May 23, 2018

CleanTech

Box-coolers are essential for a ship’s functioning. However, when unprotected, they quickly lose their effectiveness due to marine growth. Unprotected box coolers quickly look like this:

 

The pipe bundle of the box-cooler is a very attractive surface for all kinds of marine life:

  • It has an attractive temperature (normally between 25 and
    35 Celsius)
  • Because of the constant, forced flow of seawater, there is abundant
    oxygen and there are abundant nutrients.

Marine Growth Prevention Systems (MGPS)

There are different systems to prevent this marine growth, the marine growth prevention systems (MGPS). For box coolers, bucket strainers and sea chests almost universally used is the Impressed Current Anti Fouling system (ICAF). An Impressed Current Anti Fouling system consists of a set of copper bars (anodes) and steel plates (cathodes), which are placed in the sea-chest below the tube-bundle of the box-cooler. Once a current is applied, the copper anodes start dissolving, releasing copper ions into the sea-chest to poison all marine growth there.
While an Impressed Current Anti Fouling system might keep your box cooler clean, there is a major hitch: a sea-chest is per necessity an open system, hence all released copper ions end up in the sea.

Pollution by international shipping is already under strong scrutiny. CO² emissions of all international shipping equals that of Germany!  Recently an accord was reached to start curbing greenhouse emissions (click here for more information).

Regulation of antifouling paint for ship hulls is also constantly under revision, amongst others because of the copper content. Copper in antifouling paints for pleasure craft is now so restricted that many yacht owners complain about their loss of effectiveness.

Given this increased scrutiny of the environmental footprint of the maritime sector, it just seems a matter of time before the Impressed Current Anti Fouling systems will also become a topic of discussion.

Here is a quick calculation of the environmental impact of ICAF systems worldwide:
– There are around 52.000 merchant marine seagoing vessels.
– There are around 4 million fishing vessels in the world, of which 1,3 million are decked vessels.

The average number of Impressed Current Anti Fouling systems per ship is difficult to estimate: a fishing vessel might have 1, while a platform supply vessel might have 26 Impressed Current Anti Fouling systems.

Still, a rough and conservative estimate would be:
– On average 8 ICAF systems per ship for the merchant marine fleet.
– Say that of 1,3 million decked fishing vessels 1 million have at least 1 Impressed Current Anti Fouling system.

52.000 x 8 = 416.000 Impressed Current Anti Fouling systems in the merchant marine
1.000.000 Impressed Current Anti Fouling systems in the fishing fleet
1.416.000 Impressed Current Anti Fouling systems worldwide.

On average, for a small box-cooler per year 5 kilograms of copper ions are released into the environment (this is again a conservative estimate, bigger box-cooler with bigger Impressed Current Anti Fouling systems release more)

That results in a conservative estimate of 7.080.000 kilograms of copper ions released in the seas yearly!

Ultrasonic antifouling systems are an environmentally friendly alternative to Impressed Current Anti Fouling.

An ultrasonic antifouling system brings the tube-bundle of a box-cooler in ultrasonic vibration. This vibration generates an environment in which the larvae of marine organisms do not want to settle. The vibration is so weak, that organisms already present, survive. At a distance of around 20 meters or so, the ultrasonic ‘sound’ has dissipated. The impact on the environment is absolutely zero.

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