High-tech Goes Outback

BHP Billiton's Cannington mine - the world's largest and lowest-cost producer of both silver and lead - has recently implemented a Profibus fieldbus strategy in its new split flotation and zinc cleaner projects.

Cannington Mine is 850 kms south west of Townsville, and produces zinc concentrate as well as silver and lead concentrate. The ore is mined 680 m vertically underground. Rocks roughly 180 mm in diameter are milled to 120 micron in a fully autogenous mill, and then to 80 micron in a tower mill. The fines (< 6 micron) are conveyed in a slurry to the split flotation plant where methylisobutylcarbon (MIBC) is added as a frothing agent. During passage through the flotation cells, Aerophine (3418A) is dosed to 'collect'  the silver, and sodium ethyl xanthate (SEX) is dosed to 'collect' the lead.

More than 75 Endress+Hauser instruments were installed on Profibus PA on this project - bringing the total tag count for E+H at Cannington to over 140 devices. Prosonic FMU 40 ultrasonic level sensors, together with target plates, are used to measure the froth level in the flotation cells. Promass A (DN2) Coriolis flowmeters are installed for dosing the Aerophine since that is based on mass ratioing, while Promag A magmeters are used for dosing the SEX. There are over 20 large-diameter Promags monitoring the slurry flows on the zinc regrind circuit. Cerabar M pressure transmitters, together with a range of Omnigrad temperature and Deltabar dp Tx, measure the mass airflow into the aerator.

All these devices are linked into the Allen-Bradley PLC 5 and Contrologix PLCs with Profibus PA fieldbus technology, coupled through Siemens Link modules and SST DP/PA interface cards.

Some teething problems were experienced during commissioning: the extent to which the new technology would challenge the skill levels of the electrical tradespersons was not fully anticipated, and too little training was planned; the complete suite of trouble-shooting software tools was not initially available, and some implementation had to be done on a trial and error basis. However, on balance the implementation of Profibus technology has been a success.

Although the capital cost of the instrumentation and Profibus peripherals was slightly higher than conventional 4?20mA equipment, this was offset by significant labour savings during commissioning. The flexibility of being able to add further devices without further cabling is a significant and ongoing benefit. The sophisticated fault-finding capability of the Profibus network has allowed the standard instruments such as the Prosonic M ultrasonic level device to be used in difficult applications.

Key learnings identified during the project included the recognition that additional planning prior to implementation would have allowed greater exploitation of the technology, and that training of personnel in the new technology is critical to the success of a Profibus installation, as it would be with any new technology.

Cannington has recently installed the newly released Fieldgate FXA 720, the Profibus DP-Ethernet gateway. This enables electrical tradespersons to access the data''published' by the instruments, and to trouble-shoot from anywhere on the network.

"We're delighted at the positive feedback from Cannington, and to note their continuing commitment to Endress+Hauser technologies," comments John Immelman of Endress+Hauser Australia."'Profibus technology offers a host of benefits, including support for better business decision-making by enabling preventive and predictive maintenance rostering,"

phone    1300 363 707

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email:     John Immelman