FprEN ISO 21028-1

• Abstract:

  This document specifies the toughness requirements of metallic materials for use at a temperature below −80 °C to ensure their suitability for cryogenic vessels.; This document does not apply to unalloyed steels and cast materials.

• Status: Not Published
• Publication Date: 01-Dec-2026
• ICS: 23.020.40 - Cryogenic vessels
• Technical Committee: CEN/TC 268 - Cryogenic vessels
• Drafting Committee: CEN/TC 268 - Cryogenic vessels
• Current Stage: 6055 - CEN Ratification completed (DOR) - Publishing
• Start Date: 02-Oct-2026
• Completion Date: 02-Oct-2026
• Directive: 2008/68/EC - Directive 2008/68/EC of the European Parliament and of the council of 24 September 2008 on the inland transport of the dangerous goods
• Directive:

  ---

  2014/68/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/071 - Mandate to CEN for standardization in the field 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
• Mandate: M/TDG - Standards for referencing in the RID-ADR
• Ref Project: kSIST FprEN ISO 21028-1:2026 - Cryogenic vessels - Toughness requirements for materials at cryogenic temperature - Part 1: Temperatures below -80 degrees C (ISO/FDIS 21028‑1:2026)

• Consolidated By: ISO 21028-1:2026 - Cryogenic vessels — Toughness requirements for materials at cryogenic temperature — Part 1: Temperatures below ‒80 °C
• Effective Date: 12-Feb-2026
• Revises: EN ISO 21028-1:2016 - Cryogenic vessels - Toughness requirements for materials at cryogenic temperature - Part 1: Temperatures below -80 °C (ISO 21028-1:2016)
• Effective Date: 19-Jan-2023

FprEN ISO 21028-1 is a CEN/ISO draft standard for cryogenic vessels that sets toughness requirements for metallic materials used below -80 °C. It is written for material suppliers, vessel manufacturers, welders, test laboratories and inspectors who need to confirm that a material is suitable for cryogenic service. The document applies to metallic materials for cryogenic vessels, but not to unalloyed steels or cast materials.

What does FprEN ISO 21028-1 specify?

FprEN ISO 21028-1 specifies the toughness requirements for metallic materials used at temperatures below -80 °C so that they are suitable for cryogenic vessels. It organizes the subject into scope, references, terms and definitions, and detailed toughness requirements with test methods and acceptance criteria.

Annex	What it covers
Annex ZA	Relationship between this European Standard and Directive 2014/68/EU (Pressure Equipment Directive)

The main body is structured as:

• Clause 1 - Scope
• Clause 2 - Normative references
• Clause 3 - Terms and definitions
• Clause 4 - Toughness requirements, including materials, test methods, and acceptance criteria
• Annex ZA - Regulatory correspondence for the Pressure Equipment Directive

What are the key requirements of FprEN ISO 21028-1?

FprEN ISO 21028-1 requires toughness to be confirmed either by the material producer or by impact testing on each heat or lot of material. For welded vessels, impact tests are also required during welding procedure qualification and production weld tests, so toughness is checked both in the base material and in joined condition.

Steel materials

FprEN ISO 21028-1 requires steels, welds and heat-affected zones to meet the minimum impact energy or lateral expansion values in Table 1 at the minimum working temperature. Table 1 groups the requirements by steel type and service temperature, so the user must select the correct acceptance level for the material actually used.

Nickel alloy steels must meet EN 10028-4. In practice, that means the material specification is not enough on its own - the relevant low-temperature steel standard also has to be satisfied.

For cold stretched vessels, FprEN ISO 21028-1 sends the user to ISO 21009-1 Annex C or ISO 20421-1 Annex D. This matters because cold stretching changes the material condition and the vessel must be assessed against the dedicated requirements for that design route.

Aluminium and copper alloys

FprEN ISO 21028-1 treats aluminium or aluminium alloys, and copper or copper alloys, as inherently tough enough at low temperature for impact tests to be unnecessary. In practice, the material choice still needs to be correct, but this standard does not require the same impact-testing route for those metals as it does for steels.

Test methods and sampling

FprEN ISO 21028-1 bases the toughness tests on V-notch Charpy specimens to ISO 148-1. Standard specimens are used where possible, reduced-section specimens are allowed for thinner material, and no impact testing is carried out on plates thinner than 5 mm or on their welds.

For plates, the test pieces are taken transverse to the rolling direction. For welds and heat-affected zones, the sampling position depends on thickness, and Figures 1 to 3 show where the test pieces are taken. This matters because weld metal and heat-affected zones often govern cryogenic performance.

Acceptance criteria

FprEN ISO 21028-1 uses average values from sets of three specimens for impact energy and lateral expansion. It allows limited individual shortfalls, but only within defined limits, and it gives a second series of specimens when the first series is borderline. If the combined results still fail, the sample is rejected and the batch is retested.

For lateral expansion, each set of three specimens must meet the required value, and a limited retest route is possible only if the average still meets the requirement. If retesting fails, the material may be reheat-treated and tested again. In practice, this gives manufacturers a clear pass-fail route for confirming low-temperature toughness.

What terms does FprEN ISO 21028-1 define?

• Minimum working temperature - the lowest temperature likely to be reached by the vessel or one of its components during operation.
• Heat-affected zone - the part of the material next to a weld whose properties are altered by welding.
• Impact energy - the energy absorbed by a Charpy specimen during the pendulum impact test and used here as a toughness measure.
• Lateral expansion - the plastic widening measured opposite the notch in a Charpy test specimen, used as a second toughness criterion.
• Heat (lot) - the batch of material that is verified together when toughness is confirmed by testing.
• V-notch test piece - the notched Charpy specimen shape used for the impact tests in this standard.

Who uses FprEN ISO 21028-1?

FprEN ISO 21028-1 is used by cryogenic vessel manufacturers, material producers, welding engineers, inspection bodies, and quality managers. It is also relevant to buyers and specifiers who need to choose materials for vessels, welds and repairs used in cryogenic service. Because Annex ZA links the standard to the Pressure Equipment Directive, it is also useful in conformity assessment and regulatory work.

What changed in FprEN ISO 21028-1 from the previous edition?

FprEN ISO 21028-1 cancels and replaces ISO 21028-1:2016 as a technically revised edition. The stated changes are:

• expansion of Clause 2, the normative references
• addition of Table 1 in Clause 4.2 for steels

Which standards are used with FprEN ISO 21028-1?

• ISO 148-1 - gives the Charpy pendulum impact test method used for the toughness testing in this standard.
• EN 10028-4 - provides the low-temperature requirements for nickel alloy steels referenced for steel materials.
• ISO 21009-1 - supplies the annex used for cold stretched static vacuum-insulated vessels.
• ISO 20421-1 - supplies the annex used for cold stretched large transportable vacuum-insulated vessels.
• EN ISO 148-1:2016 - appears in Annex ZA as the edition linked to presumption of conformity under the Pressure Equipment Directive.

What does the FprEN ISO 21028-1 document contain?

FprEN ISO 21028-1 contains the core toughness rules, the Charpy-based test approach, and the acceptance criteria for materials used in cryogenic vessels below -80 °C. It also includes the material-specific section for steels, aluminium or aluminium alloys, and copper or copper alloys, plus the sampling rules for plates, welds and heat-affected zones. Figures 1 to 3 show test piece locations, Table 1 sets the steel toughness requirements, and Annex ZA maps the European Standard to Directive 2014/68/EU.

SLOVENSKI STANDARD
oSIST prEN ISO 21028-1:2024
01-maj-2024
Kriogene posode - Zahteve za žilavost materialov pri kriogenih temperaturah - 1.
del: Temperature pod –80 °C (ISO/DIS 21028-1:2024)
Cryogenic vessels - Toughness requirements for materials at cryogenic temperature -
Part 1: Temperatures below -80 degrees C (ISO/DIS 21028-1:2024)
Kryo-Behälter - Zähigkeitsanforderungen an Werkstoffe bei kryogenen Temperaturen -
Teil 1: Temperaturen unter −80 °C (ISO/DIS 21028-1:2024)
Récipients cryogéniques - Exigences de ténacité pour les matériaux à température
cryogénique - Partie 1: Températures inférieures à -80 degrés C (ISO/DIS 21028-
1:2024)
Ta slovenski standard je istoveten z: prEN ISO 21028-1
ICS:
23.020.40 Proti mrazu odporne posode Cryogenic vessels
(kriogenske posode)
oSIST prEN ISO 21028-1:2024 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN ISO 21028-1:2024
oSIST prEN ISO 21028-1:2024
DRAFT
International
Standard
ISO/DIS 21028-1
ISO/TC 220
Cryogenic vessels — Toughness
Secretariat: AFNOR
requirements for materials at
Voting begins on:
cryogenic temperature —
2024-03-25
Part 1:
Voting terminates on:
2024-06-17
Temperatures below -80 degrees C
Récipients cryogéniques — Exigences de ténacité pour les
matériaux à température cryogénique —
Partie 1: Températures inférieures à -80 degrés C
ICS: 23.020.40
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
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.
Reference number
ISO/DIS 21028-1:2024(en)
oSIST prEN ISO 21028-1:2024
DRAFT
ISO/DIS 21028-1:2024(en)
International
Standard
ISO/DIS 21028-1
ISO/TC 220
Cryogenic vessels — Toughness
Secretariat: AFNOR
requirements for materials at
Voting begins on:
cryogenic temperature —
Part 1:
Voting terminates on:
Temperatures below -80 degrees C
Récipients cryogéniques — Exigences de ténacité pour les
matériaux à température cryogénique —
Partie 1: Températures inférieures à -80 degrés C
ICS: 23.020.40
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2024
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 21028-1:2024(en)
ii
oSIST prEN ISO 21028-1:2024
ISO/DIS 21028-1:2024(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Toughness requirements . 1
4.1 General .1
4.2 Steels . . .2
4.3 Aluminium or aluminium alloys .2
4.4 Copper or copper alloys .2
4.5 Test methods .2
4.5.1 General .2
4.5.2 Test piece locations for plates .3
4.5.3 Test piece locations for welds and heat-affected zones .3
4.6 Acceptance criteria .5
4.6.1 For impact energy.5
4.6.2 For lateral expansion .5
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of Directive 2014/68/EU (Pressure Equipment Directive) aimed to be
covered . 7
Bibliography . 8

iii
oSIST prEN ISO 21028-1:2024
ISO/DIS 21028-1:2024(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 220 Cryogenic vessels.
This third edition cancels and replaces the second edition (ISO 21028-1:2016), which has been technically
revised.
The main changes are as follows:
— Expansion of the Section 2: Normative references;
— Addition of Table 1 – Impact Energy and Lateral Expansion Requirements for Steels in Section 4.2: Steels.
A list of all parts in the ISO 21028 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
oSIST prEN ISO 21028-1:2024
ISO/DIS 21028-1:2024(en)
Introduction
The use of materials at low temperatures entails special problems which are to be addressed. Consideration
is to be given, in particular, to changes in mechanical characteristics, expansion and contraction phenomena
and the thermal conduction of the various materials. Austenitic stainless steel can transform from the
austenitic to the martensitic phase when cooled down, leading to dimensional change that needs to be
considered during design.
However, the most important property to be considered is material to
...