SPECIALIST EQUIPMENT
The PLCs will control the sedimentation process of the concentrating mill
crushing and processing, etc. However, a number of items of plant equipment came with automation from other vendors, including PLCs that were supplied with the sedimentation facility that forms part of the mine’s concentrating mill. Te PLCs were normal industrial grade types, but housed in freeze-protected cabinets located outdoors. Since installation however, this facility has suffered a number of process stoppages because of the environment at the mine - which includes very wet and humid conditions and winter temperatures as low as -40˚C. If a process stoppage happens in winter the impact can be severe, as the weather can quickly add to the problem by freezing and blocking pipelines. Tere have been some four or five
37 INTERNATIONAL MINING ENGINEER
stoppages a year, stemming from power outages, extreme cold temperatures, or water droplets that form on the PLC modules when the cabinet doors were opened. In wintertime, condensation can happens in seconds - almost the instant the cabinet doors are opened and the benefits of the cabinet’s ingress protection are lost - because of the very low temperatures and the moisture-laden air around the concentrating mill. Te same problem can also happen in springtime, as temperatures can swing between -25 and 15˚C from night to day - leading to heavy condensation.
Improved reliability
Te mine operators decided to upgrade this part of the control system to improve
The PLCs will control the sedimentation process of the concentrating mill
reliability and uptime. ABB proposed a solution based on the XC PLC. XC is an ‘extreme conditions’ variant of the AC500 PLC family that is installed underground. It has built-in protection against a very wide variety of threats posed by harsh environmental and operating conditions including high and low temperatures, high humidity, low air pressure, salt mist and hazardous gases, and vibration and shock. In this case, the new ABB XC PLCs will be installed at the mine’s above- ground processing centre - with some I/O modules located at a remote water pumping location and connected using ProfiNET.
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