Delivering plant wide control for Arrium Mining’s Iron Knob operation

The development of a mobile and modular crushing and screening solution has enabled iron ore miner Arrium Mining to halve plant costs and significantly reduce downtime at the Iron Knob mine in South Australia.

Iron Knob, which is about 60 kilometres north-west of Whyalla in the Middleback ranges, is an entire pit-to-port operation, featuring mines, crushing and beneficiation facilities, rail, trucking and port facilities.

The mine is part of an Arrium iron ore business which exports 9-10 million tonnes of hematite ore per annum, primarily to China, while also supplying feed to the company’s integrated steelworks at Whyalla.

Arrium engaged Striker Australia, a provider of crushing, screening and materials handling equipment in the mining industry, to prepare infrastructure to access the ore reserves at the Iron Knob mine.

Striker’s task was to design, supply, assemble, install and commission modular crushing and screening equipment to process hematite from the mining area for rail transport to Arrium’s port facilities, with minimal ground works and in a short on-site construction timeframe.

To achieve this, Striker contracted SAGE Automation, a solution partner of Rockwell Automation, to supply the control system and visualisation, together with the complete electrical design, construction and installation works for a new crushing and screening plant.

Keeping it mobile and modular

The Iron Knob crushing and screening plant was designed to have a 10-year life expectancy, making the use of mobile crushing and screening equipment a cost-effective solution compared to a fixed infrastructure solution.

“The plant was originally estimated to cost approximately $40 million, but by using mobile equipment, this cost was able to be reduced by half,” SAGE Automation senior electrical engineer Christopher Poetsch said.

Poetsch knew that the control and visualisation solution from Rockwell Automation would provide the required flexibility and reliability for this application. As a result of the maintainability and easy integration of the solution into the systems at the site, Rockwell Automation was chosen as the control and visualisation vendor for Arrium.

According to Rockwell Automation executive account manager Greg Schultz, “By having the crushing in close proximity to the mine, the requirement for transport and materials handling is reduced dramatically.”

The modular design of the plant made integration easy and delivered the flexibility required to adapt to changes.

“The new plant has had a number of design revisions but because it is modular and mobile, it has been easy to adapt to changes,” Arrium principal control system/maintenance engineer Jonathan Deluao explained.

Designing a flexible control solution

The overarching control requirements for the entire plant, including the conveyors, crushers, feeders and stackers, were provided by Allen-Bradley ControlLogix.

With safety being a vital consideration for the plant, Allen-Bradley GuardLogix – with local and distributed safe POINT I/O modules – provided integrated safety control and the ability to stop either a particular piece of equipment or a section of the plant if required.

Due to the size of plant, 75 motor starters were required. The most complex of these were from the Allen-Bradley PowerFlex family, used for the synchronisation of the vibrating feeders and for the speed control of the conveyors to optimise flow rates to the crushers.

FactoryTalk View Site Edition (SE) supervisory-level HMI software is used for monitoring and controlling the plant. It provides operational insight into the complete site, including the conveyors, crushers and feeders.

“Using the Rockwell Automation platform for control and visualisation of the plant provided peace of mind, reliability and improved maintenance response times. The plant operators are familiar with, and have confidence in, the ControlLogix and FactoryTalk platform. Because it is used on other Arrium sites, maintenance requirements are also reduced,” Poetsch explained.

He added that one of the most significant challenges the project team faced was the extremely tight timeframe.

“To deliver the project within these timeframes, we leveraged previous project experience, industry knowledge, SAGE Automation team agility, and the use of the Rockwell Automation tools for the design and deployment of the control system, which proved to save significant time and cost,” Poetsch said.

Due to the delivery sequence for the crushing and screening equipment, it was necessary to start commissioning sections of the plant while others were being mechanically and electrically installed.

Poetsch explained that “the use of POINT I/O for the system allowed for flexibility in design and scope changes, right through to the commissioning and handover phase, which helped to deliver the project within time and budget.”

Reducing downtime

Being an Arrium project, the automation control system had to adhere to the strict design, implementation and testing standards that the company has developed over recent years.

“Integration between plant equipment was made easy with the integrated architecture platform from Rockwell Automation, which we stipulate as a standard for Arrium sites. This allows us to benefit from common spares and resources, minimises training requirements and helps the plant capitalise on the core infrastructure,” Deluao said.

The high availability of the ControlLogix control system and associated components gives Arrium the assurance of a high mean time between failure (MTBF) and mean time between repair (MTBR) and low mean time to repair (MTTR), which ultimately equates to minimal downtime, planned or unplanned.

Integrated device level ring (DLR) connectivity was used to optimise the network architecture, increase its fault tolerance and provide consolidated network diagnostics. The Allen-Bradley Stratix switches included integrated DLR connectivity, and although the control system did not require redundancy to the level of other Arrium plants, the DLR network topology delivered a reliable network architecture for the plant.

“The site now processes approximately five million tonnes of ore per annum and the control system has been embraced by operators and maintenance staff with minimal training. The system was designed and installed to meet Arrium’s stringent requirements, which are not only site specific but company-wide,” Poetsch said.