ISO 13734:1998
(Main)Natural gas — Organic sulfur compounds used as odorants — Requirements and test methods
Natural gas — Organic sulfur compounds used as odorants — Requirements and test methods
La présente norme spécifie les exigences et les méthodes d'essai applicables aux composés organiques soufrés, désignés ci-après comme odorisants, utilisés pour l'odorisation du gaz naturel et de ses substituts pour les réseaux publics d'alimentation en gaz.
Gaz naturel — Composés organiques soufrés utilisés comme odorisants — Prescriptions et méthodes d'essai
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 13734
First edition
1998-07-01
Natural gas — Organic sulfur compounds
used as odorants — Requirements and test
methods
Gaz naturel — Composés organiques soufrés utilisés comme odorisants —
Prescriptions et méthodes d'essai
A
Reference number
ISO 13734:1998(E)
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ISO 13734:1998(E)
Contents Page
1 Scope . 1
2 Normative reference . 1
3 Definitions . 1
4 Requirements . 2
4.1 Composition . 2
4.2 Cloud point . 2
Boiling point .
4.3 2
4.4 Evaporation residue . 2
Insoluble matter .
4.5 2
4.6 Solubility in water (optional requirement) . 2
Handling and transport .
5 3
6 Tests . 3
6.1 Test sample . 3
6.2 Test documentation . 3
6.3 Determination of composition . 3
6.4 Determination of cloud point . 3
6.5 Determination of boiling point . 4
6.6 Determination of evaporation residue . 5
Visual examination for solids or suspended matter
6.7 5
6.8 Determination of solubility in water . 5
Marking .
7 6
© ISO 1998
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or utilized in any form or by any means, electronic or mechanical, including photocopying and
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International Organization for Standardization
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Printed in Switzerland
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ISO ISO 13734:1998(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.
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.
International Standard ISO 13734 was prepared by Technical Committee
ISO/TC 193, Natural gas.
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ISO 13734:1998(E) ISO
Introduction
Processed natural gas received from suppliers normally has little or no odour. For safety reasons,
natural gas is therefore odorized to permit the detection by smell of the gas at very low concentrations in
air.
NOTE — It is a common requirement that natural gas in air be readily detectable by smell at a concentration of
20 % of the lower flammability limit (LFL). The LFL of natural gas is normally taken as a volume content in air of 4 %
to 5 %.
Odorants used for the odorization of natural gas need to meet several basic requirements:
a) They need to have an intense odour.
b) The odour needs to be distinctive and not confusable with other frequently occurring odours.
c) The odour needs to be unpleasant but not too obnoxious. The odour character needs to be the
same at different dilutions of natural gas with air.
d) The odorized gas must not be toxic or an irritant at the concentration levels at which the odorant is
employed and the addition of the odorant must not lead to the production of significant levels of
harmful combustion products.
e) The odorant needs to be volatile, and sufficiently stable in the gas phase and during storage. It
must not form deposits on burners and safety devices.
Experience in many countries has shown that these basic requirements are best met by organic sulfur
compounds — sulfides (thioethers) and mercaptans (thiols) — with boiling points below 130 °C. Since
primary mercaptans are easily oxidized to disulfides which have a much lower odour intensity,
mercaptan-based odorants need to predominantly contain secondary and tertiary mercaptans.
While it has been established that the above sulfur compounds fulfil the basic requirements listed above
under a) to e), the suitability of other compounds (e.g. non-sulfur compounds) should not be precluded,
provided they meet these basic requirements.
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INTERNATIONAL STANDARD ISO ISO 13734:1998(E)
Natural gas — Organic sulfur compounds used as odorants —
Requirements and test methods
1 Scope
This International Standard specifies requirements and test methods for organic sulfur compounds
suitable for odorization of natural gas and natural gas substitutes for public gas supply, hereafter
referred to as odorants.
2 Normative reference
The following standard contains provisions which, through reference in this text, constitute provisions of
this International Standard. At the time of publication, the edition indicated was valid. All standards are
subject to revision, and parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent edition of the standard indicated below. Members
of IEC and ISO maintain registers of currently valid International Standards.
ISO 3015:1992, Petroleum products — Determination of cloud point.
3 Definitions
For the purposes of this International Standard, the following definitions apply.
3.1
odorant
an intensely smelling organic chemical or combination of chemicals added to natural gas at low
concentration and capable of imparting a characteristic and distinctive (usually disagreeable) warning
odour so gas leaks can be detected at concentrations below their lower flammability limit
NOTE — Currently commercially used odorants belong to the following classes of substances:
a) alkyl sulfides (alkyl thioethers)
— symmetrical sulfides, e.g. C H -S-C H
2 5 2 5
— asymmetrical sulfides, e.g. CH -S-C H
3 2 5
b) cyclic sulfides (cyclic thioethers), e.g. C H S
4 8
c) alkyl mercaptans (alkane thiols)
— primary mercaptans, e.g. C H -SH
2 5
— secondary mercaptans, e.g. (CH ) CH-SH
3 2
— tertiary mercaptans, e.g. (CH ) C-SH
3 3
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ISO 13734:1998(E) ISO
3.2
diluent
an organic liquid, normally consisting of paraffinic hydrocarbons, used to reduce the concentration of an
odorant to a suitable level at which the solution may be injected into the natural gas
3.3
cloud point
the temperature at which a cloud of wax crystals first appears in a liquid when it is cooled under
specified conditions
[ISO 3015:1992]
4 Requirements
4.1 Composition
The mass content of organic sulfur compounds in the undiluted odorant when determined in accordance
with 6.3 shall be equal to or higher than 95 %. At least 80 % of the mass content of these sulfur
compounds shall consist of sulfides (thioethers) or secondary or tertiary mercaptans (thiols). The
composition of the odorant, and where applicable the dilution range, shall be declared by the producer
or distributor.
NOTE — Primary mercaptans — especially methyl and ethyl mercaptan — are more easily oxidized than secondary
or tertiary mercaptans by traces of oxygen in the gas and by iron oxide, e.g. in the form of pipe dust. It is therefore
recommended that the content of primary mercaptans in odorants be minimized.
4.2 Cloud point
The cloud point of the undried odorant, when determined in accordance with 6.4, shall be below –30 °C.
4.3 Boiling point
...
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