A subsidiary of the Damen Group, Netherlands-based Van der Velden Marine Systems B.V. is continuing to update its rudders and rudder-propeller products to offer further system efficiency gains to operators. Although developing technology of its own, the company is also working closely with other specialist suppliers including the German propeller manufacturer Mecklenburger Metallguss (MMG).
The success of this joint approach is demonstrated by the Van der Velden ESPAC (Energy Saving Package) system, which can be specified to meet individual vessel design requirements. It includes a high-efficiency fixed-pitch MMG propeller combined with an asymmetric leading edge rudder incorporating a propulsion bulb feature and adapted hub cap. The rudder bulb, often referred to as a Costa bulb, saves energy through recovery of losses in the slipstream of the propeller and is integrated into the leading edge of the rudder on the propeller axis. Boss cap fins also contribute to reduction of hub vortex losses and cavitation.
The result is a system that offers both efficient propulsion and improved manoeuvrability, with minimum levels of cavitation and reduced vibration. A further benefit is that large rudder angles can be avoided during long passages, reducing both vessel resistance and stress on components. The system has proved popular with operators and, in February 2015, Van der Velden reported on a recent project. “We are currently building a 97m2 Energy Saving Package system for a series of three 18,000 teu vessels being built for CMA CGM at the CSSC-affiliated Shanghai Waigaoqiao Shipyard (SWS) in China,” says Edwin Van Buren, director R&D at Van der Velden Marine Systems.
The announcement closely coincided with the news released from the shipyard on 10 February, that the first SWS built 18,000 teu container ship, number H6002, had been launched successfully from the company’s No.1 dock.
Van der Velden has been actively developing other steering technologies, including its innovative rudder feedback system. The Barke Optimised Steering System, or BOSS, provides information to the ship’s bridge on forces acting on the rudder, which can then be usedto optimise both vessel navigation and manoeuvring. The stresses on the rudder provide an indication of the forces applied, and hence the resistance being seen by the vessel. By minimising these, fuel consumption can be reduced and both stresses and component wear can be limited.
Values measured by the BOSS system are displayed on a dedicated LCD panel and can also be interfaced with the ship navigation system. As Mr Van Buren again points out: “Less steering correction reduces the overshoots and shortens the distance travelled. This quickly delivers significant fuel savings.”
The technology is already in operation on the CMA CGM-owned container vessels Ural and Volga, which joined the fleet in early 2015. Both vessels have a capacity of 10,622 teu and are 300m in length and 48m in width, designed to comply with the vessel constraints of the Bosphorus Strait. Van der Velden worked with Damen’s own development team to commissioning the system and carry out sea trials.