Cathelco are supplying corrosion protection systems for a series of offshore platform foundations which are being constructed for Lukoil to extract oil and gas in the Caspian Sea.
The impressed current cathodic protection (ICCP) systems have been designed to operate in the rigorous conditions of the Filanovsky field where sea ice is often experienced for more than 150 days of the year.
Cathelco have received orders to supply equipment for riser platform (RB1) and accommodation unit (PGM-1) which are currently being built at the
Krasnye Barrikady shipyard in Astrakhan. A further order has been received to protect the ice resistant fixed platform (IRFP-1) which is designed for drilling and well operation.
The riser platform (RB1) which has a unique octagonal structure will be protected against corrosion with an arrangement of 8 specially designed ice class anodes and reference electrodes which are connected to a control panel. The accommodation (PGM-1) unit with a pontoon foundation will have a similarly designed ICCP system to withstand the pressure of the winter ice.
The harsh environmental conditions and the requirement of 35 design life imposed a number of factors on the development of the system.
“The most important factors were that the anodes had to be ice resistant, diver changeable and easily integrated with the structural arrangement of the platform”, said Aneel Mumtaz, a corrosion engineer with Cathelco.
This involved the design of high strength cofferdams and special angled doubler plates which deflect ice away from the recessed anodes. To achieve the necessary wear resistance, the current emitting faces of the anodes made from mixed metal oxide (MMO) have a thickness three or four times greater 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 in order to achieve the required level of corrosion protection.
When the ICCP system is in operation the reference electrodes measure the electrical potential at the hull/seawater interface and send a signal to the control panel which automatically raises or lowers the output to the anodes. In this way, the structure receives the optimum level of corrosion protection at all times.
“Cathelco have enormous experience in designing ICCP systems for ice class vessels and offshore structures and we have worked very closely with Lukoil’s contractors to meet their specifications”, Mr Mumtaz commented.
The ICCP orders for the platforms have been won via Marine Bridge & Navigation Systems, Cathelco’s well established Russian agents based in St Petersburg.
November 1, 2012