At this year’s OTC, Huisman introduces a new patented crane type: the “Rope Luffing Knuckle Boom Crane”. The crane is suitable for subsea installation in deep water and offshore construction in severe weather conditions.
The new crane combines the benefits of a normal Rope Luffing Crane and a traditional Knuckle Boom Crane. As such, it offers a high lifting height and a large capacity at outreach. The capacities of the new cranes range from 400 up to 1200 ton and up to 5000 meter water depth.
Crane Characteristics
The overall construction weight of the crane is low. By incorporating a knuckle in the design, it is possible to reduce the pendulum of the hook and, if extended, it can allow for high lifting heights. The crane’s boom can be stored vertically saving deck space.
The main hoisting system comprises a traction and storage winch system and a separate heave compensation system. This means both lifting/lowering and heave compensation can occur simultaneously with no performance interdependency. A failure in the main hoisting system will not affect the heave compensator or the other way around.
Electrically Driven
Because the crane is fully electrically driven, the power consumption, noise levels, and the number of components are reduced. This makes it more reliable than hydraulically driven cranes and maintenance and operational costs are reduced.
Heave Compensation
The lifetime of the wire rope is significantly extended by the combined active and passive heave compensation system on the main hoist, since the number of sheave bends is minimised and there is no drum crushing or wire rope cut-ins on the winch.
The passive mode of the heave system includes built-in redundancy, so the passive system is fail-safe. During splash zone lifts, substantial reduction of the dynamic forces on the crane and the lifted object is achieved by using the passive system as a shock absorber, and can be used to avoid any resonance during subsea lifts.
Real-time active heave compensation can take place at a very low power consumption level. An anti-twist device prevents twisting of the lower block and wire rope during subsea lifts in double fall configuration. In addition, it lowers the point of application of the wire rope, which improves the stability of the vessel and reduces the boom tip motion.
Seven Arctic
The first crane of this type, a 900 ton Rope Luffing Knuckle Boom Crane for Subsea 7’s Seven Arctic, is scheduled for delivery in 2016. A model of this vessel including the crane will be presented at the OTC Huisman booth, no. 2327.
Picture: 900 mt Rope Luffing Knucle Boom Crane.
