ISO 21013-1:2008

INTERNATIONAL ISO
STANDARD 21013-1
First edition
2008-06-15


Cryogenic vessels — Pressure-relief
accessories for cryogenic service —
Part 1:
Reclosable pressure-relief valves
Récipients cryogéniques — Dispositifs de sécurité pour le service
cryogénique —
Partie 1: Soupapes refermables





Reference number
ISO 21013-1:2008(E)
©
ISO 2008

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ISO 21013-1:2008(E)
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ISO 21013-1:2008(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 Requirements . 3
4.1 General. 3
4.2 Design . 3
4.2.1 Design temperature . 3
4.2.2 Drainage. 3
4.2.3 Stem guiding . 3
4.2.4 Inserts . 3
4.2.5 Sublimating fluids service . 3
4.2.6 Electric continuity. 3
4.2.7 Set pressure . 3
4.2.8 Minimum shell thickness . 3
4.3 Materials . 4
4.3.1 General. 4
4.3.2 Metallic materials. 4
4.3.3 Non-metallic materials. 4
4.3.4 Corrosion resistance. 4
4.3.5 Gas material compability . 5
4.3.6 Acetylene compatibility. 5
5 Qualification and Testing. 5
5.1 Type approval. 5
5.1.1 Verification of the design. 5
5.1.2 Model number . 5
5.2 Type approval tests . 5
5.2.1 Ambient condition tests. 5
5.2.2 Cryogenic tests . 6
5.2.3 Alternate cryogenic tests. 7
5.3 Production testing . 7
6 Determination of the certified coefficient of discharge (K ) . 7
dr
7 Set pressure tolerances . 8
8 Re-seating pressure . 8
9 Cleanliness . 8
10 Marking . 8
10.1 Marking on the body of the pressure-relief valve. 8
10.2 Marking on an identification plate. 8
11 Sealing . 9
Bibliography . 10

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ISO 21013-1:2008(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 21013-1 was prepared by Technical Committee ISO/TC 220, Cryogenic vessels.
ISO 21013 consists of the following parts, under the general title Cryogenic vessels — Pressure-relief
accessories for cryogenic service:
⎯ Part 1: Reclosable pressure-relief valves
⎯ Part 2: Non-reclosable pressure-relief devices
⎯ Part 3: Sizing and capacity determination


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INTERNATIONAL STANDARD ISO 21013-1:2008(E)

Cryogenic vessels — Pressure-relief accessories for cryogenic
service —
Part 1:
Reclosable pressure-relief valves
1 Scope
This International Standard specifies the requirements for the design, manufacture and testing of pressure
relief valves for cryogenic service, i.e. for operation with cryogenic fluids in addition to operation at
temperatures from ambient to cryogenic. It is a requirement of this International Standard that the valves
comply with ISO 4126-1; in the event of different requirements, this International Standard takes precedence.
This International Standard is restricted to valves not exceeding a size of DN 150 designed to relieve
single-phase vapours or gases. A valve may be specified, constructed and tested such that it is suitable for
use with more than one gas or with mixtures of gases.
NOTE This part of ISO 21013 does not provide methods for determining the capacity of relief valve(s) for a particular
cryogenic vessel. Such methods are provided in ISO 21013-3.
2 Normative references
The following referenced documents are indispensable for the application 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 4126-1, Safety devices for protection against excessive pressure — Part 1: Safety valves
ISO 11114-1, Transportable gas cylinders — Compatibility of cylinder and valve materials with gas contents —
Part 1: Metallic materials
ISO 11114-2, Transportable gas cylinders — Compatibility of cylinder and valve materials with gas contents —
Part 2: Non-metallic materials
ISO 15761, Steel gate, globe and check valves for sizes DN 100 and smaller, for the petroleum and natural
gas industries
ISO 20421-1, Cryogenic vessels — Large transportable vacuum-insulated vessels — Part 1: Design,
fabrication, inspection, and testing
ISO 21009-1, Cryogenic vessels — Static vacuum-insulated vessels — Part 1: Design, fabrication, inspection,
and tests
ISO 21010, Cryogenic vessels — Gas/materials compatibility
ISO 21028-1, Cryogenic vessels — Toughness requirements for materials at cryogenic temperature — Part 1:
Temperatures below — 80 °C
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ISO 21013-1:2008(E)
ISO 21028-2, Cryogenic vessels — Toughness requirements for materials at cryogenic temperature — Part 2:
Temperatures between –80 °C and –20 °C
ISO 21029-1, Cryogenic vessels — Transportable vacuum insulated vessels of not more than 1 000 litres
volume — Part 1: Design, fabrication, inspection and tests
ISO 23208:2005, Cryogenic vessels — Cleanliness for cryogenic service
ASME B16.34-2004, Valves — Flanged, Threaded, and Welding end
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
DN
nominal size
alphanumeric designation of size for components of a pipe work system, which is used for reference purposes
NOTE 1 It comprises the letters DN followed by a dimensionless whole number which is indirectly related to the
physical size, in millimetres, of the bore or outside diameter of the end connections.
NOTE 2 Adapted from ISO 6708.
3.2
pressure
pressure for which the value is equal to the algebraic difference between the absolute pressure and the
atmospheric pressure
NOTE This is also known as gauge pressure.
3.3
rated minimum temperature
lowest temperature for which the pressure relief valve is rated by the manufacturer
3.4
valve category A
relief valve type which passed the test of the repeatability of seat tightness at re-seat for 1 000 cycles
NOTE The procedure for the seat-tightness test is described in 5.2.1.2.
3.5
valve category B
relief valve type which passed the test of the repeatability of seat tightness at re-seat for 20 cycles
NOTE The procedure for the seat-tightness test is described in 5.2.1.2.
3.6
cryogenic fluid
fluid defined as cryogenic fluid in ISO 21029-1, or ISO 21009-1, or ISO 20421-1
NOTE This includes totally evaporated liquids and supercritical fluids.
3.7
rated pressure
PR
maximum pressure difference between the inside and outside of any pressure-retaining boundary for which it
is designed to be operated at 20 °C
NOTE The PR of the valve is the lowest PR of any component of the valve.
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ISO 21013-1:2008(E)
4 Requirements
4.1 General
The valve shall satisfy all the requirements of ISO 4126-1 except in the event of different requirements, where
this part of ISO 21013 takes precedence.
4.2 Design
4.2.1 Design temperature
The valve shall be suitable for operation at all temperatures between the rated minimum temperature and
+65 °C within the intended pressure range.
4.2.2 Drainage
Unless otherwise specified in the purchase order, the valve shall avoid accumulation of water within it, even
when the expected outlet connection is fitted.
4.2.3 Stem guiding
The design of guiding shall avoid malfunction of the valve due to deposition and freezing of atmospheric
moisture on and within the valve during normal operation. The valve shall be sufficiently robust such that the
effectiveness of the guiding can not be defeated by normal handling.
4.2.4 Inserts
Where a disc soft-insert is used to ensure leak-tight shut off, the design shall be such as to prevent cold flow
of the insert to a degree that results in the valve failing to operate correctly.
4.2.5 Sublimating fluids service
Where the valve is specified as suitable for service with products that, when vented at valve operating
conditions, condense from gas or vapour directly to solid, e.g. CO , the design shall be such as to avoid the

2
valve failing to operate correctly due to deposition of solid product within the valve body or its outlet.
4.2.6 Electric continuity
For valves in flammable fluids service, the maximum electrical resistance shall not exceed 1 000 Ω with no
more than 28 V between the ports in order to ensure electrical continuity to prevent build-up of static electrictiy.
4.2.7 Set pressure
Set pressure of the valve shall not exceed its PR.
4.2.8 Minimum shell thickness
The minimum shell thickness shall be as specified in ISO 15761 or ASME B16.34 for the pressure rating and
size of the valve.
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ISO 21013-1:2008(E)
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