In 2006 A.P. Moller-Maersk (APMM) performed an internal study of different devices and solutions capable of reducing the fuel consumption and the emissions of the fleet of the Group. Initially 31 energy saving alternatives were considered. Subsequently APMM narrowed the investigation to a short list of best promising alternatives. CLT propellers were included in the short list and APMM and SISTEMAR started collaborating on a joint project.
A series of calculations and model tests were carried out on different vessels, ranging from 2.500 TEU to 8.500 TEU container vessels and from 35.000 DWT to 320.000 DWT tankers. M/V Roy Maersk, a 35.000 DWT tanker, delivered in 2005, was selected to be used as test case for a CLT propeller project.
SISTEMAR, part of the CINTRANAVAL GROUP, designed the CLT propeller.
The model test results obtained both at CEHIPAR (Madrid-Spain) and HSVA (Hamburg-Germany) were encouraging so that APMM decided to proceed to full scale.
The CLT propeller was manufactured by WÄRTSILÄ (Drunen-The Netherlands) and it was installed at LISNAVE shipyard (Setubal-Portugal) the beginning of November 2009, during an ordinary dry-dock.
After the installation the vessel was monitored by APMM in order to compare the performance of the vessel with the original conventional propeller and with the CLT propeller and also to check the reliability of the CLT propeller open water test scaling procedure.
In addition, cavitation observation and pressure pulses measurements were performed at full scale by HSVA and compared with the model test results.
The CLT propeller was also inspected from time to time to check its conditions and any eventual sign of cavitation / erosion.
The results of the above can be summarised as follows:
There is a reasonable correlation between model tests and full scale measurements with regard to the open water propeller characteristics, pressure pulses and cavitation pattern.
The performance gain looks promising at the designed speed and draft.
According to the crew the CLT propeller has resulted in a decrease of the vibrations in way of the stern of the vessel.
No traces of cavitation erosion were found on the CLT propeller during the diving inspections.
From the complete project carried out with M/V Roy Maersk it can be concluded that the CLT propeller has shown to be a well functioning technology and a potentially advantages energy saving device.
CLT propellers, thanks to the higher efficiency, help reducing the fuel consumption, the emissions and then both the Energy Efficiency Design Index (EEDI) and the Energy Efficiency Operational Index (EEOI) without requesting any modification to the vessel.
APMM and SISTEMAR are currently involved in the TRIPOD R&D project, together with ABB, VTT, CEHIPAR and CINTRANAVAL-DEFCAR. The aim of the TRIPOD project is to study the installation of CLT propellers and propulsion pods on large container vessels also in Contra Rotating Configuration.
APMM will consider CLT propellers for future projects.