Petroleum and natural gas industries - Site-specific assessment of mobile offshore units - Part 3: Floating unit (ISO 19905-3:2017)

ISO 19905-3 specifies requirements and gives guidance 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.
ISO 19905-3 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.
The requirements of ISO 19905-3 apply to the hull and stationkeeping system for all types of mobile units. The activity specific operating guideline document requirements can be modified to be appropriate to the situation being assessed.
ISO 19905-3 does not address all site considerations, and certain specific locations can require additional assessment.
ISO 19905-3 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.
ISO 19905-3 does not address design, transportation to and from site, or installation and removal from site.
ISO 19905-3 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 metocean actions on the unit;
- ISO 19906 is referenced for arctic and cold regions;
- the hull structure and airgap 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[5] is referenced for developing an activity specific operating guidelines. Agreed alternative methodologies can be used.
NOTE 1 The scope of ISO 19904‑1 specifically states that its requirements do not apply to mobile units, but the methodologies given for assessing metocean actions can be used.
NOTE 2 RCS rules and the IMO MODU code[4] 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 19905-3:2017)

Industries du pétrole et du gaz naturel - Évaluation spécifique au site d'unités mobiles en mer - Partie 3: Unité flottante (ISO 19905-3:2017)

ISO 19905-3:2017 spécifie les exigences et les lignes directrices pour l'évaluation spécifique au site d'unités mobiles flottantes à utiliser dans les industries du pétrole et du gaz naturel. Elle traite de la phase installée, au niveau d'un site spécifique, d'unités mobiles flottantes occupées par du personnel non évacuées, occupées par du personnel évacuées et non occupées par du personnel.
ISO 19905-3:2017 traite des unités mobiles flottantes monocoques (par exemple structures à profil de bateau ou barges); stabilisées par des colonnes, souvent désignées par structures semi-submersibles; ou ayant d'autres formes de coque (par exemple cylindriques/coniques). Elle n'est pas applicable aux plates-formes à ancrage tendu. 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, comprenant des fonctions de forage, d'hôtel flottant, de barge, etc. Dans les situations où des hydrocarbures sont produits, des exigences supplémentaires peuvent s'appliquer.
Les exigences du présent document s'appliquent à la coque et au système de maintien en position de tous les types d'unités mobiles. Il est possible de modifier les exigences du document d'instructions d'exploitation spécifiques à l'activité dans le but de les adapter à la situation faisant l'objet de l'évaluation.
ISO 19905-3:2017 ne traite pas de toutes les considérations du site, et il est possible que certains emplacements nécessitent une évaluation supplémentaire.
ISO 19905-3:2017 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).
ISO 19905-3:2017 ne traite pas de la conception, du transport vers et depuis un site ou de l'installation et du retrait du site.
ISO 19905-3:2017 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 actions océano-météorologiques sur l'unité;
- l'ISO 19906 est citée en référence pour les régions arctiques et froides;
- la structure et le tirant d'eau de la coque sont évalués en procédant à une comparaison entre les dispositions 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. Il est possible d'utiliser d'autres méthodologies équivalentes;
- l'IMCA M 220[5] est citée en référence pour l'élaboration d'un document d'instructions d'exploitation spécifique à l'activité. Il est possible d'utiliser d'autres méthodologies ayant fait l'objet d'un accord.
NOTE 1 Le domaine d'application de l'ISO 19904‑1 stipule spécifiquement que ses exigences ne s'appliquent pas aux unités mobiles, mais les méthodologies données pour l'évaluation des actions océano-météorolo

Industrija za predelavo nafte in zemeljskega plina - Ocenjevanje premičnih naftnih ploščadi na področju postavitve - 3. del: Plavajoča enota (ISO 19905-3:2017)

Standard ISO 19905-3 določa zahteve in podaja smernice za ocenjevanje premičnih plavajočih enot na področju postavitve za uporabo v industriji za predelavo nafte in zemeljskega plina. Obravnava fazo postavitve na določenem področju za neevakuirane premične plavajoče enote s posadko, evakuirane premične plavajoče enote s posadko in za premične plavajoče enote brez posadke. Standard ISO 19905-3 obravnava premične plavajoče enote, ki imajo en trup (npr. plovila v obliki plavila ali plovila); ki so stolpično stabilizirana in se običajno imenujejo enote, ki so pol pod vodo; ali ki imajo druge oblike trupa (npr. cilindrične ali stožčaste oblike). Ne uporablja se za navpično zasidrane ploščadi. Vzdrževalne sisteme se lahko zagotovi s sistemi zasidranja, sistemi motorno podprtega zasidranja ali z dinamičnim pozicioniranjem. Enota lahko opravlja raznovrstne funkcije, vključno z vrtanjem, plovnimi hoteli, ponudniki pomoči itd. V primerih proizvodnje ogljikovodikov lahko obstajajo dodatne zahteve. Zahteve iz standarda ISO 19905-3 veljajo za trupe in vzdrževalne sisteme za vse vrste premičnih enot. Zahteve dokumenta za delovanje, ki je specifično za dejavnost, je mogoče spremeniti tako, da ustrezajo primeru, ki se jo ocenjuje.
Standard ISO 19905-3 ne obravnava vseh pogojev mesta uporabe in določene specifične lokacije lahko zahtevajo dodatno ocenjevanje.
Standard ISO 19905-3 se uporablja samo za premične plavajoče enote, ki so strukturno trdne in ustrezno vzdrževane, kar se običajno izkazuje z veljavnim certifikatom klasifikacije RCS.
Standard ISO 19905-3 ne obravnava načrtovanja, prevoza na mesto ali z njega ali namestitve na mesto in odstranitve z njega.
Standard ISO 19905-3 podaja zahteve za oceno na mestu postavitve, vendar se na splošno sklicuje na druge dokumente glede podajanja podrobnosti o tem, kako naj poteka ocenjevanje. Splošno:
– sklic na standard ISO 19901‑7 za ocenjevanje vzdrževalnega sistema;
– sklic na standard ISO 19904‑1 za določanje meteoroloških in oceanografskih ukrepov za enoto;
– sklic na standard ISO 19906 za arktična in hladna območja;
– struktura trupa in zračna reža se ocenita s primerjavo med meteorološkimi in oceanografskimi pogoji, ki so specifični za mesto postavitve, ter njihovimi določenimi pogoji, kot je opredeljeno v s strani RCS odobrenih navodilih za uporabo;
– sklic na standarda ISO 13624‑1 in ISO/TR 13624‑2[1] za ocenjevanje morskih dvižnih cevi za vrtanje na premičnih plavajočih vrtalnih enotah. Uporabijo se lahko tudi enakovredne nadomestne metodologije;
– sklic na standard IMCA M 220[5] za razvoj smernic za delovanje, ki so specifične za dejavnost. Uporabijo se lahko tudi dogovorjene nadomestne metodologije.
OPOMBA 1: Področje uporabe standarda ISO 19904‑1 izrecno navaja, da zahteve standarda ne veljajo za premične enote, vendar je mogoče uporabiti metodologije, ki so podane za ocenjevanje meteoroloških in oceanografskih dejanj.
OPOMBA 2: Pravila RCS in kodeks IMO MODU [4] podajajo napotke za načrtovanje in upravljanje premičnih plavajočih enot.

General Information

Status
Published
Public Enquiry End Date
31-Jul-2019
Publication Date
05-Nov-2019
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
24-Oct-2019
Due Date
29-Dec-2019
Completion Date
06-Nov-2019

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SLOVENSKI STANDARD
SIST EN ISO 19905-3:2020
01-januar-2020

Industrija za predelavo nafte in zemeljskega plina - Ocenjevanje premičnih naftnih

ploščadi na področju postavitve - 3. del: Plavajoča enota (ISO 19905-3:2017)

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

- Part 3: Floating unit (ISO 19905-3:2017)

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

Einsatzgebietes - Teil 3: Schwimmende Einheiten (ISO 19905-3:2017)

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

mer - Partie 3: Unité flottante (ISO 19905-3:2017)
Ta slovenski standard je istoveten z: EN ISO 19905-3:2019
ICS:
75.180.10 Oprema za raziskovanje, Exploratory, drilling and
vrtanje in odkopavanje extraction equipment
SIST EN ISO 19905-3:2020 en,fr,de

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

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SIST EN ISO 19905-3:2020
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SIST EN ISO 19905-3:2020
EN ISO 19905-3
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2019
EUROPÄISCHE NORM
ICS 75.180.10
English Version
Petroleum and natural gas industries - Site-specific
assessment of mobile offshore units - Part 3: Floating unit
(ISO 19905-3:2017)

Industries du pétrole et du gaz naturel - Évaluation Erdöl- und Erdgasindustrie - Beurteilung von mobilen

spécifique au site d'unités mobiles en mer - Partie 3: Offshore Einheiten bezüglich ihres Einsatzgebietes -

Unité flottante (ISO 19905-3:2017) Teil 3: Schwimmende Einheiten (ISO 19905-3:2017)

This European Standard was approved by CEN on 9 September 2019.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 19905-3:2019 E

worldwide for CEN national Members.
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SIST EN ISO 19905-3:2020
EN ISO 19905-3:2019 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 19905-3:2020
EN ISO 19905-3:2019 (E)
European foreword

The text of ISO 19905-3:2017 has been prepared by Technical Committee ISO/TC 67 "Materials,

equipment and offshore structures for petroleum, petrochemical and natural gas industries” of the

International Organization for Standardization (ISO) and has been taken over as EN ISO 19905-3:2019

by Technical Committee CEN/TC 12 “Materials, equipment and offshore structures for petroleum,

petrochemical and natural gas industries” the secretariat of which is held by NEN.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by April 2020, and conflicting national standards shall be

withdrawn at the latest by April 2020.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the

United Kingdom.
Endorsement notice

The text of ISO 19905-3:2017 has been approved by CEN as EN ISO 19905-3:2019 without any

modification.
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SIST EN ISO 19905-3:2020
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SIST EN ISO 19905-3:2020
INTERNATIONAL ISO
STANDARD 19905-3
First edition
2017-10
Petroleum and natural gas
industries — Site-specific assessment
of mobile offshore units —
Part 3:
Floating unit
Industries du pétrole et du gaz naturel — Évaluation spécifique au
site d'unités mobiles en mer —
Partie 3: Unité flottante
Reference number
ISO 19905-3:2017(E)
ISO 2017
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SIST EN ISO 19905-3:2020
ISO 19905-3:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, 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 2017 – All rights reserved
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SIST EN ISO 19905-3:2020
ISO 19905-3:2017(E)
Contents Page

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

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

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

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

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 ................................................................................................................................................................................................. 5

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 .......................................................................................................................................... 7

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 ......................................................................................................................................................................................................... 9

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

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

6.5.2 Reassessment or modification of activity use limitations .........................................................10

6.5.3 Sources of data and types of activity use limitations ....................................................................10

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

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

8 Hull of unit ...............................................................................................................................................................................................................11

8.1 Strength ......................................................................................................................................................................................................11

8.1.1 General...................................................................................................................................................................................11

8.1.2 Monohull ..............................................................................................................................................................................11

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

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

8.2 Airgap and freeboard ......................................................................................................................................................................12

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

8.2.2 Monohull ..............................................................................................................................................................................12

8.2.3 Semi-submersible ........................................................................................................................................................12

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

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

8.4 Stability .......................................................................................................................................................................................................13

9 Stationkeeping system ................................................................................................................................................................................13

9.1 General ........................................................................................................................................................................................................13

© ISO 2017 – All rights reserved iii
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SIST EN ISO 19905-3:2020
ISO 19905-3:2017(E)

9.2 Moored ........................................................................................................................................................................................................13

9.3 Thruster assisted mooring ........................................................................................................................................................13

9.4 Dynamic positioning systems .................................................................................................................................................13

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

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

10.2 Assessment of site-specific activities and equipment ........................................................................................14

10.2.1 General...................................................................................................................................................................................14

10.2.2 Marine drilling riser assessment ....................................................................................................................14

10.3 Risk assessment ..................................................................................................................................................................................14

10.4 Activity specific operating guidelines ..............................................................................................................................14

11  Confirmation of compatibility between analysis and as-installed condition ....................................15

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

dynamically positioned unit and a moored unit ..............................................................................................................16

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

mobile floating unit ........................................................................................................................................................................................19

Bibliography .............................................................................................................................................................................................................................21

iv © ISO 2017 – All rights reserved
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SIST EN ISO 19905-3:2020
ISO 19905-3:2017(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 on 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 the following

URL: 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.
A list of all parts in the ISO 19905 series can be found on the ISO website.
© ISO 2017 – All rights reserved v
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SIST EN ISO 19905-3:2020
ISO 19905-3:2017(E)
Introduction

The series of International Standards applicable to types of offshore structure, ISO 19900 to ISO 19906,

addresses design requirements and assessments for all offshore structures used by the petroleum and

natural gas industries worldwide. Through their application, the intention is to achieve reliability levels

appropriate for manned and unmanned offshore structures, whatever the type of structure and the

nature or combination of the materials used.

It is important to recognize that structural integrity is an overall concept comprising models for

describing actions, structural analyses, design or assessment rules, safety elements, workmanship,

quality control procedures and national requirements, all of which are mutually dependent. The

modification of one aspect of the design or assessment in isolation can disturb the balance of reliability

inherent in the overall concept or structural system. The implications involved in modifications,

therefore, need to be considered in relation to the overall reliability of offshore structural systems.

The series of International Standards applicable to the various types of offshore structure is intended

to provide a wide latitude in the choice of structural configurations, materials and techniques

without hindering innovation. Sound engineering judgement is therefore necessary in the use of these

International Standards.

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 International Standards, the following verbal forms are used:

— “shall” and “shall not” are used to indicate requirements strictly to be followed in order to conform

to the document and from which no deviation is permitted;

— “should” and “should not” are used to indicate that, among several possibilities, one is recommended

as particularly suitable, without mentioning or excluding others, or that a certain course of action is

preferred but not necessarily required, or that (in the negative form) a certain possibility or course

of action is deprecated but not prohibited;

— “may” is used to indicate a course of action permissible within the limits of the document;

— “can” and “cannot” are used for statements of possibility and capability, whether material, physical

or causal.
vi © ISO 2017 – All rights reserved
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SIST EN ISO 19905-3:2020
INTERNATIONAL STANDARD ISO 19905-3:2017(E)
Petroleum and natural gas industries — Site-specific
assessment of mobile offshore units —
Part 3:
Floating unit
1 Scope

This document specifies requirements and gives guidance 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.

The requirements of this document apply to the hull and stationkeeping system for all types of

mobile units. The activity specific operating guideline document requirements can be modified to be

appropriate to the situation being assessed.

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 metocean actions on the unit;
— ISO 19906 is referenced for arctic and cold regions;

— the hull structure and airgap 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;

[5]

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

alternative methodologies can be used.

NOTE 1 The scope of ISO 19904-1 specifically states that its requirements do not apply to mobile units, but the

methodologies given for assessing metocean actions can be used.
[4]

NOTE 2 RCS rules and the IMO MODU code provide guidance for design and general operation of mobile

floating units.
© ISO 2017 – All rights reserved 1
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SIST EN ISO 19905-3:2020
ISO 19905-3:2017(E)
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 13624-1:2009, Petroleum and natural gas industries — Drilling and production equipment — Part 1:

Design and operation of marine drilling riser equipment

ISO 19900:2013, 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 19901-7:2013, 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: Monohulls,

semi-submersibles and spars
ISO 19906:— , Petroleum and natural gas industries — Arctic offshore structures
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

...

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