Northland Resources had high hopes when it began operations towards the end of 2012 at the Tapuli iron ore deposit outside the town of Pajala, 100 km north of the Arctic Circle. The company was in the process of developing the Sahavaara deposit in 2014 and ramping up towards full production when ore prices went into a tailspin. Liquidity issues became so severe that it filed for bankruptcy a few months later. Mining equipment, including 500-plus motors and around 200 drives, entered an indeterminate period of dormancy.
In 2018, with the backing of approximately 80 Swedish entrepreneurs, the Kaunisvaara mine rose again as Kaunis Iron. It achieved full production in 1Q19, with a targeted output of 2 million tpy.
Ore at Kaunis Iron is extracted through drilling, blasting, loading and hauling through two opencast mines. Haul trucks carry and dump the ore at the crushing station situated adjacent to the exit of each mine. Once the ore has been crushed to the right dimension, it is transferred to the enrichment plant by a 1 km long overland conveyor system.
Gisab Gällivare was appointed by Kaunis Iron to take responsibility for the operation, production, and maintenance of the mine's concentrator. 6 months before the new start, Gisab contacted ABB with a service challenge: to restart a mine that has been dormant for 4 years. ABB had originally supplied nine containerised electrical rooms with embedded medium- and low-voltage switchgear, variable-speed drives, motors and motor control centres, integrated with a plant-wide process automation system.
The mothballing of the equipment had involved a controlled shutdown that included the greasing of the motor bearings and the rotation of the motors. Another step was to keep the heaters on the motors running continuously, even during the shutdown period, to keep them warm during the cold of Sweden’s winters and prevent damaging moisture from building up.
Before the restart, extensive testing was carried out on the various dormant motors and drives. Despite having been exposed to temperatures ranging from -35°C in winter to 25°C in summer for 4 uninterrupted years, only one motor required some adjustments, and a few others had to be dried out.
Preventing costly production outages
During the restart, vibration testing detected abnormal values in the giant primary mill, which processes 800 tph of ore. It turned out that a bearing was damaged, and it would need to be replaced in 6 months. This allowed Gisab to plan the replacement during one of the scheduled maintenance stops to ensure minimum disruption to production. The Kaunis Iron enrichment plant runs 350 days per year with two planned maintenance stops per year, so being able to identify this issue early prevented costly downtime.
The current partnership between ABB and Gisab ensures high productivity at the concentrating plant and efficient maintenance planning to maximise the life of the equipment. The enrichment plant is on the brink of reaching 97% availability, and plans are afoot to extend the plant with the development of a new, much larger production line.
“Because of ABB’s close involvement from the outset in the mine’s revival, the agreement is more like a close partnership,” said Daniel Uusitalo, Gisab's Vice President and Head of Kaunisvaara. “We couldn’t have started without such a strong partner as ABB. They took us by the hand and guided us through the necessary maintenance. There has been a lot of heart and soul involved in the work, and ABB's staff have gone far beyond what one would expect.”
Further developments include the retrofitting of brush-lifting devices to existing motors which considerably reduces brush wear and minimises maintenance. Before the brush-lifting devices were installed, the motors had to be shut down every 2 weeks to inspect the brushes. Now they are only checked every 6 months.
Read the article online at: https://www.globalminingreview.com/special-reports/03112020/service-partnership-awakens-arctic-mine-from-4-year-slumber/
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