INSTALLATION VESSELS FEATURE SPONSOR
MPI RESOLUTION RECEIVES HIGH PERFORMANCE RE-INFORCEMENT
Effective operation of wind turbine maintenance vessels is critical to the efficient running of offshore wind farms. An important aspect of this is the ability of these jack-up vessels to move between locations quickly and safely.
to withstand loads from large boulders, the site clearance becomes faster, safety is increased and operational costs reduced.
RAPID INSTALLATION MV Resolution’s operators MPI had a limited window of opportunity for carrying out the strengthening. Conventional crop-and-
These provide an increased bearing area on the sea bed to spread the load and prevent the legs from penetrating the soil when located on site. The base of each spudcan is generally constructed using 40mm steel plate. However, even with this heavy design the risk of damage from boulders was considered to be unacceptably high. The SPS Overlay solution uses a new high-strength steel top plate 40mm thick, combined with a polyurethane core of 40mm.
A significant risk to safe and reliable operation is the presence of large granite boulders deposited on the sea bed after the last ice age. According to geotechnical experts, boulders more than 1m in diameter can cause concentrated loads greater than 390t on the base of the spudcan.
Without appropriate reinforcement these concentrated loads can cause major indentations and serious damage to the internal structure of the spudcans.
MPI RESOLUTION
The jack-up wind turbine installation and maintenance vessel MPI Resolution has therefore recently gone through this re-inforcement process by Intelligent Engineering’s Sandwich Plate System (SPS).
THE IMPORTANT ADVANTAGES CAN BE SUMMARISED IN DELIVERING… • Increased structural protection from highly concentrated loads caused by contact with large rocks on the sea bed
• Reduced operational risk and extended ship service capability
BACKGROUND
To reduce operational risk it is routine practice to survey site locations and clear any over-sized boulders before the vessel 'spuds in'. This minimises the risk of damage, but is an expensive and time consuming process. However by strengthening the underside of the spudcan
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replace with thicker steel was not an option. Only SPS Overlay could fulfil the strength requirements and be fitted within the docking schedule of less than four weeks. After completion of the steelwork by the shipyard, the SPS injection process took only four days for all six legs.
DETAILS
Built in 2003, MPI Resolution is 130.5m long, 38m wide, 14310 gross tonnes and a deadweight of 7000 tonnes. Six legs are used to jack the ship’s hull clear of the water when on station, providing a stable platform for wind turbine maintenance and installation. Each leg has a wide hollow tank at the base called a 'spudcan'.
On site the SPS installation was witnessed by the local DNV-GL survey team, who verified that the installation process was carried out in accordance with DNV’s guidelines for SPS construction.
Intelligent Engineering’s Sandwich Plate System
This results in an extremely strong composite sandwich panel structure with a total thickness of 120mm, capable of resisting concentrated loads from boulders up to 1m in diameter.
VERIFICATION AND TESTING The enhanced strength of the SPS reinforcement was demonstrated by IE using full non-linear Finite Element Analysis to replicate the maximum loads and their effect on the structure. The design calculations were examined and verified by DNVGL using their recently published classification note 30.11.
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