EP3009680B1 - Multi-stage centrifugal pump - Google Patents

Description

The invention relates to a multi-stage centrifugal pump with the features specified in the preamble of claim 1.

The invention is based on a prior art, as for example by the Grundfos pump series CR and CRE or Grundfos pump DE 298 17 337 U1 is known. These pumps are multi-stage, vertically operated centrifugal pumps, with a foot part and with a head part, between which at least two pump stages are arranged, each having an impeller and a surrounding housing.

The suction and the pressure connection of the pump are formed in the foot part. The liquid to be delivered passes through a suction nozzle, which is also located in the foot of the pump, first in the first and further to the last pump stage, where he returned to the foot part via an annular channel formed between the outer shell and the housings and out there via a discharge nozzle out of the pump. The drive shaft connecting the impellers of the pump is led out sealingly through the head part, where a motor chair connects, which is provided for receiving an electric drive motor, and in which the pump-side shaft of the motor-side shaft is motion-coupled. In the aforementioned pump series are pumps that are operated vertically, that is, which are operated standing on the foot with vertical impeller axes, for the present invention, however, it does not matter in principle whether the pump operated vertically or in any other position becomes.

In these known pumps head and foot are typically formed of a metallic casting material, whereas the outer shell consists of a cylinder-shaped sheet metal. The outer shell and the pump stages are clamped between the head and foot and are held by four clamping bolts, which are guided by holes in the cylinder body laterally projecting corners of the head and foot.

The pumps of the aforementioned series have proven their worth and have been introduced to the market in numerous different power and housing versions.

If such pumps are operated with high differential temperatures between the medium to be pumped and the environment, the voltage conditions within the pump may change undesirably, since the clamping bolts undergo a different thermal expansion than the housing of the pump stages. By arranged with a small distance to the housing shell clamping bolts, objects or flying parts can jam or at least deposit in this area, which is undesirable. These clamping bolts also disturb the overall visual impression of the pump, which is, moreover, characterized by the simple cylinder jacket, which is usually made of stainless steel. However, a panel of the clamping bolt is expensive and expensive.

Out US 2,957,426 is a multi-stage pump to the prior art, in which the pump stages can be connected either in parallel or in series. The individual pump stages are connected there via studs, which run partly through the pressure channel and connect the pump stages with an end portion of the pump housing, which surrounds all pump stages circumferentially and at one end face with distance.

Based on the first-mentioned prior art, the present invention has the object, a generic multi-stage centrifugal pump in such a way that the aforementioned disadvantages avoided, at least reduced.

This object is achieved according to the invention by a multi-stage centrifugal pump having the features specified in claim 1. Advantageous embodiments of the invention are specified in the subclaims, the following description and in the figures. In this case, the features specified in the dependent claims and the description in each case, but also in a suitable combination, the inventive solution according to claim 1 further.

The multi-stage centrifugal pump according to the invention has a foot part and a head part, between which at least two pump stages are arranged, each having an impeller and a housing surrounding this. These housings are surrounded at a distance by an outer jacket, so that an annular channel is formed, wherein clamping bolts are provided, which connect the head part and the foot part, including the jacket and the housings. According to the invention, the clamping bolts are arranged in the annular channel between the outer shell and the housings.

The basic idea of the present invention is thus to guide the clamping bolts, which clamp the pump stages between the head part and the foot part and the outer casing between the head part and the foot part, not on the outside of the outer casing, but inside the outer casing, in which through the housing To arrange pump stages and the outer shell formed annular channel.

The arrangement according to the invention has numerous advantages. In addition to the visually appealing appearance of the pump is hidden by the outer shell arranged clamping bolt prevents accumulate here objects or even jammed.

An essential technical advantage is that it is ensured by the arrangement of the clamping bolt in the annular channel, ie where flow of liquid flows along, that clamping bolt, outer skin and pump stage always the same temperature level, namely that of the pumped liquid have. This is particularly advantageous if, on the one hand, delivery fluids are conveyed with a strongly fluctuating temperature level and, on the other hand, the temperature of the delivery fluid deviates greatly from the ambient temperature of the pump. Due to the arrangement of the clamping bolts within the conveying fluid flow is achieved that the thermal expansion of the clamping bolt on the one hand and the pump stages on the other hand always done substantially the same, so that no temperature-induced load peaks can occur here. It is to be assumed that both the pump stages, but at least the housing and the clamping bolts, typically also the outer skin, consist of similar materials, typically metal, which have a substantially equal expansion coefficient.

In addition, it has been found that the arranged inside the annular channel studs form a kind of guide for the pumped liquid, so that at least when the annular channel is flowed through the pressure side, a significantly lower turbulence of the liquid occurs at the discharge nozzle, as compared to comparable conventional pump the case is.

Furthermore, the pressure-effective surface is reduced to the head part or the foot part to the cross-sectional area of the clamping bolt by the inwardly laying the clamping bolt.

Advantageously, the annular channel is connected so that it fluidly connects the pressure-side outlet preferably the last pump stage with the pressure port of the pump, as is the case with the pump series according to the prior art mentioned above. In this arrangement, the above-mentioned advantages arise fluidically, in addition, the pressure-effective surfaces within the pump housing and thus the effective forces are reduced by the clamping bolt.

Alternatively, however, the centrifugal pump according to the invention may also be constructed such that the annular channel is provided on the suction connection side, that is, connects a suction connection of the pump with a suction inlet, preferably in a fluid-conducting manner, to the first pump stage. In this arrangement, the pressure load, in particular of the outer shell is significantly lower than in the other variant.

It is advantageous in terms of construction if at least two clamping bolts are provided, which are arranged at the same angular distance in the annular channel. This provides a minimum of uniformity in terms of force application. Preferably, however, four clamping bolts are provided in the solution according to the invention, which are arranged at a spacing of 90 ° angle relative to the impeller axis uniformly distributed in the annular channel. This arrangement is particularly advantageous both in terms of power distribution and in terms of flow guidance.

Where the clamping bolts are arranged within the annular channel, in principle, freely selectable. However, it has proved to be particularly advantageous if the clamping bolts in the radial direction in the middle of the Ring channels are arranged, since they are then flows around low. Furthermore, the risk of acoustic noise is reduced, which could arise in the event that the outer jacket touches the clamping bolt during operation. Radially centered means between the inside of the outer shell and the outer sides of the housing of the pump stages, with the same radial distance to both.

Advantageously, the clamping bolts are provided at least one end, but preferably at both ends with an external thread, so that they can be clamped either on both sides by means of nuts, which are supported on the headboard or footboard. Advantageously, however, headboard or Fußteilseitig holes can be provided which are provided with an internal thread, in which then one end of a clamping bolt can be screwed, so that attachment by means of the mother takes place only at the other end. The bores are preferably designed as through holes, so that no corrosion-promoting liquid can collect in the bore. In this case, instead of a through-bore, a blind hole may also be provided, which near the end has an outwardly leading channel, for example in the form of a transverse bore, in order to be able to discharge this corrosive fluid to the outside if necessary. Alternatively, one end of a clamping bolt can also be formed via other positive locking means, for example in the form of a hook or a radially widened cylindrical shoulder, which engages in a corresponding receptacle on the inside of the foot or head part. If, for example, a hook is provided at the end of a clamping bolt, then a web is provided on the foot or headboard side into which it can be hooked. Also, a suitable other positive connection can be provided.

In particular, when the annular channel is arranged on the pressure side, but also in suction-side arrangement, it is expedient sealant provide between clamping bolt and headboard and / or footboard. Such sealing means are to be provided when the clamping bolt or a component connected thereto passes through the head part or the foot part. According to the invention, a variety of solutions for sealing this area are provided, which are described in detail below.

A good and cost-effective sealing results when a seal between the clamping bolt and through hole is arranged and the clamping bolt is formed thread-free in the region of this seal. This can advantageously serve an O-ring seal, this is inexpensive and reliable. At the unthreaded part of the clamping bolt, the O-ring sealingly full circumference abut, so a seal is here much more effective and easier than in the area of the thread. Through hole here is also a smooth cylindrical wall, for example, paragraphs, grooves or other aids may be provided to hold the seal, in particular the O-ring at the intended location also here.

For fixing the O-ring to the constructively provided point between the clamping bolt and, for example, the through hole in the head part is a groove-like seal seat provided according to an embodiment of the invention clamping bolt side, which has a first contact shoulder, which is formed by a ring in a groove is fixed to the clamping bolt and having a second abutment shoulder, which is formed by a further ring having an internal thread and which is fixed on a threaded portion of the clamping bolt. In this case, the arrangement is expediently such that it is a threaded portion of the thread, with which the clamping bolt is fixed and clamped on the housing side, that is typically at a portion of the provided at one end external thread.

Alternatively, the fixation of the clamping bolt on the head or foot can be done by means of a cap nut, on the one hand has a through hole radially superior collar with which it can be supported beyond the through hole on the head or foot. Furthermore, the cap nut on a hollow cylindrical portion which engages in the through hole, has on its outer circumference a circumferential groove as a seal seat for the O-ring and is provided with an internal thread, in which engages the thread at the end of the tie rod.

Alternatively, a seal seat for an O-ring may be formed by an internally threaded ring fixed on a threaded portion of the clamp bolt. Through hole side is then advantageously provided a circumferential groove, in which the O-ring is held in a form-fitting manner to rest with its inside on the sealing seat formed by the ring. It does not necessarily have a groove provided, it is also conceivable that near the end of the through hole a shoulder is provided, in which the O-ring is received. Then, the seal seat, so the receptacle for the O-ring, are formed by this stepped widened part of the through hole in conjunction with a covering annular disc, wherein the annular disc, which otherwise replaces the third wall formed by the groove in the through hole.

Since according to the invention, the clamping bolts are inside, so where they are not visible to the user, a modular construction is conceivable, for example, from clamping bolt sections which provided at one end with a bore provided with an internal thread and at the other end with an external thread are, which is thus suitable for the extension of a clamping bolt. That way you can for series of pumps of different number of stages identical clamping bolts are used, which are brought by one or more suitable extensions to the required length. Thus, the same clamping bolts can be used in pumps with different head parts, with a required adjustment is made by such an extension part.

Advantageously, according to an embodiment of the invention, the ratio of the pressure acting on the clamping bolt surfaces, which are loaded with the output pressure of the pump and the input pressure of the pump, at least two, preferably between three and five. This area ratio is particularly advantageous because then the internal arrangement of the clamping bolt has virtually no noticeable effect on the output pressure of the pump, so that the output pressure of the pump corresponds approximately to that produced by a comparable pump with externally arranged clamping bolt with the same drive power.

Fig. 1

eine Draufsicht auf eine vertikale mehrstufige Kreiselpumpe der Inline Bauart,

Fig. 2

einen Schnitt längs der Schnittlinie A - A in Fig. 1,

Fig. 3

in vergrößerter Teilschnittdarstellung den Kopfteil mit anschließendem Außenmantel und einer Zugankerverbindung der Pumpe nach Fig. 1,

Fig. 4a

in schematischer perspektivischer Explosionsdarstellung einen Kopfteil mit Hutmutter zur Befestigung eines Zugankers,

Fig. 4b

in vergrößerter perspektivischer Explosionsdarstellung die Hutmutter mit Unterlegscheibe und Dichtring,

Fig. 4c

die Bauteile gemäß Fig. 4b in montierter Form,

Fig. 4d

die Hutmutter der Fig. 4b im Längsschnitt,

Fig. 5

in schematischer perspektivischer Längsschnittdarstellung eine kopfteilseitige Verbindung mit einem Zuganker,

Fig. 6

eine alternative Ausgestaltung der Verbindung in Darstellung nach Fig. 5,

Fig. 7

in vergrößerter Schnittdarstellung eine Einzelheit einer Verbindung nach Fig. 6 mit einem Kopfteil der Pumpe,

Fig. 8

eine weitere Ausführungsform einer Verbindung zwischen Zuganker und Kopfteil in Darstellung nach Fig. 5,

Fig. 9

eine weitere Ausgestaltung der Verbindung zwischen Zuganker und Kopfteil in Darstellung nach Fig. 5,

Fig. 10

eine weitere Ausgestaltung der Verbindung zwischen Zuganker und Kopfteil in Darstellung nach Fig. 5 und

Fig. 11

eine schematische perspektivische Teilschnittdarstellung einer Befestigung des Zugankers an einem höher bauenden Kopfteil.

The invention is explained in more detail with reference to exemplary embodiments illustrated in the figures. Show it:

Fig. 1

a top view of a vertical multi-stage centrifugal pump of the inline type,

Fig. 2

a section along the section line A - A in Fig. 1 .

Fig. 3

in an enlarged partial sectional view of the head part with subsequent outer sheath and a Zugankerverbindung the pump after Fig. 1 .

Fig. 4a

in a schematic perspective exploded view of a head part with cap nut for attachment of a tie rod,

Fig. 4b

in an enlarged perspective exploded view, the cap nut with washer and sealing ring,

Fig. 4c

the components according to Fig. 4b in mounted form,

Fig. 4d

the mother of the hat Fig. 4b in longitudinal section,

Fig. 5

in a schematic perspective longitudinal sectional view of a headboard-side connection with a tie rod,

Fig. 6

an alternative embodiment of the compound in accordance with Fig. 5 .

Fig. 7

in enlarged sectional view a detail of a compound according to Fig. 6 with a head part of the pump,

Fig. 8

a further embodiment of a connection between the tie rod and headboard in illustration Fig. 5 .

Fig. 9

a further embodiment of the connection between the tie rod and headboard in representation according to Fig. 5 .

Fig. 10

a further embodiment of the connection between the tie rod and headboard in representation according to Fig. 5 and

Fig. 11

a schematic perspective partial sectional view of an attachment of the tie rod to a higher-building headboard.

Based on Fig. 1 and 2 First, the basic structure of the vertical multistage centrifugal pump described here is shown. The pump has a foot part 1 on which the pump is operated. The foot part 1 has a connecting flange 2, which forms the suction nozzle of the pump and which surrounds a suction channel 3, which opens within a suction chamber formed in the foot part 1, to which the suction mouth of a rotary impeller 4 of a first pump stage connects, through the impeller 4 and a surrounding housing 5 is formed. In the case of Fig. 2 a total of five stages each consisting of a rotary impeller 4 and a housing 5 are arranged vertically one above the other, the rotary wheels 4 sitting on a common shaft 6 which is rotatably mounted within the pump housing and at the top, namely in the region of the head part 7, is led out of this.

The housing 5 are cylindrical on its outer side and arranged sealingly against each other. They limit an annular channel 8 on the inside, which is bounded on the outside by an outer jacket 9, which consists of sheet metal and forms part of the pump housing. Outer jacket 9 and the housing 5 are clamped between the foot part 1 and the head part 7, the clamping forces required for this purpose are distributed by four at the same angular distance about the longitudinal axis 10 of the pump, which also forms the axis of rotation 10 of the shaft 6, arranged tie rods in the form of clamping bolts 11th held.

Each clamping bolt 11 is provided at its two ends with an external thread which is screwed in an internally threaded bore 12 on the foot part 1 with one end. The other end is in the execution after Fig. 2 passed through a through hole 13 in the head part 7 and clamped there by means of a nut 14.

This on the basis of Fig. 2 shown construction principle can be varied both in terms of Fußteilseitigen attachment and in terms of the headboard side attachment, as already mentioned in the introduction. As far as the headboard side attachment is concerned, appropriate alternatives based on the Fig. 3 - 11 shown, which are also suitable for a foot-side attachment in principle.

The four clamping bolts 11 are arranged not only at the same angular distance of 90 ° about the longitudinal axis 10 distributed in the annular channel 8, but also radially centered in the channel 8, so that they the same distance to the outside of the housing 5 and the inside of the outer jacket. 9 exhibit. This annular channel 8 opens within the foot part 1 in a pressure channel 15, which leads to a pressure port 16, the connection flange in the Fig. 1 and 2 is visible.

The head portion 7 of the pump is extended upwards and there formed in a conventional manner to a motor chair 17, which is provided for attachment of the coming to rest electric drive motor whose shaft via a coupling, not shown here with the free end of the shaft 6 is rotatably connected.

Since the clamping bolts 11 are defined in through holes 13 of the head part, they must be sealed against the head part to ensure the tightness of the housing in this area. In the case of Fig. 3 illustrated embodiment, the headboard side threaded end 18 of the clamping bolt 11 is not enough through the through hole 13 therethrough, but only into this. Recorded is the threaded end 18 of the clamping bolt 11 in a cap nut 19, as this is based on the Fig. 4 is shown in detail. This cap nut 19 has a head 20, which has both a hexagon socket and an external hexagon for receiving a tool in the illustrated embodiment, and is sized so that it projects beyond the through hole 13 radially. This radially projecting head rests on a washer 21 in the mounted state on the correspondingly above the through hole 13 formed in the head part 7 screw head support surface 22.

From the head 20 on the cap nut 19 is cylindrical, with a circumferential groove 23 is provided at a short distance behind the head, which serves to receive an O-ring 24 which is held within this groove 23 and the cap nut 19 within the through hole 13 in the head part 7 seals. Beyond the groove 23, the cap nut is formed as a hollow cylinder and has an internal thread 25, in which the threaded end 18 of the clamping bolt 11 engages. With this cap nut 19, the clamping bolt 11, which is fixed with its other end in the foot part 1, clamped and sealed against the through hole 13 by means of the seal in the form of the O-ring 24.

Based on Fig. 5 a headboard-side attachment of the clamping bolt 11 is shown by means of a cap nut 26, which differs from the above-described cap nut 19 in that the washer 21 provided there may be omitted by appropriate design of the annular surface below the head and the head support surface. The head part 7 is shown there only in the region of the through hole, since in this illustration only the attachment and sealing is to be shown. The through hole 13 is flared toward the interior of the pump housing, this flared portion is denoted by 27 and joins the interior of the pump housing to the cylindrical part of the through hole 13, at which the lying in the groove 23 of the cap nut 26 O-ring 24 sealingly is applied. In the cylindrical portion of the cap nut 26, in which it is provided with the internal thread 25, is near the inner end of a transverse bore 28 provided, which passes through the cap nut 26 transversely and the one hand in the internally threaded blind hole of the cap nut 26 and on the other hand in the flared portion 27 of the through hole 13 opens, so as to ensure that within the cap nut 26 no dead space is formed in the can accumulate corrosive fluid. So that this transverse bore 28 is not enclosed by the threaded portion 18 of the clamping bolt 11, in this embodiment, the clamping bolt 11 is provided in the region between its shaft and the threaded end 18 with a circumferential bead 29, which is too wide screwing into the internal thread 25th the cap nut prevents.

In the case of 6 and 7 illustrated embodiment, the clamping bolt 11 passes through the through hole 13 completely and is there fixed at its threaded end 18 by means of the nut 14 with the inclusion of a washer 21 in the head part 7. The clamping bolt 11, which in the execution after Fig. 6 is made of steel round material, has at its ends threaded portions 18 which are made by rolling, so that the diameter is slightly larger than the non-threaded portion, as is made Fig. 7 is apparent. The through hole 13 is formed offset, so that in this area, a clearance between the clamping bolt 11 and the through hole 13 is formed, which allows the incorporation of the sealing ring in the form of the O-ring 24. Since the through hole 13 is formed smooth-walled even in the remote area, two rings 30 and 31 are provided for holding the O-ring 24 in its intended position, which are clamped on the clamping bolt 11 and receive the O-ring 24. These rings can be positively or materially seated on the clamping bolt 11. It may be the ring 30 is provided with an internal thread, which then opposite Fig. 7 longer running thread on section 18 from the center can be screwed, the Ring 31 may be fixed via a groove in the clamping bolt 11. The rings 30 and 31 may be formed in two parts and clip-fastened, they may be made of plastic, since they are only slightly loaded in terms of strength. In the case of Fig. 8 illustrated embodiment, the clamping bolt 11 is made of round steel material, however, the threaded end 18 is not made there by rolling, but by cutting, so that the threaded portion 18 has a smaller diameter than the rest of the clamping bolt 11. The attachment of the clamping bolt 11 is basically as based on Fig. 6 described by means of a nut 14 with inclusion of a washer 21 possible. The seal between the clamping bolt 11 and the through hole 13 also takes place by means of the O-ring 24, which is arranged in the region of the clamping bolt 11, which carries no thread. To secure the O-ring 24 in place, the in Fig. 8 formed upper part of the through hole 13 offset, so that the O-ring 24 is held on the outer circumference and on the underside by this remote part of the through hole, on the inside by clamping bolt 11 and at the top by the washer 21.

In the execution after Fig. 9 the definition of the O-ring within a separate component 32, which on the one hand has the function of a washer, on the other hand, however, is formed offset on the inside, so that the O-ring 24 in this remote part of the component 32 of Fig. 9 is marked 33, is included. The O-ring 24 has to seal in this arrangement to the clamping bolt 11 on the one hand and to the head support surface 22 of the through hole 13.

Finally shows Fig. 10 a further sealing variant between clamping bolt 11 and through hole 13. The clamping bolt 11 has here between the smooth-walled and the threaded Area 18 a widened bead-shaped portion 36, in which a circumferential groove 37 is incorporated, in which the O-ring 24 is located. The through hole 13 in the head part 7 is here in the area where the O-ring comes to rest 24, cylindrical.

Based on Fig. 11 is a vertical multi-stage centrifugal pump in the region of the head part shown, in which the head part is higher than in the case of Fig. 2 or 3 constructed embodiment builds. There is namely between the actual head part 7 and the outer shell 9, an intermediate head part 34 incorporated, which means that the clamping bolt 11 would have to be formed at the same pump number of the pump longer than in the version according to Fig. 2 or 3 , For this purpose, the clamping bolt 11 in the basis of Fig. 11 that is, they consist of the actual clamping bolt 11 in the length, as would be provided for fixing the head part 7 and a clamping bolt part 11 a, which are connected to each other via a threaded sleeve 35. In the illustrated embodiment, the components 11a and 35 are two-piece, but it can also be provided a clamping bolt portion 11a, which is provided at one end a threaded portion 18 and at the other end threaded sleeves 35 for receiving the threaded portion 18 of the adjoining clamping bolt 11. In this way, it is possible to construct a clamping bolt modular, so that with a suitable choice of module lengths with a relatively small number of clamping bolts 11 and clamping bolt extensions 11a different designs and entire series can be covered with respect to the clamping bolt without a comparable number of different length clamping bolt would be required.

LIST OF REFERENCE NUMBERS

1

footboard

2

Connection flange of the suction channel

3

suction

4

impeller

5

casing

6

wave

7

headboard

8th

annular channel

9

outer sheath

10

Longitudinal axis, axis of rotation

11

clamping bolt

11a

Clamping bolt extension

12

Bore in the foot part

13

Through hole in the headboard

14

mother

15

pressure channel

16

pressure connection

17

motor bracket

18

Threaded end of 11

19

Hutmutter

20

Head of the hat mother

21

washer

22

head rest

23

Nut of the cap nut

24

O-ring

25

Internal thread in the cap nut

26

Hat mother in Fig. 5

27

expanded area of 13

28

cross hole

29

bead

30

ring

31

ring

32

component

33

detached part

34

Between the head part

35

threaded socket

36

bead-shaped area

37

groove

Claims (16)

1. A multi-stage centrifugal pump with a foot part (1) which comprises a suction connection (2) and a delivery connection (16), and with a head part (7), wherein at least two pump stages are arranged between the foot part (1) and the head part (7), said stages each comprising an impeller (4) and a housing (5) surrounding this, with an outer casing (9) surrounding the housing (5) at a distance and forming an annular channel (8), and with clamping bolts (11) which connect the head part (7) and the foot part (1) to one another amid the inclusion of the casing (9) and the housings (5), wherein the annular channel (8) leads the delivery fluid to one of the connections (2 or 16), characterised in that the clamping bolts (11) are arranged in the annular channel (8).
2. A centrifugal pump according to claim 1, characterised in that the annular channel (8) connects a delivery-side exit of at least one pump stage to a delivery connection (16) of the pump, in a fluid-leading manner.
3. A centrifugal pump according to claim 1, characterised in that the annular channel (8) connects a suction connection (2) of the pump to a suction entry of at least one pump stage, in a fluid-leading manner.
4. A centrifugal pump according to one of the preceding claims, characterised in that at least two, preferably four clamping bolts (11) are arranged at the same angular distance in the annular channel (8).
5. A centrifugal pump according to one of the preceding claims, characterised in that the clamping bolts (11) are each arranged radially centrally between the inner side of the outer casing (9) and the outer sides of the housing (5).
6. A centrifugal pump according to one of the preceding claims, characterised in that the clamping bolts (11) are provided with an outer thread (18) at least at one end, preferably at both ends.
7. A centrifugal pump according to one of the preceding claims, characterised in that the clamping bolts (11) on the foot part side or on the head part side are fastened in bores (12), preferably through-bores (13), which are provided with an inner thread.
8. A centrifugal pump according to one of the preceding claims, characterised in that the clamping bolts (11) on the head part side or foot part side are led up to / through through-bores (13) in the head part (7) or foot part (1) and are fastened by way of nuts (14; 19; 26).
9. A centrifugal pump according to one of the preceding claims, characterised in that sealing means (24) are provided between the clamping bolt (11) and the head part (7) and/or foot part (1).
10. A centrifugal pump according to one of the preceding claims, characterised in that a seal, preferably an O-ring (24) is arranged between the clamping bolt (11) and through-bore (13) and that the clamping bolt (11) is thread-free in the region of the seal (24).
11. A centrifugal pump according to claim 10, characterised in that a groove-like seal seat for an O-ring (24) is formed on the clamping bolt (11), with a first contact shoulder which is formed by a ring (31) fixed in a groove on the clamping bolt (11) and with a second contact shoulder which is formed by a ring (30) with an inner thread, which is fixed on a threaded section (18) of the clamping bolt (11).
12. A centrifugal pump according to one of the preceding claims 7 to 11, characterised in that the nuts (19; 26) are designed as cap nuts, each comprising a collar (20) projecting radially beyond the through-bore, as well as a peripheral groove (23) in the region of the through-bore (13), as a seal seat for an O-ring (24).
13. A centrifugal pump according to one of the preceding claims 7 to 12, characterised in that a seal seat for an O-ring (24) is formed by a ring with an inner thread, which is fixed on a threaded section of the clamping bolt, in combination with a peripheral groove (35) in the associated through-bore.
14. A centrifugal pump according to one of the preceding claims, characterised in that a seal seat is formed by the part of a through-bore (13) which is widened in a stepped manner, in combination with a covered washer (21).
15. A centrifugal pump according to one of the preceding claims, characterised in that a clamping bolt (11) is constructed in a two-part or multi-part manner, from clamping bolt sections (11a) which are connected to one another by way of thread connections (35).
16. A centrifugal pump according to one of the preceding claims, characterised in that the ratio of the surface areas which are pressure-effective for the loading of the clamping bolts (11) and which are loaded by the exit pressure of the pump and the entry pressure of the pump is at least two, preferably between three and five.

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