Speedy shutdowns in frozen conditions

Located in northern Quebec near the border of Labrador in Canada, the Bloom Lake mine deposits were first discovered in the 1950’s. In 2010, production began at the open pit mine site by Consolidated Thompson who was later acquired by producer Cliffs Natural Resources. The ore at Bloom Lake contained extremely low levels of contaminants such as aluminum oxide, phosphorous & sulphur. Low contaminant levels allow blast furnaces to operate at much higher efficiencies, making the ore more attractive on the market.  At its peak, the Bloom Lake mine was producing nearly 7 million metric tonnes or iron ore, with the total deposit estimated at close to 580 million metric tonnes of proven reserves.

The challenge at Bloom Lake: Harsh Canadian winters

With its remote northern location, the mine site at Bloom Lake faced the challenges of conducting equipment maintenance under harsh freezing conditions. Temperatures in the region can swing from summer highs of 28 degrees Celsius  to -40 degrees Celsius in the deepest parts of winter, with snowfalls reaching 445 cm. The mine’s equipment process setup included primary crushers, grinding mills, a screening step, spiral classification followed by filter dewatering, all requiring a maintenance plan to ensure maximum uptime.

For their primary crushing needs, two large Metso gyratory crushers were used (Metso models 60 x 89 MK II), installed on customized steel structures to facilitate the equipment’s accessibility. The machines required multiple wear part changes per year, requiring highly trained crews and considerable site coordination to execute. With the constant focus on reducing downtime, the mine contacted Metso to see what solution could be offered to improve their shutdown times without compromising safety.

Solution:  A Life Cycle Services (LCS) contract for crusher maintenance

In order to improve shutdown times for the two gyratory crushers, Metso proposed a Life Cycle Services (LCS) contract, comprised of a bundle of services aimed at supporting the maintenance of the equipment over a three year period.  The contract included a Single Minute for Exchange of Dies (SMED) analysis, which involved observing and recording how the mine’s current shutdown was executed.   After analyzing the recorded shutdown event, specific recommendations involving needed manpower, required tools, and parts logistics were proposed by the Metso team and rolled into a formal shutdown plan.  

As part of the agreement, Metso also put in place an on-site consignment plan for both the critical wear components and spare parts for the equipment.  This ensured that all needed parts were available for everyday maintenance as well as scheduled major component change outs.  A Wears Analysis service was also built into the contract and involved regular inspection and monitoring of wear parts in order to optimize wear rates and improve the logistics of getting parts with long lead times onsite when needed.  

With Metso taking ownership of the crusher maintenance, special tools and staff were brought in for shutdown events, ensuring that OEM procedures and check lists were followed.  The relining crew outfitted with appropriate personal protective equipment, was available for 24 hour service, had full equipment and task specific training and was supervised by Metso service experts. A major benefit to the mine was that under an LCS maintenance agreement for the crushers, a Fixed Event Fee plan was arranged with a set cost being applied per shutdown event, covering everything required for the full servicing of the machines. This allowed for better cost forecasting and management.

Results:  Higher productivity and more efficient shutdowns

Despite difficult site conditions, the crushers’ availability and reliability were improved over the life of the LCS contract. Using tools from the Metso Special Tooling group, such as a concave carrousel, shutdown durations were reduced by 17% on simpler mantle change outs and by 56% on the more complex combined mantle and concave replacements. The mine ended up extending its work with Metso, requesting customized products for other process equipment in their circuit, such as a custom feeder chute for their AG mill.

Metso Megaliner reduces number of shutdown events

The mine was also able to trial the newly introduced Metso Megaliner™ in its grinding equipment. Constructed out of Poly-Met, the liner weighs up to 60% less than traditional liner, making liners easier to handle during relining events.  Working in close collaboration with the personnel of Cliffs Bloom Lake, Metso optimized the Megaliner configuration in order to obtain a more uniform wear profile across the length of the mill’s shell throughout the liners life.  The benefit of that optimization work was greater grinding efficiency as well as a reduction in the number of shutdowns from three events per year to two, saving 5 full days of production for the mine.

A final benefit to having an LCS agreement in place was the Capex deferral that came with inventory consignment. Rather than having the mine purchase the necessary wear and spare parts inventory immediately, parts were invoiced only when they were installed, allowing the Bloom Lake Mine to lower its inventory carrying costs.

Safety first

Despite the faster turnaround on shutdown events, safety equipment and procedures were always a key focus of the Metso field team. Due to the extreme weather conditions, many steps in the changeout required the highest care in their execution. With some of the parts involved in the dismantling and reassembly of the gyratory crusher weighing 73 tonnes and having assembly tolerances of a few fractions of a millimeter, crew safety was a major priority. Leveraging its knowledge of shutdowns from installations around the world, Metso was able to ensure that best safety practices were used throughout each shutdown event.  Final inspections by the Metso Field Services team gave the mine operators peace of mind, knowing that their equipment had been serviced to OEM standards.