Specification of liquefied natural gas as a fuel for marine applications (ISO 23306:2020)

This document will specify the requirements for LNG for use as a fuel in marine engines. It will define the required values for all relevant parameters and the test method for each of these parameters

Festlegungen für Flüssigerdgas als Kraftstoff für marine Anwendungen (ISO 23306:2020)

Dieses Dokument legt die Anforderungen an die Beschaffenheit von Flüssigerdgas, das als Kraftstoff für marine Anwendungen verwendet wird, fest. Es legt die relevanten Parameter für die Messung sowie die geforderten Werte und die Bezugsprüfverfahren für alle diese Parameter fest.
Dieses Dokument gilt für LNG aus beliebigen Quellen, z. B. aus herkömmlichen Lagerstätten, Schiefergas, Kohlenflöz-Methan (Flözgas), Biomethan, synthetisches Methan. In diesem Dokument beschriebenes LNG kann aus dem Syntheseprozess von fossilen Brennstoffen oder erneuerbaren Energieträgern stammen.
Dieses Dokument nennt die geforderten Festlegungen für Kraftstoffe zum Zeitpunkt und am Ort des eichpflichtigen Verkehrs (an der Übergabestelle).

Spécification du gaz naturel liquéfié comme carburant pour les applications maritimes (ISO 23306:2020)

Specifikacija utekočinjenega zemeljskega plina kot goriva za uporabo v pomorstvu (ISO 23306:2020)

General Information

Status
Published
Public Enquiry End Date
03-Feb-2020
Publication Date
12-Nov-2020
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
12-Nov-2020
Due Date
17-Jan-2021
Completion Date
13-Nov-2020

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SLOVENSKI STANDARD
SIST EN ISO 23306:2020
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
SIST EN ISO 23306:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 23306:2020
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SIST EN ISO 23306:2020
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.
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SIST EN ISO 23306:2020
EN ISO 23306:2020 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 23306:2020
EN ISO 23306:2020 (E)
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.

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SIST EN ISO 23306:2020
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SIST EN ISO 23306:2020
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
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SIST EN ISO 23306:2020
ISO 23306:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
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SIST EN ISO 23306:2020
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 2020 – All rights reserved iii
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SIST EN ISO 23306:2020
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
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SIST EN ISO 23306:2020
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.
© ISO 2020 – All rights reserved v
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SIST EN ISO 23306:2020
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SIST EN ISO 23306:2020
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 2020 – All rights reserved 1
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SIST EN ISO 23306:2020
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
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
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SIST EN ISO 23306:2020
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
Methane Number (MN) no unit Min
index) or EN 16726

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).

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 2020 – All rights reserved 3
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SIST EN ISO 23306:2020
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
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
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SIST EN ISO 23306:2020
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 2020 – All rights reserved 5
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SIST EN ISO 23306:2020
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
PKIX=∑αβ+∑ XX (A.1)
nni m i j
i ij*
where
X is the (normalized) mole fraction,

i = CH , C H , C H , i-C H , n-C H , n-C H , i-C H , neo-C H , CO , CO, H and N ;

4 2 6 3 8 4 10 4 10 5 12 5 12 5 12 2 2 2
j = C H , C H , i-C H , n-C H , n-C H , i-C H , neo-C H , CO , CO, H and N ;
2 6 3 8 4 10 4 10 5 12 5 12 5 12 2 2 2
n = 1 to 4;
m = 1, 2;
α and β values are given in Table A.2.

The calculation is valid for PKI values ≤20 (or MN ≥ 53, see below) and the gas composition range in

(PKI)
Table A.1.
Table A.1 — Gas composition range
Species Min, mol % Max, mol %
CH 65 100
C H 0 20
2 6
C H 0 20
3 8
i-C H 0 5
4 10
n-C H 0 5
4 10
n-C H 0 2
5 12
i-C H 0 2
5 12
neo-C H 0 2
5 12
C + 0 1,5
H 0 20

1) DNV GL is a trademark of DNV GL AS. This information is given for the convenience of users of this document

and does not constitute an endorsement by ISO.
6 © ISO 2020 – All rights reserved
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SIST EN ISO 23306:2020
ISO 23306:2020(E)
Table A.1 (continued)
Species Min, mol % Max, mol %
CO 0 10
CO 0 20
N 0 20
H S 0 0,5

To account for the presence of C + and H S in the gas mixture scaling factors are derived based on

6 2
®1)

autoignition measurements in a rapid compression machine at DNV GL . These scaling factors are

used in the algorithm to translate the effect of C + and H S on the knock resistance of a gas mixture

6 2

to an equivalent fraction of n-C H . The factors are used to correct the methane and n-pentane mole

5 12
fractions as in Formulae (A.2) and (A.3).
XX=−03, ×X (A.2)
CH44,newCHingasmixtureC6+
XX=+XX+×13, (A.3)
nC51Hn25, ew nC Hi12 ngasmixtureH26SC +

Where X denotes the mole fraction. Here we note that the results of the algorithm are only valid if the

total mole percentages of the gas mixture is 100 %.
Table A.2 — α and β coefficients in Formula (A.1)
Coefficient Value Description
α 569,285 536 016 002 0 CH
CH4 4
α −650,854 339 490 7 CH ^2
(CH4) 4
α 64,359 575 257 386 2 CH ^3
(CH4) 4
α 17,214 959 222 053 6 CH ^4
(CH4) 4
α −645,099 966 662 855 0 C H
C2H6 2 6
α 694,229 376 857 102 0 C H ^2
(C2H6) 2 6
α −675,381 075 231 165 0 C H ^3
(C2H6) 2 6
α 1 474,790 791 373 33 C H ^4
(C2H6) 2 6
α 499,398 492 651 52 C H
C3H8 3 8
α −576,665 945 472 394 0 C H ^2
(C3H8) 3 8
α 252,193 674 060 28 C H ^3
(C3H8) 3 8
α 593,958 975 466 507 0 C H ^4
(C3H8) 3 8
α 934,466 273 223 240 0 N_C
n-C4H10 4
α −86,872 357 077 023 8 N_C ^2
(n-C4H10) 4
α −20 418,906 767 397 9 N_C ^3
(n-C4H10) 4
α 633 286,561 358 521 0 N_C ^4
(n-C4H10) 4
α 735,223 884 113 728 0 I_C
iso-C4H10 4
α −3 182,614 393 379 67 I_C ^2
(iso-C4H10) 4
α 20 945,186 725 021 9 I_C ^3
(iso-C4H10) 4
α 159 067,868 032 595 0 I_C ^4
(iso-C4H10) 4
α 2 571,930 793 605 35 N_C
n-C5H12 5
α 10 516,494 109 227 50 N_C ^2
(n-C5H12) 5
α −770 539,377 197 693 N_C ^3
(n-C5H12) 5
α 28 633 475,586 565 4 N_C ^4
(n-C5H12) 5
α −3 582,967 844 353 79 I_C
iso-C5H12 5
α 0 I_C ^2
(iso-C5H12) 5
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SIST EN ISO 23306:2020
ISO 23306:2020(E)
Table A.2 (continued)
Coefficient Value Description
α 403 155,950 864 334 I_C ^3
(iso-C5H12) 5
α −11 917 333,837 932 9 I_C ^4
(iso-C5H12) 5
α 1 123,396 367 098 65 NEC
neo-C5H12 5
α 1 679,728 075 248 10 NEC ^2
(neo-C5H12) 5
α −172 182,649 067 176 NEC ^3
(neo-C5H12) 5
α 3 467 918,607 466
...

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