SIST EN ISO 6974-5:2001

SLOVENSKI STANDARD
SIST EN ISO 6974-5:2001
01-december-2001
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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 6974-5:2000)
Erdgas - Bestimmung der Zusammensetzung mit definierter Unsicherheit durch
Gaschromatographie - Teil 5: Bestimmung von Stickstoff, Kohlenstoffdioxid und C1 bis
C5 und C6+ Kohlenwasserstoffen für eine Labor- und Online-Prozessanwendung mit
drei Säulen (ISO 6974-5:2000)
Gaz naturel - Détermination de la composition avec une incertitude définie par
chromatographie en phase gazeuse - Partie 5: Détermination de l'azote, du dioxyde de
carbone et des hydrocarbures (C1 a C5 et C6+) pour l'application du processus en
continu employant trois colonnes (ISO 6974-5:2000)
Ta slovenski standard je istoveten z: EN ISO 6974-5:2001
ICS:
75.060 Zemeljski plin Natural gas
SIST EN ISO 6974-5:2001 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 6974-5:2001

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SIST EN ISO 6974-5:2001
EUROPEAN STANDARD
EN ISO 6974-5
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2001
ICS 75.060
English version
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 6974-5:2000)
Gaz naturel - Détermination de la composition avec une Erdgas - Bestimmung der Zusammensetzung mit
incertitude définie par chromatographie en phase gazeuse definierter Unsicherheit durch Gaschromatographie - Teil 5:
- Partie 5: Détermination de l'azote, du dioxyde de carbone Bestimmung von Stickstoff, Kohlenstoffdioxid und C1 bis
et des hydrocarbures (C1 à C5 et C6+) pour l'application du C5 und C6+ Kohlenwasserstoffen für eine Labor- und
processus en continu employant trois colonnes (ISO 6974- Online-Prozessanwendung mit drei Säulen (ISO 6974-
5:2000) 5:2000)
This European Standard was approved by CEN on 22 June 2001.
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 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, 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
© 2001 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6974-5:2001 E
worldwide for CEN national Members.

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SIST EN ISO 6974-5:2001
EN ISO 6974-5:2001 (E)
CORRECTED  2002-03-13
Foreword
The text of the International Standard from Technical Committee ISO/TC 193 "Natural gas" of
the International Organization for Standardization (ISO) has been taken over as a European
Standard 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 2002, and conflicting national
standards shall be withdrawn at the latest by February 2002.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium, Czech
Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg,
Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of the International Standard ISO 6974-5:2000 has been approved by CEN as a
European Standard without any modifications.
NOTE Normative references to International Standards are listed in annex ZA (normative).
2

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SIST EN ISO 6974-5:2001
EN ISO 6974-5:2001 (E)
Annex ZA
(normative)
Normative references to international publications
with their relevant European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of
any of these publications apply to this European Standard only when incorporated in it by
amendment or revision. For undated references the latest edition of the publication referred to
applies (including amendments).
NOTE Where an International Publication has been modified by common modifications, indicated
by (mod.), the relevant EN/HD applies.
Publication Year Title EN Year
ISO 6974-1 2000 Natural gas - Determination of EN ISO 6974-1 2001
composition with defined
uncertainty by gas chromatography
- Part 1: Guidelines for tailored
analysis
3

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SIST EN ISO 6974-5:2001

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SIST EN ISO 6974-5:2001
INTERNATIONAL ISO
STANDARD 6974-5
First edition
2000-04-01
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
Gaz naturel — Détermination de la composition avec une incertitude
définie par chromatographie en phase gazeuse —
Partie 5: Détermination de l'azote, du dioxyde de carbone et des
hydrocarbures (C1 à C5 et C6+) pour l'application du processus en continu
employant trois colonnes
Reference number
ISO 6974-5:2000(E)
©
ISO 2000

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SIST EN ISO 6974-5:2001
ISO 6974-5:2000(E)
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ii © ISO 2000 – All rights reserved

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SIST EN ISO 6974-5:2001
ISO 6974-5:2000(E)
Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Normative references .2
3 Principle.2
4 Materials .3
5 Apparatus .3
6 Procedure .4
6.1 Gas chromatographic operating conditions.4
6.2 Calibration .5
6.3 Performance requirements.6
6.3.1 Peak resolution .6
6.3.2 Chromatogram .6
6.4 Determination.6
6.4.1 Sample valve purge .6
6.4.2 Analysis .7
7 Expression of results .7
7.1 Precision and accuracy.7
8 Test report .7
Annex A (informative) Procedure for setting valve timings and restrictor setting .11
Annex B (informative) Typical precision values .13
Bibliography.14
© ISO 2000 – All rights reserved iii

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SIST EN ISO 6974-5:2001
ISO 6974-5:2000(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 3.
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 part of ISO 6974 may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 6974-5 was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee
SC 1, Analysis of natural gas.
This part as well as the other five parts of ISO 6974 cancel and replace ISO 6974:1984 which specified only one
method.
ISO 6974 consists of the following parts, under the general title Natural gas — Determination of composition with
defined uncertainty by gas chromatography:
— Part 1: Guidelines for tailored analysis
— Part 2: Measuring-system characteristics and statistics for data treatment
— Part 3: Determination of hydrogen, helium, oxygen, nitrogen, carbon dioxide and hydrocarbons up to C using
8
two packed columns
— Part 4: Determination of nitrogen, carbon dioxide and C to C and C hydrocarbons for a laboratory and on-
1 5 6�
line measuring system using two columns
— Part 5: Determination of nitrogen, carbon dioxide and C to C and C hydrocarbons for a laboratory and on-
1 5 6�
line process application using three columns
— Part 6: Determination of hydrogen, helium, oxygen, nitrogen, carbon dioxide and hydrocarbons up to C using
8
three capillary columns
Annexes A and B of this part of ISO 6974 are for information only.
iv © ISO 2000 – All rights reserved

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SIST EN ISO 6974-5:2001
ISO 6974-5:2000(E)
Introduction
This part of ISO 6974 describes a precise and accurate method for the determination of the composition of natural
gas. The compositional data obtained are used for the calculation of the calorific value, the relative density and the
Wobbe index.
This method is based on a automatic column-switching technique in which multiple columns, chosen for their
separating ability for particular groups of components, are switched automatically.
This part of ISO 6974 provides one of the methods that may be used for determining the composition of natural gas
in accordance with parts 1 and 2 of ISO 6974.
© ISO 2000 – All rights reserved v

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SIST EN ISO 6974-5:2001

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SIST EN ISO 6974-5:2001
INTERNATIONAL STANDARD ISO 6974-5:2000(E)
Natural gas — Determination of composition with defined
uncertainty by gas chromatography —
Part 5:
Determination of nitrogen, carbon dioxide and hydrocarbons C1
up to C5 and C6+ for a laboratory and on-line process application
using three columns
1 Scope
This part of ISO 6974 describes a gas chromatographic method for the quantitative determination of natural gas
constituents using a three-column system. This method is applicable to natural gases of limited range, on-line and
automatically calibrating on a regular basis for gas samples not containing any hydrocarbon condensate and/or
water. It is applicable to the analysis of gases containing constituents within the mole fraction ranges given in
Table 1. These ranges do not represent the limits of detection, but the limits within which the stated precision of the
method applies. Although one or more components in a sample may not be detected present, the method can still
be applicable.
This part of ISO 6974 is only applicable if used in conjunction with parts 1 and 2 of ISO 6974.
Table 1 — Application ranges
Component Mole fraction range
%
Nitrogen 0,001 to 15,0
Carbon dioxide 0,001 to 8,5
Methane 75 to 100
Ethane 0,001 to 10,0
Propane 0,001 to 3,0
iso-Butane (2-methylpropane) 0,001 to 1,0
n-Butane 0,001 to 1,0
neo-Pentane (2,2-dimethylpropane) 0,001 to 0,5
iso-Pentane (2-methylbutane) 0,001 to 0,5
n-Pentane 0,001 to 0,5
Hexanes � sum of all C and higher hydrocarbons 0,001 to 1,0
6
NOTE 1 Hydrocarbons higher than n-pentane are expressed as the "pseudo-component" C which is measured as one
6�
composite peak and calibrated as such. The properties of C are calculated from detailed analyses of the individual C and
6� 6
higher hydrocarbons by extended analysis or from historical data.
NOTE 2 Oxygen is not a normal constituent of natural gas and would not be expected to be present in gas sampled for an
on-line instrument. If any oxygen is present as a result of air contamination, it will be measured with the nitrogen. The resulting
(nitrogen � oxygen) value will be in error to a small extent because of the slight difference between detector responses for
© ISO 2000 – All rights reserved 1

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SIST EN ISO 6974-5:2001
ISO 6974-5:2000(E)
oxygen and nitrogen. Nonetheless, the result for the natural gas/air mixture will be reasonably accurate since neither component
contributes to the calorific value.
NOTE 3 The content of helium and argon are assumed to be negligible and unvarying such that helium and argon need not
be determined.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this part of ISO 6974. For dated references, subsequent amendments to, or revisions of, any of these publications
do not apply. However, parties to agreements based on this part of ISO 6974 are encouraged to investigate the
possibility of applying the most recent editions of the normative documents 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 International Standards.
ISO 6142, Gas analysis — Preparation of calibration gas mixtures — Gravimetric method.
ISO 6974-1:2000, Natural gas — Determination of composition with defined uncertainty by gas chromatography —
Part 1: Guidelines for tailored analysis.
1)
ISO 6974-2:— , Natural gas — Determination of composition with defined uncertainty by gas chromatography —
Part 2: Measuring-system characteristics and statistics for data treatment.
ISO 7504:1984, Gas analysis — Vocabulary.
3Principle
Determination of nitrogen, carbon dioxide and hydrocarbons from C to C by gas chromatography using a three-
1 6�
column switching/backflush arrangement, configured as shown in Figure 1. The three chromatographic columns
are connected by two six-port valves for handling sample injection and backflushing operations (or alternatively a
single ten-port valve is used) to a thermal conductivity detector (TCD) which is used for quantification.
A single sample is injected first onto a boiling-point separation column, divided into short and long sections. The C
6
and heavier hydrocarbons are initially retained on the short section of this column. The long section of this column
retains C to C hydrocarbons. The lighter components (nitrogen, methane, carbon dioxide and ethane) pass
3 5
rapidly and unresolved through the boiling-point separation column onto a porous polymer-bead column, suitable
for their retention and separation. Following an accelerated backflush of the short column situated closest to the
detector, the heavier C hydrocarbons (determined as a recombined "pseudo component" rather than by the
6�
summation of individual component measurements) elute first and are quantified as a single peak. Next, from the
longer section of this column situated farther from the detector, the C to C hydrocarbons are separated then
3 5
quantified by TCD. Finally, by redirecting carrier gas onto the porous polymer-bead column, the lighter
component
...