All New Ships Should Be Built To A Seawater-Lubricated Sterntubeless Ship Design 


Future newbuild ships of all types should be built without a sterntube and with a seawater-lubricated propeller shaft bearing arrangement, according to Blue Ocean Alliance’s Chris Leontopoulos.

Speaking at a recent maritime industry forum in Hamburg, Mr. Leontopoulos said the sterntubeless ship design – jointly developed by Blue Ocean Alliance members ABS, Thordon Bearings, Shanghai Merchant Ship Design and Research Institute (SDARI), Wärtsilä, and the National Technical University of Athens (NTUA) – is so commercially, operationally and environmentally attractive that “I personally hope that in the future all ships are built like this”.

Principal component

Mr. Leontopoulos went on to say that the use of a seawater-lubricated bearing with a tapered key design – the principal component that makes the sterntubeless ship possible – also removes the need for an aft seal and a shaft coating system. The sterntubeless design features a seawater-lubricated bearing, a Wärtsilä forward shaft seal, a Water Quality Package and a bulkhead seal.

The technical differences were immediately obvious when a graphic was shown comparing a ship with and without a sterntube.

The sterntubeless ship, he said, also negates the need to realign the shaft throughout the vessel’s lifetime, mitigating the risk of shaft damage or indentation, which can result in substantial downtime and expenditure.

Cost benefits

Going on to reveal the cost benefits of a sterntubeless ship, Mr. Leontopoulos acknowledged that although the estimated CAPEX for additional components could add about US$10,000 to $30,000 to the cost of a newbuild depending on shaft diameter, the ROI is quick given the reduced operational expenditure. This is where the real financial gain is to be made.

He told conference delegates that aside from immediate savings of US$350,000 in lubricating oil, operators could save more than US$1 million in through-life operational costs.

On that latter point, ABS has now published a Requirements for Sterntubeless Vessels with Water-Lubricated Bearings guide, bringing together in one document all existing applicable rules for the design. ABS is also introducing a new notation for the sterntubeless ship design, for which the classification society awarded an AiP in June 2022.

Chris Leontopoulos believes the first sterntubeless ship with a Thordon seawater-lubricated propeller shaft bearing system, probably based on a SDARI design, will be ordered within the next twelve months.

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Source: Thordonbearings