From its main production plant in Mellansel, Hägglunds Drives has been manufacturing hydraulic motor systems since the 1960s. The company's Viking and Compact motors have been fitted into many thousands of ships and offshore vessels and their high-torque, low speed characteristics are now being supplied to the majority of pod propulsion manufacturers for high efficiency azimuthing electric propulsion drives.
Azimuthing propulsion is ideal for vessels requiring high manueverability, low noise, and vibration characteristics and a flexible machine arrangement. Applications for the offshore industry include semi-submersibles, shuttle tankers, cable and pipe-laying ships, offshore service vessels, icebreakers, as well as a variety of other marine and offshore operations.
One of the most notable recent achievements for podded propulsion has been on the new double-acting (DAS) icebreaking vessels where the ship moves stern first through hard ice conditions taking advantage of the azimuthing abilities of the propulsion units.
The podded propulsion concept takes advantage of the ability to eliminate long shaft lines, reduction gears, CP-propellers, rudders and transversal stern thrusters. The propulsion motors can be mounted outside the ship's hull and the diesel or gas turbine driven alternators can be placed at any location onboard to allow for maximum space optimization. This freedom in locating the machinery components lowers design and construction costs and reduces the number of components and related maintenance.
Accurate slewing
Hagglunds Drives provided motors for Rolls-Royce Mermaid podded propulsion units for Transocean Sedco Forex semi-submersibles.
The use of azimuthing propellers also has resulted in improved steering capabilities and a reduction in fuel consumption. With the drives built into the propeller housing, the propulsion unit can be turned through 360 degrees, thereby completely replacing conventional rudder arrangements.
Hägglunds motors are used for slewing of the pod and, unlike conventional drives, they can be mounted directly on a shaft without the need of a gearbox. In addition to supplying full torque driving and braking in either direction, combined with low inertia, the Hägglunds motors provide direct hydraulic drive to the pinions in a relatively lightweight and compact arrangement.
The 97% mechanical efficiency available also ensures full torque control from zero to full speed, providing a responsive and reliable slewing drive.
Last year, Hägglunds Drives marked the delivery of its 90,000th hydraulic motor to Rolls-Royce in Kristinehamn - a Compact tandem arrangement for use on a Kamewa Alstom Mermaid pod propulsion drive. "There is interest on the customer's part that we offer an overall solution, including hydraulics and piping," explains sales manager Per Erik Byström. "And it looks as if in future the vessels will be bigger and bigger, which means more stringent requirements of our motors' torque."
To achieve this need, Hägglunds have been developing a new version of its Compact motor - called the Compact CB - intended to replace the current Marathon model in the lower torque range of Marathon motors. While it has yet to be released onto the market, Hägglunds is confident that the CB motor will out-perform the Marathon in that it is 30% smaller and lighter.
For more information, contact Arne Åhmann, Hägglunds Drives. Tel: +46 660 87000, Fax: +46 660 87160, E-mail: [email protected]
