CA1208080A - Centrifugal pump - Google Patents

Abstract

ABSTRACT

A centrifugal pump having an adjustable feature en-abling precise adjustment of the impeller's location.

Description

~2~8~3 This application is divided from our Canadian application 434,446 filed August 12, 1983. This invention relates to centri-fugal pumps and to an improved impeller position adjustment fea-ture in such pumps.
Typically, centrifugally pumps have an impeller which is axially adjustable but which has no means to determine with pre-cision the exact position of the impeller.
Summary of the Invention In one aspect, the invention features a centrifugal pump having a bladed impeller in a stationary pump housing, the leading edges of the blades being adjacent a first .radially extending wall of the housing, a rotatable shaft on w~ich the impeller is mounted, a shaft support for rotatably holding the end of the shaft which is opposite the impeller, and adjustable fastening means for connect-ing the shaft support to a stationary member, the impeller, shaft and shaft support together being adapted for axial adjustment upon axial adjustment of the fastening means, the fastening means having at least two threaded bolts projecting from the stationary member in a direction parallel to the axis of the shaft, and reference nuts for fixing the position of the shaft support on the bolts, the reference nuts having marks at regular angular intervals, and at least one reference mark on the shaft support adjacent each refer-ence nut cooperating with the marks on the reference nuts for in-dicating the axial position of the impeller with respect to the pump housing.

In preferred embodiments, the impeller has a radially extending face opposite the leading edges, the pump housing fur-ther comprises a second radially extending wall adjacent the face, and an annular seal is positioned between the face and the second wall to seal against the second wall when the impeller is withdrawn from ~he first wall to the second wall; the seal is mounted on the impeller face; and the two bolts are spaced apart on opposite sides of the shaft.
The impeller blades can be precisely positioned with respect to the pump housing to assure maximum pumping efficiency, the impeller can be repositioned accurately to accommodate blade wear, and the reEerence nuts can be used to gauge the total blade wear to determine when the impeller should be replaced. The annu-lar seal assures that the seal housing is sealed off from the fluid in the pump housing when the impeller is withdrawn, so that work can be easily performed in the seal housing.
The following is a description by way of example of cer-tain embodiments of the present invention reference being had to the accompanying drawings in which:-Figure 1 is a side elevation view of the pump assembly.
Figure 2 is an enlarged sectional view of the pump assembly of Figure 1 with the motor and motor adaptor removed, showing one type of seal housing.
Figure 3 is a view, taken along line 3-3 of Figure 2.
Figure 4 is a view, taken along line 4-4 of Figure 2.
Figure 5 is a plan view, partly in section and partly broken away, of the seal housing and pump housing.

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Figure 6 is a view, taken along line 6-6 of Figure 5.
Figure 7 (sheet 1 of the Drawings) is an isometric exploded view of a seal housing with alternate coils attached to the cover.
Figure 8 is a sectional view similar to Figure 5 showing an ~2~18~80 alternativc scal housing containing a pac~ing scal.
Figure 9 is a vies~ par-tially broken alYay, ta~en along line 9-9 of Figure S.
Structure and Oocration Referring to Figurc 1 in pump assembly 10 pump housing 11 defines an impeller cllamber 1~ ~sho~n in Figure 2) in 1~hich impeller 14 rotates to pump fluid from pump inlet lG to pump outlet lS. Impeller 14 is mounted on one end of shaft 20, the other end of which is (by means of direct mount motor adaptor 22) coupled to and aligned ~ith the shaft of motor 24. Behind pump housing 11, shaft 20 is enclosed by a removable seal housing 26 \~hicll is bolted to the backplate 2S of pUll)p housing 11. Also bolted to pump housing 11 is one end of a bearing frame adaptor 32 the other end of ~hich is bolted to bearing housing 34 ~hich serves as a shaft support for the end of the shaft opposite the impeller) to assure thc a.Yial alignment of shaft '0, pump housing ll and bearing housi11g 34. Adjustable fastening means 36 arc positioned behind bearing housing 3-1 for adjusting the a~ial position of impeller 14. Rear foot 29 and casing foot 31 support the pun1p assembly foot 29 extending on each side of the center of gravity of the assembly ~hen disconnected from the impeller.
Referring to Figure 2, ~hich sho~is the pump in grcater detail shaft 20 is supported rotatably by a pair of bearings 42 44 ho-lsed ~ithin bearing 11ouse 34. The position of rear bcaring 42 is fi.Yed a.Yially ~ith respect to shaft 20 by recessed shaft surfacc 46 (adjacel1t thc or~ard end of bearing L12) and by ~asher 4S al1d t1-readed rctaincr nut 50 (adjaccnt the rear~.~ard cnc1). Bearing 12 is also hcld fi.Yed ~iithil1 a ~carillg cartridge 62 by rctainil1g surfacc 64 al1d by retaining ring G6 l~hicll is boltcd to tl1c bcaring ilZ6)8(~i8~

cartridge. Similarly, the position or fron~ bearing !-Z on s~ t _0 is sct (on the rear end) by recessed shaft surr;lce 5'. ~ sprillO retai~ lg ring 54 (wllicll seats in groove 21 in shaft 20) and retainer 56 to~ether forc^ oil seal 58 and couyling ring G0 agains~ the front end of bearillg 44, alld ass~lre proper seal compression of seal 5S.
The shaft assembly, including shaft 20, bearillgs 47, 44, bearing cartridge 62, and impeller 14 (which is screwed onto the threaded front end of shaft 20), is free to be moved axially, because the cylindrical outer surfaee of the cartridge housing 62 is free to slide in the cylindrical . bearing housing bore 68 in ~hich it is mounted, the eylindrical outer surfaee of cylindrical bearing 44 is free to slide in the bearing housing bore 70 in wllich it is mounted, the cylindrieal outer surface of oil seal 55 is free to slide in eylindrieal bearing frame adaptor bore 72 in wllicll it is mounted, and shaft 20 is free to slide in the stationary elelnent 74 of seal 7G. The axial exeursion of the shaft assembly is limited in one direetion by the radially extending wall 7S of pumy housing 11, wlliell is adjacellt to the leading edge 80 of impeller 14~ and in the other diroetion by radially e.~tending faee 82 of bae~plate 2S wllieh is adjaeent to the trailing edge 84 of impeller 14.
The axial position of the shaft assembly is determined by adjustable fastening means 36 whieh eomprise two bolts 100 (e.g.,l/2-20 or l/2-13) w11iel pass throug}l elearanee holes 102 in bearing eartrid~e 6_ alld are firmly sere~ed into the baek of bearinO housing 34, and a reference nut 104 and a loe~nut 106 serewed onto eacll bolt lO0, witll the bearill~ cartri-lge betwee them, so that they can be tightened do~n onto the bearillg c;lrtridge to adjust and fix its axial position.

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Referring to ~igure .7~ e;lch r^ferellcc n~lt b;ls a rial portion lOS
on ~-~hicll marks 110 are inscribc~ at reg-llar an~ul;lr intcrvals ~c.g. 7~.a) and are readable in connection ~ith rcfcrcncc !-arl;s 11 on bearill~7 housing 34.
In operation the a.~ial position of the i:~lpcllcr is adjllsted so that the gap betlieen edse S0 ;Illd ~all 7S ;ill l~ro~tidc ontim-lm l)ulllpillo efficiency, e.g. a gap oE 0.015 incll. This is acco~ lishcd bv loosenin~
reference nuts 10;~ to~ard the front of the pulnl? assel!lbly alld ti~-htcnillg locknuts 106 also to~ard the front of the pump asselllbly until the shaft assembly reaches an axial position at ~hich thc im~cllcr Icaclill~7 edge strikes the pump housing l~all 7S. The position ol eacll rcferellcc nut compared ~ith its assoeiated reference mar~ 11' is notcd. rl~c loc~nuts are backed off and the reference nuts are then turned bacli tol~ards the back of the pump assembly by a number of marlis 110 ~hicll correspond to the dcsired impeller gap(as determined by the ang~llar spacillg bet~-een tlle mar!is and the piteh of the threa~s of bolts 100). ~s the impeller bl;ldes ~e.lr the shaft assembly can be moved for~ard a precise distallce -to rcposition the impeller by a similar use of reference nuts 110. I3y recording the total amount of such adjustments for ~ear it is possible to determine easily ~hen the impoller should be replaced. The adjustable fastening means 36 also permits backing off the shaft assellll)ly to the point ~here the rear surface S-~ of tlle impeller reaches the pulllp housing ~all S'7, and ~hen so backed off an 0-ring seal 114 in the bacl;l~all of the impeller se~ls off seal housing 26 from fluid locatocl in the impeller chamber 17~ 50 th~t ~iork can be per~orlned in the seal housillg ~ithout the presence of the fluid ;Ind ~ithout need of drairling f1uid from impeller ch;lmber 17 .

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Referring to Figures 2 and ~ a ccntrilug;ll lubricator ~0 (of metal or plastic) is positio]led in be~ring llousing 34 for lubricating bearings ~2 44. Lubricator 40 is fi.~ed to shaft 20 by set scre~ 120.
Lubricator 40 llas an annulus 121 ~itll a circular internal tube 122 -the inner l~all of .~llich is defined by the surface of sh;lft 20. A tubular yassage through tlle outer ~all of annulus 121 defines en~rance opening 124 tangential to the tube. A number of syaced e.Yit openings 126 (oriented radially from shaft 20) in its side pass through the outer periphery of the amlulus. ~lesh screen 12S (e.g., nylon ~itll mesh oyenings bet~een 50 and 300 microns) is arrallged around tlle inner ~all of the tube eovering the exit openings.
The inner surface of bearing housing 34 is eontoured to define an oil reservoir 130 containing oil 132 to a level such tllat oil can enter entranee opening 124 during each rotation of lubricator 40 on sllaft 20.
Oil ~hiell has entered tube 122 is tllro~n eentri:;u~ally out tllrough e.~it opertings 126 (after passing through sereen 12S, ~hicll removes carbon and par-ticulate eontaminants). Oil seals 5S and 130 (housed in the oyposite ends of the bearing housing) and oil seal 131 on the outer surface of bearing eartridge 62 prevent leakage of oil from the bearing housing.
Referring to Pigures 2 and 5, seal housillg 26 contains a mechanieal seal 76 (e.g. a seal sold by A. IY. Chesterton Co. Stoneham lassachusetts under the trade mar}i SS0) having a rotating elemellt 140 (attaclled by set sere 142 to shaIt 20) and a corresponding stationary element 74 Ileld in place by seal gland lt4 bolted by bolts 146 to tlle seal llousing. Tlle seal housins is demoullt;lbly connected by bolts 147 to tlle baeliyl.lte 2S. Tlle rotatillS elemellt alld statiollary elemellt bear agaillst one allotller rotatably at seal su~f.lce l-IS.

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Seal 76 prevents lea~age to the outside of the pump of any fluid ~hich (instead of being pumL~ed itltO pump outlet lS! follol~s a fluid patll over and behind impe].ler 1~, along cavity 150 on tile Dac' of the impeller and into the seal housing. Iea~age of such fluid from the seal housing is also prevented by static (e.g., o-ring) seal 152 (bet-~een cover 30 and seal housing 26), seal 15-1 (betl-een the seal gland and the stationary element of the seal), seal 156 ~betl~een the seal housing and the backplate of the pump housing), and seal 15S (bett~een the impeller and the shaft). Cover 30 permits access to seal 76 and shaft 20 l~ithin seal housing 26 for repair, impeller 1~ being bac~ed to face 82 before cover 30 is opened to seal ch.~mber 1~ from seal housing 26. Seal housillg 26 may also contain a cooling coil comprising a eoil of tubing 170 (e.g., l/~i" or 3/S" in diameter) centered on the aYis of the sll.lft and positioned about seal 76 (there being a larger than usual space of about 1" betl~een the outer surface o shaft 20 and the inner surface of seal housing 26 ~;hieh can also accommodate electronic pressure and temperature transducers). The ends of tubing 170 pass througl and are hel-l by cover 30 alld the ends form entrance and e.Yit openings 172, 17~ igure 6) outside cover 30. Cooling fluid can be pumyed througll the eooling eoil to eool the seal.
Referring to ~igure 7, alternatively a flusl-ing coil 176 ~similar in size and configuration to the cooling coil) ean be attached to cover 30. The flushing coil has a nwllber of holes 17S througll ~hicll fluslling fluid (pumped into the flusllillg coil) is spra)ed into the se,ll housing to flusll it durillg p-l~ ) oper.ltion.
Ilusllillg of the seal housillg can altel~l;ltely l)e accolllL)lislled throu~lll fl-lsllillg al)l)aratus comL~rising a flusllill(l tul)e lS0 (ligures 5, 6 ;llld 7) 12~

having all cntrance end 1~2 outside of the scal housing and an e.~it end lS4 e.~tending througll a side wall of thc seal housing and oriented to direct flushing fluid into the scal housing in a dircction having a componcnt tan-gential to the interior of the sidc wall of thc housing and in a plane normal to tlle sllaft a.Yis. Tlle flush tube enters the seal llousing at the rear cnd of the housing nc.Yt to tlle seal gland which assures that thc entire seal housing will be thoro-tgllly flushed. The tangential oricntatio1l enables the fluid to follow the natural cur~ature of t~le inside wall and preventsflushing fluid from striking the seal directly ~hich reduces vibration and l~ear and assures efficient seal operation ~llile flushing.
Because of its demountable connection seal housing 26 can be easily replaced ~ith housings of any other desired configuration. ~or e.Yample, referring to l~igures S 9 seal housing 26 may be rcplaccd by demountable packing seal housing 200 (bolted onto backplate 2S) which llas a stepped interior surface 202 and is closed at its back end by a seal gland 204 which is adjustably bolted on by bolts 206. Gland 20'i has a central clearance llole 205 (througll ~hich shaft 20 passes) and a radially eYtending sealing wall 20S facing towards the impeller. A cylindrical rotary member 209 (fiYed on shaft 20) has a corresponding radially e.Ytending sealing wall 210 which has an inner flange 212 close to the shaft and an outer flange 21~
spaced apart from the shaft so that sealing wall 210 and flanges 212 214 form a recess in wllich rope packing 216 (e.g. ~/S" or 5/16" by 22" long) can be spirally wrapped. The radial spacillg of the two Llanges is at lcast twice the packing thickness. Thc a.Yial eYtent of the flallges is less than the packing thiclilless so tllat as glalld 20l is tightcne(l do~n Usillg bolts 206 tllc pacliing is comprcssed a.Yi;lllv betwccn thc scaling walls 20S 210. racliing 216 _ g _ lZ~8~

nol~here touches shaft ~0 and so causcs no ~ear o F thc shaft. Packing 216 is lleld fixed on rotarv member ~09 so t~l~ sealing surface is bet~een t~all 20~
and pac~ing 216 Alternatively the flanges can be part of the seal gland, the packing can be held fixed in the scaling gland and the sealing surface can be defined bet~ieen sealing ~all 210 and the packing The space ~ithin the seal housing is scaled against leakage by static O-ring seals 21~
(bet~een seal gland 20~1 and scal housillg 200), 220 (bet~een the front outer ~all of seal housing 200 and backplate 2~) and 222 (bet~een the rear end surface of the impeller and the rear radially in~ardly extending surface 226 of rotary member 209). Rotary member 209 extcnds along shaft 20 from seal gland 20-t to~iard impeller 1~ and is provided at its end adjacent backplate 2S l~ith a helically threaded outl~ardly facing labyrintll seal 230 closely spaced to e.g. 0.005 inch a~ay from facing inner surface 232 of the seal housing. The helical labyrinth seal 230 hydrodynamically pumps fluid outt~ardly from the seal housing upon rotation of the shaft reducing fluid pressure ~ithin the seal housing.
Referring to Figures 2 3 for locking shaft 20 against rotation during repair ~ork, removable shaft lock 2~0 ~ShOI~Il ill broken lines) may be employed l~hich has a central hole ~ihich fits over shat 20 the hole having a key 2~l2 ~hich mates ~ith a key~ay 2~ provided in shaft 20. The outer periphery of the shaft lock has a pair of holes 2~16 corresponding to threaded holes on the back face of the bearing cartridge for bolting on the shaft lock to prevent rotation of the shaft assembly.
Other embodiments are ~ithill the follo~ing claims.

Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A centrifugal pump comprising a bladed impeller in a stationary pump housing, the leading edges of said blades being adjacent a first radially extending wall of said housing, a rotat-able shaft on which said impeller is mounted, a shaft support for rotatably holding the end of said shaft which is opposite said impeller, and adjustable fastening means for connecting said shaft support to a stationary member, said impeller, shaft and shaft support together being adapted for axial adjustment upon axial adjustment of said fastening means, said fastening means comprising at least two threaded bolts projecting from said stationary member in a direction parallel to the axis of said shaft, and reference nuts for fixing the position of said shaft support on said bolts, said reference nuts having marks at regular angular intervals, and at least one reference mark on said shaft support adjacent each reference nut cooperating with said marks on said reference nuts for indicating the axial position of said impeller with respect to said pump housing.

2. The centrifugal pump claimed in claim 1 in which said impeller has a radially extending face opposite said leading edges, said pump housing further comprises a second radially extending wall adjacent said face, and an annular seal is positioned between said face and said second wall to seal against said second wall when said impeller is withdrawn from said first wall to said second wall.

3. The centrifugal pump claimed in claim 2 in which said seal is mounted on said impeller face.

4. The centrifugal pump of any one of claims 1, 2 or 3 in which there are two said bolts spaced apart on opposite sides of said shaft.