EN ISO 23306:2020

SLOVENSKI STANDARD
01-december-2020
Specifikacija utekočinjenega zemeljskega plina kot goriva za uporabo v pomorstvu
(ISO 23306:2020)
Specification of liquefied natural gas as a fuel for marine applications (ISO 23306:2020)
Festlegungen für Flüssigerdgas als Kraftstoff für marine Anwendungen (ISO
23306:2020)
Spécification du gaz naturel liquéfié comme carburant pour les applications maritimes
(ISO 23306:2020)
Ta slovenski standard je istoveten z: EN ISO 23306:2020
ICS:
75.160.30 Plinska goriva Gaseous fuels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 23306
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2020
EUROPÄISCHE NORM
ICS 75.160.30
English Version
Specification of liquefied natural gas as a fuel for marine
applications (ISO 23306:2020)
Spécification du gaz naturel liquéfié comme carburant Festlegungen für Flüssigerdgas als Kraftstoff für
pour les applications maritimes (ISO 23306:2020) marine Anwendungen (ISO 23306:2020)
This European Standard was approved by CEN on 22 September 2020.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, 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
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 23306:2020 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 23306:2020) has been prepared by Technical Committee ISO/TC 28 "Petroleum
and related products, fuels and lubricants from natural or synthetic sources" in collaboration with
Technical Committee CEN/TC 408 “Natural gas and biomethane for use in transport and biomethane for
injection in the natural gas grid” 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 2021, and conflicting national standards shall be
withdrawn at the latest by May 2021.
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.
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, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 23306:2020 has been approved by CEN as EN ISO 23306:2020 without any modification.

INTERNATIONAL ISO
STANDARD 23306
First edition
2020-10
Specification of liquefied natural gas
as a fuel for marine applications
Spécification du gaz naturel liquéfié comme carburant pour les
applications maritimes
Reference number
ISO 23306:2020(E)
©
ISO 2020
ISO 23306:2020(E)
© ISO 2020
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 2020 – All rights reserved

ISO 23306:2020(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope .1
2 Normative references .1
3 Terms and definitions .1
4 General requirements .2
5 Sampling .3
6 Requirements, limit values and related test methods .3
7 Main compounds removed by liquefaction process .4
Annex A (normative) Propane knock index: Methane number calculation method .6
Annex B (informative) Examples of LNG composition .12
Annex C (informative) Methane number (knock resistance) and Wobbe index (thermal
input through a restriction) .15
Annex D (informative) LNG ageing along the bunkering chain .17
Annex E (informative) Particles .18
Annex F (informative) Melting and boiling points of pure components and impurities that
can be present in different LNG.19
Bibliography .21
ISO 23306:2020(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 28, Petroleum and related products, fuels
and lubricants from natural or synthetic sources, Subcommittee SC 4, Classifications and specifications,
in collaboration with the European Committee for Standardization (CEN) Technical Committee
CEN/TC 408, Natural gas and biomethane for use in transport and biomethane for injection in the natural
gas grid, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna
Agreement).
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 2020 – All rights reserved

ISO 23306:2020(E)
Introduction
Due to numerous economic and environmental factors, the use of liquefied natural gas (LNG) as fuel
for marine applications has increased. The 0,10 % sulfur limit, in the sulfur emission controlled areas
in Europe and the US, which entered into force on 1 January 2015 has been one of the major driving
forces for using LNG as fuel for marine applications. The decision for the 0,50 % global sulfur limit from
1 January 2020 by the International Maritime Organization (IMO) might further increase the interest
in LNG. The International Code of Safety for Ships using Gases or other Low-flashpoint Fuels (IGF Code)
was a response to the need of guidance in this emerging market. Since LNG-fueled vessels are likely
to bunker LNG in different parts of the world, a common specification is needed for ship owners, ship
operators and LNG suppliers. It would help engine manufacturers and ship designers and it is beneficial
for the development of this new alternative marine fuel market.
In 2018, IMO adopted an initial strategy on reduction of greenhouse gas (GHG) emissions from ships.
The strategy includes the objective to peak GHG emissions from international shipping as soon as
possible, whilst pursuing efforts towards decarbonizing the sector as soon as possible in this century.
It also includes the objectives to reduce the CO emissions per transport work and total annual GHG
emissions from international shipping by 2050, with an interim target in 2030. Thus, LNG produced
from renewable sources as biomethane that can reduce CO emissions when used as marine fuel is also
addressed in this document.
LNG is produced in different locations in the world in liquefaction plants. Large scale production
facilities are often dedicated to specific markets such as natural gas grids and large power plants
that use their own standards. This document takes into consideration this major constraint for any
adaptation to marine applications specificities/requirements.
INTERNATIONAL STANDARD ISO 23306:2020(E)
Specification of liquefied natural gas as a fuel for marine
applications
1 Scope
This document specifies the quality requirements for Liquefied Natural Gas (LNG) used as a fuel for
marine applications. It defines the relevant parameters to measure as well as the required values and
the test reference methods for all those parameters.
This document applies to LNG from any source, e.g. gas from conventional reservoirs, shale gas, coalbed
methane, biomethane, synthetic methane. LNG described in this document can come from synthesis
process out of fossil fuels or renewable sources.
This document identifies the required specifications for fuels delivered at the time and place of custody
transfer (at the delivery point).
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 6578, Refrigerated hydrocarbon liquids — Static measurement — Calculation procedure
ISO 6974 (all parts), Natural gas — Determination of composition and associated uncertainty by gas
chromatography
ISO 6976, Natural gas — Calculation of calorific values, density, relative density and Wobbe indices from
composition
ISO 8943, Refrigerated light hydrocarbon fluids — Sampling of liquefied natural gas — Continuous and
intermittent methods
EN 16726, Gas infrastructure — Quality of gas — Group H
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
biomethane
methane rich gas derived from biogas or from gasification of biomass by upgrading with the properties
similar to natural gas
[SOURCE: ISO 14532:2014, 2.1.1.15]
ISO 23306:2020(E)
3.2
liquefied natural gas
LNG
natural gas that has been liquefied after processing
[SOURCE: ISO 14532:2014, 2.1.1.12, modified — Definition has been shortened, note to entry has been
deleted.]
3.3
methane number
MN
rating indicating the knocking characteristics of a fuel gas
Note 1 to entry: It is comparable to the octane number for petrol. One expression of the methane number is the
volume percentage of methane in a methane-hydrogen mixture, that in a test engine under standard conditions
has the same tendency to knock as the fuel gas to be examined.
[SOURCE: ISO 14532:2014, 2.6.6.1]
3.4
natural gas
complex gaseous mixture of hydrocarbons, primarily methane, but generally includes ethane, propane
and higher hydrocarbons, and some non-combustible gases such as nitrogen and carbon dioxide
Note 1 to entry: Natural gas can also contain components or contaminants such as sulfur compounds and/or
other chemical species.
[SOURCE: ISO 14532:2014, 2.1.1.1]
3.5
Wobbe index
calorific value on a volumetric basis at specified reference conditions, divided by the square root of the
relative density at the same specified metering reference conditions
[SOURCE: ISO 14532:2014, 2.6.4.3, modified — Note to entry has been deleted.]
4 General requirements
4.1 The LNG at the delivery point shall conform with the characteristics and limits given in Table 1
when tested in accordance with the specified methods.
The components listed in Table 1 and Table 2 shall be measured to enable the calculation of the physical
properties of the LNG at the delivery point.
4.2 The LNG delivered shall be free from any material at a concentration that causes the LNG to be
unacceptable for use, i.e. material not at a concentration that is harmful to personnel, jeopardizes the
safety of the ship, or adversely affects the performance of the machinery.
4.3 Physicochemical characteristics not requiring measurement are listed in Table 3.
It is not practical to require detailed chemical analysis for each delivery of fuels beyond the
requirements listed in Table 1 or Table 2. Instead, a liquefaction plant, LNG terminal or any other supply
facility, including supply barges and truck deliveries, shall have in place adequate quality assurance
and management of change procedures to ensure that the resultant LNG is in conformance with the
requirements of this document.
Examples of LNG compositions are given in Annex B.
Information on ageing of LNG can be found in Annex D and information on particles can be found in
Annex E.
2 © ISO 2020 – All rights reserved

ISO 23306:2020(E)
4.4 The reference conditions shall be 288,15 K, 101,325 kPa (see ISO 13443:1996, Clause 3) in the
gaseous phase.
5 Sampling
Samples for quality verification are not mandatory but can be taken at various locations as agreed
among the parties concerned. Samples, if any, can also be taken at multiple moments in time, as LNG
has distinct different ageing characteristics than traditional hydrocarbon maritime fuels (with regards
to ageing reference is made to Annex D). In order to ensure a representative sample, proper sampling
procedures should be followed.
When sampling of LNG for analysis is carried out, it shall be in accordance with the procedures
provided in ISO 8943 or an equivalent national standard agreed between the parties concerned. Where
specific sampling requirements are documented, the relevant parties should agree on the reference
test methods. The LNG collected in liquid state shall be instantly conditioned to gaseous state without
any partial vaporization or loss of molecular components to ensure a representative sample.
There are two methods for sampling LNG as defined in ISO 8943, continuous and intermittent. Both
methods obtain LNG from the LNG cargo/bunker line and then it is gasified in a vaporizer. The
continuous method collects the gasified LNG in a sample holder at a constant flow rate for offline
analysis. The intermittent method collects gasified LNG and directs it to an on-line analyzer at
predetermined intervals. Please refer to ISO 8943 for more details on these methods.
The requirements for sampling LNG for marine applications can vary throughout the industry,
depending on availability and equipment. Load port samples can be used for quality determination if
the sampling equipment is not available and if it is agreed between the parties.
6 Requirements, limit values and related test methods
The components and physicochemical characteristics that shall be measured or calculated using the
related test methods are given in Table 1 and Table 2.
[1]
NOTE Information can be found in ISO 6975 .
Information on MN and Wobbe index can be found in Annex C.
Table 1 — Physicochemical characteristics requiring measurement/calculation with limit values
Characteristic Unit Limit Value Test method
3 a
Net Calorific Value (NCV) MJ/m (s) Min 33,6 ISO 6976
Nitrogen % (mol) Max 1,0 ISO 6974 (all parts)
Annex A (Propane knock
b
Methane Number (MN) no unit Min
index) or EN 16726
a
Calculated for a theoretical mixture of 99 % (mol) methane and 1 % (mol) nitrogen in liquid phase. The
Gross Calorific Value can be calculated from the Net Calorific Value (see ISO 13443:1996).
b
Both the method used for determining the MN and the minimum value shall be agreed between supplier and user.
The fuel supplier shall calculate the actual MN at the delivery point and provide this information to the
user (see Clause 5 for sampling location). This information shall be given as MN or MN .
(PKI) (EN 16726)
For guidance on the MN applicability to a specific application, Original Equipment Manufacturer (OEM)
specifications should be considered.
ISO 23306:2020(E)
Table 2 — Physicochemical characteristics requiring measurement without limit values
Characteristic Unit Test method Value
a 3
Density kg/m ISO 6578 Report
Methane (CH ) % (mol) ISO 6974 (all parts) Report
Ethane (C H ) % (mol) ISO 6974 (all parts) Report
2 6
Propane (C H ) % (mol) ISO 6974 (all parts) Report
3 8
n-Butane (C H )
4 10
% (mol) ISO 6974 (all parts) Report
i-Butane
Pentane(C H ) % (mol) ISO 6974 (all parts) Report
5 12
a
Density at temperature of the liquid phase.
7 Main compounds removed by liquefaction process
Natural gas is liquid at around −160 °C under atmospheric pressure and becomes Liquefied Natural
Gas (LNG). To avoid freezing and plugging in the liquefaction plant's cryogenic heat exchangers,
usual impurities or compounds that are present in the natural gas from various sources are removed
upstream from the liquefaction process below their solubility level. Some LNG components (e.g. ethane,
propane, butane and pentane) are possibly removed for commercial reasons or to achieve a targeted
calorific value range.
LNG composition is therefore within more narrow limits compared to natural gas. The compounds
that can be considered as harmful for marine applications are removed or reduced to very low levels
(trace) so that they are no more a concern. They shall comply with 4.2. The main compounds removed
by liquefaction are listed in Table 3 and below for information and reference. The measurement of
these species is not required. However, if the parties concerned agree to measure them, they should be
measured according to the referenced methods listed in Table 3.
The melting and boiling points for a range of compounds, including those possibly present in biomethane,
are available in Table F.1.
4 © ISO 2020 – All rights reserved

ISO 23306:2020(E)
Table 3 — Main compounds removed by liquefaction and not requiring measurement
Solubility limit
in LNG (around Typical value out
Characteristic Unit Test method Remarks
−160 °C, atm. of LNG plant
Pressure)
Hexane and % (mol) ISO 6974 (all n.a. n.a. n.a.
higher parts)
hydrocarbons
3 [5] 3
Total sulfur mg(S)/m ISO 19739 (n.a.) Max 30 mg(S)/m Depends on LNG
(gas) contracts. Actual
[6]
ISO 20729
value very often
much lower.
3 3
Hydrogen sulfide mg/m ISO 19739 n.a. 4,29 mg/m (N) Removed in Acid
Gas Removal Unit
(AGRU) in liquefac-
tion plant for safety
purposes.
Mercaptan mg/m ISO 19739 Depends on size n.a. Removed in AGRU or
of molecule in heavy hydrocar-
bon removal unit in
liquefaction plant.
Carbon dioxide % (mol) ISO 6974 (all Around 0,02 % 0,005 % (mol) Removed in AGRU in
parts) (mol) liquefaction plant.
Oxygen % (mol) ISO 6974 (all n.a. n.a. Removed in
parts) liquefaction plant
3 [3] 3
Water mg/m ISO 10101 Below 0,74 mg/ 0,74 mg/m or Removed in
m below dehydration unit in
liquefaction plant
3 [2] 3
Mercury µg/m ISO 6978-2 n.a. 0,01 μg/m Removed in
liquefaction plant
NOTE  See Annex F for components in low concentration or absent, e.g. siloxanes.
n.a.  Not available.
ISO 23306:2020(E)
Annex A
(normative)
Propane knock index: Methane number calculation method
The MN of a gaseous fuel can be calculated from its composition according to several different methods,
all of which can give different results. The methodology described in this Annex shall be employed to
calculate MN .
(PKI)
For components listed in Table 3, the mole fraction can be taken as equal to "0".
®1)
DNV GL developed a MN method (“PKI MN”) that characterizes gases for their knock resistance
based on the combustion properties of the fuel mixtures themselves. The PKI MN method is based on a
[8]
methane-propane scale (PKI, Propane Knock Index) where the knock resistance of gas composition is
compared to the knock resistance of a methane-propane gas mixture under identical engine conditions.
To calculate the PKI values a polynomial, Formula (A.1) is used:
n n m
P
...