The continuing success of the cruise industry is encouraging suppliers to invest further in stabilisers as global demand rises
In response to growing demand from the cruise liner, large ferry and exploration vessel sectors, SKF has significantly upgraded its marine stabiliser production facilities in Hamburg, Germany. The new investments include a 130-tonne capacity heavy-duty overhead crane, two new assembly stations for large stabilisers, and additional production space dedicated to the manufacture of smaller units.
The expanded facilities will allow SKF to increase production of its largest S800 stabiliser system from eight to 16 sets a year. These stabilisers can be up to 12m long and 4m wide, and weigh 120 tonnes. They are used on the world’s largest cruise vessels to improve passenger comfort and safety in rough seas.
SKF’s stabiliser fin products are in service on more than 550 vessels around the world. The company has continually developed its portfolio of stabiliser technologies over that time, maintaining its position at the forefront of performance and efficiency. SKF’s latest innovation, entering production in 2017, is the Dynamic Stabiliser Cover (DSC), a flexible, inflatable Kevlar and neoprene fairing that reduces drag at the fin box opening by up to 90%, allowing vessel operators to achieve overall fuel savings of around 1%.
When a vessel is in motion, the fin box opening in the side of the hull creates turbulence, increasing drag on the vessel. With operating efficiency being a high priority for customers, SKF wanted to find a way to minimise the resistance even more and so decrease fuel consumption.
The solution is a deceptively simple, pneumatically operated design. The DSC uses two specially shaped air cushions, fitted to the top and bottom of the fin box with small steel rails. In normal operation, the cushions are inflated using compressed air from the vessel’s existing pneumatic systems. This process takes just 90 seconds.
Inflated, the cushions form a smooth, streamlined cover over the fin box opening. SKF estimates that annual fuel cost savings could be as high as €50,000 for cruise operators.
When the stabiliser fin is to be extended or retracted, air is released from the cushions by opening the valve. The cushions are then deflated by the water pressure outside the hull, creating room for the fin’s movement. When deployment or housing is complete, the cushions can be re-inflated. Control of the cover is fully integrated into the stabiliser fin control systems, requiring no additional action by the crew.
The DSC is constructed from a highly durable Kevlar mesh coated with neoprene rubber, which provides extra protection from barnacles and other marine life that may accumulate on the fin.
Another company to have invested in this technology is Aegir-Marine, which has added stabiliser and steering gear repair services to its portfolio of maritime services. The expansion of its service portfolio is part of a long-term growth strategy. The Dutch company works with brand-independent parts and provides service and parts for all major propulsion systems.
Of all the stabilisers, 99% are applied in navy and cruise ships and ferries. In cruise ships and ferries, their application prevents passengers from becoming seasick. Navy vessels have to be swift and agile, and rolling adds to the risk of the ship heeling over. Stabilisers are mounted to damp this undesired movement. Aegir-Marine is strongly represented in this part of the maritime industry.
Aegir-Marine Group service director Martin Visser explained: "We are pleased to add these specialised services to our portfolio. The first reactions from the market are encouraging. Customers really like the idea of a total propulsion service package from one source. Aegir-Marine is able to offer stabiliser repair services to new clients, as well as to our existing clients in the cruise, navy and ferry industry. In our contacts we notice that shipowners could do without the hassle of co-ordinating several parties to repair their ships. Shipowners want to focus on their core business transporting cargo, and they need strategic partners to maintain their vessels. In a time of ruthless competition, shipowners are constantly looking for ways to improve this.”
New container ships to feature Hoppe roll-damping
Three recently ordered 2,150 TEU container vessel newbuildings designed by Deltamarin are optimised to operate in the harsh ocean environment of the north Atlantic. The seakeeping performance of these vessels is therefore under a special concern in the design, which is why each of these vessels will be equipped with two Flume roll-damping tanks from Hoppe.
These tanks are designed to fit into the ship structure without any loss of container storage capacity. The tank design will be exactly aligned with the ships' loading scenarios, and the internal structure of the tank will be optimised using the most modern CFD tools. For the final performance evaluation, Hoppe Marine uses a 6 DOF moving platform, capable of simulating any ship motion, and measures the tanks' performance in that particular scenario.
This project is the sixth most modern container ship class equipped with a Flume roll-damping tank from Hoppe Marine. While for this project the intention of the tank installation is mainly crew comfort and safety, Flume roll-damping tanks are an attractive solution to increase the loading flexibility and the overall container storage capacity of ultra large container vessels by up to 10%.
Naiad introduces electric-powered fin stabilisation systems
Naiad Dynamics has introduced a new line of electric-powered stabiliser systems.
“These new stabilisers are a modern refinement of electric-powered stabilisers Naiad first developed for naval applications in 2008,” said Naiad Dynamics chief executive John Venables. “We are now introducing these systems to the recreational and commercial marine markets alongside our complete range of proven hydraulic stabilisers to provide a choice for designers and builders who may prefer not to use hydraulics,” he explained.
The initial model E-525 is available with a 7.5 or 11 kW AC servo motor drive, and is designed for fin sizes ranging from 1m2 to over 3.5 m2 for vessels typically 35m to 50m in length.
Naiad’s electric stabiliser eliminates the entire hydraulic system, reducing the number of installed components and the system’s overall complexity and weight, as well as eliminating installation costs associated with interconnecting fluid lines, all with no sacrifice in power and performance. Naiad’s electric servo motor-actuator design generates the same amount of force as two hydraulic cylinders used in an equivalent hydraulic stabiliser model.
A key safety feature of Naiad’s electric fin stabiliser design is the ability to centre the fins manually and lock in place when the stabiliser is not being operated. Other key features include Naiad’s exclusive Datum closed-loop digital control system with adaptive self-tuning capability operating on a CANbus distributed network.