A Superior Coating that Prevents Marine Biofouling Permanently
Bio-Shield® is an optimum anti-foulant coating for offshore structures. It contains two proven materials: copper-nickel and SplashTRON® splash zone protection — which were selected to work together as a unit.
Bio-Shield® keeps marine growth from attaching to conductors and platform members in the first place, allowing designers to take full advantage of the cleaner profiles, and eliminating the necessity of any expensive removal operations.
The copper-nickel compound was chosen because of its long history as an effective anti-foulant, its ease of fabrication, and its comparatively low cost. SplashTRON® was selected as the insulating layer for several reasons:
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Marine life, such as algae, barnacles, and mussels, has been the scourge of shipbuilders for centuries. Marine growth also has become a serious problem for offshore operators and platform designers today.
While there has always been advantages to keep marine growth off of ship hulls to maintain speed, save fuel, and keep ships working instead of in drydock, it is vitally important to prevent biofouling on offshore platforms for different reasons. In many areas of the world, marine life – such as barnacles, mussels, and algae – don’t build up much more than an inch or two.
However, in many areas such as offshore California and the North Sea (anywhere waters are relatively cold and thus hold more nutrients), biofouling can build up to as much as 36″ thick. At these levels, it becomes dangerous since weight increases the strength requirements of the platform.
Depending upon the type of growth, biofoulants can weigh up to 150 pounds per cubic foot. It becomes dangerous due to the added area for wave loading and drastically reduces the fatigue life of a platform. Also, the danger of platform overturn is increased. When biofouling becomes excessive, about 6″ thick or more, platforms must be constructed much stronger than normally would be necessary, or the growth must be removed regularly.
Shell Development Co., in cooperation with MARK Tool Co., worked together to produce Bio-Shield®. MARK Tool Co. manufactures Bio-Shield by license under Shell’s U.S. patent number 4,415,293.
By far the most economical approach is to prevent biofouling. Shipbuilders found that using copper sheathing not only prevented marine borers in their wooden hulls, but also kept barnacles and other marine life from attaching. Copper-hull sheathing was used on the winners of the America’s Cup races for many years, including the renowned Cutty Sark.
Traditionally, in the petroleum industry, platform designers have taken two approaches to combat the severe problem. First, some have used much thicker metal and driven pilings deeper into the ocean floor. They design as if the buildup on platform members and conductors would present a solid wall to wave action. This approach is very expensive, and on deeper platforms can cause a weight problem that makes transportation and installation difficult. A second approach is to plan for periodic removal of the marine growth, and to design and budget accordingly. Waterblasting biofoulants from 48 conductors off California costs about $75,ooo per occurrence. And, the growth comes back twice as fast as it originally formed, so subsequent removals must be more frequent.
Conductors coated with BIO-SHIELD® anti-foulant coating are protected from marine biofouling and corrosion.