Box coolers, seachests, gratings and pipework are prone to accumulating biological growth that cuts engine cooling efficiency
Engineroom cooling systems and niche areas of hulls need to be protected when open to the sea to reduce biofouling. Applying antifouling coatings to exposed surfaces or installing anode-type systems to prevent the build-up of biological growth on heat exchangers can ensure they cool engines effectively and sufficiently.
Research commissioned by Swedish biotechnology company, I-Tech discovered barnacle fouling is hugely prevalent in hull niche areas including seachests, gratings, bilge keels, seawater inlet gratings, lateral thruster tunnels and bow thrusters. It found niche areas on tugs could account for as much as a quarter of the underwater surface available for colonisation by fouling marine creatures.
Although hard fouling in these areas does not induce as much hydrodynamic drag, excessive fuel consumption and carbon emissions as biofouling on the main hull surface area, niche area fouling can significantly impact the operational and environmental performance of vessels in other ways.
Heavily fouled niche areas can impact the operational efficiency of machinery and equipment that requires seawater intake. If the seachest for a box cooler is obscured by fouling, the heat exchange is reduced, leading to the need for more energy to run the cooling system or a complete failure.
“While a vessel might have a pristine underwater hull, our research suggests there is a good chance it is highly colonised with hard fouling,” says I-Tech chief executive Philip Chaabane. “This means vessels will continue to spread invasive aquatic species and suffer sub-optimal hardware efficiency because of niche area fouling.”
Niche areas are challenging for many antifouling technologies within marine coatings as the reduced water flow reduces the efficacy of foul release coatings and the shape of these areas makes it a challenge to apply an antifouling coating effectively.
However, tug owners can reduce the accumulation of hard fouling in niche areas by using antifouling coatings with a higher polish rate for better performance in low water-flow areas, says I-Tech technical director Markus Hoffmann.
“We would also recommend that when owners are having their vessel resprayed, more attention is paid to applying additional coatings to niche areas, which will only add a few tins,” says Mr Hoffmann.
“In time, we expect improvements in the design of niche areas that support antifouling technology, such as removing angled edges and hard-to-coat gratings,” he adds.
I-Tech has extended its frame agreement with Chugoku Marine Paints to provide its antifouling products to a range of marine coatings.
There is an alternative for owners to consider to accompany coatings. Evac subsidiary Cathelco supplies electrically charged antifouling products installed in box coolers and seachests on tugs. Its latest installation was on a series of naval tugs built for the Polish Navy.
“Marine growth in box coolers and seawater pipework can be costly and time consuming to remove,” says Cathelco lead project engineer Garry Churm. “But through the protection provided by our marine growth prevention system (MGPS), these maintenance costs are eliminated while ensuring the box coolers operate with optimum effectiveness.”
Cathelco’s MGPS systems can be used to protect the engine seawater cooling lines for any type of tug and to safeguard fire-fighting pumps and pipework against blockages caused by biofouling.
An MGPS system consists of pairs of copper and aluminium anodes mounted in the seachests and fed with an electrical current. In operation, the copper anodes produce ions that are carried by the flow of seawater and create an environment where the larvae of barnacles and mussels do not settle or grow. The concentrations of copper are around two parts per billion and have no effect on the wider marine environment after discharge.
Cathelco manager Richard Woolley says an MGPS is easy to install and runs automatically. Their anodes require renewal after three to five years, which can be carried out during a scheduled drydocking.
MGPS modules need to comply with regional regulations such as the European Union’s Biocidal Product Regulations (528/2012), says Mr Woolley.
MGPS were installed in box coolers on six tugs built by Remontowa Shipbuilding in Gdansk, Poland, built to support Polish naval ship dockings, ship towing, rescue operations and pollution control along the Baltic coast.
H-1 Gniewko, H-2 Mieszko, H-3 Leszko, H-11 Bolko, H-12 Semko and H-13 Przemko have Blokland Non Ferro box coolers and Cathelco MGPS to protect the coolers from biofouling.
Blokland Non Ferro sales manager Bram Fase says MGPS ensure engines are cooled efficiently and reduce maintenance costs throughout their operational lives.
“The system has a long record of effectiveness in preventing marine growth on the heat transfer tubes of box coolers,” Mr Fase says. “This helps to achieve greater sustainability by improving fuel economy and reducing the need for unscheduled maintenance.”
In 2020, Cathelco won an order to deliver an MGPS for a new multi-purpose oil spill response and towage vessel built for Kuwait Oil Co by Uzmar Shipyard in Turkey.
To protect the pipework against marine growth and corrosion, copper and ferrous anodes were installed in five seachests. Ferrous anodes produce ions which create a protective coating on the internal surfaces of pipes to mitigate corrosion.
Mr Woolley says more tug owners are ordering MGPS. “During the past year, most of the projects have been retrofit installations,” he says. This year, systems have been supplied for four tugs owned by Zamil Offshore Services (Zamil 53, 54, 55, 71) and in South Africa a system was installed on Smit Amandla’s Aogatoa.
Cathelco’s latest order is for MGPS units for five tugs being built by PaxOcean’s Graha Trisaka Industri in Indonesia for deliveries during 2022. These tugs (Tai Chin 301-306) are being built for Taiwan Navigation Co.
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