Reliable performance of the mine winder is critical in terms of both personnel safety and efficient mining operations. The primary means of mine ingress is a 600m drift, traversed by a dolly car that carries shifts of 60-80 workers and ancillary materials. Driven by a 750-kilowatt DC motor, the powered winding system dictates the required direction and speed of the dolly car’s travel in the drift.
According to Greg Briggs, maintenance manager for Centennial Myuna, improved maintenance of the 20-year-old mine winder system was also an objective. “Although it still operated safely, the winder was very outdated,” he said. “In addition to safety compliance and reliability, we needed better techniques to monitor performance. So we had three strong reasons to upgrade the system to modern digital technology.”
Installed and commissioned during Christmas 2003 and Easter 2004, the final control and safety system is founded on the versatile Allen-Bradley ControlLogix programmable automation controller (PAC), which replaced a legacy relay control system. ControlLogix sends instructions to the winder drive system via fibre optic communications, plus handles general control functions. In conjunction, a dedicated safety control circuit, featuring an Allen-Bradley GuardPLC 1200 safety controller, monitors most of the critical emergency functions and fulfils the SIL 2 requirements.
“Basically, the winder has to run at prescribed speeds in designated zones,” said Briggs. “The system also has to make sure that everything happening on the dolly car itself – such as hydraulic pressures for brakes – are operating correctly. There are a whole host of parameters that have to be constantly monitored.”
Both the speed and position of the winder are double-checked by different sources and at different locations in the new system. Speed checking is achieved using encoders connected to the two high-speed counter inputs of the GuardPLC safety controller, plus drive tacho readings. An absolute encoder, linked to ControlLogix via a DeviceNet communications fieldbus, monitors the position of the winder in the drift to confirm readings by hunting tooth limit switches.
Briggs said feedback on the new system had been positive. The winder drivers now had basic diagnostic capability and could reset simple faults from the dolly car itself. In addition, an Allen-Bradley PanelView electronic operator interface (EOI), linked to ControlLogix via EtherNet/IP and located in the winder house with the electronics panels, displayed all alarms and a graphical representation of where the dolly car was in the drift.
“The system is performing extremely well,” said Briggs. “It’s operating reliably and safely. It gave me a sense of security to work with Rockwell Automation. They have the background experience and technical proficiency for this type of system, not to mention a cost-effective solution.”
Rockwell Automation Australia is the Australian subsidiary of $US4.3 billion-a-year industrial automation power, control and information solutions group, Rockwell Automation.
Australia's Mining Monthly.
