Multi-stage Centrifugal Pump

Abstract

The invention relates to a multi-stage centrifugal pump with a foot part (2), a head part (14) and a wall part (16, 16') which connects the foot part (2) to the head part (14) and which peripherally surrounds the pump stages at the outer periphery. The centrifugal pump moreover comprises a motor stool connecting to the head part (14) and for receiving an electric motor (20) provided for the drive of the centrifugal pump. The wall part (16) projects in the axial direction beyond the head part (14) and is connected to the motor stool (FIG. 1).

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. .sctn.119 of European Patent Application 15 164 219.6 filed Apr. 20, 2015, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The invention relates to a multi-stage centrifugal pump with multi-stage centrifugal pump with a foot part, a head part, a wall part which connects the foot part to the head part and surrounds the pump stages at the outer periphery, and with a motor stool connecting to the head part and for receiving an electric motor provided for the drive of the centrifugal pump.

BACKGROUND OF THE INVENTION

[0003] Centrifugal pumps as are known for example from the pump construction series CR and CRE of the company Grundfos, form the starting point of the invention. Hereby, it is the case of multi-stage, vertically operated centrifugal pumps, with which at least two pump stages are arranged in a pump casing between a foot part and a head part of the pump casing, and are surrounded at the outer periphery by a wall part connecting the foot part to the head part. A suction branch and a delivery branch of the centrifugal pump are formed on the foot part. The fluid to be delivered by the centrifugal pump gets through the suction branch firstly into a first pump stage and from there further to the last pump stage, from where it is again led back again into the foot part and there is led out of the centrifugal pump via the delivery branch. The pump shaft of the centrifugal pump which connects the impellers of the individual pump stages, is led out through the head part in a sealing manner, where it is coupled in movement to the motor shaft of an electrical drive motor which is mounted on a motor stool typically formed from cast steel, in a manner distanced axially to the head part. With regard to the known centrifugal pumps, the motor stool is either an integral constituent of the head part or is releasably fastened on the head part, wherein rod bolts connect the motor stool to the foot part.

SUMMARY OF THE INVENTION

[0004] It is an object of the invention to create a multi-stage centrifugal pump of the previously described type which compared to known pumps has a simplified construction and a more attractive appearance.

[0005] The multistage centrifugal pump according to the invention comprises a head part and a foot part, between which at least two pump stages each with an impeller are arranged. With regard to this centrifugal pump, it is preferably the case of a vertically operated centrifugal pump, which is to say a centrifugal pump which is operated standing on the foot part and with vertically aligned impeller axes, but it is to be noted that with regard to the centrifugal pump according to the invention, it can also be the case of a centrifugal pump operated in any other position. The pump stages of the centrifugal pump are surrounded at the outer periphery by a wall part which connects the foot part to the head part and thus together with the foot part and the head part forms a pump casing. The centrifugal pump according to the invention moreover comprises a motor stool which connects to the head part and is for receiving an electric motor provided for operation of the centrifugal pump. The electric motor is mounted on the motor stool in a manner distanced to the head part in the direction of the middle axis of the centrifugal pump, wherein an end of a pump shaft connected to the impellers of the pump stages and which projects out of the head part can be coupled to a motor shaft of the electric motor in the region of the motor stool.

[0006] Compared to the known multistage centrifugal pumps of the type being discussed here, the centrifugal pump according to the invention is characterized in that the wall part of the pump casing extends beyond the head part in the axial direction, which is to say in the direction of the middle axis of the centrifugal pump or in the direction of its impeller axes, and is connected to the motor stool for receiving the electric motor. In contrast to conventional centrifugal pumps, with the centrifugal pump according to the invention, it is thus no longer the head part but instead it is the wall part which surrounds the pump stages of the centrifugal pump at the outer periphery which carries the motor stool. The fashioning freedom with regard to the design of the centrifugal pump is increased to a significant extent by way of this. This for example relates to the design of the head part which can be simplified with regard to design and manufacturing technology due to its static loading which is significantly reduced in comparison to the known centrifugal pumps. The rod bolts which have hitherto been used for the connection of the motor stool to the foot part are no longer required with the centrifugal pump according to the invention. Completely new possibilities also result with regard to the overall optical appearance of the centrifugal pump, so that the centrifugal pump can be designed in an optically more pleasing manner.

[0007] The wall part is preferably formed by a tube, in which the head part is integrated, which is simple with regard to design and manufacturing technology. With regard to the tube, it can either be the case of a tube with a welded seam or a seamless tube. In the latter case, the tube can be manufactured for example by way of deep-drawing, by which means the wall thickness of the wall part can be easily determined. The tube, independently of its design, at one end is usefully connected to the foot part in a pressure-tight manner. The head part, in a section of the tube which is adjacent to the other end of the tube, is inserted at a distance to this end and is likewise connected to the tube in a pressure-tight manner. The head part is preferably welded in the tube in this position. Hereby, the welding connection of the head part and the tube can be provided within the tube, or the weld connection can be carried out from the outer side of the tube.

[0008] The motor stool preferably comprises an annular flange which is arranged at the end of the section of the wall part which extends beyond the head part. The annular flange is advantageously an aluminum injection molded part, as is preferably also the complete motor stool. The radial dimensions of the annular flange are preferably such that the outer periphery of the annular flange is aligned to the outer periphery of the wall part, so that the annular flange extends radially only into the clearance or in the direction of the inside of the wall part, but at the outer side does not project beyond the outer periphery of the wall part.

[0009] Further advantageously, the annular flange is configured in a shouldered manner, wherein it comprises a section engaging into the inside of the wall part, and a section lying on the end of the wall part. Hereby, the outer diameter of the section engaging into the inside of the wall part usefully corresponds to the inner diameter of the wall part, so that the wall part at its free end which is away from the foot part can be supported in the radial direction on the section engaging into the inside of the wall part, which gives the section of the wall part which forms the motor stool an increased stability.

[0010] The annular flange advantageously forms the complete motor stool. In this context, a design, with which the annular flange is configured for fastening the electric motor is preferred. The electric motor is hereby mounted on the flat side of the annular flange which is away from the foot part. The fastening of the electric motor on the annular flange is usefully effected in the region of the annular flange which extends into the clearance of the wall part, where the fastening means on the annular flange side are preferably arranged for fastening the electric motor on the annular flange. Hereby, it is preferably the case of through-holes which serve for receiving screws, with which the electric motor is screwed to the annular flange.

[0011] According to a further preferred design of the centrifugal pump according to the invention, the annular flange is configured for fastening different electric motors. In this context, it can be advantageous for several through-holes for creating a screw connection to a counter-flange of a first electric motor to be formed on the annular flange at a first radial distance to a middle axis of the annular flange, in a row distributed over the periphery of the annular flange, and for further through-holes for creating a screw connection to a counter-flange of a second electric motor to be provided on the annular flange at least at one second radial distance which is different to the radial distance of these through-holes, in a manner distributed in a row over the periphery of the annular flange.

[0012] With an advantageous design which is alternative to an annular flange and which directly forms the motor stool, an attachment (addition or extension) which projects in the axial direction and at whose end, which is away from the annular flange, a fastening flange for the electric motor is arranged, can be arranged on the annular flange for forming the motor stool. This design has been found to be advantageous for example if larger electric motors are used. Moreover, the attachment which projects axially on the annular flange permits the section of the wall part which projects beyond the head part of the centrifugal pump to be designed in a comparatively short manner, which has a positive effect on the bending and torsional stiffness of this section. The fastening flange which is arranged on the end of the attachment which is away from the annular flange, in the case of smaller electric motors can be dimensioned such that it is arranged within the clearance of the wall part, or with electric motors of a larger construction type or electric motors with a larger counter-flange than the fastening flange, can also project radially beyond the outer contour of the wall part.

[0013] Preferably, at least one window is formed on the section of the wall part which extends beyond the head part. This window is to be understood as a larger recess which is provided on the wall part and via which the inside of the wall part is accessible in the region of the section forming the motor stool, for maintenance and repair purposes. The at least one window is thus integrated into the wall part. On dimensioning the window, one is to take into account the fact that the wall part has to carry the weight of an electric motor, i.e. the at least one window where possible should have no influence on the mechanical stability of the wall part and accordingly should not be too large.

[0014] Moreover, the fact that a mechanical weakening of the wall part which is caused by the at least one window can have an unfavorable effect with regard to an undesirable natural frequency excitation of the wall part should be taken into account. In order to counteract this, it is advantageous to increase the stiffness of the wall part by way of suitable measures. One step directed toward this can lie in increasing the wall thickness of the wall part in the section projecting beyond the head part, with respect to the wall thickness at the remaining wall part. As a further measure, it is also possible for a cover plate of the window to provide a supporting function. Moreover, the mechanical structure can also be stabilized by way of suitable mechanical deformations being formed in the wall part.

[0015] Particularly advantageously, two windows are formed on the section of the wall part which extends beyond the head part, and these are arranged in a manner such that a shaft seal which seals the pump shaft with respect to the head part, as well as at least one bleed valve of the centrifugal pump which is arranged on the head part, are accessible via the windows. Preferably, two bleed valves are provided on the head part with the centrifugal pump according to the invention, and these are arranged together in a plane running through the middle axis of the centrifugal pump and its head part, on two sides which are away from the middle axis. In this case, the two windows formed on the wall part are favorably arranged lying diametrically opposite one another and radially at the outer side of the bleed valves.

[0016] The head part of the centrifugal pump according to the invention is preferably designed as a deep-drawn part of preferably stainless steel. Accordingly, a comparatively thin-walled sheet of steel and preferably of stainless steel, which is brought into a preferably arched shape by way of a deep-drawing procedure, can be used for the manufacture of the head part. The head part of the centrifugal pump according to the invention thus has a significantly reduced weight compared to the head parts which until now have been formed from cast steel, and this also has a positive effect on the total weight of the centrifugal pump. Moreover, the corrosion resistance of the head part has-been found to be advantageous when using stainless steel.

[0017] The wall part is connected to the foot part usefully in a releasable manner for maintenance, cleaning or repair purposes. In this context, one preferably envisages the wall part being clamped on the foot part with a clamping ring. Hereby, preferably a section of the foot part engages into an end section of the wall part which is away from the head part and from the motor stool, wherein the clamping ring radially surrounding the wall part at the outside presses the wall part against the foot part. Hereby, a seal is usefully arranged between the wall part and the foot part, for the pressure-tight sealing of the wall part with respect to the foot part.

[0018] The clamping ring which is used for connecting the wall part to the foot part is preferably designed in a manner divided into several ring segments in the peripheral or circumferential direction. Accordingly, the clamping ring comprises several ring segments which, arranged next to one another in the peripheral direction and connected to one another, result in the clamping ring. This divided or split design of the clamping ring is advantageous inasmuch as it permits a simple arrangement of the clamping ring at the outside of the wall part and ensures a uniform force transmission from the clamping ring onto the wall part.

[0019] The individual ring segments of the clamping ring are preferably designed in a manner such that a recess which is directly adjacent the respective end of the ring segment is formed in each case at both peripheral ends of the individual ring segments, wherein a first recess is formed on a first flat side of the ring segment which is aligned perpendicularly to the middle axis of the clamping ring, and the other recess is formed on a second flat side which is away from the first flat side and is aligned parallel to the first flat side. Accordingly, one recess is directed in the direction of the head part, whilst the other recess faces the foot part, in the condition of the ring segments assembled on the wall part. The ring segments of the clamping ring which are connected to one another are arranged overlapping one another in the axial and peripheral direction of the clamping ring, in the region of the recesses.

[0020] The individual ring segments of the clamping ring are not only connected to one another, but preferably in each case also to the foot part. Thus, according to a further advantageous design of the centrifugal pump according to the invention, one envisages the ring segments of the clamping ring being connected to the foot part amid the creation of a connection to one another. Through-holes which are aligned in the axial direction of the clamping ring are formed on the two recesses of the ring segments for this, and these through-holes are arranged in a manner such that in the assembled condition of the clamping ring and with the recesses of the ring segments which then overlap one another, the through-holes formed on the recesses overlapping one another are aligned to one another. A cap screw is led through the thus formed common through-hole in each case and is screwed in a threaded pocket hole formed on the foot part.

[0021] The invention is hereinafter explained in more detail by way of embodiment examples which are represented in the drawing--in each case, in a schematically simplified manner and in different scales. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In the drawings:

[0023] FIG. 1 is a lateral view of a vertical multi-stage centrifugal pump;

[0024] FIG. 2 is a sectional view along the section line II-II in FIG. 1;

[0025] FIG. 3 is a plan view of the centrifugal pump according to FIGS. 1 and 2;

[0026] FIG. 4 is a perspective representation, an end section of the centrifugal pump according to FIG. 1-3, in the region of a head part of the centrifugal pump;

[0027] FIG. 5 is a view in the direction V-V in FIG. 4;

[0028] FIG. 6 is a perspective representation, an end section of the centrifugal pump according to FIGS. 1-3, in the region of a foot part of the centrifugal pump;

[0029] FIG. 7 is a lateral view of an end section according to FIG. 6;

[0030] FIG. 8 is a plan view of a ring segment of a clamping ring;

[0031] FIG. 9 is a perspective representation of a ring segment according to FIG. 8;

[0032] FIG. 10 is a detail A of FIG. 2;

[0033] FIG. 11 is a perspective representation of a pump assembly with a centrifugal pump according to the FIGS. 1-3 and with an electric motor for the drive of a centrifugal pump;

[0034] FIG. 12 is a longitudinal sectional view of an end section of centrifugal pump according to a second design in the region of a head part of the centrifugal pump;

[0035] FIG. 13 is a detail of FIG. 12 in a perspective representation;

[0036] FIG. 14 is a longitudinal sectional view of an end section of a centrifugal pump according to a third design, in the region of a head part of the centrifugal pump; and

[0037] FIG. 15 is a lateral view of an end section of a pump assembly with a centrifugal pump according to a fourth design.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Referring to the drawings, the multistage centrifugal pump which is represented in the FIGS. 1-11 comprises a foot part 2. This foot part 2 is equipped with two connection flanges 4 and 6. Of these connection flanges 4 and 6, the connection flange 4 forms a suction branch and the connection flange 6 a delivery branch of the centrifugal pump.

[0039] The connection flange 4 forming the suction branch surrounds a suction channel 8 which runs out within a suction space which is formed in the foot part 2 and on which the suction port of an impeller 10 of a first pump stage of the centrifugal pump connects, said pump stage being formed by the impeller 10 and a casing 12 surrounding this. As a whole, the centrifugal pump comprises five pump stages which consist of an impeller 10 and a casing 12. The pump stages are arranged vertically above one another, wherein the impellers 10 of these pump stages are seated on a common pump shaft led out of the pump casing of the centrifugal pump at its upper side, on a head part 14 distanced to the foot part 2 in the vertical direction. This pump shaft is of no relevance concerning the invention and has therefore been omitted in the drawing for the purpose of an improved overview.

[0040] The pump casing of the centrifugal pump, apart from the foot part 2 and the head part 14 is also formed by a wall part 16 which connects the foot part 2 to the head part 14 and surrounds the pump stages of the centrifugal pump at a radial distance. A stainless steel tube serves as a wall part 16 in the present embodiment example. As can be deduced particularly well from FIGS. 1, 4 and 11, the wall part 16 comprises a section 18, which extends in the axial direction of the centrifugal pump beyond the head part 14. The head part 14 is thus integrated in the wall part 16 at a distance to the end of the wall part 16 which is away from the foot part 2, wherein the head part 14 is connected to the wall part 16 in a pressure-tight manner by way of welding. The welding is carried out at the inner side of the wall part 16 by way of laser welding.

[0041] An annular flange 24 is arranged at the end of the section 18 of the wall part 16, said end being away from the foot part 2. The annular flange 24 forms a motor stool for an electric motor 20, wherein a motor shaft of the electric motor 20 is connected via a coupling 22 to the pump shaft which is not represented, in the region of the section 18 of the wall part 16.

[0042] It can be recognized from FIG. 2 that the annular flange 24 is configured in a shouldered manner and comprises a section 26 which engages into the inside of the wall part, and a section 28 which lies on the end of the wall part 16. Hereby, the outer cross section of the section 26 of the annular flange 24 corresponds to the inner cross section of the wall part 16 and the outer cross section of the section 28 of the annular flange 24 to the outer cross section of the wall part 16.

[0043] The connection of the electric motor 20 to the annular flange 24 is effected via a screw connection. For this, four through-holes 30 which extend in the axial direction of the annular flange 24 are formed on the annular flange 24 at the same radial distance to the center of the annular flange 24 as is particularly evident from FIG. 4, and these through-holes serve for receiving screws, by way of which a counter-flange of the electric motor 20 is fastened on the annular flange 24. Moreover, four further axially directed through-holes 32 which are arranged at the same radial distance to the center of the annular flange 24 are formed on the annular flange 24, wherein the radial distance of the through-holes 32 to the center of the annular flange 24 is smaller than the radial distance of the through-holes 30 to the center of the annular flange 24. The through-holes 32 serve for the fastening of an electric motor whose counter-flange differs from the counter-flange of the electric motor 20.

[0044] Two windows 34 lying diametrically opposite one another are formed on the section 18 of the wall part 16. The inside of the section 18 of the wall part 16 is accessible from outside the wall part 16 via the windows 34. Thus, amongst other things, assembly, maintenance or repair work on the coupling 22 connecting the pump shaft to the motor shaft as well as on a shaft seal 36 sealing the pump shaft with respect to the head part 14, and on two bleed valves 38 of the centrifugal pump which are arranged on the head part 14 can thus be carried out via the windows 34.

[0045] Two recesses, into which in each case a tongue 40 directed into the inside of the wall part 16 and serving for the releasable fastening of the annular flange 24 on the wall part 16 are formed in each case on an upper side of the window 34 which faces the annular flange 24. A through-hole 42 is formed in each case in a region of the tongue 40 which covers the section 26 of the annular flange 24, and this through-hole serves for receiving a screw which is screwed into a threaded pocket hole which is formed on the section 26 of the annular flange 24 and corresponds to the through-hole 42 with regard to its position, by which means the annular flange 24 is fastened on the wall part 16.

[0046] The wall part 16 is radially widened at its end which is away from the head part 14, by way of the wall part 16 there merging via a shoulder into a radially widened section 44. A section 46 of the foot part 2 which forms a part of the flow connection between the connection flanges 4 and 6 and the pump casing (see FIGS. 2 and 10) engages into this widened section 44 of the wall part 16. An annular grove 48 which serves for receiving a sealing ring 50 sealing the wall part 16 with respect to the foot part 2 is formed on the outer periphery of the section 46 of the foot part 2 (FIG. 2).

[0047] The pressure-tight connection of the wall part 16 to the foot part 2 is effected via a clamping ring 52. This clamping ring 52 is configured in a peripherally divided manner and comprises six identical ring segments 54, whose construction is evident from the FIGS. 8 and 9. It can be deduced from FIGS. 8 and 9 that a recess 56 and 58 which is directly adjacent the respective end of the ring segments 54 is formed on the two peripheral ends in each case. Hereby, the recess 56 is formed on a flat side 60, and the recess 58 on a flat side which is away from the flat side 60, of the ring segment 54. The ring segments 54 moreover, adjacently the flat side 60, each comprise a shoulder 64 which is directed in the direction of the center of the clamping ring 52 in the assembled condition of the ring segments 54. The ring segments 54 in the assembled condition overlap one another in the region of the recesses 56 and 58 which are formed on the ring segments 54, wherein a section of a first ring segment 54 which is reduced in the axial direction of the clamping ring 52, in the region of the recess 56, contacts a section of a second ring segment 54 which is likewise reduced in the axial direction of the clamping ring 52, in the region of the recess 58.

[0048] The connection of the ring sections 54 to one another is effected via a screw connection. Through-holes 68 are formed on the ring segments 54 in the region of the recesses 56 and 58, for receiving the screws 66 which are necessary for this, and these through-holes are aligned to one another when adjacent ring segments 54 overlap one another in the region of the recesses 56 and 58. The screws 66 not only serve for the connection of the ring segments 54 to one another, but also for clamping the clamping ring 52 on the outer side of the wall part 16, which is evident from FIG. 10. For clamping the clamping ring 52 on the outer side of the wall part 16, the individual ring segments 54 of the clamping ring 52 are arranged on the outer side of the wall part 16 such that with their shoulder 64 they engage around a shoulder 70 which on the wall part 16 forms a transition to the widened section 44 of this wall part, and come to bear on six projections 72 projecting radially on the foot part 2, wherein the through-holes 68 which are formed on the sections of the ring segments 54 which overlap one another are aligned with threaded pocket holes 74 formed on the projections 72. The screws 66 which are led through the through-holes 68 of the ring segments 54 are screwed into the threaded pocket holes 74, for clamping the clamping ring 52 on the outer side of the wall part 16.

[0049] The centrifugal pump which is represented in the FIGS. 12 and 13 differs from the centrifugal pump represented in FIGS. 1-11 merely with regard to the design of the wall part connecting the foot part 2 to the head part 14, as well as with regard to the design of the motor stool and its connection to the wall part. With the centrifugal pump represented in FIGS. 12 and 13, a wall part 16' extends beyond the head part to a lesser extent than the wall part 16 of the centrifugal pump represented in FIGS. 1-12, so that a section 18' of the wall part 16' is shorter than the section 18 of the wall part 16 of the centrifugal pump represented in FIGS. 1-12.

[0050] An annular flange 24' which engages with a section 26' into the inside of the wall part 16' and lies with a section 28' on the wall part 16' is arranged at the end of the wall part 16' which is at the top in FIGS. 12 and 13. The annular flange 24' at its flat side which is away from the head part 14 comprises an attachment 76. The attachment 76 is formed by two webs 78 which are arranged lying opposite one another on the annular flange 24 and taper obliquely to a middle axis X of the centrifugal pump. Of the two webs 78, only one web 78 is visible in each case in the FIGS. 12 and 13.

[0051] A fastening flange 80 is arranged on the attachment 76 at the end of this which is away from the annular flange 24'. The fastening flange 80 serves for fastening an electric motor 20 which is screwed with a counter-flange on the fastening flange 80.

[0052] Together, the annular flange 24', the attachment 76 and the fastening flange 80 thus form a motor stool for the electric motor 20, wherein the coupling of the pump shaft to the drive shaft of the motor 20, said coupling not being represented in FIGS. 12 and 13 and being arranged between the fastening flange 80 and the annular flange 24', is easily accessible on this motor stool via intermediate spaces between the webs 78 forming the attachment 76, as is also the case with the components on the head part 14 and which are likewise to some extent not represented.

[0053] The fastening of the motor stool of the centrifugal pump which is represented in FIGS. 12 and 13 is particularly evident from FIG. 13. Two rectangular openings 82 are formed on the wall part 16', in a manner lying diametrically opposite one another and just below the region, in which the section 26' of the annular element 24' engages into the inside of the wall part 16', in order to fasten the motor stool. The openings 82 in each case serve for receiving a fastening element 84. The fastening elements 84 each comprise a base body 86 with a rectangular cross-sectional contour which corresponds to the openings 82 and which engages from the outer side of the wall part 16' through the opening 82 into the inside of the wall part 16', and an end section 88 which projects beyond the cross-sectional contour of the base body 86 and comes to bear on the outer side of the wall part 16'. In each case, a threaded hole 90 which in the installed condition of the fastening element 84 on the wall part 16' is aligned parallel to the middle axis X of the centrifugal pump extends through the base body 86 of the fastening elements 84. Two through-holes 92 are formed on the annular flange 24', in a manner corresponding to the position of the threaded hole 90 in the installed condition of the fastening elements 84 on the wall part 16'. These through-holes 92 serve in each case for receiving a head screw 94 which is screwed into the threaded hole 90 of the fastening element 84, by which means the motor stool is fastened on the wall part 16'.

[0054] The centrifugal pump represented in FIG. 14 corresponds essentially to the centrifugal pump represented in FIGS. 12 and 13 and differs from this only with regard to the fastening of the motor stool on the wall part 16'. This fastening is effected by way of a weld connection of the annular flange 24' to the wall part 16 in the region, in which the section 26' engages into the inside of the wall part 6'.

[0055] The centrifugal pump which is represented in FIG. 15 is based essentially on the centrifugal pump represented in FIGS. 1-11 and differs from the latter mentioned centrifugal pump merely with regard to the design of the motor stool. This motor stool comprises an annular flange 24'' which differs from the annular flange 24 of the centrifugal pump represented in FIGS. 1-11 only with regard to the axial dimensions of the section 28''. A fastening flange 80' is arranged on the flat side of the section 28' which is away from the wall part 16. The fastening flange 80' is configured for fastening electric motors 20 to a larger counter-flange 96 and for this purpose extends radially beyond the outer periphery of the wall part 16. The fastening flange 80' in this region extending beyond the outer periphery of the wall part 16 is supported on several reinforcement ribs 98 which project radially on the outer periphery of the section 28'' of the annular flange 24''.

[0056] While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

APPENDIX

List of Reference Symbols

[0057] 2 foot part [0058] 4 connection flange [0059] 6 connection flange [0060] 8 suction channel [0061] 10 impeller [0062] 12 casing [0063] 14 head part [0064] 16, 16' wall part [0065] 18, 18' section [0066] 20 electric motor [0067] 22 coupling [0068] 24, 24', 24'' annular flange [0069] 26, 26' section [0070] 28, 28', 28'' section [0071] 30 through-hole [0072] 32 through-hole [0073] 34 window [0074] 36 shaft seal [0075] 38 bleed valve [0076] 40 tongue [0077] 42 through-hole [0078] 44 section [0079] 46 section [0080] 48 annular groove [0081] 50 sealing ring [0082] 52 clamping ring [0083] 54 ring segment [0084] 56 recess [0085] 58 recess [0086] 60 flat side [0087] 62 flat side [0088] 64 shoulder [0089] 66 screw [0090] 68 through-hole [0091] 70 shoulder [0092] 72 projection [0093] 74 threaded pocket-hole [0094] 76 attachment [0095] 78 web [0096] 80, 80' fastening flange [0097] 82 opening [0098] 84 fastening element [0099] 86 base body [0100] 88 end section [0101] 90 threaded hole [0102] 94 cap screw [0103] 96 counter flange [0104] 98 stiffening rib [0105] A detail [0106] X middle axis

Claims

1. A multi-stage centrifugal pump comprising: a foot part; a head part; pump stages; an electric motor to drive the pump stages; a wall part which connects the foot part to the head part and surrounds the pump stages at an outer periphery; a motor stool connected to the head part and receiving the electric motor, wherein the wall part projects in an axial direction beyond the head part and is connected to the motor stool.

2. A centrifugal pump according to claim 1, wherein the wall part is formed by a tube, in which the head part is integrated by a weld connection.

3. A centrifugal pump according to claim 1, wherein the motor stool comprises an annular flange arranged at an end of a section of the wall part which extends beyond the head part.

4. A centrifugal pump according to claim 3, wherein the annular flange is configured in a shouldered manner and comprises a section which engages into an inside of the wall part and a section which lies on an end of the wall part.

5. A centrifugal pump according to claim 3, wherein the annular flange is configured for fastening the electric motor.

6. A centrifugal pump according to claim 5, wherein the annular flange is configured for fastening different electric motors.

7. A centrifugal pump according to claim 3, wherein: an attachment is formed on the annular flange and projects in the axial direction; the attachment has an end, which is away from the annular flange, on which a fastening flange for the electric motor is arranged.

8. A centrifugal pump according to claim 3, wherein at least one window is formed on the section of the wall part which extends beyond the head part.

9. A centrifugal pump according to claim 3, wherein two windows are formed on the section of the wall part which extends beyond the head part, said windows being arranged in a manner such that a shaft seal sealing the pump shaft with respect to the head part, as well as at least one bleed valve of the centrifugal pump, which is arranged on the head part, are accessible via the windows.

10. A centrifugal pump according to claim 1, wherein the head part is configured as a deep-drawn part of preferably stainless steel.

11. A centrifugal pump according to claim 1, further comprising a clamping ring, wherein the wall part is clamped on the foot part by the clamping ring.

12. A centrifugal pump according to claim 11, wherein the clamping ring, in a peripheral direction, is configured divided into several ring segments.

13. A centrifugal pump according to claim 12, wherein the clamping ring comprises ring segments that are connected to the foot part amid a creation of a connection to one another.