UK-based Delta Marine’s vessel Whalsa Lass has demonstrated its versatility during operations on the large wind farm off the coast of Grimsby, UK, for one of the “big six” energy contractors.

The wind farm consists of 73 Vestas, Denmark, V112 3MW turbines located in water depths of some 15 metres and is now providing electricity sufficient to power up to 170,000 homes.

When the Shetland-based operator chartered its Damen 2611 Multicat for a basic remit to serve as anchor handler for the cable laying vessel it had no idea what further scope of services the vessel would be called upon to perform.

The 26-metre Whalsa Lass features an 11.5-metre beam for great stability and a shallow 2.25-metre draft, advantageous for bringing cables to shore. Three Caterpillar, Germany, C32 TTA main engines generate 1902bkW to provide a powerful 37-tonne bollard pull and a speed of ten knots. A 100-tonne winch and twin Heila, Italy, 3SL 230t/m knuckleboom cranes further add to a specification which informed client and operator alike that the vessel was capable of making a broader contribution to the project than was first envisioned.

Work started with Whalsa Lass handling a six-tonne by 7.5-tonne delta flipper anchor spread for the cable lay vessel, with the anchors pre-laid and the Multicat hooking up to cable lay vessel wires in up to three knots of tide. Soon Whalsa Lass was delivering water and provisions to other project vessels within the 25-square-kilometre work area. She was then conducting cardinal buoy inspections, retrieving and returning them to shore for maintenance and subsequently redeploying them. She was called upon for the delivery of cable protection systems and the deployment of rock bags over cables in shallow water, deploying a four-tonne bag every 14 minutes.

The vessel could be equipped as a dive support platform, with a full dive spread encompassing decompression chamber, welfare, quads, a dive shack and three-point mooring, all whilst still conducting anchor handling duties with the dive spread on board. This allowed her to work with the divers moving boulders clear of the cable lay route. A full ROV spread was also brought on board, with a 20-foot (six-metre) ROV container, control shack, provision of 120A power from ship’s generators and three-point mooring, again whilst concurrently still anchor handling.

GRAPPLE

Also performed were PLGR works, dragging a grapple train along the cable route checking for other obstructions which could affect the subsequent cable lay. Whalsa Lass was even called upon to salvage containers lost overboard from a passing cargo vessel which were drifting and posed a collision risk to the wind farm, then transporting them ashore.

Delta Marine created method statements, risk assessments and storyboards for all the above tasks, reducing the workload for the client’s management and minimising delay to works proceeding. Delta sourced all rigging and anchors, replaced all worn or damaged components and provided a weekly inventory to the client detailing the location and condition of each individual component. Delta even extended the push knees at Whalsa Lass’s bow, allowing crew transfer vessels to push on for optimised safe passage of project personnel whilst on site.

Such comprehensive efforts by Whalsa Lass and Delta Marine did not go unnoticed. The client’s cable package manager told Delta: “All your efforts have been successful and executed safely and professionally. It was a pleasure having you and your team involved in mobilisation and execution meetings to gain your advice and input. Your team’s positive attitude and ambitious nature have prevented vessel and project down time on a number of occasions. We always knew that the task would be executed professionally when given to Whalsa Lass.

“From the entire construction team we would like to thank you and your team for all your hard work and efforts.”