Mammoet has completed the installation of two electrically driven leg cranes on two offshore wind farm installation vessels, the Wind Osprey and Wind Orca.
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Contracted by GustoMSC to carry out the leg replacements, Mammoet erected its 5000-tonne capacity PTC210-DS ring crane to help install the 1600-tonne capacity leg cranes that can install wind turbines with capacity ratings exceeding 14mW. According to Dirk Knoester, Senior Adviser at Mammoet, the PTC210-DS was the “perfect crane” for the job that was undertaken at Mammoet’s yard in Schiedam, allowing the global heavy lifting company to work on both projects simultaneously.
“PTC cranes can also be assembled in numerous configurations and thus a tailor-made configuration is feasible for any job: different main boom and jib lengths, fixed or luffing jib, different amounts of counterweight and two ring diameters,” he said. “These attributes made it an ideal crane for this project, where jack-up vessels were to be positioned on either side of Mammoet’s quay – which has a peninsula configuration. So, flexibility was needed to allow two vessels to be worked on together.”
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The new leg cranes comprised four main sections to be installed: the pedestal, the rotating platform, the A-Frame and the 149m boom.
To enhance stability and control during the boom lifts, an LR1800-1.0 crawler crane was used as an assist crane. Working together, the PTC210-DS lifted one end of the boom as the crawler crane lifted the other.
Performing this operation on a busy quay was a challenge that required effective space management. Mammoet’s Schiedam location serves many active projects in Belgium and the Netherlands on a daily basis. The site had to serve as a temporary laydown area for all components being added to the Wind Orca and Wind Osprey, including the large booms.
Further complicating matters was the lifting height that proved another test for the engineers. At different stages of the operation, the vessels had to be raised to a height of 73m above the quay using their jacking legs.
Jacking up the vessels to this height was necessary to keep the rigging short, since the new cranes are of the leg encircling type. This meant that the base of these cranes had to be lifted over the leg. Jacking up the vessels lessened the risk of collisions between the jack-up leg and sections of the PTC210-DS crane during lifts.
Complete maintenance works on the offshore wind farm installation vessels is set to continue this year, with Mammoet anticipating completion later in 2024.
