IEC TS 62600-10:2021

Marine energy - Wave, tidal and other water current converters - Part 10: Assessment of mooring system for marine energy converters (MECs)

IEC TS 62600-10:2021 provide uniform methodologies for the design and assessment of mooring systems for floating Marine Energy Converters (MECs) (as defined in the TC 114 scope). It is intended to be applied at various stages, from mooring system assessment to design, installation and maintenance of floating Marine Energy Converters plants.
This document is applicable to mooring systems for floating Marine Energy Converters units of any size or type in any open water conditions. Some aspects of the mooring system design process are more detailed in existing and well-established mooring standards. The intent of this document is to highlight the different requirements of Marine Energy Converters and not duplicate existing standards or processes. This document defines rules and assessment procedures for the design, installation and maintenance of mooring system with respect to technical requirements for floating marine energy converters.
This second edition cancels and replaces the first edition published in 2015. This edition includes the following significant technical changes with respect to the previous edition:
a. Added specific Design Load Cases in alignment with 62600-2.
b. Added additional robustness check requirements.
c. Rearranged document for ease of use and alignment with 62600-2.
d. Added additional informative clauses on mooring materials.

General Information

• Status: Published
• Publication Date: 21-Jul-2021
• ICS: 27.140 - Hydraulic energy engineering
• Technical Committee: TC 114 - Marine energy - Wave, tidal and other water current converters
• Current Stage: PPUB - Publication issued
• Completion Date: 22-Jul-2021

Standards Content (sample)

IEC TS 62600-10
Edition 2.0 2021-07
TECHNICAL
SPECIFICATION
colour
inside
Marine energy – Wave, tidal and other water current converters –
Part 10: Assessment of mooring system for marine energy converters (MECs)
IEC TS 62600-10:2021-07(en)
---------------------- Page: 1 ----------------------
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IEC TS 62600-10
Edition 2.0 2021-07
TECHNICAL
SPECIFICATION
colour
inside
Marine energy – Wave, tidal and other water current converters –
Part 10: Assessment of mooring system for marine energy converters (MECs)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.140 ISBN 978-2-8322-1001-5

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TS 62600-10:2021 © IEC 2021
CONTENTS

FOREWORD ......................................................................................................................... 6

INTRODUCTION ................................................................................................................... 8

1 Scope ............................................................................................................................ 9

2 Normative references..................................................................................................... 9

3 Terms and definitions .................................................................................................... 9

4 Abbreviated terms ....................................................................................................... 10

5 Principal elements ....................................................................................................... 10

5.1 General ............................................................................................................... 10

5.2 Technology qualification ...................................................................................... 10

5.3 Safety and risk consideration ............................................................................... 11

5.4 Safety levels ....................................................................................................... 11

5.5 Design procedure ................................................................................................ 11

5.6 Inspection and maintenance requirements ........................................................... 11

6 Environmental and site conditions ................................................................................ 11

6.1 General ............................................................................................................... 11

6.2 Primary environmental conditions ........................................................................ 12

6.3 Secondary environmental conditions .................................................................... 12

6.3.1 General ....................................................................................................... 12

6.3.2 Marine growth .............................................................................................. 12

6.3.3 Seabed conditions ....................................................................................... 12

6.4 Site characteristics .............................................................................................. 12

6.4.1 General ....................................................................................................... 12

6.4.2 Environmentally sensitive and protected areas and marine animals ............... 12

6.4.3 Nearshore impact ......................................................................................... 12

6.4.4 Vandalism and misuse ................................................................................. 13

6.4.5 Marine traffic ................................................................................................ 13

6.4.6 Shallow water conditions .............................................................................. 13

7 Design load cases ....................................................................................................... 13

7.1 General ............................................................................................................... 13

7.2 Analysis procedure overview ............................................................................... 13

7.3 Load categories .................................................................................................. 14

7.3.1 General ....................................................................................................... 14

7.3.2 Dynamic analysis of MEC response to environmental conditions ................... 15

7.3.3 Low frequency loads .................................................................................... 15

7.3.4 Wave frequency loads on mooring components ............................................ 15

7.3.5 Wave frequency loads on MEC ..................................................................... 15

7.3.6 High frequency loading ................................................................................. 16

7.4 Interaction with waves, currents, wind, water level and ice ................................... 16

7.4.1 General ....................................................................................................... 16

7.4.2 Resonant response ...................................................................................... 17

7.4.3 Design return period for short term deployments ........................................... 17

7.5 Mooring line components ..................................................................................... 17

7.5.1 General ....................................................................................................... 17

7.5.2 Component strength ..................................................................................... 17

7.5.3 Component fatigue life ................................................................................. 18

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IEC TS 62600-10:2021 © IEC 2021 – 3 –

7.5.4 Redundancy ................................................................................................. 18

7.5.5 Clearance .................................................................................................... 18

7.6 Umbilical considerations ...................................................................................... 18

7.6.1 Umbilical response ....................................................................................... 18

7.6.2 Umbilical strength ........................................................................................ 18

7.6.3 Umbilical offset and clearance limits ............................................................. 18

7.7 Limit states ......................................................................................................... 19

7.7.1 General ....................................................................................................... 19

7.7.2 Ultimate limit state (ULS) ............................................................................. 19

7.7.3 Accidental limit state (ALS) .......................................................................... 19

7.7.4 Serviceability limit state (SLS) ...................................................................... 19

7.7.5 Fatigue limit state (FLS) ............................................................................... 19

7.7.6 Consequence class safety factors ................................................................ 20

7.7.7 Mooring component failure ........................................................................... 20

7.7.8 Anchor holding capacity ............................................................................... 20

7.7.9 Load case modelling and simulation ............................................................. 21

7.7.10 Design conditions ......................................................................................... 22

8 In-service inspection, monitoring, testing, and maintenance .......................................... 32

8.1 General ............................................................................................................... 32

8.2 Anchor proof loading ........................................................................................... 33

8.3 Component replacement ...................................................................................... 33

8.3.1 General ....................................................................................................... 33

8.3.2 Fibre rope component inspection and replacement ....................................... 33

8.3.3 Inspection and predictive procedures ............................................................ 33

8.4 In air and splash zone mooring line sections ........................................................ 34

8.5 Submerged mooring line sections ........................................................................ 34

8.6 Commissioning and decommissioning procedures ................................................ 35

Annex A (informative) Moorings and anchoring systems ..................................................... 36

A.1 Types of moorings and anchoring systems ........................................................... 36

A.1.1 General ....................................................................................................... 36

A.1.2 Mooring systems .......................................................................................... 36

A.2 Mooring line components ..................................................................................... 38

A.2.1 General ....................................................................................................... 38

A.2.2 Chain ........................................................................................................... 38

A.2.3 Wire rope ..................................................................................................... 39

A.2.4 Synthetic rope .............................................................................................. 39

A.2.5 Elastic tethers .............................................................................................. 46

A.2.6 Clump weights ............................................................................................. 47

A.2.7 Buoyancy aids ............................................................................................. 47

A.2.8 Connectors and accessories ......................................................................... 47

A.3 Anchors .............................................................................................................. 48

A.3.1 General ....................................................................................................... 48

A.3.2 Drag embedment anchor .............................................................................. 48

A.3.3 Pile anchor .................................................................................................. 49

A.3.4 Suction anchor ............................................................................................. 49

A.3.5 Gravity installed anchor ................................................................................ 50

A.3.6 Gravity anchor ............................................................................................. 51

A.3.7 Plate anchor ................................................................................................ 52

A.3.8 Screw and rock anchors ............................................................................... 52

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– 4 – IEC TS 62600-10:2021 © IEC 2021

A.3.9 Type selection ............................................................................................. 53

A.3.10 Holding capacity .......................................................................................... 53

A.3.11 Sediment and rock conditions ....................................................................... 54

A.3.12 Fluke setting ................................................................................................ 54

A.3.13 Installation ................................................................................................... 54

A.3.14 Proof loading ............................................................................................... 55

A.3.15 Directional anchor loading ............................................................................ 55

A.3.16 Failure mode ................................................................................................ 55

A.3.17 Environmental loading .................................................................................. 55

A.3.18 Failure point ................................................................................................. 55

Annex B (normative) Safety and risk considerations ........................................................... 56

B.1 General ............................................................................................................... 56

B.2 Risk .................................................................................................................... 56

B.2.1 General ....................................................................................................... 56

B.2.2 Definition ..................................................................................................... 56

B.2.3 Consequence types ...................................................................................... 56

B.3 Risk assessment methodology ............................................................................. 57

B.3.1 General ....................................................................................................... 57

B.3.2 Methodology flowchart ................................................................................. 57

B.4 Consequence considerations for mooring failure .................................................. 59

B.5 Consequence classification ................................................................................. 59

B.5.1 General ....................................................................................................... 59

B.5.2 Consequence impact considerations ............................................................. 60

B.5.3 Risk mitigation considerations ...................................................................... 61

B.5.4 Risk acceptance ........................................................................................... 61

Annex C (informative) Numerical modelling considerations ................................................. 63

C.1 General ............................................................................................................... 63

C.2 Mooring, umbilical, and dynamic cable models ..................................................... 63

C.2.1 General ....................................................................................................... 63

C.2.2 Static and catenary models .......................................................................... 63

C.2.3 Discrete models ........................................................................................... 63

C.2.4 Floating unit numerical models ..................................................................... 63

Bibliography ....................................................................................................................... 65

Figure 1 – Recommended conceptual mooring analysis procedure ....................................... 14

Figure A.1 – Spread mooring configuration .......................................................................... 36

Figure A.2 – Catenary anchor leg mooring configuration ...................................................... 37

Figure A.3 – Single anchor leg mooring configuration .......................................................... 37

Figure A.4 – Turret mooring configuration ............................................................................ 38

Figure A.5 – Studless and studlink chain ............................................................................. 38

Figure A.6 – Typical wire rope construction ......................................................................... 39

Figure A.7 – Parallel yarn rope ............................................................................................ 41

Figure A.8 – Parallel core rope ............................................................................................ 41

Figure A.9 – Rope construction with 18+12+6+1 format ....................................................... 42

Figure A.10 – Three strand laid construction ........................................................................ 42

Figure A.11 – Rope with 8 plait braid construction ............................................................... 43

Figure A.12 – Rope with braid on braid construction ............................................................ 43

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IEC TS 62600-10:2021 © IEC 2021 – 5 –

Figure A.13 – Types of connectors ...................................................................................... 48

Figure A.14 – Drag embedment anchor ............................................................................... 49

Figure A.15 – Pile anchor .................................................................................................... 49

Figure A.16 – Suction anchor .............................................................................................. 50

Figure A.17 – Gravity installed torpedo anchor .................................................................... 51

Figure A.18 – Gravity installed anchor with rotating load arm ............................................... 51

Figure A.19 – Gravity anchor............................................................................................... 52

Figure A.20 – Suction or pile driven plate anchor ................................................................. 52

Figure A.21 – Screw anchor ................................................................................................ 53

Figure A.22 – Rock anchor .................................................................................................. 53

Figure B.1 – General risk methodology flowchart ................................................................. 58

Table 1 – Potential nearshore impacts ................................................................................. 13

Table 2 – Combinations of uncorrelated extreme events ...................................................... 17

Table 3 – Consequence class associated safety factors for dynamic analysis

techniques .......................................................................................................................... 20

Table 4 – Safety factors for holding capacity of drag anchors ............................................... 21

Table 5 – Safety factors for holding capacity of anchor piles and suction piles ..................... 21

Table 6 – Safety factors for holding capacity of gravity and plate anchors ............................ 21

Table 7 – Design load cases for WECs ................................................................................ 24

Table 8 – Design load cases for CECs ................................................................................ 26

Table A.1 – Generalized comparison of mooring line material characteristics ....................... 40

Table A.2 – Properties for selection of synthetic fibre .......................................................... 44

Table A.3 – Generalized comparison of common rope relevant material properties ............... 44

Table B.1 – Consequence categories .................................................................................. 59

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– 6 – IEC TS 62600-10:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MARINE ENERGY –
WAVE, TIDAL AND OTHER WATER CURRENT CONVERTERS –
Part 10: Assessment of mooring system
for marine energy converters (MECs)
FOREWORD

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IEC TS 62600-10 has been prepared by IEC technical committee 114: Marine energy – Wave,

tidal and other water current converters. It is a Technical Specification.

This second edition cancels and replaces the first edition published in 2015. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
a) Added specific Design Load Cases in alignment with 62600-2.
b) Added additional robustness check requirements.
c) Rearranged document for ease of use and alignment with 62600-2.
d) Added additional informative clauses on mooring materials.
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IEC TS 62600-10:2021 © IEC 2021 – 7 –
The text of this Technical Specification is based on the following documents:
Draft Report on voting
114/390/DTS 114/395/RVDTS
114/395A/RVDTS

Full information on the voting for its approval can be found in the report on voting indicated in

the above table.

A list of all parts in the IEC 62600 series, published under the general title Marine energy –

Wave, tidal and other water current converters, can be found on the IEC website.

The language used for the development of this Technical Specification is English.

This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in

accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available

at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are

described in greater detail at www.iec.ch/standardsdev/publications.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct understanding

of its contents. Users should therefore print this document using a colour printer.

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– 8 – IEC TS 62600-10:2021 © IEC 2021
INTRODUCTION

This document defines rules and assessment procedures for the design, installation and

maintenance of mooring system with respect to technical requirements for floating marine

energy converters.

The proposed work aims to bring together expert knowledge from the marine energy power and

offshore engineering industries in order to formulate a guideline specification of the design,

installation and maintenance requirements for mooring system of floating Marine Energy

Converters.

In addition to safety and ocean environmental requirements, this document focuses on the

strength requirements of mooring systems for Marine Energy Converters.
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IEC TS 62600-10:2021 © IEC 2021 – 9 –
MARINE ENERGY –
WAVE, TIDAL AND OTHER WATER CURRENT CONVERTERS –
Part 10: Assessment of mooring system
for marine energy converters (MECs)
1 Scope

The purpose of this document is to provide uniform methodologies for the design and

assessment of mooring systems for floating Marine Energy Converters (MECs) (as defined in

the TC 114 scope).
...