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.
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.
