First Rim-Drive Thruster Achieves Silent-E Notation

Kongsberg Maritime’s rim-drive azimuth thruster has achieved Silent-E notation from DNV, the first of its kind to receive this certification.

Installed on the new commissioning service operation vessel (CSOV) Norwind Hurricane and its sister vessels, the thruster demonstrated exceptional performance in reducing underwater noise pollution during a recent trial.

To assess the noise levels of the Norwind Hurricane, an extensive underwater noise study was conducted using hydrophones placed on the seabed. The results unequivocally confirmed the effectiveness of the rim-drive thruster in reducing underwater noise.

Roy Ove Standal, Chief Operating Officer at Norwind Offshore, said: “The rim-drive propulsion system stands out for its ability to reduce the need for additional support systems, leading to notable energy savings. It also contributes to increased onboard comfort due to its lower noise levels. Achieving the Silent-E notation further demonstrates our commitment to protecting the marine environment.”

Leif Vartdal, hydrodynamics specialist at Kongsberg Maritime, says that rim-drive thrusters are inherently quieter than conventional thrusters due to their simpler design with fewer moving parts and excellent hydrodynamic characteristics. “Hydrodynamically induced noise, primarily caused by tip vortex cavitation from propeller blade tips, is a major challenge in traditional thruster designs. Rim-drive thrusters eliminate this issue by using a ring propeller that lacks blade tips, thereby significantly reducing noise generation.”

The thrusters also offer energy savings and reduced maintenance costs due to the simplified propulsion system with fewer mechanical components. This translates to enhanced operational efficiency and a lower total cost of ownership.