Industrial valves - Test of flow resistance using water as test fluid

The main objectives of this revision is to clearly precise the scope of this standard which is not coherent with the content of the standard.

Industriearmaturen - Messung des Strömungswiderstandes mit Wasser als Prüfmedium

Diese Europäische Norm legt ein Verfahren zur Bestimmung der Koeffizienten für Druckverlust und Durchflussmenge
von Armaturen fest, wobei Wasser als Prüfmedium verwendet wird. Dieses Verfahren ist geeignet
für:
- Armaturen mit niedrigen ζ-Werten, jedoch über 0,1, bei Bestimmung des Druckverlustes in Abhängigkeit
vom Durchfluss und vom spezifischen Gewicht des Prüfmediums;
- sowie Armaturen mit gleichen Nennweiten auf der Ein- und Austrittsseite.
Industriestellgeräte fallen nicht in den Anwendungsbereich dieser Europäischen Norm.
ANMERKUNG 1 Bei Armaturen mit ζ > 6 ist die Messungenauigkeit des Druckverlustkoeffizienten höher als der durch die
Prüfrohre verursachte Druckverlust. Dabei entspricht die Prüfkonfiguration EN 60534-2-3.
ANMERKUNG 2 Bei Verwendung von Luft als Prüfmedium sollte auf andere Normen verwiesen werden, z. B.
EN 60534-2-3 und ISO 6358.

Robinetterie industrielle - Essai de résistance à l'écoulement utilisant l'eau comme fluide d'essai

La présente Norme européenne spécifie une méthode de détermination du coefficient de perte de charge et
du coefficient de débit du fluide d’un appareil de robinetterie en utilisant l'eau comme fluide d'essai. Cette
méthode est applicable :
⎯ aux appareils de robinetterie à faible ζ, mais plus grand que 0,1 par détermination de la perte de charge,
en fonction du débit et de la densité du fluide ;
⎯ et aux appareils de robinetterie dont les diamètres nominaux d'entrée et de sortie sont identiques.
Les robinets de régulation de procédés industriels sont exclus de la présente Norme Européenne.
NOTE 1 Pour les valeurs de zêta supérieures à 6, l'imprécision du coefficient de perte de charge est supérieure à la
perte de charge provoquée par les tubes d'essai. Il en résulte la même configuration d'essai que celle de l'EN 60534-2-3.
NOTE 2 Si l'air est utilisé comme fluide d'essai, il convient que d'autres normes telles que l'EN 60534-2-3 et l'ISO 6358
soient mises en référence.

Industrijski ventili - Preskušanje pretočne upornosti z vodo kot preskusnim medijem

Ta evropski standard določa metodo za ugotavljanje koeficienta izgube tlaka za ventile in koeficienta pretoka tekočine z vodo vode kot preskusno tekočino. Ta metoda je ustrezna za ventile z nizkimi vrednostmi zeta, vendar višjimi od 0,1, tako da se določi izguba tlaka, ob upoštevanju stopnje pretoka tekočine in specifične težnosti, ter za ventile z enako nazivno dovodno in odvodno velikostjo. Ta evropski standard ne zajema regulacijskih ventilov za industrijske procese.

General Information

Status
Published
Public Enquiry End Date
16-Nov-2009
Publication Date
29-Jan-2012
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
26-Jan-2012
Due Date
01-Apr-2012
Completion Date
30-Jan-2012

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.SUHVNXVQLPPHGLMHPIndustriearmaturen - Messung des Strömungswiderstandes mit Wasser als PrüfmediumRobinetterie industrielle - Essai de résistance à l'écoulement utilisant l'eau comme fluide d'essaiIndustrial valves - Test of flow resistance using water as test fluid23.060.01Ventili na splošnoValves in generalICS:Ta slovenski standard je istoveten z:EN 1267:2012SIST EN 1267:2012en,fr,de01-marec-2012SIST EN 1267:2012SLOVENSKI

STANDARDSIST EN 1267:20001DGRPHãþD
SIST EN 1267:2012
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 1267
January 2012 ICS 23.060.01 Supersedes EN 1267:1999English Version
Industrial valves - Test of flow resistance using water as test fluid

Robinetterie industrielle - Essai de résistance à l'écoulement utilisant l'eau comme fluide d'essai

Industriearmaturen - Messung des Strömungswiderstandes mit Wasser als Prüfmedium This European Standard was approved by CEN on 26 November 2011.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre:
Avenue Marnix 17,

B-1000 Brussels © 2012 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 1267:2012: ESIST EN 1267:2012

EN 1267:2012 (E) 2 Contents Page Foreword ..............................................................................................................................................................41 Scope ......................................................................................................................................................52 Normative references ............................................................................................................................53 Terms and definitions ...........................................................................................................................54 Test facility .............................................................................................................................................64.1 General ....................................................................................................................................................64.2 Test tube lengths ...................................................................................................................................84.3 Test tube sizes .......................................................................................................................................84.3.1 Steel test tubes ......................................................................................................................................84.3.2 Copper test tubes ..................................................................................................................................94.4 Pressure tappings..................................................................................................................................94.5 Measurement devices ........................................................................................................................ 104.6 Test fluid .............................................................................................................................................. 105 Test procedure .................................................................................................................................... 105.1 Test conditions ................................................................................................................................... 105.1.1 Permissible measurement fluctuations ............................................................................................ 105.1.2 Steady conditions ............................................................................................................................... 115.1.3 Permissible non-steady conditions .................................................................................................. 115.2 Pressure loss in test tubes ................................................................................................................ 115.3 Valve test ............................................................................................................................................. 126 Calculation ........................................................................................................................................... 136.1 Valve pressure loss determination ................................................................................................... 136.2 Coefficient calculations ..................................................................................................................... 146.2.1 Flow resistance coefficient ζζζζ (zeta)................................................................................................... 146.2.2 Flow coefficient, Kv ............................................................................................................................. 146.2.3 Flow coefficient, Cv ............................................................................................................................. 146.3 Uncertainty .......................................................................................................................................... 156.3.1 Total measurement uncertainty ........................................................................................................ 156.3.2 Flow coefficients, Kv and Cv ............................................................................................................... 156.3.3 Pressure loss coefficient, ζζζζ (zeta) ..................................................................................................... 167 Test report ........................................................................................................................................... 16Annex A (informative)

Lower ζζζζ limit considerations ..................................................................................... 18Annex B (informative)

Flow rate and physical phenomena of flow through a valve ................................. 19B.1 General ................................................................................................................................................. 19B.2 Normal flow conditions ...................................................................................................................... 20B.3 Cavitation ............................................................................................................................................. 21B.4 Flashing (self-vaporizations) ............................................................................................................. 21Annex C (informative)

Uncertainty on measurement ................................................................................... 22C.1 Introduction ......................................................................................................................................... 22C.2 Permissible measurement fluctuations ............................................................................................ 22C.2.1 General ................................................................................................................................................. 22C.2.2 Direct visual observation of signals delivered by the systems ..................................................... 22C.2.3 Automatic recording of signals delivered by measurement systems ........................................... 23C.2.4 Automatic integration of signals delivered by the measurement systems .................................. 24C.3 Measured value stability on physical quantities ............................................................................. 25C.4 Determining flow rate and pressure loss coefficients in turbulent rating condition ................... 26Annex D (informative)

Evaluation of uncertainty of flow rate coefficient (Kv) and pressure losses coefficient (ζζζζ) ....................................................................................................................................... 27D.1 Generality ............................................................................................................................................ 27D.2 Evaluation of measurement uncertainty of the Kv (Cv) .................................................................... 27SIST EN 1267:2012

EN 1267:2012 (E) 3 D.2.1 Determination of flow rate coefficient ............................................................................................... 27D.2.2 Identification of uncertainty of input quantities ............................................................................... 28D.2.3 Sensitivity coefficient .......................................................................................................................... 28D.2.4 Type A evaluation uncertainty ........................................................................................................... 29D.2.5 Expression of relative uncertainty ..................................................................................................... 29D.3 Evaluation of measurement uncertainty of the ζζζζ ............................................................................. 30D.3.1 Determination of flow resistance coefficient .................................................................................... 30D.3.2 Identification of uncertainty of input quantities ............................................................................... 30D.3.3 Sensitivity coefficient .......................................................................................................................... 30D.3.4 Type A evaluation uncertainty ........................................................................................................... 32D.4 Expression of relative uncertainty on ζζζζ ............................................................................................ 32Bibliography ...................................................................................................................................................... 33 SIST EN 1267:2012

EN 1267:2012 (E) 4 Foreword This document (EN 1267:2012) has been prepared by Technical Committee CEN/TC 69 “Industrial valves”, the secretariat of which is held by AFNOR. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by July 2012, and conflicting national standards shall be withdrawn at the latest by July 2012. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document supersedes EN 1267:1999. The main changes compared to the previous edition are the following: a) the scope was specified and editorially revised; b) the normative references were updated; c) Clause 3 on terms and definitions was revised; d) Clause 4 on test facility was changed; e) Clause 5 on test procedure was changed; f) Annex A on lower ζ limit considerations was revised; g) Annex D on evaluation of uncertainty of flow rate coefficient (Kv) and pressure losses coefficient (ζ) was added; h) a bibliography was added. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

SIST EN 1267:2012

EN 1267:2012 (E) 5 1 Scope This European Standard specifies a method for determining valve pressure loss coefficient and fluid flow coefficient using water as test fluid. This method is suitable  for valves with low zeta values but higher than 0,1 by determining pressure loss, with respect to fluid flow rate and specific gravity, and  for valves with equal inlet and outlet nominal size. Industrial process control valves are excluded from this European Standard. NOTE 1 For zeta values above 6, the pressure loss coefficient inaccuracy is higher than the pressure loss caused by the test tubes. It becomes the same configuration of tests as in EN 60534-2-3. NOTE 2 If using air as test fluid, other standards e.g. EN 60534-2-3 and ISO 6358 should be referred to. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 736-1:1995, Valves — Terminology — Part 1: Definition of types of valves EN 736-3:2008, Valves — Terminology — Part 3: Definition of terms EN 1057, Copper and copper alloys — Seamless, round copper tubes for water and gas in sanitary and heating applications EN 24006:1993, Measurement of fluid flow in closed conduits — Vocabulary and symbols (ISO 4006:1991) EN ISO 6708:1995, Pipework components — Definition and selection of DN (nominal size) (ISO 6708:1995) ISO 7-1:1994, Pipe threads where pressure-tight joints are made on the threads — Part 1: Dimensions, tolerances and designation ISO 7194:2008, Measurement of fluid flow in closed conduits — Velocity-area methods of flow measurement in swirling or asymmetric flow conditions in circular ducts by means of current-meters or Pitot static tubes 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 flow coefficient

Kv or Cv [EN 736-3:2008, 3.4.1] SIST EN 1267:2012
EN 1267:2012 (E) 6 3.2 flow resistance coefficient ζζζζ

[EN 736-3:2008, 3.4.5] 3.3 fluctuations low period modifications of the measured value of a physical quantity around its mean value during the measurement reading time 3.4 nominal diameter DN [EN ISO 6708:1995, 2.1] 3.5 stability stability, or the permanent rating conditions, which is reached, when the variations or value changes for these same physical quantities are low enough between a given reading and the next one 3.6 types of valves [EN 736-1:1995] 3.7 uncertainty [EN 24006:1993, 5.26] 4 Test facility 4.1 General A basic flow test facility is shown in Figure 1. The position of components outside the frame may be determined by the laboratory. For angle valves (Figure 1 b)), the tested valve and the tube section (L3 length) may be laid either vertically or horizontally. For multi-way valves, additional test tubes of the same type shall be used, in the same conditions. SIST EN 1267:2012

EN 1267:2012 (E) 7
NOTE L1 and L3 ≥ 10 D and L2 and L4 ≥ 2 D. a) Straight valves

b) Angle or multiport valves Key 1 water supply 6 upstream pressure measuring device 2 flow meter 7 valve under test 3 temperature measurement 8 downstream pressure tapping point 4 regulating valve 9 regulating valve 5 upstream pressure tapping point 10 differential pressure measuring device Figure 1 — Test installation SIST EN 1267:2012

EN 1267:2012 (E) 8 4.2 Test tube lengths The test tube lengths and the pressure measurement point positions shall comply with Figure 1. Lengths are measured from test tube ends. If the test facility includes two elbows in series in different planes upstream, a link L1 greater than 10 D, shall be adopted unless straightener is installed before the upstream test tube. If a flow straightener is used, length L1 may be smaller than 10 D, provided that the conditions in 5.1 are met. For other details concerning flow straighteners, refer to ISO 7194:2008, Clause 6. 4.3 Test tube sizes 4.3.1 Steel test tubes The test tubes (dimensions DN 8 to DN 150) can be threaded with an external taper thread as per ISO 7-1 (but with the pressure tap length indicated in Table 1) for use with threaded end valves, and also in order to adapt threaded flanges for flanged valves. Table 1 — Tube sizes

Nominal size of valve DN Nominal size of tube mm Thread size Gauge length mm 8 13,5 × 2,3 ¼ 11,0 10 17,2 × 2,3 ê 11,5 15 21,3 × 2,6 ½ 15,0 20 26,9 × 2,6 ¾ 16,5 25 33,7 × 3,2 1 19,0 32 42,4 × 3,2 1 ¼ 21,5 40 48,3 × 3,2 1 ½ 21,5 50 60,3 × 3,6 2 25,5 65 76,1 × 3,6 2 ½ 30,0 80 88,9 × 4,0 3 33,0 100 114,3 × 4,5 4 39,0 125 139,7 × 5,0 5 43,5 150 165,1 × 5,0 6 43,5 200 219,1 × 3,6

250 273,0 × 4,0
300 323,9 × 4,5
350 355,6 × 5,0
400 406,4 × 5,0
450 457,0 × 5,0
500 508,0 × 5,6
600 610,0 × 6,3

NOTE The nominal dimensions of DN 8 to DN 150 are in accordance with ISO 65, medium series and ISO 7598. The nominal dimensions of DN 200 to DN 600 are in accordance with ISO 4200, series C and EN ISO 1127.

SIST EN 1267:2012

EN 1267:2012 (E) 9 4.3.2 Copper test tubes Table 2 — Copper test tubes Nominal size of valve DN Nominal size of tube mm 8 10 × 0,8 10 12 × 1,0 15 15 × 1,0 15/20 18 × 1,0 20 22 × 1,0 25 28 × 1,5 32 35 × 1,5 40 42 × 1,5 50 54 × 1,5

Dimensions and tolerances shall be in accordance with EN 1057. Test tubes shall be straight. Their ends shall be cut square and deburred. Their internal surfaces shall be cleaned and free from obstructions visible to the naked eye. Inner diameters are determined by the valve manufacturer unless otherwise specified in a valve, product or application standard. For valves with low ζ coefficient, the results obtained are affected by the test tube inner diameter. Therefore, the actual test tube inner diameter shall be mentioned (see Clause 7 b)). NOTE When new test tubes are made, it is recommended to make them in accordance with Table 1 and Table 2. 4.4 Pressure tappings The number of pressure taps is determined by the laboratory. At each pressure measurement section, there can be one, two or four tabs or a slot, provided that eccentricity is controlled. There should be four measurement taps for sizes greater than DN 300. Pressure tap diameters shall comply with Table 3 and length shall be at least twice the diameter. The measurement tap hole on test tube internal surface is sharp-edged and free from burrs. The measurement tape hole centreline cuts the axis of the test tube. The pressure tap hole centreline is square to axis with a maximum tolerance of 5°. The inner diameter of connection tubes between taps and pressure measurement devices shall be at least twice the pressure tap hole diameter. To avoid dirt accumulation, no tap shall be located at measurement section bottom. Table 3 — Pressure tap hole diameter DN

Minimum mm Maximum mm < 20 1,5 2 20 to 50 2 3 > 50 3 5
SIST EN 1267:2012

EN 1267:2012 (E) 10 4.5 Measurement devices The pressure loss shall be measured with a differential pressure sensor. The sensors or methods known further to calibration or by reference to other standards, providing measurements whose systematic uncertainty does not exceed the maximum permissible values, shall be used. The accuracy of measurement shall be a) upstream pressure, differential pressure and flow rate: ± 2 % of the read value, b) temperature measurement: ± 1 °C. 4.6 Test fluid Test fluid shall be water with a temperature between 5 °C and 40 °C. 5 Test procedure 5.1 Test conditions 5.1.1 Permissible measurement fluctuations The permissible measurement fluctuation amplitude of each measurement value is given in Tables 4 and 5. If the fluctuations amplitude is greater than these values, the measurements shall be performed through a damper device. The damper installation shall not affect measurement accuracy: use a linear, symmetrical response device. Table 4 — Differential pressure fluctuations Value of ζ Fluctuations on ∆p % ζ > 20 ± 6 4 < ζ ≤ 20 ± 10 1 < ζ ≤

4 ± 17 0,1 ≤ ζ ≤ 1 ± 26

Table 5 — Flow rate and pressure fluctuations Quantity Symbol Fluctuations % Flow rate eq ± 6 Upstream pressure ep ± 6

NOTE More information about accuracy is given in Annex C. SIST EN 1267:2012
EN 1267:2012 (E) 11 5.1.2 Steady conditions

Test conditions are referred to as steady if the mean values of all measured values are time-independent. Practically, test conditions may be considered as steady if the variations of each value observed at the test operating point for at least 10 s, do not exceed 1,2 % (difference between larger and smaller values read for a quantity versus mean value). If this condition is met and the fluctuations are lower than the limit values in 5.1.1, one single measurement shall be recorded for a given operating point.

5.1.3 Permissible non-steady conditions When test conditions are not steady, the following procedure shall apply. At each tested operating point, repetitive readings of the measured quantities shall be performed at random time intervals exceeding 10 s. At least three series of measurement acquisitions shall be performed for each operating point. The percentage difference between the largest and the smallest value for each measurement shall not exceed the percentage indicated in Table 6. This leads to an uncertainty in accordance with 6.3.1. Table 6 — Difference between the largest and smallest values Number of measurement series Permissible difference to mean value % 3 1,8 5 3,5 7 4,5 9 5,8 13 5,9 > 30 6,0

The arithmetic mean of all measurements shall be taken as measured value in the scope of the test. If excessive variations cannot be avoided, the uncertainty may be calculated by statistic analysis. 5.2 Pressure loss in test tubes In order to eliminate the pressure loss of the test tubes between the upstream and downstream pressure taps from the characteristic for the tested valve, the pressure loss associated with flow rate from that tube portion may be determined as follows. For each test tube nominal dimension, connect the tubes concentrically to each other without gap between ends in the test section indicated in Figure 1. Provide a suitable water flow rate in the test facility to eliminate any entrapped air pockets. Record a series of associated flow rate and pressure loss values in the same operating flow rate range used for the valve test. Determine the relationship between test tube flow rate and pressure loss. Test this relationship again periodically, notably if the internal surface condition of the tubes has changed significantly.

SIST EN 1267:2012

EN 1267:2012 (E) 12 When the ζ coefficient of the valve is very low, it is recommended to measure, during the same test campaign, the pressure loss of the tubes and the pressure loss of the valve-tube assembly with the same configuration, and the same measurement devices. When the ζ coefficient of the valve is high, other test tube pressure loss determination methods can be used, provided that the uncertainty is in accordance with the requirements of 5.1. NOTE More information on test tubes ζ coefficient is given in Annex A. 5.3 Valve test The valve flow characteristics are determined by mounting the valve on the test facility as shown in Figure 1. The obtained flow characteristics include those of the test tubes which have to be subtracted. The characteristics of the test tubes shall be measured according to 5.2. For valves with internally threaded ends (as per ISO 7-1), the engaged thread length of screwed parts between test tubes and valve shall be as indicated in Table 7. For valves with other threaded lengths, the engaged thread length shall be the entire useful threaded length of the valve.

For valves with capillarity- or compression-type ends, the tubes used shall be mounted in thrust abatement in the valve body.

For flanged valves, connection shall be aligned without offset between the test facility flange face and the tube on which it is secured, and the fluid path shall not be obstructed by the gaskets. Provide a water flow rate so that all air is purged off the facility. The test can be performed differently according to the valve type, the scope and the specifications of the applicable product standard or of the application standard, as follows: a) determining the pressure loss for a given flow rate; b) determining the pressure loss in a range of flow rate values; c) determining the flow rate for a given pressure loss; d) determining the flow rate in a range of pressure loss values; e) determining one or more coefficients measured under different flows, in turbulent flow conditions. NOTE More information on turbulent flow and vaporisation conditions is given in Annex B. When a valve is tested to determine its flow coefficient in turbulent conditions:

 measurements shall be performed for at least three different flow rate values;

 the minimum flow rate value shall be determined so that the Reynolds number always exceeds 4 × 104;  the maximum flow rate value shall be greater than the upper value of the operating range specified by the manufacturer. If this limit cannot be reached by the test facility, the test laboratory shall establish that the maximum attainable flow rate value of its facility is satisfactory to obtain results within accuracy compatible to this European Standard;

 an intermediate flow rate value between maximum and minimum shall be determined. SIST EN 1267:2012

EN 1267:2012 (E) 13 The permissible difference between the maximum and minimum flow coefficient values shall not exceed 4 % (see examples hereto).

If the difference exceeds this tolerance, it can be due to vaporisation. Therefore, the test shall be repeated with a higher upstream pressure value. If the difference is within tolerance, the flow coefficient in turbulent flow conditions is the average between the three calculated flow coefficient values. Vaporisation shall be avoided unless in contradiction with the product standard or the application standard.

For each test, the pressure loss in the test tubes shall be subtracted from the total measured pressure loss.

Table 7 — Engaged thread length Thread dimension, ISO 7-1 ¼ ê ½ ¾ 1 1¼ 1½ 2 2½ 3 4 5 6 Engaged thread length a mm 10,0 10,5 14,0 15,5 18,0 20,5 20,5 24,5 28,5 31,5 37,5 42,0 42,0 Tolerance mm ± 1 ± 1 ± 1 ± 1 ± 1 ± 1 ± 1 ± 1 ± 1,5 ± 1,5 ± 1,5± 1,5± 1,5a The maximum engaged thread length shall be equal to that stated in column 16 of ISO 7-1:1994.

6 Calculation 6.1 Valve pressure loss determination ttvvppp∆−∆=∆+ (1) where ûpv is the pressure loss in the valve itself, in bar; ûpv+t is the pressure loss in the test tubes and in the valve, in bar; ûpt is the pressure loss in the tubes, measured without the valve, in bar. These three pressure loss values refer to the same flow rate value. SIST EN 1267:2012

EN 1267:2012 (E) 14 6.2 Coefficient calculations 6.2.1 Flow resistance coefficient ζζζζ (zeta) 22upv×∆×=ρζ (2) where ∆pv is the pressure loss in the valve, in Pascal (Pa) (1 Pa = 10-5 bar); u is the mean water velocity, in meters per second (m/s); ρ

is the density of water, in kilogram per cubic meter (kg/m3). To determine the actual measured ζ value, Equation (4) is used for mean velocity rate calculation: ×=41026Dquπ (3) where q is the flow rate, in cubic meters per second (m3/s); D is the inner diameter of the test tube, in millimetres (mm). Practically and for reference, ζ is based on a diameter equal to DN. The mean velocity is then calculated according to Equation (4) with D equal to the value of DN.

6.2.2 Flow coefficient, Kv 0ρρvvvpqK∆= (4) where qv is the flow rate, in cubic meter per hour (m3/h); ρ is the density of water, in kilogram per cubic meter (kg/m3); ρ0 is the density of water at 15 °C, in kilogram per cubic meter (kg/m3); ∆pv is the pressure loss in the valve, in bar. 6.2.3 Flow coefficient, Cv Cv = 1,16 × Kv (5) SIST EN 1267:2012

EN 1267:2012 (E) 15 6.3 Uncertainty 6.3.1 Total measurement uncertainty 6.3.1.1 Differential pressure As mentioned in 5.1.3, the random uncertainty, the total uncertainty and any other uncertainty on differential pressure measurement increase with the increase of fluctuation amplitude. Consequently, the permissible total uncertainty error value on measurement depends on ζ value as shown in Table 8. Table 8 — Maximum uncertainty value on differential pressure measurement ζ value Symbol Uncertainty % ζ > 20 eûp ± 3,5 4 < ζ ≤ 20 eûp ± 6 1 < ζ ≤ 4 eûp ± 10 0,1 ≤ ζ ≤ 1 eûp ± 15

6.3.1.2 Other quantities Total error on flow rate, upstream pressure and temperature are shown in Table 9. Table 9 — Maximum uncertainty values on flow rate measurement, upstream pressure and temperature Quantity Symbol Uncertainty Flow rate eq ± 3,5 % Upstream pressure ep ± 3,5 % Temperature ∆t ± 1 °C a a For temperature measurement, random uncertainty is negligible versus systematic erro

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