Green Marine were contracted by SIMEC Atlantis to carry out the decommissioning of their AR1000 test site in the Orkney Islands. This included the recovery of subsea cable and recovery of the turbine support structure (TSS) and ballast.
The first operation was to recovery 250m of cable, carry out the splice of a test head and re-laying of the site export cable. The engineering team developed lay tables Lay tables for both the recovery and redeployment of cables were established. This ensured that both vessel movements and cable pay-in were controlled, ensuring both static & dynamic cable tensions are kept within the properties of cable (SWL).
Creation of lay tables was conducted using catenary equations and Orcaflex simulations for dynamic checks. Alongside the laytables, the engineering team created mooring plans to ensure that the vessel could maintain station at key points through out the operation.
As part of the cable operations a test head was recovered to the vessel and removed. 250m of cable were then recovered to the deck, cut and a second test head was spliced on. This involved the vessel maintaining station in a tidal area for over 24hrs. The below images shows the deployment of the second test head.