Cathelco tank to block marine growth in Vincent FPSO pipes

June 21, 2019

Offshore staff

HELSINKI, Finland – Evac is supplying a Cathelco marine growth prevention system (MGPS) to protect seawater pipework on the Woodside-operated FPSO Ngujima-Yin.

The vessel produces oil from the Vincent field offshore Western Australia, 50 km (31 mi) northwest of Exmouth.

Recent modifications were designed to allow a 31-km (19.3-mi) subsea tieback of oil accumulations from the Greater Enfield fields.

The MGPS is designed to prevent blockages in seawater pipework caused by the growth of barnacles and mussels, saving maintenance costs throughout the vessel’s life.

According to Evac, typically pairs of copper and aluminum anodes are mounted within the strainers of FPSOs so that they can be changed at any time without the need for drydocking.

But if the drydocking interval is greater than five years, an electrolysis tank system can be more practical.

Vincent’s MGPS electrolysis tank unit will be one of the most complex ever designed by Cathelco (which was acquired by Evac last year) for an offshore production facility as it will treat seawater from three lift pumps, two of which will always be in operation.

There is a need to dose water at high and low flow rates depending on the processes being performed on the FPSO and the combination of pumps in use.

The skid-mounted electrolysis tank houses five copper anodes and seawater flow from each of the three lift pumps is controlled by automatic valves.

A self-cleaning filter prevents build-up of debris in the tank.

In operation, the anodes produce ions which are carried throughout the pipework to prevent barnacle and mussel larvae from settling and growing.

The concentration of copper in the pipes is around 12 parts per billion, sufficient to prevent blockages caused by biofouling, Evac claims, without impacting the wider marine environment.