The invention relates to a multi-stage centrifugal pump with the features specified in the preamble of claim 1.
Centrifugal pumps of this type are in many variants of the prior art. Reference is made, by way of example, to Grundfos Pumps (Applicant) of the CR Series or Lowara X Pumps (of the Xylem Group) of the SV Series. Such multi-stage centrifugal pumps have a common shaft, which carries impellers of pump stages and which is rotatably disposed within a pump housing. In this case, the drive takes place in particular in pumps of larger design usually via an external motor, which is drivingly connected via a coupling with the pump shaft. Such pumps are often provided for operation with a vertical shaft, the pump housing therefore has a foot part, which forms the footprint of the centrifugal pump and a head part, which is designed as a motor chair or has one on which the drive motor is mounted. Between head and foot, which are often at least partially made of cast metal, the pump stages are incorporated, which are closed by a circumferential sheath and connected together by tie rods, including the pump stages. If the centrifugal pump is designed as an in-line pump, it has on the foot part side a suction and a pressure connection, which are offset by 180 ° to each other. The liquid entering via the suction connection in the pump, passing through the individual pump stages, is led upwards in each case with an increase in pressure, where it returns in the head part via an annular channel formed between the nozzles and the outer jacket to the foot part and there is led to the pressure connection. The shaft carrying the wheels is guided out sealingly at the motor end. It is state of the art in this area to use a sealing cartridge to replace the seal in case of wear quickly and easily. At the other, so located within the pump housing end of the shaft bearing can be provided. It also belongs to the state of the art to act upon this end of the shaft with the pressure of the pressure side in order to compensate hydraulically for the axial forces acting on the shaft. Then it is regularly necessary to provide a seal in this area.
Regardless of whether a seal, a bearing or both are provided here, it is always expensive to change them in the event of a defect or wear. For this purpose, the pump is to be dismantled in large parts. The tie rods and other components have to be removed in order to be able to replace the bearing and / or the seal at the housing-side end, ie in the area of the foot part. This work is time consuming and therefore expensive.
Against this background, the invention has the object, a generic multi-stage centrifugal pump in such a way that the aforementioned repair and maintenance are simplified, without the production cost of the pump thereby be substantially increased.
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 the drawing. In this case, the features specified in the dependent claims and the description in each case but also in a suitable combination further form the solution according to the invention according to claim 1.
The multi-stage centrifugal pump according to the invention has a pump housing in which a shaft is rotatably mounted, which carries centrifugal wheels of the pump stages. The pump housing has a reversibly closable maintenance opening, via which a bearing arranged inside the pump housing at the shaft end and / or a seal arranged inside the pump housing at the shaft end is accessible and replaceable.
The basic idea of the solution according to the invention is to provide a maintenance opening within the pump housing, typically at the bottom, which is only opened for maintenance purposes and otherwise sealed tightly, but which makes it possible to selectively wear components on the shaft end located inside the pump housing, be it a Bearing and / or a seal, to check, to maintain or replace if necessary, without having to disassemble the entire pump, in particular to solve the tie rods. Such an additional maintenance opening can usually be provided with little manufacturing effort, it is only an occlusive opening this component optionally provide inclusion of a seal, which is structurally usually easily possible. The fact that the maintenance opening is reversibly closed, this can optionally be opened several times and closed again.
The maintenance opening can, in particular if it is arranged on the foot part, which is usually designed as a cast component, be formed by a simple recess in the ground. Can be closed such an opening in a simple form by a screw-mounted lid. This can be either the opening act across lid, which is fastened with fastening screws engaging the side of the opening in the corresponding housing member or a cover which has at its outer periphery a thread which engages in an internal thread of the opening. The first variant is advantageous in terms of cost and easy to seal, in which a flat gasket is incorporated between the components or when providing a cover or housing-side groove an O-ring.
In order to exchange the bearing or sealing parts, which are fixed to the shaft end, for example by means of a screw connection, it is advantageous to provide means for blocking the rotational movement of the shaft. This need not necessarily be at this shaft end, but may also be provided, for example, at the head of the pump outside the housing, for example where the shaft has a square or hexagonal profile on which an open-end wrench can be placed. Alternatively, a suitable profile for engagement of a tool can also be provided at the free shaft end within the housing or a transverse bore in the shaft end, through which a blocking pin can be set.
If the centrifugal pump is designed to operate with a shaft arranged vertically, then it is advantageous to arrange the maintenance opening in the bottom of the pump housing. However, there are also known multistage centrifugal pumps, which are designed for operation with horizontally arranged shaft. Even with these pumps, it is advantageous to attach the maintenance opening in a housing wall in alignment with the shaft, on the side facing away from the motor of the housing, ie on a motor-remote wall of the housing.
Basically, it is expedient to place the maintenance opening so that the bearing and / or the seal at the shaft end easily accessible is / are. This can also be done by a lateral opening in the housing. It is particularly useful, however, if the opening is arranged in alignment with the shaft. It is not to understand the strictly geometrical escape under flight to the shaft, but it may be the opening also slightly offset to the flight of the shaft so the shaft axis, depending on how this is structurally the cheapest.
It is particularly advantageous if the lid not only has a pure closure function, but also fulfills further functions at the same time. Thus, according to an embodiment of the invention, the lid may have an opening passing through the part which receives or forms a non-rotatable part of the seal or the bearing. Such an arrangement has the advantage that not only access to the seal or the bearing at the free shaft end is provided with removal of the lid, but at the same time a part of the seal or the bearing is formed or held. Then, after disassembly of the lid, a part of the bearing or the seal is disassembled, which facilitates the condition check on the one hand and, on the other hand, facilitates the replacement even in the event of a repair. Then it is advantageous if the other part of the seal or the bearing is releasably secured to the arranged inside the pump housing shaft end. In this case, the co-rotating part, for example, be fastened by means of a screw engaging in a threaded bore of the shaft end or placed on the shaft end and fastened there by means of a nut.
To release such a screw connection, it is regularly necessary to block the shaft to prevent co-rotation. This can be provided in a simple form by a mounted on the extended shaft end profile or a transverse bore through the shaft. In principle, it is also conceivable that blocking means are to be provided on the motor shaft.
If the lid according to an embodiment of the invention is designed so that it engages over the maintenance opening and is screw-mounted in the overarching part on the pump housing, then this can be easily, e.g. be sealed by a flat gasket. The assembly and disassembly is easy, since the screws are usually easily accessible with suitable orientation of the pump. In particular, when the cover performs other functions such as wearing the fixed part of the bearing or the seal, then such an arrangement is advantageous because it can be provided sufficiently large contact surfaces to ensure the required precise alignment of the components to each other. Furthermore, the machining of the housing around the lid opening and for the formation of threaded bores or stud bolts provided therein can be produced in the same clamping on the machine table. The lid itself may be formed of sheet metal or cast metal.
If the centrifugal pump is designed as an in-line pump whose suction and pressure connections are arranged on the foot part side, it is particularly advantageous to arrange the maintenance opening within the foot part, preferably on the bottom side. In this case, the centrifugal pump advantageously has an axial seal on the shaft end, whose fixed part has a ring which is arranged axially movable within the pump housing or a component incorporated therein. Such a construction, in which on the one hand a hydraulic pressurization of the free shaft end for compensating the forces acting on the pump shaft axial forces and on the other hand a low-friction but effective and less susceptible to wear axial seal is formed, is particularly advantageous. This axial seal can be quickly and easily controlled, maintained and replaced through the service opening. It is preferred that the axially movable within the pump housing mounted fixed part of the axial seal stored in the lid, with the maintenance opening is closed.
The invention is explained in more detail with reference to embodiments shown in the drawing. Show it:
- Fig. 1
- in a highly simplified schematic representation of a longitudinal section through a multi-stage centrifugal pump of the inline design with drive motor,
- Fig. 2
- an enlarged and 90 ° opposite Fig. 1 rotated longitudinal section of the pump,
- Fig. 3
- the detail III in Fig. 1 in an enlarged view,
- Fig. 4
- the detail IV in Fig. 2 in an enlarged view,
- Fig. 5
- the rotating part of the axial seal in longitudinal section,
- Fig. 6
- the components of the rotating part of the axial seal in exploded view,
- Fig. 7
- the non-rotating part of the axial seal with retaining ring for incorporation into the pump housing in longitudinal section,
- Fig. 8
- the components of the non-rotating part of the axial seal in exploded view,
- Fig. 9
- the axial seal and the foot of the centrifugal pump in exploded view and
- Fig. 10
- in an enlarged view a view of the centrifugal pump from below.
When using the Figures 1-10 The centrifugal pump shown is a multi-stage, vertically operated centrifugal pump 1 of the inline design. The pump housing has a foot part 2, a head part 3 and a cylindrical shell 4 arranged therebetween, which surrounds the pump stages and is clamped between head part 3 and foot part 2. The foot part 2 has a suction connection 5 and in alignment with a pressure connection 6. The head part 3 is designed as a motor chair and surrounds a clutch 7, which has a shaft 51 of a in Fig. 1 schematically shown mounted on the head part 3 electric motor 50 rotatably connected to a shaft 8 of the pump 1 connects. The shaft 8 of the pump 1 carries the impellers 9 of the pump stages and is rotatably disposed within the pump housing. In the head part 3, a radial seal 10 is provided and in the foot part 2 an axial seal 11. The structure of this axial seal 11 is made of the FIGS. 3 to 8 in detail and described in detail below. In operation, when the shaft 8 rotates, 5 liquid is introduced into the pump housing via the suction port, which enters the suction port 12 of the first pump stage and is supported by each formed from a gyro 9 and a surrounding nozzle 13 pump stages until they Head part 3 emerges from the last pump stage and is returned via an annular channel 14 to the pressure port 6, through which the liquid leaves the pump again.
The housing-side shaft end 15 of the pump is located in the region of the suction port 12 below the first pump stage. It has a threaded blind hole 16 in which a cap screw 17 is seated, with a retaining ring 18 is tightly and firmly attached to the shaft end 15. The retaining ring 18 has a suction mouth 12 directed towards, and except for a central recess for performing the Screw 17 closed wall 19, so it is cup-shaped and tight and firmly connected to the shaft end 15.
The retaining ring 18 is formed as a rotating part, stepped to the side facing away from the shaft end 15 side and formed with a downwardly open circumferential groove which is provided for receiving a sliding ring 20. The sliding ring 20 is made of silicon carbide and is secured against rotation by means of pins 21 in the retaining ring 18 and the rest by means of a sleeve 22 which radially overlaps the sliding ring 20 on the inside and is fastened by means of the screw 7 together with the retaining ring 18 at the shaft end 15. The sliding ring 20 has a downwardly directed, thus facing away from the shaft end 15 axial surface 23, which forms the rotating axial surface of the axial seal 11. This axial surface 23 is not completely flat, but has three uniformly distributed over the circumference macroscopic elevations, which on the one hand a defined contact with the counter surface 24, that is, the axial surface 24 of the non-rotating Axialdichtungsteils 25, and on the other the rapid construction of the Lubricating film serves. The axial surface 24 is flat and part of the non-rotating part, here the ring 25, which is arranged axially movable within a retaining ring 26 which is incorporated in a corresponding receptacle in the bottom of the foot part 2 of the pump housing.
The retaining ring 26 has a circumferential groove 27 on its inner side, in which an O-ring 28 is incorporated, which radially seals the ring 25 relative to the retaining ring 26 and thus with respect to the pump housing. The retaining ring 26 is further sealed with an outer circumferential seal 58 against the receptacle in the pump housing, as can be seen from the sectional views 4 and 7.
At the rear side facing away from the axial sealing surface 24, the non-rotating ring 25 is covered by a sheet-metal section 29, which covers this rear side of the sealing ring 25 almost completely. The sheet metal section 29 has bent tongues 30 with which the sheet metal section is incorporated in a form-fitting manner within corresponding recesses 52 on the rear side of the ring 25. These tongues 30 protrude radially over the ring 25 and engage in these recesses 52 in the ring 25 and form part of an anti-rotation of the non-rotating ring 25. In addition, the plate portion 29 offset by 90 ° to the tongues 30 two diametrically opposite tongues 31, which are bent from the plane of the base material by 90 ° upwards and the sheet metal portion 29 in the axial direction spaced connect with the ring 25, in which the ends 53 engage detent in a shoulder 54 on the inside of the ring 25.
The sheet metal portion 29 forms a closed surface of the underside of the ring 25 and has a central rectangular recess 32, in which engages a rectangular cross-section pin 55, which forms part of the retaining ring 26, on which the ring 25, which has the Axialdichtfläche 24, rotatably but axially movable is performed. The pin 55 and the recess 32 are dimensioned in cross-section so that this recess 32 with the pin 55 therein together with any gap tolerances of the sheet portion 29 form a passage gap with a cross-sectional area which is significantly smaller than the cross-sectional area of channels 33 in the foot 2 of the pump housing or in the retaining ring 26 are provided and which ensure that the interior 34 of the ring 25 with the sheet metal portion 29 and the retaining ring 26 with the pressure of the pressure side of the pump, ie with the pressure at the pressure port 6, is acted upon. These channels 33 ensure that at start-up of the pump after the pressure has been built up, first the sheet-metal section 29 with the ring 25 in contact therewith, in the direction of the free end of the shaft, thus towards the motor kraftbeaufschlagt and pushed, since the smaller cross section of the gap between the recess 32 and the pin 55 first liquid must flow into the space enclosed by the ring 25 space before a corresponding back pressure is built up. As a result, the ring 25 in Fig. 1 axially upwards, that is axially moved within the retaining ring 26 until the axial surface 24 abuts against the counter surface 23, whereby then a separation between the suction-side space in the region of the shaft end 15 and the installation space 34 of the fixed part of the axial seal 11 is formed. Once the space enclosed by the ring 25 and the sheet metal portion 29 has filled over the gap of the recess 32, the pressure of the pressure side is also within the ring 25 and thus on the front side of the shaft 8, whereby the desired during operation certain force compensation in terms of hydraulically induced axial force of the shaft 8 takes place.
As in particular from Fig. 9 can be removed, the retaining ring 26 is part of a circular disc 56, which is provided for incorporation in a bottom-side maintenance opening 60 of the pump housing, here the foot part 2. The disc 56 is this bottom-side opening 60 closes in a shoulder 64 on the underside of the foot part 2 and is connected via four screws 57 which are guided by recesses 61 in the edge 62 of the disc 56, releasably connected to the foot part 2. For sealing against the foot part 2, an O-ring 58 is arranged in the upper region of the ring 26, ie at a small distance from the disk 25, which is incorporated in a circumferential radial groove of the ring 26 and for sealing this component against a recess 63 in the foot part 2 serves. At an axial distance to a second O-ring 59 is incorporated in a circumferential radial groove in the lower part of the ring 26, which serves to seal against the maintenance opening 60 in the foot part 2. Between the O-rings 58 and 59 includes within the foot part 2, a connection to the pressure side of the centrifugal pump 1, which via Channels 33 in the ring 26 is fluidly connected to the interior of the ring 26, so that above the pressure of the pressure side at the first pressure-effective surface formed by the sheet section 29 of the non-rotating part 25 of the axial seal is present. The ring 26 is sealed over the O-ring 28 which lies in a groove on the inside of the retaining ring 26, opposite the ring 25, which forms the non-rotating part of the axial seal with the axial surface 24 of the seal. This O-ring 28 thus forms a radial seal, which, however, has to absorb only the comparatively small movements in the axial direction and is therefore subject to only slight wear.
The fact that the pump housing at the bottom, ie in the bottom of the foot part 2 has a maintenance opening 60 which is closed by the disc 56, by removing the disc 56 with the retaining ring 26 thereon, after the screws 57 have been solved, the Axial seal serviced and replaced if necessary. For this purpose, the shaft 38 of the pump must not be removed. All in the exploded view after Fig. 9 shown components of the axial seal can be replaced by the opening 61 in the bottom of the foot part 2. In the simplest form typically follows an exchange of the axial surfaces 23 and 24 having components and the O-ring 28. In order to solve the associated with the shaft 8 threaded connections, the shaft 8 in the field of motor chair on a cross-sectional profile, which through lateral engagement of a tool allows a locking of the shaft. It can thus, after the shaft 8 is rotatably held by means of a introduced in the field of motor chair open-end wrench, the cap screw 17 is released and after replacement of the sliding ring 20 and optionally further seals the retaining ring 18, these are screwed again.
The axially fixed part of the seal, so the non-rotating ring 25 with its seals and the retaining ring 26, with the disc 56 which forms the lid for closing the housing opening of the maintenance opening 60 are pulled out together with the cover 56 down, thereby the upper part of the retaining ring 26 with the peripheral O-ring 58 is pulled out of the recess 63 and the lower part of the retaining ring 26 with the O-ring 59 from the maintenance opening 60. These seals and the O-ring 28 and the non-rotating part of the axial seal 25 can then be replaced and are used together again from below into the maintenance opening 60 and the recess 63 of the foot part 2 until the upper part of the retaining ring 26 with the O Ring 58 in the recess 63 and the lower part sealingly abuts with the O-ring 59 in the maintenance opening 60.
- LIST OF REFERENCE NUMBERS
Above, the replacement of the axial seal is described at the lower end of the shaft, it is understood that according to the invention in an analogous manner provided here between shaft and housing bearing can be replaced without the shaft must change its position within the pump housing and thus larger disassembly and assembly activities are required.
- - Centrifugal pump
- - foot part
- - Headboard
- - coat
- - Suction connection
- - Pressure connection
- - coupling
- - Wave
- - rotary wheels
- - Radial seal
- - Axial seal
- - Suction mouth
- - Diaphragm
- - Ring channel
- - shaft end
- - blind hole
- - head screw
- - retaining ring
- - wall
- - Sliding ring
- - Pencils
- - Sleeve
- - Axial surface
- - Axial surface
- - non-rotating part of the axial seal, ring
- - retaining ring
- - groove
- - O-ring
- - Sheet metal section
- - tongues
- - tongues
- - recess in 29
- - Channels in the ring 26
- - Interior of 25
- - external thread
- - Mother
- - Sleeve
- - Wave
- - Engine
- - Motor shaft
- - Recesses in the ring 25th
- - ends of the tongues 31
- - heel in the ring 25
- - cones
- - disc / lid
- - screws
- - O-ring
- - O-ring
- - Maintenance opening
- - Holes for the screws 57th
- - edge of the lid
- - recess
- - heel in the foot