CS Holdings` engineering and production systems solutions division, CS System Solutions, has completed the re-automation of Transvaal Suiker Beperk (TSB)`s boiler 5 at Malelane Sugar Mill and Refinery in Mpumalanga. The three month project,commissioned in April 1999, was completed one day ahead of schedule.
The scope of the R2-million contract saw CS System Solutions responsible for a turnkey solution, which included the design, supply and procurement of all instruments, cabling infrastructure, junction boxes, programmable logic controller (PLC) and SCADA as well as the overall project management and software engineering.
"This was the fifth consecutive implementation of boiler control and information systems we have successfully achieved, reinforcing our reliable track record as specialists in the field," explains CS System Solutions business development director, Piet de Villiers. "The timing on this particular project was particularly tight. Our advantage was our depth of knowledge of the site and that our software engineers on the project had a thorough knowledge of boiler control. All operational requirements in terms of functionality, efficiency and performance were achieved without compromise."
As the largest of Malelane Mill`s boilers, Boiler 5 is vital to the efficiency of the operation. With a capacity of 205 tons per hour,the bagasse-fired boiler had an obsolete and maintenance-intensive control system based on stand-alone controller technology. This was a rigid control system not allowing for much control interaction, making the boiler unstable and prone to load changes under abnormal conditions.The control system consists of Modicons Momentum I/O communicating via a Modbus Plus network to a Quantum PLC. Wonderware`s InTouch SCADA was used for visualisation. The use of the Momentum I/O distributed at strategic points in the plant achieved a 20% cost saving, while still maintaining comprehensive and sophisticated control and not compromising safety standards. The ability to marry Modicons Concept Object orientated functionality into the Wonderware SCADA system saw the control philosophy - including three term, three element drum level and combustion control - still maintained with improved interaction between control elements.
"The re-automation has given us centralised monitoring and control of the boiler," says Hennie Loock, instrumentation engineer at the Malelane Mill. "Situations where operator intervention is required can be swiftly identified to ensure smooth running of the process. The software can also be re-programmed to cater for changing requirements, adding flexibility to the management of the system."
Operator interaction with the boiler was achieved through user-friendly objects in the Wonderware SCADA system. The software was developed to ensure the complete visualisation of the plant, real and historical trending, and loop tuning to provide optimised control of the boiler settings.With the automation of the boiler, operation intervention is limited to setpoint,load and ratio adjustments.
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