ISO 21013-2:2025

International
Standard
ISO 21013-2
Second edition
Cryogenic vessels — Pressure-relief
2025-04
accessories for cryogenic service —
Part 2:
Non-reclosable pressure-relief
devices
Récipients cryogéniques — Dispositifs de sécurité pour le service
cryogénique —
Partie 2: Dispositifs de sécurité non refermables
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 2
4.1 General .2
4.2 Design .2
4.2.1 Design temperature .2
4.2.2 Coincident temperature .2
4.2.3 Sublimating fluid service .3
4.2.4 Inserts .3
4.3 Materials .3
4.3.1 General .3
4.3.2 Metallic materials .3
4.3.3 Non-metallic materials .3
4.3.4 Corrosion resistance .3
4.3.5 Gas/material compatibility .4
5 Testing. 4
5.1 Type approval of bursting-disc holders .4
5.2 Production testing .4
5.2.1 Pressure and operational tests .4
5.2.2 Additional tests for pressure-relief devices with non-replaceable bursting-disc
assemblies .4
6 Cleanliness . 4
7 Burst pressure tolerances . 5
8 Marking . . 5
9 Prevention of substitution . 5
Bibliography . 6

iii
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
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has been established has the right to be represented on that committee. International organizations,
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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
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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 second edition cancels and replaces the first edition (ISO 21013-2:2007), which has been technically
revised. It also incorporates the Amendment ISO 21013-2:2007/Amd. 1:2018.
The main changes are as follows:
— deletion of 4.3.5.3 because acetylene is not stored in cryogenic liquid state.
A list of all parts in the ISO 21013 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
International Standard ISO 21013-2:2025(en)
Cryogenic vessels — Pressure-relief accessories for cryogenic
service —
Part 2:
Non-reclosable pressure-relief devices
1 Scope
This document specifies the requirements for the design, manufacture and testing of non-reclosable
pressure-relief devices for cryogenic service, i.e. for operation with cryogenic fluids in addition to operation
at temperatures from ambient to cryogenic.
This document is restricted to bursting-disc and buckling-pin devices not exceeding a nominal diameter
size (DN) of 200 that are designed to relieve single-phase vapours or gases. A bursting-disc or buckling-pin
assembly can be specified, constructed and tested such that it is suitable for use with more than one gas or
with mixtures of gases.
NOTE This document does not provide methods for determining the capacity of bursting-disc or buckling-pin
devices for a particular cryogenic vessel. Such methods are provided in ISO 21013-3.
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.
ISO 4126-2, Safety devices for protection against excessive pressure — Part 2: Bursting disc safety devices
ISO 21010, Cryogenic vessels — Gas/material compatibility
ISO 21028-1, Cryogenic vessels — Toughness requirements for materials at cryogenic temperature — Part 1:
Temperatures below -80 °C
ISO 21028-2, Cryogenic vessels — Toughness requirements for materials at cryogenic temperature — Part 2:
Temperatures between ‒80 °C and ‒20 °C
ISO 23208, Cryogenic vessels — Cleanliness for cryogenic service
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4126-2 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
nominal size
DN
alphanumeric designation of size for components of a pipework system, which is used for reference purposes
Note 1 to entry: It comprises the letters DN followed by a dimensionless whole number which is indirectly related to
the physical size of the bore or outside diameter of the end connections.
[SOURCE: ISO 6708:1995, 2.1, modified — The original notes have been removed, and part of the definition
was moved to Note 1 to entry.]
3.2
pressure
gauge pressure
algebraic difference between the absolute pressure and the atmospheric pressure
3.3
rated minimum temperature
lowest temperature for which the pressure-relief device is rated
3.4
rated maximum temperature
highest temperature for which the pressure-relief device is rated
3.5
coincident temperature
temperature of the bursting disc associated with a bursting pressure and which is the expected temperature
of the bursting disc when it bursts
[SOURCE: ISO 4126-2:2018, 3.14, modified — “when it is required to burst” was changed to “when it bursts”.]
3.6
cryogenic fluid
gas that is partially liquid because of its low temperature
Note 1 to entry: Cryogenic fluids include totally evaporated liquids and supercritical fluids.
[SOURCE: ISO 21009-1:2022, 3.4, modified — Note 2 to entry was removed.]
4 Requirements
4.1 General
Non-reclosing pressure-relief devices shall satisfy the requirements of ISO 4126-2. In the event of conflicting
requirements, this document takes precedence over ISO 4126-2.
4.2 Design
4.2.1 Design temperature
The rated minimum temperature shall be equal to the equilibrium temperature at atmospheric pressure of
the coldest fluid to be relieved. The rated maximum temperature shall be +65 °C unless a higher temperature
is specified in the purchase order.
4.2.2 Coincident temperature
Unless otherwise specified in the purchase order, the coincident temperatures for normal ambient
conditions shall be 20 °C. Unless otherwise specified in the purchase order, the coincident temperatures
for fire conditions shall be no greater than 649 °C. Coincident temperatures for other conditions shall be
specified in the purchase order.

4.2.3 Sublimating fluid service
Where the pressure-relief device is specified as suitable for service with products that − when vented to
atmosphere from a pressure anywhere between the device’s specified maximum and minimum operating
pressures and at a temperature anywhere between the device’s specified maximum and minimum
temperatures − condense from gas or vapour directly
...