Analyzing Impact of Becker Twisted Fin on a Container Vessel
In early 2013, global container operator Hamburg Süd, which operates a fleet of more than 105 vessels with a capacity of over 454,000 TEUs, replaced the pre-swirl stators originally installed on its Santa class vessels with the new Becker Marine Systems’ Twisted Fin (BTF), a further development of the Becker Mewis Duct.
Pekka Autere, Lead Analyst at Eniram explains in the following text how the validity of the container vessel Santa Catarina’s new propulsion system has been alayzed with the use the high frequency data collected from the vessel.
“Model tank tests of the BTF had indicated a favourable effect on the fleet, and in the case of Hamburg Süd’s Santa Catarina, since we already had existing data collected from the ship for two years previous, in the flash of a few minutes, we were easily able to select operational data from three months previous to the twisted fin installation as well as three months afterward to carry out our propulsion efficiency analysis.
Eniram’s Dynamic Trimming Assistant (DTA) including the Eniram Vessel Platform (EVP) system for collecting real time data from the vessel had been installed aboard the container vessel Santa Catarina in 2011 to optimize vessel trim.
The EVP system interfaces with a vessel’s data from the bridge and associated automated systems and measures real-time vessel performance and fuel consumption. In this case, it was important to see the results of improved efficiency of the propeller by optimizing distribution of water to the propeller.
Additionally, in order to analyze the vessel’s performance in similar conditions, periods in laden (draft more than 11 meters) and ballast (draft below 10 meters) were chosen for comparison.
The key system that produced results was Eniram’s Propulsion Power Decomposition (PPD) technology. No other major operations were done at the installation of the twisted fin, which meant that the change in performance was undoubtedly attributed to the twisted fin. The PPD model allows us to eliminate the impact of variable environmental conditions such as wind, sea state, trim and squat (called the dynamic sea margin) and create a hydrodynamic model of the vessel to simulate the impact to ensure a more accurate performance comparison in the before and after installation scenario.
We measured Santa Catarina in both laden and ballast conditions, divided the speed-power curves before and after the BTF installation and compared those to different speed areas. In laden conditions, there was no visible change under 15 knots. From 15 to 18 knots, there was a 1-3 % impact and above 18 knots, there was a 4-7% impact. The vessel’s average median operational speed being 19.4 knots.
Thanks to Eniram’s combined DTA and PPD technology and real-time sea condition data-collecting, we were able to confirm the original theoretical calculations worked. Our systems not only help continuously automate and streamline how ship efficiencies are measured but our systems also remove the possibility of human error when collecting data, saving operators time and money while providing complete clarity of a ship’s performance at sea.
Eniram, July 2, 2014