This article is part of the series about tools and equipment specifically designed by Temporary Works Design (TWD) to enable the safe and efficient installation of offshore wind turbines in deeper waters from floating installation vessels.
Introduced to the industry in 2018, the Hammock cradle makes it possible for the efficient transport of XXL monopile foundations with different diameters without having to make any changes to the seafastening spread. The Hammock can handle the largest monopiles currently envisaged, and cope with a variation of up to 4 meters in diameter. The significant cost savings following from this flexible seafastening, make it the ideal solution for contractors targeting multiple transport or installation projects of XXL monopiles
Since the introduction TWD has upgraded the design to cope with even bigger transit accelerations. The new generation floating installation vessels will benefit from the ability to sail with higher sea-states, which is particularly beneficial now windfarms are being built further offshore. Not only will installation vessels take advantage from the upgraded hammock design, but also breakbulk contractors, looking to transport XXL monopiles overseas, will benefit from the optimal use of their heavy transport vessels.
The basic principles of the Hammock cradle are the same as for those of the hammock used on sunny days in the garden:
The hammock removes the necessity to change a seafastening spread required for the transport of a 9m diameter monopile foundation used on one project, for example, for a spread made for 10m diameter monopile on the next project. This also gives the flexibility to cope with large variations of diameters within the same project.
The upgraded cradle design consists of a steel frame with a belt of rubber strips supported on steel cables strung across the cradle. This prevents the monopile from swinging back and forth. When the monopile is hoisted into the seafastening, the weight causes the frame to hinge around the monopile and closes, holding the pipe securely, and assuring that it’s integrity will be maintained.
Two hammocks are needed for each monopile. On a conventional transport and installation vessel, the design makes it possible to place two frames side by side and to mount a second set of hammocks on top. No heavy bridge-like steel construction is required, providing the additional benefit reducing the amount of steel required.
In the coming weeks we will share updates on these individual developments through our website and LinkedIn channel, so stay tuned!
Triggered your interest? Visit our stand, 1.502 at Offshore Energy Amsterdam on 8 and 9 October 2019, and learn more about our Transport & Installation Engineering in Offshore Wind.
#Floating Installations, Hammock, seafastening, Offshore Wind, XXL monopiles