Enerpac, the specialist in integrated hydraulics, have provided a solution to an engineering problem that arose during refurbishment of the Athens Olympic Stadium. The stadium’s suspended arched roof, designed Santiago Calatrava, with its two giant arches spanning 1000 feet and soaring to 262 feet, is easily the most striking part of the refurbishment. The new roof halves were built remotely so as not to interfere with the underlying Olympic Stadium. The problem then arose of how to move and position the two roof halves, each weighing 8500 tons. Enerpac proposed long stroke-pulling cylinders powered by PLC-controlled hydraulic pumps. Used for the step-by-step pulling process, these would have very little impact on the existing design. These double-acting pull cylinders are attached to shoes in a sliding and guiding system pulling the arched roof assembly step by step into the final position. Four pulling cylinders were proposed for each shoe of the arched roof assembly. Because each arch had two shoes and each shoe had four sliding pads, this meant a total of eight hydraulic cylinders were necessary to move and position each half of the roof. A two-stage PLC-controlled pump was specified to power each group of four cylinders. This arrangement offered full control of speed, acceleration and deceleration during hydraulic movement. Controlled movement is done with Enerpac integrated PLC-controlled hydraulic systems. During the roof positioning, which took place in May and June, the PLC-controlled pumps were located on the sides of each arch and carried with them during the pulling process. Each pump supplied all four cylinders with the same hydraulic pressure and the same pulling force while the stroke synchronisation was assured by the shoe structural strength. Both pumps were connected with a 1300-foot cable and synchronised by the PLC-unit to control the start and stop of the hydraulic movement of the 8500-ton roof half.