CA1193486A - High head centrifugal slicing slurry pump - Google Patents
High head centrifugal slicing slurry pumpInfo
- Publication number
- CA1193486A CA1193486A CA000456139A CA456139A CA1193486A CA 1193486 A CA1193486 A CA 1193486A CA 000456139 A CA000456139 A CA 000456139A CA 456139 A CA456139 A CA 456139A CA 1193486 A CA1193486 A CA 1193486A
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- Prior art keywords
- impeller
- pump
- bowl
- slurry
- end plate
- Prior art date
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Abstract
Applicant: Vaughan Co., Inc.
Title: High Head Centrifugal Slicing Slurry Pump ABSTRACT
A booster propeller is located at the inlet of a flared funnel leading toward arcuate inlet apertures in an end plate of a centrifugal pump casing. The pump impeller is received in a bowl capped by the end plate and has a circular shroud plate perpendicular to the axis with vanes or blades projecting toward the end plate and having cupped leading surfaces forming a sharpened edge. Such blades are swept back in the area of the end plate inlet apertures for effective slicing of chunks or lumps of solid material in the slurry in combination with sharpened leading edges of the inlet apertures.
The pump casing bowl has a semicylindrical wall portion closely encircling the impeller and providing a pressure-increasing zone for slurry accelerated outward before the bowl wall spirals volutely outward to the outlet conduit.
Title: High Head Centrifugal Slicing Slurry Pump ABSTRACT
A booster propeller is located at the inlet of a flared funnel leading toward arcuate inlet apertures in an end plate of a centrifugal pump casing. The pump impeller is received in a bowl capped by the end plate and has a circular shroud plate perpendicular to the axis with vanes or blades projecting toward the end plate and having cupped leading surfaces forming a sharpened edge. Such blades are swept back in the area of the end plate inlet apertures for effective slicing of chunks or lumps of solid material in the slurry in combination with sharpened leading edges of the inlet apertures.
The pump casing bowl has a semicylindrical wall portion closely encircling the impeller and providing a pressure-increasing zone for slurry accelerated outward before the bowl wall spirals volutely outward to the outlet conduit.
Description
HIGH HEAI:) CENTRIFUGAL 5L:I[CIN(; SLURRY PUMP
This application ic; a division of Canadian application Serial No. 391,172, filed November 30, 1981, for High Head Centrifugal Slicing Slurry PumpO
The present inventlon relates to centrifugal pumps and particularly to centrifugal pumps effective for pumping slurries of liquid, usually water, and suspended solids constituting up to about 25 percent by weight of such slurries. Usually, the slurries have chunks or lumps of solid material that could clog or otherwise reduce the efficiency of a centrifugal pump so that such slurry pumps must have mechanism for comminuting the lumps or chunks to ensure effective and consistent pumping of the slurry.
The pump of the present invention is of the same general type as the "Centrifusal Chopping Slurry Pump" disclosed in Vaughan UOSO patent No. 3,973,866, issued August 10, 1976, whi.ch is stated to be an improvement on the general type of pump disclosed in Vaughan U.S. patent No. 3~155,046, issued November 3, 1964~ The pllmps of both of those patents are designed for pumping slurries containing chunks or lumps of solid material.
In general~ each of the prior pumps has an upright drive shaft, the lower end portion o~ which projects downward into a substantially cylindr.ical pump casing~ The impeller fixed to the drive shaft within the casing has a radial shroud disc or plate with downward projecting~ generally radially extending blades or vanesO The bottom of the casing is closed by an end plate havi.ng arcuate inlet apertuxes for .`'` ~
3~
intake of slurry in an axial direction~ The sharpened lower edges of the impeller blades cooperate with the leading edges o the inlet apertures for chopping chunks or lumps of solid material in the slurry being pumped. The slurry is accelerated circumferentially and outward to a generally tangential outlet conduitD
The pump disclosed in U~S. patent No, 3,973~866 also includes a screw propeller cantilevered from the pump drive shaft outside the pump casing and adjacent to the inlet apertures in the end plate.
Such propeller has generally radial blades with somewhat sharpened leading edges for choppin~ chunks or lumps in th~ slurry~ In addition, the screw propeller i5 stated to generate a positive current flow of slurry through the end plate inlet apertures~
Another aspect of the pump of tloS~ patent No. 3~973,~66 that is pertinent to the present invention is the use of elongated "slinger" ribs or vanes of small axial height projecting from the side of the impeller shroud plate opposite the lower primary pumping impeller blades. Such upper vanes are in the form of volute ribs for slinging away from the drive shaft bearing structure the solid material component of slurry which may work its way past the edge of the shroud plate so as to reduce wear of such bearing structure See the paragraph beginning at column ~, line 21O
The prior pumps are of relatively low head and efficiency as compared to the pump of the present inventionO In such pumps flow through the end plate inlet apertures into the impeller-receiving pump casing and out of the casing through the pump outlet _~ ~
3~
is much more turbulent than in the pump of the present invention.
In accordance with the present invention, improvements made to the pump disclosed in U.S. patent No~ 3,973,866 include: changing the design of the bottom booster propeller so as to increase the head of the pump without decreasing the chopping effectiveness of such propeller; locating the booster propeller at the entrance to a downwardly flared funnel for effecting smooth gradual acceleration of slurry toward the inlet apertures; locating the inlet apertures closer to the axis of rotation of the impeller so as to eliminate or greatly reduce backflow of high-pressure slurry in the radially outer portion of the pump casing and increase the effectiveness of the impeller vanes to accelerate outward movement of the slurry; rounding the entrances to fair the inlet apertures for smooth flow into the pump casing;
enclosixlg the impeller in a semicylindrical, semivolut~ casing, the volute portion being located immediately rearward of the pump outlet; sweeping back the impeller blades for providing an improved slicing action of the sharpened lower edges of the blades in cooperation with sharpened forward edges of the inlet apertures; decreasing the thickness of the impeller blades relative to the radial width of the inlet apertures so as not to interfere with intake o slurry through the inlet apertures; merging the imp~ller blades into the shroud plate with fillets for smooth, substantially nontuxbulent acceleration of the slurry circumferentially and outward toward the pump outlet;
cupping the leadin~ faces o-f the in~pel:ler blade~s to ~-3~
3~
ensure smooth change of di.rection of the slurry and effective slicing of chunks or lumps of solid material in the slurry; recessing the apertured end plate into the pump casing to dispose its inner surface flush with the adjoining surface of the pump outlet for smoother flow of slurry into the pump outlet; and arranging the upper l'slinger" ribs or vanes for producing a slight suction in the area of the drive shaft seal for increasing the life of the seal and to enable quick and accurate detection of seal failure~
The principal object of the present invsntion is to provide an efficient, durable centrifugal pump having a high head characteristic and adapted to consistently pump slurry containing solid chunks or lumps.
This object can be accomplished in part by providing in a centrifugal pump including an impeller rotatable about an axis and a pump casing including a bowl receiving the impeller and a generally ZO circumferential outlet, the improvement comprising the bowl including a cylindrical portion, coaxial with the impeller, forming a wall closely encircling no greater than approximately one-half of the circumference of the impeller and a volute portion foxming a wall spiraled outward from said cylindrical portion in the direction of impeller rotation~
This object also can be accomplished in part by providing in a centrifugal pump including an impeller rotatable about an axis t a pump casing including a bowl encircling the impeller and an outlet conduit extending substantially tangentially from the bowl, the improvement compxising the pump bowl being o~
~, ~
substantially semicylindrical and semivolute cross section, the semicy1indrical portion of the bowl being coaxial with the impeller, forming a wall closely encircling the impeller for appro~imately on~-half thQ
circumference of the impeller and located forward of the outlet with reference to the direction of impeller rotation to form a pressure increasing zone, and the semivolute portion of the bowl forming a wall spiraled outward from the wall of the cylindrical portion to the radially outer side of the outlet conduit and encircling about one-half the circumference of the impeller.
In drawings which illustrate an embodiment of the invention:
Figure 1 is a side elevation of a centrifugal slicing slurry pump in accordance with the present invention with parts broken away and parts shown in section;
Figure 2 is a bottom plan of the pump of Figure 1;
Figure 3 is a somewhat diagrammatic;
fragmentary, top perspective of a component of the ~5--3~8~
pump of Figure 1, namely, the disintegrator or booster propeller, showing its mounting structure in phantom;
Figure 4 is a section taken on line 4--4 of Figure 3 but on a larger scale;
Figure 5 is a section taken on line 5--5 of Figure 1 with parts broken away;
Figure 6 is a fragmentary section taken on line 6--6 o Figure 5; and Figure 7 is a fragmentary, detail section taken on line 7--7 of Figure 5 on a larger scale with parts in different positions.
As indicated ~n Figure 1, the centrifugal pump of the present invention includes an upright drive shaft 1 received within an upright housing 2 forming a reservoir or oil or other lubricant. The bottom of the reservoir is closed by conventional antifriction bearings 3 for the drive shaft and a conventional seal 4~
The bottom portion of housing 2 is bolted to a pump casing 5 having a downward openirlg cavity or bowl 6 receiving the pump impeller 7O Such impeller consists of~ a cylindrical shroud disc or plate 8 projecting radially from the impeller hub 9 fixed to the drive shaft; the primary pumping vanes or blades 10 projecting downward from the shroud plate; and vanes or ribs 11 projectin~ upward from the upper face of the shroud plate opposite the primary pumping blades 10.
The top of the pump bowl 6 is closed by a conventional seal 12 encirc:Ling the drive shaft 1~ and the botto~ of the pump bowl i~ closed by an end plate 13 bolted to the bottom of the pump casing and having inlet apPrtures 14 which, as best seen in Figure 2, are arcuate and concentric with the axis of rotation of the drive shaft and the impellerO
A disintegrator or booster propeller 15 having generally radially projecting, diametrally opposed blades 16 and a streamlined~ convexly curved bottom cap 17 is fixed to the bottom end of drive shaft 1. Rotation of the drive shaftt such as by an electric motor~ ef~ects rotation of the booster propeller for propelling a slurry of liquid, usually water, and suspended solids constituting up to about 25 percent by weight of the slurry upward into the pump bowl through the arcuate inlet apertures 14 where the slurry is accelerated circumferentially and outward to the pump outlet conduit 18. Such outlet conduit extends generally tangentially from the impeller in its plane of rotation and is connected to a discharge conduit 19 for conveying the pumped slurry to a desired location~
The slurry pumped can include mixtures of water and, for exampler earth or vegetable pulp~ but the pUMp iS particularly useful for pumping mixtures of water and animal waste such as manure. Such sewage slurries usually contain fairly large chunks or lumps of solid, sometimes stringy material whichl to be pumped effectivelyt must be chopped or otherwise comminuted into relatively small pieces. Commonly the pump will be located near th~ bottom of a sump so that ~he slurry must be pumped upward a substantial distance. As a result, the pressure of the slurry at the pump outlet must be high, that is, the pump must operate at a high headD
~3~
One factor that has been found to be important in increasing the head of a centrifugal slurry pump is the specific design of the disintegrator or booster propeller 15. The preferred design shown in Figures 2 t 3 and 4 incorporates two generally radially extending, diametrally opposed blades 16 which, as shown in Figure 2~ are of substantially uniform circumferential width from their roots to their tips. As best seen in Figures 3 and 4/ the leading edge 20 of each blade is thin for chopping or comminuting chunks or lumps of solid material in the slurry passing to the pump inlet.
While the root portions of the blades project substantially radially from the propeller hubr the outer end portions of the blades are curved slightly rearward in the plane of rotation so that hard chunks or lumps of solid material will be impelled outward so as not to clog the pump inlet.
The transverse section of Figure 4 illustrates the preferred cross-sectional shape for each propeller blade 16 throughout at least the major portion of its length. Its trailing side 21 is concave generally about an axis substantially parallel to the axis of rotation. For any transverse cross section an upright element of the trailing side 21 is substantially linear~ preferably substantially parallel to the axis of rotation~ Also for any transverse cross section, preferably a laterally extending element of the lower side 22 of the blade is substantially linear and lies in a plane substantially perpendicular to the propeller axis~ and for any transverse cross section preferably a laterally _~_ extending element of the upperS slurry-propelling side 23 of the blade also is subst:antially linear or only slightly concavely curved ancl is inclined upward from the leading edge 20 of the b].ade to the upper edg~ 24 of the trailing side 21. Accordinglyr throughout at least the major portion of it:s radial extent the blade is of generally triangular cross section, and, more specifically, of generally right triangular cross section.
In side elevation, as shown in Figure 1, each blade 16 also is substan~ially triangular, the lower edge of the blade, defined by its cut.ting edge 20, appearing substantially linear and inclined upward from the root of the blade to its tip, and the upper edge 24 of the blade, defined by the junction of the trailing side 21 and the upper surface 23, appearing substantially linear and lying in a plane substantially perpendicular to the axis of rotation.
Accordingly, each blade .is tapered in axial extent substantially uniformly from its root to its tip.
As seen in Figure 3, at the tip of a blade 16 the angle of the upper surface 23 to a radial plane is sharply acute. Progressing inward, the angle increases uniformly to the roo~ of the blade and, since the blade is of substantially uniform circumferential width throughout its length, the propelling force generated by a rotating propeller blade is substantially uniform from the tip of the blade to its root because of the greater tip speed of the bladeO
While each .Eaature of the booster propeller is considered important, experiments have shown that ~9_ ~3~
of almost primary importance is that the blade be tapered in thickness from its trailing side 21 to its leading edge 20 and that the upright elements of the blade trailing side be substantially linear and r preferably, substantially parallel to the axis of rotation. Propellers substantially identical to the propeller shown in the drawings but having blades with convexly rounded trailing sides were much less effective in boosting the head of a centrifugal pump.
The head-increasing tendency of the propeller also is aided by locating it at the entrance to or substantially within an outwardly flared funnel 28 which can conveniently be formed as a recess in the pump end plate 13 leading to the arcuate inlet apertures 14O The sides of the funrel flare outward at an angle of about 45 degrees relative to the axis of rotation, and the axial depth of the funnel should be at least equal to the maximum axial extent of a blade 16 of the booster propeller 15. Such depth is about 10~ to 15% of the diameter of the end plate. The maximum radius of the funnel should be at least about one and one-half times the radial extent of a blade 16. Slurry at the radially outer margin of the end plate is accelerated smoothly through ~he funnel toward the current generated by the booster propeller.
Preferably the tips of the propeller blades extend to or slightly beyond the radially outer edges 27 of the arcuate inlet apertures which are faired by bPing rounded to assure a smooth flow into the pump.
Similarly the radially inner ~dges 27' of the inlet apertures ~re rounded for smooth flow of slurry into the pump~
'10 While it is preferred that the propeller be located at the entrance to or substantially within the end plate funnel 28~ it also is preferred that the propeller be spaced downwarcl from the inlet apertures a distance sufficient that i.t will not interfere with the slici.ng effectiveness of the impeller blades 10 and entry of slurry and small particles into the pump casing past the propeller. In the embodiment shown in the drawings, a cylindrical spacer 25 spaces the propeller downward from the flat inner portion of the end plate a distance only slightly less than the radial width of an inlet aperture. The lower portion of such spacer has a bevel 26 guiding the slurry toward the rounded radially inner edge$ 27' of the inlet apertures 14~
For assuring a compact design, the apertured end plate 13 is xeceived within the pump bowl and has a bottom annular flange 29 enabling the end plate to be bolted to the upright sides of the pump casing 5.
As shown in Figure 6~ the primary advantage of recessing the end plate into the pump bowl is that the planar upper surface 30 of the end plate can be located flush with the lower side 31 of the pump outlet conduit 18 which i.s integral with the pump casing 5. In prior pumps, such as the pump of U.S.
patent NoO 3~973,866~ an end plate extends across the lower edge of a pump casing having an integral outlet conduit, so that a substantial turbulence-promoting step occurs in the are.a of the entrance to such conduit.
To minimize backflow of high-pressure slurry in the pump cas.ing 5 out the inlet apertures 14, such ~3~
apertures are located as close to the center of the impeller as possibleO The radially outer edges of the inlet apertures are posi.tioned approximately midway between the axis of rotation and the radially outer tips of the primary pumping impeller blades 10.
Preferably at least the major portion of the inlet aperture area is located within a circle having a radius one-half the radius of the circle defined by the rotating impeller blades.
The specific design of the impeller also assures a high head and effective slicing action of chunks or lumps of solid material in the slurry being pumped. As best seen in Figures 5, 6 and 7, three primary pumping blades 10 are provided projecting downwaxd from the shroud plate 8, each of substantially constant circumferential width throughout its length. Each blade is at least several times longer than its axial height and projects first generally tangentially from the impeller hub 9 and then is curved spirally rearward in the plane of rotation~ As best seen in Figure 7, the lower leading edge 33 of eAch blade is sharpened and is in close slicing relationship to the upper side 30 of the pump casing end plate 13. For this purpose the leading axcuate sides 34 of the end plate inlet apertures are beveled to a rearward facing sharpened edge 34' ~or close slicing contact with the leadi.ng sharpened edges 33 of the bladesO
Whereas prior centrifugal slurry pumps having used blades that project generally radially in the area of the inlet apertures for abrupt choppin~ of chunks or lumps of solid material iII the slurry, the ~12-~3~
blades of the present invention are angled rearward in the area of the inlet aperture,s at a substantial angle relative to a radius, preferably at least 45O As best seen in Figure 2, the apparent movement of a blade as it approaches a sharpened lead.ing edge 34' of an inlet aperture 14 is both forward and radially outward for effecting an angular slicing action, as opposed to an abrupt chopping action 9 of chunks or lumps of solid material in the slurry~
So that the primary impeller vanes 10 do not themselves interf~re with entrance of slurry through the inlet apextures, it is preferred that the circumferential width of the blades be as small as possible at their lower sides 3S, preferably no greater than one-half the radial width of the inlet apertures~ As best seen in Figure 7, however~ the upper portions of the leading sides 32 and the txailing sides 36 of blades should be faired gently into the shroud plate by fillets extending from about the axial center of each blade for smooth change of flow direction of the slurry from a generally axial direction to accelerated movement in the plane oE
rotation. As a result of the ~airing, the blades are tapered in circumferential width from their roots to their tips suGh that the circumferential width of each blade at its tip is no greater than about one-half the circumferential width of the blade at its root~ In combination with the fairing of the leading side 32 of the blade into the shroud plate, the forward curved lower tip portion of the hlade leading to the sharpened cutting edge 33 forms a substantial forward openi.ng cup that is swep~ spirally reaxward in the ,~ ,.., ;
l3 3~
plane of rotation for ef.Eect.ive but smooth acceleration of the sl.urry circumferentially forward and outward toward the pump outletO As shown in Figure 7, the fairing of the trailing side 36 of the blade into the shroud plate 8 is more gradual than the fairing of the leading side 32 into such plate, that is, the radius of curvature of the fillet formed at the upper portion of the trailing side is greater than the radius of curvature of the fillet formed at the upper portion of the leading side.
The axially short ribs or vanes 11 projecting upward from the shroud plate are provided primarily to protect the seal 12 rather than to assist in pumping the slurry~ Such vanes are substantially shorter than the primary pumping vanes 10, and more upper vanes 11 are provided at closer spacing. Rather than being volute or curved rearward in the plane of rotation, such upper vanes 11 are substantially straisht though angled rearward as to be generally tangential to the periphery of the drive shaft 1~ As with the lower primary pumping blades 10, such upper vanes 11 are faired into the shroud plate by fillets extending from at least about their axial centers as shown in Figure 7O
The overall design of the upper vanes 11 results in development of higher pressure at the periphery and above the shroud plate 8 than below it so that there i.s some suction above the plate away from the seal 12r Accordingly, lubricant from the reservoir in housing 2 tends to be drawn through the bearings 3, the seal 4 and the seal 12~ assuring ~3~
longer life than if a positive pressure we.re exerted above the shroud plate towa:rd the seals which could force slurry through the seals and bearings into the lubricant housing. In addition, seal failure is quickly and accurately detected by a rapid decrease in the level of lubricant in the reservoir formed by the housing.
A final fa~tor af-fecting the head of the pump is the design of the pump casing 5. As shown in Figure 5, rather than being spiraled or volute throughout its circumference, that is, rather than having a progressively increasing radial extent between the casing and the radially outer ends of the pump blades in the direction of rotation, such casiny is semicylindrical and semivolute. Beginning at the outlet conduit 18 and moving opposite the direction of rotation, for about one-half the circumference of the impeller, the casing spirals inward toward the shroud plate, and for the final one-half of its circumference the casing closely encircles the shroud plate providing a semicylindrical zone. Since slurry cannot escape outward in the semicylindrical zone, pressure of the slurry increases substantially in this zone before the slurry can escape circumferentially toward the outlet conduit and, as a result, the head of the pump is substantially increased~
This application ic; a division of Canadian application Serial No. 391,172, filed November 30, 1981, for High Head Centrifugal Slicing Slurry PumpO
The present inventlon relates to centrifugal pumps and particularly to centrifugal pumps effective for pumping slurries of liquid, usually water, and suspended solids constituting up to about 25 percent by weight of such slurries. Usually, the slurries have chunks or lumps of solid material that could clog or otherwise reduce the efficiency of a centrifugal pump so that such slurry pumps must have mechanism for comminuting the lumps or chunks to ensure effective and consistent pumping of the slurry.
The pump of the present invention is of the same general type as the "Centrifusal Chopping Slurry Pump" disclosed in Vaughan UOSO patent No. 3,973,866, issued August 10, 1976, whi.ch is stated to be an improvement on the general type of pump disclosed in Vaughan U.S. patent No. 3~155,046, issued November 3, 1964~ The pllmps of both of those patents are designed for pumping slurries containing chunks or lumps of solid material.
In general~ each of the prior pumps has an upright drive shaft, the lower end portion o~ which projects downward into a substantially cylindr.ical pump casing~ The impeller fixed to the drive shaft within the casing has a radial shroud disc or plate with downward projecting~ generally radially extending blades or vanesO The bottom of the casing is closed by an end plate havi.ng arcuate inlet apertuxes for .`'` ~
3~
intake of slurry in an axial direction~ The sharpened lower edges of the impeller blades cooperate with the leading edges o the inlet apertures for chopping chunks or lumps of solid material in the slurry being pumped. The slurry is accelerated circumferentially and outward to a generally tangential outlet conduitD
The pump disclosed in U~S. patent No, 3,973~866 also includes a screw propeller cantilevered from the pump drive shaft outside the pump casing and adjacent to the inlet apertures in the end plate.
Such propeller has generally radial blades with somewhat sharpened leading edges for choppin~ chunks or lumps in th~ slurry~ In addition, the screw propeller i5 stated to generate a positive current flow of slurry through the end plate inlet apertures~
Another aspect of the pump of tloS~ patent No. 3~973,~66 that is pertinent to the present invention is the use of elongated "slinger" ribs or vanes of small axial height projecting from the side of the impeller shroud plate opposite the lower primary pumping impeller blades. Such upper vanes are in the form of volute ribs for slinging away from the drive shaft bearing structure the solid material component of slurry which may work its way past the edge of the shroud plate so as to reduce wear of such bearing structure See the paragraph beginning at column ~, line 21O
The prior pumps are of relatively low head and efficiency as compared to the pump of the present inventionO In such pumps flow through the end plate inlet apertures into the impeller-receiving pump casing and out of the casing through the pump outlet _~ ~
3~
is much more turbulent than in the pump of the present invention.
In accordance with the present invention, improvements made to the pump disclosed in U.S. patent No~ 3,973,866 include: changing the design of the bottom booster propeller so as to increase the head of the pump without decreasing the chopping effectiveness of such propeller; locating the booster propeller at the entrance to a downwardly flared funnel for effecting smooth gradual acceleration of slurry toward the inlet apertures; locating the inlet apertures closer to the axis of rotation of the impeller so as to eliminate or greatly reduce backflow of high-pressure slurry in the radially outer portion of the pump casing and increase the effectiveness of the impeller vanes to accelerate outward movement of the slurry; rounding the entrances to fair the inlet apertures for smooth flow into the pump casing;
enclosixlg the impeller in a semicylindrical, semivolut~ casing, the volute portion being located immediately rearward of the pump outlet; sweeping back the impeller blades for providing an improved slicing action of the sharpened lower edges of the blades in cooperation with sharpened forward edges of the inlet apertures; decreasing the thickness of the impeller blades relative to the radial width of the inlet apertures so as not to interfere with intake o slurry through the inlet apertures; merging the imp~ller blades into the shroud plate with fillets for smooth, substantially nontuxbulent acceleration of the slurry circumferentially and outward toward the pump outlet;
cupping the leadin~ faces o-f the in~pel:ler blade~s to ~-3~
3~
ensure smooth change of di.rection of the slurry and effective slicing of chunks or lumps of solid material in the slurry; recessing the apertured end plate into the pump casing to dispose its inner surface flush with the adjoining surface of the pump outlet for smoother flow of slurry into the pump outlet; and arranging the upper l'slinger" ribs or vanes for producing a slight suction in the area of the drive shaft seal for increasing the life of the seal and to enable quick and accurate detection of seal failure~
The principal object of the present invsntion is to provide an efficient, durable centrifugal pump having a high head characteristic and adapted to consistently pump slurry containing solid chunks or lumps.
This object can be accomplished in part by providing in a centrifugal pump including an impeller rotatable about an axis and a pump casing including a bowl receiving the impeller and a generally ZO circumferential outlet, the improvement comprising the bowl including a cylindrical portion, coaxial with the impeller, forming a wall closely encircling no greater than approximately one-half of the circumference of the impeller and a volute portion foxming a wall spiraled outward from said cylindrical portion in the direction of impeller rotation~
This object also can be accomplished in part by providing in a centrifugal pump including an impeller rotatable about an axis t a pump casing including a bowl encircling the impeller and an outlet conduit extending substantially tangentially from the bowl, the improvement compxising the pump bowl being o~
~, ~
substantially semicylindrical and semivolute cross section, the semicy1indrical portion of the bowl being coaxial with the impeller, forming a wall closely encircling the impeller for appro~imately on~-half thQ
circumference of the impeller and located forward of the outlet with reference to the direction of impeller rotation to form a pressure increasing zone, and the semivolute portion of the bowl forming a wall spiraled outward from the wall of the cylindrical portion to the radially outer side of the outlet conduit and encircling about one-half the circumference of the impeller.
In drawings which illustrate an embodiment of the invention:
Figure 1 is a side elevation of a centrifugal slicing slurry pump in accordance with the present invention with parts broken away and parts shown in section;
Figure 2 is a bottom plan of the pump of Figure 1;
Figure 3 is a somewhat diagrammatic;
fragmentary, top perspective of a component of the ~5--3~8~
pump of Figure 1, namely, the disintegrator or booster propeller, showing its mounting structure in phantom;
Figure 4 is a section taken on line 4--4 of Figure 3 but on a larger scale;
Figure 5 is a section taken on line 5--5 of Figure 1 with parts broken away;
Figure 6 is a fragmentary section taken on line 6--6 o Figure 5; and Figure 7 is a fragmentary, detail section taken on line 7--7 of Figure 5 on a larger scale with parts in different positions.
As indicated ~n Figure 1, the centrifugal pump of the present invention includes an upright drive shaft 1 received within an upright housing 2 forming a reservoir or oil or other lubricant. The bottom of the reservoir is closed by conventional antifriction bearings 3 for the drive shaft and a conventional seal 4~
The bottom portion of housing 2 is bolted to a pump casing 5 having a downward openirlg cavity or bowl 6 receiving the pump impeller 7O Such impeller consists of~ a cylindrical shroud disc or plate 8 projecting radially from the impeller hub 9 fixed to the drive shaft; the primary pumping vanes or blades 10 projecting downward from the shroud plate; and vanes or ribs 11 projectin~ upward from the upper face of the shroud plate opposite the primary pumping blades 10.
The top of the pump bowl 6 is closed by a conventional seal 12 encirc:Ling the drive shaft 1~ and the botto~ of the pump bowl i~ closed by an end plate 13 bolted to the bottom of the pump casing and having inlet apPrtures 14 which, as best seen in Figure 2, are arcuate and concentric with the axis of rotation of the drive shaft and the impellerO
A disintegrator or booster propeller 15 having generally radially projecting, diametrally opposed blades 16 and a streamlined~ convexly curved bottom cap 17 is fixed to the bottom end of drive shaft 1. Rotation of the drive shaftt such as by an electric motor~ ef~ects rotation of the booster propeller for propelling a slurry of liquid, usually water, and suspended solids constituting up to about 25 percent by weight of the slurry upward into the pump bowl through the arcuate inlet apertures 14 where the slurry is accelerated circumferentially and outward to the pump outlet conduit 18. Such outlet conduit extends generally tangentially from the impeller in its plane of rotation and is connected to a discharge conduit 19 for conveying the pumped slurry to a desired location~
The slurry pumped can include mixtures of water and, for exampler earth or vegetable pulp~ but the pUMp iS particularly useful for pumping mixtures of water and animal waste such as manure. Such sewage slurries usually contain fairly large chunks or lumps of solid, sometimes stringy material whichl to be pumped effectivelyt must be chopped or otherwise comminuted into relatively small pieces. Commonly the pump will be located near th~ bottom of a sump so that ~he slurry must be pumped upward a substantial distance. As a result, the pressure of the slurry at the pump outlet must be high, that is, the pump must operate at a high headD
~3~
One factor that has been found to be important in increasing the head of a centrifugal slurry pump is the specific design of the disintegrator or booster propeller 15. The preferred design shown in Figures 2 t 3 and 4 incorporates two generally radially extending, diametrally opposed blades 16 which, as shown in Figure 2~ are of substantially uniform circumferential width from their roots to their tips. As best seen in Figures 3 and 4/ the leading edge 20 of each blade is thin for chopping or comminuting chunks or lumps of solid material in the slurry passing to the pump inlet.
While the root portions of the blades project substantially radially from the propeller hubr the outer end portions of the blades are curved slightly rearward in the plane of rotation so that hard chunks or lumps of solid material will be impelled outward so as not to clog the pump inlet.
The transverse section of Figure 4 illustrates the preferred cross-sectional shape for each propeller blade 16 throughout at least the major portion of its length. Its trailing side 21 is concave generally about an axis substantially parallel to the axis of rotation. For any transverse cross section an upright element of the trailing side 21 is substantially linear~ preferably substantially parallel to the axis of rotation~ Also for any transverse cross section, preferably a laterally extending element of the lower side 22 of the blade is substantially linear and lies in a plane substantially perpendicular to the propeller axis~ and for any transverse cross section preferably a laterally _~_ extending element of the upperS slurry-propelling side 23 of the blade also is subst:antially linear or only slightly concavely curved ancl is inclined upward from the leading edge 20 of the b].ade to the upper edg~ 24 of the trailing side 21. Accordinglyr throughout at least the major portion of it:s radial extent the blade is of generally triangular cross section, and, more specifically, of generally right triangular cross section.
In side elevation, as shown in Figure 1, each blade 16 also is substan~ially triangular, the lower edge of the blade, defined by its cut.ting edge 20, appearing substantially linear and inclined upward from the root of the blade to its tip, and the upper edge 24 of the blade, defined by the junction of the trailing side 21 and the upper surface 23, appearing substantially linear and lying in a plane substantially perpendicular to the axis of rotation.
Accordingly, each blade .is tapered in axial extent substantially uniformly from its root to its tip.
As seen in Figure 3, at the tip of a blade 16 the angle of the upper surface 23 to a radial plane is sharply acute. Progressing inward, the angle increases uniformly to the roo~ of the blade and, since the blade is of substantially uniform circumferential width throughout its length, the propelling force generated by a rotating propeller blade is substantially uniform from the tip of the blade to its root because of the greater tip speed of the bladeO
While each .Eaature of the booster propeller is considered important, experiments have shown that ~9_ ~3~
of almost primary importance is that the blade be tapered in thickness from its trailing side 21 to its leading edge 20 and that the upright elements of the blade trailing side be substantially linear and r preferably, substantially parallel to the axis of rotation. Propellers substantially identical to the propeller shown in the drawings but having blades with convexly rounded trailing sides were much less effective in boosting the head of a centrifugal pump.
The head-increasing tendency of the propeller also is aided by locating it at the entrance to or substantially within an outwardly flared funnel 28 which can conveniently be formed as a recess in the pump end plate 13 leading to the arcuate inlet apertures 14O The sides of the funrel flare outward at an angle of about 45 degrees relative to the axis of rotation, and the axial depth of the funnel should be at least equal to the maximum axial extent of a blade 16 of the booster propeller 15. Such depth is about 10~ to 15% of the diameter of the end plate. The maximum radius of the funnel should be at least about one and one-half times the radial extent of a blade 16. Slurry at the radially outer margin of the end plate is accelerated smoothly through ~he funnel toward the current generated by the booster propeller.
Preferably the tips of the propeller blades extend to or slightly beyond the radially outer edges 27 of the arcuate inlet apertures which are faired by bPing rounded to assure a smooth flow into the pump.
Similarly the radially inner ~dges 27' of the inlet apertures ~re rounded for smooth flow of slurry into the pump~
'10 While it is preferred that the propeller be located at the entrance to or substantially within the end plate funnel 28~ it also is preferred that the propeller be spaced downwarcl from the inlet apertures a distance sufficient that i.t will not interfere with the slici.ng effectiveness of the impeller blades 10 and entry of slurry and small particles into the pump casing past the propeller. In the embodiment shown in the drawings, a cylindrical spacer 25 spaces the propeller downward from the flat inner portion of the end plate a distance only slightly less than the radial width of an inlet aperture. The lower portion of such spacer has a bevel 26 guiding the slurry toward the rounded radially inner edge$ 27' of the inlet apertures 14~
For assuring a compact design, the apertured end plate 13 is xeceived within the pump bowl and has a bottom annular flange 29 enabling the end plate to be bolted to the upright sides of the pump casing 5.
As shown in Figure 6~ the primary advantage of recessing the end plate into the pump bowl is that the planar upper surface 30 of the end plate can be located flush with the lower side 31 of the pump outlet conduit 18 which i.s integral with the pump casing 5. In prior pumps, such as the pump of U.S.
patent NoO 3~973,866~ an end plate extends across the lower edge of a pump casing having an integral outlet conduit, so that a substantial turbulence-promoting step occurs in the are.a of the entrance to such conduit.
To minimize backflow of high-pressure slurry in the pump cas.ing 5 out the inlet apertures 14, such ~3~
apertures are located as close to the center of the impeller as possibleO The radially outer edges of the inlet apertures are posi.tioned approximately midway between the axis of rotation and the radially outer tips of the primary pumping impeller blades 10.
Preferably at least the major portion of the inlet aperture area is located within a circle having a radius one-half the radius of the circle defined by the rotating impeller blades.
The specific design of the impeller also assures a high head and effective slicing action of chunks or lumps of solid material in the slurry being pumped. As best seen in Figures 5, 6 and 7, three primary pumping blades 10 are provided projecting downwaxd from the shroud plate 8, each of substantially constant circumferential width throughout its length. Each blade is at least several times longer than its axial height and projects first generally tangentially from the impeller hub 9 and then is curved spirally rearward in the plane of rotation~ As best seen in Figure 7, the lower leading edge 33 of eAch blade is sharpened and is in close slicing relationship to the upper side 30 of the pump casing end plate 13. For this purpose the leading axcuate sides 34 of the end plate inlet apertures are beveled to a rearward facing sharpened edge 34' ~or close slicing contact with the leadi.ng sharpened edges 33 of the bladesO
Whereas prior centrifugal slurry pumps having used blades that project generally radially in the area of the inlet apertures for abrupt choppin~ of chunks or lumps of solid material iII the slurry, the ~12-~3~
blades of the present invention are angled rearward in the area of the inlet aperture,s at a substantial angle relative to a radius, preferably at least 45O As best seen in Figure 2, the apparent movement of a blade as it approaches a sharpened lead.ing edge 34' of an inlet aperture 14 is both forward and radially outward for effecting an angular slicing action, as opposed to an abrupt chopping action 9 of chunks or lumps of solid material in the slurry~
So that the primary impeller vanes 10 do not themselves interf~re with entrance of slurry through the inlet apextures, it is preferred that the circumferential width of the blades be as small as possible at their lower sides 3S, preferably no greater than one-half the radial width of the inlet apertures~ As best seen in Figure 7, however~ the upper portions of the leading sides 32 and the txailing sides 36 of blades should be faired gently into the shroud plate by fillets extending from about the axial center of each blade for smooth change of flow direction of the slurry from a generally axial direction to accelerated movement in the plane oE
rotation. As a result of the ~airing, the blades are tapered in circumferential width from their roots to their tips suGh that the circumferential width of each blade at its tip is no greater than about one-half the circumferential width of the blade at its root~ In combination with the fairing of the leading side 32 of the blade into the shroud plate, the forward curved lower tip portion of the hlade leading to the sharpened cutting edge 33 forms a substantial forward openi.ng cup that is swep~ spirally reaxward in the ,~ ,.., ;
l3 3~
plane of rotation for ef.Eect.ive but smooth acceleration of the sl.urry circumferentially forward and outward toward the pump outletO As shown in Figure 7, the fairing of the trailing side 36 of the blade into the shroud plate 8 is more gradual than the fairing of the leading side 32 into such plate, that is, the radius of curvature of the fillet formed at the upper portion of the trailing side is greater than the radius of curvature of the fillet formed at the upper portion of the leading side.
The axially short ribs or vanes 11 projecting upward from the shroud plate are provided primarily to protect the seal 12 rather than to assist in pumping the slurry~ Such vanes are substantially shorter than the primary pumping vanes 10, and more upper vanes 11 are provided at closer spacing. Rather than being volute or curved rearward in the plane of rotation, such upper vanes 11 are substantially straisht though angled rearward as to be generally tangential to the periphery of the drive shaft 1~ As with the lower primary pumping blades 10, such upper vanes 11 are faired into the shroud plate by fillets extending from at least about their axial centers as shown in Figure 7O
The overall design of the upper vanes 11 results in development of higher pressure at the periphery and above the shroud plate 8 than below it so that there i.s some suction above the plate away from the seal 12r Accordingly, lubricant from the reservoir in housing 2 tends to be drawn through the bearings 3, the seal 4 and the seal 12~ assuring ~3~
longer life than if a positive pressure we.re exerted above the shroud plate towa:rd the seals which could force slurry through the seals and bearings into the lubricant housing. In addition, seal failure is quickly and accurately detected by a rapid decrease in the level of lubricant in the reservoir formed by the housing.
A final fa~tor af-fecting the head of the pump is the design of the pump casing 5. As shown in Figure 5, rather than being spiraled or volute throughout its circumference, that is, rather than having a progressively increasing radial extent between the casing and the radially outer ends of the pump blades in the direction of rotation, such casiny is semicylindrical and semivolute. Beginning at the outlet conduit 18 and moving opposite the direction of rotation, for about one-half the circumference of the impeller, the casing spirals inward toward the shroud plate, and for the final one-half of its circumference the casing closely encircles the shroud plate providing a semicylindrical zone. Since slurry cannot escape outward in the semicylindrical zone, pressure of the slurry increases substantially in this zone before the slurry can escape circumferentially toward the outlet conduit and, as a result, the head of the pump is substantially increased~
Claims (2)
1. In a centrifugal pump including an impeller rotatable about an axis and a pump casing including a bowl receiving the impeller and a generally circumferential outlet, the improvement comprising the bowl including a cylindrical portion, coaxial with the impeller, forming a wall closely encircling no greater than approximately one-half of the circumference of the impeller and a volute portion forming a wall spiraled outward from said cylindrical portion in the direction of impeller rotation.
2. In a centrifugal pump including an impeller rotatable about an axis, a pump casing including a bowl encircling the impeller and an outlet conduit extending substantially tangentially from the bowl, the improvement comprising the pump bowl being of substantially semicylindrical and semivolute cross section, the semicylindrical portion of the bowl being coaxial with the impeller, forming a wall closely encircling the impeller for approximately one-half the circumference of the impeller and located forward of the outlet with reference to the direction of impeller rotation to form a pressure increasing zone, and the semivolute portion of the bowl forming a wall spiraled outward from the wall of the cylindrical portion to the radially outer side of the outlet conduit and encircling about one-half the circumference of the impeller.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/229,700 US4842479A (en) | 1981-01-29 | 1981-01-29 | High head centrifugal slicing slurry pump |
| US229,700 | 1981-01-29 | ||
| CA000391172A CA1172906A (en) | 1981-01-29 | 1981-11-30 | High head centrifugal slicing slurry pump |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000456139A Division CA1193486A (en) | 1981-01-29 | 1984-06-07 | High head centrifugal slicing slurry pump |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000456139A Division CA1193486A (en) | 1981-01-29 | 1984-06-07 | High head centrifugal slicing slurry pump |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1193486A true CA1193486A (en) | 1985-09-17 |
Family
ID=25669495
Family Applications (4)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000456141A Expired CA1193484A (en) | 1981-01-29 | 1984-06-07 | Slicing impeller for slurry pump |
| CA000456139A Expired CA1193486A (en) | 1981-01-29 | 1984-06-07 | High head centrifugal slicing slurry pump |
| CA000456140A Expired CA1193483A (en) | 1981-01-29 | 1984-06-07 | Impeller to draw seal lubricant from outside reservoir |
| CA000456138A Expired CA1193485A (en) | 1981-01-29 | 1984-06-07 | High head centrifugal slicing slurry pump |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000456141A Expired CA1193484A (en) | 1981-01-29 | 1984-06-07 | Slicing impeller for slurry pump |
Family Applications After (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000456140A Expired CA1193483A (en) | 1981-01-29 | 1984-06-07 | Impeller to draw seal lubricant from outside reservoir |
| CA000456138A Expired CA1193485A (en) | 1981-01-29 | 1984-06-07 | High head centrifugal slicing slurry pump |
Country Status (1)
| Country | Link |
|---|---|
| CA (4) | CA1193484A (en) |
-
1984
- 1984-06-07 CA CA000456141A patent/CA1193484A/en not_active Expired
- 1984-06-07 CA CA000456139A patent/CA1193486A/en not_active Expired
- 1984-06-07 CA CA000456140A patent/CA1193483A/en not_active Expired
- 1984-06-07 CA CA000456138A patent/CA1193485A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| CA1193485A (en) | 1985-09-17 |
| CA1193483A (en) | 1985-09-17 |
| CA1193484A (en) | 1985-09-17 |
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |