A damaged ball mill causing unscheduled outage and lost production at one of the world’s largest gold mines was rapidly restored to operation with minimal delays, thanks to technical services company Furmanite, which minimised downtime and avoided massive costs and logistical issues.
Damage to the ball mill’s trunnion journal thrust face required remedial work to remove scoring some 2-3 mm deep on the thrust face and restore a sound surface for the thrust pad to run against.
Removal of the trunnion journal and thrust face to undertake the necessary repairs in a machining workshop was not a viable option (extremely expensive and logistically complex given the mine’s remote location).
Instead, Furmanite was called in for its specialist in-situ machining experience and expertise.
Some 3mm of material had to be removed from the thrust face over an area of some 80mm wide by 2 metres diameter to produce a tight specification surface finish — an onerous requirement made considerably more challenging by the very tight space envelope available.
Furmanite had to design and build a bespoke machine to be able to undertake the work required in the confined space available.
Having designed the machine and sourced the components, the machine was built by Furmanite over a weekend and mobilised to site in a matter of days.
On site, Furmanite technicians removed the trunnion bearing cover and bolted the machine to the remaining lower side trunnion seal housing flange.
The thrust face was then machined using a large diameter side and face cutter fitted with tungsten tips, driven by a hydraulic motor and power pack.
Using the same machining base rotated in part at 45 degrees, a tungsten tipped bull nose cutter was then used to reinstate the corner radius interface between the trunnion journal and thrust face.
After radius polishing, all machined surfaces were checked using crack detection Magnetic Particle Inspection equipment.
Furmanite Australia WA sales manager Kevin Hatten pointed out: “The entire machining operation, including set up and dismantling, was successfully completed in just two shifts (less than 24 hours), representing a huge advantage over any other repair options which would have involved many weeks additional downtime, massive cost, and a major logistical exercise.
“Furmanite has the capability and expertise to undertake machining projects in-situ, to workshop tolerances.
“And getting the ball mill operational again quickly represented considerable savings in lost production for the operator. In this case you could say it was ‘worth its weight in gold’. This is typical of the service we’re able to offer, applying our range of technical services to help operators maximise asset uptime.”