New T-BOSS shaft solution unveiled by Thordon Bearings for stern-tubeless vessels

Thordon Bearings has achieved a breakthrough in the evolution of a ship’s propeller shaft line with its new Thordon-Blue Ocean Stern Space (T-BOSS) designed to meet the stern-tubeless ship design proposed by the Blue Ocean Alliance.

The Blue Ocean Alliance is a consortium of industry partners that includes Thordon Bearings, the Green Marine partners Wärtsilä and the American Bureau of Shipping (ABS), as well as SDARI and the National Technical University of Athens (NTUA) to develop and promote the stern-tubeless ship concept.

Introduced at the SMM trade fair in Hamburg, the new T-BOSS will replace traditional stern-tube systems with a dry chamber that will allow for the full range of inspection and maintenance activities for a seawater-lubricated single bearing and seal arrangement. These activities can be done while the vessel remains afloat, thereby avoiding the need for shaft withdrawal or drydocking.

By creating an opening in the engine room bulkhead, adjusting stiffeners, shortening the intermedial shaft (allowing the main engine to be moved further aft), along with eliminating the stern tube, forward stern-tube bearing and aft seal and installing the T-BOSS solution, shipbuilders can take advantage of reductions in material and labour costs, while ship operators benefit from significant OPEX savings.

“Yards have been quick to see the commercial, operational and environmental advantages of a stern-tubeless ship, compared to a design with a traditional oil-lubricated shaft line,” says Craig Carter, Thordon Bearings Inc.’s VP - Business Development  “We have been asked to submit quotes for a number of newbuilds and anticipate orders soon.”

Aside from immediate savings in lubricating oil and elimination of the aft seal, ship owners opting for a T-BOSS stern-tubeless vessel could save more than US$1 million in through-life operational costs, according to Carter. The savings are based on reduced fuel consumption, drydocking and maintenance costs, along with associated loss of earnings; shaft alignment optimization, lower bearing wear rates, and better EEDI; and a potential increase in cargo-carrying capacity. The arrangement also eliminates the risk of environmental fines related to stern-tube oil pollution.

The T-BOSS features Thordon’s COMPAC polymer bearing with tapered key set (right), Thordon Bearing Condition Monitoring system, a Wärtsilä Enviroguard shaft seal, and Thordon’s Water Quality Package.