[0001] This disclosure relates generally to impellers for centrifugal slurry pumps. Slurries are usually a mixture of liquid and particulate solids, and arc commonly found in the minerals processing, sand and gravel and/or dredging industry .

Background Art

[0002] 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 includes a main liner and front and back side liners which are encased within an outer pump housing.

[0003] The impeller typically includes a hub to which the drive shaft is operatively connected, arid 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 (he closed type where two shrouds are provided with the pumping vanes being disposed therebetween. The shrouds are often referred to as the front shroud adjacent the pump inlet and the back shroud. The impeller may however be of the "open" face type which comprises one shroud only.

[0004] The impeller which is the subject of this disclosure finds particular although not exclusive application for use with front side liners of the type comprising an outer component formed at least in part of an elastomcric material such as rubber and an inner wear component formed at least in pat of high wear resistant materia), such as metal or ceramic. The two parts are adapted to be assembled together so there is an interface between the elastomerie material of the outer component and high wear resistant material of the inner wear component,

[0005] One of the major wear areas in the slurry pump is the front side liner that is adjacent to the rotating impeller. Slurry enters the impeller in. the centre or eye and is then flung out to the periphery of the impeller and into the pump casing. Because there is a pressure difference between the casing and the eye, there is a tendency for the slurry to flow back to the eye through the gap between the side liner and the impeller, resulting in high wear on the side liner,

[0006] in order to reduce the driving pressure on the slurry in the gap as well as create a centrifugal field to expel particles, it is common for slurry pumps to have auxiliary or expelling vanes on the front shroud of the impeller. Auxiliary or expelling vanes may also be provided on the back shroud. The expelling vanes rotate the slurry in the gap creating a centrifugal field and thus reducing the driving pressure for the returning flow, reducing the flow velocity and thus the wear on the side liner.

[0007] in many applications the side liner is the weakest area in the pump, wearing out before any other part. Much of the wear on. the side liner is a result of the flow generated by the rotating expelling vanes. In particular there is wear from the tip or outer edge of the expelling vanes due to the creation of fluid vortices and entrained particles. This wear is exacerbated when a combination of high wear materials and elastomerie materials are used in the construction of the side liner. In some situations the elastomer such as rubber can wear at a faster rate than the high wear materials due to specific duty conditions. Rubber liners can also suffer de-polymerisation due to high frequency compression of the surface by the expelling vane passing and hysteresis heating. The severity of the temperature rise is determined by vane clearance, vane shape and passing frequency. Summary of the Disclosure

[0008] In a first aspect, embodiments are disclosed of an impeller which can be rotated about a rotation axis X-X, the impeller comprising a shroud having opposed inner and outer faces and an outer peripheral edge portion remote from the rotation axis, a plurality of pumping vanes projecting from the inner face of the shroud, a plurality of auxiliary vanes projecting from the outer face of the shroud each auxiliary vane having an inner edge which is closer to the rotation axis and an outer edge which is closer to the outer peripheral edge portion of the shroud the auxiliary vanes extending in a direction between the rotation axis towards the outer peripheral edge portion of the shroud, wherein at least some of the auxiliary vanes have a leading side and a trailing side each of which extends from the inner edge to the outer edge with an upper side spaced from the outer face of the shroud, and said upper side having a main surface and a stepped surface which is stepped inwardly towards the outer face of the shroud, there being a step or shoulder at a junction between the main surface and the stepped surface.

[0009] In certain embodiments, two shrouds are provided one being a front shroud and the other being a back shroud each having respective opposed inner and outer faces said pumping vanes extending between the inner faces of the shrouds, the front shroud having a central intake opening therein with a first group of said auxiliary vanes on the outer face thereof which arc disposed between the intake opening and the outer peripheral edge portion of the front shroud,

[0010] In certain embodiments a second group of said auxiliary vanes are disposed on said outer face of the back shroud.

[0011] m certain embodiments the main surface of the upper side of at least some of the said auxiliary vanes is disposed inwardly towards the rotation axis X-X relative to the stepped surface. [0012] In certain embodiments the stepped surface terminates at the outer edge of the or each auxiliary vane.

[0013] In certain embodiments the outer edge of each auxiliary vane is spaced inwardly from the outer peripheral edge portion of the shroud with which it is associated.

[0014] In certain embodiments the outer face of the shroud, and the main surface and stepped surface of the upper side of the said at least some of the auxiliary vanes are generally planar and parallel to one another.

[0015] In certain embodiments the main surface is in a plane spaced from a plane containing the outer face of the shroud and the stepped surface is in a plane between the planes containing the main surface and the outer face,

[0016] hi certain embodiments the leading side of the auxiliary vanes in the region of the stepped surface has a curved profile.

[0017] In certain embodiments where DE3 is the distance from the rotation axis X- X to the outer peripheral edge portion of the shroud, DE2 is the distance from the rotation axis to the outer edge of the auxiliary vane and DEI is the distance from the rotation axis to the step or shoulder junction between the main and stepped surfaces of the upper side of the auxiliary vane, and arranged such that DE2 is from 0.70 to 0,97 of DE3.

[0018] In certain embodiments wherein HI. is the distance between the outer face of the shroud and the main surface of the upper side of the auxiliary vane, and H2 is the distance between, the outer face of the shroud and the stepped surface of the upper side of the auxiliary vane, H2 ranges from 0.06 to 0.36 of HI.

[0019] hi a second aspect, embodiments are disclosed of a combination of a pump side liner and an impeller in accordance with the first aspect, wherein the pump side liner comprises an outer component and an inner wear component, the components being adapted to be assembled together with abutting surfaces which provide an interface or junction between the two components, and wherein the said interface or junction of the pump side liner is positioned from the rotation axis X-X at a radial distance which is in use aligned with the impeller at a location between the step or shoulder and the outer edge of the auxiliary vane.

[0020] In certain embodiments, the pump side liner has an outer peripheral surface and DS1 is the distance from the rotation axis X-X to the junction and DS2 is the distance from the rotation axis and the outer peripheral surface, and arranged such that DEI ranges being from 0.94 to 0.98 of DS 1, In certain embodiments, DS2 ranges from 1 ,05 to 1.20 of DE3, In certain embodiments, DSl ranges from 0.57 to 0.86 of DS2,

[0021] 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 inventions disclosed,

Brief Description of the Drawings

[0022] The accompanying drawings facilitate an understanding of the various embodiments.

[0023] Figure 1 is a sectional side elevation of a portion of a conventional pump ;

[0024] Figure 2 is a sectional side elevation of a portion of a pump according to one embodiment of the present disclosure;

[0025] Figure 3 is an isometric view of a pump impeller according to one embodiment of the present di sclosure; [0026] Figure 4 is a further, more detailed sectional side elevation of the pump shown in Figure 2;

[0027] Figure 5 is an exploded view of the parts shown in Figures 2 and 4, so that relevant features can more readily be identified; and

[0028] Figure 6 is a more detailed partial isometric view of the impeller shown in Figure 3.

Detailed Description of Specific Embodiments

[0029] Referring to Figure 1 of the drawings, there is illustrated a partial side- sectional view of a portion of a pump 50 comprising a pump housing 60 which is mounted to a pump housing support or pedestal (not shown). The pump housing 60 generally comprises an outer casing 62 that is formed from two side casing parts or halves 64, 66 (sometimes also known as the frame plate and the cover plate) which are joined together about the periphery of the two side casings parts 64, 66, The pump housing 50 is formed with an inlet hole 68 and a discharge outlet hole 70 and. when in use in a process plant, the pump is connected by piping to the inlet hole 68 and to the outlet hole 70, for example to facilitate pumping of a mineral slurry.

[0030] The pump housing 60 further comprises a pump housing inner liner 80 arranged within the outer casing 62 and which includes a main liner (or volute) 84 and two side liners 86, 88. The side liner (or hack liner) 86 is located nearer the rear end of the pump housing 60 and closer to the pedestal and the other side liner (or front liner) 88 is located nearer the opposite, front end of the pump housing 60, The front liner 88 is sometimes referred to as a throaibush.

[0031] The two side casing parts 64, 66 of the outer casing 62 are joined together by bolts 67 which are located about the periphery of the casing parts 64, 66 when the pump is assembled for use. In the embodiment shown, the main liner (or volute) 84 is comprised of two separate halves 65, 69 (made of such material as rubber or elastomer) which are assembled within each of the side casing parts 64, 66 and brought together to form a single main liner, although in other arrangements the main liner (or volute) 84 can be made in one-piece, shaped similar to a car tyre (and made of metal material).

[0032] When the pump 50 is assembled, side openings 61. 63 in the main liner 84 are filled by the two side liners 86, 88 to form a continuously-lined pumping chamber 79 disposed within the pump outer casing 62. A seal chamber housing 73 encloses the side liner (or back liner) 86 and is arranged to seal the space, between the shaft and die side liner 86 to prevent leakage from the back area of the outer casing 62.

[0033] An impeller 75 is positioned within the main liner 84 and is mounted to a drive shaft 77 which has a rotation axis X-X aligned with central pump axis 200. A motor drive (not shown) is normally attached by pulleys to the exposed end of the shaft 77, in the region located behind the pedestal or base. As itemised in Figure 1, the impeller 75 comprises a back shroud 81 having an inner face 71, an outer face 72 and an outer peripheral edge portion 74 and a front shroud 82 haying an inner face 85, an outer face 87 and an outer peripheral edge portion 89, a series of pumping vanes 83 therebetween. Each pumping vane 83 has a leading edge portion 76 and a trailing edge portion 78. The rotation of the impeller 75 causes the fluid (or solid-liquid mixture) being pumped to pass from the pipe which is connected to the inlet hole 68 through the chamber which is defined by the main liner 84 and the side liners 86, 88, and then out of the pump 50 via the outlet hole 70.

[0034] As best illustrated in Figures 2, 4 and 5, the front liner 88 is shown in conjunction with an impeller 75, according to one embodiment. The front liner 88 comprises an outer component 9.1 which includes a side wall section 93. The side wall section 93 is formed from an elastomer, such as rubber, The side wail section 93 has an outer rim. surface 94 and an aperture or recess 97 therein having locating surface 98 (Figure 5). The front liner 88 further includes an inner wear component 90 having a side wall 101 with an outer peripheral edge surface 103 (Figure 5). The components are adapted to be assembled together as shown in Figure 4 using one or more elements such as mounting member 106 to form the front lifter. 111 the assembled position the outer peripheral surface 103 of the wear component is in contact with the locating surface 98 on the side wall section providing an interlace or junction 105 between the components (Figure 4). The wear component 90 is formed of high wear material such as metal or ceramic.

[0035] As illustrated in Figure 1, the front shroud 82 of the impeller 75 has a plurality of auxiliary or expelling vanes 20 on the outer face thereof, in the embodiments shown the auxiliary vanes are generally linear, or rectangular in shape when viewed in plan and extend generally radially from the rotation axis. The vanes could however be inclined backwaMly from the radius or curved when viewed in plan.

[0036] Figure 3 illustrates embodiments of the vanes 20 on the outer face 87 of the front shroud 82 on an impeller 75. Reference numerals have been included on one of the vanes 20 only for the sake of clarity. As shown the auxiliary vanes: 20 comprise a leading side 21. with respect to the direction of rotation of the impeller when in use, a trailing side 22, an upper side 23, an inner edge 24 and aft outer edge 25. In the embodiment of Figure 3, the upper side 23 has a main surface 31 which is generally in a plane parallel with the shroud outer face or surface 87, and at stepped surface 33 which is also parallel with face or surface 87 and is stepped down or inwardly from the main surface 31 towards face or surface 87 and is in the region of outer edge 25 of the auxiliary vanes there being a step or shoulder 34 at a junction between the surfaces 31 and 33. In this arrangement, the stepped surface 33 forms a tongue that is projecting outwards form the main surface 31 of the auxiliary vanes 20 _, with the step or shoulder 34, generally at right angles to the planes containing the main and stepped surfaces 31 , 33.

[0037] All of the surfaces 31, 33, 87 are generally flat or planar. In certain embodiments the upper side 23 may have further inclined or chamfered surfaces 24 at the leading and/or trailing sides. In certain other embodiments, not every one of the auxiliary vanes needs to have the stepped upper surface configuration on the front face of the impeller. As shown in the Figures, the outer edge 25 of the auxiliary vanes 20 is spaced inwardly from the outer peripheral edge portion 89 of the shroud 82. As shown in this embodiment, the leading side 21 of the auxiliary vanes 20 in the region of the stepped surface 31 has a. curved profile 28 extending from the step or shoulder 34 to the outer edge 25. The outer edge 25 of the auxiliary vanes 20 is also the outer edge of the stepped surface 31. Thus, the stepped surface 31 is continuous from the leading side to the trailing side of the vanes 20. The main surface 31 is in a plane which is spaced from a plane containing the outer surface 87 of the front shroud and the stepped surface 33 is in a plane located between the planes containing the main surface 31 and the outer surface 87. The leading and trailing sides 21, 22 and the outer edge 25 of the auxiliary vanes 20 may be bevelled, as illustrated.

[0038] The stepped surface 33 has a width from the leading side 21 to the trailing side 22 thereof which is substantially the same as the width of the main surface 31 of the auxiliary vane 20. The length of the stepped surface 33 from the step or shoulder 34 to the outer edge 25 thereof is such that any tip vortex generated in the region of the outer edge of the vane 25 has a greater possibility of dissipating.

[0039] Figure 4 of the drawings identifies the following parameters.

[0040] DEI is the length in a radial direction from the rotation axis to the step or shoulder 34 of the vane 20.

[0041] DE2 is the length in a radial direction from the rotation axis to the outer edge 25 of the v ane 20.

[0042] DE3 is the length in a radial direction from the rotation axis to the outer peripheral edge portion 74 of the shroud 82.

[0043] HI is I he height of the auxiliary vane 20 from the outer face 87 of the shroud 82 to the main surface 31 of the upper side 23 of the vane 20.

[0044] H2 is the height of the auxiliary vane 20 from the outer face 87 of the shroud 82 to the stepped surface 33 of the upper side 23 of the vane,

[0045] DS1 is the length from, the rotation axis to the interface or junction 105 between inner and outer components 91, 90,

[0046] DS2 is the length from the rotation axis to the outer rim smiace 94 of the outer component 91.

[0047] Preferably one or more of these parameters have dimensional ratios in. the following ranges,

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070] In certain embodiments the length of the stepped surface 33 from the step or shoulder 34 to the outer edge 25 may be at least from about 15mm. In one example embodiment the length of the stepped surface 33 from the step or shoulder 34 to the outer edge 25 is about ^' 150mm,

[0071] It has been found that the stepped upper surface 33 of the auxiliary vanes 20 ensures that any tip vortex which may be generated in the region of the outer edge 25 of the vanes 20 has a greater possibility of dissipating. Furthermore because of the stepped configuration of auxiliary vanes 20 there is less chance for generation of hysteresis temperature rise in the elastomer components of an adjacent liner when in. use in a pump. The reduction in the vane height as a result of the stepped upper surface 33 in. the region of the elastomer component of the adjacent side liner results in an overall improvement in the wear life of the said side liner. The position of the stepped surface 33 of the upper side 23 of the vane relati ve to the interface or junction of the metal and elastomer components of the side liner leads to an improvement in overall wear life of the side liner.

[0072] 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.

[0073] 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,

[0074] 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 it s "closed" sense, that is the sense of "consisting only of. A correspondmg meaning is to be attributed to the corresponding words "comprise", "comprised" and "comprises" where they appear,

[0075] 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. [0076] Furthermore, mvention(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 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.

[0077] The reference numerals in the following claims do not in any way limit the scope of the respective claims.