CN-117189616-B - Long life cycle's multistage pump of opening in middle

CN117189616BCN 117189616 BCN117189616 BCN 117189616BCN-117189616-B

Abstract

The invention discloses a multistage split pump with a long life cycle, wherein a driving side mechanical seal chamber, a first stage suction chamber, an inducer chamber, a plurality of positive impeller chambers, an impeller pressure relief chamber, a plurality of counter impeller chambers, a secondary suction chamber, a mechanical seal pressure relief chamber and a high pressure side mechanical seal chamber are sequentially arranged from a driving end to a high pressure end, the upper end of a final stage positive impeller chamber is communicated with the upper end of the secondary suction chamber through a pump cover transition channel, the lower end of the final stage positive impeller chamber is communicated with the lower end of the secondary suction chamber through a pump body transition channel, the impeller pressure relief chamber is communicated with a penultimate positive impeller chamber through a first pressure relief pipeline, and the mechanical seal pressure relief chamber is communicated with the first stage positive impeller chamber through a second pressure relief pipeline. The invention can eliminate the axial force generated by the impeller in the running process and the radial force generated by the high-low pressure liquid in the impeller cavity to the impeller in the running process, thereby eliminating the axial stress vibration and the radial stress vibration of the rotor assembly, ensuring the stable and reliable running of the pump and prolonging the running and service life of the pump.

Inventors

WANG ZEBING
ZENG QIANG
LI YI
WANG PENGYU
YE ZHIPING
GONG ZHANG
LUO WEI
LI QIXIANG
LIU YAOCHENG
LIAO DONGHUA
ZHANG WANG
JIANG JINSONG
JIANG XINHANG
YIN HAIFENG
TANG JIANYING
XU YANPENG
SHEN LI
LIAO JIANPING
LIANG KAIXIANG

Assignees

广州市昕恒泵业制造有限公司

Dates

Publication Date: 20260512
Application Date: 20230915

Claims (15)

1. The multistage split pump with the long life cycle comprises a pump body, a pump shaft, a driving side bearing box, a high-pressure side bearing box and a pump seat, wherein the pump body is composed of a pump body and a pump cover, the pump shaft is rotatably arranged on the pump body in a penetrating mode, two ends of the pump shaft penetrate out of two ends of the pump body respectively, the driving side bearing box is fixedly arranged at a driving end of the pump body and connected with the pump shaft, and the high-pressure side bearing box is fixedly arranged at a high-pressure end of the pump body and connected with the pump shaft, and is characterized in that: The pump body is sequentially provided with a driving side mechanical seal chamber, a first-stage suction chamber, an inducer chamber for accommodating an inducer, a positive impeller chamber for accommodating a positive impeller, an impeller pressure release chamber, a counter impeller chamber for accommodating a counter impeller, a secondary suction chamber, a mechanical seal pressure release chamber and a high-pressure side mechanical seal chamber from the driving end to the high-pressure end; the inlet of the pump main body, the first-stage suction chamber and the inducer chamber are sequentially communicated, the positive impeller chamber comprises a first-stage positive impeller chamber, a plurality of secondary positive impeller chambers and a final-stage positive impeller chamber which are sequentially communicated, the first-stage negative impeller chamber is communicated with the secondary suction chamber, the upper end of the final-stage positive impeller chamber is communicated with the upper end of the secondary suction chamber through a pump cover transition channel, the lower end of the final-stage positive impeller chamber is communicated with the lower end of the secondary suction chamber through a pump body transition channel, the pump cover transition channel and the pump body transition channel are symmetrically arranged up and down by taking the pump shaft as the center, the negative impeller chamber comprises a first-stage negative impeller chamber, a plurality of secondary negative impeller chambers and a final-stage negative impeller chamber which are sequentially communicated, the first-stage negative impeller chamber is communicated with the secondary suction chamber, the final-stage negative impeller chamber is communicated with the outlet of the pump main body, the inducer, the positive impellers and the negative impellers are fixedly arranged on the pump shaft, the number of the inducer wheels and the number of the negative impellers are equal to the number of the positive impellers and the number of the negative impellers are symmetrically arranged between the two adjacent positive impellers and the two negative impellers are symmetrically arranged between the two negative impellers, the radial section of the overflow channel is in a standard circular shape, and the impeller pressure release chamber is communicated with the last secondary positive impeller chamber through a first pressure release pipeline; The inducer chamber, the inducer chamber and the positive impeller chamber, the adjacent two positive impeller chambers, the final positive impeller chamber and the impeller pressure release chamber, the impeller pressure release chamber and the final counter impeller chamber the two adjacent counter-impeller chambers, the counter-impeller chamber and the secondary suction chamber, the secondary suction chamber and the mechanical seal pressure release chamber and the high-pressure side mechanical seal chamber are respectively provided with a mouth ring mounting position; wherein, the mouth ring mounting position corresponding to the inducer chamber is provided with an inducer mouth ring which is in clearance fit with the inducer; hub ring openings which are in clearance fit with hubs on two sides of the impeller are respectively arranged on corresponding opening ring installation positions between the inducer chamber and the positive impeller chamber, on corresponding opening ring installation positions between two adjacent positive impeller chambers, on corresponding opening ring installation positions between the final-stage positive impeller chamber and the impeller pressure relief chamber, on corresponding opening ring installation positions between the impeller pressure relief chamber and the final-stage counter impeller chamber, on corresponding opening ring installation positions between two adjacent counter impeller chambers and on corresponding opening ring installation positions between the counter impeller chamber and the secondary suction chamber; and a choke ring in clearance fit with the pump shaft is arranged on a corresponding choke ring mounting position between the secondary suction chamber and the mechanical seal pressure release chamber, and a choke ring in clearance fit with the pump shaft is arranged on a corresponding choke ring mounting position between the mechanical seal pressure release chamber and the high-pressure side mechanical seal chamber.
2. The multistage split pump with a long life cycle according to claim 1, wherein a positive-impeller pumping chamber, a positive-impeller annular chamber and a positive-impeller suction chamber which are sequentially communicated are formed between two adjacent positive-impeller chambers, the positive-impeller pumping chamber, the positive-impeller annular chamber and the positive-impeller suction chamber form the flow passage, the positive-impeller annular chamber is surrounded on the radial outer side of the positive-impeller pumping chamber and the radial outer side of the positive-impeller suction chamber, the positive-impeller pumping chamber and the positive-impeller suction chamber are separated by corresponding port ring installation positions, the positive-impeller pumping chamber is surrounded on the outer periphery of the upper positive-impeller chamber and is communicated with the positive-impeller chamber, the positive-impeller suction chamber is arranged on one axial side of the next positive-impeller chamber and is communicated with the positive-impeller chamber, the radial outer side of the final-stage positive-impeller chamber is surrounded with a positive-impeller pumping chamber, the upper end of the positive-impeller pumping chamber is communicated with the upper end of the secondary-impeller suction chamber through a transition passage, the lower end of the positive-impeller pumping chamber is connected with the upper end of the corresponding secondary-impeller suction chamber through a reverse-impeller transition passage, the reverse-impeller pumping chamber is formed between the reverse-impeller pumping chamber and the reverse-impeller pumping chamber, the reverse-impeller pumping chamber is formed on the radial outer side of the reverse-impeller pumping chamber and the reverse-impeller pumping chamber, the reverse-impeller pumping chamber is sequentially communicated with the reverse-impeller pumping chamber, the reverse-impeller pumping chamber is formed by the reverse-impeller pumping chamber and the reverse-impeller pumping chamber, the back-impeller pumping chamber is arranged around the periphery of the last back-impeller chamber and is communicated with the back-impeller chamber, the back-impeller suction chamber is arranged on one axial side of the next back-impeller chamber and is communicated with the back-impeller chamber, the back-impeller pumping chamber is arranged on the radial outer side of the last-stage back-impeller chamber and is communicated with the outlet of the pump main body, a plurality of pumping chamber guide vanes which are uniformly distributed in circumference are formed in the positive-impeller pumping chamber and the back-impeller pumping chamber, a plurality of suction chamber guide vanes which are uniformly distributed in circumference are formed in the positive-impeller suction chamber and the back-impeller suction chamber, and a plurality of pumping chamber guide vanes which are uniformly distributed in circumference are formed in the positive-impeller pumping chamber and the back-impeller pumping chamber.
3. The multistage split pump with the long life cycle according to claim 1, wherein the induction wheel rim, the hub rim, the choke ring and the choke ring are formed by two half rims, the two half rims are in butt joint to form a circular rim, radial convex edges are symmetrically formed on two sides of the half rims close to the opening end of the half rims, the upper surfaces of the radial convex edges are flush with the end surfaces of the opening ends of the half rims, the lower surfaces of the radial convex edges are horizontal positioning surfaces, the end surfaces of the radial convex edges far away from the half rims are radial positioning surfaces, the outer peripheral surfaces of the half rims close to the radial convex edges are anti-rotation vertical surfaces, the anti-rotation vertical surfaces on the two sides of the half rims are parallel to each other, mounting base surfaces which are respectively in fit with the horizontal positioning surfaces, the radial positioning surfaces and the anti-rotation vertical surfaces are arranged on the mounting base surfaces which are in a penetrating mode, the radial convex edges are in fit with the horizontal positioning surfaces are provided with counter bores opposite to the counter bores, and the counter bores penetrate through the counter bores are connected with the counter bores.
4. The multistage split pump with a long life cycle according to claim 1, wherein a first-stage suction guide cone through which the pump shaft passes is formed in the first-stage suction chamber, an outer wall surface of the first-stage suction guide cone smoothly transitions with an inner wall surface of the first-stage suction chamber, an outer diameter of the first-stage suction guide cone gradually decreases from the first-stage suction chamber to the inducer chamber, a second-stage suction guide cone through which the rotor assembly passes is formed in the second-stage suction chamber, an outer wall surface of the second-stage suction guide cone smoothly transitions with an inner wall surface of the second-stage suction chamber, and an outer diameter of the second-stage suction guide cone gradually decreases from the second-stage suction chamber to the first-stage counter-impeller chamber.
5. The multistage split pump with long life cycle according to claim 1, wherein the driving side machine sealing chamber and the high pressure side machine sealing chamber are respectively connected with a heat exchanger, the heat exchanger is provided with a first heat exchange medium channel and a second heat exchange medium channel, the first heat exchange medium channel is connected with a cooling water pipeline system, and the second heat exchange medium channel is connected with the driving side machine sealing chamber or the high pressure side machine sealing chamber and forms a circulation loop.
6. The multistage split pump with the long life cycle according to claim 1, wherein a driving side mechanical seal cooling chamber which is adjacent to and not communicated with the driving side mechanical seal chamber is arranged on the radial outer periphery of the driving side mechanical seal chamber, the driving side mechanical seal cooling chamber is connected with a cooling water pipeline system, a high-pressure side mechanical seal cooling chamber which is adjacent to and not communicated with the high-pressure side mechanical seal chamber is arranged on the radial outer periphery of the high-pressure side mechanical seal chamber, and the high-pressure side mechanical seal cooling chamber is connected with the cooling water pipeline system.
7. The multistage split pump with long life cycle according to claim 1, wherein the driving side bearing box comprises a first box body and a first box cover, wherein the first box cover is arranged above the first box body, a first outer side shaft seal installation position, a first sliding bearing lubricating oil chamber, a first sliding bearing installation position, a first oil return chamber, a first inner side shaft seal installation position and a first open chamber which are sequentially arranged from outside to inside along the pump shaft direction are formed around the first box cover and the first box body, a first outer side shaft seal assembly is arranged on the first outer side shaft seal installation position, a first sliding bearing assembly is arranged on the first inner side shaft seal installation position, a first inner side shaft seal assembly is arranged on the first inner side shaft seal installation position, and the first sliding bearing lubricating oil chamber is communicated with the first oil return chamber through a first oil return channel; The high-pressure side bearing box comprises a second box body and a second box cover, wherein the second box cover is arranged above the second box body, an outer cover mounting position, a rolling bearing lubricating oil chamber, a rolling bearing mounting position, a second sliding bearing lubricating oil chamber, a second sliding bearing mounting position, a second oil return chamber, a second inner shaft seal mounting position and a second open chamber which are sequentially arranged from outside to inside along the pump shaft direction are formed around the second box cover and the second box body, a sealing cover is arranged on the outer cover mounting position, a rolling bearing assembly is arranged on the rolling bearing mounting position, a second sliding bearing assembly is arranged on the second inner shaft seal mounting position, a second inner shaft seal assembly is arranged on the second inner shaft seal mounting position, the second sliding bearing lubricating oil chamber is communicated with the second oil return chamber through a second oil return channel, the second sliding bearing lubricating oil chamber is communicated with the rolling bearing lubricating oil chamber through a third oil return channel, a second opening communicated with the outside atmosphere is formed in the side wall of the second open chamber, a second cooling ripple cooling heat exchange plate is formed on the second open heat exchange plate cooling heat exchange plate, and the cooling heat exchange plate is connected with the second cooling ripple heat exchange plate cooling heat exchange plate; the top of the first oil return chamber and the top of the second oil return chamber are respectively provided with an exhaust hood.
8. The multistage split pump with long life cycle of claim 7, wherein the first sliding bearing assembly comprises a first bearing seat and a first sliding bearing, the first bearing seat is fixed on the first sliding bearing installation position through screws, the first sliding bearing is installed on the first bearing seat, a first oil slinger and a first baffle are arranged in a first sliding bearing lubricating oil chamber, the first oil slinger is sleeved on a pump shaft and rotates in a friction way with the pump shaft, the first oil slinger is close to the first sliding bearing, and the first baffle is fixed on the first bearing seat through screws and is blocked on one side of the first oil slinger away from the first sliding bearing; The second sliding bearing assembly comprises a second bearing seat and a second sliding bearing, the second bearing seat is fixed on the second sliding bearing installation position through a screw, and the second sliding bearing is installed on the second bearing seat; the second oil slinger is close to the second sliding bearing, and the second baffle is fixed on the second bearing seat through a screw and is blocked at one side of the second oil slinger away from the second sliding bearing; The rolling bearing assembly comprises a rolling bearing and a compressing piece, wherein a limiting convex ring is formed on one side, close to a second sliding bearing lubricating oil chamber, of a rolling bearing installation position, the compressing piece is fixed on one side, far away from the second sliding bearing lubricating oil chamber, of the rolling bearing installation position through screws, an outer ring of the rolling bearing is compressed between the limiting convex ring and the compressing piece, two rolling bearings are arranged in an overlapping mode along a pump shaft direction, a third oil slinger, an oil ring seat and a compressing nut are arranged in the rolling bearing lubricating oil chamber, the oil ring seat is sleeved on a pump shaft, the compressing nut is in threaded connection with the tail end of the pump shaft, the oil ring seat and an inner ring of the rolling bearing are compressed on a pump shaft shoulder, the third oil slinger is sleeved on the oil ring seat and in friction rotation with the oil ring seat, and a limiting groove matched with the third oil slinger is formed in the outer peripheral ring of the oil ring seat.
9. The multistage split pump with long life cycle according to claim 7, wherein the first outer side shaft seal assembly and the first inner side shaft seal assembly each comprise a first oil retainer, a first oil retainer and a first dust cover which are sleeved on the pump shaft, the first oil retainer is fixed on the first outer side shaft seal installation position or the first inner side shaft seal installation position through screws, a first accommodating groove for the first oil retainer to be embedded is formed in one side away from the first sliding bearing lubricating oil chamber or the first oil return chamber, and the first dust cover is arranged on the first accommodating groove and fastened on the pump shaft through screws; The second inner side shaft seal assembly comprises a second oil retainer, a second oil retainer and a second dust cover, wherein the second oil retainer is sleeved on the pump shaft, the second oil retainer is fixed on the second inner side shaft seal mounting position through screws, a second accommodating groove for the second oil retainer to be embedded is formed in one side, away from the second sliding bearing lubricating oil chamber, of the second oil retainer, and the second dust cover is arranged on the second accommodating groove and fastened on the pump shaft through screws.
10. The multi-stage split pump with a long life cycle according to claim 7, wherein the end faces of the first tank body and the second tank body, which face the pump body, are respectively provided with a first spigot semi-ring which protrudes axially; the end faces of the first box cover and the second box cover, which face the pump cover, are provided with second spigot semi-rings protruding axially; the first spigot semi-ring is matched with the second spigot semi-ring to form a spigot ring; the pump comprises a pump body, a pump shaft, a bearing box, a bearing, a pump shaft, a bearing, a lifting device, a bearing, a lifting device, a pump cover, a bearing, a lifting device, a lifting mechanism, a pump cover, a semi-ring stop part, a lifting mechanism, a lifting screw, a semi-ring stop part, a lifting taper ring and a lifting screw, wherein the semi-ring stop part is respectively arranged on end surfaces of two ends of the pump body and matched with a first spigot semi-ring, the semi-ring stop part is matched with the semi-ring stop part of the first spigot ring, the semi-ring stop part is arranged on the semi-ring, the lifting mechanism comprises a lifting taper ring and a lifting taper ring, the semi-ring connecting part and the semi-ring stop part is arranged on the lifting taper ring, the semi-ring stop part is formed at the upper end surface of the semi-ring connecting part, the semi-ring stop part is matched with the semi-ring stop part, the semi-ring stop part is arranged on the semi-ring connecting part, the semi-ring stop part is in the semi-ring, the semi-ring stop part is matched with the semi-ring stop part, the semi-ring stop part is arranged on the semi-ring connecting part, the semi-ring stop part is, the semi-ring stop part is uniformly ring stop part is respectively, the semi ring stop surface is, the semi ring stop surface is and the semi ring stop surface is and the semi ring surface the ring surface the semi ring connecting ring surface the ring and the ring surface the ring surface the ring and the ring protruding, the semi, the ring protruding ring the ring and the ring and the ring the ring and the ring protruding ring and the ring and the ring.
11. The multistage split pump with the long life cycle according to any one of claims 7 to 10 is characterized in that a first X-direction vibration probe interface, a first Y-direction vibration probe interface, a first Z-direction vibration probe interface and a first temperature probe interface are arranged on the driving side bearing box, a first X-direction vibration probe for detecting X-direction vibration of the driving side bearing box is arranged on the first X-direction vibration probe interface, a first Y-direction vibration probe for detecting Y-direction vibration of the driving side bearing box is arranged on the first Y-direction vibration probe interface, a first Z-direction vibration probe for detecting Z-direction vibration of the driving side bearing box is arranged on the first Z-direction vibration probe interface, and a first temperature probe for detecting the oil temperature in the first oil return chamber is arranged on the first temperature probe interface; The high-pressure side bearing box is provided with a second X-direction vibrating probe interface, a second Y-direction vibrating probe interface, a second Z-direction vibrating probe interface and a second temperature probe interface, the second X-direction vibrating probe interface is provided with a second X-direction vibrating probe for detecting X-direction vibration of the driving side bearing box, the second Y-direction vibrating probe interface is provided with a second Y-direction vibrating probe for detecting Y-direction vibration of the driving side bearing box, the second Z-direction vibrating probe interface is provided with a second Z-direction vibrating probe for detecting Z-direction vibration of the driving side bearing box, and the second temperature probe interface is provided with a second temperature probe for detecting the temperature of the oil in the second oil return chamber.
12. The multistage split pump with long life cycle according to claim 1, wherein shaft sealing covers are respectively arranged at two ends of the pump main body, the shaft sealing covers are respectively arranged at an outer side port of the driving side mechanical sealing chamber and an outer side port of the high pressure side mechanical sealing chamber, at least two O-shaped sealing rings are arranged between the shaft sealing covers and the pump main body, mechanical seals sleeved on the pump shafts are respectively arranged in the driving side mechanical sealing chamber and the high pressure side mechanical sealing chamber, and a sealing connection structure can be formed between the pump shafts and the shaft sealing covers by the mechanical seals.
13. The multistage split pump with long life cycle of claim 12, wherein a throttling shaft sleeve and a choking shaft sleeve are fixedly sleeved on positions of the pump shaft, which correspond to the throttling hole ring, the mechanical seal decompression chamber, the choking hole ring, the high-pressure side mechanical seal chamber, the mechanical seal and the shaft seal cover, the throttling hole ring is sleeved on the throttling shaft sleeve and forms a spiral throttling channel with the throttling shaft sleeve, and the choking hole ring is sleeved on the choking shaft sleeve and forms a spiral choking channel with the choking shaft sleeve.
14. The multistage split pump with long life cycle of claim 13, wherein the pump shaft is further sleeved with a compression shaft sleeve, a water retaining nut and a locking nut at one end of the flow blocking shaft sleeve, which is far away from the throttling shaft sleeve, the water retaining nut and the locking nut are respectively in threaded connection with the pump shaft, when the water retaining nut and the locking nut are screwed into one side of the compression shaft sleeve, the water retaining nut sequentially compresses the compression shaft sleeve, the flow blocking shaft sleeve and the throttling shaft sleeve on a shaft shoulder of the pump shaft, the locking nut is compressed on the water retaining nut, the flow blocking shaft sleeve penetrates through the shaft seal cover, an O-shaped sealing ring is clamped at the joint of the flow blocking shaft sleeve and the compression shaft sleeve, and the inner circle of the O-shaped sealing ring is tightly abutted against the outer circle surface of the pump shaft.
15. The multistage split pump with long life cycle of claim 1, wherein the pump seat is provided with a supporting leg for fixedly supporting the pump main body, a supporting leg cooling chamber is arranged in the supporting leg, and the supporting leg cooling chamber is connected with a cooling water pipeline system.

Description

Long life cycle's multistage pump of opening in middle Technical Field The invention belongs to the technical field of pumps, and particularly relates to a multistage split pump with a long life cycle. Background The multistage split pump is a special centrifugal pump with more impeller stages and extremely high pump lift, the pump flow reaches 5000m3/h and above, the pump lift reaches 4000m and above, the pump rotating speed reaches 3000r/min to 10000r/min, the pump matching power reaches 20000Kw and above, and the multistage split pump is applied to special heavy-duty industries such as large-duty sea water desalination engineering, large-duty coal exploitation engineering, large-duty oilfield water injection engineering, large-duty petroleum long-distance conveying engineering, high-pressure pipeline conveying flow of a refinery, high-pressure water supply engineering of a power plant boiler, LNG low-temperature high-pressure liquid conveying engineering, high-pressure dephosphorization system of a steel plant and the like, is a general split centrifugal pump and a multistage centrifugal pump, the stability, the reliability and the safety of the use and the operation of the multistage split pump are very important, and the design development, the production, the use and the maintenance and the spare part exchange capability of the multistage split pump are very important because the application field of the pump is special, namely the whole life cycle of the pump is very important. In the spiral volute type pumping chamber, when the flow mutual coordination condition of the pumping chamber and the impeller is destroyed, namely the working condition flow of the pump is smaller or larger than the design rated flow due to certain reasons (such as pressure change of working condition of a pipe network system, change of required flow of end of a device system, change of frequency of a power grid system, change of lift of a pump inlet pipeline system, stall or overspeed of a pump driving machine system, and the like), sharp contradiction occurs between the operating condition flow and the design rated flow, the condition that the pressure in the spiral volute type pumping chamber is symmetrically distributed along the axis of the impeller is destroyed, the high-pressure liquid pressure and the low-pressure liquid pressure in the spiral volute type pumping chamber act on the blades and the outer circle of the impeller, thereby radial force is generated, the radial force is transmitted to a pump shaft through the impeller, the pump shaft is subjected to alternating stress to generate directional disturbance, and the radial force is transmitted to a bearing box and a pump body through the pump shaft, The pump cover causes large rotor vibration, large bearing vibration and large pump body vibration of the pump, thereby damaging parts such as a pump shaft, a bearing, a mechanical seal, an impeller and the like and shortening the whole service life of the pump. In the prior art, the impeller pumping chamber of the split pump is of a single-channel spiral volute pumping chamber or double-channel spiral volute pumping chamber structure, the radial force of a pump rotor cannot be eliminated by the single-channel spiral volute pumping chamber, most of the radial force but the radial force cannot be completely eliminated by the double-channel spiral volute pumping chamber, the radial force generated by the multistage split pump is large because of more impeller stages, the number of the inter-stage pumping chambers and the inter-stage suction chambers of the impeller is large because of more impeller stages, and the pump body is a pump body, The pump cover has the error when casting to make the runner size of the pumping chamber and the suction chamber deviate from the design shape value, so that the radial force acting on the pump shaft is alternated for many times, the pump shaft bears many times of bending stress and many kinds of alternating shearing stress, so that the pump shaft has irregular chaotic disturbance and deformation, the forces and deformation can cause the friction of the rotating component and the non-rotating component of the pump to damage and cause the vibration of the pump, the friction vibration can cause the pump to generate larger noise during operation, the working environment is seriously influenced, meanwhile, the friction vibration can cause the pump set to generate serious vibration, the bolts or connections of the pump and the pump set are loosened to cause leakage of conveying medium or serious damage to the pump set to cause serious accidents, and the radial force of the rotating component and the non-rotating component of the pump, which acts on the pump shaft, is overlapped again, so that the pump shaft bears larger many times of bending stress and many kinds of alternating shearing stress, so as to cause the damage to the pump shaft. In addition, an inter-stage impeller pumpi