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Seafloor cable replacement in the Pentland Firth for SSEN

Fugro was tasked with maximising uptime on a project to provide touchdown monitoring and as-laid surveys for Global Marine Group as part of a 37 km, 33 kV power cable replacement for Scottish and Southern Electricity Networks (SSEN) in the Pentland Firth in Scotland, UK.

Challenge

The Pentland Firth is a body of water between mainland Scotland and the Orkney Isles which is known for its strong currents. The free-flying remotely operated vehicles (ROVs) normally used on cable projects cannot operate in currents of speed above 2.0 knots (1 ms-1), and Pentland Firth’s choppy waters often exceed these working limits, which risked extended downtime and costly delays. Therefore SSEN needed an asset integrity solution to maximise work class ROV (WROV) uptime on the project to increase efficiency without compromising safety. 

Solution

Fugro’s tracked skid system provided the solution for SSEN. Quickly attached to an WROV and deployed through a standard WROV A-frame and launch-and-recovery system (LARS), the tracked skid provides the WROV with greater stability and precise control, enabling it to operate in currents greater than 4.4 knots, over challenging terrain and at more than 27° pitch and roll.

"The tracked skid worked well. Considering some sections of the seabed along the route were challenging, to say the least, the WROV remained operational when monitoring the cable touchdown point and in stronger currents than expected.”

Operations

The tracked skid was fully utilised throughout the cable lay operations and logged 355 hours of operational time, of which 190 hours were in currents above 2 knots. Moreover, the tracked skid negotiated the rock-strewn seafloor and traversed inclines of up to 27°.

Innovative highlight

Fugro built the tracked skid WROV system to order for the Pentland Firth project, designing it to suit the FCV 600 WROVs that support and exceed the demands of deepwater operations. A key design feature was the ability to be launched by a standard LARS with no system modifications; it could also be easily disconnected to allow the WROV to quickly change from tracked skid to free-flying mode, which improved operational efficiency.

Tracked Skid 2

The compact tracked skid can be quickly attached to the WROV and deployed through a standard A-frame launch-and-recovery system

Impact

The project lasted 15 days, out of which 8 days recorded currents greater than 2.0 knots (1 ms-1). Regular WROVs cannot operate in free-fly mode in such conditions but the tracked skid solution allowed the WROVs to remain operational even in currents over 4.4 knots. In summary, Fugro’s tracked skid solution significantly improved the performance of the WROVs in the Pentland Firth, which resulted in the project being completed ahead of schedule.

Tracked Skid 1

  • Client

  • SSEN (Scottish and Southern Electricity Networks)
  • Regions

  • Europe and Africa
  • Location

  • Pentland Firth, Scotland
  • Project Duration

  • July 2020 – August 2020

335

Hours of operational time on the project

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