1、BRITISH STANDARD Gas analysis Preparation of calibration gas mixtures using dynamic volumetric methods Part 10: Permeation method ICS 71.040.40 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW 6145-10:2008 BS EN ISO BS EN ISO 6145-10:2008 National foreword This British Standard
2、 is the UK implementation of EN ISO 6145-10:2008. It is is withdrawn. The UK participation in its preparation was entrusted to Technical Committee PTI/15, Natural gas and gas analysis. A list of organizations represented on this committee can be obtained on request to its secretary. This publication
3、 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 confer immunity from legal obligations. ISBN 978 0 580 60362 4 Amendments/corrigenda issued since publication Date Comments 28 Februar
4、y 2009 This corrigendum renumbers BS ISO 6145-10:2002 as BS EN ISO 6145-10:2008 identical with ISO 6145-10:2002. It supersedes BS ISO 6145-10:2002 which BSI 2009 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 25 March 2002 EUROPEAN STANDARD
5、NORME EUROPENNE EUROPISCHE NORM EN ISO 6145-10 August 2008 ICS 71.040.40 English Version Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods - Part 10: Permeation method (ISO 6145-10:2002) Analyse des gaz - Prparation des mlanges de gaz pour talonnage laide de mth
6、odes volumtriques dynamiques - Partie 10: Mthode par permation (ISO 6145-10:2002) Gasanalyse - Herstellung von Kalibriergasgemischen mit Hilfe von dynamisch-volumetrischen Verfahren - Teil 10: Permeationsverfahren (ISO 6145-10:2002) This European Standard was approved by CEN on 30 July 2008. CEN mem
7、bers 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 applicat
8、ion to 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
9、the same 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, Port
10、ugal, Romania, 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 mea
11、ns reserved worldwide for CEN national Members. Ref. No. EN ISO 6145-10:2008: EForeword The text of ISO 6145-10:2002 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 6145-10:2008 by T
12、echnical Committee 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 s
13、tandards shall 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/CENEL
14、EC Internal 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, Luxembo
15、urg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 6145-10:2002 has been approved by CEN as a EN ISO 6145-10:2008 without any modification. BS EN ISO 6145-10:2008 iiiContents Page Intro
16、duction.v 1 Scope 1 2 Normative reference1 3 Principle1 4 Reagents and materials 2 5 Apparatus .2 6 Procedure .5 6.1 Preliminary checks and operating conditions5 6.2 Determination of mass loss6 7 Expression of results 7 7.1 Calculation .7 7.2 Sources of uncertainty8 7.3 Estimation of uncertainties.1
17、0 7.4 Example calculation of uncertainties 13 Annex A (informative) Example of uncertainty calculation for a two-pan continuous weighing system14 Bibliography16 BS EN ISO 6145-10:2008blank vIntroduction This part of ISO 6145 is one of a series of standards dealing with various dynamic volumetric met
18、hods used for the preparation of calibration gas mixtures. I BS EN ISO 6145-10:2008 1Gas analysis Preparation of calibration gas mixtures using dynamic volumetric methods Part 10: Permeation method 1 Scope This part of ISO 6145 specifies a dynamic method using permeation membranes for the preparatio
19、n of calibration gas mixtures containing component mole fractions ranging from 10 9and 10 6 . A relative expanded uncertainty of 2,5 % of the component mole fraction can be achieved using this method. In the mole fraction range considered, it is difficult to maintain some gas mixtures, for example i
20、n cylinders, in a stable state. It is therefore desirable to prepare the calibration gas immediately before use, and to transfer it by the shortest possible path to the place where it is to be used. This technique has been successfully applied in generating low content calibration gas mixtures of, f
21、or example, sulfur dioxide (SO 2 ), nitrogen dioxide (NO 2 ) and benzene (C 6 H 6 ) in air. If the carrier gas flow is measured as a gas mass-flow, the preparation of calibration gas mixtures using permeation tubes is a dynamic-gravimetric method which gives contents in mole fractions. 2 Normative r
22、eference The following normative document contains provisions which, through reference in this text, constitute provisions of this part of ISO 6145. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this p
23、art of ISO 6145 are encouraged to investigate the possibility of applying the most recent edition of the normative document indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid Internat
24、ional Standards. ISO 6145-1, Gas analysis Preparation of calibration gas mixtures using dynamic volumetric methods Part 1: Methods of calibration 3 Principle The calibration component for example SO 2 , NO 2 , ammonia (NH 3 ), benzene, toluene, xylene is permeated through an appropriate membrane int
25、o the flow of a carrier gas, i.e. the complementary gas of the mixture obtained. The calibration component, of known purity, is contained in a tube, which is itself contained in a temperature- controlled vessel. This vessel is purged at a known and controlled flow rate by the carrier gas. The compos
26、ition of the mixture is determined from the permeation rate of the calibration component as well as the flow rate of the high quality carrier gas, free from any trace of the calibration component and from any chemical interaction with the material of the permeation tube. The permeation rate of the c
27、alibration component through the membrane depends upon the component itself, the chemical nature and structure of the membrane, its area and thickness, the temperature, and the partial pressure gradient of the calibration component across the membrane. These factors can be kept constant by proper op
28、eration of the system. The permeation rate can be measured directly by mounting the tube on a microbalance and weighing the tube either continuously or periodically. BS EN ISO 6145-10:20082 4 Reagents and materials 4.1 Permeating substances for calibration, of the highest possible purity so as to av
29、oid any effect of impurities on the permeation rate; if this is not possible, the nature and quantities of the impurities shall be known and allowance made for their effect. 4.2 Carrier gas, of known purity, established by an appropriate analytical technique, for example, gas chromatography (GC) and
30、/or Fourier transform infrared (FTIR) spectrometry. 5 Apparatus 5.1 Permeation apparatus, typically consisting of one of two modes (5.1.1 and 5.1.2) of application of the permeation method. The materials of the permeation apparatus shall be chosen so as to avoid any effect on the content of the cali
31、bration component by sorption (chemical or physical). The smaller the desired final content, the greater the effect of adsorption phenomena. If possible, use glass as the housing of the temperature-controlled permeation tube. Choose flexible and chemically inert tube materials and metals, especially
32、 having regard to the transfer of the gas between the permeation apparatus and the analyser. Pay special attention to all junctions so as to keep them free from leaks. The flow range of the carrier gas is kept constant by a control system and is monitored by a flowmeter. The value of the flow rate c
33、an, for example, be controlled by means of a mass flow controller and determined using a mass flowmeter. The existence of an outlet for surplus gas enables the analyser under calibration to take the gas flow rate necessary for its proper operation, the remainder of the flow of gas being vented to at
34、mosphere. 5.1.1 Periodic-weighing-mode permeation apparatus, consisting of a permeation tube kept in a temperature- controlled enclosure, swept by carrier gas. The permeation tube is periodically removed from the enclosure to be weighed. Typical examples are given in Figures 1 and 2. 5.1.2 Continuou
35、s-weighing-mode permeation apparatus, consisting of a permeation tube kept in a temperature-controlled enclosure, swept by carrier gas. The permeation tube is suspended from a weighing device and weighed continuously. A typical example is given in Figure 3. BS EN ISO 6145-10:2008 3Key 1 Flowmeter 5
36、Thermometer 2 Carrier gas 6 Permeation tube 3 Drier 7 Outlet for surplus gas 4 Filter 8 Analyser Figure 1 Example 1 of a periodic-weighing-mode permeation apparatus Key 1 Outlet for surplus gas 2 Sampling system 3 Mixing bulb 4 Flowmeter 2 5 Diluent gas 6 Thermometer 7 Permeation tube 8 Copper tubin
37、g 9 Water bath 10 Flowmeter 1 11 Carrier gas 12 Drier Figure 2 Example 2 of a periodic-weighing-mode permeation apparatus BS EN ISO 6145-10:20084 Permeation tube Mass flow controller Tare mass Key 1 High purity air/N 2 2 Temperature controller 3 Water 4 Microbalance controller 5 Gas blender 6 RS232
38、link 7 PC (acquisition, analysis and diagnostics) 8 16-bit ADC 9 Flow rate calibration facility 10 Gas analyser 11 Stable mixture requiring certification Figure 3 Continuous-weighing-mode permeation apparatus BS EN ISO 6145-10:2008 55.2 Permeation membrane, made from polymers and having sufficient c
39、hemical and mechanical resistance, e.g. suitable polytetrafluoroethylene (PTFE), polyethylene, polypropylene or a copolymer of tetrafluoroethylene and hexafluoropropylene (FEP). Take into account variations of the material characteristics which occur with a change of temperature. 5.3 Permeation tube
40、s, or containers, made of stainless steel or glass, fitted with a permeation membrane (5.2) and capable of holding the calibration component in the liquid phase and gaseous phase; the membrane through which the permeation takes place may be in contact with the liquid phase only, or with the gaseous
41、phase only, or with both. See examples given in Figure 4. Before use, keep the permeation tube in an airtight container under an anhydrous atmosphere in a cold place (e.g. in a refrigerator at approximately 5 C) so as to maintain the diffusion rate as low as possible, hence to minimize loss of the c
42、alibration component and avoid any condensation on the tube. a) Cylindrical tube fitted with a membrane in contact with both phases b) Tube fitted with a membrane in contact with only the liquid phase c) Container fitted with a membrane in contact with only the gaseous phase Key 1 Membrane 2 Stainle
43、ss steel 3 Liquid level 4 Glass Figure 4 Examples of permeation tubes and container 6 Procedure 6.1 Preliminary checks and operating conditions 6.1.1 Permeation tube Before use, assess the purity of the product of the permeation tube by collecting a sample of the permeated gas for analysis by an app
44、ropriate analytical technique e.g. GC or FTIR so as to quantify any likely major contaminants. This information may be provided by the suppliers of the tube and, if so, a certificate of analysis by an accredited body shall be provided. Periodically check the permeation rate of the tube at a known, f
45、ixed temperature by measuring the mass loss. This gives a good indication as to the purity of the permeated gas. If the permeation rate changes by more than 10 % at the known, fixed temperature, discard the permeation tube. When first using the permeation tube, allow the system to reach a state of e
46、quilibrium before carrying out the first weighing so as to ensure that the permeation rate is well stabilized at the constant value. The time needed to reach BS EN ISO 6145-10:20086 equilibrium is dependant on the component contained within the permeation tube, but a value of 72 h is applicable to m
47、ost species. For most applications, it is essential to control the temperature of the enclosure to within 0,1 K because of the very strong dependence of the permeation rate upon temperature. The tube diffusion rate may, for example, double for an increase in temperature of approximately 7 K. Under c
48、ertain circumstances, in which the diffusing gas is highly soluble in the membrane polymer, an increase in temperature may reduce the permeation rate. During the period of use, maintain the permeation tube at constant temperature, principally to avoid the delay, sometimes very lengthy, which is nece
49、ssary to restore equilibrium. Avoid any rapid changes in temperature. If the operating conditions change significantly (e.g. a change in operating temperature), allow a period of 72 h for the permeation tube to re-equilibrate before resuming measurements. 6.1.2 Carrier gas flow configuration Before the carrier gas reaches the tube, it is essential that its temperature be controlled at that of the permeation tube. Any system which enables the carrier gas to remain in the temperature-controlled enclosure for a sufficient period of time is satisfac
