Processing

Upgraded bearings double service life of screens

After using the Upgraded Explorer for more than 15,000 hours without problems, one of WS Tyler’s mining customers significantly boosted efficiency by extending its time-based preventative maintenance programme to just once every three years.

BACKGROUND

Maintenance represents a significant proportion of overall operating costs in the mining and quarrying sector. As a result, mining and quarrying organisations are increasingly looking to contain and reduce costs on machinery such as vibrating screens, to sustain profitability primarily through improvements in machine performance, reliability and efficiency.
In many instances, the key to achieving these goals lies not only in the performance of large machinery but also in smaller components, including bearings and seals.

{{image2-a:r-w:250}}If these essential but frequently overlooked components fail to function, then overall system failure and downtime is inevitable. Heavy loads and harsh environmental factors place extreme demands on vibrating screens and their moving components. As a result, frequent and/or unexpected component failures can lead to costly maintenance situations, with unplanned downtime and loss of valuable productivity.

THE OPPORTUNITY

A major copper mine in Arizona was experiencing a series of costly bearing failures on the vibrating screens at its crusher plant. The failures were occurring every 5000 to 6000 hours due to a lack of lubrication, contamination or ineffective lubrication, and had become so routine the mine was scheduling a replacement or rebuild of each bearing assembly in the screen every 7500 hours, as part of a time-based preventative maintenance plan.

In 2011, as SKF was preparing to launch its Upgraded SKF Explorer bearing, it offered WS Tyler – a long-time user of SKF Explorer bearings for vibratory applications – some prototypes for testing.

WS Tyler chose to install the prototype Upgraded SKF Explorer bearings in an F-class screen destined for use at the Arizona copper mine that was experiencing costly bearing failures.

Upgraded SKF Explorer bearing steel is manufactured with a patented heat treatment to increase material hardness and provide a refined microstructure, while maintaining a high level of ductility.

The result is increased service life, reduced internal wear and a high level of fracture resistance in poorly lubricated and highly contaminated application conditions.

The bearings supplied to WS Tyler were Upgraded SKF Explorer bearings for vibrating applications.

SKF Explorer spherical roller bearings bring the benefits of the enhanced bearings to vibrating screens, resulting in lower maintenance and repair costs, reduced downtime and improved safety. SKF offers a full range of SKF Explorer spherical roller bearings for vibrating screens (VA405 and VA406 suffix), all with hardened two-piece outer ring guided cages, C4 radial internal clearance and reduced bore and outside diameter tolerances.

The SKF Explorer VA406 spherical roller bearing with PTFE-coated bore provides additional benefits in vibrating screen applications, because the PTFE coating eliminates fretting corrosion between the shaft and the bearings. All standard spherical roller bearings, spherical roller thrust bearings and CARB bearings benefit from the upgraded manufacturing process in bearing steel, which increases bearing life and reliability, especially under poor application conditions.

THE SOLUTION

After using Upgraded SKF Explorer bearings for more than 15,000 hours – double the span of the previous time-based maintenance schedule – the mine was able to modify and extend its time-based preventative maintenance plan to a period of three years. This has resulted in maintenance parts savings of $US23,660 per machine, plus no production loss at a cost of more than $US15,000 per hour.

Lyndell Fuller, general manager of Haver & Tyler Grand Canyon, a partner with WS Tyler, oversaw installation of the F-class screen equipped with the prototype Upgraded SKF Explorer bearings at the mine’s crusher plant in 2011.

“The mine is very pleased with the support our partnership with SKF gave it in helping to solve this critical bearing and lubrication issue,” Fuller said.

SKF’s global industry manager for mining, mineral processing and cement Keith Meyers said: “The F-class vibrating screen featuring the Upgraded SKF Explorer bearings is tested and proven to offer nearly double the service life in poor lubrication conditions and twice the service life in contaminated conditions.

“The operation of the F-class with Upgraded SKF Explorer bearings at the Arizona copper mine matches these results.”

Source: SKF/Minett Media

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