Vertical suspension centrifugal pump

Abstract

A vertical suspension centrifugal pump includes a deceleration system disposed between a first shaft and a second shaft to allow a speed difference between the first shaft and the second shaft. Further, the deceleration system includes a first pinion operatively connected to the main shaft configured to rotate at the first speed, a first gear set engaged with the first pinion configured to rotate at a second speed reduced from the first speed, a second gear set engaged with a second pinion configured to rotate at a third speed reduced from the second speed, and a second gear set engaged with the second pinion configured to rotate at a fourth speed reduced from the second speed. The rotating shaft is configured to rotate at the second speed; a countershaft operably connected to the second pinion of the deceleration system and configured to rotate at the second speed; and a first stage impeller coupled to the countershaft. In this way, the NPSHR of the centrifugal pump can be reduced.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application Serial No. 63 / 421,363, filed on November 1, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a vertically suspended centrifugal pump, and more particularly to a vertically suspended centrifugal pump with an integral reducer. Background Art

[0004] For a vertically suspended centrifugal pump to work properly, there must be sufficient net positive suction head (NPSH) margin (effective NPSH-required NPSH). The effective NPSH is determined by the pumping system, while the required NPSH is a parameter of the centrifugal pump design. Summary of the invention

[0005] One aspect relates to a vertically suspended centrifugal pump including: a speed reduction system disposed between a first shaft and a second shaft to allow a speed difference between the first shaft and the second shaft.

[0006] In an exemplary embodiment, a vertically suspended centrifugal pump includes a first stage operably coupled to a second shaft, a second stage operably coupled to a first shaft, and a third stage or more stages coupled to a main shaft. During operation of the vertically suspended centrifugal pump, the first stage operates at a lower speed than the second stage according to a speed difference between the first shaft and the second shaft. For example, during operation of the vertically suspended centrifugal pump, the second stage is an impeller that operates at a speed of 3,600 rpm or more.

[0007] Another aspect relates to a vertically suspended centrifugal pump, comprising: a main shaft driven at a first speed, a plurality of cascade-stage impellers coupled to the main shaft, a reduction system including a first pinion operably connected to the main shaft and configured to rotate at the first speed, a first gear set meshing with the first pinion and configured to rotate at a second speed reduced from the first speed, and a second gear set meshing with the second pinion and configured to rotate at the second speed, a secondary shaft operably connected to the second pinion of the reduction system and configured to rotate at the second speed, and the first-stage impeller coupled to the secondary shaft.

[0008] The reduced speed is reduced by the gear ratio between the first pinion and the first gear set. In an exemplary embodiment, the first gear set is larger than the second gear set. A vertically suspended centrifugal pump having a spur gear system will minimize the required net positive suction head of the first stage impeller by operating at the second speed while the plurality of tandem stage impellers operate at the first speed, e.g., at or above 3600 rpm.

[0009] Another aspect relates to a vertically suspended centrifugal pump, comprising: a main shaft driven at a first speed, a plurality of tandem-stage impellers coupled to the main shaft, a reduction system including a star gear operably connected to the main shaft and configured to rotate at the first speed, at least one planetary gear meshing with the star gear and a fixed gear and configured to rotate at a second speed reduced from the first speed, and a carrier coupled to the at least one planetary gear and configured to rotate at the second speed, a secondary shaft operably coupled to the carrier and configured to rotate at the second speed, and a first-stage impeller coupled to the secondary shaft.

[0010] A vertically suspended centrifugal pump with a planetary gear system will also minimize the net positive suction head required for the first stage impeller by running at the second speed while the multiple tandem stage impellers run at the first speed, for example, 3600 rpm.

[0011] Another aspect relates to a method, comprising: arranging a speed reduction system between two separate shafts of a vertically suspended centrifugal pump to allow a speed difference between the two separate shafts. According to arranging the speed reduction system between the two separate shafts, the net positive suction head of a first stage impeller coupled to one of the two separate shafts is minimized by operating at a lower speed than a plurality of tandem stage impellers coupled to the other of the two separate shafts.

[0012] The above and other features of structure and operation will be more readily understood and fully appreciated from the following detailed disclosure taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Some embodiments will be described in detail with reference to the accompanying drawings, wherein like reference numerals refer to like components, and wherein:

[0014] Figure 1A A first conventional vertically suspended centrifugal pump is shown including a single main shaft extending vertically through the pump;

[0015] Figure 1B A second conventional vertically suspended centrifugal pump is shown including a single main shaft extending vertically through the pump;

[0016] Figure 2 A pump having a reduction system arranged between two separate shafts according to an embodiment of the present invention is schematically shown;

[0017] Figure 3A A detailed embodiment of a vertically suspended centrifugal pump having a first deceleration system according to an embodiment of the utility model is shown;

[0018] Figure 3BA detailed embodiment of a vertically suspended centrifugal pump with a second deceleration system according to an embodiment of the utility model is shown;

[0019] Figure 4 The embodiment according to the utility model is shown Figure 3A The reduction system of the pump shown is highlighted by section A;

[0020] Figure 5 The embodiment according to the utility model is shown Figure 3B The reduction system of the pump shown is highlighted by section A;

[0021] Figure 6 Schematically shows a method according to an embodiment of the present invention having a device arranged between two separate shafts. Figure 2 pumps of the reduction system at different positions in the pumps shown in FIG. 1 ; and

[0022] Figure 7 A pump having more than one speed reduction system arranged according to an embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0023] Detailed descriptions of the embodiments of the disclosed apparatus and methods described below are presented herein by way of example, but are not limited to the accompanying drawings. Although certain embodiments are shown and described in detail, it should be understood that various changes and modifications may be made without departing from the scope of the appended claims. The scope of the present disclosure is in no way limited to the number of constituent parts, the materials of the constituent parts, the shapes of the constituent parts, the relative arrangement of the constituent parts, etc., but is disclosed only as an example of the embodiments of the present disclosure.

[0024] As a preface to the detailed description, it should be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0025] In brief overview, it is imperative to minimize the NPSH required for centrifugal pumps. Effective NPSH, usually expressed as the height of a column of liquid, is the amount of pressure above the vapor pressure of the pumped liquid at the pump suction. With reference to a certain reference point (i.e., the pump suction nozzle), the effective NPSH of a pumping system can be as low as zero (i.e., the pumped liquid is at the bubble point). The NPSH required is a function of the impeller design, flow rate, and operating speed. The NPSH required (NPSHR) can be expressed as:

[0026]

[0027] Where NPSHR is the net positive suction head required in feet, Q is the flow rate in gpm, and Nss is the suction specific speed and n is the operating speed in rpm. The lowest achievable effective NPSH is that which results in a suction specific speed within a reasonable range; the practical range is up to 13,000 in U.S. customary units, although 18,000 or even higher is possible.

[0028] In the oil and gas industry, vertically suspended multistage pumps (e.g., API 610 VS1 or VS6 pumps) are typically used for applications with low effective NPSH and high differential head because the first stage impeller is below ground level and the pump can provide effective NPSH to the first stage impeller, thereby being able to obtain sufficient NPSH margin for proper operation of the selected pump. Conventional vertically suspended multistage pumps use one or more of the following measures to obtain the required NPSH margin: a first stage impeller with a high suction specific speed; an inducer before the first stage impeller; a double suction first stage impeller; an extra long shaft (extra long pump) to obtain the required NPSH; and running the entire pump at a lower speed than the design speed.

[0029] Each of these measures has disadvantages. For example, a high suction speed impeller (N ss >13,000) and inducers tend to produce a "U" shaped NPSHR curve and cause internal recirculation, which reduces the operating range. When using a double suction first stage impeller, the reduction in NPSHR is limited to 2 compared to a single suction first stage pump impeller. 2 / 3 In addition to the high cost, using an extra-long shaft often leads to rotor dynamic problems and reliability issues. Running the entire pump at a lower speed can reduce the NPSHR by (n2 / n1) 4 / 3 ; however, it will require a larger pump, or increase the number of stages by (n2 / n1) 2 To meet the differential head requirements, this inevitably increases the cost.

[0030] Another way to reduce NPSHR is to ss and Q remain constant while reducing the operating speed. Slowing down the entire pump is not desirable. If the first stage impeller and the tandem stage impeller can be run at different speeds (i.e., the first stage impeller runs at a lower speed to obtain a low NPSHR, while the tandem stage impeller runs at a higher speed to obtain the necessary total differential head), not only a low NPSHR but also a high total differential head can be produced.

[0031] The embodiment of the utility model minimizes the NPSHR of the first stage by using an integral reducer to run the first stage (e.g., the first stage impeller) at an optimized speed lower than other stages of the centrifugal pump. The integral reducer is a reduction system that is arranged between two separate shafts of the centrifugal pump and is connected to the two separate shafts to allow a speed difference between the two separate shafts. For example, one or more impellers coupled to a main shaft driven at a first speed (e.g., high speed) can run at a higher speed than the impellers of a secondary shaft coupled to a lower speed (e.g., low speed). The use of the reduction system also minimizes the total length of the pump by generating a low NPSH or sufficient NPSH margin, and optimizes the suction specific speed, so that the pump can operate within a large flow range. In the case where the first stage impeller runs at a low speed, the tandem stage impeller can run at a speed of 3600rpm or more to optimize efficiency, thereby further shortening the length of the pump. In an exemplary embodiment, the reduction system uses a spur gear system or a planetary gear system between the first-stage impeller and the second-stage impeller of the centrifugal pump, so that the first-stage impeller can run at a different speed than the tandem-stage impeller. In another exemplary embodiment, the reduction system uses a hydraulic coupling reducer between the first-stage impeller and the second-stage impeller of the centrifugal pump, so that the first-stage impeller can run at a different speed than the tandem-stage impeller.

[0032] See now Figure 1A and Figure 1B , a conventional vertically suspended centrifugal pump includes a main shaft 5 extending vertically through the pump 1, 1'. The pump 1, 1' is a multi-stage pump, which includes a first stage, a second stage, a third stage and a fourth stage. Each stage includes an impeller 2a, 2b, 2c, 2d coupled to the main shaft 5. When the main shaft 5 is driven, for example, when it is rotated, each of the impellers 2a, 2b, 2c, 2d is rotated at the same speed. In other words, when the main shaft 5 is driven by a drive (not shown), the impeller 2a of the first stage rotates at the same speed as the other series-connected impellers 2b, 2c, 2d.

[0033] Figure 2A pump 100 having a reduction system 50 arranged between two separate shafts 10, 15 according to an embodiment of the utility model is schematically shown. The pump 100 is a vertically suspended centrifugal pump that can be used for applications in oil and gas, petrochemicals, chemicals, liquid carbon dioxide and liquid hydrogen. In an exemplary embodiment, the pump 100 is a vertically suspended centrifugal pump having two vertically oriented shafts 10, 15 sharing a common longitudinally extending rotation axis 3. The pump 100 includes a housing 8 configured to surround or at least partially surround components of the pump 100. The pump 100 includes a plurality of stages 20a, 20b, 20c, 20d. The stages 20a, 20b, 20c, 20d can be impellers, rotors or any rotating components used to accelerate the fluid passing through the pump 100. Although four stages are shown in the illustrated embodiment, the pump 100 may include two, three or more than four stages. The stage 20a is coupled to the secondary shaft 15, while the remaining stages 20b, 20c, 20d are coupled to the main shaft 10. For example, the stages 20a, 20b, 20c, 20d may be mounted directly or otherwise to the shafts 10, 15.

[0034] In addition, the pump 100 includes a reduction system 50 that allows a speed difference between the main shaft 10 and the secondary shaft 15, so that the stage 20a (e.g., the first stage) can operate at a different (e.g., lower) speed than the other stages 20b, 20c, 20d. The speed difference between the shafts 10, 15 minimizes the net positive suction head and allows the overall length of the pump 100 to be smaller. The reduction system 50 is arranged between the main shaft 10 and the secondary shaft 15. For example, the end of the main shaft 10 is attached to a component of the reduction system 50, such as a pinion or a planetary gear, and the end of the secondary shaft 15 is also attached to a component of the reduction system 50. In some embodiments, the end of the main shaft 10 and / or the end of the secondary shaft 15 are structurally integral with the components of the reduction system 50.

[0035] Figure 3A and Figure 3BA more detailed embodiment of a vertically suspended centrifugal pump 100a, 100b having a reduction system 50a, 50b respectively according to an embodiment of the utility model is shown. Instead of a single main shaft, the pump 100a, 100b includes a main shaft 10 (e.g., a first shaft) and a secondary shaft 15 (e.g., a second shaft). The reduction system 50a, 50b is arranged between the main shaft 10 and the secondary shaft 15, and is operably connected to the two shafts 10, 15. The pump 100a, 100b includes a plurality of pump stages, including a first pump stage, a second pump stage, a third pump stage, and a fourth pump stage. Although four stages are shown in the illustrated embodiment, the pump 100a, 100b may include two, three or more than four stages of impellers. The series pump stage includes impellers 20a, 20b, 20c, 20d, but the first stage impeller 20a is coupled to the secondary shaft 15, and the series stage impellers 20b, 20c, 20d are coupled to the main shaft 10. For example, when the main shaft 10 is driven to rotate, the impellers (e.g., impellers 20b, 20c, 20d) associated with the tandem pump stages following the first pump stage are caused to rotate at the same speed. Due to the integral reduction systems 50a, 50b, the secondary shaft 15 rotates at a speed reduced from the speed of the main shaft 10. As a result, when the main shaft 10 is driven by a drive (not shown), the first stage impeller 20a of the first pump stage rotates at a different (e.g., lower) speed than the other tandem impellers 20b, 20c, 20d. Therefore, there is a speed difference between the two separate shafts 10, 15.

[0036] Figure 4 The embodiment according to the utility model is shown Figure 3A The reduction system 50a of the pump 100a shown is highlighted by part A. The reduction system 50a is a gear system for generating a speed difference between the main shaft 10 and the second shaft 15. In an exemplary embodiment, the reduction system 50a is a spur gear system. The reduction system 50a includes a first pinion 51, a first gear set 52, a second gear set 53, and a second pinion 54. The first pinion 51, the first gear set 52, the second gear set 53, and the second pinion 54 each include teeth along the outer peripheral surface. The gear teeth can have various spacings, thicknesses, pitches, sizes, etc. Similarly, the sizes of the first pinion 51, the first gear set 52, the second gear set 53, and the second pinion 54 can be varied to achieve different desired speeds, gear ratios, torque transmissions, etc. of the reduction system 50a.

[0037] The first pinion 51 is operably connected to the main shaft 10. For example, the first pinion 51 can be mounted to the main shaft 10 so that the rotation of the main shaft 10 is converted into the rotation of the first pinion, and vice versa. In other embodiments, the first pinion 51 can be structurally integral with the main shaft 10. When the main shaft 10 is driven, the first pinion 50a rotates at the speed of the main shaft 10 (e.g., the first speed). The first gear set 52 meshes with the first pinion 51 so that the rotation of the first pinion 51 causes the rotation of the first gear set 52. The first gear set 52 rotates at a reduced speed (e.g., the second speed) reduced from the first speed. The reduced speed is reduced by the transmission ratio between the first pinion 51 and the first gear set 52. The second gear set 53 shares the pinion shaft 55 with the first gear set 52, so that the second gear set 53 rotates at a reduced speed than the first gear set 52. The second gear set 53 is smaller than the first gear set 52 and meshes with the second pinion 54 so that rotation of the second gear set 53 causes rotation of the second pinion 54. The second pinion 54 rotates at a reduced speed. Because the layshaft 15 is operably coupled to the second pinion 54, the layshaft 15 rotates at a reduced speed and therefore rotates at a different speed than the main shaft 10. For example, the second pinion 54 can be mounted to the layshaft 10 so that rotation of the second pinion 54 is converted into rotation of the layshaft 15, and vice versa. In other embodiments, the second pinion 54 can be structurally integral with the layshaft 15. A first stage, such as an impeller, is coupled to the layshaft 15. Arrows show the flow path of the fluid through the pump.

[0038] In addition, the deceleration system 50a is encapsulated within the diffuser 70. The diffuser 70, also referred to as a drum, includes an outer diffuser portion 70a and an inner diffuser portion 70b. The space between the outer diffuser portion 70a and the inner diffuser portion 70b is a passage 71 that allows fluid to flow through the pump to the next stage of the pump. The blades or blades are placed between the outer diffuser portion 70a and the inner diffuser portion 70b in a spiral or helical pattern to structurally couple the outer diffuser portion 70a and the inner diffuser portion 70b, and also to guide the fluid flow around the inner diffuser portion 70b to the next stage in a spiral or helical pattern. Various structural configurations of the blades or blades and / or drum configurations can be used with the deceleration system 50a. The outer diffuser portion 70a is a generally annular member having a shoulder 73, wherein the outer diameter of the diffuser 70 is reduced compared to the remaining main body of the diffuser 70.

[0039] The reduction system 50a is located within the inner diffuser portion 70b proximate the longitudinal axis of the pump 100. A cartridge assembly 76 is disposed between the inner diffuser portion 70b and the reduction system 50a. The cartridge assembly 76 may include a single structure, or may include multiple components that are fastened together to form the cartridge 76. A radial bearing 77 is disposed between the cartridge 76 and the reduction system 50a to allow the pinion shaft 55 to rotate relative to the cartridge 76.

[0040] The diffuser 70 is stationary relative to the other components of the pump 100 . Figure 4 The diffuser 70 shown in FIG. 1 is attached to a suction horn 74 where fluid is drawn into the diffuser 70. In an exemplary embodiment, the diffuser 70 is fixedly attached to the suction horn 74 via one or more fasteners, such as bolts or similar fasteners. The diffuser 70 is operably connected to the suction horn 74. Figure 4 The hub 75 of the impeller 20a of the stage (i.e., the first stage) shown. A wear ring 79 is arranged between the hub 75 and the diffuser 70. The impeller 20a is mechanically coupled to the main shaft 15 and rotates with the secondary shaft 15, while the suction horn 74 and the diffuser 70 remain stationary. The rotation of the impeller 20a draws the fluid through the suction horn 74 and into the diffuser 70, specifically, the passage 71 between the outer diffuser portion 70a and the inner diffuser portion 70b.

[0041] The diffuser 70 is operably coupled to the second-stage impeller 20b near the shoulder 73 of the diffuser 70. The second-stage impeller 20b includes a front cover plate 81 and a rear cover plate 82. A wear ring 83 is arranged between the front cover plate 81 of the second-stage impeller 20b and the diffuser 70 of the first stage. The fluid flowing through the passage 71 of the diffuser 70 is further sucked into the second-stage impeller 20 due to the rotation of the second-stage impeller 20b, which is caused by the mechanical coupling of the second-stage impeller 20b with the main shaft 10. Due to the reduction system 50, the second-stage impeller 20b rotates at a different speed from the first-stage impeller 20a.

[0042] Figure 5 The embodiment according to the utility model is shown Figure 3BThe reduction system 50b of the pump 100b is shown, highlighted by section A. The reduction system 50b is a gear system for generating a speed difference between the main shaft 10 and the second shaft 15. In an exemplary embodiment, the reduction system 50b is a planetary or epicyclic gear system. The reduction system 50b includes a star gear 55, a planetary gear 56, a fixed gear 57, and a carrier 58. The star gear 55, the planetary gear 56, and the fixed gear 57 each include teeth along the outer peripheral surface. The gear teeth can have various spacings, thicknesses, pitches, sizes, etc. Similarly, the sizes of the star gear 55, the planetary gear 56, and the fixed gear 57 can be varied to achieve different desired speeds, gear ratios, torque transmissions, etc. of the reduction system 50b.

[0043] The planetary gear 55 is operably connected to the main shaft 10. As the main shaft 10 is driven, the planetary gear 55 rotates at the same speed as the main shaft 10 (e.g., a first speed). At least one planetary gear 56 meshes with the planetary gear 55 and the fixed gear 57; the planetary gear 56 rotates at a reduced speed (e.g., a second speed) that is reduced from the first speed. A carrier 58 is coupled to the at least one planetary gear 56 so that rotation of the planetary gear 56 causes rotation of the carrier 58, which also rotates at a reduced speed. Because the secondary shaft 15 is operably coupled to the carrier 58, the secondary shaft 15 rotates at a reduced speed and therefore at a different speed from the main shaft 10. A first stage, such as an impeller, is coupled to the secondary shaft 15. Arrows show the flow path of the fluid through the pump.

[0044] In addition, the deceleration system 50b is encapsulated within the diffuser 70. The diffuser 70, also referred to as a drum, includes an outer diffuser portion 70a and an inner diffuser portion 70b. The space between the outer diffuser portion 70a and the inner diffuser portion 70b is a passage 71 that allows fluid to flow through the pump to the next stage of the pump. The blades or blades are placed between the outer diffuser portion 70a and the inner diffuser portion 70b in a spiral or helical pattern to structurally couple the outer diffuser portion 70a and the inner diffuser portion 70b, and also to guide the fluid flow around the inner diffuser portion 70b to the next stage in a spiral or helical pattern. Various structural configurations of the blades or blades and / or drum configurations can be used with the deceleration system 50b. The outer diffuser portion 70a is a generally annular member having a shoulder 73, wherein the outer diameter of the diffuser 70 is reduced compared to the remaining main body of the diffuser 70.

[0045] The reduction system 50b is located within the inner diffuser portion 70b proximate the longitudinal axis of the pump 100. The barrel assembly 76' is disposed between the inner diffuser portion 70b and the reduction system 50b. The barrel assembly 76' may include a single structure, or may include multiple components that are fastened together to form the barrel 7'. The bearing 78 is disposed between the barrel 76' and the bracket 58 to allow the bracket 59 to rotate relative to the barrel 76'.

[0046] The diffuser 70 is stationary relative to the other components of the pump 100 . Figure 6 The diffuser 70 shown in FIG. 1 is attached to a suction horn 74 where fluid is drawn into the diffuser 70. In an exemplary embodiment, the diffuser 70 is fixedly attached to the suction horn 74 via one or more fasteners, such as bolts or similar fasteners. The diffuser 70 is operably connected to the suction horn 74. Figure 5 The hub 75 of the impeller 20a of the stage (i.e., the first stage) shown. A wear ring 79 is arranged between the hub 75 and the diffuser 70. The impeller 20a is mechanically coupled to the main shaft 15 and rotates with the secondary shaft 15, while the suction horn 74 and the diffuser 70 remain stationary. The rotation of the impeller 20a draws the fluid through the suction horn 74 and into the diffuser 70, specifically, the passage 71 between the outer diffuser portion 70a and the inner diffuser portion 70b.

[0047] The diffuser 70 is operably coupled to the second-stage impeller 20b near the shoulder 73 of the diffuser 70. The second-stage impeller 20b includes a front cover plate 81 and a rear cover plate 82. A wear ring 83 is arranged between the front cover plate 81 of the second-stage impeller 20b and the diffuser 70 of the first stage. The fluid flowing through the passage 71 of the diffuser 70 is further sucked into the second-stage impeller 20 due to the rotation of the second-stage impeller 20b, which is caused by the mechanical coupling of the second-stage impeller 20b with the main shaft 10. Due to the reduction system 50, the second-stage impeller 20b rotates at a different speed from the first-stage impeller 20a.

[0048] Figure 6 Schematically shows a method according to an embodiment of the present invention having a device arranged between two separate shafts. Figure 2 The pump 100 shown in FIG. 1 is a pump 101 of the reduction system 50 at different positions in the pump 100. The structure and function of the pump 101 are similar to those of FIG. Figure 2The pump 101 in FIG. 1 is the same as the pump 101 in FIG. 1 , except that the reduction system 50 is located between the second stage 20b and the third stage 20c. For example, the stages 20a and 20b are mounted to the secondary shaft 15, and the stages 20c and 20d are mounted to the main shaft 10. The reduction system 50 allows a speed difference between the main shaft 10 and the secondary shaft 15, so that the stages 20a and 20b can operate at a different (e.g., lower) speed than the other stages 20c, 20d. The speed difference between the shafts 10, 15 minimizes the net positive suction head and allows the overall length of the pump 101 to be smaller. The reduction system 50 is arranged between the main shaft 10 and the secondary shaft 15. For example, the end of the main shaft 10 is attached to a component of the reduction system 50, such as a pinion or planetary gear, and the end of the secondary shaft 15 is also attached to a component of the reduction system 50. In some embodiments, the end of the main shaft 10 and / or the end of the secondary shaft 15 are structurally integral with the components of the reduction system 50.

[0049] Figure 7 A pump 102 having more than one deceleration system arranged according to an embodiment of the present invention is schematically shown. The structure and function of the pump 102 are similar to Figure 2 10 is the same as the pump 101 in the embodiment except that the pump 102 includes two reduction systems 50a, 50b. The first reduction system 50a is located between the first stage 20a and the second stage 20b, and the second reduction system 50b is located between the second stage 20 and the third stage 20c. For example, the stage 20a is mounted to the first secondary shaft 15a, the stage 20b is mounted to the second secondary shaft 15b, and the stage 20c and the stage 20d are mounted to the main shaft 10. The end of the main shaft 10 is attached to a component of the reduction system 50b, such as a pinion or a planetary gear, and the end of the second secondary shaft 15b is also attached to a component of the reduction system 50b, such as a pinion or a planetary gear. The opposite end of the second secondary shaft 15b is attached to the reduction system 50a, such as a pinion or a planetary gear, and the end of the first secondary shaft 15a is also attached to the reduction system 50a, such as a pinion or a planetary gear. In some embodiments, the ends of the main shaft 10 and / or the ends of the secondary shafts 15a, 15b are structurally integral with components of the reduction systems 50a, 50b, respectively.

[0050] The reduction system 50a allows a speed difference between the first countershaft 15a and the second countershaft 15b, so that the stage 20a can be operated at a different (e.g., lower) speed than the stage 20b, and thus also at a different speed than the other stages 20c, 20d. The reduction system 50b allows a speed difference between the second countershaft 15b and the main shaft 10, so that the stage 20b can be operated at a different (e.g., lower) speed than the stage 20a, and thus also at a different speed than the other stages 20c, 20d. The speed difference between the shafts 10, 15a, 15b minimizes the net positive suction head and allows the overall length of the pump 102 to be smaller.

[0051] Although the present disclosure has been described in conjunction with the above-mentioned specific embodiments, it is apparent that many alternatives, modifications and variations will be apparent to those skilled in the art. Therefore, the preferred embodiments of the present disclosure as described above are intended to be illustrative, rather than restrictive. Various changes may be made without departing from the spirit and scope of the present invention as required by the following claims. The claims provide the coverage of the present invention and should not be limited to the specific examples provided herein.

Claims

1. A vertically suspended centrifugal pump, characterized in that: The vertically suspended centrifugal pump includes a speed reduction system disposed between a first shaft and a second shaft to allow a speed difference between the first shaft and the second shaft.

2. The vertically suspended centrifugal pump according to claim 1, characterized in that: The vertically suspended centrifugal pump also includes a first stage operably coupled to the second shaft.

3. The vertically suspended centrifugal pump according to claim 2, characterized in that: The vertically suspended centrifugal pump also includes a second stage operably coupled to the first shaft.

4. The vertically suspended centrifugal pump according to claim 3, characterized in that: During operation of the vertically suspended centrifugal pump, the first stage operates at a lower speed than the second stage according to the speed difference between the first shaft and the second shaft.

5. The vertically suspended centrifugal pump according to claim 4, characterized in that: During operation of the vertically suspended centrifugal pump, the second stage is an impeller operating at a speed of 3600 rpm or above.

6. The vertically suspended centrifugal pump according to claim 1, characterized in that: The vertically suspended centrifugal pump also includes a third stage and a fourth stage operably coupled to the first shaft.

7. The vertically suspended centrifugal pump according to claim 1, characterized in that: The reduction system is a spur gear system.

8. The vertically suspended centrifugal pump according to claim 1, characterized in that: The reduction system is a planetary gear system.

9. The vertically suspended centrifugal pump according to claim 1, characterized in that: The reduction system is a hydraulic coupling reduction gear.

10. A vertically suspended centrifugal pump, characterized in that: The vertically suspended centrifugal pump includes: a main shaft driven at a first speed; a plurality of tandem-stage impellers coupled to the main shaft; A deceleration system comprising: a first pinion gear operably connected to the main shaft and configured to rotate at the first speed, a first gear set meshing with the first pinion and configured to rotate at a second speed reduced from the first speed, a second gear set meshing with the second pinion and configured to rotate at the second speed; a layshaft operatively connected to the second pinion of the reduction system and configured to rotate at the second speed; and A first stage impeller is coupled to the countershaft.

11. The vertically suspended centrifugal pump according to claim 10, characterized in that: The reduced speed is reduced by a gear ratio between the first pinion and the first gear set.

12. The vertically suspended centrifugal pump according to claim 10, characterized in that: The first gear set is larger than the second gear set.

13. The vertically suspended centrifugal pump according to claim 10, characterized in that: The net positive suction head of the first stage impeller is minimized by operating at the second speed, while the plurality of tandem stage impellers operate at the first speed.

14. The vertically suspended centrifugal pump according to claim 10, characterized in that: The first speed is 3600 rpm or above.

15. A vertically suspended centrifugal pump, characterized in that: The vertically suspended centrifugal pump includes: a main shaft driven at a first speed; a plurality of tandem-stage impellers coupled to the main shaft; A deceleration system comprising: a star gear operably connected to the main shaft and configured to rotate at the first speed, at least one planetary gear meshing with the star gear and the fixed gear, the at least one planetary gear being configured to rotate at a second speed reduced from the first speed, and a carrier coupled to the at least one planetary gear and configured to rotate at the second speed; a countershaft operably coupled to the carrier and configured to rotate at the second speed; and A first stage impeller is coupled to the countershaft.

16. The vertically suspended centrifugal pump according to claim 15, characterized in that: The net positive suction head of the first stage impeller is minimized by operating at the second speed, while the plurality of tandem stage impellers operate at the first speed.

17. The vertically suspended centrifugal pump according to claim 15, characterized in that: The first speed is 3600 rpm or above.

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