Powerful new Schottel Rudderpropeller can be installed afloat

Test rig for the SRP 800 U underwater gearbox Test rig for the SRP 800 U underwater gearbox Schottel GmbH

JUNE 27, 2017 — Schottel has successfully tested a powerful new thruster. It can be installed afloat, making it ideal for vessels that cannot be docked easily because of their size or area of operation. Available in a power range up to 5.5 MW, the underwater mountable SRP 800 U Rudderpropeller is an ideal choice for cable laying vessels, offshore construction vessels and crane ships.

"As a result of customer requests, Schottel decided to further develop the robust, well-proven rudderpropeller technology in the power range up to 5.5 MW," says Roland Schwandt, Sales Director Tug & Offshore Energy.

Calculations for increasing the power went hand in hand with developments for greater installation flexibility and higher safety factors that exceed classification society requirements.

A full load gear test for checking the gearing of the unit's bevel gear set that has now been successfully carried out in Schottel's German test facilities.

The full load gear test was preceded by model tests at Potsdam Shipbuilding Research Establishment (SVA Potsdam), Germany, and CFD simulations.

Tests were carried out with a rated torque of 80,000 Nm at the power input of the underwater gearbox. This corresponds to continuous heavy-duty operation on the open sea using a propeller with a diameter of 4,100 mm.

Two large hydraulic motors with working pressures of up to 300 bar provided the drive and braking power.

The results of the evaluation show that the position and extent of the contact pattern exactly match the simulation, indicating that, even with the high operating loads and the resulting displacements of the teeth, the torque is always transmitted ideally from tooth to tooth.

With a view to safety, customers benefit both from the rolling-contact bearings and from double-checked seals with a service life that exceeds classification society requirements.

The certified LEACON propeller shaft seal was successfully tested. The endurance test under real operating conditions simulated water pressure and temperature fluctuations, for example. The key design feature of the system is an intermediate chamber between the propeller gearbox and the water. Multiple special seals on the propeller shaft and the connecting shaft separate lubricants from the seawater.

The SRP 800 U has been optimized with a focus on maximum market coverage in terms of fit variability. The design of the interface to the vessel corresponds to that of models commonly available on the market and is thus suited both for new installation and as a replacement unit.

Using a three-way roller bearing as the slewing ring, it was possible to reduce the required installation space and increase the compactness of the drive. Additionally, the number and size of the protective caps was minimized for underwater installation.

In addition to the standard version with a 90° gearbox, Schottel also offers a variant with a propeller shaft inclined by 8 degrees. This reduces detrimental effects on the thrust of adjacent drives and interaction with the hull. In terms of flow characteristics, the azimuthing SRP 800 U thus adapts itself optimally to its area of operation, be it as a main propulsion unit in a drill ship or construction vessel, or as a positioning aid in a semi-submersible rig.

The optimal flow contour was the result of CFD calculations as well as cavitation and maneuvering trials at the SVA Potsdam, Germany.

Freedom from cavitation has been demonstrated at speeds of up to 16 knots.

Following the successful testing, the SRP 800 U is now available for newbuildings or as a replacement unit in a wide range of applications.

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