N E W S R E L E A S E from FURMANITE INTERNATIONAL
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Ore mine sees stacker life extended by specialist machining
When a slew ring bearing failed on a stacker at an Australian iron ore mine, Furmanite – the global speciality services company geared to maximising asset uptime – was called in to work round the clock to ensure highly accurate surface tolerances on the slew bearing mounting surfaces. The achievement effectively extended the life of the stacker, by avoiding the risk of premature bearing failure had a new bearing been installed on out-of-tolerance surfaces.
Rapid response was required as the failure of the bearing resulted in the stacker being out of service, and Furmanite mobilised four specialist technicians to site to enable the work to be completed in-situ in just four days, minimising delays.
The challenging conditions (the distance between the top and bottom faces to be surveyed and machined was less than 400mm) and onerous tolerances specified (accuracy to within 0.10mm per linear metre) meant that highly sophisticated machining skills and technology were needed to undertake the work and achieve the required results.
Furmanite brought in specialist low profile circular self-levelling machine (CSLM) technology, capable of machining circular structures up to 24 metres diameter to extremely high levels of accuracy, to workshop tolerances and exceptional overall flatness, on-site.
The 3.9 metre upper and lower slew bearing mounting faces were visually inspected and surveyed using laser technology, which revealed the upper face to be out of specification, with the total flatness envelope exceeding the maximum tolerance of 0.40mm over 180 degrees.
Furmanite Australia national sales manager Jim Friel explains that the CSLM consists of a wheel-mounted milling box/cutter that rolls on the face being machined as it rotates round a central pivoting system. A datum ring mounted around the central pivot is used as a reference and, with the use of electronic probes, the milling head is continuously adjusted during machining, for high level accuracy.
“The machine centre spider was installed and bucked in to plane of best fit, so as to minimise the amount of metal to be removed from the upper face,” Friel said. “The machine was then installed, with the milling cutter fitted and the hydraulics and electronics plumbed and connected, and the upper face was machined flat, with level checks carried out during the process using a box machine level accurate to 0.10mm per metre. Post-machining surveys showed the face to be well within the 0.40mm over 180 degrees specification.”
Cross checks with the lower face, however, (which should have corresponded with the upper face) revealed a discrepancy, which was found on further investigation to have a fall of some 0.75mm from inner to outer circumference. The cutting head was therefore turned over and positioned to machine the lower face – with post-machining surveys, using an independent dial test indicator and machine level checks, confirming the face to be well within specification.
A post-machining graph showed the final flatness to be less than 60% of the allowable 0.40mm total flatness over 180 degrees. Both slew bearing faces thus conformed to specification for the new bearing to be installed and perform effectively for the duration of its design life.
“This is typical of the service we are able to offer, using our extensive engineering skills and technologies to help our customers minimise downtime, representing often substantial savings,” Friel pointed out.
For further press information please contact:
Sarah Manwaring-White, Keep in Touch Ltd
Tel: +44 (0)1451 844 488, Email: sarah_mw@keepintouch.co.uk
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Issued on behalf of Furmanite Australia