Metso Insights Case studies Mining and metals refining Boliden keeps improving uptime with new mill lining solutions
Apr 23, 2020

Boliden keeps improving uptime with new mill lining solutions

It is the mill that determines the pace of the whole maintenance process at Boliden Aitik in Gällivare, Sweden. Most maintenance shutdowns are planned according to the maintenance schedule set for the reline of the mill. So if the reline can be done faster, the whole maintenance shutdown will be faster. And with Aitik's target to grind 45 million tonnes in 2020, uptime is critical.
Relining at ball mill at Boliden's mine.

For many years Boliden and Metso have had a Life Cycle Services (LCS) cost-per-tonne agreement for mill linings and additional services. This agreement, believes Kjell-Arne Johansson, Senior Technical Supervisor Concentrator at Boliden, has helped improve both the products and services.  

“Our cost-per-tonne agreement for mill linings makes development beneficial both for us and Metso. The agreement strengthens our cooperation, as we challenge and drive the development together,” says Kjell-Arne. 

Boliden Aitik is the world leader when measured by tonnes produced per employee hour. Their aim is to process 45 million tonnes of ore in 2020, and they have about 100 employees working at the concentrator. At the Boliden Aitik maintenance department, there are 3-4 employees focusing on mill linings. That number would have been higher if mill lining expertise and service had not been part of the LCS agreement, according to Malin Ömalm, Maintenance Engineer at Boliden.  

We have regular follow-up and performance improvement meetings. Weekly reconciliations, technical meetings and steering committee meetings all contribute to control, knowledge transfer and development, says Malin.  

Megaliner represents a new era 

One innovation that Boliden Aitik was first in the world to adopt was Metso Megaliner. Today, both of its primary AG mills feature Megaliner mill liners on the shell and feed-end head.  

Megaliner represents a new era and there is no going back. We haven’t had any problems since we started using Megaliner. The design and the wear life have fulfilled our expectations, and we have been able to significantly improve the reline time while also improving safety, says Kjell-Arne. 

The mill determines the maintenance schedule for the whole process, so minimizing downtime is critical. Every hour that can be saved puts pressure on other areas to also improve. This includes the maintenance schedule (wear life) as well as the length of maintenance shutdown (reline). 

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We want the mill to be up and running for as long as possible, and when the liners are worn out, they need to be changed as quickly as possible. Some 6-7 years ago, we used to have six maintenance shutdowns per year. Today we have a balanced wear life and just 2-3 shutdowns per year,” says Kjell-Arne.   

The targets set by Boliden have been clear from the start, and we always look for new ways to improve uptime. We like the challenge and the trust; it makes us want to continue to pursue improvements in both mill linings and services. When we started, the mill was a bottleneck, but the development has been continuous; today we are pushing all other areas towards fewer and shorter maintenance shutdowns. Mill availability right now is ~98%, and our team keeps improving the design of the lining and tools. That means even less downtime in the future, says Per Sundström, Product Support Manager at Metso.  

In addition to the mill lining solution, Metso is also focused on other methods of assisting Aitik to improve its shutdown times. Shutdown optimization services, such as time and motion analysis studies, mill relining simulations and special tooling, all play a part in reducing downtime. One of the goals of the LCS contract is to find the best way to bring all of these elements together to deliver the best overall result for the mine.

Raising the bar: More uptime with installation of Megaliner for discharge system

Boliden Aitik’s target for 2020 is to further reduce downtime. Metso is testing a new innovation that almost certainly will make this possible in one of the AG mills – the Megaliner for discharge system.

The Megaliner for discharge system minimizes the number of components to be installed by integrating dischargers, grates and filling segments. Reline time is much faster, as the liner has substantially fewer attachment points, and the number of liner components is reduced by up to 70%. Additional time savings are achieved when removing the bolts, which are attached from the outside of the mill. The traditional long bolts that go through the grate, pulp lifter and the mill discharge head are not used, eliminating the need for recoilless hammers.

“I see lot of potential in the Megaliner for discharge system. First of all, it is favorable from a safety point of view. And it will increase uptime, as there are fewer parts to handle and the bolts are attached from the outside of the mill. We estimate a time savings of up to 30 hours per reline; that’s a lot of money. The time savings will also mean that we will be less dependent on critical equipment, such as the liner handler and recoilless hammers. This is the equipment that must work during a maintenance break, and days can be lost if they break down,” Kjell-Arne explains.

Thomas Lundqvist from the Mine Team has 40 years of experience with relines. He supervised the test installation of the Megaliner for discharge system at Boliden Aitik. “Megaliner will undeniably help us save in reline time because of its design and attachment system. The discharge system is always a bit special, but by taking everything out and relining with the new modules, we will avoid unplanned interruptions. It will also be a safer working environment for my crew, since no one, except for the liner handler operator, needs to be inside the mill,” says Tomas.

“I am happy that we’ve now reached a point where we can make the Megaliner for discharge systems available to our customers. Improvements in uptime and safety will surely be appreciated. The test installation at Boliden Aitik is a good example. I trust it will enable a 50% faster reline of the discharge end in the SAG mill,” says Mattias Karlsson, Product Development Engineer at Metso.

How to determine the correct lining design for your grinding mill?
How to determine the correct lining design for your grinding mill?
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