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Rotech Subsea launches entity in Taiwan

4C Offshore | Tom Russell
By: Tom Russell 06/09/2022 Rotech Subsea

Aberdeen-based Controlled Flow Excavation (CFE) & Suspended Jet Trenching specialist Rotech Subsea has announced the establishment of a new entity in Taiwan. It follows cable trenching and Seabed levelling campaigns in Taiwan’s offshore wind sector dating back to 2019 - with further contracts in the pipeline into 2023.


In June 2022 Rotech Subsea completed its latest major scope of work in the country. Having been contracted by a marine infrastructure player to assist with de-burial & cable trenching operations on a key offshore wind farm, Rotech mobilised its TRS1LD jet trencher in early May 2022.

The TRS1LD tool was deployed by ship’s crane into water 30-55m deep to carry out de-burial of wet stored export cable sections, export cable remedial burial works, inter-array cable remedial burial works, and inter-array cable backfill works. With outriggers and clump weights set up forward and aft of the trenching tool and connected with running lines to control orientation, the TRS1LD remained suspended above the seabed / cable to complete all trenching operations.

The vessel’s DP positioning system was used to move the trenching tool along the cable routes with USBL transponders fitted to the tool providing accurate data on the location of the tool at all times. Trench depth was monitored real time using a tool-mounted sonar imager with the client carrying out their own survey to confirm that the completed trenching ops met the required specifications.

Rotech Subsea Director of Subsea, Stephen Cochrane, said: “This was a technically challenging scope for a valued client and we were delighted to deliver it on schedule and on budget.

“To avoid possible free span, the de-burial and remedial trenching were completed using minimal power. The TRS1LD trenching tool has a maximum outlet pressure of 140kPa and a max jet flow of 2,600L/s. To establish the appropriate power level our crew completed trials on 10m sections at various levels (between 30-80%) and at various standoff distances from the cable/seabed (1.3m standoff from cable and 2-4m offset).

“Once the trials had been completed we were able to complete the actual trenching scope with the optimal settings to achieve the client’s desired trench specification so there were no ensuing issues with the schedule.”


Rotech stated its TRS1LD unit experienced variable soil conditions at the site, from silty sand to clay and very dense gravel with cobbles. In currents of 2Kts and general sea states of 0.5-3m progress was made at 2-5m/min with BOT depths ranging from 0.35-1.20m.

In March 2022 Rotech Subsea deployed its TRS2 Sand wave levelling system, RSBG boulder grab tool and TRS1LD shallow water jet trencher at the
ChangFang and Xidao Wind Farm to conduct a sandwave clearance, debris de-burial and boulder removal scopes which is still currently ongoing.

In July, Rotech subsequently mobilised a further TRS2 to the region execute a sandwave clearance campaign at the
Yunlin site, a scope which is again, ongoing.

For more information on offshore wind farms worldwide, click here.

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