Gas infrastructure - Consequences of hydrogen in the gas infrastructure and identification of related standardisation need in the scope of CEN/TC 234

This document is written in preparation of future standardization and provides guidance on the
impact of the injection of H2 into the gas infrastructure from the input of gas into the on­shore
transmission network up to the inlet connection of gas appliances. 
Furthermore, it identifies the expected revision need of the existing CEN/TC 243 standards as
well as the need of further new standardisation deliverables. 
It examines the effects on each part of the gas infrastructure in the scope of the CEN/TC 234
Working Groups 1 to 12 inclusive, based on available studies, reports and research. Due to
several limitations at different hydrogen concentrations, the impacts are specified. 
For some specific impact, pre­standardization research is needed. 
By convention, for this technical report, the injection of pure hydrogen, i. e. without trace
components is considered. 
The information from this report is intended to define the CEN/TC 234 work program for the
coverage of H2NG in relation to the scope of the CEN/TC 234 and its WGs. 
NOTE Progress on hydrogen will develop over time. In principle this will be reflected in the
standardisation process in CEN/TC 234.

Gasinfrastruktur - Auswirkungen von Wasserstoff in der Gasinfrastruktur und Identifikation des zugehörigen Normungsbedarfs im Zuständigkeitsbereich des CEN/TC 234

Infrastructure gazière ­ Consequences d'hydrogen dans l'infrastructure gazière et l'identification des besoins relatifs à la normalisation dans le domaine d'application de CEN/TC 234

Infrastruktura za plin - Posledice zaradi vodika v infrastrukturi za plin in ugotavljanje s tem povezanih potreb po standardizaciji na področju CEN/TC 234

Ta dokument je oblikovan kot priprava na prihodnjo standardizacijo in vsebuje smernice o vplivu vbrizgavanja vodika v infrastrukturo za plin od točke vnosa plina v kopensko
plinovodno omrežje do točke vstopnega priključka plinskih naprav.
Poleg tega opredeljuje pričakovane potrebe po reviziji obstoječih standardov CEN/TC 243
ter potrebo po nadaljnjih novih standardizacijskih dokumentih.
Na podlagi razpoložljivih študij, poročil in raziskav preučuje učinke na vsak del infrastrukture za plin v okviru delovnih skupin CEN/TC 234 od 1 do vključno 12. Zaradi več omejitev pri različnih koncentracijah vodika so vplivi določeni.
Za nekatere posebne vplive so pred standardizacijo potrebne raziskave.
Po dogovoru se v tem tehničnem poročilu obravnava vbrizgavanje čistega vodika, torej
brez sestavin v sledovih.
Informacije iz tega poročila so namenjene opredelitvi delovnega programa CEN/TC 234 za zajetje H2NG glede na področje uporabe CEN/TC 234 in njegovih delovnih skupin.
OPOMBA: Napredek na področju vodika bo potekal postopoma. Načeloma se bo to odražalo v postopku standardizacije v CEN/TC 234.

General Information

Status
Published
Public Enquiry End Date
01-Dec-2021
Publication Date
18-Aug-2022
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
13-May-2022
Due Date
18-Jul-2022
Completion Date
19-Aug-2022

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SLOVENSKI STANDARD
SIST-TP CEN/TR 17797:2022
01-september-2022
Infrastruktura za plin - Posledice zaradi vodika v infrastrukturi za plin in
ugotavljanje s tem povezanih potreb po standardizaciji na področju CEN/TC 234
Gas infrastructure - Consequences of hydrogen in the gas infrastructure and
identification of related standardisation need in the scope of CEN/TC 234
Gasinfrastruktur - Auswirkungen von Wasserstoff in der Gasinfrastruktur und
Identifikation des zugehörigen Normungsbedarfs im Zuständigkeitsbereich des CEN/TC
234
Infrastructure gazière ­ Consequences d'hydrogen dans l'infrastructure gazière et
l'identification des besoins relatifs à la normalisation dans le domaine d'application de
CEN/TC 234
Ta slovenski standard je istoveten z: CEN/TR 17797:2022
ICS:
01.120 Standardizacija. Splošna Standardization. General
pravila rules
75.180.01 Oprema za industrijo nafte in Equipment for petroleum and
zemeljskega plina na splošno natural gas industries in
general
SIST-TP CEN/TR 17797:2022 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST-TP CEN/TR 17797:2022

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SIST-TP CEN/TR 17797:2022


CEN/TR 17797
TECHNICAL REPORT

RAPPORT TECHNIQUE

March 2022
TECHNISCHER BERICHT
ICS 01.120; 75.180.01
English Version

Gas infrastructure - Consequences of hydrogen in the gas
infrastructure and identification of related standardisation
need in the scope of CEN/TC 234
Infrastructure gazière - Consequences d'hydrogen dans Gasinfrastruktur - Auswirkungen von Wasserstoff in
l'infrastructure gazière et l'identification des besoins der Gasinfrastruktur und Identifikation des
relatifs à la normalisation dans le domaine zugehörigen Normungsbedarfs im
d'application de CEN/TC 234 Zuständigkeitsbereich des CEN/TC 234


This Technical Report was approved by CEN on 24 January 2022. It has been drawn up by the Technical Committee CEN/TC 234.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.





EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 17797:2022 E
worldwide for CEN national Members.

---------------------- Page: 3 ----------------------
SIST-TP CEN/TR 17797:2022
CEN/TR 17797:2022 (E)
Contents Page
European foreword . 5
Introduction . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and abbreviations . 7
3.1 Terms and definitions . 7
3.2 Symbols and abbreviations . 10
4 Executive summary . 10
5 General considerations for the entire gas infrastructure . 12
5.1 Explosion protection and prevention . 12
5.1.1 General principles . 12
5.1.2 Safety characteristics of natural gas-hydrogen mixtures and their impact on
explosion prevention. 13
5.1.3 Consequences of H2 and H2NG in NG infrastructure for explosion protection related
to identified H concentrations . 14
2
5.2 N NG mixtures in contact with materials — Pressure integrity, gas tightness and
2
functionality . 15
5.2.1 General. 15
5.2.2 Steel. 18
5.2.3 PE and PA-U . 26
5.2.4 Alloys . 26
5.2.5 Information on deterioration and chemical aggression of elastomers. 26
5.2.6 Others . 26
5.3 Volume in relation to energy content — consequences for the capacity and function
of the gas transportation, underground gas storage and distribution system. 26
6 Technical considerations per topic applicable for the different parts of the gas
infrastructure (along chain) . 27
6.1 General. 27
6.2 Gas quality . 27
6.2.1 Scope of considerations — Gas quality — EN 16726 . 27
6.2.2 Technical considerations — Identified H NG . 28
2
6.3 Gas compression . 33
6.3.1 Scope of consideration — Gas compression . 33
6.3.2 Technical considerations — Identified H NG aspects — Gas compression . 34
2
6.4 Gas pipelines with MOP over 16 bar — Gas transmission . 34
6.4.1 Scope of consideration — Gas transmission — EN 1594 . 34
6.4.2 Hydrogen piping and pipelines — ASME B31.12 . 34
6.4.3 Technical considerations — Identified H NG aspect — Gas transmission . 35
2
6.5 Gas pressure control . 38
6.5.1 Scope of consideration — Gas pressure control — EN 12186 and EN 12279 . 38
6.6 Gas metering . 39
6.6.1 Scope of consideration — Gas metering — EN 1776 . 39
6.6.2 Technical considerations — Identified H2NG aspects — Gas metering . 39
6.7 Gas supply systems up to and including 16 bar and pressure testing . 40
2

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CEN/TR 17797:2022 (E)
6.7.1 Statement for gas pipelines with MOP up to and including 16 bar for all
concentrations . 40
6.7.2 Requalifying existing pipelines for hydrogen service . 41
6.7.3 Technical consideration — Scoping considerations — EN 2007-1 to -4,
CEN/TS 12007-6, EN 12327 and EN 12732 . 41
6.8 Service lines . 45
6.8.1 Scoping considerations — Service lines — EN 12007-5 . 45
6.8.2 Technical considerations — Identified H NG aspects integrity and safety, reliability
2
and operation . 46
6.9 Industrial piping . 47
6.9.1 Scope of consideration – Industrial piping – EN 15001-1 and EN 15001-2 . 47
6.9.2 Technical considerations — Industrial piping . 48
6.10 Gas pipework for buildings . 49
6.10.1 Scope of consideration — Gas pipework for buildings – EN 1775 . 49
6.10.2 Technical considerations — Gas pipework for buildings . 49
6.11 Underground gas storage . 49
6.11.1 Scope of consideration for underground gas storage — Generals EN 1918-1 to -5. 49
6.11.2 Technical considerations — Underground gas storage . 50
6.11.3 Identified H2NG impacts — Underground gas storage . 51
6.12 Safety management and integrity management. 52
6.12.1 Scope of considerations . 52
6.12.2 Safety management system — Management of change . 52
6.12.3 Pipeline integrity management system . 53
7 Conclusions — H suitability of components, materials and procedures used in the
2
gas infrastructure related to identified H concentrations . 54
2
7.1 General . 54
7.2 H suitability —Gas quality . 55
2
7.2.1 H-gas quality – Admixture of H . 55
2
7.2.2 Hydrogen quality in converted natural gas grids . 56
7.3 H suitability — Gas compressor stations . 57
2
7.3.1 General . 57
7.3.2 Less than 1 % hydrogen in natural gas . 58
7.3.3 Over 1 Vol.-% up to 5 Vol.-% H in natural gas . 58
2
7.4 H suitability — Gas transmission pipelines with MOP over 16 bar . 61
2
7.5 H suitability — Gas pressure control . 62
2
7.5.1 Introduction . 62
7.5.2 General . 63
7.5.3 Up to 10 Vol.-% H in natural gas . 63
2
7.5.4 Over 10 Vol.-% up to 100 % H in natural gas . 64
2
7.6 H suitability — Gas metering . 65
2
7.7 H suitability — Gas pipelines with MOP up to and including 16 bar . 65
2
7.7.1 A Summary of findings for gas pipeline systems up to and including 16 bar and
pressure testing (CEN/TC 234 WG 2) . 65
7.8 H suitability — Service lines . 66
2
7.9 H suitability — Industrial piping . 66
2
7.10 H suitability — Gas pipework for buildings . 67
2
7.11 H2 suitability — Underground gas storage . 67
7.11.1 Between 0 % and 1 % hydrogen in natural gas . 67
7.11.2 Between 1 % and 20 % hydrogen in natural gas . 68
7.11.3 Above 20 % hydrogen up to full replacement of natural gas by hydrogen (100 %
hydrogen) . 68
3

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CEN/TR 17797:2022 (E)
8 Revision needs of existing CEN/TC 234 standards and additional deliverables for the
H -readiness of the gas infrastructure . 68
2
8.1 Action need. 68
8.2 Gas quality — Expected revision of EN 16726:2015+A1:2018 . 69
8.3 Gas compression — Expected revision of EN 12583:2014 . 69
8.4 Pipelines for maximum operating pressure over 16 bar — Expected revisions of
EN 1594:2013 . 70
8.5 Gas pressure control — Expected revisions of EN 12186:2014 and EN 12279:2000 71
8.6 Gas measuring systems — Expected revision of EN 1776:2015 . 73
8.7 Pipelines for maximum operating pressure up to and including 16 bar — Expected
revision of EN 12007 Parts 1 to 4 and EN 12327:2012 . 74
8.8 Pressure testing, commissioning and decommissioning procedures — Expected
revision of EN 12327:2012 . 77
8.9 Welding of steel — Expected revision of EN 12732:2013 . 78
8.10 Service lines — Expected revision of EN 12007-5:2014 . 78
8.11 Gas installation pipework– Expected revision of FprEN 15001-1:2019 and EN 15001-
2:2019 . 81
8.12 Gas pipework for buildings — Expected revision of EN 1775 . 85
8.13 Underground gas storage– Expected revision of EN 1918-1:2016 to -5:2016 . 86
8.14 Safety and Integrity Management System — Expected revision of EN 16348 and
EN 15399 by prEN 17649 (merged standard) . 91
Annex A (informative) Any issue coming up during the discussion and outside of the TC 234
scope . 92
Annex B (informative) Safety characteristics of natural gas-hydrogen mixtures . 93
Annex C (informative) Operating principles for gas warning devices [2] . 94
Annex D (informative) Hydrogen pressure versus hydrogen percentage . 96
Annex E (informative) Hydrogen pressure versus hydrogen fugacity . 97
Annex F (informative) An example of the use of an existing gas pipeline for hydrogen gas 99
Annex G (informative) Use of polyamide (PA-U) in gas piping systems in relation to
hydrogen, methane or their mixtures . 101
Annex H (informative) Netbeheer Nederland Study for biomethane and 100 % hydrogen
. 112
Annex I (informative) Responsibility of CEN/TC 234 'Gas infrastructure' Working groups
for the parts of the gas infrastructure along the chain . 114
Annex J (informative) Symbols and abbreviations . 115
Bibliography . 118

4

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SIST-TP CEN/TR 17797:2022
CEN/TR 17797:2022 (E)
European foreword
This document (CEN/TR 17797:2022) has been prepared by Technical Committee CEN/TC 234 “Gas
infrastructure”, the secretariat of which is held by DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
5

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SIST-TP CEN/TR 17797:2022
CEN/TR 17797:2022 (E)
Introduction
The injection of hydrogen in natural gas infrastructures demands considerations with regard to the
integrity, safety and performance of the systems facing increasing hydrogen levels, its fluctuation and
variation.
There is extensive research on the use of hydrogen as an admixture with natural gas in various
percentages or as pure hydrogen. Impact studies already completed or in progress are focusing on the
use of existing gas networks but also of dedicated gas networks for hydrogen. They also include the
impact of the introduction of hydrogen in various percentages into the gas infrastructure on all the
existing technologies within the gas supply chain.
Accepting hydrogen into the natural gas network requires input from many gas TCs at CEN, i.e.
CEN/TC 234 and particularly from the manufacturers of essential components, e.g. valves, gas pressure
regulators, gas meters, safety control devices, leak detection devices, and many more (see Annex A). Many
of these manufacturers are assessing the potential impact of hydrogen on existing components in natural
gas service.
Co-operation with these other CEN and ISO/TCs for various essential components and applications will
be necessary to ensure that projects to introduce hydrogen have all the essential elements of the gas chain
fully co-ordinated into the plan. The positive co-operation of the component manufacturers will be
particularly important.
In the transition scheme to hydrogen, there is a large body of knowledge and experience available from
the hydrogen industry for gas production and use. The long-established safety requirements in this sector
will aid the amendment of natural gas standards and codes of practice and the development of any new
standards
This report is written for
— CEN/TC 234 as basis for definition of a TC roadmap for standardisation
— CEN/TC 234 WGs as a guideline for the standardisation work
— interested parties to get an insight in the decision process of CEN/TC 234’s hydrogen standardisation.
NOTE This document has been elaborated in co-operation between the Working Group convenors, secretaries
and experts, TC chair and secretariat of CEN/TC 234. Respecting different working group contributions, the way in
which the content is presented and the level of details differs for the different topics. This is acceptable as the real
technical work will take place in the dedicated working groups with co-ordination of the TC 234
Convenors/Secretaries group to ensure the final coherence of the resulting standardisation deliverables.
6

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SIST-TP CEN/TR 17797:2022
CEN/TR 17797:2022 (E)
1 Scope
This document is written in preparation of future standardization and provides guidance on how
injection of H into the gas infrastructure can impact processes from the input of gas into the on-shore
2
transmission network up to the inlet connection of gas appliances.
NOTE 1 Gas infrastructure includes gas installation pipework between the delivery point of the gas and the inlet
connection to the gas appliance in buildings and on industrial sites.
The assessments refer to the concentrations of 2, 5, 10, 20 and up to 100 Vol.- % hydrogen in natural gas.
Furthermore, it identifies the expected revision need of the existing CEN/TC 234 standards as well as the
need of further new standardisation deliverables.
It examines the effects on each part of the gas infrastructure in the scope of the CEN/TC 234 Working
Groups 1 to 12 inclusive, based on available studies, reports and research. Due to several limitations at
different hydrogen concentrations, the impacts are specified.
For some specific impacts, pre-standardization research is needed.
By convention, for this technical report, the injection of pure hydrogen, i. e. without trace and/or minor
components is considered. Awareness is given that there is the need to consider trace and/or minor
components and limits set on the gas quality on European and national level, too.
The information from this report is intended to define the CEN/TC 234 work program for the coverage
of H NG in relation to the scope of the CEN/TC 234 and its WGs.
2
NOTE 2 Progress on hydrogen will develop over time. In principle this will be reflected in the standardisation
process in CEN/TC 234.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and abbreviations
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
The International Gas Union glossary on Underground Gas Storage [1] can be useful too:
3.1 Terms and definitions
3.1.1
hydrogen embrittlement
HE
interaction of hydrogen atoms and steel can have a negative effect on the mechanical behaviour of steel.
Note 1 to entry: The general term for this degrading effect is called hydrogen embrittlement
7

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SIST-TP CEN/TR 17797:2022
CEN/TR 17797:2022 (E)
3.2.2
explosive atmosphere
mixture with air, under atmospheric conditions, of flammable substances in the form of gases, vapours,
mists or dusts in which, after ignition has occurred, combustion spreads to the entire unburned mixture
[SOURCE: EN 13723:2013, 3.28]
3.2.3
hazardous explosive atmosphere
explosive atmosphere present in such quantities that precautions against ignition are required
[SOURCE: IEC 61340-4-4:2018, 3.6]
3.2.4
hazardous area
area in which an explosive atmosphere is present, or can be expected to be present, in quantities such as
to require special precautions for the construction, installation and use of equipment
[SOURCE: IEC 60079-0:2013]
3.2.5
explosion group
ranking of flammable gas-air mixtures with respect to the Maximum Experimental Safe Gap (MESG)
[SOURCE: EN ISO 16852:2016, 3.12.2]
3.2.6
temperature class
temperature range used for:
— classification of equipment, protective system for explosive atmospheres based on its maximum
surface temperature; or
— classification of flammable gases and vapours based on their auto ignition
[SOURCE: EN 13237:2012, 3.63]
3.2.7
explosion pressure
highest pressure occurring in a closed vessel during the explosion of a specific mixture of flammable
substances with air or air and inert gases determined under specified test conditions
[SOURCE: EN 15967:2011]
3.2.8
ignition temperature
lowest temperature (of a hot surface) at which under specified test conditions an ignition of a flammable
gas or flammable vapour in mixture with air or air/inert gas occurs
[SOURCE: EN 14522:2005]
8

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SIST-TP CEN/TR 17797:2022
CEN/TR 17797:2022 (E)
3.2.9
limiting oxygen concentration
LOC
maximum oxygen concentration in a mixture of a flammable substance and air and an inert gas, in which
an explosion will not occur, determined under specified test conditions
[SOURCE: EN 13237:2012, 3.49]
3.2.10
lower explosion limit
LEL
lowest concentration of the explosion range at which an explosion can occur
[SOURCE: EN 13237:2012, 3.19.1]
3.2.11
maximum experimental safe gap
MESG
maximum gap of the joint between the two parts of the interior chamber of a test apparatus which, when
the internal gas mixture is ignited and under specified conditions, prevents ignition of the external gas
mixture through a 25 mm long joint, for all concentrations of the tested gas or vapour in air
[SOURCE: EN 13237:2012, 3.51]
3.2.12
maximum explosion pressure
maximum value of explosion pressure measured in the tests for explosion pressure when the content of
the flammable substances in the mixture is varied
[SOURCE: EN 13237:2012, 3.2]
3.2.13
minimum ignition energy
MIE
lowest electrical energy stored in a capacitor, which upon discharge is sufficient to effect ignition of the
most ignitable atmosphere under specified test conditions
[SOURCE: EN 13237:2012, 3.54]
3.2.14
upper explosion limit
UEL
highest concentration of the explosion range at which an explosion can occur
[SOURCE: EN 13237:2012, 3.19.2]
9

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SIST-TP CEN/TR 17797:2022
CEN/TR 17797:2022 (E)
3.2.15
ventilation
movement of air and its replacement with fresh air due to the effects of wind, temperature gradients, or
artificial means (for example, fans or extractors)
[SOURCE: IEC 60079-10-0:2015]
3.2 Symbols and abbreviations
Symbols and abbreviations should be selected from those already established in relevant ISO and/or
CEN standards. New symbols and abbreviations should be defined only where there is no suitable
alternative and recorded in CEN/TC 234 Doc N 776 (so called N 215).
The symbols and abbreviations used in this document are listed in Annex J.
4 Executive summary
Intention of the European gas industry is to enable the use of natural gas infrastructure for hydrogen.
For the use of hydrogen in the natural gas infrastructure it is reasonable to identify:
— the similarities (what is equal) and differences (what is different) between methane (natural gas)
and hydrogen and – based on these
— the consequences or the impact of hydrogen on the gas system (e.g. materials, safety, maintenance).
NOTE 1 Acknowledging the impact of the similarities on applications, in this document only the impact on gas
infrastructure is considered a
...

SLOVENSKI STANDARD
kSIST-TP FprCEN/TR 17797:2021
01-november-2021
Infrastruktura za plin - Posledice zaradi vodika v infrastrukturi za plin in
opredelitev s tem povezanih potreb po standardizaciji na področju CEN/TC 234
Gas infrastructure - Consequences of hydrogen in the gas infrastructure and
identification of related standardisation need in the scope of CEN/TC 234
Gasinfrastruktur - Auswirkungen von Wasserstoff in der Gasinfrastruktur und
Identifikation des zugehörigen Normungsbedarfs im Zuständigkeitsbereich des CEN/TC
234
Infrastructure gazière ­ Consequences d'hydrogen dans l'infrastructure gazière et
l'identification des besoins relatifs à la normalisation dans le domaine d'application de
CEN/TC 234
Ta slovenski standard je istoveten z: FprCEN/TR 17797
ICS:
01.120 Standardizacija. Splošna Standardization. General
pravila rules
75.180.01 Oprema za industrijo nafte in Equipment for petroleum and
zemeljskega plina na splošno natural gas industries in
general
kSIST-TP FprCEN/TR 17797:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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kSIST-TP FprCEN/TR 17797:2021

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kSIST-TP FprCEN/TR 17797:2021


FINAL DRAFT
TECHNICAL REPORT
FprCEN/TR 17797
RAPPORT TECHNIQUE

TECHNISCHER BERICHT

September 2021
ICS
English Version

Gas infrastructure - Consequences of hydrogen in the gas
infrastructure and identification of related standardisation
need in the scope of CEN/TC 234
Infrastructure gazière - Consequences d'hydrogen dans Gasinfrastruktur - Auswirkungen von Wasserstoff in
l'infrastructure gazière et l'identification des besoins der Gasinfrastruktur und Identifikation des
relatifs à la normalisation dans le domaine zugehörigen Normungsbedarfs im
d'application de CEN/TC 234 Zuständigkeitsbereich des CEN/TC 234


This draft Technical Report is submitted to CEN members for Vote. It has been drawn up by the Technical Committee CEN/TC
234.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a Technical Report. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a Technical Report.


EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. FprCEN/TR 17797:2021 E
worldwide for CEN national Members.

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kSIST-TP FprCEN/TR 17797:2021
FprCEN/TR 17797:2021 (E)
Contents
Page
European foreword . 5
Introduction . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and abbreviations . 7
3.1 Terms and definitions . 7
3.2 Symbols and abbreviations . 10
4 Executive summary . 10
5 General considerations for the entire gas infrastructure . 12
5.1 Explosion protection and prevention . 12
5.1.1 General principles . 12
5.1.2 Safety characteristics of natural gas-hydrogen mixtures and their impact on
explosion prevention. 13
5.1.3 Consequences of H and H NG in NG infrastructure for explosion protection related
2 2
to identified H concentrations . 14
2
5.2 N NG mixtures in contact with materials — Pressure integrity, gas tightness and
2
functionality . 15
5.2.1 General. 15
5.2.2 Steel. 18
5.2.3 PE and PA-U . 26
5.2.4 Alloys . 26
5.2.5 Information on deterioration and chemical aggression of elastomers. 26
5.2.6 Others . 26
5.3 Volume in relation to energy content — consequences for the capacity and function
of the gas transportation, underground gas storage and distribution system. 26
6 Technical considerations per topic applicable for the different parts of the gas
infrastructure (along chain) . 27
6.1 General. 27
6.2 Gas quality . 27
6.2.1 Scope of considerations — Gas quality — EN 16726 . 27
6.2.2 Technical considerations — Identified H NG . 28
2
6.3 Gas compression . 34
6.3.1 Scope of consideration — Gas compression . 34
6.3.2 Technical considerations — Identified H NG aspects — Gas compression . 34
2
6.4 Gas pipelines with MOP over 16 bar — Gas transmission . 34
6.4.1 Scope of consideration — Gas transmission — EN 1594 . 34
6.4.2 Hydrogen piping and pipelines — ASME B31.12 . 35
6.4.3 Technical considerations — Identified H NG aspect — Gas transmission . 36
2
6.5 Gas pressure control . 38
6.5.1 Scope of consideration — Gas pressure control — EN 12186 and EN 12279 . 38
6.6 Gas metering . 39
6.6.1 Scope of consideration — Gas metering — EN 1776 . 39
6.6.2 Technical considerations — Identified H2NG aspects — Gas metering . 39
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6.7 Gas supply systems up to and including 16 bar and pressure testing . 41
6.7.1 Statement for gas pipelines with MOP up to and including 16 bar for all
concentrations . 41
6.7.2 Requalifying existing pipelines for hydrogen service . 41
6.7.3 Technical consideration — Scoping considerations — EN 2007-1 to -4,
CEN/TS 12007-6, EN 12327 and EN 12732 . 42
6.8 Service lines . 45
6.8.1 Scoping considerations — Service lines — EN 12007-5 . 45
6.8.2 Technical considerations — Identified H NG aspects integrity and safety, reliability
2
and operation . 46
6.9 Industrial piping . 48
6.9.1 Scope of consideration – Industrial piping – EN 15001-1 and EN 15001-2 . 48
6.9.2 Technical considerations — Industrial piping . 48
6.10 Gas pipework for buildings . 49
6.10.1 Scope of consideration — Gas pipework for buildings – EN 1775 . 49
6.10.2 Technical considerations — Gas pipework for buildings . 49
6.11 Underground gas storage . 49
6.11.1 Scope of consideration for underground gas storage — Generals EN 1918-1 to -5. 49
6.11.2 Technical considerations — Underground gas storage . 50
6.11.3 Identified H NG impacts — Underground gas storage . 52
2
6.12 Safety management and integrity management. 52
6.12.1 Scope of considerations . 52
6.12.2 Safety management system — Management of change . 52
6.12.3 Pipeline integrity management system . 54
7 Conclusions — H suitability of components, materials and procedures used in the
2
gas infrastructure related to identified H concentrations . 55
2
7.1 General . 55
7.2 H suitability —Gas quality . 55
2
7.2.1 H-gas quality – Admixture of H . 55
2
7.2.2 Hydrogen quality in converted natural gas grids . 57
7.3 H suitability — Gas compressor stations . 58
2
7.3.1 General . 58
7.3.2 Less than 1 % hydrogen in natural gas . 59
7.3.3 Over 1 Vol.-% up to 5 Vol.-% H in natural gas . 59
2
7.4 H suitability — Gas transmission pipelines with MOP over 16 bar . 62
2
7.5 H suitability — Gas pressure control . 63
2
7.5.1 Introduction . 63
7.5.2 General . 64
7.5.3 Up to 10 Vol.-% H2 in natural gas . 64
7.5.4 Over 10 Vol.-% up to 100 % H in natural gas . 65
2
7.6 H suitability — Gas metering . 66
2
7.7 H suitability — Gas pipelines with MOP up to and including 16 bar . 66
2
7.7.1 A Summary of findings for gas pipeline systems up to and including 16 bar and
pressure testing (CEN/TC 234 WG 2) . 66
7.8 H suitability — Service lines . 67
2
7.9 H suitability — Industrial piping . 67
2
7.10 H suitability — Gas pipework for buildings . 68
2
7.11 H2 suitability — Underground gas storage . 68
7.11.1 Between 0 % and 1 % hydrogen in natural gas . 68
7.11.2 Between 1 % and 20 % hydrogen in natural gas . 69
7.11.3 Above 20 % hydrogen up to full replacement of natural gas by hydrogen (100 %
hydrogen) . 69
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8 Revision needs of existing CEN/TC 234 standards and additional deliverables for the
H -readiness of the gas infrastructure . 69
2
8.1 Action need. 69
8.2 Gas quality — Expected revision of EN 16726:2015+A1:2018 . 70
8.3 Gas compression — Expected revision of EN 12583:2014 . 70
8.4 Pipelines for maximum operating pressure over 16 bar — Expected revisions of
EN 1594:2013 . 71
8.5 Gas pressure control — Expected revisions of EN 12186:2014 and EN 12279:2000 71
8.6 Gas measuring systems — Expected revision of EN 1776:2015 . 74
8.7 Pipelines for maximum operating pressure up to and including 16 bar — Expected
revision of EN 12007 Parts 1 to 4 and EN 12327:2012 . 75
8.8 Pressure testing, commissioning and decommissioning procedures — Expected
revision of EN 12327:2012 . 78
8.9 Welding of steel — Expected revision of EN 12732:2013 . 79
8.10 Service lines — Expected revision of EN 12007-5:2014 . 79
8.11 Gas installation pipework– Expected revision of FprEN 15001-1:2019 and EN 15001-
2:2019 . 82
8.12 Gas pipework for buildings — Expected revision of EN 1775 . 86
8.13 Underground gas storage– Expected revision of EN 1918-1:2016 to -5:2016 . 87
8.14 Safety and Integrity Management System — Expected revision of EN 16348 and
EN 15399 by prEN 17649 (merged standard) . 92
Annex A (informative) Any issue coming up during the discussion and outside of the TC 234
scope . 93
Annex B (informative) Safety characteristics of natural gas-hydrogen mixtures . 94
Annex C (informative) Operating principles for gas warning devices [2] . 95
Annex D (informative) Hydrogen pressure versus hydrogen percentage . 97
Annex E (informative) Hydrogen pressure versus hydrogen fugacity . 98
Annex F (informative) An example of the use of an existing gas pipeline for hydrogen
gas . 100
Annex G (informative) Use of polyamide (PA-U) in gas piping systems in relation to
hydrogen, methane or their mixtures . 102
Annex H (informative) Netbeheer Nederland Study for biomethane and 100 %
hydrogen . 113
Annex I (informative) Responsibility of CEN/TC 234 'Gas infrastructure' Working groups
for the parts of the gas infrastructure along the chain . 115
Annex J (informative) Symbols and abbreviations . 116
Bibliography . 119

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European foreword
This document (FprCEN/TR 17797:2021) has been prepared by Technical Committee CEN/TC 234 “Gas
infrastructure”, the secretariat of which is held by DIN.
This document is currently submitted to Vote on TR.
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Introduction
The injection of hydrogen in natural gas infrastructures demands considerations with regard to the
integrity, safety and performance of the systems facing increasing hydrogen levels, its fluctuation and
variation.
There is extensive research on the use of hydrogen as an admixture with natural gas in various
percentages or as pure hydrogen. Impact studies already completed or in progress are focusing on the
use of existing gas networks but also of dedicated gas networks for hydrogen. They also include the
impact of the introduction of hydrogen in various percentages into the gas infrastructure on all the
existing technologies within the gas supply chain.
Accepting hydrogen into the natural gas network requires input from many gas TCs at CEN, i.e.
CEN/TC 234 and particularly from the manufacturers of essential components, e.g. valves, gas pressure
regulators, gas meters, safety control devices, leak detection devices, and many more (see Annex A). Many
of these manufacturers are assessing the potential impact of hydrogen on existing components in natural
gas service.
Co-operation with these other CEN and ISO/TCs for various essential components and applications will
be necessary to ensure that projects to introduce hydrogen have all the essential elements of the gas chain
fully co-ordinated into the plan. The positive co-operation of the component manufacturers will be
particularly important.
In the transition scheme to hydrogen, there is a large body of knowledge and experience available from
the hydrogen industry for gas production and use. The long-established safety requirements in this sector
will aid the amendment of natural gas standards and codes of practice and the development of any new
standards
This report is written for
— CEN/TC 234 as basis for definition of a TC roadmap for standardisation
— CEN/TC 234 WGs as a guideline for the standardisation work
— interested parties to get an insight in the decision process of CEN/TC 234’s hydrogen standardisation.
NOTE This document has been elaborated in co-operation between the Working Group convenors, secretaries
and experts, TC chair and secretariat of CEN/TC 234. Respecting different working group contributions, the way in
which the content is presented and the level of details differs for the different topics. This is acceptable as the real
technical work will take place in the dedicated working groups with co-ordination of the TC 234
Convenors/Secretaries group to ensure the final coherence of the resulting standardisation deliverables.
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1 Scope
This document is written in preparation of future standardization and provides guidance on how
injection of H into the gas infrastructure can impact processes from the input of gas into the on-shore
2
transmission network up to the inlet connection of gas appliances.
NOTE 1 Gas infrastructure includes gas installation pipework between the delivery point of the gas and the inlet
connection to the gas appliance in buildings and on industrial sites.
The assessments refer to the concentrations of 2, 5, 10, 20 and up to 100 Vol.- % hydrogen in natural gas.
Furthermore, it identifies the expected revision need of the existing CEN/TC 234 standards as well as the
need of further new standardisation deliverables.
It examines the effects on each part of the gas infrastructure in the scope of the CEN/TC 234 Working
Groups 1 to 12 inclusive, based on available studies, reports and research. Due to several limitations at
different hydrogen concentrations, the impacts are specified.
For some specific impact, pre-standardization research is needed.
By convention, for this technical report, the injection of pure hydrogen, i. e. without trace and/or minor
components is considered. Awareness is given that there is the need to consider trace and/or minor
components and limits set on the gas quality on European and national level, too.
The information from this report is intended to define the CEN/TC 234 work program for the coverage
of H NG in relation to the scope of the CEN/TC 234 and its WGs.
2
NOTE 2 Progress on hydrogen will develop over time. In principle this will be reflected in the standardisation
process in CEN/TC 234.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and abbreviations
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
The International Gas Union glossary on Underground Gas Storage [1] can be useful too:
3.1 Terms and definitions
3.1.1
hydrogen embrittlement
HE
interaction of hydrogen atoms and steel can have a negative effect on the mechanical behaviour of steel.
Note 1 to entry: The general term for this degrading effect is called hydrogen embrittlement
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3.2.2
explosive atmosphere
mixture with air, under atmospheric conditions, of flammable substances in the form of gases, vapours,
mists or dusts in which, after ignition has occurred, combustion spreads to the entire unburned mixture
[SOURCE: EN 13723:2013, 3.28]
3.2.3
hazardous explosive atmosphere
explosive atmosphere present in such quantities that precautions against ignition are required
[SOURCE: IEC 61340-4-4:2018, 3.6]
3.2.4
hazardous area
area in which an explosive atmosphere is present, or can be expected to be present, in quantities such as
to require special precautions for the construction, installation and use of equipment
[SOURCE: IEC 60079-0:2013]
3.2.5
explosion group
ranking of flammable gas-air mixtures with respect to the Maximum Experimental Safe Gap (MESG)
[SOURCE: EN ISO 16852:2016, 3.12.2]
3.2.6
temperature class
temperature range used for:
— classification of equipment, protective system for explosive atmospheres based on its maximum
surface temperature; or
— classification of flammable gases and vapours based on their auto ignition
[SOURCE: EN 13237:2012, 3.63]
3.2.7
explosion pressure
highest pressure occurring in a closed vessel during the explosion of a specific mixture of flammable
substances with air or air and inert gases determined under specified test conditions
[SOURCE: EN 15967:2011]
3.2.8
ignition temperature
lowest temperature (of a hot surface) at which under specified test conditions an ignition of a flammable
gas or flammable vapour in mixture with air or air/inert gas occurs
[SOURCE: EN 14522:2005]
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3.2.9
limiting oxygen concentration
LOC
maximum oxygen concentration in a mixture of a flammable substance and air and an inert gas, in which
an explosion will not occur, determined under specified test conditions
[SOURCE: EN 13237:2012, 3.49]
3.2.10
lower explosion limit
LEL
lowest concentration of the explosion range at which an explosion can occur
[SOURCE: EN 13237:2012, 3.19.1]
3.2.11
maximum experimental safe gap
MESG
maximum gap of the joint between the two parts of the interior chamber of a test apparatus which, when
the internal gas mixture is ignited and under specified conditions, prevents ignition of the external gas
mixture through a 25 mm long joint, for all concentrations of the tested gas or vapour in air
[SOURCE: EN 13237:2012, 3.51]
3.2.12
maximum explosion pressure
maximum value of explosion pressure measured in the tests for explosion pressure when the content of
the flammable substances in the mixture is varied
[SOURCE: EN 13237:2012, 3.2]
3.2.13
minimum ignition energy
MIE
lowest electrical energy stored in a capacitor, which upon discharge is sufficient to effect ignition of the
most ignitable atmosphere under specified test conditions
[SOURCE: EN 13237:2012, 3.54]
3.2.14
upper explosion limit
UEL
highest concentration of the explosion range at which an explosion can occur
[SOURCE: EN 13237:2012, 3.19.2]
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3.2.15
ventilation
movement of air and its replacement with fresh air due to the effects of wind, temperature gradients, or
artificial means (for example, fans or extractors)
[SOURCE: IEC 60079-10-0:2015]
3.2 Symbols and abbreviations
Symbols and abbreviations should be selected from those already established in relevant ISO and/or
CEN standards. New symbols and abbreviations should be defined only where there is no suitable
alternative and recorded in CEN/TC 234 Doc N 776 (so called N 215).
The symbols and abbreviations used in this document are listed in Annex J.
4 Executive summary
Intention of the European gas industry is to enable the use of natural gas infrastructure for hydrogen.
For the use of hydrogen in the natural gas infrastructure it is reasonable to identify
— the similarities (what is equal) and differences (what is different) between methane (natural gas)
a
...

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