EP3540232A1 - Kreiselpumpe mit ausgleichsmittel, ausgleichsscheibe und verfahren zum ausgleichen von axialkräften der kreiselpumpe - Google Patents

Kreiselpumpe mit ausgleichsmittel, ausgleichsscheibe und verfahren zum ausgleichen von axialkräften der kreiselpumpe Download PDF

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Publication number
EP3540232A1
EP3540232A1 EP18161862.0A EP18161862A EP3540232A1 EP 3540232 A1 EP3540232 A1 EP 3540232A1 EP 18161862 A EP18161862 A EP 18161862A EP 3540232 A1 EP3540232 A1 EP 3540232A1
Authority
EP
European Patent Office
Prior art keywords
balancing
disc
centrifugal pump
permanent magnets
pump
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP18161862.0A
Other languages
English (en)
French (fr)
Inventor
Atte Posa
Timo Päivinen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sulzer Management AG
Original Assignee
Sulzer Management AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sulzer Management AG filed Critical Sulzer Management AG
Priority to EP18161862.0A priority Critical patent/EP3540232A1/de
Publication of EP3540232A1 publication Critical patent/EP3540232A1/de
Withdrawn legal-status Critical Current

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    • 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
    • F04D29/04—Shafts or bearings, or assemblies thereof
    • F04D29/041—Axial thrust balancing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D1/00—Radial-flow pumps, e.g. centrifugal pumps; Helico-centrifugal pumps
    • F04D1/06—Multi-stage 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
    • F04D29/04—Shafts or bearings, or assemblies thereof
    • F04D29/041—Axial thrust balancing
    • F04D29/0416—Axial thrust balancing balancing pistons
    • 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
    • F05D2250/00—Geometry
    • F05D2250/20—Three-dimensional
    • F05D2250/29—Three-dimensional machined; miscellaneous
    • F05D2250/294—Three-dimensional machined; miscellaneous grooved

Definitions

  • the present invention relates to a centrifugal pump with balancing means in accordance with the preamble of claim 1, a balancing disc for a centrifugal pump in accordance with the preamble of claim 9 and a method of balancing axial forces of the centrifugal pump in accordance with the preamble of claim 12. More specifically the present invention relates to single- or multi-stage centrifugal pumps having novel disc-type means for balancing the axial forces of the pump.
  • the means for balancing axial forces of centrifugal pumps are normally in use in multistage pumps, which have a high pressure head, and are provided with several subsequent centrifugal impellers on the same shaft.
  • An axial force is generated while an impeller, or a plurality of impellers, draws liquid axially in the pump and discharges the liquid radially from the pump.
  • the axial force tends to draw the impeller/s towards the pump inlet, whereby the bearings of the pump are subjected to a considerable axial force when keeping the pack of impellers in place.
  • means for balancing the axial force have been developed.
  • One is a so-called drum-type balancing means, and the other a disc-type balancing means.
  • hybrid balancing means are known, i.e. one comprising both a balancing drum and a balancing disc.
  • the balancing means are positioned on the pump shaft behind the last impeller when viewed from the pump inlet towards the pump outlet.
  • the disc-type balancing means may be considered as the preferred choice of the two basic balancing means as it adjusts its operation automatically, i.e. slight wear does not affect the operation of the balancing means at all, whereas even the slightest wear of the drum-type balancing means results in a change in the balancing capability of the balancing means. Furthermore, the disc-type balancing means occupies also less space in the axial direction than drum-type balancing means.
  • the disc-type balancing means is formed of a balancing disc fastened on the shaft of the pump and a stationary counter member.
  • the counter member is arranged to extend from the pump volute or casing radially inwardly between the impeller or one of the impellers and the balancing disc.
  • the stationary counter member is the rear wall of the last pumping stage of the centrifugal pump.
  • the balancing disc and the counter member leave a radially extending cavity, so called balancing cavity, therebetween.
  • Either the balancing disc or the counter member or both have an annular axial extension, sometimes a separate circular ring, at the outer periphery of the balancing disc for reducing the axial dimension of the cavity between the balancing disc and the counter member in order to limit the leakage flow of the pressurized liquid from the pump.
  • the balancing means i.e. balancing disc, its counter member and the balancing cavity, may also be located in front of the impeller/s when viewed from the direction of the inlet opening of the pump. In such a case it is required that the pressurized liquid is taken to the balancing cavity along a separate flow passage.
  • the disc-type balancing means functions such that a part of the liquid pressurized by the impeller or the pack of impellers enters, as is well known in centrifugal pumps, to the cavity behind the impeller of the last pumping stage, and finds its way via the gap between the shaft of the pump or the shaft sleeve of the balancing disc and the stationary counter member to a radially extending balancing cavity between the balancing disc and the stationary counter member.
  • the axial thrust loading the bearings of the pump is the difference of the two axial forces having opposite directions.
  • the two opposite forces may be equalized resulting in zero thrust, whereby the shaft bearings may be changed into slide bearings that are not able to carry any axial load.
  • the pressurized liquid flows radially outwardly in the balancing cavity between the balancing disc and its counter member, the liquid reaches the annular extension or ring and enters the annular gap between the annular extension or ring and its counter surface.
  • the annular gap is very thin, i.e. its axial depth is very small, and the pressure difference radially over the ring is relatively high (depending mostly on the head of the pump), the flow velocity of the liquid in the thin gap is high. Due to the high velocity of the liquid the pressure in the gap between the balancing disc and the counter member is low resulting in that in the area of high flow velocity, i.e. at the ring area, the disc is not able to create any significant axial force.
  • the first problem that may be seen in the operation of the balancing means is high power consumption combined with fluctuations in the power consumption due to the balancing means operating, alternatingly, in both low-friction and high-friction conditions.
  • the improvement in the means for pressure or thrust compensation includes a first set of permanent magnets arrayed around and attached to the shaft and a second set of permanent magnets arrayed on the pump housing at the shaft opening and facing the first set of permanent magnets.
  • the second set of permanent magnets magnetically attracts the first set of permanent magnets to hold the pump shaft at a fixed position along the major axis of the shaft with respect to the pump housing.
  • the permanent magnets are properly aligned when the pump is cold, heating of the pump shaft may move the surfaces of the balancing means towards one another to such an extent that a contact is possible.
  • the sensitivity to temperature requires specific attention, if the temperature of the liquid to be pumped is changed significantly, i.e. for instance the pump is moved from pumping hot liquid to pumping cold liquid.
  • a third problem involved in the pump of the US- document may be seen in the weakened operation of the balancing means. In other words, by keeping or trying to keep the shaft axially immobile the permanent magnets prevent the balancing means from operating in the manner it is designed to function, i.e. automatically adjusting the thin axial gap between the working surfaces of the balancing means.
  • an object of the present invention is to design such a novel balancing means for a centrifugal pump that prevents mechanical contact between the balancing disc and its counter member.
  • Another object of the present invention is to design such a novel balancing means for a centrifugal pump that utilizes the permanent magnets but avoids the problems involved in the prior art use of the permanent magnets.
  • a further object of the present invention is to develop such a novel balancing means for a centrifugal pump that, while effectively preventing mechanical contact between the balancing disc and its counter member still allows the balancing means to adjust automatically its operating clearance.
  • a centrifugal pump comprising a pump casing with an inlet and an outlet, a shaft sealed and mounted with bearings to the pump casing, at least one impeller fastened on the shaft for rotation therewith and a means for balancing axial forces
  • the balancing means comprising a balancing disc fastened on the shaft for rotation therewith and having an outer circumference, and a stationary counter member arranged in connection with the pump casing; the balancing disc and the counter member leaving therebetween a balancing cavity, wherein a first permanent magnet is arranged in connection with the balancing disc and a second permanent magnet is arranged in connection with the counter member, the first and the second permanent magnets facing one another such that either the north poles or the south poles of the permanent magnets face each other.
  • At least one of the above discussed problems is solved and at least one of the objects of the present invention are met with a method of balancing an axial thrust of a centrifugal pump, the centrifugal pump comprising a pump casing with an inlet and an outlet, a shaft sealed and mounted with bearings to the pump casing, at least one impeller fastened on the shaft for rotation therewith and a means for balancing axial forces
  • the balancing means comprising a balancing disc fastened on the shaft for rotation therewith and having an outer circumference, and a stationary counter member arranged in connection with the pump casing; the balancing disc and the counter member leaving therebetween radially inwardly from the outer circumference a thin gap and radially inwardly thereof a balancing cavity, the method comprising the step of:
  • Figure 1 illustrates an axial cross section of a prior art multi-stage centrifugal pump having a casing 10 with an inlet 12 and an outlet 14, the casing 10 housing a plurality of, here four, impellers 16 attached on a shaft 18 for rotation therewith and a balancing means 20.
  • FIG. 2 illustrates schematically an axial, more detailed cross section of the balancing means 20 and the end part of the prior art centrifugal pump.
  • the prior art balancing means 20 is formed of a balancing disc 22 attached on the shaft 18 for rotation therewith.
  • the balancing disc 22 there may be a separate sleeve or the balancing disc may be provided with an integrated axial extension, i.e. a cylindrical sleeve 24, either one of the sleeves extending from the disc up to the hub of the impeller.
  • the balancing means 20 further comprises a counter member 28 extending from the pump casing 10 radially inwardly between the balancing disc 22 and the impeller.
  • the counter member 28 may be either the rear wall of the centrifugal pump or a specific part attached thereto. In more general terms, the counter member is a part of the casing of the centrifugal pump or a specific part attached thereto.
  • the balancing disc 22 has an outer circumference immediately inside of which a thin gap 32 is arranged between the balancing disc 22 and its counter member 28 (here in this embodiment the counter ring 34 is the part of the counter member 28 facing the balancing disc 22). Radially inside of the thin gap 32 there is a balancing cavity 30 between the counter member 28 and the balancing disc 22.
  • a part of the pumped liquid enters along the shaft or shaft sleeve to the balancing cavity 30 between the balancing disc 22 and its counter member 28 and passes the thin gap 32 and, in normal operating conditions, the pressure conditions in the balancing cavity 30 keep the gap 32 open and prevent any mechanical contact between the surfaces of the balancing disc 22 and its counter member 28.
  • the above mentioned surfaces are, at the area of the thin gap 32, specifically designed, i.e. coated or otherwise finished, slide surfaces that take into account the momentary mechanical contact of the surfaces while starting or stopping the pump.
  • a pressure compensation system 40 comprising a first set 42 of permanent magnets arrayed around and attached to a circular disc 44 arranged to the free end of the shaft 18 and a second set 46 of permanent magnets arrayed on a cylindrical extension 48 of the pump housing at the shaft opening and facing the first set 42 of permanent magnets.
  • the second set 46 of permanent magnets magnetically attracts the first set 42 of permanent magnets to hold the pump shaft 18 at a fixed position along the major axis of the shaft with respect to the pump housing.
  • the first set 42 of permanent magnets and the second set 46 of permanent magnets oppose movement of the shaft 18 along the major axis of the shaft with respect to the housing 10.
  • the permanent magnet arrangement of prior art occupies space and is not able to take into account possible changes in the temperature of the liquid to be pumped, and also of the shaft of the pump.
  • the permanent magnets used in the manner described above prevent the thin gap from adjusting automatically as a function of the pressure in the balancing cavity, as the magnets aim at keeping the shaft immobile in axial direction.
  • Figs. 3 and 4 illustrate how the prior art balancing means of Fig. 2 are replaced with improved balancing means 50 in accordance with a first preferred embodiment of the present invention.
  • the pressure compensation system 52 is arranged in connection with the balancing means 50.
  • both the balancing disc 54 and its counter member 56 are provided radially inside the slide surfaces of the thin gap 32 at the sides of the balancing cavity 30 with annular grooves 58' and 58" ( Fig. 3 ) or an annularly arranged series of depressions that face one another.
  • the grooves or depressions are provided with permanent magnets 60 and 62 ( Fig. 4 ) such that either the north or south poles thereof face one another.
  • the magnets are positioned in relation to one another such that they repel one another.
  • the annular grooves 58' and 58" or depressions are covered by lids 64' and 64", preferably fastened and sealed to the balancing disc 54 and its counter member 56, i.e. sealed from the balancing cavity 30 by means of O-rings, for instance, such that the liquid to be pumped cannot get into contact with the magnets.
  • the grooves or depressions may be replaced with separate annular or sector-shaped "cups", manufactured of appropriate material, into which the permanent magnets are positioned whereafter the "cups' are fastened, for instance by means of screws, on at least one of the balancing disc and its counter member.
  • the "cups" may be positioned such that they face permanent magnets positioned in grooves or depressions on one of the balancing disc and the counter member, or such that they face one another.
  • FIG 5 illustrates the pressure compensation system in accordance with a second preferred embodiment of the present invention.
  • the permanent magnet 60 and its lid 64' arranged in connection with the balancing disc are equal to that shown in Figure 4 .
  • the permanent magnet 62" in the counter member 56 is arranged in a slightly different manner, as the permanent magnet/s 62" is/are inserted in its annular groove 58'" or in their depressions from the direction of the axis of the pump.
  • the annular groove 58'" is or the depressions are covered by means of a lid 64'" or lids.
  • the pressure or thrust compensation system is designed such that the distance from the magnet 60 to the surface of the balancing disc and the distance from the magnet 62' or 62" to the surface of the counter member is as short as possible, preferably of the order of one or a few millimeters. In the embodiment of Fig. 4 it equals to the thicknesses of the lids 64' and 64". And in the embodiment of Fig. 5 the thickness of the lid 64' and that of the land area between the groove 58'" or the depressions and the balancing cavity 30. The same dimension applies, naturally, to the thickness of the bottoms of the "cups" discussed above.
  • the major issues are that the material is strong or thick enough to endure mechanical stresses subjected thereto, it is water-tight such that the liquid to be pumped does not enter the cavity where the magnets are and it is insensitive to corrosion either in itself or by means of a coating applied thereon.
  • the pair of permanent magnets function such than when either the south poles or the north poles thereof are facing one another the magnets repel each other.
  • the repelling action starts at a certain distance between the magnets and the force the magnets repel each other grows exponentially when the distance between the magnets decreases further. Therefore, it is not only the thicknesses of the lids or the lid and the land area that matter but also the distance between the balancing disc and its counter member (thickness of the balancing cavity 30).
  • the thickness of the balancing cavity may be designed smaller than in prior art balancing means.
  • the thrust compensation system of the present invention allows the floating of the pump shaft on its slide bearings such that the axial clearance of the balancing means may be adjusted automatically, i.e. just as the basic operation principle of disc type balancing means is, as long as there is sufficient pressure in the balancing cavity.
  • the thrust compensation system of the present invention prevents the mechanical contact between the balancing disc and its counter member.
  • the material for the permanent magnets may be chosen to correspond to the temperature requirements the liquid to be pumped subjects to the pump and the materials used. For the highest temperatures Samarium Cobolt (SmCo) magnets are applicable.
  • the magnets used in the present invention may be formed as continuous magnet rings facing one another, magnet segments facing one another or as a magnet ring facing to a number of magnet segments. Also, the magnets may be divided in radial direction into several magnet rings or as several magnet segments.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
  • Control Of Non-Positive-Displacement Pumps (AREA)
EP18161862.0A 2018-03-14 2018-03-14 Kreiselpumpe mit ausgleichsmittel, ausgleichsscheibe und verfahren zum ausgleichen von axialkräften der kreiselpumpe Withdrawn EP3540232A1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP18161862.0A EP3540232A1 (de) 2018-03-14 2018-03-14 Kreiselpumpe mit ausgleichsmittel, ausgleichsscheibe und verfahren zum ausgleichen von axialkräften der kreiselpumpe

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EP18161862.0A EP3540232A1 (de) 2018-03-14 2018-03-14 Kreiselpumpe mit ausgleichsmittel, ausgleichsscheibe und verfahren zum ausgleichen von axialkräften der kreiselpumpe

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EP3540232A1 true EP3540232A1 (de) 2019-09-18

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EP18161862.0A Withdrawn EP3540232A1 (de) 2018-03-14 2018-03-14 Kreiselpumpe mit ausgleichsmittel, ausgleichsscheibe und verfahren zum ausgleichen von axialkräften der kreiselpumpe

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117722368A (zh) * 2024-01-02 2024-03-19 普轩特泵业股份有限公司 一种立卧双用管道泵

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3802950A1 (de) * 1988-02-02 1989-08-10 Klein Schanzlin & Becker Ag Pumpe mit permanentmagnetischer abhebevorrichtung
US5613831A (en) 1994-07-25 1997-03-25 Sulzer Pumpen Ag Apparatus for thrust compensation on shaft of rotary pump
DE102010041234A1 (de) * 2010-09-23 2012-03-29 Robert Bosch Gmbh Pumpe mit Elektromotor

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3802950A1 (de) * 1988-02-02 1989-08-10 Klein Schanzlin & Becker Ag Pumpe mit permanentmagnetischer abhebevorrichtung
US5613831A (en) 1994-07-25 1997-03-25 Sulzer Pumpen Ag Apparatus for thrust compensation on shaft of rotary pump
DE102010041234A1 (de) * 2010-09-23 2012-03-29 Robert Bosch Gmbh Pumpe mit Elektromotor

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117722368A (zh) * 2024-01-02 2024-03-19 普轩特泵业股份有限公司 一种立卧双用管道泵

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