T-BOSS (Thordon - Blue Ocean Stern Space)
with Thordon COMPAC Seawater-Lubricated Propeller Shaft Bearings

Ship designer SDARI, in partnership with Thordon and the National Technical University of Athens (NTUA), was granted an Approval in Principle (AIP) from ABS in June, 2022 for the concept design of the sterntube-less vessel with Thordon’s COMPAC Split Water-Lubricated Aft Bearing.

Thordon is calling the concept T-BOSS (Thordon-Blue Ocean Stern Space), a revolutionary sterntube-less propeller shaft system design, in which the vessel’s sterntube cooling tank is replaced with a dry irregularly shaped chamber, thus allowing for inspection and maintenance of a seawater-lubricated single bearing and seal from inside the ship, while afloat, without any need to withdraw the shaft.

The concept of a ship design that does not require a sterntube and eliminates the need for oil-lubricated sterntube seals and bearings is revolutionary. The design is also likely to save ship owners hundreds of thousands of dollars in capital and operational expenditure over a vessel’s lifespan, including zero requirement for lubricating oil or biodegradable lubricants.  ABS has estimated that in a sterntube-less ship design, a two-week dry-dock re-alignment or bearing and seal replacement job, can instead be completed in a single day while the vessel is afloat. ABS is further developing a pertinent Guide and Notation for such a ship.

The T-BOSS utilizes Thordon’s award-winning seawater-lubricated COMPAC propeller shaft bearing system and the Wärtsilä Enviroguard Seal, which requires no maintenance between planned overhauls of up to five years. As well as eliminating the need to withdraw the propeller shaft for the lifetime of the ship, the COMPAC bearing comes with a lifetime bearing wearlife guarantee.

Key Ship Owner Benefits

Lower Shaft Line Operating Expenses vs Oil Lubrication

  • No oil/EALs; no risky aft oil seal to maintain
  • Seawater is FREE
  • Lower friction with COMPAC polymer bearing in seawater = fuel savings compared to sealed oil/metal bearing shaftline

Zero Pollution

  • Open seawater-lubricated propeller shaft bearing system = regulatory compliance worldwide

No Propeller Shaft Withdrawals For Maintenance

  • Maintain and inspect bearings, liners and seals without drydocking the vessel

Improved EEDI

  • Reduced fuel consumption and Main Engine emissions

Download the Brochure

The Sterntube-less Ship System


COMPAC AFT Bearing with Tapered Keyset

Non-metallic homogeneous elastomeric polymer alloy COMPAC bearing is at the heart of the award-winning seawater-lubricated propeller shaft bearing system. The COMPAC bearing has no grooves on the lower half of the bearing to promote the early formation of a hydrodynamic film between the shaft and bearing, comparable to oil. Given the unique elastomeric nature of Thordon COMPAC bearings, this concept is more tolerant to shaft misalignment with go-home capability. Thordon COMPAC bearings do not contain PFAS.

The COMPAC bearing is supplied split with a tapered keyset that allows the bearing to be withdrawn inboard, inspected and re-installed in a matter of hours with the shaft in place.



Thordon BCM System

The Thordon Bearing Condition Monitoring System allows bearing wear measurements to be taken from inside the ship simply by pushing a button, supporting the Classification Societies’ bearing clearance monitoring requirements.


Wärtsilä Enviroguard Seal

Wärtsilä Enviroguard seals are highly engineered seals, designed to support commercial ships. With no maintenance between planned overhauls (up to 5 years), these seals support ship operators in reducing operational expenditure and vessel downtime.


Thordon Water Quality Package

A Thordon Water Quality Package delivers a consistent supply of conditioned water to the seal and bearing to ensure long predictable bearing wear life.

Today, T-BOSS with a Thordon COMPAC propeller shaft bearing system offers considerable advantages to ship owners and shipbuilders, providing easy monitoring and maintenance of bearing and seal condition, without shaft withdrawal, lower operational expenses, de-carbonization of the ship and elimination of oil emissions forever.

Contact Thordon for more information on Thordon products.

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