Mobilis buoy refurbishment for Vattenfall
Five years ago Hydrosphere sold five Mobilis JET 9000 navigation buoys to be used as temporary navigation aids during the construction of a wind farm off Scotland’s East coast. That project was completed and the buoys spent a couple of years in storage, before the customer decided to sell.
That’s when Hydrosphere next heard about them. The new owners, Vattenfall, had bought them for the Aberdeen Offshore Wind Farm and asked Hydrosphere UK to refurbish them before they were re-installed at sea.
According to Hydrosphere’s John Caskey, the buoys had fared well in storage: “Three years offshore and another two lying around in storage might take a toll on some bits of kit, but not so the JET 9000. We already knew that these buoys were built to last; their polyethylene hull floats have a UV 18 rating, so you can expect a lifespan of over 15 years.”
Work was carried out at Peterson, Aberdeen, where Hydrosphere used their experienced team to refurbish the five buoys. Partnering with suppliers that work to Hydrosphere’s high standards of quality control was essential to ensure that the buoys were in optimal condition for delivery to Vattenfall.
One of the main benefits of the Mobilis modular system is that parts can be easily replaced without compromising the buoy in any way. As it turned out, the refurbishment project was minimal. One buoy had suffered some damage during transportation, which was repaired, and the anodes on all buoys required routine replacement.
As part of the refurbishment all lights, tracking and monitoring equipment was checked and inspected. Hydrosphere also inspected the moorings and as you would expect having spent time at sea, some components were replaced.
This was also an opportunity to upgrade the East cardinal buoy to install a Datawell wave sensor and Gill weather station. These additions have saved Vattenfall a significant amount of money, says Hydrosphere. Instead of spending upwards of £60,000 on a standalone wave monitoring buoy, they have all the technology needed on an existing asset for a fraction of the price.
Wave sensors and weather buoys are invaluable for offshore projects. A navigation buoy the size of the JET 9000 has scope for multiple uses, not just as an aid to navigation. As seen with this project, the platform is ideal for carrying a range of data sensors and equipment, and therefore it can be possible to avoid the additional costs of a data platform buoy.
While the buoy refurbishment project didn’t involve any repainting as the condition of existing paintwork was very good, Hydrosphere did give one cardinal buoy a new set of colours due to a change of role.
With annual maintenance, Caskey claims that these Mobilis navigation buoys are now fit for purpose for perhaps another 10–15 years.
By Jake Frith
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