The challenges of measuring real vessel performance

The standard paint guarantee from coating suppliers allows for some fouling before a claim can be made.

The standard paint guarantee from coating suppliers allows for some fouling before a claim can be made.

Dr Raouf Kattan, managing director of Safinah, co-wrote, with Dr R.L. Townsin (Safinah) and V.N. Armstrong (ApolloSOS), a paper on the complexity of coating performance measurement for shipowners which was presented at the recent ICMCF in Singapore. Wendy Laursen reports.

With fuel at US$600 to US$700 per tonne and ocean going vessels consuming anything in the range of 40 to 220 tonnes per day even a 1-2% fuel saving can provide rapid payback on fouling prevention investment.

The standard paint guarantee from coating suppliers allows for some fouling before a claim can be made. Typically they may allow up to 2.5%, which would already be a serious problem for vessel performance in terms of fuel consumption.The shipowner wants predictable performance to ensure that costs are controlled over the period of the charter or ownership to ensure a return on investment.

The high cost of recoating, and any subsequent economic fouling penalty, has led some paint companies to attempt to devise guarantees regarding the effectiveness of their products, based upon some measures of speed/power performance of a ship from out-docking after anti-fouling coating. Such in-service data collection and analysis is notoriously difficult.

Fuel consumption is the critical factor in determining vessel performance. The specific fuel consumption of the engine is normally determined at the shop-based engine trials carried out prior to acceptance of the engine and its installation on board the vessel. During sea trials the measured mile is used to determine if the vessel is able to achieve the contract speed and if the measured power for a range of speeds is in line with the design conditions. Though increasingly there is reference in the contract to fuel consumption, sea trial fuel consumption is measured for the specific condition of the trial and can be subject to error when being adjusted (the most accurate fuel consumption figures available at that time are those from the engine trials).

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