A combined low-cavitation multistage centrifugal pump

Abstract

A combined low-cavitation multistage centrifugal pump is a multistage centrifugal pump suitable for transporting clean liquids without solid particles. More specifically, it relates to a centrifugal pump combination in which the first-stage impeller is arranged vertically and the remaining secondary impellers are arranged horizontally, providing a new structural product to achieve the performance of a low-cavitation pump and effectively reduce the total number of impeller stages. The present invention includes a vertical pump body and a horizontal pump body, and is characterized in that: the liquid outlet of the vertical pump body is connected to the input port of the horizontal pump body through a connecting pipeline.

Description

Technical Field

[0001] The present invention is applicable to a multistage centrifugal pump whose conveying medium is a clean liquid without solid particles. More specifically, it relates to a combination of centrifugal pumps with the first-stage impeller arranged vertically and the remaining secondary impellers arranged horizontally, providing a new structural product, achieving low-cavitation pump performance, and effectively reducing the total number of impeller stages. Background Art

[0002] As a general-purpose machine, centrifugal pumps are widely used in various fields of the national economy such as electric power, petroleum, and chemical industry. In the condenser system of a thermal (fossil-fuel) power generation unit for conveying condensate, and in some devices in the petrochemical field, due to limited installation space, the operating conditions of the pump are extremely demanding. Since the pump inlet is in a vacuum (negative pressure) state or an approximate saturated steam pressure condition, the pump is required to have good cavitation resistance and output a high head according to the operating conditions.

[0003] In order to increase the net positive suction head (NPSH) of the device and correspondingly reduce the NPSH of the pump, setting the first-stage impeller in a pump pit with a low position is usually the most direct and effective method. The pump is designed with a vertical structure. Traditional vertical pump bodies are mainly barrel-bag structures. The first-stage impeller and other parts such as the remaining secondary impellers are successively connected in series on the same shaft to form a rotor component. Then it is inserted into the pump barrel as a whole. When a high head is required, it is achieved by increasing the number of impeller stages. The rated speed of the pump is generally designed at the 1480 r / min level and is driven by a four-pole motor. Due to the lack of actual effective radial support in the pump barrel, when the number of impeller stages is too large, it is easy to generate the fault of excessive vibration. The designed speed at the 1480 r / min level reduces the working efficiency to a certain extent.

[0004] In addition, the shaft end seal of the vertical pump body is located at the upper end of the rotor component. During the first commissioning operation, the pumped medium cannot enter the seal cavity for flushing and cooling, which is likely to cause damage to the static and dynamic rings of the seal due to dry friction. Before starting, it is necessary to introduce an external flushing medium. When the pump is running normally, the body medium can be used for flushing and cooling, and then the external flushing medium can be appropriately closed according to actual requirements. The traditional flushing scheme needs to be switched multiple times in coordination with the start and stop of the pump, increasing the on-site pipeline layout and to a certain extent increasing the engineering costs such as manpower and material resources. Introducing external media from other devices, there are potential leakage points in the pipeline. Summary of the Invention

[0005] The present invention aims at the above problems and provides a combined low-cavitation multistage centrifugal pump that can reduce the total number of pump stages and improve the working efficiency.

[0006] To achieve the above object of the present invention, the present invention adopts the following technical solution. The present invention includes a vertical pump body and a horizontal pump body, and is characterized in that: the liquid outlet of the vertical pump body is connected to the input port of the horizontal pump body through a connecting pipeline.

[0007] As a preferred embodiment of the present invention, the present invention further includes a lubrication system, the lubrication system includes a pressure liquid storage tank, and a pressure airbag is arranged in the pressure liquid storage tank; a flushing outlet pipe and a flushing inlet pipe are arranged on the pressure liquid storage tank, and the flushing inlet pipe and the flushing outlet pipe are connected to the mechanical seal structures of the vertical pump body and the horizontal pump body; the pressure liquid storage tank is connected to a connecting pipeline, and a check valve is arranged between the pressure liquid storage tank and the connecting pipeline, and the check valve can prevent the liquid in the pressure liquid storage tank from flowing into the connecting pipeline.

[0008] As another preferred embodiment of the present invention, the vertical pump body includes a pump barrel, a discharge seat with a liquid inlet and a liquid outlet is arranged at the upper end of the pump barrel, the liquid inlet is communicated with the pump barrel, and the liquid outlet is connected to the connecting pipeline; a vertical motor is arranged at the upper end of the discharge seat through a motor bracket, a connecting pipe communicated with the liquid outlet is arranged at the lower end of the discharge seat, the vertical motor is connected to a vertical pump shaft in the connecting pipe, and a first-stage spiral casing and a first-stage impeller are arranged at the lower end of the vertical pump shaft; a mechanical seal mechanism is arranged at the upper end of the discharge seat at the position where the vertical pump shaft passes through the discharge seat.

[0009] Further, the output shaft of the vertical motor is connected to the vertical pump shaft through a rigid coupling.

[0010] Further, an intermediate guide bearing is arranged on the surface of the vertical pump shaft, and the outside of the intermediate guide bearing is connected to the connecting pipe through a fixing bracket.

[0011] Furthermore, a connecting flange is arranged at the position of the connecting pipe corresponding to the fixing bracket, and a connecting hub matching with the connecting flange is arranged outside the fixing bracket.

[0012] Furthermore, the connecting pipe is of a multi-section structure, the lower end of the upper section of the connecting pipe is fixedly integrated with the upper surface of the connecting flange, and the upper end of the lower section of the connecting pipe is fixedly integrated with the lower surface of the connecting hub.

[0013] Further, a degassing pipe is also arranged at the upper end of the discharge seat.

[0014] Further, the first-stage impeller is a double-suction impeller.

[0015] As the third preferred embodiment of the present invention, the horizontal pump body includes a pump body, a horizontal pump shaft is arranged in the pump body, the horizontal pump shaft extends out from both ends of the pump body and is connected to a support bearing, and mechanical seal structures of the horizontal pump shaft are arranged on both sides of the pump body; a secondary impeller is arranged on the horizontal pump shaft in the pump body, an input port and an output port connected to the connecting pipeline are arranged on the upper surface of the pump body, and one end of the horizontal pump shaft is connected to a horizontal motor.

[0016] Further, the output shaft of the horizontal motor is connected to the horizontal pump shaft through an elastic coupling.

[0017] Advantages of the present invention: 1. Since the primary impeller of the present invention is vertically arranged and adopts a double-suction structure, the insertion depth can be adjusted according to the actual working conditions, theoretically ensuring that the pump can meet the required net positive suction head (NPSH) of any engineering device.

[0018] 2. The number of intermediate guide bearings of the present invention can be flexibly increased according to the insertion depth of the primary impeller, fully ensuring the long-term stable operation of the primary impeller and the rotor components.

[0019] 3. The primary impeller and the secondary impeller of the present invention are designed to operate at two speeds simultaneously. According to the formula H1 / H2 =(n1 / n2 )^2, after adopting the combined structure, the total number of stages of the new pump is only 25% - 35% of that of the original single speed.

[0020] 4. The secondary impeller of the present invention adopts a high speed, the number of stages is greatly reduced, and the axial length of the corresponding horizontal pump body is greatly reduced, fully improving the operation stability of the horizontal pump body. The impeller running at high speed also has higher operating efficiency. The volume of the secondary horizontal pump body is greatly reduced, with light weight, effectively reducing costs.

[0021] 5. The rotor components of the vertical pump body and the horizontal pump body of the present invention can be separately overhauled, maintained or replaced, effectively reducing the engineering operation cost.

[0022] 6. The connection between the pressure liquid storage tank of the present invention and the sealing cavities of the two pumps is a closed-loop structure, and the flushing medium does not contact the outside world, fully ensuring the cleanliness and pollution-free of the flushing medium, extending the service life of the seal, and ensuring that the sealing cavity is filled with flushing and cooling medium whenever the pump set starts or stops. Description of the Drawings

[0023] Figure 1 is the structural schematic diagram of the present invention.

[0024] Figure 2 is the structural schematic diagram of the vertical pump body.

[0025] Figure 3 is the structural schematic diagram of the horizontal pump body.

[0026] Figure 4 is the structural schematic diagram of the existing vertical pump body.

[0027] In the attached drawings, 1 is a rigid coupling, 2 is an exhaust valve, 3 is a mechanical seal structure, 4 is a steam extraction pipe, 5 is a liquid inlet, 6 is a vertical pump body, 7 is a liquid outlet, 8 is a connecting pipeline, 9 is a check valve, 10 is a horizontal pump body, 11 is a horizontal motor, 12 is an elastic coupling, 13 is an input port, 14 is an output port, 15 is a flushing inlet pipe, 16 is a pressure airbag, 17 is a pressure liquid storage tank, 18 is a flushing outlet pipe, 19 is a vertical motor, 20 is a pump cylinder body, 21 is a first-stage impeller, 22 is a first-stage spiral casing, 23 is a vertical pump shaft, 24 is a connecting pipe, 25 is an intermediate guide bearing, 26 is a connecting hub, 27 is a connecting flange, 28 is a fixing frame, 29 is a motor frame, 30 is a support bearing, 31 is a horizontal pump shaft, and 32 is a second-stage impeller. Detailed implementation mode

[0028] The present invention includes a vertical pump body 6 and a horizontal pump body 10, and is characterized in that: the liquid outlet 7 of the vertical pump body 6 is connected to the input port 13 of the horizontal pump body 10 through a connecting pipeline 8.

[0029] As a preferred solution of the present invention, the present invention further includes a lubrication system. The lubrication system includes a pressure liquid storage tank 17, and a pressure airbag 16 is arranged inside the pressure liquid storage tank 17; a flushing outlet pipe 18 and a flushing inlet pipe 15 are arranged on the pressure liquid storage tank 17, and the flushing inlet pipe 15 and the flushing outlet pipe 18 are connected to the mechanical seal structure 3 of the vertical pump body 6 and the horizontal pump body 10; the pressure liquid storage tank 17 is connected to the connecting pipeline 8, and a check valve 9 is arranged between the pressure liquid storage tank 17 and the connecting pipeline 8, and the check valve 9 can prevent the liquid in the pressure liquid storage tank 17 from flowing into the connecting pipeline 8.

[0030] An exhaust valve 2 is arranged on the flushing outlet pipe 18.

[0031] The physical position of the lowest liquid level inside the pressure liquid storage tank 17 is higher than the sealing cavity of the mechanical seal structure 3 of the vertical pump body 6 and the horizontal pump body 10, which is beneficial to the medium entering the sealing cavity smoothly under the action of gravity and pressure.

[0032] Mechanical seal flushing inlet and outlet interfaces, liquid filling ports, bottom drainage ports, etc. are respectively arranged around the pressure liquid storage tank 17.

[0033] As another preferred solution of the present invention, the vertical pump body 6 includes a pump cylinder body 20. A discharge seat with a liquid inlet 5 and a liquid outlet 7 is arranged at the upper end of the pump cylinder body 20. The liquid inlet 5 is communicated with the pump cylinder body 20, and the liquid outlet 7 is connected to the connecting pipeline 8; a vertical motor 19 is arranged at the upper end of the discharge seat through a motor frame 29, a connecting pipe 24 communicated with the liquid outlet 7 is arranged at the lower end of the discharge seat, the vertical motor 19 is connected to a vertical pump shaft 23 inside the connecting pipe 24, and a first-stage spiral casing 22 and a first-stage impeller 21 are arranged at the lower end of the vertical pump shaft 23; a mechanical seal mechanism is arranged at the upper end of the discharge seat at the position where the vertical pump shaft 23 passes through the discharge seat.

[0034] Furthermore, the output shaft of the vertical motor 19 is connected to the vertical pump shaft 23 via a rigid coupling 1 .

[0035] Furthermore, an intermediate guide bearing 25 is disposed on the surface of the vertical pump shaft 23 , and the intermediate guide bearing 25 is externally connected to the connecting pipe 24 via a fixing frame 28 .

[0036] Furthermore, the connecting pipe 24 is provided with a connecting flange 27 at a position corresponding to the fixing frame 28 , and the fixing frame 28 is provided with a connecting hub 26 matched with the connecting flange 27 outside.

[0037] Furthermore, the pipe 24 is a multi-section structure, the lower end of the upper pipe 24 is fixed to the upper surface of the connecting flange 27 , and the upper end of the lower pipe 24 is fixed to the lower surface of the connecting hub 26 .

[0038] Furthermore, a degassing pipe 4 is also provided at the upper end of the discharge seat.

[0039] Furthermore, the first-stage impeller 21 is a double-suction impeller.

[0040] As a third preferred embodiment of the present invention, the horizontal pump body 10 includes a pump body, a horizontal pump shaft 31 is arranged in the pump body, the horizontal pump shaft 31 extends from both ends of the pump body and is connected to the support bearing 30, and a mechanical sealing structure 3 of the horizontal pump shaft 31 is arranged on both sides of the pump body; a secondary impeller 32 is arranged on the horizontal pump shaft 31 in the pump body, an input port 13 and an output port 14 connected to the connecting pipeline 8 are arranged on the upper surface of the pump body, and one end of the horizontal pump shaft 31 is connected to the horizontal motor 11.

[0041] Furthermore, the output shaft of the horizontal motor 11 is connected to the horizontal pump shaft 31 via an elastic coupling 12 .

[0042] The present invention adopts a combined structure, keeps the original first-stage impeller 21 in the same installation position, is installed on the vertical pump shaft 23, and is configured with a four-pole motor drive; the remaining secondary impellers 32 are arranged horizontally, installed on the horizontal pump shaft 31, and are configured with a two-pole motor drive.

[0043] The structure of the original vertical pump body 6 is simplified, and the first-stage impeller 21 adopts a double-suction structure to achieve automatic balancing of the axial force. The balance drum, balance sleeve and thrust bearing components of the original vertical multi-stage pump are eliminated. Since the weight of the rotor components is greatly reduced, the gravity of the rotor components of the new vertical pump body 6 is borne by the bearings of the vertical motor 19. The pump and the motor are locked and connected by a rigid coupling 1. At this time, the rotor components are light in weight and will not affect the service life of the motor bearings.

[0044] To improve the operating stability of the first-stage impeller 21, an intermediate guide bearing 25 is added to the connecting pipe 24 between the first-stage spiral casing 22 and the discharge seat. The support of the intermediate guide bearing 25 and the connecting pipe 24 adopt a hub structure. The number of the intermediate guide bearings 25 is determined by the insertion depth of the first-stage impeller 21. If the first-stage impeller 21 is inserted deeper, the number of the connecting pipes 24 and the intermediate guide bearings 25 will be increased accordingly, that is, the number of the connecting pipes 24 and the intermediate guide bearings 25 can be 2, 3 or even more.

[0045] A pressure liquid storage tank 17 is added between the outlet of the first-stage vertical pump body 6 and the inlet of the secondary horizontal pump body 10, which is used to provide flushing and cooling medium for the sealing cavities of the two pumps respectively. An elastic rubber airbag is arranged inside the pressure liquid storage tank 17, and pressure air is pre-injected through the air inlet. The rest inside the pressure liquid storage tank 17 is the flushing and cooling medium. Mechanical seal flushing inlet and outlet interfaces, liquid filling ports, bottom drainage ports, etc. are respectively arranged around the pressure liquid storage tank 17. The physical position of the lowest liquid level inside the pressure liquid storage tank 17 is higher than the sealing cavities of the vertical pump body 6 and the horizontal pump body 10, which is beneficial to the smooth entry of the medium into the sealing cavity under the action of gravity and pressure.

[0046] When the present invention is in use, the medium is pre-filled inside the pressure liquid storage tank 17, and then pressure air is injected into the pressure airbag 16 through the air inlet at the top of the pressure liquid storage tank 17, and its pressure is consistent with the rated head of the liquid outlet 7 of the vertical pump body 6.

[0047] Before the pump set starts, the valves of the flushing inlet pipes 15 of the mechanical seal structures 3 of the vertical pump body 6 and the horizontal pump body 10 are respectively opened first. The medium inside the pressure liquid storage tank 17 smoothly enters the sealing cavity of the mechanical seal structure 3 under the action of gravity and pressure air. In order to confirm that the sealing cavity is already filled with the medium, the exhaust valve 2 can be appropriately opened to discharge the air in the flushing pipe of the mechanical seal structure 3 until the medium flows out from here and then the exhaust valve 2 is closed.

[0048] According to the normal start-up procedure of the pump, the air inside the vertical pump body 6 is pumped out by the deaeration pipe 4, the vertical motor 19 is started, and the vertical pump body 6 starts. The pressure medium enters the horizontal pump body 10 from the outlet of the vertical pump body 6, and then the horizontal motor 11 is started, and the horizontal pump body 10 starts.

[0049] As the medium inside the pressure liquid storage tank 17 is gradually injected into the sealing cavity of the pump, the medium inside the pressure liquid storage tank 17 decreases, the space increases, the elastic rubber airbag expands, the internal air pressure decreases, and the pressure inside the pressure liquid storage tank 17 also decreases. At this time, the outlet pressure of the vertical pump body 6 is higher than that of the pressure liquid storage tank 17, and the medium automatically injects into the pressure liquid storage tank 17 through the check valve 9 until the pressure inside the pressure liquid storage tank 17 is consistent with the outlet pressure of the vertical pump body 6, realizing cyclic liquid replenishment.

[0050] It is understandable that the above specific description of the present invention is only for the purpose of illustrating the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced to achieve the same technical effects; as long as the usage requirements are met, they are all within the protection scope of the present invention.

Claims

1. A combined low-cavitation multistage centrifugal pump, comprising a vertical pump body (6) and a horizontal pump body (10), characterized in that: It also includes a lubrication system; the liquid outlet (7) of the vertical pump body (6) is connected to the input port (13) of the horizontal pump body (10) through a connecting pipeline (8); The lubrication system includes a pressure liquid storage tank (17), and a pressure airbag (16) is arranged inside the pressure liquid storage tank (17); a flushing outlet pipe (18) and a flushing inlet pipe (15) are arranged on the pressure liquid storage tank (17), and the flushing inlet pipe (15) and the flushing outlet pipe (18) are connected to the mechanical seal structure (3) of the vertical pump body (6) and the horizontal pump body (10); the pressure liquid storage tank (17) is connected to the connecting pipeline (8), and a check valve (9) is arranged between the pressure liquid storage tank (17) and the connecting pipeline (8), and the check valve (9) can prevent the liquid in the pressure liquid storage tank (17) from flowing into the connecting pipeline (8); The physical position of the lowest liquid level inside the pressure liquid storage tank (17) is higher than the sealing cavity of the mechanical seal structure (3) of the vertical pump body (6) and the horizontal pump body (10); The pressure liquid storage tank (17) is pre-filled with a medium inside, and then pressure air is injected into the pressure airbag (16) from the air inlet on the top of the pressure liquid storage tank (17), and its pressure is consistent with the rated head of the liquid outlet (7) of the vertical pump body (6); Before the pump group starts, first open the valves of the flushing inlet pipe (15) of the mechanical seal structures (3) of the vertical pump body (6) and the horizontal pump body (10) respectively; the medium inside the pressure liquid storage tank (17) smoothly enters the sealing cavity of the mechanical seal structure (3) under the action of gravity and pressure air; in order to confirm that the sealing cavity is already filled with the medium, open the exhaust valve (2) to discharge the air in the flushing pipe of the mechanical seal structure (3) until the medium flows out from here and then close the exhaust valve (2); According to the normal start-up procedure of the pump, the air inside the vertical pump body (6) is pumped out by the steam extraction pipe (4), the vertical motor (19) is started, and the vertical pump body (6) starts; The pressure medium enters the horizontal pump body (10) from the outlet of the vertical pump body (6), and then the horizontal motor (11) is started, and the horizontal pump body (10) starts; As the medium inside the pressure liquid storage tank (17) is gradually injected into the sealing cavity of the pump, the medium inside the pressure liquid storage tank (17) decreases, the space increases, the elastic rubber airbag expands, the internal air pressure decreases, and the pressure inside the pressure liquid storage tank (17) also decreases; at this time, the outlet pressure of the vertical pump body (6) is higher than that of the pressure liquid storage tank (17), and the medium automatically injects into the pressure liquid storage tank (17) through the check valve (9) until the pressure inside the pressure liquid storage tank (17) is consistent with the outlet pressure of the vertical pump body (6), realizing cyclic liquid supplement.

2. The combined low-cavitation multistage centrifugal pump according to claim 1, wherein: An exhaust valve (2) is arranged on the flushing outlet pipe (18).

3. The combined low-cavitation multistage centrifugal pump according to claim 1, characterized in that: The vertical pump body (6) includes a pump cylinder body (20). At the upper end of the pump cylinder body (20), a discharge seat having a liquid inlet (5) and a liquid outlet (7) is provided. The liquid inlet (5) communicates with the pump cylinder body (20), and the liquid outlet (7) is connected to the connecting pipeline (8). At the upper end of the discharge seat, a vertical motor (19) is provided through a motor bracket (29). At the lower end of the discharge seat, a connecting pipe (24) communicating with the liquid outlet (7) is provided. The vertical motor (19) is connected to a vertical pump shaft (23) inside the connecting pipe (24). At the lower end of the vertical pump shaft (23), a primary spiral casing (22) and a primary impeller (21) are provided. At the upper end of the discharge seat, at the position where the vertical pump shaft (23) passes through the discharge seat, a mechanical seal mechanism is provided.

4. The combined low-cavitation multistage centrifugal pump according to claim 3, wherein: An intermediate guide bearing (25) is provided on the surface of the vertical pump shaft (23), and the outside of the intermediate guide bearing (25) is connected to the connecting pipe (24) through a fixing bracket (28).

5. The combined low-cavitation multistage centrifugal pump according to claim 4, wherein: A connecting flange (27) is provided at the position of the connecting pipe (24) corresponding to the fixing bracket (28), and a connecting hub (26) cooperating with the connecting flange (27) is provided outside the fixing bracket (28).

6. The combined low-cavitation multistage centrifugal pump according to claim 5, characterized in that: The connecting pipe (24) is of a multi-section structure. The lower end of the upper-section connecting pipe (24) is integrally fixed to the upper surface of the connecting flange (27), and the upper end of the lower-section connecting pipe (24) is integrally fixed to the lower surface of the connecting hub (26).

7. The combined low-cavitation multistage centrifugal pump according to claim 1, characterized in that: The horizontal pump body (10) includes a pump body. A horizontal pump shaft (31) is provided inside the pump body. The horizontal pump shaft (31) extends out from both ends of the pump body and is connected to a support bearing (30). Mechanical seal structures (3) of the horizontal pump shaft (31) are provided on both sides of the pump body. A secondary impeller (32) is provided on the horizontal pump shaft (31) inside the pump body. An input port (13) and an output port (14) connected to the connecting pipeline (8) are provided on the upper surface of the pump body. One end of the horizontal pump shaft (31) is connected to a horizontal motor (11).

8. A combined low-cavitation multistage centrifugal pump according to claim 3 or 7, characterized in that: The output shaft of the vertical motor (19) is connected to the vertical pump shaft (23) through a rigid coupling (1); the output shaft of the horizontal motor (11) is connected to the horizontal pump shaft (31) through an elastic coupling (12).

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