GB2200991A - Detection of cavitation in pumps - Google Patents

Detection of cavitation in pumps Download PDF

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Publication number
GB2200991A
GB2200991A GB08702926A GB8702926A GB2200991A GB 2200991 A GB2200991 A GB 2200991A GB 08702926 A GB08702926 A GB 08702926A GB 8702926 A GB8702926 A GB 8702926A GB 2200991 A GB2200991 A GB 2200991A
Authority
GB
United Kingdom
Prior art keywords
pump
cavitation
impeller
drive member
chamber
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.)
Granted
Application number
GB08702926A
Other versions
GB8702926D0 (en
GB2200991B (en
Inventor
George Edward Preece
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.)
National Nuclear Corp Ltd
Original Assignee
National Nuclear Corp Ltd
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 National Nuclear Corp Ltd filed Critical National Nuclear Corp Ltd
Priority to GB8702926A priority Critical patent/GB2200991B/en
Publication of GB8702926D0 publication Critical patent/GB8702926D0/en
Publication of GB2200991A publication Critical patent/GB2200991A/en
Application granted granted Critical
Publication of GB2200991B publication Critical patent/GB2200991B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/02—Analysing fluids
    • G01N29/024—Analysing fluids by measuring propagation velocity or propagation time of acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/223—Supports, positioning or alignment in fixed situation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/227—Details, e.g. general constructional or apparatus details related to high pressure, tension or stress conditions
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/228—Details, e.g. general constructional or apparatus details related to high temperature conditions
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/24—Probes
    • G01N29/2462—Probes with waveguides, e.g. SAW devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/34—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor
    • G01N29/346—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor with amplitude characteristics, e.g. modulated signal
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/34—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor
    • G01N29/348—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor with frequency characteristics, e.g. single frequency signals, chirp signals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/36—Detecting the response signal, e.g. electronic circuits specially adapted therefor
    • G01N29/42—Detecting the response signal, e.g. electronic circuits specially adapted therefor by frequency filtering or by tuning to resonant frequency
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/024—Mixtures
    • G01N2291/02433—Gases in liquids, e.g. bubbles, foams
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/10—Number of transducers
    • G01N2291/101—Number of transducers one transducer

Landscapes

  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)

Abstract

Cavitation is detected in a pump, particularly a liquid sodium pump, by using the pump drive shaft (14) as an acoustic wave guide. The signal is picked up by means of an accelerometer (16) contacting the pump shaft (14) externally of the pump housing and the signal may then be transmitted to recording/display equipment via a radio link including a radio transmitter (20) mounted on the pump shaft (14). Application is to a liquid sodium cooled fast fission nuclear reactor or to water feed pumps for steam generating plant. <IMAGE>

Description

Detection of cavitation in pumps This invention relates to the detection of cavitation in pumps.
Cavitation within the pumping chamber of a pump may result in rapid wear of the pump impeller especially when the nature of the cavitation is such that the bubbles implode at the surfaces of the impeller since implosion takes place violently and rapidly and results in the application of impacts of significant amplitude and short duration to the impeller, leading to erosion or pitting of the pump impeller and loss of pumping efficiency. It is therefore desirable to have available an effective means for detecting and monitoring cavitation within the pumping chamber.
According to one aspect of the invention there is provided a method of detecting cavitation within the pumping chamber of a pump in which a drive member for transmitting drive to the impeller of the pump is used as a wave guide to transmit acoustic waves produced at the impeller as a result of cavitation and in which the acoustic waves are detected through the agency of said drive member and are processed to produce an output indicative of any cavitation present.
According to a second aspect of the invention there is provided a pump comprising a pumping chamber, an impeller within the chamber, drive means for driving the impeller, the drive means including a drive member extending externally of the chamber and coupled to the impeller so as to transmit acoustic waves produced at the impeller as a result of cavitation within the chamber, transducer means operatively associated with the drive member to detect acoustic waves coupled into the drive member via the pump impeller, and signal processing means for deriving from the transducer means a signal indicative of the presence of cavitation in said chamber.
The transducer means is preferably coupled to the drive member at a location external to the pumping chamber. The transducer means may contact a peripheral surface of the drive member and may comprise an accelerometer which may be in the form of piezoelectric transducer.
The signal processing means may be mounted on the drive member and the cavitation-indicating signal produced thereby may be transferred to recording and/or monitoring equipment via a communications link such.as a radio signal transmitter mounted on the drive member and a radio receiver which is not mounted on the drive member. Other forms of signal transmission may be employed, eg slddable electrical contacts such as slip rings.
A feature of the invention lies in the use of the drive member as a waveguide as well as a drivetransmitting member. It is already known to use acoustic detection of cavitation by means of transducers located in the pumped fluid or attached to the pump chamber but it is considered that the use of the drive member as a waveguide for the cavitation-generated acoustic waves will serve to enhance the signal produced by bubbles imploding at the surface of the pump impeller.
The signal processing means is designed to discriminate between acoustic signals attributable to cavitation and other noise sources as bearings.
The pump may be of the rotatably driven type in which the impeller comprises a number of blades for displacing the fluid to be pumped. The pump may be a liquid metal pump for use in liquid metal cooled fast fission nuclear reactor plant but other possibilities are feasible, eg water feed pumps for steam generating plant.
The invention will now be described further by way of example only with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a pump for use in liquid metal cooled fast neutron nuclear reactor plant; and Figure 2 is a block diagram of circuitry for processing and transmitting a transducer signal to monitoring and recording equipment.
As shown diagrammatically in Figure 1, the pump impeller 10 of a liquid sodium pump is driven rotatably by a motor 12 via a pump shaft assembly 14. An accelerometer 16, which may comprise a piezoelectric transducer, is connected to the shaft 14 and its electrical output is fed to a signal conditioning and transmitting unit 17 via cable 18. The unit 17 is mounted on the rotating shaft assembly 14 and incorporates an FM transmitter 20 (see Figure 2) and antenna 22. The transmitted signals are received via antenna 24 and FM receiver 26 mounted on a fixed structure, such as the pump housing, within a short range of the transmitter 20.
The accelerometer 16 picks up, via the shaft 14 (acting as a waveguide), acoustic waves generated by cavitation occurring within the pumping chamb'er and also by other noise sources (eg bearings). When erosive cavitation is present, the high frequency noise (eg 50-80 kHz) picked up by the accelerometer will be predominantly due to erosive cavitation. The signal conditioning circuit of Figure 2 is designed to extract the high frequency component of the accelerometer output and transmit the resulting signal via transmitter 20. Thus, the output of the accelerometer 16, after amplification by amplifier 28, is passed through low pass filter 30 so as to eliminate frequencies above about 80 kHz.The filtered output following further amplification by amplifier 32, is then mixed electrically by heterodyne unit 34 with an 80 kHz signal from oscillator 36 to produce an output on line 38 representing the difference in frequency between the filtered accelerometer signal and the oscillator signal. The difference signal is filtered via low pass filter 40 (upper frequency limit of the order of 20 kHz), amplified by amplifier 42 and then combined with a high frequency carrier signal (typically about 170 mHz) in the FM transmitter 20 for transmission.
The transmitted signal is picked up by receiver 26, demodulated and fed to monitoring and recording equipment 44.
The monitoring and recording equipment 44'may incorporate an alarm for providing operators with a visual or audible warning signal indicating the onset of erosive cavitation so that appropriate remedial action can be taken, eg adjustment of one or more parameters such as flow rate, pump speed etc, influencing cavitation. If desired, in suitable circumstances, the monitoring equipment may, in response to the onset of erosive cavitation, be operable to initiate automatic adjustment of one or more of the parameters mentioned in order to reduce or eliminate erosive cavitation.
The signal conditioning unit 17 may be battery powered and may be selectively.switched on and off remotely by means of a TV-type infra-red control device.
Although signal transmission in the illustrated embodiment is effected via a radio link, other forms of signal transmission are conceivable such as slip rings and by means of infra-red electromagnetic waves.
By employing the pump shaft as a waveguide, it will be seen that the instrumentation can be readily attached to an exposed part of the pump drive shaft. Dismantling or removal of the pump or its component parts is not involved. The equipment can be readily fitted to existing pumps thereby allowing cavitation performance to be monitored. The invention though described with reference to a rotatably driven liquid sodium pump may be applied to other forms of pump, eg feed water pumps in steam plant.

Claims (6)

Claims
1. A method of detecting cavitation within the pumping chamber of a pump in which a drive member for transmitting drive to the impeller of the pump is used as a wave guide to transmit acoustic waves produced at the impeller as a result of cavitation and in which the acoustic waves are detected through the agency of said drive member and are processed to produce an output indicative of any cavitation present.
2. A pump comprising a pumping chamber, an impeller within the chamber, drive means for driving the impeller, the drive means including a drive member extending externally of the chamber and coupled to the impeller so as to transmit acoustic waves produced at the impeller as a result of cavitation within the chamber, transducer means operatively associated with the drive member to detect acoustic waves coupled into the drive member via the pump impeller, and signal processing means for deriving from the transducer means a signal indicative of the presence of cavitation in said chamber.
3. A pump as claimed in Claim 2 in which the transducer means is coupled to the drive member at a location externql to the pumping chamber.
4. A pump as claimed in the transducer means contacts a peripheral surface of the drive member and comprises an accelerometer
5. A pump as claimed in any one of Claims 1-4 in which the signal processing means is mounted on the drive member and the cavitation-indicating signal produced thereby is transferred to recording and/or monitoring equipment via a communications link
6. A pump substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.
GB8702926A 1987-02-10 1987-02-10 Detection of cavitation in pumps Expired - Fee Related GB2200991B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8702926A GB2200991B (en) 1987-02-10 1987-02-10 Detection of cavitation in pumps

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8702926A GB2200991B (en) 1987-02-10 1987-02-10 Detection of cavitation in pumps

Publications (3)

Publication Number Publication Date
GB8702926D0 GB8702926D0 (en) 1987-03-18
GB2200991A true GB2200991A (en) 1988-08-17
GB2200991B GB2200991B (en) 1991-01-16

Family

ID=10611986

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8702926A Expired - Fee Related GB2200991B (en) 1987-02-10 1987-02-10 Detection of cavitation in pumps

Country Status (1)

Country Link
GB (1) GB2200991B (en)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2643458A1 (en) * 1989-02-22 1990-08-24 Nuovo Pignone Ind Mec DETECTION AND MEASUREMENT DEVICE FOR THE CONTINUOUS DETERMINATION OF CAVITATION IN DYNAMIC PUMPS
US5235524A (en) * 1990-04-02 1993-08-10 Rockwell International Corporation Ultrasonic cavitation detection system
EP0742372A1 (en) * 1995-05-11 1996-11-13 KSB Aktiengesellschaft Monitoring system for detecting cavitation intensity
GB2358705A (en) * 1999-09-16 2001-08-01 Secretary Trade Ind Brit Cavitation sensor
FR2910633A1 (en) * 2006-12-20 2008-06-27 Renault Sas Gas i.e. air, rate estimating method for e.g. hydrostatic bearing in aircraft field, involves acquiring signal emitted by pressurizing units using sensor, and estimating gas rate in liquid from characteristics of acquired signal
CN107689255A (en) * 2016-08-03 2018-02-13 泰拉能源有限责任公司 Steam raising plant
WO2018122016A1 (en) * 2016-12-30 2018-07-05 Grundfos Holding A/S Sensor assembly and method for fault detection in pumps and pump assembly comprising such sensor assembly

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2643458A1 (en) * 1989-02-22 1990-08-24 Nuovo Pignone Ind Mec DETECTION AND MEASUREMENT DEVICE FOR THE CONTINUOUS DETERMINATION OF CAVITATION IN DYNAMIC PUMPS
US5235524A (en) * 1990-04-02 1993-08-10 Rockwell International Corporation Ultrasonic cavitation detection system
EP0742372A1 (en) * 1995-05-11 1996-11-13 KSB Aktiengesellschaft Monitoring system for detecting cavitation intensity
GB2358705A (en) * 1999-09-16 2001-08-01 Secretary Trade Ind Brit Cavitation sensor
GB2358705B (en) * 1999-09-16 2003-06-11 Secretary Trade Ind Brit Cavitation Sensor
FR2910633A1 (en) * 2006-12-20 2008-06-27 Renault Sas Gas i.e. air, rate estimating method for e.g. hydrostatic bearing in aircraft field, involves acquiring signal emitted by pressurizing units using sensor, and estimating gas rate in liquid from characteristics of acquired signal
CN107689255A (en) * 2016-08-03 2018-02-13 泰拉能源有限责任公司 Steam raising plant
WO2018122016A1 (en) * 2016-12-30 2018-07-05 Grundfos Holding A/S Sensor assembly and method for fault detection in pumps and pump assembly comprising such sensor assembly

Also Published As

Publication number Publication date
GB8702926D0 (en) 1987-03-18
GB2200991B (en) 1991-01-16

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PCNP Patent ceased through non-payment of renewal fee