Cathodic protection adapted for harsh Caspian conditions

Offshore staff

CHESTERFIELD, UK – Cathelco is supplying corrosion protection systems for offshore platform foundations under construction for Lukoil’s Filanovsky field development in the Caspian Sea.

The impressed current cathodic protection (ICCP) systems have been designed to operate in harsh conditions in an area where sea ice can prevail for more than 150 days each year.

Cathelco will supply equipment for the field’s riser platform (RB1) and accommodation unit (PGM-1), under construction at the Krasnye Barrikady shipyard in Astrakhan, Russia. The company has a further order to protect the ice-resistant fixed platform (IRFP-1), which is designed for drilling and well operation.

RB1’s unique octagonal structure will be protected against corrosion via eight ice-class anodes and reference electrodes connected to a control panel. PGM-1, which features a pontoon foundation, will have a similarly designed ICCP system to withstand the pressure of the winter ice.

The project requires a 35-year design life. The anodes must be ice resistant, diver changeable, and easily integrated with the structural arrangement of the platforms.

This has necessitated design of high strength cofferdams and special angled doubler plates to deflect ice away from the recessed anodes. To achieve required wear resistance, the current-emitting faces of the anodes, made from mixed metal oxide, are three or four times thicker than conventional anodes.

Another important consideration was the low salinity of the Caspian Sea which creates higher seawater resistivity. This necessitates a higher driving voltage for the anodes to achieve the required level of corrosion protection.

When the ICCP system is in operation the reference electrodes measure electrical potential at the hull/seawater interface and send a signal to the control panel which automatically raises or lowers output to the anodes. This way, the structure receives the optimum level of corrosion protection at all times, Cathelco claims.

11/01/2012

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