December 6 - Longitude Engineering has been working with Rampion and its contractors to develop a new analysis and modelling process to understand why large monopiles oscillate in relatively small wave heights.
Monopile foundations are increasing in size as wind farms move further offshore; this research was undertaken to increase the operating window for their installation.
The Rampion Offshore wind farm is currently under construction by E.On, off the UK's south coast. The developers recognised that this oscillation could cause installation problems and invited Longitude - a division of LOC Group - to help it understanding the problem and to assist with developing solutions and more rigorous guidelines.
"The piles used for the Rampion site weigh up to 850 tonnes which is close the working limit of the crane. Dynamic effects can lead to much larger forces than purely static loads and so it was important to understand the conditions which caused the piles to oscillate," said Peter Kingsland, principal consultant and naval architect at Longitude. "We developed a numerical model of the pile and the rigging which we ran under a variety of conditions."
Longitude oversaw a series of tests and processed data gathered by the jack-up installation vessel to measure the motion of the monopile foundations. "This allowed us to develop a robust set of operating guidelines which gave confidence to Rampion and its marine warranty surveyors that pile installation would remain safe," said Kingsland.
Longitude worked with the manufacturers of the crane tugger winch control system to numerically model its functionality. This allowed for the development of an enhanced control system that would sense and damp down the motion of the piles.
Longitude said this technology is the first of its kind to be developed and applied to the offshore wind farm sector and has the potential to be used in a variety of other offshore applications.
Kingsland concluded: "In effect, working closely with Rampion and its contractors, we were able to widen the safe operating window to give more flexibility to the installation process."