EP3171028B1 - Multistage centrifugal pump with an axial thrust balancing piston, the pressure and suction sides of which are separated by a mechanical seal - Google Patents

Description

The invention relates to a multi-stage centrifugal pump with a hydraulic Axialschubausgleich.

In multi-stage centrifugal pumps, in which the impellers of the pump stages are arranged on a common shaft and rotatably disposed within a pump housing, the drive is often via an external motor, which is drivingly connected to a coupling with the pump shaft and on a motor chair, that is one for Recording the motor formed housing part, is picked up and attached. For this purpose, the one shaft end is sealingly guided through the pump housing and out of this, the other shaft end is mounted within the pump housing. It belongs to the state of the art to absorb the forces acting on the pump shaft forces through the motor bearings and within the pump housing only a radial guide, for example, by shaft sleeves, which are arranged in the pump stages, provide. For larger multi-stage pumps, however, the pump-side shaft end is mounted radially and / or axially within the pump housing to relieve the engine bearings. However, common to all constructions is an increased load and thus an increased wear of the motor bearings.

It is part of the prior art, this compensate due to the hydraulic forces resulting axial forces on the shaft, either by pressurizing the shaft end mounted in the housing with the pressure of the pressure side or by providing Recesses in the cover disks of the wheels. The latter has a significant loss of efficiency due to the resulting backflows result. In hydraulic power compensation, there is the problem that a highly stressed seal between the rotating shaft end and the fixed housing is provided, which, if it has a good sealing effect, high friction and thus high wear and the release of the sealing effect to overcurrent losses leads, The documents NL 7 712 699 A . US 1 927 543 A and WO 99/43959 A2 each reveal a pump with a hydraulic axial thrust compensation.

Before this prior art, the invention has the object, a generic multi-stage centrifugal pump in such a way that on the one hand, the hydraulically induced forces can be reduced to the shaft, on the other hand, however, a good, low friction and low-wear and thus long-term stable seal.

This object is achieved according to the invention with the features specified in claim 1. Advantageous embodiments of the invention are specified in the subclaims, the following description and the drawing. In this case, the features specified in the dependent claims and the description in each case but in a suitable combination, the inventive solution according to claim 1 further develop.

In the multi-stage centrifugal pump according to the invention, the impellers of the pump stages are arranged directly or via a support body on a shaft which is rotatably disposed within a pump housing. At one end of this shaft for connection to a drive motor from the housing is guided sealingly out, at the other end it is disposed within the pump housing, wherein the arranged inside the pump housing shaft end is acted upon by a counter force by pressurizing a line connection to a pressure side the pump is generated, typically, but not necessarily, with the pressure of the last pump stage, ie the pressure side of the pump. According to the invention, an axial seal is provided on the shaft end mounted inside the pump housing, whose rotating part is guided on the shaft end and whose non-rotating part is axially movable within the pump housing. In this case, sealing means are provided according to the invention between the non-rotating axially movably mounted part and the pump housing in order to prevent there also an overflow of liquid from the pressure side to the suction side. Under pump housing in the context of the present invention is also an intermediate component to understand, which is incorporated into the pump housing and on which attack the sealant.

The basic idea of the solution according to the invention is, on the one hand, to provide a hydraulic force compensation which reduces the axial forces of the pump shaft acting on the bearings, but on the other hand to provide an axial seal on the shaft end mounted inside the housing, which has only low friction and thus low wear, but which is simple in construction and reliable in the effect. This is achieved by providing the rotating part of the axial seal at the shaft end and the non-rotating part inside the pump housing. However, in order to compensate for possible wear or axial play of the shaft, the non-rotating part of the axial seal is mounted and guided in an axially movable manner within the pump housing, wherein sealing means are provided between the axially movable mounted part of the axial seal and the pump housing. The entire seal is thus divided into a pure axial seal and another seal, preferably a radial seal, wherein the essential movement is intercepted in the axial seal, whereas the other, in particular radial seal must perform only small axial movements and thus by design even little wear is exposed. This further particular radial seal can therefore be formed inexpensively, for example, by an elastic sealing ring, whereas the axial seal can be designed by appropriately designed sealing surfaces exclusively for sealing against the rotational movement. In this case, with a suitable embodiment of the axial seal, these also absorb axial forces and thus also take the function of a thrust bearing.

In order to compensate in particular largely for the axial forces resulting from the hydraulic forces, it is therefore provided according to the invention to pressurize the shaft end mounted inside the pump housing with the pressure of the pressure side. However, the construction according to the invention provides in a particularly advantageous manner that the sealing is not carried out by a seal between a fixed and a rotating component, but between the pump housing and the axially movable mounted and non-rotating part of the axial seal. This solution has the advantage that the seal has only to absorb the typically small axial movement of the non-rotating part of the axial seal, but not the friction-intensive and wear-promoting movement to the rotating part, which is received by the axial seal. In that regard, the seal is made by the sealing gap itself, which is sufficiently small in a correspondingly dimensioned axial seal to neglect Überströmverluste can. The sealant can therefore be designed cost-effective and long-term stability, without this having a significant impact on the efficiency of the pump.

The solution according to the invention also has the advantage that at least to a limited extent axial forces of the shaft can be absorbed by the axial seal in the pump housing. However, the essential part of the axial forces is due to the hydraulic compensation, that is, by returning the pressure level generated by the pump generated on the free shaft end within the pump housing, so that regardless of the number of stages, the drive of the pump can be ensured with a standard motor. The dynamic force compensation of the hydraulically induced axial forces acting on the shaft, limits the forces to be absorbed by the thrust bearing to a minimum. Also, the hydraulic power compensation has the advantage that in the case of dry running, if these restoring forces do not occur, no force compensation takes place, so that even then the wear keeps within acceptable limits.

The embodiment according to the invention has the additional advantage that, in accordance with constructive implementation, both the axial seal and the other sealing means, in particular the radial seal can be replaced without having to remove the shaft from the pump housing. Thus, the pump stages, that is, the wheels with the associated nozzles remain in their intended position.

It is particularly advantageous if the non-rotating part of the axial seal is acted upon by the pressure of the pressure side of the pump on its axial side facing away from the sealing surface, that is to say the rear side. As a result, the required supporting force for the axial seal or for the thrust bearing function is applied, namely dynamically, that is, depending on the output pressure of the pump.

This can advantageously be further developed by the fact that the non-rotating part of the axial seal has a ring whose one axial end side forms a sealing surface of the axial seal and the other thereof facing away from the rear axial side is closed and at least one recess whose pressure-effective cross-sectional area is smaller than the pressure-effective cross-sectional area of the line connection to the pressure side. It can Recess according to the present invention, an edge gap, an opening, one or more openings or the like or a combination thereof. It is essential that the pressure-effective cross-sectional area of the one or more recesses is always smaller than the pressure-effective cross-sectional area of the one or more line connections to the pressure side, to ensure that when starting the pump, first forms a pressure in front of this closed surface of the ring, which causes the ring to move axially towards the mating face at the shaft end, and only when, after some time, the interior space defined by the ring is completely filled with liquid will this additional axial force causing the movement of the ring wears off.

For sealing the axially movable part of the axial seal and the pump housing or the component which is provided within the pump housing for receiving the axially movable part, an O-ring is advantageously provided, which is held in a radially circumferential groove. This radially encircling groove can be provided either on the housing side or on the ring side, that is to say on the bearing side. Such an O-ring is inexpensive, easy to assemble and replace if necessary, and forms a long-term reliable seal.

It when the O-ring is located in a provided on the inside of a retaining ring circumferential groove which is fixed in the pump housing is particularly advantageous. Such a construction, in which the O-ring is not directly in the pump housing, but in an intermediate component, has the advantage that here only the retaining ring is machined and the retaining ring is incorporated, for example by compression in the pump housing, as far as no clamping the pump housing is required in the manufacture of the groove.

In order to form the closed axial side of the non-rotating part of the axial seal, this part can be made of solid material, for example as a turned part. However, it is particularly advantageous if this is formed as a ring of a pipe section and the closed axial side by a sheet metal section, which can be inexpensively manufactured by punching. This sheet metal section, which covers the back of the ring and thus forms the initially pressure-effective closed axial side with the at least one recess can also be used advantageously to form the anti-rotation of the non-rotating part of the axial seal, in particular of the ring and this either rotationally fixed to the retaining ring and / or on the pump housing. Since in this respect only small forces are to be absorbed, this function can be realized by a cost-effective stamped part, which is optionally processed according to shaping.

Shaft side is provided according to the invention to connect a retaining ring tightly and firmly with the shaft end, which is either itself formed as a sealing ring and forms an Axialdichtfläche or advantageously receives the axial sealing surface forming a sliding ring. Such a sliding ring may for example consist of highly wear-resistant silicon carbide, wherein the retaining ring may consist of a more cost-effective preferably metal material. In this case, the axial sealing surface forming the sliding ring is advantageously determined by means of a screwed into the retaining ring threaded bushing or a female form fit to this or with this. This allows the exchange of the axial sealing surface forming the sliding ring also without disassembly of the shaft, since the free end of the shaft is accessible from outside the pump housing and can be blocked by a tool against rotation.

The centrifugal pump according to the invention is advantageously designed as an in-line pump, thus has a pump housing, wherein the suction port and pressure port are arranged coaxially. In such an arrangement, a passage between the pressure port and a space receiving the non-rotating part of the axial seal and typically located in the base of the pump housing can be easily realized. It may optionally be provided more channels to realize the required cable cross-sections.

Advantageously, one of the sealing surfaces of the axial seal is designed as a three-point support, thus has distributed over the circumference three macroscopic elevations, which on the one hand ensure a defined support to the plane mating surface and on the other are particularly advantageous in terms of the structure of the lubricant film, which is when starting the Pump should build up as quickly as possible, so that the advantageous and low-wear sliding friction arises. The formation of this three-point support is advantageously carried out on the slide ring, since this can be processed as a separate component cost-effective with low tolerance than the other components.

The embodiment of the invention makes it possible to provide the axial bearing of the shaft exclusively on the motor side, wherein the axial forces occurring due to the design are so small that they can be absorbed by the engine mounts without noticeably increasing their wear. The axial bearing of the shaft is thus advantageously carried out by one or more bearings arranged on the motor side, preferably a motor-side bearing near the pump-side end of the motor shaft.

According to an advantageous embodiment of the invention may alternatively or additionally the ring of the non-rotating part of the axial seal be constructed in several parts and have a high wear-resistant part having the sealing surface and a carrier receiving the highly wear-resistant part, as already indicated above for the rotating part of the axial seal.

Advantageously, the sliding ring and / or the highly wear-resistant part of the ring of silicon carbide or a comparable highly wear-resistant material formed, which allows particularly long service life.

In order to replace the axial seal and the sealant between the non-rotating part of the axial seal and the pump housing without having to dismantle the pump, according to an advantageous embodiment of the invention, a closable opening in the pump housing, preferably aligned with the axial seal provided by which the axial seal can be exchanged.

Fig. 1

in stark vereinfachter schematischer Darstellung einen Längsschnitt durch eine mehrstufige Kreiselpumpe der Inline-Bauart mit Antriebsmotor,

Fig. 2

ein vergrößerter und um 90° gegenüber Fig. 1 gedrehter Längsschnitt der Pumpe,

Fig. 3

die Einzelheit III in Fig. 1 in vergrößerter Darstellung,

Fig. 4

die Einzelheit IV in Fig. 2 in vergrößerter Darstellung,

Fig. 5

den rotierenden Teil der Axialdichtung im Längsschnitt,

Fig. 6

die Bauteile des rotierenden Teils der Axialdichtung in Explosionsdarstellung,

Fig. 7

den nicht rotierenden Teil der Axialdichtung mit Haltering zur Eingliederung ins Pumpengehäuse im Längsschnitt,

Fig. 8

die Bauteile des nicht rotierenden Teils der Axialdichtung in Explosionsdarstellung,

Fig. 9

die Axialdichtung und das Fußteil der Kreiselpumpe in Explosionsdarstellung und

Fig. 10

in vergrößerter Darstellung eine Ansicht der Kreiselpumpe von unten.

The invention is explained in more detail with reference to embodiments shown in the drawing. Show it:

Fig. 1

in a highly simplified schematic representation of a longitudinal section through a multi-stage centrifugal pump of the inline design with drive motor,

Fig. 2

an enlarged and 90 ° opposite Fig. 1 rotated longitudinal section of the pump,

Fig. 3

the detail III in Fig. 1 in an enlarged view,

Fig. 4

the detail IV in Fig. 2 in an enlarged view,

Fig. 5

the rotating part of the axial seal in longitudinal section,

Fig. 6

the components of the rotating part of the axial seal in exploded view,

Fig. 7

the non-rotating part of the axial seal with retaining ring for incorporation into the pump housing in longitudinal section,

Fig. 8

the components of the non-rotating part of the axial seal in exploded view,

Fig. 9

the axial seal and the foot of the centrifugal pump in exploded view and

Fig. 10

in an enlarged view a view of the centrifugal pump from below.

When using the Figures 1-10 The centrifugal pump shown is a multi-stage, vertically operated centrifugal pump 1 of the inline design. The pump housing has a foot part 2, a head part 3 and a cylindrical shell 4 arranged therebetween, which surrounds the pump stages and is clamped between head part 3 and foot part 2. The foot part 2 has a suction connection 5 and in alignment with a pressure connection 6. The head part 3 is designed as a motor chair and surrounds a clutch 7, which has a shaft 51 of a in Fig. 1 schematically shown mounted on the head part 3 electric motor 50 rotatably connected to a shaft 8 of the pump 1 connects. The shaft 8 of the pump 1 carries the impellers 9 of the pump stages and is rotatably disposed within the pump housing. In the head part 3, a radial seal 10 is provided and in the foot part 2 an axial seal 11. The structure of this axial seal 11 is made of the FIGS. 3 to 8 in detail and described in detail below. In operation, when the shaft 8 rotates, 5 liquid is introduced into the pump housing via the suction port, which enters the suction port 12 of the first pump stage and is supported by each formed from a gyro 9 and a surrounding nozzle 13 pump stages until they Head part 3 emerges from the last pump stage and is returned via an annular channel 14 to the pressure port 6, through which the liquid leaves the pump again.

The housing-side shaft end 15 of the pump is located in the region of the suction port 12 below the first pump stage. It has a threaded blind hole 16 in which a cap screw 17 is seated, with a retaining ring 18 is tightly and firmly attached to the shaft end 15. The retaining ring 18 has a directed towards the suction port 12 and, except for a central recess for performing the screw 17 closed wall 19, so is cup-shaped and tightly and firmly connected to the shaft end 15.

The retaining ring 18 is formed as a rotating part, stepped to the side facing away from the shaft end 15 side and formed with a downwardly open circumferential groove which is provided for receiving a sliding ring 20. The sliding ring 20 is made of silicon carbide and is secured against rotation by means of pins 21 in the retaining ring 18 and the rest by means of a sleeve 22 which radially overlaps the sliding ring 20 on the inside and is fastened by means of the screw 7 together with the retaining ring 18 at the shaft end 15. The sliding ring 20 has a downwardly directed, thus facing away from the shaft end 15 axial surface 23, which forms the rotating axial surface of the axial seal 11. This axial surface 23 is not completely flat, but has three evenly distributed over the circumference macroscopic elevations, which on the one hand a defined contact with the counter surface 24, that is, the axial surface 24 of the non-rotating Axialdichtungsteils 25, and other serves the rapid construction of the lubricating film. The axial surface 24 is flat and part of the non-rotating part, here the ring 25, which is arranged axially movable within a retaining ring 26 which is incorporated in a corresponding receptacle in the bottom of the foot part 2 of the pump housing.

The retaining ring 26 has a circumferential groove 27 on its inner side, in which an O-ring 28 is incorporated, which radially seals the ring 25 relative to the retaining ring 26 and thus with respect to the pump housing. The retaining ring 26 is further sealed with an outer circumferential seal 58 against the receptacle in the pump housing, as can be seen from the sectional views 4 and 7.

At the rear side facing away from the axial sealing surface 24, the non-rotating ring 25 is covered by a sheet-metal section 29, which covers this rear side of the sealing ring 25 almost completely. The sheet metal section 29 has bent tongues 30 with which the sheet metal section is incorporated in a form-fitting manner within corresponding recesses 52 on the rear side of the ring 25. These tongues 30 protrude radially over the ring 25 and engage in these recesses 52 in the ring 25 and form part of an anti-rotation of the non-rotating ring 25. In addition, the sheet metal portion 29 offset by 90 ° to the tongues 30 two diametrically opposite tongues 31, which are bent from the plane of the base material by 90 ° upwards and the sheet metal portion 29 in the axial direction spaced connect with the ring 25, in which the ends 53 engage detent in a shoulder 54 on the inside of the ring 25.

The sheet metal section 29 forms a closed surface of the underside of the ring 25 and has a central rectangular recess 32 into which engages a rectangular cross-section pin 55, the part the retaining ring 26 forms, on which the ring 25, which has the Axialdichtfläche 24, rotatably but axially movably guided. The pin 55 and the recess 32 are dimensioned in cross-section so that this recess 32 with the pin 55 therein together with any gap tolerances of the sheet portion 29 form a passage gap with a cross-sectional area which is significantly smaller than the cross-sectional area of channels 33 in the foot 2 of the pump housing or in the retaining ring 26 are provided and which ensure that the interior 34 of the ring 25 with the sheet metal portion 29 and the retaining ring 26 with the pressure of the pressure side of the pump, ie with the pressure at the pressure port 6, is acted upon. These channels 33 ensure that when the pump starts after the pressure has been built up, the sheet metal section 29 with the adjoining ring 25 toward the free end of the shaft is thus subjected to force and pushing towards the motor, since the smaller cross section of the gap between the recess 32 and The pin 55 must first flow liquid into the space enclosed by the ring 25 space before a corresponding back pressure is built up. As a result, the ring 25 in Fig. 1 axially upwards, that is axially moved within the retaining ring 26 until the axial surface 24 abuts against the counter surface 23, whereby then a separation between the suction-side space in the region of the shaft end 15 and the installation space 34 of the fixed part of the axial seal 11 is formed. Once the space enclosed by the ring 25 and the sheet metal portion 29 has filled over the gap of the recess 32, the pressure of the pressure side is also within the ring 25 and thus on the front side of the shaft 8, whereby the desired during operation certain force compensation in terms of hydraulically induced axial force of the shaft 8 takes place.

As in particular from Fig. 9 is removable, the retaining ring 26 is part of a circular disc 56, which for incorporation in a bottom-side Maintenance opening 60 of the pump housing, here the foot part 2 is provided. The disc 56 is this bottom-side opening 60 closes in a shoulder 64 on the underside of the foot part 2 and is connected via four screws 57 which are guided by recesses 61 in the edge 62 of the disc 56, releasably connected to the foot part 2. For sealing against the foot part 2, an O-ring 58 is arranged in the upper region of the ring 26, ie at a small distance from the disk 25, which is incorporated in a circumferential radial groove of the ring 26 and for sealing this component against a recess 63 in the foot part 2 serves. At an axial distance to a second O-ring 59 is incorporated in a circumferential radial groove in the lower part of the ring 26, which serves to seal against the maintenance opening 60 in the foot part 2. Between the O-rings 58 and 59 includes within the foot part 2, a connection to the pressure side of the centrifugal pump 1, which is fluidly connected via channels 33 in the ring 26 with the interior of the ring 26, so that above the pressure of the pressure side of the through Sheet section 29 formed initially pressure-effective surface of the non-rotating part 25 of the axial seal is present. The ring 26 is sealed over the O-ring 28 which lies in a groove on the inside of the retaining ring 26, opposite 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, has to absorb only the comparatively small movements in the axial direction and is therefore subject to only slight wear.

The fact that the pump housing at the bottom, ie in the bottom of the foot part 2 has a maintenance opening 60 which is closed by the disc 56, by removing the disc 56 with the retaining ring 26 thereon, after the screws 57 have been solved, the Axial seal serviced and replaced if necessary. For this purpose, the shaft 38 of the pump must not be removed. All in the exploded view after Fig. 9 shown Components of the axial seal can be replaced by the opening 61 in the bottom of the foot part 2. In the simplest form typically follows an exchange of the axial surfaces 23 and 24 having components and the O-ring 28. In order to solve the associated with the shaft 8 threaded connections, the shaft 8 in the field of motor chair on a cross-sectional profile, which through lateral engagement of a tool allows a locking of the shaft. It can thus, after the shaft 8 is rotatably held by means of a introduced in the field of motor chair open-end wrench, the cap screw 17 is released and after replacement of the sliding ring 20 and optionally further seals the retaining ring 18, these are screwed again.

The axially fixed part of the seal, so the non-rotating ring 25 with its seals and the retaining ring 26, with the disc 56 which forms the lid for closing the housing opening of the maintenance opening 60 are pulled out together with the cover 56 down, thereby the upper part of the retaining ring 26 with the peripheral O-ring 58 is pulled out of the recess 63 and the lower part of the retaining ring 26 with the O-ring 59 from the maintenance opening 60. These seals and the O-ring 28 and the non-rotating part of the axial seal 25 can then be replaced and are used together again from below into the maintenance opening 60 and the recess 63 of the foot part 2 until the upper part of the retaining ring 26 with the O Ring 58 in the recess 63 and the lower part sealingly abuts with the O-ring 59 in the maintenance opening 60.

LIST OF REFERENCE NUMBERS

1

- Centrifugal pump

2

- foot part

3

- Headboard

4

- coat

5

- Suction connection

6

- Pressure connection

7

- coupling

8th

- Wave

9

- rotary wheels

10

- Radial seal

11

- Axial seal

12

- Suction mouth

13

- Diaphragm

14

- Ring channel

15

- shaft end

16

- blind hole

17

- head screw

18

- retaining ring

19

- wall

20

- Sliding ring

21

- Pencils

22

- Sleeve

23

- Axial surface

24

- Axial surface

25

- non-rotating part of the axial seal

26

- retaining ring

27

- groove

28

- O-ring

29

- Sheet metal section

30

- tongues

31

- tongues

32

- recess in 29

33

- Channels in the ring 26

34

- Interior of 25

35

- external thread

36

- Mother

37

- Sleeve

38

- Wave

50

- Engine

51

- Motor shaft

52

- Recesses in the ring 25th

53

- ends of the tongues 31

54

- heel in the ring 25

55

- cones

56

- disc / lid

57

- screws

58

- O-ring

59

- O-ring

60

- Maintenance opening

61

- Holes for the screws 57th

62

- edge of the lid

63

- recess

64

- heel in the foot

Claims (15)

1. A multistage centrifugal pump (1), with which the impellers (9) of the pump stages are arranged on a shaft (8) which is rotatably arranged within a pump casing (2-4) and which at one end is led out of the casing (2-4) for connection to a drive motor and at the other end (15) is arranged within the pump casing (2-4), wherein the shaft end (15) which is arranged within the pump casing (2-4) is subjected to a counter-force which is produced by way of pressure subjection via a conduit connection (33) to a delivery side (6) of the pump (1), wherein an axial seal (11) is provided on the shaft end (15) arranged within the pump casing (2-4), the rotating part (20) of said axial seal being led on the shaft end (15) and the non-rotating part (25) being led within the pump casing (2-4) in an axially movable manner, wherein sealing means (28) are provided between the pump casing (2-4) and the axially movably mounted part (25).
2. A centrifugal pump according to claim 1, characterised in that the non-rotating part (25, 26) of the axial seal (11) at its axial side which is away from the sealing surface (24) is subjected to the pressure of the delivery side (6).
3. A centrifugal pump according to claim 1 or 2, characterised in that the non-rotating part (25, 26) of the axial seal (11) comprises a ring (25) whose one axial face side (24) forms a sealing surface of the axial seal (11) and whose other axial side which is away therefrom is designed in a closed manner and comprises at least one recess (32), whose pressure-effective cross-sectional area is smaller than the pressure-effective cross-sectional area of the conduit connection (33) to the delivery side.
4. A centrifugal pump according to one of the preceding claims, characterised in that the sealing means comprise an O-ring (28) which is held in a radially peripheral groove (27).
5. A centrifugal pump according to claim 4, characterised in that the O-ring (28) lies in a groove (27) which is peripheral on an inner side of a holding ring (26) and which is fixed in the pump casing (2-4).
6. A centrifugal pump according to one of the preceding claims 3 to 5, characterised in that the closed axial side of the non-rotating ring (25) comprises a sheet-metal section (29) which covers the ring (25) and is connected in a rotationally fixed manner to this and to the holding ring (26) and/or the pump casing (2-4).
7. A centrifugal pump according to one of the preceding claims, characterised in that the rotating part of the axial seal (11) comprises a holding ring (18) which is sealingly and fixedly connected to the shaft end (15) and which carries a rotating ring (20) forming the axial sealing surface (23).
8. A centrifugal pump according to one of the preceding claims, characterised in that the rotating ring (20) which forms the axial sealing surface (23) is positively fixed on the holding ring (18) by way of a sleeve (22) which is integrated into the holding ring (18).
9. A centrifugal pump according to one of the preceding claims, characterised in that the pump casing (2-4) comprises a suction connection (5) and a delivery connection (6), and that a channel (33) is provided within the pump casing (2-4), said channel connecting the delivery connection (6) to the space (34) which receives the non-rotating part (25, 26) of the axial seal (11).
10. A centrifugal pump according to one of the preceding claims, characterised in that the suction connection (5) and the delivery connection (6) are arranged on the same axis and transversely to the shaft axis.
11. A centrifugal pump according to one of the preceding claims, characterised in that an axial sealing surface (23), preferably that on the rotating ring (20) forms a three-point contact.
12. A centrifugal pump according to one of the preceding claims, characterised in that the axial mounting of the shaft (8) is effected by way of a motor-side bearing.
13. A centrifugal pump according to one of the preceding claims, characterised in that the ring (25) of the non-rotating part of the axial seal (11) is constructed in a single-part manner and comprises a highly wear-resistant part having the sealing surface (24), as well as a carrier receiving the highly wear-resistant part.
14. A centrifugal pump according to one of the preceding claims, characterised in that the rotating ring (20) and/or the highly wear-resistant part of the ring consist of silicon carbide.
15. A centrifugal pump according to one of the preceding claims, characterised in that a closable opening, through which the axial seal can be exchanged, is provided in the base of the pump casing, preferably in a manner aligned to the axial seal (11).

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