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As the floating offshore wind sector moves rapidly and globally towards industrialisation and commercialisation, thought is turning to efficient management of the life cycle integrity of floating units.

Scale and scope will expand in terms of the size of the floating structure, numbers of structures in a field, depth of water in which station keeping is required, and importantly an increase in the number of jurisdictions which will host floating offshore wind arrays.

Prototypes are proving the concepts, but are designed to survive on-station for a relatively short period. The commercial scale will see life of assets of over 20 or 25 years, and the structural integrity must be retained throughout.

All of these factors are being considered to ensure common thinking for regulatory frameworks, asset integrity requirements, stakeholder management, and critically, in reducing cost to optimise return on investment.

Achieving this will need constructive discussions and collaboration between asset owners, operators, regulators, classification societies, and service providers. Integrity management programmes will have to meet regulatory, class, and environmental requirements, as well as being operationally efficient and low cost.

Collaboration through joint industry projects (JIPs) has proven to be an effective way of identifying the key challenges and solutions in a sector – one example being the hull inspection techniques and strategy (HITS) JIP set up by the Global FPSO Research Forum eight years ago.

Membership of the JIP cut across all elements of the asset integrity management supply chain from (then) oil majors, with global floating production unit operators, the major classification societies, integrity management service providers, and academia for research and development. The collaboration ensured stepping away from individual, commercial competitive tensions and a rich agreement as to where the sector needed to go in order to remain safe, cost-effective, and relevant. The JIP encouraged the introduction of diverless methods, unmanned tank inspections, and non-intrusive surveys of Ex electrical equipment, which generated a number of quantified benefits: > 50% cost and persons-on-board (POB) reductions. > Reduced carbon footprint. > Reduced safety risk. > Improved integrity assurance. > Remote inspection capability.

EM&I is a global provider of innovative asset integrity management services and was a co-founder of the HITS JIP. The EM&I Group has a deep background of experience in the floating oil and gas production sector. In that sector, EM&I-developed technology and techniques have saved money for clients, enhanced data to inform integrity management, and minimised impact on operations, thus reducing indirect cost and, above all, mitigating safety risk.

The company recognises that similar positive outcomes can be generated for the floating offshore wind industry through a similar JIP established with operators, regulators, and service providers whose focus will be to identify specific challenges and solutions for the industry.

The FloWind JIP has been convened with participation from all the major classification societies – American Bureau of Shipping (ABS), Bureau Veritas (BV), Det Norske Veritas (DNV), and Lloyd’s Register (LR) – as well as SBM Offshore representing designers and operators, DEKRA to bring inspection technology insight, Acteon Group, which develops mooring system and station keeping capability, and EM&I for asset integrity management experience.

The JIP’s agreed objective is to identify asset integrity challenges and encourage practical solutions for floating offshore wind assets and infrastructure, and the key themes which came from the inaugural meeting included a range of insights.

Regulatory frameworks

The floating oil and gas production sector benefits from globallyagreed standards and regulatory framework. Whilst the risks are similar for floating offshore wind, there are significant differences. The JIP recognised that currently, the regulatory framework for the sector is being developed. Progress is being made through prototype stage of designs, and with it comes a greater understanding by the industry stakeholders.

Those stakeholders come from a variety of sectors including utilities, oil and gas, marine, and others; all have a view on

regulatory framework requirements, which have different drivers. Ideally, the floating offshore wind sector should aim for international standards on which regulators can rely, as this will also be less expensive for the industry.

It is important to differentiate between the regulatory framework – applying project certification, or classification – and the technical standards applicable to the floating offshore wind technology. Technical standards are also clear; they provide the basis for certification and classification.

Commercialisation of floating offshore wind will take the debate to the regulatory framework, which is currently not uniform across jurisdictions; sometimes mandatory, and sometimes not, imposed by local, national authorities, or by insurers or other stakeholders, but guidelines explaining the certification and class are clear. The International Association of Classification Societies (IACS) has greatly assisted harmonisation of class rules during operations as opposed to the set-up phase in the shipping industry and offshore oil and gas, and a similar requirement exists for floating offshore wind.

The JIP will study the various regulatory frameworks based on sector and jurisdiction variations and influence a standard approach to underpin asset integrity through longer life of the commercial arrays and floating structures.

Figure 1. NoMan® optical camera.

Figure 2. Corrosion mapping from NoMan laser scan.

Learning lessons

Given the variety of experience coming together in floating offshore wind, it was agreed that the broadest research must be conducted in order to draw on the lessons for asset integrity. This included from the wind energy generation sectors – onshore and fixed offshore – oil and gas, marine, power distribution sectors, as well as working with other JIPs to learn from collaboration elsewhere.

Risk

In comparison with the oil and gas sectors where hydrocarbons led to greater risk focus on human and environmental safety, the focus for floating offshore wind asset integrity will be more financial and commercial, and therefore, there will be a greater role and interest in the regulatory frameworks for insurers and investors. Where electricity is generated on floating offshore wind assets, and green hydrogen generated through electrolysis on the asset, that will develop new risk profiles and therefore broaden the interest of a wider stakeholder group.

Prototypes are giving valuable lessons about the complexity of the floating assets, with the stresses involved through rotating blades with increasing length, significant and growing height of structures, the relatively small footprint of the floating structure, and the stresses placed on the mooring systems in increasing depth of water.

The complexity is increased when several assets are deployed in an array, with the increase in turbulence within that array having an impact on the stresses mentioned above.

As the sector develops to commercialisation, there is a requirement to understand this complexity and the impact on asset integrity management through life. The future will be risk- or criticality-based inspection, combined with sensors and routine monitoring, recognising the environmental factors, providing assurance, and contributing to cost reduction.

Working groups

Therefore, two working groups are planned initially by the JIP; one for the regulatory frameworks, and the second to review technical integrity.

Integrity management technology

Technology and techniques that have been developed with the benefit of guidance and support of participants of the HITS JIP, primarily for the floating oil and gas production sector, can be transferred to floating offshore wind to build on the technical understanding and regulatory frameworks outlined earlier.

Remote inspection techniques now support the key direction of the HITS JIP at its inception, specifically: > The elimination of the requirement for divers for in-water inspection of floating assets and their mooring systems.

> Minimising the requirement for physical entry into confined spaces, particularly cargo oil or gas tanks, as well as water ballast tanks.

Underpinning these developments has been a close working relationship with regulators, particularly class and risk-based engineering and inspection companies. Together these have maintained regulatory and client requirements for inspection and achieving long-term integrity assurance. Some examples of the technologies and techniques that will be drawn across into the floating offshore wind sector are covered next.

Diverless inspection

ODIN® diverless in-water inspection has been developed to meet regulatory requirements for the inspection of hulls and associated structures, as well as the full length of mooring systems, from the floating asset to the anchor point.

Using specialised integrity class ROVs launched and operated either from the asset itself, or importantly for the floating offshore wind sector, from a support vessel, thus minimises the requirement to board the floating structure.

Output from collaboration in the HITS JIP has expanded this requirement from inspection to repair of the underwater structure, which could benefit the floating offshore wind sector, reducing the requirement to disconnect and tow-to-port.

Remote inspection

NoMan® remote inspection of confined spaces has been developed to mitigate the significant risk of human entry into cargo oil and gas tanks, as well as water ballast tanks. This also reduces the preparation and system isolation required, and thus minimises down time of a tank enabling focus on the main output of operational availability.

NoMan was initially based on high-grade cameras developed for the nuclear industry, enabling both general and close visual remote inspection, to meet the equivalence of the class requirement for a surveyor in the tank. The capability has now developed to include laser scanning which informs 3D models and digital twins, and significantly from an asset integrity standpoint, enables digital comparison with previous inspection, particularly baseline surveys at the fabrication stage. It allows for identification of anomalies such as buckling, distortion, and corrosion mapping.

Given the inclusion of void spaces in emerging designs for floating offshore wind assets, whether for ballast or structural integrity, through life there will be a requirement for inspection for structural integrity. NoMan will meet that requirement remotely.

Structural integrity

Structural integrity management of floating and other elements, building on a broad understanding of the factors involved; engineering to predict the failure mechanisms and risk- or criticality-based engineering; and monitoring and inspection to provide data for assurance, are all critical for any offshore sector.

Drawing on experience of pressure systems and hull integrity management, EM&I has also developed ANALYSE™, a statistical tool which reinforces risk-based inspection techniques and reduces the requirement for physical inspection and measurement, particularly of wall thickness in steel structures.

Given the requirement to minimise the need for personnel to be onboard a floating offshore wind structure and the number of similar structures deployed and operating in near-equivalent environmental conditions, ANALYSE will reinforce a cost-effective risk-based approach to inspection for integrity assurance.

Figure 3. ANALYSE™ statistical representation of UTMs.

Future-proofing

Future-proofing will be critical given the design life of the floating structures and their mooring systems, to ensure that physical human intervention can be reduced further for inspection as technology develops. In itself, this requires early collaboration and a mindset of design for inspectability to ensure that early savings are developed and optimised through life.

Conclusion

There was broad agreement at the inaugural meeting of the FloWind JIP that collaboration is required to contribute to the debate which will ensure that all the factors at play for long-term asset integrity management are considered.

This debate will contribute to making the rapidly growing floating offshore wind sector safe and cost-effective, by drawing on the broad lessons of other sectors to provide asset integrity assurance and enhance the data available to do so. All of this will also lead to minimising the carbon footprint of those charged with providing that assurance.

This article has demonstrated the lessons learned from the oil and gas sectors, and how these can be transferred to floating offshore wind to generate an effective structure for asset integrity in good time for such a rapidly developing sector.