EP3805570A1 - Centrifugal pump for conveying a fluid - Google Patents

Abstract

A centrifugal pump for conveying a fluid is proposed, with a suction chamber (4), a pressure chamber (5) and an impeller (2) which is rotatable about an axial direction (A) and with which the fluid is transported from the suction chamber (4) into the Pressure chamber (5) can be conveyed, as well as with a wear ring (8) which is arranged non-rotatably on a stationary housing part (6), the wear ring (8) together with the impeller (2) delimiting a radial sealing gap (11), wherein the wear ring (8) is arranged displaceably in the axial direction (A), a preloading element (12) being provided which exerts a force on the wear ring (8) which is directed in the axial direction (A) towards the impeller (2) is, and wherein the wear ring (8) is designed and arranged in such a way that, in the operating state, a hydraulic force also acts on the wear ring (8), which is directed in the axial direction (A) towards the impeller (2).

Description

The invention relates to a centrifugal pump for conveying a fluid according to the preamble of the independent claim.

Centrifugal pumps, which are designed, for example, as centrifugal pumps with a radial impeller, are used in many different technological areas, for example in the oil and gas processing industry, in the water industry or in the context of industrial energy generation. Many different embodiments are known here, for example single-stage pumps, multi-stage pumps, single-flow pumps or double-flow pumps.

Typically, the centrifugal pump comprises a suction chamber which is flow-connected to the inlet of the pump, and a pressure chamber which is flow-connected to the outlet of the pump. An impeller, which is arranged non-rotatably on a shaft, conveys the fluid, for example water, from the suction chamber into the pressure chamber and thereby increases the pressure of the fluid. In the case of multistage pumps, in principle each stage has a suction space and a pressure space, the pressure space of one stage representing the suction space of the next stage, so to speak.

The impeller is designed, for example, as a closed impeller. In such a configuration, the impeller comprises a hub disk on which a plurality of blades are arranged, and a cover disk which completely or at least partially covers the blades on their side facing away from the hub disk. Thus, at least partially, form between the blades closed channels, which each extend from the center of the impeller to its outer radial boundary surface.

The shaft on which the impeller is arranged is set in rotation by a drive, for example an electric motor, and rotates around the axis of the shaft, which defines an axial direction.

The impeller is arranged in a stationary housing part of the pump housing. A non-rotating wear ring, which surrounds the impeller, is usually provided between the impeller, which rotates in the operating state, and the stationary housing part. The wear ring is arranged, for example, in such a way that it surrounds a central area of the cover disk of the impeller. This creates a radial sealing gap which separates the pressure chamber from the suction chamber. The area between the front side of the impeller, for example the cover plate, and the stationary housing part is also referred to as the side space of the pump.

During the operation of the pump, part of the pumped fluid flows from the pressure chamber through the side chamber and the radial sealing gap back into the suction chamber of the pump.

The wear ring is designed with a predetermined clearance with respect to the rotating impeller, so that the annular radial sealing gap is formed between a radially inner, cylinder jacket-shaped boundary surface of the wear ring and the rotating impeller, through which a leakage flow from the pressure chamber to the suction chamber is made possible. This arrangement is often referred to as a labyrinth. The leakage flow is advantageous on the one hand because it contributes to the hydrodynamic stabilization of the rotor (shaft with impeller), on the other hand it also means a certain loss in terms of the efficiency of the pump. The dimensioning of this radial sealing gap therefore plays an important role. The aim is to avoid direct physical contact between the stationary wear ring and the rotating shaft during operation of the pump. Therefore, the radial sealing gap must not be made too narrow, because radial movements of the impeller can occur during operation of the pump, for example due to the bending of the Wave. The width of the radial sealing gap, by which its extent in the radial direction is meant, can also change in the course of operation, for example due to erosion on the wear ring.

The dimensions of the radial sealing gap therefore always represent a compromise between the efficiency of the pump and the operational reliability of the pump.

Nowadays efforts are often made to provide a pump with the highest possible energy efficiency. This can be made possible in particular by reducing the return flow of the pumped fluid from the pressure chamber through the side chamber into the suction chamber as far as possible without endangering the operational safety of the pump.

It is therefore an object of the invention to provide a centrifugal pump with a particularly high efficiency which has as little return flow of the fluid from the pressure chamber into the suction chamber as possible without making concessions to the operational reliability of the centrifugal pump.

The subject matter of the invention which solves this problem is characterized by the features of the independent patent claim.

According to the invention, a centrifugal pump for conveying a fluid is proposed, with a suction chamber, a pressure chamber and an impeller arranged rotatably about an axial direction, with which the fluid can be pumped from the suction chamber into the pressure chamber, and with a wear ring that cannot rotate on a stationary housing part is arranged, wherein the wear ring delimits a radial sealing gap together with the impeller, wherein the wear ring is arranged displaceably in the axial direction, wherein a preload element is provided which exerts a force on the wear ring which is directed in the axial direction towards the impeller is, and wherein the wear ring is designed and arranged such that, in the operating state, a hydraulic force also acts on the wear ring, which is directed in the axial direction towards the impeller.

The wear ring is thus mounted in a floating manner with respect to the axial direction and is pressed onto the impeller in the axial direction by the prestressing element. During operation of the pump, the fluid to be conveyed penetrates from the pressure chamber through the radial sealing gap and thereby lifts the wear ring off the impeller in the axial direction against the force of the pretensioning element. This opens an axial sealing gap between the wear ring and the impeller. In addition, the wear ring is designed and arranged in such a way that the fluid also exerts a hydraulic force on the wear ring, this hydraulic force being directed in the axial direction towards the impeller. This additional hydraulic force thus acts on the wear ring in the same direction as the force exerted on the wear ring by the pretensioning element. The axial sealing gap is formed between the impeller and the wear ring, which forms a lubricating film between the wear ring and the impeller. Further opening of the axial sealing gap is prevented by the joint action of the hydraulic force, which tries to press the wear ring onto the impeller, and the force exerted on the wear ring by the pretensioning element.

The function of the radial sealing gap between the impeller and the wear ring, which is known from the prior art, is mainly performed by the axial sealing gap in the configuration according to the invention. The radial sealing gap can therefore be made even larger than in the prior art, that is to say with a larger width. This has the great advantage that, in the operating state, physical contact between the impeller and the wear ring in the area of the radial sealing gap can be prevented more reliably.

Since the non-rotatable wear ring is floating and is pressed by the hydraulic force together with the force generated by the preload element in the direction of the front of the impeller, a dynamic axial seal is created, which clearly increases the amount of fluid flowing back from the pressure chamber into the suction chamber reduced. Thus, the economic efficiency improves.

In order to achieve particularly good efficiency of the pump, the wear ring and the pretensioning element are preferably designed such that, in the operating state, there is an axial sealing gap between the impeller and the wear ring which is smaller than the radial sealing gap.

The prestressing element is preferably designed as a spring element, for example in the form of compression springs, cup springs or corrugated springs
Another advantageous measure is that a rotation lock is provided which prevents the wear ring from rotating. Thus, although the wear ring can be displaced in the axial direction, it cannot rotate about the axial direction.

According to a preferred embodiment, the wear ring has a front end face facing the impeller and a pressure surface facing away from the impeller, the pressure surface and the stationary housing part delimiting a rear space into which the fluid can penetrate from the pressure space. This configuration makes it particularly easy to guide the fluid to be conveyed out of the pressure chamber into an area where the fluid can exert the desired hydraulic force on the wear ring.

So that the fluid from the pressure chamber can reach the rear chamber as easily as possible, it is preferred that a radial gap is provided between a radially outer surface of the wear ring and the stationary housing part through which the fluid can penetrate from the pressure chamber into the rear chamber.

A sealing element is preferably provided between the wear ring and the stationary housing part, which sealing element is designed and arranged in such a way that it seals off the rear space from the suction space. This sealing element, which is designed as an O-ring, for example, makes it particularly easy to ensure that the fluid can only get back into the suction chamber via the axial sealing gap.

According to a preferred embodiment, the prestressing element acts on the pressure surface of the wear ring.

It is an advantageous embodiment that the wear ring is designed with a Z-shaped profile.

In the embodiment with a Z-shaped profile, the wear ring has a rear end face which is different from the pressure surface, the rear end face being parallel to the pressure surface and being arranged at a distance from the pressure surface with respect to the axial direction.

In the case of the embodiment with a Z-shaped profile, in particular, it can also be advantageous if the prestressing element acts on the rear end face.

Another preferred measure consists in that the sealing element is arranged between the rear end face and the pressure face with respect to the axial direction.

The impeller is particularly preferably designed as a closed impeller, that is to say, the impeller has a cover plate which interacts with the wear ring.

Optionally, a race can be provided on the impeller or on the cover disk, which is connected to the impeller in a rotationally fixed manner and which interacts with the wear ring.

According to a preferred embodiment, the centrifugal pump is designed as a centrifugal pump in which the impeller is designed as a radial impeller.

Further advantageous measures and configurations of the invention emerge from the dependent claims.

Fig. 1:

eine Schnittdarstellung einer Kreiselpumpe,

Fig. 2:

ein vergrösserter Ausschnitt mit dem Laufrad und mit dem Verschleissring gemäss einer erfindungsgemässen Ausführungsform,

Fig. 3:

wie Fig. 2, jedoch für eine erste Variante,

Fig. 4:

wie Fig. 2, jedoch für eine zweite Variante,

Fig. 5:

wie Fig. 4, jedoch für eine dritte Variante, und

Fig. 6:

wie Fig. 2, jedoch für eine vierte Variante.

The invention is explained in more detail below with the aid of exemplary embodiments and the drawing. In the schematic drawing show, partly in section:

Fig. 1:

a sectional view of a centrifugal pump,

Fig. 2:

an enlarged section with the impeller and with the wear ring according to an embodiment of the invention,

Fig. 3:

how Fig. 2 , but for a first variant,

Fig. 4:

how Fig. 2 , but for a second variant,

Fig. 5:

how Fig. 4 , but for a third variant, and

Fig. 6:

how Fig. 2 , but for a fourth variant.

In the following, reference is made, by way of example, to a centrifugal pump which is designed as a single-stage, single-flow centrifugal pump. It goes without saying that the invention is not restricted to such centrifugal pumps, but rather relates to centrifugal pumps in general. For example, the centrifugal pump according to the invention can also be designed as a multi-stage pump or as a double-flow pump.

Fig. 1 shows, in a sectional view, an exemplary embodiment of a centrifugal pump according to the invention for conveying a fluid, which is designated in its entirety by the reference symbol 1. Specifically shows Fig. 1 a centrifugal pump 1, which is designed as a centrifugal pump 1 with a covered impeller 2, the impeller 2 being designed as a radial impeller 2. Covered running wheels 2 are also referred to as closed running wheels 2.

The impeller 2 has a hub disk 21 which is non-rotatably connected to a shaft 3, several blades 22, which are arranged on the hub disk 21, and a cover disk 23, which the blades 22 on their side or edge facing away from the hub disk 21 at least partially covered. This creates several channels in the impeller 2 through which the fluid is conveyed.

The centrifugal pump 1 also has a suction chamber 4, which is flow-connected to an inlet 41 for the fluid, and a pressure chamber 5, which is connected to the an outlet 51 for the fluid is in flow communication. The impeller 2 is arranged in a housing part 6 and is surrounded by the housing part 6.

The shaft 3 is driven to rotate about its longitudinal or central axis, which defines an axial direction A, by a drive (not shown), for example an electric motor. In the operating state, the shaft 3 rotates together with the impeller 2 arranged on it in the axial direction A. This rotation sucks the fluid out of the suction chamber 4 and delivers it from the impeller 2 into the pressure chamber 5, from where the fluid goes to the outlet 51 of the pump 1 can stream.

In the following, when referring to the axial direction A, the direction of the longitudinal axis of the shaft 3 is always meant. The radial direction then means a direction perpendicular to the axial direction A.

During the operation of the centrifugal pump 1, part of the delivered fluid flows back from the pressure chamber 5 through a side chamber 7 of the centrifugal pump into the suction chamber 4 of the centrifugal pump 1. The side space 7 is that space which is delimited in the axial direction A on the one hand by the stationary housing part 6 and on the other hand by the cover plate 23 of the impeller 2 a non-rotatably arranged wear ring 8 is provided on the stationary housing part 6, which wear ring cooperates with the impeller 2, more precisely with the cover plate 23 of the impeller 2.

Fig. 2 shows in an enlarged detail the impeller 2, the stationary housing part 6 and the wear ring 8 of an embodiment of the centrifugal pump 1 according to the invention. In this embodiment, the wear ring 8 has an L-shaped profile, with one leg of the L-shaped profile - here the longer leg - The cover plate 23 surrounds radially on the outside. The other leg of the L-shaped profile forms an axial front end face 81 which faces the impeller 2 and rests on the end face of the cover disk 23.

The wear ring 8 is arranged in an annular groove 9 which is provided in the stationary housing part 6 and which surrounds the shaft 3 coaxially.

The wear ring 8 is secured against rotation or rotation about the axial direction A in the groove 9 by a rotation lock 10. The rotation lock 10 is designed, for example, as a pin which engages on the one hand in the stationary housing part 6 and on the other hand in a bore in the wear ring 8. With respect to the axial direction A, the wear ring 8 is arranged displaceably.

The longer leg of the wear ring 8 is designed in such a way that a radial sealing gap 11 is formed between this leg and the cover plate 23 of the impeller 2. This means that the radially inner surface of the leg of the wear ring 8 and the radially outer surface of the cover disk 23 of the impeller 2 delimit the radial sealing gap 11.

Such an arrangement, in which a sealing gap is provided between a suction space and a pressure space or more generally between two spaces in which different pressures prevail in the operating state, which is limited on the one hand by a rotating part and on the other hand by a stationary part of the pump, is often also known as a labyrinth.

Furthermore, in the case of the centrifugal pump 1, a prestressing element 12 is provided which exerts a force on the wear ring 8 which is directed in the axial direction A towards the impeller 2. The prestressing element 12 is preferably designed as a spring element. In particular, the prestressing element 12 can comprise one or more springs, each spring being designed, for example, as a compression spring, a plate spring or a corrugated spring.

The wear ring 8 also has an axial pressure surface 82 which faces away from the impeller 2. The pressure surface 82 is arranged in the groove 9 of the stationary housing part 6, so that the pressure surface 82 and the stationary housing part 6 - namely the bottom of the groove 9 - delimit a rear space 14. The prestressing element 12 is arranged in this rear space 14, which is supported on the one hand on the stationary housing part 6 and on the other hand on the pressure surface 82 of the wear ring 8, so that the wear ring 8 is prestressed by the prestressing element 12 against the cover plate 23 of the impeller 2.

In addition, the wear ring 8 is designed in such a way that a radial gap 15 is provided between a radially outer surface 83 of the wear ring 8 and the stationary housing part 6, through which the fluid can pass from the pressure chamber 5 into the rear chamber 14. Thus, during operation of the centrifugal pump 1, the delivered fluid can flow from the pressure chamber 5 through the radial gap 15 into the rear chamber 14 and build up a pressure there.

Furthermore, a sealing element 16 is provided between the wear ring 8 and the stationary housing part 6, which sealing element 16 is arranged in such a way that it seals off the rear space 14 from the suction space 4. The pressure drop from the pressure in the rear space 14 to the suction pressure in the suction space 4 takes place via this sealing element 16. The sealing element 16 is preferably designed as an O-ring. The sealing element 16 is arranged on the radially inner wall of the groove 9. For this purpose, this wall of the groove 9 can have an annular recess into which the sealing element 16 is inserted. It is also possible that an annular recess is provided in the wear ring 8, into which the sealing element 16 is inserted. be.

During operation of the centrifugal pump 1, the pressurized fluid can penetrate from the pressure chamber 5 through the radial gap 15 into the rear chamber 14, but cannot flow out of the rear chamber 14 into the suction chamber 4 due to the sealing element 16. In the operating state, therefore, a pressure builds up in the rear space 14 which, in addition to the prestressing element 12, exerts a hydraulic force on the wear ring 8, which tries to push it in the axial direction A in the direction of the impeller 2.

Furthermore, the pressurized fluid from the pressure chamber 5 passes through the radial sealing gap 11 to the front end face 81 of the wear ring 8. The pressure of the fluid also acts on the wear ring 8 in the operating state, which forces the wear ring 8 in the axial direction A from the impeller 2, more precisely the cover plate 23 tries to push away. Thus, in the operating state with respect to the axial direction A, three forces act on the wear ring: the hydraulic force generated by the pretensioning element 12 and the pressure in the rear chamber 14 act in the direction of the impeller 2 on the wear ring 8, and furthermore, the one under pressure Fluid generates a force which tries to push the wear ring 8 away from the impeller 2. These three forces are coordinated in such a way that, in the operating state, an axial sealing gap 17 opens between the front end face 81 of the wear ring 8 and the impeller 2, more precisely the cover plate 23, which allows a leakage flow from the pressure chamber 5 through the radial sealing gap 11 and the axial sealing gap 17 in the suction chamber 4 allows.

Since the sealing function between the pressure chamber 5 and the suction chamber 4 is primarily realized by the axial sealing gap 17, the radial sealing gap 11 between the wear ring 8 and the impeller 2 can be made wider than is possible in the prior art. The width of the radial sealing gap 11 means its extension in the radial direction. A wider radial sealing gap 11 has the advantage that physical contact between the impeller 2 and the wear ring 8 can be avoided even when the impeller 1 moves in the radial direction, as can be caused, for example, by bending of the shaft 3. In the operating state, the axial sealing gap 17 between the impeller 2 and the wear ring 8 preferably has a smaller width than the radial sealing gap 11.

The centrifugal pump 1 works as follows. When the centrifugal pump 1 is at a standstill, the front end face 81 of the wear ring rests against the cover disk 23 of the impeller 2. When the centrifugal pump is put into operation and the impeller 2 rotates, a fluid film builds up in the axial sealing gap 17, which is delimited by the floating wear ring 8, which keeps the axial sealing gap 17 open. At the same time, the now additionally acting pressure in the rear space 14 ensures that the axial sealing gap 17 does not open too far. A dynamic equilibrium is therefore established, which enables a small leakage flow from the pressure chamber 5 into the suction chamber 4.

Of course, it is also possible to provide a race 24 on the impeller 2, more precisely on the cover plate 23, which rotates together with the impeller 2 and which interacts with the wear ring 8. Such a configuration is shown in Fig. 3 first variant shown. Apart from the race 24, this first variant is configured the same as that in FIG Fig. 2 illustrated embodiment. The race 24 is in a correspondingly shaped recess arranged in the cover disk 23 of the impeller 2 in such a way that its radially outer boundary surface is opposite the radially inner boundary surface of the wear ring 8. The wear ring 8 and the race 24 are arranged coaxially and together delimit the radial sealing gap 11, which is arranged between the wear ring 8 and the race 24. With regard to its extension in the radial direction, the race 24 is designed in such a way that it extends inwards at least as far in the radial direction as the axial end face 81 of the wear ring 8. Preferably, the race 24 extends somewhat further inwards in the radial direction than Axial end face 81 of the wear ring 8. The same applies to the extension of the race 24 in the axial direction A: The race 24 extends in the axial direction A in the direction of view of the impeller 2 at least as far as the longer leg of the L-shaped profile of the wear ring 8 The race 24 preferably protrudes beyond the longer leg of the wear ring 8, as seen in the direction of the blades 22 of the impeller 2 with respect to the axial direction A.

This configuration ensures that the wear ring 8 can only come into contact with the race 24 of the impeller, but not with other components of the cover plate 23 or the impeller 2.

With regard to the material from which the wear ring 8 and optionally the race 24 are made, many possibilities are known to the person skilled in the art. Martensitic stainless steels or stainless steels are mentioned here as an example. Ceramic materials can also be used for the wear ring 8 and / or the race 24.

In some configurations of the centrifugal pump 1 ( Fig. 1 ) compensating bores 25 are provided in the impeller 2, more precisely in the hub disk 21, each of which extends completely through the hub disk 21 in the axial direction A. These compensating bores 25 reduce the axial thrust acting on the impeller 2 and thus relieve the axial bearing of the centrifugal pump 1. The compensating bores 25 relieve the pressure on the side of the hub disk 21 facing away from the cover disk 23 in the area of the shaft 3. The radially outer region of the hub disk 21 delimits a rear side space 71, which adjoins the pressure space 5 in a similar manner to the side space 7 To seal the rear side space 71 from the area that is essentially subjected to the suction pressure due to the compensating bores 25, a further labyrinth 10 is provided on the radially inner area of the hub disk 21, which creates a radial annular gap between the hub disk 21, which rotates in the operating state, and that of the hub disk 21 opposite stationary part includes. It goes without saying that this labyrinth 10 can also be designed in the same way with a wear ring floating in the axial direction A, as has been explained with reference to the wear ring 8. Optionally, the labyrinth 10 can also comprise a raceway in the same way as was explained with reference to the raceway 24.

In the following, based on the representations in the Fig. 4 , Fig. 5 and Fig. 6 even more variants for the in Fig. 2 illustrated embodiment or in Fig. 3 illustrated first variant explained. Only the differences to the one in Fig. 2 illustrated embodiment or in Fig. 3 illustrated first variant explained. Otherwise, the explanation of the exemplary embodiment in FIG Fig. 2 and the first variant in Fig. 3 in the same or analogously in the same way for those in the Fig. 4-6 shown variants. In particular, components that are the same or have the same function in terms of their function are provided with the same reference symbols as those already in connection with Fig. 1 , Fig. 2 and Fig. 3 have been explained.

At the in Fig. 4 The second variant shown, the wear ring 8 has an essentially Z-shaped profile, with an annular radially outer part 86, an annular radially inner part 87 and a middle part 85, which connects the radially outer part 86 to the radially inner part 87. The pressure surface 82, which delimits the rear space 14, is formed by the middle part 85. The wear ring 8 also has a rear end face 84 which delimits the radially inner part 87 in the axial direction A. The rear end face 84 is therefore different from the pressure surface 82, the rear end face 84 and the pressure surface 82 being parallel to one another and spaced apart from one another with respect to the axial direction A.

The prestressing element 12 is arranged such that it acts on the rear end face 84, that is, the prestressing element 12 is supported on the one hand on the stationary housing part 6 and on the other hand on the rear end face 84 of the wear ring 8.

In the Fig. 5 The third variant shown corresponds to that in Fig 4 shown second variant, except that in the third variant in the same way as in the first variant ( Fig. 3 ) the race 24 is provided on the cover plate 23 of the impeller 2.

In the Fig. 6 The fourth variant shown is very similar to the second variant ( Fig. 4 ), but in the fourth variant the prestressing element 12 is arranged in the rear space 14 so that the prestressing element 12 acts on the pressure surface 82 of the wear ring 8. The prestressing element 12 is supported on the one hand on the stationary housing part 6 and on the other hand on the pressure surface 82 of the wear ring 8. The sealing element 16 is also arranged in the fourth variant with respect to the axial direction A between the pressure surface 82 and the rear end surface 84, so that the sealing element 16 seals the rear space 14 from the suction space 4.

It goes without saying that the in Fig. 6 The fourth variant shown in the same way as for the first variant ( Fig. 3 ) or with the third variant ( Fig. 5 ) a race 24 can be provided on the cover plate 23 of the impeller 2.

As already mentioned, the invention is not limited to one-step or single-flow inventions. Thus, the centrifugal pump according to the invention can in particular be designed as a double-flow pump. It goes without saying that both labyrinths, namely that between the first suction space and the pressure space and that between the second suction space and the pressure space, can then be designed according to the invention.

The invention is suitable for every labyrinth in a centrifugal pump, the labyrinth being an arrangement in which two rooms, in which different pressures prevail in the operating state, are connected to one another via a sealing gap between a rotating part of the centrifugal pump and a relative the pump housing is arranged stationary part. The that is, each labyrinth in a centrifugal pump can be designed according to the invention.

In the case of multi-stage pumps, the labyrinth between two adjacent stages can in particular also be designed according to the invention.

Claims (15)

Centrifugal pump for conveying a fluid, with a suction chamber (4), a pressure chamber (5) and an impeller (2) which is rotatable about an axial direction (A) and with which the fluid is transported from the suction chamber (4) into the pressure chamber (5) can be conveyed, as well as with a wear ring (8) which is non-rotatably arranged on a stationary housing part (6), the wear ring (8) together with the impeller (2) delimiting a radial sealing gap (11), the wear ring (8 ) is arranged displaceably in the axial direction (A), and wherein a biasing element (12) is provided which exerts a force on the wear ring (8) which is directed in the axial direction (A) towards the impeller (2), thereby characterized in that the wear ring (8) is designed and arranged in such a way that, in the operating state, a hydraulic force also acts on the wear ring (8), which is directed in the axial direction (A) towards the impeller (2). Centrifugal pump according to claim 1, wherein the wear ring (8) and the pretensioning element (12) are designed so that, in the operating state, there is an axial sealing gap (17) between the impeller (2) and the wear ring (8) which is smaller than the width the radial sealing gap (11). Centrifugal pump according to one of the preceding claims, wherein the prestressing element (12) is designed as a spring element. Centrifugal pump according to one of the preceding claims, wherein a rotation lock (10) is provided which prevents rotation of the wear ring (8). Centrifugal pump according to one of the preceding claims, wherein the wear ring (8) has a front end face (81) which faces the impeller (2) and a pressure surface (82) which faces away from the impeller (2), the pressure surface ( 82) and the stationary housing part (6) delimit a rear space (14) into which the fluid can penetrate from the pressure space (5). Centrifugal pump according to Claim 5, in which a radial gap (15) is provided between a radially outer surface (83) of the wear ring and the stationary housing part (6), through which the fluid can penetrate from the pressure chamber (5) into the rear chamber (14) . Centrifugal pump according to one of claims 5-6, wherein a sealing element (16) is provided between the wear ring (8) and the stationary housing part (6) which is designed and arranged in such a way that it opens the rear space (14) opposite the suction space (4 ) seals. Centrifugal pump according to one of Claims 5-7, the pretensioning element (12) acting on the pressure surface (82) of the wear ring (8). Centrifugal pump according to one of Claims 5-8, in which the wear ring (8) is designed with a Z-shaped profile. Centrifugal pump according to one of Claims 5-9, in which the wear ring (8) has a rear end face (84) which is different from the pressure surface (82), the rear end face (84) being parallel to the pressure surface (82), and is arranged at a distance from the pressure surface (82) with respect to the axial direction (A). A centrifugal pump according to claim 10, wherein the biasing element (12) acts on the rear end face (84). Centrifugal pump according to one of Claims 10-11, in which the sealing element (16) is arranged between the rear end face (84) and the pressure surface (82) with respect to the axial direction (A). Centrifugal pump according to one of the preceding claims, wherein the impeller (2) has a cover disk (23) which cooperates with the wear ring (8). Centrifugal pump according to one of the preceding claims, wherein a race (24) is provided on the impeller (2) or on the cover plate (23), which is connected non-rotatably to the impeller (2) and which cooperates with the wear ring (8). Centrifugal pump according to one of the preceding claims designed as a centrifugal pump, in which the impeller (2) is designed as a radial impeller (2).

Images