CENTRIFUGAL PUMP IMPELLER FOR SLUDGE

Abstract

A centrifugal slurry pump impeller comprising a rear shield and a front shield, each having opposing inner and outer faces and an outer peripheral edge and a central shaft, a plurality of pumping vanes extending between the main inner faces of the rear and front shields, each pumping vane comprising opposing main side faces, a leading edge in the region of the central shaft and a trailing edge in the region of the outer peripheral edges of the rear and front shields with a passage between adjacent pumping vanes, each passage comprising a blended region between each of the main side faces of the pumping vanes and the inner faces of the front and rear shields wherein an inner face surface of at least one of the front and rear shields comprises a raised portion located between the blended regions of adjacent pumping vanes.

Description

This description refers in general to a slurry pump impeller for use in centrifugal pumps and more particularly, though not exclusively, to pumps for handling abrasive materials such as, for example, slurries and the like. Several stages in the mineral processing industry involve erosive contact with equipment components, resulting in significant wear and tear that necessitates frequent replacement. However, component wear is often not uniform, depending on the specific process stage. For example, in the process of pumping abrasive slurries using a centrifugal slurry pump, a limiting factor in the service life of the wet-end component of the centrifugal slurry pump may be localized wear in the form of deep grooves or very high wear rates in certain locations of the slurry pump impeller even though other parts of the impeller may wear at a relatively low rate. The high wear on the front and rear impeller shields is related to the speed and degree of turbulence in the flow in these regions. This description aims to provide a centrifugal pump impeller that results in less wear in these areas. The various aspects described in this description can be applied to all centrifugal sludge pumps and particularly to those that experience high rates of wear on the impeller guards. SUMMARYAccording to one aspect, a centrifugal slurry pump impeller is provided, comprising a rear shield and a front shield, each with opposing inner and outer faces and an outer peripheral edge and a central axis; the front shield including an impeller inlet, and the rear shield including an impeller tip raised from the inner face of the rear shield facing the impeller inlet and aligned with the central axis; a plurality of pumping vanes extending between the main inner faces of the front and rear shields; the pumping vanes being arranged separately; each pumping vane including opposing main side faces, a leading edge in the region of the central axis, and a trailing edge in the region of the outer peripheral edges of the front and rear shields, with a passage between adjacent pumping vanes.each passage that includes a blended region between each of the main side faces of the pumping vanes and the inner faces of the front and rear guards where a surface of the inner face of the, QRcrnn / cznz / E / YiAi less one of the front and rear protectors includes a raised portion located between the mixed regions of the adjacent pumping vanes. In certain embodiments, each passage extends from an inner region of the passage that begins adjacent to the leading edge of the plurality of pumping vanes to an outer region of the passage where the outer region terminates at the outer peripheral edge of the front and rear protectors and where the raised portion is located in the inner region of the passage. In certain embodiments, the raised portion extends from the inner region adjacent to the leading edge of the plurality of pumping vanes and terminates approximately three-quarters of the way along the passage length. In another embodiment, the raised portion terminates approximately halfway along the passage length from the region adjacent to the leading edge of the plurality of pumping vanes. In certain models, the inner surfaces of the front and rear protector in the outer region are substantially flat and are in a plane that is substantially perpendicular to the central axis. In certain embodiments, one of the opposite side faces of adjacent pumping vanes is a pressure-side face and the other of the opposite side faces is a suction-side face where a vertex of the raised portion is located closer to the suction-side face than the pressure-side face. In certain forms, the raised portion includes a convex surface. In certain models, the distance between the inner faces of the front and rear protector is greater in the outer region than in the inner region of the passage. In certain modalities, the raised portion provides a surface on the inner face of the front and / or rear guard that continues from the mixed region associated with one of the opposite side faces to the mixed region of the other of the opposite side faces of the adjacent pumping vanes. In certain configurations, the apex of the raised portion is located adjacent to the suction-side face to which it is closest in order to modify the flow of mud through the passage during use and thereby reduce turbulence and / or inhibit the formation of vortices adjacent to the main inner face of the front and / or rear protector. In certain models, the raised portion is located on the inner face of the front protector. In certain models, the raised portion is located on the inner face of the rear protector. In certain configurations, the elevated portion is located in each of the passages located between the adjacent pumping vanes. In certain models, the apex of the raised portion is separated from the mixed region located between the main side faces of the pumping vanes and the inner face of the front and / or rear protector. QRcrnn / cznz / E / YiAi In certain configurations, the pumping vanes are backward-swept. In one form, the impeller has no more than six pumping vanes. In another form, the impeller has four pumping vanes. According to another aspect, a centrifugal slurry pump impeller is provided, comprising a back shield with an inner and outer face and an outer peripheral edge and a central shaft. The back shield includes an impeller tip raised from the inner face and aligned with the central shaft. A plurality of pumping vanes extending between the main inner face of the back shield and the pumping vanes, which are arranged separately, are also provided. Each pumping vane includes opposite main side faces, a leading edge in the region of the central shaft, and a trailing edge in the region of the outer peripheral edge of the back shield, with a passage between adjacent pumping vanes.Each passage includes a blended region between each of the main side faces of the pumping vanes and the inner face of the rear guards, wherein a surface of the inner face of the rear guard includes a raised portion located between the blended regions of the adjacent pumping vanes. Other aspects, elements, and benefits will become apparent from the following detailed description together with the accompanying drawings, which form part of the present description and illustrate, by way of example, the principles of the inventions described. DESCRIPTION OF THE FIGURES The attached drawings facilitate the understanding of the various modalities. Figure 1 is a schematic partial cross-sectional side elevation of a form of a pump apparatus according to a modality; Figure 2 is a more detailed schematic partial cross-sectional side elevation of a portion of a pump apparatus from Figure 1; Figure 3 is a cross-sectional view of a prior art impeller depicting the rear guard in a plan view; Figure 4 is a rendered cross-sectional view of an impeller representing the rear guard according to one modality of the present description; Figure 5 is a symmetrical rendered sectional view of the impeller in Figure 4; Figure 6 is a schematic cross-sectional view of the impeller in Figure 4; Figure 7 is a rendered cross-sectional view of an impeller representing the front guard according to one modality of the present description; Figure 8 is a rendered cross-sectional view of the impeller in Figure 7; Figure 9 is a schematic cross-sectional view of the impeller in Figure 7; Figure 10 is a rendered cross-sectional view of an impeller according to one modality of the present description; QRcrnn / cznz / E / YiAi Figure 11 is a schematic cross-sectional view of the impeller in Figure 7 depicting the contour lines on the front guard; Figure 12 is a schematic cross-sectional view of the impeller in Figure 4 depicting the contour lines on the rear guard; Figure 13 is a schematic cross-sectional view of an impeller according to another modality of the present description, representing the contour lines on the front guard; Figure 14 is a schematic cross-sectional view of a prior art impeller depicting contour lines on the front shield; Figure 5 is a rendered cross-sectional view of the impeller of the above technique depicted in Figure 14; Figure 6 is an isometric cross-sectional view of the impeller of the previous technique depicted in Figures 14 and 15; Figure 7 is a schematic cross-sectional view of an impeller of the prior art depicting the contour lines on the rear shield; Figure 18 is a rendered cross-sectional view of the impeller of the above technique depicted in Figure 17; Figure 19 is an isometric cross-sectional view of the impeller of the prior art depicted in Figure 17 and Figure 18; and, Figure 20 is a rendered cross-sectional view of the impeller of the above technique represented in Figures 14 to 19. DETAILED DESCRIPTION With reference to Figure 1 of the drawings, a pump apparatus 200 is generally illustrated, comprising a pump 10 and a pump housing support in the form of a pedestal or base 112 on which the pump 10 is mounted. In pump technology, pedestals are also called frames. The pump 10 generally comprises an outer casing 22 formed from two casing side parts or sections 23, 24 (sometimes also called the frame plate and cover plate) joined together around the periphery of the two casing side sections 23, 24. The pump 10 is formed with side openings, one of which is an inlet 28 where there is also a discharge outlet 29, and, when used in a processing plant, the pump is connected by piping to the inlet 28 and the outlet 29, for example, to facilitate the pumping of a mineral slurry. The pump 10 further comprises an inner pump liner 11 disposed within the outer casing 22 and including a main liner 12 and two side liners 14, 30. The side liner 14 is located closer to the rear end of the pump 10 (i.e., closer to the pedestal or base 112), and the other side liner (or front liner) 30 is located closer to the front end of the pump and the inlet port 28. Lining 4 QRcrnn / cznz / E / YiAi Side 14 is also called the rear side part or frame plate lining insert, and side lining 30 is also called the front side part or throat bearing. The main lining 12 comprises two side openings thereon. The two outer casing 23, 24 side parts are joined together by screws 27 located around the periphery of the casing 23, 24 when the pump is assembled for use. In some embodiments, the main liner 12 may also consist of two separate parts that are assembled within each of the outer casing 23, 24 side parts and joined to form a single main liner, although in the example shown in Figure 1, the main liner 12 is a single piece, shaped similarly to an automobile tire. The liner 11 may be made of materials such as rubber, elastomer, or metal. 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 outer pump casing 22. A sealing chamber housing 114 covers the side liner (or rear side portion) 14 and is arranged to seal the space or chamber 118 between the drive shaft 116 and the pedestal or base 112 to prevent leakage from the rear area of ​​the outer casing 22. The sealing chamber housing takes the form of a circular disc section and an annular section with a central hole, and in one arrangement is known as a stuffing box 117. The stuffing box 117 is disposed adjacent to the side liner 14 and extends between the pedestal 112 and a shaft sleeve and packing surrounding the drive shaft 116. As shown in Figures 1 and 2, an impeller 40 is positioned within the main casing 12 and is mounted or operatively connected to the drive shaft 116, which is adapted to rotate about a rotation axis XX, or center axis. A motor drive (not shown) is normally coupled by pulleys to an exposed end of the shaft 116, in the region behind the pedestal or base 112. Rotation of the impeller 40 causes the pumped fluid (or solid-liquid mixture) to pass from a pipe connecting to the inlet 28 through the pumping chamber 42, which is inside the main casing 12 and the side casings 14, 30, and then out of the pump through the discharge outlet 29. The impeller 40 includes a hub 41 from which a plurality of circumferentially spaced pumping vanes 43 extend. A tip portion 47 extends forward from the hub 41 along the axis of rotation to an impeller inlet 48 and an inlet passage 33 in the front liner 30. The impeller 40 further includes a front guard 50 and a rear guard 51, the vanes 43 being arranged and extending between these. In an alternative embodiment, the impeller may have a semi-open configuration with a rear guard but without a front guard, for applications in foam pumping and / or use in vertical pumps. QRcrnn / cznz / E / YiAi The front impeller guard 50 includes an inner face 55, an outer face 54, and a peripheral rim portion 56. The rear guard 51 includes an inner face 53, an outer face 52, and a peripheral rim portion 57. The front guard 50 includes an inlet 48, which is the impeller inlet, and vanes 43 that extend between the inner faces of the guards 50 and 51. The tip portion 47 extends in the form of a rounded surface from the inner face 53 of the rear guard 51, facing the inlet and aligned with the rotation axis XX. The guards are generally circular or disc-shaped when viewed in elevation; that is, in the direction of the rotation axis XX. As illustrated in Figure 2, each impeller guard has a plurality of auxiliary or ejection vanes on its outer faces 52, 54, of which there is a first group of auxiliary vanes 60 on the outer face 54 of the front guard 50 and a second group of auxiliary vanes 61 on the outer face 52 of the rear guard 51. The auxiliary vanes are an optional element of the impeller. With reference to Figure 3, a cross-section of a centrifugal slurry pump impeller 40 is shown with the front guard 50 not shown, providing a plan view of the rear guard 51. The impeller 40 includes a rear guard 51 with four pumping vanes 43 extending from the rear guard 51 in a direction generally aligned with an axis of rotation X of the slurry pump impeller 40 when in use, providing that the pump impeller 40 rotates counterclockwise as shown in Figure 3. The inner face 55 of the rear guard 51 is axisymmetric and also generally in a plane that is at right angles to the axis of rotation X.Each of the four pumping vanes 43 includes a trailing edge 70 and a leading edge 71, where the leading edge 71 of the pumping vanes is adjacent to the center, or to the tip 47 and the inlet 48 of the impeller 40 where the sludge enters during operation of the associated centrifugal sludge pump (not shown). The slurry passes through inlet 48, towards tip 47, and is then moved by the orientation and rotation of the slurry pump impeller through the four passages 6 located between the adjacent pumping vanes 43. The pumping vanes 43 further include the opposing main side faces 7, 8. The opposing side faces include a pressure-side face 7, also known as the pump-side face, and a suction-side face 8. Each of the opposing main side faces 7, 8 defines the passages 6 together with the inner face of the rear guard 53, and the inner face of the front guard 55 (not shown). The location and function of the four passages 6 means that this section of the sludge pump impeller 10, and particularly the area of ​​the passages 6 along the surfaces of the inner face of the rear guard 53 and the inner face of the front guard 55, are subject to significant erosion and wear during the operation of a centrifugal sludge pump impeller 40. Typically, during operation there is a higher velocity on the suction side of the 6 QRcrnn / cznz / E / YiAi pumping vanes 43 adjacent to the suction side face 8 and a lower speed on the pressure or pump side face 7, of pumping vane 43 near the leading edge. This speed differential leads to the formation of vortices adjacent to the inner faces 53, 52 of the front and rear guards 51, 50. With reference to Figures 4 through 10, an embodiment of a centrifugal slurry pump impeller 40 is shown, in accordance with the present description. The impeller 40 includes a rear shield 51 and a front shield 50, each with opposing inner faces 53, 55 and outer faces 52, 54, an outer peripheral rim 57, 56, and a central shaft. The central shaft X is located at the center of the tip 47 on the rear shield 51 and at the center of the inlet of the front shield 50. The impeller 40 further includes a plurality of pumping vanes 43 extending between the main inner faces 53, 55 of the front and rear guards 51, 50. The four pumping vanes 43 are spaced equally apart around the impeller 40 and include opposite main side faces 7, 8, a leading edge 71 in the region of the central axis X, and a trailing edge 70 in the region of the outer peripheral edges 57, 56 of the rear and front guards 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 passage 6 is located between each adjacent pumping vane 43. Each passage 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 rear guards 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 rear guards 50, 51. In addition to the blended regions 110, the surface of the inner face 53, 55 of the front and / or rear guard 50, 51 includes a raised portion 120 located between the blended regions 110 of the adjacent pumping vanes 43 in the passages 6 of the impeller 40. The raised portion 120 is integrally formed with the inner surface 53, 55 of the front and / or rear shield 50, 51. This ensures that the raised portion 120 has a generally smooth shape and does not obstruct the flow of fluid through the impeller passage 6. In any case, the raised portion 120 does not impede the movement of slurry particles through passage 6 during pump operation. The raised portion 120 is separated from the tip 47 located in the center of the inner face 53 of the rear protector 51. The tip 47 can be separated by a blended region 110 that acts as a transition surface between the surface of the tip 47 and the surface of the raised portion 120. QRcrnn / cznz / E / YiAi The surface of the raised portion 120 defines a region of the inner face 53, 55 of the front and / or rear guard located in the passages 6 between the adjacent pumping vanes 43. The raised portion 120 is separated from a plane perpendicular to the axis of rotation that defines the remainder of the surface in the outer region of the inner face 53, 55 of the front and / or rear guard 50, 51. The raised portion 120 reduces the distance between the inner faces 53, 55 of the front and / or rear guard in its immediate vicinity. Otherwise, the distance between the surface of the raised portion 120 and the other of the inner face 53, 55 of the front and / or rear guard is less than the distance between the inner faces 53, 55 in the outer region of the front and / or rear guard 50, 51.The raised portion 120 also provides that the inner faces 53, 55 of the front and rear guard differ in profile from each other, since the raised portion appearing on each of the inner faces 53, 55 of the front and / or rear guard may not be equal in size, shape, or location. Furthermore, the raised portion 120 provides that the inner faces 53, 55 of the front and / or rear guard (when considered separately from the plurality of pumping vanes 43) are not axiasymmetric, in the sense that the raised portion 120 on the inner faces 53, 55 of the front and / or rear guard results in guard profiles that are asymmetric in a plane perpendicular to the axis of rotation, compared to the impellers of the prior art, as exemplified in Figure 3. With reference to Figures 4 to 9, each passage 6 of the impeller 40 extends from an inner region 125 of the passage 6 that begins between two adjacent pumping vanes 43 near their leading edges 71. The passage 6 continues to an outer region 130 of the passage where the outer region 130 terminates at the outer peripheral edge 56, 57 of the front and rear guards 50, 51. The raised portion 120 can be located in the inner region 125 of the passage. In one embodiment, as shown in the outlines depicted on the front guard shown in Figure 13, the inner region 125 of passage 6 can terminate approximately three-quarters along the length of passage 6 from the beginning of passage 6 adjacent to the front edge 71 of the plurality of pumping vanes 43. Alternatively, the inner region 125 can terminate approximately halfway along the length of passage 6 from the beginning adjacent to the front edge 71 of the plurality of pumping vanes 43 as shown in the embodiment depicted in Figures 4 to 9. In comparison with the inner region 125 of the inner surfaces 53, 55 of the front and rear protector, the outer line 135 of passage 6 includes the inner surfaces 53, 55 which can be substantially flat and are located in a plane that is substantially perpendicular to the central axis. In certain configurations, the raised portion 120 may include a vertex 135. The vertex may be in the form of a convex surface appearing on the inner surfaces 53, 55 of the rear and front guards 51, 50. The vertex 135 of the raised portion 120 provides a surface on the inner face of the rear / front guard 51, 50 that is closer to the inner face of the other front / rear guard. The vertex 135 may be located closer to the suction-side face 8 QRcrnn / cznz / E / YiAi of the pumping vanes that the pressure side face of the pumping vanes 43 in passages 6. With reference to the impeller depicted in Figures 4 through 10, the raised portion 120 provides a surface on the inner faces 53, 55 of the rear and / or front guard 51, 50 that is a continuous raised surface extending from the mixed region 110 associated with one main face of a pumping vane 43 to the mixed region 110 of the other main face of an adjacent pumping vane. The raised portion 120 located on the rear guard 51 is separated from the tip 47 located at the center of the inner face 53 of the rear guard 51. The tip 47 of the impeller is also separated by a mixed region 110 that acts as a transition surface between the surface of the tip 47 and the surface of the raised portion 120 appearing on the rear guard 51. It has been found that placing a raised portion 120 in the inner region 125 of passage 6 between the pumping vanes and on the inner faces 53, 55 of the rear and / or front guard 51, 50 can modify the mud flow through the passage when the impeller is in use, thereby reducing turbulence and inhibiting the formation of vortices adjacent to the main inner faces 53, 55 of the rear and front guards 51, 50. By reducing turbulence and inhibiting vortex formation, wear in this region of the impeller can be substantially reduced and its commercial service life increased. With reference to Figures 11 to 13, the schematic views of the front and rear guards 50, 51 show the surface contours of the raised portion 120 and its vertex 135 located in the inner region 125 of the passages 6. The location of the vertex 135 is closer to the suction-side face 8 of the pump vanes than to the pressure-side face 7. With reference specifically to Figures 11 and 13, the vertex 135 of the raised portion 120 can be located on the inner face 55 of the front guard 50 closer to the suction-side face 8 of the pump vane 43 approximately 1 / 4 to approximately 1 / 2 of the length of the pump vane 43 from the front edge 71, and preferably approximately 1 / 3 of the length of the pump vane 43 from the front edge 71. With reference specifically to Figure 12, the vertex 135 of the raised portion 120 can be located on the inner face 53 of the rear protector 51 closer to the suction side 8 of the pumping vane 43 approximately aligned with the leading edge 71 of the pumping vane at approximately 1 / 5 of the pumping vane length from the leading edge, and preferably approximately 1 / 15 to approximately 1 / 8 of the pumping vane length 43 from the leading edge 71. Conversely, Figures 14 to 20 depict the front and rear guards 50 and 51 respectively of the same prior art impeller. The concentric contours illustrated in Figures 14 and 15 clearly show the surface of the inner faces 53 and 55 of the guards. QRcrnn / cznz / E / YiAi front and rear 50, 51 are axisymmetric, or substantially flat or smooth and are located in a plane that is perpendicular to the axis of rotation. In the preceding description of certain modalities, specific terminology has been used for the sake of clarity. However, the description is not intended to be limited to the specific terms thus selected, and it should be understood that each specific term includes other technical equivalents that function similarly to achieve a similar technical purpose. Terms such as “left” and “right,” “front” and “rear,” “above” and “below,” and the like are used as convenient words to provide points of reference and should not be interpreted as limiting terms. In this description, the expression “that comprises” should be understood in its “open” sense, that is, in the sense of “that includes,” and therefore is not limited to its “closed” sense, that is, the sense of “that consists only of.” A corresponding meaning should be attributed to the corresponding words “comply,” “comprised,” and “comprises” where they appear. Additionally, the above describes only some modalities of the invention(s), and alterations, modifications, additions and / or changes can be made without departing from the scope and spirit of the modalities described; the modalities are illustrative and not restrictive. Furthermore, the invention(s) have been described in relation to what are currently considered the most practical and preferred embodiments. It should be understood that the invention is not to be limited to the embodiments described, but rather is intended to encompass various modifications and equivalent arrangements included within the spirit and scope of the invention(s). Moreover, the various embodiments described above may be implemented in conjunction with other embodiments; for example, aspects of one embodiment may be combined with aspects of another embodiment to implement still other embodiments. In addition, each independent element or component of any given unit may constitute an additional embodiment. QRcrnn / cznz / E / YiAi Parts list Pump Apparatus200 Pump10 Pedestal112 Outer casing22 Side casing parts 23, 24 Entry 28 Download output 29 Interior cladding11 Main cladding12 Rear side panel14 Front side paneling30 Pumping chamber42 Bolts27 Sealing chamber housing114 Sealing space 118 Drive shaft116 Cable gland box 117 Passages6 Pressure side face7 Side suction face8 Top surface9 Impulsor40 Front protector 50 Rear protector51 Pumping vanes43 Rear edge 70 Front edge71 Inner face of the front protector55 Outer face of the front protector54 Portion of the peripheral edge of the front protector 56 Inner face of the rear protector53 Outer face of the rear protector52 Portion of the peripheral edge of the rear protector 57 Cube41 Impeller tip47 Impeller input 48 Step 33 Auxiliary pallets 60, 61 Mixed region110 High portion 120 Interior region of passage 125 Exterior region of passage 130 Vertex of the elevated portion135

Claims

1. A centrifugal slurry pump impeller comprising a rear shield and a front shield, each having opposing inner and outer faces and an outer peripheral edge and a central axis, the front shield including an impeller inlet, and the rear shield including an impeller tip raised from the inner face of the rear shield facing the impeller inlet and aligned with the central axis, a plurality of pumping vanes extending between the main inner faces of the rear and front shields, the pumping vanes being arranged separately, each pumping vane including opposing main side faces, a leading edge in the region of the central axis, and a trailing edge in the region of the outer peripheral edges of the rear and front shields with a passage between adjacent pumping vanes,each passage that includes a blended region between each of the main side faces of the pumping vanes and the inner faces of the front and rear guards, wherein a surface of the inner face of at least one of the front and rear guards includes a raised portion located between the blended regions of the adjacent pumping vanes and wherein the raised portion is separated from the tip of the impeller.

2. The centrifugal sludge pump impeller according to claim 1, wherein each passage extends from an inner passage region beginning adjacent to the leading edge of the plurality of pumping vanes to an outer passage region, wherein the outer region terminates at the outer peripheral edge of the front and rear guards and wherein the raised portion is located in the inner passage region.

3. The centrifugal sludge pump impeller according to claim 1 or claim 2 wherein the raised portion extends from the inner region adjacent to the leading edge of the plurality of pumping vanes and terminates approximately three-quarters along the length of the passage.

4. The impeller of the centrifugal sludge pump according to claim 1 or claim 2, wherein the raised portion extends from the inner region adjacent to the leading edge of the plurality of pumping vanes and terminates approximately halfway along the length of the passage.

5. The centrifugal sludge pump impeller according to any of the preceding claims, wherein the inner surfaces of the front and rear shields in the outer region are substantially flat and lie in a plane that is substantially perpendicular to the central axis. QRcrnn / cznz / E / YiAi 6. The impeller of the centrifugal sludge pump according to any of the preceding claims wherein one of the opposite side faces of the adjacent pumping vanes is a pressure-side face and the other of the opposite side faces is a suction-side face wherein a vertex of the raised portion is located closer to the suction-side face than the pressure-side face.

7. The centrifugal sludge pump impeller according to any of the preceding claims wherein the raised portion includes a convex surface.

8. The centrifugal sludge pump impeller according to any of claims 2 to 7, wherein the distance between the inner faces of the rear and front protector is greater in the outer region than in the inner region of the passage.

9. The centrifugal sludge pump impeller according to any of the preceding claims wherein the raised portion provides a surface on the inner face of the rear and / or front guard that continues from the mixing region associated with one of the opposite side faces to the mixing region of the other of the opposite side faces of the adjacent pumping vanes.

10. The impeller of the centrifugal slurry pump according to any of claims 6 to 9, wherein the apex of the raised portion is located adjacent to the suction-side face to which it is closest in order to modify the flow of the slurry through the passage in use and thereby reduce turbulence and / or inhibit the formation of vortices formed adjacent to the main inner face of the passage and / or the rear and / or front guard.

11. The centrifugal sludge pump impeller according to any of the preceding claims wherein the raised portion is located on the inner face of the front guard.

12. The impeller of the centrifugal sludge pump according to any of claims 1 to 10, wherein the raised portion is located on the inner face of the rear guard. QRcrnn / cznz / E / YiAi 13. A centrifugal pump impeller for sludge according to any of the preceding claims wherein the raised portion is located in each of the passages located between the adjacent pumping vanes.

14. A centrifugal pump impeller for sludge according to any of claims 6 to 13, wherein the apex of the raised portion is separated from the mixed region located between the main side faces of the pumping vanes and the inner face of the rear and / or front guard.

15. A centrifugal pump impeller for sludge according to any of the preceding claims wherein the pumping vanes are of a backward sweep shape.

16. A centrifugal pump impeller for sludge according to any of the preceding claims wherein the impeller has no more than six pumping vanes.

17. A centrifugal pump impeller for sludge according to any of the preceding claims wherein the impeller has four pumping vanes.

18. A centrifugal slurry pump impeller comprising a back shield with an inner and outer face and an outer peripheral edge and a central shaft, the back shield comprising an impeller tip raised from the inner face aligned with the central shaft, a plurality of pumping vanes extending between the main inner face of the back shield, the pumping vanes being arranged in separate relationships, each pumping vane comprising opposite main side faces, a leading edge in the region of the central shaft and a trailing edge in the region of the outer peripheral edge of the back shield with a passage between adjacent pumping vanes,each passage that includes a blended region between each of the main side faces of the pumping vanes and the inner face of the back shield, wherein a surface of the inner face of the back shield includes a raised portion located between the blended regions of the adjacent pumping vanes and wherein the raised portion is separated from the tip of the impeller.

Images