December 19 2013

On Thursday December 19^th the Greek Section of SNAME held its 4^th meeting for this year. The meeting was held at the Anangel Auditorium, kindly made available by the upper management of the aforementioned company. The topic of the presentation was on the performance and monitoring of antifouling coatings. Presenters were Dr. Andreas Krapp and George Vranakis of Jotun of Norway and Greece. The title of the presentation was: “A Practical Way to Evaluate the In-Service Performance of Antifouling Coatings”.

We were also honored to have a distinguished guest amongst the attendees, namely Professor Sander Calisal and Dean of Piri-Reis University in Turkey.

The Jotun presentation was focused on Hull Performance Solution, HPS, scheme offered by the company to the ship owners. This is an effort to stretch the importance of keeping a “clean” hull towards greener shipping achieving significant savings at the same time. The presentation was mainly on the procedures and techniques associated with the scheme. At the same time a wealth of actual data were presented to show how the scheme works. The performance of a vessel's underwater hull deteriorates over a sailing interval (the interval between two dry-dockings). This deterioration is mainly caused by biological fouling and by mechanical damage to hull and propellers. Average speed loss over a docking interval is around 7% corresponding to a 20% loss in efficiency or about 2.4% for a 12 month window.

The basic idea of the scheme is that there is a benchmark period of one year in order to establish a reference speed-power curve. The scheme is based on quite basic hardware and it does not entail the installation of fancy sensors and equipment. Interestingly enough speed measurement is based on the Doppler log as opposed to the GPS system. In an effort to get rid of data of high degree of uncertainty, measurements which will be used for the generation of the reference curve are not considered if the wind speed exceeds a force of 4 in the Baufort scale. There is a lot of confidence in the scheme to allow the company to guarantee a very low deviation (0.2 knots over speed of 14 knots) from the reference curve. It is also noted that data pertinent to maneuvering or power below 50% are not utilized as well. The method will be the backbone of the ISO standard on hull performance, number 19030 parts 1 to 3. The measurements and monitoring is a necessary step given the high degree of uncertainty in the correlation between hull roughness and hull friction coefficient. One of the key elements of the scheme is also the reproducibility of the speed measurements. The condition of underwater hull surface has a great impact on its energy efficiency for a vessel and this effort aims at elimination of the high fuel cost and CO2 emissions attributed to fouling of hull and propeller. The expected return of investment time will vary depending on a broad range of factors including vessel type, trade, activity level, voyage policies, current level of hull performance, current main engine bunker consumption, expected cost per ton of bunker fuel etc.

The presentation ended with a very lively question and answers period where many clarifications were provided by the speakers and replied to various comments related to their work and experience with the HPS scheme. The meeting closed in a festive atmosphere with the traditional reception and get-together time.