Gold Fields Reduces Control System Risk Using PlantPAx

Gold Fields Limited owns and operates 12 gold mines in South Africa, Ghana, Peru and Australia, producing roughly 2.1 million gold equivalent ounces annually. Gold Fields is listed on both the Johannesburg Stock Exchange (JSE) and the New York Stock Exchange (NYSE), and employs roughly 50 000 people globally.

South Deep Gold Mine, Gold Field’s only operational mine in South Africa, is situated 45 kilometres southwest of Johannesburg, is comprised of two shaft systems and a central metallurgical plant.

This project involving Rockwell Automation falls within Gold Fields’ long-term vision: ‘To be the global leader in sustainable gold mining,’ and is a flagship growth project in South Africa.

Challenge

The metallurgical plant at South Deep Mine was upgraded in 2011/2012 to increase its throughput. This involved the addition of a second ball mill circuit, a pebble crushing circuit, an additional thickener, four leach tanks and an extra elution column.

To better manage reagent, energy and water usage throughout the upgraded plant, while at the same time improve the quality of mine tailings, South Deep Mine needed a complete control and reporting system upgrade that would integrate all existing field systems with the new ore processing systems. This would have to allow for faster, more informed business decisions at a management level, and help the mine meet its long-term sustainability objectives.

Gold Fields also needed to reduce the risk of unplanned downtime with a control system that could seamlessly integrate all field devices, plant control, visualisation, reporting and overall performance monitoring into a single, simplified system that could also be expanded in future plant upgrades.

The metallurgy plant was originally based on Rockwell Automation RSView®32 component-based HMI and L62 controllers for process monitoring and control. This required further optimisation: all I/O, interlocks, sequences and other process routines needed to be re-evaluated to eliminate unnecessary complexities throughout the new control system.

Solution

With the metallurgical plant running Rockwell Automation technology since 2001, Gold Fields directly commissioned Rockwell Automation to perform the control system upgrades. Rockwell Automation became involved with the new processing system via an EPCM contractor at South Deep Gold Mine. These two projects needed to culminate in a single, fully-integrated control, visualisation and reporting system.

The mining solution using PlantPAx

The mining solution using PlantPAx™ is based on decades of mining domain expertise which has been formalised into a highly standardised, lifecycle-managed and easily commissioned solution that’s capable of reducing control system risks, improving diagnostics and reporting, and reducing system-wide complexities.

A more tailored and cost-effective alternative to a traditional DCS-based (distributed control systems) solution, the PlantPAx provides additional flexibility, managed mining-specific standards and reduced commissioning time and costs. This control system also helps ensure the same, high functional standards of a DCS-based system in terms of standardisation and single-tag databases.

System-Wide Implementation

The solution consists of a PlantPAx controller platform, configured to buffer up to 1 000 time-stamped data entries (plant history, events and alarms) to provide uninterrupted data logging in the event of a network failure.

For comprehensive visualisation of plant processes, the PlantPAx visualisation software, based on server-client architecture, was built into the system. ViewTools, licenced to PlantPAx, was also incorporated to provide the benefit of direct client access to the controller without the need for a path through the server.

Microsoft SQL, with built-in reporting services, was installed and configured to log all plant history, events and alarms. The mining solution’s licenced software, SQX, was also installed to allow the SQL to be populated directly by the controllers.

Rockwell Automation engineers further created unique interfaces to support third-party field devices, such as drives and instrumentation.

The final changeover was completed in November, 2012.

Results

Gold Fields was able to improve plant control, visualisation and reporting capabilities with the mining solution using PlantPAx.

Standardisation and comprehensively managed data logging enables the mining solution to provide users with a single, highly accurate status of the plant in real-time.

With the SQL configured to log history, events and alarms, users are able to follow trends, trace individual entries to specific end users, and keep track of analogue and digital inputs such as flow rates, temperatures and various other inputs from across the plant. All data is time stamped by the PlantPAx controllers, helping to ensure data integrity while allowing entries to be accurately injected into the SQL after a network failure has been corrected. Also, by adding SQX software, the SQL database can be added as I/O to the controllers.

The PlantPAx software processes signals from instruments and only report the minimum, maximum and average values per reporting period, which minimises the data logged to the database – as opposed to logging every signal from the field device.

Acknowledgement of alarms is user and time-stamped and logged, which protects operators from being reproached for ignoring essential warnings, while at the same time, improving accountability. This improves overall plant safety, especially at South Deep Gold Mine where cyanide alarms and other safety warnings are critical indicators.

Advanced Reporting

A series of reporting services are built into the SQL, which generates and relays comprehensive operation and production reports to management levels for corporate monitoring of key performance indicators (KPIs).

Reports include information on the amount of ore processed during each 12-hour shift. Other figures include a water consumption report generated by a flow meter which totalises hourly flow rates, while MV switchgear reporting provides information on megawatt hours used. KPIs can also be monitored from a web-based page that indicates plant statuses in colours.

The mining solution using PlantPAx removes unnecessary operational complexity as interlocking descriptions and tags are standardised to be intuitive. This reduction in complexity means that Gold Fields requires fewer highly skilled operators, addressing a common industry problem of applicable skills shortage.

Future

Rockwell Automation is currently designing an underground ore management system for South Deep Gold Mine for integration with the mining solution.

To further improve reporting from operator to technician to management levels, Gold Fields plans to change over a series of remaining field devices to the mining solution. Systems to be included into the central control and visualisation system are shaft conveyors, a fridge plant, bulk air coolers, among various others processing systems.