Patent Application
20240254999
This disclosure relates in general to a pump impeller for use in centrifugal pumps. More particularly, though not exclusively, to pumps for handling abrasive materials such as for example slurries and the like.
Various process steps in the minerals processing industry involve erosive contact with components of equipment which results in significant wear to the extent that frequent replacement is required. However, often the wear of a component is uneven depending on the nature of the process step.
For example, in the process of pumping abrasive slurries using a centrifugal slurry pump, a limiting factor on the centrifugal slurry pump wet end component wear life can be localised wear or very high wear rates in certain locations of the slurry pump liner or casing. In particular, it was identified that interaction of the centrifugal slurry pump impeller pumping vanes with the slurry, or fluid, gives rise to the formation of ‘horseshoe’ type vortices at the pressure side of the pumping vanes and in a similar way at the suction side of the pumping vanes. These vortices leave the centrifugal slurry pump impeller passageways and move around the pump casing in the form of an impeller wake. This wake causes erosion on the casing forming a ‘twin vortices’ like erosion pattern. In addition, it was identified that this wake affects the fluid entering the gap formed by the frame plate liner insert (also knowns as a back liner or drive side liner) and the impeller back shroud. As these vortices are strongest when leaving the impeller passageways, their action on the fluid entering the gap is strongest when the pumping fluid passes by the casing cutwater. This gives origin to a velocity enhanced area, which causes significant wear on the casing or liner at this location.
The various aspects disclosed herein may be applicable to all centrifugal slurry pumps and particularly to those that experience high wear rates on the liner or casing.
According to one aspect there is provided a centrifugal slurry pump impeller including: a back shroud with opposed inner and outer faces and an outer peripheral edge, a central axis, a plurality of pumping vanes extending from the inner main face of the back shroud, the pumping vanes being disposed in spaced apart relation, each pumping vane including opposed main side faces, a leading edge in the region of the central axis and a trailing edge in the region of the outer peripheral edge of the back shroud with passageways between adjacent pumping vanes, wherein the inner main face of the back shroud along the length of the passageways, leading from the leading edge to the trailing edge, includes a generally planar inner region beginning adjacent the leading edge of the plurality of pumping vanes, and an outer region ending at the outer peripheral edge of the back shroud, wherein the outer region of the inner face of the back shroud includes a lip formation with an apex including a convex surface.
According to another aspect, there is provided a centrifugal slurry pump assembly including: an outer casing, an inner liner arranged within the outer casing, the inner liner including a main liner and two side liners which form a pumping chamber when assembled, an impeller mounted for rotation within the pumping chamber, the impeller including: a back shroud with opposed inner and outer faces and an outer peripheral edge, a central axis, a plurality of pumping vanes extending away from the inner main face of the back shroud, the pumping vanes being disposed in spaced apart relation, each pumping vane including opposed main side faces, a leading edge in the region of the central axis and a trailing edge in the region of the outer peripheral edge of the back shroud with passageways between adjacent pumping vanes, wherein the inner main face of the back shroud along the length of the passageways, leading from the leading edge to the trailing edge, includes a generally planar inner region beginning adjacent the leading edge of the plurality of pumping vanes and an outer region ending at the outer peripheral edge of the back shroud, wherein the outer region of the inner face of the back shroud includes a lip formation with an apex including a convex surface, and wherein the pumping chamber includes a void between the outer peripheral edge of the back shroud and an inner peripheral surface of the inner liner to provide for the circulation of fluid in the pumping chamber when in use
In certain embodiments, the lip formation is located adjacent, or at the outer peripheral edge of the back shroud.
In certain embodiments, the surface of the inner region of the back shroud is in a plane which is perpendicular to the central axis.
In certain embodiments, the surface of the lip formation includes a transition region which blends with the surface of the inner region, wherein as the transition region moves away from the inner region, the transition region thickens in a direction away from the inner face of the back shroud.
In certain embodiments, the transition region begins after a midpoint along the length of the passageways. In a preferred form, the transition region begins after 75% of the length of the passageways. In a further preferred form, the transition region begins after 85% of the length of the passageways.
In certain embodiments, the transition region is in the form of a radius positioned tangent to the apex of the lip formation and tangent to the inner face of the back shroud.
In certain embodiments, the back shroud has a thickness between the inner face and the outer face of h, and the apex has a height from the inner face of the back shroud of about 0.3 h to about 0.5 h. In a further form, a length of the transition region and the lip formation is about 3 h to about 5 h. In yet a further form, a diameter of circle defining the convex surface of the apex is about 0.3 h to about 0.5 h.
In certain embodiments, the centrifugal slurry pump impeller further includes a front shroud with opposed inner and outer faces and an outer peripheral edge wherein the plurality of pumping vanes extend between the inner faces of the back shroud and the front shroud.
In certain embodiments, an inner region of the inner face of the front shroud located in the passageways is substantially planar, and is in a plane that is substantially perpendicular to the central axis.
In certain embodiments, an outer region of the inner face of the front shroud located in the passageways is substantially planar and is in a plane that is substantially perpendicular to the central axis.
Other aspects, features, and advantages will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of the inventions disclosed.
The accompanying drawings facilitate an understanding of the various embodiments.
Referring to
The pump 10 further comprises a pump inner liner 11 arranged within the outer casing 22 and which includes a main liner 12 and two side liners 14, 30. The side liner 14 is located nearer the rear end of the pump 10 (that is, nearest to the pedestal or base 112), and the other side liner (or front liner) 30 is located nearer the front end of the pump and inlet hole 28. The side liner 14 is also referred to as the back side part or frame plate liner insert and the side liner 30 is also referred to as the front side part or throatbrush. The main liner 12 comprises two side openings therein.
The two side casing parts 23, 24 of the outer casing 22 are joined together by bolts 27 located about the periphery of the casing parts 23, 24 when the pump is assembled for use. In some embodiments the main liner 12 can also be comprised of two separate parts which are assembled within each of the side casing parts 23, 24 and brought together to form a single main liner, although in the example shown in
When the pump is assembled, the side openings in the main liner 12 are filled by or receive the two side liners 14, 30 to form a continuously-lined pumping chamber 42 disposed within the pump outer casing 22. There is a space or void provided in the pumping chamber between the outer circumferential edge of the impeller 40 leading to the inner peripheral surface of the main liner 12 which allows the fluid pumped via the action of the impeller to circulate in the pumping chamber which then exits via the discharge outlet 29.
A seal chamber housing 114 encloses the side liner (frame plate liner insert, or back side part) 14 and is arranged to seal the space or chamber 118 between drive shaft 116 and the pedestal or base 112 to prevent leakage from the back area of the outer casing 22. The seal chamber housing takes the form of a circular disc section and an annular section with a central bore, and is known in one arrangement as a stuffing box 117. The stuffing box 117 is arranged adjacent to the side liner 14 and extends between the pedestal 112 and a shaft sleeve and packing that surrounds drive shaft 116.
The impeller 40 includes a hub 41 from which a plurality of circumferentially spaced pumping vanes 43 extend. A nose portion 47 extends forwardly from the hub 41 towards an impeller inlet 48 and an inlet passage 33 in the front liner 30. The impeller 40 further includes a front shroud 50 and a back shroud 51, the vanes 43 being disposed and extending therebetween and an impeller inlet 48.
The impeller front shroud 50 includes an inner face 55, an outer face 54 and a peripheral edge portion 56. The back shroud 51 includes an inner face 53, an outer face 52 and a peripheral edge portion 57. The front shroud 50 includes the inlet 48, being the impeller inlet and the vanes 43 extend between the inner faces of the shrouds 50, 51. The shrouds are generally circular or disc-shaped when viewed in elevation; that is in the direction of rotation axis X-X.
As illustrated in
Referring to
The location and function of the four passageways 6 means that this section of the slurry pump impeller 10 and particularly the area of the passageways 6 along the surfaces of the inner face of the back shroud 53 and the inner face of the front shroud 55 are the location of significant slurry flow. Typically, during operation there is a higher velocity on the suction side of the pumping vanes 43 adjacent the suction side face 8 and a lower velocity on the pressure, or pumping side face 7, of the pumping vane 43 near the leading edge. This differential in velocity leads to the formation of vortices adjacent the inner faces 53, 55 of the back and front shrouds 51, 50. Another type of known impeller is referred to as a semi-open impeller. A semi-open impeller includes just one back shroud and the pumping vanes extend from the back shroud towards the inlet of the centrifugal pump.
In
Turning to
The impeller 40 further includes a plurality of pumping vanes 43 extending between the inner main faces 53, 55 of the back and front shrouds 51, 50. The four pumping vanes 43 are disposed equally spaced from one another around the inner main faces 53, 55 of the back and front shrouds 51, 50 of the impeller 40. The pumping vanes 43 each include opposed main side faces 7, 8 a leading edge 71 in the region of the central axis and a trailing edge 70 in the region of the outer peripheral edges 57, 56 of the back and front shrouds 51, 50. The main side faces of the pumping vanes 43 include a pumping or pressure side face 7 and a suction side face 8.
A passageway 6 is located between each adjacent pumping vane 43. Each passageway 6 includes a blended region 110 located between each of the main side faces 7, 8 of the pumping vanes 43 and the inner faces 53, 55 of the front and back shrouds 50, 51. The blended regions act as a transition surface between the surface of the main side faces 7, 8 and the inner faces 53, 55 of the front and back shrouds 50, 51.
The inner main faces 53, 55 of the back and front shrouds 50, 51 along the length of the passageways 6 leading from the leading edge 71 to the outer peripheral edge 57, 56 include an inner region 125 which starts at the beginning of the passageways 6 adjacent the leading edge 71 of the plurality of pumping vanes 43, and also an outer region 130, which ends at the outer peripheral edge 56, 57 of the front and back shrouds 50, 51. The outer region 130 of the back shroud includes a lip formation 105 whereas the outer region of the front shroud in the embodiment shown does not include a lip formation 105. Rather the outer region of the inner face of the front shroud is substantially planar. The present disclosure also envisages embodiments where the front shroud of a closed impeller also includes a lip formation.
As is shown in
The surface of the inner region 125 located on the inner face 53 of back shroud 51 is generally planar and may also be generally in line with a plane that is perpendicular to the central axis.
The surface of the lip formation 105 includes a transition region 140 which blends with the planar surface of the inner region 125 of the back shroud 51. As the transition region 140 moves away from the inner region 125 in a direction towards the outer peripheral edge 57 of the back shroud 51, the transition region thickens. Otherwise stated, the back shroud thickens so that the inner face 53 of the back shroud 51 moves towards the inner face 55 of the front shroud 50. Alternatively, in the case of a semi-open impeller, the inner face of the back shroud moves towards the direction of the inlet when the impeller is installed in a centrifugal pump assembly.
The transition region continues to thicken as the inner face of the back shroud moves towards the outer peripheral edge 57 until reaching an apex 135 of the lip formation 105. At the location of the apex 135, the inner face 53 of the back shroud 51 is closer to the inner face 55 of the front shroud 50 than at the transition region 140 and the inner region 125.
The transition region 140 may begin after a midpoint along the length of the passageways 6. In a preferred form, the transition region 140 begins after 75% of the length of the passageways 6. In yet a further preferred form, the transition region 140 begins after 85% of the length of the passageways 6. The transition region 140 may also be in the form of a concave surface, whereas the apex 135 of the lip formation 105 is preferably rounded in the form of a convex surface in a radial direction from the central axis. Furthermore, the ramp or transition region 140 may be in the form of a radius positioned tangent to the apex of the lip formation 135 and tangent to the inner face 53 of the back shroud.
Referring specifically to the embodiment shown in
The inner regions 125 of the front and back shrouds 50, 51 are substantially planar and may be in a plane that is substantially perpendicular to the central axis. The outer region of the front shroud 50 may also be substantially planar, and is generally in a plane that is perpendicular to the central axis.
As previously discussed herein, the interaction of the centrifugal slurry pump impeller pumping vanes with the slurry, or fluid, gives rise to the formation of ‘horseshoe’ type vortices at the pressure side of the pumping vanes and in a similar way at the suction side of the pumping vanes. These vortices leave the centrifugal slurry pump impeller passageways and move around the pump casing in the form of an impeller wake. This wake causes erosion on the casing forming a ‘twin vortices’ like erosion pattern and affects the fluid entering the gap formed by the back liner and the impeller back shroud. As these vortices are strongest when leaving the impeller passageways, their action on the fluid entering the gap is strongest when the pumping fluid passes by the casing cutwater. It was found that the lip formation 140 appearing on the outer region 130 of the back shroud 51 guides these vortices towards the center line of the casing in the pumping chamber, making the vortices weaker and therefore reducing their capacity of inducing velocity and causing erosive wear of the pump casing.
It was also found that including a lip formation with a convex or rounded surface at the apex provided reduced fluid flow separation at the peripheral edge of the back shroud. Flow separation, where part of the fluid stays attached to the inner surface of the back shroud, was also found to create a secondary group of vortices. By providing the convex or rounded surface at the apex of the lip formation, flow separation was significantly reduced enhancing the benefits of the lip formation for reducing localized wear during use.
Referring to
The lip formation is shown to reduce the intensity of vortices leaving the impeller during operation. This reduces the vortex capacity of inducing velocities around it, in particular on the fluid entering the gap between the back liner and the back shroud of the impeller significantly reducing wear in these regions.
In the foregoing description of certain embodiments, specific terminology has been resorted to for the sake of clarity. However, the disclosure is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes other technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as “left” and right”, “front” and “rear”, “above” and “below” and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms.
In this specification, the word “comprising” is to be understood in its “open” sense, that is, in the sense of “including”, and thus not limited to its “closed” sense, that is the sense of “consisting only of”. A corresponding meaning is to be attributed to the corresponding words “comprise”, “comprised” and “comprises” where they appear.
In addition, the foregoing describes only some embodiments of the invention(s), and alterations, modifications, additions and/or changes can be made thereto without departing from the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not restrictive.
Furthermore, invention(s) have described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention(s). Also, the various embodiments described above may be implemented in conjunction with other embodiments, e.g., aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. Further, each independent feature or component of any given assembly may constitute an additional embodiment.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021901936 | Jun 2021 | AU | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AU2022/050650 | 6/24/2022 | WO |
