The situation
Overland conveyors in Bowen Basin coal operations run continuously through the production season. Any unplanned stoppage — whether from a mechanical failure or a control system fault — immediately affects coal movement from pit to train loadout.
The PLC-5 system on this conveyor had been in service for over 20 years. Spare processor cards were sourced from the secondary market at significant cost. The site electrical team had documented three near-miss events in the prior 12 months where a main processor fault had required a manual restart sequence.
The decision to migrate was straightforward. The timing — within the constraints of a planned shutdown window — required careful planning.
The engineering approach
The critical element of this project was front-loading the engineering work. We spent 6 weeks on the site prior to shutdown:
- Full I/O audit of the existing control panels, verifying wiring against aging drawings and correcting discrepancies
- Logic capture from the PLC-5 program, translated to commented ControlLogix structured text
- Signal simulation on a workshop bench with the new hardware, running the translated program against simulated I/O states
By the time the shutdown window opened, the ControlLogix hardware was fully assembled, configured, and tested. The shutdown was used for three things only: physical hardware swap, field I/O verification, and handover walk-through with the site electrical team.
Result
The conveyor was handed back inside the planned window with a complete commissioning record, updated as-built drawings, and a structured fault-finding guide for the maintenance team. The site electrical team can now order spare parts from standard Rockwell distributors.