d6.3 recommendations for rcs

Pre-normative REsearch for Safe use of Liquid Hydrogen (PRESLHY)

Project Deliverable

D6.3 Recommendations for RCS

Deliverable Number: 6.3

Work Package: 6

Version: Final

Author(s), Institution(s): D. Houssin (AL), L. Bernard (AL), S. Jallais (AL), D. Cirrone (UU), T. Jordan (KIT), A. Tchouvelev (HySAFE)

Submission Date: 31 May 2021

Due Date: 31 May 2021

Report Classification: Public

This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 779613.

Grant Agreement No: 779613 D6.3 Recommendations for RCS

ii

History

Nr. Date Changes/Author

1.0 August 2020 Discussions on the table of content of the deliverable regarding needs / D. Houssin (AL), S. Jallais (AL), D. Cirrone (UU), T. Jordan (KIT), V. Molkov (UU)

1.1 August 2020 MS30 Detailed table of content / D. Houssin, S. Jallais,

1.2 April 2021 Discussions on the main content of the deliverable and dissemination strategy / D. Houssin (AL), L. Bernard (AL), T. Jordan (KIT), A. Tchouvelev (HySAFE)

2.0 27.04.2021 Version for approval by reviewers / D. Houssin

2.1 30.04.2021 Final version for review by AB / D. Houssin

Final 31.05.2021 Update taking into account comments from AB / D. Houssin

Approvals

Version Name Organization Date

2.0 D. Cirrone UU 29.04.2021

2.0 A. Tchouvelev HySAFE 28.04.2021

2.0 T. Jordan KIT 30.04.2021

Final - PRESLHY Consortium & AB 31.05.2020

Acknowledgements

This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under

the European Union’s Horizon 2020 research and innovation programme under grant agreement

No 779613.

Disclaimer

Despite the care that was taken while preparing this document the following disclaimer applies:

The information in this document is provided as is and no guarantee or warranty is given that the

information is fit for any particular purpose. The user thereof employs the information at his/her

sole risk and liability.

The document reflects only the authors’ views. The FCH JU and the European Union are not

liable for any use that may be made of the information contained therein.

Key words

Liquid hydrogen, cryogenic hydrogen, safety, dispersion, fire, hazard distances, engineering

correlations and tools, good practices, recommendations, RCS (regulations, codes and standards)


iii

Publishable summary

Outcomes from PRESLHY project were extracted and translated into suitable information and

tools for international SDOs, regulatory bodies and industry, so that they can be implemented

into performance-based Regulations, Codes and Standards (RCS).

Thus, this document summarizes and prioritizes the findings of WP3 to WP5 to identify RCS

recommendations concerning the safe use of liquid hydrogen and to propose a roadmap for

bringing these recommendations to international bodies. The report represents the consensus of

the PRESLHY group regarding RCS recommendations.

Fourteen recommendations were formulated in order to be addressed to RCS organizations.

They are relating to:

Phenomena, concrete consequences and potential associated mitigation ways, for the

following topics:

o Release, flowrate, dispersion in free field

o Ignition, flame propagation and explosion

o Burst of the storage vessel

Calculation means to evaluate consequences through:

o Analytical models,

o Engineering correlations,

o Numerical modelling.

The PRESLHY consortium members are aware that this “simple” document will not allow the

integration of the described recommendations. It is necessary to actively participate in technical

committees and other working groups.

Thus, dissemination of these recommendations is already launched since numerous of

PRESLHY project partners are already involved in mentioned RCS organizations, working

groups and technical committees (e.g. ISO/TR/15916, a specific task force in on-going revision

has been set up to draft a specific chapter on liquid hydrogen to be integrated for the update of

the existing document).


iv

Abbreviations

BCGA British Compressed Gas Association

BLEVE Boiling Liquid Expanding Vapour Explosion

CEN European Committee for Standardization

CFD Computational Fluid Dynamics

CGA Compressed Gas Association

CNG Compressed Natural Gas

CSA Canadian Standards Association

Dx.x Deliverable x.x

DDT Deflagration to Detonation Transition

EIGA European Industrial Gases Association

FC Fuel Cell

GH2 Gaseous Hydrogen

GTR Global Technical Regulation

H2 Hydrogen

HVG Heavy Goods Vehicle

HRS Hydrogen Refuelling Station

HyRAM Hydrogen Risk Assessment Models

IEC International Electrotechnical Commission

IMO International Maritime Organization

ISO International Organization for Standardization

LFL Lower Flammability Limit

LH2 Liquefied Hydrogen

LHRS Liquid Hydrogen-based Refuelling Station

LNG Liquid Natural Gas

MIE Minimum Ignition Energy

NFPA National Fire Protection Association

NMA Norwegian Maritime Authority

PT Project Team

RCS Regulations, Codes and Standards

RPT Rapid phase transition

SDO Standard Development Organization

TCO Total Cost of Ownership

TC Technical Committee

TF Task Force

TR Technical Report

TSC Technical Sub-Committee

UVCE Unconfined Vapour Cloud Explosion

WG Working Group

WP Work Package


v

Table of Contents

Acknowledgements ............................................................................................................. ii

Disclaimer ............................................................................................................................. ii

Key words ............................................................................................................................. ii

Publishable summary ......................................................................................................... iii

Abbreviations ...................................................................................................................... iv

Table of Contents ................................................................................................................. v

List of figures ..................................................................................................................... vii

List of tables ....................................................................................................................... vii

1 Introduction and scope..................................................................................................... 8

2 Brief description of LH2 installations ............................................................................... 9

2.1 Liquid supply chain and refuelling stations .................................................................... 9

2.2 Activities with potential needs in liquid hydrogen ........................................................ 10

3 Review of feared events and PRESLHY outcomes ....................................................... 11

3.1 Main feared events and studied phenomena .............................................................. 11

3.2 PRESLHY main outcomes .......................................................................................... 12

4 Recommendations for RCS ............................................................................................ 14

4.1 Release, flowrate, dispersion in free field .................................................................... 14

4.2 Ignition, flame and explosion ...................................................................................... 16

4.3 Burst of the storage vessel ......................................................................................... 18

4.4 Calculation means for risk assessment ....................................................................... 18

5 Proposed path forward ................................................................................................... 18

5.1 Recommendations to be forwarded to ISO/TC ........................................................... 18

5.1.1 Secretariat of ISO/TC 197 – Hydrogen Technologies ........................................... 18

5.1.2 Secretariat of ISO/TC 220 – Cryogenic vessels ................................................... 19

5.1.3 Secretariat of ISO/TC 8 – Ships and Marine technology....................................... 19

5.1.4 Secretariat of ISO/TC 67 – Materials, equipment and offshore structures for

petroleum, petrochemical and natural gas industries ......................................... 19

5.2 Recommendations to be forwarded to the Secretariat of CEN/TC .............................. 19

5.2.1 Secretariat of CEN CLC JTC 6 – Hydrogen in energy systems ............................ 19

5.2.2 Secretariat of CEN/TC 268 – Cryogenic vessels .................................................. 20

5.3 Recommendations to be forwarded to the Secretariat of EUROCAE/SAE .................. 20

5.4 Recommendations to be forwarded to the Secretariat of NFPA .................................. 20

5.5 Recommendations to be forwarded to the Secretariat of CSA .................................... 20

5.6 Recommendations to be forwarded to the Secretariat of EIGA ................................... 20

5.7 Recommendations to be forwarded to the Secretariat of CGA .................................... 20


vi

5.8 Recommendations to be forwarded to the Secretariat of BCGA ................................. 20

5.9 Recommendations to be forwarded to additional associations .................................... 21

6 Conclusions .................................................................................................................... 21

Annex 1. List of engineering correlations and tools ....................................................... 22

Annex 2. Short list of relevant RCS working groups, technical committees,

organizations and documents .......................................................................................... 23


vii

List of figures

Figure 1. Structure and global organization of the PRESLHY project. ............................... 8

Figure 2. Hydrogen supply chain, from production to use for H2 mobility. ......................... 9

Figure 3. Focus on liquid hydrogen supply for hydrogen refuelling stations. ...................... 9

Figure 4. Simplified comparison between gaseous and liquid hydrogen refuelling stations.

..................................................................................................................................................... 10

Figure 5. H2 vehicles snapshot with existing and/or under investigation hydrogen on-

board storage type..................................................................................................................... 11

Figure 6. Simplified view of feared events and associated consequences ............................ 12

List of tables

Table 1. Comparison between LHRS and HRS. .................................................................... 10


1 Introduction and scope

PRESLHY project was a pre-normative research project aiming at assessing relevant and

poorly understood phenomena related to high-risk scenarios for liquid hydrogen supply and

use. With the new knowledge generated by the project science-based and validated tools,

which are required for hydrogen safety engineering and risk-informed, performance-based,

LH2 specific, international standards, have been developed.

Main feared events were identified and were investigated in the project through the

phenomena-oriented work packages WP3, WP4 and WP5:

Release and mixing (WP3). Hazards associated with cryogenic and LH2 releases,

including but not limited to: characterisation of steady-state and transient hydrogen

releases in a multiphase or gaseous state, assessment of extent and evaporation rate of

LH2 pools, and extent of a flammable cloud following a release, characterisation of the

final state following mixing of cryogenic hydrogen and air.

Ignition (WP4). Ignition risks associated with situations unique to liquid hydrogen

releases, where factors of cryogenic temperatures are significant. Areas of particular

interest are ignition potential at a reduced temperature in the vapour phase, electrostatic

charging in liquefied/multiphase mixtures.

Combustion (WP5). Hazards of LH2 and cryogenic hydrogen combustion associated

with conditions of 5-10 for condensed matters and 3-4 times higher density for

flammable cryogenic gaseous compositions, and different reactivity characteristics

from hydrogen at atmospheric temperature. Attention is paid to thermal and pressure

hazards from hydrogen jet fires, assessment of the laminar flame speed and expansion

ratio, the potential for flame acceleration and transition to detonation, assessment of a

fireball size following a LH2 spill or BLEVE phenomena.

Figure 1. Structure and global organization of the PRESLHY project.

The objective of this deliverable is to summarize and prioritize the findings of WP3 to WP5

to identify regulations, codes and standards (RCS) recommendations concerning the safe

use of liquid hydrogen and to propose a roadmap for bringing these recommendations to

international bodies. The report represents the consensus of the PRESLHY group regarding

RCS recommendations.


Note that Deliverables of the PRESLHY project cited in this document are available on the

PRESLHY dedicated website (www.preslhy.eu).

2 Brief description of LH2 installations

2.1 Liquid supply chain and refuelling stations

LH2 being much denser than GH2, it appeared appealing to develop new approach in order

to increase station capacity and decrease the TCO (Total Cost of Ownership) by using

liquid hydrogen as feedstock.

Figure 2 gives the different elements of hydrogen – liquid and gas – supply chain, from the

production to the use for hydrogen mobility.

Figure 2. Hydrogen supply chain, from production to use for H2 mobility.

Figure 3 is a simplified scheme of the liquid hydrogen supply chain showing that, after

hydrogen production, a liquefier is required to liquefy hydrogen at cryogenic temperature.

Then LH2 tanker trucks (with a capacity up to 4000 kg of H2) are used for hydrogen

transportation to LHRS, where the transfer from a truck to LHRS storage is performed

thanks to a small vaporizer.

Figure 3. Focus on liquid hydrogen supply for hydrogen refuelling stations.

Primary production

CO2

Liquid station

Gas station

Liquid supply chain

Gas supply chain

Steam methane reformer + Carbon

captureLarge electrolyser

Large liquefier

Liquid trailers & tanks

Filling Center Gas transport

Light duty (cars) stationHeavy duty (buses, trucks, trains, ships) station

Light duty (cars) stationHeavy duty (buses, trains) station

Logistic tools Next Gen composite storage

Logistic tools

Liquid hydrogen maritime

Pipeline


Refuelling stations based on compressed hydrogen storage are better known and more

widely deployed. Thus, a brief and simplified comparison between these two types of

refuelling stations used for fuelling of fuel cell vehicles with on-board compressed gaseous

hydrogen tank(s) is shown on Figure 4 and Table 1.

Figure 4. Simplified comparison between gaseous and liquid hydrogen refuelling stations.

Top: gaseous HRS, Bottom: liquid HRS.

Table 1. Comparison between LHRS and HRS.

Topic LHRS HRS

Storage

Liquid hydrogen, cryogenic

temperature (-240°C), low

pressure (up to 10 bar)

Gaseous hydrogen, ambient

temperature, high pressure (from

200 to 500 bar)

Replenishment of the station

storage inventory

Transfer of liquid hydrogen from

tanker truck to storage Mainly swap (= full for empty)

Pressurization of hydrogen Cryogenic pump and vaporizer

required to deliver gaseous H2 Compressor

2.2 Activities with potential needs in liquid hydrogen

Liquid hydrogen is, up to now, commonly used for off-board storage and transportation to

end-user sites.

There are few existing mobile applications using liquid hydrogen directly in on-board

storage. However, projects on this kind of applications are recently emerging for goods and

public transportation.


Figure 5. H2 vehicles snapshot

with existing and/or under investigation hydrogen on-board storage type.

Examples of on-going projects are given below:

LH2-based ships: SH2IFT project, MARHySAFE project

LH2-based planes: HEAVEN project, ENABLEH2 project

LH2-based trains: under consideration

LH2-based trucks: recent communication of Daimler AG announced a LH2 truck

prototype - Mercedes Benz GenH2 Truck - for 2023.

Thus, this document – regarding RCS recommendations – can target working groups and

technical committees developing standards for these applications and fields as well in order

to early consider findings of PRESLHY outcomes for on-going and future developments

and deployments.

Airports, maritime ports, trucks platform… will be impacted by these changes including

new risks to be managed in these environments with already complex and non-uniform

rules. Safety should be integrated taking into account existing infrastructures, co-activities

and bunkering operations.

3 Review of feared events and PRESLHY outcomes

3.1 Main feared events and studied phenomena

Three blocks and associated feared events were identified:

Loading/unloading of the storage

o Medium pressurized liquid release

Liquid storage

o BLEVE leading to the burst of the storage

o Massive spillage of liquid hydrogen leading to

A pool with vaporization and flammable cloud formation

Potential RPT in case of interaction with water

Piping, connections and equipment from the storage to the dispenser

o Ignition / electrostatic discharge / Jet fire / Explosion of:

Medium pressure liquid release

High pressure liquid release

High pressure gaseous release


Figure 6. Simplified view of feared events and associated consequences

Most of these phenomena was studied in PRESLHY project through experimental

approaches, and associated analytical and numerical tools were developed to assess

consequences and hazardous distances.

Work performed is available in reports and presentations on PRESLHY website

(www.preslhy.eu).

3.2 PRESLHY main outcomes

The following points can be highlighted from the experimental work:

No rainout was observed and pools formed only for vertical releases. However,

rainout can not be ruled out as a credible scenario for the moment.

Pools could form on any substrates but the delay of formation is longer when the

material has a high porosity. However, the ignition of the cloud above the gravel

pool (highly porous) showed by far the strongest combustion loads in comparison

with sand, concrete and water. These results show that the use of gravel or any other

porous material as a ground material for filling stations should be forbidden.

The ignition properties of hydrogen are affected very little by the temperature. The

MIE of cryogenic hydrogen is slightly higher than for ambient hydrogen. Hot

surface ignition temperature of about 600°C is also not affected by the cryogenic

temperature. Consequently, the same safety measures as for ambient hydrogen-air

mixtures may be employed.

In small and large scale releases, strong electrostatic fields were observed but no

spontaneous ignition occurred. In large scale releases, the flow of LH2 in pipes

causes electrostatic charges so it is advised to design LH2 pipework to limit the

development of two-phase flows and ensure that the pipework contains no

electrically isolated sections.


The use of sprinklers and water jets on a pool of LH2 did not generate any RPT so

they can be employed as mitigation measures to control the flow or accumulation

of frozen/condensed air and potentially LH2. This may prevent condensed air/LH2

detonations and disperse and potentially lift LH2-vapour and limit risk from dense

gas dispersion. However, they enhance the vaporization rate that could lead to a

larger fireball if the cloud is ignited.

The run-up distance for detonation transition was reduced in cryogenic mixtures

due to density effects. The influence of blockage ratio on cold mixtures DDT has

the same effect as usual.

For risk assessment of a release in an obstructed area:

o For low levels of congestion, the risk of uncontrollable flame acceleration

is low.

o For high levels of congestion, it is appropriate to assume that a violent

deflagration or DDT at hydrogen concentration above 15-16% of H2 could

occur. The strength of explosion is proportional to the density factor (3-4

times).

o It might be appropriate to assume that a severe explosion could occur for

intermediate levels of congestion. However, some additional experimental

work is required to determine with more precision the boundary beyond

which severe explosions happen.

o As a rule of thumb, if all of the cloud could be in the congested area, the

explosive energy release for 1 bar tanker pressure would be approximately

20 MJ and for 5 bar pressure 50 MJ.

For the design and consequences assessment, several calculation means have been

developed during the project. Simple engineering tools as well as numerical simulation

tools are presented in D6.2 PRESLHY deliverable “Novel guidelines for safe design and

operation of LH2 systems and infrastructure” and the full details about their range of

applicability and validation can be found in D6.5 PRESLHY deliverable “Detailed

description of novel engineering tools for LH2 safety”.

One relevant aspect of PRESLHY to industry is the determination of hazard distances for

liquid hydrogen installations. For this purpose, the following tools have been developed

(see Annex 1 as well):

The similarity law has been validated for cryogenic jets and can be used to

determine the distance to LFL;

A correlation for hydrogen jet flames can be used to estimate a cryogenic gaseous

hydrogen jet fire flame length and associated hazard distances;

An engineering tool for cryogenic hydrogen jet fire can be used to estimate the

thermal radiative heat flux and thermal dose in the surroundings and associated

hazard distances;

An engineering tool for hydrogen jet fire can be used to estimate the maximum

overpressure that can be expected from its delayed ignition and associated hazard

distances;

An engineering tool to evaluate the spatial and concentration bounding conditions

for strong explosion and detonations at cryogenic temperatures can be proposed for

maximum combustion pressure and hazard potential assessment;


A correlation for spills can be used to determine a fireball size after liquid hydrogen

spill combustion;

A CFD approach can be used to assess hazard distances for horizontal jet fires with

inclusion of the buoyancy effect.

Regarding these outcomes, specific recommendations for RCS are defined in Section 4

p 14 of this report.

4 Recommendations for RCS

Following recommendations are made in view of disseminate them to standard

development organizations (SDO) and international bodies.

The main RCS recommendations – focusing on medium scale liquid hydrogen inventory,

i.e. lower than 5 t-H2 - are listed in the following sections.

4.1 Release, flowrate, dispersion in free field

RCS recommendation #1. Limit potential liquid release in case of accidental

events.

Experiments performed in PRESLHY project on large-scale liquid and multiphase releases

showed significantly large and persistent flammable clouds due to high density and low

temperature of liquid hydrogen.

Specifically for loading/unloading operation (bunkering of liquid hydrogen), occurrence of

leak during this phase by hose rupture for instance is high and consequences are large.

Thus, some safety devices, equipment and procedures have to be considered. Technical

barriers, like excess flow safety valve, breakaway, quick connect/disconnect-coupling,

passive means and automation must be considered and set up as much as possible (e.g. like

recommended in LNG bunkering standard ISO 20519).

For piping directly connected to the liquid storage vessel, shut-off valves – automatic and

manual – would allow to stop quickly release and avoid massive and long release.

RCS recommendation #2. Limit liquid release flow rate.

Smart sizing of piping to limit flowrate, in accordance with technical needs of the

application has to be considered and optimized in order to limit the flow rate in case of full-

bore rupture of the piping for instance.

Indeed, by limiting the maximum flow of an accidental hydrogen release, the potential

effects will be reduced: thermal radiation due to the jet flame in case of immediate ignition

and size of the cloud and corresponding overpressure effects in case of delayed ignition.


For instance, diameters and lengths of the pipelines must be defined in order to provide

sufficient flow rate required by the system and keeping in mind consequences in case of

accidental release in order to reduce as much as possible the effects.

Additionally, shut-off valves – automatic and manual – strategically located throughout the

installation would allow for quick termination of releases, and hence limit the duration of

fires or the size of flammable clouds.

RCS recommendation #3. Ground medium in liquid hydrogen infrastructures

Even if the porosity of some substrates tends to delay the pool formation in case of liquid

releases as observed in the experimental part of PRESLHY project, they can foster air

condensation and lead to liquid oxygen enrichment. Thus, complementary experiments on

ignition of a flammable cloud showed high probability of liquid hydrogen/liquid oxygen

explosion and stronger combustion pressure loads in these conditions.

Ground medium has to be chosen in order to limit potential oxygen condensation in case

of liquid hydrogen release, particularly in the vicinity of large hydrogen inventories. For

instance concrete, steel… meet this requirement, better than sand, and very much better

than gravels.

Additionally, asphalt has to be banned to avoid the risk of condensed air falling onto its

surface.

The main attention must be paid to the following areas:

- Liquid hydrogen loading/unloading area;

- Under and close to the liquid hydrogen storage vessel.

RCS recommendation #4. Avoid retention pit under liquid hydrogen storage

vessel.

Without retention pit under the liquid storage vessel, in case of massive release of liquid

hydrogen, the vaporization in free field will be quicker, thereby reducing the probability of

ignition of the potential flammable cloud by limiting the duration of the critical phase of

dispersion.

RCS recommendation #5. Leak detection required to monitor potential accidental

events.

Leak detection, associated with active emergency procedure are strongly recommended to

avoid escalating events.



- Under and close to the liquid hydrogen storage vessel;

- Close to connections.

Additionally, sensors must be able to operate at very low temperatures (cryogenic fog close

to the sensors is foreseeable in case of accidental liquid release).


4.2 Ignition, flame and explosion

RCS recommendation #6. Avoid ignition: no ignition sources close to the

connections.

Even if experiments performed in PRESLHY project showed a slight increase of the

minimal ignition energy and no change of hot surface temperature required to ignite a

flammable H2-air mixture at very low temperature compared to ambient temperature,

ignition sources and hot surfaces (above 600°C) close to connections are not acceptable.

Electric equipment must be Ex-certified.

RCS recommendation #7. Avoid electrostatic charges formed from an

established cryogenic jet by piping thermally or electrically insulated.

Results from PRESLHY experiments showed that the flow of LH2 in pipes could cause

electrostatic charges and that certain conditions encourage it. These findings could be used

for either designing LH2 pipework so that the development of two-phase flows are limited

(through vacuum insulation for instance) or ensuring that the pipework contains no

electrically isolated sections.

RCS recommendation #8. Limit congestion in a liquid hydrogen-based

infrastructure.

Results obtained in PRESLHY project in case of ignition of a flammable hydrogen-air

mixture encourage limiting congestion ratio, since:

- For low levels of congestion, the risk of uncontrollable flame acceleration is

low;

- But for high levels of congestion, it is appropriate to assume that a violent

deflagration or DDT could occur;

- All communications and equipment should be blocked as solid units – when

possible – to prevent flame acceleration and strong explosion.

In this way, size and design of some equipment, distances between equipment, location,

number, etc. have to be considered to reduce blockage ratio of the area.

Additionally, considering accidental releases, the presence of obstacles can foster:

- Impinging jets and increase potential local accumulation;

- Potential charges increasing the probability of ignition;

- Any source of turbulent mixing should be avoided to prevent an additional

flame acceleration and formation of very cold hydrogen-air composition with

strong explosion pressure.


RCS recommendation #9. Avoid liquid hydrogen confinement for large

inventory.

At least, no confinement for large storage or large inventory of liquid hydrogen to foster

hydrogen quick dispersion in case of accidental release and to limit consequences in case

of ignition.

RCS recommendation #10. Limit fire propagation by avoiding combustible

materials in the nearby areas.

Pure hydrogen burns with a near invisible flame, with low emissivity relative to

hydrocarbons. However, the heat load from the hydrogen flame may initiate pyrolysis and

devolatilisation reactions in nearby structures, including paint. A specific danger of

hydrogen flame in case of its attachment to human skin should be avoided because of steam

condensation and very high convective heat transfer, much higher than the radiant heat flux

of the same flame, leading to much stronger hazard degree.

RCS recommendation #11. Water deluge in case of fire.

Experiments performed in PRESLHY showed that contact between water and LH2 do not

necessarily cause a Rapid Phase Transition (RPT) and gave reassurance that sprinklers and

water jets could be used as mitigation measures to control the flow or accumulation of LH2;

it recommended to use water deluge in case of fire to avoid burst of hydrogen storages for

instance.

Nevertheless, in emergency procedures, the frozen water on safety devices – like shut-off

valve, PSV – can block the functioning of this equipment. And blocking escape of gas from

the liquid hydrogen storage, may lead to a BLEVE with high hazard distances and dramatic

consequences on people and structures. Thus it is necessary to manage and correctly locate

this safety measure.

RCS recommendation #12. Fire detection required to monitor accidental events.

Fire detection, associated to active emergency procedure are strongly recommended to

avoid escalating events by early detection and action when possible.



- Close to the liquid hydrogen storage vessel;

- Close to connections.


4.3 Burst of the storage vessel

RCS recommendation #13. Measures avoiding storage burst are required

Experiments and calculations performed in PRESLHY project showed unacceptable

distances of effects regarding the burst of the liquid storage.

The following measures are recommended:

- Pressure relief valves, and/or rupture disks on the hydrogen liquid storage to

protect against damaging overpressures;

- Periodic inspection of tank insulation against accidental pressure increase by

thermal insulation loss.

4.4 Calculation means for risk assessment

RCS recommendation #14. Effects assessment and hazardous distances

definition

Experimental, analytical and numerical studies performed in PRESLHY project allowed in

developing specific calculation approaches or enlarging range of use of existing

methodologies. It is recommended to use these tools for liquid hydrogen-based

infrastructures risk assessment.

They are inventoried in Annex 1, with other existing toolkits.

5 Proposed path forward

For all the recommendations #1-14 of Section 4 of this document, the following active and

published standards may be considered by the technical committee (additional list is given

in Annex 2).

The PRESLHY consortium members are aware that this “simple” document will not allow

the integration of the described recommendations. It is necessary to actively participate in

technical committees and other working groups. This action is already engaged by some

partners.

5.1 Recommendations to be forwarded to ISO/TC

5.1.1 Secretariat of ISO/TC 197 – Hydrogen Technologies

Active:

ISO/TC 197, WG 29

ISO/DTR 15916 Ed 2. Basic considerations for the safety of hydrogen systems

(A specific task force in on-going revision has been set up to draft a specific

chapter on liquid hydrogen to be integrated for the update of the existing

document)


Published:

ISO/TR 15916:2015

Basic considerations for the safety of hydrogen systems

5.1.2 Secretariat of ISO/TC 220 – Cryogenic vessels

Active:

ISO/TC 220 – Ships and marine technology

Published:

ISO 20521-1:2019

Cryogenic vessels – Large transportable vacuum-insulated vessels – Part 1:

Design, fabrication, inspection and testing

ISO 20521-2:2017

Cryogenic vessels – Large transportable vacuum-insulated vessels – Part 2:

Operational requirements

5.1.3 Secretariat of ISO/TC 8 – Ships and Marine technology

Active:

ISO/TC 8 – Ships and marine technology

SC2 – Marine liquefied hydrogen transfer arms (Link with IMO)

5.1.4 Secretariat of ISO/TC 67 – Materials, equipment and offshore structures for petroleum, petrochemical and natural gas industries

Active:

ISO/TC 67

SC9 - Liquefied natural gas installations and equipment

Published:

ISO TS 20519:2017

Ships and marine technology – Specification for bunkering of liquefied natural

gas fuelled vessels

5.2 Recommendations to be forwarded to the Secretariat of CEN/TC

5.2.1 Secretariat of CEN CLC JTC 6 – Hydrogen in energy systems

CEN CLC JTC 6, WG 3

Hydrogen safety


5.2.2 Secretariat of CEN/TC 268 – Cryogenic vessels

Published:

EN 17127

Hydrogen refuelling stations

EN ISO 27268

Refuelling connectors

5.3 Recommendations to be forwarded to the Secretariat of EUROCAE/SAE

EUROCAE/SAE, WG80

AE-7AFC: Hydrogen Fuel Cell Aircraft Fuel Cell Safety Guidelines

5.4 Recommendations to be forwarded to the Secretariat of NFPA

NFPA2

Hydrogen Technologies code

NFPA 55 Compressed gases and Cryogenic fluids code

5.5 Recommendations to be forwarded to the Secretariat of CSA

HGV 4.9

HRS guidelines

5.6 Recommendations to be forwarded to the Secretariat of EIGA

EIGA, WG11

Hydrogen energy

5.7 Recommendations to be forwarded to the Secretariat of CGA

CGA Hydrogen technology committee (Strategy task group and RCS gap analysis task

group on-going)

5.8 Recommendations to be forwarded to the Secretariat of BCGA

TSC9 H2 CNG LNG refuelling


5.9 Recommendations to be forwarded to additional associations

Hydrogen council – PT safety

Hydrogen France

Hydrogen Europe

AICHE Center for Hydrogen Safety

JPEC

Public road filling

HySUT - research association of Hydrogen Supply / Utilization Technology

H2 refuelling technology TF

FCCJ Fuel Cell Commercialized Conference of Japan

H2 safety Task Force

FC H2 powered industrial trucks technologies and refuelling technologies Task

Force

6 Conclusions

Fourteen recommendations were formulated in order to be addressed to RCS organizations.

They are relating to:

Phenomena, concrete consequences and potential associated mitigation ways, for

the following topics:

o Release, flowrate, dispersion in free field

o Ignition, flame and explosion

o Burst of the storage vessel

Calculation means to evaluate consequences through:

o Analytical models,

o Engineering correlations,

o Numerical modelling.

For more details concerning each point highlighted in this document, PRESLHY outcomes

are available – through reports, presentations, photos and videos – on PRESLHY dedicated

website (www.preslhy.eu).

The PRESLHY consortium members are aware that this “simple” document will not allow

the integration of the described recommendations. It is necessary to actively participate in

technical committees and other working groups.

Thus, dissemination of these recommendations is already launched since numerous of

PRESLHY project partners are already involved in mentioned RCS organizations, working

groups and technical committees (e.g. ISO/TR/15916, a specific task force in on-going

revision has been set up to draft a specific chapter on liquid hydrogen to be integrated for

the update of the existing document).


Annex 1. List of engineering correlations and tools

Fourteen engineering correlations and tools were developed and validated in the framework

of the PRESLHY FCH JU funded project, distributed per phenomena as follows:

5 engineering tools associated to release and mixing phenomena,

2 engineering tools associated to ignition,

7 engineering tools associated to combustion.

The list of the engineering correlations and tools developed throughout the project is given

in the Table hereafter.

N. Correlation title

1 The similarity law for concentration decay in momentum jets

2 The non-adiabatic blowdown model for a hydrogen storage tank

3

DISCHA tool - to calculate accurate physical properties of pure

substances and perform discharge calculations either in transient

(blowdown) or steady state mode with account of discharge line

4 Extent of cryogenic pools

5 Method for calculating the final state when mixing liquid

hydrogen and moist air

6 Ignition Energy for hydrogen-air mixtures

7 Electrostatic field-up generated during hydrogen releases

8 Laminar burning velocity and expansion ratios for hydrogen-air

mixtures

9 Flame length correlation and hazard distances for jet fires

10 Thermal load from hydrogen jet fires

11 Maximum pressure load from delayed ignition of turbulent

hydrogen jets

12 Flame acceleration and detonation transition criteria for cryogenic

hydrogen-air mixtures

13 Maximum combustion pressure evaluation

14 Fireball size after liquid hydrogen spill combustion

These engineering correlations and tools are described in details (approaches, equations,

parameters, range of validation, range of use…) in the public Deliverable 6.5 “Detailed

description of novel engineering correlations and tools for LH2 safety” of the PRESLHY

project.

Some of these tools, and others, are already available on the e-Laboratory platform

developed within the Net-Tools project (https://fch2edu.eu/home/e-laboratory/).

Additionally, the HyRAM toolkit (Hydrogen Risk Assessment Model) developed by

Sandia National Laboratories – available under an open source licenses – can be consulted

and used to quantify accident scenarios (https://energy.sandia.gov/programs/sustainable-

transportation/hydrogen/hydrogen-safety-codes-and-standards/hydrogen-risk-assessment-

model-hyram/).


Annex 2. Short list of relevant RCS working groups, technical committees, organizations and documents

In this annex is presented a non-exhaustive list of existing and active working groups,

existing standards dealing with LH2… or potential documents and SDOs that can or should

integrate LH2 topic regarding the future developments and use of LH2.

Active International RCS working groups

List of active RCS working groups.

Working Group Work items

ISO/TC 197 WG 29 ISO/DTR 15916 Ed 2. Basic considerations for the safety of hydrogen

systems

Published International Standards

List of published RCS documents for cryogenic applications in general.

# Item

International standards

ISO 20421-1:2019 Cryogenic vessels — Large transportable vacuum-insulated

vessels — Part 1: Design, fabrication, inspection and testing

ISO 20421-2 Cryogenic vessels — Large transportable vacuum-insulated

vessels – Part 2: Operational requirements

ISO 21010 Cryogenic vessels – Gas/material compatibility

ISO 21011 Cryogenic vessels – Valves for cryogenic service

ISO 21013-1, 2, 3

Cryogenic vessels – Pressure-relief accessories for cryogenic

service – Part 1: Reclosable pressure-relief valves. Part 2: Non-

reclosable pressure-relief devices, Part 3: Sizing and capacity

determination

ISO 21028-1 Cryogenic vessels – Toughness requirements for materials at

cryogenic temperature – Part 1: Temperatures below -80°C

ISO 21029-1:2018

Cryogenic vessels – Transportable vacuum insulated vessels of

not more than 1 000 litres volume – Part 1: Design, fabrication,

inspection and tests

ISO 24490 Cryogenic vessels - Pumps for cryogenic service


# Item

National standards

US: 29 CFR § 1910.103

Chapter XVII - Occupational safety and health administration,

department of labor

Hydrogen – (c) Liquefied hydrogen systems

Codes

EIGA Doc. 06/19 Safety in Storage, Handling and Distribution of Liquid Hydrogen

IGC Doc 7/03 Metering of cryogenic liquids

IGC Doc 24/02 Vacuum insulated cryogenic storage tank systems pressure

protection devices

IGC Doc 41/89/E Guidelines for transport of vacuum insulated tank containers by

sea

IGC Doc 43/01/E Hazards associated with the use of activated charcoal cryogenic

gas purifiers

IGC Doc 59/98/E Prevention of excessive pressure in cryogenic tanks during filling

IGC Doc 77/01/E Protection of cryogenic transportable tanks against excessive

pressure during filling

IGC Doc 93/03/E Safety features of portable cryogenic liquid containers for

industrial and medical gases

IGC 103/03/E Transporting gas cylinders or cryogenic receptacles in “enclosed

vehicles”

IGC Doc 114/03/E Operation of static cryogenic vessels


List of published RCS documents on hydrogen.

# Item

ISO/TR 15916:2015 Basic considerations for the safety of hydrogen systems

NFPA 2:2020

Hydrogen Technologies Code – chapter 8: Liquefied Hydrogen –

chapter 11: LH2 Fueling Facilities

NFPA 55:2020 Compressed Gases and Cryogenic Fluids Code

List of published RCS documents not addressing hydrogen yet.

# Item

OMI-IMO 109E – IGF

code:2017

International code of safety for ships using gases

or other low-flashpoint fuels

MSC.1/Circ 1455:2013

Guidelines for the approval of alternatives and equivalents as

provided for in various IMO instruments. International Maritime

Organization

NMA Circular Series R. RSR

18:2016

Regulations on ships using fuel with a flashpoint of less than 60°C

and amendments to Regulations on the construction of ships and

amendments to other regulations (on construction, on

qualifications, on fire protection and on safety management

systems) – implementation of the IGF Code

ISO TS 20519:2017 Ships and marine technology – Specification for bunkering of

liquefied natural gas fuelled vessels

… …

In this Table, a non-exhaustive list of standards that can or should include LH2 content, or

develop separate documents on this topic.

Regulations

Regulations that apply to all the scenarios described above:

GTR 13 for fuel and hydrogen vehicles – section on LH2

IEC 60079-10-1:2020 – section on LH2

d6.3 recommendations for rcs

Documents