Buhler has implemented Wonderware’s InControl soft PLC and InTouch scada solutions at Meadow Feeds’ Paarl plant to help the mill manage the complex production processes that generate 32 000 tons of varied animal feeds every month.
Meadow Feeds is part of Astral Operations Agri and Poultry Division and is the market leader in the South African animal feed industry serving a wide range of customers in the poultry, egg, livestock and dairy industries. The company operates six animal feed mills, located in Randfontein, Delmas, Welkom, Paarl, Pietermaritzburg and Humansdorp. Astral Foods has other initiatives in Zambia, Malawi and Mauritius.
The company's Paarl plant is one of the largest in southern Africa and produces 65 tons of a variety of animal feeds per hour. With this volume, there is little tolerance for production process errors. "This is the third implementation of a control system at the plant in 22 years," says Albie Wheatley, Meadow Feeds IT and the mill's Project Manager for the implementation of the new control system. "The previous systems were typical of the legacy concept of production processes being divorced from business processes and of engineering being something apart from the rest of the company. The result was scada systems that could only be maintained or changed at great cost by a few specialists and that never integrated with the rest of the organisation's information pipelines except in the most rudimentary way. This all had to change."
The dependency on expensive and inflexible PLC hardware, that could have a lengthy repair turnaround, coupled to a lack of production information throughout the plant, prompted Meadow Feeds to look for a solution that would free it from specific PLC hardware, proprietary software and dependence on a few specialists, and which would also provide the flexibility, reliability and information flows required to run the plant as management wanted it run now and in the future.
Meadow Feeds chose Buhler as system integrator, not only because of the company's successful track record with over 80 plants in southern Africa but mainly because of Buhler's concept of doing away with the logic of PLCs and integrating the realtime production processes with normal IT operations.
"If you take the L out of PLC, you end up with PC," says Ralph Hauselmann, Manager of the Automation and Electronic (AE) department at Buhler. "And that is exactly what we have done at eight of our most recent installations which have been running for a considerable time with far more reliability than they experienced previously. PLC hardware is costly and PLC expertise is far more costly. PLCs also do not readily lend themselves to networking using standard IT networks. On the other hand, a standard and low-cost PC running Wonderware's InControl software does away with the inflexible and specialist-dependent LOGIC part of PLCs while allowing for the integration of realtime production process information with IT using standard network technology. In this way, the most important processes of the company - those that create the wealth - can be integrated on-line and in realtime with all the other processes such as planning, preventative maintenance and down-time analysis as well as supply chain management and others. For the first time, the shop floor can rely on the considerable expertise and infrastructure of IT while IT - again for the first time - becomes the logical custodian for the company's extended production information chain."
While business and ERP systems deal with the abstract reality of transactions, they never really addressed the needs of a manufacturing company's production processes, which have always tended to be treated as a technological 'Black Box'. This, together with specialist hardware and embedded software in the form of PLCs, has tended to isolate production processes from the mainstream of the company's networked IT processes. The soft PLC approach does away with this isolation by making realtime production information available to anyone who needs it through the use of standard, low-cost, off-the-shelf and well-understood software and hardware technologies.
"The Meadow Feeds Paarl installation consists of five InTouch scada HMI (Human Machine Interface) nodes, three InControl nodes and one Microsoft SQL node," says Buhler's Chief Project Engineer, Willie Liebenberg, who, together with colleague Paul Hales, was responsible for the installation at the mill. "The implementation took 18 months and in that time the mill lost little production time during the six days needed for commissioning. No special code had to be generated which means that the mill can take full ownership of the control system and need not rely on external specialist knowledge. Another important consideration is that any node can, in addition to its own function, also assume the function of another node. This means that PC replacements or enhancements as well as system expansion can occur without impacting production in any way."
"I was impressed by the faultless way in which every phase was implemented," continues Wheatley. "A major contributor to this was the plant simulator which Buhler developed. This allowed us to model every conceivable condition and was invaluable for operator training. The simulation is so real that operators cannot tell the difference between the simulation and the real thing. The result was that they moved from simulator to the live control system without problem."
Today, Meadow Feeds' Paarl mill can be run remotely if necessary and its production processes rely on standard software technologies from Microsoft and Wonderware. This approach allows IT to contribute its vast resources to what was previously an isolated island of information and to make this information available to every level of the mill - again, using standard technologies. The mill also now fully owns its control system, which can be modified or expanded at will to cater for changing needs. By changing one's mindset to embrace the use of standard and evolving technologies, approaches and tool sets, it would appear that the concept of plug-and-play can now also be applied to the most sophisticated and complex control systems.
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