Hundreds of years ago, marine life (including algae, barnacles, and mussels) created headaches for shipbuilders, sailors, and anyone else who worked at sea.
Some things never change. In 2017, these pesky ocean-bound critters are the bane of offshore oil and gas operators and drilling platform operations. In fact, governments and industry spend more than $5.7 billion a year to fight what is known in offshore drilling as "marine biofouling.”
Depending upon the type of growth, "biofoulants” can weigh up to 150 pounds per cubic foot. So it’s easy to see how the additional weight can create a strain on coastal infrastructure. Preventing biofouling on offshore platforms is critical because this added weight:
- Increases the strength requirements of the platform
- Increases the wave loading area of the structure
- Reduces the fatigue life of a platform
- Increases danger of a platform overturning
Centuries ago, shipbuilders discovered that copper sheathing prevented marine borers (any mollusk or crustacean that destroys wood by boring into and eating it) from attaching to ship hulls. They also found that copper was effective at keeping barnacles and other marine life from attaching.
All these years later, we’re still using copper. But we found a way to make it better.
Mark Tool Co., Inc. partnered with Shell Development Co. to produce an optimum anti-foulant coating for offshore structures. We call it Bio-Shield®, and we believe it will add life to your risers, conductors, and platforms.
Waterblasting biofoulants from conductors costs about $75,000 per occurrence. Unfortunately, the growth comes back twice as fast as it originally formed, so subsequent removals must be more frequent. Bio-Shield® eliminates the need for marine biofouling cleanup and removal operations
Bio-Shield® works by combining two ingredients:
- SplashTRON®, our anticorrosive system based on advanced neoprene technology
- A copper-nickel compound
Bio-Shield® sheathing will prevent biofouling on conductors, platform legs and diagonals, J-tubes, and risers. It works on any piping or structure in an area that typically sees buildup. In a standard application, Mark Tool Co. applies a 1/2" thick layer of SplashTRON®, bonded completely to the pipe; and a 1/16" thick plate of 90-10 copper-nickel is bonded to the outside of the SplashTRON®. The alloy is completely insulated from any contact with the steel and will retain its anti-fouling ability for the projected life of the installation.
- A 24-inch conductor coated with Bio-Shield® was driven with a D-36 hammer capable of exerting 83,000 ft/lbs of force. The test pipe was subjected to 240 blows per foot at final depth. There was no slippage of the alloy/rubber sheath that makes up Bio-Shield®, and there was no sign of movement or bond tearing.
- A test piece of 6 5/8" pipe was installed on a platform off the coast of California in 1978, just below the waterline (where marine growth is heaviest). On the test piece, a band of copper-nickel was centered on a layer of SplashTRON®. The test piece was inspected by divers after 237 days, and no marine growth was found on the copper-nickel, while there were 3-4 inches of build-up on adjacent surfaces. The test pipe has been inspected several times in the years since, and there is still no buildup on the copper-nickel.
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A series of laboratory tests were conducted to show the bond strength of SplashTRON® to copper/nickel, the electrical insulating ability of SplashTRON®, and long-term anti-biofoulant performance under temperature tests. The bond test showed a shear bond strength between the alloy and rubber (SplashTRON®) of 389.63 psi, well above the estimated 15 psi exerted by normal driving forces.
After 96 cycles to 80°C (176°F), and cooling to 30°C (86°F) in artificial seawater, a sample of the alloy/rubber, bonded to steel, showed no signs of separation and no change in the SplashTRON® or the copper-nickel allow. Additionally, electrical resistance of the SplashTRON® material was measured at 125 million ohms (125 mega ohms).
Success in the Field
After the laboratory tests, Bio-Shield® was used to design the Eureka platform, installed in more than 700 feet of water off the California coast in 1984. Eureka featured 60 24-inch OD well conductors (0.6 meter OD).
Bio-Shield® eliminated the need for 250 tons of structural steel, otherwise required to handle the extra wave, tide, and current load from the marine growth. After several years, the Cu-Ni surface was free of bio-fouling, while the unprotected areas were covered with an 8-13 cm thick layer of barnacle and mussel growth.
Operational savings were enormous, both regarding reduced steel needed to account for corrosion and fatigue loads in the structural nodes (estimated at $377,000) and in savings per cleaning (estimated at $50,000 to $100,000).
Mark Tool is a leading manufacturer of custom molded rubber products, including rubber rollers, tensioner pads and other custom molded rubber products. We got our start in oilfield and marine applications, but our product line has grown to meet the needs of virtually every industry from manufacturing to food goods processing. Contact us to learn more about our products or to request a quote.