prEN ISO 21009-1

SLOVENSKI STANDARD
01-julij-2024
Kriogene posode - Stabilne, vakuumsko izolirane posode - 1. del: Konstruiranje,
izdelava, nadzor in preskusi (ISO/DIS 21009-1:2024)
Cryogenic vessels - Static vacuum-insulated vessels - Part 1: Design, fabrication,
inspection and tests (ISO/DIS 21009-1:2024)
Kryo-Behälter - Stationäre vakuumisolierte Behälter - Teil 1: Konstruktion, Herstellung,
Kontrolle und Prüfung (ISO/DIS 21009-1:2024)
Récipients cryogéniques - Récipients fixes isolés sous vide - Partie 1: Conception,
fabrication, inspection et essais (ISO/DIS 21009-1:2024)
Ta slovenski standard je istoveten z: prEN ISO 21009-1
ICS:
23.020.40 Proti mrazu odporne posode Cryogenic vessels
(kriogenske posode)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 21009-1
ISO/TC 220
Cryogenic vessels — Static vacuum-
Secretariat: AFNOR
insulated vessels —
Voting begins on:
Part 1: 2024-06-06
Design, fabrication, inspection and
Voting terminates on:
2024-08-29
tests
Récipients cryogéniques — Récipients isolés sous vide
statiques —
Partie 1: Exigences de conception de fabrication, d'inspection, et
d'essais
ICS: ISO ics
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
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This document is circulated as received from the committee secretariat.
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Reference number
ISO/DIS 21009-1:2024(en)
DRAFT
ISO/DIS 21009-1:2024(en)
International
Standard
ISO/DIS 21009-1
ISO/TC 220
Cryogenic vessels — Static vacuum-
Secretariat: AFNOR
insulated vessels —
Voting begins on:
Part 1:
Design, fabrication, inspection
Voting terminates on:
and tests
Récipients cryogéniques — Récipients isolés sous vide
statiques —
Partie 1: Exigences de conception de fabrication, d'inspection, et
d'essais
ICS: ISO ics
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
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Published in Switzerland Reference number
ISO/DIS 21009-1:2024(en)
ii
ISO/DIS 21009-1:2024(en)
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 5
5 General requirements . 7
6 Mechanical loads. 7
6.1 General .7
6.2 Load during the pressure test.8
7 Chemical effects . 8
8 Thermal conditions . 8
9 Material. 8
9.1 General .8
9.2 Selection of materials .9
9.3 Inspection certificate .9
9.4 Materials for outer jackets and service equipment .9
10 Design . 9
10.1 Design options .9
10.1.1 General .9
10.1.2 Design by calculation .9
10.1.3 Design by calculation when adopting pressure strengthening (if allowed) .9
10.1.4 Design of components by calculation supplemented with experimental methods .10
10.2 Common design requirements .10
10.2.1 General .10
10.2.2 Design specification and documentation .10
10.2.3 Design loads .11
10.2.4 Inspection openings .14
10.2.5 Pressure relief .14
10.2.6 Valves . 15
10.2.7 Filling ratio .16
10.2.8 Electrical continuity .16
10.3 Design by calculation .16
10.3.1 General .16
10.3.2 Inner vessel .16
10.3.3 Outer jacket .18
10.3.4 Supports and lifting points .19
10.3.5 Piping and accessories .19
10.3.6 Calculation formulae . 20
10.3.7 Calculations for operating loads . 26
11 Fabrication .48
11.1 General . 48
11.2 Cutting . . 48
11.3 Cold forming . 49
11.3.1 Austenitic stainless steel . 49
11.3.2 Ferritic steel . 49
11.4 Hot forming. 50
11.4.1 General . 50
11.4.2 Austenitic stainless steel . 50
11.4.3 Ferritic steel . 50
11.5 Manufacturing tolerances .52
11.5.1 General .52

iii
ISO/DIS 21009-1:2024(en)
11.5.2 Plate alignment .52
11.5.3 Thickness .52
11.5.4 Dished ends . 53
11.5.5 Cylinders . 53
11.6 Welding . . 55
11.6.1 General . 55
11.6.2 Qualification . 55
11.6.3 Temporary attachments . 55
11.6.4 Welded joints . 55
11.7 Non-welded permanent joints . 56
12 Inspection and testing .56
12.1 Quality plan . 56
12.1.1 General . 56
12.1.2 Inspection stages during manufacture of an inner vessel . 56
12.1.3 Additional inspection stages during manufacture of a static cryogenic vessel .57
12.2 Production control test plates .57
12.2.1 Requirements .57
12.2.2 Extent of testing . 58
12.3 Non-destructive testing . 58
12.3.1 General . 58
12.3.2 Extent of examination for surface imperfections . 58
12.3.3 Extent of examination for weld imperfections .59
12.3.4 Acceptance levels .59
12.4 Rectification . 60
12.4.1 General . 60
12.4.2 Manually welded seams . 60
12.4.3 Seams produced using automatic welding processes . 60
12.5 Pressure testing .61
13 Marking and labelling . 61
14 Final assessment .62
15 Periodic inspection .62
Annex A (normative) Elastic stress analysis .63
Annex B (normative) Additional requirements for 9 % Ni steel .72
Annex C (normative) Pressure strengthening of vessels from austenitic stainless steels . 74
Annex D (informative) Pressure limiting systems .88
Annex E (normative) Further use of the material cold properties to resist pressure loads .89
Annex F (informative) Specific weld details .93
Annex G (normative) Additional requirements for flammable fluids .97
Annex H (informative) Flammable gas vents and relief systems .98
Annex I (normative) Outer jacket relief devices .99
Annex J (normative) Increased material property for austenitic stainless steel .100
Annex K (informative) Base materials .101
Annex L (normative) Cylindrical shells and dished ends subject to external pressure(pressure
on the convex surface) — Calculation .109
Annex M (normative) Design of openings in cylinders, spheres and cones — Calculation .114
Annex N (normative) Design of ends for internal pressure .125
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of Directive 2014/68/EU (Pressure Equipment Directive) aimed to be
covered .127

iv
ISO/DIS 21009-1:2024(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).
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. Details of any patent
rights identified during the development of the document will be in the Introduction and/or on the ISO list of
patent declarations received (see www.iso.org/patents).
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 21009-1:2022), which has been technically
revised.
The main changes are as follows:
— Subclause 11.6.1 Correction and specification of Welding Manufacture;
— Subclause 12.2.2; Correction of References and Table 5;
— Subclause C.3.1 Dividing the Table C.1.1 for European Material and C.1.2 Non-European Material;
— Subclause C.3.3 Correction for Test Plates related Cold strengthening;
— Subclause C.3.4 Correction of preparing of Test Plate;
— Subclause C.3.5 shifted;
— Subclause C.3.6 shifted;
— Subclause C.3.7 shifted;
— Annex K Dividing the Table K.1.1 for European Material and K.1.2 Non-European Material and Table K.2.1
for European Material and K.2.2 Non-European Material.
A list of all parts in the ISO 21009 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.

v
DRAFT International Standard ISO/DIS 21009-1:2024(en)
Cryogenic vessels — Static vacuum-insulated vessels —
Part 1:
Design, fabrication, inspection and tests
1 Scope
This document specifies requirements for the design, fabrication, inspection and testing of static vacuum-
insulated cryogenic vessels designed for a maximum allowable pressure of more than 0,5 bar.
This document applies to static vacuum-insulated cryogenic vessels for fluids and does not apply to vessels
designed for toxic fluids.
This document also gives guidance for static vacuum-insulated cryogenic vessels designed for a maximum
allowable pressure of not more than 0,5 bar.
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 3834-2, Quality requirements for fusion welding of metallic materials — Part 2: Comprehensive quality
requirements
ISO 3834-3, Quality requirements for fusion welding of metallic materials — Part 3: Standard quality
requirements
ISO 4126-2, Safety devices for protection against excessive pressure — Part 2: Bursting disc safety devices
ISO 4136, Destructive tests on welds in metallic materials — Transverse tensile test
ISO 5817, Welding — Fusion-welded joints in steel, nickel, titanium and their alloys (beam welding excluded) —
Quality levels for imperfections
ISO 9016, Destructive tests on welds in metallic materials — Impact tests — Test specimen location, notch
orientation and examination
ISO 9328-4, Steel flat products for pressure purposes — Technical delivery conditions — Part 4: Nickel-alloy
steels with specified low temperature properties
ISO 9606-1, Qualification testing of welders — Fusion welding — Part 1: Steels
ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel
ISO 10474:2013, Steel and steel products — Inspection documents
ISO 10675-1, Non-destructive testing of welds — Acceptance levels for radiographic testing — Part 1: Steel,
nickel, titanium and their alloys
ISO 14732, Welding personnel — Qualification testing of welding operators and weld setters for mechanized and
automatic welding of metallic materials
ISO 15613, Specification and qualification of welding procedures for metallic materials — Qualification based
on pre-production welding test

ISO/DIS 21009-1:2024(en)
ISO 15614-1:2017, Specification and qualification of welding procedures for metallic materials — Welding
procedure test — Part 1: Arc and gas welding of steels and arc welding of nickel and nickel alloys
ISO 17635, Non-destructive testing of welds — General rules for metallic materials
ISO 17636-1, Non-destructive testing of welds — Radiographic testing — Part 1: X- and gamma-ray techniques
with film
ISO 17636-2, Non-destructive testing of welds — Radiographic testing — Part 2: X- and gamma-ray techniques
with digital detectors
ISO 21009-2, Cryogenic vessels — Static vacuum insulated vessels — Part 2: Operational requirements
ISO 21010, Cryogenic vessels — Gas/material compatibility
ISO 21011, Cryogenic vessels — Valves for cryogenic service
ISO 21013-3, Cryogenic vessels — Pressure-relief accessories for cryogenic service — Part 3: Sizing and capacity
determination
ISO 21028-1, Cryogenic vessels — Toughness requirements for materials at cryogenic temperature — Part 1:
Temperatures below -80 degrees C
ISO 21028-2, Cryogenic vessels — Toughness requirements for materials at cryogenic temperature — Part 2:
Temperatures between -80 degrees C and -20 degrees C
ISO 23208, Cryogenic vessels — Cleanliness for cryogenic service
EN 13445-3, Unfired pressure vessels — Design
ASME Boiler and Pressure Vessel Code, Section VIII, Division 2: Alternative Rules
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
accessories
service equipment which has a safety-related function with respect to either pressure containment or
control or both
EXAMPLE Protective or limiting devices, controlling and monitoring devices, valves and indicators.
3.2
automatic welding
welding in which all operations are performed without welding operator intervention during the process
Note 1 to entry: Manual adjustment of welding variables by the welding operator during welding is not possible.
[SOURCE: ISO 14732:2013, 3.1]
3.3
bursting disc device
non-reclosing pressure relief device ruptured by differential pressure
Note 1 to entry: The bursting disc device is the complete assembly of installed components including, where
appropriate, the bursting disc holder.

ISO/DIS 21009-1:2024(en)
3.4
cryogenic fluid
refrigerated liquefied gas
gas which is partially liquid because of its low temperature
Note 1 to entry: This includes totally evaporated liquids and supercritical fluids.
Note 2 to entry: In the ISO 21009 series, the refrigerated, but non-toxic gases, and mixtures of them, shown in Table 1,
are referred to as cryogenic fluids.
Table 1 — Refrigerated but non-toxic gases
Classification
Identification number, name and description
code
3° A Asphyxiant gases
1 913 Neon, refrigerated liquid
1 951 Argon, refrigerated liquid
1 963 Helium, refrigerated liquid
1 970 Krypton, refrigerated liquid
1 977 Nitrogen, refrigerated liquid
2 187 Carbon dioxide, refrigerated liquid
2 591 Xenon, refrigerated liquid
3 136 Trifluoromethane, refrigerated liquid
3 158 Gas, refrigerated liquid, not otherwise specified (NOS)
3° O Oxidizing gases
1 003 Air, refrigerated liquid
1 073 Oxygen, refrigerated liquid
2 201 Nitrous oxide, refrigerated liquid, oxidizing
3 311 Gas, refrigerated liquid, oxidizing, NOS
3° F Flammable gases
1 038 Ethylene, refrigerated liquid
1 961 Ethane, refrigerated liquid
1 966 Hydrogen, refrigerated liquid (medium resistance criteria considered for Hydrogen)
1 972 Methane, refrigerated liquid or natural gas, refrigerated liquid, with high methane content
3 138 Ethylene, acetylene and propylene mixture, refrigerated liquid, containing at least 71,5 % ethylene
with not more than 22,5 % acetylene and not more than 6 % propylene
3 312 Gas, refrigerated liquid, flammable, NOS
The flammable gases, and mixtures of them, may be mixed with: helium, neon, nitrogen, argon, carbon dioxide.
Oxidizing and flammable gases shall not be mixed.
NOTE The classification code, identification number, name and description are according to UN codes.
3.5
documentation
technical documents delivered by the manufacturer to the owner
Note 1 to entry: Documentation consists of:
— all certificates establishing the conformity with this document (e.g. material, pressure test, cleanliness, safety
devices);
— a short description of the vessel (e.g. including characteristic data);
— a list of fluids and their net mass for which the cryogenic vessel is designed;
— an operating manual (for the user) that contains:
— a short description of the vessel (e.g. including characteristic data),

ISO/DIS 21009-1:2024(en)
— a statement that the vessel is in conformity with this document, and
— the instructions for normal operation (3.10).
3.6
gross volume
(3.7) internal volume of the inner vessel determined at minimum design temperature and
atmospheric pressure
3.7
inner vessel
pressure vessel intended to contain the cryogenic fluid (3.4) to be stored
3.8
manufacturer of the static cryogenic vessel
company that carries out the final assembly, including the final acceptance test, of the static cryogenic
vessel (3.17)
3.9
maximum allowable pressure
maximum pressure (3.13) permissible at the top of the vessel in its normal operating position
3.10
normal operation
intended operation of the vessel either up to the maximum allowable pressure (3.9) or subjected to handling loads
Note 1 to entry: Handling loads are exerted on the static cryogenic vessel (3.17) in all normal transport operations
including, e.g. loading, unloading, pressure loading during transportation, installation.
3.11
outer jacket
gas-tight enclosure which contains the inner vessel (3.7) and enables the vacuum to be established
3.12
piping system
tubes, pipes and associated components which can come in contact with cryogenic fluids (3.4) including
valves, fittings, pressure relief devices, and their supports
3.13
pressure
gauge pressure
pressure relative to atmospheric pressure
3.14
pressure strengthened vessel
pressure vessel, which has been subjected to a calculated and controlled internal pressure (strengthening
pressure) after completion
Note 1 to entry: The wall thickness of such a vessel is calculated on the basis of the stress at the strengthening pressure
and not on the basis of the conventional design stress value of the material used.
Note 2 to entry: Pressure vessels made from solution heat treated material will be subject to a controlled plastic
deformation during the strengthening operation as its yield point is raised. Pressure vessels made from work-
hardened material will be subject to little or no plastic deformation.
3.15
relief plate
plate retained by atmospheric pressure which allows relief of excess internal pressure, generally from the
vacuum jacket
ISO/DIS 21009-1:2024(en)
3.16
service equipment
accessories, equipment or instruments that will be used to measure the level, to fill or discharge the tank,
to vent the tank, to protect the tank against overpressure and to raise the tank pressure and its thermal
insulation
Note 1 to entry: The thermal insulation is a vacuum inter-space between the inner vessel (3.7) and the outer jacket (3.11).
3.17
static cryogenic vessel
thermally insulated vessel intended for use with one or more cryogenic fluids (3.4) in a stationary condition
Note 1 to entry: Static cryogenic vessels consist of inner vessel(s) (3.7), an outer jacket (3.11) and the piping system (3.12).
4 Symbols
A cross sectional area of reinforcing element mm
A area of reinforcing ring mm
A elongation at fracture %
s
b width of pad, ring or shell reinforcement mm
C design factors —
β
c allowances for corrosion mm
D shell diameter mm
D outside diameter e.g. of a cylindrical shell mm
a
D outside diameter of connected cylinder (see Figure 7) mm
a1
D outside diameter at effective stiffening (see Figure 9) mm
a2
D , D flat end diameters mm
1 2
D internal diameter e.g. of a cylindrical shell mm
i
D design diameter (see Figure 7) mm
k
D shell diameter at nozzle (see Figure 8) mm
s
d outside diameter of tube or nozzle mm
a
d diameter of opening mm
i
d d opening diameter mm
1, 2
E Young's modulus N/mm
f narrow side of rectangular or torispherical plate mm
H Safety coefficient for pressure test —
h thickness of pad-reinforcement mm
I moment of inertia of reinforcing element mm
K material property used for design (see 10.3.2.3.1) N/mm

ISO/DIS 21009-1:2024(en)
K material property at t °C used for design (e.g. K for material property N/mm
t 20
at 20 °C) (see 10.3.2.3.2)
L cone length between effective stiffenings (see Figure 9) mm
l ligament (web) between two nozzles mm
l buckling length mm
b
l′ length of nozzle reinforcement outstandings mm
s
l length of nozzle reinforcement in stand mm
s
m protruding length of nozzle mm
n number —
p design pressure as defined by 10.2.3.2.1 and 10.3.3.2 bar (or MPa)
p external pressure bar (or MPa)
e
p allowable external pressure limited by elastic buckling bar (or MPa)
e1
p allowable external pressure limited by elastic buckling including rein- bar (or MPa)
e2
forcement
p strengthening pressure bar (or MPa)
k
p allowable external pressure limited by plastic deformation bar (or MPa)
p
p maximum allowable gauge pressure bar (or MPa)
s
p test pressure [see 10.2.3.2.3] bar (or MPa)
T
R radius of curvature e.g. inside crown radius of dished end mm
r inside radius of knuckle mm
S safety factor at design pressure —
S safety factor against elastic buckling at design pressure —
k
S safety factor against plastic deformation at design pressure —
p
S safety factor against plastic deformation at proof test pressure —
T
s minimum wall thickness mm
s required wall thickness at opening edge mm
A
s actual wall thickness mm
e
s required wall thickness outside corner area mm
g
s required wall thickness within corner area mm
l
s wall thickness of nozzle mm
S
T temperature °C
t wall thickness of nozzle mm
ISO/DIS 21009-1:2024(en)
u out-of-roundness —
V factor indicative of the utilization of the permissible design stress in —
joints or factor allowing for weakenings
ν Poisson ratio —
x (decay-length zone) distance over which governing stress is assumed to mm
act
x characteristic lengths (i = 1,2,3) to define corner area [Figures 7 a) and mm
i
b) and 10.3.6.5.4]
Z auxiliary value —
φ cone angle °
σ design stress value N/mm
k
5 General requirements
5.1 The static cryogenic vessel shall safely withstand the mechanical and thermal loads and the chemical
effects encountered during pressure test and normal operation. These requirements are deemed to be
satisfied if Clauses 6 through 11 are fulfilled. The vessel shall be tested in accordance with Clause 12, marked
in accordance with Clause 13, and operated in accordance with ISO 21009-2.
5.2 Static cryogenic vessels shall be equipped with valves, pressure relief devices, etc., configured and
installed in such a way that the vessel can be operated safely. The number of openings in the inner vessel for
this equipment shall be kept to a minimum.
5.3 The static cryogenic vessel shall be clean for the intended service in accordance with ISO 23208.
5.4 The manufacturer shall retain the documentation, and all supporting documents (including those from
subcontractors, if any), taking legal compliance into consideration (e.g. product liability). In addition, the
manufacturer shall retain all supporting and background documents (including those from subcontractors,
if any) which establish that the vessel conforms to this document.
6 Mechanical loads
6.1 General
The static cryogenic vessel shall resist the mechanical loads mentioned in this clause without such
deformation which can affect safety and which can lead to leakage.
The mechanical loads to be considered are:
— loads exerted during the pressure test as specified in 6.2;
— loads imposed during installation and removal of the vessel;
— dynamic loads during transport of the vessel.
The following loads shall be considered to act in combination where relevant:
— a pressure equal to the maximum allowable pressure in the inner vessel and pipework;
— the pressure exerted by the liquid when filled to capacity;

ISO/DIS 21009-1:2024(en)
— loads produced by the thermal movement of the inner vessel, outer jacket and inter-space piping;
— full vacuum in the outer jacket;
— a pressure in the outer jacket equal to the set pressure of the relief device protecting the outer jacket;
— mass of vessel when filled to capacity;
— wind loads and other site conditions (e.g. seismic loads, thermal loads) to the vessel when filled to
capacity.
6.2 Load during the pressure test
The load exerted during the pressure test used for calculation shall be:
pH≥+p 1 bar or pH≥+pM01, Pa
() []()
Ts Ts
where
H is 1,43 in Europe and 1,3 in North America and for other parts of the world, a value consistent with
the applicable pressure vessel code;
+ 1 (in bar) or [+0,1 (in MPa)] is the allowance for external vacuum.
7 Chemical effects
Due to operating temperatures and the materials of construction, the possibility of chemical action on the
inner surfaces in contact with the cryogenic fluids can be discounted.
Due to the fact that the inner vessel is inside an evacuated outer jacket, neither external corrosion of the inner
vessel, nor corrosion on the inner surfaces of the outer jacket will occur. Therefore, inspection openings are
not required in the inner vessel or the outer jacket.
Corrosion allowance is also not required on surfaces in contact with the operating fluid or exposed to the
vacuum inter-space between the inner vessel and the outer jacket.
The material and the protection for the surfaces exposed to the atmosphere shall be suitable for intended
use (e.g. resistant to industrial and marine atmospheres).
8 Thermal conditions
The following thermal conditions shall be taken into account:
a) for the inner vessel and its associated equipment, the full range of temperatures expected;
b) for the outer jacket and equipment thereof [other equipment than covered by a)]:
— a minimum working t
...