ISO 10665:2024

Ships and marine technology - Ship design - CNG and LNG propulsion system

This document specifies the requirements for the installation of compressed natural gas (CNG) and liquefied natural gas (LNG) propulsion systems and components on ships and crafts. This document does not apply to large sea-going ships covered by SOLAS Chapter II-1 vessels. This document does not cover appliances with directly attached gas cylinders, such as portable container.

Navires et technologie maritime — Conception maritime — Système de propulsion GNC et GNL

General Information

• Status: Published
• Publication Date: 26-Nov-2024
• ICS: 47.020.20 - Marine engines and propulsion systems
• Technical Committee: ISO/TC 8/SC 8 - Ship design
• Drafting Committee: ISO/TC 8/SC 8 - Ship design
• Current Stage: 6060 - International Standard published
• Start Date: 27-Nov-2024
• Due Date: 26-May-2025
• Completion Date: 27-Nov-2024

Overview

ISO 10665:2024 - Ships and marine technology - Ship design - CNG and LNG propulsion system - defines requirements for the installation of compressed natural gas (CNG) and liquefied natural gas (LNG) propulsion systems and associated components on ships and crafts. The standard targets marine applications other than large sea‑going vessels covered by SOLAS Chapter II‑1 and excludes appliances with directly attached portable gas cylinders. It emphasizes technical suitability, safety, and environmental considerations associated with using natural gas as a marine fuel.

Key topics and technical requirements

ISO 10665 covers the full installation lifecycle and provides requirements and procedures for:

• Components: requirements for CNG cylinders, LNG fixed containers, vaporizers and fuel system components; fittings and container‑mounted devices.
• Installation requirements: general provisions for installers, structural modifications, container/cylinder mounting, lockers and securing arrangements.
• Gas distribution: design criteria for gas pipes, hoses, fittings, remote shut‑off valves and filling units.
• Safety systems: gas detection placement and alarm positions, forced ventilation and purging of engine spaces, and integration with electrical systems.
• Fire protection: provisions for fire‑extinguishing equipment appropriate to gas‑fueled propulsion.
• Operational documentation: mandatory owner’s manual (contents and format), commissioning records and certificates.
• Commissioning and testing: commissioning steps including tightness and leakage tests, initial filling procedures, fuel system tests and water trials.
• Environmental and human‑safety considerations: references to lifecycle and environmental aspects and training/qualification of technical personnel.

Applications and users

ISO 10665 is intended for practical use by:

• Naval architects and ship designers specifying CNG/LNG propulsion for small and medium vessels.
• Shipbuilders and outfitters installing fuel storage, piping, detection and ventilation systems.
• Marine engineers and system integrators commissioning and testing gas propulsion systems.
• Owners and operators implementing operational procedures, maintenance and owner’s manuals.
• Classification societies and regulators assessing compliance for non‑SOLAS II‑1 vessels. Practical applications include newbuild and retrofit installations on ferries, workboats, tugs, recreational craft and other non‑SOLAS sea‑going vessels where CNG/LNG is chosen to reduce emissions and meet environmental regulations.

Related standards

ISO 10665 references and complements other standards such as:

• ISO 11439, ISO 12991 (onboard storage tanks and cylinders)
• ISO 12614, ISO 14469, ISO 15500 (fuel system components and connectors)
• ISO 13297 (electrical systems)
• IEC 60529 (IP code) and EN 3‑7 (portable fire extinguishers) These related standards support component design, testing, personnel qualification and electrical protection for safe CNG/LNG marine propulsion installations.

Keywords: ISO 10665, CNG, LNG, ship design, marine technology, propulsion system, gas detection, ventilation, maritime safety, installation requirements.

Standards Content (Sample)

International
Standard
ISO 10665
First edition
Ships and marine technology —
2024-11
Ship design — CNG and LNG
propulsion system
Navires et technologie maritime — Conception maritime —
Système de propulsion GNC et GNL
Reference number
© ISO 2024
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
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CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and Definitions . 2
4 Components . 6
4.1 General provisions .6
4.2 CNG cylinders and LNG containers . .7
4.2.1 General provisions .7
4.2.2 Cylinders .7
4.2.3 Fixed container .7
4.2.4 Components fitted to the cylinder or fixed container .7
4.3 Fuel system components .8
4.3.1 Vaporizer .8
4.3.2 Other components .8
5 Installation requirements . 9
5.1 General requirements .9
5.2 Installer of the CNG or LNG system .10
5.3 Additional CNG or LNG systems not connected to the propulsion system .10
5.4 Modifications to the structure of the ship or craft.10
5.5 Container or cylinder installation .11
5.5.1 General .11
5.5.2 Fixed containers/cylinders .11
5.5.3 Cylinders and Containers . . . 12
5.5.4 Cylinders and containers lockers . 12
5.6 Components fitted to the fixed container/cylinder . 13
5.6.1 General requirement . . 13
5.6.2 Remote-controlled service valve and excess flow valve on the container . 13
5.6.3 Pressure relief valve. 13
5.6.4 Filler valve . 13
5.6.5 Level indicator . 13
5.6.6 Fittings . 13
5.6.7 Pressure relief device . 13
5.7 Gas pipes and hoses .14
5.8 Other components . 15
5.8.1 Gas connections between components of the CNG or LNG system . 15
5.8.2 Remote-controlled shut-off valve .16
5.8.3 Filling unit .16
5.9 Electrical installation .16
5.10 Fuel selection system .17
5.11 Gas detection .17
5.11.1 General .17
5.11.2 Alarm position .18
5.11.3 Sensors position .18
5.12 Forced ventilation .18
5.12.1 General .18
5.12.2 Purging of engine space .18
5.12.3 Position of venting .18
6 Fire-extinguishing equipment .18
7 Owner's manual .18
8 Commissioning. 19
8.1 Tightness test .19

iii
8.2 Leakage test .19
8.3 Initial filling of the container and cylinder and the system with LNG/CNG .19
8.4 Fuel System test .19
8.5 Water trial. 20
Annex A (normative) Owner's manual .21
Annex B (informative) Example of installation certificate .24
Annex C (informative) Example CNG or LNG identification label .25
Bibliography .27

iv
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 document 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)
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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 8, Ships and marine technology, Subcommittee
SC 8, Ship design.
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.

v
Introduction
This document specifies requirements for the installation of equipment for the use of compressed natural
gas (CNG) and liquefied natural gas (LNG) in the propulsion systems of ships and crafts.
This document includes procedures which the use substances and procedures that can be injurious to health
if adequate precautions are not taken. This document refers only to technical suitability.
Natural gas, either in gaseous (CNG) or liquid phase (LNG), is a very efficient and ready-to-use solution which
can facilitate compliance with the more stringent environmental regulations as well as the compliance with
the principles of the circular economy. Regulations can concern the impact of a product on the environment
during its entire life cycle, including the expenditure of energy and during all phases such as use, scrapping
and recycling of materials. Some parts of this document also address environmental aspects.

vi
International Standard ISO 10665:2024(en)
Ships and marine technology — Ship design — CNG and LNG
propulsion system
1 Scope
This document specifies the requirements for the installation of compressed natural gas (CNG) and liquefied
natural gas (LNG) propulsion systems and components on ships and crafts.
This document does not apply to large sea-going ships covered by SOLAS Chapter II-1 vessels.
This document does not cover appliances with directly attached gas cylinders, such as portable container.
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 9094, Small craft — Fire protection
ISO 10240, Small craft — Owner's manual
ISO 11105, Small craft — Ventilation of petrol engine and/or petrol tank compartments
ISO 11439, Gas cylinders — High pressure cylinders for the on-board storage of natural gas as a fuel for
automotive vehicles
ISO 11591, Small craft — Field of vision from the steering position
ISO 12217-1, Small craft — Stability and buoyancy assessment and categorization — Part 1: Non-sailing boats
of hull length greater than or equal to 6 m
ISO 12217-2, Small craft — Stability and buoyancy assessment and categorization — Part 2: Sailing boats of hull
length greater than or equal to 6 m
ISO 12217-3, Small craft — Stability and buoyancy assessment and categorization — Part 3: Boats of hull length
less than 6 m
ISO 12614 (all parts), Road vehicles — Liquefied natural gas (LNG) fuel system components
ISO 12617, Road vehicles — Liquefied natural gas (LNG) refuelling connector — 3,1 MPa connector
ISO 12991, Liquefied natural gas (LNG) — Tanks for on-board storage as a fuel for automotive vehicles
ISO 13297:2020, Small craft — Electrical systems
ISO 14469, Road vehicles — Compressed natural gas (CNG) refuelling connector
ISO 15500 (all parts), Road vehicles — Compressed natural gas (CNG) fuel system components
ISO 23684, Road vehicles — Technical personnel dealing with natural gas vehicles (NGVs) — Training and
qualification
ISO 24671, Road vehicles — Qualification and certification of technical personnel dealing with natural gas
vehicles (NGVs)
IEC 60529, Degrees of protection provided by enclosures (IP Code)
EN 3-7:2004+A1:2007, Portable fire extinguishers — Part 7: Characteristics, performance requirements and
test methods
EN 14291, Foam producing solutions for leak detection on gas installations
EN 28846, Seagoing vessels — Aluminum alloy castings for machinery and general engineering use - Chemical
composition and mechanical properties
3 Terms and Definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
accessible
capable of being reached for inspection, removal or maintenance without removal of permanent ship/craft
structures
Note 1 to entry: Hatches are not regarded as permanent ship/craft structures in this sense, even if tools such as
wrenches or screwdrivers are needed to open them.
3.2
appliance
device designed for heating, cooking, lighting, refrigeration, hot water production or electricity production
(fuel cell or generator), using natural gas as its energy source
3.3
automatic valve
valve which is not operated manually
3.4
bi-fuel engine
engine that has two independent fuel systems (one of them for natural gas) and can run alternatively on
either fuel, but only on one fuel at a time
3.5
check valve
automatic valve (3.3) which allows gas to flow in only one direction
3.6
cockpit
volume open to the air intended for the accommodation of people
Note 1 to entry: For the purpose of this document, the term "cockpit” is used either for a proper cockpit or for any
recess as clarified in Note 2.
Note 2 to entry: Bulwarks can create a large cockpit, open crafts can effectively comprise a cockpit which includes
nearly all the craft, cockpit(s) can be situated anywhere in the craft, and a cockpit can open aft to the sea.
Note 3 to entry: Cockpits can retain water, however briefly, due to rain, waves, ship heeling, etc.

3.7
compressed natural gas propulsion system
CNG propulsion system
fuel system which includes cylinder or cylinders, the assembly, one or more refuelling connectors, and the
components described in ISO 10665
Note 1 to entry: Cylinders are replaceable items and cannot be supplied with the boat system
Note 2 to entry: See ISO 11439 for information on cylinders; see ISO 14469 for information on the assembly; and see
the ISO 15500 series for the components listed.
3.8
compressed natural gas
CNG
natural gas which has been compressed and stored for use as a fuel
3.9
connector
fitting used to join a conduit, tubing, or hose systems
3.10
container
cryogenic vessel used for the storage of liquefied natural gas (3.28)
3.11
container housing
ventilated enclosure intended solely for storage of one or more compressed natural gas (3.8) cylinders (3.13)
or liquefied natural gas (3.28) containers (3.10), pressure regulators and safety devices, which is located on
the exterior of the ship or craft where any leakage would flow overboard
3.12
container locker
gas-tight enclosure on a ship or craft with an overboard drain, where any leakage would flow overboard,
intended solely for storage of one or more compressed natural gas (3.8) cylinders (3.13) or liquefied natural
gas (3.28) containers (3.10) in a cockpit or recessed into the ship or craft
3.13
cylinder
transportable, refillable container (3.10) with a water capacity from 0,5 l up to and including 150 l for the
storage of compressed natural gas (3.8)
3.14
design pressure
highest pressure related to the circumstances for which the system has been designed and is intended to be used
3.15
dual-fuel engine
engine system that is designed to simultaneously operate with liquid fuel and a gaseous fuel, both fuels
being metered separately, where the consumed amount of one of the fuels relative to the other one may vary
depending on the operation
[SOURCE: ISO 8178-4:2020, 3.17]
3.16
excess flow valve
valve which automatically shuts off or limits the gas flow when the flow exceeds a set design value
3.17
filler valve
valve system for fill service
3.18
filter
component containing a screen or media that is intended to remove foreign debris from the gas stream
3.19
fixed container
compressed natural gas (3.8) cylinder (3.13) or liquefied natural gas (3.28) container (3.10) permanently
installed to the structure of the ship and craft
3.20
fuel pipeline
tubing or hose through which natural gas flows
Note 1 to entry: Flexible fuel lines are also part of fuel pipeline.
3.21
gas/air mixer
device for mixing the gaseous fuel and intake air for the engine
3.22
gas detection
revealing of the presence of natural gas due to exposure outside the natural gas containment system
3.23
gas flow adjuster
gas flow restricting device, installed downstream of a pressure regulator, controlling gas flow to the engine
3.24
gas injector
device for introducing gaseous fuel into the engine or associated intake system
3.25
gas-tight housing
device which vents gas leakage to outside the vehicle including the gas ventilation hose, the clear opening of
which is at least 450 mm
3.26
installer
organization or person, who by qualification, training, experience and resources can assume technical
responsibility for the installation of a compressed natural gas (3.8) or liquefied natural gas (3.28)
propulsion system
3.27
level indicator
fuel content gauge based on the pressure difference between the top and bottom of the fuel in LNG tank or
the pressurized device (a gauge or a sensor) which indicates the gas pressure inside the CNG cylinder
Note 1 to entry: The system measures the weight of the liquefied gas in case of LNG.
Note 2 to entry: Other systems can be used to measure the level of LNG inside the tanks.
3.28
liquefied natural gas
LNG
natural gas which has been liquefied after processing for storage, transportation, or use as a fuel
[SOURCE: ISO 12614-1:2021, 3.11]

3.29
liquefied natural gas propulsion system
LNG propulsion system
fuel system using liquefied natural gas (LNG) which includes container(s), mounting, one or more fuelling
connectors and the components described in ISO 10665
Note 1 to entry: LNG containers are replaceable items; it is not possible to supply them with the ship system.
Note 2 to entry: See ISO 12991 for further details on containers; see ISO 21593 for further details on connectors; and
see ISO 22547 and ISO 22548 for details on the components described.
3.30
manual valve
valve which is operated manually and controls the flow of gas to the fuel system
3.31
mono-fuel engine
engine which operates on natural gas only
3.32
natural gas
NG
complex gaseous mixture of hydrocarbons comprising primarily methane, but generally includes ethane,
propane and higher hydrocarbons, and some non-combustible gases such as nitrogen and carbon dioxide
3.33
permanently installed
securely fastened so that it is necessary to use for removal
3.34
pressure indicator
pressurized device that indicates the gas pressure; it can be an indicator or a sensor
3.35
pressure regulator
device used to control the delivery pressure of gaseous fuel to the engine
3.36
pressure relief device
PRD
safety device that releases gases or liquids above a specified pressure value in cases of emergency or
abnormal conditions
Note 1 to entry: PRDs can be activated by pressure or another parameter, such as temperature, and can be either
re-closing devices (such as valves) or non-re-closing devices (such as rupture disks and fusible plugs). Common
designations for these specific types of PRDs are as follows:
— Pressure safety valve (PSV): pressure activated valve that opens at specified set point to protect a system from
rupture and re-closes when the pressure falls below the set point.
— Thermally-activated pressure relief device (TPRD): a PRD that opens at a specified temperature to protect a
system from rupture and remains open.
[SOURCE: ISO 19880-1:2020, 3.59, modified — Note 2 to entry removed.]
3.37
pressure relief valve
PRV
discharge valve
self-closing device which opens to prevent a pre-determined pressure being exceeded

3.38
qualified person
individual subjected to a qualification process, and who has passed the qualification
[SOURCE: ISO 23684:2023, 3.26]
3.39
qualification
demonstrated education, training and work experience, where applicable, required to properly perform the
assigned task as awarded or conferred as described in the document
Note 1 to entry: Adapted from ISO/IEC 17024:2012, 3.7
3.40
readily accessible
capable of being reached for operation, inspection or maintenance without the removal of any ship or craft
structure, the use of any tools, or the removal of any item of portable equipment stowed in places intended
for storage of portable equipment such as lockers, drawers or shelves
3.41
rigid fuel line
tubing which has been designed not to flex in normal operation and through which natural gas flows
3.42
service valve
manual valve which is closed only when servicing the engine
3.43
shut-off valve
valve to provide a leak-tight seal which is operated either manually, remotely or is self-closing
3.44
valve
device by which the flow of a fluid may be controlled
3.45
vaporiser
device intended to vaporise the cryogenic liquid fuel to a gaseous state with a gas range from -40 °C to +85 °C
3.46
ventilation system
assembly of ducts and an electrical ventilator that is capable of extracting hydrocarbons from the inside of
the craft and allowing the entrance of fresh air
4 Components
4.1 General provisions
4.1.1 All operations on the CNG and LNG systems and propulsion systems shall be operated by a
qualified person.
4.1.2 Individual components of the system, and the system as a whole, shall be designed to withstand
the combined conditions of pressure, vibration, shocks, corrosion and movement encountered under normal
operation.
4.1.3 All materials used in CNG or LNG systems shall be compatible with CNG and LNG and with other
liquids or compounds with which it can come into contact under normal operating conditions, e.g. grease,
lubricating oil, bilge solvents, fresh and sea water.

4.1.4 Efforts should be made to prevent grease, lubricating oil, bilge solvents and other chemicals
contaminating the marine environment.
4.2 CNG cylinders and LNG containers
4.2.1 General provisions
The CNG cylinders and LNG container(s) shall be protected from corrosion in the marine environment by an
adequate surface treatment system, or be constructed from materials suitable for the marine environment.
For the purpose of this document, two types of NG storage systems are identified:
— cylinders;
— fixed containers.
4.2.2 Cylinders
4.2.2.1 CNG cylinders can be used to fuel the engine of a ship/craft in gaseous phase depending on the
choice of technology (e.g. mono-fuel, bi-fuel, dual-fuel) and the required power. The cylinders used on ship/
craft shall conform to ISO 11439.
4.2.2.2 The quantity of fuel on board shall be indicated by the use a pressure indicator.
4.2.2.3 A PRV shall be fitted to any cylinder.
4.2.3 Fixed container
4.2.3.1 Fixed containers shall conform to ISO 12991.
4.2.3.2 The quantity of fuel on board shall be indicated by the use of a level indicator.
4.2.3.3 Consideration shall be given to the potential of liquid movement within the fixed container and
measures put in place. e.g. appropriate design by installing a number of baffles inside.
4.2.3.4 A primary and secondary PRV shall be fitted to any container.
4.2.4 Components fitted to the cylinder or fixed container
4.2.4.1 The cylinders shall be equipped with the following components, which can be either separate or
combined (e.g. multivalve):
a) filler valve;
b) manual valve;
c) automatic valve;
d) pressure indicator;
e) PRD;
f) excess flow valve.
4.2.4.2 The cylinders can be equipped with a:
a) gas-tight housing; or
b) PRV.
4.2.4.3 All components fitted to the container shall comply with the applicable part of the ISO 15500 series.
4.2.4.4 The filler valve shall conform to ISO 14469.
4.2.4.5 Containers shall be equipped with the following components, either separated or combined:
a) filler valve;
b) manual valve;
c) automatic valve;
d) level indicator;
e) PRD;
f) excess flow valve;
g) pressure regulator;
h) PRV primary or secondary;
i) check valve;
j) excess flow valve.
4.2.4.6 All components fitted to the container shall conform to the applicable part of the ISO 12614 series.
4.3 Fuel system components
4.3.1 Vaporizer
4.3.1.1 The vaporizer shall comply with ISO 12614-16 and shall be suitable for use in the marine
environment with anticorrosion treatment and stainless-steel bolts.
4.3.1.2 The materials of the vaporizer, which are in contact with the engine coolant, shall be compatible
with the coolant and shall be designed to withstand a working pressure as per ISO 12614-16.
4.3.2 Other components
The following components of the CNG fuel system, where used, shall conform with the following parts of the
ISO 15500 series:
— the gas injector shall be in accordance with ISO 15500-7;
— the pressure regulator shall be in accordance with ISO 15500-9;
— the gas flow adjuster shall be in accordance with ISO 15500-10;
— the gas/air mixer shall be in accordance with ISO 15500-11;
— PRV shall be in accordance with ISO 15500-12;
— rigid fuel lines in stainless steel shall be in accordance with ISO 15500-16;
— flexible fuel lines shall be in accordance with ISO 15500-17;
— the filter shall be in accordance with ISO 15500-18;

— fittings shall be in accordance with ISO 15500-19;
— rigid fuel lines in material other than stainless steel shall be in accordance with ISO 15500-20.
These components shall also be suitable for use in the marine environment.
The following components of the LNG fuel system, where used, shall comply with the following parts of the
ISO 12614 series
1)
— the overpressure regulator shall be in accordance with ISO 12614-6 ;
— rigid fuel lines in stainless steel shall be in accordance with ISO 12614-10;
— fittings shall be in accordance with ISO 12614-11;
— rigid fuel lines in copper and its alloys shall be in accordance with ISO 12614-12.
These components shall also be suitable for use in the marine environment.
5 Installation requirements
5.1 General requirements
5.1.1 The CNG or LNG system shall be installed by a qualified person in accordance with ISO 23684 and
ISO 24671, taking into account the manufacturers’ instructions and sound engineering practice.
5.1.2 All parts of the CNG or LNG system shall be permanently installed.
5.1.3 All parts of the CNG or LNG system shall be securely fastened.
5.1.4 The completed CNG or LNG system shall be adequately protected against corrosion.
5.1.5 All valves and other components intended to be manually operated, or observed during normal
operation of the ship/craft, or for emergency purposes, shall be readily accessible.
5.1.6 All other components of the CNG or LNG system shall be accessible.
5.1.7 No component of the fuel system shall be located within 100 mm of the exhaust or similar heat
source, unless adequate shielding against heat is provided.
5.1.8 Clearance between dry exhaust components and an LNG container or CNG cylinder shall not be less
than 250 mm, unless an equivalent thermal barrier is provided.
5.1.9 Fuel containers and cylinders and components of fuel systems shall not be installed directly above
batteries, unless the batteries are protected against the effects of fuel leakage.
5.1.10 The fuel system shall function in such a manner that the pressure for which it has been designed and
approved cannot be exceeded.
5.1.11 The fuel system shall be adequately protected against every kind of damage (e.g. those caused by the
movement of the goods stored on board).
5.1.12 No component of the CNG or LNG system shall obstruct the field of vision from the helm position in
accordance with the requirements of ISO 11591.
1) Withdrawn.
5.1.13 Permanent and clearly visible labels indicating CNG or LNG shall be fixed on one or more of the
following locations:
— on or close to the engine(s);
— on or adjacent to the container housing(s);
— on or close to container and cylinder lockers(s); and
— on the exterior of the ship/craft.
NOTE Annex C provides an example of a suitable label.
5.2 Installer of the CNG or LNG system
5.2.1 The installer shall possess the competence and expertise necessary for the proper installation of the
CNG or LNG system and ensure that the installation of the system meets the requirements of this document.
The competence and expertise of the installer is assumed if the installation activities are made by or under
the control of a technical manager qualified in accordance with ISO 23684 and ISO 24671.
5.2.2 The installer shall install components in accordance with the manufacturer's instructions or other
limitations.
5.2.3 The installer shall endeavour to minimize wastage of materials used and shall dispose of surplus
materials in an environmentally friendly manner.
5.2.4 Material segregation bins shall be used for recycling materials.
5.2.5 The installer shall maintain records of the commissioning tests as detailed in Clause 8.
5.2.6 The installer shall issue a signed installation certificate incorporating a certificate of conformity to
this document upon satisfactory completion of the CNG or LNG system installation and commissioning.
NOTE An example of an installation certificate is given in Annex B.
5.2.7 The installer shall supply an owner's manual for the CNG or LNG system as per Clause 7.
5.3 Additional CNG or LNG systems not connected to the propulsion system
The operation of the propulsion system shall not be affected by the introduction of additional CNG or LNG
systems.
5.4 Modifications to the structure of the ship or craft
5.4.1 Any alteration or modification to any ship or craft resulting from the installation of CNG or LNG
equipment shall be carried out in accordance with sound engineering practices.
5.4.2 The installation of CNG cylinders/LNG containers shall not adversely affect the stability and
buoyancy of the ship/craft when evaluated in accordance with ISO 12217-1, ISO 12217-2 and ISO 12217-3
5.4.3 Where any substantial modification is made to the ship/craft structure to facilitate the installation
of the fuel system, a written agreement, accompanied by a detailed drawing, shall be obtained from the
manufacturer of the ship/craft or a notified body.

5.5 Container or cylinder installation
5.5.1 General
5.5.1.1 The container or cylinder shall:
— be stowed either in the open air or in a container locker;
— not be stowed in the engine compartment, unless in a container locker (see 5.5.4);
— not be stowed in accommodation spaces;
— be securely fastened to the ship/craft;
— be installed in the correct orientation in accordance with the container manufacturer instructions;
— be installed in such a manner that it does not form an obstruction:
— be installed in such a way that provisions for escape in the event of fire or inversion, or both, are not
negatively affected; and
— allow drainage from their surfaces when the ship/craft is in its static flotation position.
5.5.1.2 When stored in open air CNG cylinder/ LNG containers, pressure regulators and safety devices
shall be shielded from direct solar radiation and shall have the vents protected against the ingress of dirt
and water by positioning or shielding.
5.5.1.3 Containers/cylinders, pressure regulators and safety devices located below decks or in cockpits
shall be mounted in container lockers.
5.5.1.4 No provision shall be made in a container locker or container housing for the storage of loose
components that can damage the container/cylinder, pressure regulator, piping or hose installation or
obstruct the locker drain.
5.5.1.5 Containers and cylinders shall be installed and fixed so that a 3 g acceleration can be absorbed
without any damage in any direction of movement while the container is fully loaded.
5.5.1.6 Containers and cylinders shall not be directly in contact with the floor and shall be spaced a
minimum of 20 mm from the floor.
5.5.1.7 The container/cylinders shall be installed so that there is no metal-to-metal contact, other than at
any permanent fixing points.
5.5.2 Fixed containers/cylinders
5.5.2.1 Containers and cylinders shall be permanently installed in such a manner that they do not support
decks, bulkheads or other ship/craft structures, unless they are designed for the purpose.
5.5.2.2 Containers and cylinders shall not be integral with the hull.
5.5.2.3 Containers and cylinders shall be installed in a manner that allows inspection and maintenance of
fittings, hose connections, etc.
5.5.2.4 Supports, chocks or hangers shall be separated from the surface of metal containers by a non-
metallic, non-hygroscopic, non-abrasive material, unless welded to the container.

5.5.2.5 Foam shall not be the sole means used to secure containers and cylinders in place. Where foam is
in contact with the container/cylinder, due care shall be taken to avoid corrosion.
5.5.2.6 Metallic containers and cylinders within the hull shall be installed with the container and cylinder
bottom no less than 25 mm above the normal maximum bilge water level.
5.5.3 Cylinders and Containers
5.5.3.1 Cylinder and containers shall be securely fastened by a dedicated system to the structure of the
ship/craft. This requirement also applies to unconnected cylinders.
5.5.3.2 Cylinders and containers shall be installed so that they are readily accessible.
5.5.4 Cylinders and containers lockers
5.5.4.1 Cylinders lockers openable from inside the cockpit shall be opened only from the top, while
containers lockers openable from inside the cockpit shall be opened from the top or from the front.
5.5.4.2 Lockers, when closed, shall be gas-tight to the ship/craft interior, vented at the bottom by a drain
of not less than an internal diameter of 19 mm (or the equivalent area if not circular) for containers having a
combined capacity of up to 15 kg. The check valves shall remain accessible.
5.5.4.3 The internal diameter of the drain shall be enlarged pro rata where additional containers are
carried, or where the capacity exceeds 15 kg.
5.5.4.4 The locker drain shall be run directly overboard, i.e. to the outside of the ship/craft; and shall not
be fitted with sumps which can retain water. The locker drain shall either:
a) have the exit at the highest point possible to avoid inhalation or the possibility of ignition. The designer,
in positioning the exit, shall consider:
1) the places where people can stay continuously;
2) the presence of either ignition or heat sources, or both;
3) the physical state of the fuel;
4) the possibility of indicating by suitable means the possible presence of gas in the specific area;
or:
b) be fitted with forced ventilation meeting the following requirements:
1) a gas sensor, connected to a suitable acoustic signal that indicates the presence of gas and to a safety
system shall be inserted in the locker at the highest level where the gas can be accumulated;
2) the ventilation system shall be explosion proof;
3) the ventilation fan shall be flameproof and run for a minimum of 60 s before the engine can be
started; and
4) at least one outlet duct situated at the highest part shall be fitted to the locker.
The outlet duct can be made with flexible lines compatible with the type of fuel used and with the marine
environment.
5.5.4.5 The outlet duct shall be:
— remote (at least 250 mm) from the engine exhaust system;

— protected from blockage by virtue of its position or other means; and
— located at least 500 mm from any hull opening to the interior of the ship/craft.
5.5.4.6 All hoses or metal piping penetrating the locker walls shall be sealed at the wall so as to maintain
gas tightness to the ship/craft interior.
5.6 Components fitted to the fixed container/cylinder
5.6.1 General requirement
The components on and in the container and cylinder shall be installed under the responsibility of the holder
of the bonfire test certificate as described in ISO 11439 and ISO 12991.
5.6.2 Remote-controlled service valve and excess flow valve on the container
5.6.2.1 The remote-controlled service valve shall be installed directly on the container/
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