dnvgl-se-0422 certification of floating wind turbines...life-cycle phases from the early floating...

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DNV GL AS

SERVICE SPECIFICATION

DNVGL-SE-0422 Edition July 2018

Certification of floating wind turbines

FOREWORD

DNV GL service specifications contain procedural requirements for obtaining and retainingcertificates and other conformity statements to the objects, personnel, organisations and/oroperations in question.

© DNV GL AS July 2018

Any comments may be sent by e-mail to [email protected]

This service document has been prepared based on available knowledge, technology and/or information at the time of issuance of thisdocument. The use of this document by others than DNV GL is at the user's sole risk. DNV GL does not accept any liability or responsibilityfor loss or damages resulting from any use of this document.

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Service specification — DNVGL-SE-0422. Edition July 2018 Certification of floating wind turbines

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CONTENTS

Changes – current.................................................................................................. 3

Section 1 General....................................................................................................61.1 Introduction......................................................................................61.2 Objective...........................................................................................71.3 Scope................................................................................................ 71.4 Application........................................................................................71.5 References........................................................................................ 81.6 Definitions and abbreviations......................................................... 111.7 Technology readiness levels........................................................... 181.8 Deliverables.................................................................................... 18

Section 2 Service overview................................................................................... 232.1 General........................................................................................... 232.2 Certification modules for floating wind turbines.............................232.3 Concept level certification.............................................................. 262.4 Prototype level certification............................................................262.5 Site type level certification.............................................................262.6 Project level certification................................................................272.7 In-service level certification........................................................... 28

Section 3 Detailed service description.................................................................. 293.1 General........................................................................................... 293.2 Concept level certification.............................................................. 293.3 Prototype level certification............................................................333.4 Site type level certification.............................................................383.5 Project level certification................................................................473.6 In-service level certification........................................................... 54

Section 4 Certificate and statements - procedural requirements......................... 564.1 General........................................................................................... 564.2 Assessment documents...................................................................564.3 Deviations....................................................................................... 564.4 Modification and recertification...................................................... 564.5 Integration of certificates...............................................................574.6 Combination of standards...............................................................574.7 Customer obligations...................................................................... 584.8 Rules for use of the certificate....................................................... 58

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4.9 Certification requirements and quality management...................... 594.10 Survey requirements and personnel safety...................................59

Appendix A Technology qualification.................................................................... 60A.1 Technology assessment.................................................................. 60A.2 Risk assessment............................................................................. 61A.3 Risk matrix..................................................................................... 61A.4 Technology qualification plan......................................................... 64

Appendix B Deliverable examples......................................................................... 65B.1 Project certificate........................................................................... 65B.2 Statement of compliance................................................................ 66

Changes – historic................................................................................................67


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SECTION 1 GENERAL

1.1 IntroductionCertification according to this service specification (SE) is a procedure by which DNV GL gives writtenassurance that a product design, the manufacturing, the testing, transport and installation, thecommissioning, operation and maintenance processes or services, conform to requirements specified in thisdocument.The certification scheme for floating wind turbines and related components presented herein constitutes arobust means to provide, through independent verification, evidence to stakeholders (financiers, partners,utility companies, insurance companies, the public, governmental and non-governmental organizations) thata set of requirements laid down in standards are being met during design and construction, and maintainedduring operation of a floating wind turbine project.The floating wind industry is fairly young and there is a need for different levels of services to reflect thelife-cycle phases from the early floating concept to the complete floating wind power plant as well as forindividual components and modules and to allow for risk management. It is the intention to cover the specialrequirements for floating wind turbines and their components.This service specification is an extension to the DNV GL service specifications for type and projectcertification for bottom mounted on- and offshore wind turbines. It should be considered in combination withDNVGL-SE-0441 Type and component certification of wind turbines and DNVGL-SE-0190 Project certificationof wind power plants. The services described herein consider the specific floating wind turbine requirementswhich are not covered by DNVGL-SE-0441 or DNVGL-SE-0190.For each life-cycle phase this service specification applies best practice and state-of-the-art proceduresavailable for floating wind turbine systems and related technical systems. The scope of work described in thisservice specification reduces for each life-cycle phase the characteristic risks by performing expert reviews,independent parallel calculations, full size or model testing, or inspections and surveillances depending on thespecific needs. For novel designs the risk-based approach is embedded in the service specification. As partof the technology qualification process it provides a robust and transparent system to deal with uncertaintiesand novelties without limiting innovation.The typical life-cycle phases of a floating wind turbine are shown in Figure 1-1.

Figure 1-1 Certification services aligned with the technology levels

The shown order of certification services may vary or overlap in specific certification projects. For instance,it is possible to follow-up with a project certification right after a successful completion of the prototypecertification. In such a case it shall be assured that the technical requirements of skipped or mergedcertification levels are covered by the applied higher level certification procedure.

Figure 1-2 Optional arrangement of certification services


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Guidance note:It is assumed that the extent of the steps will vary, as the industry maturity increases. It may be the case that for demonstratorprojects the prototype certification includes all elements of site type certification and parts of project certification. It is expected,that site type and project certification are performed in one step until mass component production will make a type certificationnecessary.National or other authority requirements may lead to variation or overlap of requirements.

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This service specification is divided into four main sections:

— Sec.1 provides general information on the scope of this service specification, definitions and references aswell as the structure of DNV GL deliverables for floating wind turbines.

— Sec.2 provides a service overview for the certification of floating wind turbines and the certificationmodules, the deliverables and their validity periods.

— Sec.3 provides a detailed service description from concept towards the complete project certification forfloating wind farms. Herein the required documentation for each certification module is listed.

— Sec.4 describes the procedural and contractual requirements for the certification services as well as themaintenance of the certificates.

1.2 ObjectiveThis document has a dual objective:

— it serves as a publicly available description of DNV GL’s services related to certification of floating windturbines, related components according to DNV GL’s standards and possible other relevant standards

— it shall be referred to as a contractual document in the certification contract between the customer andDNV GL. The document specifies the obligations of the customer when his floating wind turbine andrelated components are within the certification process. The document also specifies the obligations ofDNV GL and the tasks carried out by DNV GL for certification.

1.3 ScopeThis service specification specifies DNV GL's services for the certification of floating wind turbines and relatedcomponents from the floating concept, the installation of a prototype, the begin of a serial production, upto the development and operation of a complete floating wind power plant. This service specification coversconcept, prototype, site type, project certification and in-service of floating wind turbines in a modular andstraightforward system.Furthermore, it provides a common communication platform for describing the scope and extent of activitiesperformed for the certification of floating wind turbines and related components and give guidance forcommercial aspects of certification contracts.Due to the possibility to select individual certification modules depending on the specific needs this servicespecification defines the certification deliverables corresponding to an individual scope of work.It specifies the delivery and validity of DNV GL reports, statements of feasibility, statements of complianceand certificates and how to maintain these deliverables.

1.4 ApplicationA floating wind turbine is characterised by a floating substructure which is subject to hydrodynamic loading,vertically supported by the buoyancy of the structure. The substructure carries a wind energy conversionsystem. The forces induced by waves, currents, wind, etc. are balanced by a station keeping system.This service specification may be applied for the certification of floating wind turbines or the certification ofcomponents such as floaters, mooring systems or station keeping systems. If the term floating wind turbineis being used within this document it may be either mean the complete floating wind turbine unit or singlecomponents.


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This service specification applies to several certification levels and related assessment tasks for each life-cycle phase of a floating wind component, of a single unit, or of a complete floating wind farm.This service specification complies with the other service specification descriptions issued by DNV GL and isan extension to the below mentioned service specifications:

— DNVGL-SE-0190 Project certification of wind power plants— DNVGL-SE-0441 Type and component certification of wind turbines— DNVGL-SE-0073 Project certification of wind farms according to IEC 61400-22— DNVGL-SE-0074 Type and component certification of wind turbines according to IEC 61400-22.

Hence, the focus of this service specification is on the certification of specific floating wind turbinecomponents such as the floater and the station keeping system.The rotor-nacelle assembly (RNA) of a floating wind turbine typically carries already a certification which maybe integrated in the certification process according to [4.5]. Generally, the certification of the RNA accordingto this service specification is following the requirements given in DNVGL-SE-0441 and DNVGL-SE-0190.For certification of components of floating wind turbines not defined herein, DNVGL-SE-0441 shall be usedaccordingly.For the certification of other floating wind farm assets, such as substation(s), inner array cables, powercables, control stations, etc., reference is made to DNVGL-SE-0190.DNV GL service specifications, standards and recommended practice documents with relevance for floatingwind turbines are given in [1.5.2].

1.5 References

1.5.1 GeneralThis document makes reference to relevant DNV GL standards and other documents and to internationalcodes and standards. Unless otherwise specified in the certification agreement or in this service specification,the latest valid revision of each referenced document applies.In the following sections DNV GL documents of relevance for floating offshore wind farms are listed in Table1-1. External references are listed in Table 1-2.

1.5.2 DNV GL documentsThe DNV GL service document system is organized according to a three-level document hierarchy, with thesemain features:

— principles and procedures related to DNV GL’s certification and verification services are separated fromtechnical requirements and are presented in DNV GL service specifications (SE), and they present thescope and extent of DNV GL’s services, here for floating wind turbines

— technical requirements are issued as self-contained DNV GL standards (ST). These standards are issuedas neutral technical standards to enable their use by national authorities, as international codes and ascompany or project specifications without reference to DNV GL's services

— associated product documents are issued as DNV GL recommended practices (RP). Recommendedpractices provide DNV GL’s interpretation of safe engineering practice for general use by the industry.Guidance note:The latest revision of all DNV GL documents may be found in the list of publications on the DNV GL website www.dnvgl.com - DNVGL rules and standards.


#http://www.dnvgl.com


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Table 1-1 DNV GL documents

Document code Title

DNVGL-OS-B101 Metallic materials

DNVGL-OS-C101 Design of offshore steel structures, general - LRFD method

DNVGL-OS-C103 Structural design of column-stabilized units - LRFD method

DNVGL-OS-C105 Structural design of TLPs - LRFD method

DNVGL-OS-C106 Structural design of deep draught floating units/spars - LRFD method

DNVGL-OS-C301 Stability and watertight integrity

DNVGL-OS-C401 Fabrication and testing of offshore structures

DNVGL-OS-D101 Marine and machinery systems and equipment

DNVGL-OS-E301 Position mooring

DNVGL-OS-E302 Offshore mooring chain

DNVGL-OS-E303 Offshore fibre ropes

DNVGL-OS-E304 Offshore mooring steel wire ropes

DNVGL-RP-0360 Subsea power cables in shallow water

DNVGL-RP-0416 Corrosion protection for wind turbines

DNVGL-RP-C203 Fatigue design of offshore steel structures

DNVGL-RP-E305 Design, testing and analysis of offshore fibre ropes

DNVGL-RP-A203 Technology qualification

DNVGL-RP-C205 Environmental conditions and environmental loads

DNVGL-RP-C103 Column-stabilised units

DNVGL-RP-C212 Offshore soil mechanics and geotechnical engineering

DNVGL-RP-E301 Design and installation of fluke anchors

DNVGL-RP-E302 Design and installation of plate anchors in clay

DNVGL-RP-E303 Geotechnical design and installation of suction anchors in clay

DNVGL-RP-E304 Damage assessment of offshore fibre ropes for offshore mooring

DNVGL-RP-E305 Design, testing and analysis of offshore fibre ropes

DNVGL-SE-0073 Project certification of wind farms according to IEC 61400-22

DNVGL-SE-0074 Type and component certification of wind turbines according to IEC 61400-22

DNVGL-SE-0160 Technology qualification management and verification

DNVGL-SE-0176 Certification of navigation and aviation aids of offshore wind farms

DNVGL-SE-0190 Project certification of wind power plants

DNVGL-SE-0436 Shop approval in renewable energy

DNVGL-SE-0439 Certification of condition monitoring


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Document code Title

DNVGL-SE-0441 Type and component certification of wind turbines

DNVGL-SE-0448 Certification of service and maintenance activities in the wind energy industry

DNVGL-SE-0263 Certification of lifetime extension of wind turbines

DNVGL-SE-0420 Certification of meteorological masts

DNVGL-SE-0477 Risk based verification of offshore structures

DNVGL-ST-0119 Design of floating wind turbine structures

DNVGL-ST-0054 Transport and installation of wind power plants

DNVGL-ST-0076 Design of electrical installations for wind turbines

DNVGL-ST-0126 Support structures for wind turbines

DNVGL-ST-0359 Subsea power cables for wind turbines

DNVGL-ST-0361 Machinery for wind turbines

DNVGL-ST-0376 Rotor blades for wind turbines

DNVGL-ST-0437 Loads and site conditions for wind turbines

DNVGL-ST-0438 Control and protection systems for wind turbines

DNVGL-ST-C502 Offshore concrete structures

GL-IV-2 Rules and Guidelines - IV Industrial Services -Part 2: Guideline for the Certification of OffshoreWind Turbines

GL-IV-1 Rules and Guidelines - IV Industrial Services -Part 1: Guideline for the Certification of WindTurbines

GL-IV-7 Rules for the Certification and Construction - IV Industrial Services - Part 7: Offshore Substations

1.5.3 External documentsTable 1-2 External documents

Document code Title

BS EN 60812 Analysis techniques for system reliability - Procedure for failure mode and effects analysis (FMEA)

BSH 7005 Standard Design - Minimum requirements concerning the constructive design of offshore structureswithin the Execlusive Economic Zone (EEZ), Bundesamt für Seefahrt und Hydrographie, Germany

IEC 60300-1 Dependability management - Part 1: Guidance for management and application

IEC 61400-1 Wind Turbines - Part 1: Design requirements

IEC 61400-3 Wind Turbines - Part 3: Design requirements for offshore wind turbines

IEC 61400-13 Wind Turbines - Part 13: Measurement of mechanical loads

IEC 61400-22 Wind Turbines - Part 22: Compliance testing and certification

IEC/ISO 17000 Compliance assessment - Vocabulary and general principles


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Document code Title

IEC/ISO 17025 General requirements for the competence of testing and calibration laboratories

IEC/ISO 17065 Conformity assessment - Requirements for bodies certifying products, processes and services

IEC/ISO 31010 Risk management - Risk assessment techniques

IEC TS 61400-3-2 Design requirements for floating offshore wind turbines (under preparation)

IS-Code IMO Intact Stability Code IS-Code, 2008 - Resolution MSC 267(85)

ISO 9000 Quality management systems - Fundamentals and vocabulary

ISO 9001 Quality management systems - Requirements

1.6 Definitions and abbreviationsIn the following sections the verbal forms used herein, description of technical terms, abbreviationsand symbols are specified and defined. Additionally, various floating concepts and the definition of theircomponents are described and classified.

1.6.1 Definition of verbal formsTable 1-3 Definition of verbal forms

Term Definition

shall verbal form used to indicate requirements strictly to be followed in order to conform to thedocument

shouldverbal form used to indicate that among several possibilities one is recommended as particularlysuitable, without mentioning or excluding others, or that a certain course of action is preferred butnot necessarily required

may verbal form used to indicate a course of action permissible within the limits of the document

1.6.2 Definition of termsTable 1-4 Definition of terms

Term Definition

anchor heavy object attached to a rope or chain and used to moor a substructure to the sea bottom

anchor foundation structural device attached to the end of a tendon or mooring line of a floater and transferringforces to the seabed, e.g. deep foundations or pile foundations

asset

used in the context of wind farm projects to describe the project or object to be developed,manufactured and maintained.In this service specification the term refers either to floating wind turbines, offshore substation(s),inner array cables, power cables, and converter station onshore.

certification third-party issue of a statement, based on a decision following review, that fulfilment of specifiedrequirements has been demonstrated related to products, processes or systems (ISO 17000)


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Term Definition

certification basisrequirements for the product's, component's, assembly's or system's specifications, operatingconditions, performance targets and reliability targets, and the basis to which the product,component, assembly or system shall be assessed during certification

certification plandocument created at the conclusion of the technology qualification by DNV GL, including thestandards and qualification methods agreed upon for the product, component, assembly and/orsystem - the document contains the plan for all actions to be carried out during certification

certification report

reference document prepared for the certification of components of floating wind turbinesor full systems, providing documentation of the assessment of the elements and modules inthe certification process for floating wind turbines, including a reference list of all supportingdocumentation, an assessment of whether the detailed documentation is complete and incompliance with referenced requirements and standards - it serves as a basis for a statement ofcompliance

certification scheme sequence of phases or modules to be completed prior to the issue of a certificate

componentmain part of the floating wind turbine system. In this service specification, the term refers torotor and machinery, support structure tower, support structure floater, station keeping system,mooring system, anchors, electric power transmission and cables

componentcertificate

certificate issued by a certifying body, when it has been demonstrated that a product typein question, here a floating wind turbine component or system, complies with the applicablerequirements, allowing the customer to manufacture certified floating wind turbine components orsystems during the period of validity of the certificate

componentcertification

certification of a specific floating wind turbine component such as rotor blade, generator, gearbox,brake, coupling, pitch system, yaw system, nacelle frame, tower, floater, mooring, anchor androtor-nacelle assembly - covers relevant modules of type certification with the extent dependingon the component/system in question

customer DNV GL's contractual partner (applicant)

design brief supporting document for describing methodologies for design calculations, mostly issued by thedesigner

design basiscovers the site conditions and the basis for design including general specifications, criteria,parameters, design approach, manufacturing, basic quality requirements, suppliers' qualificationsand all other assumptions relevant for design

final certificationreport

final report, issued as reference document for the certificate, and providing documentation ofthe assessment of the elements and modules of certification, including a reference list of allsupporting product documentation, an assessment of whether the detailed documentation iscomplete and all relevant requirements are confirmed by test results, and a review of the finalproduct documentation

floating wind turbine

entire system consisting of wind turbine (rotor-nacelle assembly), floating support structure andstation keeping system. A system of two or more wind turbines mounted on the same floater isreckoned as one floating wind turbine unitThe term is also used in cases, where the support structure is of a kind that the floating windturbine is only partly supported by buoyancy, for example when the support structure consists ofan articulated tower or a compliant tower.

manufacturer the manufacturer of the floating wind turbine or of any component or system in question

mooring device (such as line, chain or tendon) by which an object is secured in position

offshore wind farmproject

assets of an offshore wind farm including total number of offshore wind turbines, supportstructures, substations with topside and support structure and power cables


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Term Definition

other installations installations such as meteorological mast, secondary structures and other equipment

outstanding issue used to denote a incomplete fulfilment of requirements of standards and technical requirementsspecified in the certification agreement, and which needs to be completed for full compliance

primary structure

consists of the load-bearing structure that transfers permanent loads, live loads andenvironmental loads, caused by gravity and environment and actions on the support structure, tothe seabed and structural parts whose failure will have substantial consequences shall be classifiedas primary structure

project certificate document signed by DNV GL and affirming that, at the time of assessment, the asset referred toin the certificate met the requirements stated in the normative documents

prototype one floating wind turbine deployed at a specified position where the objective is to demonstratetechnology and performance

prototype certificate shall allow the customer to manufacture, install and operate a prototype floating wind turbineduring the period of validity of the certificate

recommendation non-mandatory advice

riskthe qualitative or quantitative likelihood of an accident or unplanned event occurring, consideredin conjunction with the potential consequences of such a failure - in quantitative terms, risk is thequantified probability of a defined failure mode multiplied by its quantified consequences

rotor-nacelleassembly

rotor and machinery unit, for horizontal axis machines typically the wind energy converter abovetower top flange

secondary structure boat landings, access ladders and access platforms etc.

special structuresame as primary structure, and in addition its structural parts are subject to particularly arduousconditions (e.g. stress condition that may increase the probability of brittle fracture, multi-axialstresses)

statement ofcompliance

statement signed by a qualified party affirming that, at the time of assessment, a product or aservice meets specified requirements

statement offeasibility

document issued by DNV GL affirming that, at the time of assessment, the technology isconsidered conceptually feasible and suited for further development and qualification according tocriteria agreed at the commencement of certification

station keepingsystem

system to maintain a floating structure in a fixed position relative to a fixed point or within adefined sector relative to the fixed point, including the mooring lines or tendons, as applicable, aswell as the anchor foundations that transfer forces from the system to the seabed

tendon structural component used as part of the station keeping system for a tension leg platform, alsoreferred to as tether

tension leg platform vertically moored floating structure which station keeping system consists of tethers or tendonsanchored in the seabed

type certificate

certificate issued by a certifying body when it has been demonstrated that the product type inquestion, here a floating wind turbine type, complies with the applicable normative documents,and the type certificate shall allow the customer to manufacture certified floating wind turbinesduring the period of the validity of the certificate

verificationan evaluation or assessment to confirm that an activity, a product or a service is in accordancewith specified requirements, and upon confirmation according to an agreed scope of work for thecertification service, DNV GL will issue a statement of compliance


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Term Definition

substation

term referring to transformer stations or converter stations or platforms, with or withoutaccommodations - an onshore or offshore substation may be defined as an integral asset of thewind farm project or as a separate asset for DNV GL project certificationWhenever, in this service specification the term is used in general, it describes the substationincluding the support structure, as this is the electrical power transferring unit.

substructurestructure below the wind turbine tower (interface tower bottom/transition piece). The substructurein this service specification is comprising the transition piece (if present), the floater and thestation keeping system of a floating wind turbine

support structure

the support structure of a wind turbine is defined as the structure below the yaw system of therotor-nacelle assembly and includes tower structure, floater and station keeping systemThe term is also used to designate the structure below of the topside structure of a substation andincludes substructure and foundation of the substation.

wind turbinesystem which converts the kinetic energy of the wind into electrical energy - the wind turbinecomprises of the rotor-nacelle assembly, the tower and the electrical system including the windturbine electrical terminals

1.6.3 AbbreviationsAbbreviations and symbols used in this service specification are listed in Table 1-5.

Table 1-5 Abbreviations

Abbreviation Description

AC alternating current

ALS accidental limit state

BOEM Bureau of Ocean Energy Management

BSH Bundesamt für Seeschifffahrt und Hydrographie (Federal Maritime and Hydrographic Agency,Germany)

CC component certificate

CIGRÉ Conseil International des Grands Reseaux Électriques

CMS Condition monitoring system

CVA certified verification agent

DAkkS Deutsche Akkreditierungsstelle GmbH

DC direct current

DDF deep draught floater

DLC design load case

DT destructive testing

EN European Standard

FAT factory acceptance test

FEM finite element method


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FLS fatigue limit state

FMEA failure mode effect analysis

FMECA failure mode effects and criticality analysis ranking

FMIRR failure mode identification and risk

FOWT floating offshore wind turbine

FRT fault ride-through

FTA fault tree analysis

GCC grid code compliance

HMI human machine interface

HRDDF heave restrained DDF

HRTLP heave restrained TLP

IEC International Electrotechnical Commission

ISO International Organization for Standardization

ITP inspection and test plan

LIDAR light detection and ranging

LVRT low voltage ride through

Met meteorological

NDT non-destructive testing

PC project certificate

PT prototype certificate

PT C prototype certificate - c level

RNA rotor-nacelle assembly

RP DNV GL recommended practices

QM quality management

SCADA supervisory control and data acquisition

SDC site design conditions

SE DNV GL service specifications

SLS serviceability limit state

SOC statement of compliance

SOF statement of feasibility

SOF D statement of feasibility - d level

SSDA site specific design assessment

ST DNV GL standards


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TC type certificate

TC A type certificate - A level

TC B type certificate - B level

TC Site type certificate - site level

TLP tension leg platform

TQ technology qualification

TRL technology readiness level

ULS ultimate limit state

VCG vertical centre of gravity

WT wind turbine

1.6.4 Definition of floating designsThe term floating wind turbine, when used in this service specification describes the entire system of rotor-nacelle assembly (RNA), tower, transition piece, floater, station keeping including anchors, and power cables/transmission. The term floating wind turbine also includes specific, standalone components (e.g. floater,mooring lines, etc.) of a floating system, if not expressed otherwise. In case there are more than one RNA onthe same floater the term covers the entire system.Support structures for floating wind turbines may either be compliant, or restrained for some of the globalmodes of motions i.e. surge, sway, heave, roll, pitch and yaw. For easy reference Figure 1-3 shows thedifferent floater types with basis in floating offshore structures. This overview may not cover all possiblesolutions, however the main types are believed to be captured. Restrained modes will not imply a totalfixation, but displacements in the order of centimetres shall be encountered (e.g. an elastic stretch of atension leg platform (TLP) tendon) compared to displacement in the order of metres for a compliant mode.In Table 1-6 C denotes compliant and R denotes restrained. The given design types comply with DNVGL-ST-0119.

Table 1-6 Typical floaters and boundary conditions

Type Surge Sway Heave Roll Pitch Yaw

spar 1) C C C C C C

semisubmersibles C C C C C C

barges C C C C C C

tension legplatforms (TLP) C C R R R C

heaverestrained TLP(HRTLP) 2)

C C R C C C

heaverestrained DDF(HRDDF) 3)

C C R C C C


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Type Surge Sway Heave Roll Pitch Yaw

articulatedtower 4) C C R C C C

complianttower 4) C C R R R R

1) classic, truss & cell spar, deep draught semi submersible, buoys

2) special type TLP which has not been built, but proposed and developed to a certain level

3) special type DDF

4) these structures are fixed to the seabed as fixed structures, but uses buoyancy as a vital part of the loadbearingsystem

In Figure 1-3 exemplary floating wind turbines with their stability principles are shown.

Figure 1-3 Examples of floating wind turbine components


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1.7 Technology readiness levelsTechnology readiness levels (TRLs) have been defined for different innovative industries such as automotive,aviation or oil and gas industries. The defined levels provide a general indication of the developmentstages and comparability of novel technologies. The rating of technology readiness levels of floating windturbines applied in this service specification refers to the definition of the European Union in HORIZON2020 - WORK PROGRAMME 2014-2015 General Annexes, Extract from Part 19 - Commission DecisionC(2014)4995. Certification services support the achievement of specific TRLs and are directly linked to thedefined technology development stages, see Figure 1-4.

Figure 1-4 Technology readiness levels according to EU definition and corresponding certificationlevels

1.8 Deliverables

1.8.1 GeneralSubmitted documents shall be reviewed by DNV GL against the defined standards. As a result, verificationcomments shall be issued for each reviewed assessment package. The certification report shall detailthe exact scope of work, key findings and observations for the floating component or system considered,and a statement about conditions and possible open issues with respect to the fulfilment of predefinedrequirements.Each certification module is completed with a statement of compliance (for the concept level with astatement of feasibility) based on the relevant certification reports. A statement of compliance shall beissued, once that all open issues found in the review phase are closed. If full compliance is not obtained


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during assessment with non-safety critical outstanding issues, a provisional statement of compliance, with alimited validity of up to 1 year, may be issued.The customer may choose a selection of certification modules and may contract a reduced number ofstatements of compliance compared to the given scope for a certain certification level (concept, prototype,site type, project or in-service level). However, for a certificate the full scope shall be performed as definedfor the selected certification level.It is also possible to select only specific assessments from a specific certification level as given in Table 2-1.In this case only a certification report shall be issued documenting the assessments performed.A provisional certificate may be issued if non-safety critical outstanding issues are documented by provisionalstatements of compliance. The validity of the provisional certificate shall not be longer than the provisionalstatement of compliance.The deliverables indicate the incremental nature of the certification process with each phase contributing tothe next step. The deliverables correspond to the gradual increase in detail and scope from the concept levelthrough to certification of a fully developed product. Typically, these deliverables shall be termed according to[1.8.2].The validity of DNV GL reports, statements of compliance and certificates for the different certification levelsare given in Sec.2.

1.8.2 Reports and statements of complianceFor each certification module given in Table 2-1, DNV GL may issue statements of feasibility or statements ofcompliance together with the corresponding certification reports:

— statement of feasibility— statement of compliance prototype design— statement of compliance prototype test— statement of compliance prototype manufacturing— statement of compliance site type design basis— statement of compliance site type design— statement of compliance site type test— statement of compliance site type manufacturing— statement of compliance project design basis— statement of compliance project design— statement of compliance project test (update site type test)— statement of compliance project manufacturing— statement of compliance project transport and installation— statement of compliance project commissioning, operation and maintenance— statement of compliance project in-service.

1.8.3 CertificatesIn order to account for the different development stages of a floating wind turbine DNV GL may issue thefollowing certificates on the basis of the relevant final certification report:

— prototype certificate— site type certificate— project certificate.

In the following figures the deliverables for the different certification levels are shown. Previous certificationdeliverables may be implemented optionally in agreement with DNV GL as described in detail in Sec.3.


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Figure 1-5 DNV GL deliverables for concept and prototype certification


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Figure 1-6 DNV GL deliverables for site type certification


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Figure 1-7 DNV GL deliverables for project and in-service certification


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SECTION 2 SERVICE OVERVIEW

2.1 GeneralThe objective of this section is to provide an overview of the various verification activities related to thecertification of floating wind turbines and the validity of DNV GL deliverables.

2.2 Certification modules for floating wind turbinesThe DNV GL certification scheme for floating wind turbines is divided into levels which account for typical life-cycle phases of a floating wind turbine unit, its related components or a floating wind farm project.The five certification levels defined herein (concept, prototype, site type, project and in-service, see Figure1-1) correspond closely to the technology readiness levels (TRLs) commonly used in oil & gas and aerospaceindustry, see [1.7]. This service specification is using the definition of the European Union for the rating ofthe development stages of floating wind turbine projects, see Figure 1-4.Each certification level includes several certification modules as shown in Table 2-1. Depending on thelife-cycle phases the modules comprise various verification activities such as design (documentation)assessment, testing, measurements and surveillance of critical processes.Upon the successful completion of all mandatory assessments within a certification module, DNV GL issues acertification report and a statement of compliance (or a statement of feasibility for the concept level). Whenall mandatory statements of compliances for a specific level have been successfully completed the respectivecertificate shall be issued. Further details regarding DNV GL deliverables are given in [1.8].The intention of this certification scheme is to make use of previous certification deliverables as muchas possible and to benefit from a straight forward certification process with high synergy effects. Thedocumentation from previous certification deliverables may need updating and extension to comply withthe requirements of a more detailed certification level. In such case the applicable results of a previouscertification shall be agreed with DNV GL. The general aim is to avoid examining same items more than once.In the following table the certification levels and its modules for floating wind turbines are listed. The table isvertically divided into the main verification activities such as design assessment, testing and measurements,as well as inspections and surveillances.

Table 2-1 DNV GL modular certification system for floating wind turbines

Certificationlevel Design assessment modules Test and

measurement modules Surveillance modules Final deliverable

Conceptlevel

— design basis and designassessment

— technology qualification,qualification plan consideringnovel technology

— integration of RNA D leveldesign assessment

optional: model tests SOF

Statement of feasibility


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Prototypelevel

SOC PT design:

— SOF— design basis including site

conditions of prototype site— full integrated load analysis

ULS, ALS, FLS / code validation— structural integrity of support

structure including stationkeeping system

— integration of RNA C leveldesign assessment

SOC PT test:

— model test— comparison of

model tests versusassumptions

— tests plan— tightness tests

(e.g. of tanks,compartments)

— stability tests, testof behaviour

— anchor tests

SOC PTmanufacturing:

— critical componentmanufacturingsurveillance ( e.g.floater, mooringlines)

— transport andinstallation plan

PT

Prototype certificate

Site typelevel

SOC site type design basis

SOC site type design:

— PT design— detailed structural integrity of

support structure— electrical installation including

cables— control and protection system,

manuals— integration of RNA A level

design SOC

SOC site type test:

— PT-test— comparison

prototypemeasurementsaccording totest plan versusassumptions

— component testsaccording to testplan

— integration of RNAA level test SOC

SOC site typemanufacturing:

— PT manufacturing— manufacturing

plan of maincomponentsmanufacture

— QM certificate— integration of

RNA A levelmanufacturing SOC

TC site

Site type certificate

Projectlevel

SOC PC design basis

SOC PC design:

— site design basis— site design— transport and installation plan— integration of RNA A level type

certificate

— site type test— soil tests and

dynamic piletesting (ifapplicable)

SOC PC manufacturing

SOC PC transport andinstallation

SOC PCcommissioning:

— site typemanufacturing

— project relatedmanufacturingsurveillance

— transport andinstallationsurveillance

— commissioningsurveillance

— operation andmaintenancemanuals

PC

Project certificate


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In-servicelevel

SOC in-service:

— periodic monitoringand/or

— inspection/auditsaccording toinspection program

PC

Maintenance of projectcertificate

The certification levels described above correspond to the levels defined in other DNV GL service specificationdocuments given in Table 1-1.The certification of the RNA of a floating wind turbine in particular follows directly the scheme of DNVGL-SE-0441 which defines the following RNA certification levels:Dlevel

= RNA concept level certification

Clevel

= RNA prototype level certification

Blevel

= RNA provisional type level certification

Alevel

= RNA type level certification (complete, no open issues)

Sitelevel

= RNA site type level certification

For the implementation of an RNA design into a floating wind turbine certification the RNA levels shall bereferenced for the corresponding certification levels of floating wind turbines, see [4.5]. Table 2-2 shows themandatory certification levels of the RNA for the different certification schemes.

Table 2-2 Mandatory RNA certification levels for floating wind turbines

Floating wind turbinecertification accordingto DNVGL-SE-0422

DNVGL-SE-0441(DNV GL type

and componentcertification)

DNVGL-SE-0074(IEC type certication)

DNVGL-SE-0190(DNV GL project

certification)

DNVGL-SE-0073 (IECproject certification)

Statement offeasibility (conceptlevel)

RNA D levelcertification

Prototype certificate RNA C level prototypecertification

IEC 61400-22prototype certificate

Provisional site typecertificate

RNA B level typecertification

IEC 61400-22provisional (class B)type certificate

Provisional projectcertificate

IEC 61400-22provisional projectcertificate

Site type certificate RNA A level typecertification

IEC 61400-22 typecertificate

Type certificate, site-specific

Project certificate RNA A level typecertification

Project certificate IEC 61400-22 projectcertificate


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2.3 Concept level certificationThe concept level certification/conceptual design assessment supports the development of a floating conceptin an early stage by an individual scope of assessment and content of reviews. This stage correspondstypically to a TRL 3, see Figure 1-4. The conceptual design assessment is usually based on a completeplausibility check of the design basis, the design loads, the control and safety concepts as well as theconceptual design of the floating wind turbine structure or component in question (e.g. tower, floater orcomplete support structure). For the rotor-nacelle assembly a D level certification according to DNVGL-SE-0441 is required, see Table 2-2.For novel technologies or applications, where no applicable standards exist a technology qualification processshall be applied. The technology qualification comprises at least a technical assessment, a failure modeidentification and a risk ranking of the considered sub components, leading towards a certification plan. Thecertification plan concerning the new technologies shall be reported by DNV GL as a part of the conceptualdesign assessment and indicates the measures necessary to achieve the next certification level. Scaled modelor component tests may be part of the conceptual design assessment in the path of increasing TRLs. Thedetailed scope is given in [3.2] and App.A.Following a successful completion, DNV GL will issue a certification report and a statement of feasibility.The statement of feasibility has a limited validity of 3 years in order to ensure that the certification is basedon recent technology developments. Renewal shall require a new assessment with focus on the technologydevelopments and learnings since the previous issue.

2.4 Prototype level certificationA successful prototype typically corresponds to a technology readiness level of TRL 6 or 7 (technology/systemprototype demonstration in operational environment).In case a prototype is part of the development plan to test a full size floating wind turbine design duringa limited period, DNV GL may provide a confirmation for a safe prototype installation and operation. HereDNV GL provides the prototype certificate which covers all relevant elements of the design assessment incombination with a manufacturing surveillance of critical components (e.g. floater and mooring lines) andstability, system behaviour testing, anchor tests and tightness tests (e.g. of tanks, compartments), see [3.3].The assessment of the prototype design is usually based on a complete plausibility check of the loads andthe floating support structure, the control and safety concepts, the safety system, as well as of the electricalinstallations. An integrated load analysis is required to confirm dynamic loads on the structure. Model testsare required to validate and support numerical analysis. National or local regulations may have stricterrequirements for certification of prototypes e.g. site type level certification for the floating support structure.The certification level of the applied for the RNA type shall correspond to C level certification accordingDNVGL-SE-0441.Following a successful completion of each module, DNV GL will issue statements of compliance and when allmodules are successfully concluded, DNV GL shall issue the prototype certificate, see Table 2-1.The prototype certification is limited for 3 years but may be extended to the full life time of a project basedon experience build up during operation, see DNVGL-SE-0263 Certification of lifetime extension of windturbines.The prototype certificate may also be issued if the test of the RNA behaviour is outstanding or if other welldefined issues are outstanding, however, the validity is limited to 1 year in these cases.

2.5 Site type level certificationThe site type level certification covers the design, testing and manufacturing of a floater, a station keepingsystem, other specified floating components or a full site specific floating wind turbine including theintegration of RNA. The site type certification serves as preparation for project certification for the floatingwind turbine or its related components in question. As demonstrated in Figure 1-2 the certification modules


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of site type level may be incorporated in the scope of a project certification in case the project certification isinitiated right after a concept or prototype certification.The assessment of the design basis requests clearly defined boundary conditions and methodologies forperforming the design without having a detailed design ready. The site design assessment covers the stepsnecessary to achieve a TRL 8. The assessment includes an independent load calculation and a verificationof the code validation. Verification of the integrated structural system consisting of RNA and supportstructure (tower, floater and station keeping system) is an inherent part of the design assessment. Furtherassessments comprise the assessment of the electrical system as well as the safety, the power cables andcontrol system.When the development reaches manufacturing of a number of turbines or components (e.g. floaters)for a specific project or in serial production, the site type certification covers the surveillance during themanufacturing of the components and a type testing programme of one of the first units as described in[3.4].In case a previously performed prototype certification reveals synergies to a site type certification, such asthe design basis, tests or specific manufacturing surveillances, these modules may be taken over for the sitelevel certification after agreement with DNV GL.In case a site type certification should cover the RNA, the applied RNA type shall correspond to A levelcertification according DNVGL-SE-0441 and the floating specific requirements given in DNVGL-ST-0119. Theintegration of an existing RNA type certificate into a site type certification is described in detail in [4.5].Furthermore, the design quality control shall be covered by a certified quality management system complyingwith ISO 9001, otherwise the quality management system shall be assessed by DNV GL.Following a successful completion of the modules site type design, site type test, and site type manufacturingsurveillance DNV GL shall issue a site type certificate.The site type certificate is valid for 5 years after date of first issuance.Changes of the RNA or support structure design may lead to issuance of a new revision of the certificateupon successful review. The new revision shall have the same expiry date as the original certificate. In caseof major changes, a new certificate with a 5 year validity shall be issued upon successful review.Maintenance of the type certificate is conditional on annual reporting by customer covering all installedfloating wind turbines of the certified type and including information about:

— abnormal or deviant operating experience or operating failures— minor modifications.In case the applied RNA type owns only a B level certification the issue of a provisional site type certificate ispossible. The provisional site type certificate may only have outstanding issues that are not safety-relevant.The provisional site type certificate has then a validity period of 1 year.

2.6 Project level certificationA successfully completed project certificate typically corresponds to a TRL ≥ 8 since the certified actualsystem may be regarded proven in an operational environment. For the planning, the installation, and theoperation of a full floating wind farm the project certification is recommended. It stipulates that the risksarising from site assessment, design basis, design, manufacture, transport, installation, commissioning,operation and maintenance are considered and managed.The project certification of floating wind turbines refers generally to the certification according to DNV-GL-SE-0190 and may be considered as an extension of the DNVGL-SE-0190. In this service specification focus isgiven to the floating wind turbine components and peculiarities to allow an easier application. However, partsof DNVGL-SE-0190 are included herein to improve readability of the document.A project certificate may be based on a completed site type certificate. In case a site type certification doesnot exist all certification modules of the site type are part of the corresponding project certification. For theRNA an A level type certificate according to DNVGL-SE-0441 shall be provided covering the floating specificrequirements for the RNA given in DNVGL-ST-0119. In addition, a condition monitoring system (CMS) shallbe in place and shall be certified according to DNVGL-SE-0439.


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The conditions of a specific site and the compatibility with the type certified design shall be checked, see[3.5]. A manufacturing surveillance of the specific components appointed for the site in question shall beperformed and their transport and installation shall be witnessed by DNV GL inspectors. Upon a successfulconclusion of the above mentioned tasks and the successful commissioning of the floating wind farm theproject certificate shall be issued.The validity of the project certificate is limited to the design lifetime of the floating wind farm stated in theproject certificate. Maintenance of the project certificate is conditional on periodic in-service evaluations byDNV GL. The project certificate shall be confirmed one year after the date of first issuance by a statement ofcompliance for in-service, see [2.7].If one or more certification modules or statements of compliances within the project certification havea provisional status the project certificate receives a provisional status as well. The provisional projectcertificate has a validity of 1 year. During this period the customer shall document the closing of theoutstanding issues and these shall be evaluated by DNV GL.

2.7 In-service level certificationUpon of a successful confirmation of the validity of the project certificate during operations by means of in-service activities a floating wind turbine design may be considered to be at TRL 9.After the completion of the project certificate, the certificate shall be maintained by annual periodicmonitoring of the installed floating units which involves in-service surveillance and approval of themaintenance, repair and inspection programme.The objective of in-service or periodic monitoring (PM) is the inspection of the entire floating wind farm andits components by DNV GL in a predefined sequence. The documents of the different modules of the projectcertification shall be available as they contain relevant information and conditions.Within the scope of the in-service or periodic monitoring are the RNA, the support structures includingfloaters, station keeping systems and seabed level anchors. Structural integrity, electrical systems,machinery, functioning of safety and braking systems shall be examined as well.In-service or periodic monitoring shall be carried out on the basis of DNVGL-SE-0190. Additional standardsand regulations valid at the site shall be observed and applied.In case an in-service agreement for the floating wind farm is in place between DNV GL and the customer,the interval of confirmation of the project certificate is set to the duration of the service agreement plus oneyear; however, 5 years is the maximum period of confirmation. The certification report in-service shall beissued yearly, the related statement of compliance at the end of the validity of the agreement or every 5years, whatever applies earlier.


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SECTION 3 DETAILED SERVICE DESCRIPTION

3.1 GeneralThe scope of work given in the following sections represents the basic work packages for the certification offloating wind turbines and its related components. This scope might be reduced or extended with respect tothe specific design of the floating wind turbine and shall be clearly documented within the design basis.

3.2 Concept level certification

3.2.1 GeneralThe purpose of a concept level certification/conceptual design assessment may be decided on a case bycase basis depending on the development stage of the floating wind turbine concept. A conceptual designassessment is usually based on a complete plausibility check of the conceptual design of the floater, thestation keeping system, the design loads, the rotor blades, the main machinery components, the tower aswell as the control and safety concepts and the electrical installations. Technology readiness levels (TRL)may be applied to identify the development stage of a concept, see example TRLs in Figure 1-4. In an earlyphase the purpose may be to assess if the concept is technically feasible and suited for further development.In cases of novel technology, a technology qualification (TQ) is performed as part of the conceptual designassessment, see App.A.The conceptual design assessment of a floating wind turbine's RNA corresponds to D level certificationaccording to DNVGL-SE-0441.The conceptual design assessment is meant to assist stakeholders (developers, financiers, partners, utilitycompanies, insurance companies and the public) in understanding the present status of a technology underdevelopment and in how to proceed in further technology developments.The conceptual design assessment shall be understood as a concept review which gives DNV GL anopportunity to assess a selection of documents and drawings towards a set basis of design, codes, standardsand regulations.For novel technological concepts or solutions not covered by the scopes of established rules, standards,recommended practices or available, relevant operational experience, adequate acceptance criteria shall firstbe established using technology qualification principles, see App.A. Based on the documentation received,DNV GL shall amend the certification scope to the next certification level of the certification scheme, i.e.prototype certification, type and project certification. The methodology described is adapted from DNVGL-SE-0160 and DNVGL-RP-A203.The conceptual certification scope provides means for the customer to understand the current status of thetechnology without having to submit all the documentation normally needed for a prototype, type or projectcertification. It shall be noted however that the technical documentation submitted for review shall be aconclusive and self-contained package, with sufficiently detailed technical information allowing for a 3rd partyreview, see more details in Sec.4. A concept certification does not replace the need or requirement (givene.g. by authorities) for DNV GL to carry out the detailed design verification scope included in the certificationmodules as described herein.Together with the customer a suitable target confidence level will be agreed upon in every respective case.


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Figure 3-1 Concept certification including technology qualification

3.2.2 Conceptual design basis assessmentThe purpose of the conceptual design basis review is to evaluate the technology and whether the siteconditions and the basis for design are properly established and documented. This includes generalspecifications, criteria, parameters, design approaches and other assumptions for design.The conceptual design basis submitted to DNV GL for evaluation shall comprise information about thefunctionality, safety strategy, environmental conditions, boundaries of the technology to be certifiedand limiting operating parameters for the device as well as other requirements such as conditions formanufacturing, transportation, installation, commissioning, operation and maintenance.The design basis assessment in general includes:

— plausibility check of site conditions:

— review that a complete set of environmental conditions is selected for the evaluation (but not review ofspecific site conditions):


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— wind conditions— water depth— oceanographic (e.g. wave and current) conditions— general soil conditions, depth of effective foundation level below (soil or water) surface— seismicity (if applicable)— grid connection possibilities resp. distance to main consumers, local rules of authorities, if applicable— logistic accessibility for large components and human resources.

— codes, standards and analysis methodology review:

— The hierarchy of the standards should also to be agreed upon. The main DNV GL standards applicablefor floating wind turbine structures are listed in [1.5.2].

— identification of novel technology

— integration of component/floater/RNA in the complete floating wind turbine system.Interface definitions:

— design basis for integrated loads evaluation review:

— general methodology for the analysis— plan for sensitivity analysis— design load cases for feasibility evaluation— fatigue methodology for feasibility evaluation— ALS criteria and floating wind turbine type.

— design basis for design structure evaluation review:

— design criteria for the design evaluation— material specifications— material factors— SLS criteria— corrosion protection methodology— stability requirements.

Depending on the status of the concept and the component considered, certain items may be left out. It maybe the case that some data may be replaced by simplified assumptions. It is also assumed that operation andmaintenance methodologies documentation shall be provided on a very basic level. The design basis includesall information required in the qualification basis and certification basis as defined in DNVGL-RP-A203 for atechnology qualification of novel technology.

3.2.2.1 Qualification basisFor novel technology the purpose of the qualification basis is to provide a common set of criteria againstwhich all qualification activities and decisions shall be assessed. The qualification basis provides a technologydescription, a performance description and a manufacturing description including installation,and statesthe basic claim that the qualification aims to prove true. The qualification basis also includes the necessaryinformation to agree on the certification basis.

3.2.2.2 Certification basisThe purpose of creating a certification basis document as part of the technology qualification process is todefine the expectations of the novel technology in the absence of directly applicable codes and procedures.The certification basis shall also include reference to codes, standards and regulations which shall be followedfor the part of the concept which is fully or partly based on known technology. The hierarchy of the standardsshall also be agreed upon.The certification basis may either be compiled by DNV GL using inputs provided by the customer or writtenby the customer and verified by DNV GL.


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3.2.3 Conceptual design assessmentThe conceptual design assessment module covers the design concept including preliminary loads, principlesof the control and protection system, main dimensions as well as methods and basis for the detailed design.The purpose of the review is to identify potential decisive factors in the design and to recommend riskmitigation measures. This shall be done by a review of documents and drawings in regard to the compliancewith the conceptual design basis.

Note:DNV GL shall not perform the actual selection of mitigation measures. DNV GL shall not in any way assume responsibility for orownership of the solutions described in the qualification basis.

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It is to some extent up to the customer to define which documentation shall be included in the assessment.Depending on the component and floating wind turbine type the conceptual design assessment shall includereview of:

— stability analysis (methods and static stability results), see DNVGL-ST-0119:

— in place— load out/flat out— transport and installation

— feasibility evaluation of the anchor design

— verification of preliminary analysis of station keeping system, with focus on the methodology for theanalysis

— review of documentation provided with respect to applied methodologies and preliminary analysis:

— floating wind turbine model— model test information, when model tests are performed— analysis model calibration against model tests— assumptions for ULS, FLS and ALS analysis.

— structural design briefs and methodologies:

— preliminary analysis of selected critical spots— methodolodgy for the analysis of the different parts of the structure.

— preliminary drawings:

— DNV GL shall focus the review on the most relevant details to guarantee the feasibility of the concept,e.g. critical connections

— review of overview drawings and critical component drawings of mechanical systems

— review of the methodology for load out, transport and installation as well as operations, from a feasibilitypoint of view

— check if safety-relevant operating values are monitored, processed and made available to the safetysystem. Furthermore, the review of the existence of sufficient redundancies for safety relevant operations.

For the review of the RNA reference is made to DNVGL-SE-0441 [2.5] D level certification.The detailed procedure comprising technology assessment, risk assessment including failure modeidentification and risk ranking and the setup of a technology qualification plan is described in App.A.

3.2.4 Certification planFinally, the certification plan defines the certification requirements for the floating wind turbine orcomponent. It contains a breakdown into systems and components, standards and codes to be applied in


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addition to DNVGL-ST-0119, the required level of DNV GL activities for the project phases and qualificationmethods that adequately address the identified failure modes not covered by available standards.The qualification methods, in most cases, include technical analyses, testing or combinations of the twowhere the purpose of the testing is to reduce uncertainty in the analysis model or calibrate it. They may alsoinvolve collection of available reliability data and review of procedures intended to reduce the probabilityor consequence of failure. The list of qualification methods does not include proposed improvements of theconcept and further design details to be defined.The certification plan is a result of the technology qualification activities, as described in App.A, resulting ina fit for purpose set of requirements. The plan shall be issued by DNV GL and it is the responsibility of thetechnology owner to provide evidence that the requirements have been met.

3.2.5 Statement of feasibilityAfter completion of all elements of the concept level certification the documentation subjected to the reviewshall be stated together with review comments. DNV GL shall provide a certification report detailing thereview performed, state key findings and observations for the technology considered. The results of thetechnology assessment will be reported and reference to the certification plan shall be made.The certification report summarises all assumptions and conditions related to the performed assessments andspecify open items if any non-conformity regarding the applied standards have been detected.Following a concept level certification, a statement of feasibility shall be issued. The statement of feasibilitymay be issued if it can be shown that all risks can be satisfactorily managed. If the concept is concluded tobe feasible, the statement of feasibility issued by DNV GL shall state, that at the time of assessment, thetechnology is considered conceptually feasible and suited for further development and qualification accordingto the criteria of certification.

3.3 Prototype level certification

3.3.1 GeneralThe prototype certification provides designers and developers a third-party confirmation for the installationand testing of a prototype at a specific test site for a limited period.With regard to the prototype certification of the RNA the requirements of DNVGL-SE-0441 apply. Regardingthe floating structure and the station keeping system the requirements of DNVGL-ST-0119 apply.If a conceptual design assessment has been performed prior to the prototype development phase anda statement of feasibility is available, the adaptation of specific concept certification modules may beconsidered. An existing certification plan shall be applied.The applicability of previous certification modules is dependent on the degree of modifications introduced tothe current conditions and configurations and shall be agreed with DNV GL on beforehand.


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Figure 3-2 Prototype certification modules

The scope given below is also applicable for a sub component or a stand-alone module of a floating windturbine. In case that only a specific component certification is of interest the component design basis shalldefine additionally the boundary conditions and all relevant interfaces to the generic floating wind turbinedesign. However, in the following description only the entire floating wind turbine unit is mentioned, meaningthat component certification is included as well.For a complete prototype certification three main certification modules are required, prototype designassessment including design basis, prototype testing and prototype manufacturing surveillance.

3.3.2 Prototype design basis assessmentThe design basis shall include all parameters relevant for the design of the floating wind turbine prototype orcomponent, stating the site conditions, the basis for design and the methods to be used. If values are takenfrom background documents, those shall be referenced and handed in. The design basis shall be assessed forplausibility, quality issues and completeness.In the case that a conceptual design basis has been successfully assessed by DNV GL and parts thereincovering the present prototype certification these parts may be applied after agreement with DNV GL, seealso [3.2.2].


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The prototype design basis shall be provided to DNV GL and shall include documentation of at least thefollowing:

— name and address of the owner, position of the prototype— site conditions— standards, codes and additional requirements— design criteria— model test description— description of analysis methods— manufacturing, transport, installation and commissioning requirements— operation and maintenance requirements.A more complete list of items to be included in the design basis is given in [3.2.2].For detailed design basis requirements, specifically for the site conditions, the RNA and the offshore supportstructure, reference is made to DNVGL-SE-0190 [2.3] Design basis.Floating specific requirements regarding environmental conditions, design criteria, model tests, design, loads,floating stability, materials, transport and installation are given in DNVGL-ST-0119.

3.3.3 Prototype design assessmentThe purpose of the prototype design assessment is to verify that the floating wind turbine or componentdesign complies with the approved design basis for the dedicated lifetime of the prototype.The tools for the design of the floating prototype shall be validated. It shall be demonstrated that the appliedcodes are capable to analyse main influences of the component considered or the full floating wind turbine.Validation with test results from similar type of structures or scaled models are possible after agreement withDNV GL. This may be measurements, internal analysis, publications or results of R&D projects.For the prototype design assessment, the customer shall submit at least the following documentation:

— prototype design basis— description of control and protection system— description of model used for the load analysis— load assumptions consisting of:

— analysis code validation— integrated extreme load analysis (ULS, ALS)— integrated fatigue load analysis (FLS)— calibration of hydrodynamic coefficients e.g. by model tests.

— floating stability analysis

— validation of load and stability simulations by model tests or measurements on full scale structures ofsimilar design

— RNA C level design assessment according to DNVGL-SE-0441 or corresponding mandatory modules

— structural integrity of primary structures, secondary structures for access of personnel (e.g. boat landing,access platform, etc.) and station keeping system

— transport and installation plan for the entire floating wind turbine unit.Following a successful assessment of the prototype design, DNV GL issues a certification report. The reportsummarises all conditions related to the performed assessments and specifies open items if any non-conformity regarding the applied standards have been detected. This certification report forms the basis forthe statement of compliance for prototype design.


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3.3.4 Prototype manufacturing surveillanceFor the prototype manufacturing surveillance the critical components shall be selected which may have asignificant impact on the structural integrity and the stability of the floating wind turbine. The customer andDNV GL shall agree on the selection of such potentially critical components. For typical floating designs asshown in Table 1-6 the survey shall cover at least the manufacturing of the floater (hull which provides thebuoyancy) and the station keeping system. For novel technology, special requirements apply.At least the following documentation shall be submitted to DNV GL:

— selection of critical prototype components— production plan— work instructions and quality control procedures— qualification of work shop employees (e.g. welder's certificates)— production drawings— material certificates— coating procedure— quality management system certification of selected manufacturers— tank test (e.g. ballast tank) protocols according to DNVGL-ST-0119— visual inspection of finished components before shipping— visual inspection of ongoing jobs, testing (e.g. NDT) and repair work.The surveillance shall be performed by DNV GL surveyors. Since the survey focuses on critical manufacturingprocesses with respect to the design, the surveyors are ideally the experts who already have been involved inthe prototype design assessment of the floater and the station keeping system.The prototype manufacturing surveillance covers the review of the manufacturing documentation, an initialaudit at the work shop and, depending on the results, further inspections at the production site of thecomponent in question. The application of a risk based approach for the determination of the quantity ofinspections is possible, see DNVGL-SE-0477.For the detailed scope of the prototype manufacturing surveillance reference is made to DNVGL-SE-190.Following a successful assessment of the prototype manufacturing surveillance, DNV GL issues a certificationreport. The report summarises all conditions related to the performed assessments and inspections andspecifies open items if any non-conformity regarding the applied standards have been detected. Thiscertification report forms the basis for the statement of compliance for prototype manufacturing surveillance.

3.3.5 Prototype testingThe purpose of the prototype testing is to prove the design assumptions and verify the floating wind turbine'ssystem behaviour and capabilities. Further it delivers valuable measurement data of the operational loadsand the power performance which may be utilised in following development phases to come.The prototype testing consists of:

— model tests— the test plan for the type testing. These are the measurements needed to verify loads and power curve

assumptions and are performed when the prototype is in operation— the tests required for the safe operation of the prototype.

3.3.5.1 Model testsModel tests of the floating system are required for the analysis of the loads and the behaviour of the floatingwind turbine:

— The code used for the integrated load analysis shall be validated by model tests or full scale testing. Theprincipal dynamics of the system shall be adequately represented. Model tests for code verification maybe performed on designs of similar size, characteristics and behaviour as the actual design under review.


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The software shall be identical, although minor changes or upgrades are possible. Changes and upgradesshall be described.

— The hydrodynamic coefficients applied for the load analysis shall be derived from or at least validated withmodel tests, using a floater and station keeping system representative to the one under consideration.

— The behaviour of the actual model used for numerical analysis shall be validated with model tests. The fullsystem dynamics, the coupling of hydrodynamic and aerodynamic (turbine) loads and the control systemshall be investigated.

The validation shall be documented and supplied to DNV GL for review. The documentation of the validationshall include at least:

— description of the test facility and its measurement equipment— scaling approach and ratio— model design and material selection— test plan including decay tests, extreme wave tests, and wind wave combination tests— sensor positions and dimensions— calibration protocols— scaled wave conditions— scaled wind conditions— environmental conditions during testing— validation of code— derivation and/or validation of hydrodynamic coefficients used— comaparison of measurements with simulation of applied code for selected test cases.

3.3.5.2 Test planAs a basis a test plan shall be established which provides an overview of the test campaign schedule, themeasurement equipment and methodology for analysing the measured data.The elements of the prototype testing may be carried out by accredited laboratories. Otherwise, DNV GLshall verify that the testing is carried out fulfilling ISO/IEC 17020 or ISO/IEC 17025, as applicable. Thetest plan shall be evaluated by DNV GL before the test starts. The measurement points, the planned scopeof the measurements, and their assessment shall be coordinated with DNV GL before installation of themeasurement equipment commences.At least the following documentation shall be submitted at least for the prototype testing:

— test plan for the measurements that shall be performed on the floating offshore prototype, especiallyregarding load and power curves measurements

— for the RNA DNVGL-SE-0441 requirements for tests apply. Special attention shall be paid to changes tothe certified design when adapted for floating operation. It is assumed, that the bulk of tests may beperformed on a fixed structure and are valid for the floating wind turbine. Additionally, load and powercurve measurements shall be planned to consider the floating structure behaviour (change from fixed tofloating).

3.3.5.3 Prototype testsDuring commissioning of the prototype following tests regarding the safe prototype operation are required:

— RNA C level type test according to DNVGL-SE-0441 or corresponding mandatory modules. The typetesting as required by DNVGL-ST-0438 Sec.6 Test of the wind turbine behaviour shall be appliedconsidering adaptations for floating offshore operation

— floating stability test for verification of stability manual according to DNVGL-ST-0119— post installation anchor tests according to DNVGL-ST-0119 on prestressed rock anchors

3.3.5.4 Certification report and statement of complianceA certification report shall be issued to the customer as a reference document for the DNV GL assessmentsperformed within the prototype testing assessment. This report comprises the results of the specificassessments, surveillances, and measurements. Furthermore, it summarises all conditions related to the


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performed assessments and surveillances and specifies open items if any non-conformity regarding theapplied standards have been detected.Upon successful completion of all testing modules listed above, a statement of compliance for prototypetesting shall be issued.

3.3.6 Prototype certificateAfter successful completion of the modules:

— prototype design basis— prototype design— prototype manufacturing— prototype testinga final assessment shall be performed comprising the results of the specific modules in a certification report.This report shall be issued to the customer as a reference document for the DNV GL assessments of theprototype. Furthermore, it summarises all conditions related to the performed assessments and specifiesopen items if any non-conformity regarding the applied standards have been detected. The final certificationreport forms the basis for the prototype certificate.The prototype certificate is valid for one specific floating wind turbine prototype identified by its type andaddress or a demonstration wind farm with up to 5 units. If a floating prototype is modified, e.g. with anotherRNA configuration, a different operating mode or in other points influencing the loads, a new or revisedprototype certificate shall be required.

3.4 Site type level certification

3.4.1 GeneralThe site type level certification is intended to prepare for project certification. All parts of the site type maybe merged into the project certification. It focuses on the assessment of the floater, the station keepingsystem, individual floating components or the full floating wind turbine including an integrated RNA. Theenvironmental conditions having an impact to the floating wind turbine or component shall be defined in adesign basis and may be taken from a specific site or from generic environmental classes. In case the scopeof the certification covers a full floating wind turbine the assessment of the RNA shall be performed either byapplying DNVGL-SE-0441 (A level and floating specific requirements of DNVGL-ST-0119), or by integratinga corresponding RNA type certificate according to [4.5]. It is the aim of site type level certification that theelements of the wind farm are assessed only once for multiple installations. Site type certification coversthe assessment of the environmental conditions, applied codes and standards, design methodologies, thecomplete design, manufacturing surveillances and specific testing modules.


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Figure 3-3 Site type certification modules

During a site type certification of a floating wind turbine following constellations may be considered:

— assessment of specifically designed components e.g. floating structure and/or station keeping systemfor the given site conditions and the RNA. The RNA is already certified according to DNVGL-SE-0441 orDNVGL-SE-0074

— assessment of an RNA designed for generic environmental conditions (e.g. according to defined classes)and already certified per DNVGL-SE-0441 or DNVGL-SE-0074, for floating conditions according to DNVGL-ST-0119

— assessment of site specific design changes on a structure or component certified according to DNVGL-SE-0441 or DNVGL-SE-0074 for floating conditions

— integration of a certified RNA into a floating structure for specific conditions— assessment of an integrated floating wind turbine (RNA, floating structure, station keeping system) for

specific conditions— combinations of the above.The site type certification may be applied to a single unit of a floating wind turbine or to a type intended forserial production.If a previous floating prototype certification has been performed successfully relevant modules such asprototype design basis, type testing, design or manufacturing surveillances may be utilised within the sitetype certification after agreement with DNV GL.


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3.4.2 Site type design basis assessmentThe purpose of the verification of the design basis is to assess whether the site conditions and the basisfor design are properly established and documented. The design basis shall include the site conditions, thebasis for design, general specifications, criteria, design approach, manufacturing, basic quality requirements,suppliers' qualifications and all parameters and assumptions relevant for design of the floating wind turbine.If values are taken from background documents, those shall be referenced and handed in. In case that nosite specific environmental data are available generic assumptions or defined environmental classes may beapplied. Often the RNA of a floating wind turbine holds a type certificate according to a defined class. In thiscase it shall be demonstrated that the assumptions made within the RNA type certificate are covering thesite specific conditions of the present design basis. The design basis shall be assessed for plausibility, qualityissues and completeness.In case a floating prototype design basis has been successfully assessed by DNV GL and parts therein arecovering the present site these parts may be applied after agreement with DNV GL, see also [3.3.2].The design basis shall be provided to DNV GL and shall include documentation of at least the following:

— site conditions— safety philosophy, standards, codes and additional requirements, e.g. from certification plan— design criteria— type and model test description— manufacturing, transport, installation and commissioning requirements— operation and maintenance requirements— description of analysis methods.Floating specific requirements regarding environmental conditions, design criteria, model tests, materials,transport and installation are given in DNVGL-ST-0119.For detailed design basis requirements, specifically for site conditions of the RNA and the offshore supportstructure, reference is made to DNVGL-SE-0190. For generic site conditions wind and wave classes accordingto DNVGL-ST-0437 applies.Once the evaluation of the design basis has been successfully completed, DNV GL shall issue a certificationreport and a statement of compliance for site type design basis.

3.4.3 Site type design assessmentThe purpose of the site type design assessment is to verify that the floating wind turbine or componentdesign complies with the approved design basis and the safety level defined in DNVGL-ST-0119.In case of a site specific component design or e.g. for component certifications of RNAs, towers, floatingstructures, station keeping systems or other site specific installations this section may be applied, too.The RNAs applied for a floating project often have already a type certificate according to a generic type class,e.g. according to DNVGL-SE-0441 or DNVGL-SE-0074.Typically, a type certified RNA needs some design changes (e.g. adaptation of control system) to upgrade theRNA for the site conditions and the requirements of the floating supporting structure dynamics as defined inDNVGL-ST-0119. The integration of such an existing RNAs type certificate into a floating project certificate isdescribed in [4.5].The site design assessment is based on and shall be considered in combination with the design certificationmodule of DNVGL-SE-0441. Depending on the components considered it includes following elements:

— control and protection system— loads and environmental conditions— floating stability— material selection— rotor blade design— machinery and housing design


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— design of floating support structure and station keeping system (mooring, anchor design)— electrical installations— power cable design— corrosion protection— manuals (transportation, installation, commissioning, operation and maintenance).

3.4.3.1 Control and protection systemThe assessment shall be performed according to DNVGL-SE-0441 [3.3.2] Control and protection system.The control and protection system for the RNA is typically designed for fixed on- and offshore wind turbinesand is verified in component or type certification. In that case only site specific design changes shall beconsidered in the assessment.If the control system has been developed based on a fixed support structure, adjustments may be necessary;since the floating platform introduces additional motions that shall be taken into account actively orpassively. For the application of existing wind turbine control algorithms in floating system, the requirementsof DNVGL-ST-0119 for control system apply.DNV GL shall review the documentation for floating structure motion control systems to verify that theyare in compliance with functional requirements of DNVGL-ST-0119. The modified and adopted wind turbinecontrol and protection system shall be examined in accordance with DNVGL-ST-0438.

3.4.3.2 Integrated load analysisThe load assumptions for a floating wind turbine shall fulfil the requirements of DNVGL-ST-0437 and DNVGL-ST-0119 and the design basis.The requirements for the content of the load analysis and corresponding design documentation are asfollows, but not limited to:

— analysis shall be performed for the RNA together with its floating support structure and station keepingsystem (integrated analysis)

— analysis shall be performed for the relevant load cases as defined in DNVGL-ST-0437 and DNVGL-ST-0119— wake effects from neighbouring floating wind turbines shall be taken into account using the method

described in the approved design basis— the interaction of the turbine and the support structure dynamics with the control and protection system

shall be investigated— selected load cases shall also represent situations with low aerodynamic damping. Such cases may include

misaligned wind and wave directions, yaw error due to grid loss or malfunctions of the control system.The documentation shall as a minimum include:

— a complete list of load cases— description of the model used and verification— the design report shall provide ULS, FLS, SLS and ALS loads at relevant cross sections for the RNA, the

tower, the floater and the station keeping system. About evaluation of the loads, see DNVGL-ST-0437App.C

— as part of the documentation, the calculated time histories shall be supplied to DNV GL in an agreedformat.

The loads and responses shall be verified based on documentation review and independent analysis forcompliance with the approved design basis and DNVGL-ST-0119, and other identified standards. To assessthe site-specific loads for the turbines in question DNV GL shall perform an independent load and responseanalysis for a selected sub-set of load cases. It is a requirement that DNV GL performs independent load andresponse analysis due to the limited long term experience of coupled structural behaviour of floating windturbines. Such an independent analysis shall be carried out with a full dynamic load model of the integratedsystem of RNA, support structure and station keeping system, considering aeroelastic and hydrodynamicinteraction.The integrated load analysis is preferably performed by a single computer program. It should consider thesimultaneous dynamic impacts of all relevant environmental forces such as wind, waves, currents, etc. on thecomplete system. The model of the complete system shall comprise rotor and machinery, support structure


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and station keeping system. This enables an analysis of the dynamic system response taking the correlationof all acting environmental impacts into account. In the event that parts of the floating wind turbine aremodelled with a separate computer programme, e.g. with a specific wind turbine code or a specific offshorecode, it shall be shown that each sub system represents the relevant dynamic properties of the completesystem by equivalent elements. The transfer of loads between the various sub-systems shall be aligned atdefined interfaces. The load alignment at the sub-system interfaces may be achieved by an iterative process.Model or full scale tests of the floating system are required for the support and verification of the loadanalysis and the system behaviour, see [3.3.5.1].

3.4.3.3 Rotor-nacelle assemblyDNV GL shall assess that the rotor-nacelle assembly (RNA) is in compliance with the verified design basis.The RNAs blades, structure, machinery, electrical installation etc. shall be certified in accordance with DNVGL SE-0441 site level certification (A level). The additional technical requirements and modifications in designstipulated in DNVGL-ST-0119 shall be considered. Special consideration will be given to adaptations of thecontrol and protection system, interaction with the motion control system as well as additional load casesdefined in DNVGL-ST-0119 and DNVGL-ST-0438. Changed boundary conditions e.g. acceleration and heelingangle limits shall be taken into account in machinery specifications.It shall be demonstrated that the RNA is able to withstand the site loads and the responses resulting from theintegrated load analysis of the floating system. Furthermore, the assessment shall also identify componentsthat will require reinforcement or modifications. The assessment shall include ultimate, fatigue, serviceabilityand accidental limit states.Account shall be taken of the more aggressive offshore environment and possibly higher motions oraccelerations of floating structures. Environmental conditions other than wind and marine conditions mayaffect the integrity and safety of the RNA by thermal, photochemical, corrosive, mechanical, electrical andother physical actions.Moreover, combinations of the environmental parameters given may increase their effects. Hence, thedocumentation for utilization ratios used shall be subject to special considerations.In particular, electrical components like generator, converter, transformer, switch gear and enclosures shallbe designed for the appropriate site conditions. Systems using liquids or lubrications shall be checked againstunfavourable inclinations and motions. The corrosion protection systems shall be able to withstand the site-specific marine environment.Design documentation shall be provided for new, modified or reinforced components and systems, such ascorrosion protection systems, which are not fully covered by the type certificate for the RNA.

3.4.3.4 Support structureThe floating support structure comprises the tower, the floater, the station-keeping system and the anchorfoundations, which transfer the loads into the seabed, see Figure 1-3.Distinction is made between primary and secondary structures for the floating support structure. Primarystructures transfer permanent and environmental loads to the station keeping system with its tendons,mooring lines and anchor foundations. The primary structure typically consists of the hull structure, thetopside deck structure, the tower and the main intersections between the tower and the hull. Also, tendons,mooring lines and anchors are considered a part of the primary structure. Secondary structures coveredby the DNV GL scope comprise access ladders, main structural elements in external access platforms andboat landings. About structural categories see selection of metallic materials in DNVGL-ST-0119 and DNVGL-ST-0126 [4.2] Selection of steel materials and structural categories.DNV GL shall assess that the design of the support structure is in compliance with the design basis, DNVGL-ST-0119 and DNVGL-ST-0126. The verification of the structural design shall include design review andindependent design analyses, if deemed necessary.The following verification activities shall be conducted:

— ulitimate limit state analysis— fatigue limit state analysis— accidental limit state analysis— serviceability limit state analysis


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— water tight integrity of the hull and openings— dynamic behaviour/natural frequency checks— vortex induced motions analysis— corrosion protection system— design drawings and general notes— manufactruing specifications.The assessment covers transport, installation and service phases. The assessment may also includeindependent analysis, in particular for high utilized structural connections, of the floating support structureusing appropriate methods, such as FEM analysis. For the independent analysis the environmental loads fromwind, wave and current, acting on the floating support structure, shall be based on a load analysis of theintegrated system of RNA and floating support structure. The design documents shall be based on DNVGL-ST-0119.

3.4.3.5 Electrical systemThe design of the electrical systems, that shall be covered by the site type design assessment, comprises theelectrical design not covered by the RNA type certification, i.e. electrical systems beyond the RNA terminals.The design shall be assessed for compliance with DNVGL-ST-0076, DNVGL-ST-0359 and DNVGL-RP-0360and the appropriate standards focusing on the safety of the installations as defined in the approved designbasis. The assessment shall be carried out on the basis of diagrams, specifications and calculations of thedistribution system. Design documentation of the following items shall be submitted for review by DNV GL, ifrelevant:

— cabling including free hanging cables— semiconductor devices— switchboards— transformers— converters— energy storage systems— other equipment (e.g. diesel generators for emergency power supply).

3.4.3.6 Station keepingFor design of the station keeping system, see DNVGL-ST-0119. DNV GL shall assess that the station keepingdesign is in compliance with DNVGL-ST-0119 and the verified design basis.The purpose of the station keeping system is to keep the floating wind turbine in position such that it maygenerate electricity and such that the transfer of electricity may be maintained. The station keeping systemrefers to the catenary or taut mooring systems for compliant structures, or to the tendon systems of tethersfor restrained support structures. It includes mooring lines or tendons, fairleads and/or other structuralcomponents that transfer the loads acting on the floater to mooring lines or tendons, structural componentsthat transfer loads from mooring lines or tendons to anchor foundations. The assessment of the structuraldesign will focus on:

— review of detailed design reports, design drawings and manufacturing specifications for the detaileddesign of the station keeping system

— review of design calculations for ULS, SLS, FLS and ALS. The design calculations shall consider temporaryphases as well

— review of component certificates or witness of material tests, if not certified— review of installation and manufacturing methods, however, only with respect to the structural integrity of

the installed station keeping system— review of compliance with redundancy requirements— review of installation manuals.


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3.4.3.7 Anchor foundationsFor geotechnical design of anchor foundations, see DNVGL-ST-0119. Anchors shall be designed accordingto DNVGL-ST-0126, DNVGL-OS-C101, DNVGL-RP-E301 and DNVGL-RP-E302, whatever is applicable for theselected anchor type.The following design documentation shall be submitted for the final structural and geotechnical design:

— design documentation for the structural and geotechnical design calculations, for ULS, SLS and ALS.The documentation shall include description of the assumptions made for the calculations, for exampleregarding manufacturing and installation methods

— design report containing design calculations for the corrosion protection system(s)— design report for the driveability study, if applicable— design drawings, including general note drawing(s)— design documentation regarding scour and scour protection design, if relevant.

3.4.3.8 Floating stabilityRequirements for floating stability are specified in DNVGL-ST-0119 and shall be met in the following servicemodes:

— in-service condition, i.e. a normal working condition with the RNA operating or idling— temporary conditions, i.e. transient conditions such as installation and changing of draught— survival condition, i.e. conditions during extreme storms— transit, in particular tow-out.The following documentation shall be submitted for verification of sufficient floating stability in accordancewith requirements specified in DNVGL-ST-0119 and possible additional requirements specified in the designbasis:

— determination of vertical centre of gravity, including prototype lightweight survey or inclination test result.For different fabrication yards and depending on the analysis provided DNV GL will ask for witness ofadditional inclination tests during commissioning of one of the first units

— design documentation for intact floating stability, according to DNVGL-ST-0119 on floater-turbine coupledcontrol. The analysis shall cover operation at maximum rotor thrust and stand-still of the RNA in severestorm conditions with:

— no fault and— fault such that the rotor is not yawed out of the wind direction.

— damaged stability according to DNVGL-ST-0119 on interaction with other systems, or for unmannedstructures documentation for waiving damage stability requirements

— documentation for dynamic analysis demonstrating adequate dynamic floating stability

— stability manual, see DNVGL-ST-0119 on control system

— documentation on water tightness of openings according to DNVGL-ST-0119 on watertight integrity

— drawing showing position of load lines.

3.4.3.9 Mechanical systemsDNV GL shall review the documentation for mechanical systems (which are not part of the RNA) to assessthat these meet the requirements specified in DNVGL-ST-0119, in DNVGL-OS-D101 and DNVGL-OS-E301 asapplicable. Mechanical systems that shall be covered may comprise, but are not limited to:

— bilge system— ballast system— bearings— compartment venting— mooring equipment (winches, chain stoppers, fairleads etc.)— cranes— installation systems and pull-in system


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— turret system— fire-fighting system and equipment.

3.4.3.10 Corrosion protection systemIt shall be demonstrated, that the floating wind turbine and its components have adequate corrosionprotection in accordance with requirements specified in the relevant DNV GL standards and possibleadditional requirements specified in the design basis. Requirements for corrosion protection are specified inDNVGL-ST-0119, DNVGL-RP-0416 and DNVGL-ST-0126.The following documentation shall be submitted:

— description of the coating and corrosion protection concept— documentation on deviations from the certified RNA type, such as additional corrosion protection or other

site-specific configurations— drawings showing the splash zone and position of anodes— design report containing design calculations for the corrosion protection systems for floating units,

appurtenances (such as fairleads, pad-eyes and chain stoppers), tendons, mooring lines and anchors, asapplicable

— manuals and inspection plan.

3.4.3.11 Transport, installation and commissioning planThe transport, installation (incl. loading and unloading, such as lifting loads) and commissioning processes forthe floating wind turbines, the floating support structure, the station keeping system and other installationsshall be reviewed by DNV GL for compliance with the agreed requirements stated in the approved designbasis as well as DNVGL-ST-0119 and DNVGL-ST-0054.The overall DNV GL aim is to assess that the final structure in-situ has not been exposed to unforeseenloading and structural damage during transport, installation and commissioning. Exposure to fatigue loadingduring transport and installation may be of relevance, e.g. anchors consisting of driven piles experiencefatigue loads during driving.DNV GL shall review the manuals for the RNA, the floating support structure, the station keeping systemsand anchor foundations and verify their compliance with the RNA type certification and the approved designbasis. The review and verification shall cover the following:

— transport procedures considering loading— installation procedures— environmental conditions, e.g. required weather windows— interface points, e.g. connection to mooring lines, anchor foundations and to the electrical system— commissioning procedures including check lists describing function tests of protection system, initial

connection of the electrical system, testing after installation to confirm proper, safe and functionaloperation of all devices, controls and equipment safe start-up, procedures for safe shutdown and safeemergency shutdown

— quality control, measurements and inspections— personnel safety.A review of transportation and installation requirements (transport, lifting) shall be conducted by DNV GL inorder to assess compliance of the transport and installation procedures with the approved design basis andDNVGL-ST-0119.For the floating wind turbine, DNV GL shall require the preparation of transport and installation manuals,which as a minimum shall consist of the transport and installation procedures and the emergency proceduresspecified by the RNA manufacturer. The manuals may be based on the transport and installation manuals forthe type-certified RNA, duly updated with a view to the site-specific application.Normally the different manuals are not all finalized at the design stage. However, in the design assessmentthe assumptions influencing the design shall at a minimum be documented in the respective manuals. Thefinal site-specific RNA manuals and manuals for the floating support structure shall be reviewed prior to thestart of the transport, installation and commissioning.


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3.4.3.12 In-service planFor the floating wind turbine, DNV GL shall require preparation of a user's manual and in-service andmaintenance manual(s), which as a minimum shall consist of the service and maintenance requirementsand emergency procedures specified by the manufacturer for the RNA and the floating support structuredesigners. DNVGL-ST-0119 shall be observed regarding in-service inspection, maintenance and monitoring.The manuals may be based on the user's manual and the service and maintenance manual(s) for the typecertified RNA, duly updated with a view to the site-specific application.DNV GL shall review the user's manual and the service and maintenance manual(s) for the floating windturbine and shall assess that these manuals are in compliance with the RNA type certification system and theapproved design basis. The review and verification shall cover the following:

— scheduled maintenance actions including inspection intervals and routine actions— condition monitoring system(s)— safety related operational procedures or maintenance activities— quality recording and record keeping processes.For the floating support structure, the station keeping systems and other installations, DNV GL shall requirethat relevant input to the inspection and maintenance plan shall be prepared. The input to the inspectionplan and the maintenance manual shall be seen as help to the operations and maintenance organization thatnormally will be established later. Examples of issues that shall be covered are inspections and checks of thecorrosion protection system and inspections for fatigue cracks, bilge systems, scour protection (if any).The above mentioned documentation may not be finalized during the design phase and the verification ofthis documentation shall therefore be covered in the transport and installation phase. However, in the designphase the assumptions influencing the design shall at least be documented.

3.4.3.13 Certification report and statement of complianceA certification report shall be issued to the customer as a reference document for the DNV GL assessmentsperformed within the design assessment. This report comprises the results of the specific assessments.Furthermore, it summarizes all conditions and specifies open items if any non-conformity regarding theapplied standards have been detected.Upon successful completion of all certification modules listed above, a statement of compliance for the sitetype design shall be issued.

3.4.4 Site type manufacturing planThe manufacturing processes for the floating support structure, the station keeping system and otherinstallations shall be reviewed by DNV GL for compliance with the agreed requirements stated in theapproved design basis and the DNVGL-ST-0119 and DNVGL-ST-0054. For the RNA the requirementsaccording to DNVGL-SE-0441 [2.7.6] manufacturing certification module for level A apply.If manufacturing surveillances have been performed within the prototype certification and the design ofinspected components has been taken over for site type level certification the results of the prototypecomponent surveillance may be included to the site type manufacturing assessment. For the floatingstructure, the tower, the station keeping system and foundations the quality management system of themanufacturer and its sub-suppliers should be certified as complying with ISO 9001, otherwise the qualitymanagement system shall be assessed by DNV GL.The focus of the manufacturing plan shall be on the critical manufacturing processes.Changes in the manufacturing processes which influence the production quality or the component propertiesshall be reported to DNV GL. In the event of major changes, the relevant documentation shall be submittedfor renewed assessment and, if necessary, a repeated DNV GL surveillance shall be made.A final certification report shall be issued to the customer as a reference document for the DNV GLassessments performed within the site type manufacturing assessment. Furthermore, it summarises allconditions related to the assessed manufacturing plan and specifies open items if any non-conformityregarding the applied standards have been detected.


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Upon successful completion of all surveillance modules a statement of compliance for site type manufacturingsurveillance shall be issued.

3.4.5 Site type testingSite type testing is focusing on the implementation of the production of the approved design and theverification of the assumptions made within the design assessment by full size measurements on a prototypeor one of the first units installed. The tests on the floating turbine shall be performed based on the agreedtest plan for the prototype see [3.3.5].Type testing shall include:

— all component tests necessary, as required by DNVGL-SE-0441 or DNVGL-SE-0074— component tests specified in the design basis or required for qualification of components, see DNVGL-

ST-0119— results of the prototype tests as defined in the test plan and comparison to design assumptions— measurements of the system dynamic behaviour (natural periods of movement) and comparison to the

design assumptions— function test of additional systems like bilge system, ballast system, venting systems, firefighting systems

according to design and specifications.The elements of the type testing shall be carried out by accredited laboratories. Otherwise, DNV GL shallverify that the testing is carried out fulfilling ISO/IEC 17020 or ISO/IEC 17025, as applicable. The testprogramme/plan shall be evaluated by DNV GL before the test starts. The test methodology, especially wind,wave and load measurements shall be agreed with DNV GL during test plan assessment.A certification report shall be issued to the customer as a reference document for the DNV GL assessmentsperformed within the site type testing assessment. This report comprises the results of the assessment ofthe different tests performed. Furthermore, it summarises all conditions and specifies open items if any non-conformity regarding the applied standards have been detected.Upon successful completion of site type testing a statement of compliance for the site type test shall beissued.

3.4.6 Site type certificateUpon successful completion of the following modules:

— site type design basis— site type design— site type manufacturing— site type testinga final assessment shall be performed comprising the results of the specific modules in a certificationreport. This report shall be issued to the customer as a reference document for the DNV GL assessment.Furthermore, it summarises all conditions related to the performed assessments and specifies open items ifany non-conformity regarding the applied standards have been detected. The final certification report formsthe basis for the site type certificate.

3.5 Project level certification

3.5.1 GeneralThis section provides the details of DNV GL project certification service for a farm consisting of a singleor several floating wind turbines. For the DNV GL project certification the entire process chain, startingfrom the design basis up the operation of the full power plant, is accompanied by tailored inspections andsurveillances.


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The floating wind turbine or farm certification corresponds to the certification schemes stipulated in DNVGL-SE-0190 or DNVGL-SE-0073. In the present document, peculiarities for floating structures are given.The project certification consists of following certification phases:

— design basis assessment— design assessment— manufacturing surveillance— project related tests— transport and installation surveillance— commissioning surveillance.A successfully completed site type certification, see [3.4], may be considered in project certification. Theelements of site type level certification can be performed together with project certification as integral part ofit. In case the site conditions considered in site type certification are corresponding to the project certificationin question or project site conditions are more benign than assumed in site type certification, significantreduction of assessment for all phases may be achieved. The focus of the assessment shall be on variants,extensions and modifications of the site type certified parts.

Figure 3-4 Project certification phases


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3.5.2 Project design basis assessmentThe design basis shall include all parameters relevant for the floating wind power plant design, stating themethods to be used for design, manufacturing, transportation, installation and operation. If values are takenfrom background documents, those shall be referenced and handed in. The design basis shall be assessedfor plausibility, quality issues and completeness. In the design basis, all assets of the wind farm shall beconsidered and described (RNA, floating support structures, station keeping system including anchors, seacables, substation, control centre) see [1.4].The design basis shall include all relevant topics, as defined in DNVGL-SE-0190 [2.3]:

— site environmental conditions, including metocean and geotechnical conditions— ground investigations and tests— descrption of rotor-nacelle assembly (RNA), floater and station keeping system— safety philosophy— standards to be applied— additional requirements of developers and/or authorities— site type certification elements to be considered— documentation relevant for load and response analysis— design criteria— RNA type certificate and additional specifications— specifications and requirements for manufacturing, transport installation and commissioning— specifications and requirements for operation and maintenance— description of analysis method.In the design basis the floating structure specific requirements as stipulated in DNVGL-ST-0119 shall betaken into account.In case a site type design basis has been successfully assessed by DNV GL and parts therein cover thepresent project certification, these parts may be applied after agreement with DNV GL, see also [3.4.2].In case the site specific environmental conditions and external impacts deviate unfavourably from theassumptions made for the site type certification or RNA type certification the full scope of the design basisreview shall be performed. Load and structural assessment shall be adapted accordingly. The extend of thereview shall be agreed with DNV GL. The assessment may focus only on the relevant parts of the system andshall consider operational limits and load envelopes.The final design basis document shall be submitted at the beginning of the design phase, at the latest. As anoptional intermediate step the design principles given in design briefs may be verified before the final designdocumentation is delivered to DNV GL.Once the evaluation of the design basis has been successfully completed, DNV GL shall issue a certificationreport and a statement of compliance for project design basis.

3.5.3 Project design assessmentThe purpose of the project design assessment is to verify that the floating wind turbine or farm designcomplies with the approved design basis and the requirements stated in DNVGL-ST-0119.DNV GL shall evaluate the final design for compliance with design criteria and design basis according to[3.5.2].The project design assessment shall comply with the requirements of DNVGL-SE-0190 or DNVGL-SE-0073.In case a site type design assessment has been successfully performed by DNV GL for conditionscorresponding to the project site, this shall be considered in the project certification, see also [3.4.3].The project design assessment includes following elements:

— control and protection system, see [3.4.3.1]— integrated load analysis, see [3.4.3.2]


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— verification with model or full size tests if not performed within site type certification, see [3.4.3.2]— integration of RNA type certificate according ot DNVGL-SE-0441 or site type certificate according to

[3.4.3.3]— floating stability, see [3.4.3.8]— material selection— design of floating support structure and station keeping system (moorings and anchors) according to

DNVGL-ST-0119, see [3.4.3.4] and [3.4.3.6]— anchor foundation, see [3.4.3.7]— electrical installations, see [3.4.3.5]— mechanical systems, see [3.4.3.9]— power cable design— corrosion protection, see [3.4.3.10]— manuals (transportation, installation, commissioning, operation and maintenance).A site-specific load analysis based on the design basis shall be performed. For floating wind farms thedesigner of the support structure and the RNA supplier normally complete integrated analyses of thefull floating wind turbine system using an integrated simulation model, which includes aero-elastic andhydrodynamic effects. This analysis may be performed for one or a few locations only. The loads andresponses for the remaining locations are then determined based on governing parameters. DNV GLshall check that loads and responses determined for the remaining locations are representative. If thetransferability of loads and responses may not be proven for the entire wind farm, conservative assumptionsshall be applied. The requirements of [3.4.3.2] apply. Critical load cases and load combinations shall beanalysed by DNV GL in order to assess loads and responses in an independent load analysis.Typically, a type certified RNA and a site-specific support structure are used for floating wind projects. TheRNA shall hold a valid A level certificate according to DNVGL-SE-0441 pr DNVGL-SE-0074 and shall coverthe floating specific requirements of DNVGL-ST-0119. As an alternative, a site type certificate of the RNAaccording to [3.4] may be used.The RNA shall be equipped with a certified condition monitoring system (CMS). The certification shall bebased on DNVGL-SE-0439 and include both the system and the monitoring body.DNV GL shall verify that a valid type certificate is in place for the RNA and pre-existing componentcertificates see [4.5].Adequate implementation and site-specific adaptations of the type certified turbine for the project are part ofthe project certification process. Potential synergies from type certification may be taken into account whereidentified and possible. Permissions required by suppliers shall be provided to DNV GL by the developer orcontractor.The support structure comprises the tower, the floater, the station keeping system incl. anchors, whichtransfer the loads into the soil and the access system etc. For the assessment of the support structure thedefinitions and requirements of DNVGL-SE-0190 [2.4.2] apply. The evaluation of the structural design shallinclude design review and independent design analyses, if deemed necessary. The design evaluation shallbe carried out to an extent sufficient to enable DNV GL to state that the support structure complies withthe approved design basis and DNVGL-ST-0119. All phases of the project, including transport, installation,commissioning, operation and maintenance shall be considered.In project certification for floating wind farms the turbine tower shall be assessed during project certification,regardless of whether a valid type or component certificate of the tower exists.For the substation DNVGL-SE-0190 shall be applied.Cable design is highly dependent on the site conditions of the floating wind farm and the dynamic behaviourof the floating wind turbine. The assessment shall be performed in compliance with DNVGL-SE-0190 [2.4.4].For cable design DNVGL-ST-0119 and DNVGL-ST-0359 shall be applied and requirements stipulated thereinshall be fulfilled for certification.A certification report shall be issued to the customer as a reference document for the DNV GL assessmentsperformed within the project design assessment. This report comprises the results of the specificassessments. Furthermore, it summarises all conditions related to the performed assessments and specifiesopen items if any non-conformity regarding the applied standards have been detected.


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Upon successful completion of all certification modules listed above, a statement of compliance for theproject design shall be issued.

3.5.4 Project manufacturing surveillanceThe project manufacturing surveillance contains requirements for state-of-the-art quality managementmeasures, which shall be applied to achieve desired lifetimes and availability rates of the floating wind powerplant. This may support the applicant to determine and eliminate at an early stage possible defects duringengineering, manufacturing and installation, which may impact the later availability of the plant or parts of it.DNV GL shall conduct manufacturing surveillance in order to evaluate compliance of the approved design andthe product in the workshop. For the manufacturing surveillance DNVGL-SE-0190 [3.2] shall apply.If a quality management system certified according to ISO 9001 is not available, DNV GL shall evaluate thesystem. The DNV GL project certification shall in addition to this, perform inspection and audit activities inorder to evaluate that the manufacturing of the floating wind turbines for the specific project are carried outaccording to the approved design and with the intended quality.Manufacturing surveillance consists of (initial) audits and inspections of project related components.The surveillance activities comprise both document review and on-site inspections. This means that themanufacturing surveillance consists of three main activities, document review, initial audit and inspection,see Figure 3-5.

Figure 3-5 Activities of manufacturing surveillance

For the manufacturing surveillance the critical components having a significant impact on the structuralintegrity and the stability of the floating wind turbine has to be selected using a risk based approach, seeDNVGL-SE-0190 [3.2].Manufacturing surveys performed during prototype or site type certification of the floating wind turbine orcomponents may be used as input for reducing the extent of the project manufacturing surveillance.Components certificates and pre-existing shop approvals shall be considered when defining the extent ofsurveillance. Shop approvals shall be performed in accordance with DNVGL-SE-0436.For typical floating designs the survey shall cover at least the manufacturing of the:

— RNA according to DNVGL-SE-0190— floater (hull which provides the buoyancy)— electrical and mechanical systems as defined in DNVGL-ST-0119 on electrical and mechanical systems— mooring lines— mooring attachment points and fairleads— anchors— corrosion protection system— cable connection point— power cable.For novel technologies special requirements apply.


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Following a successful assessment of the project manufacturing surveillance, DNV GL issues a certificationreport. The report summarises all conditions related to the performed assessments and surveys and specifiesopen items if any non-conformity regarding the applied standards have been detected. This certificationreport forms the basis for the statement of compliance for project manufacturing, see Figure 1-6.

3.5.5 Project related testsFor project certification, testing of the floating wind turbine and its components shall be performed in orderto demonstrate compliance with the design assumptions. It is assumed that these tests are assessed duringthe prototype and site type certification.In addition, tests required by national authorities may have to be performed. DNV GL shall witness the testsperformed.As a minimum the following tests shall be completed:

— model tests and/or full scale tests, as required for prototype or site type certification, see [3.3.3], [3.3.5]and [3.4.3.3] as required by DNVGL-ST-0119

— site type testing, see [3.4.5]— material and component tests for mooring lines as required by DNVGL-ST-0119 on selection of material

for chains, wires, tethers and station keeping system in general.Upon successful assessment the statement of compliance site type testing shall be upgraded.

3.5.6 Project transport and installation surveillanceTransport and installation is a crucial temporary phase in a floating wind farm project. DNV GL shall performtransport and installation surveillance as part of the project certification process.Prior to the transport/towing of the first floating support structure and RNA to the wind farm, methodstatements for lifting, transport, towing and installation manuals including loading and unloading shall beissued for DNV GL review. Installation shall include installation of anchors, mooring system and attachmentto the floating structure. All critical phases shall be considered.For the transport and installation survey DNVGL-SE-0190 [3.3] shall apply. The requirements of DNVGL-ST-0054 and DNVGL-ST-0119 on transport and installation shall be considered.For floating projects the surveillance starts when loading at the manufacturers' production sites and ends atthe wind farm site.Post installation tests shall be witnessed. This applies especially to anchor post-installation test programme ifrequired by the anchor design, see DNVGL-ST-0119 on design of anchor foundations.The final as-built documentation shall be issued for DNV GL review.The DNV GL project certification surveyor shall be present during the first installation and during one otherinstallation randomly chosen among the remaining floating support structures and RNAs within the windfarm. However, the final number of installations to be attended by the DNV GL project certification surveyormay be larger depending on the project details, the number and types of floating wind turbines and findingsduring survey.The surveillance may be combined with the marine warranty surveillance, if both are carried out by DNV GLor other acknowledged marine warranty surveyor and agreed at the beginning of the project.The surveillance shall be followed up by a detailed surveillance report. This surveillance report shall includephoto documentation whenever deemed necessary. Permissions required by suppliers shall be provided toDNV GL by the developer or contractor.A certification report shall be issued to the customer as a reference document for the DNV GL assessmentsperformed within the transport and installation surveillance.Tests performed during site type testing may be omitted. Upon successful completion of all surveillancemodules such as load out, transport, towing and installation floating wind turbine units, a statement ofcompliance for the project transport and installation survey shall be issued.


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3.5.7 Project commissioning surveillanceDNV GL shall perform a commissioning surveillance as part of the project certification with the purpose toverify that the RNAs with their floating support structures installed on site are commissioned according to therequirements of the manufacturers and in compliance with relevant documentation provided in the designphase. The task includes also the assessment of the operation and maintenance manuals.The commissioning survey shall be performed in accordance with DNVGL-SE-0190 [4.2].The number of floating wind turbines for commissioning surveillance shall be agreed between customerand DNV GL. However, the final number to be witnessed in commissioning may be larger depending on thefindings during the commissioning surveillance. A larger number may also be agreed, on customer's demandor if it is required by national legislation.

3.5.7.1 Commissioning of the floating wind turbineThe floating wind turbine commissioning shall be carried out in accordance with the submitted proceduresreviewed and approved by DNV GL in advance of the commissioning.During commissioning, main systems and equipment shall be checked for compliance with approveddocumentation and procedures. Surveyors shall review the as-built systems and assess their compliance withcustomer specifications and typical industry practice. Commissioning documentation shall be reviewed foradequacy and completeness.The relevant systems shall be functionally tested, as far as is practicable, in accordance with approvedprocedures, to confirm proper, safe and functional operation of all devices, controls' and equipment's safestart-up. The commissioning requirements defined in the RNA type certification shall be considered.At least the following procedures shall be witnessed by DNV GL or tested in presence of the attendingsurveyor:

— test of the emergency stop buttons— triggering of the brakes and witnessing of turbine's behaviour— test of the yaw system— behaviour at grid loss— behaviour at over speed— test of automatic operation— visual inspection of the entire installation.

3.5.7.2 Commissioning of floating suppoert structureThe DNV GL surveyor shall review the as-installed floater system and assess its compliance with customerspecifications and typical industry practice. Commissioning documentation shall be reviewed for adequacyand completeness. The focus shall be on the commissioning of potential active systems. The following floaterspecific elements within the commissioning shall be considered as a minimum:

— functionality of safety relevant systems and alarms— functionality of ballast systems and bilge pumps, if applicable— draught (the hull shall be marked with load lines to allow for easy inspection of the draught and

identification of any water ingress)— stability of the floating structure according to DNVGL-SE-0119 on floating stability— floating position (inclanation)— watertightness— corrosion protection (to be carried out after less than 365 days to verify adequate corrosion protection)— floater motion controller according to DNVGL-SE-0119 on control system, if applicable— functionality of CMS.

3.5.7.3 Operation and maintenance manualsThe operation and maintenance manuals shall include information regarding the description and specificationof all relevant operation and maintenance activities that shall be carried out during the operational life of the


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floating wind turbine. The documentation shall include further an inspection plan for the periodic monitoringinspections as preparation for the in-service level certification, see [3.6].For details regarding scope and the documentation requirements of the assessment of the operation andmaintenance manuals see DNVGL-SE-0190 [4.3] and DNVGL-SE-0190 [4.4].

3.5.7.4 Certification report and statement of complianceA certification report shall be issued to the customer as a reference document for the DNV GL assessmentsperformed within the project commissioning surveillance and operation and maintenance manualsassessment. This report comprises the results of the specific assessments and inspections. Furthermore,it summarizes all conditions related to the performed surveillances and specifies open items if any non-conformity regarding the applied standards have been detected.Upon successful completion of all certification modules listed above, a statement of compliance for theproject commissioning shall be issued.

3.5.8 Project certificateA final assessment shall be performed including the results of specific modules in a certification report, basedon successful completion of the following modules:

— project design basis— project design assessment— project manufacturing— project related tests— project transport and installation— project commissioning.This report shall be issued to the customer as a reference document for the DNV GL assessment.Furthermore, it summarises all conditions and specifies open items if any non-conformity regarding theapplied standards have been detected. This certification report forms the basis for the project certificate.Substations, power cables and control stations are optional assets for the floating project certificate. Itcomplements the assets substation and power cables of floating power plant up to the grid connectionand energy feed in at the land based converter station. For the scope of work for these assets and thecertification phases reference is made to DNVGL-SE-0190.

3.6 In-service level certification

3.6.1 GeneralThe in-service level certification corresponds to the DNVGL-SE-0190.The in-service level implies an activity by which the RNA, the tower, the floater, the station keepingsystem and other installations are monitored regularly during their entire operational life. DNV GL or otheracknowledged in-service inspectors shall conduct periodic in-service surveillance. The in-service surveillanceresults shall be evaluated to verify that the standards, manuals and conditions defined during projectcertification are observed and maintained. Each unit of a floating wind farm shall be inspected at least every5 years. The in-service phase serves to confirm the validity of the project certificate.Additional to the scope defined in DNVGL-SE-0190 [4.5], the following in-service surveillances are requiredfor floating wind turbines:

— inspection of the corrosion protection system— draught levels— station keeping connection points— pretension of moorings of tethers if applicable— power cable(s) below sea level


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— further requirements defined in DNVGL-ST-0119 on in-service inspection, maintenance and monitoring— hull status and corrosion.The periodic monitoring concept comprises the requirements and conditions for the operation of thefloating wind turbine or wind farm resulting from the design, manufacturing, transport and installation andcommissioning phases. It forms the basis for the check lists applied by the inspectors during in-servicesurveillance. The periodic monitoring concept shall include at least the following inputs:

— operating instructions— requirements defined in the maintenance manuals— requirements and conditions defined during project design assessment— requirements and conditions defined during project manufacturing surveillance— requirements and conditions defined during transport, installation and commissioning surveillance of the

project— modification or repair reports— requirements generated from previous in-service surveillance(s)— building permissions if applicable.

Guidance note:In-service level certification is optional according to DNVGL-SE-0441 and IEC 61400-22. However, it is mandatory according toDNVGL-SE-0190 and DNVGL-SE-0073, if the maintenance of project certificate is chosen. It is strongly recommended to performthe maintenance of the certificate over the lifetime. The resuming of certificate maintenance of a suspended or invalid projectcertificate may be difficult or even impossible.


For periodic monitoring of other assets such as substation, power cables or control station, DNVGL-SE-0190[4.5.3], DNVGL-SE-0190 [4.5.4] and DNVGL-SE-0190 [4.5.5] apply.Before the inspection commences, the structure shall be cleaned if the marine growth limits that havebeen assumed in the load calculations are exceeded or are likely to be exceeded. Inspection intervals ofsubmerged parts shall not exceed 5 years. It is recommended to make more frequent inspections during thefirst five years or if the design limits are likely to be exceeded.The in-service report for all floating units or a representative number, which will be selected on random basisor project specific needs, shall be completed and submitted to DNV GL.A certification report shall be issued to the customer as a reference document for the DNV GL assessmentsperformed within the in-service surveillance. This report comprises the results of the specific inspections.Furthermore, it summarises all conditions and specifies open items if any non-conformity regarding theapplied standards have been detected.

3.6.2 Maintenance of the project certificateOnce the verification of the in-service surveillance has been successfully completed, DNV GL shall issue astatement of compliance for the in-service that confirms the validity of the project certificate for a definedperiod.


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SECTION 4 CERTIFICATE AND STATEMENTS - PROCEDURALREQUIREMENTS

4.1 GeneralUpon the successful completion of a certification module, a statement of compliance shall be issued togetherwith a certification report. The certification report shall be issued if the work has been carried out successfullyfor the certification module, the report contains a reference list of all supporting documentation.Certificates and corresponding final certification reports shall be issued based on the statements ofcompliances for the certification modules of the selected certification level. The final certification report shallinclude the final conclusion for the certification including the integration of the statements.A certificate may also refer to one or more component certificates. Component certificates issued by anothercertification body may only be included if agreed with DNV GL beforehand, see [4.5].All issued certificates will be listed on the DNV GL internet site.

4.2 Assessment documentsDocumentation submitted for certification shall be in English language unless otherwise agreed with DNV GL.

Each document shall have a unique and clear reference which also identifies the actual revision of thedocument. The documentation shall be controlled according to the quality management system of thecustomer. The quality procedures shall be submitted to DNV GL on request.The documentation submitted for the certification process shall be complete and self-explanatory. Thecontent shall meet the requirements of the agreed and applied standards.Further information on the documentation required for certification is given in this document as well as in thereferenced DNV GL service documents. Additional information shall be provided by DNV GL on request.

4.3 DeviationsDeviations from this service specification, without exception, are permitted only with the consent of DNV GL.The certification may in individual cases involve inclusion of locally applicable regulations and codes.The level of safety set in this service specification shall be applied, even if national or regional laws orregulations require less.In the case of designs to which this service specification cannot be applied, DNV GL reserves the right toproceed in the spirit of the service specification.If analysis concepts of different standards shall be applied, these shall generally not be mixed.

4.4 Modification and recertificationModifications of a floating wind turbine for which a prototype, site type or project certificate has been issuedare permitted only if they do not change or affect the principal characteristics at all, or if they change oraffect the principal characteristics within the extent specified in the applicable design code or standard. Thesame applies in case of components or systems of the floating wind turbine are subjected to componentcertification.Details regarding acceptable changes on the RNA are given in DNVGL-SE-0441.Major changes may lead to recertification if required by the applicable standard or if deemed necessary byDNV GL.DNV GL may require recertification if additional requirements for maintenance of the certificate are set bynational authorities or by the applicable design codes or standards.Upon failure to conform to the conditions of the certificate, the customer shall be requested by DNV GL tocorrect the non-conforming situation within a specified time frame.


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If no satisfactory corrective action is taken, the certificate in question shall be withdrawn and theaccreditation authority, under whose authority the certificate was issued, shall be informed accordingly.Certification documents issued by DNV GL shall upon withdrawal or suspension be returned to DNV GL.Major revisions of a referenced standard as well as other new industry learning during the validity period of acertificate shall be evaluated by DNV GL. If such a revision is judged to have implications for the integrity andsafety of the certified floating wind turbine or component, it shall have to be modified and/or re-evaluated inorder to retain its certificate. Transition periods and guidance for the implementation of new revisions shall beestablished by DNV GL for each individual case.

4.5 Integration of certificatesComponent certificates issued according to DNV GL service specifications, as given in [1.4], by DNV GLor other accredited certification bodies may, after a successful evaluation, be integrated in a certificate.To support this evaluation, the customer shall document that the component certificate and its definedinterfaces comply with the floating wind turbine design basis, load assumptions and other requirementsrelevant for integration of the component.The RNA of a floating wind turbine often owns a certification, e.g. a type certification according to a servicespecification as listed in [1.4]. The certification level of the RNA for a floating wind turbine shall comply withthe requirements of the respective certification phases defined within this service specification, see Table 2-2.The terms conformity statement and evaluation report are used by the IEC and within the servicespecification DNVGL-SE-0073 and DNVGL-SE-0074. These terms comply with the terms statement ofcompliance and certification report used e.g. in DNVGL-SE-0441 or DNVGL-SE-0190.Detailed requirements for the integration of existing certificates into a floating wind turbine project are givenin DNVGL-SE-0190 [8.10].The validity of the certificates described in this service specification shall not exceed the validity of theintegrated component certificates.DNV GL shall not take any responsibility for the certification work carried out by other certification bodies.

4.6 Combination of standardsDNV GL certification according to internationally recognized standards shall follow the principles described inthis service specification. Wherever combinations of such standards and external criteria are used, the exactterms of reference and documents that shall be issued shall be agreed at the beginning of the project andshall be specified in detail in the design basis.The application of standards other than those referenced here does not allow for a reduction of the targetedsafety level as described in the philosophy of DNVGL-ST-0119 in combination with the related technicalstandards.DNV GL reserves the right to ask for additional requirements to cover issues essential for the certificationprocess and not covered by the standards in question.It is not allowed to combine safety measures of different standard systems due to the possible differences inthe underlying safety philosophies of the different standard systems.In case standards are combined, caution shall be exercised and the choice of standards is subject toacceptance by DNV GL.

Guidance note:Within a particular standard, aspects such as requirements for partial safety factors for calculations of design loads and designresistance are generally mutually balanced to give an overall acceptable safety level. In another standard with the same overallacceptable safety level, the requirements for the safety factors may have been balanced differently. Picking requirements for loadfactors from one standard and material factors from another is not allowed and may therefore easily result in unpredictable, andpossibly too low or too high, safety levels.



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4.7 Customer obligationsThe customer shall take appropriate actions according to the requirements of the ISO 9001 certificationscheme with respect to complaints and any deficiencies that affect compliance with the requirements for thecertificate. The customer shall keep records of all complaints relating to the compliance of the floating windturbine, component or system with the standards and requirements used for the certificate. These recordsas well as documentation for actions taken shall be available to DNV GL and to the certification body whichhas certified the customer's quality system. Reports of these records and actions taken as well as reports ofminor modifications to the design shall be submitted to DNV GL, at least once a year.Proposals for major modifications to the design, to procedures, and to specifications and other documentsshall be reported without delay together with all documentation affected by the modification in order for thecertificate to be maintained and extended.Following an issue of a site type/component certificate surveys of randomly chosen specimens of each typeof floating wind turbine/component shall be carried out during the validity period of the certificate. Thepurpose is a verification of the manufacturer's design procedures, their maintenance and implementationsin relation to the design procedures and the design parameters initially approved by DNV GL. The customershall provide access to the floating wind turbine/component chosen for inspection.Once a safety-related accident or failure of the installed certified floating turbines or components comes tothe customer's knowledge, the customer shall report this accident or failure to DNV GL. Such major accidentsor failures may result in a request by DNV GL for information about the accident and the causes as wellas corrective actions that shall be taken by the customer in order to maintain the site type/component/project certificate. Based on an evaluation of the accident or failure and, if relevant, an evaluation of thecorrective actions, DNV GL shall decide if a certificate shall be suspended until a satisfactory corrective actionis implemented. A suspension implies that floating wind turbines or components may not be advertised, sold,manufactured or installed with reference to the suspended the certificate.Certificates may be suspended up to a maximum of one year provided that a plan for corrective action by thecustomer is agreed with DNV GL.If no satisfactory corrective action is taken, the type or component certificate in question shall be withdrawnand the accreditation authority, under whose authority the certificate was issued, shall be informedaccordingly. Certification documents issued by DNV GL shall upon withdrawal or suspension be returned toDNV GL.

4.8 Rules for use of the certificateThe DNV GL certification deliverables such as certificates, statements and reports shall be provided when thecertification project is successfully concluded. The aim of the certification deliverables is to provide all thestakeholder's with a transparent proof of the certification result. Examples of a statement of compliance anda project certificate and is included in App.B.The certification services described in this service specification are delivered as accredited services incompliance with ISO/IEC 17065. ISO/IEC 17065 contains requirements to both competence and impartialityof the certification body in connection with the delivery of conformity assessment services.ISO/IEC 17065 also includes requirements to the certificate/statement holder as follows:

— the certificate/statement of compliance shall not be used in such a manner as to bring DNV GL intodisrepute. Furthermore, misleading or unauthorized statements regarding the certificate are not allowed

— the DNV GL issued certification documents such as certificates, statements of compliance/feasibility andcertification reports shall only be provided to others in their entirety

— any claims regarding certificates or statements of compliance/feasibility shall be promoted with referenceto a specific item in the scope for the certification.

Floating wind turbines and components may also carry a certification mark stating the certificate covering theproduct, see App.B.


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4.9 Certification requirements and quality managementThe customer shall provide evidence of a consistent quality management system covering all aspects ofthe development and operation of the floating wind turbine or its components. In particular the customershall show quality relevant procedures to DNV GL for his procedures and his suppliers, covering design,manufacturing, transport, installation, inspection, operation and documentation processes. If a validcertificate for ISO 9001 of an accredited certification body is in place, the project certification body mayreduce this assessment to a plausibility check.In general subsequent certification phases should not be initiated before previous or dependent phases arecompleted and approved. For example, prior to evaluation of the manufacturing phase, the design basisphase and the design phase should both be completed and approved. Alternative ways are possible and maybe agreed with DNV GL.In general test reports delivered shall be prepared by accredited testing laboratories and meet therequirements of ISO 17025 and relevant standards. For non-accredited test laboratories, DNV GL shall verifythat the testing is carried out according to ISO 17025, e.g. by witnessing the tests as applicable.

4.10 Survey requirements and personnel safetyThe customer, or other entity having legal responsibility for the premises where DNV GL personnel willwork, shall inform DNV GL of any safety and health hazards related to the work and/or any safety measuresrequired for the work, prior to starting the work, or if such information is not available at that time, duringthe performance of the work.Whenever DNV GL undertakes to work on site, the customer shall provide all adequate safety measures toensure a working environment that is safe and in accordance with all relevant legislation.If at any time during the execution of work on site a DNV GL employee judges that the work situation isunsafe the work shall be suspended until such situation has been made safe.


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APPENDIX A TECHNOLOGY QUALIFICATION

A.1 Technology assessmentDesigns of floating wind turbines may contain subsystems or components which have no relevant servicehistory, are not covered by current standards or have novel aspects that are not adequately addressed.Technology assessment is the process by which component novelty is evaluated through a structuredmethodology.This assessment shall to be performed at a level of detail necessary to separate proven from new technology.It shall consider aspects regarding subsystem or component safety control, layout, material, structuralintegrity, fabrication, installation, testing and maintenance procedures. The methodology is described inDNVGL-RP-A203 [7].The technology assessment may be carried out by DNV GL with participation by the customer and otherstakeholders, or may be carried out by the customer and verified by DNV GL.The technology assessment includes the following steps:

— division of the technology into manageable elements— assessment of the technology elements with respect to the novelties that require technology qualification— identification of the main challenges and uncertainties related to the novel technology— identification of relevant standards and/or mitigation measures to be considered.The technology assessment shall be carried out by dividing the technology into subsystems and componentswith a clear statement regarding their function. Technology classification will then be applied to eachsubsystem or component according to the classification matrix shown in Table A-1.

Table A-1 Technology classification

Technology statusApplication area

Proven Limited field history Unproven

Known 1 2 3

Limited knowledge 2 3 4

New 3 4 4

The classification matrix implies the class definitions shown in Table A-2. Proven technology is considereda technology classified as 1 - No new technical uncertainties. All other classes reflect varying levels oftechnology novelty.

Table A-2 Technology class definition

Technology class Definition

1 No new technical uncertainties

2 New technical uncertainties

3 New technical challenges

4 Demanding new technical challenges

All systems and design phases (from manufacturing to decommissioning) shall be considered. Newtechnology (classes 2-4) will be subject to technology qualification in addition to the traditional certificationprocesses, and proven technology (class 1) shall be subject to a criticality assessment and certification usingapplicable standards.


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A.2 Risk assessment

A.2.1 GeneralThe first step in the risk assessment is the threat assessment. The objective of the threat assessment is toidentify relevant failure modes with underlying causes and failure mechanisms for the technology, and toassess the associated risks.The failure mode identification and risk ranking involves:

— general preparations including selection of threat assessment methods to be employed— determination of probability and consequence classes and defining the risk matrix when used— failure mode assessment involving relevant expertise.The threat assessment is performed using methods described in DNVGL-RP-A203 [8] and is used as the basisfor defining and prioritizing the activities in the certification plan.The result of the threat assessment contains a register of all identified risks and it identifies those to beaddressed by the continued technology qualification. For each risk determined not to be addressed by thetechnology qualification, it also provides either reference to acceptance criteria of referenced standards ormitigation measures that are considered adequate for that risk, or reference to evidence substantiating thatthe risk has been adequately accounted for.

A.2.2 Failure mode identification and risk rankingA systematic approach for the identification of possible failure modes and their related failure mechanismsshall be established and described. There are many failure evaluation procedures available to identify thehazards, including the hazard and operability study (HAZOP), process hazard analysis (PHA), failure modeeffects and criticality analysis (FMECA), what-if etc.

Guidance note:FMECA methodology is described in BS EN 60812 Analysis techniques for system reliability. Procedure for failure mode and effectsanalysis (FMEA).


The failure mode identification and risk ranking (FMIRR) is a quantitative procedure which ranks failuremodes according to their probability and consequences (i.e. the resulting effect of the failure mode on safety,environment, operation and asset).Recommended actions to control the risks are consolidated into a certification plan together with thestandards and novelties identified in the technology assessment. After evaluation of the results from theimplementation of the certification plan, re-ranking of the risk may be performed. Where a risk remains high,further action is required to be defined and the FMIRR cycle repeated with the updated information. Datafrom the in-service life is to be used as a way to re-evaluate the FMIRR and its conclusions.In lieu of data obtained from specific application or technology, the probability of the event/failure to beused during the risk assessment may be derived from relevant data from other industries, provided that anassessment of the impact of the new application is taken into account and agreed with DNV GL. Conservativeestimates may be used in lack of evidence to support more accurate estimates of failure probabilities orfailure margins.

A.3 Risk matrixFor the FMIRR the probability and consequence classes adapted for floating wind turbines are defined in TableA-3, Table A-4 and Table A-5. The risk matrix is defined in Figure A-1.


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Table A-3 Probability classes

Class Name Description Indicative annualfailure rate (up to) Reference

1 Very Low Negligible eventfrequency 1.0E-04 Accidental (event not

failure)

2 Low Event unlikely to occur 1.0E-03 Strength / ULS

3 Medium Event rarely expectedto occur 1.0E-02 Fatigue / FLS

4 HighOne or several eventsexpected to occurduring the lifetime

1.0E-01 Operation lowfrequency

5 Very highOne or several eventsexpected to occureach year

1.0E+00 Operation highfrequency

Table A-4 Consequence classes - floating turbine (or component)

Description of consequences (impact on)Class

Safety Environment Operation Assets Cost (€)

1 Negligible injuryor health effects

Negligiblepollution orno effect onenvironment

Negligible effecton production(hours)

Negligible 1k

2 Minor injuries orhealth effects

Minor pollution /slight effect onenvironment(minimumdisruption onmarine life)

Partial loss ofperformance(retrieval notrequired outsidemaintenanceinterval)

Repairable withinmaintenanceinterval

10k

3Moderate injuriesand/or healtheffects

Limited levelsof pollution,manageable /moderate effecton environment

Loss ofperformancerequiringretrieval outsidemaintenanceinterval

Repairable outsidemaintenanceinterval

100k

4 Significant injuries

Moderatepollution, withsome clean-up costs /Serious effect onenvironment

Total loss ofproduction up to 1m (€)

Significant butrepairable outsidemaintenanceinterval

1m


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5 A fatality

Major pollutionevent, withsignificantclean-up costs /disastrouseffects on theenvironment

Total loss ofproduction greaterthan 1 m (€)

Loss of device,major repairneeded byremoval of deviceand exchange ofmajor components

10m

Table A-5 Consequence classes - project



1 Negligible injuryorhealth effects

Negligiblepollution orno effect onenvironment

Negligible effecton production(hours)

Negligible 10k

2 Minor injuries orhealth effects

Minor pollution /slight effect onenvironment(minimumdisruption onmarine life)

Loss of arrayperformance(remedial activitytakes placewithin scheduledmaintenance)

Repairable withinmaintenanceinterval

100k

3Moderate injuriesand/or healtheffects

Limited levelsof pollution,manageable /moderate effecton environment

Loss of arrayperformancerequiringretrieval outsidemaintenanceinterval

Repairable outsidemaintenanceinterval

1m

4 Significant injuries

Moderatepollution, withsome clean-up costs /Serious effect onenvironment

Total loss of arrayproduction up to10 m (€)

Loss of onedevice orassociated arrayinfrastructure

10m

5 A fatality

Major pollutionevent, withsignificantclean-up costs /disastrouseffects on theenvironment

Total loss ofproduction greaterthan 10 m (€)

Loss of multipledevices and/or arrayinfrastructure

100m

Guidance note:The currency referred to in the consequence cost are to be adapted for different locations worldwide representing the generaldescription of the consequences given in Table A-4 and Table A-5. The cost consequences in the mentioned tables are related tooperation and assets and not directly to safety and environment which are to be considered separately.



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Figure A-1 Risk categories

A.4 Technology qualification plan

A.4.1 GeneralThe purpose of the technology qualification plan is to describe what evidence is required in order to considerthe novel technology qualified. This shall include a description of the qualification basis, and an identificationof suitable qualification methods. The technology qualification plan shall also address the mitigation of thefailure modes in the risk register.The technology qualification methods described in the plan shall:

— identify the pieces of evidence the qualification methods are intended to produce— trace this evidence back to claims made of functionality and performance and the failure modes the

methods intend to mitigate and the required failure margins— entail an unambiguous description of the acceptance criteria to determine if the qualification activities

were successful in providing the required evidence.

A.4.2 Qualification methodsThe analytical approach of technology qualification may be supported and complemented by results obtainedby testing to handle uncertainties and novelty in the technology. Tests as described below are used formaterials, components, assemblies and sub-assemblies. Typical tests may be:

— basic tests, such as testing of material properties and degradation mechanisms— tests of components, sub-assemblies and assemblies to verify the functional requirements of a new type

design— full size test or small scale prototype tests in order to gain experience of the novel component/system

including indicative reliability and performance data in an uncontrolled environment.Qualification by testing shall address failure modes for components or systems identified as novel or high riskthrough the technology qualification process. DNV GL involvement in technology qualification tests shall beagreed as part of the certification plan.


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APPENDIX B DELIVERABLE EXAMPLES

B.1 Project certificate

Figure B-1 Project certificate


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B.2 Statement of compliance

Figure B-2 Statement of compliance

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CHANGES – HISTORICThere are currently no historical changes for this document.

About DNV GLDNV GL is a global quality assurance and risk management company. Driven by our purpose ofsafeguarding life, property and the environment, we enable our customers to advance the safetyand sustainability of their business. We provide classification, technical assurance, software andindependent expert advisory services to the maritime, oil & gas, power and renewables industries.We also provide certification, supply chain and data management services to customers across awide range of industries. Operating in more than 100 countries, our experts are dedicated to helpingcustomers make the world safer, smarter and greener.

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