Volute for a centrifugal pump, method for producing a volute for a centrifugal pump and a centrifugal pump with a volute

Abstract

The invention relates to a volute casing for a centrifugal pump, a method for manufacturing a volute casing for a centrifugal pump, and a centrifugal pump with a volute casing. In particular, the invention relates to a volute casing made predominantly of plastic. The volute casing for a centrifugal pump according to the invention comprises a feed opening for a medium and an insert for securing a unit that can close the volute casing.

Description

[0001] The invention relates to a volute casing for a centrifugal pump, a method for manufacturing a volute casing for a centrifugal pump, and a centrifugal pump with a volute casing. In particular, the invention relates to a volute casing made predominantly of plastic. The volute casing for a centrifugal pump according to the invention comprises a feed opening for a medium and an insert for securing a unit that can close the volute casing.

[0002] Spiral casings for pumps are well-known. The spiral casing of a centrifugal pump, together with a casing cover, encloses the flow chamber in which the medium, usually a fluid, is pumped by an impeller. Spiral casings are primarily used in radial pumps. A radial pump, also known as a centrifugal pump, is a type of centrifugal pump in which the pumped medium exits the impeller radially, i.e., perpendicular to the pump shaft. In contrast to axial pumps, the flow deflection in the impeller allows the use of centrifugal force for higher delivery pressures, although the flow rate is correspondingly reduced.

[0003] The medium to be pumped, primarily a fluid, enters the pump via the suction pipe, is captured by the rotating impeller, and carried outwards in a spiral path. Due to the widening of the area between the impeller blades, the radial velocity of the fluid decreases towards the outside, while simultaneously the tangential velocity and pressure increase. The pressure and momentum (mass times tangential velocity) propel the fluid into the attached discharge pipe.

[0004] The central component of a pump is the impeller, which transfers mechanical energy as momentum to the fluid. The impeller can be single-stage or multi-stage within the pump. Multi-stage means that, in radial and semi-axial pumps, several impellers are mounted in series. It is also possible to construct double-flow or multi-flow impellers. In this case, one or more impellers are mirrored, which largely cancels out the axially acting forces.

[0005] Key features of centrifugal pump casings are the shapes of the flow inlet and outlet to the impeller. The discharge of the impeller flow is crucial for the pump's function. There are two main ways to create these flow channels: one using a guide vane equipped with a diffuser, and the other using a volute casing. These flow channels serve to convert the kinetic energy induced in the flow by the impeller into static pressure.

[0006] The unavoidable circumferential gap between the impeller shaft and the housing primarily determines the efficiency of such a pump. The shaft must be sealed against the housing. The permissible or tolerable leakage depends on the medium. For example, the technical effort required for toxic or corrosive media is very high.

[0007] Shaft sealing can be achieved using various methods. For example, a polytetrafluoroethylene (PTFE) cord can be wrapped around the shaft and pressed into a chamber. If the leakage rate increases due to wear, the packing gland's ram is tightened. If this is no longer possible, a new sealing cord is inserted. However, this solution requires significant maintenance.

[0008] Another sealing method uses a radial shaft seal. An elastic lip contacts the rotating shaft. To ensure sufficient pressure, a circumferential tension spring is located inside the seal. The seal is replaced when worn. Modern seals are often made of PE or PTFE.

[0009] The most common sealing solution is probably the mechanical seal. Two plates (often made of ceramic) are pressed together by springs. One plate is fixed to the housing, the other rotates with the shaft. Ceramic plates are extremely hard and therefore exhibit very little wear. With a comparatively high level of design complexity, this results in a low-maintenance solution.

[0010] A non-contact seal is the labyrinth seal, which is mostly used in extreme operating conditions, such as high speeds and pressures and / or temperatures.

[0011] In special cases (such as with toxic or corrosive media), barrier liquids or gases are used. Instead of a leakage flow from the inside to the outside, the barrier medium flows from the outside to the inside. The barrier medium must be continuously replenished.

[0012] Another sealing system option for a centrifugal pump is a magnetic coupling. These pumps are called magnetic coupling pumps. In contrast to dynamic seals, the drive torque is transmitted contactlessly from permanent magnets through the pump housing to the impeller.

[0013] The pump's spiral casing must withstand high pressure and prevent leakage when handling toxic or corrosive media. Therefore, these pumps are usually armored, meaning they are encased in a complete outer metal shell that holds the pump components together under high pressure and protects them against leakage. However, this requires a significant amount of material for the pumps and also complicates assembly and disassembly.

[0014] It is common practice in unarmored (i.e., without an additional outer metal casing) plastic pumps for the volute casing to be clamped between a metal drive lantern and a metal retaining ring. However, known solutions for such pumps require access to both the front and rear of the pump during assembly or disassembly in order to tighten and loosen the screw connection using a bolt and nut principle. Furthermore, clamping the plastic volute casing carries the risk that deformation of the plastic (e.g., due to temperature or continuous stress (flow)) will reduce the compression of the main casing seal, potentially leading to leakage.

[0015] The present invention therefore aims to overcome the disadvantages of the prior art. In particular, it seeks to provide a spiral casing for centrifugal pumps, primarily made of plastic, which, in conjunction with the other pump components, achieves a better sealing effect. Furthermore, it aims to simplify assembly and disassembly and reduce the number of pump components.

[0016] This problem is solved by a volute casing for centrifugal pumps with the features according to claim 1, a method for manufacturing a volute casing for a centrifugal pump with the features of claim 10, and a centrifugal pump with a volute casing according to claim 14. Preferred embodiments of the invention are defined in the respective dependent claims.

[0017] According to the invention, a spiral casing for a centrifugal pump is provided, wherein the spiral casing comprises a feed opening for a medium and an insert for attaching a unit that can be positively closed to the spiral casing.

[0018] According to a preferred embodiment of the spiral casing, the insert comprises a metal, carbon fibers, metal matrix composites (MMC), tungsten carbide-cobalt (WC-Co) cemented metals, titanium carbide cemented metals, tantalum carbide cemented metals, niobium carbide cemented metals (gamma phase), and / or steel, stainless steel, carbon steel, and / or is partially or completely made of these materials. The insert may be formed from other materials as long as they exhibit high dimensional stability. For example, the insert could even be formed from high-performance plastics that exhibit high dimensional stability.

[0019] According to another preferred embodiment of the spiral casing, it is made of plastic, preferably polyvinylidene fluoride (PVDF), polypropylene (PP), glass fiber reinforced polypropylene (PP-GF), polyethylene (PE), polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), ethylene chlorotrifluoroethylene (ECTFE), ethylene tetrafluoroethylene copolymer (ETFE), polyetheretherketone (PEEK) and / or a combination of these plastics.

[0020] According to a further preferred embodiment of the spiral housing, the insert has several blind holes with threaded bores and, correspondingly, the spiral housing has several through holes through which fastening means can be passed, wherein the insert can be releasably connected to the unit that closes the spiral housing by means of the fastening means in a form-fitting manner.

[0021] Furthermore, according to a preferred embodiment of the spiral housing, the insert is designed in an annular or cylindrical shape, which is arranged radially around the central axis of the spiral housing within the spiral housing and / or is partially enclosed by the spiral housing.

[0022] According to a further preferred embodiment of the spiral housing, the insert has one or more grooves and the spiral housing has one or more matching springs, wherein the insert and the spiral housing are positively connected by means of the one or more grooves and the one or more springs and / or that the insert and the spiral housing are positively connected via one or more dovetail and / or tenon joints.

[0023] According to another preferred embodiment of the volute casing, it has a recess for a flat gasket. Advantageously, this recess is located at the edge of the volute casing. Furthermore, one side of the insert can, together with the volute casing, create this recess. The flat gasket can be annular and fits snugly into the recess. During pump assembly, the flat gasket is then placed between the volute casing and a unit that closes off the volute casing. The insert supports this compartmentation and prevents the volute casing from deforming excessively, which could lead to pump leakage in the installed state due to the high contact pressures. The compartmentation also serves to largely retain the flat gasket in its position, thus preventing leakage.

[0024] According to a further preferred embodiment of the volute casing, the unit closing the volute casing comprises a drive lantern, a drive shaft, a sealing insert, a pump impeller, a motor lantern, a bearing support, a containment shell, a sliding bearing support, a casing cover, and / or a volute casing rear, wherein the volute casing can be releasably and positively connected to the drive lantern, the drive shaft, the sealing insert, the pump impeller, the motor lantern, the bearing support, the containment shell, the sliding bearing support, the casing cover, and / or the volute casing rear by means of the insert. Preferably, the components of the volute casing closing unit are made of the same materials as the insert. Furthermore, these components are also designed such that, together with the insert, they enclose a flat gasket and / or the volute casing.Advantageously, the unit closing the spiral casing is designed such that, together with the insert, it enables four-sided chambering of the flat gasket or the spiral casing. For the purposes of the invention, chambering means that the material of the flat gasket or the spiral casing is protected from flow, i.e., from deformation, by the material of the insert or the unit closing the spiral casing. Chambering does not mean that a form-fitting, completely closed chamber is required, but merely that the material of the spiral casing or the flat gasket should be protected from deformation, which could lead to leakage of the entire pump in the assembled state. Advantageously, the unit closing the spiral casing has a projection that supports the chambering. Preferably, this is a radially extending projection.

[0025] According to a further preferred embodiment of the spiral casing, the spiral casing further comprises a discharge opening for the medium, a recess for a pump impeller, fastening means for a suction port, fastening means for a pressure port, an inlet pressure gauge, an outlet pressure gauge and / or a closable opening for carrying out maintenance or cleaning work.

[0026] According to a further preferred embodiment of the spiral casing, the spiral casing is designed in multiple stages, wherein the spiral casing includes several recesses for pump impellers arranged one behind the other and / or wherein the spiral casing is designed for a multi-flow centrifugal pump assembly.

[0027] According to the invention, a method for manufacturing a spiral casing with an integrated insert for centrifugal pumps with one or more of the above-mentioned features is further provided, wherein the method comprises the following steps: Positioning an insert in a tool, overmolding and / or overpressing the insert with plastic to form the spiral casing (100).

[0028] According to the invention, a centrifugal pump with a volute casing is further provided, wherein the volute casing comprises one or more of the features described above. In addition, the pump can further comprise a drive, a control system, and other conventional components of centrifugal pumps.

[0029] According to a preferred embodiment of a centrifugal pump with a volute casing, the pump comprises a casing-closing unit and a flat gasket, wherein the flat gasket is enclosed within a chamber between the volute casing and the casing-closing unit. In particular, the volute casing insert supports this chambering, thus preventing the flat gasket or the volute casing from deforming excessively or from shifting from its original position, which would be possible due to the pressure holding the pump components together. This design prevents pump leakage.

[0030] According to a preferred embodiment of the centrifugal pump with a spiral casing, this is a magnetically coupled centrifugal pump.

[0031] It should also be noted that aspects of the invention have been described with reference to different subject matter. In particular, some aspects or embodiments have been described with reference to device-type claims, while other aspects have been described with reference to process-type claims. However, the person skilled in the art will understand from the above and the following description that, unless otherwise stated, in addition to any combination of features belonging to one type of subject matter, any combination of features relating to different types of subject matter is also deemed to be disclosed by this text. In particular, combinations of features relating to device-type claims and features relating to process-type claims are deemed to be disclosed.Furthermore, features relating to one embodiment can be combined with other features of another embodiment, the drawings, or the claims, provided this is possible. The invention and its embodiments are described in more detail below in conjunction with the figure(s). Figures 1a and 1b each show a schematic representation of a centrifugal pump with an integrated volute casing according to the prior art. Figure 2 shows, in a schematic, not-to-scale view, a section of a longitudinal cross-section through a centrifugal pump with a volute casing according to an embodiment of the invention. Figure 3 shows, in a schematic, not-to-scale view, a section of a longitudinal cross-section through a centrifugal pump with a volute casing according to an embodiment of the invention. Figure 4 shows, in a schematic, not-to-scale, three-dimensional view, a volute casing with an insert according to an embodiment of the invention. Figure 5 shows, in a schematic, not-to-scale view, a longitudinally centered cross-section through a volute casing with an insert according to a further embodiment of the invention.

[0032] Figures 1a and 1bThe figures show centrifugal pumps with volute casings from the prior art. It can be seen that, typically in unarmored (i.e., without an additional outer metal casing) plastic pumps, the volute casing is clamped between a metal drive lantern and a metal clamping ring using a screw-nut principle (see marking with arrows in the figures). Figures 1a and 1b (which demonstrate this type of clamping). However, the known solutions require access to both the front and back of the pump during assembly in order to tighten and lock the screw connection, and to loosen it again during disassembly. Furthermore, clamping the plastic spiral housing carries the risk that deformation of the plastic (e.g., due to temperature or continuous stress (flow)) will reduce the compression of the main housing seal, potentially leading to leaks.

[0033] Figure 2 as well as Figure 3Figure 1 shows a section of a longitudinal cross-section through a centrifugal pump with a volute casing 100 according to an embodiment of the invention. The volute casing 100 with insert 110 according to the invention is visible. In this example, the insert 110 is made of metal, while the volute casing 100 is made of plastic. Figure 2 The illustrated cross-section passes centrally through a blind hole 130 with a threaded bore of the insert 110, or centrally through the through-hole 131 within the spiral housing 110. Figure 3 In contrast, the cross-section is located in the center of the entire pump. Furthermore, in Figure 2The pump's drive lantern 210 can be seen, which is attached to the insert 110 of the volute casing 100 by means of fasteners 400, thus forming a positive-locking connection between the volute casing 100 and the drive lantern 210. Suitable fasteners 400 include, for example, stud bolts, studs, and the like. A sealing insert 240 is also visible between the volute casing 100 and the drive lantern 210. A flat gasket 300, which is arranged here between the sealing insert 240, the metal insert 110, and the volute casing 100, seals the volute casing 100 against the drive lantern 210 from the outside. The design of the metal insert 110 and the volute casing 100 provides a chamber for and support to the flat gasket 300. The metal insert 110 in the volute casing 100 performs two functions.Firstly, the threaded holes allow the spiral casing 100 to be screwed to the pump's drive lantern 210, thus closing the pump housing. A continuous screw connection / clamp is not necessary; the screw connection is made directly within the spiral casing 100. Secondly, the sealing effect of the flat gasket 300 between the spiral casing 100 and the drive lantern 210 is improved because the plastic, which is prone to deformation / flow, is supported and held in shape by the metal ring 110. The compression of the flat gasket 300 can therefore be significantly higher than in a purely plastic housing. By inserting a metal insert 110 into a plastic spiral casing 100, a better sealing effect is achieved in plastic pumps, assembly is simplified, and the number of components is reduced.Thus, the invention can significantly reduce resources and costs in the manufacture and maintenance of centrifugal pumps made primarily of plastic. The impeller of the pump 260 within the volute casing 100 and, in this case, a mechanical seal are also visible. The mechanical seal seals the unavoidable gap between the shaft 250 of the pump and the component(s) surrounding the shaft. Furthermore, dovetail-shaped grooves 120 are visible on the metal insert 110, which additionally secure the metal insert 110 in the volute casing 100 against slipping or tilting, thereby contributing to increased stability of the entire component. At the inlet and outlet of the volute casing 100, where the suction pipe and discharge pipe can be attached, further fastening aids 180 (e.g., connections by means of a flange or a screw fitting) for the suction pipe and discharge pipe are provided in this example.Pressure pipe (only in . Fig. 3 (recognizable) attached to the outside of the spiral casing 100.

[0034] Figure 4Figure 1 shows a three-dimensional, schematic representation (not to scale) of a spiral casing 100 with an insert 110 according to a further embodiment of the invention. Visible are the inlet and outlet for the medium to be pumped 140, 170, as well as the recess for the impeller of the pump 160 and a recess for a flat gasket 150. Also visible are the through-holes 131 at the outer edge of the spiral casing with the underlying threaded bores 130 of the insert 110. Fastening means 400 (not shown) can use these bores to form a positive connection between the spiral casing 100 and other components of the pump, such as the drive lantern 210, the sealing insert 240, the shaft 250, and / or other elements of the pump, thus forming the pump chamber. The insert 110 placed in the spiral case 100 is preferably made of a suitable material such as a metal which has high dimensional stability.The insert can be inserted using a forming process such as plastic injection molding or compression molding. The insert 110 is positioned in a mold and then overmolded or pressed with plastic, forming the spiral casing 100. The insert 110 is then partially or completely encased in plastic, except for the threaded holes. There is no contact with the pumped medium, and therefore no separate seal is required. The pump is mounted using studs or bolts 400 screwed into the metal insert 110 through holes, for example, in the drive housing 230. The connection can then be tightened on the back of the drive housing 210 using a washer and nut. This allows for assembly and, if necessary, disassembly of the pump from only one side.

[0035] Figure 5Figure 1 shows a schematic, non-scale cross-section through a spiral casing 100 with an insert 110 according to a further embodiment of the invention. The arrangement of the insert 110 within the spiral casing 100 is clearly visible. The insert 110 extends in a ring-shaped manner, radially to the central axis of the spiral casing or the drive shaft of the pump. According to this embodiment, the insert 110 is not completely surrounded by the material of the spiral casing 100, but has a radially continuous section. Furthermore, the spiral casing material also has a radially extending recess 150 at this point. This allows, for example, the insertion of the insert 110 into the casing. Figure 2 or 3It has been shown that a flat gasket 300 can be chambered or protected in this area, which allows the spiral casing 100 to be mounted to the other components of the pump with more compression, thus improving the long-term sealing capability of the pump chamber.

[0036] Furthermore, the spiral casing with insert according to the invention can be installed in a magnetically coupled centrifugal pump. In this configuration, the flat gasket is enclosed between the spiral casing with insert and a magnetic coupling insert. The magnetic coupling insert is made of a dimensionally stable material such as metal. Together with the drive lantern of the magnetically coupled centrifugal pump, which is also usually made of metal, the flat gasket and / or part of the spiral casing are thus dimensionally stable and protected from deformation. This design allows the drive lantern to compress the spiral casing and the magnetic coupling insert under high pressure, thereby preventing leakage even in this magnetically coupled centrifugal pump.

[0037] It should be noted that the term "comprising" does not exclude other elements or steps, and that "a" or "an" does not exclude multiple elements. Furthermore, elements described in connection with different embodiments may be combined. It should also be noted that reference numerals in the claims are not to be understood as limiting the scope of the claims. Reference sign

[0038] 100 Spiral casing 110 Insert 120 Dovetail joint 130 Blind hole 131 Through hole in spiral casing 140 Inlet opening for a medium 150 Recess for flat gasket 160 Recess for pump impeller 170 Outlet opening for a medium 180 Fastening device for nozzle or flange 190 Lockable opening for carrying out maintenance or cleaning work 200 Spiral casing closing unit 210 Drive lantern 220 Projection 230 Through holes 240 Sealing insert 250 Drive shaft 260 Pump impeller 300 Flat gasket 400 Fastening device

Claims

1. Spiral casing (100) for a centrifugal pump comprising an inlet opening for a medium (140), characterized by the fact that the spiral casing (100) includes an insert (110) for attaching a unit (200) that can be positively closed to the spiral casing.

2. Spiral casing (100) according to claim 1, characterized by the fact that the insert (110) comprises a metal, carbon fibers, metal matrix composites (MMC), tungsten carbide-cobalt hard metals (WC-Co), titanium carbide hard metals, tantalum carbide hard metals, niobium carbide hard metals (y-gamma phase) and / or steel, stainless steel, carbon steel, and / or is partially or completely made of these materials.

3. Spiral casing (100) according to one of the preceding claims, characterized by the fact thatthe spiral casing (100) made of plastic, preferably made of polyvinylidene fluoride (PVDF), polypropylene (PP), glass fiber reinforced polypropylene (PP-GF), polyethylene (PE), polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), ethylene chlorotrifluoroethylene (ECTFE), ethylene tetrafluoroethylene copolymer (ETFE), polyetheretherketone (PEEK) and / or a combination of these plastics.

4. Spiral casing (100) according to one of the preceding claims, characterized by the fact that the insert (110) has several blind holes (130) with or without threaded bores and the spiral housing (100) has several through holes (131) through which fastening means can be passed, wherein the insert (110) can be releasably connected to the unit (200) that closes the spiral housing by means of the fastening means (400) in a form-fitting manner.

5. Spiral casing (100) according to one of the preceding claims, characterized by the fact thatthe insert (110) is designed in an annular or cylindrical shape, which is arranged radially around the central axis of the spiral housing (100) within the spiral housing (100) and / or is partially enclosed by the spiral housing (100).

6. Spiral casing (100) according to one of the preceding claims, characterized by the fact that the insert (110) has one or more grooves and the spiral housing (100) has one or more springs to match, wherein the insert (110) and the spiral housing (100) are positively connected by means of the one or more grooves and the one or more springs and / or that the insert (110) and the spiral housing (100) are positively connected via one or more dovetail and / or tenon joints (120).

7. Spiral casing (100) according to one of the preceding claims, characterized by the fact that the spiral housing (100) has a recess for a flat gasket (150).

8. Spiral casing (100) according to one of the preceding claims, characterized by the fact that the unit (200) closing the spiral casing comprises a drive lantern (210), a sealing insert (240), a pump impeller (260), a drive shaft (250), a motor lantern, a bearing support, a containment pot, a sliding bearing support, a casing cover, and / or a spiral casing rear, wherein the spiral casing (100) can be releasably connected to the drive lantern (210), the drive shaft (250), the sealing insert (240), the pump impeller (260), the motor lantern, the bearing support, the containment pot, the sliding bearing support, the casing cover, and / or the spiral casing rear by means of the insert (110) in a form-fitting manner.

9. Spiral casing (100) according to one of the preceding claims, characterized by the fact thatthe spiral casing (100) further comprises a discharge opening for the medium (170), a recess for a pump impeller (160), fastening means for a suction port (180), fastening means for a pressure port (180), an inlet pressure gauge, an outlet pressure gauge and / or a lockable opening for carrying out maintenance or cleaning work (190).

10. Spiral casing (100) according to one of the preceding claims, characterized by the fact that the spiral casing (100) is designed in multiple stages, wherein the spiral casing (100) includes several recesses for pump impellers (160) in succession and / or wherein the spiral casing (100) is designed for a multi-flow centrifugal pump assembly.

11. Method for manufacturing a spiral casing (100) with an integrated insert (110) for a centrifugal pump according to any one of claims 1 to 10 comprising the following steps: - Positioning an insert (110) in a tool, - Overmolding and / or overmolding the insert (110) with plastic to form the spiral casing (100).

12. Centrifugal pump with a spiral casing (100) according to any one of claims 1 to 10.

13. Centrifugal pump according to claim 12, characterized by the fact that the spiral housing (100) comprises a unit (200) closing the spiral housing and a flat gasket (300), wherein the flat gasket (300) is chambered between the spiral housing (100) and the unit (200) closing the spiral housing.

14. Centrifugal pump according to claim 12 or 13, characterized by the fact that The centrifugal pump is a magnetically coupled centrifugal pump.

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