Petroleum and natural gas industries - Site-specific assessment of mobile offshore units - Part 3: Floating units (ISO 19905-3:2021)

This document specifies requirements and recommendations for the site-specific assessment of mobile floating units for use in the petroleum and natural gas industries. It addresses the installed phase, at a specific site, of manned non-evacuated, manned evacuated and unmanned mobile floating units.
This document addresses mobile floating units that are monohull (e.g. ship-shaped vessels or barges); column-stabilized, commonly referred to as semi-submersibles; or other hull forms (e.g. cylindrical/conical shaped). It is not applicable to tension leg platforms. Stationkeeping can be provided by a mooring system, a thruster assisted mooring system, or dynamic positioning. The function of the unit can be broad, including drilling, floatel, tender assist, etc. In situations where hydrocarbons are being produced, there can be additional requirements.
This document does not address all site considerations, and certain specific locations can require additional assessment.
This document is applicable only to mobile floating units that are structurally sound and adequately maintained, which is normally demonstrated through holding a valid RCS classification certificate.
This document does not address design, transportation to and from site, or installation and removal from site.
This document sets out the requirements for site-specific assessments, but generally relies on other documents to supply the details of how the assessments are to be undertaken. In general:
—     ISO 19901‑7 is referenced for the assessment of the stationkeeping system;
—     ISO 19904‑1 is referenced to determine the effects of the metocean actions on the unit;
—     ISO 19906 is referenced for arctic and cold regions;
—     the hull structure and air gap are assessed by use of a comparison between the site-specific metocean conditions and its design conditions, as set out in the RCS approved operations manual;
—     ISO 13624‑1 and ISO/TR 13624‑2[1] are referenced for the assessment of the marine drilling riser of mobile floating drilling units. Equivalent alternative methodologies can be used;
—     IMCA M 220 is referenced for developing an activity specific operating guidelines. Agreed alternative methodologies can be used.
NOTE    RCS rules and the IMO MODU code[13] provide guidance for design and general operation of mobile floating units.

Erdöl- und Erdgasindustrie - Beurteilung von mobilen Offshore-Einheiten bezüglich ihres Einsatzgebietes - Teil 3: Schwimmende Einheiten (ISO 19905-3:2021)

Industries du pétrole et du gaz naturel - Évaluation spécifique au site d'unités mobiles en mer - Partie 3: Unités flottantes (ISO 19905-3:2021)

Le présent document spécifie les exigences et les recommandations pour l'évaluation spécifique au site d'unités mobiles flottantes destinées à être utilisées dans les industries du pétrole et du gaz naturel. Il traite de la phase en place, au niveau d'un site spécifique, d'unités mobiles flottantes occupées par du personnel non évacué, occupées par du personnel évacué et non occupées par du personnel.
Le présent document traite des unités mobiles flottantes monocoques (par exemple, structures à profil de bateau ou barges); stabilisées par des colonnes, souvent désignées par le terme «structures semi-submersibles»; ou ayant d'autres formes de coque (par exemple, cylindriques/coniques). Il n'est pas applicable aux plates-formes à lignes d'ancrage verticales tendues (TLP). Le maintien en position peut être assuré par un système d'ancrage, un système d'ancrage assisté par des propulseurs, ou un système de positionnement dynamique. L'unité peut avoir plusieurs fonctions, notamment des fonctions de forage, d'hôtel flottant, de barge, etc. Dans les situations où des hydrocarbures sont produits, des exigences supplémentaires peuvent s'appliquer.
Le présent document ne traite pas de toutes les considérations relatives au site, et certains emplacements peuvent nécessiter une évaluation supplémentaire.
Le présent document n'est applicable qu'aux unités mobiles flottantes dont la structure est saine et entretenue de manière adéquate, ce qui est normalement démontré par la tenue à jour d'un certificat de classification en cours de validité, délivré par une société de classification reconnue (RCS).
Le présent document ne traite pas de la conception, du transport vers et depuis un site ou de l'installation et du retrait du site.
Le présent document spécifie les exigences pour des évaluations spécifiques aux sites, mais s'appuie généralement sur d'autres documents pour fournir les informations détaillées sur la manière dont les évaluations doivent être effectuées. En général:
—          l'ISO 19901-7 est citée en référence pour l'évaluation du système de maintien en position;
—          l'ISO 19904-1 est citée en référence pour la détermination des effets des actions océano-météorologiques sur l'unité;
—          l'ISO 19906 est citée en référence pour les régions arctiques et froides;
—          la structure de la coque et la garde d'air sont évaluées en procédant à une comparaison entre les conditions océano-météorologiques spécifiques au site et les conditions de conception de la coque, comme indiqué dans le manuel d'exploitation approuvé par une société de classification reconnue (RCS);
—          l'ISO 13624-1 et l'ISO/TR 13624-2[1] sont citées en référence pour l'évaluation des tubes prolongateurs pour les forages en mer des unités de forage mobiles flottantes. D'autres méthodologies équivalentes peuvent être utilisées;
—          l'IMCA M 220 est citée en référence pour l'élaboration d'un document d'instructions d'exploitation spécifiques à l'activité. D'autres méthodologies approuvées peuvent être utilisées.
NOTE  Les règles RCS et le code MODU de l'OMI[13] fournissent des recommandations pour la conception et l'exploitation générale des unités mobiles flottantes.

Industrija za predelavo nafte in zemeljskega plina - Ocenjevanje premičnih naftnih ploščadi na področju postavitve - 3. del: Plavajoče enote (ISO 19905-3:2021)

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SLOVENSKI STANDARD
oSIST prEN ISO 19905-3:2022
01-april-2022

Industrija za predelavo nafte in zemeljskega plina - Ocenjevanje premičnih naftnih

ploščadi na področju postavitve - 3. del: Plavajoče enote (ISO 19905-3:2021)

Petroleum and natural gas industries - Site-specific assessment of mobile offshore units

- Part 3: Floating units (ISO 19905-3:2021)

Erdöl- und Erdgasindustrie - Beurteilung von mobilen Offshore-Einheiten bezüglich ihres

Einsatzgebietes - Teil 3: Schwimmende Einheiten (ISO 19905-3:2021)

Industries du pétrole et du gaz naturel - Évaluation spécifique au site d'unités mobiles en

mer - Partie 3: Unités flottantes (ISO 19905-3:2021)
Ta slovenski standard je istoveten z: prEN ISO 19905-3
ICS:
75.180.10 Oprema za raziskovanje, Exploratory, drilling and
vrtanje in odkopavanje extraction equipment
oSIST prEN ISO 19905-3:2022 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 19905-3:2022
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oSIST prEN ISO 19905-3:2022
INTERNATIONAL ISO
STANDARD 19905-3
Second edition
2021-03
Petroleum and natural gas
industries — Site-specific assessment
of mobile offshore units —
Part 3:
Floating units
Industries du pétrole et du gaz naturel — Évaluation spécifique au
site d'unités mobiles en mer —
Partie 3: Unités flottantes
Reference number
ISO 19905-3:2021(E)
ISO 2021
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oSIST prEN ISO 19905-3:2022
ISO 19905-3:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
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oSIST prEN ISO 19905-3:2022
ISO 19905-3:2021(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3  Terms and definitions ..................................................................................................................................................................................... 2

4 Abbreviated terms .............................................................................................................................................................................................. 4

5 Overall considerations ................................................................................................................................................................................... 5

5.1 General ........................................................................................................................................................................................................... 5

5.1.1 Competency .......................................................................................................................................................................... 5

5.1.2 Planning ................................................................................................................................................................................... 5

5.1.3 Reporting ................................................................................................................................................................................ 5

5.1.4 Regulations ........................................................................................................................................................................... 5

5.1.5 Classification of unit ..................................................................................................................................................... 5

5.2 Assessment ................................................................................................................................................................................................. 6

5.3 Exposure levels ....................................................................................................................................................................................... 6

5.4 Selection of limit states .................................................................................................................................................................... 6

5.5 Determination of assessment situations .......................................................................................................................... 7

5.5.1 General...................................................................................................................................................................................... 7

5.5.2 Arctic operations and ice .......................................................................................................................................... 8

5.5.3 Earthquake ............................................................................................................................................................................ 8

5.6 Models and analytical tools .......................................................................................................................................................... 8

6 Data to be assembled for each site .................................................................................................................................................... 8

6.1 Applicability .............................................................................................................................................................................................. 8

6.2 Mobile floating unit data ................................................................................................................................................................ 8

6.3 Stationkeeping data ............................................................................................................................................................................ 9

6.3.1 General...................................................................................................................................................................................... 9

6.3.2 Moored units ....................................................................................................................................................................... 9

6.3.3 Moored units with thruster assist..................................................................................................................... 9

6.3.4 Dynamically positioned units ............................................................................................................................... 9

6.4 Site data ......................................................................................................................................................................................................10

6.5 Data on activity/use limitations ...........................................................................................................................................10

6.5.1 General...................................................................................................................................................................................10

6.5.2 Reassessment or modification of activity/use limitations .......................................................11

6.5.3 Sources of data and types of activity/use limitations ...................................................................11

6.6 Post installation data ......................................................................................................................................................................11

7 Actions ..........................................................................................................................................................................................................................11

8 Hull of unit ...............................................................................................................................................................................................................12

8.1 Strength ......................................................................................................................................................................................................12

8.1.1 General...................................................................................................................................................................................12

8.1.2 Monohull ..............................................................................................................................................................................12

8.1.3 Semi-submersible ........................................................................................................................................................12

8.1.4 Other hull forms ............................................................................................................................................................12

8.2 Air gap and freeboard ....................................................................................................................................................................12

8.2.1 General...................................................................................................................................................................................12

8.2.2 Monohull ..............................................................................................................................................................................13

8.2.3 Semi-submersible ........................................................................................................................................................13

8.2.4 Other hull forms ............................................................................................................................................................13

8.3 Temperature ...........................................................................................................................................................................................13

8.4 Stability .......................................................................................................................................................................................................14

9 Stationkeeping system ................................................................................................................................................................................14

9.1 General ........................................................................................................................................................................................................14

© ISO 2021 – All rights reserved iii
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oSIST prEN ISO 19905-3:2022
ISO 19905-3:2021(E)

9.2 Moored ........................................................................................................................................................................................................14

9.3 Thruster assisted mooring ........................................................................................................................................................14

9.4 Dynamic positioning systems .................................................................................................................................................14

10  Activity specific assessments ................................................................................................................................................................14

10.1 General ........................................................................................................................................................................................................14

10.2 Assessment of site-specific activities and equipment ........................................................................................15

10.2.1 General...................................................................................................................................................................................15

10.2.2 Marine drilling riser assessment ....................................................................................................................15

10.3 Risk assessment ..................................................................................................................................................................................15

10.4 Activity specific operating guidelines ..............................................................................................................................15

11  Confirmation of compatibility between analysis and as-installed condition ....................................16

Annex A (informative) Outline of an activity specific operating guideline document for a

dynamically positioned unit and a moored unit ..............................................................................................................17

Annex B (informative) Suggested process for completing a site-specific assessment of a

mobile floating unit ........................................................................................................................................................................................20

Bibliography .............................................................................................................................................................................................................................22

iv © ISO 2021 – All rights reserved
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oSIST prEN ISO 19905-3:2022
ISO 19905-3:2021(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.

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 67, Materials, equipment and offshore

structures for petroleum, petrochemical and natural gas industries, Subcommittee SC 7, Offshore

structures.

This second edition cancels and replaces the first edition (ISO 19905-3:2017), which has been

technically revised.
The main changes compared to the previous edition are as follows:

— removed definitions of drift off and drive off in Clause 3 and consolidated under loss of position;

— Table 1 in Clause 5 removed and reference made to ISO 19900;
— FLS removed from 8.1.2 and 8.1.3;
— air gap requirements modified in 8.2;
— ISO 35104 referenced in 10.4;
— editorial revision.
A list of all parts in the ISO 19905 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.
© ISO 2021 – All rights reserved v
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oSIST prEN ISO 19905-3:2022
ISO 19905-3:2021(E)
Introduction

The International Standards on offshore structures prepared by TC 67 (i.e. ISO 19900, the ISO 19901

series, ISO 19902, ISO 19903, ISO 19904-1, the ISO 19905 series, ISO 19906) constitute a common

basis addressing design requirements and assessments of all types of offshore structures used by the

petroleum and natural gas industries worldwide.

NOTE These are sometimes referred to as the ISO 19900 series on offshore structures.

Through their application, the intention is to achieve adequate structural integrity and performance

based on reliability levels appropriate for manned and unmanned offshore structures, whatever the

nature or combination of the materials used.

Structural integrity is an overall concept comprising: models for describing actions; structural

analyses; design or assessment rules; safety elements; workmanship; quality management; and

national requirements, all of which are mutually dependent. The modification of any of these elements

in isolation can cause an imbalance or inconsistency, with possible impact on the reliability inherent in

the offshore structure. The implications involved in modifying one element, therefore, are considered

in relation to all the elements and the overall reliability of the offshore structure.

The International Standards on offshore structures prepared by TC 67 are intended to provide latitude

in the choice of structural configurations, materials and techniques and to allow for innovative

solutions. Sound engineering judgement is, therefore, necessary in the use of these documents.

This document states the general principles and basic requirements for the site-specific assessment of

mobile floating units. The technical information used in the assessment primarily resides in documents

referenced herein. This document is intended to be used for assessment and not for design.

Site-specific assessment is normally carried out when an existing mobile floating unit is to be installed

at a specific site. The assessment is not intended to provide a full evaluation of the unit; it is assumed

that aspects not addressed herein have been addressed at the design stage using other practices and

standards.

The purpose of the site-specific assessment is to demonstrate the adequacy of the mobile floating

unit, its stationkeeping system and any connected systems for the applicable assessment situations

and defined limit states, taking into account the consequences of failure. The results of a site-specific

assessment should be appropriately recorded and communicated to those persons required to know or

act on the conclusions and recommendations. Alternative approaches to the site-specific assessment

can be used provided that they have been shown to give a level of reliability equivalent, or superior, to

that implicit in this document.
In this document, the following verbal forms are used:
— “shall” indicates a requirement;
— “should” indicates a recommendation;
— “can” indicates a possibility or a capability;
— “may” indicates a permission.
vi © ISO 2021 – All rights reserved
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oSIST prEN ISO 19905-3:2022
INTERNATIONAL STANDARD ISO 19905-3:2021(E)
Petroleum and natural gas industries — Site-specific
assessment of mobile offshore units —
Part 3:
Floating units
1 Scope

This document specifies requirements and recommendations for the site-specific assessment of mobile

floating units for use in the petroleum and natural gas industries. It addresses the installed phase, at a

specific site, of manned non-evacuated, manned evacuated and unmanned mobile floating units.

This document addresses mobile floating units that are monohull (e.g. ship-shaped vessels or barges);

column-stabilized, commonly referred to as semi-submersibles; or other hull forms (e.g. cylindrical/

conical shaped). It is not applicable to tension leg platforms. Stationkeeping can be provided by a

mooring system, a thruster assisted mooring system, or dynamic positioning. The function of the unit

can be broad, including drilling, floatel, tender assist, etc. In situations where hydrocarbons are being

produced, there can be additional requirements.

This document does not address all site considerations, and certain specific locations can require

additional assessment.

This document is applicable only to mobile floating units that are structurally sound and adequately

maintained, which is normally demonstrated through holding a valid RCS classification certificate.

This document does not address design, transportation to and from site, or installation and removal

from site.

This document sets out the requirements for site-specific assessments, but generally relies on other

documents to supply the details of how the assessments are to be undertaken. In general:

— ISO 19901-7 is referenced for the assessment of the stationkeeping system;

— ISO 19904-1 is referenced to determine the effects of the metocean actions on the unit;

— ISO 19906 is referenced for arctic and cold regions;

— the hull structure and air gap are assessed by use of a comparison between the site-specific

metocean conditions and its design conditions, as set out in the RCS approved operations manual;

[1]

— ISO 13624-1 and ISO/TR 13624-2 are referenced for the assessment of the marine drilling riser of

mobile floating drilling units. Equivalent alternative methodologies can be used;

— IMCA M 220 is referenced for developing an activity specific operating guidelines. Agreed alternative

methodologies can be used.
[13]

NOTE RCS rules and the IMO MODU code provide guidance for design and general operation of mobile

floating units.
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 2021 – All rights reserved 1
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oSIST prEN ISO 19905-3:2022
ISO 19905-3:2021(E)

ISO 13624-1, Petroleum and natural gas industries — Drilling and production equipment — Part 1: Design

and operation of marine drilling riser equipment

ISO 19900, Petroleum and natural gas industries — General requirements for offshore structures

ISO 19901-1, Petroleum and natural gas industries — Specific requirements for offshore structures —

Part 1: Metocean design and operating considerations

ISO 19901-7, Petroleum and natural gas industries — Specific requirements for offshore structures —

Part 7: Stationkeeping systems for floating offshore structures and mobile offshore units

ISO 19904-1, Petroleum and natural gas industries — Floating offshore structures — Part 1: Ship-shaped,

semi-submersible, spar and shallow-draught cylindrical structures

ISO 19906:2019, Petroleum and natural gas industries — Arctic offshore structures

ISO 35104, Petroleum and natural gas industries — Arctic operations — Ice management

International Marine Contractors Association, “Guidance on Operational Activity Planning”, IMCA M 220

3  Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 19900, ISO 19901-1,

ISO 19901-7, ISO 19904-1 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
activity specific operating guidelines
ASOG

document that sets out the activities that need to be undertaken at specific alert level thresholds (3.4)

for specified changes in conditions

Note 1 to entry: These guidelines are in a document that sets out high level actions to be undertaken at specific

alert level thresholds.

Note 2 to entry: The ASOG for drilling operations is often called the well specific operating guideline

document (WSOG).

Note 3 to entry: An example ASOG for DP (dynamic positioning) and moored units is given in Annex A.

3.2
air gap

distance between the highest water elevation and the lowest exposed part of the primary deck structure

and permanent equipment not designed to withstand associated environmental action effects

[SOURCE: ISO 19900:2019, 3.5, modified — “structure” and “action effects” not defined herein, “and

permanent equipment” added and “for defined return period” deleted.]
2 © ISO 2021 – All rights reserved
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oSIST prEN ISO 19905-3:2022
ISO 19905-3:2021(E)
3.3
alert level

condition when certain parameters are below the lower limit, or between limits, or above the upper limit

Note 1 to entry: Alert levels are often colour-coded. The colour-coding will often be green for normal, blue for

advisory, yellow alert for reduced status, and red alert for emergency status. Parameters affecting the change

of colour-coded alert levels can be, for example, approach of limiting metocean conditions, loss of equipment

function, reduced available power levels, offset limits are reached [watch circles (3.17)], excessive vessel motions

are predicted, etc. Actions to be taken can include, for example, discontinue drilling, disconnect riser, suspend

lifts, etc.
3.4
alert level threshold
boundary between alert levels (3.3)
3.5
assessment
site-specific assessment

evaluation of a mobile floating unit and activity specific equipment to determine conformity with

specific requirements

Note 1 to entry: The specific requirements are the requirements of this document (i.e. 19905-3).

Note 2 to entry: Definition derived from ISO 19905-1:2016, 3.4.
3.6
assessment situation

mobile floating unit configuration together with the metocean and ice actions that need to be assessed

3.7
assessor
entity performing the site-specific assessment (3.5)
[SOURCE: ISO 19905-1:2016, 3.6]
3.8
extreme storm event

extreme combination of wind, wave and current conditions used for the assessment (3.5) of the mobile

floating unit

Note 1 to entry: This is the metocean event used for ULS storm assessment and varies depending on what is being

assessed. For example, the metocean event for the ULS assessment of the mooring system can be different from

that used in the ULS assessment of the hull strength or air gap.
3.9
loss of position

unintended move of a dynamically positioned or thruster-assisted vessel from its intended location

[watch circle (3.17)] relative to its set point position (3.13), generally caused by loss of stationkeeping

control or propulsion

Note 1 to entry: Loss of position can take on three main forms drift off, drive off, or force off.

3.10
operating manual
marine operations manual

latest approved document that defines the operational characteristics and capabilities of the mobile

floating unit

[SOURCE: ISO 19905-1:2016, 3.45, modified — “jack-up” has been replaced by “mobile floating unit”,

Note 1 to entry has been deleted, and “manual” replaced by “latest approved document”.]

© ISO 2021 – All rights reserved 3
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oSIST prEN ISO 19905-3:2022
ISO 19905-3:2021(E)
3.11
operator
representative of the company or companies leasing the site

Note 1 to entry: The operator is normally the oil company acting on behalf of co-licensees.

Note 2 to entry: The operator can be termed the owner or the duty holder.
[SOURCE: ISO 19900:2019, 3.35]
3.12
recognized classifi
...

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