Multistage centrifugal pump with shaft hydraulic force compensation

Abstract

A multistage centrifugal pump (1) has impellers (9) arranged on a common shaft (8), which is rotatably arranged within a pump casing (2-4). One end of the shaft (8) is led out of the casing (2-4) for connection to a drive motor and another shaft end (15) is rotatably mounted in the pump casing (2-4). The shaft end (15) which is mounted within the pump casing (2-4) is subjected to a counter-force which is produced by way of pressure subjection via a conduit connection to a delivery side of the pump. An axial seal (11) is provided on the shaft end (15) arranged within the pump casing (2-4). The rotating part of the axial seal is led on the shaft end and the non-rotating part is led, axially movably, within the pump casing (2-4). A sealing arrangement is provided between the pump casing and the axially movably mounted part.

Claims

1. A multistage centrifugal pump comprising: a pump casing; a shaft rotatably arranged within the pump casing with one shaft end led out of the casing for connection to a drive motor and another shaft end arranged within the pump casing; pump stage impellers arranged on the shaft; a conduit connection to a delivery side of the pump, wherein the shaft end which is arranged within the pump casing is subjected to a counter-force which is produced by way of pressure subjection via the conduit connection; an axial seal provided on the shaft end arranged within the pump casing, the axial seal having a rotating part that is led on the shaft end which is arranged within the pump casing and the axial seal having a non-rotating and axially movable part that is mounted within the pump casing in an axially movable manner; and a sealing device provided between the pump casing and the axially movable part.

2. A centrifugal pump according to claim 1, wherein the non-rotating and axially movable part of the axial seal is subjected to a pressure of the delivery side.

3. A centrifugal pump according to claim 1, wherein the non-rotating and axially movable part of the axial seal comprises a non-rotating ring with an axial face side forming a sealing surface of the axial seal and with axial side away therefrom is configured closed and comprises at least one recess having a pressure-effective cross-sectional area that is smaller than a pressure-effective cross-sectional area of the conduit connection to the delivery side.

4. A centrifugal pump according to claim 1, wherein sealing device comprises an O-ring held in a radially peripheral groove.

5. A centrifugal pump according to claim 1, wherein an O-ring lies in a groove which is peripheral and on an inner side of a holding ring and which is fixed in the pump casing.

6. A centrifugal pump according to claim 3, wherein the closed axial side of the non-rotating ring comprises a sheet-metal section which covers the non-rotating ring and is connected in a rotationally fixed manner to this and to a holding ring of the non-rotating and axially movable part and/or the pump casing.

7. A centrifugal pump according to claim 1, wherein the rotating part of the axial seal comprises a holding ring which is sealingly and fixedly connected to the shaft end and which carries a rotating ring forming an axial sealing surface.

8. A centrifugal pump according to claim 7, wherein the rotating ring is positively fixed on the holding ring by way of a sleeve which is integrated into the holding ring.

9. A centrifugal pump according to claim 1, wherein the pump casing comprises a suction connection and a delivery connection, and a channel is provided within the pump casing, said channel connecting the delivery connection to a space which receives the non-rotating part of the axial seal.

10. A centrifugal pump according to claim 9, wherein the suction connection and the delivery connection are arranged on a same axis and transversely to a shaft axis.

11. A centrifugal pump according to claim 1, wherein the rotating part comprises a rotating ring including an axial sealing surface that forms a three-point contact.

12. A centrifugal pump according to claim 1, further comprising motor-side bearing wherein an axial mounting of the shaft is effected by the motor-side bearing.

13. A centrifugal pump according to claim 1, wherein the non-rotating and axially movable part of the axial seal comprises a ring configured as a single-part and comprising a wear-resistant part having a sealing surface as well as a carrier receiving the wear-resistant part.

14. A centrifugal pump according to claim 13, wherein: the rotating part comprises a rotating ring including an axial sealing surface; and the rotating ring or the wear-resistant part of the ring or both the rotating ring and the wear-resistant part is comprised of silicon carbide.

15. A centrifugal pump according to claim 1, wherein a closable opening, through which the axial seal can be exchanged, is provided in a base of the pump casing, aligned to the axial seal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a greatly simplified schematic, longitudinal, sectional view through a multi-stage centrifugal pump of the inline construction type with a drive motor;

(3) FIG. 2 is an enlarged longitudinal, sectional view of the pump which is rotated by 90 with respect to FIG. 1;

(4) FIG. 3 is an enlarged view of the detail III in FIG. 1;

(5) FIG. 4 is an enlarged view of the detail IV in FIG. 2;

(6) FIG. 5 is a longitudinal, sectional view showing the rotating part of the axial seal;

(7) FIG. 6 is an exploded view of the components of the rotating part of the axial seal;

(8) FIG. 7 is an exploded view of the non-rotating part of the axial seal with a holding ring for integration into the pump casing;

(9) FIG. 8 is an exploded view of the components of the non-rotating part of the axial seal;

(10) FIG. 9 is an exploded view of the axial seal and the foot part of the centrifugal pump; and

(11) FIG. 10 is an enlarged view of the centrifugal pump from below.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(12) With the centrifugal pump which is represented by way of FIGS. 1-10 it is the case of a multi-stage centrifugal pump 1 of the inline construction type which is operated in a standing manner. The pump casing comprises a foot part 2, a head part 3 and a cylindrical jacket 4 which is arranged therebetween and which surrounds the pump stages and is clamped between the head part 3 and the foot part 2. The foot part 2 comprises a suction connection 5 as well as, aligned to this, a delivery connection 6. The head part 3 is designed as a motor stool and surrounds a coupling 7 which connects a shaft 51 of an electric motor 50 schematically represented in FIG. 1 and attached on the head part 3, to a shaft 8 of the pump 1 in a rotationally fixed manner. The shaft 8 of the pump 1 carries the impellers 9 of the pump stages and is rotatably arranged within the pump casing. A radial seal 10 is provided in the head part 3, and an axial seal 11 is provided in the foot part 2. The construction of this axial seal 11 is evident in detail from the FIGS. 3 to 8 and is described in a detailed manner further below. Fluid is brought into the pump casing on operation via the suction connection 5, when the shaft 8 rotates, and this fluid enters into the suction port 12 of the first pump stage and is delivered through the pump stages which are formed in each case by an impeller 9 and a surrounding diffuser 13, until it exits from the last pump stage in the head part 3 and is led back via an annular channel 14 to the delivery connection 6, through which the fluid leaves the pump again.

(13) The casing-side shaft end 15 of the pump in the region of the suction port 12 lies below the first pump stage. It comprises a pocket-hole bore 16 which is provided with a thread and in which a cap screw 17 is seated, with which cap screw a holding ring 18 is sealingly and fixedly fastened on the shaft end 15. The holding ring 18 comprises a wall 19 which is directed to the suction port 12 and is closed with the exception of a central recess for leading through the screw 17, thus is configured in a pot-like manner and is fixedly connected to the shaft end 15 in a sealed manner.

(14) The holding ring 18 is configured as a turned part, is stepped to the side which is away from the shaft end 15 and is formed with a peripheral groove which is open to the bottom and which is provided for receiving a rotating ring 20. The rotating ring 20 consist of silicon carbide and is rotationally secured in the holding ring 18 by way of pins 21 and is otherwise fastened together with the holding ring 18 on the shaft end 15, by way of a sleeve 22 which radially encompasses the rotating ring 20 on the inner side and by way of the screw 7. The rotating ring 20 comprises a downwardly directed axial surface 23 thus which is directed away from the shaft end 15 and this surface forms the rotating axial surface of the axial seal 11. This axial surface 23 is not completely planar, but comprises three macroscopic prominences which are uniformly distributed over the periphery and which on the one hand form a defined contact on the counter-surface 24, which is to say on the axial surface 24 of the non-rotating axial seal part 25, and on the other hand serve for the rapid build-up of the lubricative film. The axial surface 24 is configured in a planar manner and is part of the non-rotating part, here of the ring 25 which is arranged in an axially movable manner within a holding ring 26 integrated in a corresponding receiver in the lower side of the foot part 2 of the pump casing.

(15) The holding ring 26 comprises a peripheral groove 27 on its inner side, in which groove an O-ring 28 is integrated, said O-ring radially sealing the ring 25 with respect to the holding ring 26 and thus with respect to the pump casing. The holding ring 26 is moreover yet sealed with respect to the receiver in the pump casing by way of an outer-peripheral seal 58, as is evident from the sectioned representations 4 and 7.

(16) The non-rotating ring 25 at the rear side which is away from the axial sealing surface 24 is covered by a sheet metal section 20 which almost completely covers this rear side of the sealing ring 25. The sheet-metal section 20 comprises bent-over tongues 30, with which the sheet metal section is integrated within corresponding recesses 52 on the rear side of the ring 25 with a positive fit. These tongues 30 project radially beyond the ring 25 and engage into these recesses 52 in the ring 25 and form part of a rotation lock of the non-rotating ring 25. Moreover, the sheet-metal section 29 comprises two diametrically opposite tongues 31 which are offset by 90 to the tongues 30 and which are bent away upwards out of the plane of the main material by 90 and connect the sheet-metal section 29 in an axially distanced manner to the ring 25, in which the ends 53 engage into a shoulder 54 on the inner side of the ring 25 in a locking manner.

(17) The sheet-metal section 29 forms a closed surface of the lower side of the ring 25 and comprises a central rectangular recess 32, into which a pin 55 which is rectangular in cross section engages, said pin forming part of the holding ring 26, on which the ring 25 comprising the axial sealing surface 24 is guided in a rotationally fixed, but axially movable manner. The pin 55 and the recess 32 with regard to cross section are dimensioned such that this recess 32 with the pin 55 located therein, together with any gap tolerances of the sheet-metal section 29 form a through-gap with a cross-sectional area which is significantly smaller than the cross-sectional area of channels 33 which are provided in the foot part 2 of the pump casing or in the holding ring 26 and which ensure that the interior 34 of the ring 25 with the sheet-metal section 29 and the holding ring 26 is subjected to the pressure of the delivery side of the pump, thus to the pressure at the delivery connection 6. These channels 33, on starting up the pump after an effected pressure build-up ensure that the sheet-metal section 29 with the ring 25 bearing thereon is firstly subjected to force and is pushed, in the direction of the free shaft end, thus towards the motor, since firstly fluid must flow via the smaller cross section of the gap between the recess 32 and the pin 55, into the space enclosed by the ring, before a corresponding counter-pressure is built up. The ring 25 is moved axial upwards in FIG. 1, which is to say is moved axially within the holding ring 26 by way of this, until the axial surface 24 bears on the counter-surface 23, by which means a separation between the suction-side space in the region of the shaft end 15 and the installation space 34 of the stationary part of the axial seal 11 is then also formed. The pressure of the delivery side also prevails within the ring 25 and this at the face side of the shaft 8, as soon as the space which is enclosed by the ring 25 and the sheet-metal section 29 has filled via the gap of the recess 32, by which means the certain force compensation with regard to the hydraulically caused axial force of the shaft 8 and which is desired on operation is effected.

(18) As can particularly be deduced from FIG. 9, the holding ring 26 is part of a circular disc 56 which is provided for integration in a base-side maintenance opening 60 of the pump casing, here of the foot part 2. The disc 56, in a manner closing this base-side opening 60, lies in a shoulder 64 on the lower side of the foot part 2 and is releasably connected to the foot part 2 via four screws 57 which are led through recesses 61 in the edge 62 of the disc 56. An O-ring 58 which is integrated in a peripheral radial groove of the ring 26 and serves for sealing this component with respect to a recess 63 in the foot part 2, is arranged in the upper region of the ring 26, thus at a small distance to the disc 25, for sealing with respect to the foot part 2. A second O-ring 59 is integrated at an axial distance to this, in a peripheral, radial groove in the lower part of the ring 26 and serves for sealing with respect to the maintenance opening 60 in the foot part 2. A connection to the delivery side of the centrifugal pump 1 which is connected in a fluid-leading manner to the interior of the ring 26 via channels 33 in the ring 26, connects within the foot part 2, between the O-rings 58 and 59, so that the pressure of the delivery side via this connection is present at the surface of the non-rotating part 25 of the axial seal, said surface being formed by the sheet-metal section 29 and at the beginning being pressure-effective. The ring 26 via the O-ring 28 lying in a groove on the inner side of the holding ring 26 is sealed with respect to the ring 25 which forms the non-rotating part of the axial seal with the axial surface 24 of the seal. This O-ring 28 thus forms a radial seal which however only has to accommodate the comparatively small movements in the axial direction and therefore is only subjected to a low wear.

(19) The axial seal can be overhauled and exchanged as the case may be, by way of removing the disc 56 with the holding ring 26 which is located thereon, after the screws 57 have been released, due to the fact that the pump casing at the lower side, thus in the base of the foot part 2, comprises a maintenance opening 60 which is closed by the disc 56. The shaft 38 of the pump does not have to be removed for this. All components of the axial seal which are represented in the exploded representation according to FIG. 9 can be exchanged through the opening 61 in the base of the foot part 2. An exchange of the components comprising the axial surfaces 23 and 24 as well as of the O-ring 28 is effected in the simplest case. The shaft 8 in the region of the motor stool has a cross-sectional profile which permits a locking of the shaft by way of laterally engaging a tool, in order to be able to release the threaded connections which are connected to the shaft 8. Thus, the cap screw 17 can be released after the shaft 8 is held in a rotationally fixed manner by way of a spanner introduced in the region of the motor stool, and this screw can then be tightly screwed again after exchange of the rotating ring 20 and, as the case may be, further seals of the holding ring 18.

(20) The axially stationary part of the seal, thus the non-rotating ring 25 with its seals and the holding ring 26 which with the disc 56 forms the cover for closure of the casing opening of the maintenance opening 60, together with the cover 56 are pulled out downwards and thereby the upper part of the holding ring 26 with the peripheral O-ring 58 is pulled out of the recess 63, and the lower part of the holding ring 26 with the O-ring 59 is pulled out of the maintenance opening 60. These seals as well as the O-ring 28 and the non-rotating part of the axial seal 25 can then be exchanged and together are inserted from below into the maintenance opening 60 or the recess 63 of the foot part 2, until the upper part of the holding ring 26 with the O-ring 58 sealingly bears in the recess 63 and the lower part with the O-ring 59 sealingly bears in the maintenance opening 60.

(21) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

APPENDIX

List of Reference Numerals

(22) 1centrifugal pump 2foot part 3head part 4jacket 5suction connection 6delivery connection 7coupling 8shaft 9impellers 10radial seal 11axial seal 12suction port 13diffuser 14annular channel 15shaft end 16pocket-hole bore 17cap screw 18holding ring 19wall 20rotating ring 21pins 22sleeve 23axial surface 24axial surface 25non-rotating part of the axial seal, ring 26holding ring 27groove 28O-ring 29sheet-metal section 30tongues 31tongues 32recesses in 29 33channels in ring 26 34interior of 25 35outer thread 36nut 37sleeve 37shaft 50motor 51motor shaft 52recesses in ring 25 53ends of the tongues 31 54shoulder in ring 25 55pin 56disc/cover 57screws 58O-ring 59O-ring 60maintenance opening 61bores for the screws 57 62edge of cover 62recess 64shoulder in foot