Houlder worked with self-propelled jack-up vessel operator, Seajacks to provide design and seafastening expertise for the vessel Seajacks Zaratan, ahead of its project to transport and install wind turbine foundations at the Akita and Noshiro port offshore wind farms in Japan.

Seajacks Zaratan is designed specifically to service the wind farm installation market, hosts an 800t crane and comprises a 2,000m² deck space. Houlder’s role was to design the monopile cradles and upending system seafastening, transition piece seafastening system, gangway access tower, hydraulic piling hammer grillage, and seafastening for all project mission and support equipment for the vessel.

When it comes to seafastening, there are many factors to consider to ensure a safe and efficient process. For example, the payload onboard is almost always pushed to the limit and the vessel loading conditions must be checked to ensure the vessel is going to operate within allowable conditions. Additionally, bespoke vessel motion must be calculated to determine the loads the equipment will impart into the vessel hull, as the vessel rolls and pitches while at sea. In the case of the Zaratan, part of the length monopiles overhang the extent of the vessel, and so additional green water analysis was conducted.

James Smith, Senior Structural Engineer, Houlder, said: “In pursuit of efficiency, the size of offshore wind components such as turbines and blades for both fixed and floating foundations has grown considerably. Ultimately, the risks associated with transporting these components is higher as vessels are pushed to their operational capacity and beyond. Houlder is a trusted expert across the maritime industry and is well placed to support the accelerated transformation of the offshore wind space, unlocking efficiencies, providing accurate analysis and promoting continued growth. We stand shoulder to shoulder with our customer to deliver a robust and flexible engineering service using ingenuity at every step of the process.”

Andrew Garrod, Engineering Superintendent, Seajacks, commented: “The Seajacks Zaratan is a proven vessel for offshore wind farms. However, as projects get bigger and more complicated, accessing Houlder’s experienced team of engineers ensures we meet all the challenges of ensuring a safe and efficient transit and installation. Having accurate analysis and knowledge of options available when an allowable vessel limit is exceeded is essential to the success of the project.”

Since completing this project, Houlder is now working on the second phase of the project – designing the tower and nacelle seafastening, the blade rack substructures to support twelve blades for four wind turbines and the supporting project equipment seafastening. Houlder has a detailed understanding of the offshore wind operating environment, having supported projects for other customers including Siemens Gamesa, Jan De Nul, and GEOSEA.