International metals company partners with LSI to modernize SAG mill controls to boost performance at a major molybdenum processing mill.
An international metals company known for its expertise in mining copper and gold, operates a large mining and processing site specializing in molybdenum ore. This site has a complex setup, with the mine and mill connected by a 15-mile conveyor belt system that runs through a 10-mile tunnel beneath a mountain range, highlighting the operation’s scale and logistical challenges. With aging control systems on their SAG mills, they needed an experienced systems integrator to modernize the mills’ controls and unlock the full potential of an upgraded system.
The situation
The mill was built in the late 1970s and faced significant operational issues due to its original relay logic-based design. This outdated system lacked modern diagnostic tools and alarms, making troubleshooting difficult. Upgrading to a modern control system was crucial to improve reliability, reduce costly downtimes, and provide the real-time monitoring necessary to keep pace with today’s production demands. In 2015, LSI upgraded one of the Semi-Autogenous Grinding (SAG) mill’s relay control panels to PLC control. However, a decline in molybdenum prices caused delays in modernization projects until market conditions improved.
In 2021, with molybdenum prices recovering, the client was ready to upgrade the remaining three mills. This restart was complicated by significant workforce turnover, resulting in a knowledge gap. The client lacked personnel familiar with the earlier upgrade and needed help overseeing project charters, budgets, engineering, construction, and project management.
The Solution
To support the client’s goal of modernizing the mill’s control systems, LSI played a crucial role in defining the project by providing initial budgetary and project charter documentation. This included extending the original scope of the first mill upgrade to modernize the outdated lubrication and ore feed relay controls. The upgrade involved transitioning to the Allen-Bradley ControlLogix platform, which brought many benefits, including alarming, diagnostics, and other process improvements.
The project required several investigatory trips that were coordinated with the mill’s scheduled downtimes to assess the current wiring conditions. Many of the existing drawings were outdated or completely inaccurate. Ultimately, the design required a combination of existing cabling and new cabling to ensure a seamless transition from the old controls to the new system.
With a clear understanding of the mill’s current state, LSI’s team tackled the complex task of modernizing the controls for the massive mechanical rheostats (which act as a soft-start mechanism for the mill’s 3000 hp, 13.8 kV motors), allowing for precise control through a new servo drive system. The upgrade also involved interfacing with existing 13.8 kV breakers that had outdated and sometimes inaccurate wiring documentation. To improve the reliability of lubrication systems, four lubrication pump panels were replaced and upgraded using E-300 overloads for improved control of motor starters and auxiliary I/O functions. Additionally, six control panels were replaced to function as marshaling units for a centralized lubrication control panel, streamlining operations.
As part of the project, LSI designed and installed a new control panel for the ore feed conveyor and another panel that managed three DC drives, which regulated the flow of ore from storage piles to the conveyor system. LSI also ensured the existing HMI system could properly interface with the new controller – on a system that the mill itself rarely modified (Foxboro DCS).
LSI’s efforts included:
- Creation of over 200 drawings
- Defining mechanical and electrical scopes of work
- Complete design of all electrical and mechanical hardware
- Complete design of all electrical and mechanical hardware
- Configuration of the complete control system including:
- PLC Code, New HMI, SCADA, and tags for Data Analytics
- Managing the fabrication and procurement of all necessary hardware
- Project management support
- Construction management support
- Commissioning services
The onsite execution and construction phase of the project was supported by over 30 individuals (LSI, electrical contractors, mechanical contractors, and client employees) working seamlessly in a three-month pre-work stage, followed by a three-week mill downtime to install and commission the new systems.
The Results
Successfully completing upgrades for two of the four SAG Mills marked a significant achievement for both the client and LSI. Each mill was brought back online within the planned schedule and functioned as expected, meeting all performance requirements. The engineering, maintenance, and operations teams expressed their satisfaction, commending LSI for a successful project execution. Outcomes of the project:
- Improved efficiency and reduced downtime
- Improved control reduces interruptions and maximizes ore throughput.
- Better process control and quality
- Precise monitoring optimizes grinding, ensuring consistent, high-quality output.
- Improved maintenance
- Enhanced monitoring, diagnostics, and alarm features support predictive maintenance,
- Scalable, future-ready technology
- Upgraded systems can adapt easily to changing operational needs.
What's Next
The success of these projects solidified LSI’s reputation as the preferred system integrator for the mill. This strengthened partnership has evolved into an ongoing collaborative relationship, with the client’s engineering team frequently consulting LSI for technical insights and recommendations on future improvements. Building on this trust, LSI is currently leading the design phase for a remaining SAG Mill upgrade.
LSI’s strong partnership with the site is evident in its extended presence through support contracts. Beyond mill-specific projects, LSI is also actively assisting with broader modernization initiatives throughout the plant.