US2668501A - Multiple stage centrifugal pump - Google Patents

Description

Feb. 9, 1954 M. w. L UTz MULTIPLE STAGE CENTRIFUGAL PUMP med oct. 27, 1949 1| ll.' *N ww mw am. \\l/., [lll] fl@ N Y i m Il 3 w w v w N w .N am. Nuss L .N f \v n m if M. M( .mh VM WN. .f QN \|l mm wwf. on N NN QN F. Il, l .I MM. 1| Q/ m .Q Q YS Patented Feb. 9, 1954 Milton Lutz, Wauwatcsa, wis.,

.assignerto `Allis-Chalmers Manufacturing Qompany, --Milwauhee, Wis., a corporaticntnfhelaware .Applicatiomctober 1949, =Serial"-No. 123,856v

4....claims.

This invention :relates to: multiple "stage centrifugalgpumps. Morefspecically this; invention relates to improvementsina` sea1ing..arrangements between the pumping stages of `a-niultiplestage centrifugal pump. .The principalA ebiect of this invention is the. provision. of -anew and improved liquidipumpingzmachine.

Inmultiple-stage centrifugalpumps, one ofthe problems, has been they-sealing of .-the-outboard ends of a pumpf-casingfto .an impeller.shaft.pass ing-.therethreugn .To l'simplify-this problem, `the pumping fstagesrhave -been Iarranged-with the first stageononeendmf the shaft, the second .stage .on .the :appositel end Yof the shaft and all lsuisse- .quent .stages :arranged between the first-.and second stage. With thisarrangement ,of-stages, Vthe outboard .shaft-.seals need .only resistthe intake pressure on-cneend and rststage discharge pressureion the other-end--of the-pumpmeasing. This arrangement. of stages results in vhaving -a greaterpressure` diiTerential-.betweenfsome of. the adjacentstagesthanothers. .When-this. pressure diierential is quite high, vra substantial floss in eiiciency may result from the 1 higher pressure liquid leaking into the :stageedeveleprlg 'lower pressure. .For instance, apump .developing 2,0(10 lbs. .per square :inch .in eleven stages, with .the seventh. stage inboardof. and adjacent .totheiirst stage, Amayhewe yas much as i 1,000 lbs. ,perysquare inch `vpressure differential between .these two stages.. .Accordingly ay .primaryobject of..this .in vention is A.to ..provide interstage .sealing means that .willeffectively reduce lleallzagetfrom apumpingstagedevelopng. high pressureyinto. an vadj acent. stage` developing.lesspressura Another. .object of .this i inventonis f to,V provide interstage sealing means .that will .utilize v.the higher pressure within an adjacent-stargate compresspacking material about .the impeller. shaft into :sealing engagement therewith.

Still another object olthisv invention isto .provide interstage sealing `means that will. protect the .impeller from wearand .wilLitselfbe easily and .cheaply replaceable when worn.

Objects and advantages. other. thanthose .above set4 forth will be. apparent as the .description-of the inventionproceeds.

The novel features oflthe invention andhow the "objects are attained'will appearifrom this specification Vand the Aaccompanying drawing showingftwo embodiments-fof; the invention and formi-nga partf of this application: and 4a1l= these nov'elffeatures are intended-toi be painted-out fin the,` claims. Y

'.In the drawing:

Figlisa sectional 'viewf.of..a-.sevenstagerdculzzle Acasing centrifugal, y:punit iernleo.clrvilflgftwo,1. embodiments ofithe invention;.:and. y

Fig.Y ais-.an enlarged View; of one.l ofthe. ernbcdiments of ;the;invention.

.Fi-g` 1 discloses a ipumpA 'comprising' an y guter .casing `l 0 :with: a `divided.. 1 inner f casing -2 zpaued within. -Dividingaef fthe Yinnen csa-.Singin toil-facilitate. assembly is .Well known fthefpriorp'art .as shown by the; patent tQiHe1-lander.,;U. 5..z1t5i6z The inner casingf2'2qcontainsfa series efspllmpipg stages l :to '1, in which. the pressure. @fthe-liquid is 4progressively raised. Stufling; boxt- Inemhers l and VH support. the casings yHJ,52H11 lirflperf.arial alignment.

-:The .outerfcasng A|20 is dividedintoan intake chamber ll andnasdischarge chamber --I;2,sep a rated by: an Vannular-projectionst3. An inletpassage or. passageway i4 transmits: liquid at intake pressure-tothe intakefchamber il. discharge passage f. orf outlet passageway i |15 transmits the liquid from the discharge chamber l 2 at `*..d-ischarge pressure. :The outer casing-illisfopensat 4the discharge chamber i2 end of thefcasing This open end is tted with a casing cover'gili which is attached tc. theeuter casingfl-.bv means ef .bolts.- I'Lfandf a liduidtight sealjis insured .by a. gasket ,20-.whiohis set'` in a recess .2l to-.avoid the; pessibilityzot:blowing. out. The -innerfcasng 22vis inserted into the openend. offtheroutereasing l 0in-and .mounted Atherein. :'Ihexradi-al`r shoulder 23 ,of .the inner casing 12.2 :is .-seatedagainst the annular proiection within thecuter casing I0. -Thefinner casing 22 isheldrmlywagainst .the projection I3 by the :discharge pressure .of`= the liquid -withinthe;dischargeachamber i2. aA gasketf24 ris fitted .betweenftheshoulder ,23 ,gand..the project-.ioni 3' to lprovide aliqudtight sealbetween the inta-ke chamber `Il .and .the-discharge. chamber .12, Boltsgz provide aninitial .seal andkcep the inner -casing- 22r ingposition durillgnperedsaef starting .fand stopping. when vthe y, pressure.-.within the dischargercha-rnber il may not :hegeneugh-to maintain .the seal. AKeys 12.5, :21. also-aid in: Sup:- porting the inner casing 2zingprepemalsnment. inE that theyz keepft-he:innerfcasingfyirem turning Wthinitheputerrcasing i0. f

Afshaft Z8 .isimountedfinthe .inner. easing and: extendsfthroughi: bothfends of-fthe. enter-,case` ingl0. .The pumping-s ages comprise. ,a` series-ef annular. passages orcompartments 9 toi-i fwhichare ,formedfinathe mier-.casing 22. for directing the fluid .rthroughtheainner casing :2.2;.;-as .shown bythe dotuashilowlinesinrFiasi. .Theannular passagesforcompartments 2.9 te earehydrauli cally connected in series relation by means of impellers 36 to 43 mounted on the shaft. The impellers 36 to 43 are operatively disposed to establish predetermined pressures in the respective compartments into which they impel uid. Each of impellers 36 to 43 has an inlet similar to the inlets 45 of the impellers 40, 43.

A section 10 of the inner casing 22 extends into the intake chamber H of the outer casing i0. A stuffing box member 1| is fitted about the shaft 28 to the outer casing l0 and extends through the outer casing l into the intake chamber il. An annular sleeve 12 extends from the section 10 and embraces the stuffing box member 1 I thereby supporting the section 10 in proper axial alignment.

A special stuffing box arrangement is provided for sealing the inner casing 22 to the shaft 28 and to the end cover I6. This arrangement will allow axial expansion of the inner casing 22 relative to the outer casing i0 in response to changes in pressure and/or temperature within the inner casing 22. When a pump of this general type is used for pumping a liquid at high temperature such as boiler feed water, the axial movement of the inner casing 22 relative to the outer casing I0 may be quite substantial and frequent as changes in demand are made upon the pump. To permit this relative movement and yet maintain an effective seal, an annular member 5l is fitted to the inner casing 22 and extends through an opening 68 in theend cover i8. Glands 52, 53 and packing 55, 56 placed concentrically about and within the member 5l thereby effect a seal between member 5l and the end cover I6, and between the member 5l and the shaft 28. Bolts 6I, 68 keep the glands 52, 53 drawn up tight on the packing 55, 56 to maintain the seal at all times. This stuffing box arrangement is described and claimed in the copending application of Hugh L. Ross, Serial No. 123,768, filed October 26, 1949. It will be understood that as far as the invention of the present application is concerned, means of other form may be provided for sealing the inner casing 22 to the shaft 28 and to the cover I8. f

The pressure of the fluid as it passes through the inner casing 22 is raised in the pumping stages l through 1. The first stage comprises two impellers 36, 31 both of which take suction from the intake chamber H and discharge into the passages 29 which direct the liquid to the opposite end of the inner casing 22, where the liquid enters stage 2. The liquid is then directed through the remainder of the stages 2 to 1, which have a single impeller 38 to 43 in each, and the path of the liquid is shown by the passages numbered 38 to 35. The fluid passes from the final pumping stage 1 to the passage 35 which discharges into the pressure chamber i2 of the outer casing I8 and the fluid is then discharged from the pump through the discharge passage I5. The arrangement and location of the stages is further described and claimed in the copending application of Edward J. Blackwell, Serial No. 123,719, filed October 26, 1949.

The arrangement and number of stages as i1- lustrated results in having between stage i and stage 5, fourth stage pressure in the fluid passage 32 adjacent the passage 29 having rst stage pressure therein, and between stage 1 and stage 4, seventh stage pressure in the passage 35 adjacent the passage 32 having fourth stage pressure therein. The high differential in pressure at these two locations requires a special high pressure sealing means or liquid seal structures 8l,

4 82 to reduce leakage of the high pressure liquid into the passage of lower pressure, resulting in a loss of pump efficiency. The sealing means 8l illustrates an embodiment to be used between the adjacent stages I and 5 in which the impellers 31, 4| are both facing in the same direction. The sealing means 82 illustrates an embodiment to be used between the adjacent stages 4 and 1 in which the impellers 48, 43 are mounted back to back.

The sealing means 82 shown in greater detail in Fig. 2 comprises a sleeve 83 having annular radially extending surfaces 92, 93 presented respectively to compartments 35, 32 adjacent each end of the sleeve 83. The sleeve 83 is concentrically mounted on shaft segment 46. Shaft segment 46 is defined as that part of shaft 28 extending between impellers 48, 43. The sleeve 83 telescopically surrounds at least a portion of each of the collars 84, 85 of impellers 49, 43 disposed in the adjacent compartments. The co1- lars 84, 85, respectively, extend rearwardly of the inlet 45 of each of the impellers 48, 43. The sleeve 83 presents intermediate its ends a first external axially extending sealing surface 96 and a second interna1 axially extending sealing surface 91. The first external surface 96 of sleeve 83 is in slidable sealing engagement with the internal surface 9i of the casing portion 89 which may be integral with casing or in the form of a bushing inserted in the casing as shown in Figs. 1 and 2. The second internal sealing surface 91 has a first inwardly directed flange means, shown as flange 86 and an axially extending means 99. Flange 86 presents a third surface 98 which embraces the shaft segment 46 and is in slidable sealing engagement therewith. The axially extending means 99 embraces portions of collars 84, 85 and is in slidable and nonrotatable engagement with portions of collars 84, 85. Means cooperating with the shaft 28 and the sleeve 83, shown as key 81, prevents the sleeve 83 and the flange 86 from rotating about the shaft 28 but allows them to slide axially relative to the shaft 28. The sleeve 83 and the flange 86 define with the collar 84, a space about the shaft 28 for resilient means, shown as packing rings 88. The differential pressure of seventh stage over fourth stage will act upon the sleeve 83 and the flange 88 to force the packing rings tightly against the collar 84 and the shaft 28 to thereby prevent leakage along the shaft 28. The internal surface 9i of the casing bushing or portion 89 embraces the outer surface of the sleeve 83. Circumferentially disposed grooves 99 on sleeve 83 reduce leakage between the bushing 89 and the sleeve 83.

rJihe embodiment illustrated by the sealing means 8l in Fig. 1 is exactly the same as the sealing means 82 except that the sleeve 83a is mounted about the collar 84a of a single impeller 31. The sleeve 83a does not extend beyond the flange 86a as in the sealing means 82. The cross sectional surface of the sleeve 83a and flange 88a is therefore L-shaped rather than the T-shape that is presented by the corresponding surface in the sealing device 82.

Both of these sealing means 8l, 82 reduce the leakage between adjacent passages by utilizing their pressure differential to act upon packing to create an effective seal. The greater the differential in pressure, the greater will be the force on the packing to resist leakage along the shaft.-

The sleeve 83, 83a turns with the shaft 28 and protects the impeller collars 84, 84a, 85 from wear. The sleeve 83, 83a and the bushing89, 89a will in time become worn but can be replaced at relatively low cost.

In operation, as the shaft 28 is rotated, the first stage impellers 36, 3'1 take suction from the intake chamber Il. Impellers 36, 31 discharge the liquid into annular passages 29 including the one adjacent the sealing means 8|. Passages 29 convey the liquid from the first stage to the suction portion of the impeller 38 mounted in passage 30 which forms the second stage. The liquid is pumped from the intake chamber Il to the discharge chamber I2 through a series arrangement of seven pumping stages. Fourth stage liquid discharge and seventh stage liquid discharge appear on opposite sides of sealing means 82, and first stage liquid discharge and fourth stage liquid discharge appear on opposite sides of sealing means 8l.

The higher fourth sta-ge liquid pressure acts on sleeve 83a and causes it to compress packing rings` 88 against collar 84a thereby sealing the first stage from the fourth stage.

Sealing means 82 operates in a like manner except that inthis arrangement sleeve 83 telescopically surrounds portions of the two collars 84 and 85. The seventh stage liquid pressure urges sleeve 83 against the packing rings 88 which in turn are compressed against collar 84 to seal the fourth stage from the seventh.

From the foregoing it will be apparent to those skilled in the art that the illustrated embodiments of the invention provide a new and improved liquid pumping machine and accordingly accomplish the objects of the invention. On the other hand, it will also be obvious to those skilled in the art that the illustrated embodiments of the invention may be variously changed and modied, or features thereof, singly or collectively, embodied in other combinations than those illustrated, Without departing from the spirit of the invention, or sacrificing all of the advantages thereof, and that accordingly the disclosure herein is illustrative only, and the invention is not limited thereto.

It is claimed and desired to secure by Letters Patent:

1. In a centrifugal pump comprising a casing defining an inlet passageway, an outlet passageway and a plurality of compartments adapted for fluid communication, a shaft supported for rotation in said casing and extending between and through said compartments, a plurality of impellers mounted on said shaft and hydraulically Vconnecting said compartments in series relation between said inlet and outlet passageways for the fiow of liquid therethrough, each of said impellers having a collar extending rearwardly of the inlet of each of said impellers and surrounding said shaft, a first one of said impellers being operatively disposed for rotation in said casing to establish a first predetermined pressure in a first one of said compartments and a second one of said impellers being operatively disposed for rotation in said casing to establish a second predetermined pressure in a second one of said compartments adjacent said first compartment, said first predetermined pressure being higher than said second predetermined pressure, said second impeller being disposed with its collar extending toward said first compartment, the improvement comprising a liquid seal structure including a portion of said casing extending between said rst and second compartments, said casing portion surrounding a segment of said shaft and presenting an internal annular sealing surface in radially spaced concentric relation thereto, a sleeve concentrically mounted on said shaft segment between said casing portion and said shaft, means cooperating with said shaft and said sleeve for securing said sleeve in nonrotatable and axially slidable relation to said shaft, said sleeve having a part telescopically surrounding at least a portion of said collar of said second impeller, said sleeve presenting at each end thereof annular radially extending surfaces opened to said first and second compartments and presenting intermediate said ends a first external axially extending sealing surface and a second internal axially extending sealing surface, said second surface having a first inwardly directed flange means and an axially extending means, said first surface being in slidable sealing engagement with said internal surface of said casing portion and said flange means presenting a third surface in slidable sealing engagement with said shaft segment, said axially extending means being in slidable and nonrotatable engagement with said portion of said collar of said second impeller, and resilient means surrounding said shaft between said flange means and said portion of said collar of said second impeller, said resilient means being compressible into positive sealing engagement with said shaft segment and said flange means and said portion of said collar of said second impeller in response to the difference between said first and second predetermined pressures on said annular radially extending surfaces.

2. The liquid seal structure of claim 1 in which said second surface presents a first part in slidable sealing engagement with said shaft segment and a second part radially spaced from said first part of said second surface in slidable sealing engagement with said portion of said collar of said second impeller.

3. The liquid seal structure of claim 1 in which said sleeve presents intermediate said ends a first external circumferentially grooved axially extending sealing surface.

4. The liquid seal structure of claim 1 in which said first and second impellers are disposed in spaced back to back relation with their collars extending toward each other and said sleeve has parts telescopically surrounding at least a portion of each of said collars of said first and second impellers.

MILTON W. LUTZ.

References Cited in the file of this patent

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