Industrial-process control valves -- Part 2-3: Flow capacity - Test procedures

Applies to industrial-process control valves and provides the flow capacity test procedures for determining some of the variables used in the equations given in EN 60534-2.

Stellventile für die Prozeßregelung -- Teil 2-3: Durchflußkapazität - Prüfverfahren

Vannes de régulation des processus industriels -- Partie 2-3: Capacité d'écoulement - Procédures d'essais

S'applique aux vannes de régulation des processus industriels et donne les procédures d'essai relatives à la capacité d'écoulement pour la détermination de certaines variables utilisées dans les équations de la EN 60534-2.

Industrial-process control valves - Part 2-3: Flow capacity - Test procedures (IEC 60534-2-3:1997)

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Industrial-process control valves - Part
2-3: Flow capacity - Test procedures (IEC 60534-2-3:1997)Stellventile für die Prozeßregelung -- Teil 2-3: Durchflußkapazität - PrüfverfahrenVannes de régulation des processus industriels -- Partie 2-3: Capacité d'écoulement - Procédures d'essaisIndustrial-process control valves -- Part 2-3: Flow capacity - Test procedures25.040.40Merjenje in krmiljenje industrijskih postopkovIndustrial process measurement and control23.060.40Pressure regulatorsICS:Ta slovenski standard je istoveten z:EN 60534-2-3:1998SIST EN 60534-2-3:1998en01-november-1998SIST EN 60534-2-3:1998SLOVENSKI

SIST EN 60534-2-3:1998

SIST EN 60534-2-3:1998

SIST EN 60534-2-3:1998

SIST EN 60534-2-3:1998

SIST EN 60534-2-3:1998

NORMEINTERNATIONALECEIIECINTERNATIONALSTANDARD60534-2-3Deuxième éditionSecond edition1997-12Vannes de régulationdes processus industriels –Partie 2-3:Capacité d’écoulement – Procédures d’essaiIndustrial-process control valves –Part 2-3:Flow capacity – Test procedures Commission Electrotechnique Internationale International Electrotechnical
CommissionPour prix, voir catalogue en vigueurFor price, see current
catalogueÓ IEC 1997
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¾ Copyright - all rights reservedAucune partie de cette publication ne peut être reproduite niutilisée sous quelque forme que ce soit et par aucunprocédé, électronique ou mécanique, y compris la photo-copie et les microfilms, sans l'accord écrit de l'éditeur.No part of this publication may be reproduced or utilized inany form or by any means, electronic or mechanical,including photocopying and microfilm, without
permission inwriting
from the publisher.International Electrotechnical Commission3, rue de Varembé
Geneva, SwitzerlandTelefax: +41 22 919 0300e-mail: IEC web site
http: //www.iec.chCODE PRIXPRICE CODETSIST EN 60534-2-3:1998

60534-2-3 © IEC:1997– 3 –CONTENTSPageFOREWORD.5Clause1 Scope.72 Normative references.73 Definitions.94 Symbols.95 Test system.116 Accuracy of tests.197 Test fluids.198 Test procedure for incompressible fluids.219 Data evaluation procedure for incompressible fluids.2710 Test procedure for compressible fluids.3311 Data evaluation procedure for compressible fluids.41Annex A – Typical examples of test specimens showing appropriate pressure tap locations47SIST EN 60534-2-3:1998

60534-2-3 © IEC:1997– 5 –INTERNATIONAL ELECTROTECHNICAL COMMISSION___________INDUSTRIAL-PROCESS CONTROL VALVES –Part 2-3: Flow capacity – Test proceduresFOREWORD1)The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprisingall national electrotechnical committees (IEC National Committees). The object of the IEC is to promoteinternational co-operation on all questions concerning standardization in the electrical and electronic fields. Tothis end and in addition to other activities, the IEC publishes International Standards. Their preparation isentrusted to technical committees; any IEC National Committee interested in the subject dealt with mayparticipate in this preparatory work. International, governmental and non-governmental organizations liaisingwith the IEC also participate in this preparation. The IEC collaborates closely with the International Organizationfor Standardization (ISO) in accordance with conditions determined by agreement between the twoorganizations.2)The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, aninternational consensus of opinion on the relevant subjects since each technical committee has representationfrom all interested National Committees.3)The documents produced have the form of recommendations for international use and are published in the formof standards, technical reports or guides and they are accepted by the National Committees in that sense.4)In order to promote international unification, IEC National Committees undertake to apply IEC InternationalStandards transparently to the maximum extent possible in their national and regional standards. Anydivergence between the IEC Standard and the corresponding national or regional standard shall be clearlyindicated in the latter.5)The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for anyequipment declared to be in conformity with one of its standards.6)Attention is drawn to the possibility that some of the elements of this International Standard may be the subjectof patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.International Standard IEC 60534-2-3 has been prepared by subcommittee 65B: Devices, ofIEC technical committee 65: Industrial-process measurement and control.The second edition cancels and replaces the first edition published in 1983, of which itconstitutes a technical revision.The text of this standard is based on the following documents:FDISReport on voting65B/319/FDIS65B/329/RVDFull information on the voting for the approval of this standard can be found in the report onvoting indicated in the above table.Annex A forms an integral part of this standard.SIST EN 60534-2-3:1998

60534-2-3 © IEC:1997– 7 –INDUSTRIAL-PROCESS CONTROL VALVES –Part 2-3: Flow capacity – Test procedures1 ScopeThis section of IEC 60534-2 is applicable to industrial-process control valves and provides theflow capacity test procedures for determining the following variables used in the equationsgiven in IEC 60534-2-1 and IEC 60534-2-2:a)flow coefficient C;b)liquid pressure recovery factor without attached fittings FL;c)combined liquid pressure recovery factor and piping geometry factor of a control valve withattached fittings FLP;d)piping geometry factor Fp;e)pressure differential ratio factors xT and xTP;f)valve style modifier Fd;g)Reynolds number factor FR.2 Normative referencesThe following normative documents contain provisions which, through reference in this text,constitute provisions of this section of IEC 60534-2. At the time of publication, the editionsindicated were valid. All normative documents are subject to revision, and parties toagreements based on this section of IEC 60534-2 are encouraged to investigate the possibilityof applying the most recent editions of the normative documents indicated below. Members ofIEC and ISO maintain registers of currently valid International Standards.IEC 60534-1:1987, Industrial-process control valves – Part 1: Control valve terminology andgeneral considerationsIEC 60534-2:1978, Industrial-process control valves – Part 2: Flow capacity – Section One:Sizing equations for incompressible fluid flow under installed conditionsIEC 60534-2-2:1980, Industrial-process control valves – Part 2: Flow capacity – Section Two:Sizing equations for compressible fluid flow under installed conditionsIEC 60534-8-2:1991, Industrial-process control valves – Part 8: Noise considerations –Section 2: Laboratory measurement of noise generated by hydrodynamic flow through controlvalvesIEC 61298-1:1995, Process measurement and control devices – General methods andprocedures for evaluating performance – Part 1: General considerationsIEC 61298-2:1995, Process measurement and control devices – General methods andprocedures for evaluating performance – Part 2: Tests under reference conditionsSIST EN 60534-2-3:1998

60534-2-3 © IEC:1997– 9 –3 DefinitionsFor the purpose of this section of IEC 60534-2, the definitions given in IEC 60534-1,IEC 60534-2, IEC 60534-2-2, IEC 61298-1, and IEC 61298-2 apply.4 SymbolsSymbolDescriptionUnitCFlow coefficient (Kv, Cv)Various (see IEC 60534-1)CRFlow coefficient at rated travelVarious (see IEC 60534-1)dNominal valve size (DN)mmFdValve style modifier1FFLiquid critical pressure ratio factor1FLLiquid pressure recovery factor of a control valve withoutattached fittings1FLPCombined liquid pressure recovery factor and piping geometryfactor of a control valve with attached fittings1FpPiping geometry factor1FRReynolds number factor1FgSpecific heat ratio factor1MMolecular mass of flowing fluidkg/kmolNNumerical constants (see table 3)Various (see note 1)pcThermodynamic critical pressurekPa or bar (see note 2)pvVapour pressure of liquid at inlet temperaturekPa or barp1Inlet absolute static pressure measured at the upstreampressure tapkPa or barp2Outlet absolute static pressure measured at the downstreampressure tapkPa or barDpDifferential pressure (p1 – p2) between upstream anddownstream pressure tapskPa or barDpmaxMaximum pressure differentialkPa or barDpmax(L)Maximum effective Dp without attached fittingskPa or barDpmax(LP)Maximum effective Dp with attached fittingskPa or barQVolumetric flow ratem3/h (see note 3)QmaxMaximum volumetric flow rate (choked flow conditions)m3/hQmax(L)Maximum volumetric flow rate for incompressible fluids (chokedflow conditions without attached fittings)m3/hQmax(LP)Maximum volumetric flow rate for incompressible fluids (chokedflow conditions with attached fittings)m3/hQmax(T)Maximum volumetric flow rate for compressible fluids (chokedflow conditions without attached fittings)m3/hQmax(TP)Maximum volumetric flow rate for compressible fluids (chokedflow conditions with attached fittings)m3/hRevValve Reynolds number1T1Inlet absolute temperatureKtsReference temperature for standard conditions°CSIST EN 60534-2-3:1998

60534-2-3 © IEC:1997– 11 –Symbols (continued)SymbolDescriptionUnitxRatio of pressure differential to inlet absolute pressure (Dp/p1)1xTPressure differential ratio factor of a control valve withoutattached fittings for choked flow1xTPPressure differential ratio factor of a control valve with attachedfittings for choked flow1YExpansion factor1ZCompressibility factor (Z = 1 for gases that exhibit ideal gasbehaviour)1gSpecific heat ratio1nKinematic viscositym2/s (see note 4)zVelocity head loss coefficient of a reducer, expander or otherfitting attached to a control valve1r1/roRelative density (r1/ro = 1 for water at 15,5 °C)1NOTE 1 – To determine the units for the numerical constants, dimensional analysis may be performed on theappropriate equations using the units given in table 3.NOTE 2 – 1 bar = 102 kPa = 105 Pa.NOTE 3 – For compressible fluid volumetric flow rates in m3/h, identified by the symbol Q, refer to standardconditions which are an absolute pressure of 101,325 kPa (1,013 25 bar) and a temperature of either 0 °C or15 °C (see table 3).NOTE 4 – 1 centistoke = 10-6 m2/s.5 Test systemA basic flow test system is shown in figure 1.Figure 1 – Basic flow test systemFlow measuring deviceUpstreamthrottlingvalveFlowTemperaturemeasuringdevicePressure tapsTest sectionTest specimen(see 5.1)DownstreamthrottlingvalveIEC
1 757/97SIST EN 60534-2-3:1998

60534-2-3 © IEC:1997– 13 –5.1 Test specimenThe test specimen is any valve or combination of valve, reducers, expanders, or other fittingsfor which test data are required.Modeling of test specimens to a smaller scale is an acceptable practice in this section,although testing of full-size specimens or models is preferable. Good practice in modelingrequires attention to significant relationships such as Reynolds number in the flow of fluidthrough a completely filled conduit, Mach number where compressibility is important, andgeometric similarity.5.2 Test sectionThe test section shall consist of two straight lengths of pipe as shown in table 1. The upstreamand downstream piping adjacent to the test specimen shall conform to the nominal size of thetest specimen connection.The inside diameter of the pipe shall be within ±2 % of the actual inside diameter of the ends ofthe test specimen for valves up to and including DN 250 having a pressure rating up to andincluding PN 100. For valves larger than DN 250 or valves with a pressure rating higher thanPN 100, the inside diameter at the inlet and outlet of the test specimen should be matched withthe inside diameter of the adjacent piping.The inside surface shall be free from rust, scale, or other obstructions which may causeexcessive flow disturbance.5.3 Throttling valvesThe upstream throttling valve is used to control the inlet pressure to the test section. Thedownstream throttling valve is used for control during testing. Together they are used to controlthe pressure differential across the test section pressure taps and to maintain a specificdownstream pressure. There are no restrictions as to the type of these valves. However, theupstream valve should be selected and located so as not to affect the accuracy of the flowmeasurement. The downstream throttling valve may be larger than the nominal size of the testspecimen to ensure that choking will occur in the test specimen. Vaporization at the upstreamvalve shall be avoided when testing with liquids.SIST EN 60534-2-3:1998

60534-2-3 © IEC:1997– 15 –Table 1 – Test section piping requirementsl1l2l3l4Two times nominal pipediameterSix times nominal pipediameterEighteen times nominalpipe diameter minimumOne times nominal pipediameter minimumStandard test section configurationPressure
tapTest specimenFlowPressure
tapI1 + I3I2I1I2 + I4I4I3NOTE 1 – Straightening vanes may be used where beneficial. If employed, the length l3 may be reduced to notless than eight times the nominal pipe diameter.NOTE 2 – The location of the pressure taps are upstream and downstream of the test specimen as a whole. Thetest specimen may be simply the control valve or the control valve with any combination of attached fittings (seeannex A).NOTE 3 – If upstream flow disturbance consists of two elbows in series and they are in different planes, thedimension l3 should exceed 18 nominal pipe diameters unless straightening vanes are used.5.4 Flow measurementThe flow measuring instrument may be located upstream or downstream of the test section,and may be any device which meets the specified accuracy, and shall be calibrated asfrequently as necessary to maintain this accuracy. This instrument shall be used to determinethe true time-average flow rate within an accuracy of ±2 % of the actual value.5.5 Pressure tapsPressure taps shall be provided on the test section piping in accordance with the requirementsin table 1 and shall conform to the construction illustrated in figure 2. When the flow patternacross the pipe is not uniform, multiple taps may be necessary to achieve the desired accuracyof measurement.The pressure tap diameter b shall be at least 3 mm and shall be not larger than 12 mm, or one-tenth nominal pipe diameter, whichever is less. Upstream and downstream taps shall be of thesame diameter.The hole shall be circular and its edge shall be clean and sharp or slightly rounded, free fromburrs, wire edges, or other irregularities.Any suitable method of making physical connection is acceptable provided the aboverecommendations are adhered to; however, in no case shall any fitting protrude inside the pipe.IEC
1 758/97SIST EN 60534-2-3:1998

60534-2-3 © IEC:1997– 17 –5.5.1 Incompressible fluidTap centrelines shall be located horizontally to reduce the possibility of air entrapment or dirtcollection in the taps and shall intersect the pipe centreline at right angles.5.5.2 Compressible fluidTap centrelines shall be oriented horizontally or vertically above the pipe to reduce thepossibility of dirt entrapment and shall intersect the pipe centreline at right angles.5.6 Pressure measurementAll pressure and pressure differential measurements shall be made to an accuracy of ±2 % ofreading. Pressure measuring devices shall be calibrated as frequently as necessary to maintainspecified accuracy.5.7 Temperature measurementThe fluid inlet temperature shall be measured to an accuracy of ±1 °C. The temperaturemeasuring probe should be chosen and positioned to have minimum effect on the flow andpressure measurements.5.8 Valve travelThe valve travel shall be fixed within ±0,5 % of the rated travel during any one specific flowtest.5.9 Installation of test specimenAlignment between the centreline of the test section piping and the centreline of the inlet andoutlet of the test specimen shall be within:Pipe sizeAllowable misalignmentDN 15 through DN 250,8 mmDN 32 through DN 1501,6 mmDN 200 and larger0,01 nominal pipe diameterThe test specimen shall be oriented so that the flow pattern does not produce a velocity headat the pressure tap. For example, when a rotary valve is being tested, the valve shaft shall bealigned with the test section pressure taps.The inside diameter of each gasket shall be sized and the gasket positioned so that it does notprotrude inside the pipe.SIST EN 60534-2-3:1998

60534-2-3 © IEC:1997– 19 –Minimum 2,5 bRecommended 5 bb = pressure tap diameterbSize of pipeNot exceedingNot less thanLess than 50 mm6 mm3 mm50 mm to 75 mm9 mm3 mm100 mm to 200 mm13 mm3 mm250 mm and greater19 mm3 mmFigure 2 – Recommended pressure tap connection6 Accuracy of testsWhen the procedures outlined in this section are used, the value of all sizing coefficients iswithin ±5 % for valves having a C/d2 ratio of equal to or less than N25.7 Test fluids7.1 Incompressible fluidsWater within a temperature range of 5 °C to 40 °C shall be the basic fluid used in this testprocedure. Inhibitors may be used to prevent or retard corrosion and to prevent the growth oforganic matter provided that the test results are not adversely affected.7.2 Compressible fluidsAir or other compressible fluids shall be used as the basic fluid in this test procedure.Saturated vapours are not acceptable as test fluids. Care shall be taken to avoid internal icingduring the test.IEC
1 759/97SIST EN 60534-2-3:1998

60534-2-3 © IEC:1997– 21 –8 Test procedure for incompressible fluidsIn the following subclauses, specific instructions are given for the performance of various tests.Evaluation of data obtained from these tests is contained in clause 9.8.1 Test procedure for flow coefficient CDetermination of the flow coefficient C requires the following test procedure. Data shall beevaluated using the procedure in
Install the test specimen without attached fittings in accordance with pipingrequirements in table
Flow tests shall include flow measurements at three widely spaced pressuredifferentials (but not less than 0,1 bar) within the turbulent, non-vaporizing region. Thesuggested differential pressures area)just below the onset of cavitation (incipient cavitation) or the maximum available in the testfacility, whichever is less (see IEC 60534-8-2);b)about 50 % of the pressure differential of a);c)about 10 % of the pressure differential of a).The pressures shall be measured across the test section pressure taps with the valve at theselected travel.For very small valve capacities, non-turbulent flow may occur at the recommended pressuredifferentials. In this case, larger pressure differentials shall be used to ensure turbulent flow;however, a minimum valve Reynolds number Rev of 105 is recommended (see equation (10)).Deviations from the differential pressures specified above shall be recorded. Indicate reasonsfor the deviations.8.1.3
In order to keep the downstream portion of the test section filled with liquid and toprevent vaporization of the liquid, the inlet pressure shall be maintained equal to or greaterthan the minimum values in table 2. This minimum inlet pressure is dependent on the liquidpressure recovery factor FL of the test specimen. If FL is unknown, a conservative estimate forthe minimum inlet pressure shall be made.8.1.4
Flow tests shall be performed to determine:a)the rated flow coefficient CR using 100 % of rated travel;b)inherent flow characteristics (optional), using 5 %, 10 %, 20 %, 30 %, 40 %, 50 %, 60 %,70 %, 80 %, 90 % and 100 % of rated travel.NOTE – To determine the inherent flow characteristic more fully, flow tests may be performed at travel intervalsless than 5 % of rated travel.SIST EN 60534-2-3:1998

60534-2-3 © IEC:1997– 23 –Table 2 – Minimum inlet absolute test pressure in kPa (bar) as related to FL and DpMinimum inlet absolute test pressure – kPa (bar)DDp kPa(bar)®FL¯35(0,35)40(0,40)45(0,45)50(0,50)55(0,55)60(0,60)65(0,65)70(0,70)75(0,75)0,5280(2,8)320(3,2)360(3,6)400(4,0)440(4,4)480(4,8)520(5,2)560(5,6)600(6,0)0,6190(1,9)220(2,2)250(2,5)270(2,7)300(3,0)330(3,3)360(3,6)380(3,8)410(4,1)0,7150(1,5)160(1,6)180(1,8)200(2,0)220(2,2)240(2,4)260(2,6)280(2,8)300(3,0)0,8150(1,5)160(1,6)160(1,6)170(1,7)170(1,7)190(1,9)200(2,0)220(2,2)230(2,3)0,9150(1,5)160(1,6)160(1,6)170(1,7)170(1,7)180(1,8)180(1,8)190(1,9)190(1,9)NOTE 1 – For large valves where flow source limitations are reached, lower pressure differentials (but not lessthan 0,1 bar) may be used optionally as long as turbulent flow is maintained.NOTE 2 – For pressures not listed, use the following equation to calculate the upstream pressure: p1,min =2Dp/FL2.8.1.5
Record the following data:a)valve travel;b)inlet pressure p1;c)pressure differential (p1 – p2) across the pressure taps;d)fluid inlet temperature T1;e)volumetric flow rate Q;f)barometric pressure;g)physical description of test specimen (i.e. type of valve, nominal size, pressure rating, flowdirection).8.2 Test procedure for liquid pressure recovery factor FL and combined liquid pressurerecovery factor and piping geometry factor FLPThe maximum flow rate Qmax (referred to as choked flow) is required in the calculation of thefactors FL (for a given test specimen without attached fittings) and FLP (for a given testspecimen which includes attached fittings). With fixed inlet conditions, choked flow isevidenced by the failure of increasing pressure differentials to produce further increases in theflow rate. The following test procedure shall be used to determine Qmax. The data evaluationprocedure is found in 9.4. The tests for FL and corresponding C shall be conducted at identicalvalve travel. Hence, the tests for both of these factors at any valve travel shall be made whilethe valve is locked in a fixed position.SIST EN 60534-2-3:1998

60534-2-3 © IEC:1997– 25 –8.2.1
The test section of 5.2 shall be used with the test specimen locked at the desiredposition.8.2.2
The downstream throttling valve shall be in the wide-open position. With a preselectedinlet pressure, the flow rate shall be measured and the inlet and outlet pressures recorded.This test establishes the maximum pressure differential (p1 – p2) for the test specimen in thistest system. With the same inlet pressure, a second test shall be conducted with the pressuredifferential reduced to 90 % of the pressure differential determined in the first test. If the flowrate in the second test is within 2 % of the flow rate in the first test, the flow rate measured inthe first test may be taken as Qmax.If not, repeat the test procedure at a higher inlet pressure. If Qmax cannot be achieved at thehighest inlet pressure for the test system, use the following procedure. Calculate a value of FLsubstituting the flow rate obtained at maximum obtainable values of inlet pressure andpressure differential. For the valve under test, report that FL is greater than the valuecalculated as described in the previous sentence.8.2.3
Record the following data:a)valve travel;b)inlet pressure p1;c)outlet pressure p2;d)fluid inlet temperature T1;e)volumetric flow rate Q;f)barometric pressure;g)physical description of test specimen (i.e. type of valve, nominal size, pressure rating, flowdirection).8.3 Test procedure for piping geometry factor FpThe piping geometry factor modifies the valve flow coefficient C for fittings attached to thevalve. The factor Fp is the ratio of C for a valve installed with attached fittings to the rated C ofthe valve installed without attached fittings and tested under identical service conditions. Toobtain this factor, replace the valve with the desired combination of valve and attached fittings.Conduct flow tests according to 8.1 treating the combination as the test specimen for thepurpose of determining test section pipe size. For example, a DN 100 valve between a reducerand an expander in a DN 150 line would use pressure tap locations based on a DN 150 line.The data evaluation procedure is found in Test procedure for liquid critical pressure ratio factor FFThe liquid critical pressure ratio factor FF is almost exclusively a property of the fluid and itstemperature. It is the ratio of the apparent vena contracta pressure at choked flow conditions tothe vapour pressure of liquid at inlet temperature.The quantity of FF may be determined experimentally by using a test specimen for which FLand C are known. The valve without attached fittings is installed in accordance with the pipingrequirements in table 1. The test procedure outlined in 8.2 for obtaining Qmax shall be usedwith the fluid of interest as the test fluid.The data evaluation procedure is found in 9.6.SIST EN 60534-2-3:1998

60534-2-3 © IEC:1997– 27 –8.5 Test procedure for Reynolds number factor FR for incompressible flowTo produce values of the Reynolds number factor FR, non-turbulent flow conditions shall beestablished through the test valve. Such conditions will require low pressure differentials, highviscosity fluids, small values of C, or some combination of these. With the exception of valveswith very small values of C, turbulent flow will always exist when flowing tests are performed inaccordance with the procedure outlined in 8.1, and FR under these conditions will have thevalue of 1,0.Determine values of FR by carrying out flowing tests with the valve installed in the standard testsection without attached fittings. These tests should follow the procedure for C determinationexcept thata)test pressure differentials may be any appropriate values provided that no vaporization ofthe test fluid occurs within the test valve;b)minimum upstream test pressure values shown in table 2 may not apply if the test fluid isnot fresh water at 20 °C ± 14 °C;c)the test fluid should be a Newtonian fluid having a viscosity considerably greater than that ofwater unless instrumentation is available for accurately measuring very low pressuredifferentials.Carry out a sufficient number of tests at each selected valve travel by varying the pressuredifferential across the valve so that the entire range of conditions, from turbulent to laminarflow, is spanned.The data evaluation procedure is given in Test procedure for valve style modifier FdThe valve style modifier takes into account the effect of trim geometry on the Reynoldsnumber. It is defined as the ratio of the hydraulic diameter of a single flow passage to thediameter of a circular orifice, the area of which is equivalent to the sum of areas of all identicalflow passages at a given travel.The value of Fd should be measured at the desired travels. This value can only be measuredwhen fully laminar flow is obtained using the test procedure outlined in 8.5.Fully laminar flow is defined as a condition where RevR/F is constant with a ±5 % tolerancerange (typically with Rev values below 50).The data evaluation procedure is given in 9.8.9 Data evaluation procedure for incompressible fluids9.1 Non-choked flowThe basic flow equation for non-choked, incompressible fluids is:QNFFCp=1RpoDrr/(1)For a valve installed without attached fittings, Fp = 1, and for turbulent flow conditions, FR = 1.SIST EN 60534-2-3:1998

60534-2-3 © IEC:1997– 29 –9.2 Choked flowFor choked flow, two conditions shall be considered:9.2.1 Without attached fittingsWhen the control valve is installed without attached fittings:QNFCpFpmax(L)1L1Fvo/=-rr(2)NOTE – For a valve installed without attached fittings, the maximum pressure differential that is effective inproducing flow under choked conditions is:()DpFpFpmax(L)L21Fv=-(3)9.2.2 With attached fittingsWhen the control valve is installed with attached fittings:QNFCFFpFpmax()/LPpLPpFvo=æèççöø÷÷-æèçöø÷121rr(4)The common form of equation (4) is:QNFCpFpmax(LP)1LP1Fvo/=-æèçöø÷rr(5)NOTE – For a valve installed with attached fittings, the maximum pressure differential that is effective in producingflow under choked conditions is:()DpFFpFpmax(LP)LPp21Fv=æèçöø÷-(6)9.3 Calculation of flow coefficient CThe flow coefficient C may be calculated as Kv or Cv. See table 3 for the appropriate value ofN1, which will depend upon the coefficient selected and the pressure measurement unit.Using the data obtained in 8.1, calculate C for each flow test using the equation:CQNp=1o/rrD(7)For water in the prescribed temperature range, r/ro = 1.The three values obtained for each flow test shall be such that the largest value is not morethan 4 % greater than the smallest value. If the difference exceeds this tolerance, the flow testsshall be repeated. If excessive differences are caused by cavitation, the tests shall be repeatedat a higher inlet pressure.The flow coefficient at each travel shall be the arithmetic mean of the thre

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