The first tunnel thrusters from Finnish propulsion specialist Steerprop will enter service in the coming months, with a strong early orderbook highlighting the market need for more reliable and precise thrusters. The new range challenges the conventional approach to developing tunnel thrusters, delivering project-optimized solutions with competitive initial and lifecycle costs.
Two early tunnel thruster projects, for Finnish Border Guard patrol vessels and on what will become the world’s largest cable laying vessel, fall within Steerprop’s established customer base of high-demand applications for challenging operations. And orders for more than 50 TT thrusters to date indicate that Steerprop’s flexible, purpose-specific designs not only meet operator expectations—for safety, reliability and performance—but also satisfy shipyard requirements on initial cost and delivery.
Steerprop Director, Sales & Project Development, Juha Rekola said: “Tunnel thrusters are a standard feature that is thus often applied without the attention given to other propulsion elements. The result can be power either above or below requirements, and a lifetime of frustrating maintenance demands. Steerprop does things differently. By optimizing for the hull form and the application, our tunnel thrusters meet specifications and minimize lifecycle cost—at the same time dispelling the myth that purpose-designed solutions cannot compete on initial cost or meet short project timeframes.”
Steerprop’s design approach results in tunnel thrusters that perfectly align with the specific requirements of each vessel. The holistic optimization process covers every detail, including computer analysis of the vessel’s hull and tunnel parameters, with customization of every element—from propeller to motor—available to develop the ideal solution. These design capabilities are increasingly important as operators aim to improve comfort by reducing vibrations and minimize impact on marine life by reducing underwater radiated noise.
Design flexibility is built into Steerprop’s development approach. As an example, the company does not offer a standard size range of propellers. Instead, each propeller is dimensioned precisely for purpose. Similar adaptability can be implemented where needed across the propulsion design. This includes the drive configuration and permanent magnet motor or induction motor—as well as adjustments to the mounting and gearbox to improve durability and fit space constraints. This responsiveness and the inherent efficiency of Steerprop’s thrusters translate to low lifecycle costs while retaining competitive capital outlay.
The entire tunnel thruster line features fixed pitch propellers (FPP). Compared to controllable pitch propellers, these deliver up to 20% more thrust, allowing for installed power to be reduced and a smaller tunnel aperture to be used, because FP propellers only use energy to generate thrust, instead of spinning at full speed in standby, they also reduce operational costs. This also helps to reduce noise and vibrations.
In line with Steerprop’s Arctic heritage, all units can be delivered also to highest ice class. Uniquely, Steerprop’s tunnel thrusters do not require ice grids to meet ice class, eliminating the effects of ice clogging and reducing maintenance by simplifying access to the propeller.
The most recent tunnel thruster design, the 2,100kW SP 40 TT, is suitable for deployment on heavy-duty offshore vessels. Larger units for cruise vessels and smaller units for ferries and workboats are also available, with the full range covering 500 to 7,000kW. A model of the new SP 40 TT will be on display at Nor-Shipping in Oslo, 2–6 June.
