Automation company Iritron is executing a project for a major South African packaged-goods company, which requires refurbishing and upgrading a plant with the latest optimised control systems.

The scope of work revolves around replacing 11 wheat mill programmable logic controllers (PLCs) with one Siemens S7-1500 PLC. The old PLC programs were reverse-engineered and reprogrammed into the new Siemens PLC.

The contract was awarded at the end of last year and Iritron is conducting on-site testing, with commissioning under way.

The estimated R7.5-million project, in Gauteng, is expected to be completed by the end of this month, says Iritron divisional manager Gerhard Greeff.

The eleven-storey plant comprises more than 7 000 instruments that are all connected to the control system. Iritron is replacing all the panels, switchgear and PLCs connecting to the original supervisory control and data acquisition (Scada) system.

The remote input/output systems have been installed in the existing enclosures on site, with all the instrument cables having been removed and reconnected.

New communication cables and power cables have been supplied and installed. Some changes had to be made to the legacy InTouch Scada so that it can communicate with the new Siemens PLC while connecting to and operating with other plant PLCs.

“Old, redundant PLCs and other equipment have been replaced with modern equipment, ensuring a modern plant control system with available spares. “The new equipment will reduce unplanned downtime, owing to control equipment failure, thus increasing plant reliability and throughput. It also ensures a reduction in control equipment and potential points of failure and maintenance in the long term.”

Greeff adds that new technology was used in, for example, the roller mill electrical works, with a new motor control centre (MCC) designed, manufactured, fitted, supplied and installed by Iritron.

The MCC is equipped with automation company ABB Robotics’ switchgear and OEM-supplied free issue variable-speed drives (VSDs). The MCC is equipped with 45 direct online starters and 26 VSD starters.