EN 18191:2026

• Abstract:

  This document applies to industrial metallic valves for hydrogen use. It contains recommendations and additional requirements applicable to material selection, design, manufacture, and final assessment.; This document addresses the following four services/damage mechanisms, which might exist in combinations:; — low temperature applications;; — hydrogen environmental embrittlement (HEE) or hydrogen-induced cracking (HIC);; — high temperature hydrogen attack (HTHA);; — hydrogen service with cyclic loads (fatigue).; This document considers the difference between gaseous hydrogen (GH2) and liquid hydrogen (LH2), where necessary.; The additional provisions set out in this document do not cover corrosion such as electro-chemical corrosion of metals under participation of hydrogen (e.g. sour gas).; This document is based on the requirements contained in the standards specified below:; — applications with a maximum allowable pressure PS greater than 0,5 bar in accordance with the European legislation for pressure equipment, the applicable provisions of EN 16668 apply;; — additional requirements for valves in chemical and petrochemical applications are specified in EN 12569;; — additional requirements for valves in gas distribution systems are specified in EN 13774;; — additional requirements for valves in gas transportation systems are specified in EN 14141.

• Status: Published
• Publication Date: 04-Aug-2026
• ICS: 23.060.01 - Valves in general
• ICS: 27.075 - Hydrogen technologies
• Technical Committee: CEN/TC 69 - Industrial valves
• Drafting Committee: CEN/TC 69/WG 19 - Valves for hydrogen applications and networks
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 05-Aug-2026
• Due Date: 16-Jul-2026
• Completion Date: 05-Aug-2026
• Directive: Harmonized Standard2014/68/EU - Directive 2014/68/EU of the European Parliament and of the Council of 15 May 2014 on the harmonisation of the laws of the Member States relating to the making available on the market of pressure equipment
• Mandate: M/601 - COMMISSION IMPLEMENTING DECISION of 1.3.2024 on a standardisation request to the European Committee for Standardization and the European Committee for Electrotechnical Standardization as regards pressure equipment and assemblies in support of Directive 2014/68/EU of the European Parliament and of the Council
• Ref Project: SIST EN 18191:2026 - Industrial valves - Additional requirements for metallic valves for hydrogen application

• Refers: EN 13479:2017 - Welding consumables - General product standard for filler metals and fluxes for fusion welding of metallic materials
• Effective Date: 02-Sep-2026
• Refers: EN 12266-2:2012 - Industrial valves - Testing of metallic valves - Part 2: Tests, test procedures and acceptance criteria - Supplementary requirements
• Effective Date: 02-Sep-2026

Overview

EN 18191:2026 - Industrial valves: Additional requirements for metallic valves for hydrogen application is an essential European standard developed by CEN. It establishes comprehensive guidelines and recommendations for industrial metallic valves intended for use in hydrogen applications. The document addresses specific hydrogen-related risks by providing additional requirements for material selection, design, manufacturing processes, and the final assessment of valves utilized in hydrogen environments.

This standard is particularly relevant as hydrogen technologies expand across industries such as energy, chemical processing, storage, transportation, and distribution. EN 18191:2026 supports the safe and reliable integration of metallic valves in systems handling both gaseous hydrogen (GH2) and liquid hydrogen (LH2), ensuring compliance with stringent safety regulations and proven engineering practices.

Key Topics

• Material Selection: Guidance for choosing materials resistant to hydrogen-specific damage, including embrittlement, high temperature hydrogen attack, and suitability under cyclic loads. Special attention is given to susceptibility of steels, stainless steels, cast irons, copper alloys, aluminium alloys, nickel, titanium, and zirconium in hydrogen applications.

• Design Considerations: Criteria for stress assessment, temperature ranges, and accommodation for hydrogen partial pressures in valves. Emphasis is placed on robust sealing, minimization of stress concentrators, and design provisions tailored to hydrogen’s unique properties.

• Manufacturing and Assembly: Requirements for welding (including consumables), cold forming, strain hardening, and quality control measures. Sound manufacturing practice is mandated to mitigate porosity, leakage risks, and to maintain structural integrity.

• Testing and Final Assessment: Testing protocols for tightness, shell and seat integrity, and specific tests for low temperature hydrogen service. The standard outlines inspection documentation and marking requirements to certify compliance.

• Damage Mechanisms Addressed:

  • Low temperature applications (including cryogenic hydrogen)
  • Hydrogen environmental embrittlement (HEE) / hydrogen-induced cracking (HIC)
  • High temperature hydrogen attack (HTHA)
  • Cyclic load fatigue in hydrogen service

• GH2 vs. LH2: Differentiates requirements where necessary, recognizing the distinct handling and operational challenges each hydrogen state presents.

Applications

EN 18191:2026 applies to the full lifecycle of metallic industrial valves used in hydrogen service, including:

• Hydrogen production plants: Valves in electrolyzers, reformers, and compression systems.
• Processing and storage: Cryogenic storage tanks, high-pressure vessels, and related piping networks.
• Transport and distribution: Hydrogen pipelines, fueling stations, and gas distribution networks.
• End-use sectors: Industrial applications, laboratories, chemical processing plants, and energy systems (including hydrogen fuel cells and renewable energy integration).

Adherence to this standard enables organizations to:

• Enhance safety and reliability in hydrogen systems.
• Prolong service life and reduce maintenance costs of valves.
• Demonstrate compliance with European safety directives and emerging hydrogen legislation.
• Facilitate interoperability and trade in the growing hydrogen value chain.

Related Standards

EN 18191:2026 is complemented by several other European standards to ensure comprehensive valve performance and safety:

• EN 16668: Requirements and testing for metallic valves as pressure accessories
• EN 12569: Chemical and petrochemical valve applications
• EN 13774: Gas distribution system valves
• EN 14141: Gas transportation system valves
• EN 12516 series: Valve design, materials, and component requirements
• EN 12266 series: Testing procedures for industrial valves
• EN 10213: Steel castings for pressure purposes
• EN ISO 28921: Isolating valves for low-temperature applications

These standards collectively establish a harmonized framework for the safe deployment of metallic industrial valves in hydrogen environments.

---

By following EN 18191:2026, industries adopting hydrogen technologies can optimize valve selection and system design, achieving superior safety, performance, and regulatory compliance across the hydrogen supply chain.

SLOVENSKI STANDARD
01-september-2026
Industrijski ventili - Dodatne zahteve za kovinske ventile za vodik
Industrial valves - Additional requirements for metallic valves for hydrogen application
Industriearmaturen - Zusätzliche Anforderungen an metallische Armaturen für
Wasserstoffanwendungen
Robinetterie industrielle - Exigences supplémentaires pour les appareils de robinetterie
métalliques pour application hydrogène
Ta slovenski standard je istoveten z: EN 18191:2026
ICS:
23.060.01 Ventili na splošno Valves in general
27.075 Tehnologija vodika Hydrogen technologies
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 18191
EUROPEAN STANDARD
NORME EUROPÉENNE
August 2026
EUROPÄISCHE NORM
ICS 23.060.01; 27.075
English Version
Industrial valves - Additional requirements for metallic
valves for hydrogen application
Robinetterie industrielle - Exigences supplémentaires Industriearmaturen - Zusätzliche Anforderungen an
pour les appareils de robinetterie métalliques pour metallische Armaturen für Wasserstoffanwendungen
application hydrogène
This European Standard was approved by CEN on 29 June 2026.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye 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
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 18191:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 General. 11
5 Hydrogen service (damage mechanisms) . 11
5.1 Metallic materials . 11
5.2 Non-metallic materials . 11
6 General information on material selection for each hydrogen service (damage
mechanism) . 12
6.1 Hydrogen in low temperature applications . 12
6.2 Hydrogen environmental embrittlement (HEE) . 12
6.2.1 General. 12
6.2.2 Ferritic steels except austenitic ferritic stainless steels . 12
6.2.3 Austenitic stainless steels . 13
6.2.4 Austenitic-ferritic steels . 13
6.2.5 Aluminium and aluminium alloys . 13
6.2.6 Cast irons . 13
6.2.7 Steel casting . 13
6.2.8 Copper and its alloys. 13
6.2.9 Nickel, nickel alloys, titanium and titanium alloys . 14
6.2.10 Zirconium . 14
6.2.11 Other metallic materials . 14
6.3 High temperature hydrogen attack (HTHA) . 14
6.4 Hydrogen service with cyclic loads (fatigue) . 16
6.4.1 General requirements . 16
6.4.2 Fatigue in combination with the other hydrogen services (damage mechanisms) . 16
6.5 Non metallic materials . 17
7 Additional specifications . 17
7.1 Design . 17
7.1.1 General. 17
7.1.2 Design temperature . 17
7.1.3 Hydrogen partial pressure . 17
7.1.4 Tightness aspects . 17
7.2 Materials . 18
7.2.1 General. 18
7.2.2 Metallic and non metallic materials . 19
7.2.3 Delivery conditions of finished valve components . 20
7.3 Manufacture . 20
7.3.1 Welding . 20
7.3.2 Welding consumables . 21
7.3.3 Cold forming . 21
7.3.4 Strain hardening . 21
7.3.5 Hardness of welds . 21
7.3.6 Mechanical properties of welds . 21
7.4 Final assessment . 21
7.5 Marking . 21
Annex A (informative) Harmonized European industrial valve product standards . 22
Annex B (informative) Materials for components of metallic industrial valves intended to be
used in hydrogen applications . 23
Annex C (normative) Tightness and additional testing . 54
Bibliography . 62
European foreword
This document (EN 18191:2026) has been prepared by Technical Committee CEN/TC 69 “Industrial
valves”, the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by February 2027, and conflicting national standards shall
be withdrawn at the latest by February 2027.
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.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United
Kingdom.
Introduction
Metallic industrial valves are considered as essential pressure accessories in hydrogen applications. They
are used in various hydrogen technologies and applications, for example production, processing, storage,
transportation, distribution, and usage.
Metallic industrial valves are integral pressure accessories of industrial piping, gas transportation and
distribution systems.
CEN/TC 69 worked in cooperation with the following other technical committees: CEN/TC 267,
CEN/TC 54, CEN/TC 234 and CEN/TC 235.
This document defines additional requirements for metallic industrial valves for hydrogen application
from those in published European standards.
The document is an application standard to provide consolidation of requirements on known and proven
solutions for hydrogen applications. Furthermore, it is intended to describe or exclude specific
specifications for hydrogen service.
For this purpose, this document addresses damage mechanisms of hydrogen services, which might exist
in combinations.
1 Scope
This document applies to industrial metallic valves for hydrogen use. It contains recommendations and
additional requirements applicable to material selection, design, manufacture, and final assessment.
This document addresses the following four services/damage mechanisms, which might exist in
combinations:
— low temperature applications;
— hydrogen environmental embrittlement (HEE) or hydrogen-induced cracking (HIC);
— high temperature hydrogen attack (HTHA);
— hydrogen service with cyclic loads (fatigue).
This document considers the difference between gaseous hydrogen (GH2) and liquid hydrogen (LH2),
where necessary.
The additional provisions set out in this document do not cover corrosion such as electro-chemical
corrosion of metals under participation of hydrogen (e.g. sour gas).
This document is based on the requirements contained in the standards specified below:
— applications with a maximum allowable pressure PS greater than 0,5 bar in accordance with the
European legislation for pressure equipment, the applicable provisions of EN 16668 apply;
— additional requirements for valves in chemical and petrochemical applications are specified in
EN 12569;
— additional requirements for valves in gas distribution systems are specified in EN 13774;
— additional requirements for valves in gas transportation systems are specified in EN 14141.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 19, Industrial valves - Marking of metallic valves
EN 736-1, Valves - Terminology - Part 1: Definition of types of valves
EN 736-2, Valves - Terminology - Part 2: Definition of components of valves
EN 736-3, Valves - Terminology - Part 3: Definition of terms
EN 1011 (all parts), Welding - Recommendations for welding of metallic materials
EN 1708-1, Welding - Basic welded joint details in steel - Part 1: Pressurized components
EN 1708-2, Welding - Basic weld joint details in steel - Part 2: Non internal pressurized components
EN 1976, Copper and copper alloys - Cast unwrought copper products
EN 12074, Welding consumables - Quality requirements for manufacture, supply and distribution of
consumables for welding and allied processes
EN 12266-1, Industrial valves - Testing of metallic valves - Part 1: Pressure tests, test procedures and
acceptance criteria - Mandatory requirements
EN 12266-2, Industrial valves - Testing of metallic valves - Part 2: Tests, test procedures and acceptance
criteria - Supplementary requirements
EN 13479, Welding consumables - General product standard for filler metals and fluxes for fusion welding
of metallic materials
EN 16668:2025, Industrial valves - Requirements and testing for metallic valves as pressure accessories
EN ISO 3651-2:1998, Determination of resistance to intergranular corrosion of stainless steels - Part 2:
Ferritic, austenitic and ferritic-austenitic (duplex) stainless steels - Corrosion test in media containing
sulfuric acid (ISO 3651-2:1998)
EN ISO 15792-1, Welding consumables - Test methods - Part 1: Preparation of all-weld metal test pieces
and specimens in steel, nickel and nickel alloys (ISO 15792-1)
EN ISO 15848-1:2015, Industrial valves - Measurement, test and qualification procedures for fugitive
emissions - Part 1: Classification system and qualification procedures for type testing of valves (ISO 15848-
1:2015)
EN ISO 15848-2, Industrial valves - Measurement, test and qualification procedures for fugitive emissions -
Part 2: Production acceptance test of valves (ISO 15848-2)
EN ISO 28921-1, Industrial valves - Isolating valves for low-temperature applications - Part 1: Design,
manufacturing and production testing (ISO 28921-1)
EN ISO 28921-2, Industrial valves - Isolating valves for low-temperature applications - Part 2: Type testing
(ISO 28921-2)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 736-1, EN 736-2, EN 736-3 and
the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
3.1
diffusion
flux of a fluid through another fluid or material due to concentration gradient
EXAMPLE The motion of hydrogen gas through air, or the movement of hydrogen gas through the wall of a
rubber hose.
Note 1 to entry: The diffusion coefficient is the mass of material diffusing across a unit of area in a unit of time at a
unit concentration gradient.
[SOURCE: ISO/TR 15916:2015, 3.29]
3.2
fugitive emission
chemical or mixture of chemicals, in any physical form, which represents an unanticipated or spurious
leak from equipment on an industrial site
[SOURCE: EN ISO 15848-1:2015, 3.5]
3.3
gaseous hydrogen
hydrogen under gaseous form
[SOURCE: ISO 14687:2019, 3.10]
3.4
glass transition
reversible change in an amorphous polymer or in amorphous regions of a partially crystalline polymer
from (or to) a viscous or rubbery condition to (or from) a hard and relatively brittle one
[SOURCE: EN ISO 472:2013, 2.440]
3.5
glass transition temperature
Tg
approximate midpoint of the temperature range over which the glass transition takes place
Note 1 to entry: The glass transition temperature varies significantly, depending upon the specific property and the
test method and conditions selected to measure it.
Note 2 to entry: The glass transition temperatures of polymers and elastomers describe the temperature ranges at
which polymers and elastomers turn from a hard, brittle material (below Tg) to a ductile or elastic material (above
or equal Tg).
[SOURCE: EN ISO 472:2013, 2.441, modified— Symbol “Tg” added, Note 2 to entry added]
3.6
hardness
property of a material involving resistance to indentation, deformation, and/or abrasion
Note 1 to entry: It is measured as yield strength, work hardening, true tensile strength, modulus of elasticity, and
other material characteristics.
3.7
high-temperature hydrogen attack
HTHA
damage mechanism which results from exposure of steels to hydrogen gas at elevated temperatures and
pressures; dissociated hydrogen atoms react with carbon and carbides in the steel to form CH4
3.8
hydrogen
colourless, odourless, tasteless and flammable substance that is the simplest chemical element in the
periodic table.
3.9
hydrogen applications
wide range of industrial processes handling hydrogen in the physical state gaseous or liquified and gas
mixtures with H in various concentrations
3.10
hydrogen compatibility
ability of a material to exhibit and maintain reliable mechanical integrity and low probability of failure,
or leakage, in hydrogen applications within accepted risk parameters
Note 1 to entry: Hydrogen compatibility is a function of material susceptibility, application, applied stress and
environment.
3.11
hydrogen environmental embrittlement
HEE
loss in strength, ductility, and/or fracture toughness of susceptible materials due to the penetration and
diffusion of atomic hydrogen resulting from gaseous environment that can lead to brittle cracking
Note 1 to entry: The term HEE is more appropriate to describe these phenomena, but in some parts of the industries
it might be referred to as hydrogen induced cracking (HIC).
3.12
hydrogen partial pressure
HPP
total operating pressure multiplied by mole fraction or percentage volume of hydrogen
Note 1 to entry: HPP is calculated as the mole fraction of hydrogen multiplied by the total pressure of the mixture.
3.13
liquid hydrogen
hydrogen that has been liquefied, i.e. brought to a liquid state
[SOURCE: ISO 14687:2019, 3.1.15]
3.14
permeability
rate of transmission of a pressurized gas through a material
[SOURCE: ISO/TR 15916:2015, 3.78]
3.15
permeation
flow of a media through another (usually solid) material by diffusion without a defect or opening of the
latter
Note 1 to entry: To be distinguished from leak flow which is not based on diffusion.
[SOURCE: ISO/TR 15916:2015, 3.79]
3.16
rapid gas decompression
RGD
depressurization
explosive decompression
rapid pressure-drop in a high pressure gas-containing system which disrupts the equilibrium between
external gas pressure and the concentration of gas dissolved inside any polymer, with the result that
excess gas tries to escape from the solution at points throughout the material, causing expansion
Note 1 to entry: If large enough, and if the pressure drop rate is faster than the natural gas diffusion rate, blistering
or rupturing can occur.
[SOURCE: ISO 23936-2:2011, 3.1.10]
3.17
shell
pressure containing envelope of the valve
Note 1 to entry: It normally comprises the body and when included in the design a bonnet or cover and the body.
[SOURCE: EN 736-2:2016, 3.1]
3.18
sour gas
gas containing significant amount of acid gases such as carbon dioxide and sulphur compounds
Note 1 to entry: Sour gas is failing the qualification as pipeline quality natural gas due to the inclusion of undesirable
components such as hydrogen sulfide (H S) or carbon dioxide in significantly greater amounts than those quoted
for pipeline quality natural gas.
[SOURCE: EN ISO 14532:2017, 2.1.1.8, modified — Notes to entry removed and new Note 1 to entry
added
3.19
trim
functional components of a valve excluding the shell components which are in contact with the fluid
inside the valve
Note 1 to entry: The components are specified in the relevant product standards. Table B.1 provides an overview.
Note 2 to entry: Metallic trim components are categorized into two subgroups, based on the requirement that the
component is under an applied stress for the effect of hydrogen degradation of metallic materials to occur:
— loaded: trim components that are under tension or torsion, that is either constant or cyclic;
— other: all other trim components, either with no applied load or in compression.
[SOURCE: EN 736-2:2016, 3.2, modified — Note 1 and Note 2 to entry added]
3.20
wetted sub-components
components fitted inside a valve exposed to or in direct contact with the medium, that do not fall under
the definition of trim nor shell
4 General
This document does not claim to define or restrict hydrogen applications as intended use in detail. It
considers hydrogen use applications as wide range of industrial processes handling hydrogen.
In the sense of an intended use, awareness should be given to the applicability of the specifications in this
document with regard to the selection of material, specific design considerations, specific manufacturing
processes and final assessment (testing and inspection).
Furthermore, the requirements of EN 16668 and, in addition, those of the respective application standard
as well as the relevant harmonized European valve standards listed in Annex A are considered.
The performance and life of valves that are exposed to hydrogen for long periods may be, among others,
limited by material characteristics that increase the susceptibility of metals to absorption and permeation
of hydrogen. To achieve an optimum between design life and service life of hydrogen-exposed valve
components, detailed analysis of operating conditions, appropriate selection of materials, suitable valve
design and effective quality control during all stages of engineering, processing and manufacturing are
therefore recommended. effective maintenance and monitoring are additional factors to consider.
Material groups used in this document are according to CEN ISO/TR 15608, EN 12516-1:2014+A1:2018,
Annex B, and EN 1092-1:2018, Annex B.
NOTE Further information on material groups and corresponding materials are provided in
CEN ISO/TR 20172.
5 Hydrogen service (damage mechanisms)
5.1 Metallic materials
Table 1 summarizes the services considered in this document. It contains damage mechanisms caused by
hydrogen (HEE, HTHA) or applications in combination with hydrogen which require additional
measures.
NOTE In Table 1 the temperature of 170 °C as lower limit of HTHA considers a safety margin of 30 °C.
Table 1 — Summary of services
Service/damage Hydrogen in low Hydrogen High Hydrogen
mechanism temperature Environmental Temperature service with
b
application Embrittlement Hydrogen cyclic loads
a,c
(HEE) Attack (HTHA) (fatigue)
Temperature −253 °C ≤ TS < −150 °C −150 °C ≤ TS < 170 °C TS ≥ 170 °C all
Hydrogen All pressures p (H ) > 1 bar p (H ) > 3,5 bar p (H ) > 1 bar
2 2 2
partial pressure
a
HEE typically occurs up to a temperature of 150 °C. The temperature of 170 °C is specified to close the gap
between HEE and HTHA.
b
In accordance with EN 13445-3:2021, Clause 17 and 18.
c
For nickel and nickel alloys HEE can also occur at temperatures above 170 °C.
5.2 Non-metallic materials
Non-metallic materials exhibit varying behaviour in the presence of hydrogen service. The damaging
mechanisms in the presence of hydrogen are different from those for metallic materials.
Some general information has been included in Annex B.
6 General information on material selection for each hydrogen service (damage
mechanism)
6.1 Hydrogen in low temperature applications
The proneness to brittle fracture of the selected materials shall be evaluated for the respective
application.
For multiple process operation modes (e.g. H2 purging, cool-down, warm-up…), other requirements
linked to HEE, HTHA damage mechanism that may apply shall be evaluated.
NOTE Hydrogen plants to low temperature covered by EN 13445, EN 13480, Annex B method 2 are in safe
operation for years. The influence of hydrogen to the transition temperature is investigated in separate scientific
projects.
Unless there is any other information available, a limitation to −40 °C (NL1) and to −50 °C (NL2) is
considered sound engineering practice according to harmonized material standards for plates, pipes and
forging.
6.2 Hydrogen environmental embrittlement (HEE)
6.2.1 General
Materials shall be selected for industrial valves intended for hydrogen applications.
In the following clauses, materials according to harmonized European material standards are considered.
6.2.2 Ferritic steels except austenitic ferritic stainless steels
Here are listed the main metallic materials:
a) Materials of group 1.1, 1.2 (3E0, 7E0, 7E1) and 1.2 (3E1, 8E2, 8E3):
— The nominal minimum yield strength shall be less than or equal to 370 MPa with a nominal
minimum tensile strength less than or equal to 620 MPa as defined within the applicable
material standard.
— Materials of group 1.1, 1.2 (3E0, 7E0, 7E1) and 1.2 (3E1, 8E2, 8E3) are suitable for hydrogen
applications.
NOTE 1 Values for yield strength or tensile strength are nominal values as per material standard at room
temperature.
b) Materials of group 5.1 (5E0), 5.2 (6E0) and 9.1 (7E2, 7E3): Materials belonging to these groups are
suitable for hydrogen applications.
c) Material of group 6.3 (-) 20CrMoV13-5-5 (1.7779): Materials belonging to this group can be
susceptible to hydrogen embrittlement and should be evaluated for application.
NOTE 2 More information can be found in Annex B, Table B.2.
d) Material of group 9.2 (7E3) namely 12Ni14 (1.5637) may be considered, provided the application
temperatures do not exceed 50°C and no welding takes place on the parent material.
NOTE 3 The advice can also be found in Table B.2.
6.2.3 Austenitic stainless steels
Materials of group 8.1 (11E0, 12E0, 13E0, 13E1, 14E0, 15E0) and 8.2 (13E0) are suitable for hydrogen
applications.
All materials of group 8.1 and 8.2 shall satisfactorily pass intergranular corrosion test (ICC) according to
EN ISO 3651-2:1998, Method A.
NOTE The intergranular corrosion test can be replaced by other methods to demonstrate a proper micro-
structure.
6.2.4 Austenitic-ferritic steels
Austenitic-ferritic steels of group 10.1 such as 1.4462 (16E0) are suitable for hydrogen applications if
cold forming is below 5 %. During processing, strain-hardening shall be avoided.
6.2.5 Aluminium and aluminium alloys
Aluminium alloys as specified in EN 12516-4 are suitable for hydrogen dry environment applications
otherwise additional provisions should be addressed. In case the aluminium alloy EN AW 6061 is used
for welded constructions, it is susceptible to hydrogen embrittlement.
6.2.6 Cast irons
The use of cast iron containing lamellar graphite shall be avoided.
Ductile cast iron may be selected based on suitability evaluation if product and application standards
provide for it.
6.2.7 Steel casting
Steel castings according to EN 10213 are suitable for hydrogen applications, whereby the requirements
mentioned for the corresponding material groups in this document shall be considered.
Due to the nature of casting a higher porosity can be expected. Adverse effects of porosity (e.g. leakage)
need to be considered. A sound casting design is crucial to enable foundries to achieve a high and
reproducible casting quality, especially around large changes in thickness. Castings shall not be peened,
plugged or impregnated.
NOTE Good manufacturing practice on casting quality and NDT can be found in EN 16668:2025, Annex E.
6.2.8 Copper and its alloys
Copper (material group 31 according to CEN ISO/TR 15608), and its alloys (material group 32-38
according to CEN ISO/TR 15608) can be embrittled in hydrogen gas due to a reaction between dissolved
hydrogen and oxygen (either in solution or from oxides) to form water, resulting in pores that promote
material failure. For this reason, the use of copper shall be limited to oxygen-free grades only. For copper
alloys (material groups 32-38 according to CEN ISO/TR 15608), the effect of deoxidation and oxygen
binding is achieved through alloying elements, so these material groups show no sensitivity to hydrogen.
The oxygen content shall be controlled so that the material conforms to the hydrogen embrittlement
requirements in accordance with EN 1976.
Some copper and its alloys (i.e. bronze, brass) are specified in EN 12516-4.
NOTE More information on copper and its alloys can be found in EIGA IGC Doc 121/14 and ISO/TR 15916.
6.2.9 Nickel, nickel alloys, titanium and titanium alloys
Nickel and nickel alloys (material group 41-48 according to CEN ISO/TR 15608) are generally considered
to be susceptible to hydrogen embrittlement. Nickel and nickel alloys are neither covered by
EN 12516-1 nor EN 12516-4.
Titanium and titanium alloys (material group 51-54 according to CEN ISO/TR 15608) are susceptible to
hydrogen embrittlement. Titanium and titanium alloys are neither covered by EN 12516-1 nor
EN 12516-4.
6.2.10 Zirconium
Zirconium (material group 61 according to CEN ISO/TR 15608) are susceptible to hydrogen
embrittlement. Zirconium and zirconium alloys are neither covered by EN 12516-1 nor EN 12516-4.
6.2.11 Other metallic materials
The selection and limits of 6.2.2 to 6.2.4 represent the intentionally conservative status reflecting user
experience within the existing hydrogen producing and processing industry at the time of writing this
document.
Materials with higher yield and/or tensile values can be used if experience is available for the particular
technical application or if further investigations have been made.
Materials not mentioned are not necessarily unsuitable for hydrogen services; rather, their omission
indicates a lack of data in European material standards. It is an obligation to assess and validate the
suitability of such materials for the use within HEE.
6.3 High temperature hydrogen attack (HTHA)
Material selection shall be based on Figure 1 and Table 2 using the relevant material temperature.
For materials not listed in Figure 1, the suitability for the relevant application shall be demonstrated.
NOTE 1 The safety margin of 30 °C (see NOTE in 5.1) is already considered in the graphs.
Key
X Hydrogen partial pressure (bar)
Y Temperature (°C)
a) Carbon steel welded with no PWHT
b) Carbon steel welded with PWHT
Figure 1 — Additional requirements for high temperature hydrogen attack (HTHA)
The relevant material temperature shall be determined, so that the actual metal temperature is
considered (for standard industrial valves the maximum operating temperature is taken into account).
An increase in operating temperature requires a re-verification of the material selection.
For industrial valves where the HTHA mechanism is considered a possible factor, the basis for material
selection shall be recorded in the related technical documentation.
Table 2 — Additional requirements for high temperature hydrogen attack (HTHA)
Material designation Group according to Examples of Remark
(used in Figure 1) EN 12516-1+A1 European
(group according to harmonized
CEN ISO/TR 15608:2017) materials
Carbon steel
3E0, 7E0, 7E1 The graphs in
(welded with no
(1.1, 1.2) Figure 1 for
PWHT)
refer to Annex B,
and Carbon Steels
Table B.2
Carbon steel
3E1, 8E2, 8E3 apply as well as
(welded with PWHT or
(1.2) 16Mo3 (1.5415).
non-welded)
Material designation Group according to Examples of Remark
(used in Figure 1) EN 12516-1+A1 European
(group according to harmonized
CEN ISO/TR 15608:2017) materials
1 Cr – 0,5 Mo 5E0
—
(5.1)
a
1,25 Cr – 0,5 Mo — —
2,25 Cr – 1,0 Mo 6E0 refer to Annex B,
—
(5.2) Table B.2
b
3 Cr – 1 Mo — —
b
6 Cr - 0,5 Mo — —
a
Higher chromium and molybdenum content enhance the resistance against hydrogen attack. Higher
alloyed materials such as those of group 6E0 can be used instead.
b
Higher chromium and molybdenum content enhance the resistance against hydrogen attack Higher
alloyed materials such as materials of group 9E0 and 9E01 can be used instead.
Austenitic stainless steels are generally not decarburised in hydrogen at any temperature or hydrogen
pressure, therefore 18-10 CrNi austenitic stainless steel materials of groups 10E0, 11E0, 12E0 (8.1) and
13E0 (8.2) are suitable. For examples on European harmonized materials refer to Annex B, Table B.3.
NOTE 2 For oxygen-containing unalloyed copper materials (material group 31 according to CEN ISO/TR 15608),
a reaction between copper oxide and hydrogen can occur at temperatures above 300 °C, resulting in water vapor
and copper (HTHA). In this material group, alloying with phosphorus can achieve deoxidation and bind remaining
oxygen (EN 1976).
NOTE 3 For copper alloys (material groups 32–38 according to CEN ISO/TR 15608), the effect of deoxidation
and oxygen binding is achieved through alloying elements, so these material groups show no sensitivity to
hydrogen.
6.4 Hydrogen service with cyclic loads (fatigue)
6.4.1 General requirements
Fatigue is a material failure mode particular to cyclic loading. Fatigue is arguably the most important
failure mechanism in structures subjected to cyclic stress, therefore this failure mechanism shall be
considered, if applicable, in the design of industrial valves subjected to pressure cycling.
For the assessment of fatigue life EN 12516-2:2014+A1:2021, Clause 12 applies.
When required by application, any specific limitations either for a reduced design life or the number of
cyclic loads shall be provided in the accompanying documentation.
6.4.2 Fatigue in combination with the other hydrogen services (damage mechanisms)
6.4.2.1 Low temperature service
Only austenitic steels, copper alloys and aluminium are considered in this case. As hydrogen has no
negative effects in this range of application, the materials mentioned in this document are suitable.
6.4.2.2 Hydrogen environmental embrittlement (HEE)
Shell of welded constructions should be avoided. If welded seams cannot be avoided, the welds shall be
designed as full-penetration seams and be designed in areas with low loads. Permanent backing strips
shall not be used.
6.4.2.3 High temperature hydrogen attack (HTHA)
Materials shall be selected in accordance with 6.3 considering high temperature hydrogen attack. The
rules for fatigue verification shall be fulfilled as a minimum.
Any additional requirements other than standard requirements should be agreed.
6.5 Non metallic materials
Material behaviour for selection of polymer and elastomer in gaseous hydrogen environment, obtained
from scientific literature data, are given in Annex B.
7 Additional specifications
7.1 Design
7.1.1 General
The design requirements of EN 16668 and the relevant European harmonized standards for valves are
applicable.
NOTE The list of harmonized European industrial valve product standards is given in Annex A.
Dependant upon application, further design-related requirements, as specified in the application
standards, should be considered. Information on some commonly used materials for metallic industrial
valves according to EN valve product standards, for use with hydrogen is provided in Annex B.
The design verification for the intended hydrogen use application and for the reasonably foreseeable
conditions should be completed.
7.1.2 Design temperature
When selecting the materials, the entire temperature range shall be considered, not only those applicable
according to Table 1.
NOTE 1 With regard to austenitic stainless steels and their lowest minimum metal temperature T , for additional
M
information are contained in EN 13480-2:2024, Table B.2-11, EN 13445, Table B.2-11.
NOTE 2 Further details related to toughness requirements of materials at cryogenic temperatures can be found
in EN ISO 21028-1.
7.1.3 Hydrogen partial pressure
The hydrogen partial pressure is the total operating pressure multiplied by the number of moles in
percentage or the volume in percentage of hydrogen. The limit value of partial pressure for each damage
mechanisms is specified in Table 1.
7.1.4 Tightness aspects
Positive sealing of packing is important in hydrogen service. Therefore that aspects affecting tightness
shall be considered. The operating frequency and wear as well as material ageing of sealing materials
have an influence on the service life of the sealing device and therefore ultimately on the tightness of a
valve.
Any foreseeable internal or external leakages (i.e. leakages into the atmosphere/environment) that could
pose a hazard due to pressure shall be identified as part of the analyses of hazards and risks.
Sealing components shall be selected for long-term tightness taking into account required frequency of
operation.
Requirements for testing and maintenance of the sealing systems shall be specified in the accompanying
documentation, i.e. operating instructions.
Bellow seals shall not be used as the sole sealing element against atmosphere and provide added
assurance to integrity.
The tightness and additional testing requirements are given in Annex C.
NOTE Annex C is not intended to be applied to safety accessories.
7.2 Materials
7.2.1 General
A valve consists of various components which are made of different metallic and non-metallic materials.
Each material that is used (for example, seats, seals, adhesives, lubricants, electrical insulation, springs,
bolts, and piping) shall be evaluated for its use in the design and foreseeable operating conditions to
which it is exposed.
Shell within this document, is always made of metallic materials.
A material should be evaluated carefully before it is used for hydrogen use application. The provisions in
this document focus on the main topic of avoiding damage caused by hydrogen embrittlement. Hydrogen
embrittlement is counteracted by suitable design and selection of materials. Materials that have been
used successfully with hydrogen should be preferred over materials with little or no history of use with
hydrogen.
For components of valves that are continuously exposed to hydrogen or may become exposed in case of
failure of seals, only materials suitable for hydrogen applications shall be selected.
Information on materials are provided in Annex B.
Where the behaviour of a material can be affected by manufacturing processes or operating conditions,
to an extent that would adversely affect the safety or service life of the metallic industrial valve, this shall
be taken into consideration when specifying material.
Adverse effects may arise from:
— manufacturing processes: e.g. degree of cold forming and heat treatment, reticulation or
crystallization degree, for thermoset and elastomer, or thermoplastics;
— operating conditions: e.g. hydrogen embrittlement, RGD.
When selecting materials and manufacturing methods the following subjects shall be considered:
— degradation effects of hydrogen on the mechanical performance of a material;
— material’s corrosion and wear resistance;
— electrical conductivity;
— impact strength;
— ductile behaviour;
— aging resistance;
— effects of temperature variations;
— effects arising when materials are combined (for example, galvanic corrosion).
NOTE Guidance to account for the degradation effects of hydrogen on the mechanical performance of a
material can be found in ISO/TR 15916.
Non-metallic materials shall retain their mechanical stability with respect to strength for the full range of
service conditions and design lifetime
7.2.2 Metallic and non metallic materials
7.2.2.1 Metallic materials
EN 16668 contains provisions to be observed when selecting shell materials.
Reference to materials for trim components are provided in the valve product standards.
NOTE EN 16668 provides an informative overview of European harmonized standards for materials for shell
parts.
7.2.2.2 Non metallic materials
In the selection of non-metallic materials, application standards and harmonized European valve
standards apply.
Hydrogen effect on non-metallic materials should be considered, this includes:
— diffusion;
— permeability;
— rapid gas decompression (RGD);
— low/elevated temperatures;
— thermal cycling;
— chemical compatibility;
...