Coatings World - June 2012

12 months after application of the “new” paint system. Other factors need to remain the same e.g. no engine overhaul at drydock.

3. Directly measuring the same fouling control system over a given time period. This method uses an industry view that a vessel on average will lose five percent speed over a 60- month period. This five percent speed loss would translate to roughly a maximum average of 15 percent increase in fuel in order to maintain speed. This assumption is not specific on fouling control type. The baseline data is then compared to the performance predicted or measured in service.

Analysis – using antifoulings as examples

Using Method 1, comparing a 60-month docking cycle of a typical rosin-based system with another 60-month docking cycle with Intersmooth SPC, International Paint has calculated an annual average four percent fuel saving for Intersmooth SPC over the rosin-based system.

If Method 2 were to be used, and compared 12 months before dry dock for a rosin-based system with 12-months after dry dock with Intersmooth SPC, International Paint has calculated fuel savings would be higher, at nine percent. However, as the periods in service are at different time periods in the docking cycle, the company argues that there are limitations of this method, and that the resultant high value of the improvement is misleading. It suggests that this method should not be used.

As for Method 3, International Paint points out that in 1986 evidence was published on vessel performance using SPC technology. Townsin et al1 showed that the effect of hull roughness on fuel consumption could be related in a fairly simple formula, % Power Increase= A(AHR2-1/3 – AHR1-1/3), that for every increase in hull roughness of 25 microns there would be approximately a one percent penalty in the fuel consumption of the vessel. For typical rosin-based antifouling systems, hull roughness increases by around 40 microns per year. However, due to polishing, smoothing and minimal build up of leached layer, an SPC antifouling increases in roughness by only 20 microns per year.

Therefore for SPC technology, the fuel consumption increase over the full period (of 60-months) would be just under one percent per year, reaching four percent in year five (for the vast majority of vessels that return from service in a clean condition).

Using data generated in the comprehensive Townsin paper and a detailed analysis of antifouling performance from Dataplan, the fuel consumption increase over a 60-month period for a rosin-based system can be calculated as 15 percent, the same figure as what has been described as the ‘industry view’.

The calculation of 15 percent is as follows; Rosin containing systems were measured to increase in average hull roughness by 40 microns/year. Over a 60-month period, this would be a 200- micron increase. A 25-micron increase in average hull roughness equates to a one percent fuel increase. This means an eight percent fuel increase on roughness alone. Between 36- and 60- months a rosin-based system is highly likely to foul, typically due to the build up of a large leached layer preventing biocide release. This results in increased roughness and drag. The effect of

this on fuel consumption has been measured and then calculated to increase by seven percent; this gives the total increase in fuel consumption of 15 percent.

If only SPC products are measured, then the fuel consumption increase over the 60-month period will be four percent. Not being specific on fouling control type highlights a potential flaw in using an industry view average of fuel loss, International Paint says.

One important omission in Method 3 is that there is no allowance given for any fuel consumption rise effects that are nonfouling related such as a damaged propeller, mechanical damage to the coating or general engine wear and tear.

Going forward, International Paint has stated that it recognizes the importance of providing owners with as much information on the performance of its products as it can.

Breaking new ground

The new relationship with BMT will provide the independent monitoring that the partners believe will make both the evidence and methodology cited above incontrovertible.

The BMT Smart Services system, developed by BMT Argoss, will capture and compile real vessel data and independently monitor and report on vessel performance. It will record data automatically from ships’ sensors to monitor engine torque, the speed log, navigational signals (heading and speed over ground), and provide performance information to the crew and to shore-based management for analysis. The system, which can be installed at the newbuilding stage or as a retro-fit, automatically records thousands of readings per day, providing analysis of vessel performance.

The system will clearly and transparently measure the in-service performance of International Paint’s hull coatings, drawing on BMT’s 24/7 in house high quality and validated MetOcean data.

The MetOcean data gathered automatically from high resolution, accurate satellite monitoring is essential to monitor information on board, such as the relationship between hull roughness condition and fuel consumption. This information needs to be integrated with the environmental conditions being experienced by the ship. This MetOcean data includes factors such as wind speed and direction, currents, (speed and direction)