One of Helix Energy Solutions Group’s newest assets, the T1200 trenching unit, has completed its first mobilization and is currently working on its first offshore project in the southern North Sea.

The T1200, operated by Helix ESG’s robotics business unit Canyon Offshore, began its first trenching job in early July at the Sheringham Shoal Offshore Wind Farm and on its first dive spent more than 30 consecutive hours on the bottom. Since then, the T1200 has continued to operate on this challenging project with very little downtime.

”Most trenchers suffer teething problems post-delivery, however, T1200 has really hit the ground running,” said Gary Aylmer, Canyon Offshore’s General Manager of Renewable Energy. “This is due in part to using a proven trencher (T750) as a bench mark, the time and effort from all involved in design and assembly and conducting extensive in and out of water testing at the manufacturer’s test tank which allowed the complete system to be run until all the teething problems were ironed out, avoiding costly delays post-delivery”

The T1200 was built in the UK by Forum Energy Technologies’ Perry Slingsby Systems ROV brand. While the project called for the inter-turbine power cables to be trenched and buried at a depth of 0.5m (1.6ft), the T1200 out performed all other trenching units used to date on the field by burying the cables beyond specification in a single pass in stiff clay in the range of 75-250 kpa.

The 88 turbine Sheringham Shoals offshore wind farm has an area of approximately 35km² and is located about 17km to 23km (10 miles to 14 miles) offshore of Sheringham, North Norfolk UK. The water depth in the area varies between 15m and 22m (49ft and 72ft). The wind farm is owned equally by Statoil and Statkraft through joint-venture company Scira Offshore Energy Limited, the installation of the cables is by the Dutch Marine Contractor VSMC part of the Royal VolkerWessels group who have contracted the burial to Canyon Offshore.

The T1200’s design was based around the time proven T750 trencher but has over 50 percent greater power and the capacity to trench larger diameter products (36”) to burial depths of 3m (10ft), depending on soil strength, in water depths of up to 3,000m (10,000ft).

• Mid 2010 – Canyon starts extensive technical review and evaluation for a 2nd generation T750 trencher
• Early January 2011 – ROV manufacturer Forum’s Perry Slingsby Systems awarded contract to start detailed engineering and design of T1200.
• June 2011 – ROV manufacturer Forum’s Perry Slingsby Systems awards sub-contract for construction on the duplex-stainless steel chassis for the T1200 in the UK.
• February 2012 –T1200’s hydrodynamic buoyancy shells, duplex stainless steel chassis and enormous tracks are completed.
• March 2012 – The T1200 components are assembled and the vehicle undergoes its first water tank trials.
• May 2012 – The T1200 is mobilized for sea trials and lowered into the open sea for the first time.
• June 2012 – The T1200 is loaded onboard an ROV support vessel and heads out to the North Sea.
• July 2012 – After reaching the Sheringham Shoals offshore wind farm the T1200 begins its first project to trench and bury power cables from the wind farm to shore.