The Problem
Keeping ageing structures sound in a working wind farm
The client needed a subsea inspection of offshore wind farm structures that gave a clear, measured picture of the condition of eight wind turbine generators (WTGs) and the offshore substation (OSS) at an operating wind farm: monopiles, transition pieces, cable protection systems (CPS) and the sacrificial anodes that protect them.
Subsea structures at a wind farm are under constant load from current, waves and moving sediment. Thick hard and soft marine growth on monopiles, anodes and CPS components adds hydrodynamic loading, hides the steel beneath it and gets in the way of maintenance. Scour around monopiles and cable entries can undermine a structure. Sacrificial anodes lose effectiveness over time, and once they do the steel starts to corrode. Any of these, left unchecked, turns into repair costs, downtime and questions about compliance.
The brief was to inspect every asset by visual and sonar methods, measure what mattered and hand over data the client could act on.
The Inspection
Visual, close visual and measured
Every structure on video
High-definition video surveys of the monopiles, transition pieces and CPS components on all nine assets, recording overall condition and any structural deviation. Scour was assessed around each monopile and cable inlet.
The details that matter
Close visual inspection of anode connections, grout seals in the pile sleeves and the key structural joints, with marine growth thickness and anode potential measured rather than estimated.
One report per asset
Each asset was reported separately with high-resolution imagery, sonar data and Spot.On survey files, plus the anomalies and the recommended actions.
Our Solution
The V8 M500 with sonar and measurement tooling
The team deployed the Ocean Modules V8 M500 ROV fitted with high-definition video, imaging sonar and the tooling needed to take readings on the structure. The V8 M500 is compact enough to mobilise without a large marine spread and stable enough to hold position against a monopile while measurements are taken.
Marine growth thickness was measured at several depths on the monopiles and jacket structures to show how much the environment is loading each component. Anode potential was measured at a range of depths to confirm the cathodic protection was doing its job.
The Scope
What was inspected on each asset
Monopiles and transition pieces
General visual inspection by high-definition video, recording condition and any structural deviation.
Cable protection systems
CPS components documented on every asset, including where they meet the structure and the seabed.
Scour
Seabed around each monopile and cable inlet assessed for sediment displacement.
Marine growth
Thickness of hard and soft growth measured at multiple depths on the monopiles and jacket structures.
Anodes
Connections inspected and protective potential measured at depth to confirm the corrosion protection is working.
Grout seals and joints
Close visual inspection of grout seals in the pile sleeves and the key structural joints.
From the ROV
The Result
Structures confirmed sound, with the numbers to prove it
No major defects were found on the monopiles, transition pieces or CPS components. Marine growth was at manageable levels, no significant scour was found, and every anode potential reading fell within the acceptable range for effective corrosion protection.
That gave the client a baseline for each asset and a short list of items to plan maintenance around, rather than a long list of unknowns.
Delivered to the client
- High-definition video of every asset
- Imaging sonar data and Spot.On survey files per asset
- Marine growth thickness measurements at depth
- Anode potential readings at depth
- Scour assessment around each monopile and cable inlet
- A report per asset with anomalies and recommended actions
Regular subsea inspection of offshore wind farm structures is what keeps an offshore wind farm compliant and out of unplanned repair. Done with a compact ROV and a team that measures rather than estimates, it gives the asset team data they can compare year on year.
Why Atlantas Marine
What made the difference
Compact system
The V8 M500 covered nine assets without a large containerised spread, keeping the vessel requirement and the cost down.
Measured, not estimated
Marine growth thickness and anode potentials were measured at depth, so the client has numbers to trend, not a visual impression.
Operational experience
The team runs this equipment on real jobs, so it knows how to hold station on a monopile in current and how to get clean sonar and video in poor visibility.
Clean reporting
A report per asset with imagery, sonar and survey files, built for the asset integrity team to act on.
Nine structures. One compact system. Save time. No dive. No risk.
Planning a wind farm inspection campaign?
Talk to a team that has inspected monopiles, transition pieces, CPS and anodes across a working wind farm, and can mobilise a compact ROV spread in hours.
How can we help?
Tell us about your inspection campaign
Send the ROV operations team a few details about the asset, the location and the timing, and we will come back to you with how we would approach it.