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TERNATIONAL ISO7g1g-5

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Mechanical vibration of non-reciprocatingmachines

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Measurements on rotatingshafts and evaluation criteria

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Part 5:Machine sets in hydraulic power generatingand pumping plants

vibrations meicaniques des machines non alternatives -

Mesurages surles arbres tournants et criteres d'6valuation

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Partie 5: Machines equipant les centrales hy,orcelectriques et les siationsde pompage

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Foreword

ISO (the lnternational Organization for Standardization)_ is. a_.worldwidei"J.rarion of national stanJards bodies (lSO member bodies)' The work of;;;;;; international Standards is normally carried out through ISO[""[ni"ui committees. Each member body interested in a subiect for*ni"n a technical committee has been established has the' right to bei"pru*","0 on that committee. lnternat'ronal organizations. governmentaland nonSovernmental, in liaison with lso, also take part in the work. lso.ottuOor.i"r closely with the lnternational Electrotechnical Commission(lEC) on all matters of electrotechnical standardization'

Draft lnternational Standards adopted by the technical committees arecirculated to the member bodies for voting- Publication as an lnternationalita'ndard requires approval by at least 75 Vo ol the member bodies castinga vote.

lnternational standard lso 79is5 was prepared by Technical-committeeiionc rog. Mechanical vibration and shock, Subcommittee sc 2,Mllrrrr"*"nt and evaluation of mechanicat vibration and shock as appliedn machines, vehicles and structures'

lso 7919 consists of the following parts. under the general titleMechanicat vibration of non-reciprocating machines

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Measurements onrotating shafts and evaluation criteria"

Part 1: General guidelines

Part 2: Large lan*based steam turbine generator sets

Part 3: Caupled industrial machines

Part 4: Gas turbine sets

Part 5: Machine sets rn hydrautic power generating and pumpingplants

Annex A forms an integral part of this part of lSo 7919. Annexes B and care for information onlY.

o tso 1997Att rights roserved. Unless otherwise specrfiod' no part of lhis publication may be,eprojuceO or utilized in any lorm or by arry means, electronic or mechanical. rncludingpnotocopyingandmicrofrlm.wrthoutpermrssioninlvritrngfromthepub|isher-

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Mechanical vibration of non-reciprocating machines -Measurements on rotating shafts and evaluation criteria

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Part 5:Machine sets in hydraulic power generating and pumping plants

1 ScopeThis part of ISO 7919 gives guidelines for applying shaft vibration evaluation criteria, under normal operatingconditions, measured at or close to the bearings of machines or machine sets in hydraulic power generating andpumping plants. These guidelines are presented in terms of both steady-state running vibration and any amplitudechanges which ma), occur in these steady values. The numerical values specified are not intended to serve as theonly basis for vibration evaluation since, in general, the vibratory condition of a machine is assessed byconsideration of both the shaft vibration and the associated structural vibration (see ISO 79'191).This part of tSO 7919 applies to machines or machine sets in hydraulic power generating and pumping plantswhere the hydraulic machines have speeds from 60 r/min to 1 800 r/min, shell- or shoe-type sleeve bearings, andmain engine power of at least 1 MW. The position of the shaft line may be vertical, horizontal or at an arbitraryangle between these two directions.

Machine sets covered by this part of ISO 7919 may be a combination of

hydraulic turbines and generators,pumps and electrical machines operating as motors.pump-turbines and motorenerators,

including auxiliary equipment (e.9. starting turbines or exciters lying in the shaft line).This part of ISO 7919 is also applicable to turbines or pumps connected to generators or electrrcal motors via gearsand/or radially flexible couplings. However, electrical machines with speeds between 'l 000 r/min and 1 800 r/minshould be evaluated according to the criteria specified in ISO 791g-3.

This part of ISO 7919 is not applicable to

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,,pumos in thermal power plants or industrial installations (for these machines, see ISC 7919-3).hydraulic machines or machine sets having rolling element bearings, orhydraulic machines having water-lubricated Learings

Consistent with ISO 7919-1, sha{t vrbration o{ machines or machrne sets in hydraulic po'.,rer generating andpumping plants may be determined wilh regard to the following tasks.

lask A: changes in vibrational behaviour;task B excessive kinetic load;lecL, i/- 1|\^ ,_^^,1^/i^^

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2 Normative referencesThe following standards contain provisions which, through reference rn this text, constitute provisions of this partof ISO 7919. At the timeof publication, the edrtions indicated were valid All standards are subiect to revision. andparties to agreements based on this part of ISO 7919 are encouraged ro investigate the possrbility of applying themost recent edilions of the standards indicated below- Members of IEC and ISO maintain registers of current[yvalid lnternational Standards.

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ISO 791$1 :1996, Mechanical vibration of non-reciprocating machines -

Measurements on rotating shafts ahdevaluation criteria

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Part 1: General guidelines.

ISO 10817-1:-ll, Rotating shaft vibration measLtrement sfsterns -

Part 1: Betative and absolute signal iensing ofra d i a I v ib n t io n f rom rotati ng shafts.

IEC 994:1991, Guide for field measurement of vibrations and pulsations in hydraulic machines (turbines, storagep u m ps a nd pumytu hi nes).

3 Measurement proceduresThe measurement procedures to be followed and the instrumentation used shall be as described in lSo 79191 andrEC 994.

3.1 Measurement typeRelative and absolute shaft vibration measurements are carried out on hydraulic machine sets using non-contactingtransducers. Shaft-riding probes with seismic transducers cannot generally be used due to the very-low-frequencyrange of the measuring equipment required for low-speed hydraulic machinery.

For relative measurements, transducers should be mounted directly on the bearing shell or the bearing pad. lf thetransducers are installed on the bearing support structure or bearing housing, as it is common for verticalmachines, care shall be taken that the relative motion between the bearing shell or pad and the transducer itself issmallcompared with the shaft motion. lf this is not so, the measured signal cannot be said to be representative ofthe relative movement between the shaft and bearing shell or bearing pad, respectively. This requirement may beassessed by static analysis of the structure or additional measurement, the latter is usually difficult and expensive.

For absolute vibration measurements. non-contacting transducers shall be installed on rigid frameworks, fixed tothe turbine or generator pit wall. Signals from these transducers can only be regarded as representative of theabsolute shaft vibration when the absolute vibration of the supporting structure itself at the point of attachment ofthe transducer is less than 10 o/o of the measured peak-to.peak value. with 25 p.m as an upper limit.

With regard to the transducer support structures. it is advisable that the lowest natural frequency of those vibrationmodes which create significant movements in the working direction of shaft displacement transducers should begreater than seven times the synchronous rotational frequency and should not be a direct multiple of thesynchronous rotational f requency.

The absolute vibration of the support frame should always be measured using seismic transducers installed on thesupport frame as close as possible to the shaft movement transducer and in the same direction of actton. Thereadings f rom the seismic transducers may be used af ter conversion into drsplacementg to 6Gluate the absoluteshaf t drsplacement

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Apart lrom the shart vrbration. the vrbration of the bearing support is frequently monitored as well. The vibrationmeasurement at the lower guide bearinqs of vertrcal machines may, however. be misnterpreted; the vibration value measureclat the bearrngs and therr supports whrch are lgrclly embedded in the buildrng rs sometrmes produced by hyclraLrlic lorces.rJirectly trilnsmilted frorn the hydraulrc nr.,chrrr,r vrl the {oundatron. arrcl rs rrot produced by radial shaft vibratron

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3.2 Measurement PlanesMeasurement tasks A and B in clause t ,"quir" measurements to be taken at ail rnain bearings of the machine setli possible, the setting of the transducers at the different bearings should be in line. For vertical machines, in mostcases the preferred measurement directions are upstream and g0" apart in the direction of rotation. For horizontalmachines, for practical reasons the measurement directions are often chosen to be t 45" f rom the vertrcal-

For monitoring purposes (task A only, in some cases measurement planes can be reduced lo the most importantones. mainly at machine sets with four or more bearings. The selection should be based on vibration performanceanalyses, simulating alltypes ol faults or disturbing events. Preferred measurement planes should be those wherepossible disturbing events produce significant shaft amplitudes.

Measurement task C requires the installation oi transducers near to or inside the hydraulic machine seals orlabyrinths, or at positions from where it is possible to reconstruct the shaft line deflection within the hydraulicmachine for all relevant vibration modes. Appropriate measurements are, in special cases, part of thecommissioning of a machine set. They may yield transfer functions for the different permanent measurementplanes.

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\n/hen judging the behaviour of the whole machine, it is important to measure also at a distance Irom the bearings- (e.g- in the coupling area) to obtain information about the amplitude distribution along the sha{t line. lf a bearing plane is near to

a vibration node, the vibration behaviour and the actual shart line deflection can be underestimated.

3-3 Measuring equipmentThe measuring equipment performance should be in accordance with the requirements of ISO 1OB'l 7-1 andrEC 994.

The frequency iange of the measuring equipment shall correspond to the wide excitation spectrum of shaftvibration in hydraulic machines. lt should be from a quarter of the nominal rotationalfrequency of the machine up totwo times the bucket or blade passing frequency.

The amplitude range of the measurement system should be at least two times the values of the borderltnebetween zones C and D (see clause A.2), so that transient operating conditions can be accurately monitored.

4 Evaluation criteria4.1 Turbine operation conditionsEvaluation criteria for vibration magnitude and changes in vibration rnagnitude lor machine sets rn turbrne operatronconditions are presented in annex A. They are in accordance with the general guidelines given in ISO 7919-1

With respect to the special nature of the vibration orbits of vertical shaft hydromachines, the preferredmeesurement quantity shall be the maximum vibratory displacement Smax. Since most oi the monitorrng systemsdisplay displacement amplitudes as S1r-r1 values (vibratory displacement peak-to-peak in the direclion ofmeasurement; see ISO 79-l9-l), the evaluation criteria are specified for both measurement quantities Applicationcf tltrese criteria is valid for machine sets with nominal speeds between 60 rinrin and I 800 r/min operating vvrthrnihscontractually permissible steady-state load range as well as at other loaci condrrrons. rf the machrne has beenmade suitable for these particular. conditions.

The lrmrting values are apphcable for all kinds of turbine-drrven machine sets rndeperident ol the tyl.ae, hu.,d airrjpo\J^./er except for the restrrctions Stated in clause 1. For hydromechanically smoother rrinnrng turbrne types (t: clPelton turbines), lower shaft vrbration amplitudes can normally be expectedln th'e case of pump-turbines. hrgher shaft vibration amplttudes lhan norrnally exlrectr:d {or zortp A itatr r.rccttr :l r;'l()the runner design, which is a compromise of the optimal design for turbine and prrrn;r rurrner

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4.2 Pump operation conditionsAt present, insufficient data are available to prepare criteria for machinewillbe added to a future edition of this part of ISO 7919.

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4.3 Special operating conditionsAttention should be paid to the following operating conditions.

a.) steady-state operating conditions at low partial load, at overload, andconditions during startrp and shutdown;

b) rare transient operating conditions such as emergenc'i shutdown, no discharge operation, and running through A'ithe brake quadrant with pumps and pumpturbines.

The evaluation of such processes is much more difficult than that of operation in the specified load range. Atpresent there are insufficient values determined from experience to establish limiting curves for these operatingconditions. The less the operating conditioo corresponds to the nominal conditions. the more the flow within thehydraulic machine is disturbed; disturbances-such as separation and swirl generate violent stochastic excitation.Due to the density of water. the forces caused by the stochastic excitation are much greater than in thermal '-turbomachines.

Therefore. during operations outside the specified load range, the shaft vibration caused by mass unbalances are,as a rule, totally masked by the stochastic components. Because of these large stochastic components inextrpordinary operating conditions, one should rely less on the instantaneous value and more on the mean valueover at least'10 rotations of the shaft.

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lt should be noted that, in general. an overall judgement ol the vibratory state of the machine is made on the basisof both shaft relative vibration as def ined above and measurements made on non-rotating parts (see ISO 1 081 6-jl ).

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