Manufacturing of the new drilling vessel, the Aker Spitsbergen was split over two different sites to make the platform in half the time. The deck was built in Aker Kvaerner’s Stord, Norway yard, and the legs were fabricated at Dubai dry dock and shipped to Stord. It was Sarens Transrig’s job to roll out the deck to a dock, jack it up, and float in the platform legs.
The first job was to roll out the deck section from the fabrication shop a few hundred metres to the dock edge, and load it out on to a barge Aker Kvaerner bought specially for the job. The deck measures 70m (230ft) by 90m (300ft) by 10m (33ft) high, and weighs about 10,000t. It took a total of 452 axles of self-propelled modular trailers to move the entire load.
Although this inventory is 10 times many large firms’ total supply of axles, it represented only 75% of Sarens’ entire fleet of 600 axles. Still, for one job in northern Europe to consume all of these axles took a huge effort.
“In today’s market the main challenge was to collect and mobilise all the axles,” says Transrig managing director Helge Kvalvik. “We are a subsidiary of Sarens, and we have close cooperation with the project department at Sarens Belgium.” He says that the company subcontracted some special transport work to other companies to meet committments, reorganised other jobs, and sent trailers from as far as southern Europe to gather the necessary numbers.
The trailers carried the deck on to a barge in a closed dock which, as it was loaded, pumped out ballast water to keep it afloat. A Sarens-owned 10-pump ballast system removed 600 cubic metres of water per hour to support the 12,000t weight of the trailers and the load.
Before the load-out, a goliath portal crane installed four 39m-high Sarens-designed modular lifting towers along one side of the dock (sitting on concrete bases with anchors). Each 12m by 12m tower held with two Hydrospex 450t strand jacks, and each strand jack took 31 strands.
There was not enough room for the second row of towers to be installed during roll-out. Only after the deck was securely on the barge, and the barge was shifted over, could Sarens’ Liebherr LR 1800 crawler crane lift in the four remaining 260t lift towers, complete with strand jacks. All 16 Hydrospex jacks were operated with a central control system. The system had a total lift capacity of 12,400t.
With the towers in place, the barge was moved back in place and the strands were connected. “The most critical thing with the lift was the capacity of the deck itself. We were lifting a pancake, and the tolerance of each jack stroke was tight. There was a lot of pink supporting steel installed.”
Even with this supporting steel, the job cut down on money and time by resting the load on the modular trailers’ tyres, rather than adding another 2,000t of standard steel beam grillage. Kvalvik said that the procedure was perfectly safe, as long as extra safety precautions–such as closing down some axle groups–were carried out. He added that such an arrangement was safe only in the controlled environment of a closed dock.
With favourable weather, the load-out-to-lift job would have taken two days. The job, delayed from the summer until November, actually took seven, because of stormy Norwegian weather. It was a painful wait for Sarens depot managers across Europe desperate for trailers.
The wait was not easy on site, either. It took 14 hours to lift the deck to 30m high. The team had planned for winter conditions at the site, designing the towers and lifted deck to withstand a sustained 26m/s wind (averaged over 10 minutes) at 10m height. Maximum wind speed for the lift was 12m/s, but at certain stable points during the lift, such as full height, speeds could reach the design maximum. As the team waited for the legs to arrive with the deck 30m in the air, winds picked up to 20m/s. Kvalvik said that no-one on the lifting team panicked, but that there was unease. “We were confident of our engineering, but it would have been nicer to have 10m/s winds,” he says.
Once the weather had settled, the team reopened the dock and pushed in the legs and lowered the deck on to it. With the bulk of the heavy lifting complete, the platform will remain in the dock for a few months while Transrig’s LR 1800 installs the drilling derrick, offshore crane and other deck equipment.
Once it is shipped out, Transrig will start to gear up for the second platform, due for roll-out this summer.
