When Norwegian oil and gas services company Island Offshore needed a very special support ship, capable of meeting wide-ranging offshore roles, it turned to Rolls-Royce to design the vessel, selecting the latest and longest (99.8 metres) UT 776 CD with its proven low motions in a seaway.
Stability is fundamental for Island Crown’s various roles. Positioned alongside rigs and platforms, it serves as a hotel ship for offshore work crews, but the Rolls-Royce design also had to take account of additional offshore roles – including support for subsea construction and ROV operations, and transportation of liquid and bulk supplies required by rigs and platforms.
Ship systems selected for Island Crown are similar to others we have supplied during our long and fruitful relationship with Island Offshore. A propulsion arrangement comprising a four-generator diesel electric system, AzipullTM main thrusters, twin tunnel thrusters and a swing-up azimuth thrusters at the bow provides the high level of redundancy demanded for the DP2 class dynamic positioning system.
Such capabilities are vital for a vessel that spends much of its life alongside offshore platforms in all sea states. Island Crown is designed to meet tough SPS (special purpose ship) rules, including strict limits on stability and other safety factors.
Transferring up to 40 crew members from their accommodation quarters to platforms, which may be of varying construction, is no straightforward task. The ship utilises a telescopic tower and staircase to accommodate height differences, plus a hydraulically-drive gangway positioned between the top of the tower and the docking point on the rig. The gangway is of variable length and is free to pivot, allowing for relative motion.
A helicopter platform, located above the ship’s hotel block, enables transport from ship to shore. For platform service and subsea construction roles, Island Crown is also equipped with a 10-100 tonne capacity long-boom crane, located on the starboard side.