faster to change
“Extended service life and faster relining. At the Boliden Kevitsa nickel-copper mine in Sodankylä, we set these two clear objectives for the adoption of Metso Megaliner mill linings. Achieving these allows us to increase the uptime of the mills and enhance the grinding capacity to meet the mine’s production increases.” The realization of the objectives, expressed to Metso in a concise manner by Mechanical Maintenance Engineer Kimmo Haatainen from Boliden Kevitsa Mining Oy, is progressing at a swift pace. Megaliner mill linings have now been installed in all three of the mine's grinding mills. “The results are very promising. The installation of Megaliner mill linings is 40–50% faster than the installation of the original linings. Metso’s optimized lining elements also have a significantly longer service life, which extends the replacement interval from 9 to 15 months,” Haatainen says.
In June 2017, new mill linings were also installed to a third mill, the 14 MW pebble mill with the diameter of 8.5 m. The lining for a mill this size requires 56 Megaliner elements, each weighing more than one tonne, while the original lining had several hundred elements. “In addition to saving time, safety is a major benefit of the Megaliner system. Elements are moved using a mill liner handler, requiring less manpower inside the mill. Bolts can be fixed safely from outside the mill shell,” says Area Sales Manager Jouko Tolonen of Metso. When changing the lining type, the biggest effort was enlarging a total of 504 fixing holes, carried out by the Metso mill lining team. Drilling the holes and installing the Megaliner elements both took a little under two days. All the work, from dismantling the old lining to drilling and the installation of new elements, took less than the projected seven days. Metso’s maintenance team also replaced the lifter bars and grates at the mill’s discharge end as well as lifter bars and head plates at the mill’s feed end head outer ring during the project.
faster to change
Kimmo Haatainen gave good feedback to Metso's maintenance team before the busy working week was even finished. “Relining is proceeding according to plan, and we are very happy with the service Metso provides us. I believe that in the future, we will be able to replace the lining for one mill in four days.” “We will plan the work so that during one service shutdown, lining is replaced in one grinding mill,” Haatainen says.
Kevitsa has two Metso MP800 cone crushers for secondary and fine crushing. Earlier, the ore fed into the MP crushers was fairly large and difficult to crush. Therefore, the material produced by the original chamber was too coarse for the mills. Now the crusher chambers have pockets specifically designed for Kevitsa, keeping the crusher load more even. This will extend the service life of the wear parts and with them, the whole crusher. “Metso optimized the chamber profile of the MP crushers to suit the ore. The profile ensures more efficient crushing, and the grain size of the material fed to the mills is finer and more even,” says Heikki Kamula, who is responsible for the mechanical maintenance of the concentration plant at Boliden Kevitsa Mining Oy. “We have a three-year life-cycle services agreement for the primary crusher, including key maintenance work and the development and delivery of wear parts. We aim to extend the service life of the parts and to speed up the replacement process. We have already made good progress in these areas. We continue on the right track. Metso has also been able to develop the lining system for a direction that benefits our process.”
Acquired by Boliden last year, Kevitsa has continued to develop the plant's production process to allow higher production volumes. The target for the current year is to process 7.8 million tonnes of ore. While nickel is the main product for Kevitsa, the mine also produces copper, gold, platinum and palladium. The annual volume of concentrated nickel produced at the mine exceeds 30,000 tonnes.