Offshore instrumentation and monitoring
Monitoring the structural response in the field for large novel offshore structures provides essential data for optimizing design, early warning of degradation, and condition-based maintenance. Load histories and recorded corrosion rates in situ can provide essential data for future lifetime extensions.
NGI has experience with instrumentation for offshore structural health monitoring since the 1970-ies, and can offer subsea and topside monitoring solutions that survive the harsh conditions expected at offshore wind farms, and all types of offshore installations.
Through a network of sub-suppliers, NGI provides turn-key structural health monitoring systems. We focus on providing monitoring solutions that generate valuable data for the client. This includes advice and specifications of the instrumentation we believe is fit for purpose. As a system provider without our own sensor brands, we are always looking for new components to improve monitoring performance.
The system supply is followed up from concept to installation and commissioning. This often results in novel solutions for a simplified and robust installation and structural integration and ensures that the sensor readings represent the parameters to be monitored. "Prototypes are our standard."
Functionality, integrity, and accuracy tests have high priority in our system supplies. With an offshore instrumentation track record dating back to the 70s, we have learned that the "Devil is in the details," and nothing can be left for certain.
An integrated monitoring system implies a mixed sensor configuration providing all necessary data to assess the structural response and health of the foundation. Different parameters are often linked, and it is essential to record them all to understand the measured response.
Combined use of infrastructure such as cables and one common data acquisition system will reduce the overall costs compared to installing several independent systems.
NGI can, together with sub-suppliers, provide integrated monitoring systems for measurements of the following parameters above and below sea level:
- pore pressure and total stress in the soil
- dynamic motion and vibrations
- structural strain and stress
- levelling of structure
- deformations and displacement (grouted connections)
- load distribution
- wind and wave height
- temperature and air quality (TP)
- water levels and current
- seabed scour
- corrosion rate (ER/LPR nodes)
- cathodic protection (reference electrodes)
The sensors are hooked up to a modular data acquisition system customized for each instrumentation scheme.
Retrofitted instrumentation systems
NGI has developed instrumentation solutions customized for offshore retrofit, including distributed data acquisition by means of EtherCAT modules/WIFI sensors to minimize cabling and smart magnetic mounts for a rapid fixture to the structure.
Other retrofitted monitoring solutions for subsea grouted connections and strain measurements are also being developed. Simple retrofit allows existing offshore foundations to be monitored on demand and provides mobility for relocation of the structural health monitoring system to different wind turbines or structures.