What was our brief for this project?

PPC, in their commitment to safety and continuous process improvement, expressed the need to upgrade two of their crushing plants. They wished to increase and stabilise their production and to adhere to the relevant Department of Minerals and Energy (DME) and Mine Health and Safety Act (MHSA) standards. We were appointed to design the electrical, instrumentation and control solution to upgrade both the Tertiary Road Stone and the Primary Sand Crushing Plants.

Hannes du Plessis, Resident Electrician at Leazonia Quarry and Gideon Roux, Electrical Design Engineer at IRITRON. They are standing next to MCC 2A for the Primary & Secondary Crushing Plant and MCC2B for the Tertiary Road Stone Crushing Plant.

Which solution did we propose?

IRITRON proposed installing new MCC’s complete with PLC’s to control all the processes remotely via new Wonderware InTouch version 10.1 SCADA systems. This was done utilising electronic motor controllers, soft starters and variable speed drives (VSD’s) to operate all the electrical motors and subsystems for each plant. We also introduced safety sirens, pull ropes, emergency stops, local motor isolators and various measuring and protection instrumentation to increase the safe operation of the plants. Lastly, we installed a PLC to Wonderware InTouch touch-panel control system that is based on a visual representation of the plant.

Operator is controlling the plant via a Wonderware SCADA Interface. The control room is located such that the operator can view the product input to the crusher as this is the process choke point (as identified by Henk Wiltz, Leazonia Quarry Works Manager).

What value did we add for the client?

The old operator stations relied on push-button start signals hardwired to contactors and outdated overloads that were interlocked in order to facilitate manual sequence starting. Although this was solid engineering practise many years ago, trying to do faultfinding without drawings on such a system is a time consuming and frustrating exercise. In order to receive individual equipment operating parameters like pressures, temperatures and lubrication levels the operator would have to leave the operating station unmanned to do so and therefore this is not an ideal situation.

The new Wonderware InTouch SCADA system allows the plant operator to sequence start the whole plant with one touch to the screen. We added safety operator acknowledgement icons that remind the operator to check on given mechanical conditions before a relevant sequence can resume.

The operator gets real-time information on equipment status, safety interlocks, stockpiles -and process water levels and electrical drive current levels from the instrumentation in the field. This data is being used to prevent overloading of equipment or as an early warning of possible equipment failure.

Where did the challenge lie?

The challenge lay in converting the existing old system to a fully automated system with min. production losses. Implementation was done on a system in full production with only a very short shutdown in which to bring about the change over.

What was special about this project?

We worked in close co-operation together with the client to ensure minimal down time and maximum plant availability. Doing installation work on a production plant that is still running is a difficult and dangerous operation. With a well managed construction crew and a lot of co-operation from the PPC team, we overcame all challenges without too many problems.

Cable rack to the secondary screening building.

What was new in this project?

We embarked on a fully automated control solution to ensure maximum throughput by minimizing downtime and optimising start-up sequences through close monitoring of equipment. We moved from an archic relay logic manual system to a state of the art electrical, instrumentation and control system to maximize throughput and minimum downtime.

Which team worked on this project within IRITRON?

Gideon Roux (Team leader and Electrical Design Engineer), Etienne van Dyk (Instrumentation Design Engineer) Judy Flynn (CAD Operator) and Edgar Chauke (Electrical Engineer in training). Absent from the photo: Adrian Cloete (Engineering Manager), Danie Smit (PLC Systems Engineer) and Renier Greyvenstein (SCADA Systems Engineer).