SIST EN ISO 6145-6:2008
(Main)Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods - Part 6: Critical orifices (ISO 6145-6:2003)
Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods - Part 6: Critical orifices (ISO 6145-6:2003)
This part of ISO 6145 specifies a method for the continuous production of calibration gas mixtures, containing two or more components, from pure gases or other gas mixtures by use of critical orifice systems. By selection of appropriate combinations of orifices and with the use of pure gases, the volume fraction of the calibration component in the calibration gas mixture can be varied by a factor of 104. Additionally, it can be changed by a factor of 102 by changing the initial pressures in the orifice systems. The uncertainty of the method depends mainly upon the flow calibration method and the variations in temperature and outlet pressure. The relative expanded uncertainty in the volume fraction obtainable for a binary mixture (at a coverage factor of 2) is 3 %. If pre-mixed gases are used instead of pure gases, much lower volume fractions can be obtained (see Annex A). The mass flow rates or volume flow rates, from which the mass or volume fractions are determined, can be calculated and can be independently measured by a suitable method given in ISO 6145-1. The merits of the method are that multi-component mixtures can be prepared as readily as binary mixtures if the appropriate number of orifices is utilized, and that a large quantity of calibration gas mixture can be prepared on a continuous basis. The range of flow rates can be from several millilitres per minute to approximately 10 l/min. Although particularly applicable to preparation of gas mixtures at barometric pressure, the method also provides a means of preparation of calibration gas mixtures at pressures above barometric pressure. Annex B gives practical hints on the use of the method.
Gasanalyse - Herstellung von Kalibriergasgemischen mit Hilfe von dynamisch-volumetrischen Verfahren - Teil 6: Kritische Düsen (ISO 6145-6:2003)
Dieser Teil der ISO 6145 legt ein Verfahren zur kontinuierlichen Herstellung von Kalibriergasgemischen mit
zwei oder mehr Komponenten aus reinen Gasen oder anderen Gasgemischen mit Hilfe von Systemen kritischer
Düsen fest. Durch Wahl geeigneter Kombinationen von Düsen und bei Verwendung reiner Gase lässt
sich der Volumenanteil der Kalibrierkomponente in dem Kalibriergasgemisch um einen Faktor von 104
variieren. Zusätzliche Änderungen um einen Faktor von 102 lassen sich durch Änderung der Anfangsdrücke in
den Düsensystemen erzielen. Die Unsicherheit des Verfahrens hängt in erster Linie ab von dem Verfahren zur
Durchflusskalibrierung sowie den Variationen der Temperatur und des Ausgangsdrucks. Die relative
erweiterte Unsicherheit des Volumenanteils, die bei einem binären Gemisch erreichbar ist, beträgt 3 % (bei
einem Überdeckungsfaktor von 2).
Wenn Vorgemische an Stelle von reinen Gasen verwendet werden (siehe Anhang A), so lassen sich viel
niedrigere Volumenanteile erreichen (siehe Anhang A). Die Massenströme oder Volumenströme, aus denen
die Massenanteile bzw. Volumenanteile bestimmt werden, können berechnet werden, und sie können mit
einem geeigneten Verfahren aus ISO 6145-1 unabhängig gemessen werden.
Die Vorteile des Verfahrens bestehen darin, dass sich bei Verwendung einer entsprechenden Zahl von Düsen
Multikomponenten-Gemische ebenso leicht herstellen lassen wie binäre Gemische, und dass eine große
Menge Kalibriergasgemisch auf kontinuierlicher Basis hergestellt werden kann. Die erreichbaren Volumenströme
gehen von etlichen Millilitern je Minute bis zu annähernd 10 l/min.
Obwohl besonders geeignet für die Herstellung von Gasgemischen bei Umgebungsdruck, ist das Verfahren
jedoch auch bei der Herstellung von Kalibriergasgemischen bei Drücken über Umgebungsdruck anwendbar.
Anhang B gibt praktische Hinweise zur Anwendung des Verfahrens.
Analyse des gaz - Préparation des mélanges de gaz pour étalonnage à l'aide de méthodes volumétriques dynamiques - Partie 6: Orifices critiques (ISO 6145-6:2003)
L'ISO 6145-6:2003 spécifie une méthode de préparation en continu de mélanges de gaz pour étalonnage, contenant au moins deux constituants, à partir de gaz purs ou d'autres mélanges de gaz à l'aide de systèmes à orifices critiques. En sélectionnant les combinaisons appropriées d'orifices et à l'aide de gaz purs, la fraction volumique du constituant pour étalonnage dans le mélange de gaz pour étalonnage peut varier d'un coefficient de 104. En outre, elle peut changer d'un coefficient de 102 en modifiant les pressions initiales dans les systèmes d'orifices. L'incertitude de la méthode dépend principalement de la méthode d'étalonnage du débit et des variations de température et de pression de sortie. L'incertitude élargie relative sur la fraction volumique qu'il est possible d'obtenir pour un mélange à deux constituants (avec un coefficient d'élargissement de 2) est 3 %.
Si des prémélanges de gaz sont utilisés à la place de gaz purs, des fractions volumiques beaucoup plus faibles peuvent être obtenues. Les débits massiques ou débits volumiques, à partir desquels les fractions massiques ou volumiques sont déterminées, peuvent être calculés et mesurés de manière indépendante selon une méthode appropriée donnée dans l'ISO 6145-1.
La méthode a pour mérite de permettre la préparation de mélanges à constituants multiples aussi aisément que des mélanges à deux constituants si un nombre approprié d'orifices est utilisé. Elle permet également de préparer une grande quantité de mélange de gaz pour étalonnage en continu. La gamme de débits peut être comprise entre plusieurs millilitres par minute et environ 10 l/min.
Bien que particulièrement applicable à la préparation de mélanges de gaz à pression atmosphérique, la méthode offre également la possibilité de préparer des mélanges de gaz pour étalonnage à des pressions supérieures à la pression atmosphérique.
Analiza plinov - Priprava kalibracijske plinske zmesi z uporabo dinamičnih volumetričnih metod - 6. del: Kritične odprtine (ISO 6145-6:2003)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 6145-6:2008
01-oktober-2008
$QDOL]DSOLQRY3ULSUDYDNDOLEUDFLMVNHSOLQVNH]PHVL]XSRUDERGLQDPLþQLK
YROXPHWULþQLKPHWRGGHO .ULWLþQHRGSUWLQH ,62
Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods
- Part 6: Critical orifices (ISO 6145-6:2003)
Gasanalyse - Herstellung von Kalibriergasgemischen mit Hilfe von dynamisch-
volumetrischen Verfahren - Teil 6: Kritische Düsen (ISO 6145-6:2003)
Analyse des gaz - Préparation des mélanges de gaz pour étalonnage à l'aide de
méthodes volumétriques dynamiques - Partie 6: Orifices critiques (ISO 6145-6:2003)
Ta slovenski standard je istoveten z: EN ISO 6145-6:2008
ICS:
71.040.40 Kemijska analiza Chemical analysis
SIST EN ISO 6145-6:2008 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 6145-6:2008
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SIST EN ISO 6145-6:2008
EUROPEAN STANDARD
EN ISO 6145-6
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2008
ICS 71.040.40
English Version
Gas analysis - Preparation of calibration gas mixtures using
dynamic volumetric methods - Part 6: Critical orifices (ISO 6145-
6:2003)
Analyse des gaz - Préparation des mélanges de gaz pour Gasanalyse - Herstellung von Kalibriergasgemischen mit
étalonnage à l'aide de méthodes volumétriques Hilfe von dynamisch-volumetrischen Verfahren - Teil 6:
dynamiques - Partie 6: Orifices critiques (ISO 6145-6:2003) Kritische Düsen (ISO 6145-6:2003)
This European Standard was approved by CEN on 30 July 2008.
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 national
standards may be obtained on application 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 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, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6145-6:2008: E
worldwide for CEN national Members.
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SIST EN ISO 6145-6:2008
EN ISO 6145-6:2008 (E)
Contents Page
Foreword.3
2
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SIST EN ISO 6145-6:2008
EN ISO 6145-6:2008 (E)
Foreword
The text of ISO 6145-6:2003 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 6145-6:2008 by
Technical 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 standards 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/CENELEC 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, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 6145-6:2003 has been approved by CEN as a EN ISO 6145-6:2008 without any modification.
3
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SIST EN ISO 6145-6:2008
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SIST EN ISO 6145-6:2008
INTERNATIONAL ISO
STANDARD 6145-6
Second edition
2003-05-15
Gas analysis — Preparation of calibration
gas mixtures using dynamic volumetric
methods —
Part 6:
Critical orifices
Analyse des gaz — Préparation des mélanges de gaz pour étalonnage à
l'aide de méthodes volumétriques dynamiques —
Partie 6: Orifices critiques
Reference number
ISO 6145-6:2003(E)
©
ISO 2003
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SIST EN ISO 6145-6:2008
ISO 6145-6:2003(E)
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©
ii ISO 2003 – All rights reserved
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SIST EN ISO 6145-6:2008
ISO 6145-6:2003(E)
Contents Page
1 Scope . 1
2 Normative references . 1
3 Principle . 1
4 Application to preparation of gas mixtures . 2
4.1 Description of the orifice system and the experimental procedure . 2
4.2 Area of validity . 4
4.3 Operating conditions . 4
5 Calculation of operating parameters and results . 4
5.1 Selection of suitable orifice systems . 4
5.2 Calculation of volume fraction . 5
5.3 Sources of uncertainty . 5
5.4 Uncertainty of volume fraction . 6
Annex A (informative) Premixed gases for preparation of mixtures of high dilution . 7
Annex B (informative) Practical hints . 9
Bibliography . 11
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SIST EN ISO 6145-6:2008
ISO 6145-6:2003(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International
Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 6145-6 was prepared by Technical Committee ISO/TC 158, Analysis of gases.
This second edition cancels and replaces the first edition (ISO 6145-6:1986), which has been technically
revised.
ISO 6145 consists of the following parts, under the general title Gas analysis — Preparation of calibration gas
mixtures using dynamic volumetric methods:
— Part 1: Methods of calibration
— Part 2: Volumetric pumps
— Part 4: Continuous injection method
— Part 5: Capillary calibration devices
— Part 6: Critical orifices
— Part 7: Thermal mass-flow controllers
— Part 9: Saturation method
— Part 10: Permeation method
Diffusion will be the subject of a future Part 8 to ISO 6145. Part 3 to ISO 6145, entitled Periodic injections into a
flowing gas, has been withdrawn.
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SIST EN ISO 6145-6:2008
ISO 6145-6:2003(E)
Introduction
This part of ISO 6145 is one of a series of standards that present various dynamic volumetric methods used for
the preparation of calibration gas mixtures.
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SIST EN ISO 6145-6:2008
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SIST EN ISO 6145-6:2008
INTERNATIONAL STANDARD ISO 6145-6:2003(E)
Gas analysis — Preparation of calibration gas mixtures using
dynamic volumetric methods —
Part 6:
Critical orifices
1Scope
This part of ISO 6145 specifies a method for the continuous production of calibration gas mixtures, containing
two or more components, from pure gases or other gas mixtures by use of critical orifice systems. By selection
of appropriate combinations of orifices and with the use of pure gases, the volume fraction of the calibration
4
component in the calibration gas mixture can be varied by a factor of 10 . Additionally, it can be changed by a
2
factor of 10 by changing the initial pressures in the orifice systems. The uncertainty of the method depends
mainly upon the flow calibration method and the variations in temperature and outlet pressure. The relative
expanded uncertainty in the volume fraction obtainable for a binary mixture (at a coverage factor of 2) is 3%.
If pre-mixed gases are used instead of pure gases, much lower volume fractions can be obtained (see
Annex A). The mass flow rates or volume flow rates, from which the mass or volume fractions are determined,
can be calculated and can be independently measured by a suitable method given in ISO 6145-1.
The merits of the method are that multi-component mixtures can be prepared as readily as binary mixtures if the
appropriate number of orifices is utilized, and that a large quantity of calibration gas mixture can be prepared on
a continuous basis. The range of flow rates can be from several millilitres per minute to approximately 10 l/min.
Although particularly applicable to preparation of gas mixtures at barometric pressure, the method also provides
a means of preparation of calibration gas mixtures at pressures above barometric pressure.
Annex B gives practical hints on the use of the method.
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 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: Methods of calibration
3 Principle
When passed through a critical orifice at increasing upstream pressure p , the volume flow rate of gas passing
1
through the orifice will increase. When the ratio of the gas pressure upstream p and the gas pressure
1
downstream of the orifice p has reached a critical value, on further increase of p the volume flow rate of the
2 1
gas becomes independent with respect to p .
2
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SIST EN ISO 6145-6:2008
ISO 6145-6:2003(E)
For a given gas, and at constant temperature the critical pressure ratio is:
γ
� � � �
γ−1
p 2
2
= (1)
p γ + 1
1
crit
where γ is the ratio of the molar heat capacities of the gas at constant pressure and at constant volume.
For monatomic, diatomic and triatomic gases, this critical pressure ratio is approximately 0,5.
Orifice systems which are operated at pressure ratios p /p less than (p /p ) are termed “critical orifices”.
2 1 2 1
crit
Use of such systems provides a means of maintaining constant flow rates of gases. In actual practice it is
convenient to arrange the system so that p is equal to the prevailing barometric pressure.
2
To prepare calibration gas mixtures, the complementary gas is supplied at known flow rate, from a critical
orifice, to meet the calibration component emerging from another critical orifice. The mixture is then allowed to
pass along a mixing tube, at the end of which the flow rate is measured by a suitable method as given in
ISO 6145-1. Since the volume flow rate of the calibration component remains the same whether or not the
complementary gas is flowing, it can be measured after the flow of complementary gas has been stopped. The
concentration of the calibration gas mixture is calculated from the two measured critical flow rates.
4 Application to preparation of gas mixtures
4.1 Description of the orifice system and the experimental procedure
A schematic diagram of the arrangement for preparation of binary mixtures is shown in Figure 1.
In Figure 1, the orifices 9 and 10, respectively, for the complementary gas and the calibration component to be
added are mounted in the orifice system (11). Cylinders 1 and 13, respectively, contain the complementary gas
and the other gaseous component, and are connected to the mixing system via pressure-reducing valves (3
and 15) and metallic filters (5 and 17), which provide protection against contamination. In each of the lines, and
upstream of the filters, are a pressure-reducing valve and a pressure gauge. A shut-off valve (8) is provided in
the complementary gas line and a venting valve is included in the other line.
To operate the gas-mixing system, the valves of the gas cylinders are opened and the readings on the pressure
gauges 4 and 16 are adjusted, each to a value approximately 200 kPa (2 bar) above the values anticipated at
pressure gauges 7 and 20 respectively.
The pressure regulators (6 and 18) are opened so that the complementary gas and the calibration component
flow through the respective orifices. The flow of
...
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