1
24-062
Navigating Operational Hurdles in SAG Mills: Identifying and
Addressing Common Challenges
Kevin Erwina
Ausenco, Vancouver, BC, Canada
Connor Meinkea
Ausenco, Vancouver, BC, Canada
Rajiv Chandramohana
Ausenco, Vancouver, BC, Canada
ABSTRACT
This paper explores prevalent operational challenges
encountered globally in SAG mills, including suboptimal
throughput, liner wear, excessive energy consumption, and
SAG mill load stability. The paper delves into the root causes
behind these issues, such as ore variability, poor operating
strategy, or inadequate process control. Drawing on indus-
try experience and case studies, the paper highlights the sig-
nificance of addressing these challenges to enhance overall
mill performance and efficiency. It underscores the neces-
sity of tailored strategies, encompassing improved monitor-
ing, optimized liner designs, and refined control techniques
to mitigate these challenges and promote sustainable SAG
mill operation.
INTRODUCTION
The semi-autogenous grinding (SAG) mill is the heart of
the milling circuit and is often the primary throughput
limiting constraint. The SAG mill load must be stable to
maximize the SAG mill power draw to achieve maximum
throughput [1].
There are challenges to maintaining a stable load in the
SAG mill. These challenges are contributed, quite often, by
interplaying variables related to the ore conditions (com-
petency, hardness, size distributions, viscosity) perform-
ing in set mill-operating conditions. This paper explores
the common operational challenges frequently observed
through constraints assessments and operational optimiza-
tion projects, highlights the root causes of SAG mill load
instability, and provides a path forward.
Stabilizing the load within the SAG mill is the critical
parameter in maximizing SAG mill performance. Yet, sev-
eral factors influence it, including feed size distribution, the
responsiveness of process control systems, and the design
and state of wear and design of the mill liners and discharge
grates [1]. A poorly tuned control system or suboptimal
operator decisions can result in excessive control actions,
leading to instability in mill operations. Proactive feed rate
and mill speed management is essential in addressing these
issues. Neglecting the wear state of mill liners can result
in increased mill filling, which negatively impacts milling
efficiency and throughput [2].
Objective of the Paper
To maintain a stable SAG mill load for changing ore compe-
tency and feed size distribution, the following key variables
need to be manipulated, controlled or fixed (Figure 1).
The paper focuses on the following four opportuni-
ties and strategies for maintaining a stable SAG mill load,
which are some of the key prevalent issues at most SAG-
based operations—where immediate opportunities can be
achieved:
24-062
Navigating Operational Hurdles in SAG Mills: Identifying and
Addressing Common Challenges
Kevin Erwina
Ausenco, Vancouver, BC, Canada
Connor Meinkea
Ausenco, Vancouver, BC, Canada
Rajiv Chandramohana
Ausenco, Vancouver, BC, Canada
ABSTRACT
This paper explores prevalent operational challenges
encountered globally in SAG mills, including suboptimal
throughput, liner wear, excessive energy consumption, and
SAG mill load stability. The paper delves into the root causes
behind these issues, such as ore variability, poor operating
strategy, or inadequate process control. Drawing on indus-
try experience and case studies, the paper highlights the sig-
nificance of addressing these challenges to enhance overall
mill performance and efficiency. It underscores the neces-
sity of tailored strategies, encompassing improved monitor-
ing, optimized liner designs, and refined control techniques
to mitigate these challenges and promote sustainable SAG
mill operation.
INTRODUCTION
The semi-autogenous grinding (SAG) mill is the heart of
the milling circuit and is often the primary throughput
limiting constraint. The SAG mill load must be stable to
maximize the SAG mill power draw to achieve maximum
throughput [1].
There are challenges to maintaining a stable load in the
SAG mill. These challenges are contributed, quite often, by
interplaying variables related to the ore conditions (com-
petency, hardness, size distributions, viscosity) perform-
ing in set mill-operating conditions. This paper explores
the common operational challenges frequently observed
through constraints assessments and operational optimiza-
tion projects, highlights the root causes of SAG mill load
instability, and provides a path forward.
Stabilizing the load within the SAG mill is the critical
parameter in maximizing SAG mill performance. Yet, sev-
eral factors influence it, including feed size distribution, the
responsiveness of process control systems, and the design
and state of wear and design of the mill liners and discharge
grates [1]. A poorly tuned control system or suboptimal
operator decisions can result in excessive control actions,
leading to instability in mill operations. Proactive feed rate
and mill speed management is essential in addressing these
issues. Neglecting the wear state of mill liners can result
in increased mill filling, which negatively impacts milling
efficiency and throughput [2].
Objective of the Paper
To maintain a stable SAG mill load for changing ore compe-
tency and feed size distribution, the following key variables
need to be manipulated, controlled or fixed (Figure 1).
The paper focuses on the following four opportuni-
ties and strategies for maintaining a stable SAG mill load,
which are some of the key prevalent issues at most SAG-
based operations—where immediate opportunities can be
achieved: