Rotech Subsea wraps up cable work at UK offshore wind farm

Rotech Subsea, a provider of subsea tools to the energy industry, has completed cable de-burial, cut and recovery, and cable burial operations, at an offshore wind farm in UK waters.

Illustration (Courtesy of Rotech Subsea)

Rotech did not disclose any other details about the project, but it did say it is “one of the world’s largest offshore wind farms”.

The UK company mobilized its RS1-3 hybrid controlled flow excavation (CFE) tool to carry out the trenching scope of works and its proprietary RSG-C IRM tool to complete the cable cut and recovery operations.

The Aberdeen-based company has pointed out that the project, completed in late 2022, saw Rotech Subsea’s RS1-3 de-bury 7.5 kilometers of export cable.

Multiple cuts were carried out by the trenching and excavation sector company with scrap cable recovered to the deck of the support vessel, after which new cable was laid and buried to 1.5 meters (ToP).

Operating in water depths ranging from 4-17 meters, and soils ranging from medium dense to very dense sand and soft clay to very stiff clay, 7.5 kilometers of cable buried at 3 meters below mean sea bed level (MSBL) was de-buried by the precision RS1-3 hybrid CFE tool.

Rotech explained that its RS1-3, developed in-house by the company, has a standard operating depth range of 1-300 meters, a speed of up to 14 meters per second, and a controlled flow rate of 0-14,000 liters per second.

After carrying out the de-burial of the cable, the RSG-C tool was deployed on grab, cutting, and recovery operations.

Positioned using a tool-mounted USBL transponder and survey nav screen in the Rotech control cabin, the cable was located using the tool-mounted sonar head.

Rotech said that once located and grabbed, cable-cutting operations took less than 15 minutes, with the process repeated at multiple locations along the cable. The RSG-C tool then recovered the cable to the deck.

“This was another successful deployment for our RS1-3 and RSG-C tools which are in high demand globally for cable trenching and IRM scopes. Cable de-burial was completed in one pass at vessel speeds from 2–6 meters per minute and in total 14 cuts of the 200 millimeters diameter cable was completed, each taking between 5–15 minutes, said Stephen Cochrane, Director of Subsea at Rotech Subsea.

“Our RS1-3 jet trencher, developed and built in-house, was specifically selected for the de-burial and burial (at a depth of 1.5 meters top of cable) operations of the new cable because very stiff clay conditions were expected. With an outlet pressure of 350kPa, the tool completed the work scope successfully and efficiently with burial completed in two passes at vessel speeds from 1–4 meters per minute.”

From the most recent company-related news, it is worth mentioning that Rotech Subsea carried out the cable cut and recovery operation at an offshore wind farm in Denmark using its proprietary RSG/C tool.  

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