A major gold mine in NSW’s central west is turning to plastic rollers in response to high steel roller failure rates.
At the mine, conveyor roller failure generally occurred due to advanced wearing of the steel shell. This created further issues as failed rollers can potentially cause extreme damage to the conveyor belt.
According to site management, the steel V-Return rollers with a 5mm thick shell on the site’s main incline continually failed in between planned shutdowns.
Significant carry back was building up on the rollers which rapidly increased shell wear and caused extensive roller failure and time lost on unscheduled stoppages for maintenance and repairs.
Tackling the roller failure issues
The mine operates four main incline conveyors, all of which are steel cord conveyor belt running at speeds in excess of 4.3mtr/sec.
The mine was operating on a planned five weekly cycle for shutdowns, with bulk changes of rollers at three to six monthly intervals. Unfortunately, the steel rollers continued to fail in high wear areas in between planned shutdowns making the cost of bulk change outs expensive and resulting in considerable down time.
Site management noted that the steel rollers were lasting as little as one month in the worst areas and an average of three to six months overall.
It was calculated that unplanned roller change outs in these locations due to split shells accumulated to an average of 17 hours per annum. At the current rate of production, 17 hours of unscheduled downtime could equate to approximately $1.2 million dollars of lost production per annum.
With the steel rollers installed, the site was operating at a less than acceptable percentage run time between planned shutdowns. With this in mind, site management sought a solution.
Site management discussed the issue with the local Flexco distributor which identified the potential to further reduce downtime on site and convinced them to run trials in the first six months of 2014 using the company’s CoreTech nylon conveyor rollers.
Site management was initially sceptical of the durability and wear life of the nylon material, however it agreed to trial CoreTech Nylon Vee Return Rollers.
Six of the heavy-duty rollers were installed on the worst incline conveyor, specifically in the area with the highest wear rate.
According to site management, three months after installation a shell thickness datum point was taken which showed promising results.
After the rollers had been in service for six months the shells were tested for lineal wear rates which showed the CoreTech rollers lasted four times longer than the steel rollers.
Starting at 16mm, after 28 weeks of operation the nylon shell thickness was 9.2mm at the thinnest point of the poorest roller. Based on this data, if this lineal wear continued the mine would still gain a minimum of 12 months life from CoreTech nylon rollers in the most extreme areas on the conveyor.
According to site management, testing results were impressive.
The site estimates plant downtime due to roller shell failure will improve by four times, and bulk roller changes have already been pushed out to 12 monthly intervals rather than the three to six monthly intervals that was required while the steel rollers were installed.
Impressed with these and other test results, site management at the gold mine is looking at changing to CoreTech site-wide.
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