EN ISO 6974-3:2018

Natural gas - Determination of composition and associated uncertainty by gas chromatography - Part 3: Precision and bias (ISO 6974-3:2018)

This document describes the precision that can be expected from the gas chromatographic method that is set up in accordance with ISO 6974-1. The stated precision provides values for the magnitude of variability that can be expected between test results when the method described in ISO 6974-1 is applied in one or more competent laboratories. This document also gives guidance on the assessment of bias.

Erdgas - Bestimmung der Zusammensetzung und der zugehörigen Unsicherheit durch Gaschromatographie - Teil 3: Präzision und Bias (ISO 6974-3:2018)

Gaz naturel - Détermination de la composition et de l'incertitude associée par chromatographie en phase gazeuse - Partie 3: Fidélité et biais (ISO 6974-3:2018)

Le présent document décrit la fidélité que l'on peut attendre d'une méthode par chromatographie en phase gazeuse, mise en place conformément à l'ISO 6974-1. La fidélité déterminée permet d'évaluer l'étendue de la variabilité envisageable entre les résultats des essais, lorsque la méthode décrite dans l'ISO 6974-1 est appliquée dans un ou plusieurs laboratoires compétents. Le présent document donne également des recommandations quant à l'évaluation du biais.

Zemeljski plin - Določevanje sestave s plinsko kromatografijo in s tem povezana negotovost - 3. del: Natančnost in odstopanje (ISO 6974-3:2018)

Ta dokument opisuje natančnost, ki jo je mogoče pričakovati pri metodi plinske kromatografije, pripravljene v skladu s standardom ISO 6974-1. Navedena natančnost zagotavlja vrednosti za obseg variabilnosti, ki ga je mogoče pričakovati med rezultati preskusa, ko se metoda, opisana v standardu ISO 6974-1, uporablja v enem ali več merodajnih laboratorijih. Ta dokument podaja tudi smernice za ocenjevanje
odstopanja.

General Information

• Status: Published
• Publication Date: 27-Nov-2018
• Withdrawal Date: 30-May-2019
• ICS: 75.060 - Natural gas
• Technical Committee: CEN/TC 238 - Test gases, test pressures and categories of appliances
• Drafting Committee: CEN/SS N21 - Gaseous fuels and combustible gas
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 28-Nov-2018
• Completion Date: 28-Nov-2018
• Ref Project: SIST EN ISO 6974-3:2019 - Natural gas - Determination of composition and associated uncertainty by gas chromatography - Part 3: Precision and bias (ISO 6974-3:2018)

Relations

• Replaces: EN ISO 6974-3:2001 - Natural gas - Determination of composition with defined uncertainty by gas chromatography - Part 3: Determination of hydrogen, helium, oxygen, nitrogen, carbon dioxide and hydrocarbons up to C8 using two packed columns (ISO 6974-3:2000)
• Effective Date: 05-Dec-2018

Overview

EN ISO 6974-3:2018 - Natural gas: Determination of composition and associated uncertainty by gas chromatography - Part 3: Precision and bias (ISO 6974-3:2018) defines the expected measurement precision and gives guidance for assessing bias when applying the gas chromatographic method configured in accordance with ISO 6974-1. Prepared by ISO/TC 193 and adopted by CEN, this part complements the analytical procedure by quantifying variability between competent laboratories and by describing how to evaluate systematic error (bias).

Key topics and technical requirements

• Precision metrics: Defines how precision is expressed for natural gas composition analysis - primarily repeatability (short-term, same conditions) and reproducibility (between laboratories/conditions).
• Reference precision values: Provides reference repeatability and reproducibility values derived from statistical evaluation of interlaboratory data (14 proficiency testing exercises organized from 2012–2014).
• Bias assessment: Gives guidance on estimating and interpreting measurement bias and laboratory bias, including how to compare test results to assigned or reference values.
• Principle and scope: Clarifies that the precision values apply to the gas chromatographic method set up per ISO 6974-1 and are intended for use by one or more competent laboratories.
• Terms, symbols and definitions: Standardizes terminology (e.g., measurement precision, error of measurement, repeatability standard deviation sr, reproducibility standard deviation sR).
• Proficiency testing data: Includes an informative annex on proficiency scheme data evaluation and the statistical basis for deriving precision estimates.
• Normative references: Cross-references relevant documents, notably ISO/IEC 17025 and ISO 5725-series for statistical methods.

Applications and users

This standard is essential for organizations involved in natural gas analysis and quality assurance:

• Analytical laboratories performing gas chromatography for natural gas composition and uncertainty estimation.
• Gas producers, suppliers and pipeline operators performing custody transfer, quality control, and regulatory compliance testing.
• Regulatory bodies and certification entities that require harmonized precision and bias assessment methods.
• Proficiency testing providers and interlaboratory comparison organizers using standardized evaluation methods.

Practical uses include method validation, reporting measurement uncertainty, evaluating laboratory performance, and supporting contractual or regulatory decisions where accurate natural gas composition data are required.

Related standards

• ISO 6974-1 (method setup for GC analysis of natural gas)
• ISO/IEC 17025 (laboratory competence)
• ISO 5725 (accuracy - trueness and precision of measurement methods)
• ISO 6974 series (other parts covering components and data handling)

Keywords: EN ISO 6974-3:2018, natural gas, gas chromatography, precision, bias, measurement uncertainty, repeatability, reproducibility, proficiency testing.

Standards Content (Sample)

SLOVENSKI STANDARD
01-marec-2019
1DGRPHãþD
SIST EN ISO 6974-3:2001
=HPHOMVNLSOLQ'RORþHYDQMHVHVWDYHVSOLQVNRNURPDWRJUDILMRLQVWHPSRYH]DQD
QHJRWRYRVWGHO1DWDQþQRVWLQRGVWRSDQMH,62
Natural gas - Determination of composition and associated uncertainty by gas
chromatography - Part 3: Precision and bias (ISO 6974-3:2018)
Erdgas - Bestimmung der Zusammensetzung und der zugehörigen Unsicherheit durch
Gaschromatographie - Teil 3: Präzision und Bias (ISO 6974-3:2018)
Gaz naturel - Détermination de la composition et de l'incertitude associée par
chromatographie en phase gazeuse - Partie 3: Fidélité et biais (ISO 6974-3:2018)
Ta slovenski standard je istoveten z: EN ISO 6974-3:2018
ICS:
71.040.50 Fizikalnokemijske analitske Physicochemical methods of
metode analysis
75.060 Zemeljski plin Natural gas
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 6974-3
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2018
EUROPÄISCHE NORM
ICS 75.060 Supersedes EN ISO 6974-3:2001
English Version
Natural gas - Determination of composition and associated
uncertainty by gas chromatography - Part 3: Precision and
bias (ISO 6974-3:2018)
Gaz naturel - Détermination de la composition et de Erdgas - Bestimmung der Zusammensetzung und der
l'incertitude associée par chromatographie en phase zugehörigen Unsicherheit durch Gaschromatographie -
gazeuse - Partie 3: Fidélité et biais (ISO 6974-3:2018) Teil 3: Präzision und Bias (ISO 6974-3:2018)
This European Standard was approved by CEN on 14 November 2018.

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, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6974-3:2018 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 6974-3:2018) has been prepared by Technical Committee ISO/TC 193 "Natural
gas" in collaboration with Technical Committee CEN/TC 238 “Test gases, test pressures, appliance
categories and gas appliance types” the secretariat of which is held by AFNOR.
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 May 2019, and conflicting national standards shall be
withdrawn at the latest by May 2019.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 6974-3:2001.
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,
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, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 6974-3:2018 has been approved by CEN as EN ISO 6974-3:2018 without any
modification.
INTERNATIONAL ISO
STANDARD 6974-3
Second edition
2018-10
Natural gas — Determination
of composition and associated
uncertainty by gas chromatography —
Part 3:
Precision and bias
Gaz naturel — Détermination de la composition et de l'incertitude
associée par chromatographie en phase gazeuse —
Partie 3: Fidélité et biais
Reference number
ISO 6974-3:2018(E)
©
ISO 2018
ISO 6974-3:2018(E)
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

ISO 6974-3:2018(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 4
5 Principle . 4
6 Reference precision values . 4
7 Practical applications . 5
8 Bias . 6
Annex A (informative) Proficiency scheme data evaluation . 7
Bibliography .11
ISO 6974-3:2018(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso
.org/iso/foreword .html.
This document 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 6974-3:2000), which has been technically
revised.
A list of all parts in the ISO 6974 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 6974-3:2018(E)
Natural gas — Determination of composition and
associated uncertainty by gas chromatography —
Part 3:
Precision and bias
1 Scope
This document describes the precision that can be expected from the gas chromatographic method
that is set up in accordance with ISO 6974-1. The stated precision provides values for the magnitude
of variability that can be expected between test results when the method described in ISO 6974-1 is
applied in one or more competent laboratories. This document also gives guidance on the assessment
of bias.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 17025, General requirements for the competence of testing and calibration laboratories
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at: http: //www .electropedia .org/
3.1
measurement precision
closeness of agreement between indications or measured quantity values obtained by replicate
measurements on the same or similar objects under specified conditions
Note 1 to entry: Measurement precision is usually expressed numerically by measures of imprecision, such as
standard deviation, variance, or coefficient of variation under the specified conditions of measurement.
Note 2 to entry: The ‘specified conditions’ can be, for example, repeatability conditions of measurement,
intermediate precision conditions of measurement, or reproducibility conditions of measurement (see
ISO 5725-1).
Note 3 to entry: Measurement precision is used to define measurement repeatability, intermediate measurement
precision, and measurement reproducibility.
Note 4 to entry: Sometimes “measurement precision” is erroneously used to mean measurement accuracy.
[SOURCE: JCGM 200:2012, 2.15]
ISO 6974-3:2018(E)
3.2
error of measurement
measured quantity value minus a reference quantity value
Note 1 to entry: The concept of ‘measurement error’ can be used both
a) when there is a single reference quantity value to refer to, which occurs if a calibration is made by means of
a measurement standard with a measured quantity value having a negligible measurement uncertainty or if
a conventional quantity value is given, in which case the measurement error is known, and
b) if a measurand is supposed to be represented by a unique true quantity value of a set of true quantity values
of negligible range in which case the measurement error is not known
Note 2 to entry: Measurement error should not be confused with production error or mistake.
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