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

IEC TS 62600-10:2015(E) provides uniform methodologies for the design and assessment of mooring systems for floating MECs. It is intended to be applied at various stages, from mooring system assessment to design, installation and maintenance of floating MEC plants. Is applicable to mooring systems for floating MEC units of any size or type in any open water conditions. The intent of this technical specification is to highlight the different requirements of MECs.

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Status
Published
Publication Date
26-Mar-2015
Current Stage
DELPUB - Deleted Publication
Completion Date
22-Jul-2021
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IEC TS 62600-10
Edition 1.0 2015-03
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 62600-10:2015-03(en)
---------------------- Page: 1 ----------------------
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IEC TS 62600-10
Edition 1.0 2015-03
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 978-2-8322-2431-1

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

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TS 62600-10:2015 © IEC 2015
CONTENTS

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

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

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

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

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

4 Abbreviated terms ....................................................................................................... 11

5 Principal element ......................................................................................................... 12

5.1 General ............................................................................................................... 12

5.2 Mooring and anchor systems ............................................................................... 12

5.3 Design considerations ......................................................................................... 12

5.4 Safety and risk consideration ............................................................................... 13

5.5 Analysis procedure .............................................................................................. 13

5.6 Inspection and maintenance requirements ........................................................... 13

6 Types of moorings and anchoring systems ................................................................... 13

6.1 General ............................................................................................................... 13

6.2 Mooring systems ................................................................................................. 13

6.2.1 General ....................................................................................................... 13

6.2.2 Spread moorings (catenary, taut-line and semi-taut-line) ............................... 13

6.2.3 Single point moorings (SPM) ........................................................................ 14

6.3 Mooring line components ..................................................................................... 15

6.3.1 General ....................................................................................................... 15

6.3.2 Chain ........................................................................................................... 15

6.3.3 Wire rope ..................................................................................................... 16

6.3.4 Synthetic rope .............................................................................................. 17

6.3.5 Clump weights ............................................................................................. 17

6.3.6 Buoyancy aids ............................................................................................. 17

6.3.7 Connectors and accessories ......................................................................... 17

6.4 Anchors types ..................................................................................................... 18

6.4.1 General ....................................................................................................... 18

6.4.2 Drag embedment anchor .............................................................................. 18

6.4.3 Pile anchor .................................................................................................. 19

6.4.4 Suction anchor ............................................................................................. 19

6.4.5 Gravity installed anchor ................................................................................ 20

6.4.6 Gravity anchor ............................................................................................. 20

6.4.7 Plate anchor ................................................................................................ 21

6.4.8 Screw anchor ............................................................................................... 21

7 Design consideration ................................................................................................... 22

7.1 General ............................................................................................................... 22

7.2 Limit states ......................................................................................................... 22

7.2.1 Ultimate limit state (ULS) ............................................................................. 22

7.2.2 Accidental limit state (ALS) .......................................................................... 22

7.2.3 Serviceability limit state (SLS) ...................................................................... 22

7.2.4 Fatigue limit state (FLS) ............................................................................... 22

7.3 External conditions .............................................................................................. 23

7.3.1 General ....................................................................................................... 23

7.3.2 Metocean conditions .................................................................................... 23

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IEC TS 62600-10:2015 © IEC 2015 – 3 –

7.3.3 Marine growth .............................................................................................. 23

7.3.4 Marine life .................................................................................................... 23

7.3.5 Environmentally sensitive and protected areas and marine animals ............... 23

7.3.6 Nearshore impact ......................................................................................... 23

7.3.7 Vandalism and misuse ................................................................................. 23

7.3.8 Marine traffic ................................................................................................ 24

7.4 Assorted loading ................................................................................................. 24

7.4.1 General ....................................................................................................... 24

7.4.2 Low frequency loads .................................................................................... 24

7.4.3 Wave frequency loads on mooring components ............................................ 24

7.4.4 Wave frequency loads on MEC ..................................................................... 25

7.4.5 High frequency loading ................................................................................. 25

7.5 Mooring line components ..................................................................................... 25

7.5.1 Component strength ..................................................................................... 25

7.5.2 Component fatigue life ................................................................................. 25

7.5.3 Redundancy ................................................................................................. 25

7.5.4 Clearance .................................................................................................... 25

7.6 Umbilical considerations ...................................................................................... 26

7.6.1 Umbilical response ....................................................................................... 26

7.6.2 Umbilical strength ........................................................................................ 26

7.6.3 Umbilical offset and clearance limits ............................................................. 26

7.7 Anchors .............................................................................................................. 26

7.7.1 Type selection ............................................................................................. 26

7.7.2 Holding capacity .......................................................................................... 26

7.7.3 Sediment and rock conditions ....................................................................... 26

7.7.4 Fluke setting ................................................................................................ 27

7.7.5 Installation ................................................................................................... 27

7.7.6 Proof loading ............................................................................................... 27

7.7.7 Directional anchor loading ............................................................................ 27

7.7.8 Failure mode ................................................................................................ 27

7.7.9 Environmental loading .................................................................................. 27

8 Safety and risk considerations ..................................................................................... 27

8.1 Overview ............................................................................................................ 27

8.2 Risk .................................................................................................................... 27

8.2.1 General ....................................................................................................... 27

8.2.2 Definition ..................................................................................................... 28

8.2.3 Consequence types ...................................................................................... 28

8.2.4 General risk mitigation ................................................................................. 28

8.2.5 ALARP principle ........................................................................................... 28

8.3 Risk assessment methodology ............................................................................. 28

8.3.1 General ....................................................................................................... 28

8.3.2 Methodology flowchart ................................................................................. 29

8.3.3 Basic considerations .................................................................................... 30

8.3.4 Probability assessment ................................................................................ 31

8.3.5 Consequence classification assessment ....................................................... 31

8.4 Consequence considerations for mooring failure .................................................. 31

8.5 Consequence classification ................................................................................. 31

8.5.1 General ....................................................................................................... 31

8.5.2 Consequence impact considerations ............................................................. 32

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– 4 – IEC TS 62600-10:2015 © IEC 2015

8.5.3 Waterway navigation impacts ....................................................................... 33

8.5.4 Environmentally sensitive and protected sites ............................................... 33

8.5.5 Archaeological sites ..................................................................................... 33

8.6 Risk mitigation considerations ............................................................................. 33

8.6.1 Mitigation overview ...................................................................................... 33

8.6.2 Probability reduction .................................................................................... 33

8.6.3 Consequence reduction ................................................................................ 33

8.7 Risk acceptance .................................................................................................. 34

8.7.1 Acceptance overview ................................................................................... 34

8.7.2 Documentation ............................................................................................. 34

9 Analysis procedure ...................................................................................................... 34

9.1 General ............................................................................................................... 34

9.2 Basic considerations ........................................................................................... 34

9.3 Analysis procedure overview ............................................................................... 35

9.4 Modelling consideration ....................................................................................... 36

9.4.1 General ....................................................................................................... 36

9.4.2 Mooring and umbilical models ...................................................................... 36

9.4.3 Floating unit numerical models ..................................................................... 36

9.4.4 Coupled and uncoupled analysis .................................................................. 37

9.5 Analysis procedure considerations ....................................................................... 37

9.5.1 Metocean directionality ................................................................................ 37

9.5.2 Resonant response ...................................................................................... 37

9.5.3 Dynamic mooring analysis ............................................................................ 37

9.5.4 Design situations of ULS .............................................................................. 38

9.5.5 Design situations of ALS .............................................................................. 38

9.5.6 Design situations of FLS .............................................................................. 38

9.5.7 Design situations of SLS .............................................................................. 38

9.6 Mooring design criteria ........................................................................................ 38

9.6.1 Design return period .................................................................................... 38

9.6.2 Consequence class design factor ................................................................. 38

9.6.3 Mooring line component failure ..................................................................... 39

9.6.4 Anchor holding capacity ............................................................................... 39

10 In-service inspection, monitoring, testing, and maintenance .......................................... 40

10.1 General ............................................................................................................... 40

10.2 Mooring system proof loading .............................................................................. 41

10.3 Component replacement ...................................................................................... 41

10.4 In air and splash zone mooring line sections ........................................................ 41

10.5 Submerged mooring line sections ........................................................................ 41

10.6 Commissioning and decommissioning procedures ................................................ 42

Annex A (informative) Sample mooring design .................................................................... 43

A.1 General ............................................................................................................... 43

A.2 Problem layout .................................................................................................... 43

A.3 Consequence class identification ......................................................................... 44

A.4 Mooring design process ...................................................................................... 47

Bibliography ....................................................................................................................... 50

Figure 1 – Spread mooring configuration ............................................................................. 14

Figure 2 – Catenary anchor leg mooring configuration ......................................................... 14

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IEC TS 62600-10:2015 © IEC 2015 – 5 –

Figure 3 – Single anchor leg mooring configuration ............................................................. 15

Figure 4 – Turret mooring configuration ............................................................................... 15

Figure 5 – Studless and studlink chain ................................................................................ 16

Figure 6 – Typical wire rope construction ............................................................................ 16

Figure 7 – Types of connectors ........................................................................................... 18

Figure 8 – HHP drag embedment anchor ............................................................................. 19

Figure 9 – Pile anchor ......................................................................................................... 19

Figure 10 – Suction anchor ................................................................................................. 20

Figure 11 – Gravity installed anchor .................................................................................... 20

Figure 12 – Gravity anchor .................................................................................................. 21

Figure 13 – Plate anchor ..................................................................................................... 21

Figure 14 – Screw anchor ................................................................................................... 22

Figure 15 – General risk methodology flowchart .................................................................. 30

Figure 16 – Conceptual mooring analysis procedure ............................................................ 35

Figure A.1 – Potential tidal current MEC installation locations A, B; artificial reef C;

fish farm D; marine traffic corridor E .................................................................................... 43

Figure A.2 – Mooring line component minimum ASF for each return period environment

5, 10, 20, 50, and 100 plotted to determine mooring ULS return period ................................ 48

Figure A.3 – Anchor minimum ASF for each return period environment 5, 10, 20, 50,

and 100 plotted to determine anchor ULS return period ....................................................... 48

Table 1 – Potential nearshore impacts ................................................................................. 23

Table 2 – Consequence categories ..................................................................................... 31

Table 3 – Consequence class ............................................................................................. 32

Table 4 – Consequence class associated design factors ...................................................... 39

Table 5 – Safety factors for ULS and ALS conditions ........................................................... 39

Table 6 – Safety factors for holding capacity of drag anchors factors ................................... 40

Table 7 – Safety factors for holding capacity of anchor piles and suction piles ..................... 40

Table 8 – Safety factors for holding capacity of gravity and plate anchors ............................ 40

Table A.1 –Consequence classification matrix: location A .................................................... 45

Table A.2 – Consequence classification matrix: location B ................................................... 46

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– 6 – IEC TS 62600-10:2015 © IEC 2015
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, which is a technical specification, has been prepared by IEC technical

committee 114: Marine energy – Wave, tidal and other water current converters.
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IEC TS 62600-10:2015 © IEC 2015 – 7 –
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
114/140/DTS 114/150A/RVC

Full information on the voting for the approval of this technical specification can be found in

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– 8 – IEC TS 62600-10:2015 © IEC 2015
...

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