05.12.2003

Set in stone

The Netherlands-based high pressure hydraulics specialist Enerpac, recently provided all the lifting power to main contractor, NESCO, during construction of the world’s largest concrete blocks designed to protect the Cartegena Port harbour in Southern Spain from violent ocean conditions.

Each enormous 70 x 35 x 35 metre concrete block was produced in a huge catamaran-style concrete block builder. Purpose-built for the project by NECSO, the “KUGIRA” block builder is capable of producing one of the super-sized blocks every seven days.

The “KUGIRA” uses a sophisticated hydraulic integrated system to lift and lower a so-called ‘construction umbrella’ that is responsible for holding the block construction formers. A total of 15 sets of stage-lifting hydraulic units align each side of the catamaran which are operated by 3 high-flow power sources and controlled by a synchronized PLC system. It is these stage-lifting hydraulic units that operate the 35 metres wide x 70 metres long umbrella, which is shaped to form the blocks, including internal cells for stiffness and valves for controlling the sinking process.

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The near complete concrete block is almost ready to be dragged from the KUGIRA block builder.

The shear size of the concrete blocks and the umbrella structure means that twisting and locking of the umbrella between the catamaran walls is a constant risk. So to keep the risk to a minimum, Enerpac supplied a fully PLC controlled synchronized hydraulic integrated system, designed and built at its European Construction Centre of Excellence.

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Each climbing unit consists of two, 63.5 tonnes double acting cylinders and two, 18.14 tonnes locking cylinders.

Each of the 30 climbing units incorporate an Enerpac hydraulic system, which comprises two long stroke hydraulic double acting cylinders of 63.5 tonnes capacity and two double acting hydraulic locking cylinders of 18.14 tonnes.

The long stroke cylinders are used for the actual lifting and lowering process and inform the central PLC system of the plunger’s position through a built-in sensoring system. The locking cylinders also include stroke sensors that signal their position to the PLC system. During the lift, the PLC system processes all the data sent via the stroke sensors and communicates it back to the pumps, while valves control all 120 cylinders in all 30 climbing units. The locking cylinders are used to fix the climbing units during the climbing process.

All movements throughout the phase of the lift can be closely monitored through the main PLC system’s touch screen user interface. The overall lifting and lowering accuracy of the entire system is 0,01 millimetres.

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A tug boat drags the massive completed 70 x 35 x 35 metres concrete block to its final destination in the Cartegena port.