Crane and offshore equipment builder Huisman has received a letter of intent to deliver a pair of 10,000 tonne capacity cranes. As the world’s largest slewing cranes, they will be mounted on a semi-submersible crane vessel planned for fellow Dutch company Heerema.
Each crane will lift 10,000 tonnes at a radius of 48 metres in offshore conditions, Huisman said. The booms will be 145 m long. The cranes will be tub mounted rather than the usual mast crane design.
Instead of bogies or large wheels for their slew system, the new cranes will use bearings designed and manufactured by Huisman in a 30 m diameter ring. This slew ring design has already been used for the 5,000 tonne capacity offshore mast crane on the Seven Borealis and for the 4,000 tonne one on Heerema’s Aegir.
Benefits of the slew ring design, Huisman said, are more accurate control of the slewing motion, minimal maintenance and a significant weight saving. It is a segmented roller bearing with a 30 year design life. Testing for this has already been done and all components can be inspected or replaced in situ, the manufacturer said.
Another feature will be a 2,500 tonne capacity auxiliary hoist and a whip hoist with a reach of 155 m. In a reduced reeving configuration the main hoist will be able to lift 1,000 tonnes to a water depth of 1,000 m. In total there will be 11 winches, excluding the tugger winches. All will be electrically driven by frequency controlled AC motors. Active heave compensation will also be fitted.
Anne de Groot, Huisman project director, said, “We are extremely proud of this commitment from Heerema. Firstly, the fact that Heerema has shown their confidence in our ability to build the largest cranes ever and secondly that yet another important Huisman innovation will deliver a contribution to the success of our client and the progression of the crane industry.”
Huisman said that the final decision to build this new semi-submersible crane vessel will be made by Heerema before the end of 2014. The cranes will be built at the Huisman factory in China.