CEN ISO/TR 24094:2007

SLOVENSKI STANDARD
01-januar-2008
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Analysis of natural gas - Validation methods for gaseous reference materials (ISO/TR
24094:2006)
Erdgasanalyse - Validierungsverfahren für gasförmige Referenzmaterialien (ISO/TR
24094:2006)
Analyse du gaz naturel - Méthodes de validation pour matériaux de référence gazeux
(ISO/TR 24094:2006)
Ta slovenski standard je istoveten z: CEN ISO/TR 24094:2007
ICS:
75.060 Zemeljski plin Natural gas
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL REPORT
CEN ISO/TR 24094
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
November 2007
ICS 75.060
English Version
Analysis of natural gas - Validation methods for gaseous
reference materials (ISO/TR 24094:2006)
Analyse du gaz naturel - Méthodes de validation pour Erdgasanalyse - Validierungsverfahren für gasförmige
matériaux de référence gazeux (ISO/TR 24094:2006) Referenzmaterialien (ISO/TR 24094:2006)
This Technical Report was approved by CEN on 2 November 2007. It has been drawn up by the Technical Committee CEN/SS N21.
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.
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© 2007 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN ISO/TR 24094:2007: E
worldwide for CEN national Members.

Foreword
The text of ISO/TR 24094:2006 has been prepared by Technical Committee ISO/TC 193
"Natural gas” of the International Organization for Standardization (ISO) and has been taken
over as CEN ISO/TR 24094:2007 by Technical Committee CEN/SS N21 "Gaseous fuels and
combustible gas", the secretariat of which is held by CMC.

Endorsement notice
The text of ISO/TR 24094:2006 has been approved by CEN as CEN ISO/TR 24094:2007
without any modifications.
TECHNICAL ISO/TR
REPORT 24094
First edition
2006-05-15
Analysis of natural gas — Validation
methods for gaseous reference materials
Analyse du gaz naturel — Méthodes de validation pour matériaux de
référence gazeux
Reference number
ISO/TR 24094:2006(E)
©
ISO 2006
ISO/TR 24094:2006(E)
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ii © ISO 2006 – All rights reserved

ISO/TR 24094:2006(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Development of the validation methods. 2
4 Results of the VAMGAS project . 5
Annex A (informative) Report on the validation methods for gaseous reference materials . 6
Bibliography . 47

ISO/TR 24094:2006(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
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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.
In exceptional circumstances, when a technical committee has collected data of a different kind from that
which is normally published as an International Standard (“state of the art”, for example), it may decide by a
simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely
informative in nature and does not have to be reviewed until the data it provides are considered to be no
longer valid or useful.
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/TR 24094 was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee SC 1, Analysis
of natural gas.
iv © ISO 2006 – All rights reserved

TECHNICAL REPORT ISO/TR 24094:2006(E)

Analysis of natural gas — Validation methods for gaseous
reference materials
1 Scope
This Technical Report describes the validation of the calorific value and density calculated from current
practice natural gas analysis by statistical comparison with values obtained by measurement using a
reference calorimeter and a density balance.
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 6142, Gas analysis — Preparation of calibration gas mixtures — Gravimetric method
ISO 6974-1, Natural gas — Determination of composition with defined uncertainty by gas chromatography —
Part 1: Guidelines for tailored analysis
ISO 6974-2, Natural gas — Determination of composition with defined uncertainty by gas chromatography —
Part 2: Measuring-system characteristics and statistics for processing of data
ISO 6974-3, 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 6974-4, Natural gas — Determination of composition with defined uncertainty by gas chromatography —
Part 4: Determination of nitrogen, carbon dioxide and C1 to C5 and C6+ hydrocarbons for a laboratory and
on-line measuring system using two columns
ISO 6974-5, Natural gas — Determination of composition with defined uncertainty by gas chromatography —
Part 5: Determination of nitrogen, carbon dioxide and C1 to C5 and C6+ hydrocarbons for a laboratory and
on-line process application using three columns
ISO 6974-6, Natural gas — Determination of composition with defined uncertainty by gas chromatography —
Part 6: Determination of hydrogen, helium, oxygen, nitrogen, carbon dioxide and C1 to C8 hydrocarbons using
three capillary columns
ISO 6976, Natural gas — Calculation of calorific values, density, relative density and Wobbe index from
composition
Guide to the expression of uncertainty in measurement (GUM), BIPM/IEC/IFCC/ISO/IUPAC/IUPAP/OIML, 1995
ISO/TR 24094:2006(E)
3 Development of the validation methods
The validation methods for gaseous reference materials (VAMGAS) project was established by a group of
European gas companies as an approach to confirming the practices used in natural gas analysis and
physical property calculations.
The VAMGAS project proposed comparing the calorific value and density calculated from the current practices
for natural gas analyses with values obtained by measurement using a reference calorimeter (located at the
Ofgas, UK laboratory) and density balance (located at the Ruhrgas, Germany laboratory). Robust statistical
comparisons allowed an assessment of the validity of the practices.
The natural gas analysis practice covered by the VAMGAS project can be divided into the following steps:
⎯ The gravimetric preparation of gas mixtures used as calibrants in the analysis of natural gas in
accordance with ISO 6142. At the highest level, these mixtures are categorized as primary reference gas
mixtures (PRMs) and are available from national institutes such as Bundesanstalt fur Materialforschung
und -prüfung (BAM) of Germany and Nederlands Meetinstituut (NMi) of the Netherlands.
⎯ The analysis of natural gas by gas chromatographic methods, such as those given is ISO 6974 (all parts).
This is a multiple part International Standard that provides a number of different approaches to the gas
chromatographic analysis of natural gas. ISO 6974-2 describes the processing of calibration and
analytical data to determine the uncertainties on sample component concentrations that are required for
the calculation of uncertainties on calculated physical property values of the sample gas.
⎯ The calculation of the values of physical properties from the results of the gas chromatographic analyses
as described in ISO 6976.
The VAMGAS project was divided in two parts:
a) Part 1: comparison of the calorific values and densities of two PRMs calculated from the gravimetric
preparation data against the values obtained from the reference calorimeter and density balance (see
Figure 1);
b) Part 2: gas chromatography intercomparison exercise, in which calorific values and densities calculated
from the analyses of two natural gases (with bracketing calibration using PRMs) were compared to the
values obtained from the reference calorimeter and density balance (see Figure 2).
The two separate exercises would enable problems arising from either the gravimetric preparation or the gas
chromatographic analyses to be identified.
The participants in the VAMGAS project were Ruhrgas AG (Germany and project co-ordinator), Gasunie (the
Netherlands), Gaz de France (France), BAM (Germany), NMi (the Netherlands) and Ofgem (previously Ofgas,
the UK). In addition, a total of 18 laboratories participated in the gas chromatography intercomparison.
The technical report from the VAMGAS is given in Annex A.
2 © ISO 2006 – All rights reserved

ISO/TR 24094:2006(E)
Figure 1 — Schematic concept of part 1 of the VAMGAS project
ISO/TR 24094:2006(E)
Figure 2 — Schematic concept of part 2 of the VAMGAS project
4 © ISO 2006 – All rights reserved

ISO/TR 24094:2006(E)
4 Results of the VAMGAS project
The project report provides results on two sets of comparisons.
a) The results of the exercise using the PRMs showed statistical agreement between the calorific values and
densities calculated from the gravimetric preparation data and the values of these physical properties
obtained from direct measurement using reference instruments.
b) The results of the gas chromatographic intercomparison showed statistical agreement between the
calorific values and densities calculated from gas chromatographic analyses, carried out using PRMs as
calibrants, and the values of these physical properties obtained from direct measurements using
reference instruments.
It can be concluded that the VAMGAS project has validated the current systems of natural gas analyses and
calculation of physical property data involving the previously mentioned ISO International Standards. As a
result, all parties in the supply and use of natural gas, whether supplier or consumer, can have confidence in
these. The current ISO International Standards for calibration gas preparation and natural gas analysis, if
carefully applied, give values of calorific value and density that are in agreement with values that were
independently determined by reference measurements. This also includes the tabulated values in ISO 6976,
which are used in calculations of thermal energy for billing/fiscal transfer purposes.
The VAMGAS project was carried out as an integrated project to study the complete system of natural gas
analysis involving the gravimetric preparation of calibration gas mixtures,
...