New rear layout design gains ABS AiP


Written by

Nick Blenkey

Illustration of ABS AIP award winning sterntube design.

ABS has granted Approval in Principle (AiP) for a revolutionary vessel design with a new aft layout designed to eliminate pollution and promote efficient vessel operations. It can also better support compliance with EEXI and CII terms.

The design was developed by China Shanghai Merchant Ship Design and Research Institute (SDARI) in cooperation with Thordon Bearings Inc. and National Technical University of Athens (NTUA). It takes a new approach to the vessel’s aft layout that includes eliminating stern tube casting, using seawater for lubrication and creating a chamber to allow for maintenance in the water for the first time.

These innovations allow shipyards and owners to eliminate oil leaks from shaft bearings, simplify maintenance and reduce costs.

The use of sea water for the lubrication of the stern tube bearing eliminates the risk of oil leakage. By allowing shipyard engineers and craftsmen to access the stern tube without the need for dry-docking, the non-hire time incurred for bearing inspection and replacement will be reduced from two weeks to one day. afloat.

Installing a suitable torsional vibration damper can also eliminate the locked speed range, which is present in the vast majority of direct drive diesel powered vessels. The new aft layout can thus better support simplified compliance with environmentally-focused regulations, such as the Energy Efficiency Index for Existing Vessels (EEXI), and can enable more efficient use of the propulsion power of the vessel. motor as the entire RPM speed range is available for continuous use. operation.

It allows owners to easily consider an Engine Power Limiting (EPL) solution if necessary, to comply with Carbon Intensity Indicator (CII) power output requirements.

The resulting design proposal complies with all ABS rules and regulations and the propeller shaft study can be maintained at a maximum interval of 15 years if the ABS TCM-W notation is adopted.

“The concept of using seawater as a lubricant is well established and the proposed design goes further by eliminating the stern tube casting, decreasing the length of the shaft line, reducing the space engine room and increasing cargo space,” said Dr Chris Leontopoulos. , director of the Global Ship Systems Center at ABS Athens. “Eliminating the locked speed range and creating a rear chamber to allow inspection in the water, provides significant efficiencies and savings for operators,”

“Besides the benefits for operators, the new concept also provides more possibilities and flexibility for designers to optimize the layout of the machine room,” said Wang Gangyi, Chief Engineer, SDARI. “Therefore, for shipbuilding, the initial cost including construction materials and labor cost can be reduced accordingly. This will bring a series of benefits to all parties involved in the vessel.

“Our technical discussions led to a revolutionary design of the propeller shaft bearing system that offers easy monitoring and maintenance of bearing and seal condition without shaft removal, reduced operating expenses and eliminating oil emissions forever,” said Anthony Hamilton, Technical Manager, Thordon Bearings, Canada.

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