Mammoet cuts Scarborough topsides load out time with integrated jacking system

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Mammoet has completed the weighing, jacking and load out of the 33,000 tonne floating production unit topsides for Woodside Energy’s Scarborough Project at Qingdao McDermott Wuchuan’s fabrication yard in China, using an integrated Mega Jack lifting and weighing configuration designed years before fabrication began.

The operation involved two major structures comprising the topsides and the deck support frame for the offshore development. According to the company, early involvement during the engineering phase allowed fabrication and heavy transport activities to be aligned long before steel construction started.

The project traces back eight years, when Mammoet joined discussions with the design team to evaluate alternative build methods for the Scarborough topsides. Rather than fabricating the structure directly on top of its support frame, engineers proposed a lower height construction strategy combined with an integrated weighing and jacking solution.

That decision changed the sequence of the entire project.

By allowing the topsides to be fabricated closer to ground level, the yard reduced the need for elevated working areas and heavy crane lifts at height. For offshore fabrication teams, it is similar to moving work from the upper floors of a building site back to street level. Access becomes easier, lifting operations become less complex, and construction can continue in parallel.

The system also enabled work on the topsides before the deck support frame had been completed.

The operation marked the first deployment of Mammoet’s Mega Jack 10000 system, designed for lower starting heights and higher lifting capacities.

The topsides were supported by four Mega Jack towers positioned beneath the structure’s strongest load points. Multiple jacking bases were connected in a modular arrangement, spreading the load across the system and increasing total lifting capacity without expanding the operational footprint.

A total of 80 load cells, each with a 750 tonne measurement capacity, were integrated directly into the jacking system. This allowed the topsides to be weighed and lifted simultaneously.

Richard Verhoeff, Sales Director at Mammoet, said combining both operations reduced the transition time between project phases.

“The alternative method would have been to use load cells, with hydraulic cylinders incorporated underneath, positioned at different locations around the topsides,” he said.

“We explained that we could perform the weighing of the topsides with the same system we use for the jacking.”

Mammoet engineers also designed a specialist load spreading starter beam that was fabricated directly into the underside of the topsides during construction.

The beam served multiple purposes. During fabrication it acted as structural support for construction teams. During load out it allowed the topsides to stand directly on four lifting points without requiring additional load spreading structures.

Once the final weight verification was completed, the topsides were jacked to a height of 16 metres, allowing the deck support frame to be positioned underneath and connected.

The combined structure was then transferred onto an installation barge using eight SJ850 strand jacks and a skidway system. Mammoet also managed barge ballasting during the operation to maintain vessel stability as the load shifted across the deck.

According to the company, using the integrated lifting arrangement reduced the amount of steel required, minimized ground reinforcement work and lowered the volume of equipment mobilized to the yard.