IMPELLERS FOR CENTRIFUGAL PUMPS

Abstract: A centrifugal pump impeller (1) comprising auxiliary vanes (3) located on one side surface thereof and joining an annular projection (5) extending around the periphery of the impeller, the vanes being further joined with at least one further projection (7) extending between adjacent auxiliary vanes so as to form pockets (9) on the surface of the impeller to prevent the setting up of a re-circulating flow pattern in the clearance between the impeller and the adjacent stationary wall of the pump casing.

Description: IMPELLERS FOR CENTRIFUGAL PUMPS This invention relates to improvements in centrifugal pumps; more particularly to pumps used for pumping fluids wi abrasive solids in suspension. A problem in pumping fluids o this nature is the abrasive action and wear on the components and resultant enlargement of clearances between the rotary an stationary members and consequent leakage and slippage of the fluid pumped, serious loss of head and efficiency and a reduction in serviceable life of the wearing parts, particularly the impeller and parts of the casing, or the casing liners, adjacent the sides of the impeller. A means commonly employed to alleviate this problem is t provide the sides of the impeller with a plurality of auxilliary vanes projecting towards, and conforming with suitable running clearance .to the walls of the casing adjacen the impeller. These auxiliary vanes can be of various design such a straight radial, straight inclined to radial, curved o a combination of such shapes; their objective being to minimise, by their centrifugal action on the fluid in the sid clearance spaces, leakage and ingress thereto of fluid with abrasive suspended particles discharged from the impeller. Such vanes as are in use have been described for this purpose as outwardly diverging so that at the circumference of the impeller the periphery space between adjacent vanes is much greater - typically two or three times as great - as it is at the inner ends of the vanes. (see Australia Patent 22513) . In more recent improvements (Australia Patent Applicatio 30237/84) a ring has been extended around the periphery of th .- impeller to minimise the inward penetration of fluid discharged from the impeller and the associated ingress of abrasive particles into the side clearances between the impeller and casing. A problem however with all these previous inventions is that the centrifugal pressure field generated by these auxilliary vanes causes a net flow of fluid from the inner (boss end) of the vane passage to the periphery. This flow sets up a recirculating pattern in the clearance between the rotating impeller and the stationary side of the casing as the fluid flows back along the wall of the casing to replace that which is pumped out between the auxiliary vanes (see figure 1) . This recirculating flow of abrasive fluid causes severe wear problems which result in increased clearances which further exacerbates the resulting recirculation and wear. It is the primary objective of the present invention to provide auxilliary impeller side vanes so designed as to restrict this recirculation and thus improve the wear life of the impeller and casing or casing liners. In one broad form the invention comprises a centrifugal slurry pump impeller comprising: auxilliary vanes located on at least one side surface thereof; an annular projection joining the vanes, at or adjacent the periphery of the impeller; and at least one further projection extending between adjacent auxilliary vanes. The peripheral annular projection extends all the way around the circumference however the internal projections may form an annular ring or rings or be discontinuous forming pockets between the auxilliary vanes. The main aim of these annular projections is to disrupt the smooth flow of abrasive fluid from the impeller boss to the periphery and thus reduce the level of recirculation. .5 The invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 2 illustrates a sectional view of the impeller according to one embodiment of the present invention in the casing of a centrifugal pump. 10 Fig. 3 illustrates a bottom plan view of the impeller illustrated above showing the position of the back auxilliary vanes and projections. Fig. 4 illustrates a bottom plan view of a second embodiment of the invention showing the discontinuous "' annular 15 projections and auxiliary vane ' s. * The embodiments of the present invention shown in the beforementioned drawings comprises a plurality of auxilliary vanes outwardly projecting from the sides of the impeller 1 and conforming with suitable running clearances to the walls of the 20 casing 2 within which the impeller rotates ' . As shown in figures 2 and 3 there is provided a plurality of radially extending auxiliary vanes 3 and 4 (backwardly sloping with respect to the direction of rotation) located on the shaft side and inlet side respectively of the impeller 1. ι 25 Located in this embodiment on the periphery of the impeller 1 are annular projections 5 and 6 which join the respective radial auxilliary vanes 3 and 4. Concentric projections 7 and 8 are provided on the back surface of the impeller to form ._ pockets 9 thereon. The heights of the various auxilliary vanes and projections are identical but could vary depending upon the individual pump geometry. Likewise the number of concentric annular projections could vary. Another embodiment of the present invention is shown in figure 4 wherein the internal projections 10 are staggered with respect to adjacent internal projections, to produce irregular shaped pockets 11. While the projections 10 are shown as arcuately extending they could be of any suitable shape or configuration such as straight, sloping or bent. Further it should be obvious to people skilled in the art that modifications can be made jtCKthe impeller described above ^ • without departing from the spirit or the scope of the present invention.

Claims: THE CLAIMS : 1. a centrifugal slurry pump impeller comprising: auxilliary vanes located on at least one side surface thereof; an annular projection joining the vanes, at or adjacent the periphery of the impeller; and at least one further projection extending between adjacent auxilliary vanes. 2. a centrifugal slurry pump impeller according to claim 1 wherein said at least one further projection comprises an annular projection concentric to the first annular projection. 3. a concentric slurry pump impeller according to claim 1 wherein the said at least one further projection comrpises discontinuance projections achieving adjacent auxilliary vanes 4. a concentric slurry pump impeller substantially as hereinbefore described with reference to figures 2,3 and 4 of the accompanying drawings

Inventors: WALKER CRAIG IAN, WALKER, CRAIG, IAN
Applicants: WARMAN INT LTD, WARMAN INTERNATIONAL LIMITED
Application year: 1987
Main classification: F04D7
IPC codes: F04D7, F04D29