US2340787A - Means for balancing rotary pumps - Google Patents

Description

Feb. 1, 1944. G. H. ZENNER ETAL 2,340,787

MEANS FOR BALANCIG ROTARY PUMPS l Filed April 11, 1941 5 shees-sheetV 1 v /ATTORNEYS I INVENTORS Fbl, 1944- G. H. zENNl-:R Erm.

MEANS FOR BALANCING' ROTARY PUMPS Filed April 11, 1941 5 Sheets-Sheet 2 Feb. 1, 1944. G. H. zENNR Erm. 2,340,787

MEANS FOR BALANCING ROTARY PUMPS Filed April ll, 1941 5 Sheets-Sheet 3 1 ATTORNEY Feb. 1, 1944. G. H. ZENNER ETAL MEANS FOR BALANCING ROTARY PUMPS 5 Sheets-Sheet 4 Filed April l1, 1941 F425- 1, G. H, zENNER ETAL 2,340,787

MEANS FOR BALANCING ROTARY PUMPS Filed April 11,'1941 5 sheets-sheet 5 /5 INVENTO 55 Patented Feb. l, 1944 MEANS Foa BALANcmG ROTARY PUMPS George H. Zenner and Edward F. Yendall, Kenmore, N. Y., assignors to The Linde Air Products Company, New York, N. Y., a corporation of Ohio Application April l1, 1941, Serial No. 388,048

(Cl. 103-112)A i 7 Claims.

This invention relates to means for balancing forces in rotary pumps, and particularly to means for balancing the reactive forces, due to the outlet pressure in multi-stage turbine pumps when arranged for pumping a highly volatile liquid, such as liqueed gas having a boiling point temperature at atmospheric pressure less than 273 K., for example, liquid oxygen.v

'The invention has for its object generally the provision of an improved arrangement of pumping elements for balancing the pressure in rotary type pumps whereby liquids, particularly volatile liquids of the character indicated, may be pumped and dischargeed against relatively high heads of pressure without employing high values of the unit loading on the bearings. `More speciflcally,'the invention has for its 0bject the provision of an arrangement for pumping liquid oxygen in a, plurality of stages against heads of pressure of moderately high value, for example, against heads up to 400 lbs. per square inch gauge, by rotary elements using self-lubrieating bearings without undue wear on the bearings and without incurring undue leakage between stages.

Another object is to provide a multi-stage turbine pump with a rotary element carrying axially displaced sets of pumping blades with an arrangement for readily achieving the desired centering in operation of the Iblades without undue friction and without the .need for precise preadjustrnent of clearances. l

Another object is to provide a multi-stage turbine pump for pumping liquid oxygen with a common shaft for the rotating elements journaled in bearings of bonded graphite, the journals being arranged to be self-centering.

Still another object is to provide a casing for' a multi-stage pump of the character indicated with a pressure chamber arranged to equalize the bearing pressures on opposite sides of the-shaft carrying the rotor element so as to compensate for unequal reactive forces on the bearings, whereby a turbine' pump having a relatively long operating life and requiring-little servicing is provided.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

'I'he invention accordingly comprises the features of construction, combination of elements, and arrangements of parts, which will be exemplied in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and 'a modification of the invention in which balancing is achieved by the use of a special chamber; Fig.` 4 is another end elevational view with parts broken away to show sectionally certain details of the balancing chamber used in the modification of Fig. 3; and

Figs. 5 and 6 are explanatory diagrams.

The principles which apply to the pumping of [a volatile liquid, such as a liquefied gas with boiling Point temperature at atmospheric pressure materially below 273 K., are taught in U. S. Patent to Thompson, No. 1,930,731, patented October 17, 1933. Here, a i-lrst stage is provided in which the liquid is discharged against'l a relatively low head but the presure is suiiiciently raised to achieve what in eiiect is subcooled liquid supplied to the second stage where the liquid being pumped may be discharged against relatively high heads of pressure. In rotary type pumps.

. when it is necessary to pump against relatively high heads of pressure, the multi-stage pump is resorted to; the advantage being that the liquid impellers of the several stages may be mounted on a single shaft and driven from a single source of. mechanical power.

Referring now to the drawing, and particularly to Figs. 1 and 2, a two-stage or compound turbine type pump is shown by way of illustrating a rotary pump in which balancing is achieved in accordance with the invention; balancing being desirable in multi-stage pumps by reason of the relatively high discharge heads against which they work, whereas in single-stage pumps. by

reason of their relatively low discharge heads, unbalance is generally of a negligible order. lI-Iere a pump casing, shown generally at l0, is formed of interfltting members H0, III, H2, and H3;

`members IIU and H3 being closures for the casing proper, member I I0 having a central opening closed by a plate lllwhich `carries a tubular extension i2. This latter serves as a' housing for an entering shaft l31that carries the rotary pumping elements. Shaft I3 has an enlargement at the inner end, as shown at |30 (that may be keyed to the shaft I3 by a key I6) and runs in a bearing bushing I5, held in place by a closure plate Il. The latter element is directly secured to the member II3 which has a boss or hub I4 formed to support plate I1. Any suitable securing means. such as bolts I8, may be employed. The assembled casing members may likewise be securecllstogether by means of bolts, as shown at I9 and The bushing I5 is preferably of a solid selflubricating material, such as a bonded graphite. The other end of shaft I3 is passed to the exterior through extension I2 for receiving driving power, in any suitable manner known to the prior` art,` for example, as shown in Fig. 3, as hereinafter more fully explained.

The member III, when closed by member I I0, is arranged to provide a pumping channel for the first stage, the pumping channel being denoted |20 and provided with a rotary liquid impeller or turbine wheel 20. The working margin of Wheel 20 is arranged to clear the walls of channel |20 by a considerable space. Members III and II2 are likewise arranged to provide a second stage,- or pumping channel denoted I2I, while another channel |22 is provided by the I. hub, denoted 20', 2|', and 22 in the drawings, which is keyed to the shaft I3. Each of these hubs is arranged to run between thrust bearings of substantially the same material as the bearing bushing I5, and at least one such thrust bearing may be'adiustably mounted in the casing I0, in order to maintain proper centering for the impellers (the specific showing of any such addusting means being omitted in theinterest of simplicity).

latter of which is carried by a suitably formed recess in the casing member I I for receiving the same. centering impellers 2| and 22. The casing I0 has a supporting base; any convenient supporting means may be used; webbed legs being shown at |06 by way of example.

'Ihe unbalanced effect here considered is the resultant of the reactions from the liquid pressure distributed about the periphery of the impeller. Such reactions are in a generally radial direction but increase from the inlet to the outlet of the channel in which the impeller works, the force diagram of the same being graphically shown in Fig. 5 where it is seen there is a large unbalanced portion which gives a resultant R which may be considered as a force concentrated at some point in the pumping channel; for example, one concentrated at a point displaced from the outlet ,of the pumping channel by an angle of approximately 90. To achieve a balancing of such resultant, the second stage of the two-stage pump may be divided, or another-stage may be added, as shown, for example, in Fig. 6, where three channels are depicted at a, b, and c, respectively. The' last channel is connected to Impeller 20 v is accordingly showx` running between bearing rings 24 and 25, the

channel b by a conduit d. Channel c provides Y another resultant which is arranged to be directly opposed to that otherwise had from channel b, so as to balance it.

'I'he unbalanced force can be balanced in several ways: (1) by using two second-stage impellers in parallel as shown in Figs. l and 2 of this invention with the suction and discharge ports of one impeller diametrically opposite from those of the other impeller. In this case the unbalanced force from one impeller will exactly balance the force from the other impeller. (2) By using a cylinder mountedon the pump shaft, one-half the. periphery of the cylinder being in a region of high pressure and the other half being in a region of lower pressure. The cylinder proportions are then chosen such that the differential pressure acting over its periphery will balance the force from the second-stage impeller. The high pressure half of the cylinder can be connected to the pump discharge and the low pressure half to a region of lower pressure, sayx the first-stage discharge. I'hen the difference between these two pressures multiplied by the projected area of the balance cylinder gives the force which acts to balance the force from the impeller. (3) By using a three-stage pump, as shown diagrammatically in Fig. 6. The three- .stage arrangement also contemplates the emstage c as the opening at valve f is increased.'

Under most conditions valve e will be fully open but it may be employed where desired to produce t modification of the balancing effects. As valve e Similar constructions are provided for is closed the discharge fromstage b will be constricted, increasing the discharge Apressure in stage b and increasing correspondingly the unbalanced force in that stage. Simultaneously the constriction in the inlet to stage c will tend to reduce the inlet pressure to stage c and this may effect a reduction in the unbalanced resultant in stage c. This latter may in turn, however, be varied by adjustment of valve f as described above.

The divided stage arrangement is shown in Fig. 1, and is seen to comprise pumping channels I2I and |22, which may have their inlets and 'outlets so disposed that the resultant of one channel opposes that of the other and a balanced effect achieved. 'Io this end, the arrangement of the channels I2I and |22 in the casing I0 is such that the inlet channels thereto are on substantially opposite sides of the casing, the outlets being similarly disposed. Conduits for receiving the discharge from the outlet of the first stage, dividing the same and leading the portions to the two second-stage inlets, are accordingly associated with the casing I0. External conduits are advantageous and conducive to compactness in casing construction and are shown in Fig. 2.

In Fig. 2, the inlet connection for the first channel is shown at |I6 and is relatively large since it is connected to a low pressure source of supply of the, volatile liquid to be pumped. Such inlet connection leads into the channel |20 by a impeller 32.

channel that is streamlined, as taught in co- -pending application, Serial No. 345,308, filed July 13, 1940, in the name of O. A. Hansen. The outlet connection from the first stage is at ||1 at a point in the'top half of the casing relatively close to the inlet H6, which is here shown as leading into the lowerv half. Outlet connection ||1 has a dividing nipple or T-connectlon ||8 located at substantially diametrically opposite points in the casing I0.

The outlet from the first-named second-stage pumping channel is at |21, that for the secondnamed second-stage pumping channel at |21'. These outlets are, by thearrangement here employed, also at substantially diametrically opposite points on casing I0. A conduit at |28 receives the discharge from the channel |2| and leads across under the casing to discharge into a union T-like coupling |29 that is placed to receive dl-A rectly the discharge from channel |22. Here the liquid from the two .pumping channels ofthe second stage is united and discharged at a high pressure, such as 400 p. s. i. gauge, into a common conduit or other receiver.

In operation, it is seen that the pressures at both the inlets and the outlets of the channels of the divided second stage are so placed las to offset one another and hence a balanced reaction is achieved. p

In Figs. 3 and 4, another modification is disclosed, using a pressure chamberadapted to apply pressure to counteract the unbalance directly There is also shown in Fig. 3, by way of example, a gland for the outer end of shaft |3'; such gland being for use with a compression packing in a stufng box (the complete showing of the packing material and the stuffing box being omitted from therdrawingsin the interestso f clearness lof illustration. In general the gland illustrated comprises a carbon bushing 43 in a sleeve M, that avoids galling and is held in place by means of a nut 45 which is secured in any suitable manner, for example, by screwthreaded shown. g

By reference to the arrangement, as shown-in Fig. 4, it is seen that outlet pressure is conveyed through channel.55-to the chamber portion 323" which is positioned in the channel somewhat in advance of the outlet 321. There is a balancing force, in consequence, exerted on the shaft I3' due to the presence of this chamber, ywhich force is substantially at right angles to a line passing through the center ofthe shaft and the outlet. This force is seen to counteract that which results from the gradual increase in pressure around the pumping channel., such increase being graphically shown in Fig. 5. The pump casing here employed may, if desired, be provided with peepholes leading to the pumping channels `of the rst and second stages for inspection purposes, and normally closed by plugs, as shown atl |09.

Since certain changes `may be made in the above construction and different embodiments of the invention could be made without departing from the'scope thereof, it is intended that all matter. contained iny the\above description or shownin`the accompanying drawings shallv be l Aas new and desire to secure by Letters Patent is:

to a rotatable shaft, here denoted I3', which car ries the first-stage and second-stage impellers 3| and 32. The, impellers are shown running in ilrstand second-stage pumping channels 32| and 322 formed in a casing generally similar to that at IIJ, but having only two stages and hereI The shaft |3' is shown having anenlargement 30 to which the impellers 3| and 32 are keyed. The inner smaller end of shaft |3' is enlarged by a sleeve member 330, keyed thereto and arranged to run in the bushing bearing I5'. Member 33|! has an enlarged ange portion 325 comprising a -piston member that runs in a pressure chamber 323 formed in the boss 3H. Such chamber is divided into non-communicating portions by ribs 5| and 52 which extend axially out .from

Vin said casing,

1. vIn a multi-stage rotary type pump, the combination with a casing provided with a plurality of pumping channels each having separate inlet and outlet channels, oi a driving shaft journaled a plurality of bladed impellers having their working circurnferences arranged for running respectively in said pumping channels mounted on said shaft and forming therewith a rotor forthe pump, conduit connections effecting working communication between said inlets and outlets, bearings associated with said casing for said shaft, and a balancing chamber in said casing vhaving a cylindrical element and extension |2 arranged as above described.-

the wall of lchamber 323 a distance such as just to clear the cylindrical wallofportion 325. The uppermost chamber portion 323" is connected by a channel 55, provided as a bore in the casing exthe hub chamber of cooperatively associated with said shaft adapted to apply force thereto; said chamber having communication with a point of-relatively high pressure in said channels and arranged so as to expose a portion only of said element in the circumferential direction to said high pressure, the remaining circumferential area being exposed to a lower pressure and said chamber being `so located angularly about said shaft whereby there is provided a radial force operating upon said shaft in magnitude and direction to counteract substantially the resultant arising from the gradfual increase of pressure around the periphery of said rotor.

2. In a multi-stage rotary type pump, the combination with a casing provided with a plurality of pumping channels each having separate inlet and outlet channels, of a driving shaft journaled in said casing, a plurality of bladed impellersl having their` working circumference's arranged for running respectively in said pumping channels mounted on said shaft and forming therewith a rotor for the pump, conduit connections engagement, as'

effecting working communication between said inlets and outlets, bearings associated with said casing for said shaft, an enlargement on one 'end of said shaft running in said casing, and a balancing chamber formed about said enlargement and divided into portions in the circumferontial direction, each of said portions having communication with a source of pressure taken from selected points in said connected channels and arranged to provide a resultant for balancing that arising mainly from the: gradual increase' of pressure around the of said rotor.

3. In a multi-stage rotary type pump, the combination with a casing provided with a plurality of pumping channels each having separate inlet and outlet channels, of a driving shaft journaled in said casing, a, plurality of bladed impellers having their working circumferences arranged for running respectively in said pumping channels mounted on said shaft and forming therewith a rotor for the pump, conduit connections effecting working communication between said inlets and outlets, bearings associated with said casing for said shaft, and a balancing means in said casing comprising a rotatable element mounted on said shaft and provided with a circumferential channel in said casing, said lastnar'ned channel having communication with said last-stage pumping channel and extending over a part of the area only of said element in the circumferential direction which gives a force counteracting that arising mainly from the gradual increase of pressure about the periphery of the last stage of said rotor.

4. In a rotary pump the combination with a casing, a driving shaft journaled in said casing, rota-ry fluid impeller means mounted on said shaft and adapted to operate in said casing, an auxiliary drum-like member mounted on said shaft, a iiuid chamber formed about and extending over aportion only of said member in the peripheral direction, connections for admitting fluid to said chamber from the fluid discharge side of the pump, and means for exposing a radially 4opposing part of the periphery of said member to a lower pressure, the arrangement andproportions being such as to produce a net radial force on said member of a character and direction to counteract the resultant of the radial forces acting on said fluid impeller means from the pumping action.

5 In a multi-stage rotary pump the combination with a casing, a plurality of bladed impellers operating in pumping channels in said pump. uidconduit means-for connecting said impeller periphery of the last stage means in series, a driving shaft journaled in said pellers, a drum-like counterbalancing member mounted in said casing on said shaft, a fluid chamber formed about and extending over a portion only of said member in the peripheral direction, connections for admitting uld to said chamber from the discharge of the high pressure stage, an opposing part of the periphery of said member being exposed to' a lower pressure and the arrangement and proportions being such as to produce a net resultant radial force on said member counter to the resultant of the radial forces acting on said high pressure stage impeller from its pumping action.

6. In a rotary pump the combination of a casing, a driving shaft mounted therein and extending outwardly therefrom, a pumping channel in said casing and a rotary *impeller mounted on said shaft operative in said channel, the inner end -of said shaft terminating in and being completely enclosed within said casing and provided therein with a radial bearing of solid self-lubricating material, a fluid chamber adjacent the periphery of said inner end restricted to a portion only in the circumferential direction thereof, a fluid connection from the pump discharge to said chamber for applying such pressure to said inner end over a limited area in the peripheral direction, and means connecting` a limited peripheral area at the opposite side of said shaft to a point of lower uicl pressure, the arrangement being such as to produce a net radial force on said shaft in a direction to counteract the resultant of the radial forces acting on said iiuid impeller from the pumping action.

'7. In a rotary uid pump, the combination of a casing, a driving shaft journaled in said casing, rotary fluid impeller means mounted on said shaft and adapted to operate in a pumping channel in said casing, the pumping action producing a resultant radial force on said impeller acting in a certain direction, a radial bearing in said 'casing for one end of said shaft, a uid chamber associated with said bearing adjacent the periphery of said shaft end restricted to a portion only in the circumferential direction thereof, a fluid connection to said chamber for exposing it to the pressure of the pump discharge and thereby applying such pressure to the shaft over a limited area in the peripheral direction, and means connecting a limited peripheral area at. the opposite side of said shaft to a point of lower fluid pressure, the arrangement being such as to produce a net radial force on said shaft in a direction to counteract the said resultant force from the pumping action.

GEORGE H. ZENNER. EDWARD F. YENDALL.

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