Introducing ‘the most significant ship design intervention in more than a century’

Beyond the environmental advantages, the sterntubeless design also presents compelling economic benefits. Through modifications to the vessel’s aft end, including the creation of a bulkhead opening, adjustments to structural stiffeners, and a shortening of the intermediate shaft, shipbuilders can realise "reductions in weight, material and labour costs”, according to Mr Hamilton.

Mr Carter indicates while the initial capital expenditure is "about the same as an oil-lubricated system, the opex is really, really lower”. Thordon projects potential savings exceeding US$1M over a vessel’s operational lifespan, factoring in reduced fuel consumption, lower drydocking and maintenance expenditures, optimised shaft alignment and potential for increased cargo capacity.

A key operational advantage arises from the ready accessibility of the bearing and seal within the dry chamber. This facilitates routine inspections and maintenance, including bearing replacement if needed, without necessitating the vessel’s removal from service in a drydock.

Dr Leontopoulos contrasted this with traditional vessels where accessing tail shaft bearings requires a complex and potentially hazardous process of dismantling the shaft line. The sterntubeless arrangement comprehensively "addresses all these issues”, encompassing both the risk of pollution and accessibility for inspection and maintenance.

While the sterntubeless concept presents a promising trajectory for the industry, certain challenges persist. Dr Leontopoulos acknowledged for very small vessels, the stern inspection chamber might be too restricted for practical human access, limiting the benefits of onboard maintenance.

Mr Carter highlights the crucial need to "educate shipyards and naval architects around the world" about this fundamental change to the vessel’s aft end. He notes a prevailing lack of familiarity with water-lubricated shaft lines in many yards, with the open nature of the seawater-lubricated system being "very foreign to many newbuilding shipyards around the world”.

Despite these initial hurdles, industry engagement has been encouraging. Mr Carter revealed Thordon has already submitted quotation requests for T-BOSS to major shipbuilders in China and South Korea for container ships and gas carriers. He reported "very, very high" interest from shipowners and shipyards globally, including in Europe, the USA and Canada.

Speaking on the sidelines of the SeaAsia exhibition in Singapore, Thordon Bearings regional manager for the Asia Pacific, Sam Williams, said Chinese and South Korean yards’ receptiveness to the design’s potential derived in large measure from the streamlined construction processes and the significant long-term operational advantages it offers to their clients.

Mr Williams emphasised the reduced reliance on consumables like lubricating oil and the elimination of costly emergency seal repairs are key selling points in Asia. He also pointed out the potential for engineroom reconfiguration due to the shorter shaft line, which can lead to enhanced cargo capacity, particularly for owners in the bulk carrier and tanker segments.

While no vessels currently feature this sterntubeless design, Mr Carter expressed optimism about the prospect of imminent orders, noting overwhelmingly positive feedback from shipowners who consider the concept a "no-brainer”. Echoing this view, Dr Chen Kang of SDARI reports "considerable market interest" since ABS granted approval in principle in 2022 and attributes this to the systems environmental credentials.

The sterntubeless design directly addresses increasingly stringent environmental regulations, particularly within United States waters, where the Vessel General Permit encourages or mandates the elimination of the oil-to-sea interface.

While the adoption of water lubrication is not currently factored into Energy Efficiency Design Index (EEDI), Energy Efficiency Existing Ship Index (EEXI), or Carbon Intensity Indicator (CII) calculations, it directly mitigates the risk of oil pollution, which carries substantial penalties.

Thordon’s Mr Hamilton summarises the overall advantages succinctly, calling the sterntubeless ship design featuring water-lubricated bearings "the most significant ship design intervention in more than a century”.

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