6500 ton dragline lift in Australia
The job was to remove the Marion 8750 Series B’s tub, which weighs 942t, for maintenance. This is understood to be a world-first for the mining industry.
The control point for the jacking system was a laptop computer. It proved surprisingly easy to use, while allowing jacking accuracies of multiple cylinders to within 1mm.
RCR, which provides construction and maintenance services to the Queensland and NSW coal industry, was contracted to carry out the work on the dragline over a 12 week period. The job started in July.
The challenge was to develop, in consultation with the client’s representative, engineering to jack and level the machine after it had been stepped up to the “high cam” position on the walking arms.
Two jacking frames, each with a 1000t working load limit, were used for this procedure. Each housed two 500t Larzep cylinders.
The remaining three of the seven jacks were fitted in custom-built jacking haunches at 120 degrees around the circumference of the tub to allow for the lowering and raising of the tub for the removal and installation phases.
RCR opted for a modular lifting system from Larzep that allows up to three high-capacity hydraulic power packs to be connected to a programmable logic controller. This, in turn, was controlled from the laptop computer. Larzep supplied the seven 500t lifting cylinders for the tub lift-and-split, along with an electric power pump incorporating valving controlled via a PLC – all controlled by the laptop.
Another 22 cylinders, each with 100t capacity and also from Larzep, were bought to compliment RCR’s existing stock of 100t cylinders. These were used to unload the dragline’s left hand side propel walking arm for later removal.
Larzep also flew in an engineer from Spain to work alongside RCR’s team and provided another two local engineers to oversee the initial commissioning.
Linear and pressure transducers on each cylinder let the operator see on the laptop screen the displacement of each jacking cylinder and the hydraulic pressure in each cylinder in real time. Total mass and centre of gravity also can be shown on the screen. Users even have enough control over the cylinders to tilt the load if necessary.