 4 is provided along the main axis 2.
It is inclined upward along the radial direction outward of 0. Therefore, the gas near the inlet 25 can be reliably released from the gas vent valve 41 along the four sides of the upper wall surface. In order to cool and lubricate the ball bearings 21 and 53, a portion of the liquefied gas from the first stage diffuser chamber 33 of the upward flow section 2 is transferred to the chamber 5.
The liquefied natural gas in the chambers 59, 60 passes through the ball bearings 21, 53, enters the motor chamber 39, and is discharged into the space 42 of the barrel casing.

As a result, cooling and lubrication of the ball bearings 21 and 53 are reliably achieved, and power loss of the pump is reduced by supplying such relatively low pressure liquefied gas to the ball bearings 21 and 53. Liquefied gas is pumped into the chamber 59 for the ball bearing 21 on the downward flow section 3 side, so that the pressure in the chamber 59 and the space 37 does not drop.

Therefore, the liquefied gas will not be vaporized within the room 59 and the space 37. The force of the liquefied gas in the room 59 and the space 37 acts stably on the balance body 36, and a constant upward force always acts on the balance body 36, thereby stabilizing the operation. Furthermore, since the liquefied gas does not vaporize in the chamber 59 and the space 37, the ball bearing 21 can be cooled and lubricated stably. The valve body 45 has large-diameter portions and small-diameter portions alternately formed in the wirth line direction, so that the radially inward force due to the gas and liquefied gas acting on the outer peripheral surface of the valve body 45 is almost uniform in the circumferential direction. becomes.

Therefore, the valve body 45 can be stably moved up and down. Furthermore, dust that may be present between the inner circumferential surface of the valve chamber 46 and the valve body 45 enters the small diameter portion, thus ensuring smooth movement of the valve body 45. Upward flow section 2
, a plurality of volute casings 12 surrounding each impeller 11 and forming a diffuser chamber 33 are connected between the suction cover and the stage casing 10 by fixing bolts 13, and are connected to the stage casing 10 in the downward flow section 3. A plurality of volute casings 16 surrounding each impeller 15 to form a diffuser chamber are connected to the member 14 by fixing bolts 17.
A motor casing 29 is connected to the top by bolts, and a motor casing cover is placed on the motor casing 29.
are connected by bolts, a barrel cover 31 is connected to the motor casing cover 1 by bolts, and the barrel cover 31 is connected to the upper end of the barrel casing by bolts to close the upper end of the barrel casing 1, and the stage casing 1 is connected to the motor casing cover 1 by bolts. In the river, an outlet 23 of the upward flow section 2 and an outlet 26 of the downward flow section 3 are formed, and an inlet 25 of the downward flow section 3 is formed in the connecting member 14, and an outlet 26 of the downward flow section 3 is formed. It forms the space 37 that fits into the chamber 59 for the ball bearing 21 on the side of the counterflow section 3, and further forms the flow section 28 through which the conduit 27 connected to the outlet 26 of the downward flow section 3 is carried. A flow section 30 that communicates with the flow section 28 of the connecting member 14 is formed in the motor casing 29, and a flow section 30 formed in the motor caning 29 is formed in the motor casing cover. The barrel cover 31 is formed with a discharge port 6 that communicates with a flow part formed in the motor casing cover 1.
A gas vent port 56 is formed that communicates with the inner space 42,
At the lower part of the motor casing 29, there is also a flow section 35 which is connected to a pipe machine 34 which communicates with the chamber 59 facing the pond end of the ball bearing on the side of the downward flow section 3 and which guides the liquefied gas from the first stage diffuser chamber 33. is formed in the motor casing cover, and a chamber 6 facing the pond end of the other upper ball bearing 53 is connected to a pipe line 54 branched from the pipe line 34 for guiding the liquefied gas. Since the flow section 55 is formed, piping work for the flow section can be largely omitted, and it can be disassembled, making maintenance extremely easy.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of the gas vent valve 41 in FIG. It is a diagram. 1... Barrel casing, 2... Upward flow section, 3... Downward flow section, 4... Motor, 11, 15... ... Impeller, 20... Main shaft, 21, 53... Ball bearing, 22, 25... Inlet,
23, 26... Outlet, 24, 27, 34... Piping, 41... Gas vent valve. Figure 3 Figure 1 Figure 2

Claims (1)

[Claims] 1 Inside the space 42 of the bottomed cylindrical barrel casing 1 that is open upward into which liquefied gas is introduced, from bottom to top, an upward flow section 2, a downward flow section 3, and a pump chamber of the motor casing 29 are installed. 39 and the motor 4 housed in the upper flow section 2.
is provided with a plurality of stages of impellers 11, and the downward flow section 3 is provided with the same multi-stage impeller 15 as the upward flow section 2, and these impellers 11 and 15 are connected to a single main shaft 20. This main shaft 2
0 is driven by a motor 4, the inlet 22 of the upward flow section 2 faces downward, and the outlet 23 of the upward flow section 2 is connected to the inlet 25 of the downward flow section 3 through a conduit 24. , the upper wall surface 40 of the inlet 25 is formed to be inclined upward along the radial direction outward of the main shaft 20, and the valve body 43 of the degassing valve 41 is formed in the downward flow section 3.
The lower part of the valve chamber 46 extending vertically formed in the valve body 43 is connected to the inlet 25 of the downward flow section 3 on the upper wall surface 40, and the seat formed in the lower part of the valve chamber 46 is fixed near the inlet 25 of the valve chamber 46. The lower end surface 58 of the valve body 45, which is vertically displaceable within the valve chamber 46 and has a generally right circular column shape, is seated on the surface 50, and the valve body 45 extends from the seating surface 50 along the axis of the valve body 43. A recess 51 facing the chamber 46 is formed, and the valve body 45 is configured by forming large diameter portions and small diameter portions alternately in the axial direction. Facing valve seat 4
9 and a gas vent hole 48 connected to the space 42 in the barrel casing 1, and each one end on the motor 4 side of a pair of ball bearings 21, 53 located on both sides in the axial direction of the motor 4,
Each other end of each ball bearing 21, 53 faces the motor chamber 39 in the motor casing 29, and a portion of the liquefied gas from the first-stage differential user chamber 33 of the upward flow section 2 is directed away from the motor 4 from the conduit 34. The pump chamber 39 is communicated with the space 42 of the barrel casing 1, and the liquefied gas supplied to the chambers 59, 60 passes through the pump chamber 39 to the space 42 of the barrel casing 1. Flow into the
A gas vent port 56 is formed in the upper part of the barrel casing 1, and the balance body 36 fixed to the main shaft 20 has a cylindrical shape, projects radially outward from the main shaft 20, and has both ends 36a and 36b facing downward. The space 37 communicating with the inlet 25 of the flow section 3 and the chamber 59 for the ball bearing 21 on the downward flow section 3 side are respectively faced, and the balance body 36 has a space 37 for the ball bearing 21 on the downward flow section 3 side. The force of the liquefied gas at the inlet 25 of the downward flow section 3 acts more strongly than the force of the liquefied gas in the room 59 and the space 37, and in the upward flow section 2, each blade is placed between the suction cover and the stage casing 10. A plurality of volute casings 12 surrounding the car 11 and forming a differential user chamber 33 are connected by fixing bolts 13, and each impeller 15 is connected between the stage casing 10 and the connecting member 14 in the downward flow section 3. A plurality of volute casings 16 surrounding the fixing bolt 1 form a differential user chamber.
7, a motor casing 29 is connected to the connecting member 14 by bolts, a motor casing cover is connected to the motor casing 29 by bolts, and a barrel cover 31 is connected to the motor casing cover by bolts. are connected by bolts, and the barrel cover 3
1 is connected to the upper end of the barrel casing 1 with a bolt to close the upper end of the barrel casing 1, and the stage casing 10 has an outlet 23 for the upward flow section 2 and an outlet 23 for the downward flow section 3. an outlet 26 is formed in the connecting member 14, an inlet 25 of the downward flow section 3 is formed, and the space 37 communicating with the chamber 59 for the downward flow section 3 side ball bearing 21 is formed; Furthermore, a flow section 28 is formed in which a pipe line 27 connected to the outlet 26 of the downward flow section 3 is communicated,
A flow portion 30 communicating with the flow portion 28 of the connecting member 14 is formed in the motor casing 29, a flow portion communicating with the flow portion 30 formed in the motor casing 29 is formed in the motor casing cover, The barrel cover 31 is formed with a discharge port 6 that communicates with a flow section formed in the motor casing cover, and the barrel cover 31 is formed with a discharge port 6 that communicates with a flow section formed in the motor casing cover.
A gas vent port 56 communicating with the inner space 42 is formed,
The lower part of the motor casing 29 is also provided with a flow section that communicates with the chamber 59 facing the other end of the ball bearing on the downward flow section 3 side and is connected to the pipe line 34 that guides the liquefied gas from the first-stage differential user chamber 33. 35 is formed in the motor casing cover, and is connected to a conduit 54 branched from the conduit 34 that communicates with the chamber 60 facing the other end of the other upper ball bearing 53 and guides the liquefied gas. A multistage centrifugal pump for liquefied gas, characterized in that a flow section 55 is formed.