SIST EN ISO 20421-2:2017

SLOVENSKI STANDARD
oSIST prEN ISO 20421-2:2016
01-junij-2016
.ULRJHQHSRVRGH9HOLNHSUHPLþQHYDNXXPVNRL]ROLUDQHSRVRGHGHO=DKWHYH
]DREUDWRYDQMH,62',6
Cryogenic vessels - Large transportable vacuum-insulated vessels - Part 2: Operational
requirements (ISO/DIS 20421-2:2016)
Kryo-Behälter - Große ortsbewegliche vakuumisolierte Behälter - Teil 2:
Betriebsanforderungen (ISO/DIS 20421-2:2016)
Récipients cryogéniques - Grands récipients transportables, isolés, sous vide - Partie 2:
Exigences de fonctionnement (ISO/DIS 20421-2:2016)
Ta slovenski standard je istoveten z: prEN ISO 20421-2
ICS:
23.020.40 Proti mrazu odporne posode Cryogenic vessels
(kriogenske posode)
oSIST prEN ISO 20421-2:2016 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 20421-2:2016

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oSIST prEN ISO 20421-2:2016
DRAFT INTERNATIONAL STANDARD
ISO/DIS 20421-2.2
ISO/TC 220 Secretariat: AFNOR
Voting begins on: Voting terminates on:
2016-05-05 2016-07-04
Cryogenic vessels — Large transportable vacuum-insulated
vessels —
Part 2:
Operational requirements
Récipients cryogéniques — Grands récipients transportables, isolés, sous vide —
Partie 2: Exigences de fonctionnement
ICS: 23.020.40
ISO/CEN PARALLEL PROCESSING
This draft has been developed within the International Organization for
Standardization (ISO), and processed under the ISO lead mode of collaboration
as defined in the Vienna Agreement.
This draft is hereby submitted to the ISO member bodies and to the CEN member
bodies for a parallel five month enquiry.
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
To expedite distribution, this document is circulated as received from the
IN ADDITION TO THEIR EVALUATION AS
committee secretariat. ISO Central Secretariat work of editing and text
BEING ACCEPTABLE FOR INDUSTRIAL,
composition will be undertaken at publication stage.
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 20421-2.2:2016(E)
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. ISO 2016

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oSIST prEN ISO 20421-2:2016
ISO/DIS 20421-2.2:2016(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved

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oSIST prEN ISO 20421-2:2016
ISO/DIS 20421-2.2:2016(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Preliminaries before putting into service . 2
4.1 General . 2
4.2 Marking and labelling . 2
4.2.1 Marking . 2
4.2.2 Labelling (or placarding) . 3
4.3 Handover documents . 3
5 Personnel training . 3
6 General safety requirements . 4
6.1 General . 4
6.2 Safety considerations . 4
7 Putting into service . 5
8 Location . 5
9 Transport . 6
10 Filling . 6
10.1 General . 6
10.2 Prefill checks . 7
10.3 Preparations . 7
10.4 After-fill check . 8
11 Product withdrawal . 8
12 Change of service. 8
13 Taking out service . 9
14 Maintenance and repair . 9
15 Periodic inspection .10
16 Additional requirements for flammable gases .11
16.1 General safety requirements .11
16.1.1 General.11
16.1.2 Electrical equipment .11
16.1.3 Grounding (earthing) system .11
16.2 Putting into service (see also Clause 7) .12
16.3 Location (see also Clause 8) .12
16.4 Transport (see also Clause 9) .12
16.5 Filling (see also Clause 10) .12
16.6 Change of service (see also Clause 12) .12
16.7 Taking out of service (see also Clause 13) .12
16.8 Maintenance and repair (see also Clause 14).12
16.9 Emergency equipment and procedures .13
Bibliography .14
© ISO 2016 – All rights reserved iii

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oSIST prEN ISO 20421-2:2016
ISO/DIS 20421-2.2:2016(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 20421-2 was prepared by Technical Committee ISO/TC 220, Cryogenic vessels, Subcommittee, and
by Technical Committee CEN/TC 268, Cryogenic vessels in collaboration.
This second edition cancels and replaces the first edition of ISO 20421-2:2005, which has been
technically revised.
ISO 20421 consists of the following parts, under the general title Cryogenic vessels — Large transportable
vacuum-insulated vessels:
— Part 1: Design, fabrication, inspection and testing
— Part 2: Operational requirements
iv © ISO 2016 – All rights reserved

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oSIST prEN ISO 20421-2:2016
ISO/DIS 20421-2.2:2016(E)

Introduction
Elements of this part of ISO 20421 support the requirements of the UN-Recommendations on the
Transport of Dangerous Goods and other international, national or local requirements.
Large transportable cryogenic vessels are often partly equipped by the manufacturer, but may be
completed or re-equipped by another party, such as the operator or owner. For this reason some of the
scope of this part of ISO 20421, which includes putting into service, inspection, filling, maintenance and
emergency procedures, overlaps with ISO 20421-1.
This part of ISO 20421 applies to vessels for cryogenic fluids, primarily as specified in ISO 20421-1. It
may also be used for vessels for cryogenic fluids manufactured and designed to other standards, e.g.
EN 13530 2. In case of conflict between the requirements of this standard with applicable regulations,
regulations take precedence.
© ISO 2016 – All rights reserved v

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oSIST prEN ISO 20421-2:2016

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oSIST prEN ISO 20421-2:2016
DRAFT INTERNATIONAL STANDARD ISO/DIS 20421-2.2:2016(E)
Cryogenic vessels — Large transportable vacuum-insulated
vessels —
Part 2:
Operational requirements
1 Scope
This part of ISO 20421 specifies operational requirements for large transportable vacuum-insulated
cryogenic vessels.
The scope includes putting into service, filling, withdrawal, transport within the location, storage,
maintenance, periodic inspection and emergency procedures.
For the transport of these vessels by public road, rail, waterway, sea and air, additional requirements
can apply; these are defined in specific regulations.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 20421-1, Cryogenic vessels — Large transportable vacuum-insulated vessels — Part 1: Design,
fabrication, inspection and testing
ISO 23208, Cryogenic vessels — Cleanliness for cryogenic service
ISO 21010, Cryogenic vessels — Gas/materials compatibility
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
putting into service
operation by which a new vessel being used for the first time or an existing vessel being returned to
service is prepared for use
Note 1 to entry: ISO 20421-1 or similar design standard e.g. EN 13530-2
3.2
filling
operation by which a transportable vessel undergoes a prefill check, filling with a cryogenic fluid and
an after-fill check
3.3
withdrawal
operation by which the product is taken from a vessel connected to the supply system
© ISO 2016 – All rights reserved 1

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oSIST prEN ISO 20421-2:2016
ISO/DIS 20421-2.2:2016(E)

3.4
outdoor location
location outside of any building or structure and not enclosed by more than two walls or one wall if a
roof is also present
3.5
underground location
area or room whose ground or floor is on all sides significantly lower than the adjacent ground surfaces
3.6
large transportable cryogenic vessel a thermally insulated vessel of more than 450 l intended
for the transport of one or more cryogenic fluids, consisting of an inner vessel, an outer jacket,
all of the valves and service equipment together with the structural parts
Note 1 to entry: The large transportable cryogenic vessel comprises a complete assembly that is ready for service.
Note 2 to entry: A “large transportable cryogenic vessel” is hereinafter referred to as “vessel”.
3.7
authorized person
person authorized by the applicable regulations
3.8
enterprise
any person or company that has a legal duty of care
3.9
filler
any enterprise which loads cryogenic fluids into a cryogenic vessel
3.10
owner
enterprise that legally owns the cryogenic vessel
3.11
operator
any enterprise for filling, storage, transport and withdrawal of cryogenic product
3.12
Holding time
time that will elapse from the establishment of the initial filling condition until the pressure has risen
due to heat influx to the lowest set pressure of the pressure limiting device(s)
4 Preliminaries before putting into service
4.1 General
Before putting into service, verification shall take place to ensure that the vessel is suitable for the
intended service and that the marking, labelling and handover documents are complete.
4.2 Marking and labelling
4.2.1 Marking
Marking shall be in accordance with the applicable design standard and/or regulations, e.g. ISO 20421-1.
2 © ISO 2016 – All rights reserved

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oSIST prEN ISO 20421-2:2016
ISO/DIS 20421-2.2:2016(E)

4.2.2 Labelling (or placarding)
For labelling the following shall be affixed:
a) a flow sheet denoting operation;
b) danger labels and marks in accordance with transport regulations;
c) risk and safety phrases associated with the gas content;
d) name of the owner;
e) name of the operator;
f) actual holding time for gases being transported;
g) maximum permissible gross mass;
h) unladen (tare) mass;
i) an unshortened identification of the fluid which is transported in accordance with the transport and
substance regulations and its net mass in accordance with the documentation. As an alternative,
this information can be included in a transport document.
NOTE 1 The items a) to i) may appear on the tank, tank plate or transport document depending on the
requirements of the particular transport mode or operator requirements. Specific transport regulations must
always be consulted prior to carriage.
NOTE 2 Item e) to i) can be required by the design standards and don’t need to be repeated.
NOTE 3 The holding time has to be calculated for each journey in accordance with applicable transport
regulations.
4.3 Handover documents
In addition to the manufacturer’s documentation, where necessary the cryogenic vessel shall be
accompanied by vessel specific documents and instructions for all items supplied covering the
— operation;
— auxiliary equipment;
— inspection records.
These documents shall be retained by the owner of the vessel.
The operator shall have appropriate instructions available. Such instructions may be attached to the
vessel in a permanent manner, or carried by or available to the operator.
5 Personnel training
Only persons trained for the specific task shall be allowed to put into service, fill, handle, operate or
maintain the vessel and its equipment.
The training programme shall include:
— normal procedures;
— product and hazard identification;
— safe operating limits;
— emergency procedures;
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oSIST prEN ISO 20421-2:2016
ISO/DIS 20421-2.2:2016(E)

— physical and chemical properties of the vessel’s content and their effects on the human body;
— personal protection;
— confined spaces entry, if applicable.
Training shall be repeated as necessary to ensure that personnel remain competent. A record should be
maintained which details the training personnel have received.
6 General safety requirements
6.1 General
Before any operation the operator shall ensure that all equipment is free from any obvious damage or
defect which could affect its safe operation.
Marking and labelling shall not be removed or defaced.
Consideration shall be given to the product properties and the use of appropriate personal protective
equipment.
Parts under pressure shall be disconnected only if they have been previously depressurized.
Leaking valves or connections shall be depressurized before rectification. When this is not possible,
leaking valves under pressure shall be tightened using suitable tools and procedures.
Direct flame or direct intense heat shall never be used to raise the pressure or de-ice frozen components.
All surfaces which may come in contact with the product shall be clean for the intended service. For
cleanliness requirements, see ISO 23208.
Outlets, seals and transfer hoses shall be checked to be clean, dry and free from contaminants and
visible defects before connection.
Vessels and transfer hoses shall not be modified without proper authorization. It is recommended that
the couplings be attached to the vessels and/or hoses in a manner that prevents unauthorized removal
of the product couplings.
Operating valves should be opened and closed slowly.
6.2 Safety considerations
In all operations and training, the following safety considerations shall be taken into account.
— Small amounts of cryogenic fluids will produce large volumes of vaporized gas. Spillage of oxygen can
result in an oxygen-enriched atmosphere; spillage of other cryogenic fluids can result in an oxygen-
deficient atmosphere. Appropriate measures shall be taken for all these cases, e.g. ventilation.
— Because of the possibility of cold embrittlement, cryogenic fluids shall only be used in product
systems with components which are suitable for low temperatures.
— Vaporizing cryogenic fluids produce gases that are heavier than air and can accumulate in lower
areas (e.g. pits, trenches).
— Because of their extremely low temperatures, cryogenic fluids will produce cold burns when
coming into contact with the skin. Cold burns can also be produced from contact with uninsulated
equipment and piping.
— Oxygen enrichment due to liquefaction of ambient air can occur on the cold surfaces of uninsulated
equipment which contains a fluid with a boiling point lower than that of oxygen.
4 © ISO 2016 – All rights reserved

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oSIST prEN ISO 20421-2:2016
ISO/DIS 20421-2.2:2016(E)

— Consideration should be given to establishing proper safety distances during parking or product
transfer.
7 Putting into service
This operation shall follow a written procedure and the results of the steps involved should be recorded
(e.g. in a check list). Such lists should be retained by the operating company.
Vessels and accessories shall be visually checked for damage.
The following shall be verified.
— The vessel and accessories are appropriate for the intended service, comply with the flow sheet and
are appropriately marked and labelled; all labels shall be clearly displayed and appropriate for the
product.
— A relief device with a set pressure not higher than the maximum allowable working pressure of
the vessel is fitted. Pressure, size and installation shall comply with the documentation. Devices
requiring approval shall be correctly stamped and matching certificates shall be available.
— All valves are operable.
— All required checks and tests have been carried out.
Ensure that the vessel and accessories are clean and compatible for the intended service; see ISO 23208
and ISO 21010.
The vessel should be purged with an appropriate gas until the gas emerging from the vessel is
sufficiently dry and pure for the intended service.
The vessel shall be cooled down according to the manufacturer’s recommendations. Steps shall be
taken to avoid uncontrolled pressure rise due to rapid liquid vaporization. The cool-down gas chosen
shall take into account the risk of solidification.
Measuring and controlling devices (level gauge, pressure gauge, etc.) shall be checked for correct
operation and setting.
8 Location
The requirements listed in this clause are valid for storage and parking, as well as for other activities
such as filling and withdrawal.
— Vessels shall be located in a suitable area such as in the open air or in a sufficiently ventilated
enclosed area, away from sources of heat (welding source, open fire, etc.). Hot work shall be subject
to appropriate safety measures. The area shall be kept appropriately clean and suitable access shall
be provided.
— Adequate ventilation shall be provided. In locations at or above ground level, natural ventilation is
generally sufficient, provided that the room is large enough or that the outdoor area is not closely
surrounded by walls. In other circumstances, forced ventilation or other precautions shall be
provided.
— Vessels should not be located underground. However, where this is unavoidable, relief device
outlet(s) should be piped to a safe external venting point. As an alternative, appropriate marking
(e.g. indicating the risk of asphyxiation) and sufficient continuous ventilation to deal with product
releases should be provided. The vent pipework shall be designed in such a way as to ensure
proper pressure relief from the vessel and to prevent the accumulation or blockage of rainwater by
airborne material. The same measures shall be taken if vessels are indoors for extended periods (i.e.
overnight or weekends).
© ISO 2016 – All rights reserved 5

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oSIST prEN ISO 20421-2:2016
ISO/DIS 20421-2.2:2016(E)

— The floor of the designated trans-shipment area shall be level and strong enough to take the mass
of the full transport unit. The vessel shall be located at a sufficient distance from the normal paths
used by people or vehicles. Water accumulation in the vicinity of the vessel shall be avoided.
— For filling and withdrawing oxidizing liquids and cryogenic liquids colder than liquid nitrogen, the
connections shall be located over a non-combustible surface, like concrete.
— Vessels and their components shall be protected against mechanical damage.
— In case of emergency, adequate means of escape shall be provided. Emergency exits shall be kept
clear at all times.
— All doors/gates should be preferably outward opening and wide enough to provide an easy access
and exit route for personnel.
— A vessel should only be left parked unattended in a location such that operation of the vessel relief
devices will not constitute a hazard.
— The operating area should be clearly marked with appropriate warning signs. These may be
displayed on the vessel.
— Operation by unauthorized persons shall be prevented, e.g. by locking the valve cabinet.
When large transportable vessels are temporarily used as static vessels, the requirements defined for
static vessels shall be considered.
9 Transport
This clause refers to the transport of filled vessels. Additional requirements can apply for transport by
public road, rail, waterway, sea and air.
Before transport, the vessels shall be examined for signs of damage or leaks, and valves shall be checked
to ensure that they are operational and in the correct position.
Cryogenic vessels shall never be subjected to impacts or falls; these could damage the outer jacket or
the suspension system of the inner vessel, causing loss of insulating properties. If any vessel is known
to have been subjected to accidental impact or fall, this shall be reported to an appropriate authorized
person before further use.
Vehicles used for transport shall have well-ventilated cargo areas and shall have separate cargo and
passenger compartments. Vessels shall be transported in their correct position and shall be securely
fixed by appropriate means.
The vessels shall be handled only by those means for which they are designed and equipped.
Carriage of empty and uncleaned tank is adequately safe if suitable measures have been taken to
ensure equivalent safety commensurate with the provisions of the applicable regulation to prevent the
uncontrolled release of the dangerous goods.
10 Filling
10.1 General
The following operations shall be carried out in accordance with a written procedure following the
applicable regulation for filling limits (pressure, weight, temperature, etc.).
Holding times should be calculated and recorded as required by particular regulations.
6 © ISO 2016 – All rights reserved

...

SLOVENSKI STANDARD
oSIST prEN ISO 20421-2:2013
01-december-2013
.ULRJHQHSRVRGH9HOLNHSUHPLþQHYDNXXPVNRL]ROLUDQHSRVRGHGHO=DKWHYH
]DREUDWRYDQMH,62',6
Cryogenic vessels - Large transportable vacuum-insulated vessels - Part 2: Operational
requirements (ISO/DIS 20421-2:2013)
Kryo-Behälter - Große ortsbewegliche vakuumisolierte Behälter - Teil 2:
Betriebsanforderungen (ISO/DIS 20421-2:2013)
Récipients cryogéniques - Grands récipients transportables, isolés, sous vide - Partie 2:
Exigences de fonctionnement (ISO/DIS 20421-2:2013)
Ta slovenski standard je istoveten z: prEN ISO 20421-2
ICS:
23.020.40 Proti mrazu odporne posode Cryogenic vessels
(kriogenske posode)
oSIST prEN ISO 20421-2:2013 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 20421-2:2013

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oSIST prEN ISO 20421-2:2013
DRAFT INTERNATIONAL STANDARD
ISO/DIS 20421-2
ISO/TC 220 Secretariat: AFNOR
Voting begins on: Voting terminates on:
2013-09-19 2014-02-19
Cryogenic vessels — Large transportable vacuum-insulated
vessels —
Part 2:
Operational requirements
Récipients cryogéniques — Grands récipients transportables, isolés, sous vide —
Partie 2: Exigences de fonctionnement
[Revision of first edition (ISO 20421-2:2005)]
ICS: 23.020.40
ISO/CEN PARALLEL PROCESSING
This draft has been developed within the International Organization for
Standardization (ISO), and processed under the ISO lead mode of collaboration
as defined in the Vienna Agreement.
This draft is hereby submitted to the ISO member bodies and to the CEN member
bodies for a parallel five month enquiry.
Should this draft be accepted, a final draft, established on the basis of comments
received, will be submitted to a parallel two-month approval vote in ISO and
THIS DOCUMENT IS A DRAFT CIRCULATED
formal vote in CEN.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
To expedite distribution, this document is circulated as received from the
IN ADDITION TO THEIR EVALUATION AS
committee secretariat. ISO Central Secretariat work of editing and text
BEING ACCEPTABLE FOR INDUSTRIAL,
composition will be undertaken at publication stage.
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 20421-2:2013(E)
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. ISO 2013

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oSIST prEN ISO 20421-2:2013
ISO/DIS 20421-2:2013(E)

Copyright notice
This ISO document is a Draft International Standard and is copyright-protected by ISO. Except as
permitted under the applicable laws of the user’s country, neither this ISO draft nor any extract
from it may be reproduced, stored in a retrieval system or transmitted in any form or by any means,
electronic, photocopying, recording or otherwise, without prior written permission being secured.
Requests for permission to reproduce should be addressed to either ISO at the address below or ISO’s
member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Reproduction may be subject to royalty payments or a licensing agreement.
Violators may be prosecuted.
ii © ISO 2013 – All rights reserved

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oSIST prEN ISO 20421-2:2013
ISO/DIS 20421-2
Contents Page
Foreword . v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Preliminaries before putting into service . 2
4.1 General . 2
4.2 Marking and labelling . 2
4.2.1 Marking . 2
4.2.2 Labelling . 2
4.3 Handover documents . 3
5 Personnel training . 3
6 General safety requirements . 3
6.1 General . 3
6.2 Safety considerations . 4
7 Putting into service . 4
8 Location . 5
9 Transport . 6
10 Filling . 6
10.1 General . 6
10.2 Prefill checks . 6
10.3 Preparations . 7
10.4 After-fill check . 8
11 Product withdrawal . 8
12 Change of service . 8
13 Taking out service . 9
14 Maintenance and repair . 9
15 Periodic inspection . 10
16 Additional requirements for flammable gases . 11
16.1 General safety requirements . 11
16.1.1 General . 11
16.1.2 Electrical equipment . 11
16.1.3 Grounding (earthing) system . 11
16.2 Putting into service (see also Clause 7) . 11
16.3 Location (see also Clause 8) . 11
16.4 Transport (see also Clause 9) . 12
16.5 Filling (see also Clause 10). 12
16.6 Change of service (see also Clause 12) . 12
16.7 Taking out of service (see also Clause 13) . 12
16.8 Maintenance and repair (see also Clause 14) . 12
17 Emergency equipment and procedures . 12
Bibliography . 14
© ISO 2013 – All rights reserved iii

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oSIST prEN ISO 20421-2:2013
ISO/DIS 20421-2
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 20421-2 was prepared by Technical Committee ISO/TC 220, Cryogenic vessels, Subcommittee, and by
Technical Committee CEN/TC 268, Cryogenic vessels in collaboration.
This second edition cancels and replaces the first edition (2005 which has been technically revised.
ISO 20421 consists of the following parts, under the general title Cryogenic vessels — Large transportable
vacuum-insulated vessels:
 Part 1: Design, fabrication, inspection and testing
 Part 2: Operational requirements
iv © ISO 2013 – All rights reserved

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oSIST prEN ISO 20421-2:2013
ISO/DIS 20421-2
Introduction
Elements of this part of ISO 20421 support the requirements of the UN-Recommendations on the Transport of
Dangerous Goods and other international, national or local requirements.
Large transportable cryogenic vessels are often partly equipped by the manufacturer, but may be installed or
re-installed by another party, such as the operator or owner. For this reason some of the scope of this part of
ISO 20421, which includes putting into service, inspection, filling, maintenance and emergency procedures,
overlaps with ISO 20421-1.
© ISO 2013 – All rights reserved v

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oSIST prEN ISO 20421-2:2013

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oSIST prEN ISO 20421-2:2013
DRAFT INTERNATIONAL STANDARD ISO/DIS 20421-2

Cryogenic vessels — Large transportable vacuum-insulated
vessels — Part 2: Operational requirements
1 Scope
This part of ISO 20421 specifies operational requirements for large transportable vacuum-insulated cryogenic
vessels of more than 1 000 l volume.
The scope includes putting into service, filling, withdrawal, transport within the location, storage, maintenance,
periodic inspection and emergency procedures.
For the transport of these vessels by public road, rail, waterway, sea and air, additional requirements can
apply; these are defined in specific regulations.
This part of ISO 20421 applies to vessels for cryogenic fluids as specified in ISO 20421-1. The additional
requirements for flammable fluids are detailed in Clause 16.
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 20421-1, Cryogenic vessels — Large transportable vacuum-insulated vessels — Part 1: Design,
fabrication, inspection and testing
ISO 23208, Cryogenic vessels — Cleanliness for cryogenic service
ISO 21010, Cryogenic vessels — Gas/materials compatibility
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
putting into service
operation by which a new vessel being used for the first time or an existing vessel being returned to service is
prepared for use
3.2
filling
operation by which a transportable vessel undergoes a prefill check, filling with a cryogenic fluid and an after-
fill check
3.3
withdrawal
operation by which the product is taken from a vessel connected to the supply system
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3.4
outdoor location
location outside of any building or structure and not enclosed by more than two walls or one wall if a roof is
also present
3.5
underground location
area or room whose ground or floor is on all sides significantly lower than the adjacent ground surfaces
3.6
vessel
large transportable cryogenic vessel as defined in ISO 20421-1
3.7
authorized person
person authorized by the applicable regulations
3.8
enterprise
any person or company that has a legal duty of care
3.9
filler
any enterprise which loads cryogenic fluids into a cryogenic vessel
3.10
owner
enterprise that legally owns the cryogenic vessel
3.11
operator
any enterprise for filling, storage, transport and withdrawal of cryogenic product
4 Preliminaries before putting into service
4.1 General
Before putting into service, verification shall take place to ensure that the vessel is suitable for the intended
service and that the marking, labelling and handover documents are complete.
4.2 Marking and labelling
4.2.1 Marking
Marking shall be in accordance with the applicable design standard and/or regulations, e.g. ISO 20421-1.
4.2.2 Labelling
For labelling the following shall be affixed:
a) a flow sheet denoting operation;
b) an unshortened identification of the fluid which is transported in accordance with the transport and
substance regulations and its net mass in accordance with the documentation;
c) danger labels in accordance with transport regulations;
d) risk and safety phrases associated with the gas content;
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e) name of the owner;
f) name of the operator;
g) actual holding time for gases being transported;
h) maximum permissible gross mass;
i) unladen (tare) mass.
4.3 Handover documents
In addition to the manufacturer’s documentation, where necessary the cryogenic vessel shall be accompanied
by vessel specific documents and instructions for all items supplied covering the
 operation;
 auxiliary equipment;
 inspection records.
These documents shall be retained by the owner of the vessel.
The operator shall have appropriate instructions available. Such instructions may be attached to the vessel in
a permanent manner, or carried by or available to the operator.
5 Personnel training
Only persons trained for the specific task shall be allowed to put into service, fill, handle, operate or maintain
the vessel and its equipment.
The training programme shall include:
 normal procedures;
 product and hazard identification;
 safe operating limits;
 emergency procedures;
 physical and chemical properties of the vessel’s content and their effects on the human body;
 personal protection;
 confined spaces entry, if applicable.
Training shall be repeated as necessary to ensure that personnel remain competent. A record should be
maintained which details the training personnel have received.
6 General safety requirements
6.1 General
Before any operation the operator should ensure that all equipment is free from any obvious damage or defect
which could affect its safe operation.
Marking and labelling shall not be removed or defaced.
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Consideration should be given to the product properties and the use of appropriate personal protective
equipment.
Parts under pressure shall be disconnected only if they have been previously depressurized.
Leaking valves or connections should be depressurized before rectification. When this is not possible, leaking
valves under pressure shall be tightened using suitable tools and procedures.
Direct flame or direct intense heat shall never be used to raise the pressure or de-ice frozen components.
All surfaces which may come in contact with the product shall be clean for the intended service. For
cleanliness requirements, see ISO 23208.
Outlets, seals and transfer hoses shall be checked to be clean, dry and free from contaminants and visible
defects before connection.
Vessels and transfer hoses shall not be modified without proper authorization. It is recommended that the
couplings be attached to the vessels and/or hoses in a manner that prevents unauthorized removal of the
product couplings.
Operating valves should be opened and closed slowly.
6.2 Safety considerations
In all operations and training, the following safety considerations shall be taken into account.
 Small amounts of cryogenic fluids will produce large volumes of vaporized gas. Spillage of oxygen can
result in an oxygen-enriched atmosphere; spillage of other cryogenic fluids can result in an oxygen-
deficient atmosphere. Appropriate measures shall be taken for all these cases, e.g. ventilation.
 Because of the possibility of cold embrittlement, cryogenic fluids shall only be used in product systems
with components which are suitable for low temperatures.
 Vaporizing cryogenic fluids produce gases that are heavier than air and can accumulate in lower areas
(e.g. pits, trenches).
 Because of their extremely low temperatures, cryogenic fluids will produce cold burns when coming into
contact with the skin. Cold burns can also be produced from contact with uninsulated equipment and
piping.
 Oxygen enrichment due to liquefaction of ambient air can occur on the cold surfaces of uninsulated
equipment which contains a fluid with a boiling point lower than that of oxygen.
 Consideration should be given to establishing proper safety distances during parking or product transfer.
7 Putting into service
This operation shall follow a written procedure and the results of the steps involved should be recorded (e.g. in
a check list). Such lists should be retained by the operating company.
Vessels and accessories shall be visually checked for damage.
The following shall be verified.
 The vessel and accessories are appropriate for the intended service, comply with the flow sheet and are
appropriately marked and labelled; all labels shall be clearly displayed and appropriate for the product.
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 A relief device with a set pressure not higher than the maximum allowable working pressure of the vessel
is fitted. Pressure, size and installation shall comply with the documentation. Devices requiring approval
shall be correctly stamped and matching certificates shall be available.
 All valves are operable.
 All required checks and tests have been carried out.
Ensure that the vessel and accessories are clean and compatible for the intended service; see ISO 23208 and
ISO 21010.
The vessel should be purged with an appropriate gas until the gas emerging from the vessel is sufficiently dry
and pure for the intended service.
The vessel shall be cooled down according to the manufacturer’s recommendations. Steps shall be taken to
avoid uncontrolled pressure rise due to rapid liquid vaporization. The cool-down gas chosen shall take into
account the risk of solidification.
Measuring and controlling devices (level gauge, pressure gauge, etc.) shall be checked for correct operation
and setting.
8 Location
The requirements listed in this clause are valid for storage and parking, as well as for other activities such as
filling and withdrawal.
 Vessels shall be located in a suitable area such as in the open air or in a sufficiently ventilated enclosed
area, away from sources of heat (welding source, open fire, etc.). Hot work shall be subject to appropriate
safety measures. The area shall be kept appropriately clean and suitable access shall be provided.
 Adequate ventilation shall be provided. In locations at or above ground level, natural ventilation is
generally sufficient, provided that the room is large enough or that the outdoor area is not closely
surrounded by walls. In other circumstances, forced ventilation or other precautions shall be provided.
 Vessels should not be located underground. However, where this is unavoidable, relief device outlet(s)
should be piped to a safe external venting point. As an alternative, appropriate marking (e.g. indicating
the risk of asphyxiation) and sufficient continuous ventilation to deal with product releases should be
provided. The vent pipework shall be designed in such a way as to ensure proper pressure relief from the
vessel and to prevent the accumulation or blockage of rainwater by airborne material. The same
measures shall be taken if vessels are indoors for extended periods (i.e. overnight or weekends).
 The floor of the designated trans-shipment area shall be level and strong enough to take the mass of the
full transport unit. The vessel shall be located at a sufficient distance from the normal paths used by
people or vehicles. Water accumulation in the vicinity of the vessel shall be avoided.
 For filling and withdrawing oxidizing liquids and cryogenic liquids colder than liquid nitrogen, the
connections shall be located over a non-combustible surface, like concrete.
 Vessels and their components shall be protected against mechanical damage.
 In case of emergency, adequate means of escape shall be provided. Emergency exits shall be kept clear
at all times.
 All doors/gates should be preferably outward opening and wide enough to provide an easy access and
exit route for personnel.
 A vessel should only be left parked unattended in a location such that operation of the vessel relief
devices will not constitute a hazard.
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 The operating area should be clearly marked with appropriate warning signs. These may be displayed on
the vessel.
 Operation by unauthorized persons should be prevented, e.g. by locking the valve cabinet.
When large transportable vessels are temporarily used as static vessels, the requirements defined for static
vessels shall be considered.
9 Transport
This clause refers to the transport of filled vessels. Additional requirements can apply for transport by public
road, rail, waterway, sea and air.
Before transport, the vessels shall be examined for signs of damage or leaks, and valves shall be checked to
ensure that they are operational and in the correct position.
Cryogenic vessels shall never be subjected to impacts or falls; these could damage the outer jacket or the
suspension system of the inner vessel, causing loss of insulating properties. If any vessel is known to have
been subjected to accidental impact or fall, this shall be reported to an appropriate authorized person before
further use.
Vehicles used for transport should have well-ventilated cargo areas and shall have separate cargo and
passenger compartments. Vessels should be transported in their correct position and shall be securely fixed
by appropriate means.
The vessels shall be handled only by those means for which they are designed and equipped.
10 Filling
10.1 General
The following operations shall be carried out in accordance with a written procedure.
10.2 Prefill checks
Prior to filling, the filler shall examine the condition of the vessel as indicated in Table 1.
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Table 1 — Prefill checks
Acceptance criteria for filling

Labelling and marking
Data plate Present, legible and in accordance with 4.2
Inspection date Within required period
Product identification labels Fitted, legible and for the correct product
Vessel
No obvious signs of damage, corrosion, contamination, oil or grease
No unusual ice
No loss of vacuum
Accessories
All accessories (valves, PRD, No obvious signs of damage or corrosion
connections etc,)
Free from dirt, oil or grease
No unusual ice
Valves Operable
Pressure relief devices In place, free from ice and other visible obstructions
Appropriate connection fitted for product, identified by the product identification
Filling couplings and transfer hoses
label, and cap-fitted if required
Check for leakage and damage of hoses
Pressure gauge Positive pressure in vessel

An external visual inspection of the vessel and equipment shall be performed, to ensure that the vacuum
between inner vessel and outer jacket remains intact (checking of abnormal frosting on tank surface; gas
venting from a vacuum protection device; relief valves are continually venting). If the vessel has lost vacuum,
the owner of the cryogenic vessel shall immediately investigate the cause of the vacuum loss. Where a
vacuum loss is believed to be associated with an internal pipe failure, for example vapour escaping from the
vacuum relief device(s), then the cryogenic vessel must be made safe by immediately reducing the pressure
to atmospheric and emptying all cryogenic liquid in a safe manner. The reduction of pressure is the most
significant action to reduce the level of hazard. For more information, in particular to differentiate between loss
of vacuum and vacuum decay, see Appendix E of EIGA IGC doc 115/12 or CGA SB-45.
10.3 Preparations
The vehicle carrying the vessel shall be immobilized by an appropriate device.
Depending on the type of the cryogenic vessel, it may be filled to capacity either by volume or by mass, taking
into account product density to the level for which the vessel is designed. The necessary measuring
equipment shall be in good working order and within the calibration period, where required.
If there is no residual pressure in the vessel prior to filling, it should be purged to remove possible
contaminants. For carbon dioxide vessels, only gaseous carbon dioxide should be used for purging.
If the vessel is warm, it should be cooled down according to the manufacturer’s recommendations. Carbon
dioxide vessels shall be pressurized to at least 0,7 MPa (7 bar) with gaseous carbon dioxide before
introducing liquid CO
2
The purity of the residual product in the vessel shall be analysed and recorded where required by
specification. Where the purity of the residual product is outside specification, the vessel should be purged
until it meets specification.
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The fill hose should be securely connected, purged and cooled down.
Where it is necessary, the pressure shall be reduced by venting to facili
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