BS 6199-1 2-1991 Measurement of liquid flow in closed conduits using weighing and volumetric methods - Weighing method - Procedures for checking static weighing systems《用称重及体积法测定密封.pdf

1、BRITISH STANDARD BS 6199-1.2: 1991 ISO 9368-1: 1990 Measurement of Liquid flow in closed conduits using weighing and volumetric methods Part 1: Weighing method Section 1.2 Procedures for checking static weighing systemsBS6199-1.2:1991 This British Standard, having been prepared under the directionof

2、 the Industrial-process Measurement and Control Standards Policy Committee, waspublished under the authorityof the Standards Boardand comes into effect on 31October 1991 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference PCL/2 Draft for comment 89/20801

3、 DC ISBN 0 580 20133 3 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Industrial-process Measurement and Control Standards Policy Committee (PCL/-) to Technical Committee PCL/2, upon which the following bodies were represented: British

4、Compressed Air Society British Gas plc Department of Energy (Gas and Oil Measurement Branch) Department of Trade and Industry (National Engineering Laboratory) Electricity Industry in United Kingdom Energy Industries Council GAMBICA (BEAMA Ltd.) Institute of Measurement and Control Institute of Petr

5、oleum Institute of Trading Standards Administration Institution of Gas Engineers Institution of Mechanical Engineers Society of British Gas Industries Water Services Association of England and Wales The following body was also represented in the drafting of the standard, through subcommittees and pa

6、nels: University of Surrey Amendments issued since publication Amd. No. Date CommentsBS6199-1.2:1991 BSI 10-1999 i Contents Page Committees responsible Inside front cover National foreword ii Introduction 1 1 Scope 1 2 Normative references 1 3 Definitions and symbols 1 4 Certification 1 5 General pr

7、inciples 2 6 Procedures for checking operations 2 7 Calculation of the overall uncertainty 4 Annex A (normative) Estimation of systematic and random errors introduced by the weighing device 6 Annex B (normative) Study of diverter operation 9 Annex C (normative) Assessment of flowrate stability withi

8、n the integration interval 12 Annex D (normative) Assessment of flowrate stability between integration intervals 13 Annex E (normative) Study of flow characteristics 15 Annex F (informative) Bibliography 15 Figure B.1 Graph of the filling process for the measuring tank 11 Figure B.2 Diagram of measu

9、rement of switching time and switching time difference of the diverter 11 Table 1 Symbols 1 Table 2 Students t distribution for various degrees of freedom and 95 % confidence level 5 Table A.1 Values of S %mas a function of 7 Table A.2 Example of measurement results of a weighing device test 8 Table

10、 B.1 Results of switching time difference tests for the diverter 10 Table C.1 Results of flow stability test during the integration interval 12 Table D.1 Values of A (Abbe criterion) 14 Table D.2 Results of flow stability tests between integration 14 Publication(s) referred to Inside back cover mR o

11、 + ()BS6199-1.2:1991 ii BSI 10-1999 National foreword This Section of BS6199 has been prepared under the direction of the Industrial-process Measurement and Control Standards Policy Committee. It is identical with ISO9368-1:1990 “Measurement of liquid flow in closed conduits by the weighing method P

12、rocedures for checking installations Part1: Static weighing systems”, published by the International Organization for Standardization (ISO). This is Section1.2of a series of Parts and Sections of BS 6199 on weighing and volumetric methods, as follows. Part 1: Weighing method; (It is intended to renu

13、mber Part 1 as Section 1.1 when it is next reviewed.) Part 2: Method for measurement by collection of the liquid in a volumetric tank. It is envisaged that a further Part of BS 6199 will be published in due course that will be identical with ISO9368-2 “Measurement of liquid flow in closed conduits b

14、y the weighing method Procedures for checking installations Dynamic weighing methods”. Cross-references International Standard Corresponding British Standard ISO 3354:1988 BS 1042 Measurement of fluid flow in closed conduits Section2.4:1989 Method of measurement of clean water flow using current met

15、ers in full conduits and under regular flow conditions (Identical) ISO 3966:1977 Section2.1:1983 Method using Pitot static tubes (Identical) ISO 4006:1991 a BS 5875:1991 Glossary of terms and symbols for measurement of fluid flow in closed conduits (Identical) ISO 4185:1980 BS 6199 Measurement of li

16、quid flow in closed conduits using weighing and volumetric methods Part1:1981Weighing method (Identical) ISO 5168:1978 BS 5844:1980 Methods of measurement of fluid flow:estimation of uncertainty of a flow-rate measurement (Identical) BS 7118 Measurement of fluid flow: assessment of uncertainty in th

17、e calibration and use of flow measurement devices ISO 7066-1:1989 Part 1:1990 Linear calibration relationships (Identical) ISO 7066-2:1988 Part 2:1989 Non-linear calibration relationships (Identical) ISO 7194:1983 BS 1042 Measurement of fluid flow in closed conduits Section 2.3:1984 Methods of flow

18、measurement in swirling or asymmetric flow conditions in circular ducts by means of current-meters or Pitot static tubes (Identical) ISO 7278-3:1986 BS 6866 Proving systems for meters used in dynamic measurement of liquid hydrocarbons Part3:1987Methods for pulse interpolation (Identical) a The refer

19、ence in the text is to an undated standard which has now been published.BS6199-1.2:1991 BSI 10-1999 iii The Technical Committee has reviewed the provisions of OIML International Recommendation33, to which reference is made in the text, and has decided that they are acceptable for use in conjunction

20、with this standard. There is no related British Standard to OIML International Recommendation33. 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 doe

21、s not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages1to16, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This

22、will be indicated in the amendment table on the inside front cover.iv blankBS6199-1.2:1991 BSI 10-1999 1 Introduction The weighing method of liquid flowrate measurement, as described in ISO4185, is one of the basic methods of measurement, it is widely used in hydraulic research, in the testing of pu

23、mps and turbines and for flowmeter calibration. To obtain comparative results when such measurements are carried out in various installations, it is necessary to standardize the procedures for carrying out the measurements and the tests. 1 Scope This part of ISO9368 specifies methods of testing inst

24、allations for flowrate measurement by the static weighing method. Methods of testing by dynamic weighing are given in ISO9368-2. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO9368. At the time of publ

25、ication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO9368 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of

26、 currently valid International Standards. ISO 4006:, Measurement of fluid flow in closed conduits Vocabulary and symbols 1) . ISO 4185:1980, Measurement of liquid flow in closed conduits Weighing method. ISO 5168:1978, Measurement of fluid flow Estimation of uncertainty of a flow-rate measurement. O

27、IML International Recommendation 33:1973, Conventional values of the result of weighing in air. 3 Definitions and symbols 3.1 Definitions For the purposes of this part of ISO9368, the definitions given in ISO4006 apply. 3.2 Symbols The symbols used in this part of ISO9368 are given in Table 1. Table

28、 1 Symbols 4 Certification If the installation for flowrate measurement by the weighing method is used for purposes of legal metrology, if shall be certified and registered by the national metrology service. Such installations are then subject to periodic inspection at stated intervals, if a nationa

29、l metrology service does not exist, a certified record of the basic measurement standards (length, mass, time and temperature), and error analysis in accordance with this part of ISO9368 and ISO5168, may also constitute certification for legal metrology purposes. The person responsible for carrying

30、out the checks shall evaluate the results in accordance with this part of ISO9368 and shall issue and sign a written report on the results. 1) To be published. (Revision of ISO 4006:1977.) Symbol Quantity Dimension a SI unit E R Random uncertainty, relative value Dimensionless e R Random uncertainty

31、, absolute value b b E s Systematic uncertainty, relative value Dimensionless e s Systematic uncertainty, absolute value b b m Mass M kg q v Volumetric flowrate L 3T 1 m 3 /s q m Mass flowrate M T 1 kg/s S Standard deviation, relativevalue dimensionless s Standard deviation, absolute value b b t Tim

32、e T s V Volume L 3 m 3 Liquid density M L 3 kg/m 3 a M = mass; L = length; T = time. b The dimensions and units are those of the quantity for whichthe uncertainty is stated.BS6199-1.2:1991 2 BSI 10-1999 5 General principles 5.1 Main items of installation Static weighing installations generally compr

33、ise the following main items: sump, test section, diverter, weightank, weighing device, receiving tank, timer, one or more pumps. The requirements for these main items are specified in ISO4185. 5.2 Test liquid Clean water is generally used as the test liquid when verifying installations for flowrate

34、 measurement by the weighing method. Other liquids may be employed provided that the liquid vapour pressure is low enough to make vaporization effects negligible. For practical reasons (particularly to limit the drainage time of the weightank) it is recommended that the kinematic viscosity of the li

35、quid does not exceed about35 10 6m 2 /s. 5.3 Principle of verification Following the construction of a system, tests are carried out to assess the systematic and random errors. Further tests are conducted at regularly established intervals to determine the errors and to compare them with the previou

36、s results to determine the required intervals between successive checks. The general principle of the verification of flow calibration systems is to check separately the errors for each item of the installation and to combine them to determine the overall uncertainty of the whole installation. ISO41

37、85:1980, subclause6.2, covers methods for assessing the weighing device and diverter errors. This part of ISO9368 amplifies certain aspects of verification and testing of the system. In particular, alternative procedures are given for checking the weighing device (see6.1 andAnnex A), checking the di

38、verter (see6.2 andAnnex B), checking the timer (see6.3), checking the density measurement system (see6.4), assessment of flowrate stability (see6.5 andAnnex C andAnnex D), study of flow characteristics (see6.6 andAnnex E), and calculating the overall measurement uncertainty (see clause7). 5.4 Prelim

39、inary operations Before undertaking the detailed checks the following preliminary operations shall be carried out: a) examine the technical description and written procedures for operating the installation; b) check the characteristics of the main and auxiliary instrumentation and equipment, and ver

40、ify that it conforms with the characteristics given in the documentation; c) check the operation of the hydraulic system in order to establish any additional sources of error; d) determine the operational flow range of the installation. The maximum operational flowrate of an installation shall be th

41、e lower of the following two values: a) the maximum flowrate which can be produced by the flow supply system when operating in a flow circuit with minimum hydraulic resistance; b) the flowrate corresponding to the minimum allowable time for filling the weightank up to its maximum level, the minimum

42、time having to satisfy the requirements given in ISO4185:1980, subclause3.3, i.e.30s. 6 Procedures for checking operations 6.1 Checking the weighing device The mass of liquid collected is determined by weighing the weightank before and after the diversion period (double weighing) and the tare is the

43、n subtracted from the gross weight. Checking of the weighing device used with the double weighing method shall allow the determination of the corrections to be applied and the systematic and random uncertainties due to the weighing device. Procedures for assessing these uncertainties are given in de

44、tail in ISO4185 and Annex A of this part of ISO9368. 6.1.1 Checking by means of standard weights in order to check the weighing device, standard weights of a total mass not less than the maximum possible mass of liquid collected shall be used whenever possible. The maximum permissible error of the s

45、tandard weights shall be20 % or less of the expected uncertainty of the weighing device.BS6199-1.2:1991 BSI 10-1999 3 If the total mass of the standard weights used in the process of verification is less than the maximum possible mass of liquid collected, then a method of successive substitution may

46、 be used for checking the weighing device, in this case, the total of the standard weights shall not be less than25 % of the maximum possible mass of liquid to be weighed. Nevertheless, this value of25% may be reduced provided that it is possible to determine experimentally, according to the repeate

47、d procedures of successive substitution, that the required accuracy is achieved. When a high accuracy is required, the effects of aerostatic buoyancy on the standard weights and test liquid shall be taken into account in accordance with OIML Recommendation33and ISO4185. 6.1.2 Checking by means of st

48、andard volumetric tanks In certain cases, for instance for large capacity weightanks or when some structures are not completely immersed according to the amount of water stored in the weightank, it is better to check the weighing device by means of standard volumetric tanks, the volume of which shal

49、l be between5 % and10 % of the maximum volume stored in the weightank. It is then necessary to known the density of the water for the measurement conditions with an uncertainty less than0,01%. This implies in particular the determination of the water temperature with an uncertainty less than0,5 C. The checking procedure is identical to that used with standard weights (see6.1.1). 6.2 Checking the diverter Before starting testing, the diverter shall be checked at minimum and maximum flowrates to ensure