EP2978975B1

EP2978975B1 - Slurry pump impeller

Info

Publication number: EP2978975B1
Application number: EP14774127.6A
Authority: EP
Inventors: Craig Ian Walker
Original assignee: Weir Minerals Australia Ltd
Current assignee: Weir Minerals Australia Ltd
Priority date: 2013-03-28
Filing date: 2014-03-28
Publication date: 2019-01-02
Anticipated expiration: 2034-03-28
Also published as: PH12015501912A1; AU2014245856B2; MX2015013549A; PT2978975T; WO2014153616A1; US20160040682A1; CL2015002887A1; CN105074225B; PH12015501912B1; EA201591520A1; EP2978975A1; MX365143B; AP2015008763A0; PE20151584A1; EA031306B1; ES2709199T3; EP2978975A4; AU2014245856A1; CA2902759A1; CN105074225A

Description

Technical Field

This disclosure relates generally to impellers for centrifugal slurry pumps. Slurries are usually a mixture of liquid and particulate solids, and are commonly found in the minerals processing, sand and gravel and/or dredging industry.

Background Art

Centrifugal slurry pumps generally include a pump casing having a pumping chamber therein which may be of a volute configuration with an impeller mounted for rotation within the pumping chamber. A drive shaft is operatively connected to the pump impeller for causing rotation thereof, the drive shaft entering the pump casing from one side. The pump further includes a pump inlet which is typically coaxial with respect to the drive shaft and located on the opposite side of the pump casing to the drive shaft. There is also a discharge outlet typically located at a periphery of the pump casing. The pump casing may be in the form of a liner which is encased within an outer pump housing.
The impeller typically includes a hub to which the drive shaft is operatively connected, and at least one shroud. Pumping vanes are provided on one side of the shroud with discharge passageways between adjacent pumping vanes. The impeller may be of the closed type where two shrouds are provided with the pumping vanes being disposed therebetween. The impeller may however be of the "open" face type which comprises one shroud only.
In some applications conventional pumping vanes are laid over such that a section through the vane forms an acute angle to the shroud on a pressure surface of the vane and provides for a smooth transition from inlet to discharge along the vane length.
Two examples of impellers having warped vanes are illustrated in US2010/0284812 and US 6,082,000 . US 2010/0284812 discloses a centrifugal water pump having an impeller which has aerofoil shaped vanes with a thick base (portion in contact with back shroud) tapering to a thin tip (portion closest to the fluid inlet). Although the vanes are twisted along their length, they would not be suitable for use in slurry pumps. In US 6,082,000 , the vanes of D2 are typical of the mixed flow type, that is the vanes are of a double curvature type. The patent is concerned with a novel method to produce such a vane. EP2570674 describes an erosion restraint impeller vane made of metallic laminate, the vane comprising a first metallic core material and a wear resistant material, the hardness of the wear resistant material being higher than that of the metallic core material.
For slurry pumps handling heterogeneous slurries (with settling particles of typical size 0.5mm) it is common for there to be solids concentration gradients throughout the flows in the inlet pipe and within the impeller and pump casing. The concentration gradients are caused by the various forces acting on the particle including: gravity, fluid drag and centrifugal forces. As the slurry enters the impeller it has to turn through a 90 degree angle of flow so as to be directed out of the pump, and with both inertial forces and Coriolis forces (exerted by the vane), the slurry particles are at their highest concentration at the root of the vane on the back shroud of the impeller, that is, in the region where a side edge of the vane contacts the shroud.
A consequence of this flow of concentrated particles along the root of the vane is high and uneven wear due to grooving of the impeller at that point, which can prematurely render the impeller ineffective.

Summary of the Disclosure

In a first aspect of the present invention, there is provided a pump impeller which includes:

a front shroud and a back shroud having an inner main face with an outer peripheral edge and a central axis, the inner main faces being generally at right angles to the central axis, the impeller in use being rotatable about the central axis in a direction of rotation,
a plurality of pumping vanes extending from the inner main face of the back shroud to the inner main face at the front shroud, the pumping vanes being disposed in spaced apart relation, and each pumping vane including:
- opposed first and second side faces wherein the first side face is a pumping or pressure side face,
- a leading edge in the region of the central axis,
- a trailing edge in the region of the outer peripheral edge of the front and back shrouds, and
- with a passageway between adjacent pumping vanes,

The configuration of the vane is such that in use the Coriolis force generated by the vane disperses particles across that vane at its trailing edge thereby reducing wear near the region where the vane abuts against the face of the back shroud.
In certain embodiments, the first side face at the trailing edge is in a plane which is at an obtuse angle in a range of greater than about 90° to about 135°. In certain embodiments, the first side face at the leading edge is in a plane which is at an acute angle in a range of about 45° to less than about 90°.
The angle of the first side face progressively changing when moving from the leading edge to the trailing edge of the vane may be in a continuous form of curvature when moving from the leading edge to the trailing edge, or in multiple straight sectors at different acute or obtuse angles to form the shape of the pumping vane.
The first side face is a leading face with respect to the direction of rotation, so that fluid being pumped is impacted against it.
In certain embodiments each pumping vane includes a leading edge section terminating at the leading edge the leading edge section tapering inwardly towards the leading edge, and a trailing edge section terminating at the trailing edge the trailing edge section tapering inwardly towards the trailing edge, each pumping vane including a main section between the leading and trailing edge sections which has a width or thickness which is generally constant from one side edge thereof to an opposed side edge and along its length from the leading edge section to the trailing edge section.
In certain embodiments, the first side face is configured such that the surface thereof, at any line between the leading and trailing edges which is at 90° from one side edge to the other, is flat or linear in the direction of that line. To put it another way, the first side face is a face of a rectangular flat strip with the leading edge and trailing edge forming two shorter sides of the rectangular flat strip and side edges forming two longer sides of the rectangular flat strip, said rectangular flat strip being twisted about an axis extending from the leading edge to the trailing edge, said rectangular flat strip also being curved between the leading edge and the trailing edge such that the first side face is backward-curved and the first side face of the rectangular flat strip is linear or flat in the direction of a line which is drawn from one side edge to the other at any point between the leading edge and the trailing edge of the first side face where the line meets each of the side edges at an angle of 90°.
In certain embodiments the pumping vanes are curved in a lengthwise direction between the leading and trailing edges although in some other embodiments the impeller pumping vanes can be straight along their distal length.
In certain embodiments, the vanes are backwardly curved with respect to the direction of rotation of the impeller, although for some applications the direction of curvature may be forwardly curved with respect to the direction of rotation of the impeller, depending on the nature of fluid.
Also described herein is an example of a pump impeller which includes:

a back shroud having an inner main face with an outer peripheral edge and a central axis, the impeller in use being rotatable about the central axis in a direction of rotation,
a plurality of pumping vanes extending from the inner main face of the back shroud, the pumping vanes being disposed in spaced apart relation, and each pumping vane including:
- opposed first and second side faces,
- opposed side edges one of which is located at the back shroud,
- 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, and
- with a passageway between adjacent pumping vanes,

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 present invention.

Brief Description of the Drawings

Notwithstanding any other forms which may fall within the scope of the apparatus as set forth in the Summary, specific embodiments of the apparatus will now be described, by way of example, and with reference to the accompanying drawings in which:

Figure 1 illustrates a schematic, partial cross-sectional side elevation of a pump incorporating an impeller and an impeller and liner combination, in accordance with one embodiment of the present invention;
Figure 2 illustrates a schematic view of part of an impeller and a pumping vane in accordance with one embodiment of the present invention;
Figures 3 to 5 depict sectional views of an impeller shroud and an impeller pumping vane taken along the lines 1, 2 and 3 in Figure 2 in accordance with the present invention; and
Figures 6 and 7 are pictorial views of a portion of an impeller illustrating features of the pumping vanes according to one embodiment of the present invention.
Figure 8 is a top, perspective view of an impeller illustrating features of the pumping vanes according to one embodiment of the present invention.
Figure 9 is a bottom, perspective view of an impeller illustrating features of the pumping vanes according to one embodiment of the present invention.
Figure 10 illustrates an exemplary schematic view of part of an impeller and a pumping vane in accordance with another embodiment of the present invention.

Detailed Description of Specific Embodiments

Referring to Figure 1, there is illustrated a typical example of a pump 10 which includes a pump casing or volute 12, a back liner 14, a front liner 30 and a pump outlet 18. An internal chamber 20 is adapted to receive an impeller 40 for rotation about rotational axis X-X.
The front liner 30 includes a cylindrically-shaped delivery section 32 through which slurry enters the pump chamber 20. The delivery section 32 has a passage 33 therein with a first, outermost end 34 operatively connectable to a feed pipe (not shown)
and a second, innermost end 35 adjacent the chamber 20. The front liner 30 further includes a side wall section 15 which mates in use with the pump casing 12 to form and enclose the chamber 20, the side wall section 15 having an inner face 37. The second end 35 of the front liner 30 has a raised lip 38 thereat, which is arranged in a close facing relationship with the impeller 40.
The impeller 40 includes a hub 41 from which a plurality of circumferentially spaced pumping vanes 42 extend. An eye portion 47 extends forwardly from the hub towards the passage 33 in the front liner. The impeller further includes a front shroud 50 and a back shroud 51, the vanes 42 being disposed therebetween.
Referring now to Figure 2, this illustrates an impeller according to one embodiment of the present invention. The same reference numerals as used to identify parts in Figure 1 are used to identify similar parts in the embodiment of Figure 2. The pumping vanes include a leading edge section 60 having a leading edge 43 and a trailing edge section 61 having a trailing edge 44. The leading edge section 60 is tapered inwardly towards the leading edge 43 and the trailing edge section 61 is tapered inwardly towards the trailing edge 44. The pumping vanes have a main section 63 between the leading edge section 60 and trailing edge section 61 which at any planar height above the back shroud 51 has a width or thickness 64 which is generally constant from one side edge 56 to the other side edge 57 and along its length from the leading edge section 60 to the trailing edge section 61.
In Figure 2 only one exemplary pumping vane 42 is shown which extends between opposing main inner faces 53, 54 of the shrouds 50, 51. Normally such an impeller has a plurality of such pumping vanes spaced evenly around the area between the shrouds 50, 51. Typically three, four or five pumping vanes are usual in slurry pumps. In this drawing only one pumping vane has been shown for convenience to illustrate the features. As shown in Figure 2, the pumping vane 42 is generally arcuate in cross-section and includes an inner leading edge 43 and an outer trailing edge 44, opposed side edges 56, 57 and opposed first and second faces 45, 46 between the side edges 56, 57, the face 45 being a pumping or pressure side face. The vanes of this type are normally referred to as
backward-curving vanes when viewed with the direction of rotation. The side edge 56, 57 are disposed against respective inner faces of the shrouds 50, 51. The inner faces 53, 54 are generally at right angles to the central rotation axis X-X. The face 45 which is a pumping or pressure side face of the pumping vane 42 is configured such that the surface thereof at any line between the leading and trailing edges 43, 44 which is at 90° from one side edge 56 to the other 57 is flat or linear in the direction of that line.
Described in another way, the face 45 may be likened to a face of a rectangular flat strip with the leading edge 43 and the trailing edge 44 forming the two shorter sides of the rectangular flat strip and the side edges 56, 57 each forming the two respective longer sides of the rectangular flat strip. The rectangular flat strip is twisted about an axis that extends from the leading edge 43 to the trailing edge 44. In addition to being twisted, the rectangular flat strip is also curved between the leading edge 43 and the trailing edge 44 which provides that face 45 is backward-curved. A face (that is face 45) of the rectangular flat strip that is twisted and curved in this way, is linear or flat in the direction of a line which is drawn from one longer side (that is side edge 56) to the other longer side (that is side edge 57) at any point between the two shorter sides (that is the leading edge 43 and the trailing edge 44) of the rectangular flat strip when the line meets each of the longer sides at an angle of 90°.
In certain embodiments, the first face 45 is flat or linear when viewed at any cross-section along its length from the leading edge 43 to the trailing edge 44, each cross-section being taken at rights angles to the side edges 56, 57 of the vane. Examples of such cross-sections are illustrated in Figures 3 to 5 showing cross-sections taken along the lines 1, 2, and 3 in Figure 2. As is apparent from viewing these Figures, the first face 45 is flat or linear at these cross sections. Described in another way, it means that the first face 45 is not bowed or convex at any of the cross-sectional views in question. In the embodiment described, the second face 46 is also flat or linear when viewed at any cross section.
As illustrated, the angle of inclination Y of the side face 45 with respect to the main inner face 53 of the back shroud 51 progressively changes along the length of the vane 42 when moving from its leading edge 43 to its trailing edge 44. This change in angle is clearly shown in Figures 3 to 5. The angle of inclination Y is also referred to as the leading angle of the vane with respect to the direction of rotation of the impeller in use. As shown in Figure 3 the angle of inclination Y is an acute angle at the leading edge 43. Preferably the angle is in a range from about 45° to less than 90°, more preferably the angle is in a range from about 70° to about 80°, and more preferably is about 75°. The angle progressively changes and, at the position shown in Figure 4, it is at right angles (perpendicular). In the position shown in Figure 5 at the trailing edge 44 of the vane, the angle of inclination is obtuse. Preferably the angle at the trailing edge is in a range from greater than 90° up to about 135°, more preferably the angle is in a range from about 100° to about 130°, and more preferably is about 110°.
In operation, the Coriolis force (Arrow B in Figure 2), which is generated as a result of the in use rotation of the impeller in the direction of arrow A in Figure 2, causes the particulates C in a slurry or fluid which is being conveyed by the pump impeller of the present embodiment, to disperse over the face of the vane as the particulates travel along the vane from the leading edge to the trailing edge. The vane shape arrangement can assist to break up solid particle concentration gradients within the impeller where the slurry particles are at their highest concentration at the root of the vane on the back shroud of the impeller, that is, in the region where a side edge of the vane contacts the shroud. This can result in a reduction of the wear due to grooving of the impeller at that point.
Figures 6, 7, 8 and 9 illustrate an impeller according to one embodiment. The same reference numerals as used to identify parts in Figures 1, 2, 3, 4 and 5 are used to identify similar parts in the embodiment of Figures 6, 7, 8 and 9. Figures 6 and 7 depict portions of an impeller 40 from different sides looking into the discharge passageways between the vanes 42, and Figures 8 and 9 each show an impeller 40 in its entirety. As can be seen, the angle of inclination of the side face 45 with respect to the main inner face 53 of the back shroud 51 progressively changes along the length of the vanes 42 when moving from the leading edge (now shown) to its trailing edge 44.
Figure 10 illustrates a modified form of the arrangement shown in Figure 2. The same reference numerals as used to identify parts in Figure 2 are used to identify similar parts in the modified form of Figure 10. The change in the angle of inclination Y along the length of the vane 42 as shown in Figure 10 is greater than the change in the angle of inclination Y along the length of the vane 42 as shown in Figure 2.
In the foregoing description of preferred embodiments, specific terminology has been resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as "front" and "rear", "inner" and "outer", "above", "below", "upper" and "lower" and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms.
The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as, an acknowledgement or admission or any form of suggestion that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.
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 of the claims, the embodiments being illustrative and not restrictive.

Furthermore, invention(s) have been 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 scope of the invention(s) as defined by the claims. 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.

Table of Parts

Pump

	10
Pump casing (volute)	12
Back liner	14
Front liner	30
Pump outlet	18
Internal chamber	20
Central or rotational axis	X-X
Delivery section
	32
Passage	33
Outer end	34
Inner end	35
Sidewall section	15
Inner face	37
Lip	38
Impeller	40
Hub	41
Pumping vanes	42
Eye portion	47
Leading edge section	60
Leading edge	43
Impeller inlet	48
Trailing edge section	61
Trailing edge	44
Main section	63
Width or thickness	64
Outlet	49
Front shroud	50
Back shroud	51
First face	45
Second face	46
Side edge	56
Side edge	57

Claims

A slurry pump impeller (10) which includes:
- a front shroud (50) and a back shroud (51) each having an inner main face (54, 53) with an outer peripheral edge and a central axis (X-X), the inner main faces (53, 54) being generally at right angles to the central axis (X-X), the impeller (10) in use being rotatable about the central axis (X-X) in a direction of rotation,

- a plurality of pumping vanes (42) extending from the inner main face of the back shroud (53) to the inner main face of the front shroud (54), the pumping vanes (42) being disposed in spaced apart relation, and each pumping vane (42) including:
- opposed first and second side faces (45, 46) wherein the first side face (45) is a pumping or pressure side face,

- a leading edge(43) in the region of the central axis (X-X),

- a trailing edge (44) in the region of the outer peripheral edge of the front and back shrouds (54, 53), and

- with a passageway between adjacent pumping vanes,

characterised in that the first side face (45) at the leading edge (43) is in a plane which is at an acute angle with respect to a plane of the inner main face of the back shroud (53), and the first side face (45) at the trailing edge (44) is in a plane which is at an obtuse angle with respect to the plane of the inner main face of the back shroud (53) wherein the angle of the first side face (45) progressively changes when moving from the leading edge (43) to the trailing edge (44).
A slurry pump impeller (10) according to claim 1, wherein the first side face (45) at the leading edge (43) is in a plane which is at an acute angle in a range of about 45° to less than about 90°.
A slurry pump impeller (10) according to claim 1 or claim 2 wherein the first side face (45) at the trailing edge (44) is in a plane which is at an obtuse angle in a range of greater than about 90° to about 135°.
A slurry pump impeller according to any one of the preceding claims, wherein the first side face (45) is a face of a rectangular flat strip with leading edge (43) and trailing edge (44) forming two shorter sides of the rectangular flat strip and side edges (56, 57) forming two longer sides of the rectangular flat strip, said rectangular flat strip being twisted about an axis extending from the leading edge (43) to the trailing edge (44), said rectangular flat strip also being curved between the leading edge (43) and the trailing edge (44) such that the first side face (45) is backward-curved and the first side face (45) of the rectangular strip is linear or flat in the direction of a line which is drawn from one side edge to the other (56, 57) at any point between the leading edge (43) and the trailing edge (44) of the first side face (45) where the line meets each of the side edges (56, 57) at an angle of 90°.
A slurry pump impeller (10) according to any one of the preceding claims, wherein the pumping vanes (42) are curved in a lengthwise direction between the leading and trailing edges (43, 44).
A slurry pump impeller (10) according to claim 5 wherein the vanes (42) are backwardly curved with respect to the direction of rotation of the impeller (10).