SPS of mobile offshore units
Verification of the cathodic protection system is an important part of a rig SPS every five years.
All MOU/rigs need to renew the main classification certificates every five year, through the special periodical survey (SPS).
During the SPS, it is time to test, check and verify the performance of the cathodic protection system. Malfunctions shall be rectified and necessary amount of sacrificial anode material must be replenished.
Equally important to the survey work during the SPS, is what is done in advance. Digitisation has certainly reached the offshore industry, and a modern MOU has a vast number of sensors and opportunities for data collection. This is also the case for the ICCP and MGPS control panels on board. Whether these are modern CathSense® or CathFlow® control panels, with a range of options for data collection and communication with control room and/or to shore, or if the panels are of a more basic type, ICCP and MGPS log data should be collected. The analysis of reference electrode potentials, current and voltage levels, trended over time, will give a good foundation for a predictable scope during the SPS of mobile offshore units.
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For rigs with sacrificial anodes as the external hull cathodic protection system, potential measurements with portable reference electrode should be done in advance of the SPS, in order to collect data for the anode system in operational draft. This, in addition to anode survey data, can be used by a cathodic protection engineer to make the final design for the coming five year period.