Cathelco are supplying an impressed current cathodic protection (ICCP) system for the OKHA FPSO, which is being converted by Single Buoy Moorings.
After conversion, OKHA will operate in oil fields off the North West Shelf of Australia by Woodside Energy Ltd, replacing the FPSO Cossack Pioneer.
Conversion work will take place at the Keppel Shipyard in Singapore. During the installation of the ICCP system, local support will be provided by Cathelco S.E.A., also based in Singapore.
"Before designing the system a study was undertaken by Force Technology, using computer modelling, to determine whether 'interference' from the sacrificial anodes on the riser column would have an effect on the performance of the ICCP equipment," said Aneel Mumtaz, a corrosion engineer, based at Cathelco's headquarters in Chesterfield, United Kingdom.
The study identified the potential risk of 'interference' with the ICCP system and as a result the design was modified to achieve the most effective form of corrosion protection. It was also proposed to utilise silver/silver chloride reference electrodes due to their higher stability at negative potentials.
The reference electrodes provide efficient monitoring of 'potential' at the hull/seawater interface and send a signal to the control panel which raises or lowers the anode output. In this way, the hull receives the optimum level of corrosion protection at all the times.
Cathelco will be supplying a new 1,000 amp ICCP system for OKHA. The forward unit will consist of a control panel wired to two 250 amp linear loop anodes and the aft unit will be of an equivalent size. The advantage of linear loop anodes is that they provide a high output from a relatively small surface area making them ideal for this type of application.
Cathelco ICCP systems are increasingly being installed on FSOs, FPSOs and semi-submersibles. The OKHA project will be the fourth to be carried out for Single Buoy Moorings since 2005.
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