Cathelco have designed special box cooler anti-fouling systems for two tugs which are used by Rio Tinto to berth iron ore carrying vessels in the port of Dampier, Australia.
The Pilbara Vulcan and Pilbara Neptune both experienced problems with bio-fouling which caused their box coolers to overheat. In response to this, the box coolers were extended and deliberately left with uncoated surfaces to improve heat transfer.
“Rio Tinto approached Cathelco to provide a solution to the fouling problem, but as the box coolers were uncoated and electrically isolated from the seachests they also wanted to be sure that the anti-fouling system would not cause corrosion problems in the future” , said Stephen Ellis, project development manager at Cathelco Ltd.
On each of the tugs, the Cathelco system will protect nine box coolers against mussel and barnacle growth which can impair the efficiency of the heat transfer process. The order for the equipment was won by Marine Plant Systems, Cathelco’s well established agent in Australia.
Copper anodes, fed with an electric current from a control panel, are mounted horizontally beneath the box coolers to create an even distribution of ions when the system is in operation. The ions create an environment where barnacles and mussel larvae do not settle or breed and are passed harmlessly to discharge.
“The client wanted to eliminate the risk of ‘stray currents’ which could have a corrosive effect on the seachest. To minimise this risk, we designed special perforated cathode plates which cover the anode to provide an effective earth return ”, said Garry Churm from Cathelco’s technical department.
In addition, Cathelco designed a corrosion monitoring system to measure the difference in voltage between the box coolers and the seachests to check that there is electrical isolation. In the event of a failure in the isolation an alarm is registered on the control panel.
Tugs and other vessels working in-shore with frequent periods alongside are particularly vulnerable to bio-fouling in their seawater pipework systems. In tropical waters where barnacles and mussels breed more prolifically the problem is intensified.
Cathelco seawater pipework anti-fouling systems have been fitted to more than 30,000 vessels over a period of more than 50 years. These range from tugs and workboats to the largest oil tankers and cargo vessels.
[mappress] World Maritime News Staff, January 3, 2012; Image: WesTug