Key findings from the NorMoor joint industry project (JIP), led by DNV, have been incorporated into the third edition of ISO 19901-7:2026, an international standard governing station-keeping systems for floating offshore structures and mobile offshore units. The revision introduces a more consistent, reliability-based framework for designing and assessing offshore mooring systems, with the potential to reduce costs while maintaining required safety levels.

Floating offshore installations depend on mooring systems to remain safely positioned throughout their operational lives. Failures can have serious safety, environmental and financial consequences, making reliable design and assessment essential as offshore energy developments become increasingly complex.

The updated standard reflects more than a decade of collaborative research under the DNV-led NorMoor JIP, which has developed and calibrated safety factors for ultimate, accidental and fatigue limit state assessments.

Established in 2011, NorMoor brings together operators, engineering companies, manufacturers, regulators and technical specialists to improve offshore mooring design. Around 20 organisations have participated in the project, sharing technical expertise and operational experience across the offshore energy value chain.

“NorMoor has become much more than a research project. It is a unique meeting place where companies openly share mooring system design and operational experience,” said Siril Okkenhaug, Project Manager for the NorMoor JIP at DNV. “The work has shown that safety factors can be reduced through reliability-based calibration while maintaining the required level of safety. Seeing these results now incorporated into ISO 19901-7 is an important milestone for all of us involved."

Prajeev Rasiah, Senior Vice President and Regional Director, Northern Europe, Energy Systems at DNV, said the development highlights the importance of international standards in supporting safe and reliable offshore projects.

“The incorporation of NorMoor results into ISO 19901-7 provides the industry with a more consistent framework for mooring system design and assessment. As offshore energy systems evolve, including the growth of floating wind, this type of collaborative work will be essential in building confidence and supporting sustainable development,” he said.

Reliability-based approach targets cost reductions

Across its first three phases, NorMoor developed reliability-based methodologies and calibrated safety factors covering three key design conditions: ultimate limit state (ULS), accidental limit state (ALS) and fatigue limit state (FLS).

The methodologies were progressively incorporated into DNV's offshore standards, with ULS and ALS approaches introduced in DNV-OS-E301 in 2018 and the FLS methodology added in 2024. Their inclusion in ISO 19901-7:2026 extends the framework's application through an internationally recognised standard.

DNV contributed to the ISO working group and the Norwegian national committee responsible for revising the standard. This work helped align the updated requirements with the NorMoor reliability-based approach. The calibrated ULS and ALS safety factors were incorporated into Annex B.2, which contains requirements applicable to the Norwegian Continental Shelf.

Kjell Larsen, Advisor Marine Technology at Equinor, said the earlier implementation of the findings in DNV-OS-E301 helped establish confidence among regulatory authorities during the revision process.

"The fact that DNV implemented the results continuously in DNV-OS-E301 was crucial. It helped establish confidence with the authorities when Annex B.2 was revised and demonstrates the value of long-term research and collaboration between the industry and DNV,” he said.

Benefits for new projects and existing assets

According to Equinor, projects applying the 2026 edition of ISO 19901-7 have achieved significant reductions in mooring-related costs while maintaining required safety levels. The benefits apply to both new developments and existing installations, including the Wisting floating production, storage and offloading (FPSO) vessel and Heidrun B floating storage and offloading (FSO) vessel.

The findings incorporated into Annex B.2 are relevant to new and existing offshore assets on the Norwegian Continental Shelf. Compliance with the annex will be required by the Norwegian Ocean Industry Authority (Havtil) and the Norwegian Maritime Authority (NMA).

The revised framework is also expected to support lifetime-extension assessments by helping operators determine whether existing mooring components can remain in service safely. Equinor said calibrated safety factors could reduce the need for expensive component replacement and system redesign, enabling more informed decisions about ageing assets.

Fourth phase focuses on ageing mooring systems

The NorMoor JIP is now in its fourth phase, which focuses on methodologies for assessing mooring-chain degradation and establishing criteria for chain replacement. The phase is scheduled for completion in 2027.

Findings from the first three phases indicate that substantial savings can be achieved while maintaining required safety levels. For a typical 16-line mooring system, estimated savings are approximately NOK 40 million for a two-year life extension and NOK 100 million for a five-year extension.

The fourth phase aims to strengthen the industry's ability to assess ageing mooring systems and optimise replacement strategies. The work is expected to help operators balance safety, asset life and maintenance expenditure as offshore installations approach the end of their original design lives.

The incorporation of NorMoor research into ISO 19901-7:2026 marks a further step in translating collaborative engineering research into international standards, supporting more consistent offshore mooring assessments and potentially improving the economics of both new developments and existing floating assets. -OGN/TradeArabia News Service