EP3929444B1 - Centrifugal pump for conveying fluids containing solids - Google Patents

Centrifugal pump for conveying fluids containing solids Download PDF

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Publication number
EP3929444B1
EP3929444B1 EP21181101.3A EP21181101A EP3929444B1 EP 3929444 B1 EP3929444 B1 EP 3929444B1 EP 21181101 A EP21181101 A EP 21181101A EP 3929444 B1 EP3929444 B1 EP 3929444B1
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EP
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centrifugal pump
pump according
wear
gpa
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EP21181101.3A
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German (de)
French (fr)
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EP3929444C0 (en
EP3929444A1 (en
Inventor
Markus PITTROFF
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KSB SE and Co KGaA
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KSB SE and Co KGaA
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D7/00—Pumps adapted for handling specific fluids, e.g. by selection of specific materials for pumps or pump parts
    • F04D7/02—Pumps adapted for handling specific fluids, e.g. by selection of specific materials for pumps or pump parts of centrifugal type
    • F04D7/04—Pumps adapted for handling specific fluids, e.g. by selection of specific materials for pumps or pump parts of centrifugal type the fluids being viscous or non-homogenous
    • F04D7/045—Pumps adapted for handling specific fluids, e.g. by selection of specific materials for pumps or pump parts of centrifugal type the fluids being viscous or non-homogenous with means for comminuting, mixing stirring or otherwise treating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/02—Selection of particular materials
    • F04D29/026—Selection of particular materials especially adapted for liquid pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/08—Sealings
    • F04D29/16—Sealings between pressure and suction sides
    • F04D29/165—Sealings between pressure and suction sides especially adapted for liquid pumps
    • F04D29/167—Sealings between pressure and suction sides especially adapted for liquid pumps of a centrifugal flow wheel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/40—Casings; Connections of working fluid
    • F04D29/42—Casings; Connections of working fluid for radial or helico-centrifugal pumps
    • F04D29/426—Casings; Connections of working fluid for radial or helico-centrifugal pumps especially adapted for liquid pumps
    • F04D29/4286—Casings; Connections of working fluid for radial or helico-centrifugal pumps especially adapted for liquid pumps inside lining, e.g. rubber
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2230/00—Manufacture
    • F05D2230/90—Coating; Surface treatment
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2300/00—Materials; Properties thereof
    • F05D2300/20—Oxide or non-oxide ceramics
    • F05D2300/22—Non-oxide ceramics
    • F05D2300/224—Carbon, e.g. graphite

Definitions

  • the invention relates to a centrifugal pump for conveying media containing solids with an open impeller and a counter-element that interacts with it.
  • An example of a medium containing solids is wastewater, especially municipal and industrial wastewater.
  • This usually includes raw wastewater (e.g. dirty water, faeces), wastewater (mechanically cleaned water from clarification tanks), sludge (e.g. activated, fresh, digested and inoculating sludge) and rainwater.
  • raw wastewater e.g. dirty water, faeces
  • wastewater mechanically cleaned water from clarification tanks
  • sludge e.g. activated, fresh, digested and inoculating sludge
  • rainwater e.g. activated, fresh, digested and inoculating sludge
  • Industrial wastewater can, under certain circumstances, have a very corrosive or abrasive effect on the centrifugal pumps used, especially on the components of the centrifugal pump that come into contact with the media.
  • impellers can be used in centrifugal pumps for pumping media containing solids, for example channel impellers, vortex impellers or single blades.
  • An open impeller interacts in the pump chamber with a so-called wear wall, which is fixed in the pump housing.
  • a free, unconstricted impeller passage is referred to as a ball passage. It describes the largest permissible diameter of the solids to ensure a blockage-free passage. It is given as the ball diameter in millimeters and corresponds at most to the nominal width of the suction or pressure port.
  • the blade shape plays a crucial role in the design of open impellers.
  • the construction of the leading edge is particularly important.
  • the leading edge is often covered with fibers present in the pumped medium.
  • the fibers are usually not transported away from the impeller leading edge. If fibers are deposited on the leading edge, further fibers can attach, resulting in larger occupancies. This behavior is particularly beneficial when ensuring high ball passages.
  • large flow cross-sections lead to dead water zones with no flow through, which in turn lead to occupancy.
  • a cutting edge at the inlet of the pump housing in the form of an inlet edge or a cutting device on the pump impeller can be used to shred fibers in the medium containing solids in order to avoid the formation of deposits.
  • cast components are often used in centrifugal pumps.
  • a solid body in the desired shape is created from a liquid material after it solidifies. This means that the desired housing structures, wear walls and impellers of the centrifugal pump can be created in a targeted manner.
  • Cast materials in centrifugal pump construction are usually iron-carbon alloys.
  • the wear protection layer is introduced as a preform into a casting tool and then cast with a casting material, preferably with a metallic casting material.
  • the DE 10 2017 223 602 A1 specifies a pump housing in which, instead of a wear wall in the pump housing, ceramic wear protection plates are arranged, which are already glued in the casting tool before casting with metallic casting material. These wear protection plates are preferably made of silicon carbide.
  • This chilled cast iron is characterized by high corrosion resistance in aggressive media and high wear resistance at the same time.
  • the wear walls based on silicon carbide are significantly harder compared to components made of gray cast iron and increase the service life. However, these components are considerably more complex and expensive to produce.
  • the object of the invention is to provide a centrifugal pump for conveying media containing solids. Damage to the pump housing caused by abrasive wear should be effectively reduced by a device. In addition, the pump should maintain operational efficiency for a long time. Furthermore, a shredding edge on the wear wall should remain sharp for as long as possible.
  • the centrifugal pump should be characterized by high reliability and a long service life. It should also ensure easy installation. Furthermore, the centrifugal pump should impress with the lowest possible manufacturing costs.
  • a centrifugal pump for conveying media containing solids comprises an open impeller and a counter-element that interacts with it, the surfaces of which are coated with a carbon layer to protect against abrasive effects.
  • the counter element is designed as a wear wall.
  • the wear wall is fastened in the pump housing so that it can be easily replaced. It protects the pump housing from wear.
  • the wear wall can be designed in the form of a hollow cone segment or a trumpet funnel-shaped, hollow segment.
  • the surface of the wear wall is provided with a carbon layer which gives the wear wall an extremely high hardness. This effectively protects the wear wall, which is subject to enormous abrasive effects when conveying media containing solids, from wear.
  • the wear wall advantageously has a cutting groove in order to cut long-fiber elements and braid-like contaminants in the conveying medium into small pieces. Ideally, this effectively prevents the centrifugal pump from becoming blocked.
  • the cutting groove of the wear wall is preferably coated with carbon. This gives the cutting edge of the cutting groove a special hardness and a wear-resistant sharpness, which also resists the abrasive effects of small solid particles in the long term.
  • the cutting groove runs spirally from the inside to the outside. In its course it therefore encloses an angle of more than 150°, preferably more than 170°, in particular more than 190° and/or less than 320°, preferably less than 300°, in particular less than 280°.
  • the cutting groove is designed such that it has a depth of more than 0.5 mm, preferably more than 1.0 mm, in particular more than 1.5 mm and/or less than 5.0 mm, preferably less than 4 mm, in particular less than 3.0 mm.
  • the width of the cutting groove is adapted to the wear wall inner diameter of the suction side, so that it is more than 5%, preferably more than 10%, in particular more than 15% and / or less than 40%, preferably less than 35%, in particular less than 30% of the inner diameter of the suction side. Due to the shape described and the coating with carbon, the cutting groove is particularly suitable for shredding long-fiber and plait-shaped elements in the pumped medium and for protecting the centrifugal pump from clogging.
  • the open impeller of the pump interacts with the wear wall, so that the smallest possible gap is created between the wear wall and the open impeller, which is called the power gap.
  • This gap is designed to be as small as possible in order to avoid unwanted flows from the pressure side to the suction side of the pump.
  • Both the impeller and the wear wall are coated with a carbon layer, which gives the surfaces of the components extreme hardness. This also protects the components from touching or brushing against each other, which could certainly occur due to the small gap width.
  • the wear wall is made of a metallic material, preferably a cast material and/or stainless steel material.
  • a metallic material preferably a cast material and/or stainless steel material.
  • the surface forming the power gap and in particular the cutting groove of the wear wall are provided with a carbon layer according to the invention.
  • the cutting groove in particular is exposed to abrasive stress due to the formation of fibrous deposits and the collision of solid particles and is particularly protected by the carbon layer.
  • the wear wall works together with an open impeller.
  • an open impeller can be an open diagonal single-blade wheel or an open channel wheel. Coating the open impeller with carbon is particularly advantageous, which provides effective protection against abrasive wear and enables the longest possible operating time with constant pump efficiency.
  • a centrifugal pump with an open diagonal single-blade wheel which is provided with a carbon layer, is used to convey media containing solids.
  • the flow line of the blade runs diagonally outwards. This can advantageously be used to convey uncleaned, solids-laden and outgassing wastewater as well as media with higher viscosity.
  • Carbon layers are layers in which carbon is the predominant component.
  • the carbon layer can be applied, for example, using a PVD (Physical Vapor Deposition), a physical vapor deposition such as by evaporation or sputtering) or a CVD (Chemical Vapor Deposition) process.
  • PVD Physical Vapor Deposition
  • CVD Chemical Vapor Deposition
  • tetrahedral hydrogen-free amorphous carbon layer also known as a ta-C layer referred to as.
  • the atomic bonds belonging to the crystal lattice of graphite (3 in total) are identified with the designation “sp2”. This is an sp2 hybridization.
  • each carbon atom forms a tetrahedral arrangement with four neighboring atoms.
  • all atomic distances are equally small. There are therefore very high binding forces between the atoms, in all spatial directions. This results in the high strength and extreme hardness of the diamond.
  • the atomic bonds belonging to the crystal lattice of diamonds, four in total, are identified with the designation "sp3". This means that sp3 hybridization is present.
  • the carbon layer consists of a mixture of sp3 and sp2 hybridized carbon.
  • This layer is characterized by an amorphous structure.
  • Foreign atoms such as hydrogen, silicon, tungsten or fluorine can also be incorporated into this carbon network.
  • a smooth axial surface with non-stick properties is created without the need for complex mechanical post-processing of the impeller.
  • several wear walls can be introduced into a coating reactor, which is preferably designed as a vacuum chamber, where the ta-C coating is applied under moderate thermal load.
  • the centrifugal pump according to the invention with a wear wall is therefore characterized by relatively low manufacturing costs.
  • the carbon layer is applied as a coating to a wear wall.
  • the thickness of the layer is advantageously more than 0.5 ⁇ m, preferably more than 1.0 ⁇ m, in particular more than 1.5 ⁇ m. Furthermore, it proves to be advantageous if the carbon layer is less than 18 ⁇ m, preferably less than 16 ⁇ m, in particular less than 14 ⁇ m.
  • the carbon coating has an extremely smooth surface with non-stick properties, in which the average roughness value R a of the carbon layer is less than 0.7 ⁇ m, preferably less than 0.5 ⁇ m, in particular less than 0.3 ⁇ m.
  • the ta-C coating has a very low coefficient of friction and at the same time very good chemical resistance.
  • the hardness of the coating is very close to the hardness of diamonds, the hardness preferably being more than 20 GPa, preferably more than 30 GPa, in particular more than 40 GPa and less than 120 GPa, preferably less than 110 GPa, in particular less than 100 GPa .
  • ta-C coatings are harder than a-C:H coatings.
  • ta-C does not contain any hydrogen. It can therefore be assumed that ta-C is more stable in contact with water (at temperatures above 80 °C) than a-C:H. In contact with other - especially polar - liquids that contain molecules in which hydrogen is bonded, ta-C could also be more stable than a-C:H.
  • the carbon layer is not applied directly to the wear wall, but rather an adhesion promoter layer is first provided.
  • This preferably consists of a material that both adheres well to steel and prevents carbon diffusion, e.g. B. through the formation of stable carbides.
  • Thin layers of chromium, titanium or silicon are appropriately used as adhesion-promoting layers that meet these requirements. Chromium and tungsten carbide have proven particularly useful as adhesion promoters.
  • the coating has an adhesion promoter layer, which preferably contains a chromium material.
  • the adhesion promoter layer preferably consists of more than 30% by weight, preferably more than 60% by weight, in particular more than 90% by weight of chromium.
  • the ta-C coating according to the invention is a simple, quickly realizable and economical coating for wear walls in centrifugal pumps. In addition to very high hardness, the coating according to the invention also has excellent sliding properties and good chemical resistance.
  • the invention also makes it possible to coat wear wall geometries with special dimensions.
  • wear wall geometries can be realized that were previously difficult to achieve from ceramic materials due to production reasons.
  • PECVD/PACVD processes can preferably be used for coating.
  • Plasma excitation of the gas phase occurs through the coupling of pulsed direct voltage (“pulsed DC”), medium-frequency (KHz range) or high-frequency (MHz range) power.
  • pulsed direct voltage (“pulsed DC”)
  • KHz range medium-frequency
  • MHz range high-frequency
  • PVD processes are used for coating. These processes are particularly simple and have a low process temperature. This technology leads to layers in which foreign atoms can also be incorporated, if necessary.
  • the process is preferably carried out in such a way that structural and dimensional changes in the materials to be coated (metallic, gray cast iron, etc.) are excluded.
  • the ta-C coating Compared to a CVD diamond layer, the ta-C coating has the advantage that the coating temperature for CVD diamond layers is 600 to 1000 °C and for amorphous carbon layers such as ta-C it is well below 500 °C. This is of high technical relevance, particularly for the coating of metallic materials. The production of PVD diamond layers is not possible.
  • Fig. 1 shows a sectional view of a centrifugal pump for pumping media containing solids.
  • This exemplary embodiment is a horizontally positioned volute casing pump with a diagonally open single-blade wheel 4 and a counter-element 2 that interacts with it.
  • the counter-element 2 is designed as a wear wall.
  • the solid-containing medium flows into the pump via the suction mouth 1 and is fed by the open diagonal single-blade wheel 4, which is rotatably connected to the shaft 6, is acted upon by kinetic energy and leaves the pump housing 3 via the pressure port 5.
  • the shaft 6 is rotatably mounted by the ball bearing 7 and the mechanical seal 9.
  • the bearing carrier cover 10 closes the pump chamber in the direction of the drive.
  • the blade edges 13 of the diagonally open single blade wheel 4 form a gap with the wear wall, the so-called power gap.
  • the wear wall is coated with a carbon layer, namely an amorphous carbon layer, namely ta-C. This provides particularly ideal protection against abrasive wear, which inevitably affects the wear wall when conveying media containing solids.
  • the wear wall has a spiral-shaped cutting groove 12 running from the inside to the outside.
  • Fig. 2 shows a sectional view of a centrifugal pump for pumping media containing solids.
  • This exemplary embodiment is a thick matter pump in which an open impeller 4 interacts with a counter element 2.
  • the counter element 2 is designed as a wear wall in this exemplary embodiment.
  • the wear wall is used to protect the pump housing 3 against wear and is easily replaceable.
  • the wear wall is provided with a carbon layer in order to be particularly wear-resistant against the abrasive effect of the medium containing solids.
  • the solid-containing medium is sucked in via the suction mouth 1 and accelerated by the open impeller 4, which is connected to the shaft 6 in a rotationally fixed manner and is rotatably mounted by the bearing 7.
  • the medium containing solids leaves the pump housing 3 via the pressure port 5.
  • Fig. 3 shows a detailed section of the suction mouth area.
  • the counter element 2 is designed as a wear wall and interacts with the open impeller 4.
  • the blade flanks of the open impeller 4 extend radially outwards from the hub in a backwards curved course.
  • the blade edges 13 form a gap with the wear wall.
  • the wear wall is coated with a carbon layer, namely with ta-C. This ensures effective protection against abrasive wear and tarnishing of the two components.
  • Fig. 4 shows a front view of the counter element 2, which is designed as a trumpet funnel-shaped, hollow wear wall.
  • the wear wall has a spiral-shaped cutting groove 12 running from the inside to the outside.
  • the cutting groove 12 encloses an angle of more than 150°, preferably more than 170°, in particular more than 190° and/or less than 320°, preferably less than 300°, in particular less than 280°.
  • the depth of the cutting groove 12 is more than 0.5 mm, preferably more than 1.0 mm, in particular more than 1.5 mm and/or less than 5.0 mm, preferably less than 4 mm, in particular less than 3.0 mm.
  • the cutting groove 12 has a width of more than 5%, preferably more than 10%, in particular more than 15% and/or less than 40%, preferably less than 35%, in particular less than 30% of the inside diameter of the wear wall on the suction side .
  • the wear wall and in particular the cutting groove 12 is coated with a carbon layer, namely with ta-C.
  • the cutting groove remains extremely sharp due to the edge coated with ta-C and can therefore cut long-fiber or pigtail-shaped elements that may be contained in the pumped medium into small pieces. This effectively prevents the centrifugal pump from becoming blocked.

Description

Die Erfindung betrifft eine Kreiselpumpe zur Förderung feststoffhaltiger Medien mit einem offenen Laufrad und einem damit zusammenwirkenden Gegenelement.The invention relates to a centrifugal pump for conveying media containing solids with an open impeller and a counter-element that interacts with it.

Beispielgebend für ein feststoffhaltiges Medium ist Abwasser, insbesondere kommunales und industrielles Abwasser. Dieses umfasst in der Regel Rohabwasser (z. B. Schmutzwasser, Fäkalien), Abwasser (mechanisch gereinigtes Wasser aus Klärbecken), Schlamm (z. B. Belebt-, Frisch-, Faul- sowie Impfschlamm) und Regenwasser. Industrielles Abwasser kann unter Umständen sehr korrosiv oder abrasiv auf die eingesetzten Kreiselpumpen, insbesondere auf die medienberührenden Bauteile der Kreiselpumpe, wirken.An example of a medium containing solids is wastewater, especially municipal and industrial wastewater. This usually includes raw wastewater (e.g. dirty water, faeces), wastewater (mechanically cleaned water from clarification tanks), sludge (e.g. activated, fresh, digested and inoculating sludge) and rainwater. Industrial wastewater can, under certain circumstances, have a very corrosive or abrasive effect on the centrifugal pumps used, especially on the components of the centrifugal pump that come into contact with the media.

Bei Kreiselpumpen zur Förderung feststoffhaltiger Medien können unterschiedliche Laufräder eingesetzt werden, beispielsweise Kanalräder, Freistromräder oder Einschaufler. Ein offenes Laufrad wirkt im Pumpenraum mit einer sogenannten Schleißwand, die im Pumpengehäuse fixiert ist, zusammen.Different impellers can be used in centrifugal pumps for pumping media containing solids, for example channel impellers, vortex impellers or single blades. An open impeller interacts in the pump chamber with a so-called wear wall, which is fixed in the pump housing.

Als Kugeldurchgang wird ein freier, unverengter Laufraddurchgang bezeichnet. Er beschreibt den größten zulässigen Durchmesser der Feststoffe, um einen verstopfungsfreien Durchgang zu gewährleisten. Er wird als Kugeldurchmesser in Millimeter angegeben und entspricht maximal der Nennweite des Saug- bzw. Druckstutzens.A free, unconstricted impeller passage is referred to as a ball passage. It describes the largest permissible diameter of the solids to ensure a blockage-free passage. It is given as the ball diameter in millimeters and corresponds at most to the nominal width of the suction or pressure port.

Die Schaufelform spielt bei der Gestaltung von offenen Laufrädern eine entscheidende Rolle. Insbesondere die Konstruktion der Eintrittskante ist von großer Bedeutung. Bei Abwasserpumpen belegt sich die Eintrittskante häufig mit im Fördermedium vorhandenen Fasern. Die Fasern werden meist nicht von der Laufrad-Eintrittskante abtransportiert. Kommt es zu einer Anlagerung von Fasern an der Eintrittskante, können sich weitere Fasern anlagern, sodass sich größere Belegungen bilden. Begünstigt wird dieses Verhalten insbesondere bei der Gewährleistung hoher Kugeldurchgänge. Gerade im Teillastbetrieb der Kreiselpumpe führen große Strömungsquerschnitte zu nicht durchströmten Totwasserzonen, welche wiederum zu Belegungen führen.The blade shape plays a crucial role in the design of open impellers. The construction of the leading edge is particularly important. In wastewater pumps, the leading edge is often covered with fibers present in the pumped medium. The fibers are usually not transported away from the impeller leading edge. If fibers are deposited on the leading edge, further fibers can attach, resulting in larger occupancies. This behavior is particularly beneficial when ensuring high ball passages. Particularly in part-load operation of the centrifugal pump, large flow cross-sections lead to dead water zones with no flow through, which in turn lead to occupancy.

Bei Einschauflern führen solche Belegungen dazu, dass eine höhere Leistung zum Betrieb der Kreiselpumpe erforderlich ist. Bei Mehrschauflern kann es durch die Belegungen auch zu einer asymmetrischen Strömung in den Kanälen kommen. Solche asymmetrischen Strömungen beeinflussen nicht nur die erforderliche Leistung, sondern auch den zu fördernden Volumenstrom sowie die zu erzielende Förderhöhe.In the case of single-shovel pumps, such assignments mean that higher performance is required to operate the centrifugal pump. In the case of multi-blade vessels, the occupancy can also lead to an asymmetrical flow in the channels. Such asymmetrical flows not only influence the required power, but also the volume flow to be pumped and the delivery head to be achieved.

Eine Schnittkante am Eingang des Pumpengehäuses in Form von einer Eintrittskante oder einer Schneidvorrichtung am Pumpenlaufrad kann zum Zerkleinern von Fasern im feststoffhaltigen Medium genutzt werden, um eine Belagbildung zu vermeiden.A cutting edge at the inlet of the pump housing in the form of an inlet edge or a cutting device on the pump impeller can be used to shred fibers in the medium containing solids in order to avoid the formation of deposits.

Generell kommen bei Kreiselpumpen häufig Gussbauteile zum Einsatz. Beim Gießen entsteht aus einem flüssigen Werkstoff nach dem Erstarren ein fester Körper in der gewünschten Form. Somit können gezielt die gewünschten Gehäusestrukturen, Schleißwände bzw. Laufräder der Kreiselpumpe erzeugt werden. Gusswerkstoffe im Kreiselpumpenbau sind in der Regel Eisen-Kohlenstoff-Legierungen.In general, cast components are often used in centrifugal pumps. When casting, a solid body in the desired shape is created from a liquid material after it solidifies. This means that the desired housing structures, wear walls and impellers of the centrifugal pump can be created in a targeted manner. Cast materials in centrifugal pump construction are usually iron-carbon alloys.

Insbesondere bei Kreiselpumpen, die zur Förderung von feststoffhaltigen Medien eingesetzt werden, können im Bereich der Bauteile, die mit dem Fördermedium in Kontakt kommen, Verschleiß- und/oder Korrosionserscheinungen auftreten. Die strömenden Feststoffe können die Werkstoffe der Schleißwände sowie der offenen Laufräder abtragen, wodurch der Spalt zwischen den Bauteilen mit zunehmendem Betrieb größer wird.Particularly in centrifugal pumps that are used to pump media containing solids, signs of wear and/or corrosion can occur in the area of the components that come into contact with the pumped medium. The flowing solids can wear away the materials of the wear walls and the open impellers, causing the gap between the components to increase with increasing operation.

Dadurch verringert sich der Pumpenwirkungsgrad mit der Dauer des Betriebes, bis die Schleißwand erneuert werden muss.As a result, the pump efficiency decreases with the duration of operation until the wear wall needs to be replaced.

In der DE 43 26 545 C2 ist eine Schleißwand auf keramischer Basis, insbesondere auf Basis von Siliziumkarbid beschrieben, die mittels Schlickergussverfahren hergestellt wird. Diese wird formschlüssig in das Gehäuse einer Kreiselpumpe eingebettet und mit einer Gummierung an der Gehäusewand abgedichtet.In the DE 43 26 545 C2 describes a ceramic-based wear wall, in particular based on silicon carbide, which is produced using a slip casting process. This is positively embedded in the housing of a centrifugal pump and sealed on the housing wall with a rubber coating.

In der DE 10 2013 200 680 B4 ist ein Verfahren zur Erzeugung einer Schleißwand beschrieben. Hierin wird die Verschleißschutzschicht als Vorformling in ein Gusswerkzeug eingebracht und dann mit einem Gusswerkstoff, vorzugsweise mit einem metallischen Gusswerkstoff, ausgegossen.In the DE 10 2013 200 680 B4 a method for creating a wear wall is described. Here, the wear protection layer is introduced as a preform into a casting tool and then cast with a casting material, preferably with a metallic casting material.

Die DE 10 2017 223 602 A1 gibt ein Pumpengehäuse an, in welchem anstatt einer Schleißwand im Pumpengehäuse, keramische Verschleißschutzplatten angeordnet sind, die vor dem Gießen mit metallischem Gussmaterial bereits im Gusswerkzeug verklebt sind. Diese Verschleißschutzplatten sind vorzugsweise aus Siliziumkarbid.The DE 10 2017 223 602 A1 specifies a pump housing in which, instead of a wear wall in the pump housing, ceramic wear protection plates are arranged, which are already glued in the casting tool before casting with metallic casting material. These wear protection plates are preferably made of silicon carbide.

Die DE 4409278A1 und die EP000000750686A1 offenbaren einen Hartguss für Pumpen und Armaturen zur Förderung feststoffhaltiger Medien mit einer Zusammensetzung in Gew.-% Cr = 26 bis 36, Ni ≤ 10, Mo = 2 bis 6, Cu ≤ 3, N ≤ 0,2, Si ≤ 1,5, Mn ≤ 1,5, V = 4 bis 9, C = 1,4 bis 1,9, Rest Eisen und erschmelzungsbedingte Verunreinigungen. Dieser Hartguss zeichnet sich durch eine hohe Korrosionsbeständigkeit in aggressiven Medien bei gleichzeitig hoher Verschleißbeständigkeit aus.The DE 4409278A1 and the EP000000750686A1 disclose a chilled cast iron for pumps and fittings for conveying media containing solids with a composition in % by weight of Cr = 26 to 36, Ni ≤ 10, Mo = 2 to 6, Cu ≤ 3, N ≤ 0.2, Si ≤ 1.5 , Mn ≤ 1.5, V = 4 to 9, C = 1.4 to 1.9, remainder iron and impurities caused by melting. This chilled cast iron is characterized by high corrosion resistance in aggressive media and high wear resistance at the same time.

Die Dokumente US 2007/071907 A1 und US 2019/112933 A1 gehören auch zum technischen Hintergrund der Erfindung.The documents US 2007/071907 A1 and US 2019/112933 A1 also belong to the technical background of the invention.

Die Schleißwände auf Basis von Siliziumkarbid sind im Vergleich zu Bauteilen aus Grauguss deutlich härter und erhöhen die Standzeit. Jedoch sind diese Bauteile in der Fertigung erheblich aufwändiger und teurer.The wear walls based on silicon carbide are significantly harder compared to components made of gray cast iron and increase the service life. However, these components are considerably more complex and expensive to produce.

Aufgabe der Erfindung ist es, eine Kreiselpumpe zur Förderung feststoffhaltiger Medien anzugeben. Die Beschädigung des Pumpengehäuses durch abrasiven Verschleiß soll durch eine Vorrichtung wirksam verringert werden. Darüber hinaus sollte die Pumpe den Wirkungsgrad im Betrieb lange aufrechterhalten können. Weiterhin sollte eine Zerkleinerungskante an der Schleißwand möglichst lange scharfkantig bleiben. Die Kreiselpumpe soll sich durch eine hohe Zuverlässigkeit und eine lange Lebensdauer auszeichnen. Sie soll zudem eine einfache Montage gewährleisten. Weiterhin soll die Kreiselpumpe durch möglichst geringe Herstellungskosten überzeugen.The object of the invention is to provide a centrifugal pump for conveying media containing solids. Damage to the pump housing caused by abrasive wear should be effectively reduced by a device. In addition, the pump should maintain operational efficiency for a long time. Furthermore, a shredding edge on the wear wall should remain sharp for as long as possible. The centrifugal pump should be characterized by high reliability and a long service life. It should also ensure easy installation. Furthermore, the centrifugal pump should impress with the lowest possible manufacturing costs.

Diese Aufgabe wird erfindungsgemäß durch eine Kreiselpumpe zur Förderung feststoffhaltiger Medien mit den Merkmalen des Anspruchs 1 gelöst. Bevorzugte Varianten sind den Unteransprüchen, der Beschreibung und den Figuren zu entnehmen. Erfindungsgemäß umfasst eine Kreiselpumpe zur Förderung feststoffhaltiger Medien ein offenes Laufrad und ein damit zusammenwirkendes Gegenelement, deren Oberflächen zum Schutz vor abrasiver Einwirkung mit einer Kohlenstoffschicht beschichtet ist.This object is achieved according to the invention by a centrifugal pump for conveying media containing solids with the features of claim 1. Preferred variants can be found in the subclaims, the description and the figures. According to the invention, a centrifugal pump for conveying media containing solids comprises an open impeller and a counter-element that interacts with it, the surfaces of which are coated with a carbon layer to protect against abrasive effects.

Erfindungsgemäß ist das Gegenelement als Schleißwand ausgebildet. Vorteilhafterweise ist die Schleißwand im Pumpengehäuse leicht auswechselbar befestigt. Sie schützt das Pumpengehäuse vor Verschleiß.According to the invention, the counter element is designed as a wear wall. Advantageously, the wear wall is fastened in the pump housing so that it can be easily replaced. It protects the pump housing from wear.

Dabei kann die Schleißwand in Form eines hohlen Kegelsegments oder eines trompetentrichterförmigen, hohlen Segments ausgeführt sein. Gemäß der Erfindung ist die Oberfläche der Schleißwand mit einer Kohlenstoffschicht versehen, die der Schleißwand eine extrem hohe Härte verleiht. Dadurch wird die Schleißwand, die einer enormen abrasiven Einwirkung beim Fördern von feststoffhaltigen Medien unterliegt, wirksam vor Verschleiß geschützt.The wear wall can be designed in the form of a hollow cone segment or a trumpet funnel-shaped, hollow segment. According to the invention, the surface of the wear wall is provided with a carbon layer which gives the wear wall an extremely high hardness. This effectively protects the wear wall, which is subject to enormous abrasive effects when conveying media containing solids, from wear.

Feststoffhaltige Medien, insbesondere Abwasser, beinhalten oft langfasrige Elemente und fasrige Zöpfe, die eine Kreiselpumpe verstopfen können. Vorteilhafterweise weist die Schleißwand eine Schneidnut auf, um langfasrige Elemente und zopfähnliche Verunreinigungen im Fördermedium in kleine Stücke zu zerteilen. Idealerweise wird hierdurch eine Verstopfung der Kreiselpumpe wirksam vermieden.Media containing solids, especially wastewater, often contain long-fiber elements and fibrous braids that can clog a centrifugal pump. The wear wall advantageously has a cutting groove in order to cut long-fiber elements and braid-like contaminants in the conveying medium into small pieces. Ideally, this effectively prevents the centrifugal pump from becoming blocked.

Vorzugsweise ist die Schneidnut der Schleißwand mit Kohlenstoff beschichtet. Dadurch wird der Schneidkante der Schneidnut eine besondere Härte und eine verschleißbeständige Schärfe verliehen, die auch der abrasiven Wirkung kleiner Feststoffteilchen langfristig widersteht.The cutting groove of the wear wall is preferably coated with carbon. This gives the cutting edge of the cutting groove a special hardness and a wear-resistant sharpness, which also resists the abrasive effects of small solid particles in the long term.

In einer vorteilhaften Variante der Erfindung verläuft die Schneidnut spiralförmig von innen nach außen. Sie schließt in ihrem Verlauf dadurch einen Winkel von mehr als 150 °, vorzugsweise mehr als 170 °, insbesondere mehr als 190 ° und/oder weniger als 320 °, vorzugsweise weniger als 300 °, insbesondere weniger als 280 ° ein. Die Schneidnut ist derart gestaltet, dass sie eine Tiefe von mehr als 0,5 mm, vorzugsweise mehr als 1,0 mm, insbesondere mehr als 1,5 mm und/oder weniger als 5,0 mm, vorzugsweise weniger als 4 mm, insbesondere weniger als 3,0 mm aufweist. Des Weiteren ist die Breite der Schneidnut an den Schleißwandinnendurchmesser der Saugseite angepasst, so dass sie mehr als 5 %, vorzugsweise mehr als 10 %, insbesondere mehr als 15 % und/oder weniger als 40 %, vorzugsweise weniger als 35 %, insbesondere weniger als 30 % des Innendurchmessers der Saugseite beträgt. Aufgrund der beschriebenen Form und der Beschichtung mit Kohlenstoff ist die Schneidnut besonders gut geeignet, langfasrige sowie zopfförmige Element im Fördermedium zu zerkleinern und die Kreiselpumpe vor einer Verstopfung zu schützen.In an advantageous variant of the invention, the cutting groove runs spirally from the inside to the outside. In its course it therefore encloses an angle of more than 150°, preferably more than 170°, in particular more than 190° and/or less than 320°, preferably less than 300°, in particular less than 280°. The cutting groove is designed such that it has a depth of more than 0.5 mm, preferably more than 1.0 mm, in particular more than 1.5 mm and/or less than 5.0 mm, preferably less than 4 mm, in particular less than 3.0 mm. Furthermore, the width of the cutting groove is adapted to the wear wall inner diameter of the suction side, so that it is more than 5%, preferably more than 10%, in particular more than 15% and / or less than 40%, preferably less than 35%, in particular less than 30% of the inner diameter of the suction side. Due to the shape described and the coating with carbon, the cutting groove is particularly suitable for shredding long-fiber and plait-shaped elements in the pumped medium and for protecting the centrifugal pump from clogging.

Gemäß der Erfindung wirkt das offene Laufrad der Pumpe mit der Schleißwand zusammen, so dass ein möglichst geringer Spalt zwischen Schleißwand und offenem Laufrad entsteht, der Leistungsspalt genannt wird. Dieser Spalt wird so gering wie möglich bemessen, um unerwünschte Ströme von der Druckseite auf die Saugseite der Pumpe zu vermeiden. Sowohl das Laufrad als auch die Schleißwand sind mit einer Kohlenstoffschicht beschichtet, wodurch die Oberflächen der Bauteile eine extreme Härte erhalten. Dadurch sind die Bauteile auch gegen ein gegenseitiges Berühren oder Anstreifen geschützt, was aufgrund der geringen Spaltweite durchaus auftreten könnte.According to the invention, the open impeller of the pump interacts with the wear wall, so that the smallest possible gap is created between the wear wall and the open impeller, which is called the power gap. This gap is designed to be as small as possible in order to avoid unwanted flows from the pressure side to the suction side of the pump. Both the impeller and the wear wall are coated with a carbon layer, which gives the surfaces of the components extreme hardness. This also protects the components from touching or brushing against each other, which could certainly occur due to the small gap width.

Idealerweise wird die Schleißwand aus einem metallischen Werkstoff, vorzugsweise einem Gusswerkstoff und/oder nichtrostenden Stahlwerkstoff, gefertigt. Dadurch sind der geometrischen Gestaltung der Schleißwand nur geringe Grenzen gesetzt und gleichzeitig zeichnen sich die meisten metallischen Werkstoffe durch eine höhere Duktilität im Vergleich zu keramischen Werkstoffen sowie eine kostengünstigere Realisierung aus.Ideally, the wear wall is made of a metallic material, preferably a cast material and/or stainless steel material. As a result, there are only small limits to the geometric design of the wear wall At the same time, most metallic materials are characterized by higher ductility compared to ceramic materials and a more cost-effective implementation.

Insbesondere die leistungsspaltbildende Fläche und im Besonderen die Schneidnut der Schleißwand sind gemäß der Erfindung mit einer Kohlenstoffschicht versehen. Gerade die Schneidnut ist durch die fasrige Belagsbildung und das Kollidieren von Feststoffpartikel einer abrasiven Belastung ausgesetzt und durch die Kohlenstoffschicht besonders geschützt.In particular, the surface forming the power gap and in particular the cutting groove of the wear wall are provided with a carbon layer according to the invention. The cutting groove in particular is exposed to abrasive stress due to the formation of fibrous deposits and the collision of solid particles and is particularly protected by the carbon layer.

In einer Kreiselpumpe zur Förderung von feststoffhaltigen Medien wirkt die Schleißwand mit einem offenen Laufrad zusammen. Ein solches offenes Laufrad kann erfindungsgemäß ein offenes diagonales Einschaufelrad oder ein offenes Kanalrad sein. Besonders vorteilhaft ist die Beschichtung des offenen Laufrades mit Kohlenstoff, wodurch ein wirksamer Schutz vor abrasiven Verschleiß entsteht und eine möglichst lange Betriebszeit bei konstantem Wirkungsgrad der Pumpe ermöglicht wird.In a centrifugal pump for pumping media containing solids, the wear wall works together with an open impeller. According to the invention, such an open impeller can be an open diagonal single-blade wheel or an open channel wheel. Coating the open impeller with carbon is particularly advantageous, which provides effective protection against abrasive wear and enables the longest possible operating time with constant pump efficiency.

Gemäß der Erfindung wird zur Förderung feststoffhaltiger Medien eine Kreiselpumpe mit einem offenen diagonalen Einschaufelrad eingesetzt, welches mit einer Kohlenstoffschicht versehen ist. Bei diesem Laufrad verläuft die Flusslinie der Schaufel schräg nach außen. Vorteilhafterweise kann damit ungereinigtes, feststoffbeladenes und ausgasendes Abwasser sowie Medien mit höherer Viskosität gefördert werden.According to the invention, a centrifugal pump with an open diagonal single-blade wheel, which is provided with a carbon layer, is used to convey media containing solids. With this impeller, the flow line of the blade runs diagonally outwards. This can advantageously be used to convey uncleaned, solids-laden and outgassing wastewater as well as media with higher viscosity.

Unter den Kohlenstoffschichten werden Schichten verstanden, in denen Kohlenstoff der überwiegende Bestandteil ist. Die Kohlenstoffschicht kann beispielsweise mit einer PVD- (engl. Physical Vapor Deposition), einer physikalischen Gasphasenabscheidung etwa durch Verdampfen oder Sputtern) oder einem CVD- (engl. Chemical Vapor Deposition; Chemische Gasphasenabscheidung) Verfahren aufgebracht werden.Carbon layers are layers in which carbon is the predominant component. The carbon layer can be applied, for example, using a PVD (Physical Vapor Deposition), a physical vapor deposition such as by evaporation or sputtering) or a CVD (Chemical Vapor Deposition) process.

Erfindungsgemäß handelt es sich um eine tetraedrische wasserstofffreie amorphe Kohlenstoffschicht, die auch als ta-C Schicht be-zeichnet wird. Die dem Kristallgitter von Graphit zugehörigen Atombindungen (insgesamt jeweils 3) kennzeichnet man mit der Bezeichnung "sp2". Dabei liegt eine sp2-Hybridisierung vor.According to the invention, it is a tetrahedral hydrogen-free amorphous carbon layer, also known as a ta-C layer referred to as. The atomic bonds belonging to the crystal lattice of graphite (3 in total) are identified with the designation “sp2”. This is an sp2 hybridization.

Bei einer Diamantschicht bildet jedes Kohlenstoffatom mit vier benachbarten Atomen eine tetraederförmige Anordnung. Bei dieser räumlichen Anordnung sind alle Atomabstände gleich gering. Es wirken daher sehr hohe Bindungskräfte zwischen den Atomen, und zwar in allen Raumrichtungen. Daraus resultieren die hohe Festigkeit und die extreme Härte des Diamanten. Die dem Kristallgitter von Diamanten zugehörigen Atombindungen, insgesamt jeweils vier, kennzeichnet man mit der Bezeichnung "sp3". Somit liegt eine sp3-Hybridisierung vor.In a diamond layer, each carbon atom forms a tetrahedral arrangement with four neighboring atoms. In this spatial arrangement, all atomic distances are equally small. There are therefore very high binding forces between the atoms, in all spatial directions. This results in the high strength and extreme hardness of the diamond. The atomic bonds belonging to the crystal lattice of diamonds, four in total, are identified with the designation "sp3". This means that sp3 hybridization is present.

Bei einer besonders günstigen Variante der Erfindung besteht die Kohlenstoffschicht aus einer Mischung von sp3- und sp2-hybridisiertem Kohlenstoff. Diese Schicht ist durch eine amorphe Struktur gekennzeichnet. In dieses Kohlenstoffnetzwerk können auch Fremdatome wie Wasserstoff, Silizium, Wolfram oder Fluor eingebaut sein.In a particularly favorable variant of the invention, the carbon layer consists of a mixture of sp3 and sp2 hybridized carbon. This layer is characterized by an amorphous structure. Foreign atoms such as hydrogen, silicon, tungsten or fluorine can also be incorporated into this carbon network.

Die erfindungsgemäße Anordnung einer Kohlenstoffschicht auf einer Schleißwand und einem offenen Laufrad führt zu einer erheblichen Reduzierung des abrasiven Abtrags.The arrangement according to the invention of a carbon layer on a wear wall and an open impeller leads to a significant reduction in abrasive removal.

Durch die Anordnung einer Kohlenstoffschicht auf einer Schleißwand wird eine glatte axiale Oberfläche mit Antihafteigenschaften geschaffen, ohne dass eine aufwendige mechanische Nachbearbeitung des Laufrads erforderlich ist. Des Weiteren können mehrere Schleißwände in einem Beschichtungsreaktor, der vorzugsweise als Vakuumkammer ausgeführt ist, eingebracht werden, wo bei mäßiger thermischer Belastung, die ta-C Beschichtung aufgebracht wird. Somit zeichnet sich die erfindungsgemäße Kreiselpumpe mit einer Schleißwand durch verhältnismäßig geringe Herstellungskosten aus.By arranging a carbon layer on a wear wall, a smooth axial surface with non-stick properties is created without the need for complex mechanical post-processing of the impeller. Furthermore, several wear walls can be introduced into a coating reactor, which is preferably designed as a vacuum chamber, where the ta-C coating is applied under moderate thermal load. The centrifugal pump according to the invention with a wear wall is therefore characterized by relatively low manufacturing costs.

Erfindungsgemäß wird die Kohlenstoffschicht als Be-schichtung auf eine Schleißwand aufgebracht. Die Dicke der Schicht beträgt vorteilhafterweise mehr als 0,5 µm, vorzugsweise mehr als 1,0 µm, insbesondere mehr als 1,5 µm. Weiterhin erweist es sich als günstig, wenn die Kohlenstoffschicht weniger als 18 µm, vorzugsweise weniger als 16 µm, insbesondere weniger als 14 µm beträgt.According to the invention, the carbon layer is applied as a coating to a wear wall. The thickness of the layer is advantageously more than 0.5 μm, preferably more than 1.0 μm, in particular more than 1.5µm. Furthermore, it proves to be advantageous if the carbon layer is less than 18 μm, preferably less than 16 μm, in particular less than 14 μm.

Für den Schutz gegen Partikelverschleiß und Anlaufen ist eine Schichtdicke zwischen 4 und 12 µm anzustreben.To protect against particle wear and tarnishing, aim for a layer thickness between 4 and 12 µm.

Idealerweise weist die Beschichtung aus Kohlenstoff eine äußerst glatte Oberfläche mit Antihafteigenschaften auf, bei der der Mittenrauheitswert Ra der Kohlenstoffschicht weniger als 0,7 µm, vorzugsweise weniger als 0,5 µm, insbesondere weniger als 0,3 µm beträgt.Ideally, the carbon coating has an extremely smooth surface with non-stick properties, in which the average roughness value R a of the carbon layer is less than 0.7 µm, preferably less than 0.5 µm, in particular less than 0.3 µm.

Die ta-C Beschichtung weist einen sehr geringen Reibbeiwert bei gleichzeitig sehr guter chemischer Beständigkeit auf. Die Härte der Beschichtung kommt der Härte von Diamanten sehr nahe, wobei die Härte vorzugsweise mehr als 20 GPa, vorzugsweise mehr als 30 GPa, insbesondere mehr als 40 GPa und weniger als 120 GPa, vorzugsweise weniger als 110 GPa, insbesondere weniger als 100 GPa beträgt.The ta-C coating has a very low coefficient of friction and at the same time very good chemical resistance. The hardness of the coating is very close to the hardness of diamonds, the hardness preferably being more than 20 GPa, preferably more than 30 GPa, in particular more than 40 GPa and less than 120 GPa, preferably less than 110 GPa, in particular less than 100 GPa .

Mit durchschnittlich 40 bis 75 GPa sind ta-C Beschichtungen härter als a-C:H Schichten. Zudem enthält ta-C keinen Wasserstoff. Deshalb ist davon auszugehen, dass ta-C im Kontakt mit Wasser (bei Temperaturen oberhalb 80 °C) beständiger ist als a-C:H. Im Kontakt mit anderen - insbesondere polaren - Flüssigkeiten, die Moleküle enthalten, in denen Wasserstoff gebunden ist, könnte ta-C ebenfalls besser beständig sein als a-C:H.With an average of 40 to 75 GPa, ta-C coatings are harder than a-C:H coatings. In addition, ta-C does not contain any hydrogen. It can therefore be assumed that ta-C is more stable in contact with water (at temperatures above 80 °C) than a-C:H. In contact with other - especially polar - liquids that contain molecules in which hydrogen is bonded, ta-C could also be more stable than a-C:H.

Vorzugsweise wird die Kohlenstoffschicht nicht unmittelbar auf die Schleißwand aufgebracht, sondern es wird zunächst eine Haftvermittlerschicht vorgesehen Diese besteht bevorzugt aus einem Werkstoff, der sowohl gut an Stahl haftet als auch eine Kohlenstoffdiffusion verhindert, z. B. durch die Bildung stabiler Carbide. Als Haftvermittlungsschichten, die diese Anforderungen erfüllen, kommen passenderweise dünne Schichten aus Chrom, Titan oder Silizium zum Einsatz. Insbesondere haben sich Chrom- und Wolframcarbid als Haftvermittler bewährt.Preferably, the carbon layer is not applied directly to the wear wall, but rather an adhesion promoter layer is first provided. This preferably consists of a material that both adheres well to steel and prevents carbon diffusion, e.g. B. through the formation of stable carbides. Thin layers of chromium, titanium or silicon are appropriately used as adhesion-promoting layers that meet these requirements. Chromium and tungsten carbide have proven particularly useful as adhesion promoters.

Bei einer vorteilhaften Variante der Erfindung weist die Beschichtung eine Haftvermittler-schicht auf, die vorzugsweise einen Chromwerkstoff beinhaltet. Vorzugsweise besteht die Haftvermittlerschicht zu mehr als 30 Gew.-%, vorzugsweise mehr als 60 Gew.%, insbesondere mehr als 90 Gew.-% aus Chrom.In an advantageous variant of the invention, the coating has an adhesion promoter layer, which preferably contains a chromium material. The adhesion promoter layer preferably consists of more than 30% by weight, preferably more than 60% by weight, in particular more than 90% by weight of chromium.

Bei der erfindungsgemäßen ta-C Beschichtung handelt es sich um eine einfache, schnell realisierbare und wirtschaftliche Beschichtung für Schleißwände in Kreiselpumpen. Die erfindungsgemäße Beschichtung weist neben einer sehr großen Härte auch hervorragende Gleiteigenschaften und eine gute chemische Beständigkeit auf.The ta-C coating according to the invention is a simple, quickly realizable and economical coating for wear walls in centrifugal pumps. In addition to very high hardness, the coating according to the invention also has excellent sliding properties and good chemical resistance.

Zudem ermöglicht die Erfindung auch eine Beschichtung von Schleißwandgeometrien mit speziellen Abmessungen. Darüber hinaus lassen sich Schleißwandgeometrien realisieren, die zuvor aus keramischen Werkstoffen fertigungsbedingt schwer realisierbar waren.In addition, the invention also makes it possible to coat wear wall geometries with special dimensions. In addition, wear wall geometries can be realized that were previously difficult to achieve from ceramic materials due to production reasons.

Der Vorteil der höheren Härte durch die ta-C Beschichtung liegt darin begründet, dass kleine und große Feststoffpartikel, die oft in den feststoffhaltigen Medien enthalten sind, nun stark vermindert abrasiv auf die Schleißwand wirken können. Durch die Strömung wirken diese Feststoffteilchen normalerweise wie ein Schleifmittel. Laufräder und Schleißwände, die mit ta-C beschichtet sind, verfügen über eine äußerst harte Schutzschicht gegen Abrasion, wodurch deren Einsatzzeit in der Förderung feststoffhaltiger Medien deutlich erhöht ist.The advantage of the higher hardness due to the ta-C coating is that small and large solid particles, which are often contained in media containing solids, can now have a greatly reduced abrasive effect on the wear wall. Due to the flow, these solid particles normally act like an abrasive. Impellers and wear walls that are coated with ta-C have an extremely hard protective layer against abrasion, which significantly increases their service life when conveying media containing solids.

Vorzugsweise können zur Beschichtung PECVD/PACVD-Verfahren eingesetzt. Dabei erfolgt eine Plasmaanregung der Gasphase durch die Einkopplung von gepulster Gleich-spannung ("pulsed DC"), mittelfrequenter (KHz-Bereich) oder hochfrequenter (MHz-Bereich) Leistung. Aus Gründen einer maximierten Prozessvariabilität bei unterschiedlichen Werkstückgeometrien und Beladungsdichten hat sich zudem die Einkopplung von gepulster Gleichspannung bewährt.PECVD/PACVD processes can preferably be used for coating. Plasma excitation of the gas phase occurs through the coupling of pulsed direct voltage (“pulsed DC”), medium-frequency (KHz range) or high-frequency (MHz range) power. In order to maximize process variability with different workpiece geometries and load densities, the coupling of pulsed direct voltage has also proven successful.

Erfindungsgemäß werden zur Beschichtung PVD Verfahren eingesetzt. Diese Verfahren sind besonders einfach und weisen eine niedrige Prozesstemperatur auf. Diese Technologie führt zu Schichten, in die je nach Bedarf auch Fremdatome eingebaut sein können. Die Prozessführung erfolgt vorzugsweise so, dass Gefüge- und Dimensionsänderungen der zu beschichtenden Werkstoffe (metallisch, Grauguss, etc.) ausgeschlossen sind.According to the invention, PVD processes are used for coating. These processes are particularly simple and have a low process temperature. This technology leads to layers in which foreign atoms can also be incorporated, if necessary. The process is preferably carried out in such a way that structural and dimensional changes in the materials to be coated (metallic, gray cast iron, etc.) are excluded.

Gegenüber einer CVD-Diamantschicht hat die ta-C Beschichtung den Vorteil, dass die Beschichtungstemperatur für CVD-Diamantschichten 600 bis 1000 °C beträgt und für amorphe Kohlenstoffschichten wie ta-C deutlich unter 500 °C liegt. Dies ist insbesondere für das Beschichten metallischer Werkstoffe von hoher technischer Relevanz. Die Herstellung von PVD-Diamantschichten ist nicht möglich.Compared to a CVD diamond layer, the ta-C coating has the advantage that the coating temperature for CVD diamond layers is 600 to 1000 °C and for amorphous carbon layers such as ta-C it is well below 500 °C. This is of high technical relevance, particularly for the coating of metallic materials. The production of PVD diamond layers is not possible.

Weitere Merkmale und Vorteile der Erfindung ergeben sich aus der Beschreibung von Ausführungsbeispielen anhand der Zeichnungen und aus den Zeichnungen selbst.Further features and advantages of the invention result from the description of exemplary embodiments based on the drawings and from the drawings themselves.

Dabei zeigt:

Fig. 1
Schnittdarstellung einer Kreiselpumpe zur Förderung feststoffhaltiger Medien mit einem offenen diagonalen Einschaufelrad,
Fig. 2
Schnittdarstellung einer Kreiselpumpe zur Förderung feststoffhaltiger Medien mit einem offenen Laufrad,
Fig. 3
Detailschnitt eines offenen Laufrads mit Schleißwand,
Fig. 4
Frontansicht der Schleißwand.
This shows:
Fig. 1
Sectional view of a centrifugal pump for pumping media containing solids with an open diagonal single blade wheel,
Fig. 2
Sectional view of a centrifugal pump for pumping media containing solids with an open impeller,
Fig. 3
Detailed section of an open impeller with wear wall,
Fig. 4
Front view of the wear wall.

Fig. 1 zeigt eine Schnittdarstellung einer Kreiselpumpe zur Förderung feststoffhaltiger Medien. Bei diesem Ausführungsbeispiel handelt es sich um eine horizontal aufgestellte Spiralgehäusepumpe mit einem diagonal offenen Einschaufelrad 4 und einem damit zusammenwirkenden Gegenelement 2. Das Gegenelement 2 ist in diesem Ausführungsbeispiel als Schleißwand ausgestaltet. Über den Saugmund 1 strömt das feststoffhaltige Medium in die Pumpe ein, wird von dem offenen diagonalen Einschaufelrad 4, welches drehfest mit der Welle 6 verbunden ist, mit Bewegungsenergie beaufschlagt und verlässt das Pumpengehäuse 3 über den Druckstutzen 5. Die Welle 6 ist durch das Kugellager 7 und die Gleitringdichtung 9 drehbar gelagert. Der Lagerträgerdeckel 10 verschließt den Pumpenraum in Richtung Antrieb. Die Schaufelkanten 13 des diagonal offenen Einschaufelrades 4 bilden mit der Schleißwand einen Spalt, den sogenannten Leistungsspalt. Erfindungsgemäß ist die Schleißwand mit einer Kohlenstoffschicht, nämlich mit einer amorphen Kohlenstoffschicht, nämlich mit ta-C, beschichtet. Somit wird ein besonders idealer Schutz vor abrasiven Verschleiß, der bei der Förderung feststoffhaltiger Medien zwangsläufig auf die Schleißwand einwirkt, erzielt. Die Schleißwand weist eine von innen nach außen verlaufende, spiralförmige Schneidnut 12 auf. Fig. 1 shows a sectional view of a centrifugal pump for pumping media containing solids. This exemplary embodiment is a horizontally positioned volute casing pump with a diagonally open single-blade wheel 4 and a counter-element 2 that interacts with it. In this exemplary embodiment, the counter-element 2 is designed as a wear wall. The solid-containing medium flows into the pump via the suction mouth 1 and is fed by the open diagonal single-blade wheel 4, which is rotatably connected to the shaft 6, is acted upon by kinetic energy and leaves the pump housing 3 via the pressure port 5. The shaft 6 is rotatably mounted by the ball bearing 7 and the mechanical seal 9. The bearing carrier cover 10 closes the pump chamber in the direction of the drive. The blade edges 13 of the diagonally open single blade wheel 4 form a gap with the wear wall, the so-called power gap. According to the invention, the wear wall is coated with a carbon layer, namely an amorphous carbon layer, namely ta-C. This provides particularly ideal protection against abrasive wear, which inevitably affects the wear wall when conveying media containing solids. The wear wall has a spiral-shaped cutting groove 12 running from the inside to the outside.

Fig. 2 zeigt eine Schnittdarstellung einer Kreiselpumpe zur Förderung feststoffhaltiger Medien. Bei diesem Ausführungsbeispiel handelt es sich um eine Dickstoffpumpe, bei der ein offenes Laufrad 4 mit einem Gegenelement 2 zusammenwirkt. Das Gegenelement 2 ist in diesem Ausführungsbeispiel als Schleißwand ausgestaltet. Die Schleißwand wird zum Schutz des Pumpengehäuses 3 gegen Verschleiß verwendet und ist leicht auswechselbar. Des Weiteren ist die Schleißwand mit einer Kohlenstoffschicht versehen, um besonders verschleißbeständig gegen die abrasive Wirkung des feststoffhaltigen Mediums zu sein. Das feststoffhaltige Medium wird über den Saugmund 1 angesaugt und durch das offene Laufrad 4, welches mit der Welle 6 drehfest verbunden ist und durch die Lagerung 7 drehbar gelagert ist, beschleunigt. Das feststoffhaltige Medium verlässt das Pumpengehäuse 3 über den Druckstutzen 5. Fig. 2 shows a sectional view of a centrifugal pump for pumping media containing solids. This exemplary embodiment is a thick matter pump in which an open impeller 4 interacts with a counter element 2. The counter element 2 is designed as a wear wall in this exemplary embodiment. The wear wall is used to protect the pump housing 3 against wear and is easily replaceable. Furthermore, the wear wall is provided with a carbon layer in order to be particularly wear-resistant against the abrasive effect of the medium containing solids. The solid-containing medium is sucked in via the suction mouth 1 and accelerated by the open impeller 4, which is connected to the shaft 6 in a rotationally fixed manner and is rotatably mounted by the bearing 7. The medium containing solids leaves the pump housing 3 via the pressure port 5.

Fig. 3 zeigt einen Detailschnitt des Saugmundbereiches. Das Gegenelement 2 ist in diesem Anwendungsbeispiel als Schleißwand ausgeführt und wirkt mit dem offenen Laufrad 4 zusammen. Die Schaufelflanken des offenen Laufrads 4 erstrecken sich ausgehend von der Nabe radial in einem rückwärts gekrümmten Verlauf nach außen. Die Schaufelkanten 13 bilden mit der Schleißwand einen Spalt. Erfindungsgemäß ist die Schleißwand mit einer Kohlenstoffschicht, nämlich mit ta-C, beschichtet. Dadurch wird ein wirksamer Schutz gegen abrasiven Verschleiß sowie gegen Anlaufen der beiden Bauteile gewährleistet. Fig. 3 shows a detailed section of the suction mouth area. In this application example, the counter element 2 is designed as a wear wall and interacts with the open impeller 4. The blade flanks of the open impeller 4 extend radially outwards from the hub in a backwards curved course. The blade edges 13 form a gap with the wear wall. According to the invention, the wear wall is coated with a carbon layer, namely with ta-C. This ensures effective protection against abrasive wear and tarnishing of the two components.

Fig. 4 zeigt eine Frontansicht des Gegenelements 2, welches als trompetentrichterförmige, hohle Schleißwand ausgebildet ist. Die Schleißwand weist eine von innen nach außen verlaufende, spiralförmige Schneidnut 12 auf. In ihrem spiralförmigen Verlauf schließt die Schneidnut 12 einen Winkel von mehr als 150 °, vorzugsweise mehr als 170 °, insbesondere mehr als 190 ° und/oder weniger als 320 °, vorzugsweise weniger als 300 °, insbesondere weniger als 280 ° ein. Die Tiefe der Schneidnut 12 beträgt mehr als 0,5 mm, vorzugsweise mehr als 1,0 mm, insbesondere mehr als 1,5 mm und/oder weniger als 5,0 mm, vorzugsweise weniger als 4 mm, insbesondere weniger als 3,0 mm. Dabei umfasst die Schneidnut 12 eine Breite von mehr als 5 %, vorzugsweise mehr als 10 %, insbesondere mehr als 15 % und/oder weniger als 40 %, vorzugsweise weniger als 35 %, insbesondere weniger als 30 % des Innendurchmessers der Schleißwand auf der Saugseite. Erfindungsgemäß ist die Schleißwand und insbesondere die Schneidnut 12 mit einer Kohlenstoffschicht, nämlich mit ta-C, beschichtet. Fig. 4 shows a front view of the counter element 2, which is designed as a trumpet funnel-shaped, hollow wear wall. The wear wall has a spiral-shaped cutting groove 12 running from the inside to the outside. In its spiral course, the cutting groove 12 encloses an angle of more than 150°, preferably more than 170°, in particular more than 190° and/or less than 320°, preferably less than 300°, in particular less than 280°. The depth of the cutting groove 12 is more than 0.5 mm, preferably more than 1.0 mm, in particular more than 1.5 mm and/or less than 5.0 mm, preferably less than 4 mm, in particular less than 3.0 mm. The cutting groove 12 has a width of more than 5%, preferably more than 10%, in particular more than 15% and/or less than 40%, preferably less than 35%, in particular less than 30% of the inside diameter of the wear wall on the suction side . According to the invention, the wear wall and in particular the cutting groove 12 is coated with a carbon layer, namely with ta-C.

Dadurch wird die Oberfläche der Schleißwand besonders hart und verschleißbeständig gegenüber der abrasiven Einwirkung von feststoffhaltigen Medien. Im Besonderen bleibt die Schneidnut durch die mit ta-C beschichtete Kante extrem scharf und kann dadurch langfasrige bzw. zopfförmige Elemente, die im Fördermedium enthalten sein können, in kleine Stücke zerteilen. Hierdurch wird eine Verstopfung der Kreiselpumpe wirksam vermieden.This makes the surface of the wear wall particularly hard and wear-resistant to the abrasive effects of media containing solids. In particular, the cutting groove remains extremely sharp due to the edge coated with ta-C and can therefore cut long-fiber or pigtail-shaped elements that may be contained in the pumped medium into small pieces. This effectively prevents the centrifugal pump from becoming blocked.

Claims (10)

  1. Centrifugal pump for conveying solids-containing media, comprising an open impeller (4) and a counterpart element (2) which cooperates therewith, wherein the counterpart element (2) is configured as a wearing wall, characterized
    in that the surface of the counterpart element (2) is at least partially provided with a carbon layer, wherein it is a tetrahedral hydrogen-free amorphous carbon layer, wherein PVD methods are used for coating purposes.
  2. Centrifugal pump according to Claim 1, characterized in that the counterpart element (2) is configured in the form of a hollow cone segment.
  3. Centrifugal pump according to Claim 1 or 2, characterized in that the counterpart element (2) is configured as a trumpet bell-shaped hollow segment.
  4. Centrifugal pump according to one of Claims 1 to 3, characterized in that the counterpart element (2) comprises a cutting groove (12).
  5. Centrifugal pump according to one of Claims 1 to 4, characterized in that the cutting groove (12) runs in a spiral-shaped manner from the inside to the outside and encloses an angle of more than 150°, preferably more than 170°, in particular more than 190°, and/or less than 320°, preferably less than 300°, in particular less than 280°.
  6. Centrifugal pump according to one of Claims 1 to 5, characterized in that the cutting groove (12) has a depth of more than 0.5 mm, preferably more than 1 mm, in particular more than 1.5 mm, and/or less than 5.0 mm, preferably less than 4 mm, in particular less than 3.0 mm.
  7. Centrifugal pump according to one of Claims 1 to 6, characterized in that the width of the cutting groove (12) is more than 5%, preferably more than 10%, in particular more than 15%, and/or less than 40%, preferably less than 35%, in particular less than 30%, of the inner diameter of the suction side.
  8. Centrifugal pump according to one of Claims 1 to 7, characterized in that the counterpart element (2) is manufactured from a metallic material, preferably a cast material and/or stainless steel material.
  9. Centrifugal pump according to one of Claims 1 to 8, characterized in that the thickness of the carbon layer is more than 0.5 µm, preferably more than 1.0 µm, in particular more than 1.5 µm, and/or less than 18 µm, preferably less than 16 µm, in particular less than 14 µm.
  10. Centrifugal pump according to one of Claims 1 to 9, characterized in that the surface hardness of that surface of the counterpart element (2) which is coated with carbon layer is more than 20 GPa, preferably more than 30 GPa, in particular more than 40 GPa, and/or less than 120 GPa, preferably less than 110 GPa, in particular less than 100 GPa.
EP21181101.3A 2020-06-26 2021-06-23 Centrifugal pump for conveying fluids containing solids Active EP3929444B1 (en)

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JP2017180179A (en) * 2016-03-29 2017-10-05 三菱重工コンプレッサ株式会社 Impeller having erosion resistance at surface part comprising composite material and manufacturing method of impeller
US20190112933A1 (en) * 2017-10-16 2019-04-18 Onesubsea Ip Uk Limited Erosion resistant blades for compressors

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EP3929444A1 (en) 2021-12-29
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