The pile Gripper Arms, installed this week, stabilize 6m diameter 650t steel piles as they are driven into the seabed by the MPI Discovery installation jack up vessel. Installed on the vessel’s stern below deck level, they provide resistance to wave, tide and current forces in water depths of up to 40m. Their position and the additional control this provides significantly reduces installation times providing a valuable enhancement to the Discovery’s capability, Houlder said.
“The challenge of handling offshore wind turbine piles has grown along with their size.” commented Frederic Perdrix, Chief Technical Officer, as Houlder delivered its latest piece of equipment.
Frederic added, “MPI’s specific requirement was a great opportunity for our engineers to demonstrate their ingenuity and ambition. The result combines heavy duty structural, mechanical and hydraulic engineering with precision control.”
The hydraulically driven arms, weighing circa 90t each, have three main cylinders: one to deploy the arms from their stowage position and two to provide a horizontal gripping motion able to withstand up to 150t of horizontal load in any direction. These cylinders are actuated by touchscreen and single joystick controls that allow an operator to engage the arms, close the jaws and then maintain the pile in the vertical plane as it is hammered down. Any risk of operator caused collision is reduced through automated constraints based on the pile diameters.
Houlder’s Project Manager, Andy Lovell, added “The contract was managed by a dedicated team from Houlder’s Tyneside office and used engineering capability from company offices across the U.K. Houlder acted as MPI’s design and engineering partner from initial concept design through to delivery. This included deck arrangements which, given the constraints of a working installation vessel, focused on minimizing the required footprint. The company also designed and validated the foundations and required deck modifications.”