Offshore staff
HORDALAND, Norway — Vestdavit has developed a heavy-duty davit for larger offshore wind workboats to be delivered for a green-fueled service operation vessel (SOV) newbuild as part of a multiple davit contract with Esvagt.
Earlier this year, Danish shipowner Esvagt announced the order at Turkey’s Cemre Shipyard of the world’s first SOV to operate on green fuels under a joint newbuild project with compatriot offshore wind operator Ørsted.
Powered by batteries and dual-fuel engines, the 93-m-long vessel will be capable of sailing on renewable e-methanol produced from wind energy and biogenic carbon, leading to a significant annual reduction of CO2 emissions. The SOV is lined up to work at Hornsea 2, the world’s largest offshore wind farm, off the UK’s east coast after scheduled delivery in late 2024.
Decarbonization
Vestdavit is participating in this project to decarbonize offshore wind operations after being selected by Esvagt to provide a total of five davit systems for the vessel: two large FF-30000 dual-point workboat davits featuring a solution for flexible hook distance as well as a pair of L-3500 liferaft davits and one PLRH-5000 davit for fast rescue craft.
The FF-30000 system, with heavyweight lifting capacity of 25,000 kg, has been specially adapted from an existing Vestdavit design to handle Esvagt’s newly in-house developed Safe Transfer Boat 15 (STB15), a workboat that is longer, wider and heavier than existing such craft used in the offshore wind sector.
The STB15 has a length of 15 m versus the industry standard of 12 m, and it is intended to provide a more stable and comfortable working platform for technicians servicing wind turbines, thus giving operational benefits.
Boat-handling challenges
“But the greater dimensions and weight of this workboat pose handling challenges for existing davits to ensure that personnel and equipment can be deployed safely and reliably under variable sea conditions,” according to Bjørnar Dahle, Vestdavit’s sales and business development director. “Therefore, Vestdavit was required by the client to devise a more suitable technical solution based on the basic design and shape of an existing davit, while working within the structural and practical constraints of the ship design, which meant clearing several obstacles to find a workable concept.”
The solution was to adapt the so-called F-frame (FF) system that comprises a large frame with no structure behind or underneath the daughter craft, which allows for greater flexibility in the shape and volume of the boat being handled, with the main structure aft/forward of the boat.
Flexible hook distance
In addition, the FF-30000 has two lifting points for dual-point lifting of the daughter craft with a dual-winch system consisting of two winches each with autonomous tension function so they can operate independently of each other.
“This dual-point lifting functionality permits a wider weather window as the vessel can still launch and recover daughter craft even in rough sea conditions,” Dahle said.
But he said probably the best feature of the system is the flexible hook distance function whereby the aft lifting wire can be adjusted forward to cater for smaller boats with a narrower hook distance.
This enables the system to also operate as a single-point davit from the aft lifting point to bring onboard the smaller and more available STB12 workboat as a temporary replacement for the STB15 if the latter needs to be serviced.
09.07.2022
