US1151965A - Balancing of centrifugal pumps. - Google Patents

Description

y P. A. PETERSON. BALANCING 0F CENTRIFUGAL PUMPS.

` APPLICATION FILED AUG. I2. 1913.

Patented Aug. 31, A1915.

`following is a sliiecification.

UNirun sauras rafranfr carica.'

PER Anvil) PETERSON,

TUB/EINE COMPANY, OF TRENTON, 'NEW JERSEY, A CORPORATION OF NEW JERSEY.

BALANCING OF CNTRIFUGAL PUMPS.

T all whomz't may concern.

Be it known that l, Pun Auvrn Pii'rausoiv, a subject of the King of Sweden, and a resident of Trenton, in the county of Mercer and State of New Jersey, have invented certain new and usefullmprovements in Balancing of Centrifugal Fumps, of which the l for. the au My invention relates to means tomatic balancing of centrifugal pumps lagainst end thrust, and comprises means whereby centrifugal pumps, either of the one stage or of the multistagel type, are

balanced against end thrust at all times,

making the provision of thrust bearings unnecessary.' A l The objects of my invention are to maintain the impellers of centrifugal pumps in 'packing rings Yaxial clearance indicated the usual" perfect balance at all times, toavoid ythe use of thrust bearings, to reduce wear and leakage in such pumps to a minimum, and to simplify the construction of such pumps.

, 'I will now proceed to describe my invenl' tion with reference 25 to the accompanying drawings, and will then point out the novel features in claims.

In the drawings; Figure llfshows a frag, mentary axial section of a. single stage centrifugal pump embodying my invention, the axial clearance between the labyrinthine being exaggerated, and Fig. 2 shows a similar section ofa multistage centrifugal pump embodying my invention, the being similarly exaggerated; and Fig. 3 is a detail axial sectional view o the labyrinthine packing rings at the rear of the impeller, and on a larger scale than the previous views, showing the radial and axial clearance between the labyrinthine vpacking rings.

Referring first to Figs. 1 and 3, '1 desig-V nates the casing of .a centrifugal'pump, 2

the impeller shaft of such a pump, 3 animpeller mounted on such shaft, 4 the usual admission duct and the usual discharge chamber. The impeller is provided withthe usual passages 6,l receiving. liquid from the admission duct 4 and discharginginto the space 7 and thence into the discharge duct 5. In rear of the impeller there is, as customary, a balancing chamber 8.

On the .inlet side Aof the impeller have labyrinthine packing comprising a stationarylabyrinthine ring 9 f 4in ring 12. Of

tween the ends of flanges 13 and 14 and the Specicaton of Letters Patent. Paten-(ged Aug, 31, 1915. Application inea August 12,

1913. Serial No. 784,433.

and a rotating labyrinthine ring 10,the latter' mounted upon the impeller and rotat- OF. TRENTON, NEW JERSEY, ASSIGNDB TO DELAVA'L S'lIEal-Ylvlll ingv with it; the two rings, 9 and 10, having 1 intermeshing iianges providing a labyrinring 11 being stationary and ring 12 beingmounted upon and rotating with the -im-l peller; these rings 11and 12 likewise having intermeshing flanges providing a labyrinthine passage; but the rings 11 and 12face- 1n directions opposite that which has been the practice heretofore in centrifugal pumps; for according to former practice it has been common for thevstationary impeller ring on the rear side of the im eller to have its flanges facing toward t e impeller; and

correspondingly, according to former practice, the rotating labyrinthine ring on the rear side of the impeller has had its flanges facing from the impeller; whereas -just thel reverse is true of the construction herein illustrated and described.

The impeller shaft is allowed slight play for longitudinal motion; which movement will reduce or increase, as the case may be, the distance between the vends of the anges 13 of ring 12 spending grooves of ring 11, and will correspondingly decrease or increase, as the case lmay be, the distance between the ends ofthe flanges 1'4 of the stationary ring 11,

and the ends of the correandthe ends of the corresponding groovesl course as the distance be ends of the corresponding grooves increases, the distance between the flanges 15 of the ring 10 and the ends of the grooves of the ring 9,'.will increase, and vice versa.

1n the operation of this pump, since the pressure at 'i' is necessarily greater than the pressure at 4, while the pump is in operation, there is a tendency for leakage from spa-ce 7 between rings 9 and 10 back into the inlet 4 and a corresponding tendency for leakage from space 7 between rings 11 and 12 back into balancing chamberS; and this latterl leakage, if no vent were provided from chamber 8, would lead to a pressure inchamber 8 equal to that in space 7 therefore 1 provide a' passage 16 between the cas ing 1 and the impeller shaft, and a duct 17 connecting this passage 16 with the inlet rice duct 4 of the pump. I also provide on the impeller shaft a throttling ring 18', the purpose of which will be explained below.

It will be seen that in the construction shown ifthere be an excess of thrust toward the right the 'impeller will move slightly to the right, increasing the distance between the flanges of rings 12 and 11 and the ends of the grooves in which those flanges are located; and so permitting increased flow between the rings 12 and 11, while at the same time the throttling ring 18- will restrict the flow from chamber 8 through passage 16, with a resulting building up of pressure in the balancing `chamber 8 sufficient to restore equality of thrust in both directions; conversely, if the thrust toward the left be greater than that toward they right, the impeller will move slightly to the left, decreasing the distance between the ends of the flanges of rings 11 and 12 andv the ends of the grooves in which those rings are located, and correspondingly decreasing the distance between the flanges of the rings 9 and 10 and the ends of the grooves in whichthose flanges are located, and decreasin@ the throttling of passage 16 by throttling ring 1S, with a resulting decrease of pressure in balancing chamber 8.

` Heretofore in centrifugal pumps provided with labyrintliine packing, it has been customary to provide radial clearance between the flanges of the stationary and the rotary labyrinthine rings and the grooves in which such flanges are located; such clearance amounting in some cases to as much.

as one sixty-fourth of an inch. Such clearance has necessarily resulted in considerable leakage into the balancing chamber and into the inlet duct ofthe pump. It has also been commento employ a balancing duct,

through the impelle'r, connecting such balancing chamber in rear ofthe impeller with the inlet portion of the impeller; and the area of such balancing ductshould be proportionate to the leakage through the labyrinthine packing into the balancing chamber. But this leakage cannot be calculated with any degree of accuracy, being affected by a great many factors, one of which is contraction ofthe flow throughthe rings,l

the coefficient of which cannot be determined with any degree of accuracy. Further the flow through the balancing ducts is also affected. by many factors,vsuch as contraction, velocity of water entering the impellen,

and velocity of impeller; and several of these factorsare variable; for which reason it has been commonly considered necessary to provide thrust bearings for the impeller, notwithstanding the presence of a balancing chamber-in rartof the impeller,` andnotwithstanding theiprovigsion of a .balancing duct through the-impller. Moreover, in

these former pumps, the leakage through the labyrinthine packing into the balancing chamber has been of a progressively increasl VAccording to 'my invention I provide lend clearance for tightening between the ends of the flanges of the labyrinthine rings and the ends of the grooves in which such flanges are located; which end clearance varies according to the position assumed by the impeller at any instant, usually from 1/64 as a maximum to a few thousandths of an inch, according to the size of the balancing ducts andposition assumed by the impeller at the moi ment. The scale of Figs. 1` and 2 is too small topermit the showing, to anything approaching scale, of the relation of radial to axial'clearance; and indeed, in these figures, in order to indicate axial clearance at all, it has been necessary to greatly exaggerate such axial clearance; but in Fig. 3, the relation of axial clearance to radial clearance is indicated with some approximation to their normal relative values, thoughfeven in this figure it has been necessary to exaggerate both clearances considerably; the radial clearance being, usually, less than 1/64 and the axial clearance being, in practice, less than this amount, ordinarily, as previously explained.

The axial clearance is the factor which principally controls the leakage into the balancing chamber 8, this axial clearance being normally, as previously stated, less than the radial clearance; but the horizontal or axially'extending portions of the passages between the flanges of the labyrinthine packing rings also exerts animportant limitmg action upon the leakage, (the width of these horizontal or axially4 extending vpassages, such width being-that of the radial clearance between the flanges, being small,) because of the great resistance which such narrow passages exert to the flow of water, and because the leakage passages-between the labyrinthine packing rings are very tortuous.

Since, according to throttling action in the labyrinthine rings by which the automatic balancing of the pump is effected, occurs mainly between the ends of the flanges of the labyrinthine rings, and the ends of the grooves in which such flanges run, wear of these flanges'has very my invention, the

sumes a `position whereby the leakage is regulated to give the required pressure in the balancing chamber, and therefore in practice renewal ofthe' labyrinthine rings geous to have in the the inlet o the impeller.

' the left of the impeller s the totalfforce acting 'peller multiplied by such pressures actshould be equal to the pressures per unit area acting on theright is yvery seldom required. It also follows from my invention, that the smaller be the area of cross section of the balancing `duct or ducts 16 and 17, the smaller is the leal:- age .which can be ftaken care of by these ducts andv consequently a smaller axial clearance will automatically be established between the ends of the flanges of rings 12 and 11, and the ends of the grooves in which such ianges run. Ofcourse,v there is a minimum permissible clearance between the ends of these flanges and the ends of the grooves in which they run, which minimum clearance may vary under dierent conditions `of use; and the area of the balancing duct or ducts 16 and 17 should be propo-12 tioned inthe design of the pump, to give that minimum axialclearance of the flanges of the labyrinthine rings 11 and 12 which the conditions of use require. l. For various reasons, it is often advantabalancing chamber 8 a pressure much greater than the pressure in To insure such greater pressure in the balancing chamber, the rear impeller labyrinthine ring 12 is made of greater 'diameter than the front impeller-labyrinthine ring 10; for in order to balance the impeller the pressures per unit area acting on the left hand side of the imthe areas upon which hand side of the impeller multiplied by corresponding areas. It' the diameter of the rear impeller labyrinthine ring 12 is made of the same diameter as the front impeller labyrinthine ring 10,'it can easily be seen that approximately suction pressure has to prevail in balancing chamber 8 in order to balance impeller. If the diameter of the rear impeller ring -be made greater than the diameter of. he front impeller ring and if suction pressure should then exist in balancing chamber 8, the total force acting on will be greater than on the right of the impeller, consequently there will be a thrust 'toward the right. In order to ycounteract this/thrust and make the impeller balanced it will be necessary to` have a pressure greater than thesuction pressure in balancing chamber 8. This pressure may be selected to suit the operating conditions' and thel diameter of the rear impeller ring can easily be calculated when the pressure, which is desired in balancing chamber, has been selected.` Since, as I have shown above, the impeller automatically assumes. a position such that the leakage between rings 11 and 12 is regulated to ypreserve that pressure in the balancing chamber which keeps the impeller in balance, it follows, that with a rear impeller ring 12 of greater diameter and area than the front impeller ring 10,

the pump shown in Fig. 2,

a greater pressure will be maintained in the' anced momentarily,'and with thrust on the impeller toward the right in Fig.' 1; but the throttling ring, by regulating the escape from the balancing chamber 8, causespressure to build up quickly in this balancing chamber and to an extent suflicient to keep the impeller structure in balance.

In Fig. 2 I have illustrated my invention as lapplied to a three stage centrifugal pump. It will be obvious that the number of stages of such pump might be greater or less than they are shown. The construction is the same as in Fig. 1, packing is provided on the rear side of the last impellerl only, ingchamber 8 is provided on the rear side of such last impeller only; the balancing duct 17 extending from the left hand or front side oi. the lirst impeller to a passage 16 communicating with the balancing chamber 8 on the rear,` side of the last impeller. In the construction shown in Fig. 2 the throttling ring, there designated by numeral 18', -is carried by the last impeller, instead of by the impeller shaft. The operation of as to automatic balancing, is the same as that of the pump shown in Fig. 1.

I am aware that the automatic balancing as to end thrust. of the impellers of single stage and multistage pumpsl has been proposed heretofore; but so Jfar. as I know this is the first instance of automatic balancing obtained by throttling action between the ends of flanges of labyrinthine packing rings, and the ends of grooves in which such anges work, regulated by automatic axial motion of the impeller.

In a companion application, led August 12, 1913, Ser. No.7 84,/1l82, I have illustrated a centrifugal pump embodying the same illustrated and, described, the construction of the Apump oi' my said application iiled August 12, 1913, Ser. No. 784,432 being similar tothat of the pump herein illustrated and described, except that instead of employing balancing ducts 16 and 17 connectinof the balancing chamber 8 with the inlet duct of the pump, I have provided a balancing duct extending through the impeller from the balancing chamber to the inlet portion 'of the impeller, and except that, in the multistage pump shown in my except that labyrinthinev and. except that a balene-- Generic invention as does the pump lherein said companion application filed August 12, 1913, Ser. No. 784,432, labyrinthine packing is provided between the stages of the pump. The construction of this present case is preferable in multistage pumps wherein the diifference in pressures existing in discharge duct?" of lastimpeller and balancing chamber 8 is not extremelygreat. lf this dit ference in pressures is too great, excessive wear of the rings may occur, and in such a case I prefer to use the construction shown in my companion application. rlhe claims generic Ato the constructions of this appli- .'cation, and of my said companion application, are found in this application.

rlhe principle of automatic balancing herein illustrated and described are applicable to steam andother fluid pressure turbines and blowers. Hence, in one of the ollowing claims I have employed the term pressure engine as inclusive of centri'l'm,

gal pumps, blowers, and steam" and other fluid pressure turbines, and have employed the term rotor as generic to the impeller structure of a centrifugal pump, to the iinpeller structure cfa blower, and to the ro- I tary member of a fluid pressure turbine.

What l" claim is 1, A pressure engine com-arising in coinbination a casing having a flow passage [within it and a rotor within .said casing 'mounted for slight axial motion therein as well as for rotary motion, there being a balancing chamber between the impeller and casing, of means for controlling leakage with respect to such balancing chamber comprising labyrinthine packing rings, one carried by the casing and the other by the rotor,

and one provided with a cylindrical flange and the other with a corresponding'cylindrical groove adapted to receive suchflange, there being end clearance between the end of such flange and the base of such groove, that side of the rotor labyrinth'ine ring which coacts with the casing labyrinthine ring facing toward the rotor, whereby axial movement of the rotor, dueto unbalanced thrust, tends to restore balance of thrust by -.'increase or decrease, as the case may be, or

- flow between such labyrinthine rings.

2. A centrifugal pump conn'irising in conibination a 'casing having a flow passage within it and an impeller within said casing mounted for slight axial motion therein ance between the end of such flange and the base of such groove, that side ofthe impeller labyrinthine ring which coacts with tlie casing labyrinthine ring facing toward the iinpeller. whereby axial movement of the impeller, due to unbalanced thrust, tends to restore balance of thrust, by increase or decrease, as the case may be, 'of flow between such labyrinthine rings.

3. A centrifugal pump comprising in combination a casing having a flow passage within it and an inipellerwithin said casing mounted for slight axial motion therein as well as for rotary motion, there being a balancing chamber on the rear side of such impeller and between theiinpeller and casing, of means for controlling leakage from the flow passage of such casing to said balancing chamber comprising labyrinthine packingrings, one carried by the casing and the other by the impeller, and one provided with a cylindrical flange and the other with a corresponding cylindrical groove adapted to receive/such flange, there being end clearance between the end of such flange and the base of such groove, that side of the impeller labyrinthine ring which coacts with the casing labyrinthine ring facing toward the impeller, a duct permitting escape from such balancing chamber, and means axially movable with the-impeller, controlling flow through such duct.

vl. centrifugal pump comprising in com- Y bination a casing having a flow passage within it andan inipeller within said casing mounted for slight axial motion therein as well as for rotary motion, there being a balancing chamber on the rear side of such impeller and between the impeller and casing, of means for controlling leakage from the flow passage of such casing to said balancing chamber comprising labyrinthine packing rings, one carried by the casing and the other by the impeller, and one provided with a cylindrical flange and the other with a corresponding cylindrical groove adapted to receive such flange, there being end clearance between the end of such flange and the base of such groove, that side of the iinpeller labyrinthine ring which coacts with the casing labyrinthine ring facing toward the iinpeller, a duct permitting escape from .such balancing-chamber, and a throttling ring axially movable with the iinpeller, and arranged to restrict variably iiow through. such duct.

5. A centrifugal pump comprising in combination a casing having an inlet duct and a i'iow passage, and a single suction impeller within said casing mounted for slight axial motion therein, as well as for rotary motion, there being a balancing chamber on the vrear side of such impeller `and between thev impeller and casing, labyrinthine packing on the inlet side of the rmpeller comprising .annees intermeshinglabyrinthine rings, one carried by the impeller and the other by the casing, labyrinthine packing on `the rear side of the impeller controlling leakage from the flow 'passage of the casing to said balancing chamber and comprising labyrinthine packing rings having the one a cylindrical fiange and the other corresponding cylindrical groove adapted to receive such flange, one of such rear labyrinthine rings being carried by the casing and the other by the impeller, the working face of such latter'ring facing the impeller, there being end clearance between said rings, such rear labyrinthine impeller ring being of greater area than 'thefront labyrinthine A packing ring.

6. A centrifugal pump comprisingl in combination a casing having an inlet duct and a flow passage, and va single suction iinpeller within said casing mounted for slight axial motion therein, aswell as for rotary motion, there being a balancing chamber on the rear side of sucl'rimpeller and between the impeller and casing, labyrinthine packing on the inlet vside of the impeller comprisingintei-meshing labyrinthine rings, one carried by the impeller and the other by 'the casing,

labyrinthine packing on the rear side of the impeller controllingleakage from 'the fiow passage of the casing to saidbalancing l chamber and comprising labyrinthine packing rings having the one a cylindrical ange and the other a corresponding cylindrical groove adapted to receive such fiange, one of s'uch rea-r labyrinthine rings being car ried by the casing and the other by the impeller, the Working face of such latter' ring facing the impeller, there being end clearance between said rings, such rear labyrinthine impeller ring being of greater area lthan the'front labyrinthine packing ring,

. and a balancing duct connecting such balancing chamber with the inlet duct of the pump.

7. A centrifugal pump comprising in com bination a casing having an inlet duct a -iow passage, and a single suction impeller within said casing mounted for slight axial motion therein, as well as for rotary motion, there being a balancing chamber on the .rear side of such impeller and between the impeller and casing, labyrinthine packing on theinlet side of the impellerA comprising.

intermeshing labyrinthine rings, one carried by the impeller and the other by thev casing, labyrinthirie packing on the rear side of the impeller controlling leakage from the flow passage of the casing to said balancing chamber and comprising labyrinthine packing rings having the one a cylindrical flange and the other a corresponding cylindrical groove adapted to receive such iiange, one of such rear labyrinthine rings being carried by the casing andthe other' by the impeller, the working face of such latter ring facing the impeller, there'being end clearance betweenl said rings, lsuch rear labyrinthine impeller ring being of greater area than the front labyrinthine packing ring,

and a balancing duct connecting such balancing chamber with the inlet duct of the pump, and means axially movable with the impeller for variably restricting flow through such balancing duct.

8. A multistage centrifugal pump comprising in combination a casing formed in a plurality of stages' with flow passages therethrough, and an inlet duct communicating with one stage and an exit duct communicating with another stage, and a rotary impeller structure Within such lcasing comprising animpeller for each such stage, there being a balancing chamber on the' rear side of the .last impeller'and'between that impeller and the casing, of leakage preventing means between the outlet duct and inlet duct of each' impeller, leakage preventing means between the balancing chamber on the rear side of the last impeller and the casing, comprising labyrinthine packing rings one carried by the casing and the other bythe impeller, and the one provided with a cylindrical flangeand the other with a correrien Anvil) PETERSON.

Vitnesses:

C. R. WALLER, GEO. B. PAGE. l

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