EP1422424B1 - Method and apparatus for the early detection of failures in a centrifugal pump - Google Patents
Method and apparatus for the early detection of failures in a centrifugal pump Download PDFInfo
- Publication number
- EP1422424B1 EP1422424B1 EP03021880.4A EP03021880A EP1422424B1 EP 1422424 B1 EP1422424 B1 EP 1422424B1 EP 03021880 A EP03021880 A EP 03021880A EP 1422424 B1 EP1422424 B1 EP 1422424B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- centrifugal pump
- spring element
- fault detection
- early fault
- axial
- 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.)
- Expired - Lifetime
Links
- 238000000034 method Methods 0.000 title claims description 19
- 238000001514 detection method Methods 0.000 title claims description 14
- 238000005259 measurement Methods 0.000 claims description 11
- 238000009826 distribution Methods 0.000 claims description 3
- 238000001228 spectrum Methods 0.000 claims description 2
- 238000012545 processing Methods 0.000 description 5
- 125000006850 spacer group Chemical group 0.000 description 4
- 238000013461 design Methods 0.000 description 3
- 230000005489 elastic deformation Effects 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 208000024891 symptom Diseases 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Images
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
- F04D15/00—Control, e.g. regulation, of pumps, pumping installations or systems
- F04D15/0088—Testing machines
-
- 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
- F04D29/0413—Axial thrust balancing hydrostatic; hydrodynamic thrust bearings
Description
Gegenstand der Erfindung sind ein Verfahren und eine Vorrichtung zur Störungsfrüherkennung bei einer mit einer Entlastungseinrichtung ausgestatteten Kreiselpumpe, wobei die Entlastungseinrichtung einen axialen Spalt und gegebenenfalls einen oder mehrere radiale Spalte besitzt, über welche ein Entlastungsstrom geführt wird, wobei ferner ein die Entlastungseinrichtung im Sinne eines Abhebens von dem axialen Spalt beaufschlagendes Federelement vorhanden ist.The invention relates to a method and apparatus for early fault detection in a centrifugal pump equipped with a relief device, wherein the relief device has an axial gap and optionally one or more radial gaps over which a discharge current is passed, further wherein the relief device in the sense of lifting is provided by the axial gap acting on spring element.
Zur Störungsfrüherkennung bei Kreiselpumpen wurden bisher Sensoren eingesetzt, welche von einer Norm abweichende Schwingungen, Erwärmungen, Geräusche oder andere meßbare Größen feststellten und einer Überwachungseinheit übermittelten. Eine Vielzahl der Sensoren war zu diesem Zweck an der Außenseite des Pumpengehäuses angeordnet. Eine direkte Verbindung mit dem Ort einer Störungsentstehung bestand somit nicht. Die von den Sensoren bezogenen Signale waren nicht immer klar und eindeutig, so daß Fehlmeldungen nicht ausgeschlossen werden konnten. Vor allem bestand die Gefahr, daß solche Meldungen erst spät erfolgten, ein Schaden also bereits eingetreten war.For the early detection of disturbances in centrifugal pumps, sensors have hitherto been used which detected vibrations deviating from one standard, heating, noise or other measurable variables and transmitted them to a monitoring unit. A plurality of the sensors were arranged for this purpose on the outside of the pump housing. A direct connection with the place of a fault formation thus did not exist. The signals obtained from the sensors were not always clear and unambiguous, so that false reports could not be ruled out. Above all, there was a danger that such reports would come late, so that damage had already occurred.
Eine wesentliche Störung im Inneren der Kreiselpumpe ergibt sich, wenn Lager verschleißen oder wenn eine Entlastungseinrichtung nur noch unzureichend arbeitet. Eine solche Störung kann schleichend erfolgen. So mag sie in ihren Anfängen noch ohne außen an der Kreiselpumpe feststellbare Symptome bleiben und erst nach Eintritt eines erheblichen Schadens und einem möglichen Ausfall der Kreiselpumpe manifest werden.A significant disturbance inside the centrifugal pump results when bearings wear out or when a relief device only works insufficiently. Such a disturbance can occur creepingly. Thus, in its beginnings, it may still remain without symptoms on the outside of the centrifugal pump and become manifest only after the occurrence of considerable damage and possible failure of the centrifugal pump.
Es kann zwar auch eine Bestimmung von Axialkräften mit Hilfe eines axial berührenden Sensors, einer Kraftmeßdose, vorgenommen werden. Eine solche Kraftmeßdose kann aber aus konstruktiven Gesichtspunkten nicht dauerhaft eingesetzt werden.Although it can also be a determination of axial forces by means of an axially contacting sensor, a load cell, made. Such But load cell can not be used permanently from a design point of view.
Die
Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren und eine Vorrichtung zur Störungsfrüherkennung bei Kreiselpumpen der eingangs genannten Art zu schaffen, welche bei weitgehender Nutzung bereits vorhandener Elemente eine zuverlässige Aussage über sich anbahnende Störungen erbringen.The invention has for its object to provide a method and apparatus for early fault detection in centrifugal pumps of the type mentioned, which provide a reliable statement about impending disturbances with extensive use of existing elements.
Die gestellte Aufgabe wird erfindungsgemäß dadurch gelöst, daß während des Betriebes der Kreiselpumpe, ausgehend von der Pumpenkennlinie der Kreiselpumpe und der Federkonstanten des Federelementes, die Verformung des Federelementes gemessen und ein Rückschluß auf den aktuellen Betriebspunkt der Kreiselpumpe gezogen wird.The stated object is achieved in that measured during operation of the centrifugal pump, starting from the pump characteristic of the centrifugal pump and the spring constant of the spring element, the deformation of the spring element and a conclusion is drawn to the current operating point of the centrifugal pump.
In zweckmäßiger Ausgestaltung der Erfindung wird vorgeschlagen, daß jeweils für den mittels der Störungsfrüherkennung zu überwachenden Kreiselpumpentyp und das zu fördernde Medium Basismessungen vorgenommen werden, die die Axialkraft, die Entlastungskraft und die Druckverteilung im Radseitenraum mit Betriebspunkten auf der Kennlinie der Kreiselpumpe ins Verhältnis setzt.In an advantageous embodiment of the invention, it is proposed that in each case for the means of early fault detection to be monitored centrifugal pump type and the medium to be delivered measurements are made, the axial force, the unloading force and the pressure distribution in the Radseitenraum with operating points on the characteristic of the centrifugal pump in proportion.
Außerdem wird vorgeschlagen, daß eine die Frequenzspektren des Federelementes ermittelnde dynamische Messung zur Feststellung von Frequenzbändern, welche dem Förderstrom zugeordnet werden und damit einen Hinweis auf mögliche Störungen in der Kreiselpumpe geben, vorgenommen wird.It is also proposed that a frequency spectra of the spring element determining dynamic measurement for detecting frequency bands, which are assigned to the flow and thus give an indication of possible disturbances in the centrifugal pump, is made.
In besonders gelagerten Fällen, insbesondere bei einer grundsätzlichen Untersuchung der auf die Welle einer Kreiselpumpe einwirkenden Axialkräfte, kann es von Vorteil sein, mit Hilfe eines zweiten Federelementes, welches in Gegenrichtung zum ersten Federelement angeordnet ist, auch eine Kontrolle auf einen in Richtung der Druckseite der Kreiselpumpe erfolgenden Axialschub und gegebenenfalls eine Messung dieses Axialschubes vorzunehmen. Ein solcher Axialschub kann bei extremer Überlast und einer daraus resultierenden Schubumkehr auftreten.In particularly stored cases, in particular in a fundamental examination of the forces acting on the shaft of a centrifugal pump axial forces, It may be advantageous to make with the aid of a second spring element, which is arranged in the opposite direction to the first spring element, a check on a taking place in the direction of the pressure side of the centrifugal pump axial thrust and optionally a measurement of this axial thrust. Such an axial thrust can occur under extreme overload and resulting thrust reversal.
Eine besonders vorteilhafte Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens ergibt sich, wenn als Federelement ein kardanischer Ring verwendet wird, der so dimensioniert ist, daß er durch eine aufgrund der Auslegung der Entlastungseinrichtung vorgegebene definierte Rest-Axialkraft zur Einstellung eines ebenfalls vorgegebenen Axialspaltes verformt wird. Eine mit den genannten Elementen ausgestattete Entlastungseinrichtung ist bekannt durch die
Der Einsatz des erfindungsgemäßen Verfahrens und der dieses Verfahren nutzenden Vorrichtung empfiehlt sich insbesondere für die Erkennung eines beginnenden Lagerverschleißes oder unzulässiger hydraulischer Vorgänge sowie zur Vermeidung eines Anlaufens des Rotors am Gehäuse der Kreiselpumpe.The use of the method according to the invention and of the device using this method is recommended, in particular, for the detection of an incipient bearing wear or inadmissible hydraulic processes and for avoiding a start-up of the rotor on the housing of the centrifugal pump.
Das erfindungsgemäße Verfahren und seine Vorrichtung kommen mit einem Minimum an Sensoren aus. Durch ihre unmittelbare Anbindung an die Entlastungseinrichtung ergibt sich eine sehr frühzeitig und zuverlässig reagierende Störungserkennung. Durch das elastische Verhalten des in der als besonders vorteilhaft angesehenen Vorrichtung verwendeten Kardanringes kann im übrigen das rotordynamische Verhalten der Kreiselpumpe stabilisiert werden.The inventive method and its device come with a minimum of sensors. Their direct connection to the relief device results in a very early and reliable reactive fault detection. By the elastic behavior of the gimbals used in the device considered to be particularly advantageous device can be stabilized otherwise the rotor dynamic behavior of the centrifugal pump.
Anhand eines Ausführungsbeispiels wird die Erfindung näher erläutert. Die Zeichnung zeigt In
- Fig.1
- einen Ausschnitt aus einer im Schnitt dargestellten mehrstufigen Kreiselpumpe mit einem saugseitig angeordneten kardanischen Ring, der sowohl zur Einstellung eines vorgegebenen Axialspaltes an einer Entlastungseinrichtung als auch als Element einer AxialkraftMeßeinrichtung zur Durchführung des erfindungsgemäßen Verfahrens dient;
- Fig. 2
- einen Ausschnitt aus einer im wesentlichen der Ausführung der
Fig. 1 entsprechenden Kreiselpumpe mit einem saugseitig und einem druckseitig angeordneten kardanischen Ring zur Schaffung einer in beiden Schubrichtungen wirkenden Axialkraft-Meßvorrichtung; - Fig. 3
- eine schematische Darstellung einer Kreiselpumpe mit einer Einrichtung zur Verarbeitung der von der Axialkraft-Meßvorrichtung aufgenommenen Signale.
- Fig.1
- a section of a multi-stage centrifugal pump shown in section with a suction side arranged gimbal ring, both for setting a predetermined axial gap on a relief device and as an element of a AxialkraftMeßeinrichtung serves to carry out the method according to the invention;
- Fig. 2
- a section of a substantially the execution of
Fig. 1 corresponding centrifugal pump with a suction side and a pressure side arranged gimbal ring to provide a force acting in two directions of thrust Axialkraft measuring device; - Fig. 3
- a schematic representation of a centrifugal pump with a device for processing the signals recorded by the Axialkraft-measuring device.
Wie In der
Auf der Welle 2 ist im übrigen der Doppelkolben 4 einer erfindungsgemäßen Entlastungseinrichtung befestigt. Der Doppelkolben 4 wird umgeben von einem Gehäuseteil 5, mit dem er zwei radiale Spalte 6 und 7 bildet. Zwischen den radialen Spalten 6 und 7 befindet sich ein axialer Spalt 8. Der axiale Spalt 8 hat eine veränderliche Weite s.On the
Am druckseitigen Ende der Kreiselpumpe wird die Welle 2 durch ein hydrodynamisches Axiallager 9 aufgenommen. Dem Axiallager 9 ist ein kardanischer Ring 10 zugeordnet. Der kardanische Ring 10 dient zunächst in bekannter Weise dem Ausgleich von Fluchtungsfehlern, die bei der Montage einer mehrstufigen Kreiselpumpe unvermeidlich sind. Im übrigen ist der kardanische Ring 10 so dimensioniert, daß er durch den in der Kreiselpumpe auftretenden, zur Saugseite hin gerichteten Restschub elastisch verformt wird. Dabei ist die Federkonstante des kardanischen Ringes 10 an die übrigen Gegebenheiten der Entlastungseinrichtung angepaßt:
- Die Entlastungseinrichtung ist so ausgelegt, daß sich in allen Betriebszuständen der Kreiselpumpe ein Restschub ergibt, der in Richtung der Saugseite wirkt. Ausgehend von einer maximalen Weite s des axialen Spaltes 8 im Ruhezustand der Kreiselpumpe wird nun durch eine elastische Verformung des
kardanischen Ringes 10 der Spalt 8 unter Betriebsbedingungen bis auf eine vorgegebene Minimalweite geschlossen, bei welcher eine Berührung der den Spalt 8 begrenzenden Flächen desDoppelkolbens 4 und desGehäuseteils 5 noch vermieden wird. Dabei kommt der Entlastungseinrichtung zustatten, daß der axiale Spalt 8 eine selbstregelnde Funktion besitzt.
- The relief device is designed so that there is a residual thrust in all operating conditions of the centrifugal pump, which acts in the direction of the suction side. Starting from a maximum width s of the axial gap 8 in the idle state of the centrifugal pump is now by an elastic deformation of the
gimbal ring 10 of the gap 8 under operating conditions to a predetermined Minimum closed, in which a touch of the gap 8 limiting surfaces of thedouble piston 4 and thehousing part 5 is still avoided. In this case, the relief device is sufficient that the axial gap 8 has a self-regulating function.
Durch die Integration des kardanischen Ringes 10 in eine geeignete Meßvorrichtung werden frühzeitig solche Kräfte erkennbar, die auf unzulässige hydraulische Zustände oder einen einsetzenden Lagerverschleiß hindeuten. Die während des Pumpenbetriebes erfolgende Verformung des kardanischen Ringes 10 wird durch ein geeignetes Mittel, beispielsweise einen - nicht dargestellten - Dehnungsmeßstreifen bekannter Art, festgestellt und als Signal über eine Leitung 11 zu einer Einrichtung zur Signalverarbeitung übermittelt. Die direkte mechanische Ankopplung des als Axialkraftaufnehmer wirkenden kardanischen Ringes 10 an das Meßsystem ermöglicht die Messung von Signalen ohne den dämpfenden Einfluß eines Fluidfilms, welcher sich bei berührungslosen Aufnehmern stets zwischen Sensor und Bauteil befindet.By integrating the
Die in der
Die Krafteinleitung in die Vorrichtung erfolgt ausgehend vom Pumpenrotor über einen Axiallagerteller 18, welcher drehfest mit der Welle 2 verbunden ist. Der Axiallagerteller 18 überträgt je nach Wirkungsrichtung des Axialschubs die Kraft auf eines von zwei Axialrillenkugellagern 19, 20, welche direkt an die kardanischen Ringe 14, 15 gekoppelt sind. Die kardanischen Ringe 14, 15 werden auf Durchbiegung beansprucht und stellen somit Federelemente in einer Kraftschlusskette dar. Unausgeglichene Restkräfte werden über den Distanzring 16 oder die Distanzbuchse 17 in das Gehäuse weitergeleitet. Durch jeweils einen Zylinderstift 21 werden die kardanischen Ringe 14, 15 gegen ein Verdrehen gesichert. Über Leitungen 22 und 23 wird der Verformungszustand einer Einrichtung zur Signalverarbeitung übermittelt.The introduction of force into the device takes place starting from the pump rotor via an
In der
Das Ausgangssignal wird über einen DMS-Verstärker 25 an einen Meßwertumformer 26 weitergeleitet. Dieser wandelt das Signal in eine Ausgangsspannung von 0-10V um. Anschliessend wird das Signal an eine Meßwerterfassungskarte eines Computers 27 geleitet, wodurch eine Darstellung und Weiterverarbeitung der aufgenommenen Meßdaten möglich ist.The output signal is forwarded via a
Die in
Claims (8)
- Method for early fault detection in a centrifugal pump equipped with a balancing device (4, 6, 7, 8), wherein the balancing device has an axial gap (8) and possibly one or more radial gaps (6, 7), through which a balancing flow is conducted, wherein furthermore there is a spring element (10, 14), which acts on the balancing device in the sense of lifting it off from the axial gap, characterized in that, during the operation of the centrifugal pump (24), the deformation of the spring element (10, 14) is measured on the basis of the pump characteristic of the centrifugal pump (24) and the spring constant of the spring element (10, 14), and a conclusion is drawn with respect to the current operating point of the centrifugal pump (24).
- Method according to Claim 1, characterized in that baseline measurements are taken in each case for the type of centrifugal pump that is to be monitored by means of the early fault detection and for the medium that is to be pumped, said baseline measurements relating the axial force, the balancing force and the pressure distribution within the impeller chamber to operating points on the characteristic curve of the centrifugal pump (24).
- Method according to Claim 1, characterized in that a dynamic measurement is taken in each case for the type of centrifugal pump that is to be monitored by means of the early fault detection and for the medium that is to be pumped, said dynamic measurement determining the frequency spectra of the spring element (10, 14) to establish frequency bands that are associated with the pumped flow and consequently indicate possible faults in the centrifugal pump (24).
- Method for early fault detection according to one of Claims 1 to 3, characterized in that a check is made on an axial thrust occurring in the direction of the delivery side of the centrifugal pump (24) with the aid of a second spring element (15), which is arranged in the opposite direction to the first spring element (14), and possibly a measurement of this axial thrust is taken.
- Apparatus for carrying out the method according to one of Claims 1 to 4, characterized in that a cardanic ring (10, 14), which is dimensioned such that it is deformed by a residual axial force predetermined by the configuration of the balancing device for setting a likewise predetermined axial gap, is used as the spring element.
- Use of the method for early fault detection according to one of Claims 1 to 4 for detecting incipient bearing wear.
- Use of the method for early fault detection according to one of Claims 1 to 4 for avoiding running of the rotor against the casing of the centrifugal pump.
- Use of the method for early fault detection according to one of Claims 1 to 4 for detecting impermissible cavitation conditions.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE10254041 | 2002-11-20 | ||
DE10254041A DE10254041B4 (en) | 2002-11-20 | 2002-11-20 | Method and apparatus for early fault detection in centrifugal pumps |
Publications (3)
Publication Number | Publication Date |
---|---|
EP1422424A2 EP1422424A2 (en) | 2004-05-26 |
EP1422424A3 EP1422424A3 (en) | 2009-05-20 |
EP1422424B1 true EP1422424B1 (en) | 2016-08-10 |
Family
ID=32185857
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP03021880.4A Expired - Lifetime EP1422424B1 (en) | 2002-11-20 | 2003-09-27 | Method and apparatus for the early detection of failures in a centrifugal pump |
Country Status (4)
Country | Link |
---|---|
US (1) | US6877947B2 (en) |
EP (1) | EP1422424B1 (en) |
JP (1) | JP4093949B2 (en) |
DE (1) | DE10254041B4 (en) |
Families Citing this family (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7552176B2 (en) * | 2003-03-12 | 2009-06-23 | Microsoft Corporation | Reducing unwanted and unsolicited electronic messages by exchanging electronic message transmission policies and solving and verifying solutions to computational puzzles |
DE102013223806A1 (en) * | 2013-11-21 | 2015-05-21 | Ksb Aktiengesellschaft | relief device |
CN103629121A (en) * | 2013-12-12 | 2014-03-12 | 兰州理工大学 | Dynamic axial force testing device for impeller of centrifugal pump |
CN104121179B (en) * | 2014-07-11 | 2016-05-18 | 兰州理工大学 | A kind of testing arrangement of impeller blade surface liquid pressure of centrifugal pump |
CN104500413B (en) * | 2014-11-21 | 2017-01-11 | 江苏大学 | Measuring unit for measuring axial force of submerged pump |
CN106907337B (en) * | 2017-05-10 | 2018-05-25 | 沈阳工业大学 | The Research on Testing System of Thrust on Aluminum and method of canned motor pump |
CA3081681C (en) * | 2017-12-29 | 2022-05-31 | Halliburton Energy Services, Inc. | Sensor failure diagnosis in a pump monitoring system |
WO2019132953A1 (en) * | 2017-12-29 | 2019-07-04 | Halliburton Energy Services, Inc. | Valve failure determination in a pump monitoring system |
RU181078U1 (en) * | 2018-02-13 | 2018-07-04 | Федеральное государственное автономное образовательное учреждение высшего образования "Северо-Восточный федеральный университет имени М.К.Аммосова" | Sectional type electric pump unit |
DE102018210842B4 (en) * | 2018-07-02 | 2020-01-16 | KSB SE & Co. KGaA | Arrangement for receiving the axial thrust of a centrifugal pump |
DE102019001120A1 (en) | 2019-02-15 | 2020-08-20 | KSB SE & Co. KGaA | Relief device |
Family Cites Families (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE886250C (en) * | 1951-11-10 | 1953-08-13 | Klein | Lifting device for relief disks of centrifugal machines |
CH501839A (en) * | 1966-11-12 | 1971-01-15 | Zabrzanska Fabryka Masz Gornic | Dynamic pump |
US3542494A (en) * | 1967-11-09 | 1970-11-24 | Nikkisco Co Ltd | Canned motor pump |
JPS5587889A (en) * | 1978-12-27 | 1980-07-03 | Kubota Ltd | Abnormal balancing detector for multistage pump |
US4578018A (en) * | 1983-06-20 | 1986-03-25 | General Electric Company | Rotor thrust balancing |
US4884942A (en) * | 1986-06-30 | 1989-12-05 | Atlas Copco Aktiebolag | Thrust monitoring and balancing apparatus |
DE3725754A1 (en) | 1987-08-04 | 1989-02-16 | Busch Dieter & Co Prueftech | DEVICE FOR MONITORING PUMPS FOR HAZARDOUS CAVITATION |
US5104284A (en) * | 1990-12-17 | 1992-04-14 | Dresser-Rand Company | Thrust compensating apparatus |
JP2636097B2 (en) | 1991-08-08 | 1997-07-30 | 動力炉・核燃料開発事業団 | Monitoring device for the amount of wear of thrust bearings in immersion type electric pumps |
DE29500744U1 (en) * | 1995-01-18 | 1996-05-15 | Sihi Ind Consult Gmbh | Fluid machine with relief piston |
SE516957C2 (en) | 1995-04-25 | 2002-03-26 | Abs Pump Prod Ab | Ways to determine for a centrifugal pump the operating conditions of the torque in terms of call height and volume flow by measuring the resulting radial force on the impeller shaft for size and direction |
EP0971212B1 (en) * | 1998-07-10 | 2011-04-20 | Levitronix LLC | Method to determine the pressure loss and the flow rate through a pump |
DE19927135A1 (en) | 1999-06-15 | 2000-12-21 | Ksb Ag | Relief device for multi-stage centrifugal pumps |
-
2002
- 2002-11-20 DE DE10254041A patent/DE10254041B4/en not_active Expired - Fee Related
-
2003
- 2003-09-27 EP EP03021880.4A patent/EP1422424B1/en not_active Expired - Lifetime
- 2003-11-19 US US10/715,831 patent/US6877947B2/en not_active Expired - Fee Related
- 2003-11-20 JP JP2003390257A patent/JP4093949B2/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
DE10254041A1 (en) | 2004-06-03 |
DE10254041B4 (en) | 2011-07-07 |
US6877947B2 (en) | 2005-04-12 |
EP1422424A3 (en) | 2009-05-20 |
US20040151581A1 (en) | 2004-08-05 |
EP1422424A2 (en) | 2004-05-26 |
JP4093949B2 (en) | 2008-06-04 |
JP2004169704A (en) | 2004-06-17 |
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