Anodes counter marine growth, corrosion on Keppel offshore vessels

Offshore staff

CHESTERFIELD, UK Cathelco is supplying protective equipment for two offshore facilities projects under construction at Keppel yards in Singapore.

One order is for a marine growth protection system (MGPS) for a semisubmersible drilling rig tender (Project B374). This is designed to eliminate blockages in seawater pipework caused by build-up of barnacles and mussels.

Four sea chests will be protected, each with flow rates of 1,160 cu m/hr (40,965 cu ft/hr), with one aluminium and two copper anodes wired to a control panel in each sea chest.

In operation, the copper anodes will generate ions which create an environment that prevent barnacles and mussel larvae from settling or breeding, instead carrying them through the system for discharge.

The aluminium anode will produce ions that form an anti-corrosive coating on the internal surfaces of pipes.

In addition, Cathelco is supplying MGPS and hull corrosion protection equipment for an FPSO conversion for Armada Madura EPC at Keppel Shipyard.

The FPSO, due to be completed next summer, will be deployed in the Madura Strait block BD, 65 km (40.4 mi) east of Surbaya, and 16 km (9.9 mi) south of Madura Island, Indonesia.

Cathelco’s equipment will protect pipework connected to the main sea chests, fire water sea chest and seawater lift sea chest, the largest with flow rates of up to 1,300 cu m/hr (45,909 cu ft/hr).

The impressed current cathodic protection (ICCP) system should protect the hull against corrosion throughout its 20-year design life.

ICCP systems will be installed fore and aft on the 246.8-m (810-ft) long vessel. The 300-A forward system will comprise two C-Max disc anodes mounted port and starboard and two reference electrodes connected to a thyristor control panel. 

C-Max disc anodes maintain a smooth hull profile, Cathelco says, and are diver changeable which means that anode replacement can be performed at sea. The 300-A aft system employs two linear loop anodes and two reference electrodes.

Reference electrodes will measure the electrical potential at the hull/seawater interface and send a signal to the control panel to raise or lower output to the anodes. This way, the hull should receive the optimum level of corrosion protection at all times.

12/02/2015

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