Impeller locking collar

Abstract

Generally described is a technique for holding an impeller of a pump assembly axially in position using an impeller locking collar by loading the impeller locking collar against a ring element. In a centrifugal pump assembly, one side of the shaft has a larger diameter for the impeller to abut against. The other side of the shaft can be fitted with an impeller locking collar comprising two parts that can be threaded together and held in position by being fastened against a ring element such as a split ring or a spiral lock. Anti-rotation can be achieved to prevent loosening of the impeller locking collar by providing a counter thread that prevents the shaft from rotating. Secondary anti-rotation can be provided by one or more set screws in the impeller locking collar.

Description

Background Art

[0001] Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.

[0002] A centrifugal pump is a rotary machine designed to move fluid by transferring rotational energy through a driven rotor to an impeller. Fluid enters the centrifugal pump at the suction port where the impeller is located. The rotation of the impeller is controlled by a driver that rotates a shaft connected to the impeller. The rotational motion of the impeller generates a centrifugal force that increases the velocity of the fluid, causing the fluid to flow through the pump casing to the outlet. At startup, a centrifugal pump has a flooded suction line around the impeller with enough fluid to create a pressure differential and thus pump the fluid.

[0003] Although the main force acting on the impeller is the rotational force provided by the shaft of the pump, axial thrust loads can also be caused by the uneven distribution of pressure between the front and rear shrouds of the impeller. The radial impeller rotating in the liquid produces a centrifugal effect, which generates discharge pressure. The difference between the discharge pressure and the suction pressure causes axial thrust to act on the impeller. In a multistage pump, the axial thrust can increase with the number of stages. Summary of the invention

[0004] The present disclosure generally describes an impeller locking collar that holds an impeller of a pump assembly axially in place by loading the collar against a ring element.

[0005] According to some examples, an impeller locking collar for a pump may include a first portion configured to fit around a shaft of the pump proximate a base of an impeller of the pump, the first portion including a first set of threads facing the shaft; a second portion configured to fit around the shaft and partially fit between the first portion and the shaft, the second portion including a second set of threads facing the first portion and a recess away from the base of the impeller; and a ring element fitted around the shaft within the recess of the second portion, the ring element being configured to receive a thrust load of the impeller during operation of the pump.

[0006] According to other examples, the impeller locking collar may further include at least one set screw that is assembled into a hole in the second portion, the at least one screw being configured to secure the second portion to the shaft. The first set of threads may be convex and the second set of threads may be concave. Alternatively, the first set of threads may be concave and the second set of threads may be convex. The ring element may be an open ring, a retaining ring, or a spiral lock. The open ring may include two complementary parts configured to surround the shaft. The directions of the first set of threads and the second set of threads may be selected so that the first and second parts move away from each other in response to vibration of the shaft during operation of the pump. At least a portion of the first portion, the second portion, and the ring element may be in a cavity of the head portion that is different from the waterway cavity of the pump housing to avoid exposure to the fluid conveyed by the impeller.

[0007] According to another example, a centrifugal pump assembly may include a housing, an impeller positioned within a first cavity of the housing and configured to transfer a fluid between a suction opening of the pump assembly and a discharge opening of the pump assembly, a shaft coupled to the impeller and configured to rotate the impeller to transfer the fluid between the suction opening of the pump assembly and the discharge opening of the pump assembly, and an impeller locking collar. The impeller locking collar is fitted around the shaft in a second cavity of the housing to relieve residual thrust loads of the impeller during operation of the pump assembly and includes a first portion configured to fit around the shaft near a base of the impeller, the first portion including a first set of threads facing the shaft, a second portion configured to fit around the shaft and partially fit between the first portion and the shaft, the second portion including a second set of threads facing the first portion and a recess away from the base of the impeller, and a ring element fitted around the shaft within the recess of the second portion, the ring element being configured to receive thrust loads of the impeller during operation of the pump assembly.

[0008] According to other examples, the diameter of the shaft on the opposite side of the impeller relative to the side having the impeller locking collar may be greater than the diameter of the shaft on the side of the impeller having the impeller locking collar. The pump assembly may be a multi-stage pump assembly and include another impeller coupled to the shaft in series with the impeller. The impeller locking collar may also include at least one set screw, the at least one set screw being assembled into a hole in the second portion, the at least one screw being configured to secure the second portion to the shaft. The ring element may be a split ring, a retaining ring, or a spiral lock. The split ring may include two complementary portions configured to surround the shaft. The directions of the first set of threads and the second set of threads may be selected so that the first portion and the second portion move toward each other in response to vibration of the shaft during operation of the pump assembly.

[0009] According to some examples, a method for maintaining an axial position of an impeller in a pump is described. The method may include fitting a first portion of an impeller locking collar around a shaft of the pump proximate a base of the impeller, the first portion including a first set of threads facing the shaft; fitting a second portion of the impeller locking collar around the shaft and partially between the first portion and the shaft by screwing into the second portion, the second portion including a second set of threads facing the first portion and a recess away from the base of the impeller; positioning a ring element around the shaft within the recess of the second portion; and screwing out the second portion to push against the ring element so that the ring element receives thrust loads of the impeller during operation of the pump.

[0010] According to other examples, the method may further include fitting at least one set screw into a hole in the second portion to secure the second portion to the shaft. Positioning the ring element around the shaft may include positioning a two-part split ring around the shaft. The method may further include fitting the first portion and the second portion in a cavity of the head portion that is different from a waterway cavity of the pump housing to avoid exposure to fluid conveyed by the impeller. The method may further include selecting the orientation of the first set of threads and the second set of threads so that the first portion and the second portion move toward each other in response to vibration of the shaft during operation of the pump.

[0011] The foregoing summary is illustrative only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims taken in conjunction with the accompanying drawings. It should be understood that these drawings depict only several embodiments according to the present disclosure and, therefore, should not be considered to limit the scope of the present disclosure, which will be described with additional specificity and detail through the use of these drawings, in which:

[0013] Figure 1 An exemplary single-stage radially split pump having an impeller in which an impeller locking collar may be implemented is shown;

[0014] Figure 2 shows a cross-sectional cutaway view of a single-stage pump having an impeller;

[0015] Figure 3 shows a cross-sectional cutaway view of a two-stage pump having an impeller locking collar; and

[0016] Figure 4 A close-up cross-sectional view of an impeller with an impeller locking collar is shown,

[0017] Some of them are arranged according to at least some embodiments described herein. DETAILED DESCRIPTION

[0018] Reference is made to the accompanying drawings in the following detailed description, which form a part of this document. In the drawings, similar symbols generally identify similar components unless the context otherwise dictates. The illustrative embodiments described in the detailed description, drawings, and claims are not intended to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. The various aspects of the present disclosure as generally described herein and shown in the drawings may be arranged, substituted, combined, separated, and designed in a variety of different configurations, all of which are expressly contemplated herein.

[0019] The present disclosure relates generally, and more particularly, to methods, apparatus, systems and / or devices for axially holding an impeller of a pump assembly using an impeller locking collar by loading the collar onto a ring element.

[0020] Briefly, technology is generally described for holding an impeller of a pump assembly axially in position using an impeller locking collar by loading the collar onto a ring element. In a centrifugal pump assembly, one side of the shaft has a larger diameter for the impeller to abut against. The other side of the shaft can be fitted with an impeller locking collar, which includes two parts that can be threaded together and hold the impeller in position by fastening against a ring element such as a split ring or a spiral lock. Anti-rotation can be achieved by providing a counter-thread that prevents the shaft from rotating to avoid loosening of the impeller locking collar. Secondary anti-rotation can be provided by one or more set screws in the impeller locking collar.

[0021] Figure 1 An exemplary single-stage radially split pump having an impeller is shown, wherein an impeller locking collar may be implemented in accordance with at least some embodiments described herein.

[0022] like Figure 1 As shown, the exemplary pump 100 may include a pump housing 102, a bearing housing 110, a shaft 104, a suction port 108, and an output port 106. In operation, an external drive (not shown) coupled to the shaft 104 may rotate the shaft 104, which in turn may rotate an impeller inside the pump housing 102, thereby transferring fluid from the suction port 108 to the output port 106.

[0023] Centrifugal pumps are used to transport fluids by converting rotational kinetic energy into the hydrodynamic energy of the fluid stream. The rotational energy usually comes from an engine or electric motor (external drive). The fluid enters the pump impeller along or near the axis of rotation and is accelerated by the impeller, flowing radially outward into the diffuser or vortex chamber (housing) where it exits. Part of the energy goes into the kinetic energy of the fluid. The fluid enters axially through the perforations of the housing, is captured in the impeller blades, and rotates tangentially and radially outward until it exits through the circumferential portion of the impeller into the diffuser portion of the housing. The fluid gains velocity and pressure as it passes through the impeller.

[0024] The impeller is the rotating component of a centrifugal pump that transfers energy from the motor driving the pump to the fluid being pumped by accelerating the fluid outward from the center of rotation. The speed achieved by the impeller is transferred to the pressure when the outward movement of the fluid is restricted by the pump casing. Centrifugal pumps can be single-stage or multi-stage. Pumps containing two or more impellers are called multi-stage centrifugal pumps. The impellers can be mounted on the same shaft or on different shafts. At each stage, the fluid is directed to the center and then on the outside diameter to the discharge port. For higher pressures at the outlet, the impellers can be connected in series. For higher flow output, the impellers can be connected in parallel.

[0025] An exemplary centrifugal pump according to the present disclosure may include an impeller locking collar assembly that holds the impeller axially in place by loading the impeller locking collar against a split ring. The impeller locking collar may be threaded to allow installation and adjustment against the split ring. Anti-rotation may be achieved to prevent loosening of the impeller locking collar during operation by providing a counter thread that prevents shaft rotation. Secondary anti-rotation may be provided by one or more set screws in the impeller locking collar.

[0026] Figure 2 A cross-sectional cutaway view of a single-stage pump with an impeller is shown.

[0027] As shown, exemplary single-stage pump 200 may include port 202 (suction or output), housing 204 , first bearing housing 206 , shaft 208 , impeller 210 , cavity 212 within housing 204 , wear ring 214 , and second bearing housing 216 .

[0028] In operation, fluid may enter axially through suction port 202 and be pushed tangentially and radially outward until exiting through a circumferential portion of impeller 210 into a diffuser portion of housing 204. The fluid may gain both velocity and pressure as it passes through impeller 210. In some cases, first bearing housing 206 may include radial bearings and second bearing housing 216 may include axial (thrust) bearings. Wear rings 214 may be used to stabilize impeller 210.

[0029] In operation, the impeller 210 is subjected to different forces. Although an ideal impeller will only receive rotational force from the shaft 208, the axial thrust caused by the uneven distribution of pressure between the front and rear shrouds of the impeller (the difference between the discharge pressure and the suction pressure) can cause the impeller to be pushed laterally to the shaft axis. Axial thrust loads can cause vibration and power transmission losses, as well as reduce the life expectancy of pump bearings (and / or shafts). Some pump systems may include an impeller lock nut fixed by threads on the shaft near the impeller, which may cause reliability problems due to bending moments and stresses. Threads can form stress concentrations that can cause premature fatigue failure of the shaft 208. Other systems can load the impeller with a thrust load to push the impeller against the shaft 208, but this approach may involve custom machined parts (wear rings), etc., thereby increasing the complexity of the pump assembly and thereby reducing reliability.

[0030] Figure 3 Shown is a cross-sectional cutaway view of a two-stage pump having an impeller locking collar, arranged in accordance with at least some embodiments described herein.

[0031] Figure 3The exemplary two-stage pump 300 in FIG. 1 includes a port 302 (suction or output), a housing 304, a first bearing housing 310, a shaft 308, a first stage impeller 314, a second stage impeller 312, a cavity 306 within the housing 304, a head 320 portion of the housing 304, a second bearing housing 316, and an impeller locking collar 318. The first bearing housing 310 can be a radial bearing housing and include a deep row of radial ball bearings close to the impeller. The second bearing housing 316 can be an axial (thrust) bearing housing and include angular contact bearings mounted back-to-back on the thrust side. Although referred to as thrust bearings, bearings at thrust locations in a pump can generally absorb loads in both the axial and radial directions.

[0032] The main components of the centrifugal pump assembly according to some examples may include a housing 304, an impeller (e.g., impeller 314) positioned in a first cavity of the housing, and a shaft coupled to the impeller and configured to rotate the impeller to transfer fluid between the suction opening of the pump assembly and the output opening of the pump assembly. The impeller may be configured to transfer fluid between the suction opening of the pump assembly and the output opening of the pump assembly. The pump assembly may also include an impeller locking collar 318. The impeller locking collar 318 may be assembled around the shaft 308 to relieve the residual thrust load of the impeller during operation of the pump assembly. The impeller locking collar 318 includes a first portion (concave impeller piece) configured to be assembled around the shaft near the base of the impeller. The first portion may include a first set of threads facing the shaft. The impeller locking collar 318 may also include a second portion configured to be assembled around the shaft and partially assembled between the first portion and the shaft. The second portion may include a second set of threads facing the first portion and a recess away from the base of the impeller. The ring element may be assembled around the shaft in the recess of the second portion. The first and second portions may hold the impeller in place by being secured against a ring element configured to receive thrust loads of the impeller during operation of the pump assembly.

[0033] In some examples, the diameter of the shaft on the side of the impeller opposite the side having the impeller locking collar can be greater than the diameter of the shaft on the side of the impeller having the impeller locking collar so that the impeller can abut the larger diameter shaft portion. The direction of the threads on the first and second portions of the impeller locking collar can be selected so that the first and second portions move toward each other (tighten and do not loosen) in response to vibration of the shaft during operation of the pump assembly. The secondary anti-rotation mechanism can include at least one set screw that fits into a hole in the second portion of the impeller locking collar and secures the second portion to the shaft.

[0034] Although examples are discussed herein using a specific pump design, embodiments are not limited to the exemplary configuration. An impeller locking collar that holds the impeller of a pump assembly axially in place by loading the collar against a ring element can be implemented in a variety of pump types, such as cantilever pumps, single-stage or multi-stage pumps, axially split bearing pumps, radially split cartridge multi-stage pumps, vertical double-casing pumps, and the like. Embodiments can also be implemented in other forms of rotating machines that utilize shafts and impeller-shaped components that are subject to axial thrust.

[0035] Figure 4 Shown is a close-up cross-sectional cutaway view of an impeller having an impeller locking collar, arranged in accordance with at least some embodiments described herein.

[0036] As shown in diagram 400, impeller 410 can be coupled to shaft 416 and cavity 406 of the pump housing. An impeller locking collar as discussed herein can include a first portion 404 (e.g., a female collar piece), a second portion 402 (e.g., a male collar piece), and a ring element 414 received in a second cavity 422 of a head portion 418 of the pump housing. The impeller locking collar can also include a set screw 412 and complementary threads 420 on opposing surfaces of the first and second portions. Wear ring 408 can be one of a pair of wear rings on either side of impeller 410 to help stabilize the impeller and reduce wear thereon.

[0037] The first portion 404 of the impeller locking collar can be configured to fit around the shaft of the pump near the base of the impeller 410. The first portion 404 may include a first set of threads facing the shaft 416. The impeller locking collar may also include a second portion 402 configured to fit around the shaft 416 and partially fit between the first portion 404 and the shaft 416. The second portion may include a second set of threads facing the first portion 404 and a recess away from the base of the impeller 410. The ring element 414 around the shaft 416 that fits within the recess of the second portion 402 can be arranged to receive the thrust load of the impeller 410 during operation of the pump. The impeller locking collar may also include at least one set screw 412 that fits into a hole in the second portion 402 to secure the second portion 402 (and thereby the impeller locking collar) to the shaft 416. In some examples, two or more set screws may be used. The complementary threads of the first and second portions (420) may be a male / female pair or a female / male pair, respectively. The ring element 414 may be a split ring, a retaining ring, or a screw lock.The split ring may include two complementary parts configured to surround a shaft.

[0038] The orientation of the first set of threads and the second set of threads may be selected so that the first portion and the second portion move (tighten) away from each other in response to vibration of the shaft during operation of the pump. The first portion 404, the second portion 402, and at least a portion of the ring element 414 may be in a cavity different from the head 418 portion of the waterway cavity 406 of the pump housing to avoid exposing the impeller locking collar parts and the gaps associated with these parts to the high-speed fluid conveyed by the impeller. This separation may increase the life expectancy and reliability of the pump by reducing the likelihood of failure due to solids in the pumped fluid becoming stuck in the gaps and reducing the effectiveness of the impeller locking collar.

[0039] When assembling the exemplary pump, the first portion 404 of the impeller locking collar can be assembled around the shaft 416 near the base of the impeller 410, with the first set of threads facing the shaft first. Next, the second portion 402 of the impeller locking collar (whose second set of threads faces the first portion) can be assembled around the shaft 416 and partially assembled between the first portion 404 and the shaft 416 by threading in the second portion 402. The ring element 414 can be positioned around the shaft 416 within a recess of the second portion 402, which is away from the base of the impeller 410, and the second portion 402 can be screwed out to push against the ring element 414 so that the ring element (e.g., a split ring) receives the thrust load of the impeller 410 during operation of the pump. In addition, at least one set screw 412 can be inserted into a hole in the second portion 402 to secure the second portion 402 (and thereby the entire impeller locking collar) to the shaft 416.

[0040] Disclosed herein are methods and apparatus for maintaining an impeller in an axial position in the presence of axial thrust during pump operation. The benefits of the presently disclosed pump assembly configuration are numerous. For example, the methods and apparatus employed herein can increase the life expectancy of a pump without modifying the thrust profile of an impeller with a different diameter wear ring or similar approach. In addition, the dual anti-rotation measures of the reverse thread direction and the set screw ensure that thrust load relief is maintained in the presence of rotational and vibrational forces.

[0041] The present disclosure is not limited to the specific embodiments described in this application, and the embodiments are intended to be illustrations of various aspects. Many modifications and variations may be made without departing from the spirit and scope of the present disclosure. In addition to the methods and devices listed herein, functionally equivalent methods and devices within the scope of the present disclosure are also possible according to the foregoing description. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is limited only by the terms of the appended claims and the full scope of equivalents authorized by the claims. The terms used herein are only used to describe specific embodiments and are not intended to be restrictive.

[0042] The subject matter described herein sometimes illustrates different components that are contained in or connected to different other components. Such depicted architectures are merely examples, and many other architectures that realize the same functionality can actually be implemented. In a conceptual sense, any component arrangement that realizes the same functionality is actually "associated", so that the desired functionality is realized. Therefore, any two components that are combined to realize a specific functionality herein can be considered to be "associated" with each other, so that the desired functionality is realized, regardless of the architecture or intermediate components. Similarly, any two components that are so associated can also be considered to be "operably connected" or "operably connected" to realize the desired functionality, and any two components that can be so associated can also be considered to be "operably connected" to realize the desired functionality. The specific examples that can be operably connected include but are not limited to components that can be physically connected and / or physically interact, and / or components that can wirelessly interact and / or wirelessly interact, and / or components that logically interact and / or can logically interact.

[0043] With respect to the use of substantially any plural and / or singular terms herein, those skilled in the art may convert the plural to the singular and / or the singular to the plural as appropriate to the context and / or application. For clarity, various singular / plural arrangements may be expressly set forth herein.

[0044] In general, the terms used herein and particularly in the appended claims (e.g., the appended claim bodies) are generally intended to be "open" terms (e.g., the term "including" should be interpreted as "including but not limited to", the term "having" should be interpreted as "having at least", the term "includes" should be interpreted as "includes but is not limited to", etc.). It will be further understood by those skilled in the art that if a specific number of introduced claim recitations is intended, such intent will be explicitly recited in the claim, and in the absence of such a recitation, no such intent is present. For example, to aid understanding, the following appended claims may include the use of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed as implying that a claim recitation introduced by the indefinite article "a" or "an" will limit any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim contains the introductory phrases "one or more" or "at least one" as well as the indefinite article "a" or "an" (e.g., "a" and / or "an" should be construed to mean "at least one" or "one or more"); the same holds true for the use of the definite article used to introduce a claim recitation. In addition, even if a specific number of introduced claim recitations is expressly recited, one skilled in the art will recognize that such recitation should be construed to mean at least that number (e.g., the express recitation "two recitations" without other modifiers means at least two recitations or two or more recitations).

[0045] Furthermore, in those instances where a convention similar to "at least one of A, B, and C, etc." is used, generally such construction is intended in a sense that one skilled in the art would understand the convention to mean (e.g., "a system having at least one of A, B, and C" would include, but not be limited to, systems having only A, only B, only C, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). One skilled in the art would further understand that virtually any disjunctive word and / or phrase indicating two or more alternative terms, whether in the specification, claims, or drawings, would be understood to encompass the possibility of including one of the terms, either of the terms, or both of the terms. For example, the phrase "A or B" would be understood to include the possibility of "A" or "B" or "A and B."

[0046] For any and all purposes, such as in providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any enumerated range can be easily identified by being fully described, and the same range can be decomposed into at least the same two, three, four, five, ten, etc. As a non-limiting example, each range discussed herein can be easily decomposed into a lower third, a middle third, and an upper third, etc. It will also be understood by those skilled in the art that all languages, such as "up to", "at least", "exceeding", "less than", etc., contain the enumerated numbers and refer to the ranges that can be subsequently decomposed into subranges as discussed above. Finally, the range includes each individual member. Therefore, for example, a group with 1-3 units refers to a group with 1, 2, or 3 units. Similarly, a group with 1-5 units refers to a group with 1, 2, 3, 4, or 5 units, and so on.

[0047] While various aspects and embodiments have been disclosed herein, other aspects and embodiments are possible.The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

1. An impeller locking collar for a pump, the impeller locking collar comprising: a first portion configured to fit around a shaft of the pump proximate a base of an impeller of the pump, the first portion including a first set of threads facing the shaft; a second portion configured to fit around the shaft and partially between the first portion and the shaft, the second portion including a second set of threads facing the first portion and a recess in the base distal from the impeller, wherein the first set of threads and the second set of threads are arranged to mate in an orientation that prevents rotation of the shaft, and wherein the orientations of the first set of threads and the second set of threads are selected to effectively cause the first portion and the second portion to move away from each other in response to vibration of the shaft during operation of the pump; as well as A ring element including a split ring fits around the shaft within the recess of the second portion, the ring element being configured to receive thrust loads of the impeller during operation of the pump.

2. The impeller locking collar of claim 1, further comprising: At least one set screw is fitted into a hole in the second portion, the at least one set screw being configured to secure the second portion to the shaft.

3. The impeller locking collar of claim 1 , wherein the first set of threads are male and the second set of threads are female.

4. The impeller locking collar of claim 1 , wherein the first set of threads are female and the second set of threads are male.

5. The impeller locking collar of claim 1, wherein said split ring comprises two complementary portions configured to surround said shaft.

6. The impeller locking collar of claim 1, wherein the first portion, the second portion, and at least a portion of the ring element are located in a cavity of the head portion that is different from a waterway cavity of a pump casing to avoid exposure to fluid conveyed by the impeller.

7. A centrifugal pump assembly, comprising: shell; an impeller positioned within the first cavity of the housing and configured to transfer fluid between a suction opening of the pump assembly and an output opening of the pump assembly; a shaft coupled to the impeller and configured to rotate the impeller to transfer the fluid between the suction opening of the pump assembly and the delivery opening of the pump assembly, wherein a diameter of the shaft on an opposite side of the impeller from a side having the impeller locking collar is greater than a diameter of the shaft on a side of the impeller having the impeller locking collar; as well as an impeller locking collar, the impeller locking collar being fitted around the shaft in the second cavity of the housing to relieve residual thrust loads of the impeller during operation of the pump assembly, the impeller locking collar comprising: a first portion configured to fit around the shaft near a base of the impeller, the first portion including a first set of threads facing the shaft; a second portion configured to fit around the shaft and partially between the first portion and the shaft, the second portion including a second set of threads facing the first portion and a recess in the base distal from the impeller, wherein the first set of threads and the second set of threads are arranged to mate in an orientation that prevents rotation of the shaft, and wherein the orientations of the first set of threads and the second set of threads are selected to effectively cause the first portion and the second portion to move toward each other in response to vibration of the shaft during operation of the pump assembly; and A split ring element fits around the shaft within the recess of the second portion, the split ring element being configured to receive a thrust load of the impeller during the operation of the pump assembly.

8. The pump assembly of claim 7, wherein the pump assembly is a multi-stage pump assembly and includes a further impeller coupled to the shaft in series with the impeller.

9. The pump assembly of claim 7, wherein the impeller locking collar further comprises: At least one set screw is fitted into a hole in the second portion, the at least one set screw being configured to secure the second portion to the shaft.

10. The pump assembly of claim 7, wherein the split ring element includes two complementary portions configured to surround the shaft.

11. A method for maintaining the axial position of an impeller in a pump, the method comprising: fitting a first portion of an impeller locking collar about a shaft of the pump proximate a base of the impeller, the first portion including a first set of threads facing the shaft, wherein a diameter of the shaft on an opposite side of the impeller to a side having the impeller locking collar is greater than a diameter of the shaft on a side of the impeller having the impeller locking collar; Fitting a second portion of the impeller lock ring around the shaft and partially between the first portion and the shaft by screwing it into the second portion, the second portion comprising a second set of threads facing the first portion and a recess away from the base of the impeller, wherein the first set of threads and the second set of threads are arranged to cooperate in a direction that prevents rotation of the shaft; positioning a split ring element about the shaft within the recess of the second portion; as well as unscrewing the second portion to push against the split ring element, thereby effectively causing the split ring element to receive the thrust load of the impeller during operation of the pump, Wherein, the method further comprises: selecting the directions of the first set of threads and the second set of threads to effectively cause the first portion and the second portion to move toward each other in response to vibration of the shaft during the operation of the pump.

12. The method of claim 11, further comprising: At least one set screw is fitted into the hole in the second portion to secure the second portion to the shaft.

13. The method of claim 11, further comprising: The first and second parts are assembled in a cavity of the head portion that is different from the waterway cavity of the pump housing to avoid exposure to the fluid conveyed by the impeller.

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