Technology Pipeline:
Jack-up Leg Cushion & Push-up System
Lack of Offshore Wind Installation Capacity
Offshore wind turbine installation relies on the purpose-built jack-up vessel, so-called WTIV. It is mostly self-propelled, with a heavy-lift crane onboard. When installing turbines, the hull of the vessel will be jacked up from the water with its four legs standing on the seabed.
A modern WTIV costs $350+M, or $250~350k a day. However, the average effective working days of a WTIV in North Sea is no more than 120 per year. Based on the statistics, approx. 50% of the idle days are due to bad weather or environmental conditions.
By 2025, there were only 20 WTIVs worldwide (excl. China), and only half of them can install turbines larger than 15MW. A lot of studies have already revealed the large mismatch between the installation market demand and vessel fleet capacity in the coming decades. The shortage of WTIVs is becoming a serious issue for wind farm developers and EU energy officials, and there will be huge pressure to increase the vessels’ productivity.
WTIV Workability & Safety Issues to Be Improved
Issue-1: Leg Impact
Turbine installation operations will be stopped when the wind speed is over 12m/s, and this corresponds to sea states of Hs = 2.5~3m. However, in most cases, when the waves are higher than Hs = 1~1.5m, the jack-up vessel cannot lower its legs to seabed and reach its working height. Future WTIV designs shall close the gap of allowable working sea states so as to maximize the vessel’s workability.
Issue-2: Spudcan Extraction
On very soft seabed, like soft clay or loose silt, a spudcan can be settled at a depth over 15m; extracting the spudcan from soil could take a couple of days, or even weeks, since the equipped water jetting system may not always work. This is extremely dangerous in typhoon/hurricane areas, as the WTIVs are not designed for those extreme conditions.
Issue-3: Eccentric Leg Load
For lattice-legged jack-ups working in non-flat or uneven seabed conditions, RPD (Rack Phase Difference) is a common issue and an indication of eccentric loading on legs, which may lead to severe structural damage. There is no automatic measurement and control of RPD during jacking/preloading operations, and this could cause delays or safety issues in the operation.
Issue-4: Base Tip Overstress
In most designs, a cone-shaped base tip is provided at the bottom center of the spudcan for easy positioning of the leg onto the desired spot when landing. On hard rocky seabeds, the conical tip may lead to stress concentration beyond the limit; this can complicate the landing process or require costly exchange of all spudcans before starting the job.
Our Solution – JLC System at Bottom of Legs
- Hydraulic and control systems are enclosed in a clean and accessible space, and all vulnerable parts are replaceable at harbor with leg retracted to its upmost position
- System design will follow fail-safe principle – malfunctions will end up with the footing returning to its “closed” position and not negatively affect the safety and other operations of the vessel
- As the JLC is placed inside the footing — at the bottom of the vessel when in transit — increased weight of the footings will not affect the vessel’s payload
Validation – Leg Impact Damping
Validation – Spud can Extraction
Highlights of JLC System
- Reduce leg landing impact load and increase jacking operation sea states to Hs = 2.5~3 m; boost productivity of WTIVs by approx. 35%
- Provide 50% extra capacity to pull out legs in case the spudcan is entrapped in the soil
- Monitor leg load and its eccentricity to prevent RPD damage during jacking and preloading operations
- Exchangeable base cone of footing to suit different soil types without replacing the complete spudcan
- Added to the bottom of jack-up legs, no impact to vessel payload and other operations
- Particularly advantageous for hard and very soft seabed, with improved operating safety and efficiency
Development Status
- Concept design for a WTIV with max leg load of 15,000t has been completed, and technically verified by DNV in early 2026, see News
- The concept validation was funded by UNIIQ, an investment fund supported by the Netherlands Enterprise Agency (RVO) and South Holland Province
- Next step would be to validate the sand prevention system and conduct a HAZID for the leg handling operations with a WTIV operator
3D Animation of JLC