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One of the world's largest precision lifting tasks of land-based equipment has been successfully undertaken in Australia. An Enerpac synchronous hydraulic lifting system has been employed by G&S Engineering Services in Queensland to lift, within tolerances of 0,5 mm, a huge mining dragline weighing more than 3500 tons.

The PLC-controlled precision hydraulic system was used to lift the dragline for essential maintenance of the bearing surfaces on which the dragline swivels. It also delicately tilted the huge suspended weight to simulate different loads on the structure so bearing surfaces could be precisely machined to accommodate them and maximise the bearing surfaces' lifespan.

G&S Engineering Services used the PLC-controlled Enerpac synchronous hydraulic lifting system to simultaneously control 80 x 100-ton capacity hydraulic cylinders used to lift the dragline at Curragh Coal mine in the Bowen Basin in July.

The cylinders, controlled in groups of four around the perimeter of the dragline's base, lifted it 10 mm at a time for optimum precision and control. They raised it a total of 200 mm to allow machining between the upper and lower rails on which a bearing is placed. The system simulated actual loading on the dragline to maximise and accurately predict the life of this bearing.

The whole operation involved Enerpac specialists from Australia, Singapore and Europe overseeing work performed by G&S and Curragh staff. They were all witness to the world's first lifting of a dragline using the synchronous hydraulic system.

Draglines are probably the largest land-based equipment moving across on the face of the earth, typically ranging in size from 2500 tonnes to 6500 tons. Throughout Australia they "walk" across the surface of the land, progressing a few metres at a time as they pause to scoop huge masses of overburden to expose resources being mined.

Pinpoint accuracy The synchronous system provides pinpoint accuracy by minimising the difference between leading and lagging lifting points, ensuring optimum safety and stability throughout the entire lift. In addition to great safety and stability, the high-pressure (700 bar, 10,000psi) cylinders employed offer great weight and space savings compared with the much larger lower-pressure types of hydraulic cylinders previously used.

On-site the benefits of these smaller and lighter cylinders translate into more space under and around the job, permitting G&S Engineering Services to employ uninterrupted use of the latest laser-guided machining systems when they are machining the upper rail on which the dragline rotates.

The precision achieved by G&S Engineering Services Enerpac synchronous system is so great that it can be used to safely tilt massive objects during lifting to enable exact aligning of upper and lower bearing surfaces.