New generation of stabilisers optimised for ice operations
The benefits of Rolls-Royce’s Stabilisation-at-Rest (SAR) concept will be brought to ice-class ships in its Aquarius and Neptune stabilisation systems.
Using active fin-control technology and advanced hydrodynamic design, the SAR system delivers high levels of roll reduction when vessels are at rest and can also maintain stabilisation performance when vessels are under way.
The new design is especially suitable for ice-class vessels as it allows stabiliser fins to be fully retracted into a custom-designed fin box, meaning there are no protrusions from the hullform and therefore safe ice navigation can be undertaken. It also features reduced fin area and lower fin angle to meet stabilisation performance requirements. Dynamic drag is reduced when fins are deployed under way, resulting in lower fuel costs. The stabiliser fin also incorporates Rolls-Royce’s trailing edge design, which eliminates vibration and noise.
Rolls-Royce Motion Control Dunfermline’s managing director Martin Cunningham said: “The one-piece fin construction offers simple maintenance, reducing through-life cost. The fin shape is designed to improve zero speed performance, as more chord is behind the fin centreline. This is achieved because the ice-class SAR system is based on the well-established Rolls-Royce Aquarius and Neptune retractable stabilisers. Both initial and operational costs are minimised due to the units being easily installed, the fin box custom-designed to exactly match the ship’s hull profile, small hull openings and a simple, reliable design.”
As vessels fitted with ice-class SAR stabilisers are likely to operate in environmentally-sensitive areas, this has also been incorporated into the design. A special quad-seal arrangement minimises the risk of leakage, and the machinery is compatible with many environmentally acceptable lubricants (EALs).
Mr Cunningham said: “The sealing arrangement and compatibility with EALs mean the ice class SAR systems meet the requirements for VGP Permit vessels, while the low drag results in less fuel being burned, which also benefits the environment.”
The latest developments in ice operations from RS
The Russian Maritime Register of Shipping (RS) has several developments aimed at promoting safe operations in ice conditions
In view of demand for transit through the Northern Sea Route by larger-tonnage ships, optimising the structural configuration of a vessel’s hull is a key issue to ensure efficiency while moving both in open water and in ice.
One solution to enable a ship to effectively operate in heavy ice is the stern-first motion concept. This means the bow and stern ends of the ship are designed for different operational modes. The ship's bow is optimised for obtaining high performance characteristics on clear water, while stern end shape ensures movement in ice.
Upon completion of research and development, the ice-strengthening structure of a vessel’s hull is addressed toward stern-first operations. Based on the design scenarios of ice-hull interaction, ice loads are calculated through prescriptive formulations towards the local scantlings determined under RS class notation specific to stern-first mode. For hull-load estimating, the availability of one, two or three steerable thrusters will be taken into consideration.
RS is also about to deliver requirements for corrosion and wear allowance in terms of the gross thickness of outer-shell plating, dependent on the type and properties of protective coatings, as well as requirements for outer-shell coatings in terms of ice strengthening (coating technology, evaluation of technical condition in service, repair, etc). Such an approach to determining wear and abrasion margins will allow optimisation of steel weight without compromising structural safety.
Also, the requirements and distinguishing marks in class notation for ships equipped with automated hull monitoring systems and actual stability systems are being prepared for implementation in RS’s rules. The application of such systems is essential for increasing the operating safety of ships because it enables ship operators to evaluate strength and stability parameters in motion on a real-time basis during the voyage and, depending on weather conditions, make a decision on changing the ship’s operating mode.