Case study - FLSmidth Krebs / Fosterville gold mine gMAX cyclone liner material upgrade


Courtesy of FLSmidth KREBS

The change from FLSmidth Krebs rubber to FLSmidth Krebs ceramic lined cyclones has seen significant improvements in cyclone life, mill operation, and maintenance requirements of the mill and flotation circuits at Fosterville Gold Mine.

The highest wearing component of the cyclones is the underflow apex (spigot). The rubber apexes had typically worn from a diameter of 82mm when new to 105mm after 672hrs (4 weeks) of operation. As there are four cyclones in operation the standard practice was to replace 1 apex per week to stagger the hours. After the 4th apex (2688hrs) the cyclone was removed from service and was rebuilt with new liners by the maintenance personnel. Each rebuild cost approximately $8000 in materials and $1000 in labour, including the time to replace the apex liners.

This practice of replacing the worn apexes with new ones introduced a positive ledge where the new liner met the worn one above it which interrupted the flow of slurry through the cyclone and rejected oversize material to the overflow. The effect of this could be observed in the bottom of the flotation cells which contained a lot of coarse material which inhibited the dart plug operation and accelerated the wear of the rotors and stators.

The worn apexes also allowed excess fine particles to report to the underflow which increased the recirculating load and unnecessarily accelerated the wear of the mill components and discharge pumps. It also decreased the percentage of the underflow which could report to the flash flotation cell.

The FLSmidth Krebs ceramic lined cyclones have a much greater life with the underflow apex diameters wearing approximately 20x slower compared to rubber. However, they are not allowed to increase to as large of a diameter as the old rubber apexes. Instead the cyclones are removed from service after 8,760hrs (1 year) of service when the apex reaches 95mm.

The four cyclones are staggered to replace 1 per quarter. The ceramic lined cyclones are supplied to site as a complete assembled unit. The maintenance team replace the whole unit and no longer have to commit time to replacing the liners. The overflow p80 sizing is now less variable, but more noticeable is the significant reduction in coarse material in the flotation cells observed during shutdowns.

The reduction in fines bypass to the underflow and the lower recirculating load has allowed for smaller, more efficient FLSmidth Krebs millMAX pumps to be installed in the mill discharge application. The new Krebs Mill Discharge pumps have proven to achieve long operating hours, consume less power and achieve overall significant cost reductions to the mill pump operations.

FLSmidth Krebs patented millMAX on-line suction side wear clearance adjustment technology was developed exclusively for mill discharge duties and adapted for other severe abrasive slurries. We refer to the Krebs millMAX technology as “zero downtime” impeller gap adjustment. It has removed the down time required for impeller, bearing assembly and pulley/ belt adjustments. This helps eliminate any down time while ensuring optimum pump efficiency is maintained and achieved throughout the life of the pumps wet end.

Customer comments

No comments were found for Case study - FLSmidth Krebs / Fosterville gold mine gMAX cyclone liner material upgrade. Be the first to comment!