1、BRITISH STANDARD Gas analysis Preparation of calibration gas mixtures using dynamic volumetric methods Part 4: Continuous syringe injection method ICS 71.040.40 BS EN ISO 6145-4:2008This British Standard was published under the authority of the Standards Policy and Strategy Committee on 23 March 200
2、5 ISBN 978 0 580 60359 4 National foreword This British Standard is the UK implementation of EN ISO 6145-4:2008. It is identical with ISO 6145-4:2004. It supersedes BS ISO 6145-4:2004 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee PTI/15, Natural gas
3、 and gas analysis. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot
4、confer immunity from legal obligations. Amendments/corrigenda issued since publication Date Comments This corrigendum renumbers BS ISO 6145-4:2004 as BS EN ISO 6145-4:2008 BS EN ISO 6145-4:2008 28 February 2009 BSI 2009EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 6145-4 August 2008 ICS 7
5、1.040.40 English Version Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods - Part 4: Continuous syringe injection method (ISO 6145-4:2004) Analyse des gaz - Prparation des mlanges de gaz pour talonnage laide de mthodes volumtriques dynamiques - Partie 4: Mthode
6、continue par seringue dinjection (ISO 6145-4:2004) Gasanalyse - Herstellung von Kalibriergasgemischen mit Hilfe von dynamisch-volumetrischen Verfahren - Teil 4: Kontinuierliches Spritzen-Injektionsverfahren (ISO 6145- 4:2004) This European Standard was approved by CEN on 30 July 2008. CEN members ar
7、e 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
8、the CEN 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 Management Centre has the sam
9、e status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, R
10、omania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Brussels 2008 CEN All rights of exploitation in any form and by any means rese
11、rved worldwide for CEN national Members. Ref. No. EN ISO 6145-4:2008: EForeword The text of ISO 6145-4:2004 has been prepared by Technical Committee ISO/TC 158 “Analysis of gases” of the International Organization for Standardization (ISO) and has been taken over as EN ISO 6145-4:2008 by Technical C
12、ommittee CEN/SS N21 “Gaseous fuels and combustible gas” the secretariat of which is held by CMC. 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 February 2009, and conflicting national standards s
13、hall be withdrawn at the latest by February 2009. 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. According to the CEN/CENELEC Interna
14、l Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta
15、, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 6145-4:2004 has been approved by CEN as a EN ISO 6145-4:2008 without any modification. BSENISO6145-4:2008 iii Contents Page 1 Scope 1 2 Normativ
16、e references 1 3 Principle 1 4 Application to preparation of gas mixtures 2 4.1 Description of the experimental procedure 2 4.2 Area of validity . 3 4.3 Operating conditions 4 5 Expression of results 4 5.1 Volume fraction 4 5.2 Sources of uncertainty . 4 5.3 Uncertainty of volume fraction 5 Annex A
17、(informative) Pre-mixed gases for preparation of mixtures of high dilution . 6 Annex B (informative) Example of apparatus for preparation of calibration gas mixtures . 7 Annex C (informative) Practical hints . 9 Annex D (informative) Example of the determination of the uncertainty in the concentrati
18、on of a calibration gas mixture prepared by the continuous injection method 12 Bibliography . 15 BSENISO61454:2008blank v Introduction This part of ISO 6145 is one of a series of standards dealing with various dynamic volumetric methods used for the preparation of calibration gas mixtures. BSENISO61
19、454:2008blankANRETNIITOTS LANDNADRA OSI -54164002:4)E( ISO 2004 All rights reserved 1 Gas analysis Preparation of calibration gas mixtures using dynamic volumetric methods Part 4: Continuous syringe injection method 1S c o p e This part of ISO 6145 specifies a method for continuous production of cal
20、ibration gas mixtures, containing two or more components, from pure gases or other gas mixtures by continuous injection of the calibration component(s) into a complementary gas stream by means of a syringe. If pre-mixed gases are used instead of pure gases (see Annex A), much lower volume fractions
21、can be obtained. The volume flow rates, from which the volume fractions are determined, can be calculated from the individual flow rates and can be independently measured by a suitable method given in ISO 6145-1. The merits of the method are that a substantial quantity of the gas mixture can be prep
22、ared on a continuous basis and that multi-component mixtures can be prepared almost as readily as binary mixtures if the appropriate number of syringes is utilized, or if the syringe already contains a multi-component mixture of known composition. This method also provides a convenient means for inc
23、reasing the volume fraction of the calibration component in the mixture in small steps. It is therefore a useful method for evaluation of other characteristics of gas analysers, such as minimum detection limit and dead zone, as well as accuracy. The relative expanded uncertainty in the volume fracti
24、on obtainable for a binary mixture (at a coverage factor of 2) isand the range of applicability is 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
25、latest edition of the referenced document (including any amendments) applies. ISO 6143, Gas analysis Comparison methods for determining and checking the composition of calibration gas mixtures ISO 6145-1, Gas analysis Preparation of calibration gas mixtures using dynamic volumetric methods Part 1: M
26、ethods of calibration 3 Principle The calibration component, either in the gaseous or liquid phase, is displaced from a syringe, through a capillary which may be the needle of the syringe, the plunger of which is continuously driven by a suitable variable-speed motor, into a complementary gas stream
27、. The volume fraction, of calibration component, , in a mixture with complementary gas, , is given by Equation (1): (1) 5% 10 5 10 2 A AB A =q A /(q A +q B ) 1 1 BSENISO61454:20082 ISO 2004 All rights reserved where is the volume flow rate of the calibration component, ; is the volume flow rate of t
28、he complementary gas, . If the calibration component is injected in the liquid phase, the flow rate in the gaseous phase on evaporation is given by Equation (2): (2) where is the volume flow rate of the injected liquid, in the same units as ; is the density of the liquid component at the temperature
29、 at which the mixture is prepared; is the density of the component in the gaseous phase, expressed in the same units and at the same temperature as . Substitution of Equation (2) in Equation (1) then provides the value of in terms of the parameters listed above. 4 Application to preparation of gas m
30、ixtures 4.1 Description of the experimental procedure 4.1.1 Apparatus Schematic diagrams of examples of apparatus for preparation of binary mixtures are shown in Annex B; Figure B.1 presents the apparatus for filling a syringe with a gaseous calibration component and Figure B.2 shows a mixing system
31、 for preparation of the calibration gas mixture. 4.1.2 Selection and calibration of syringe for the calibration component The flow rate of the calibration component is determined by parallel selection of the cross-sectional area of the syringe barrel and the linear velocity of the plunger. Sometimes
32、, for preparation of a mixture of given volume fraction of the calibration component, it may be preferable to use a syringe of larger cross-section (larger capacity) in combination with a lower plunger velocity, and in other cases a smaller cross-section with higher plunger velocity may provide the
33、better combination (refer for practical hints to Annex C). Select a suitable combination of linear speed of the syringe drive mechanism and metering syringe of volume appropriate to the volume fraction, and the uncertainty in that volume fraction, of the calibration gas mixture to be prepared. In or
34、der to validate the uniformity of the syringe barrel, since this is a dynamic method, determine the volume of the gas or liquid delivered by the syringe at several graduation marks, and at the temperature at which the gas mixture is prepared. It is necessary, therefore, to allow time for the syringe
35、 to return to ambient temperature after it has been warmed, for example by handling, before any measurements are made at any stage. This volume calibration shall be derived from traceable mass measurements of a suitable liquid of known density in the syringe. Since the calibration is to be carried o
36、ut at several points, i.e. with the syringe partially filled, precautions shall be taken to ensure that the meniscus of the liquid is horizontal when observations of its position are made. An example of the methodology is presented in Annex C. q A A q B B q A =(q A,l A,l ) / A,g q A,l q A A,l A,g A,
37、l A 2 2 BSENISO61454:2008 ISO 2004 All rights reserved 3 4.1.3 Calibration of the syringe driver Calibrate the syringe driver at the temperature at which the gas mixture is prepared, and against reference equipment which is traceable to international length and time standards. A recommended method f
38、or calibration against a digital micrometer and a digital timer is also presented in Annex C. 4.1.4 Preparation of the calibration gas mixture When the calibration component is in the gaseous phase apparatus, an example of which is shown in Figure B.1, for evacuating, purging and filling the reservo
39、ir and filling the syringe shall be used. The procedure is then as follows. a) Close the shut-off valve on the cylinder of calibration component. b) Evacuate the entire apparatus until the pressure has been reduced to a value which is sufficiently low, such that any residual gas in the reservoir mak
40、es no significant contribution to the volume fraction and has no effect on the stability of the final calibration gas mixture. A residual pressure of approximately ( ) has been found to be suitable. However, the ultimate vacuum required will depend in practice on the nature and composition of the fi
41、nal gas mixture. Due consideration should therefore be given to the partial pressure of the residual gas when the uncertainty in the volume fraction of the calibration gas mixture is evaluated. c) Close the shut-off valve between the vacuum pump and the reservoir and fill the reservoir with the cali
42、bration component, to a pressure of approximately ( ). Re-evacuate and refill the reservoir in the same manner. In the final filling operation, adjust the pressure of the calibration component in the reservoir so that the over-pressure is sufficient for the syringe to be filled. Make appropriate pro
43、vision to ensure that hazardous gaseous components are vented safely from the working area. d) With the plunger pushed fully home, insert the needle of the empty metering syringe through the septum (see Figure B.1) into the reservoir. Raise and lower the plunger several times to ensure that the syri
44、nge is thoroughly flushed with the calibration component without any significant contamination. e) Fill the syringe by fully withdrawing the plunger, then remove the syringe from the septum of the reservoir. With the needle retained in position on the syringe, set the plunger to the first graduation
45、 mark and connect the syringe to the mixing system (Figure B.2). NOTE A convenient way by which to make the connection is again to use a septum. In some cases, it is convenient to introduce the calibration component into the syringe in the liquid phase, then allow it to evaporate after it has issued
46、 from the nozzle. The filling procedure is then straightforward but precautions are still required to ensure that no significant amount of air or other contaminants are introduced into the syringe with the liquid. f) Pass the complementary gas through a pressure regulator and a shut-off valve to a c
47、onditioning train, which may consist of a purifier and/or a humidifier and/or a heat exchange unit immersed in a thermostat bath as required. (It may be the case that none of these components is required.) g) Pass the conditioned gas stream through a calibrated flow meter to a gas-mixing vessel, whi
48、ch may be of any suitable configuration, and at the input of which it meets the calibration component. Inject the calibration component by means of the syringe, filled as described in e), equipped with a mechanically-driven plunger and a variable speed motor, at the predetermined, constant speed. 4.
49、2 Area of validity The method is applicable to preparation of mixtures of non-reacting species, i.e. those which do not react with any material of construction of the flow path of the complementary gas or that of the calibration component being injected. Particular care shall be exercised if the method is considered as a means of preparation of gaseous mixtures which contain components that form potentially explosive mixtures in air. S
