EP0359136A1 - Sealless centrifugal pump suited for cleaning - Google Patents

Abstract

A cleanable centrifugal pump without stuffing box, in particular a side channel pump, comprises at least one impeller (5) driven by means of a magnetic, synchronously transmitting rotary coupling arranged inside the impeller (5). The two halves of the coupling are mutually separated by a dividing wall (6) which delimits the space for the fluid to be delivered against the atmosphere and is rigidly and sealingly connected to the pump housing (1). One half of the rotary coupling (7, 12) is mounted in or on the impeller and the dividing wall (6) penetrates the impeller (5) concentrically, serves as a bearing journal for the impeller and, together with the impeller, forms an annular bearing gap (13). The dividiing wall (6) is tubular and statically sealed on both sides of the impeller (5) in the housing of the centrifugal pump (1; 1a; 1b). The annular bearing gap (13) is connected, directly or indirectly, with a region of the suction connection piece (1c) and with a region of the delivery connection piece (1d).

Description

The invention relates to a cleanable glandless centrifugal pump according to the preamble of claim 1.

Centrifugal pumps of the type identified in the introduction are used where the requirement for increased occupational and operational safety as well as greatest environmental friendliness is a priority. Magnetically acting, synchronously transmitting rotary couplings use the attraction and repulsion forces between magnets in two coupling halves. They are used for the contactless transmission of torques, whereby, unlike the hysteresis and eddy current clutches, a slip between the two coupling halves cannot occur.

Permanent magnetic synchronous clutches are known which, in connection with glandless centrifugal pumps, are preferably designed as so-called central rotary couplings. They require a partition, the so-called can. This has the task of separating the space for the fluid to be pumped from the atmosphere. The inner magnetic rotor, which is also equipped with permanent magnets, is arranged within this containment shell. This in turn is mounted in a bearing flange and medium-lubricated plain bearings and transfers the torque given off by the motor to the impeller without slippage. A housing forms the end of this completely sealed unit. A shaft passage from the room for the fluid to be pumped is not available and therefore is only a static seal between the housing and the containment shell is required. An overview of glandless centrifugal pumps with permanent magnetic synchronous coupling according to the state of the art can be found in the magazine Chemische Industrie, 3/87, pages 46 to 49.

In the known centrifugal pumps, the inner magnetic rotor is attached to the impeller at an axial distance from it by a connecting part. The connecting part also serves to mount the impeller and the inner magnet rotor within the housing. The containment shell encloses the inner magnet rotor and parts of the bearing arrangement. The lubrication of the slide bearing for mounting the impeller in connection with the inner magnet rotor is usually carried out via the fluid to be pumped.

The known design of the containment shell has a cavity which is connected to the impeller housing via the bearing gap of the slide bearing. Due to the mode of operation of the hydrodynamically operating plain bearing, the fluid to be conveyed reaches the free spaces of the containment shell via the bearing gap. A complete exchange of the fluid located in the sometimes very intricate dead spaces of the containment shell over the bearing gap of the slide bearing is excluded.

The known centrifugal pumps are therefore completely unsuitable for the reasons mentioned above if the delivery of the fluid has to take place under hygienic or sterile or bacteriologically perfect conditions. Such requirements are placed in particular in the food and beverage industry, in pharmacy or in the sterile field of various fields of application.

Centrifugal pumps that meet the aforementioned requirements must be automatically cleanable in the flow. In this context, one speaks of the so-called CIP cleanability (CIP: cleaning in place), which means that the facilities to be cleaned must allow an automatic supply of cleaning liquid and cleaning of the product or product residues in all areas on the spot . In the centrifugal pumps described above, automatic cleaning of the critical areas, in particular the dead spaces within the containment shell, is not possible under the conditions to be demanded.

A glandless centrifugal pump has already been proposed (GM 19 82 247), in which a partition designed as a containment shell penetrates the impeller concentrically, serves as a cantilevered bearing journal and forms a bearing ring gap with it. This known solution does not disclose any information as to how a defined flow can be ensured in the critical areas, in particular in the bearing ring gap and in the dead space between the impeller hub that is not exposed to the flow and the rear housing wall.

It is an object of the present invention to simplify the construction of a cleanable glandless centrifugal pump of the type identified in the introduction in such a way that it is CIP-cleanable and allows the conveyance of fluids under hygienic or sterile or bacteriologically perfect conditions.

This object is achieved by the characterizing features of claim 1. Advantageous embodiments of the centrifugal pump according to the invention are described in dependent claims 2 to 13.

The proposed design and sealing of the partition wall gives the glandless centrifugal pump a particularly simple and easy-to-clean design. Conventional centrifugal pumps are usually designed so that the hydraulic efficiency is as high as possible. This is achieved, among other things, by dimensioning the liquid-loaded gaps between stationary and moving components as closely as possible. In the centrifugal pump according to the invention, there is a deviation from this dimensioning rule insofar as all the gaps located in areas that are critical in terms of cleaning technology, in particular the bearing gap, are subjected to a flow ensuring adequate cleaning. Due to the mechanism of action of the pump, there is a pressure difference in the fluid between the suction and pressure ports within the pump housing, which pressure difference is used to flow through the column in question in a defined radial and axial direction. A deterioration in the hydraulic efficiency associated with this gap flow is accepted.

So that the bearing ring gap is flowed through in a defined manner with the fluid to be conveyed and on the one hand can be cleaned properly and on the other hand can develop its hydrodynamic load-bearing capacity, an advantageous embodiment of the centrifugal pump according to the invention provides that the bearing ring gap is connected on both sides to a hub-side annular space, the latter in each case via Column with a defined passage cross-section is connected to the space of the impeller blades.

Another advantageous embodiment of the centrifugal pump according to the invention provides a hub-side annular space separated by the impeller into two partial spaces, one of which has a first opening with a defined passage cross-section with the area of the suction port and the other in the same way via a second opening with the Area of the pressure port is connected. As a result, the pressure difference formed between the suction and pressure ports results in a particularly pronounced, defined gap flow oriented in the radial and axial direction between stationary and moving components within the housing of the conveying device.

The arrangement of the bearing ring gap and its connection on both sides to the hub-side annular space ensures that, in particular during cleaning, the cleaning fluid to be conveyed flows through the bearing ring gap in sufficient quantity, since its two ends are connected to areas which are due to the pressure distribution in the housing of the impeller have different pressure levels.

In order to clean the critical area of the centrifugal pump, the bearing ring gap, particularly intensively, another advantageous embodiment of the centrifugal pump provides that measures are provided in the bearing ring gap and / or at its inlet which increase the kinetic energy of the gap flow in the bearing ring gap.

Another embodiment of the centrifugal pump according to the invention provides that a bearing bush arranged in the impeller in the region of the bearing ring gap is in turn designed as an impeller. As a result, the gap flow in this area is forced by an additional increase in its kinetic energy.

In order to intensify the cleaning of the bearing ring gap by the formation of flow turbulence during the cleaning run, another embodiment of the centrifugal pump according to the invention provides that the boundary surface of the partition wall and / or the bearing bush facing the bearing ring gap are provided with axial or helical grooves or elevations or is.

The arrangement of the impeller-side half of the rotary coupling in a recess in a hub of the impeller, as provided by a further embodiment of the centrifugal pump according to the invention, ensures a compact arrangement while avoiding dead spaces in this area.

The hermetically sealed chamber of the impeller-side half of the rotary coupling in the recess of the hub of the impeller, as is provided by a further embodiment of the centrifugal pump according to the invention, ensures a particularly easy-to-clean arrangement, which moreover promotes the conveyance of the fluid under hygienic or sterile conditions or bacteriologically perfect conditions guaranteed.

According to another advantageous embodiment of the centrifugal pump according to the invention, a compact and easy-to-clean arrangement of the impeller-side half of the rotary coupling is achieved in that the latter is hermetically sealed by the hub and a cover part on the one hand and a bearing bush enclosing the partition wall on the other hand.

As a result of the pressure distribution which arises via the housing of the centrifugal pump, forces act on the impeller which attempt to displace it in the axial and radial directions. So that the connection between the bearing ring gap and the associated hub-side annular space is ensured under these conditions, a further embodiment of the centrifugal pump according to the invention provides that the bearing bush is provided on both sides with a thrust surface which limits its axial displaceability in the housing. The contact surface is designed in such a way that when it is in contact with the housing there is still sufficient liquid passage between the contact surface and the housing.

The same effect is achieved with another embodiment of the centrifugal pump according to the invention, in which the impeller is provided on both sides towards the housing with a contact surface which has the same properties with regard to its liquid permeability as the contact surfaces on the bearing bush.

In order to ensure wear resistance and hardness, chemical resistance and good temperature properties and, furthermore, to keep power losses due to eddy current formation when cutting the partition wall small with the magnetic field lines of the central rotary coupling, another development of the centrifugal pump according to the invention provides that the partition wall and bearing bush are made of a wear-resistant, chemically resistant, high electrical resistance material, preferably a ceramic.

In order that a gap-wise flow that is sufficient in terms of cleaning technology is ensured under all operating conditions of the pump, in particular at low delivery heights, a method for operating the cleanable glandless centrifugal pump is provided, regardless of Conveying task between suction and pressure nozzle required pressure difference to provide a minimum pressure difference ensuring the gap flows in each application.

An embodiment of the invention is shown in the drawing and will be described in more detail below.

• Fig. 1 einen Meridianschnitt durch eine vorteilhafte Ausfüh­rungsform der Kreiselpumpe gemäß der Erfindung und
• Fig.2 einen Meridianschnitt durch eine andere Ausgestaltung der Kreiselpumpe gemäß der Erfindung mit einem besonders wirksamen Anschluß des nabenseitigen Ringraumes an Saug- und Druckstutzen.

Show it

• Fig. 1 shows a meridian section through an advantageous embodiment of the centrifugal pump according to the invention and
• 2 shows a meridian section through another embodiment of the centrifugal pump according to the invention with a particularly effective connection of the hub-side annular space to suction and pressure ports.

Figure 1 shows, representative of other centrifugal pumps, a meridian section through a so-called self-priming side channel pump. At this point it should be particularly emphasized that the present invention can also be used without restriction on so-called normal-suction centrifugal pumps or also on rotating positive displacement pumps.

In the present exemplary embodiment, the self-priming side channel pump allows both the conveyance of gaseous and liquid fluids, and a reversal of the conveying direction is also possible by changing the direction of rotation. In the housing 1 of the centrifugal pump, which consists of a motor-side housing part 1b and a housing cover 1a, there is an open parallel-walled rotor with radially directed blades, hereinafter referred to as impeller 5, as the characteristic component.

The housing cover 1a has a suction and a pressure port 1c or 1d, which are connected to a side channel 1e. The housing 1 is on its engine side Housing part 1b in connection with the housing cover 1a and connecting means 18 connected to a lantern housing 3, the latter being centered and fastened to a flange of a motor 2 via connecting means 17.

A pot-shaped hub 5a is formed on the impeller 5, a recess 5b receiving the impeller-side half of the central rotary coupling 8, 9. Part 8 is a multiplicity of rotationally symmetrically arranged “permanent magnets”, while part 9 represents a soft iron covering that enhances the magnetic effect. The parts 8 and 9 of the impeller-side half of the central rotary coupling are hermetically sealed by the hub 5a and a cover part 10 welded to it on the one hand and a bearing bush 11 on the other hand. A bore formed on the inside of the bearing bush 11 is penetrated concentrically by a partition 6, which is tubular, the latter being accommodated on both sides in the housing parts 1a and 1b in a statically sealing manner via seals 15.

The tubular partition 6 serves the hub 5a of the impeller 5 in connection with the bearing bush 11 as a journal. Bearing bush 11 and partition 6 form a bearing ring gap 13. The latter is connected on both sides to an annular space 19 which surrounds the hub 5 a of the impeller 5. Since the impeller 5 is arranged with a lateral play, which is ensured under all operating conditions, in relation to the adjacent housing parts 1a and 1b in the housing 1 of the centrifugal pump; there is a connection between the hub-side annular space 19 and the space of the impeller blades through column 20, which result from the aforementioned game. The partition 6 and the bearing bush 11 are preferably made of a wear-resistant, chemically resistant, high electrical resistance material. Ceramic materials, especially silicon carbides, have proven to be advantageous.

The boundary surface of the partition 6 and / or the bearing bush 11 facing the bearing ring gap 13 are or are provided with axial or helical grooves or elevations 14, as a result of which the cleaning action within the bearing ring gap 13 can be intensified.

A motor shaft 4 is guided through the motor-side housing part 1b and extends through the tubular partition 6. The motor shaft 4 carries on its circumference in the area of the hub 5a of the impeller 5 another half of the central rotary coupling 7, 12, part 7 being permanent magnets distributed rotationally symmetrically over the circumference, while part 12 represents a soft iron ring which increases the magnetic effect .

A flywheel 21 is provided on the motor shaft 4 in the area of the lantern housing 3. While seals 15 seal the partition 6 from the housing parts 1a and 1b to the shaft-side part of the central rotary coupling 7, 12, a housing seal 16 ensures that the housing parts 1a and 1b are sealed from their external environment.

When the motor shaft 4 is driven, the half of the central rotary coupling 7, 12 assigned to it transmits a torque to the half of the central rotary coupling 8, 9 on the impeller side. Under load, the two coupling halves 8, 9 and 7, 12 rotate against each other so far that the required torque acts between them. The speed of the motor shaft 4 is transferred to the impeller 5 synchronously. Due to effective pressure differences in the housing 1 of the centrifugal pump, the latter fills with the fluid to be delivered, so that the hub-side annular space 19 and the bearing ring gap 13 connected to it are also acted upon with the fluid to be delivered. Differences in pressure in the annular space 19 on both sides of the impeller 5 result in a Flow through the bearing ring gap 13, so that in it the liquid film required for the hydrodynamic lubrication effect and on the other the cleaning flow necessary for its cleaning with cleaning agent is ensured.

The cleaning of the hub-side annular space 19 is unproblematic since a liquid exchange between the latter and the space of the impeller blading is readily provided via the gaps 20, the cleaning of the surfaces delimiting the hub-side annular space 19 by the hub 5a of the impeller rotating in this area 5 is supported extraordinarily intensively.

To force the gap flow within the bearing ring gap 13, the bearing bush 11 is in turn designed in this area as an impeller. There are several ways to do this. On the one hand, the blades can extend over the entire axial length of the bearing bush 11, on the other hand, the bearing bush is bladed either only at the entry of the bearing ring gap 13 or at its outlet or on both sides.

The axial fixation of the impeller 5 with respect to the housing cover 1a and the motor-side housing part 1b takes place via thrust faces 22, which are formed on both sides of the bearing bush 11 in such a way that liquid passage is ensured even in the case of one of the thrust faces 22 on the housing.

The same effect as described above is achieved with thrust faces 23, which are provided on both sides of the impeller 5 towards the housing parts 1a and 1b, respectively. The radial position of these contact surfaces 23 can be located within the radial extension of the impeller 5, preferably completely inside or outside.

The impeller side half of the central rotary coupling 8.9 is hermetically chambered within the recess 5b of the hub 5a, the cover part 10 being welded to the hub 5a and the bearing bush 11, which delimits the chamber for the central rotary coupling 8.9 radially inwardly, with absolutely no leakage the cover part 10 and the hub 5a is cast.

In principle, it is also possible for the shaft-side half of the rotary coupling to be equipped with electromagnets which correspond in function and mode of operation to the permanent magnets described above.

Figure 2 shows a meridian section through a further embodiment of the centrifugal pump according to the invention. In contrast to Figure 1, the pressure port 1d is formed on the motor-side housing part 1b. According to the invention it is provided that the hub-side annular space 19, into which the bearing ring gap 13 ends with its two ends, is separated by the impeller 5 into two partial spaces, of which the one arranged to the left of the impeller 5 has a first opening 20 * with a defined passage cross-section with the The area of the suction nozzle 1c and the other is connected in the same way via a second opening 20 ** to the area of the pressure nozzle 1d.

As a result of the pressure difference present between the pressure nozzle 1d and the suction nozzle 1c during operation of the centrifugal pump, fluid passes from the area of the pressure nozzle 1d via the second opening 20 ** into the subspace of the hub-side annular space 19 located to the right of the impeller 5. From here, the fluid penetrates over the entire circumference of the bearing ring gap 13, flows through it, in order to emerge into the subspace of the hub-side annular space 19 located to the left of the impeller 5. The fluid reaches the area of the suction nozzle 1c via the first opening 20 *. Consequently quasi-recirculating to the main flow, a gap flow flowing through the critical areas of the conveying device is ensured as a result of the pressure difference present between the suction and pressure ports within the housing of the conveying device.

Claims (13)

1. Cleanable glandless centrifugal pump, in particular a side channel pump, with at least one impeller, which is driven by a magnetically acting, synchronously transmitting rotary coupling, the two halves of the coupling by a space limiting the fluid to be pumped against the atmosphere, with the housing the centrifugal pump has a fixed and sealingly connected partition, one half of the rotary coupling is arranged in or on the impeller, and the partition penetrates the impeller concentrically, serves as a journal and forms a bearing ring gap with it, characterized in that
that the partition (6) is tubular and statically sealed on both sides of the impeller (5) in the housing of the centrifugal pump (1; 1a, 1b), and that the bearing ring gap (13) directly or indirectly on the one hand with an area of the suction nozzle (1c) and on the other hand is connected to an area of the pressure port (1d). 2. Cleanable glandless centrifugal pump according to claim 1, characterized in that
that the bearing ring gap (13) is connected on both sides to a hub-side annular space (19), the latter being connected to the space of the impeller blading via a column (20) with a defined passage cross section. 3. Cleanable glandless centrifugal pump according to claim 1, characterized in that
that the bearing ring gap (13) is connected on both sides to a hub-side annular space (19), the latter being separated by the impeller (5) into two partial spaces, one of which has a first Opening (20 *) with a defined passage cross-section is connected to the area of the suction port (1c) and the other is connected in the same way via a second opening (20 **) to the area of the pressure port (1d). 4. Cleanable glandless centrifugal pump according to one of claims 1 to 3, characterized in
that measures are provided in the bearing ring gap and / or at its entry which increase the kinetic energy of the gap flow in the bearing ring gap. 5. Cleanable glandless centrifugal pump according to claim 4, with a bearing bush (11) arranged in the impeller (5), characterized in that
that the bearing bush (11) in the region of the bearing ring gap (13) is designed as an impeller. 6. Cleanable glandless centrifugal pump according to one of claims 4 or 5, characterized in that
that the bearing ring gap (13) facing the boundary surface of the partition (6) and / or the bearing bush (11) with axial or helical grooves or elevations (14) are or is. 7. Cleanable glandless centrifugal pump according to one of claims 1 to 6, characterized in
that the impeller side half of the rotary coupling (8, 9) is arranged in the recess (5b) of a hub (5a) of the impeller (5). 8. Cleanable glandless centrifugal pump according to claim 7, characterized in that
that the impeller side half of the rotary coupling (8, 9) in the recess (5b) is hermetically sealed. 9. Cleanable glandless centrifugal pump according to claim 7 or 8, characterized in
that the impeller side half of the rotary coupling (8, 9) of the hub (5a) and a cover part (10) on the one hand and a bearing bush (11) enclosing the partition (6) on the other hand is hermetically sealed. 10. Cleanable glandless centrifugal pump according to one of claims 5 to 9, characterized in
that the bearing bush (11) is provided on both sides with a thrust surface (22) that limits its axial displacement in the housing (1a, 1b). 11. Cleanable glandless centrifugal pump according to one of claims 1 to 10, characterized in that
that the impeller (5) is provided on both sides towards the housing (1a or 1b) with a contact surface (23). 12. Cleanable glandless centrifugal pump according to one of claims 1 to 11, characterized in
that partition (6) and bearing bush (11) consist of a wear-resistant, chemically resistant, high electrical resistance material, preferably a ceramic. 13. A method for operating the cleanable glandless centrifugal pump according to one of claims 1 to 12, characterized in that
that, regardless of the pressure difference required on the part of the conveying task between suction and pressure ports (1c or 1d), a minimum pressure difference ensuring the gap flows is provided in every application.

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