Online corrosion monitoring on foundations validating corrosion protection strategy

Operation and maintenance of offshore wind is challenging and costly, a challenge which is becoming bigger with bigger sites, bigger structures, and having sites placed further and further offshore, and hence with a limitation on accessibility for any operation and maintenance activity.  

Following and documenting integrity of structures has therefore become increasingly important, also as structures are optimized to keep the cost of electricity down, and any unforeseen or unforeseeable maintenance and repair activity may penalize the business case. 

Measurements and inspections of structures are performed on a regular basis using visual inspections and using manual equipment. Results from manual measurements are however subject to uncertainty and inaccuracy and in some cases manual measurements cannot provide information on the structural integrity, for instance below seabed or in the tidal zone.  

To address the need for design validation and enable planned maintenance activity, Ørsted has become frontrunner in applying online measurements and evaluating unique long-term corrosion measurement data utilizing ER (Electrical Resistance) sensors and loggers. A variety of sensors have been installed internally and externally, above and below seabed at selected foundations on in total nine operating OWF up until 2022, and is planned for installation also on upcoming assets. This paper describes the measurement principle, the rationale behind the monitoring and some of the learnings so far.