After considering a number of alternatives EM&I came up with the solution of an anode which can be inserted through a class approved access port in the hull bottom plating – usually in the engine room – which has sufficient headroom for the ‘periscope type’ anode and its launching tube.
Drilling holes safely in hulls had to be proven first, so EM&I initially conducted tests on a 9 metre high tank at the National Hyperbaric Centre in Aberdeen, UK. These tests and special cold water welding procedures were observed by the client and class who were entirely satisfied that it was safe.
The next step in the development was to design an anode which could be inserted easily through the access port and incorporate a dielectric shield to protect the hull in the immediate area of the anode.
A number of alternatives were considered, but eventually a tubular style anode with a non-conductive part nearest the hull was adopted. The anode itself is titanium with a mixed metal oxide coating. This is designed to have an operational life of around 25 years.
The launching mechanism comes from the hydraulic industry but is operated by compressed air in this particular case for ease of use on site. For the average FPSO only two HullGuard® anodes will be required and can cope with a hull coating breakdown of around 7.5%. If more coating breakdown is present, or occurs over time, this can be covered by varying the ICCP current or introducing additional anodes.
The ‘wetted area’ of an FPSO hull is around the size of over two football pitches so there is a significant area requiring protection.
“We are delighted with this development which will help to extend the life of floating assets easily” commented Danny Constantinis (Executive Chairman) of the EM&I Group. “The HullGuard anodes can be installed in a fraction of the time required to do this with divers or other means and is much safer. They can also be retracted easily for inspection, cleaning or replacement. Although HullGuard can be readily retrofitted it also makes sense where possible to install the HullGuard access ports in the shipyard at the conversion or new build stage.”
Read the article online at: https://www.oilfieldtechnology.com/product-news/19082019/emi-provides-diverless-periscope-type-retractable-anode/