GUIDELINES FOR THE
DEVELOPMENT OF
LIQUEFIED HYDROGEN BUNKERINGSYSTEMS AND PROCEDURESGUIDELINES FOR THE DEVELOPMENT OF LIQUEFIED HYDROGEN BUNKERING SYSTEMS AND PROCEDURES – JUNE 2024

Abbreviations and Definitions
Abbreviation

Definition

ASME

The American Society of Mechanical Engineers

DDT

Deflagration-to-detonation Transition

LH2

Liquefied hydrogen

IGC Code

The International Code for the Construction and Equipment of Ships Carrying
Liquefied Gases in Bulk

IGF Code

The International Code of Safety for Ship Using Gases or Other Low-flashpoint Fuels

IMO

International Maritime Organization

LNG

Liquefied Natural Gas

MEPC

IMO’s Marine Environment Protection Committee

MSC

Maritime Safety Committee

MTF

Maritime Technologies Forum

SGMF

The Society for Gas as a Marine Fuel

SIGTTOThe Society of International Gas Tanker and Terminal Operators

SMS

Safety Management System

STCW CodeThe International Convention on Standards of Training, Certification andWatchkeeping for Seafarers,1978

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Executive Summary
The Maritime Technologies Forum (MTF) is a group of flag States and classification societies which aims
to bridge the gap between technological progress and regulatory process. In relation to the adoptionof liquefied hydrogen gas (LH2) as a relevant fuel for the maritime sector, MTF carried out a study on
the current technological progress, and potential regulatory gaps, relating to liquefied hydrogen withemphasis on the bunkering of the fuel.
IMO is currently working on the development of guidelines for the safe design of ships with hydrogenas fuel, with the target completion already at CCC10 in September 2024. Those guidelines will however
focus on the ship installations and stop at the bunkering manifold on the ship. The details related to the
bunkering operations are not part of the scope for that work. The goal with this work is to supplement
CCC10 with input on the bunkering side of liquified hydrogen fuel safety.
This report discusses the potential use of hydrogen as a zero-emission fuel to meet the IMO Strategy
on Reduction of GHG Emissions from Ships by 2050. It acknowledges the lack of experience in themaritime sector with hydrogen as cargo and fuel, and the increased risks associated with its use as afuel compared to LNG. As of the writing of this report, there are no international standards covering the
bunkering of liquefied hydrogen. However, information collected from ongoing developments in ISO for
related areas, as well as the experience gained from the Norwegian ferry “Hydra”, serves as the basis forthe guidelines and recommendations of this report.
The objective of this project is to review barriers and enablers to safe bunkering operations of liquidhydrogen (LH2) with focus on the ship-to-shore interface and to produce a framework for LH2 bunkering
guidelines. Experience with bunkering of hydrogen for ships is limited and the design, operation andregulatory approval processes are complex. The project has conducted a review of existing standards
and experience that can be applied to LH2 marine bunkering and proposed structure and main topics ofimportance for bunkering guidelines which can help to accelerate the development and standardisationof LH2 bunkering procedures for ships.
Proposed draft guidelines are recommended to be further developed by industry.
The bunkering processes for LH2 will need to be developed with the properties of liquefied hydrogenclearly in mind. This report provides a starting point for development of guidelines for bunkering of LH2,
and this work is recommended to be discussed at IMO and further developed by industry.
Experience from bunkering LNG as fuel cannot directly be re-used.
The properties of hydrogen, and in particular the very low temperature of liquified hydrogen, means thatexperience gained from bunkering arrangements for liquid natural gas, LNG, cannot be re-used directly.
The bunkering process will be more complex than what is known for LNG, since no nitrogen can bepresent inside the piping systems when LH2 is introduced, as this will freeze and clog the systems.
Extreme properties of hydrogen require careful material selection and more temperature insulation.
The potential risks associated with hydrogen properties such as extremely low temperature, flammability,
explosivity, permeability can lead to damage to equipment and detonation. A careful material selection
is required to prevent hydrogen embrittlement and leakage. The extremely low temperature also meansthat more extensive use of vacuum insulation for components and piping will be necessary.
More complex bunkering procedures may bring more automated processes.
Vessel-specific procedures for bunkering operations will be needed, and the added complexities with LH2
bunkering may also lead to a need for more automated bunkering processes.
Inherent complexity of LH2 systems requires high emphasis on training and safety management.
The added complexities will also mean that the need for crew training and certification is of even higher
importance than for other bunkering processes. The Safety Management System should be updated tocater for the additional safety aspects with the liquified hydrogen bunkering, as outlined in another work
carried out by MTF, ‘Guidelines to develop and implement Safety Management System for alternative
fuels onboard ships’.

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Background and Objective
The Maritime Technologies Forum (MTF) is a group of flag States and classification societies which aims
to bridge the gap between technological progress and regulatory process. MTF has been establishedto provide technical and regulatory expertise for the maritime industry. MTF’s role is to publish researchbased on its members’ expertise and offer unbiased advice to the maritime industry. The current research
focuses on the common challenges that are faced by the maritime industry such as decarbonisation,
alternative fuels and increased levels of automation therefore allowing safe adoption of newtechnologies. MTF’s work can be found on our website: www.maritimetechnologiesforum.com.
The IMO Strategy on Reduction of GHG Emissions from Ships aims to reduce GHG emissions frominternational shipping as soon as possible and strive to reach net-zero GHG emissions around 2050 andrecognizes that the introduction of new energy carriers (alternative fuels) and new energy converters(engines/fuel cells/batteries) is necessary to achieve the strategic targets. Such new fuels and energy
converters will have to be devised, designed, tested, and implemented in commercial shipping ina safe manner.
Hydrogen is among the zero-emission fuels that may be highly relevant for commercial shipping to meetthe 2050 targets. However, the maritime sector has little-to-no experience with hydrogen, both as cargo
and as fuel. Research is still ongoing for the safe use of hydrogen as fuel and its potential wide use as abunker fuel implies a shift from one-off operations with hydrogen to progressively extensive use, which
increases the risks considerably.
The uptake of this technology relies equally on ensuring that the ship-to-shore interface is also factored in
the regulatory development process and standardisation. This can involve high complexity in terms of risk
management and mitigation but also from a planning and administration point of view.
For ports, hydrogen bunkering operations will require particularly careful attention. Detailed risk
considerations will be significant for developing the right design protecting the ship, its personnel, and theenvironment.
IMO is currently working on the development of guidelines for the safe design of ships with hydrogen fuel,with the target completion already at CCC10 in September 2024. These guidelines will however stop at
the bunkering manifold on the ship, and not consider in detail the matter of bunkering operations.
As of the writing of this report, there are no international standards covering the bunkering of liquefiedhydrogen. However, information collected from ongoing developments in ISO for related areas, as wellas the experience gained from the Norwegian ferry “Hydra”, serves as the basis for the guidelines andrecommendations of this report. An extract of the technical details of the bunkering arrangement for
Hydra is found in Appendix 1.
The objective of this project is to review barriers and enablers to safe bunkering operations of liquidhydrogen (LH2) with focus on the ship-to-shore interface and to produce a framework for LH2 bunkering
guidelines. Experience with bunkering of hydrogen for ships is limited and the design, operation andregulatory approval processes are complex. The project has conducted review of existing standards andexperience that can be applied to LH2 marine bunkering and proposed structure and main topics ofimportance for bunkering guidelines which can help to accelerate the development and standardisationof LH2 bunkering procedures for ships. There is experience with the transport of liquefied hydrogen as
cargo on the vessel Suiso Frontier, operating between Japan and Australia, and the project has also
considered if there are relevant learnings to gain from that operation.

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Introduction to the Guidelines
The structure of these guidelines can be summarised as follows:1.

Properties of Hydrogen

2.

Regulatory Framework and Available Experience

3.

LH2 Bunkering System

4.

Bunker Piping System

5.

Bunkering Operations and Safety Equipment

6.

Bunkering Procedures and Manuals

7.

Crew Training and Certification

The format change in the document between Section 1 to 7 is intentional to provide the reader witha clear difference between the guidelines and the rest of the document.

Disclaimer
While the advice given in this report has been developed using the best currently available information,
it is intended to be used solely as guidance. No responsibility is accepted by MTF or its members forany consequences resulting directly or indirectly from the adoption of any of the recommendationsin this report.

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1. Properties of Hydrogen
Flammability and Explosivity
Hydrogen, as a highly flammable fuel, mixes with oxygen whenever air is allowed to enter a hydrogen
vessel, or when hydrogen leaks from any vessel into the air. Hydrogen is flammable over a very wide
range of concentrations in air (4 – 75% vol in air). As a result, even small leaks of hydrogen havethe potential to ignite. The wide flammability range of hydrogen also leads to larger flammableclouds compared to LNG, which has a flammability range of 5-17%, and hence will quickly reach aconcentration that is too rich for ignition.
The flame speed of hydrogen is very high (265-325 cm/s), which also incurs the risk of detonation (DDT),
quicker pressure peaks and higher explosion pressures. At the same time the required minimum ignitionenergy for hydrogen is very low, meaning that hydrogen can ignite with a weaker ignition source (as little
as static electricity is sufficient for certain concentrations). Hydrogen is colourless and odourless therefore
leaks are difficult to detect and same goes for the flame that is almost invisible to human eyes. Hydrogengas is lighter than air and provides a fire and explosion hazard in confined spaces. While the risk of
explosion in open air is lower, it should not be neglected.

Hydrogen Permeation and Embrittlement
As the molecules of hydrogen gas are smaller than all other gases, it will leak through many materials
considered airtight or impermeable to other gases, by diffusion through the material itself. This property
makes hydrogen more challenging to contain than most other gases. The properties of the hydrogenmolecule will also incur the risk of hydrogen embrittlement to metallic materials. Higher risk of leakage
through small crevices is also a direct consequence of the molecule size.

Cryogenic
The boiling point of liquid hydrogen is extremely low, which creates several specific additional challenges
in the design of ships and associated bunkering systems. First, the materials must be suitable for the fueltemperature, but also, at -253°C, both oxygen and nitrogen will become solid. This means that nitrogencannot be used as an inert gas in the same way as for LNG systems. If there is any N2 left in the systems
when liquid hydrogen is introduced clogging of filters and fouling of valves and other sensitive equipment
may occur. It is also necessary to consider the risk of air condensation on the outside surfaces, to mitigate
the risks arising from presence of concentrated oxygen such as cold effects on equipment and increased
fire risk. The low temperature also means that it can cause severe frostbite and burns when in contact withskin. In case of liquid hydrogen leakage, surrounding structure may suffer brittle fracture if not constructedusing low temperature material.

Hydrogen Dispersion
The dispersion properties of hydrogen when released from containment can be considered both positive
for safety due to its buoyancy, and a safety risk due to the volumes and flammability range. In the caseof a leakage of liquid hydrogen, the expansion ratio between the liquid and gas phase of 1:848 creates avery large volume of flammable gas. The expansion rate also means that liquid hydrogen leakages cause
a considerably larger flammable cloud size compared with leakage of hydrogen in the gas phase, andwhile a higher storage pressure increases the expansion ratio of gaseous hydrogen, the expansion ratioof compressed hydrogen still remains well below liquefied hydrogen (Hydrogen gas stored at 250 barg
typically has an expansion ratio of 1:240). Additionally, compared with LNG, the flammable cloud sizes
are also exacerbated by the larger flammability range of hydrogen (4-75%).
However, as hydrogen also very readily disperses in air and is extremely buoyant, this property can beused to mitigate the explosive nature of hydrogen, by arranging the installations in open air to allow the
rapid dispersion of hydrogen. This is a typical safety barrier for land-based installations with single walled
piping and components.

Toxicity and Asphyxiation
Hydrogen is not toxic, but it can displace oxygen in the air, which can lead to asphyxiation.

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2. Regulatory Frameworks and Available Experience
The bunkering of liquefied hydrogen is currently not covered by any international standards.
There are however ongoing developments in ISO for:• Design and testing of marine transfer arms for liquefied hydrogen (ISO 24132).
• Ships and marine technology test procedures for liquid hydrogen valve of hydrogen ships(ISO/AWI 21341).
There are also several hydrogen standards for land-based applications which could be usedin the development of regulation for hydrogen bunkering, such as:• ISO/TR 15916 for Basic consideration for the safety of hydrogen systems.
• ASME-B31.12. (2019) on Hydrogen piping and pipelines.
• ISO 13984:1999 on Liquid Hydrogen-Land vehicle fueling system interface.
The Norwegian ferry “Hydra” is at time of writing the only vessel in operation with liquefied hydrogenas fuel and has conducted bunkering operation approximately every 2nd week since April 2023.
The experience gained from this project will be very valuable for the future LH2 fuelled vessels.

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3. LH Bunkering System
2

Bunkering operations for ships and similar past experiences are almost completely absent for
liquid hydrogen, however many different compressed hydrogen supply solutions are available
with technologies from car and bus refueling systems. Taking into account the vast LNG bunkeringexperience will be highly recommended in the design of the LH2 bunkering systems.
The onboard LH2 bunkering system will comprise bunkering station located on either side of thevessel. Bunkering stations would have provision for one bunkering liquid line and possibly one vapor
return line together with inert gas purging facility, associated relief/safety valves, safety systems,
and a dedicated control station. The LH2 is led by piping from the bunker station to the gas storagetank(s).
Consideration should be given to hydrogen bunkering infrastructure, equipment and piping
regarding hydrogen permeation, embrittlement, material compatibility, low temperature use(insulation), grounding (static) and hydrogen attack.
The bunkering station as a minimum will require:• Manifolds, valves, coupling of dry-disconnect type and emergency release system appropriate
for LH2.
• A suitable gas and flame detection system with an alarm system combined with a shut-off andshutdown system.
• Emergency Shutdown System (ESD) arrangements.
• Control and monitoring system.
• Open bunkering stations are preferred solutions for hydrogen, but if semi-enclosed or enclosed
solutions is the only option, ventilation will likely be necessary. Mechanical ventilation inconnection with hydrogen has its additional challenges, as the ventilation system itself may
create an ignition and explosion risk, if flammable concentrations are ventilated. Assessment of
the risks involved will be required, and additional tests may be required to validate the designs.
• Drip tray beneath bunkering connections and a low-pressure water curtain to protect the hullfrom low temperatures.
• Drainage and inerting systems.
• Firefighting System

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4. Bunker Piping System
Bunker pipes are sized according to the design flow rates through the system. The design flow rate isbased on the LH2 fuel tank capacity, pressure, temperature, and other factors such as vapour returncapability, flow velocity limits and bunkering time window. The flow rate is also dependent on theachievable bunkering rate from the bunker vessel or shore facility. Some vessels may require a shorter
bunker time than others depending on their operating profile. Depending on the size of the fuel tanks andfrequency of bunkering, owners may wish to maximize the bunker rate. A vapor return from the receivingtank, back to the supplier’s tank, will help achieve a higher flow rate.
Materials that may be directly exposed to hydrogen or hydrogen rich gases during normal operations
are to be suitable for their application considering, but not limited to, hydrogen-specific metallurgicalphenomena such as hydrogen permeation, hydrogen-induced cracking, stress corrosion cracking,hydrogen embrittlement and hydrogen attack.
Hydrogen embrittlement is a phenomenon that results in a significant reduction in material tensile
strength, ductility, and fracture toughness. The initiation and severity of hydrogen embrittlement depends
upon the interaction of materials used, the mechanical loading, and environmental variables. Suchdeterioration in properties in turn leads to accelerated fatigue crack growth and consequently shorter
equipment life. Furthermore, if not properly accounted for, material degradation due to hydrogen can
result in catastrophic unpredicted failure.
Full welded pipes will be preferred as hydrogen will be leaking through flanges. Special welding
procedures and welder qualification will be needed.
LH2 piping between bunkering connection and tank will need vacuum double barriers to prevent air
condensation.
Hoses subject to tank pressure, or the discharge pressure of pumps or vapor compressors, should bedesigned for a bursting pressure not less than five times the maximum pressure the hose can be subjected
to during bunkering. The means to prevent electrical arcing at the manifold is to be evaluated andaddressed. Instead of bunker hoses, loading arms may be used for transferring LH2 to the receiving ship.
Loading arms generally consist of a rigid structure with swivel joints to allow for articulation of the LH2
connection and relative movements between the receiving ship and the supplier, and may include a
powered emergency release system. LH2 fluid can pass through either a flexible hose supported within
the arm or solid pipes with swivel joints. Loading arms will typically be more mechanically automated andeliminate some of the handling issues that are present with hoses, but loading arms can induce higher
reaction forces on the bunker manifold that need to be considered in the design of the bunker station.
Again, due to the lower temperature of the LH2, the hose and connections will be required in addition
to be designed to prevent and mitigate condensation of air constituent gases on the components’surfaces. This may be achieved by additional vacuum insulated double barriers or similar double barriers
on sections of the hose not previously arranged with double barriers, as well as design considerations forloading arms and cradles to prevent damage from condensed air.

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5. Bunkering Operations and Safety Equipment
Emergency Shutdown (ESD)
Having a means to quickly and safely shut down the bunkering operation by closing the manifold
valves, stopping pumps, and closing tank filling valves, is essential to ensure safety. The ESD should becapable of activation from both the bunker receiving ship and the bunker supplier, and the signal should
simultaneously activate the ESD on both sides of the transfer operation. No release of gas or liquid shouldtake place as a result of ESD activation. Particular attention should be given to the fact that due to theproperties of hydrogen (wide flammability range, low ignition energy, giving larger flammable clouds incase of a leakage) rapid reaction will be even more important for hydrogen compared with LNG systems.
So, where LNG bunkering valves have a closing time requirement of 5 seconds, an even shorter closing
time may be considered, if safely possible with the working pressure, for the hydrogen bunkering valves.
Typical reasons for activation of the ESD include the following:• Leak detection• Fire detection• Manual activation from either the supplier or receiver• Excessive ship movement• Power failure• High level in receiving tank
• Abnormal pressure in transfer system• High tank pressure
Quick release of bunker connections in case of emergency is also to be provided.

Purging
For LNG bunkering, the IGF Code requires the bunkering system to be purged with inert gas (nitrogen)after bunkering. Nitrogen is not a directly suitable solution for cryogenic hydrogen (freezing point)
without intermediate steps ensuring nitrogen does not come into contact with cryogenic hydrogen. The
risk of keeping the hydrogen in the bunkering piping can be managed by other means, like reductionof the pressure, and monitoring, to keep the consequences of a leakage under control. For the Hydra
ferry, hydrogen gas remains in the bunkering system between the bunkering operations, and this is also
the solution applied in projects with compressed hydrogen. But the bunkering connection will need tobe air/hydrogen free before connections and disconnections, so for this purpose, creating a vacuum
and injecting a small amount of Helium gas is the solution chosen in the Hydra ferry. Such procedures
introduce the need for vacuum pumps and helium storage, which for Hydra, is stored on the bunkering
tower on the shore.

Personal Safety
All personnel involved directly in LH2 handling operations should be equipped with personal protective
equipment (PPE) suitable and certified for LH2 use. PPE includes gloves, face protection and other suitable
clothing to protect against LH2 drips, spray, spills, and leaks. PPE is also required to protect against skindamage caused by contact with potentially cold pipes, hoses, or equipment. Although no standard
exists for required PPE during bunkering procedures, guidance for LNG is provided by SIGTTO and others.
Industry practice in shore hydrogen plants can be adopted to develop PPE requirements in regulations.
In addition, additional PPEs such portable gas detectors and intrinsically safe portable IR/UV cameras canalso be considered to aid in the early detection of leakages and hydrogen flames, that will otherwise beinvisible to naked eyes.
Regarding bunkering operations, processes should be automated, reducing human intervention as muchas possible. Areas to be avoided during bunkering should be marked accordingly.  

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Low Temperature Insulation
Due to the need for limiting the heat ingress to the LH2 during the transfer, and additionally the risk ofoxygen accumulation on the outside of surfaces that hold -253°C, better insulation is necessary for the
bunkering connections and hoses compared with LNG. Vacuum insulation is generally the most efficientand safest solution for hydrogen.

Drip Tray
Drip trays are commonly used to contain LNG leakage and prevent damage to the ship’s structure
and the same will apply to LH2. Drip trays should be sized to contain the maximum amount of leakage
expected and made from suitable material, such as stainless steel.
The bunkering station drip tray should serve as protection from liquid hydrogen spills, but should in
addition be designed to account for the additional aspect of condensation of air constituent gases.
Due to the extremely low temperature of liquefied hydrogen, the main air constituent gases (nitrogenand oxygen) may freeze and/or condensate on surfaces of the bunkering connection and skid, anddrip to the tray. This will likely not affect the dimensioning and placement of the drip tray(s), but may
affect secondary considerations such as prevention of oxygen rich atmospheres below the bunkering
connection.

Bunker Control Room
Bunkering control arrangements are to allow for remote operations from a safe location. At thatlocation, monitoring with CCTV and display of the tank pressure and tank temperature should beavailable. High temperature and high-pressure alarm, automatic and manual shutdown are also to be
indicated at this location.

Leakage Detection
Bunker stations are to be fitted with permanently installed gas detectors and low temperature detection(differential temperature may also be relevant). For the vacuum insulated bunkering piping, othersolutions for rapid detection of leakages will be relevant, like pressure monitoring. Diversity in applied
detection methods is generally recommended for hydrogen leakage detection.

Fire Detection
All bunker stations are to be fitted with permanent fire detection suited to detect hydrogen flames.
Hydrogen flames are invisible and have low radiant heat therefore detectors’ technology should besuitable for the specific fuel. Solutions such as thermal, infrared and UV cameras will be relevant.

Tank Levels
The filling limit of an LH2 tank is the maximum allowable liquid volume in the tank, expressed as apercentage of the total tank volume. The filling limit is not the same as the loading limit. The maximum
filling limit for LH2 cargo tanks, and IGF Code LH2 fuel tanks, is 98 percent at the reference temperature.

Communication
Communication between the receiving ship and the bunkering facility is always important, but it iseven more critical when handling LH2, because of the greater potential for hazardous situations during
LH2 bunkering. Written operational procedures, including the fuel handling manual required by the IGF
Code, should be followed and understood between the person- in-charge on the bunkering facility
and receiving ship. It is also expected that many of the processes in the bunkering operation will be
automated.

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Security and safety zones around the bunkering operation need to be set up to reduce the risk ofdamage to personnel and property from the LH2 hazards, reduce the risk of outside interference with
the LH2 bunkering operation, and to limit the potential for expansion of a hazardous situation should
LH2 release take place. The determination of such security and safety zone can be established using
a recognized and validated gas dispersion model to calculate the distance to the lower flammability
limit (LFL) based on the maximum credible release to be agreed upon with the relevant port authorities
for the planning of suitable areas for such an operation to be carried out.
Confirmation that both the bunker supplier and receiver can monitor the bunkering operation, andboth can initiate an emergency shutdown of the complete transfer operation is of vital importance.
Radio equipment to be used in the safety zone during the operation should be designed for use inhazardous areas and should be intrinsically safe.

Vent Mast
Venting should be prevented under all normal operating conditions, except for emergency cases.
IGF Code includes prescribed requirements for the vent masts locations however exact venting
arrangements should be validated for the specific design upon gas dispersion simulation. As aminimum, both receiving ships and loading facility should be equipped with a venting mast.

Compatibilty
Compatibility studies should be carried out well in advance to confirm mooring and bunker equipment
are compatible in design so the bunker operation can be conducted safely. At a minimum, thecompatibility of the following equipment and installation should be assessed and confirmed:• Communication/ESD systems• Bunker connection and bunker station location• The relative freeboard differences• Transfer system specifications (e.g. type and size of hose connections), locations and loading on
manifolds, and connection sequences• Transfer system specifications (flow rate, temperature, pressure, etc.)• Vapor return line, (if applicable)• Nitrogen and/or helium line, if applicable• Mooring arrangement/equipment• Lifting gear and lifting appliances with sufficient SWL and outreach for bunkering hoses andequipment• Personnel transfer arrangement• Hazardous (flammable)/safety zones

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6. Bunkering Procedures and Manuals
Vessel-specific procedures for the bunkering operation should be developed to include any uniquecharacteristics or features to the bunkering facility and receiving vessel or location.
A specific hydrogen bunkering plan should be developed to ensure the safe and effective operationof bunkering processes. This plan should demonstrate and document all proof of compliance with theregulations of all relevant authorities, industry practices, and vessel Safety Management System (SMS)
requirements. The bunkering plan should include, but not be limited to, the following:• Purpose, objective, and safety policies• Compatibility assessment• Risk management• Organization planning• Communication• Management of change• Emergency procedure• Training• Operations, procedures, and checklists (include SIMOPS if applicable)
Before each bunkering operation, a coordination meeting should be carried out between ship’s crew
and bunker ship’s or terminal’s crew to discuss the bunkering plan.
Simultaneous operations as Hydrogen bunkering while unloading containers or other cargoes, or landing
passengers will be depending on Port authorities. Safety distances and procedures will be required andstudied during risk assessment.

7. Crew Training and Certification
Crew training and competence will be similar to LNG, as both are dominated by flammability andcryogenic concerns but, the depth of cryogenic temperatures, invisible flame and flammability ofhydrogen, compared to LNG, will certainly have an influence in emphasis in the detailed training programas explained in the SGMF introduction of hydrogen as a marine fuel (2023).

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Conclusions
IMO is currently working on the development of guidelines for the safe design of ships with hydrogenas fuel, with the target completion already at CCC10 in September 2024. Those guidelines will however
focus on the ship installations and stop at the bunkering manifold on the ship. The details related tothe bunkering operations are not part of the scope for that work. The goal with this work is hence tosupplement CCC10 with input on the bunkering side of liquified hydrogen fuel safety.
As of the writing of this report, there are no international standards covering the bunkering of liquefiedhydrogen. However, information collected from ongoing developments in ISO for related areas, as wellas the experience gained from the Norwegian ferry “Hydra”, serves as the basis for the guidelines andrecommendations of this report.
To provide a framework for the considerations necessary to implement LH2 as a fuel, the report provides
detailed information on the properties of hydrogen, including its extremely low temperature, flammability,
explosivity, permeability, and embrittlement effects on metallic materials. The potential risks associatedwith these properties, such as damage to equipment, detonation, and asphyxiation are also listed forconsideration.
The report further provides a detailed description of the expected required functions and design
considerations for an LH2 bunkering system, including the bunkering station layout, piping system, safety
equipment, and necessary functions and procedures. It emphasizes the need for careful material
selection to prevent hydrogen embrittlement and leakage, and the need for vacuum insulation due tothe cryogenic nature of LH2. A key aspect that differentiates the bunkering systems for LH2 from bunkeringof LNG, which is the closest comparable system, is that LH2 is colder than the freezing point of Nitrogen,which vastly increases the complexity of the bunkering connection and necessitates several additional
ancillary systems.
Key observations:• The properties of hydrogen, and in particular the very low temperature of liquified hydrogen, meansthat experience gained from bunkering arrangements for liquid natural gas, LNG, cannot be re-useddirectly.
• The bunkering process will be more complex than what is known for LNG, since no nitrogen can bepresent inside the piping systems when LH2 is introduced, as this will freeze and clog the systems.
• The material choices, need for more insulated components and piping will also be slightly different.
All in all, the development of vessel-specific procedures for bunkering operations, maybe more
automated bunkering procedures, will be necessary.
• The added complexities will mean that the need for crew training and certification is of even higher
importance than for other bunkering processes.
• The Safety Management Systems should be updated to cater for the additional safety aspects with theliquified hydrogen bunkering, as outlined in another work carried out by MTF, ‘Guidelines to develop
and implement Safety Management System for alternative fuels onboard ships’.

Conclusion
Engineering

Concludingly, the bunkering processes for LH2 will need to be developed with the properties of liquefiedhydrogen clear in mind. This report provides a starting point for development of guidelines for bunkeringof LH2, and this work is recommended to be discussed at IMO and further developed by industry.

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References
1.

IMO, “The International Safety Management (ISM) Code”.

2.

IMO, “The International Convention on Standards of Training, Certification and Watchkeeping for
Seafarers (STCW), 1978”.

3.

IMO, “International Code of Safety for Ship Using Gases or Other Low-flashpoint Fuels (IGF Code)”.

4.

IMO, “International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in
Bulk (IGC Code)”.

5.

IMO, “MSC.1/Circ.1455 – Guidelines for the Approval of Alternatives and Equivalents” 2023.

6.

ISO 20519:2021 “Ships and Marine Technology — Specification for Bunkering of Liquefied Natural Gas
Fuelled Vessels”, 2021

7.

SIGTTO, “Guidelines for the Alleviation of Excessive Surge Pressures on ESD for Liquefied Gas Transfer
Systems”,2018

8.

SIGTTO, “Recommendations for Liquefied Gas Carrier Manifolds”,2018

9.

SIGTTO, “Liquefied Gas Handling Principles on Ships and in Terminals, (LGHP4)”,

10. SGMF, “Hydrogen as a Marine Fuel”,2023
11. ISO 31000:2019 “Risk Management – Principles and Guidelines”

Acknowledgements:
Organization

Name

ABS

Sebastien Le Moigne
Vangelis Karageorgo

ClassNK

Tsubasa Ando

DNV

Hans Jacob Horgen
Torill Grimstad Osberg (Project Manager)

MCA

Andrew Clarke

MPA

Jeremy Wong Xing Wei

NMA

Simen Diserud Mildal

For any enquires about this report please send a message to:contact@maritimetechnologiesforum.com.

15 Maritime Technologies ForumGUIDELINES FOR THE DEVELOPMENT OF LIQUEFIED HYDROGEN BUNKERING SYSTEMS AND PROCEDURES – JUNE 2024

Appendix 1
Hydra Bunkering: Extract of Informationfrom Linde ‘Basis of Design’
Onshore Bunkering Equipment
Bunkering is done by truck, so the below description are for the
shore systems between truck and ship, main components:• Vacuum insulated process line (DN50)• Cryogenic, vacuum insulated flexible hose, supported bya loading arm• Female part of quick connect coupling attached to theloading arm of the bunkering system (male counterpart
on the ship)• Parking station for female part of bunkering coupling to an
additional male coupling, for safe storage, and for functional
check and cool down prior to bunkering• Purging/vacuumization single wall lines• Vacuum pump for purging purposes• Vent mast for a safe release of hydrogen or He to theatmosphere• Expansion tank, collecting the liquid hydrogen when
depressurizing the process line after end of bunkering• Air heated vaporizer downstream of the expansion tank andupstream of the vent mast for ensuring that only warmed up gaseous hydrogen enters the vents mast
The equipment is installed on a skid, mounted on wheels, to ensure easy transportation to the quayside.

Connection
The bunkering connection is an LH2 quick coupling. The female part is attached to the loading arm of the
bunkering tower, and male part (receptacle) is attached to the tank system of the ship. Both parts arevacuum insulated to limit freezing during the operation. Additionally, an integrated emergency releasesystem is included, to protect the loading arm in case ship is drifting away. The spring loaded ejector isplaced at the interface of the loading arm with the female part of the coupling.

Process Description
Bunkering processes are mainly done by several automatically run sequences, and the following list is notincluding all actions:• Bunkering first tightness test – to be performed after commissioning or repair when no trailer is attached,
and the quick coupling is in parking position• Bunkering – procedure for intended operation/unloading of LH2 distribution equipment, e.g. LH2-trailer– Tightness test
– Cool down and cold keeping– Filling (includes purge with He for segments in contact with air)
– Filling end (LH2 flow is stopped, QC coupling is purged and slightly pressurized at the end with He
Valves closed in defined sequence and coupling disconnected. Couplings put in parking position,
purge with He)– LH2 removal-controlled relief of hydrogen to vent mast
• Bunkering unit stop – leads to a safe stop of the bunkering procedure for intended and unintended
operations• Bunkering unit depressurize – leads to a safe depressurization for intended and unintended operations

16 Maritime Technologies Forum