US2951449A - Centrifugal pump - Google Patents

Description

Sept. 6, 1960 .1. P. VAN BLARCOM, JR., r-:T AL 2,951,449

CENTRIFUGAL PUMP Original Filed Feb. l5, 1957 United States Patent O CENTRIFUGAL PUMP James P. Van Blarcom, Jr., Ridgewood, and Joseph L.

Gatto, Wyckoff, NJ., assignors to Bell & Gossett Company, a corporation of Illinois Continuation of application Ser. No. 640,548, Feb. 15, 1957. This application July 30, 1957, Ser. No. 675,127

6 Claims. (Cl. 10S-113) This invention relates to centrifugal pump constructions and is an improvement upon the pump shown and described in patent application Serial No. 640,548, tiled February 15, 1957, the disclosure of which, to the extent it is not inconsistent herewith, is specifically incorporated by reference.

The pump of the aforesaid application is intended for universal application and, towards that end, provides a plurality of peeling vanes spaced about the lperiphery of the pump impeller with substantial peeling clearances between the vanes and the impeller. The arrangement had the important capability of handling solid laden liquids and of minimizing noise and wear while developing adequate peeling action to permit fast self-priming even against a positive discharge head. Liquid volume relationships were correlated to compensate for the syphoning eiects accompanying a suction break on the inlet side during a high suction lift pumping operation and permit the pump to retain a reserve of liquid suiilcient for reprime of the unit.

The principal object of the present invention is to improve the syphon-breaking action of the arrangement without impairing its priming ability.

Another object is to minimize the reserve of liquid required for ecient repriming.

Generally speaking, this is accomplished by employing a plurality of peeling vanes spaced about the periphery of the impeller, with one of the vanes being extended in the form of a main shroud that curves around the impeller periphery in outwardly spiralling relationship from a point on the lower side of the impeller to the top of the impeller periphery for discharging a liquid curtain across the top of the impeller periphery, and with a second vane extended in the form of a secondary shroud that curves around the impeller periphery in outwardly spiralling relationship forming a top point in the discharge path of the main shroud to extend beneath the reserve liquid level of the pump. The discharge from the main shroud is directed across the space between the inner end of the secondary shroud and the outer end of the main shroud.

i. This space provides a syphon-breaking passage adjacent the top of the impeller chamber and insures an early syphon break and, hence, an adequate reserve of liquid.

In spite of the fact that this passage at the top of the impeller chamber is physically open during priming, the discharge from the main shroud is directed across this passage and functions as a liquid curtain that seals the passage and permits efficient priming.

The arrangement of the invention is characterized by a small, economical casing of the minimum height necessary to enclose the shrouds. The secondary shroud is arranged to discharge into the bottom of the casing and provide a desirable sweeping action that renders the pump -self-cleaning.

Other objects and advantages of the invention will Patented Sept. 6, 1960 p. ICC

become apparent during the course of the following description.

In the accompanying drawings forming a part of this specification and in which like numerals are employed to designate like parts throughout the same,

Fig. 1 is a vertical sectional view along the center line of the pump casing, with certain internal walls broken away and sectioned to better illustrate the arrangement; and Fig. 2 is a vertical sectional view taken substantially along the line 2-2 of Fig. l.

. Referring now to the drawings, the pump of the present invention includes a divided casing 10 having a discharge outlet 11 and a suction passage 12 terminating at a suction inlet 13.v With the arrangement shown, the lower lip of the suction passage 13 denes a static drain level 14 and, while the elevation of this level may be varied somewhat by appropriately rearranging the suction passage and suction inlet, it will become apparent that a certain minimum level must be maintained to permit the pump to reprime.

The casing itself consists of a generally hollow main section 16, both sides of which are open and the top of which is formed with the discharge outlet 11 and with a fill plug opening 17, a cover plate section 18 that actually forms the suction side of the pump secured across one of the open sides of section 16, and a recessed closure flange 19 secured across the other open side of casing 16 and sandwiched between the bearing ilange 20 and casing section 16 to seal o the interior of the pump.

The casing is provided with a novel internal wall arrangement that defines a generally cylindrical impeller chamber 21, a flow conversion chamber 22 surrounding the periphery of the impeller chamber, and a plenum chamber 23 defined by the remainder of the casing, with the flow conversion chamber arranged to effect a reduction of the velocity head of the liquid discharged from the impeller chamber before delivering this discharge to the plenum chamber.

An impeller 25, which is here shown as including a plurality of blades 26, is rotatably mounted in the im- Apeller chamber for counter-clockwise rotation, as seen communicates directly with the suction passage 12. The

drive shaft 27 for the impeller projects through a seal well 28 formed'by the closure flange 19, and a rotatable ring assembly 29 seals the impeller to the closure flange an-d isolates the interior of the pump at this point.

In the preferred form of the invention, the chambers mentioned above are defined in part by a replaceable, one-piece diifuser member, ydesignated generally as 30, that is gripped and held by oppositely facing annular shoulders, 31 and 32, respectively, formed on the cover plate section 18 and closure flange 19. The illustrated diffuser member includes a tubular inlet stub 33 that forms an extension of the inner end of suction passage 12, a first generally annular Wall 34 that surrounds the suction passage, a second generally annular wall 35 axially spaced from the tirst wall, and a plurality of vanes 36 spaced circumferentially around the diiiuser and spiralling outwardly between the walls 34 and 35.

According to the invention, the flow conversion chamber 22, which, as described thus far, includes the passages formed by the vanes 36, is provided with main and secondary shrouds, 38 and 39, respectively. These shrouds actually are extensions of two of the vanes 36 vand spiral outwardly to form collecting channels of progressively increasing capacity to receive and conduct the liquid emerging from various points on the periphery of the impeller.

The plurality of vanes 36 of the preferred arrangement provide multiple peeling points to achieve eticient priming, even against positive discharge heads, without requiring critically close clearances.

While some, or all, of the walls of the diffuser and some of 4the par-ts of the casing could be cast integral, the separate arrangement of the present disclosure, permits easy disassembly for repair or replacement and, additionally, simplifies the coring problems in casting the various parts. peller, it is merely necessary to take off the cover plate 18.

The 'wall 34 forms concentric outer and inner annular surfaces 40 and 41, respectively, with the inner surface 40 cooperating with a corresponding Aannular surface 42 provided on the fiat, recessed wall 44 of the closure flange 19 to define the end walls ofthe impeller chamber 21. The annular Wall 35 provides a generally annular surface 43, which cooperates with annular surface 4i y land the vanes 36 to define a plurality of diverging liquid flow passages `45, the inlets of which originate adjacent the periphery `of the impeller chamber, while their out-lets extend outwardly and forwardly in the direction of the impeller rotation. As is apparent to those familiar with this art, these diffuser passages 45 receive a relatively turbulent discharge from the impeller chamber and convert it into -a stream-like flow for discharge into the plenum chamber while effecting a change from velocity head to pressure head.

The principal purpose of the shroud yarrangement is to provide a pump t-hat is able to prime against a positive discharge head and also to provide .a pump that has an effective syphon-breaking action for insuring that a sucient reserve of liquid will be retained for repriming. It will be seen that the main shroud 38 is an extension of one of the vanes at the lower side of the pump and it 4i-s brought around the side of the pump and terminated to form a horizontal discharge outlet in substantially the same vertical plane `as the axis of the impeller. The secondary shroud 39 is an extension of one of the upper vanes that passes beneath the discharge outlet of the main shroud 38 and it extends around the other `side `of the pump to discharge the liquid that is collected in it into the bottom of the casing. As mentioned previously, the passageways formed by the shrouds may diverge in order to handle, without veloci-ty conversion, if desired, the progressively increasing liquid volume due to the incremental flow added by each ksuccessive passage 45 that is bounded by the particular shroud.

It will become apparent that, while the shroud arrangement does not form an imperforate enclosure hood for physically blocking off the top of the impeller chamber from contact with the discharged `air during the priming cycle, it does achieve this result by depending upon the discharge from the main shroud, which forms an isolating .liquid curtain across the open passage that exists between the shrouds. rThis liquid curtain effectual- -ly seals this passage during the priming cycle, but the passage is open during a syphoning action, such as results from breaking suction on the inlet side of the pump to provide an early syphon break.

For best results, it is preferred that the discharge outlet of the main shroud 38 be generally rectangular to` permit the liquid curtain discharged therefrom -t-o completely ood the outlet 46. The velocity imparted to the discharged liquid by the impeller is sufficient to carry it over the opening 46 with little or no backow.

Finally, the wall 34 is provided with one or more prime holes 47 to provide a return path for the airfree liquid that occupies the plenum chamber during the priming cycle. Preferably, these holes are formed in the portion of the Wall 34 that .is beneath the liquid level in the pump during prim-ing although, of course, 'the priming passages could be embodied in various other form-s without departing from the spirit of the invention. For example, the holes could be at the uppermost region of the impeller chamber with tubing extended intothe To removethe diffuser and/or the implenum chamber to a point beneath the liquid level. Alternatively the passages could be brought through the other end wall of the impeller chamber.

In the prim-ing cycle the pump operation is as follows:

The rotation of the impeller 2S exhausts the reserve of liquid from the impeller chamber 21 and air is drawn through the suction passage 12 and into the eye of the impeller. A pressure differential will exist between the region of the liquid ow passages 45 and the region of theyeye of the impeller, and this pressure differential develops a reverse flow of the initially exhausted liquid. The impact of the reversely flowing liquid against the tips of the impeller vanes sets up a turbulence and splashing of liquid at the periphery ofthe impeller, and incoming air from the suction side is then taken up to form a foamy mechanical mixture of air and liquid.

As the impeller vanes sweep past the foarny mixture, a hydraulic seal is established at the periphery of the impeller and, due to the centrifugal force effect of the impeller and the increased volume of the mechanical mixture, the foamy mixture of air and liquid is forced outwardly through the passages 45. As is conventional, these passages are arranged to develop a stream-like flow and effect a velocity transition to a lower flow rate.

During this action, air bubbles, as indicated at 48, are peeled off by the inner tips of the vanes 36 and carried with the flow streams into the relatively quiescent plenum chamber where the air is separated and vented through outlet 11. To maintain the priming action, air-free liquid is recireulated to the impeller chamber 21 for mixing with more of the air that is drawn in from the suction side of the pump until finally, the air is exhausted from the suction line and the pump is fully primed. During the priming cycle, a limited amount of air-free liquid returns along the air-free surfaces of the peeling vanes, but the majority of the recirculating liquid is handled by the ports 47 formed in the wall 34. the liquid recirculation paths along the uppermost vanes may be physically located above the liquid level of the pump since such paths are shielded against return of vented air by the sealing action of the flowing liquid curtain that is established across the open passage 46 between the overlapping portions of the imperforate shrouds 38 and 39. The other ends of the shrouds are carried beneath the liquid level so that the only conceivable access point for returning air is the syphon-breaking passage 46, but the discharge from the main shroud continuously seals this passage.

One of the primary advantages of the present pump arrangement is that it includes a syphon-breaking passage that opens directly into the upper region of the impellet chamber for insuring immediate and effective -syphon-breaking action so that a maximum reserve of liquid is retained in the pump casing. The level of this reserve of liquid is basically determined by the elevation of the lower lip of the suction intake 13; however, in applications involving a high suction lift, each time suction is broken on the intake side of the pump and the liquid being pumped drains back through the pump casing and down the suction line, a severe syphoning effect develops which tends to carry the level of the reserve of liquid below the static level that is defined by the lower lip of the suction intake. The relatively large and direct syphon-breaking passage of the present invention limits the loss of liquid due to syphoning effects.

Experiments with vthe present pump construction have indicated that the elev-ation of the suction inlet may be varied to a considerable extent without impairing the ability of the pump to prime or reprime. It has been lfound that the pump can prime with the suction inlet directly yin line with the impeller axis or at any higher point within the confines of the pump casing. In the illustrated case, wherein the suction inlet is considerably above the eye of the impeller, the liquid level, in applications involving severe syphoning elects, would sta- It should be noted that sein-te bilize in the vicinity of the impeller axis or slightly above it. However, if the suction inlet is Yin line ,with the eye of the impeller, the liquid level would stabilize at a point only slightly beneath the level of the lowervlip of the suction inlet.

In determining the effective level of the reserve of liquid in the pump, consideration should be :given to the dynamic conditions existing due to the impeller rotation. For example, as the impeller rotates counterclockwise as viewed in Fig. l, the level of the reserve of liquid tilts, the left side, where the blades pass downwardly through the liquid, being lowered and the right side, where the blades pass upwardly through the liquid, being raised. Furthermore, the mechanical mixture nof `air and liquid swells the overall volume of the reserve of liquid and produces an increase in the elective liquid level.

It must be understood that these considerations alter vthe static liquid level so that the term, liquid drain level, as used in the description and claims is hereafter understood as meaning the level thatpresults fromthe composite elfects of the elevation of the suction inlet, .the dynamic effects of the impeller, andsyphoning elfects. The criterion for priming of the pump is merely that the liquid drain level behigh enough to completely cover the prime holes during the priming action. Of course, the volume relationships of the various chambers of the pump must be such that the volume of the reserve of liquid exceeds the combined liquid volume capacity of the impeller chamber and the ow conversion chamber.

As pointed out previously, the only critical relationship concerning the discharge outlet of the secondary shroud 39 is that it be located beneath the liquid drain level of the pump in order that vented air may not recirculate and disrupt the priming action. lt is preferred, however, that this discharge opening may be loc-ated well towards the bottom of the casing to direct its discharge in la lsteady stream across the bottom of the casing and develop a desirable self-cleaning action. More particularly, the bottom of the casing -is formed with a smoothly curving, concave surface, and the discharge outlet is directed along a line that is substantially tangent to the -adjacent part of this surface to develop a smooth sweeping action.

Thus, it may be seen that the objects of the invention have been accomplished in that the pump construction provides a syphon-breaking passage of optimum effectiveness that extends directly into thetop of the impeller chamber and that is automatically sealed during priming due to the novel relationship of the main and secondary shrouds. r effective that no suction-check valve is required` for retaining a reserve of liquid adequate to permit repriming. The priming characteristics of the pump, as respects the speed of priming, the type of material that may be handled, the ability to prime against discharge heads, Iand the ability to prime with minimum reserves of liquid, is retained in full measure. The easing is of a simplified yform and of minimum size and is arranged to facilitate the self-cleaning action provided by the location of the discharge outlet of the secondary shroud. In addition, the pump casing is formed in sections Vthat are readily assembled and disassembled to permit repair or replacement of internal parts of the pump.

It should be understood that the description of the preferred form of the invention is for the purpose of complying with Section 112 of Title 35 of the U.S. Code, and that the appended claims should be construed as broadly'as the prior art will permit.

l. A centrifugal pump comprising a casing having a discharge outlet and a suction passage terminating at a suction inlet with said suction passage and said suction inlet cooperating in defining a liquid drain level; internal surface portions carried by said casing to form an im- The syphon-breaking action is so 6. peller chamber that communicates with the suction passage, a ow conversion chamber around the periphery of the impeller chamber, and a plenum chamber occupying the remainder of said casing and communicating'with the discharge outlet; and a centrifugal impeller rotatable in a given direction in said impeller chamber and having a suction eye around its axis with the eye facing said suction passage: wherein said internal surface portions include a rst wall having inner and outer surface portions of generally annular shape, said inner surface portion surrounding saidA suction passage and cooperating with said casing to form the end walls of a generally cylindrical impeller chamber, one of said end Walls having priming passage means extending therethrough and connecting said impeller chamberA to a region of said plenum chamber beneath the liquid drain level, a third generally annular surface, of substantially the same size and shape as said outer surface portion, spaced from and facing the same to form the end walls of the flow conversion chamber, and a plurality of vanes spaced about the periphery of said impeller chamber with their inner ends cooperating with the impeller `and providing a plurality of peeling points, said vanes being ldisposed between said outer surface portion and said third annular surface to dene therewith a plurality of divergent, intermediate liquid passages having inlet terminating adjacent the periphery of the impeller chamber and having outlets extending outwardly and forwardly in the direction of impeller rotation, a lower one of said vanes being extended, from a point beneath the liquid drain level, in the form of an arcuate wall portion that spirals outwardly in the direction vof impeller rotation with its opposite sides in sealing cooperation with peripheral -portions of said outer surface portion and said third annular surface to forma channel for collecting part of the fluid discharged from the impeller chamber, said channel terminating in adischarge outlet directed substantially tangent to and across the top of the ow conversion chamber, and an Vupper one of said vanes that overlaps said discharge outlet of said channel beingextended, to a point beneath said drain level, in the form of an arcuate wall portion that spirals outwardly in the direction of impeller rotation,Y vn'th its opposite sides in sealing cooperation with peripheral portions of said outer surface portion and said third annular surface to form a channel for collecting anddischarging fluid discharged from the impeller chamber. g

2. A centrifugal pump comprising a casing havinga discharge outlet and a suction passage terminating at a suction inlet with said suction passage and said suction inlet cooperating in delining a liquid drain level; internal surface portions carried by said casing to form an impeller chamber that communicates with the suction passage, a ow conversion chamber around the periphery of the impeller chamber, and a plenum chamber occupying the remainder of said casing and communicating with the discharge outlet; and a centrifugal impeller rotatable in a given direction in said impeller chamber and having a suction eye around its axis IWith the eye facing said suction passage: wherein said internal surface portions include a first Wall having inner and outer surface portions of generally annular shape, said inner surface portion surrounding said suction passage and cooperating with said casing to form the end Walls of a generally cylindrical impeller chamber, one of saidend walls having priming passage means extending therethrough and connecting said impeller chamber to a region of said plenum chamber beneath the'liquid drain level, a third generally annular surface, of'substantially the same-size and shape as said outer surface portion spaced from and facing the same, and a plurality of vanes spaced uniformly about the periphery of said impeller chamber with their inner ends cooperating with the impeller and providing a plurality of peeling points, said vanes being disposed between said outer surface portion and said third annular surface yto deine therewith a plurality of divergent intermediate liquid kpassages having inlets terminating adjacent the periphery of the impeller chamber and having outlets extending outwardly and forwardly in the direction of impeller rotation, a lower one of said varies being extended, from a point beneath said drain level, in-the form of Ian arcu- .ate wall portion that spirals outwardly in the direction of impeller rotation with its opposite sides in sealing cooperation with peripheral portions of said outer surface portion and said third annular surface to form a channel for collecting the iiuid streams discharged from the intermediate passages communicating therewith, said channel terminating in a discharge outlet directed substantially tangent to and across the top of the periphery of said intermediate passage outlets, and anV upper one of said vanes that overlaps said discharge outlet of said channel being extended, to a point beneath the liquid drain level, in the form of an arcuate wall portion that spirals outwardly in the direction of impeller rotation, -with its opposite sides in sealing cooperation with pe ripheral portions of said outer surface portion and said third annular surface to form a channel for collecting the fluid streams discharged from the intermediate pas sages communicating therewith.

3. The arrangement of claim 1 wherein the casing is provided with a smoothly curving, concave bottom surface and the last-mentioned channel terminates ina dischlarge outlet that is directed substantially tangent to said surface to discharge liquid and establish a smooth liquid ow across said bottom surface for maintaining the bottom of the casing free of foreign deposits.

4. A self-priming pump comprising a casing for holding a reserve of liquid, said casing having a suction passage terminating at a suction inlet and having a discharge outlet, a diffuser disc fixed in said casing and being formed at its center with a suction opening in communication with said suction inlet passage and having about its periphery a plurality of diffusion vanes defining intermediate liquid passages, and an impeller positioned within the contines of said disc and rotatably mounted in said casing in said reserve of liquid, said impeller having vanes radially aligned with said intermediate liquid passages, wherein one of the lower diffuser vanes is extended in an outward spiral, from a point within said reserve of liquid, in the direction of impeller rotation to form a main shroud that collects the uid streams discharged from the liquid passages communicating therewith, said shroud terminating in a discharge outlet directed sub,- stantially tangent to and across the top of the periphery of said liquid passages, and an upper one of said vanes spirals outwardly, from a point adjacent the top of the periphery of said liquid passages and in the discharge path of said main shroud, to a point within said reserve of liquid, in the direction of impeller rotation to form a secondary shroud that collects the fluid streams discharged from the liquid passages communicating therewith.

5. A centrifugal pump comprising a casing having a discharge outlet and Ia suction passage terminating at a suction inlet with said suction passage and said suction inlet cooperating in defining a liquid drain level; internal surface portions carried by said casing to form an impeller chamber that communicates with the suction passage, a ow conversion chamber around the periphery of the impeller chamber, and a plenum chamber occupying the remainder of said casing and communicating with the discharge outlet, with priming passage means connecting said impeller chamber to a region of said plenum chamber beneath the liquid drain level; and a centrifugal impeller rotatable in a given direction in said impeller chamber and having a suction eye around its axis with the eye facing` said suctionV passage: wherein said internal surface portions include a plurality of vanes spaced about the periphery of said impeller chamber with their inner ends cooperating with the impeller andV providing a plurality of peelingv points, opposing, spaced apart, annular side walls flanking said vanes and defining therewith a plurality of intermediate liquid passages each beginning adjacent the periphery of the impeller chamber and extending outwardly and forwardly in they direction of impeller rotation, and arcuate wall portions extending in the direction of impeller rotation with opposite sides thereof in sealing cooperation with peripheral portions of said side walls to form a iirst channel extending around the periphery of and in communication with a plurality of said liquid passages y,from a point on the underneath side of the impeller chamber to terminate in a discharge outlet directed substantially tangent to and across the top of the flow conversion chamber and a second channel extending around the periphery of and in communication with others of said liquid passages from a point beginning at an upper vane that overlaps said discharge outlet to terminate in a discharge outlet at a point beneath said liquid drain level.

6. A centrifugal pump comprising a casing having a discharge outlet and a suction passage terminating at a suction inlet with said suction passage and said suction inlet cooperating in defining a liquid drain level; internal `surface portions carried by said casing to form an impeller chamber that communicates with the suction passage, a flow conversion chamber around the periphery of the impeller chamber, `and a plenum chamber occupying the remainder of said casing and communicating with the discharge outlet, with priming passage means connecting `plurality of intermediate liquid passages each beginning adjacent the periphery of the impeller chamber and extending outwardly and forwardly in the direction of impeller rotation, and arcuate wall portions extending in the direction of impeller rotation with opposite sides thereof in sealing cooperation with peripheral portions of said side walls to form a iirst channel extending around the periphery of and in communication with a plurality of said liquid passages from a point on the underneath side of the impeller chamber to terminate in a discharge outlet located in the vertical plane of the impeller axis and directed substantially tangent to and across the top of the periphery of said intermediate liquid passages and a second channel extending around the periphery of and in communication with others of said liquid passages from a point beginning at an upper vane that overlaps said discharge outlet to terminate in la discharge outlet at a point beneath said liquid drain level.

References Cited in the tile of this patent UNITED STATES PATENTS Gudmundsen May 21, 1957

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