3777
The Logical Next Step in SAG and Ball Mills with
Gearless Mill Drives
R. von Kaenel, D. Bermudez, D. Casado, N. Vijayakumar, V. Garcia
ABB
D. Bordi
Metso
A. Doll
Alex G Doll Consulting Ltd
ABSTRACT: Horizontal grinding mills have been around for well over a century, while the first gearless
mill drive (GMD) was commissioned more than 50 years ago. Historically, both SAG and ball mills have
continuously increased in size and power, improving plant capacity and efficiency. This was not only driven by
technological progress, but also by more demanding ore bodies with lower head grades. In addition, market
demand for higher productivity combined with the need to have a short return on investment led to increased
equipment sizes.
However, almost 15 years ago this continuous growth halted at 40 ft, 28 MW SAG mills and 28 ft, 22 MW ball
mills, which have nowadays become common and well-proven sizes. In 2010 a 42 ft SAG mill and its 28 MW
GMD were manufactured but unfortunately never installed due to project permitting challenges.
Today, average ore body grade and accessibility continue to decline. Concurrently, the demand for minerals is
forecasted to increase tremendously due to the global push to reduce carbon footprint. It is therefore expected
that mill sizes will soon make another step to 44 ft gearless driven SAG mills and 30 to 32 ft gearless driven ball
mills, with a rated power of more than 30 MW. This paper will present the required close cooperation of the mill
and GMD suppliers, as well as the challenges they face when creating a reliable design. Obviously the current
available and well proven designs cannot just be scaled-up without any further investigation, but a proper design
process needs to be in place and strictly followed.
INTRODUCTION
Horizontal mills have been an essential component of grind-
ing circuits for more than a century. Initially these mills
were ring-gear driven, meaning that an electrical motor
transmits the power mechanically to the mill via one or two
pinions and a ring-gear, sometimes with a gearbox between
the motor and pinion. To improve the plant capacity and
efficiency mills continuously increased in size over decades.
The larger mills required more powerful drives and as a
result the stress on the mechanical components increased
to the point of becoming the limiting factor.
The simplest way to solve the limitation of the mechan-
ical transmission was found to remove it. With gearless mill
The Logical Next Step in SAG and Ball Mills with
Gearless Mill Drives
R. von Kaenel, D. Bermudez, D. Casado, N. Vijayakumar, V. Garcia
ABB
D. Bordi
Metso
A. Doll
Alex G Doll Consulting Ltd
ABSTRACT: Horizontal grinding mills have been around for well over a century, while the first gearless
mill drive (GMD) was commissioned more than 50 years ago. Historically, both SAG and ball mills have
continuously increased in size and power, improving plant capacity and efficiency. This was not only driven by
technological progress, but also by more demanding ore bodies with lower head grades. In addition, market
demand for higher productivity combined with the need to have a short return on investment led to increased
equipment sizes.
However, almost 15 years ago this continuous growth halted at 40 ft, 28 MW SAG mills and 28 ft, 22 MW ball
mills, which have nowadays become common and well-proven sizes. In 2010 a 42 ft SAG mill and its 28 MW
GMD were manufactured but unfortunately never installed due to project permitting challenges.
Today, average ore body grade and accessibility continue to decline. Concurrently, the demand for minerals is
forecasted to increase tremendously due to the global push to reduce carbon footprint. It is therefore expected
that mill sizes will soon make another step to 44 ft gearless driven SAG mills and 30 to 32 ft gearless driven ball
mills, with a rated power of more than 30 MW. This paper will present the required close cooperation of the mill
and GMD suppliers, as well as the challenges they face when creating a reliable design. Obviously the current
available and well proven designs cannot just be scaled-up without any further investigation, but a proper design
process needs to be in place and strictly followed.
INTRODUCTION
Horizontal mills have been an essential component of grind-
ing circuits for more than a century. Initially these mills
were ring-gear driven, meaning that an electrical motor
transmits the power mechanically to the mill via one or two
pinions and a ring-gear, sometimes with a gearbox between
the motor and pinion. To improve the plant capacity and
efficiency mills continuously increased in size over decades.
The larger mills required more powerful drives and as a
result the stress on the mechanical components increased
to the point of becoming the limiting factor.
The simplest way to solve the limitation of the mechan-
ical transmission was found to remove it. With gearless mill
