Delta workboat is a windfarm winner

When the Shetland based operator chartered the vessel 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.

Work started with Whalsa Lass handling a six 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 3 knots of tide.

Soon Whalsa Lass was delivering water and provisions to other project vessels within the 25sq/km work area. It then conducted cardinal buoy inspections, retrieving and returning them to shore for maintenance and subsequently re-deploying them.

The vessel was also called upon for the delivery of cable protection systems and the deployment of rock bags over cables in shallow water, a four tonne bag every 14 minutes. It was also equipped as a dive support platform, with a full dive spread encompassing decompression chamber, welfare, quads, a dive shack and three point mooring. This allowed it to work with the divers moving boulders clear of the cable lay route.

A full ROV spread was also brought onboard, with a 20’ ROV container, control shack, provision of 120A power from ship’s generators and three point mooring, again whilst concurrently anchor handling.

The vessel was alsocalled upon to salvage containers lost overboard from a passing cargo vessel which were drifting and posed a collision risk to the windfarm, then transporting them ashore.

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. It also 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.

The 26m Whalsa Lass features an 11.5m beam for great stability and a shallow 2.25m draft, advantageous for bringing cables to shore. Three Caterpillar C32 TTA main engines generate 1,902 bkW to provide a powerful 37 tonne bollard pull and a speed of 10 knots. A 100 tonne winch and twin Heila3 SL 230t/m knuckleboom cranes further add to its capabilities which allowed it to make a broader contribution to the project than was first envisioned.

The windfarm consists of 73 Vesta V112 3MW turbines located in water depths of some 15m. It provides electricity for up to 170,000 homes.

By Larz Bourne