Helping the offshore wind industry prepare for a new generation of wind turbines
Business development manager
Damen Shiprepair & Conversion
It’s no secret that the next generation of offshore wind turbines are going to be very large indeed. 6 megawatt is average these days for new installations, but turbines that are 200 metres or more in height with 10-12 megawatt generating capacity are just around the corner. For the operators of wind turbine installation vessels, with many of whom Damen Shiprepair & Conversion (DSC) works closely, this has created the need to upgrade all but the latest jack-ups in their fleets so they can handle the heights and weights involved. DSC has both the skills and the yards in the right locations to undertake these upgrades, and over the past year has undertaken a number of projects designed to deliver precisely these capabilities. Typically, the contracts involve crane extensions for extra height, however another project type that is becoming more common is that of fitting or replacing spudcans on the bottom of jack-ups’ columnar legs. This is typically done to increase the load-bearing area when the vessel is jacked up and so reduce the penetration into the seabed.
When jack-up specialist Seafox won a contract with GeoSea to install 66 sixmegawatt wind turbines at the Merkur wind farm off the coast of Germany, it appointed Damen Verolme Rotterdam (DVR) to manage the lengthening of the main boom of a 1,200 tonne Liebherr BOS 45000-1200 crane on board its Seafox 5. This was to allow it to reach heights of 200-metres plus. Modifying the crane required four months in the yard, but while she was there a series of other works were undertaken to take advantage of the stopover. Seafox 5 rig manager Alex Eijgenraam commented: “All the scheduled works were completed on time and without incident.”
Seafox 5 left the yard as good as new and ready for her next assignment for the offshore wind industry.
A few months later, the 132-metre jack-up owned and operated by Fred. Olsen Windcarrier came to Damen Shiprepair Amsterdam (DSAm) for the insertion of a 20-metre section into the main boom of its 800-tonne crane to increase its reach to 120 metres. Over the course of 30 days all the crane wires were unreeved so that the crane boom could be dropped down to rest on a support structure built from containers. The boom was then cut in two and the new section inserted and secured using flanges. Following the completion of the new boom, the wires were re-reeved and a series of load tests conducted before the crane was certified ready for operations. This was an exceptionally fast turnaround time for a project of this type. Ove Rylandsholm from Fred. Olsen Windcarrier, commented:
We were very impressed with the service and support provided by managers and staff at Damen Shiprepair Amsterdam.
Fitting and replacing spudcans
In one recent example of this type of refit, the 132-metre jack-up vessel Sea Installer operated by A2SEA came to Damen Shiprepair Dunkerque (DSDu) for four new spudcans. These massive pieces of steelwork are fitted at the end of the legs to distribute the mass of the rig across the seabed, thereby reducing penetration. Those for the Sea Installer weighed 160 tonnes each and required self-propelled modular transporters to move them into position and a 700-tonne crawler crane to lift them. While Sea Installer was in the drydock at DSDu, the client also took the opportunity to prepare her for the next contract.
This required a substantial amount of steel work related to the installation and securing of equipment on deck including stairs, grillages and containers. The entire project was completed in just eight days thanks to careful planning, and the Sea Installer left on time to install 42 Siemens 7 megawatt wind turbines at the Rentel offshore wind farm off the coast of Ostend, Belgium.
Torben Breyen, Vessel Superintendent at A2SEA, commented, “Prior to the docking we had several planning meetings as, with the installation of the shoes, modification of the jetting system, maintenance of two bow thrusters and painting of the topsides, the entire operation could have ended up a logistical nightmare given the short time available.”
However due to the good planning all the jobs were executed on time and with a satisfactory result.
Damen Verolme Rotterdam (DVR) completed a similar refit project on the 120-metre MPI Enterprise, owned and operated by MPI Offshore, itself now part of the Van Oord Group. This was more complex, with sixteen tensioning bolts required per spudcan and an unusual mechanical linkage solution that was implemented using shim plates to divert radial and torsional movement from the tensioning bolts. Other works included architectural work in the lower quarters and cylinder foundations were also fitted for the leg lashing system. The MPI Enterprise departed DVR in early April to work on offshore wind farms in the North and Baltic seas.