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Optimization and Evolution of Large Ring Geared Mill Drives
During the First 10 Years of Operation
Leon Dias
ABB–Mining Drive Solutions, North America
Ian Pepping
Agnico Eagle, Detour Lake Mine
ABSTRACT: For a decade four large ring geared grinding mills (two SAG mills and two ball mills) have been
operating at a mining site in Ontario. During this time continuous optimizations have resulted in throughput
increases. As grinding is a critical stage in this process for which there is no redundancy or ability to bypass,
the reliability and high availability of the four grinding mills have been crucial in meeting the ever-increasing
production targets. Each mill is equipped with a 2 × 7.5 MW low speed dual pinion mill drive with Active
Front End. The mine operates in a remote area, and the power required for the mine and concentrator is fed via
long transmission lines. Consequently, the grinding mills are operating on a weak power system network, that
is characterized by low short circuit power capacity resulting in voltage stability challenges.
The first part of this paper will present the initial operational challenges, and the mitigation actions taken to
operate the mill drives in this demanding environment. These actions have ultimately resulted in the equip-
ment being able to reliably operate in a wide voltage supply range of 70–124%. Further optimizations based
upon analysis of real data will be described, that improved the overall availability, resulting in increased produc-
tion. Lastly, the paper will not only explore the active power factor correction feature but also various ongoing
optimization strategies. These include methods to reduce mechanical vibrations and methods to lower stress on
worn gear, thereby extending the lifetime of certain mechanical components.
INTRODUCTION
Detour Lake Mine is one of Canada’s largest operating open
pit gold mines. The operation is in Ontario, 185 kilome-
ters northeast of Cochrane in the Abitibi greenstone belt.
The first gold deposit at Detour Lake Mine was discov-
ered in 1974. The first mining operation on site ran from
1983 to 1999, as an open pit and later as an underground
gold mine. The properties were acquired by Detour Gold
Corporation and the construction of the current low grade,
high volume, open pit mine began in 2010. Mine produc-
tion commenced in 2012 and the first bars were poured in
February 2013. The mine is currently owned and operated
by Agnico Eagle Corporation.
The grinding process at Detour Lake Mine, is facili-
tated by 4 large mills, setup as two parallel lines, each one
having one dual pinion 36 ft diameter by 20ft length Semi
Autogenous Grinding (SAG) mill and one dual pinion
26ft diameter by 40.5ft length ball mill. In the SAG, the
ore is ground down to a range between 2 mm to 200 mm,
and further size reduction is achieved in the ball mill. The
grinding plant was initially designed for a total feed rate of
2,300 Tonnes Per Operating Hour (TPOH).
Optimization and Evolution of Large Ring Geared Mill Drives
During the First 10 Years of Operation
Leon Dias
ABB–Mining Drive Solutions, North America
Ian Pepping
Agnico Eagle, Detour Lake Mine
ABSTRACT: For a decade four large ring geared grinding mills (two SAG mills and two ball mills) have been
operating at a mining site in Ontario. During this time continuous optimizations have resulted in throughput
increases. As grinding is a critical stage in this process for which there is no redundancy or ability to bypass,
the reliability and high availability of the four grinding mills have been crucial in meeting the ever-increasing
production targets. Each mill is equipped with a 2 × 7.5 MW low speed dual pinion mill drive with Active
Front End. The mine operates in a remote area, and the power required for the mine and concentrator is fed via
long transmission lines. Consequently, the grinding mills are operating on a weak power system network, that
is characterized by low short circuit power capacity resulting in voltage stability challenges.
The first part of this paper will present the initial operational challenges, and the mitigation actions taken to
operate the mill drives in this demanding environment. These actions have ultimately resulted in the equip-
ment being able to reliably operate in a wide voltage supply range of 70–124%. Further optimizations based
upon analysis of real data will be described, that improved the overall availability, resulting in increased produc-
tion. Lastly, the paper will not only explore the active power factor correction feature but also various ongoing
optimization strategies. These include methods to reduce mechanical vibrations and methods to lower stress on
worn gear, thereby extending the lifetime of certain mechanical components.
INTRODUCTION
Detour Lake Mine is one of Canada’s largest operating open
pit gold mines. The operation is in Ontario, 185 kilome-
ters northeast of Cochrane in the Abitibi greenstone belt.
The first gold deposit at Detour Lake Mine was discov-
ered in 1974. The first mining operation on site ran from
1983 to 1999, as an open pit and later as an underground
gold mine. The properties were acquired by Detour Gold
Corporation and the construction of the current low grade,
high volume, open pit mine began in 2010. Mine produc-
tion commenced in 2012 and the first bars were poured in
February 2013. The mine is currently owned and operated
by Agnico Eagle Corporation.
The grinding process at Detour Lake Mine, is facili-
tated by 4 large mills, setup as two parallel lines, each one
having one dual pinion 36 ft diameter by 20ft length Semi
Autogenous Grinding (SAG) mill and one dual pinion
26ft diameter by 40.5ft length ball mill. In the SAG, the
ore is ground down to a range between 2 mm to 200 mm,
and further size reduction is achieved in the ball mill. The
grinding plant was initially designed for a total feed rate of
2,300 Tonnes Per Operating Hour (TPOH).