Natural gas - Performance evaluation for analytical systems (ISO 10723:2012)

This International Standard specifies a method of determining whether an analytical system for natural gas analysis is fit for purpose. It can be used either a) to determine a range of gas compositions to which the method can be applied, using a specified calibration gas, while satisfying previously defined criteria for the maximum errors and uncertainties on the composition or property or both, or b) to evaluate the range of errors and uncertainties on the composition or property (calculable from composition) or both when analysing gases within a defined range of composition, using a specifiedIt is assumed that a) for evaluations of the first type above, the analytical requirement has been clearly and unambiguously defined, in terms of the range of acceptable uncertainty on the composition, and, where appropriate, the uncertainty in physical properties calculated from these measurements, b) for applications of the second type above, the analytical requirement has been clearly and unambiguously defined, in terms of the range of composition to be measured and, where appropriate, the range of properties which may be calculated from these measurements, c) the analytical and calibration procedures have been fully described, and d) the analytical system is intended to be applied to gases having compositions which vary over rangesIf the performance evaluation shows the system to be unsatisfactory in terms of the uncertainty on the component amount fraction or property, or shows limitations in the ranges of composition or property values measurable within the required uncertainty, then it is intended that the operating parameters, including a) the analytical requirement, b) the analytical procedure, c) the choice of equipment, d) the choice of calibration gas mixture, and e) the calculation procedure, be reviewed to assess where improvements can be obtained. Of these parameters, the choice of the calibration gas composition is likely to have the most significant influence. This International Standard is applicable to analytical systems which measure individual component amount fractions. For an application such as calorific value determination, the method will be typically gas chromatography, set up, as a minimum, for the measurement of nitrogen, carbon dioxide, individual hydrocarbons from C1 to C5 and a composite measurement representing all higher hydrocarbons of carbon number 6 and above. This allows for the calculation of calorific value and similar properties with acceptable accuracy. In addition, components such as H2S can be measured individually by specific measurement methods to which this evaluation approach can also be applied. normally found in gas transmission and distribution systems. Performance evaluation of an analytical system is intended to be performed following initial installation to ensure that errors associated with assumed response functions are fit for purpose. Thereafter, periodic performance evaluation is recommended, or whenever any critical component of the analytical system is adjusted or replaced. The appropriate interval between periodic performance evaluations will depend upon both how instrument responses vary with time and also how large an error may be tolerated. This first consideration is dependent upon instrument/operation; the second is dependent on the application. It is not appropriate, therefore, for this International Standard to offer specific recommendations on intervals between performance evaluations.

Erdgas - Bewertung der Leistungsfähigkeit von Analysensystemen (ISO 10723:2012)

1.1   Diese Internationale Norm legt ein Verfahren fest, mit dessen Hilfe ermittelt werden kann, ob ein Erdgas-Analysensystem gebrauchstauglich ist. Sie kann für Folgendes eingesetzt werden:
a)   die Bestimmung des Bereichs von Gaszusammensetzungen, auf den das Verfahren unter Einsatz eines festgelegten Kalibriergases angewendet werden kann, wobei zuvor definierte Kriterien für die maximalen Fehler und Unsicherheiten der Zusammensetzung, der Eigenschaft oder von beiden erfüllt werden, oder
b)   die Bewertung des Bereichs der Fehler und Unsicherheiten der Zusammensetzung oder der (aus der Zusammensetzung berechenbaren) Eigenschaft oder von beiden bei der Analyse von Gasen innerhalb eines definierten Bereichs von Zusammensetzungen und unter Einsatz eines festgelegten Kalibriergases.
1.2   Es wird vorausgesetzt, dass:
a)   für Bewertungen des ersten der vorstehend genannten Typen die analytische Anforderung klar und eindeutig in Form des Bereichs der annehmbaren Unsicherheit der Zusammensetzung und, sofern angemessen, der Unsicherheit der aus diesen Messungen berechneten physikalischen Eigenschaften definiert wurde,
b)   für Anwendungen des zweiten der vorstehend genannten Typen die analytische Anforderung klar und eindeutig in Form des zu messenden Bereichs von Zusammensetzungen und, sofern angemessen, des Bereichs der aus diesen Messungen berechenbaren Eigenschaften definiert wurde,
c)   das Analyse- und das Kalibrierverfahren vollständig beschrieben sind und
d)   das Analysensystem dafür vorgesehen ist, auf Gase angewendet zu werden, deren Zusammensetzung in Bereichen schwankt, wie sie im Normalfall in Transport- und Versorgungsnetzen für Gas vorliegen.
1.3   Sofern die Bewertung der Leistungsfähigkeit ergibt, dass das System in Bezug auf die Unsicherheit des Stoffmengenanteils oder der Eigenschaft des Bestandteils nicht zufriedenstellend ist oder Begrenzungen der Bereiche von Zusammensetzungen oder Eigenschaftswerten aufweist, die innerhalb der erforderlichen Unsicherheit messbar sind, ist vorgesehen, dass die Betriebsparameter, einschließlich
a)   der analytischen Anforderungen,
b)   des Analysenverfahrens,
c)   der Geräteauswahl,
d)   der Auswahl des Kalibriergasgemisches und
e)   des Berechnungsverfahrens,
geprüft werden, um beurteilen, wo Verbesserungen möglich sind. Von diesen Parametern hat die Auswahl der Zusammensetzung des Kalibriergases wahrscheinlich den stärksten Einfluss.
1.4   Diese Internationale Norm ist auf Analysensysteme anwendbar, mit denen Stoffmengenanteile einzelner Bestandteile gemessen werden. Bei Anwendungen wie der Bestimmung des Wärmewerts handelt es sich beim Prüfaufbau typischerweise um den für die Gaschromatographie, mindestens für die Messung von Stickstoff, Kohlenstoffdioxid, einzelnen Kohlenwasserstoffen von C1 bis C5 und eine zusammengesetzte Messung, die alle höheren Kohlenwasserstoffe mit einer Kohlenstoffzahl von mindestens 6 repräsentiert. Dies erlaubt die Berechnung des Wärmewerts und von vergleichbaren Eigenschaften mit einer annehmbaren Genauigkeit. Darüber hinaus können Bestandteile wie H2S einzeln unter Anwendung bestimmter Verfahren gemessen werden, auf die dieser Bewertungsansatz ebenfalls anwendbar ist.
1.5   Die Bewertung der Leistungsfähigkeit eines Analysensystems soll nach dessen Erstaufbau vorgenommen werden um sicherzustellen, dass das System auch bei Vorliegen der mit den angenommenen Response¬funktionen verbundenen Fehler gebrauchstauglich ist. Es wird empfohlen, im Anschluss daran die Bewertung der Leistungsfähigkeit in regelmäßigen Abständen oder immer dann vorzunehmen, wenn ein kritischer Bestandteil des Analysensystems angepasst oder ersetzt wird. Das angemessene Intervall zwischen den regelmäßig erfolgenden Bewertungen der Leistungsfähigkeit ist sowohl davon abhängig, wie der Geräte-response über die Zeit schwankt, sowie auch davon, wie groß der tolerierbare Fehler ist. (...)

Gaz naturel - Évaluation des performances des systèmes d'analyse (ISO 10723:2012)

L'ISO 10723:2012 spécifie une méthode permettant de déterminer si un système d'analyse pour l'analyse du gaz naturel est adapté à l'usage prévu. Elle peut être utilisée pour déterminer une gamme de compositions de gaz à laquelle la méthode peut s'appliquer, en utilisant un gaz d'étalonnage spécifié, tout en satisfaisant à des critères préalablement définis pour les erreurs et incertitudes maximales associées à la composition et/ou à la propriété, ou aux deux, ou évaluer la plage d'erreurs et d'incertitudes associées à la composition ou à la propriété (calculable à partir de la composition), ou aux deux, lors de l'analyse de gaz compris dans une gamme de composition définie, en utilisant un gaz d'étalonnage spécifié.

Zemeljski plin - Vrednotenje zmogljivosti analitskih sistemov (ISO 10723:2012)

Ta mednarodni standard določa metodo za ugotavljanje ustreznosti analitskega sistema za analizo zemeljskega plina. Uporablja se lahko za a) določitev obsega sestav plinov, za katere je mogoče uporabiti metodo, pri čemer se uporabi določen kalibracijski plin in so izpolnjena predhodno opredeljena merila za največje dopustno število napak in negotovosti pri sestavi ali lastnosti ali obeh, ali b) oceno razpona napak in negotovosti pri sestavi ali lastnosti (se lahko izračuna iz sestave) ali obeh med analizo plinov, katerih sestava je v opredeljenem obsegu. Predpostavlja se, da a) je bila pri zgoraj navedenih ocenah prvega tipa analitska zahteva jasno in nedvoumno opredeljena v smislu razpona sprejemljive negotovosti pri sestavi in, kadar je primerno, negotovosti fizikalnih lastnosti, izračunanih iz teh meritev, b) je bila pri načinih uporabe drugega zgoraj navedenega tipa analitska zahteva jasno in nedvoumno opredeljena v smislu obsega sestave, ki jo je treba izmeriti, in, kadar je primerno, razpona lastnosti, ki se lahko izračunajo iz teh meritev, c) so bili analitski in kalibracijski postopki v celoti opisani in d) je analitski sistem namenjen za pline, katerih sestave se po obsegih razlikujejo. Če se pri vrednotenju zmogljivosti ugotovi, da sistem ni zadovoljiv v smislu negotovosti pri deležu količin sestavnih delov ali lastnosti ali je omejen pri obsegih sestave ali vrednostih lastnosti, ki so merljive v okviru zahtevane negotovosti, je treba pregledati parametre delovanja, vključno z a) analitsko zahtevo, b) analitskim postopkom, c) izbiro opreme, d) izbiro kalibracijske plinske mešanice in e) postopkom izračuna, da se ocenijo možnosti za izboljšave. Od navedenih parametrov bo imela verjetno največji vpliv izbira sestave kalibracijskega plina. Ta mednarodni standard se uporablja za analitske sisteme, s katerimi se merijo posamezni deleži količin sestavnih delov. Pri uporabah, kot je določevanje kalorične vrednosti, se običajno uporabi metoda plinske kromatografije, ki se nastavi vsaj za merjenje dušika, ogljikovega dioksida, posameznih ogljikovodikov od C1 do C5 in sestavljeno meritev vseh višjih ogljikovodikov z najmanj šestimi ogljikovimi atomi. To omogoča sprejemljivo natančnost pri izračunu kalorične vrednosti in podobnih lastnosti. Poleg tega je mogoče s posebnimi merilnimi metodami, pri katerih se lahko prav tako uporabi ta pristop k vrednotenju, izmeriti posamezne sestavine, kot je H2S. Običajno se pojavlja v sistemih za prenos in distribucijo plina. Vrednotenje zmogljivosti analitskega sistema se izvede po začetni namestitvi, s čimer se zagotovi ustreznost napak v zvezi s predvidenimi odzivnimi funkcijami. Pozneje je priporočljivo, da se vrednotenje zmogljivosti izvaja periodično ali kadar se prilagodi ali zamenja pomemben sestavni del analitskega sistema. Ustrezna obdobja med periodičnimi vrednotenji zmogljivosti so odvisna od tega, kako odzivi instrumentov variirajo skozi čas in kako velike napake so dopustne. Prvi dejavnik je odvisen od instrumenta/delovanja, drugi pa od uporabe. Ta standard zato ne zajema specifičnih priporočil o obdobji med periodičnimi vrednotenji, saj to ni primerno.

General Information

Status
Published
Public Enquiry End Date
16-Aug-2011
Publication Date
08-Jan-2013
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
14-Dec-2012
Due Date
18-Feb-2013
Completion Date
09-Jan-2013

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SLOVENSKI STANDARD
SIST EN ISO 10723:2013
01-februar-2013
1DGRPHãþD
SIST EN ISO 10723:2002
SIST EN ISO 10723:2002/AC:2004
Zemeljski plin - Vrednotenje zmogljivosti analitskih sistemov (ISO 10723:2012)
Natural gas - Performance evaluation for analytical systems (ISO 10723:2012)
Erdgas - Bewertung der Leistungsfähigkeit von Analysensystemen (ISO 10723:2012)

Gaz naturel - Évaluation des performances des systèmes d'analyse (ISO 10723:2012)

Ta slovenski standard je istoveten z: EN ISO 10723:2012
ICS:
75.060 Zemeljski plin Natural gas
SIST EN ISO 10723:2013 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 10723:2013
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SIST EN ISO 10723:2013
EUROPEAN STANDARD
EN ISO 10723
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2012
ICS 75.060 Supersedes EN ISO 10723:2002
English Version
Natural gas - Performance evaluation for analytical systems
(ISO 10723:2012)

Gaz naturel - Évaluation des performances des systèmes Erdgas - Bewertung der Leistungsfähigkeit von

d'analyse (ISO 10723:2012) Analysensystemen (ISO 10723:2012)
This European Standard was approved by CEN on 30 November 2012.

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-CENELEC 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-CENELEC Management Centre has the same

status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United

Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 10723:2012: E

worldwide for CEN national Members.
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SIST EN ISO 10723:2013
EN ISO 10723:2012 (E)
Contents Page

Foreword ....................................................................................................................................................... 3

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SIST EN ISO 10723:2013
EN ISO 10723:2012 (E)
Foreword

This document (EN ISO 10723:2012) has been prepared by Technical Committee ISO/TC 193 "Natural gas".

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 June 2013, and conflicting national standards shall be withdrawn at

the latest by June 2013.

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.

This document supersedes EN ISO 10723:2002.

According to the CEN/CENELEC Internal Regulations, the national standards organisations of the following

countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech

Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,

Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,

Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

Endorsement notice

The text of ISO 10723:2012 has been approved by CEN as a EN ISO 10723:2012 without any modification.

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SIST EN ISO 10723:2013
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SIST EN ISO 10723:2013
INTERNATIONAL ISO
STANDARD 10723
Second edition
2012-12-01
Natural gas — Performance evaluation
for analytical systems
Gaz naturel — Évaluation des performances des systèmes d’analyse
Reference number
ISO 10723:2012(E)
ISO 2012
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SIST EN ISO 10723:2013
ISO 10723:2012(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2012

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any

means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the

address below or ISO’s member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2012 – All rights reserved
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SIST EN ISO 10723:2013
ISO 10723:2012(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 2

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Symbols .......................................................................................................................................................................................................................... 3

5 Principle ........................................................................................................................................................................................................................ 4

6 General procedure .............................................................................................................................................................................................. 5

6.1 Analytical requirements ......... ......................................................................................................................................................... 5

6.2 Response function types ................................................................................................................................................................. 6

6.3 Calibration gas reference data ................................................................................................................................................... 7

6.4 Working measurement standards (WMS) ....................................................................................................................... 8

6.5 Experimental design .......................................................................................................................................................................... 9

6.6 Calculation procedures .................................................................................................................................................................11

7 Interpretation .......................................................................................................................................................................................................16

7.1 General considerations .................................................................................................................................................................16

7.2 Pre-defined performance specification ..........................................................................................................................16

7.3 Determination of the analytical range of the instrument ...............................................................................16

7.4 Criteria for selection of hypothetical compositions .............................................................................................17

Annex A (informative) Example of application using chromatography ........................................................................18

Annex B (informative) Explanation of approach used for instrument benchmarking .................................30

Bibliography .............................................................................................................................................................................................................................32

© ISO 2012 – All rights reserved iii
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SIST EN ISO 10723:2013
ISO 10723:2012(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 10723 was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee SC 1, Analysis

of natural gas.

This second edition cancels and replaces the first edition (ISO 10723:1995), which has been technically

revised. It also incorporates Technical Corrigendum ISO 10723:1995/Cor.1:1998.
iv © ISO 2012 – All rights reserved
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SIST EN ISO 10723:2013
ISO 10723:2012(E)
Introduction

This International Standard describes a method for evaluating the performance of analytical systems

intended for the analysis of natural gas. Natural gas is assumed to consist predominantly of methane,

with other saturated hydrocarbons and non-combustible gases.

Performance evaluation makes no assumption about equipment for and/or methodology of analysis

but gives test methods which can be applied to the chosen analytical system, including the method,

equipment and sample handling.

This International Standard contains an informative annex (Annex A) that shows the application for an

on-line gas chromatographic system which, as described, is assumed to have a response/concentration

relationship for all components that is represented by a straight line through the origin. This International

Standard contains an additional informative annex (Annex B) that gives a rationale for the approach

used for instrument benchmarking.
© ISO 2012 – All rights reserved v
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SIST EN ISO 10723:2013
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SIST EN ISO 10723:2013
INTERNATIONAL STANDARD ISO 10723:2012(E)
Natural gas — Performance evaluation for analytical systems
1 Scope

1.1 This International Standard specifies a method of determining whether an analytical system for

natural gas analysis is fit for purpose. It can be used either

a) to determine a range of gas compositions to which the method can be applied, using a specified

calibration gas, while satisfying previously defined criteria for the maximum errors and uncertainties

on the composition or property or both, or

b) to evaluate the range of errors and uncertainties on the composition or property (calculable from

composition) or both when analysing gases within a defined range of composition, using a specified

calibration gas.
1.2 It is assumed that

a) for evaluations of the first type above, the analytical requirement has been clearly and unambiguously

defined, in terms of the range of acceptable uncertainty on the composition, and, where appropriate,

the uncertainty in physical properties calculated from these measurements,

b) for applications of the second type above, the analytical requirement has been clearly and

unambiguously defined, in terms of the range of composition to be measured and, where appropriate,

the range of properties which may be calculated from these measurements,
c) the analytical and calibration procedures have been fully described, and

d) the analytical system is intended to be applied to gases having compositions which vary over ranges

normally found in gas transmission and distribution systems.

1.3 If the performance evaluation shows the system to be unsatisfactory in terms of the uncertainty on the

component amount fraction or property, or shows limitations in the ranges of composition or property values

measurable within the required uncertainty, then it is intended that the operating parameters, including

a) the analytical requirement,
b) the analytical procedure,
c) the choice of equipment,
d) the choice of calibration gas mixture, and
e) the calculation procedure,

be reviewed to assess where improvements can be obtained. Of these parameters, the choice of the

calibration gas composition is likely to have the most significant influence.

1.4 This International Standard is applicable to analytical systems which measure individual component

amount fractions. For an application such as calorific value determination, the method will be typically

gas chromatography, set up, as a minimum, for the measurement of nitrogen, carbon dioxide, individual

hydrocarbons from C to C and a composite measurement representing all higher hydrocarbons of

1 5

carbon number 6 and above. This allows for the calculation of calorific value and similar properties

with acceptable accuracy. In addition, components such as H S can be measured individually by specific

measurement methods to which this evaluation approach can also be applied.
© ISO 2012 – All rights reserved 1
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SIST EN ISO 10723:2013
ISO 10723:2012(E)

1.5 Performance evaluation of an analytical system is intended to be performed following initial

installation to ensure that errors associated with assumed response functions are fit for purpose.

Thereafter, periodic performance evaluation is recommended, or whenever any critical component of

the analytical system is adjusted or replaced. The appropriate interval between periodic performance

evaluations will depend upon both how instrument responses vary with time and also how large an

error may be tolerated. This first consideration is dependent upon instrument/operation; the second

is dependent on the application. It is not appropriate, therefore, for this International Standard to offer

specific recommendations on intervals between performance evaluations.
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/IEC Guide 98-3:2008, Uncertainty of measurement —Part 3: Guide to the expression of uncertainty in

measurement (GUM:1995)

ISO 6143:2001, Gas analysis — Comparison methods for determining and checking the composition of

calibration gas mixtures

ISO 6974-2, Natural gas — Determination of composition and associated uncertainty by gas

chromatography — Part 2: Uncertainty calculations

ISO 6976:1995, Natural gas — Calculation of calorific values, density, relative density and Wobbe index

from composition
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
uncertainty of measurement

parameter, associated with the result of a measurement, that characterizes the dispersion of values that

can reasonably be attributed to the measurand

NOTE In keeping with ISO/IEC Guide 98-3, in this International Standard the uncertainty of the composition

is expressed as a standard uncertainty or as an expanded uncertainty calculated through the use of an appropriate

coverage factor.
3.2
certified reference gas mixture
CRM

reference gas mixture, characterized by a metrologically valid procedure for one or more specified

properties, accompanied by a certificate that provides the value of the specified property, its associated

uncertainty, and a statement of metrological traceability
[3]

NOTE 1 The above definition is based on the definition of “certified reference material” in ISO Guide 35 .

“Certified reference material” is a generic term; “certified reference gas mixture” is more suited to this application.

NOTE 2 Metrologically valid procedures for the production and certification of reference materials (such as

[4] [3]

certified reference gas mixtures) are given in, among others, ISO Guide 34 and ISO Guide 35 .

[5]
NOTE 3 ISO Guide 31 gives guidance on the contents of certificates.
2 © ISO 2012 – All rights reserved
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SIST EN ISO 10723:2013
ISO 10723:2012(E)
3.3
working measurement standard
WMS

standard that is used routinely to calibrate or verify measuring instruments or measuring systems

[ISO/IEC Guide 99:2007, 5.7]
NOTE A working measurement standard is usually calibrated against a CRM.
3.4
calibration gas mixture
CGM

gas mixture whose composition is sufficiently well established and stable to be used as a working

measurement standard of composition

NOTE In this International Standard, a CGM is used for routine (e.g. daily) component calibration of the

analyser. It is independent of the WMSs used to perform the evaluation.
3.5
response
output signal of the measuring system for each specified component

NOTE In the case of gas chromatography this will be either peak area or peak height, depending upon the

instrument configuration.
3.6
response function
functional relationship between instrumental response and component content

NOTE 1 The response function can be expressed in two different ways as a calibration function or an analysis

function, depending on the choice of the dependent and the independent variable.

NOTE 2 The response function is conceptual and cannot be determined exactly. It is determined approximately

through calibration.
3.7
calibration function
relationship describing instrument response as a function of component content
3.8
analysis function
relationship describing component content as a function of instrument response
4 Symbols
a parameters of the calibration function (z = 0, 1, 2 or 3)
b parameters of the analysis function (z = 0, 1, 2 or 3)
x amount fraction of the specified component
xˆ adjusted (estimated) amount fraction from the response function
y′ raw instrumental response
y corrected instrumental response
s standard deviation of response
ˆy adjusted (estimated) response from the response function
© ISO 2012 – All rights reserved 3
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SIST EN ISO 10723:2013
ISO 10723:2012(E)
F calibration function
G analysis function
M (sample of) reference gas mixture
P general characteristic (physical property)
p pressure (in kPa)
u standard uncertainty
U expanded uncertainty
k coverage factor
Γ goodness-of-fit measure in generalized least squares
δ error in the estimated value
5 Principle

Performance characteristics of the instrument are determined when used in combination with a

specified calibration gas mixture. Therefore, the evaluation procedure can be used to

— determine errors and uncertainties in measured composition and properties over a pre-defined

range for each specified component, and

— determine a range for each specified component over which the errors and uncertainties in measured

composition and properties do not exceed a predefined measurement requirement.

In each case, the performance characteristics are calculated for the instrument when used in combination

with a specified calibration gas mixture of known composition and uncertainty.

NOTE 1 The method can also be used to establish the most appropriate composition of the calibration gas

mixture to be used routinely with the instrument such that the errors and uncertainties are minimized over a

predefined range of use.

A complete assessment of the errors and uncertainties arising from the use of an instrument could be

performed by measuring an infinite series of well-defined reference gas mixtures whose compositions

lie within the specified range of operation. However, this is practically impossible. Instead, the principle

used in this International Standard is to measure a smaller number of well-defined reference gases

and to determine a mathematical description of the response functions for each specified component

over a predefined content range. The performance of the instrument can then be modelled offline using

these “true” response functions, the response functions assumed by the instrument’s data system and

the reference data for the calibration gas mixture specified for the instrument. The measurement of

a large number of gas mixtures can then be simulated offline using numerical methods to determine

performance benchmarks inherent in the measurement system.

The general procedure for determining the performance characteristics of the instrument is

summarized below.

a) Specify the components required to be measured by the instrument and the range for each over

which the instrument shall be evaluated.

b) Establish the functional descriptions of the response functions assumed by the instrument (or the

instrument’s data system) for each specified component.

NOTE 2 These functions are referred to as the assumed response functions of the system at the time of

calibration/evaluation. These are generally analysis functions used by the instrument to determine the amount

from the measured response, x = G ( y).
asm
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ISO 10723:2012(E)

c) Establish the composition and uncertainty of the calibration gas mixture specified for routine

calibration of the instrument.

d) Design a set of reference gas mixtures with compositions covering all ranges for all components

specified in a).

e) Perform a multi-point calibration experiment by collecting instrument response data to

measurements of the reference gas mixtures designed and produced in accordance with d). The

entire experiment should be conducted within a time period equivalent to that between routine

calibrations.

f) Calculate the calibration functions and analysis functions for each specified component using

regression analysis and validate the compatibility of the functions with the calibration data set.

NOTE 3 These functions are referred to as the true response functions of the system at the time of

calibration/evaluation, y = F (x) and x = G ( y).
true true

g) Calculate instrumental errors and uncertainties for each component and property over a specified

range of compositions using the functions and reference data collated in d), e) and f) above.

h) From the distribution of errors and the unbiased uncertainty estimates calculated in g) above,

determine the mean error and its uncertainty for each measurand.

The mean errors and their uncertainties on component content and properties resulting from step h)

can be compared to performance requirements for the analytical system. If performance benchmarks

are poorer than the analytical requirements of the measurement, then it is clear that the method

fails to provide the desired performance over the fully specified range. The method shall be modified

accordingly and the entire evaluation procedure repeated. Alternatively, the offline calculations shall be

repeated over a restricted range of operation in order to improve system performance. In this case, the

instrument may be shown to perform adequately over a limited range.

It may be possible to modify the data system on the instrument to allow for the difference between

the true response functions and the analysis function assumed by the instrument. In this case, the

instrument should be adjusted following the evaluation to account for this difference. If the function

form of G and G are the same, then the parameters of G in the instrument’s data system can

true asm asm

be updated with those determined for G in step f) above, thereby eliminating systematic errors due

true

to the instrument. However, it is important to remember that the parameters of G are only valid for

true

each component over the content range used to establish the analysis function. That is, the instrument

should not be used outside the ranges defined, designed and evaluated in steps a), b) and c).

6 General procedure
6.1 Analytical requirements
6.1.1 General considerations

Users of this International Standard should first decide which components measured by the instrument

are to be used in the evaluation of the performance. These are termed specified components. For each

specified component, the range of amount fractions over which the response function is to be evaluated

shall then be decided.
6.1.2 Specified components

For measurement systems set up to determine the major components in natural gas, the components

typically specified are nitrogen, carbon dioxide, methane, ethane, propane, 2-methylpropane (iso-butane),

n-butane, 2-methylbutane (iso-pentane) and n-pentane. In addition, some analytical requirements

include 2,2-dimethylpropane (neo-pentane). This component is typically present in very low amounts in

natural gas and might not be specified in many systems for measurement. In a typical chromatography

method, higher hydrocarbons are often specified as a summed component such as hexanes+ (C ) where

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SIST EN ISO 10723:2013
ISO 10723:2012(E)

all hydrocarbons containing six carbon atoms or greater are included in one specified component. The

instrumental method may measure such a component as an individual chromatographic peak which

is typically backflushed through the system, and all components elute at the same time through the

detector. Alternatively, in systems where valve switching is not possible, the heavier hydrocarbons

elute in a forward fashion through the columns and the component is simply measured as the sum of

individual peaks. However, the system may be set up to measure all hexanes (C s) individually and the

summed peak C + may be specified. This is often the case should the C + amount be significant and a

7 6

more detailed breakdown of this component be required to minimize errors on the measurement. This

principle can be extended such that the system is set up to measure in a C , C , C , C or even C

6+ 7+ 8+ 9+ 10+

mode. Users of this International Standard shall decide which of these components are to be included in

the evaluation of the instrument’s performance based upon the significance of the amounts of each of

the components specified in the instrument set-up.
6.1.3 Component content ranges

Once it is clear which measured components are going to be included in the evaluation, the user shall

determine, for each of these, over what range of amount fractions the instrument is expected to be used.

Such ranges shall generally be greater than that which is expected to be measured by the instrument in

regular duty. If the data from the performance evaluation is used subsequently to update the response

functions assumed by the instrument, then it is vital that the component content ranges used in the

evaluation extend beyond the specified operating range. Should this not be the case, considerable

measurement errors might result from extrapolation outside the determined response function.

6.2 Response function types
6.2.1 Assumed functional descriptions

The instrument data system will assume a relationship between response and content of a component in

the gas. This is the assumed analysis function of the instrument, x
...

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