ISO 8943:2025

Refrigerated light hydrocarbon fluids — Sampling of liquefied natural gas — Continuous and intermittent methods

This document specifies methods for the continuous and intermittent sampling of liquefied natural gas (LNG) while it is being transferred through an LNG transfer line.

Hydrocarbures liquides légers réfrigérés — Échantillonnage de gaz naturel liquéfié — Méthodes en continu et par intermittence

L'ISO 8943:2007 prescrit une méthode d'échantillonnage en continu et une méthode d'échantillonnage par intermittence du GNL lors de son transfert par une conduite de transfert de GNL.

General Information

• Status: Not Published
• Publication Date: 09-Apr-2025
• ICS: 75.060 - Natural gas
• Technical Committee: ISO/TC 28/SC 5 - Measurement of refrigerated hydrocarbon and non-petroleum based liquefied gaseous fuels
• Drafting Committee: ISO/TC 28/SC 5 - Measurement of refrigerated hydrocarbon and non-petroleum based liquefied gaseous fuels
• Current Stage: 6060 - International Standard published
• Start Date: 10-Apr-2025
• Due Date: 06-Jan-2025
• Completion Date: 10-Apr-2025

Relations

• Revises: ISO 8943:2007 - Refrigerated light hydrocarbon fluids — Sampling of liquefied natural gas — Continuous and intermittent methods
• Effective Date: 06-Jun-2022

Standards Content (Sample)

International
Standard
ISO 8943
Third edition
Refrigerated light hydrocarbon
2025-04
fluids — Sampling of liquefied
natural gas — Continuous and
intermittent methods
Hydrocarbures liquides légers réfrigérés — Échantillonnage de
gaz naturel liquéfié — Méthodes en continu et par intermittence
Reference number
ISO 8943:2025(en)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
ii
ISO 8943:2025(en)
Contents  Page
Foreword .iv
Introduction .v
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 1
4  Outline of sampling system .3
4.1 General .3
4.2 Direct sampling .4
4.3 Indirect sampling .4
4.3.1 General .4
4.3.2 Spot sampling .5
4.3.3 Incremental composite sampling .5
4.4 Multiple LNG transfer lines .5
5  Precautions .10
5.1 Precautions in handling LNG .10
5.2 Partial fractionation of the LNG sample .11
5.3 Supervision during sampling . .11
6  Apparatus .11
6.1 Materials used .11
6.2 Sampling probe .11
6.3 LNG sample vaporizer . 12
6.4 Compressor for transferring gasified LNG . 12
6.5 Pressure regulator . 12
6.6 Gas sample holder . 12
6.7 Gas sample compressor . 13
6.8 Gas sample cylinder or CP/FP sample cylinder . 13
6.9 Piping arrangement.14
6.10 Sample filter .14
7  Sampling procedure .15
7.1 General . 15
7.2 Sampling of LNG . 15
7.3 Suspension of sampling . 15
7.4 Continuous sampling . 15
7.4.1 Filling the gas sample holder with gasified LNG . 15
7.4.2 Filling the gas sample cylinder .16
7.5 Intermittent sampling .16
7.5.1 Filling the CP/FP sample cylinder with gasified LNG .16
7.5.2 Purging the CP/FP sample cylinder .16
7.6 Online gas chromatograph .16
8  Sampling report . 17
Annex A (informative)  Example of calculation of degree of sub-cooling .18
Annex B (informative)  Constant pressure (CP)/floating piston (FP) sample cylinder with
technical specifications .21
Annex C (informative)  Example of sampling report .24
Bibliography .25

iii
ISO 8943:2025(en)
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
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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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
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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 28, Petroleum and related products, fuels and
lubricants from natural or synthetic sources, Subcommittee SC 5, Measurement of refrigerated hydrocarbon
and non-petroleum based liquefied gaseous fuels.
This third edition cancels and replaces the second edition (ISO 8943:2007), which has been technically
revised.
The main changes are as follows:
— an overview of gasified LNG sampling has been added;
— a CP/FP sample holder has been introduced;
— a multiple shore transfer pipeline has been considered;
— a stable flow rate has been specified;
— an approach to find an outlier of online analysis results has been introduced;
— an example of a sampling report has been added.
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 8943:2025(en)
Introduction
In the custody transfer of liquefied natural gas, hereinafter referred to as LNG, it is common practice to
determine the quantity transferred on a calorific-content basis. The total calorific content of the quantities
of LNG quoted in the custody transfer is determined by the liquid volume, liquid density and gross calorific
value of the LNG delivered.
Knowledge of the composition of LNG is required to calculate its density and calorific content. Therefore,
precise sampling is a prerequisite for precise analysis.
LNG is a complex mixture of low-molecular-weight hydrocarbons with nitrogen as a principal inert impurity.
Typically, methane is the major component. Minor-component concentrations vary with the source of the
raw gas, the liquefaction pre-treatment, the liquefaction process and the storage conditions.

v
International Standard ISO 8943:2025(en)
Refrigerated light hydrocarbon fluids — Sampling of liquefied
natural gas — Continuous and intermittent methods
1  Scope
This document specifies methods for the continuous and intermittent sampling of liquefied natural gas
(LNG) while it is being transferred through an LNG transfer line.
2  Normative references
There are no normative references in this document.
3  Terms and definitions
For the purposes of this docu
...