December 2023

Fast-track cable replacement for offshore wind farm

MDL has supported DEME in a quick-turnaround replacement of a damaged cable on a North Sea wind farm offshore Belgium.

The scope covered transpooling of array cables between the shore and the vessel, using MDL’s portable flex-lay equipment and expert field service personnel. The operations were carried out at the client’s quayside facility in the Netherlands, within 5 days of MDL receiving the enquiry.

In phase one of the operations, a new 33kV submarine array cable, at 2400m length, was loaded onto the carousel on-board DEME’s Offshore Support Vessel, the Viking Neptun. The vessel then sailed to the wind farm to recover the damaged 2200m cable and perform the replacement.

Subsequently, the vessel returned to port where MDL transpooled the excess length of the new cable onto a storage reel. The damaged cable was then spooled on top of the new cable for ease of storage and shipment.

To carry out the scope, MDL mobilised a complete transpooling package, consisting of a 2-track tensioner, 3.5m overboarding chute and under-rollers.

The MDL TTS-2/90 Series Tensioner is a 2-track system, with 16Te line-pull at 0.09 CoF (Coefficient of Friction) and 3.35m track contact length – larger than comparable systems available on the market. The tensioner’s increased track contact length allows a higher line-pull to be maintained by applying less squeeze to the product, as the squeeze load is spread over a larger area. This is particularly beneficial for delicate products with low allowable squeeze, such as cables.

By providing the transpooling package on a short turnaround, MDL enabled the client to swiftly replace the damaged offshore connection cable and by doing so, restore full power generation capacity while minimising revenue loss.

Sarah Purvin, MDL Project Manager, commented:

“Our extensive transpooling expertise, coupled with our portable and versatile equipment fleet ensured successful execution of this fast-track project.

“This achievement is an example of MDL's adaptability in different markets, mirroring the vessel’s versatility where MDL spreads have been deployed on various flex-lay scopes in the past.

“Handling cables with special care is critical as cable damage can lead to substantial cost increases for wind projects and a considerable percentage of these inter-array and subsea cable failures can be attributed to the installation process.

“Our tensioners feature a Failsafe Grip technology, ensuring a consistent, secure hold on the product at all stages. This technology ensures that the squeeze is precisely calibrated, striking the right balance between firmness and product protection and preserving its integrity."