prEN 18191

SLOVENSKI STANDARD
01-junij-2025
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: prEN 18191
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.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2025
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 draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 69.
If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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.
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 European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 18191:2025 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. 10
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)
............................................................................................................................................................................. 11
6.1 Hydrogen in low temperature applications . 11
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 . 12
6.2.4 Austenitic-ferritic steels . 12
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 . 13
6.2.10 Zirconium . 13
6.2.11 Other metallic materials . 14
6.3 High temperature hydrogen attack (HTHA) . 14
6.4 Hydrogen service with cyclic loads (fatigue) . 14
6.4.1 General requirements . 14
6.4.2 Fatigue in combination with the other hydrogen services (damage mechanisms) . 14
6.5 Non metallic materials . 14
7 Additional specifications . 15
7.1 Design . 15
7.1.1 General. 15
7.1.2 Design temperature . 15
7.1.3 Hydrogen partial pressure . 15
7.1.4 Tightness aspects . 15
7.2 Materials . 16
7.2.1 General. 16
7.2.2 Metallic and non metallic materials . 17
7.2.3 Delivery conditions of finished valve components . 17
7.3 Manufacture . 18
7.3.1 Welding . 18
7.3.2 Welding consumables . 19
7.3.3 Cold forming . 19
7.3.4 Strain hardening . 19
7.3.5 Hardness . 19
7.3.6 Mechanical properties of welds . 19
7.4 Final assessment . 19
7.5 Marking . 19
Annex A (informative) Harmonized European industrial valve product standards . 20
Annex B (informative) Materials for components of metallic industrial valves intended to be used
in hydrogen applications . 21
B.1 General . 21
B.2 Materials for hydrogen applications . 21
B.3 Overview of valve components made from metals and non-metals . 22
B.4 Operating mechanism sealings and other sealing components . 25
B.5 Operating mechanism sealings and other sealing components . 26
B.6 Lubricants. 26
B.7 Overviews of materials . 27
Annex C (normative) Tightness and additional testing . 56
C.1 General . 56
C.2 Definitions and symbols . 56
C.2.1 Test category . 56
C.2.2 TC Level . 56
C.2.3 Symbol . 56
C.2.4 Actuator . 56
C.3 Options . 56
C.4 Summary of inspection and testing . 57
C.4.1 General . 57
C.4.2 Determination of TC levels . 57
C.4.3 Application examples . 58
C.4.4 Summary of final assessment (inspection and testing) . 60
C.5 Inspection and test procedures, and acceptance criteria . 61
C.5.1 General requirements . 61
C.6 Inspection and test procedures, and acceptance criteria . 61
C.6.1 Shell and seat production test . 61
C.6.2 H2 low temperature service (liquid H2), production test . 62
C.7 Documentation . 62
C.8 Additional marking provisions . 63
Bibliography . 64

European foreword
This document (prEN 18191:2025) has been prepared by Technical Committee CEN/TC 69 “Industrial
valves”, the secretariat of which is held by AFNOR.
This document is currently submitted to the CEN Enquiry.

Introduction
Metallic industrial valves are considered as essential pressure accessories in hydrogen applications. They
are used in various hydrogen technologies 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
published in EN standards and establishes the relationship to harmonized EN standards covering
material, design considerations, specific manufacturing processes and final assessment (testing and
inspection).
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 technical
matters.
For this purpose, the standard 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).
The 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 19:2023, 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 1708-1, Welding — Basic welded joint details in steel — Part 1: Pressurized components
EN 1976, Copper and copper alloys — Cast unwrought copper products
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 10213+A1, Steel castings for pressure purposes
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 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, 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)
EN ISO 15848-2, Industrial valves — Measurement, test and qualification procedures for fugitive emissions
— Part 2: Production acceptance test of valves (ISO 15848-2:2015)
EN 16668:2025, Industrial valves — Requirements and testing for metallic valves as pressure accessories
EN ISO 28921-1:2022, Industrial valves — Isolating valves for low-temperature applications — Part 1:
Design, manufacturing and production testing (ISO 28921-1:2022)
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
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.
EXAMPLE The motion of hydrogen gas through air, or the movement of hydrogen gas through the wall of a
rubber hose.
3.2
gas permeability coefficient
number of moles of test gas passing through a test piece of unit thickness, per unit area, per unit time,
with unit partial-pressure difference between the two sides of the test piece
[SOURCE: ISO 2782-1:2022, 3.2]
3.3
gas solubility coefficient
test gas concentration inside a test piece divided by the partial pressure of the test gas at the surface of
the test piece
[SOURCE: ISO 2782-1:2022, 3.4]
3.4
gaseous hydrogen
hydrogen under gaseous form
[SOURCE: ISO 14687:2019, 3.10]
3.5
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]
3.6
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]
3.7
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.
3.8
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
3.9
hydrogen
colourless, odourless, tasteless, flammable substance that is the simplest chemical element in the periodic
table. It is virtually non-existent in its free form on earth and requires energy to liberate it from the
material forms in which it is found. Hydrogen can be produced either by electrolysis of water, or by a
chemical process
3.10
hydrogen applications
wide range of industrial processes handling hydrogen in the physical state gaseous or liquified and gas
mixtures with H in various concentrations
3.11
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.
3.12
hydrogen environmental embrittlement (HEE) / hydrogen induced cracking (HIC)
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
3.13
hydrogen partial pressure
total operating pressure multiplied by mol.- % or vol.- % of hydrogen
3.14
liquid hydrogen
hydrogen that has been liquefied, i.e. brought to a liquid state
[SOURCE: ISO 14687:2019, 3.1.15]
3.15
permeability
rate of transmission of a pressurized gas through a material
3.16
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
3.17
rapid gas decompression
RGD
Depressurization or 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, modified — NOTE 1 to entry added]
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 (H2S) 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. Annex B, Table B.1 provides an
overview
Note 1 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.
The valve manufacturer determines which trim components are loaded or not
[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
Note 1 to entry: Components that are neither pressure-bearing nor pressure-retaining components
Note 2 to entry: In the absence of standard requirements or unless otherwise agreed, the sub-components are to be
specified by the manufacturer
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 i.a. 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, a careful analysis of operating conditions, proper selection of material, suitable valve design
and effective quality control during all stages of engineering, processing and manufacturing are therefore
recommended. Proper maintenance and care are further 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 20172:2021.
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
(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 13480-3, Clause 10, resp. in accordance with EN 13445-3:2021, Clause 17 and 18

5.2 Non-metallic materials
Non-metallic materials exhibit varying behaviour in the presence of hydrogen. 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 considered 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 considered.
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
project.
Unless there is any other information available, a limitation to minus 40 °C (NL1) and to minus 50 °C
(NL2) is considered sound engineering practice.
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 (3EO, 7E0) and 1.2 (3E1, 8E2, 8E3):
— The nominal minimum yield strength shall be less than or equal to 360 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 (3EO, 7E0) 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 are slightly
susceptible to hydrogen embrittlement under certain conditions. A case-by-case verification is
therefore considered appropriate.
NOTE 2 More information can be found in Annex B, Table B.2.
d) Material of group 9.2 (7E3) 12Ni14 (1.5637, 1.5638) only 12Ni14 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 Annex B, 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 might 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+A1 are suitable for hydrogen dry environment applications
otherwise additional provisions should be addressed. Aluminium alloy EN AW 6061 is susceptible to
hydrogen embrittlement.
6.2.6 Cast irons
Cast irons are generally susceptible to hydrogen embrittlement.
Therefore, 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+A1 are suitable for hydrogen applications, whereby the above-
mentioned requirements for the corresponding material groups 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 and copper alloys shall be limited to oxygen-free grades
only.
The oxygen content shall be controlled by the manufacturer 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+A1.
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+A1 nor EN 12516-4+A1.
NOTE For nickel and nickel alloys HEE could also occur at temperatures above 170 °C.
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+A1 nor
EN 12516-4+A1.
6.2.10 Zirconium
Zirconium (material group 61 acc. to CEN ISO/TR 15608) are susceptible to hydrogen embrittlement.
Zirconium and Zirconium alloys are neither covered by EN 12516-1+A1 nor EN 12516-4+A1.
6.2.11 Other metallic materials
The outlined selection and provisions reflect a somewhat conservative state of experience for avoidance
of conventional hydrogen embrittlement within the existing hydrogen producing and processing
industry at the time of writing this document.
Materials with higher yield and/or tensile values may be used if experience is available for the particular
technical application or if further investigations have been made.
6.3 High temperature hydrogen attack (HTHA)
Austenitic stainless steel is generally not decarburised in hydrogen at any temperature or hydrogen
pressure, therefore materials of group 8.1 (10E0, 11E0, 12E0) are suitable.
NOTE When selecting ferritic steels, information provided in API RP 941 is useful to take in consideration.
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 is worth to
be considered 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.
The service life shall be specified by the valve manufacturer in the accompanying documentation, i.e.
operating instructions.
NOTE Provisions for determining whether cyclic loads are provided in EN 13480-3, Clause 10, respectively in
accordance with EN 13445-3:2021, Clauses 17 and 18.
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 embrittlement. 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 harmonized European valve standards listed in
Annex A shall apply.
Depend on the 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 done.
7.1.2 Design temperature
When selecting the materials, the entire temperature range shall be considered, not only those applicable
according to Table 1 of this document.
NOTE 1 With regard to austenitic stainless steels and their lowest minimum metal temperature TM, for
additional 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
Hydrogen partial pressure, according to 3.12, is total operating pressure multiplied by mol. - % or vol.
- % 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 glands is important in hydrogen service. It is therefore vital 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 devices shall be selected that provide long-term tightness.
NOTE The term “fugitive emissions” covers all losses of (usually volatile) substances due to unforeseen or
unintentional leaks.
Requirements for testing and maintenance of the sealing systems shall be specified in the accompanying
documentation, i.e. operating instructions.
The use of live loaded (energised) packing system is a preferred technique for fugitive emissions control.
Bellow seals shall not be used as the sole sealing element against atmosphere.
The tightness and additional testing are given in Annex C.
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 parts (pressure-bearing parts), within this document, are always made of metallic materials.
Internals can be made of both metallic and non-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 physically induced hydrogen
cracking (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
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