In 2008, ASSMANG Limited, which is jointly managed and controlled by African Rainbow Minerals Limited and Assore Limited, decided to increase the mining and processing of manganese ore from the Nchwaning II and III Mines. These mines are located at Black Rock which is in the Kalahari (about eighty kilometres North West of Kuruman and seventeen kilometres from Hotazel).

“We are planning to produce more than five million tons a year eventually from our mining operations,” says Sechaba Letaba, the senior general manager of BRMO. “As production is ramped up at Nchwaning, the existing surface beneficiation plant was identified as a bottleneck as it did not provide sufficient surface crushing, screening and washing capacity”.

Accordingly system integrator Iritron was appointed as a role player of the EPCM team together with TWP to design, procure and manage the construction of ASSMANG’s Nchwaning III Beneficiation Plant. Alwyn Rautenbach, Group Managing Director of IRITRON, expressed his gratitude to ASSMANG for their continued faith in Iritron to deliver quality EC&I turnkey solutions. He summed up the project by stating that the company had “once again supplied ASSMANG with a quality automation solution that is within budget, on time, easy to maintain and which meets all their operating requirements.”

The new beneficiation plant sources ore from either Nchwaning II or Nchwaning III mines which is placed in one of four ±2500-ton silos depending on the customer/grade required. Via a conveyor system, the ore then goes through a series of crushing, washing and sampling processes and is sized and graded into load-out bins in accordance with various customer requirements. The new beneficiation plant provides for a production changeover from low to high-grade ore in less than twenty minutes.

Iritron tied into the existing 22KV reticulation with two new 22kV distribution stations. The motor control centres (MCCs) were not only designed but also supplied by the Iritron group. The quality up-front design work necessitated very few on-site modifications resulting in a very neat racking and cabling installation where locations are far apart due to the nature of the operations. The instrumentation design was done on Dessoft’s engineering software 1Des and based on remote I/O distribution in the field and cabled to I/O collection points in the MCCs.

Iritron’s brief was to develop an automation solution based on best practices and standards that also cater for future expansion. A leading-edge PLC/SCADA solution was offered that leverages the latest features of Schneider Electric’s Unity Pro v4.0 collaborative engineering software and AVEVA System Platform based on ArchestrA technology, supplied by IS³. The corresponding ArchestrA and Schneider Unity DDT templates were developed for the project and these provide the platform for standardisation, simplified coding and accelerated engineering. AVEVA’s Historian provides the required historical logging, trending and reporting functionality while Information Server web portal allows management and other data clients to view the plant mimics remotely and to keep an eye on continuously-updated production reports. The reports relay real-time and accumulated production throughput and capacity utilisation on a per-shift and daily basis.

At the specific request of Black Rock, Iritron’s Operations Director André Roeloffze, was appointed as the commissioning manager for the new plant on behalf of the mine. The plant was handed over for production in May 2010.