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Winning the fight against barnacles

May 1 2012
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Anti fouling paint on Dan Eagle

 

Customised antifouling paint for shuttle tankers helps Lauritzen Offshore combat barnacle build-up that increases water resistance and boosts fuel consumption and emissions.

The general description of a barnacle sounds innocent enough: “a marine crustacean that in the adult stage forms a hard shell and remains attached to submerged surfaces, such as rocks and ships' bottoms”.

The problem is that especially in warmer seas, as in Brazil, the little monsters multiply like mad and can quickly add an unwanted 30-50 mm layer to a ship’s hull. Because rapid movement of water along the hull creates a polishing effect, vessels on the move do not experience heavy barnacle build-up with ordinary antifouling paint.

Shuttle tankers, however, have short voyages and longer periods of stationary time, which creates ideal conditions for barnacles to attach and grow and disrupt the carefully engineered hydrodynamics of the hull. The ship then has to use more power and fuel to plough through the water.

When the shuttle tanker Dan Eagle went to dry-dock recently for scheduled three-year maintenance, a thick layer of barnacles not only covered large areas of the hull but was also found to be choking cooling water inlet pipes. “Barnacle build-up was causing 15- 20% more fuel consumption,” says Hans Gundestrup, vessel manager for LO, “which meant that the vessel either had to increase power and fuel consumption to maintain speed or add time to her schedule.”

It was a tough and time-consuming job to remove what turned out to be 40 tons of barnacles with high-pressure hoses: a total of eight to ten days, which included paint treatment of the hull.

Keeping clean

To protect against future build-up on Dan Eagle, JL chose to apply an advanced antifouling paint – SeaQuantum Ultra from Jotun – which is customised for such a ship’s operation pattern.

The paint system gives a controlled release of copper particles that prevent marine growth. The paint consists of a soft polymer that binds the copper, and as water flows over it the coating diminishes layer by layer until virtually nothing is left by the time for the next dry dock.

This particular paint system is designed to work with minimal water flow, at low speeds down to one knot, which makes it ideal for Dan Eagle.

“JL is constantly on the lookout for custom-made products for our operating patterns, like this antifouling paint,” says Hans Gundestrup. “We expect very good performance from this paint system, which naturally is also in compliance with international environmental standards and regulations. When you consider that the difference between a clean hull and a fouled hull can easily add up to ten per cent in fuel consumption and emissions, this paint is clearly worth the higher price we pay for it, both in terms of our bottom line and for the environment,” Hans Gundestrup adds

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