Boskalis_Annual Report_2017

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transported the 24,300-ton topside from Ulsan. This operation was carried out with the White Marlin, the newest and second largest vessel in the Dockwise fleet. In addition to transporting the two main platform components to Norway we were also tasked with the installation of the topside on the substructure. Following its arrival in Norway the SPAR was offloaded from the Vanguard and moved into an upright position and submerged at a safe and sheltered position in the fjord by a third party. Here the substructure was waiting for the installation of the topside.” TOPSIDE INSTALLATION Once the White Marlin arrived in Norway, the topside was transferred onto two S-class vessels. After accurately positioning these two smaller transport vessels on either side of the White Marlin, they started de-ballasting whilst the White Marlin ballasted down and maneuvered out from underneath. “The result was a ‘catamaran barge structure’ with the topside linking the two hulls,” explains Polkamp. “Then the catamaran barge confguration had to go to the ‘mating location’ where the topside was installed onto the substructure. At this stage there were four tugs alongside and one deployed for contingency purposes. With this marine spread, we travelled to the mating location in the fjord 16 nautical miles away. The catamaran barge with the topside was safely towed out to the vertical SPAR hull. The float-over process started with the ‘entry operation’, where the topside was positioned above the substructure. We used the tugs and then used the mooring-mating wires to further fne-tune the positioning. Once the topside was in the right position the mating operation commenced: the substructure was de-ballasted and the catamaran barge was ballasted down. In other words, another load transfer, yet this time from the catamaran barge to the substructure.” PREPARATION “Preparing for this fnal operation alone represents more than two years of detailed engineering,” explains Polkamp. “In the last four weeks of the project, we established an offce on-site with more than 50 people based there, including representatives from the owner Statoil and our client HHI. We mobilized the core team on 22 November and successfully completed the dual float-over on 14 December – in just three weeks!” BIGGEST CHALLENGE “Executing this operation in the Norwegian wintertime was for sure the biggest challenge”, said Polkamp. “The project was extremely weather sensitive, with very strict limits on the maximum current and wind speed that could be handled. And at this time of the year, there was a low pressure front coming every few days. We had to have many go/no-go meetings to decide whether it was safe to carry out the operations in the next time window. There are big storms at that time of the year, with gusts of up to 40 knots. In fact, we had to wait four days on one occasion for a suitable weather window. We employed a dedicated meteorologist who was providing a presentation to the team every four hours and outlining whether we could proceed to the next stage.” COMMUNICATION AND TEAMWORK “Communication was absolutely crucial. The team had all worked together in the simulation exercises carried out at Maritime Research Institute Netherlands (MARIN), and this showed as it worked perfectly well. The maneuvering with the tugs, de-ballasting the SPAR substructure and ballasting the two vessels had all been simulated extremely realistically - as it happened in the feld. It was vital to have the same team and great, dedicated operational people. Of course we have the right assets – the White Marlin, the Vanguard, the tugs, but the most important thing is the people; it is all about teamwork!”

Topside float-over installation with the tip of the SPAR hull above the waterline in between the S-class vessels.