Direct Pipe machine lifted from sea in Scotland 14 Dec 2017

Pipeline contractor Stockton Drilling has completed multiple lifts of a 28 tonne, 18m-long Herrenknecht Direct Pipe TBM that was working beneath the sea at the Beatrice Offshore Windfarm project at Portgordon, Scotland. The lifts were performed using a Modulift custom lifting beam mounted on a rented barge.

The TBM is lifted by the 120 tonne capacity crane

The Herrenknecht Direct Pipe system was chosen, using an AVN1000 micro tunneling machine, to install two 48-inch by 450m steel landfalls to carry high-velocity cables. This system lines the tunnel as it advances, and was selected due to difficult geology at the site.

In what is believed to be a world-first, the TBM was recovered from the sea after each drive. Divers attached the 34 tonne capacity, 16.6m-long beam designed by Modulift to the TBM so that a 120 tonne capacity crane, placed on a rented jack-up barge, could lift it out of the water and place it on a multi-cat for return to the harbour.

“The product satisfied the requirements and standards set out at the beginning of the project,” said Patric Ridge, Business Development Manager at Stockton Drilling. “Lifting the TBM in one piece was a swift, safe and efficient process. Weather conditions had to be just right in order to perform the lift, so it had to be completed in a timely and safe manner. The process was complicated by a depth of water less than 10m.”

The TBM was submerged for less than 48 hours for each 420m drive, approximately half-a-mile offshore. Surface alluvial comprising pebbles and cobbles and overlaying bedrock of weathered sandstone prevented the use of more traditional horizontal directional drilling methods. The beach area around the landfall site is also a designated Site of Specific Scientific Interest (SSSI). Stockton has retained the beam for future use.

The Beatrice Offshore Windfarm project is one of the largest private investments ever made in Scottish infrastructure and produces 584 megawatts from 84 turbines situated in the outer Moray Firth, powering approximately 450,000 homes at a cost of £2.6 billion to its investors SSE, Copenhagen Infrastructure Partners and Red Rock Power.