Centrifugal pump with a backflow reduction arrangement

Description

[0001] The invention relates to a centrifugal pump with an arrangement for reducing backflow from a pressure chamber into a suction chamber, wherein a rotating element is arranged on a cover plate of an impeller, which interacts with a non-rotating element which is arranged on a housing part.

[0002] This type of arrangement is intended to minimize backflow of pumped fluid from the pressure section of the centrifugal pump into its suction section. In the prior art, gap seals are frequently used for this purpose. The gap remaining between the surfaces of the two sealing parameters is dimensioned to ensure an acceptable compromise between the efficiency and operational reliability of the centrifugal pump. It should be noted that the minimum achievable gap width depends on various factors. For example, shaft deflection and vibrations can result in only a relatively wide gap being possible, leading to correspondingly high leakage losses.

[0003] Furthermore, with contaminated liquid, a widening of the gap caused by the abrasive action of the dirt particles must be expected. Therefore, a decreasing loss of efficiency is to be expected, especially with wastewater centrifugal pumps.

[0004] To account for the continuous wear of the gap seal on centrifugal pumps for conveying abrasive fluids, it has already been proposed to provide a gap adjustment mechanism using adjustable sealing elements. DE 35 13 116 A1 describes such a gap seal. Such a manually adjustable gap seal is comparatively complex to manufacture and requires considerable experience from the operating personnel. A relatively high level of labor is required for adjusting, monitoring, and timely readjustment of the sealing elements.

[0005] DE 195 19 322 A1 describes a seal arranged between the housing wall and the cover plate of the impeller of a centrifugal pump. The sealing parameters, housing wall and cover plate, are provided with essentially annular surfaces. At least one of the two sealing parameters is designed as a brush. The brush-shaped surface rests on a smooth mating surface of the other sealing component.

[0006] GB 268 197 A describes a centrifugal pump in which the impeller has considerable radial play in all parts of its chamber. Accordingly, a self-adjusting or self-centering sealing device is provided, comprising a first ring and a second ring. The first ring rests tightly against a cylindrical surface on the impeller hub, and the second ring sits in a recess or depression in the side wall of the impeller chamber.

[0007] US Patent 2 021 346 A discloses a device with a sealing effect between two parts moving relative to each other in a centrifugal pump, wherein a rubber sealing ring is provided which, in one embodiment, is kept in contact with the impeller by means of a plurality of spring elements.

[0008] From FR 786.795 a device for reducing internal leakage and wear on centrifugal pumps and turbines through which sludge-like liquids flow is known.

[0009] From US 6234748 B1, a wear ring arrangement for a pump is known, wherein the wear ring arrangement comprises an inner wear ring with an outer groove and an inner recess in the impeller for receiving the inner wear ring. The recess has an inner groove for axial alignment with the outer groove. The wear ring arrangement further comprises at least one substantially arcuate retainer for simultaneously engaging in the inner groove and the outer groove to hold the inner wear ring relative to the impeller, and an outer wear ring that interacts with the inner wear ring and is generally coaxially aligned with respect to the inner wear ring.

[0010] US 2011 / 0064566 A1 describes a device for impeller sealing in centrifugal pumps, wherein a sealing ring consisting of a rigid pressure ring and an elastic part connected to the pressure ring is arranged in the pump housing between the pressure side and the suction side of the impeller, the elastic part of which slidably rests against a sliding surface of the axial or radial circumferential contour of the impeller over its entire circumference in the area of ​​the impeller inlet, and the sealing ring is positioned in the pump housing such that its elastic part is pre-tensioned against the sliding surface and is thereby pressed against the sliding surface in a sealing manner.

[0011] GB 643 307 A discloses a centrifugal pump in which the fluid flows to the center of the impeller through a tubular element which is subjected to an end load by means of a helical spring arranged coaxially to the tubular element, which tends to increase the effective length of the element in an axial direction, so that one of the end faces of the element rests against a rotating surface without clearance to form a seal.

[0012] The object of the invention is to provide a centrifugal pump that further reduces backflow from a pressure chamber to a suction chamber. The pump should employ an arrangement that requires no manual adjustment. The centrifugal pump should be characterized by reliable operation and the highest possible efficiency. Furthermore, the centrifugal pump should be easy to operate, even by personnel without specialized training. Finally, the centrifugal pump should be characterized by a long service life and versatile application possibilities.

[0013] This problem is solved according to the invention by a centrifugal pump having the features of claim 1. Preferred embodiments can be found in the dependent claims, the description and the drawings.

[0014] According to the invention, the centrifugal pump has an arrangement in which a rotating element, which is arranged on the cover plate of a closed impeller, interacts with a non-rotating element, which is slidably mounted and is pressed against the rotating element by a force-generating element, whereby a fluid film can form between the rotating and non-rotating elements.

[0015] According to the invention, the centrifugal pump has a closed radial impeller with a cover plate on which the rotating element is arranged. In contrast to conventional gap seals, in the design according to the invention the non-rotating element is slidably mounted. A force-generating element exerts pressure on the non-rotating element and presses it, preferably in an axial direction, against the rotating element.

[0016] The resulting friction is minimized by making the rotating and / or non-rotating elements from a ceramic material. Preferably, a silicon carbide-containing material is used, with sintered silicon carbide (SSiC) being particularly suitable. This design creates a minimal gap between the two flat ceramic surfaces. Lubrication is provided by the conveying medium.

[0017] The rotating element and / or the non-rotating element are preferably ring-shaped or have ring-shaped areas. The two ceramic rings are pressed against each other by a force-generating element, so that the housing part is sealed against backflow from the rotating impeller.

[0018] According to the invention, the force-generating element is designed as an elastic element in the form of a spring. The spring can, for example, be designed as a wave spring. Disc springs or compression springs can also be used.

[0019] The force-generating elements are preferably arranged on or in a housing part. The force-generating element is supported by the stationary housing part and presses against the slidably mounted, non-rotating element. The non-rotating element is moved axially against the rotating element.

[0020] It proves advantageous if the non-rotating element is guided. The housing part can have a surface for guiding the axially displaceable, non-rotating element. This surface of the housing part provides a stop against radial displacement.

[0021] In one variant of the invention, the housing part has an annular groove in which the force-generating element and / or the axially displaceable non-rotating element is arranged.

[0022] Preferably, at least one sealing element is arranged between the non-rotating element and the housing part. This can be, for example, an O-ring. The O-rings are selected to ensure a reliable seal while still allowing axial movement.

[0023] In one embodiment of the invention, the centrifugal pump additionally comprises a radial guidance device. This device serves to radially guide the impeller and prevents the impeller from rubbing against the housing. This guidance device includes a rotating component and a non-rotating component. The rotating component can, for example, be a bearing ring, and the non-rotating component can be a gap ring arranged on the housing.

[0024] The running ring is preferably arranged on the cover plate of the impeller. If the guide device is provided in addition to the backflow reduction arrangement, it is advantageous for the running ring to be arranged on a radial outer side of the cover plate and to interact with the corresponding radially arranged gap ring. In this variant, the rotating element of the backflow reduction arrangement is preferably arranged on the end face of the cover plate of the closed radial impeller and interacts axially with the non-rotating element located on the housing part.

[0025] According to the invention, the rotating element has a section that serves for radial guidance. Thus, according to the invention, a separate bearing ring is not required in addition to the rotating element; instead, the bearing ring of the radial guidance device is formed by the rotating element of the arrangement for reducing backflow. According to the invention, the rotating element is annular with an L-shaped cross-sectional profile. In the case of the cup-shaped rotating element, the radial outer surface serves as a guide, which interacts with a gap ring, preferably also made of a ceramic material, in particular a sintered silicon carbide. According to the invention, the axial end face interacts with the non-rotating element, which is pressed against this axial end face.

[0026] Additionally, the non-rotating element of the arrangement can also have a section for radial guidance. This allows the non-rotating element to take over the function of the gap ring. Thus, in this variant of the invention, no additional gap ring is required; this function is performed by the non-rotating element. It proves advantageous if the non-rotating element is ring-shaped with an L-shaped profile. The cup-shaped non-rotating element is mounted for axial displacement and has an axial end face that is pressed against an axial counter-surface of the rotating element. Furthermore, the non-rotating element has a radial inner surface that serves as a radial guide. The radial inner surface preferably interacts with a radial outer surface of the rotating element, thereby preventing displacement in the radial direction.In this variant of the invention, the arrangement for reducing backflow simultaneously performs the function of radial guidance. An additional radial guidance device with a bearing ring and a gap ring is therefore no longer required.

[0027] Further features and advantages of the invention will become apparent from the description of exemplary embodiments with reference to drawings and from the drawings themselves.

[0028] This shows: Figure 1 shows a sectional view of a centrifugal pump, Figure 2 shows a close-up of a non-inventive arrangement and an additional device for radial guidance, Figure 3 shows an arrangement according to the invention in which the rotating element takes on the function of a running ring, Figure 4 shows an arrangement not according to the invention in which the non-rotating element takes on the function of a gap ring,

[0029] Figure 1Figure 1 shows a centrifugal pump with an impeller 1. The impeller 1 is designed as a closed radial impeller and has a support disc 2 and a cover disc 3. Blades 4 are arranged on the support disc. Passages for conveying the medium are formed between the support disc 2 and the cover disc 3.

[0030] The impeller 1 is driven by a shaft 5 rotating around the central longitudinal axis A.

[0031] The impeller 1 is surrounded by a housing part 6. The housing part 6 forms a suction opening 7, which is integrally formed with the housing part 6.

[0032] Figure 2Figure 10, which is not part of the invention, shows a close-up of the suction inlet 7 according to a first embodiment. The centrifugal pump has a radial guidance device 8 designed as a gap seal. The radial guidance device 8 comprises a rotating component 9, designed as a bearing ring, and a non-rotating component 10, designed as a gap ring. The rotating component 9 is arranged on a radial outer surface of the cover plate 3 of the impeller 1. The rotating component 9 thus rotates with the impeller 1. The non-rotating component 10 is arranged on the housing part 6 and has a radial inner ring as a guide, which interacts with the radial outer ring of the rotating component 9 and together they form the gap seal.

[0033] When executed according to the illustration in Figure 2In addition to the device 8, an arrangement 11 is provided, comprising a rotating element 12 and a non-rotating element 13. The rotating element 12 is designed as a ring arranged on the axial end face of the cover plate 3. For this purpose, the rotating element 12 has an axially extending projection 14 that engages in a groove 15 in the cover plate 3. The non-rotating element 13 is designed as an axially displaceable ring that is guided against radial displacement by a surface 16 of the housing part 6. A force-generating element 17 exerts a force on the non-rotating element 13 and presses the non-rotating element 13 against the rotating element 12. The force-generating element 17 is designed as a spring. In the exemplary embodiment, a wave spring is used. The non-rotating element 13 is sealed to the housing part 6 by a sealing element 18.The sealing element 18 is preferably an O-ring.

[0034] In this embodiment, the rotating element 12 and the non-rotating element 13 are made of sintered silicon carbide (SSiC). The two axially oriented end faces of the rotating element 12 and the non-rotating element 13 are pressed together by the force-generating element 17. This creates a minimal gap. Friction is minimized by the ceramic materials. A lubricating film of the conveyed medium forms in the gap between the contacting surfaces of the rotating element 12 and the non-rotating element 13.

[0035] The arrangement 11, together with the device 8, prevents backflow from a pressure chamber 19 of the pump into a suction chamber 20 of the pump.

[0036] In the variant according to Figure 2In addition to the device 8, an arrangement 11 is provided. Due to the pressed-together ceramic surfaces, the arrangement 11 minimizes backflow and thus increases the efficiency of the pump.

[0037] Figure 3Figure 1 shows an embodiment of the invention in which the rotating element 12 arranged on the impeller has a section 21 for radial guidance. The rotating element 12 is angled. The rotating element 12 is designed as a ring with an L-shaped profile. The section 21 is one leg of this profile. The section 21 has a radial outer surface that interacts with a radial inner surface of the non-rotating component 10. The non-rotating component 10 is designed as a ceramic gap ring. Preferably, the non-rotating component 10 consists of sintered silicon carbide (SSiC). Furthermore, the rotating element 12 has an axial end face. The axial end face of the non-rotating element 13 with the force-generating element 17 is pressed against the axial end face of the rotating element 12.

[0038] At the in Figure 3In the illustrated embodiment of the invention, the running ring of the device for radial guidance is formed by the rotating element 12 of the arrangement 11. Thus, this variant requires fewer components.

[0039] At the in Figure 4In the illustrated variant, which is not part of the invention, the non-rotating element 13 has a section 22 for radial guidance. The non-rotating element 13 is angled. It is a ring with an L-shaped cross-sectional profile. The section 22, which forms the leg of this profile, serves for radial guidance. The section 22 has a radial inner surface that interacts with the radial outer surface of the rotating element 12 arranged on the impeller 1. A gap is formed between the two surfaces. The section 22 ensures guidance in the radial direction. The non-rotating element 13 is mounted axially displaceably in a groove of the housing part 6 and is pressed axially against the rotating element 12 by the force-generating element 17. This presses an axial surface of the non-rotating element 13 and an axial surface of the rotating element 12 against each other.

[0040] In the Figure 4 In the depicted variant, the non-rotating element 13 thus takes over the function of a split ring. This variant requires even fewer components. In the Figure 4 In the depicted variant, the arrangement takes over the function of the radial guidance device. Thus, in the variant according to Figure 4 A radially extending gap and an axially extending gap are formed, the radially extending gap being minimized by the compression of two surfaces and lubricated by the conveying medium. Furthermore, radial guidance is ensured.

[0041] If the dimensions allow or require it, both the [unclear] in the Fig. 3 The rotating element 12 shown, as well as the one in the Fig. 4 The non-rotating element 13 shown is provided.

Claims

1. Centrifugal pump comprising an arrangement (11) for reducing a backflow from a pressure chamber (19) into a suction chamber (20), wherein on a cover plate (3) of an impeller (1) is disposed a rotating element (12), which cooperates with a non-rotating element (13) disposed on a casing part (6), wherein the non-rotating element (13) is arranged displaceably, wherein a force-generating element (17) causes the non-rotating element (13) to act against the rotating element (12), wherein the rotating element (12) and / or the non-rotating element (13) consist of a ceramic material, wherein the rotating element (12) has an L-shaped profile and the force-generating element (17) is configured as an elastic element in the form of a spring, in particular a corrugated spring.

2. Centrifugal pump according to Claim 1, characterized in that the rotating element (12) and / or the non-rotating element (13) consist of a silicon-carbide-containing material.

3. Centrifugal pump according to Claim 1 or 2, characterized in that the non-rotating element (13) is arranged axially displaceably.

4. Centrifugal pump according to one of Claims 1 to 3, characterized in that the non-rotating element (13) is guided, wherein the casing part (6) preferably has a face (16) for the guidance in an axial direction.

5. Centrifugal pump according to one of Claims 1 to 4, characterized in that between the non-rotating element (13) and the casing part (6) is arranged a sealing element (18).

6. Centrifugal pump according to one of Claims 1 to 5, characterized in that the centrifugal pump has a device (8) for the radial guidance, comprising a rotating component (21) and a non-rotating component (10).

7. Centrifugal pump according to one of Claims 1 to 6, characterized in that the rotating element (12) has a portion (21) for the radial guidance.

8. Centrifugal pump according to one of Claims 1 to 7, characterized in that the non-rotating element (13) is configured with an L-shaped profile.

9. Centrifugal pump according to one of Claims 1 to 8, characterized in that the rotating element (12) and / or the non-rotating element (13) are of ring-like configuration.