SSIT – Thor
Secondary Steel Installation Tool and Seafastening – from Design to Delivery
TWD was awarded the design of the Secondary Steel Installation Tools (SSITs) equipment and seafastening structures for the Thor Offshore Wind Farm (OWF). Additionally, TWD supported RWE by providing EPC (Engineering, Procurement, and Construction) services, managing multiple interfaces while ensuring smooth and complete project execution. TWD’s multidisciplinary teams provided end-to-end ownership of the process and delivered the project within a strict timeline.
End-to-End Engineering
To help RWE deliver the SSIT equipment on time under a demanding schedule, TWD adopted a fast-track engineering approach, working with multiple teams in parallel. All SSIT components – including six storage towers, four seafastening grillages, and the Hawkeye modular tugger frame designed to streamline installation – were engineered by TWD. The urgency of the timeline shaped every aspect of the project, from concept to execution. TWD’s EPC-service played a central role in enabling a rapid yet reliable design cycle, ensuring alignment across disciplines and stakeholders. Drawing on extensive experience, the equipment was designed with a philosophy that prioritized simplicity alongside time optimization. The result: equipment optimized for fast installation and lean fabrication. Furthermore, TWD led the design verification process with certifying bodies.
Strategic Procurement Across Europe
To reduce risk and remain on schedule, fabrication was distributed among three contractors across Europe: the storage towers and seafastening grillages were produced in Greece, the Hawkeye – a modular tugger frame developed to streamline installation – was built in Belgium, and additional tools such as the External Working Platform Storage Towers (EWP STs), External Working Platform Installation Tool (EWPIT), Internal Cassette Installation Tool (ICIT), and Boat Landing Installation Tool (BLIT) were fabricated in the Netherlands.
Given the tight schedule, procuring large quantities of structural steel was a concern for RWE. With TWD overseeing both design and procurement, our engineers could initiate early involvement across several project teams. TWD’s independent position allowed flexibility and transparency in supplier selection. Leveraging a network of pre-qualified suppliers helped secure production slots and keep the project moving forward.
Construction & Quality Control
The fabrication phase covered a broad scope, including the construction of both the SSIT tools and the seafastening components. The strategy of choosing multiple fabricators for the SSIT components enabled parallel production but demanded strong coordination and stakeholder management. TWD played a key role in monitoring the fabrication process, proactively highlighting tight tolerance requirements to RWE and the fabricator. During mobilization, TWD was instrumental in overcoming the resulting challenges through hands-on support, close coordination, and practical problem-solving on-site.
TWD actively supported construction through the review of fabrication documents, quality assurance, and frequent monitoring of the progress. Regular site visits to fabricators in Antwerp (BE), Rotterdam (NL), and Volos (GR) were conducted to monitor quality.
Agile On-Site Mobilization
During the mobilization phase, we provided support across Factory Acceptance Testing (FAT), Site Acceptance Testing (SAT), and the overall mobilization process. TWD added value by responding swiftly to unexpected challenges, making rapid design updates, and ensuring smooth integration on-site. Our rigorous approach to alignment and quality control proved essential, enabling us to achieve a high level of precision.
FAT procedures developed by the fabricators were reviewed by TWD to ensure all critical functions – particularly related to drive and control systems – were verified. Tailored SAT procedures developed internally focused on validating the integration of all systems and provided operators with the opportunity to test the complete setup prior to the first offshore installation. Continuous on-site support was provided, including final deck interface checks and adjustments. Mobilization focused on assembling components fabricated at different locations and ensuring the elements fit together seamlessly on the vessel. By comparing measurement reports across all tools, we safeguarded consistency in quality and fit. Additionally, operator training was provided to ensure the equipment could be used effectively from day one.
Project highlights
- Delivered over 50,000 engineering hours within 12 months, meeting a challenging project timeline without compromise
- Coordinated multiple contractors across Belgium, the Netherlands, and Greece through consistent site visits and transparent reporting
- Managed the design verification process in collaboration with certifying bodies
- Provided end-to-end engineering support, from concept development to on-site supervision and mobilization
- Applied innovative method engineering to create straightforward, practical tool designs that simplify structure and speed up installation while ensuring high safety for personnel and equipment
- TWD efficiently executed a complex project for RWE while minimizing interfaces, showcasing TWD’s transparency and reliability
- TWD designed the SSIT to enable the rapid and efficient installation of all secondary steel components
