This guidance document intends to provide a standardised methodology for defining the mechanical limits of subsea cables to support developers, manufacturers and operators in the offshore wind industry.
Overview
The Mechanical Limitations (MecLim) I and II Joint Industry Projects (JIPs) were set up to address inconsistencies in how mechanical limits of subsea cables are defined and interpreted across the industry, to more accurately reflect their true performance capabilities.
Through consolidating industry knowledge and establishing consistent requirements, this guideline proposes a performance testing approach to defining mechanical limits, supported by a safety factor philosophy and associated design and test methodology that enhances confidence in cable design and specification.
Key elements of the guideline include:
- Performance testing approach: Performance testing is recommended when determining the actual mechanical capability of cables rather than conformance testing alone, which existing mechanical limits are based on.
- Safety factor philosophy: Considering the key stages of a cable’s lifecycle, this introduces a consistent framework for applying safety factors to mechanical limits at each stage, to improve transparency and comparability across manufacturers. The guidelines apply to parameters including minimum bending radius, sidewall pressure limit, tension limit, compression limit, crush load limit, impact capacity and bending stiffness.
- Modelling flexibility: Guidelines on numerical modelling support the use of various modelling techniques for testing, providing guidance on key variables, component interactions and uncertainties.
- Enhancing existing cable tests: Several improvements are proposed including adaptation of the tensile bending test, including 4-point testing as industry-standard and testing at varying temperatures and displacement rates to best represent operating conditions.
The standardised methodology offered by MecLim II JIP is intended to be a valuable resource for all stakeholders involved in the development and operation of offshore wind farms.
This report is issued by the Carbon Trust under the Offshore Wind Accelerator (OWA) cables technical working group, which facilitated the delivery of the project by Wood in collaboration with industry partners, following a year of stakeholder workshops with cable OEMs.
