Hundreds of technicians and tons of parts go into action in an instant as operations at Boliden Kevitsa Mining’s nickel mine in Sodankylä stop for the longest maintenance shutdown of the year. Everything has to work seamlessly and precisely on a tight schedule so that the processing of ore can get up and running again as soon as possible. With its highly competent international team of 60 maintenance professionals, Metso completed its part of the demanding project with its customary high-quality standards and precisely on schedule.
Markku Lehto, Mining Service Manager at Metso, at the feed opening of the grinding mill. The Megaliner lining elements are installed through the feed opening using a mechanical liner handler.
During the shutdown, Metso was responsible for replacing the concaves and the mantle of the primary gyratory crusher, the linings of three grinding mills, and the lower frame of the large cone crusher, in addition to repairing two apron feeders.
“Metso had prepared carefully for its four jobs, which was positively reflected in the end result. Risk levels during the work remained low, and the sites were completed on time, or even ahead of schedule,” says Heikki Kamula, Head of Mechanical Maintenance at Boliden Kevitsa Mining.
“One positive thing was that we spent considerably more time and resources on the risk assessments for the work than we used to. This was evident in the high level of safety and order on the site,” Kamula continues.
“In addition, Metso very actively monitored operations to detect any dangerous situations and responded to deviations immediately.”
The Boliden Kevitsa mine has eight maintenance breaks a year, with each break lasting for around 16 hours. In addition, there is a six-day shutdown every year, which this year was in mid-May. In addition to the mine’s 380 employees, the maintenance shutdown involved around 300 external workers.
At Metso, planning for the shutdown began four months beforehand.
“We allowed plenty of time for planning in our team. For most of our projects, we prepared hourly schedules divided into work phases. These were printed out for the sites for easy monitoring of progress,” says Lauri Ylönen, Mining Maintenance Manager at Metso Finland, based in Tampere.
“Our four projects were completed ahead of schedule, meaning our entire team did excellent work. Our international maintenance team included people from Finland, Sweden, Canada and New Zealand.”
One segment in each layer of lining must be flame-cut to be removed.
During the maintenance shutdown, one of the most demanding projects was to replace the concaves and the mantle of the primary gyratory crusher. Metso has been optimizing these wear parts and supplying them to the mine since 2016.
Philippe Lemieux and Kallejussi Pakisjärvi from Metso Life Cycle Services documented the entire replacement process using single-minute exchange of die (SMED) technology. Three cameras recorded the process at three images per minute.
“Metso has been carrying out SMED analyses for ten years. The series of images enables us to detect which work phases are prone to delays. We receive information for the next development steps, and we provide our customers with support for future investments,” Lemieux explains.
Metso has also developed tools that accelerate the work and improve safety. For example, one entire tier of the concave segments for the primary gyratory could be lifted in place at once using two installation carousels developed by Metso.
Using an installation carousel developed by Metso, an entire layer of concave segments can be moved into place safely at the same time.
According to Heikki Kamula from Kevitsa, Metso has been able to considerably reduce the replacement times for primary gyratory crusher’s liners.
“Thanks to good work planning and new tools, the work has been completed more rapidly each time, in line with our goals. We aim to reach a replacement pace that will increase the production of primary crushing and our entire mining process.”
Made from rubber and ceramic inserts, the Poly-Cer protective lining provides protection for the crusher’s mainframe by improving impact resistance. Kevitsa has two MP800 cone crushers. The first was equipped with Poly-Cer protective lining in March 2017 and the second during the recent maintenance shutdown.
The first mainframe lining has been in use for more than a year and remains in good condition. In earlier installations, the wear life of the durable Poly-Cer material has been proven to be four times longer than that of steel.
During the maintenance shutdown, the second of Kevitsa’s two MP800 cone crushers was equipped with a rubber-and-ceramic mainframe lining to improve durability.