1、BRITISH STANDARD BS5857-1.1: 1980 ISO2975-I: 1974 Methods for measurement of Fluid flow in closed conduits, using tracers Part1: Measurement of water flow Section1.1General ISO title: Measurement of water flow in closed conduits Tracermethods Part I: General UDC 532.542:532.574.8 CONFIRMED JANUARY 2
2、008BS5857-1.1:1980 This BritishStandard, having been prepared under the directionof the Industrial-process Measurement and Control Standards Committee, was published under the authority ofthe Executive Board and comesinto effect on 31 March1980 BSI11-1999 The following BSI references relate to the w
3、ork on this standard: Committee reference PCL/2 Draft for comment77/28083 DC ISBN 0 580 11245 4 Cooperating organizations The Industrial-process Measurement and Control Standards Committee, under whose direction this BritishStandard was prepared, consists of representatives from the following Govern
4、ment department and scientific andindustrial organizations: British Gas Corporation British Industrial Measuring and Control Apparatus Manufacturers Association British Steel Corporation CBMPE (Council of British Manufacturers of Petroleum Equipment) Control and Automation Manufacturers Association
5、(BEAMA) Department of Industry (Computers Systems and Electronics) Electrical, Electronic, Telecommunications and Plumbing Union Electricity Supply Industry in England and Wales* Electronic Engineering Association Engineering Equipment Users Association* Institute of Measurement and Control Institut
6、ion of Electrical Engineers Institution of Gas Engineers Oil Companies Materials Association Post Office Engineering Union Scientific Instrument Manufacturers Association Sira Institute The organizations marked with an asterisk in the above list, together with thefollowing, were directly represented
7、 on the committee entrusted with thepreparation of this BritishStandard: Department of Energy (Gas Standards) United Kingdom Atomic Energy Authority Amendments issued since publication Amd. No. Date of issue CommentsBS5857-1.1:1980 BSI 11-1999 i Contents Page Cooperating organizations Inside front c
8、over National foreword ii 0 Introduction 1 1 Scope and field of application 1 2 Vocabulary and symbols 1 3 Units 1 4 Choice of method 1 5 Choice of tracer 2 6 Choice of measuring length and adequate mixing distance 3 7 Errors 6 Annex Distribution table of # 2(Pearsons law) 8 Figure 1 Theoretical res
9、ults 9 Figure 2 Reynolds number effect on mixing distance 10 Figure 3 Experimental results 11 Publications referred to Inside back coverBS5857-1.1:1980 ii BSI 11-1999 National foreword This BritishStandard has been prepared under the direction of the Industrial-process Measurement and Control Standa
10、rds Committee and is identical with ISO2975-I:1974 “Measurement of water flow in closed conduits Tracer methods Part1: General” published by the International Organization for Standardization (ISO). Terminology and conventions. The text of the International Standard has been approved as suitable for
11、 publication, without deviation, as a British Standard. Some terminology and certain conventions are not identical with those used in BritishStandards; attention is especially drawn to the following. The comma has been used throughout as a decimal marker. In BritishStandards it is current practice t
12、o use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, they should be read as “BritishStandard”. With reference to footnote1) to clause2, ISO4006 “Measurement of fluid flow in closed conduitsVocabulary and symbols” wa
13、s published in1977. 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 of itself confer immunity from legal obligations. Cross-reference Inter
14、national Standard Corresponding BritishStandard ISO4006:1977 BS5875:1980 Glossary of terms and symbols for measurement of fluid flow in closed conduits (Identical) Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to12, an inside back cover and a bac
15、k cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS5857-1.1:1980 BSI 11-1999 1 0 Introduction This International Standard is the first of a series of standards covering trace
16、r methods of water flow measurement in closed conduits. The complete series of standards will be as follows: PartI: General; PartII: Constant rate injection method using non-radioactive tracers; PartIII: Constant rate injection method using radioactive tracers; PartIV: Integration (sudden injection)
17、 method using non-radioactive tracers; PartV: Integration (sudden injection) method using radioactive tracers; PartVI: Transit time method using non-radioactive tracers; PartVII: Transit time method using radioactive tracers. 1 Scope and field of application This International Standard deals with th
18、e measurement of water flow in closed conduits by using tracer methods; the flow of other liquids and of gases will be dealt with in subsequent International Standards These methods apply to flow measurement in conduits into which a solution can be injected and those cases where effective mixing of
19、this solution with the water flowing in the conduit can be achieved, this last condition being fundamental Three fundamental procedures are used: Two procedures, known as the constant rate injection method and the integration (sudden injection) method, are based on the dilution principle: a tracer s
20、olution is injected into the conduit and the dilution (ratio) of this tracer in the water flowing in the conduit is determined, this dilution being proportional to the rate of flow The third is a method of measurement of the mean transit time (formerly called Allen velocity method): the tracer is in
21、jected into the conduit and the time taken by the tracer to travel a specified length between two cross-sections in each of which it is detected, is measured. In these three methods, the advantages and disadvantages of which are considered in clause4, the distance between injection and measuring sec
22、tions should be great enough to achieve adequate mixing of the tracer with the water flowing in the conduit; the problem of an adequate mixing distance is considered in clause6. A large number of different tracers may be used, such as radioactive or non-radioactive, mineral or organic materials. The
23、 choice of tracer depends on the circumstances of the measurement (clause5). The error in measurements using tracers can be less than1% under good conditions (clause7). 2 Vocabulary and symbols The vocabulary and symbols used in this International Standard will be defined in ISO ., Glossary of terms
24、 and symbols relative to the measurement of fluid flow in closed conduits 1) . 3 Units The basic units in this International Standard are SI units. 4 Choice of method 4.1 Comparison between dilution methods and methods based on transit time measurement 4.1.1 Advantage of the dilution methods It is n
25、ot necessary to know the geometrical characteristics of the conduit. 4.1.2 Advantages of methods based on transit time measurement It is necessary only to determine the concentration-time distribution at two measuring cross-sections separated by a known volume of pipe. It is not necessary to know vo
26、lumes, masses, rates offlow or characteristics of the injected solutions. 4.2 Comparison between the two dilution methods (constant rate injection and integration (sudden injection) procedure) 4.2.1 Advantages of the constant rate injection method If the rate of flow of the injection is known to be
27、of the required accuracy and constancy it is not necessary to measure any period of injection. It is simple to check good mixing by using only one instrument when samples can be taken at different locations in the plane of the points of measurement. However, several instruments in parallel should be
28、 used when the same verification is required in the integration method. 1) In preparation.BS5857-1.1:1980 2 BSI 11-1999 It is simpler to determine random errors. It is not necessary to know the volume of injected solution. 4.2.2 Advantages of the integration method This method requires a smaller mas
29、s of tracer and less time than the constant rate injection method. Method of injection does not matter and the apparatus is simple. With the same quantity of tracer it is possible to make the measurement over a greater length of pipe. 5 Choice of tracer 5.1 General A large number of different tracer
30、s may be used, such as radioactive or non-radioactive, mineral or organic, but it is necessary for any tracer to comply with the following requirements: a) it should mix easily with water; b) it should cause only negligible modifications of the rate of flow; c) it should be detectable at a concentra
31、tion lower than the highest permissible concentration while taking account of toxicity, corrosion, etc. It is also preferable for the tracer to comply with the following requirements: d) it should be cheap; e) it should only be present in the water flowing in the conduit at a negligible or constant
32、concentration. In addition, for dilution methods, it is important that the tracer f) can, at low concentrations, be analysed accurately; g) should not react with the water flowing in the conduit or with any other substance with which it may come into contact in such a way as to affect the measuremen
33、t. Furthermore, for transit time methods, it is absolutely necessary that the tracer be such that h) its concentration in the measuring cross-sections can be determined at any moment. The following substances are given as examples, together with final minimum concentrations at which they can be dete
34、cted at the required levels after dilution in water: 5.1.1 Non-radioactive tracers sodium dichromate (Na 2 Cr 2 O 7 .2H 2 O): 2 10 1 mg/l with direct analysis 2 10 3 mg/l after reconcentration sodium chloride (NaCl):1to10mg/l depending on original conductivity rhodamine B (C 28 H 31 ClN 2 O 3 ):2 10
35、 4 mg/l rhodamine Wt lithium chloride (LiCl) fluorescein (C 20 H 10 O 5 Na 2 ):5 10 3 mg/l Other tracers have been used, and in particular: sodium nitrite (NaNO 2 ) manganese sulphate (MnSO 4 .4H 2 O) sulfo-rhodamine G 5.1.2 Radioactive tracers Dilution and transit time methods: bromine82 (half-life
36、36h, energies of0,55 to1,48MeV) sodium24 (half-life15h, energies of1,37 to2,75MeV) Other isotopes such as: gold198 (half-life2,7days, energies of0,41to1,09MeV) iodine131 (half-life8,04days, energies of0,25to0,81MeV) chromium51 (half-life27,8days, energy of0,32MeV) may be used if preliminary measurem
37、ents confirm that no adsorption of tracer occurs on the walls of the conduit or on the walls of sampling and counting containers. Tritium (half-life12,26years, energy of0,018MeV) may also be used. In addition, for transit time methods, because the effect of wall adsorption on the measurement is not
38、as great as in the dilution methods, other isotopes may be used, in particular, isotopes obtained from radioactive cows, such as: 137caesium137m barium (half-life2,6min, energy of0,66MeV) 113tin113m indium (half-life104min, energy of0,39MeV) 5.2 Advantages or disadvantages of the different tracers 5
39、.2.1 Comparison between radioactive and non-radioactive tracers 5.2.1.1 ADVANTAGES OF RADIOACTIVE TRACERS These can be detected by means of probes located outside the conduit (for tracers emitting radiation). The measurements are less affected by turbidity of the water than are those made with non-r
40、adioactive tracers.BS5857-1.1:1980 BSI 11-1999 3 If the basic substance of tracers with a short half-life is inoffensive, any contamination danger disappears very quickly and there is no permanent pollution. The cost of the tracer is not proportional to the rate of flow to be measured, and this make
41、s its use attractive in the case of large rates of flow. 5.2.1.2 PARTICULAR ADVANTAGES OF RADIO-ELEMENT GENERATORS A practically inexhaustible quantity of radioactive tracer of short half-life is availabe at the measuring place from a small quantity of “mother” substance of long half-life at a very
42、low cost. It is possible to make repeated measurements in recirculating systems when the “daughter” substance has a sufficiently short half-life 5.2.1.3 ADVANTAGES OF NON-RADIOACTIVE TRACERS It is not necessary for the operators to be specially trained and classified. Substances generally remain sta
43、ble with time; delays and distances between the supply and the use of the substance do not matter. Transport and injection of the substance do not require particular safety procedures; containers can be light. Administrative authorizations are not necessary for each measurement. 5.2.2 Comparison of
44、various non-radioactive tracers in general use 5.2.2.1 ADVANTAGES OF DICHROMATE Small concentrations can be analyzed by colorimetric procedures which do not require specialised operators; it can easily be reconcentrated. It is not present in natural waters. It is very stable when in crystalline form
45、 and relatively stable when in solution in pure waters, even in sunshine. It is very soluble in water (more than600g/l). It is relatively cheap. 5.2.2.2 DISADVANTAGES OF DICHROMATE Instability in certain reducing conditions. Need of a reagent. Toxic in concentrated solutions. 5.2.2.3 ADVANTAGES OF R
46、HODAMINES They can be analyzed in smaller concentrations than can dichromate. Their concentration can be recorded during measurements as they do not need any reagent for the analysis. They are not present in natural waters. They are not significantly toxic and do not affect animal life. 5.2.2.4 DISA
47、DVANTAGES OF RHODAMINES Not very soluble. Rather expensive. The characteristics of certain rhodamines are affected by sunlight, temperature or the presence of certain silts in water (problems due to adsorption effects). Residual colour is difficult to remove. 5.2.2.5 ADVANTAGES OF SODIUM CHLORIDE Th
48、e resistivity of the sodium chloride solution is proportional to concentration over a wide range. It is relatively cheap. 5.2.2.6 DISADVANTAGE OF SODIUM CHLORIDE It cannot be used at very low concentrations. 6 Choice of measuring length and adequate mixing distance 6.1 Introduction When a tracer is
49、used to measure the flow of water in a conduit, there should be sufficient distance between the region in which the tracer is injected or produced and the region in which concentration or transit time measurements are made. The distance which is required in order to allow the tracer to mix with the water in the conduit is known as the mixing distance. The mixing distance is defined as the shortest distance at which the
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1