Offshore staff
ABERDEEN, UK — Rotech Subsea has completed cable de-burial, post-lay and remedial trenching on an unnamed wind farm offshore Taiwan.
The program involved deployment of the company’s TRS1 LD jet trencher in water depths of 30-55 m and currents up to 2 Kts. The work scope covered de-burial of wet stored export cable sections, export cable remedial burial, inter-array cable remedial burial works, and inter-array cable backfill.
Rotech operated the trencher in sea states of 0.5 - 3 m off the vessel’s starboard side using the ship’s crane with outriggers and clump weights installed forward and aft of the trencher and connected to it with running lines to control tool orientation.
Using the vessel’s DP system, the trencher was moved along the cable route with USBL transponders providing location data. The team monitored and verified in real time de-burial progress and trench depth for burial works using a sonar imager.
Rotech director of Subsea, Stephen Cochrane, commented that although the trencher has a maximum outlet pressure of 140 kPa and a max jet flow of 2,600l/s, in this case de-burial and remedial excavation was undertaken using minimal power to avoid possible free-span.
Main problems were coping with variable soils with silty sands, clays, and dense gravel with cobbles.
10/3/2023
