EN ISO 20257-2:2021

Installation and equipment for liquefied natural gas - Design of floating LNG installations - Part 2: Specific FSRU issues (ISO 20257-2:2021)

This document provides specific requirements and guidance for the design and operation of floating LNG storage and regasification units (FSRU) described in ISO 20257-1.
This document is applicable to offshore, near-shore or docked FSRUs and to both new-built and converted FSRUs.
This document includes requirements to the jetty when an FSRU is moored to a jetty.

Anlagen und Ausrüstung für Flüssigerdgas - Auslegung von schwimmenden Flüssigerdgas-Anlagen - Teil 2: Spezifische Anmerkungen zu FSRU (ISO 20257-2:2021)

Dieses Dokument enthält spezifische Anforderungen und Anleitungen in Bezug auf die Auslegung und den Betrieb von schwimmenden Einheiten für die Speicherung und Wiederverdampfung (FSRU, en: floating storage regasification unit) von Flüssigerdgas (LNG, en: liquefied natural gas), wie in ISO 20257 1 beschrieben.
Dieses Dokument ist auf Offshore-Anlagen, Anlagen in Küstennähe oder angedockte FSRU anwendbar und gilt sowohl für neu gebaute als auch für umgebaute FSRU.
Dieses Dokument enthält Anforderungen an den Pier, wenn eine FSRU an einen Pier vertäut ist.

Installations et équipements de gaz naturel liquéfié - Conception des installations flottantes de GNL - Partie 2: Questions spécifiques aux FSRU (ISO 20257-2:2021)

Le présent document fournit des recommandations et exigences spécifiques pour la conception et l'exploitation des unités flottantes de stockage et de regazéification de GNL (FSRU) tel que décrites dans l'ISO 20257-1.
Le présent document s’applique aux FSRU en mer, côtiers ou à quai et tant aux FSRU construits à neuf qu'à ceux convertis.
Le présent document inclut l'appontement dans le cas de l'amarrage d'un FSRU.

Napeljave in oprema za utekočinjeni zemeljski plin - Načrtovanje plavajočih napeljav za utekočinjeni zemeljski plin - 2. del: Posebne zahteve za plavajoča skladišča z enotami za uplinjanje (FSRU) (ISO 20257-2:2021)

General Information

• Status: Published
• Publication Date: 22-Jun-2021
• Withdrawal Date: 30-Dec-2021
• ICS: 75.200 - Petroleum products and natural gas handling equipment
• Technical Committee: CEN/TC 282 - Installation and equipment for LNG
• Drafting Committee: CEN/TC 282 - Installation and equipment for LNG
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 23-Jun-2021
• Completion Date: 23-Jun-2021
• Ref Project: SIST EN ISO 20257-2:2021 - Installation and equipment for liquefied natural gas - Design of floating LNG installations - Part 2: Specific FSRU issues (ISO 20257-2:2021)

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 20257-2:2021
01-oktober-2021
Napeljave in oprema za utekočinjeni zemeljski plin - Načrtovanje plavajočih
napeljav za utekočinjeni zemeljski plin - 2. del: Posebne zahteve za plavajoča
skladišča z enotami za uplinjanje (FSRU) (ISO 20257-2:2021)

Installation and equipment for liquefied natural gas - Design of floating LNG installations

- Part 2: Specific FSRU issues (ISO 20257-2:2021)
Anlagen und Ausrüstung für Flüssigerdgas - Auslegung von schwimmenden
Flüssigerdgas-Anlagen - Teil 2: Besondere Anmerkungen zu FSRU (ISO 20257-2:2021)

Installations et équipements de gaz naturel liquéfié - Conception des installations

flottantes de GNL - Partie 2: Questions spécifiques aux FSRU (ISO 20257-2:2021)
Ta slovenski standard je istoveten z: EN ISO 20257-2:2021
ICS:
75.200 Oprema za skladiščenje Petroleum products and
nafte, naftnih proizvodov in natural gas handling
zemeljskega plina equipment
SIST EN ISO 20257-2:2021 en,fr,de

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

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SIST EN ISO 20257-2:2021
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SIST EN ISO 20257-2:2021
EN ISO 20257-2
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2021
EUROPÄISCHE NORM
ICS 75.200
English Version
Installation and equipment for liquefied natural gas -
Design of floating LNG installations - Part 2: Specific FSRU
issues (ISO 20257-2:2021)

Installations et équipements de gaz naturel liquéfié - Anlagen und Ausrüstung für Flüssigerdgas - Auslegung

Conception des installations flottantes de GNL - Partie von schwimmenden Flüssigerdgas-Anlagen - Teil 2:

2: Questions spécifiques aux FSRU (ISO 20257-2:2021) Besondere Anmerkungen zu FSRU (ISO 20257-2:2021)

This European Standard was approved by CEN on 28 May 2021.

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

© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 20257-2:2021 E

worldwide for CEN national Members.
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SIST EN ISO 20257-2:2021
EN ISO 20257-2:2021 (E)
Contents Page

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

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SIST EN ISO 20257-2:2021
EN ISO 20257-2:2021 (E)
European foreword

This document (EN ISO 20257-2:2021) has been prepared by Technical Committee ISO/TC 67

"Materials, equipment and offshore structures for petroleum, petrochemical and natural gas industries"

in collaboration with Technical Committee CEN/TC 282 “Installation and equipment for LNG” the

secretariat of which is held by AFNOR.

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 December 2021, and conflicting national standards

shall be withdrawn at the latest by December 2021.

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 20257-2:2021 has been approved by CEN as EN ISO 20257-2:2021 without any

modification.
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SIST EN ISO 20257-2:2021
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SIST EN ISO 20257-2:2021
INTERNATIONAL ISO
STANDARD 20257-2
First edition
2021-06
Installation and equipment for
liquefied natural gas — Design of
floating LNG installations —
Part 2:
Specific FSRU issues
Installations et équipements de gaz naturel liquéfié — Conception des
installations flottantes de GNL —
Partie 2: Questions spécifiques aux FSRU
Reference number
ISO 20257-2:2021(E)
ISO 2021
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SIST EN ISO 20257-2:2021
ISO 20257-2:2021(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: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
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SIST EN ISO 20257-2:2021
ISO 20257-2:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................vi

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

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

3 Terms, definitions and abbreviated terms ................................................................................................................................ 2

3.1 Terms and definitions ....................................................................................................................................................................... 2

3.2 Abbreviated terms ............................................................................................................................................................................... 2

4 Basis of design ......................................................................................................................................................................................................... 3

4.1 General description of FSRU........................................................................................................................................................ 3

4.2 Main design criteria for process facilities ........................................................................................................................ 5

4.3 Reliability, availability and maintainability of LNG floating installation .............................................. 6

4.4 Specific requirements for FSRU operating as LNG carrier ................................................................................ 6

4.5 Specific FSRU studies ......................................................................................................................................................................... 6

4.5.1 General...................................................................................................................................................................................... 6

4.5.2 Environmental impact of seawater intake and discharge study............................................. 6

4.5.3 Recirculation study ........................................................................................................................................................ 7

4.5.4 Scour protection study ............................................................................................................................................... 7

5 Specific health, safety and environmental issues ............................................................................................................... 7

5.1 General ........................................................................................................................................................................................................... 7

5.2 Environmental considerations related to water heating and cooling issues .................................... 7

5.3 Safety considerations ........................................................................................................................................................................ 8

5.3.1 General requirements .................................................................................................................................................. 8

5.3.2 Layout constrains ............................................................................................................................................................ 8

5.3.3 Layout constraints with respect to surroundings ............................................................................... 9

5.3.4 Layout constraints with respect to facility arrangement ...........................................................10

5.3.5 Risk prevention measures ....................................................................................................................................11

6 Mooring and stationkeeping .................................................................................................................................................................16

7 Hull design ...............................................................................................................................................................................................................16

8 LNG storage .............................................................................................................................................................................................................17

8.1 Specific requirements for cargo tank pressure management .....................................................................17

8.2 Specific requirements for LNGC overpressure protection .............................................................................17

8.3 Rollover risk ...........................................................................................................................................................................................17

9 Transfer systems ...............................................................................................................................................................................................17

9.1 General ........................................................................................................................................................................................................17

9.2 Send-out natural gas: NG gas transfer requirements ..........................................................................................17

9.2.1 Functional requirements .......................................................................................................................................17

9.2.2 Transfer systems design .........................................................................................................................................18

9.2.3 Emergency disconnection .....................................................................................................................................19

9.2.4 Operating envelope ........................................................................................................................................... ..........19

9.3 LNG sampling ........................................................................................................................................................................................20

10 BOG handling and recovery ....................................................................................................................................................................21

10.1 General ........................................................................................................................................................................................................21

10.2 LNG tank design pressure flexibility .................................................................................................................................21

10.3 Specific requirements for recondenser ..........................................................................................................................21

10.4 Specific requirements for gas compressors ................................................................................................................22

10.4.1 General...................................................................................................................................................................................22

10.4.2 Specific functional requirements for LD compressors .................................................................22

10.4.3 Specific functional requirements for HD compressors ................................................................22

10.4.4 Specific functional requirements for HP or MSO compressors ............................................22

11 Regasification equipment requirements .................................................................................................................................23

11.1 LNG pumps ..............................................................................................................................................................................................23

© ISO 2021 – All rights reserved iii
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SIST EN ISO 20257-2:2021
ISO 20257-2:2021(E)

11.1.1 General...................................................................................................................................................................................23

11.1.2 Functional requirements .......................................................................................................................................23

11.1.3 Materials selection ......................................................................................................................................................23

11.1.4 In-tank LNG pump .......................................................................................................................................................23

11.1.5 HP LNG pump ..................................................................................................................................................................23

11.2 LNG vaporization system ............................................................................................................................................................24

11.2.1 Functional requirements .......................................................................................................................................24

11.2.2 Vaporization type .........................................................................................................................................................24

11.2.3 Materials selection ......................................................................................................................................................25

11.2.4 Protective coating ........................................................................................................................................................25

11.2.5 Marine growth ................................................................................................................................................................25

11.2.6 Stability/vibration .......................................................................................................................................................25

11.2.7 Safety relief valves .......................................................................................................................................................26

11.3 Trim heater..............................................................................................................................................................................................26

11.4 Venting from regasification systems .................................................................................................................................26

12 Gas send out............................................................................................................................................................................................................26

12.1 High integrity pressure protection system ..................................................................................................................26

12.1.1 Send-out pressure control ....................................................................................................................................26

12.1.2 Typical description of HIPPS ..............................................................................................................................27

12.1.3 Design requirements for HIPPS .......................................................................................................................28

12.2 Send-out gas metering ...................................................................................................................................................................29

12.2.1 Uses of send-out gas metering ..........................................................................................................................29

12.2.2 Measurement devices type ..................................................................................................................................29

12.2.3 Accuracy ...............................................................................................................................................................................29

12.2.4 External influences .....................................................................................................................................................29

12.2.5 Gas chromatograph – Gas analyser ...............................................................................................................30

12.2.6 Sparing philosophy .....................................................................................................................................................30

12.2.7 Z-configuration ...............................................................................................................................................................30

12.3 Odorization systems ........................................................................................................................................................................30

13 Utilities ........................................................................................................................................................................................................................30

13.1 General ........................................................................................................................................................................................................30

13.2 Cooling and heating medium ...................................................................................................................................................30

13.2.1 Cooling medium ...................................................................... .......................................................................................30

13.2.2 Heating medium ............................................................................................................................................................31

13.2.3 Nitrogen system ...................................................................... .......................................................................................31

13.2.4 Fuel gas ...................................................................... ............................................................................................................31

14 Process and safety control systems ...............................................................................................................................................32

14.1 General requirements ....................................................................................................................................................................32

14.2 Interfaces between FSRU and gas export connection ........................................................................................32

14.3 Communication onshore/offshore .....................................................................................................................................32

15 Security management ..................................................................................................................................................................................32

16 Commissioning ....................................................................................................................................................................................................32

17 Inspection and maintenance .................................................................................................................................................................33

17.1 General requirements ....................................................................................................................................................................33

17.2 Cargo tank ................................................................................................................................................................................................33

17.3 In-tank LNG pump .............................................................................................................................................................................33

17.4 Regasification equipment ...........................................................................................................................................................33

17.4.1 HP LNG pump ..................................................................................................................................................................33

17.4.2 LNG vaporizer..................................................................................................................................................................33

17.5 Recondenser ...........................................................................................................................................................................................33

17.6 Handling/Crane equipment ......................................................................................................................................................33

18 Preservation and corrosion protection .....................................................................................................................................34

19 Conversion of existing unit to floating LNG installations ........................................................................................34

Annex A (informative) Regasification system description..........................................................................................................35

iv © ISO 2021 – All rights reserved
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SIST EN ISO 20257-2:2021
ISO 20257-2:2021(E)

Bibliography .............................................................................................................................................................................................................................40

© ISO 2021 – All rights reserved v
---------------------- Page: 11 ----------------------
SIST EN ISO 20257-2:2021
ISO 20257-2:2021(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 9, Liquefied natural

gas installations and equipment, in collaboration with the European Committee for Standardization

(CEN) Technical Committee CEN/TC 282, Installation and equipment for LNG, in accordance with the

Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
A list of all parts in the ISO 20257 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.
vi © ISO 2021 – All rights reserved
---------------------- Page: 12 ----------------------
SIST EN ISO 20257-2:2021
INTERNATIONAL STANDARD ISO 20257-2:2021(E)
Installation and equipment for liquefied natural gas —
Design of floating LNG installations —
Part 2:
Specific FSRU issues
1 Scope

This document provides specific requirements and guidance for the design and operation of floating

LNG storage and regasification units (FSRU) described in ISO 20257-1.

This document is applicable to offshore, near-shore or docked FSRUs and to both new-built and

converted FSRUs.

This document includes requirements to the jetty when an FSRU is moored to a jetty.

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 20257-1:2020, Installation and equipment for liquefied natural gas — Design of floating LNG

installations — Part 1: General requirements
AGA 9, Measurement of Gas by Multipath Ultrasonic Meters
AGA 10, Speed of Sound in Natural Gas and Other Related Hydrocarbon Gase
...

SLOVENSKI STANDARD
oSIST prEN ISO 20257-2:2020
01-september-2020
Napeljave in oprema za utekočinjeni zemeljski plin - Načrtovanje plavajočih

napeljav za utekočinjeni zemeljski plin - 2. del: Posebne zahteve za FSRU (ISO/DIS

20257-2:2020)

Installation and equipment for liquefied natural gas - Design of floating LNG installations

- Part 2: Specific requirements for FSRU (ISO/DIS 20257-2:2020)
Anlagen und Ausrüstung für Flüssigerdgas - Auslegung von schwimmenden
Flüssigerdgas-Anlagen - Teil 2: Besondere Anforderungen an FSRU (ISO/DIS 20257-
2:2020)

Installations et équipements de gaz naturel liquéfié - Conception des installations

flottantes de GNL - Partie 2: Exigences spécifiques pour FSRU (ISO/DIS 20257-2:2020)

Ta slovenski standard je istoveten z: prEN ISO 20257-2
ICS:
75.200 Oprema za skladiščenje Petroleum products and
nafte, naftnih proizvodov in natural gas handling
zemeljskega plina equipment
oSIST prEN ISO 20257-2:2020 en,fr,de

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

---------------------- Page: 1 ----------------------
oSIST prEN ISO 20257-2:2020
---------------------- Page: 2 ----------------------
oSIST prEN ISO 20257-2:2020
DRAFT INTERNATIONAL STANDARD
ISO/DIS 20257-2
ISO/TC 67/SC 9 Secretariat: AFNOR
Voting begins on: Voting terminates on:
2020-06-19 2020-09-11
Installation and equipment for liquefied natural gas -
Design of floating LNG installations —
Part 2:
Specific FSRU issues

Installations et équipements de gaz naturel liquéfié - Conception des installations flottantes de GNL —

Partie 2: Exigences spécifiques pour FSRU
ICS: 75.200
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
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 20257-2:2020(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 2020
---------------------- Page: 3 ----------------------
oSIST prEN ISO 20257-2:2020
ISO/DIS 20257-2:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

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: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST prEN ISO 20257-2:2020
ISO/DIS 20257-2:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................vi

Introduction ..............................................................................................................................................................................................................................vii

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

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

3 Terms, definitions and abbreviated terms ................................................................................................................................ 2

3.1 Terms and definitions ....................................................................................................................................................................... 2

3.2 Abbreviated terms ............................................................................................................................................................................... 2

4 Basis of design ......................................................................................................................................................................................................... 3

4.1 General description of FSRU........................................................................................................................................................ 3

4.2 Main design criteria for process facilities ........................................................................................................................ 4

4.3 Reliability, availability and maintainability of LNG floating installation .............................................. 5

4.4 Specific requirements for FSRU operating as LNG carrier ................................................................................ 5

4.5 Specific FSRU studies ......................................................................................................................................................................... 5

4.5.1 General...................................................................................................................................................................................... 5

4.5.2 Environmental impact of seawater intake and discharge study............................................. 5

4.5.3 Recirculation study ........................................................................................................................................................ 5

4.5.4 Scour protection study ............................................................................................................................................... 6

5 Specific health, safety and environmental issues ............................................................................................................... 6

5.1 General ........................................................................................................................................................................................................... 6

5.2 Environmental considerations related to water heating and cooling issues .................................... 6

5.3 Safety considerations ........................................................................................................................................................................ 6

5.3.1 General requirements .................................................................................................................................................. 6

5.3.2 Layout constrains ............................................................................................................................................................ 7

5.3.3 Layout constraints with respect to surroundings ............................................................................... 7

5.3.4 Layout constraints with respect to facility arrangement .............................................................. 8

5.3.5 Risk prevention measures ....................................................................................................................................10

6 Mooring and stationkeeping .................................................................................................................................................................14

7 Hull design ...............................................................................................................................................................................................................15

8 LNG storage .............................................................................................................................................................................................................15

8.1 Specific requirements for cargo tank pressure management .....................................................................15

8.2 Specific requirements for LNGC overpressure protection .............................................................................16

8.3 Rollover risk ...........................................................................................................................................................................................16

9 Transfer systems ...............................................................................................................................................................................................16

9.1 General ........................................................................................................................................................................................................16

9.2 Send-out natural gas: NG gas transfer requirements ..........................................................................................16

9.2.1 Functional requirements .......................................................................................................................................16

9.2.2 Transfer systems design .........................................................................................................................................17

9.2.3 Emergency disconnection .....................................................................................................................................17

9.2.4 Operating envelope ........................................................................................................................................... ..........18

9.3 LNG sampling ........................................................................................................................................................................................19

10 BOG handling and recovery ....................................................................................................................................................................20

10.1 General ........................................................................................................................................................................................................20

10.2 LNG tank design pressure flexibility .................................................................................................................................20

10.3 Specific requirements for recondenser ..........................................................................................................................20

10.4 Specific requirements for gas compressors ................................................................................................................21

10.4.1 General...................................................................................................................................................................................21

10.4.2 Specific requirements for LD compressors ............................................................................................21

10.4.3 Specific requirements for HD compressors ...........................................................................................21

10.4.4 Specific requirements for HP or MSO compressors .......................................................................21

10.5 Specific requirements for reliquefaction unit ...........................................................................................................21

© ISO 2020 – All rights reserved iii
---------------------- Page: 5 ----------------------
oSIST prEN ISO 20257-2:2020
ISO/DIS 20257-2:2020(E)

11 Regasification equipment requirements .................................................................................................................................22

11.1 LNG pumps ..............................................................................................................................................................................................22

11.1.1 General...................................................................................................................................................................................22

11.1.2 Functional requirements .......................................................................................................................................22

11.1.3 Materials selection ......................................................................................................................................................22

11.1.4 In-tank LNG pump .......................................................................................................................................................22

11.1.5 HP LNG pump ..................................................................................................................................................................22

11.2 LNG vaporization system ............................................................................................................................................................23

11.2.1 Functional requirements .......................................................................................................................................23

11.2.2 Vaporization type .........................................................................................................................................................23

11.2.3 Materials selection ......................................................................................................................................................24

11.2.4 Protective coating ........................................................................................................................................................24

11.2.5 Marine growth ................................................................................................................................................................24

11.2.6 Stability/vibration .......................................................................................................................................................24

11.2.7 Safety relief valves .......................................................................................................................................................24

11.3 Trim heater..............................................................................................................................................................................................25

11.4 Venting from regasification systems .................................................................................................................................25

12 Gas send out............................................................................................................................................................................................................25

12.1 High integrity pressure protection system ..................................................................................................................25

12.1.1 Send-out pressure control ....................................................................................................................................25

12.1.2 Typical description of HIPPS ..............................................................................................................................26

12.1.3 Design requirements for HIPPS .......................................................................................................................27

12.2 Send-out gas metering ...................................................................................................................................................................28

12.2.1 Uses of send-out gas metering ..........................................................................................................................28

12.2.2 Measurement devices type ..................................................................................................................................28

12.2.3 Accuracy ...............................................................................................................................................................................28

12.2.4 External influences .....................................................................................................................................................29

12.2.5 Gas chromatograph – Gas analyser ...............................................................................................................29

12.2.6 Sparing philosophy .....................................................................................................................................................29

12.2.7 Z-configuration ...............................................................................................................................................................29

12.3 Odorization systems ........................................................................................................................................................................29

13 Utilities ........................................................................................................................................................................................................................29

13.1 General ........................................................................................................................................................................................................29

13.2 Cooling and heating medium ...................................................................................................................................................30

13.2.1 Cooling medium ...................................................................... .......................................................................................30

13.2.2 Heating medium ............................................................................................................................................................30

13.2.3 Nitrogen system ...................................................................... .......................................................................................30

13.2.4 Fuel gas ...................................................................... ............................................................................................................31

14 Process and safety control systems ...............................................................................................................................................31

14.1 General requirements ....................................................................................................................................................................31

14.2 Interfaces between FSRU and gas export connection ........................................................................................31

14.3 Communication onshore/offshore .....................................................................................................................................31

15 Security management ..................................................................................................................................................................................31

16 Commissioning ....................................................................................................................................................................................................31

17 Inspection and maintenance .................................................................................................................................................................32

17.1 General requirements ....................................................................................................................................................................32

17.2 Cargo tank ................................................................................................................................................................................................32

17.3 In-tank LNG pump .............................................................................................................................................................................32

17.4 Regasification equipment ...........................................................................................................................................................32

17.4.1 HP LNG pump ..................................................................................................................................................................32

17.4.2 LNG vaporizer..................................................................................................................................................................32

17.5 Recondenser ...........................................................................................................................................................................................32

17.6 Handling/Crane equipment ......................................................................................................................................................33

18 Preservation and corrosion protection .....................................................................................................................................33

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oSIST prEN ISO 20257-2:2020
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19 Conversion of existing unit to floating LNG installations ........................................................................................33

Annex A (informative) Regasification system description..........................................................................................................35

Bibliography .............................................................................................................................................................................................................................40

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oSIST prEN ISO 20257-2:2020
ISO/DIS 20257-2:2020(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 9, Liquefied natural

gas installations and equipment.
A list of all parts in the ISO 202572 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.
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oSIST prEN ISO 20257-2:2020
ISO/DIS 20257-2:2020(E)
Introduction

This document addresses specific issues related to floating LNG storage and regasification units (FSRU)

and supplements the general requirements for floating LNG installations as provided in ISO 20257-1.

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oSIST prEN ISO 20257-2:2020
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oSIST prEN ISO 20257-2:2020
DRAFT INTERNATIONAL STANDARD ISO/DIS 20257-2:2020(E)
Installation and equipment for liquefied natural gas -
Design of floating LNG installations —
Part 2:
Specific FSRU issues
1 Scope

This document provides specific requirements and guidance for the design and operation of floating

LNG storage and regasification unit (FSRU) as described in ISO 20257-1.

This document is applicable to offshore, near-shore or docked FSRU and applies to both new-built and

converted FSRU.
This document includes jetty in the case of mooring to of an FSRU.
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 20257-1:2020, Installation and equipment for liquefied natural gas — Design of offshore installations —

Part 1: General requirements
AGA 9, Measurement of Gas by Multipath Ultrasonic Meters
AGA 10, Speed of Sound in Natural Gas and Other Related Hydrocarbon Gases
EN 1776, Gas infrastructure — Gas measuring systems — Functional requirements

EN 12186, Gas infrastructure — Gas pressure regulating stations for transmission and distribution -

Functional requirements

EN 14382, Safety devices for gas pressure regulating stations and installations — Gas safety shut-off

devices for inlet pressures up to 100 bar

IEC 61508 (all parts), Functional safety of electrical/electronic/programmable electronic safety-

related systems

IEC 61511 (all parts), Functional safety — Safety instrumented systems for the process industry sector

ISO 5168, Measurement of fluid flow — Procedures for the evaluation of uncertainties

ISO 6976, Natural gas — Calculation of calorific values, density, relative density and Wobbe indices from

composition

ISO 8943, Refrigerated light hydrocarbon fluids — Sampling of liquefied natural gas — Continuous and

intermittent methods

ISO 12213-1, Natural gas — Calculation of compression factor — Part 1: Introduction and guidelines

ISO 12213-2, Natural gas — Calculation of compression factor — Part 2: Calculation using molar-

composition analysis
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oSIST prEN ISO 20257-2:2020
ISO/DIS 20257-2:2020(E)

ISO 13709, Centrifugal pumps for petroleum, petrochemical and natural gas industries

ISO 16903, Petroleum and natural gas industries — Characteristics of LNG, influencing the design, and

material selection

ISO 17089-1, Measurement of fluid flow in closed conduits — Ultrasonic meters for gas — Part 1: Meters for

custody transfer and allocation measurement

Code IGC International Code of the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk,

International Maritime Organization (IMO)
OIML R 137-1, Gas meters — Part 1: Metrological and technical requirements
OIML R 137-2, Gas meters — Part 2: Metrological controls and performance tests
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 20257-1:2020 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/
3.1.1
fiscal metering

metering aimed to define the quantity and financial value of hydrocarbon product transaction

3.1.2
custody transfer
physical transfer of hydrocarbon
...