Damen Shipyards of the Netherlands, German engine manufacturer MTU Friedrichshafen, a subsidiary of Rolls-Royce Power Systems, and Denmark’s SVITZER have teamed up to bring the first Reverse Stern Drive (RSD) Compressed Natural Gas (CNG) tug to the market, with a planned introduction in 2016. The new RSD CNG tug combines high power with lower fuel costs and a substantial reduction in emissions.
A stern drive unit is a marine propulsion system in which the engine is connected to a drive unit (comprising both transmission and propeller) mounted on the stern of the vessel. When the captain turns the steering wheel, the entire drive turns; i.e., no rudder is needed. By contrast, an inboard system is enclosed within the hull of the boat; the driveshaft runs from the inboard transmission to a propeller outside of the boat, which is steered with a rudder when the steering wheel is turned by the captain.
The new Reverse Stern Drive (RSD) is essentially an azimuth stern drive (ASD) and tractor tug in one—i.e., it is able to sail ahead and astern, with the same bow height forward and aft. Azimuth thrusters have the propeller screws in pods that can be rotated to any horizontal angle (azimuth) on the reference plane; Damen is a world leader in ASDs.
The new 16-cylinder pure gas engine being developed by MTU is based on its proven workboat Series 4000 M63 diesel engine. It will be complemented with a multipoint gas injection system, a dynamic engine control and an optimized safety concept.
We are developing our new gas Series in order to meet the extreme load profile of the tugboat. The acceleration will be comparable to the level of our diesel engines. Due to the clean combustion concept, compliance with IMO Tier 3 emission legislation will be ensured without the need of additional exhaust gas after treatment. The 2,000 kW MTU gas engine is characterized by high power density combined with low fuel consumption—Dr. Ulrich Dohle, CEO of Rolls-Royce Power Systems AG