Successful test of simultaneous four-crane lifting method
An innovative method known as 'QUAD' lifting has been successfully trialled by Heerema Marine Contractors (HMC) in the Gulf of Mexico.
The trial, which took place on 22 October, involved semi-submersible crane vessels Thialf and Balder operating in dynamic positioning mode, using four cranes in parallel.
DNV GL has certified the technology that enables the QUAD lifting process, which will allow engineers greater design freedom in terms of layout in relation to weight and dimensions of topsides and jacket structures, according to HMC. The company also said the method will make it possible for the entirety of a topside structure to be built onshore as a total package during commissioning.
Commenting on the project, HMC chief executive Koos-Jan van Brouwershaven said: “With our QUAD lifting method, we enter a new era with more flexibility and efficiency throughout the entire process - from engineering, procurement and construction up to and including the commissioning and installation of the jacket and/or the topside - with lower project costs as a result.”
Using the technology, HMC plans to offer even greater lifting capacity: “As soon as Sleipnir, the largest semi-submersible crane vessel ever built, is in full operation, we are ready to perform the ultimate QUAD lift, using our two giants with a combined lifting capacity of Thialf’s 14,000 tonnes and Sleipnir’s 20,000 tonnes," said Mr Van Brouwershaven.
OHT orders semisub heavy lifter from CMHI
OHT’s semi-submersible heavy-lift vessel will be equipped with a Liebherr HLC 150000 crane
Norwegian company Offshore Heavy Transport (OHT) has ordered a semi-submersible heavy-lift vessel from China Merchants Heavy Industry (CMHI).
The vessel is a customised Ulstein Alfa Lift design, which has been developed by Ulstein Design & Solutions along with owner OHT. The contract includes options for a further three vessels.
As well as installing bottom-fixed offshore wind foundations for the renewable energy market, the vessel will also be able to transport and install topsides, subsea modules and other cargoes within the oil and gas sector.
Currently under construction, the vessel is scheduled to enter service in 2021. It is anticipated it will be able to transport and install up to 10 1,500 tonne ultra-large jacket foundations or 11 2,000 tonne XXL monopiles and transition pieces.
Ulstein Design & Solutions BV managing director Edwin van Leeuwen said: “We started the development of the Ulstein Alfa Lift idea back in 2015 with the driver to increase the safety of submerged operations and at the same time increase the operability window for subsea installations using a crane.
“Creating a new design with this combination of functionalities has its own, specific challenges. But then again, challenges are what we are good at.”
OHT’s chief executive Torgeir E Ramstad said: “When we approached Ulstein with our intended strategy to enter the offshore renewables market and the idea of adding crane capacity to a semi-submersible heavy lift transport vessel, Ulstein presented their Alfa Lift solution on the spot.
“That was a direct ‘hit’, as it allows us to enter the installation market, at the same time expanding on our capabilities in OHT’s core market.”
The finished vessel will have a length of 216.3 m, a beam of 56 m and a summer draft of 9.4 m. When submerged there is a maximum depth above deck of 15 m.
Free deck length is 148 m, with a total area of 7,840 m2 plus 3,470 m2 on the forecastle, with a maximum deck load of 30 tonnes per m2 on the main deck and 7.5 m2 on the forecastle.
Propulsion will come in the form of three 5,500 kW thrusters along with 3,000 kW retractable thrusters and three 3,000 kW forward thrusters, giving the vessel a service speed of 13 knots.
Kongsberg secured a contract worth US$13M to provide DP2 dynamic positioning, navigation, thruster control and automation systems for the vessel, along with an electrical package including hybrid battery power and energy-management systems.
Liebherr is providing an HLC 150000 crane with a lifting capacity of 3,000 tonnes and a lattice boom more than 70 m long for the vessel. In addition to its main single-hook operational mode, the crane will also be able to operate with dual hooks, each with a 1,500-tonne capacity.
With accommodation capacity for 100 people, the vessel will be Norwegian-flagged and DNV GL will be the class society.
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