SCHIEDAM, the Netherlands – Huisman has introduced a range of large offshore cranes, based on the company’s 200- to 400-metric ton (220- to 441-ton) offshore mast crane design.
The new series, suited to ultra-deepwater and harsh environment operations, include a 300- to 600-metric ton (330- to 661-tons) active heave compensation (AHC) subsea crane and a 450- to 900-metric ton (496- to 992-ton) AHC subsea crane. Huisman has received two orders from yards in Norway and South Korea.
Main hoist of the new cranes will be outfitted with either a 300-metric ton or 450-metric ton traction winch. A storage winch in the hold of the vessel will maintain the center of gravity as low as possible.
The storage winch can contain 200, 400, or 600 metric tons of wire rope, reeved into two falls to achieve the maximum capacity. Huisman sales manager Gerben Roks said the company decided against single fall following research and operational feedback from clients.
“Besides the obvious handling problems with very large diameter wire ropes, the short life span results in tremendous operational expenditures for the operator,” he added. For this reason, Huisman has developed an anti-twist device to mitigate the risk of twisting of the lower block and wire rope (“cabling”) during subsea lifts in double-fall configuration.
Heave compensation on the main hoist is achieved using a combined active and passive system. The passive part widens the weather window for lifting operations as it reduces the dynamic loading on the crane during splash zone lifts up to 50%.
The active part is designed to maintain effective active heave compensation performance at a low power consumption. Wear and tear on the wire rope is lower than with traditional AHC systems, Huisman claims, as there is no drum crushing or wire rope cut-ins on the winch and the number of sheaves is minimized. All sheaves have a diameter ratio of 25 compared to the wire rope.
VARD shipyard in Norway, owned by Fincantieri, has ordered a 900-metric ton AHC subsea crane for a 161-m (528-ft) long subsea construction vessel for DOF Subsea.
Hyundai Heavy Industries will install a 600-metric ton AHC subsea crane on a new 160-m (525-ft) DP-3 heavy construction and flexible pipelay vessel for Subsea 7.