BS EN 24185-1981 Measurement of fluid flow in closed conduits - Weighing method《封闭管道中流体流量测量 称重法》.pdf

1、BRITISH STANDARD BSEN 24185:1993 ISO4185:1980 Incorporating Amendment Nos.1 and 2 Measurement of fluid flow in closed conduits Weighingmethod The European Standard EN24185:1993 has the status of a British Standard UDC 532.575:531.753BSEN24185:1993 This British Standard, having been prepared under th

2、e directionof the Industrial-process Measurementand Control Standards Committee, was published under the authority ofthe Board of BSI and comesintoeffect on 31 December1981 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference PCL/2 Draft for comment78/289

3、36DC ISBN 0 580 12474 6 Cooperating organizations The Industrial-process Measurement and Control Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following: British Gas Corporation* British Industrial Measuring and Control Apparatus

4、Manufacturers Association* British Steel Corporation Control and Automation Manufacturers Association (BEAMA) Department of Industry Department of Industry (Computers, Systems and Electronics) Department of Industry (National Engineering Laboratory)* Department of the Environment (Water Engineering

5、Division, Including Water Data Unit) Electrical, Electronic, Telecommunications and Plumbing Union Electricity Supply Industry in England and Wales* Energy Industries Council* Engineering Equipment Users Association* Institute of Measurement and Control* Institution of Gas Engineers* Oil Companies M

6、aterials Association Post Office Engineering Union Scientific Instrument Manufacturers Association Sira Institute The organizations marked with an asterisk in the above list, together with the following, were directly represented on the Technical Committee entrusted with the preparation of this Brit

7、ish Standard: British Compressed Air Society Department of Energy (Gas Standards) Department of Trade (Metrology, Quality Assurance, Safety and Standards Division) Institute of Petroleum Institute of Trading Standards Administration National Water Council Society of Chemical Industry United Kingdom

8、Atomic Energy Authority Individual expert Amendments issued since publication Amd. No. Date of issue Comments 7979 October1993 8774 October1995 Indicated by a sideline in the marginBSEN24185:1993 BSI 12-1999 i Contents Page Cooperating organizations Inside front cover National foreword ii Foreword 2

9、 1 General 3 1.1 Scope and field of application 3 1.2 References 3 1.3 Definitions 3 1.4 Units 4 1.5 Notation 4 1.6 Certification 4 2 Principle 4 3 Apparatus 9 4 Procedure 12 5 Calculation of flow-rate 13 6 Calculation of the overall uncertainty of the measurement of the flow-rate 13 Annex A Correct

10、ions on the measurement of filling time 19 Annex B Density of pure water 21 Annex C Definition of terms and procedures used in error analysis 22 Annex D Students t-distribution 24 Annex ZA (normative) Normative references to international publications with their relevant European publications 24 Fig

11、ure 1A Diagram of an installation for calibration by weighing (static method, supply by a constant level head tank) 5 Figure 1B Diagram of an installation for flow-rate measure by weighing (used for an hydraulic machine test; static method, supply by a constant level head tank 6 Figure 1C Diagram of

12、 an installation for calibration by weighing (static method, direct pumping supply) 7 Figure 1D Diagram of an installation for calibration by weighing (dynamic method, supply by a constant level head tank) 8 Figure 2 Examples of diverter design 10 Figure 3 Operational law of diverter 10 Figure 4 Tim

13、e metering for a diverter the operation law of which is identical in both directions 11 Figure 5 Example of error distribution in calibration of weighing machine 14 Figure 6 Typical graph used in evaluation of (E R ) pfor a diverter system 16 Figure 7 Plotting of results of diverter timer actuator a

14、s given inA.1.2 20 Figure 8 Illustration of the correction to allow for mean estimated error 23 Figure 9 Uncertainty =$t 23 Table 1 Values of Students t 24 Publications referred to Inside back coverBSEN24185:1993 ii BSI 12-1999 National foreword This British Standard has been prepared under the dire

15、ction of the Industrial-process Measurement and Control Standards Committee and is identical with ISO4185 “Measurement of liquid flow in closed conduits Weighing method, including Technical Corrigendum1” published in1980 by the International Organization for Standardization (ISO). In1993 the Europea

16、n Committee for Standardization (CEN) accepted ISO4185:1980 as European Standard EN24185:1993. As a consequence of implementing the European Standard this British Standard is renumbered as BSEN24185 and any reference to BS6199-1:1981 should be read as a reference to BS EN24185. Terminology and conve

17、ntions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is especially drawn to the following. Wherever the words “I

18、nternational Standard” appear, referring to this standard, they should be read as “British Standard”. The comma has been used throughout as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. OIML Recommendations Nos.1,2,3,20,28 an

19、d33, which are referred to in3.4, are international recommendations of the International Organization of Legal Metrology (OIML). In complying with this British Standard, implementation of these recommendations is not mandatory. Copies of OIML Recommendations may be purchased from the following addre

20、ss. The Director International Bureau of Legal Metrology 11 rue Turgot 75009 Paris France A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not o

21、f itself confer immunity from legal obligations. Cross-references International Standard Corresponding British Standard ISO4006:1977 BS5857:1980 Glossary of terms and symbols for measurement of fluid flow in closed conduits (Identical) ISO5168:1978 BS5844:1980 Methods of measurement of fluid flow: e

22、stimation of uncertainty of a flow-rate measurement (Identical) Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, the EN title page, pages2 to24, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had ame

23、ndments incorporated. This will be indicated in the amendment table on the inside front cover.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN24185 June1993 UDC 532.575:531.753 Descriptors: Flow measurement, liquid flow, pipe flow, measuring instruments, flowmeters, calibrating, weight measureme

24、nt, error analysis English version Measurement of fluid flow in closed conduits Weighing method (ISO4185:1980) Mesure de dbit des liquides dans conduites fermes Mthode par pese (ISO4185:1980) Durchflumessung von Flssigkeiten in geschlossenen Leitungen Wgeverfahren (ISO4185:1980) This European Standa

25、rd was approved by CEN on1993-06-18. 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 na

26、tional standards may be obtained on application to the Central Secretariat or to any CEN member. The 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 n

27、otified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kin

28、gdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1993 Copyright reserved to CEN members Ref. No. EN24185:1993 EEN24185:1993 BSI 12-1999 2 Foreword In1991, ISO4185:1980 Measurement o

29、f fluid flow in closed conduits Weighing method was submitted to the CEN Primary Questionnaire procedure. Following Resolution BT C42/1992, ISO4185:1980 was submitted to the formal vote; the result was positive. This European Standard shall be given the status of a national standard, either by publi

30、cation of an identical text or by endorsement, at the latest by December1993, and conflicting national standards shall be withdrawn at the latest by December1993. According to the CEN/CENELEC Internal Regulations, the following countries are bound to implement this European Standard: Austria, Belgiu

31、m, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. NOTEThe European references to international publications are given in Annex ZA (normative).EN24185:1993 BSI 12-1999 3 1 General 1.1 Sc

32、ope and field of application This International Standard specifies a method of liquid flow-rate measurement in closed conduits by measuring the mass of liquid delivered into a weighing tank in a known time interval. It deals in particular with the measuring apparatus, the procedure, the method for c

33、alculating the flow-rate and the uncertainties associated with the measurement. The method described may be applied to any liquid provided that its vapour pressure is such that any escape of liquid from the weighing tank by vaporization is not sufficient to affect the required measurement accuracy.

34、Closed weighing tanks and their application to the flow measurement of liquids of high vapour pressure are not considered in this International Standard. This International Standard does not cover the cases of corrosive or toxic liquids. Theoretically, there is no limit to the application of this me

35、thod which is used generally in fixed laboratory installations only. However, for economic reasons, usual hydraulic laboratories using this method can produce flow-rates of1.5m 3 /s or less. Owing to its high potential accuracy, this method is often used as a primary method for calibration of other

36、methods or devices for mass flow-rate measurement or volume flow-rate measurement provided that the density of the liquid is known accurately. It must be ensured that the pipeline is running full with no air or vapour pockets present in the measuring section. 1.2 References ISO4006, Measurement of f

37、luid flow in closed conduits Vocabulary and symbols. ISO5168, Measurement of fluid flow Estimation of uncertainty of a flow-rate measurement. OIML, Recommendations Nos.1,2,3,20,28,33. 1.3 Definitions Only terms which are used in a special sense or the meaning of which merits restatement are defined

38、below. 1.3.1 static weighing the method in which the net mass of liquid collected is deduced from tare and gross weighings made respectively before and after the liquid has been diverted for a measured time interval into the weighing tank 1.3.2 dynamic weighing the method in which the net mass of li

39、quid collected is deduced from weighings made while fluid flow is being delivered into the weighing tank. (A diverter is not required with this method.) 1.3.3 diverter a device which diverts the flow either to the weighing tank or to its by-pass without changing the flow-rate during the measurement

40、interval 1.3.4 flow stabilizer a structure forming part of the measuring system, ensuring a stable flow-rate in the conduit being supplied with liquid; for example, a constant level head tank, the level of liquid in which is controlled by a weir of sufficient length 1.3.5 buoyancy correction the cor

41、rection to be made to the readings of a weighing machine to take account of the difference between the upward thrust exerted by the atmosphere, on the liquid being weighed and on the reference weights used during the calibration of the weighing machineEN24185:1993 4 BSI 12-1999 1.4 Units The units u

42、sed in this International Standard are the SI units, metre, kilogram, and second; the degree Celsius is used for convenience instead of the kelvin. 1.5 Notation 1.6 Certification If the installations for flow-rate measurement by the weighing method are used for purposes of legal metrology, they shou

43、ld be certified and registered by the national metrology service. Such installations are then subject to periodical inspection at stated intervals. If a national metrology service does not exist, a certified record of the basic measurement standards (weight and time), and error analysis in accordanc

44、e with this International Standard and ISO5168, shall also constitute certification for legal metrology purposes. 2 Principle 2.1 Statement of the principle 2.1.1 Static weighing The principle of the flow-rate measurement method by static weighing (for schematic diagrams of typical installations, se

45、e Figure 1A, Figure 1B, Figure 1C) is: to determine the initial mass of the tank plus any residual liquid; to divert the flow into the weighing tank (until it is considered to contain a sufficient quantity to attain the desired accuracy) by operation of the diverter, which actuates a timer to measur

46、e the filling time; to determine the final mass of the tank plus the liquid collected in it. The flow-rate is then derived from the mass collected, the collection time and other data as discussed in clause5 and Annex A. Symbol Designation Dimension SI Units q m q V m V t a p s x x e e s E s e R E R

47、Mass flow-rate Volume flow-rate Mass Volume Time Density of liquid Density of air Density of standard weights Estimated standard deviation Standard deviation of variable x Uncertainty of measurement Systematic uncertainty Percentage systematic uncertainty Random uncertainty Percentage random uncerta

48、inty MT 1 L 3 T 1 M L 3 T ML 3 ML 3 ML 3 kg/s m 3 /s kg m 3 s kg/m 3 kg/m 3 kg/m 3EN24185:1993 BSI 12-1999 5 Figure 1A Diagram of an installation for calibration by weighing (static method, supply by a constant level head tank)EN24185:1993 6 BSI 12-1999 Figure 1B Diagram of an installation for flow-

49、rate measure by weighing (used for an hydraulic machine test; static method, supply by a constant level head tank)EN24185:1993 BSI 12-1999 7 Figure 1C Diagram of an installation for calibration by weighing (static method, direct pumping supply)EN24185:1993 8 BSI 12-1999 2.1.2 Dynamic weighing The principle of the flow-rate measurement method by dynamic weighing (see Figure 1D for a schematic diagram of a typical installation) is: to let the liquid collect in the tank to a predetermined