Rotech Subsea has completed “challenging” cable de-burial, cut and recovery works at the Triton Knoll offshore wind project in the UK for a dredging and marine contractor.
The Aberdeen-based company deployed its RS2-3 Hybrid controlled flow excavation (CFE) tool to complete the de-burial of approximately 500 metres of cable, with its RSG-C tool completing the cable cutting at both ends and recovery to the vessel’s deck.
Operating in water depths of 12-15 metres, Rotech’s RS2-3 was launched into the North Sea by vessel crane where it was suspended, traveling along half a kilometre of cable to complete de-burial operations.
With a total excavation depth of two metres required, the depth was monitored in real-time using a tool-mounted sonar imager, with the de-burial completed in two passes, Rotech said.
Launched from the vessel stern, the RSG-C spread of equipment grabbed, cut and recovered the de-buried cable to deck.
“With hard soils expected, this promised to be a challenging project. In preparation we deployed an extra RS2 excavator to have on standby to give the option of using the tools in twin TRS2 configuration to give maximum flow,” said Rotech Subsea director of Subsea, Stephen Cochrane.
“Despite hard, sticky clay experienced, the works were carried out in just two passes, one with the RS2-3 hybrid solution, which boasts a maximum outlet pressure of 300kPa and a max jet flow of 4000L/s, and one pass with the TRS2 configuration capable of 8000L/s of flow.”
Triton Knoll comprises 90 Vestas 9.5 MW turbines located offshore Lincolnshire which were commissioned at the beginning of this year.
The 857 MW offshore wind farm represents an investment of around GBP 2 billion that includes the construction of the project and the grid connection.
It is jointly owned by RWE (59 per cent), J-Power (25 per cent) and Kansai Electric Power (16 per cent). RWE led the development and construction and will also operate and maintain it on behalf of the project partners.